Summary

SUMMARY

In October 2001 the Highways Agency appointed WSP Group to undertake an environmental study to examine potential options to improve the A417 between Cowley Roundabout and the end of the Brockworth bypass, Gloucestershire. The aims were to identify the environmental constraints within a study area centred on the existing route, prepare a constraints map and identify if options were available to improve this section of road which did not have unacceptable environmental consequences. In addition, consultation with environmental statutory organisations and "other" local stakeholders was to be undertaken and a public open day organised to provide local people and interested parties an opportunity to discuss the results of the study process.

Background

This section of the A417 has a poor safety record and suffers from severe congestion. This section of the road is the only remaining single carriageway section on the A417/A419 route between the M4 (Jnc.15) and M5 (Jnc.11a). Traffic volumes are currently between approximately 28,000 and 31,000 vehicles per day of which approximately 12-14% are Heavy Goods Vehicles. Queues occur regularly at peak periods.

There are steep hills at Nettleton and Crickley Hill and slow moving Heavy Goods Vehicles (HGV) compound queuing issues. In places the road standard is generally poor with tight bends and narrow lanes. Vehicle shunts occur regularly at Air Balloon and there are accident clusters at Nettleton Bottom, Birdlip, Air Balloon and on Crickley Hill.

Three small scale improvement schemes have been completed recently to improve safety at the Golden Heart Public House, Air Balloon Roundabout and Birdlip junction. A number of additional small scale improvements are also planned in the next few years. However, it is recognised that a longer term solution is required.

Constraints

Environmental and engineering constraints have been identified and translated onto a constraints plan. Information was gathered from a wide range of organisations, from earlier studies and from limited walk-over surveys.

The entire study area falls within the Cotswolds Area of Outstanding Natural Beauty (AONB).

Option Development

Possible improvement options were developed using a staged approach in discussion with environmental statutory bodies, Local Authorities and other Stakeholders. A number of options were initially identified which have been systematically reduced on assessment of data collected or on the advice of those consulted.

As a result of this process three options remain. Two of these are on-surface options that only differ in their treatment of Crickley Hill and the Air Balloon Roundabout. The third is a tunnel option which would pass between Nettleton Bottom and the foot of Crickley Hill. The options are summarised below:

Option Assessment

Engineering Comparison

All three options are buildable, although Options 2 and 3 would cause less disruption during construction to vehicle flows up Crickley Hill. In addition remodelling of the Air Balloon roundabout under Options 1 and 2 would cause disruption while the schemes were built.

Options 1 and 2 would retain steep gradients on Crickley Hill (in the order of 10%). Option 3, the tunnel, would have an average gradient of 4.4%.

Option 1 would require departures from standards, however, there are safety concerns with the signalised junction which cannot be overcome by careful detailed design and for this reason Option 1 should be discarded. Departures from standards would be required on Option 2 but safety would not be compromised. Option 3 would not require departure from standards.

Temporary contractors camps would be required for all three options, although these would be potentially larger for Option 3. Option 1 would take less than 2 years to construct, Option 2 would take approximately 2.5 years, and Option 3, 3 years or more (depending on hydraulic conditions encountered).

Option 2 would have a severe impact on properties.

Economic Comparison

The preliminary economic assessment has identified that all options have positive Net Present Values (NPV's) at high growth. Options 1 and 2 have positive NPV's at low growth whereas Option 3 is negative. All three options contribute time savings and reduction in accidents.

Option 1 would be the least expensive option at approximately £40 million, but has the least benefits and would only provide a short to medium term improvement for relief of congestion. Option 2 represents best value for money as it has the highest NPV's and Benefit/Cost Ratio. This option would cost in the region of £60 million. Option 3, at a cost of approximately £200 million, has the greatest benefits but due to the anticipated tunnelling costs is also the most expensive.

Environmental Comparison

An environmental appraisal of the three options has been undertaken using the Guidance on the Methodology for Multi-Modal Studies (GOMMMS) approach.

In terms of landscape, Option 1 would have a moderate adverse impact on the AONB and landscape character, whilst both Options 2 and 3 would have large adverse impacts, the latter due to the link roads and portals particularly at the northern end.

Cultural and archaeological resources are many and varied within the study area. Options 1 and 3 would have slight adverse impacts whilst Option 2 would have a moderate adverse impact, mainly due to its affect on the context of Crickley Hill.

In terms of ecology, the two surface options largely avoid nationally and locally designated sites. However, dewatering for the tunnel may potentially severely affect Bushley Muzzard SSSI which relies on spring water. It is possible that mitigation measures could be designed to minimise impact. However, given the uncertainty at this time, there remains a high risk of permanent damage and a very serious adverse impact has been predicted for Option 3.

Water in the underlying Major Aquifer is a major issue in the study area and its presence has had a major impact on previous road schemes in the study area. Mitigation measures for Options 1 and 2 could reduce the impact on the water regime such that the long term impact on the ground and surface water regime is predicted to be slight adverse. However, there is considerably more risk about the potential impact of the tunnel and the Environment Agency have expressed serious concerns. The tunnel option, therefore, has been awarded a large adverse impact score.

In terms of local air quality, Options 1and 2 would increase localised air pollution although along the whole route there would be an overall decrease. Under Option 3 overall local air quality would improve, although the pollutants would be concentrated at the tunnel portals. Both Options 1 and 2 would also lead to an increase in the release of greenhouse gasses, whilst the tunnel option would lead to a decrease.

Up to 29 properties would experience an increase in noise levels under option 1 and 4 properties would experience a decrease in noise levels. Under Option 2, up to 32 properties would experience an increase and 6 a decrease in noise levels. Under Option 3, 12 would experience an increase in noise and 37 a decrease.

Public Open Day

A Public Open Day was held in Birdlip Village Hall on the 15th and 16th of February 2002. It was attended by approximately 200 people, including Local Councillors, MP's and local residents. Members of the consultants team and the Highway Agency were present to answer questions.

The issues raised and discussed related to:


Summary

1 introduction

1 INTRODUCTION

1.1 The safety and congestion issues on the A417 south of Cheltenham have long been recognised. The road is part of the core trunk road network and the remaining single carriageway section between Cowley (Nettleton) Roundabout and the bottom of Crickley Hill urgently requires improvement. It comprises the only single carriageway section on the route between the M5 at Junction 11a and the M4 at Junction 15.

1.2 Small scale improvements have been completed along the route since the opening of the Birdlip Bypass in 1995. Further small scale schemes are being planned over the next few years by the Highways Agency and the network maintenance contractor, RMS. These would provide short term amelioration of safety and congestion issues. However, a long-term solution is required for this section of the road.

1.3 Discussions with Local Authorities (County, Borough, District and Parish Councils) have resulted in all agreeing that the current situation is limiting economic growth in the area and resulting in significant congestion and safety problems along the route. They also agree that it is unacceptable not to improve the A417 within the study area.

1.4 Options developed in the past for a long-term road based solution have all resulted in the identification of unacceptable environmental impacts and so have not been taken forward.

Terms of Reference

1.5 In October 2001, the Highways Agency appointed WSP Group to undertake a study of the environmental and engineering issues related to the A417 between Cowley Roundabout and the bottom of Crickley Hill. The Terms of Reference were to consider if the route could be improved without unacceptable environmental impacts and to hold discussions with statutory bodies to ascertain their views on whether an option(s) could be taken forward for more detailed assessment. The Terms of Reference are given in Table 1-1.

1.6 The work undertaken comprises a pre-investment study. As such it utilises the "Plan" elements of the Guidance on Multi-Modal Methodology Studies (GOMMMS) Assessment and Stage 1 methodologies as given in the Design Manual for Roads and Bridges (DMRB).

Table 1-1 Study Terms of Reference
Terms of Reference. Cowley to Air Balloon Improvement. Environmental Study
  • The study should be conducted in close liaison with statutory consultees and should produce a comprehensive environmental constraints plan and environmental data report.
  • This should be used as a basis for considering whether environmentally acceptable improvements could be made to the trunk road to address the safety and congestion problems that currently exist on the A417.
  • Preliminary proposals for improvement that emerge should be discussed and agreed with statutory consultees.
  • Whether or not a tunnel is an appropriate solution should be given consideration.
  • The consultants should agree with the statutory consultees whether or not it will be necessary to carry out additional surveys on a particular issue and if so, a survey brief should be agreed with them. The consultant should advise the Agency when such surveys should be carried out, even when they could be outside the timescale for this study.
  • The consultants should take into account the views of local residents, local groups, representative bodies and other interested organisations.
  • The consultants should carry out an appropriate environmental and economic appraisal in accordance with GOMMMS and summarise the results in an Appraisal Summary Table (AST).
  • The final report should include comments made on the issues, so that Ministers will have sufficient information to be able to make informed decisions on whether an improvement scheme(s) could go forward and be added to the TPI programme.

Study Area

1.7 The study area is shown on Figure 1.1. The area is based on the line of the A417 from a point adjacent to the A46 junction in the west (at NGR SO 9100 1634) and a point near Highgate Farm, Elkstone in the east (at SO 9546 1264). The study area extends for 1 km in all directions from the road and covers approximately 14.5 km². The study area was extended to the west of the escarpment to cover possible offline corridors. The area is within the Gloucestershire civil parishes of Badgeworth and Great Witcombe in Tewkesbury Borough and Brimpsfield, Coberley, Cowley and Elkstone in Cotswold District. The entire area is within the Cotswold Area of Outstanding Natural Beauty and it also overlaps the Brimpsfield Conservation area.


1 introduction

2 traffic, congestion and safety issues

2 TRAFFIC, CONGESTION AND SAFETY ISSUES

2.1 The section of the A417 from Cowley Roundabout to the Brockworth Bypass, known as the "Missing Link", suffers from severe congestion and has a poor accident record. These problems are likely to get worse if, as predicted, future traffic levels increase. This section of road is single carriageway and its layout is below the acceptable standard for a road of its type and with its high traffic flows (see Figure 2.1).

2.2 The Personal Injury Accident record for this section is provided in Table 2-1 below. The figures refer to the number of accidents, rather than the number of casualties. Anecdotal evidence also suggests that there are a large number of near misses and minor damage only accidents along this section that do not find their way into official statistics. More recently, in May 2002, there was a fatal accident on Crickley Hill involving a car and a light goods vehicle.

Table 2-1 Personal Injury Accidents
Year Number of Personal Injury Accidents (NOT casualties)
Slight Serious Fatal Total
1996 7 2 1 10
1997 8 1 0 9
1998 13 1 1 15
1999 11 2 0 13
2000 13 5 1 19
Total 52 11 3 66

2.3 The national trunk road speed limit applies along the route with the exception of a 40 mph zone through Nettleton Bottom.

2.4 Congestion along the route (especially at Cowley and Air Balloon roundabouts) results in 'rat-running' on local roads and through villages including Birdlip, Elkstone and Syde. Local Parish Councils have also informed that Leckhampton is affected when problems occur on Crickley Hill and the Air Balloon roundabout.

2.5 A number of small scale improvements have recently been implemented along the route and these are described in the sections below. Although these schemes have provided short-term improvements all parties acknowledge that a long-term solution is required.

Cowley Roundabout

2.6 At Cowley Roundabout the dual carriageway terminates and the road becomes a single carriageway for the next 6km. This creates a traffic bottleneck resulting in severe peak hours congestion with traffic queues extending several kilometres to the south-east. There are approximately 28,000 vehicles daily using this section of the road, with approximately 12% being HGVs.

Nettleton Bottom

2.7 Nettleton is in a pronounced and localised dip in the trunk road, where forward visibility is not as good as it should be for this standard of road.

2.8 Vehicles tend to develop high downhill speeds, well in excess of the 40 mph speed limit, in an effort to build up speeds before the uphill section. The steep gradients entering the dip (approximately 10%) make vehicle control under braking more difficult.

2.9 The access to the Golden Heart Public House is located at the lowest point of the dip making right turns into and out of the car park a hazardous manoeuvre.

2.10 The high traffic volumes and speeds along this section create a high degree of severance and accessibility problems.

2.11 Recent safety improvements at Nettleton Bottom have been completed which include localised widening of the existing carriageway, a right turn lane into the Golden Heart Public House car park, traffic calming measures and the implementation of a 40 mph speed limit.

Stockwell Junction

2.12 Vehicles turning into and out of this junction can hold up through traffic on the A417. The volumes of traffic using this junction are low but there was a serious personal injury accident at this location in 1999.

A417/B4070 Birdlip Junction

2.13 Birdlip Junction is a major/minor junction where the B4070 terminates with the A417. The A417 is single lane dualled through the junction with a central island and a dedicated right turn lane. The majority of the accidents at the junction involve right-turning traffic out of the B4070 and a fatal personal injury accident occurred in August 2000.

2.14 Right-turning traffic from the A417 has difficulty crossing the northbound carriageway due to high traffic volumes and high vehicle speeds. There is also potential for vehicles waiting to turn right to queue back onto the running carriageway of the A417, obstructing through traffic.

2.15 There is also a problem with traffic turning right out of the B4070 local road from Birdlip Village. Visibility is restricted by the existing vertical alignment and by queuing right turning traffic. Drivers turning right out of the junction also misjudge speeds of vehicles coming up Birdlip Hill.

2.16 In order to improve the operation of the junction, the layout has recently been improved. A longer right turn lane on the A417, reflective marker posts, differential surfacing and improved road markings have been installed.

Shab Hill Lane

2.17 Vehicles turning into and out of Shab Hill Lane can hold up trunk road traffic. The turning vehicles are vulnerable to tail end shunts since they have to contend with high vehicle flows and high vehicle speeds.

Air Balloon Roundabout

2.18 Congestion often occurs at the junction during peak hours, with southbound traffic queues regularly extending for several hundred metres down Crickley Hill.

2.19 Vehicles have difficulty turning into the Air Balloon Public House and Crickley Hill private residence because of the fast moving trunk road traffic.

2.20 The horizontal alignment of the existing roundabout produces tight vehicle turning movements, particularly for vehicles travelling along the A417 from Cirencester and heading towards Gloucester. The turning circle for large vehicles can result in conflict with other vehicles approaching the roundabout from the Gloucester direction in the outside lane.

2.21 Vehicles continuing along the A417 heading to Cirencester have to undertake an approximate 300 degree turning manoeuvre to travel from Crickley Hill towards the Birdlip Bypass.

2.22 Recent improvements at the junction have extended the climbing lane and provided two right turn lanes on Birdlip bypass. The roundabout has also been widened which has increased the existing capacity and helped increase traffic flow. Accident figures show that there are no serious personal injury accidents at the junction with congestion being the major concern.

Grove Farm and Cold Slad Accesses

2.23 Both the Grove Farm and Cold Slad junctions have dangerous direct accesses onto the A417. Work is currently being undertaken to investigate whether it might be possible to carry out safety improvements at both junctions.

2.24 Contributing factors that make these junctions dangerous include high traffic volumes, high vehicle speeds (some exceeding the 60 mph speed limit) and the steep gradient of Crickley Hill (approximately 10%). Cold Slad also sits on the inside of the bend and has restricted visibility.

2.25 Right turning traffic from Gloucester into Grove Farm access wait in the fast outside lane to turn across the downhill lane. These turning vehicles risk shunts from behind and driver stress is increased whilst waiting for a gap in the high speed downhill traffic.

2.26 Articulated heavy goods vehicles from Air Balloon sometimes move over the central white line, into the line of onward uphill traffic, in order to negotiate the tight left turn into Grove Farm. A number of impatient drivers travelling downhill have also been reported to move into the uphill lane when overtaking vehicles slowing down to turn left into Grove Farm. Vehicles waiting to turn right into Cold Slad obstruct all downhill traffic causing congestion and the risk of shunt type accidents. Right turning vehicles out of both Cold Slad and Grove Farm have to cross lanes of fast moving traffic.

2.27 The historical accident record does not indicate a major problem but increased flows and evidence of many reports of near misses have given rise to the perception of the junction being dangerous. The high speeds especially of HGVs on the downhill (10%) approach to the access causes particular stress for drivers making left turns into Grove Farm access.

Crickley Hill

2.28 Crickley Hill has two lanes up (one being a climbing lane) and one lane down. The maximum gradient of the road is approximately 10% and there is no central reservation or safety barrier. The road layout is well below the acceptable standard for this type of road and the traffic volumes (nearly 31,000 vehicles per day and 14% HGV) are high.

2.29 Slow moving vehicles regularly restrict uphill and downhill traffic. This leads to driver frustration, with some drivers making the dangerous manoeuvre of overtaking slow moving vehicles by the crossing the solid white central lines.

2.30 Due to the steep gradient, vehicle brake failure is one of the main causes of accidents. HGV drivers travelling up Crickley Hill have also been seen to struggle to maintain control their vehicles.

2.31 Broken down vehicles are another consequence of the steep gradient. These cause severe congestion and pose a significant safety hazard.


2 traffic, congestion and safety issues

3 geotechnical issues

3 GEOTECHNICAL ISSUES

Background Information on Soils and Geology

3.1 The geology of the study area has been obtained from the British Geological Survey of Britain Sheet 234 (Solid and Drift).

3.2 Excerpts from the relevant 1:10560 geological mapping, Sheet SO 91 SW, have also been studied as part of this assessment.

3.3 The British Geological Survey borehole database has been consulted.

3.4 The records of Gloucester County Council were searched regarding this section of the A417. Some data was recovered regarding the improvements (provision of the third lane below the escarpment) carried out during the 1960s. However, the drawings are not dated.

3.5 A number of records were examined from the Local Studies Section of the Gloucester Library.

Previous Studies

3.6 Reports from previous studies in the area have been reviewed as part of this study. The reports studied include the following:

Topography and Outline Geomorphology

3.7 Within the study area the Cotswold Escarpment runs approximately SSW to NNE. To the east of the escarpment the land is formed by a plateau at an approximate elevation of between 240 and 290m AOD, whereas, to the west, the land drops away to an approximate elevation of 100m AOD. The lower slopes are generally at a shallower angle, ranging from 6º to 16º, while the higher slopes below the escarpment itself rise at between 30º to 45º.

3.8 In many places the slopes below the escarpment can be seen to exhibit evidence of past ground movements with features such as soil lobes, back scars and springs dominating. Many areas are hummocky in appearance indicating the possible existence of secondary landslipping masking the deeper-seated historic failures.

Geology

3.9 The study route commences at the top of the Cotswold Escarpment where the Inferior Oolite Group outcrops and descends to the Vale of Gloucester within the outcrop of the Lower Lias. In the south-east part of the study area further landslip material is encountered together with some deposits of Fullers Earth.

3.10 Almost all of the route below the escarpment to is within landslipped material (colluvium). Over this section of the study area the Upper and Middle Lias Formations, together with the upper horizons of the Lower Lias, are mantled by the colluvial deposits.

3.11 For details of the geological structure and information about soil types, see Appendix A.


3 geotechnical issues

4 environmental constraints

4 ENVIRONMENTAL CONSTRAINTS

4.1 Environmental background data were collected and collated for the study area in a desktop review exercise. Data was collected from a wide range of statutory and non-statutory sources and from previous studies undertaken for the Highways Agency on parts of the route. The sources contacted and a description of the data collected are given in Appendix B. In addition, a report containing all of the baseline information was prepared in November 2001 (the Environmental Data Report).

4.2 The data collected was used to prepare a constraints plan shown on Figure 4.1.

4.3 Several preliminary surveys have been undertaken by specialists within the team to supplement desktop data collected.

4.4 A summary of the environmental constraints is given below. Further details are available in Appendix B and in the Environmental Data Report.

Ecology and Nature Conservation

4.5 The study contains four sites designated at a National Level. These are:

4.6 At a Regional and Local level, Ullen Wood, Cowley Woods and Wards Woods are designated as Key Wildlife Sites. Ancient woodlands occur within the study area and are shown on Figure 4.1. These include Ullen Wood and Witcombe Wood.

4.7 Records show that a range of rare, nationally declining or protected species occur within the area. These include the Grey Partridge, Wood Warbler, Slow Worms and Adders. These are described in more detail in Appendix B.

4.8 The study area contains a range of habitat types which contribute to the nature of the Cotswolds. Field surveys have been undertaken as part of previous studies. These are described in Appendix B.

Landscape and Visual Impact

4.9 The entire study area falls within the Cotswolds Area of Outstanding Natural Beauty (AONB). Parts of the northern section of the study area also fall within the Cheltenham and Gloucester Green Belt. These are shown on Figure 4.1. There are no National Parks within the study area.

4.10 The National Trust own land at Crickley Hill. This is open to, and well used by, the public and is designated as a Country Park.

4.11 There are a number of Tree Preservation Orders (TPO's) concentrated in the northern section of the study area and these are shown in Figure 4.1.

4.12 Three areas of common land exist within the study area. These are along the western edge of Crickley Hill County Park, either side of Barrow Wake viewing area and at Birdlip. The latter includes Buckle, Cranham and Buckholt Woods. These are shown on Figure 4.1.

4.13 The most important feature of the study area is the escarpment slope which defines the eastern edge of the River Severn valley and the north-western boundary of the Cotswolds. From the top of the escarpment the plateau slopes gently to the east and is incised with a number of steep sided valleys, some containing spring fed rivers. The largest of these is the Churn valley in the north-eastern part of the study area.

4.14 Woodland cover is mainly restricted to the escarpment slope and the valleys, the plateau being largely open allowing long distance views.

4.15 There are no major settlements in the study area, the small villages of Birdlip and Brimpsfield are the largest settlements present. Elsewhere individual properties and small clusters of properties are scattered throughout the study area.

4.16 The landscape within the study area can be divided into three character zones which are discussed in detail in Appendix B. The three character zones are:

Cultural Assets and Archaeology

4.17 Over 400 important sites are listed on the Gloucestershire Sites and Monuments Register for the study area. Numerous archaeological surveys have been undertaken in the area as a result of previous developments. These surveys indicate a high potential for archaeological finds.

4.18 Six Scheduled monuments occur within the study area. These are:

4.19 A total of 31 listed buildings exist within the study area. These are detailed in Appendix B and are shown on Figure 4.1.

Land-Use and Material Assets

4.20 The majority of land within the study area is used for farming. The land primarily comprises Grade 3 with Grade 4 on steep slopes. Small areas of Grades 2 and 3a are present at the foot of the escarpment and around Birdlip.

4.21 There are two long distance footpaths, the Cotswold Way and Gloucestershire Way which cross the study area. These form part of a network of footpaths and bridleways across the study area. These are shown on Figure 4.1.

4.22 Two public houses lie adjacent to the existing route, the Golden Heart and the Air Balloon. The Royal George Hotel and Conference Centre is located in Birdlip and village halls exist in Brimpsfield and Birdlip.

4.23 Public Open Space occurs at the picnic area on Barrow Wake and at Crickley Hill Country Park.

Water Resources

4.24 The study area falls into the catchment of the rivers Thames and Severn. The eastern area drains into the River Churn which is largely spring fed in its upper reaches. The river suffers from low flow and has dried out in the past, most notably in 1995. A low flow alleviation plan for the river is currently in action with the Environment Agency. The catchment also provides head waters to the River Frome.

4.25 Public water supplies are drawn from the River Churn (the Baunton source) and are used to supply the Gloucestershire region including Cirencester. Water is also supplied to Swindon.

4.26 The slopes of the escarpment contain a large number of springs which cross the Vale of Gloucester towards the River Severn.

4.27 The chemical and biological quality of the River Churn is very good. Hatherley Brook and Horsbere Brook, both within the vale, have good to very good chemical quality but only fair biological quality.

4.28 The limestones comprising the upper strata in the escarpment contain a major aquifer and fall within a groundwater protection zone. Major drinking water abstractions lie within 4km of the current route.

4.29 The hydrological constraints are shown in Figure 4.2.

Air Quality

4.30 The study area is predominantly rural with no major polluting industries and so air quality is expected to be good. Concern over roadside air quality has been expressed by local residents, and was raised in Cotswold District Councils (CDC) Stage 1 Air Quality review due to the volumes of traffic using the A417. However, modelling carried out in CDC's Stage 2 assessment showed that air quality standards are not currently being exceeded and would not be exceeded in 2005 (the date by which Local Authorities have to show compliance with set Air Quality Standards). No further assessment was, therefore, warranted.

Noise and Vibration

4.31 Since the study area is predominantly rural the existing A417 is the dominant noise source in the area. A number of noise complaints have been received by Local Authorities relating to traffic flows along the A417. Many of these related to the opening of the Cirencester Bypass which terminates at Cowley Roundabout and are potentially the result of a concrete surface to this section of road. Noise was also cited as a major concern to the project team by the residents of Cold Slad.


4 environmental constraints

5 option development

5 OPTION DEVELOPMENT

5.1 Prior to assessment a process of option development was undertaken. This comprised:

Initial Reviews

5.2 The option development process began with two reviews. These were;

Environmental and Physical Constraints

5.3 A review of the information provided in Chapter 4 was undertaken to identify areas/sites that should be considered invaluable areas, which should be avoided wherever possible. The criteria used are given in Table 5-1. In addition to these environmental issues, the schemes would need to meet engineering and economic criteria.

5.4 In particular, the schemes should be:

Table 5-1 Criteria used in Option Development
1. Sites ring fenced and considered inalienable
  • SSSI's
  • The Scrubs Nature Reserve
  • Scheduled Monuments
  • Conservation Zones
  • Listed Buildings
  • Crickley Hill Country Park
  • The Star Centre
  • Ancient Woodland
2. Areas to be avoided wherever possible
  • Areas of archaeological potential
  • Trees and woods covered by TPO's
  • Local nature reserves/SNCI
  • Local properties - options which avoid or where possible, reduce existing impact preferred
  • Minimum impact on broad aquifers and surface waters (springs and rivers)
  • Minimum noise and local air quality issues
  • Minimum waste produced, or which generate opportunities for re-use or waste.
  • Avoid cutting local rights of way
  • Ensure access to local properties
3. Opportunities
  • Options which allow improved crossing on public rights of way
  • Options which decrease green house gas emissions from vehicles using the scheme

Review of Previous Options

5.5 A review of earlier studies undertaken for the Highways Agency in the study area was undertaken to assess if the initial assessments of these schemes could be revised due to:

5.6 Following the reviews a "long list" of initial potential options was developed. These are shown in Table 5-2.

Table 5-2 List of Options Initially Identified
Options Identified
  • On-line options within highway boundary
  • Mainly on-line options with widening/offline sections
  • Off-line options to the east of the current route alignment
  • Off-line options to the west of the current vents alignment
  • "short" tunnel option
  • "long" tunnel option
  • "very long" tunnel option
  • "toolkit" options
  • "do nothing" option

Initial Discussions with Environmental Statutory Consultees

5.7 Early in the study process a meeting was held with environmental statutory consultees. Those attending are listed in Table 5-3. A separate meeting was held with English Heritage. English Nature and the Environmental Agency were invited to the meeting but were unable to send representatives.

5.8 The meetings comprised a review of the environmental constraint procedure for the study and outline discussions on options for development. The following was agreed:

Table 5-3 Attendees at Initial Statutory Consultee Meeting
Attendees
  • Countryside Agency
  • National Trust
  • Tewkesbury Borough Council
  • Gloucestershire County Council
  • Cotswold National Trail
  • Cotswold District Council

Initial Option Development

5.9 Following the initial meeting with the statutory consultees the list of initial options was reconsidered and screened. Several options were ultimately discarded including:

5.10 Further work was undertaken on the remaining options and indicative corridor plans were prepared for consideration at the subsequent "optioneering" meeting.

Optioneering Meeting

5.11 An "optioneering" meeting was held at the Highways Agency's offices in December 2001. This considered the indicative options identified in light of the environmental and physical constraints. The meeting was attended by personnel from the Highways Agency, WSP, Gloucester Archaeology and Cooper Partnership.

5.12 The meeting confirmed the rationale used in discarding the "do nothing" option and options to the east and west of the existing route. Three further options were also discarded at this meeting. These were:

5.13 Three options were taken forward for further consideration and assessment:-

5.14 Each option is discussed in more detail in Chapter 6. Plans showing the three schemes are given in Figures 5.1 to 5.3.

Second Meetings with Statutory Consultees

5.15 Two further meetings were held with Statutory Consultees on the 28th January 2002 in Bristol. The attendees at each meeting are given in Table 5-4. The meetings were intended to discuss the options to be taken forward to the assessment stage and to gather initial feedback from attendees.

Table 5-4 Attendees at the Second Consultation Meeting
Session 1 Session 2
  • English Heritage
  • Countryside Agency
  • English Nature
  • Environment Agency
  • Cheltenham Borough Council
  • Gloucester County Council
  • Cotswold District Council
  • Cheltenham Borough Council
  • National Trust

5.16 The results of these meetings with environmental statutory consultees were in summary:

Option 1

5.17 The Environment Agency (EA) questioned why a short term option was being considered. Concerns over the impact of the scheme on designated sites and loss of vegetation at Air Balloon were highlighted. Despite these concerns it was agreed that the option should be considered for further assessment.

Option 2

5.18 Concerns were expressed over the potential impacts on designated sites and the loss of vegetation at Crickley Hill. Visual impacts of the grade separated junction, its proximity to Crickley Hill and its affect on the context of the designated sites on Crickley Hill were also highlighted. However, in principle, consultees accepted that the scheme had some merit and agreed that it could be considered for further assessment.

Option 3

5.19 The EA voiced serious concerns over the need for de-watering during construction and post construction and on the potential for pollution of the aquifer. These were confirmed at a subsequent meeting with the EA in February 2002. They did accept, however, that pollution control equipment would be incorporated in the scheme (as with all options considered). They were concerned over effects on groundwater, springs and the River Churn. They stated that significant assessment work would be required if this option were to be taken forward. English Nature voiced concern over possible impacts on two SSSIs. Other concerns were the visual impact of the portal and link roads. Despite these concerns it was agreed that this option should be considered for further assessment.

5.20 The results of the second meeting with local authorities in summary were:

Option 1

5.21 Concerns over the short-term nature of this option. Issues relating to archaeology, ecology, landscape and impact on the context of National Trust land were particularly highlighted.

Option 2

5.22 Concerns over landscape impact, archaeology and the two additional lanes down Crickley Hill, loss of vegetation and impacts on the setting of Crickley Hill (Archaeology, National Trust and Ecology) were highlighted. Access to Cold Slad Lane and Grove Farm was also a concern.

Option 3

5.23 This option resulted in significant discussion and many concerns were raised. Cotswold District Council thought this to be the best option. Concerns over safety/accidents within the tunnel were also highlighted.

5.24 It was agreed that all three options should be considered for further assessment.


5 option development

6 options considered further

6 OPTIONS CONSIDERED FURTHER

6.1 Three main options have been taken forward for assessment. Two alternatives for the Air Balloon Junction have also been considered. These are discussed below.

Option 1

6.2 Option 1 is shown in schematic preliminary form in Figure 5.1. It should be noted that this is an indicative drawing for information only. Detailed design has not been undertaken at this stage. The scheme comprises the following elements:

Option 2

6.3 Option 2 includes all elements as listed above, differing only at Air Balloon Roundabout and on Crickley Hill, as described below.

6.4 At the Air Balloon roundabout, the current arrangement would be replaced with a new grade separated junction and a new roundabout further up the A436 at the Leckhampton road junction. This is shown in Figure 5.2.

6.5 On Crickley Hill an additional two downhill lanes would be provided on a separated alignment that would run parallel to the existing road but at lower level. The existing three lanes would be retained for eastbound ("up") traffic with one being used as a climbing lane (see Figure 5.2). There would be loss of vegetation on the southern side of the existing road.

Option 3

6.6 Option 3 comprises a twin bore tunnel with two lanes in each bore. Each bore would be D shaped with a maximum diameter of 14m. The bores would have linking tunnels every 100m. The tunnel would be in the order of 2.8km long and be at a gradient of approximately 4.5%. The tunnel would be mechanically ventilated and no ventilation shafts would be required.

6.7 Cowley roundabout would be removed and excavation of a cutting through the hill immediately to the north followed by a short section of road on embankment opposite the Golden Heart Public House would be provided. A control building would be required at this end of the quarry and it is possible that it could be located behind screening in the former Birdlip quarry potentially using the existing gate to the quarry for access.

6.8 The southern tunnel portal would be located in the northern slope of the hillside in the dry valley opposite the Golden Heart.

6.9 A small (500m3) reservoir for fire fighting purposes at the southern portal and possibly a small pump-house would be required. These could be located either in the landscaping within the valley opposite the Golden Heart, or within the Birdlip Quarry.

6.10 The northern portal would be close to the A417 at the bottom of Crickley Hill near Crickleigh Farm. Both portals could be faced with limestone from the excavation of the tunnel. A control building would be required. Two link roads would provide access to Crickley Hill and the A436 from the end of the Brockworth Bypass. Opportunities for landscaping and re-use of material excavated from the tunnel, would be considered to reduce impacts in the AONB.

6.11 This option is shown in Figure 5.3.


6 options considered further

7 engineering comparison of options

7 ENGINEERING COMPARISON OF OPTIONS

7.1 This chapter considers the engineering issues associated with each of the three options being considered. Because of the importance of geotechnical and groundwater issues for this scheme, this section is divided into two sections: Geotechnical Engineering and Highway Engineering. However, all assessments carried out to-date should be treated as preliminary and require more extensive investigation and analysis to refine the points made.

Geotechnical Engineering

Options 1 and 2 - Crickley Hill

7.2 Above the escarpment route options would be constructed over the limestones of the Lower Inferior Oolites, which are likely to provide relatively simple construction conditions, although some minor solution features may be present. It should also be noted that the Geotechnical Feedback Report for Birdlip Bypass (Gloucester County Council, 1989) indicates that toward the edge of the escarpment the limestone becomes cambered and a series of deep fissures (sub-parallel to the escarpment) were encountered during construction of the present route south of the Air Balloon Roundabout.

7.3 Where options cross the unstable escarpment slopes, it is considered that a combination of cutting, particularly within side-sloping ground, and embankment would be required to provide suitable vertical alignments. Special stabilisation and drainage measures would also be required for highway construction. Although not prohibiting construction within the escarpment slopes, the presence of this significant thickness of unstable ground on the slopes below the escarpment would provide considerable engineering and construction difficulties.

7.4 The slopes below the escarpment consist of a complex mass of landslipped material, masked by a mantle of soliflucted Head deposits. In general, the fines content of the colluvial deposits increases westwards towards the Vale of Gloucester. Three main types of colluvial deposit have been identified as forming the slopes and comprise the following:

7.5 Where the ground comprises silts and sands, slope angles of up to about 20o (in most groundwater conditions) may be achieved. However, where silty clays are present, i.e. below, say, Cold Slad, a slope of approximately 10o (typical of much of the middle and lower slopes) is considered to be only marginally stable, assuming the presence of relic shear zones. Therefore, it is considered that even minor changes to the groundwater regime or disturbance could reactivate failure, which could affect a significant area up slope.

7.6 Stability analysis carried out as part of this study suggests that, within the colluvium, unsupported cut slopes should not exceed approximately 2m. Where cut slopes are required in excess of 2m, a retaining measure would be needed.

7.7 In general, groundwater conditions are not well understood, but Hutchinson (1991) has identified some areas of artesian and near-artesian groundwater. In addition, during the construction of the present alignment in the 1960's an area of the slope below Crickley Hill is recorded to have failed due to a significant groundwater issue. This section was stabilised with the use of deep counterfort drainage.

7.8 The extent of colluvial (landslipped) materials within the study area can be seen from the constraint mapping to generally cover the area from the top of the escarpment to the floor of the Vale of Gloucester. These slopes are likely to comprise soliflucted and landslipped material, comprising a mixture of the overlying and underlying strata, with a number of randomly located springs, indicating the complex nature of the hydrogeological regime. They comprise unstable ground on which special stabilisation and drainage measures would be required for highway construction. However, various options are available for the proposed highway improvements below the escarpment. Each option would affect the marginally stable valley slopes to a varying degree. At this stage and in light of the uncertainties regarding depth of existing potential failure surfaces, groundwater pressures and soil properties, the amount of stabilisation works required would be dependant upon the route alignment adopted.

0 to 400 metres from the Balloon roundabout

7.9 Improvement options over the initial 400 metres from Air Balloon Roundabout, are likely to involve on-line widening on one or both sides of the existing carriageway within the existing highway boundary. However, Option 2 includes some off-line construction in the vicinity of the existing roundabout together. Existing cut slopes in this area would appear to be stable and, therefore, slopes at the existing gradient (approximately 30º) should be assumed at this stage, where these can be accommodated. Where options require slopes to be steeper than approximately 30º retaining measures, probably in the form of walls, would be required.

7.10 No significant engineering constraints are anticipated over the initial section and it is proposed that widening at existing slope angles to both the north and south could be achievable. Similarly, where new or deeper cuttings are proposed, these could be achieved at the angles of the existing slopes.

7.11 Where required, widening of the shallow cut slopes on both the northern and southern sides of the existing carriageway could be achieved by cutting at similar slope angles and maximising the use of the relatively wide verges, particularly to the north of the existing carriageway. Where there is a need to create new cuttings similar slope angles to those already adopted within the limestone should be employed. Further investigation would be required where steepening of the existing slopes is required or where new or deeper cuttings are proposed. To achieve widening within existing land-take, low retaining structures may be required to support cut slopes and minimise land take.

7.12 The northern slope, below Crickley Hill, is observed to be within the Oolitic Limestone Group. Improvement options are constrained by these slopes and would require construction of an anchored retaining wall (probably by top-down construction) together with deep drainage measure to stabilise the slope.

7.13 With the slopes above the northern boundary of the A417 being designated as SSSIs, together with them being nationally important rock exposures, widening options to the south side of the existing route are considered the only ones viable. 400 metres from the Air Balloon Roundabout to Grove Farm Access and Cold Slad

7.14 Below approximately 400m from the roundabout the ground drops away steeply on the southern side of the existing carriageway. The carriageway is, currently, partly supported by an embankment at about 18º supported by a minor retaining measure. To the north, the cut slopes comprise 30º to 40º separated by wide benches within the Oolitc Limestone Group.

7.15 The road improvement options over this section are again constrained to the north by the slopes below the Crickley Hill escarpment. Widening options of these slopes would require cutting back of a substantial part of this rock slope at a similar angle. This is not considered possible due to the adjacent SSSI, National Nature Reserve and National Trust land and, therefore, construction of an anchored wall (by top-down construction) and deep drainage would be required to stabilise the slope. However, founding such a wall on potentially unstable ground below the limestone, i.e. from approximately 450m west of the Air Balloon Roundabout, may require substantial piles to support the wall and to stabilise the slope. Stabilisation methods, such as piled dowels and drainage techniques, may also be required in combination with the retaining measures in order to provide a stable solution.

7.16 Off-line widening to the south could be achieved over this section of the route by the use of earthworks and retaining walls between carriageways. The use of a split-level carriageway in Option 2 may be considered, thus, reducing the volume of imported fill and, hence, the potential destabilising effect of filling on these slopes. However, careful consideration is required to the founding of any retaining measures used between the carriageways within the potentially unstable ground, particularly where the carriageways start to converge toward Air Balloon Roundabout (it is recognised that the retained height would decrease over this transition). This option would potentially involve the demolition of the former Cotswold Restaurant, although has the advantage of having little impact on the existing road during construction as well as not impacting upon the SSSI to the north. As a result of the recorded artesian groundwater pressures in this area, it is likely that a provision of a drainage blanket would be required beneath any earthworks to ensure dissipation is achieved.

7.17 Provision of a piled carriageway may be considered should land-take issues constrain the route of this section.

7.18 Further culverting of the stream would be required in Option 2. Agreement from the Environment Agency would be required to culvert or divert the stream below the embankment.

7.19 The Crickley Hill escarpment, again, constrains the improvement options over this section. Widening to the northern side of the existing carriageway may also cause considerable disruption to the traffic during the construction phase and may require single lane traffic flow during some phases of the works.

7.20 Widening to the south could be achieved over this section of the route by the use of earthworks and retaining walls between carriageways. Embankment widening of up to 6m high together with the use of a split-level carriageway may be considered. This potentially involves the demolition of the former Cotswold Restaurant. This option has the advantage of having little impact on the existing road during construction as well as not impacting upon the SSSI.

Cold Slad / Grove Farm Access Road to Dog Lane

7.21 The ground is likely to comprise a mixture of the colluvium types described in previous sections, but it is likely to be dominated by clays and silts on these lower slopes. The ground and groundwater conditions are likely to be highly variable over this section of the route and, as a result of previous ground movements, a detailed investigation would be required to provide sufficient data to design earthworks and stabilisation / retention measures.

7.22 The improvement options over this section are again constrained to the north by the slopes below the Crickley Hill escarpment. However, as a result of the wide verge, minor widening to the north may be achieved without disturbing the existing slopes.

7.23 Widening to the south could be achieved over this section of the route by the use of earthworks and possibly retaining walls between carriageways. The use of a split-level carriageway may be considered, thus reducing the volume of imported fill and, hence, reducing potential destabilising effects of filling on these slopes. Further culverting or realignment of the stream would be required should a southern widening option be taken forward. As a result of the recorded artesian groundwater pressures in this area, it is likely that a provision of a drainage blanket (together with other slope drainage measures) would be required beneath any earthworks to ensure dissipation is achieved.

7.24 Widening works to the south would encounter deep soft organic deposits within the valley floor. Construction of embankments over these materials are likely to lead to considerable, potentially uneven, settlement and may interfere with the existing groundwater regime as a result of the stream re-alignment/culverting. These settlements may affect the existing carriageway, particularly where the toes of existing fill slopes are close to the valley centre. Likely differential settlement between the existing and new carriageways may be significant and careful consideration of these would be required in design of the widening options.

7.25 The anticipated engineering problems associated with widening to the south, while still significant, are considered to be less than those associated with widening to the north of the existing alignment.

7.26 The road improvement options over this section are again constrained to the north by the slopes below the Crickley Hill escarpment. However, minor widening to the north, within the existing wide verge, may be achieved without disturbing the existing slopes.

7.27 Widening to the south could be achieved over this section of the route by the use of earthworks and retaining walls between carriageways. The use of a split-level carriageway may be considered.

7.28 Significant widening works to the northern side of the existing carriageway may also cause considerable disruption to the traffic during the construction phase and may require single lane traffic flow during some phases of the works.

7.29 The anticipated engineering problems associated with widening to the south, while still significant are considered to be less than those associated with widening to the north of the existing alignment and, therefore, widening to the south is considered more appropriate.

Dog Lane to the Brockworth Bypass.

7.30 The ground is likely to comprise a mixture of the colluvium types described previously, although clays and silts will dominate. The groundwater conditions are likely to remain highly variable over this section of the route as a result of the highly variable ground conditions and a detailed investigation would be required to provide sufficient data for geotechnical design.

7.31 Widening to the north of the existing carriageway is constrained by the marginally stable shallow angle slopes below Crickley Hill. However, minor widening may be achieved by a series of retaining measures, particularly below the section of Dog Lane that runs close to the existing alignment (1200 to 1420 metres from the Air Balloon Roundabout).

7.32 Widening could be achieved to the south of the existing carriageway by the construction of further earthworks. Again a split-level carriageway may be considered. Comments made previously regarding the provision of adequate drainage measures and differential settlement of the carriageway would apply here.

7.33 Agreement from the Environment Agency would be required to culvert or divert the stream below the embankment.

Option 3 - Tunnel

7.34 The tunnel option has been assumed to consist of two road tunnels, connected at approximately 100 m intervals by cross passages (DMRB:BD 78/99). Both tunnels would have twin lanes. At approximately 2.8 km, the tunnel is long by UK standards, but is modest compared with many existing road tunnels outside of the UK.

7.35 The tunnels are considered to be within the practical limit for longitudinal ventilation (less than 5 km) and a ventilation shaft/shafts is not considered, at this stage, to be necessary.

Secondly, the Cotswolds Escarpment at this location is quite steep and is recorded as being unstable. Therefore, ventilation shafts would be difficult to accommodate on the lower parts of the tunnel. Lastly, ventilation shafts would cause additional visual impact within the AONB.

7.36 The cross passages should not be used to ventilate the road tunnels in the event of a fire in the road tunnels. Each tunnel would require its own separate ventilation system. Some ventilation control equipment may be located in the cross passages.

7.37 It is assumed that the tunnels would have an excavated diameter of 14 m, similar to the Round Hill Tunnel at Folkestone. Some allowance could also be made for additional verge/walkway width, if required, on the slow lane side, as with the Southwick Hill Tunnel at Brighton. The excavation height would be about 10m. The cross passages are assumed to have an excavated diameter of about 4m and a length of less than 25m.

7.38 It is assumed that the tunnel bores have been assessed on the basis that no side ducts would be required to supply ventilation air and as such are giving bore diameters as follows:

7.39 The road tunnels would be designed to the requirements of BD78 (DMRB:BD78/99). However, the recent series of fires within road and rail tunnels in Europe has resulted in new recommendations from the UN. There is also new guidance as to the requirements for tunnel ventilation and smoke control due from the EEC. This guidance is yet to be published and, when released, could seriously affect the way that tunnel ventilation systems are designed. While it would be inconsistent with the requirements of BD78, consideration should be given to a local variation in the distance between adjacent cross passages.

Summary of Geology within the Tunnel Corridor

7.40 The published geological mapping suggests that the south-east portal would be excavated in landslip material and Fullers Earth. The tunnels would probably pass through the Fullers Earth at shallow depth and then encounter in sequence the Upper, Middle and Lower Inferior Oolite, Cotteswold Sands, Upper Lias, Marlstone Rock, Middle Lias and possibly the Lower Lias. The lower, 850 to 900 m and the north-west portal itself would be driven through a major landslip. Some landslip material and surface deposits (drift, scree and head) may also be encountered at both portals. Some weak organic material may also be present at levels within and below the lower sections of the slips. The limestones are generally more permeable than the underlying Lias and the contact is assumed to form the spring line.

7.41 Towards ground surface, the Oolitic limestones is recorded as becoming thin/very thinly bedded and having numerous vertical fissures. The upper 0.5 to 1.5 m is fractured. Bands of silty/sandy clay and rare, thin marl also occur. The fissures are not usually continuous from bed to bed. Some fissures were found in surface excavations to have an open width of 20 to 300 mm and an estimated depth of over 17 m. The open width tends to decrease with depth. The excavation of surface trenches with a backactor resulted in considerable overbreak. Cutting slopes 1:1 to 1:2 and rock embankment slopes of 1:1.5 are reported. The Upper and Lower Inferior Oolites are limestones. The Middle Inferior Oolite is a limestone with clay and sand.

7.42 As described in Section 3, the slopes below the Cotswold Escarpment and those located near the proposed south-eastern portal comprise landslipped material. Two forms of landslip may be encountered by the tunnel:

Construction Issues

7.43 The portals are some 3 km apart and the roads between them are not considered suitable for continual movement of construction plant. Other than for an initial section of clays, the upper 1/3 of the tunnel would be excavated in hard limestone rock and the lower 2/3 section of the tunnel would be excavated in clays and silts and, probably, landslipped material. The methods of excavation and support, and the plant to be used for these two tunnel sections are likely to be different. Each portal/tunnel section should therefore be considered as being in effect two separate sites.

Brockworth Portal

7.44 The tunnels are likely to encounter landslip material (consisting of gravel to boulder sized pieces of limestone within unstratified clays, silts and fine sands) at the Western portal and probably in the first 870 m of the tunnel drives. There are several private properties and public roads built on the landslip material. Several streams and springs are also present. It should be assumed that the landslips are in a marginal state of equilibrium and the portal should be designed such that the least possible ground deformation occurs during construction.

7.45 It is likely that the two portals would be constructed in a similar way to the UK portals of the Channel Tunnel, which were excavated through a glacial landslip on the side of Castle Hill (Harris, Hart, Varley and Warren 1995) and the Serre la Voute Road Tunnel, Turin. The slips at Castle Hill were assumed in the design to be only marginally stabile. Following a major site investigation; which included detailed orientated core logging, instrument installation (surface survey points, inclinometers and piezometers) and an exploration tunnel, substantial toe weighting was placed over the toe of the slips to increase their apparent stability. The portals to the three tunnels at Castle Hill were constructed within a box with end walls and side-walls, formed of bored piles. Tension piles were also installed through the basal slip plane below the subsequent floor of the box to prevent heave due to the excavation of the ground within the box. The roof slab was cast on top of the piles at ground surface. The ground within the box was then excavated in benches from the top down; the excavated material being deposited above and around the box to limit the net change in ground load on the slip planes caused by the excavation. The tunnel eyes were made through the piles in the end walls, while the tunnels were driven towards the portal from the opposite side of the hill. Drainage galleries were subsequently installed to further increase the long term stability of the slipped mass. The lining of the running tunnels was built in 5 m long, reinforced sections through the slips. These allow minor movements along the slip to continue in the long term, without damage to the lining.

7.46 There is little information on the location and current stability of the landslipped materials below Crickley Hill. The slipped mass at Crickley Hill appears to contain more soft, non-cohesive material, flowing water and groundwater standing (although this is very variably) within 1 m of ground surface. The material would appear to be more sensitive to shallow excavation than those encountered at Castle Hill and it would, probably, be necessary to lower the water table by pump wells prior to portal excavation. Moving the portal further to the north-west could put the portal in the Lower Lias, outside of the slipped materials, but would also increase the length of the tunnel within the water-bearing silts of the Middle Lias.

7.47 Although a site investigation would be required, slip planes within clay materials are very difficult to locate and to evaluate and, therefore, it should be assumed that the slopes have only a marginal stability and require additional long term instrumentation and stabilisation measures. The topography, scenic location and diversity of the slips would probably not allow wide scale toe weighting. However, deep drainage may be a viable solution. In addition, it may be possible to install gravity drainage in the Lias Clays, without significantly affecting the overlying springs seen within the landslipped material. Where the slope drainage does effect the surface springs, it may be possible to use the drainage to re-supply water to the streams and to any properties currently abstracting from well or spring sources.

Cowley Portal

7.48 The geological mapping suggests that the southern portal and first 100 m of the tunnels would be excavated in a shallow landslip, probably formed of weathered Fullers Earth. The slip may only effect the portal and first few metres of the tunnel, but its apparent direction of movement (approximately 45º to the proposed axis of the tunnel) complicates the design and it would be preferable either to move the portal or to remove the slip material in an open cut.

7.49 It is probable that the portal would need to be excavated by first constructing a bored pile, or other structural head wall, to secure the ground at the tunnel face and then excavating the portal in open cut with protected (probably shotcreted and drained) side walls. Excavation with normal surface excavation plant would probably be adequate until the limestone is reached. A single cutting pick and a de-mountable impact hammer should also be provided to assist in the excavation of any rock bands and the underlying limestone until a full face of secure limestone is established.

7.50 The low intersection angle between the Oolitc Limestone and the over-lying Fullers Earth would probably result in some blasting as the limestone rises in the lower face. Continuous lattice arch, shotcrete and rock dowel support are likely to be required and some spilling; particularly close to ground surface, is likely. The Fullers Earth is probably an aquaclude and the dip of the underlying, permeable, limestone may result in initial sub-artesian water inflows from the limestone. Forward and downward probing would be necessary as the contact is approached in order to assess likely water ingresses.

Pilot Tunnel

7.51 Most of the tunnel alignment would encounter the Upper Lias clay and the Inferior Oolite limestone, but some Middle Lias, a weakly cemented silt, may also be encountered towards the lower end of the tunnel; particularly if the portal is located out of the landslip, within the Lower Lias. The ground pressure (from approximately 100 m of overburden and 50 m of groundwater) is likely to be very much greater than the mass strength of the ground and squeezing conditions can be expected in the Middle Lias. Prior drainage through a pilot tunnel would increase face stability during the excavation of the larger road tunnels; although drainage could also result in ground shearing and this would require careful consideration during the detailed design. It is considered at this stage that a pilot tunnel should be excavated in advance of the excavation of the portal and the breakout of the road tunnels from the portal. While this tunnel could be excavated with a roadheader and supported with lattice arches and shotcrete in the Lias, the consequences of a face collapse in this critical area close to the main basal slip plane are considered to be too high for this method of excavation and, therefore, it is recommended that the tunnel is excavated with a road header mounted in a shield and supported with a one-pass, bolted, segmental concrete tunnel lining. Ports in the lining should be provided to permit drainage holes to be drilled towards the road tunnels and cross passages. Filters may be required to prevent the silt from washing into the pilot tunnel.

7.52 The north-west portals would take some time to establish and it is recommended that the pilot tunnel should be driven from the base of an adjacent shaft while the portal box and stabilisation work are being undertaken. The shaft should be lined with concrete segments and the ground/lining annulus grouted to restrict ground movement. The stability of the shaft floor during excavation (possible boiling) needs to be considered in the detailed design. The shaft would be replaced by a portal as part of the permanent drainage of the slope.

Oolitic Limestone

7.53 Excavating down grade would result in the flow of any groundwater infiltration, rain or construction water towards the face, from where it would need to be pumped out to permit face excavation. This is not considered to be a critical factor; at least for the initial section within the Oolitic Limestone. Excavation up grade would result in gravity drainage away from the face towards the Brockworth Portal and is, therefore, preferred for the softer Lias deposits.

7.54 Groundwater is anticipated in the oolitic limestone and is likely to flow laterally along the sub-horizontal discontinuities; particularly above low permeability beds such as marl bands, and vertically along the open fissures. Clay beds and clay filled fissures (possibly including faults) are likely to act as aquacludes, resulting in perched water. The Upper Lias can be considered to be an aquaclude, such that the groundwater within the overlying limestone is likely to impose an additional pore water pressure within the Lias and landslides. Excavation of the pilot tunnel is likely to reduce the pore water pressure within the Lias prior to the excavation of the larger road tunnels, although as a result of relative difference in permeability, drainage of the Lias may only result in a marginal benefit.

7.55 The bedding is sub-horizontal (+/-50 dip towards the south-east, Hutchinson, 1991). Frank Graham's 1989 Crickley Hill Tunnel Study, includes a geological section; which shows the strata to have an apparent dip of about 20 towards the south in the plane of the tunnel section, which agrees with the published geological mapping and data presented in Gloucestershire County Council's 1989 Geotechnical Feedback Report. The bedding would, therefore, dip towards the face where the tunnel is excavated down slope from the south-east towards the north-west. This has a positive benefit; in that a forward probe hole would be more likely to intersect any beds of water bearing or soft strata before they appear in the tunnel face. Such strata would first be encountered in the lower part of the face, rather than in the roof and would be more likely to drain before intersecting the roof. There is a risk in excavating the face in the up slope direction that any water bearing strata or beds acting as aquacludes to water bearing strata above, could be undetected by the probe holes and approach the roof at the face above the section of tunnel previously excavated. A face collapse could, therefore, run back for some distance (given the low strata/tunnel intersection angle) from the face.

7.56 The Brockworth Portal and landslip additional stabilisation works are likely to take longer to construct than are the Cowley Portal and tunnel excavation within the Fullers Earth. The Oolite limestones are also likely to be easier to excavate and support than the Lias deposits. Excavation of the two road tunnels at the upper end is, therefore, likely to be well advanced before excavation of the road tunnels at the lower end begins.

7.57 The limestone is probably too strong for excavation with roadheaders. Impact hammers could be used, if the bedding and joint planes are close enough for the hammer to breakout the intervening blocks. The most likely method of excavation would be by 'drill and fire'. The sub- horizontal bedding in the limestone is likely to result in a flat, stepped longitudinal roof profile. The sub-vertical jointing is likely to control the lateral profile; blocks falling from the shoulders and walls. A stepped, square profile is likely to result. Tensioned rock bolt support with local mesh is anticipated. Lattice arches and shotcrete are not generally suitable for these conditions but would be required to some extent to support broken, faulted and clay/marl ground. Arches are designed to deform under load and this can result in long term problems (for example, Lewes Road Tunnel in chalk rock). Some face grouting may be required to seal any fissures giving large water inflows, but this is unlikely to be a major problem given the proximity of the tunnel to the escarpment edge. A D-shaped tunnel profile with a flat invert is recommended.

7.58 As the Crickley Hill Tunnels would be permanently lined with a concrete lining, it is reasonable to reduce the support to that suitable for the temporary condition. Any instability would be dominated by block falls and therefore the rock bolts and arches need to be maintained, whereas the amount of shotcrete can be reduced. Under normal conditions it is anticipated that the upper heading can be advanced in 3 m rounds, the bench in 3 m+ rounds to suit the contractor's operational requirements. Most of the support in the heading would be provided by 3.5 m long (4.5 m long for the three-carriageway tunnel), tensioned rock bolts at 2 m centres. Some, 100 mm thick, mesh-reinforced shotcrete would be required where the ground is locally fractured. Elsewhere, open mesh, supported by rock bolts, would be sufficient. Some roof support; consistent with safety would be required close to the face. The rock bolts should be retensioned and the remaining support installed within 20 m of the face. Little, if any support would be required in the bench walls.

7.59 Slightly longer rock bolts of 4 to 5 m at 1.5 m centres, 100 mm thick, mesh-reinforced shotcrete and shorter advance lengths of 1.5 m may be required in the heading in the areas of more fractured ground. Some colliery arches would also be required. Most of the support would need to be installed at the face and should be completed within 10 m of the face. The arch legs would need to be extended after bench excavation. Advance lengths of 3.0 m+ would still be possible in the bench.

The Upper and Lower Lias

7.60 As with the Fullers earth, the Upper and Lower Lias clays could be excavated with either a roadheader or with surface excavators (Volvo EC series or similar). A demountable impact hammer and single cutting tooth should be provided to excavate any rock bands. Some explosives may be required to excavate hard bands of rock intersecting the invert and roof. The upper heading would probably need to be excavated in two sections with a temporary invert arch. Bands of sand would require foreprobing and possibly glassfibre face dowel support. A curved invert arch would be required. The detailed design should consider the excavation sequence and support requirements in detail.

7.61 Instrumentation in the pilot tunnel should be used to verify the excavation and support design for the larger road tunnels. Instrumentation in the road tunnels should be used to verify the design of the lining.

7.62 Taking the example of Castle Hill, it is initially considered likely that the tunnels would require 200 mm of fibre or mesh-reinforced shotcrete, lattice arches at 1.5 m centres, 4 m long rock dowels at 1.5 m centres and 4 m long spiles across the roof at 0.5 m centres. The face should be protected between each advance with shotcrete. The heading would require a temporary invert arch. The invert arch would require to be closed to prevent continued tunnel deformation.

The Middle Lias and Cotteswold Sand

7.63 The weakly cemented, water-bearing silts of the Middle Lias and Cotteswold Sand are likely to present the most challenging tunnel excavation problems of all of the ground types on the project. Partial face excavation, continuous face support and overlapping roof support are probably required. The intersection lengths are probably too short to make a Perforex solution viable, unless this system is used to excavate all of the none-hard rock sections.

7.64 These are both weakly cemented, probably water-bearing, sandy silts. Some strong, massive, medium to thickly bedded limestone bands may also be present. The in situ condition of these silts needs to be determined by a site investigation. Even a small amount of cohesion would have a positive effect on face stability and hence in the speed of construction and amount of support needed.

7.65 Assuming that the unweathered material at tunnel depth is encountered as a weakly cemented silt/sand, it is probable that the heading would need to be advanced as a partial face with a central buttress, under the cover of an umbrella of grouted or jet grouted pipe spiles. The heading would require an arch of at least 200 mm thick, mesh-reinforced shotcrete, supported by 'elephants feet' or jet grouted foundations. A temporary invert arch may be necessary. The face would need to be supported with shotcrete between each excavation cycle. Lattice arches and rock dowels would be required at 1 m centres.

7.66 The bench would need to be excavated in tandem with the heading to allow early closure of the invert.

Cross Passages

7.67 Cross passages would be excavated within each of the rock types. Wherever possible, the distance between adjacent cross passages should be reviewed where this requires their excavation within the Middle Lias or Cotteswold Sand. Where it is unavoidable, a method of excavation and support similar to that for the road tunnels is required.

7.68 Those cross passages eyes within limestone rock are likely to be excavated concurrent to the adjacent road tunnel bench. The subsequent rounds could be drilled while the bench (at some point remote from the cross passage being extended) is being mucked. The method of support would be similar to that for the road tunnels. Arches should be located such that the adjacent cross passage can be excavated without removing the arch.

7.69 Cross passages within the Upper and Lower Lias, and the Fullers Earth would probably be excavated by hand tools, unless the contractor has a small roadheader available.

Tunnel Ventilation Options

7.70 The general parameters for ventilation design would be taken from Department of Transport Existing Standards pending the receipt of revised requirements from the EEC, which are understood to be issued imminently.

7.71 There are three options for the ventilation of the tunnel, these are transverse ventilation, semi-transverse ventilation and longitudinal ventilation. The systems differ as follows:

Transverse Ventilation

7.72 Transverse ventilation comprises a supply and extract system with graded inlet and outlet jets over the tunnel length which supplies and extracts air over the whole length of the tunnel. This system requires both supply and extract ducts over the length of the tunnel bores. As a result of the length of the tunnel and the required ventilation air volume, vertical ventilation ducts would be required at points along the line of the tunnel. The spacing of the vertical supply and extract shafts is governed by their possible locations and a requirement to limit the dimensions of the bore. Therefore, if shafts are provided at the lower level and at the upper level the necessary duct capacity can be quartered providing that a uniform spacing is feasible. This would mean that with the proposed tunnel alignment one of the shafts would need to penetrate the landslip area at the lower end of the bores. The location of the other shaft at the upper end is not so critical as the ground is more solid.

7.73 The shafts would contain input and extract fans separate to each tunnel bore. Generally the airflow would be side, inlet and crown outlet so that fresh air would be introduced at low level and exhausted at high level. This system tends to ensure that combustion products in the case of a fire are induced upwards and are exhausted to leave the lower occupied areas of the tunnel clear of smoke and products of combustion.

Semi-Transverse Ventilation

7.74 In this option the air generally enters through the tunnel portals and is uniformly exhausted along the length of the tunnel. Similarly to fully transverse systems ventilation shafts would be required, but these would be extracted only with air being extracted at high level. Generally this system would maintain clear air at low level in the case of fire, though in this case the airflow would be from the portals to the point of extract. This system may require reversible fans to control smoke in the case of fire.

Longitudinal Ventilation

7.75 In this option air is moved unidirectionally, generally in the same direction as the traffic flow, by jet fans mounted at high level in the bores.

7.76 This system requires no shafts but the airflow is generally in the same direction as the traffic flow. In case of fire, this would tend to move smoke and products of combustion away from the source in the case of a vehicle fire. On the assumption that traffic would stop and that the traffic in front of the fire would exit the tunnel, this should provide reasonable smoke clearance. Sufficient redundancy is required to be provided to cover failure and maintenance plus the possibility of a fire affecting the fan operation. Generally such fans are capable of operating in temperatures of up to 300°C and can be reversible to permit the tunnel to be operated in either direction under normal operation. However, bearing in mind the slope of the tunnel, a fire in the downgrade bore could permit smoke to travel against the direction of traffic flow.

7.77 As a result of the geological instability of overlying rock and the environmental sensitivity of the area, options requiring ventilation shafts would not be taken forward.

Alternative Option

7.78 There is the possibility for a compound arrangement of semi-transverse ventilation with jet fan assistance. In this option the jet fans may be used to create opposing airflow in the case of fire and hence confine the smoke to a prescribed area of the tunnel where it may be extracted by the exhaust system. The disadvantage of this option is that ventilation shafts are still required, but potentially more effective smoke control may be maintained particularly in the downgrade tunnel.

Fire Fighting

7.79 Consideration would need to be given for the provision of fire hose reels and fire hydrants over the length of the tunnel bore. The availability of a water supply bearing in mind the level differential between lower and upper portals and the extent of the local distribution may possibly require the installation of a reservoir and pump near the southern portal.

7.80 The local water reticulation at the upper area (Cowley Portal) may be adequate.

7.81 Hydrant and hose reel spacing in each tunnel bore would need to ensure that there is overlap in prospective hose lengths so that more than one hydrant or hose reel may be applied to a fire and to allow for the fact that facilities may be in accessible due to the fire. The provision of hand held equipment need also be considered.

Drainage

7.82 Internal roadway drainage would need to be considered within the overall design and section of the tunnel. The provision of gullies at the tunnel entrance and exit would reduce the quantity of water carried into the tunnel leaving only driven rain through the portals and such as may be carried in be vehicles. However, drainage would be required in the tunnel bores to allow for the disposal of fire fighting water, foam etc. As the tunnel is used by vehicles, fuel and oil entrapment would be required prior to discharge.

Engineering Risk Evaluation

7.83 An engineering risk evaluation has been undertaken and is presented in Appendix C.

Highway Engineering

7.84 A detailed description of the three option taken forward for assessment is provided in Chapter 6. However, for ease of reference, brief descriptions of the Options are included below.

7.85 A comparison of the construction issues and general engineering issues associated with the different options is included in Table 7-1 and Table 7-2.

7.86 The options have only been developed to the stage where outline design elements of the proposed routes have been identified. The detailed design of the scheme has not been undertaken and therefore the comparison of engineering issues is based on the preliminary information currently available.

7.87 As part of the examination of the potential options, consultation has taken place with the local Police and Fire Services to gain their views. Further details are provided in Chapter 11. However, the key issues raised by each are summarised below.

7.88 Gloucester Constabulary have formally expressed a preference for a conventional 'open air' highway layout. This is because of the large financial and operational burden to the service of a tunnel. They also expressed an opinion that the length of the tunnel would see many motorists choosing to use the alternative 'open air' routes through fear of the unknown.

7.89 Gloucestershire Fire Service have also formally expressed support for a surface option. They have expressed concerns regarding public safety and the risk to fire-fighters as well as the potential cost of providing dedicated services at the tunnel.

7.90 As part of the assessment of the Options, a preliminary safety review was carried out on Option 1, the at grade option with traffic signals, because of the safety issues associated with traffic signals on steep gradients. The review identified a number of safety issues that are particular to this Option.

7.91 The downhill gradient, of generally 5% or 6% on Birdlip Hill would encourage high approach speeds to the signals, particularly as they would need to be visible from some distance. This would give rise to overshoot and rear shunt type accidents. The traffic bound for the A436 would need to move out to the offside lane to go 'straight ahead', which is likely to give rise to further rear shunt type accidents.

7.92 The link road between Birdlip Hill and Crickley Hill would have a downhill gradient of about 9% leading to the left-hand bend to join the existing Crickley Hill. The gradient, although in character, would be well below desirable standards. The bend would also be well below desirable standards, particularly so after the steep downhill gradient and could lead to loss of vehicle control and HGV's overturning.

7.93 The traffic signals would require a speed limit, preferably even lower than the current 60 mph, however compliance is likely to poor and enforcement unlikely. In itself a lower speed limit is unlikely to reduce the problems to any great extent, as even 30mph on the link road could be excessive for some vehicles.

7.94 The combination of geometric features present with Option 1 is likely to result in a hazardous road layout. This cannot be overcome by careful detailed design.


7 engineering comparison of options

8 economic comparison of options

8 ECONOMIC COMPARISON OF OPTIONS

8.1 Economic appraisals of Options 1, 2 and 3 have been undertaken to evaluate the comparative economic value of constructing the different layouts taken forward for assessment.

8.2 The appraisals have been undertaken for the standard 30 year assessment period, using the cost-benefit analysis computer program COBA in accordance with Volume 13 of the Design Manual for Roads and Bridges (DMRB), Economic Assessment of Road Schemes. A predicted scheme opening year of 2010 has been used and therefore the final appraisal year is 2039.

8.3 The objective of an economic evaluation is to assess the value for money of the scheme by comparing those elements of scheme benefits that can be expressed in monetary values against the total cost of having the scheme in place. The benefits of a scheme that are included in an economic assessment are time savings to travellers, savings in accident costs and vehicle operating cost savings.

8.4 The scheme costs, which form the basis for the calculation of the value of Present Value of Cost (PVC) includes works, land, statutory utilities and future preparation and supervision. The scheme costs are discounted to 1998 to provide a comparison with the Present Value of Benefits (PVB) which are also discounted to 1998.

8.5 The currently estimated scheme costs (without applying COBA discount values to obtain the PVC in 1998 prices) are approximately £40 Million for Option 1, £55 Million for Option 2 and £200 Million for Option 3. The Option 3 estimated cost of £200M includes the tunnelling operations, disposal of spoil and the associated roadworks at either end of the tunnel. As the options have only been developed to the stage where outline design elements of the routes have been identified, the detailed design has not been undertaken and therefore the cost estimates are based on the preliminary information currently available. Land costs, future design fees and site supervision costs are excluded from the above costs.

8.6 The difference between the PVB and PVC is known as the Net Present Value (NPV). A positive NPV indicates that a scheme is economically worthwhile. A further measure of a scheme's economic worth can be obtained by dividing the PVB by the PVC to obtain the Benefit to Cost ratio (BCR). The BCR thus gives the benefits per unit cost. A BCR of more than 1.0 indicates a scheme that is economically worthwhile.

8.7 An economic appraisal for each option has been calculated using both high and low traffic growth forecasts. A summary of the economic results obtained, for both high and low growth scenarios, is included in Table 8-1 below.

Table 8-1 Economic Comparisons of Options 1, 2 and 3
  SCHEME OPTION
Option 1 Option 2 Option 3
Low Growth High Growth Low Growth High Growth Low Growth High Growth
Time Benefits (£M) 58.3 75.5 101.9 138.6 113.0 148.9
Vehicle Operating Benefits (£M) 0.4 0.8 1.4 1.9 7.3 8.7
Accident Benefits (£M) 5.6 6.7 10.8 12.4 7.5 8.7
Total Benefits (£M) 64.2 83.0 114.1 152.9 127.8 166.3
Cost (£M) 26.9 26.9 36.9 36.9 144.3 144.3
Benefit / Cost Ratio 2.39 3.09 3.09 4.14 0.88 1.15
Net Present Value (£M)
(Benefit minus Cost)		 37.4 56.1 77.1 116.0 -16.6 21.9
Notes Costs and Benefits are in 1998 prices
Costs and Benefits are in multiples of a Million Pounds Figures based on COBA

Discussion of Economic Assessment

8.8 The results indicate that, with the exception of the low growth scenario for Option 3, the schemes would represent value for money with positive NPV's.

8.9 The primary economic benefits for each of the options are from the time savings resulting from the removal of congestion along the route. Each of the options would also result in accident benefits due to the predicted reduction in accidents.

8.10 Option 1 would be the least expensive option but has the least benefits, primarily due to the low time saving benefits because of the traffic signals at the Air Balloon roundabout.

8.11 Option 2 represents the best value for money as it has the highest NPV's and BCR's. The NPV's are more than twice those for Option 1.

8.12 Option 3 has the highest total benefits but, due to the costs of the tunnelling operations, is also the most expensive option and therefore has the lowest NPV's and BCR's. Due to the high cost of the tunnelling operations the low growth scenario for Option 3 would not be economically viable. Although the tunnel route is considerably shorter than Option 1 and 2, this would only benefit approximately 60% of the traffic as traffic using the A436 would continue to use the existing route.

8.13 To reflect an overall benefit from the low growth and high growth economic scenarios, a weighted average of benefits (60% of low growth benefits plus 40% of high growth benefits) can be used. The weighted average of benefits results in a BCR of 2.67 for Option 1, 3.51 for Option 2 and 0.99 for Option 3. Using the weighted average of benefits Option 3 would have a poor return because the benefits are less than the costs, and it would therefore be difficult to justify a case in economic terms.

8.14 Overall, Option 2 is considered to represent better value for money.

Estimated Tunnel Costs

8.15 A large and complex project such as this is likely to produce a variation in the bid prices. Assumptions on the chosen method of construction have been made here, but other methods are possible which could alter the programme and the bid price. For example, the contractor may price the hard rock section assuming a computer controlled, three four-boom drilling rig to advance the full tunnel face without a heading. The Laerdal Road Tunnel in Norway for example adopted 500 kg of explosive and 100 drill holes per 5 m deep round, giving 500 m3 of spoil and an advance rate of 60 to 70 m/week. Similarly a Perforex type system could be used to excavate the Lias clays and silts, landslip material and Fullers Earth, again as a full face without the need for a heading and bench.

8.16 To produce a reasonable estimate of the tunnel construction costs it would be necessary to estimate the labour, engineering, equipment and material quantities and to make some allowance for site facilities, office, overhead, profit, contingency and inflation. This could be done by adapting the rates given in Spon's, Wessex, Laxton, etc to current inflation prices. At this early stage, it is probably sufficient to make a less detailed assessment based on contractor's advice. To this end both Skanska and Amec were asked what in their opinion would be the likely construction costs of the project. Skanska suggested a sum of £100 to £120 million for the construction of the twin, 2 and 3 lane tunnels, exclusive of the finishing works (for the excavation and lining, but not for the lighting, road surface, ventilation etc). With contingency, they suggested £150 million. By comparison, the 4.5 km Dublin Port Tunnel (TBM) was estimated to cost £204 million, equating to approximately £136 million for the Cowley - Brockworth tunnel at current prices. The A3 Hindhead, twin tube, twin carriageway 1.5 km tunnel was estimated at ~£75 million (1995), which is equivalent to £150 million for Crickley Hill (£193.5 million at current prices). Amec suggested a rate of between £12,000 and £13,000/lin.m for the excavation, support and lining; based on their current estimate for the Stonehenge Tunnel. This is equivalent to a much lower figure of ~£75 million for the Cowley - Brockworth tunnel if two, twin carriageway tunnels are selected (approximately £94 million if one, three lane carriageway is included). Stonehenge is a relatively straightforward tunnel in relatively good ground and this would be reflected in their estimate for Cowley - Brockworth.

8.17 The only comprehensive analysis of recent road tunnel construction costs that we are aware of was undertaken by STUVA in Germany. They made detailed cost analyses for both cut and cover, and bored road tunnels of various standard profiles, construction methods, ground types and lengths in Germany (described in English in ref. 13, reproduced as a guideline in ref. 15). A comparison could be made using the data presented by STUVA, but this would reflect the German market and some allowance would also need to be made with contemporary (1996) and current UK prices. There is also no English language version of this report.

8.18 Considering German road tunnels as an example; four twin bore, twin carriageway road tunnels were opened on the A71 German Federal Motorway in 2001/2002. The Rennsteig (7.8 km) and Alte Borg (0.865 km) Tunnels are in a combination of hard lava flows, siltstone and clay. The Hochwald (1.06 km) and Berg Bock (2.74 km) Tunnels are in granite. The tubes are 25 m apart and connected by cross passages at 300 m intervals. The final lining is 300 mm of unreinforced concrete. The cost of these four tunnels averaged 22,000 DM/linear metre/tube. This is equivalent to about £7,000/lin.m/tube, or approximately £42 million for the Cowley - Brockworth Tunnel. This is much less than suggested by Skanska and Amec. The excavation and support of the two running tunnels through Castle Hill averaged £3,900/lin.m/tube (1992). The lining similarly averaged 4,000/lin.m/tube. The excavation and support (concrete segments) of the 1.5 m diameter pilot tunnel cost £1,100/lin.m. This suggests an equivalent value of about £48.5 million for the excavation and lining of Crickley Hill at 1992 prices, £68 million at current prices, which is similar to the price suggested by Amec.

8.19 Recent information developed by the Highways Agency gives a bored cost of £40 million per kilometre for twin bore two lane tunnels. This would give a cost of £112 million for the Cowley -Brockworth tunnel.

8.20 Given the wide range of possible construction prices, it is suggested that a price of £100 million be taken for the excavation and lining at this initial stage. To this would be added road construction through the tunnel, access roads and links, M&E, signage and lighting, and construction of the control buildings and reservoir. With contingency, a figure of £150 million should be adopted. This excludes waste disposal costs which would increase the overall cost to approximately £200 million.

Cost Comparisons with Other Tunnels

8.21 The Pen y clip Tunnel on the A55 in North Wales is a single bore tunnel of 930 m in length, 9.95 m width and 7.1 m height. The heading broke through after 33 months and the tunnel was completed in 48 months. The tunnel was excavated by drill and fire, with 130 holes per face, pulling an average 3.5 m advance. The initial and final thirds of the tunnel were in highly fractured rock, requiring steel arch support. The central third was less broken and was supported with steel mesh-reinforced shotcrete and rock bolts.

8.22 The Trattenbach Tunnel in Austria is a twin lane, single tube road tunnel of 419 m in length, about 85m2 face area and 2.5% gradient. The tunnel was excavated by NATM using a heading and bench. A 250 mm thick concrete lining with a membrane was installed. The project included some 750 m of slope stabilisation. The rock types are metamorphic sandstones and phyllites. Constructed took 24 months (1988 to 1990) at a cost of 261 million Aus.sch. This is roughly equivalent to £255 million at current value for a twin tube tunnel of the length of Crickley Hill.

8.23 Zell am See Tunnel in Austria is a twin lane, single tube road tunnel of 5109 m length and about 80 m2 face area. This project also has a 35 m long ventilation cavern, 480 m deep ventilation shaft, 652 m ventilation tunnel, 682 m of interchange tunnels and 375 m emergency exit tunnel. There is also a 4.7 km, 3.2 m diameter pilot tunnel, built by TBM. Also in metamorphic sandstones and phyllites, the project was constructed over 42 months (1992 to 1996) by NATM at a cost of 1200 million Aus.sch. This is roughly equivalent to £79 million for Crickley Hill at current prices.

8.24 Karawanken expressway tunnel on the Austria/Yugoslavia border is a twin tube, twin carriageway tunnel of 7,864 m and a face area of 86 to 100 m2. The tunnel has a gradient of 0 to 1.35% and was constructed by NATM through hard and soft rock. The tunnel ventilation is divided into two, about 3.5 km long sections for semi-transversal ventilation at each side. The central 1.2 km has only longitudinal ventilation. There are ventilation stations at each portal, but no ventilation shafts. The project was constructed between 1986 and 1991 at a cost about 2,600 million Aus.sch. This is roughly equivalent to £68 million for Crickley Hill at current prices.

8.25 Four, twin tube, three lane motorway tunnels were built along the Adana Toprakkale Gaziantep motorway in Turkey. These tunnels (Tasoluk Tunnel is 361 m, Ayran Tunnel is 600 m, Kizlac Tunnel is 520 m and the Aslanli Tunnel is 1360 m) were built through sedimentary and metamorphic rock by NATM and have face areas of 126 to 152 m2. The tunnels are lined with 0.4 m concrete. The tunnels were constructed at a cost of $150 million between 1990 and 1996 (equivalent to $189 million at current prices).

8.26 A twin tube, three lane tunnel of 3.24 km and 126 to 152 m2face area was built through sedimentary and metamorphic rocks by NATM along the Anatolian Motorway in Turkey. The tunnel has a 0.4 m thick concrete lining and longitudinal ventilation. The tunnel was built between 1992 and 1996 at a cost of $270 million. This is roughly equivalent to $340 million at current prices.


8 economic comparison of options

9 environmental appraisal of options

9 ENVIRONMENTAL APPRAISAL OF OPTIONS

9.1 The assessment methods used are as described in the "Guidance on the Methodology for Multi-Modal Studies" (GOMMMS) published by the DETR (now the DTLR). Further guidance on the application of GOMMMS on highway schemes has been taken from the bridging document "Applying the Multi-modal New Approach to Appraisal to Highway Schemes" published in March 2001.

9.2 At this stage in the scheme design, there is a limited amount of detail available on each of the options. The assessment that has been undertaken is thus equivalent to a DMRB Stage1 assessment.

9.3 GOMMMS considers five main objectives, namely:

9.4 Within each of these areas, a number of sub-objectives are assessed according to specific assessment and significance criteria, each having its own worksheet detailing the results. The assessment scores are then combined into an Appraisal Summary Table (AST) for each option. When reading the assessment results, ASTs and worksheets it should be borne in mind that the GOMMMS methodology assumes that all appropriate mitigation measures will be incorporated. This includes the Highways Agency own best practice guidelines as well as other recognised best practice measures such as pollution control technology, landscaping, good construction site management, environmental enhancements and sustainable drainage systems. The following sections describe the results of the assessments under the Environment Objective. This covers the following topics:

9.5 The corresponding ASTs are provided in Appendix D. A summary table comparing all the options is provided at the end of this chapter (Table 9-7).

OPTION 1 - Dualling of A417, signalised junction at the Air Balloon, and an additional lane down Crickley Hill

9.6 A plan showing the indicative road layout and alignment is provided in Figure 5.1.

OBJECTIVE : ENVIRONMENT

Noise

9.7 The change in alignment for the A417 to the north of Cowley Roundabout would move the carriageway closer to one dwelling (with a resulting potential increase in noise levels) but further away from 4 other dwellings (with a resulting potential decrease in noise levels).

9.8 The new slip road at the Air Balloon Roundabout would move traffic closer to one dwelling, with a resulting potential increase in noise levels.

9.9 The additional downhill lane for Crickley Hill could be largely accommodated within the existing highway boundary. However, the 27 dwellings in the vicinity of Crickley Hill would be affected by increased noise levels due to an increase in average traffic speeds on Crickley Hill. Mitigation measures, such as fences, could be designed to reduce noise impacts.

9.10 Other noise sensitive locations (e.g. Birdlip County Primary School and Crickley Hill Country Park) would be likely to remain relatively unaffected. However, the Gloucestershire Way, Cotswold Way and other footpaths might experience an increase in noise levels due to the widened carriageways between the Air Balloon and Cowley Roundabouts and increased traffic flow. Alternative quieter road surfacing could be considered to reduce noise at source.

9.11 A comparison of the number of properties that would be likely to experience a net benefit / disbenefit under Option 1 is shown in Table 9-1.

9.12 Movement of the road away from the Golden Heart public house, but closer to Stockwell Farm would result in changes in noise impacts. Possible noise mitigation measures would reduce overall impact at Nettleton Bottom and Stockwell.

Table 9-1 Number of properties likely to experience a change in noise levels for Option 1
Option 1: Online (signals) Number of Properties/People Within 300m
Likely number of properties/people that would experience an increase in noise levels 34/82
Likely number of properties/people that would experience a reduction in noise levels 4/10
Likely number of properties/people that would be relatively unaffected 15/24

Local Air Quality

9.13 For the GOMMMS assessment, changes in air quality adjacent to both the existing route and the proposed route were examined. For the assessment of the change in air quality along the existing route two receptors were chosen at which the DMRB Stage 3 assessment methodology was applied. One receptor was located on the kerbside of the existing road at Crickley Hill Farm, the other was located at the kerbside by the Golden Heart Inn near to the Cowley roundabout. For the existing route and the proposed option, property counts were carried out along the length of the road in question.

9.14 For the assessment of the changes in air quality along the existing route for Option 1 no traffic data were provided for the existing section at Nettleton, as the route here would become offline. The existing road would only be used for access to properties. By doing this, the assessment is very worst-case but it would still provide an indication as to the change in air pollution properties along the existing route would experience as a result of the proposed alignment of the A417.

9.15 The total score calculated in the assessment is given below in Table 9-2.

Table 9-2 Air quality assessment score for Option 1
Route Option PM10 NO2
Option 1 (Online with signals at Air Balloon) 57 1295

9.16 Table 9-2 shows that for Option 1 the scores are positive numbers indicating that the proposed route would generate an increase in air pollution or exposure of properties to air pollution.

9.17 In terms of the number of properties affected by air pollution, Option 1 would result in approximately 8 properties experiencing a reduction in local air pollution (principally those at Nettleton), whilst approximately 6 properties would experience an increase in local air pollution.

Greenhouse Gases

9.18 The results for this part of the air quality assessment have been used to compare the concentrations of CO2 for each option with the amount produced by the existing alignment both in 2002 and in 2012.

9.19 The results indicate that the existing route option would produce an increase in CO2 of approximately 3117 tonnes per annum between the present year and 2012. Under Option 1, there would be a decrease of approximately 550 tonnes per annum in 2012 compared to the 2012 'do minimum'. This is due primarily to the reduction in congestion and increased traffic speed along the new dual carriageway sections.

Landscape

9.20 The following sections describe the impact of the proposed improvement on the landscape using the sub-headings proscribed in the GOMMMS assessment methodology.

9.21 This option would follow the alignment of the A417 as its climbs Crickley Hill, widening to four lanes (two up and two down) within the current highway boundary. At the Air Balloon, a signalised roundabout is proposed. A new sliproad to the south of the Air Balloon Roundabout would be required as part of the signalised roundabout.

9.22 South of the Air Balloon Roundabout, the alignment closely follows that of the existing A417 as far as Parson's Pitch, deviating only where the eastern carriageway is taken off-line to avoid potential impacts on Barrow Wake SSSI.

9.23 At Parson's Pitch, the route corridor is taken off-line approximately 250m to the north of Nettleton, before returning to link back with the A417 at Cowley Roundabout. Cowley Roundabout would be removed and a new junction with the old A417 established.

Impact on Landscape Pattern

9.24 Widening to only four lanes up Crickley Hill would minimise potential impact on landscape pattern. Existing vegetation either side of the A417 would be retained and no significant impact on landform has been determined. At the Air Balloon Roundabout, the signalised roundabout and, in particular, the associated signage and lighting would be a little at odds with the character of the local pattern. This section of the route corridor would give rise to a Slight Adverse Impact on Pattern.

9.25 Between the Air Balloon Roundabout and Parson's Pitch, the new alignment remains mostly at grade and within the current alignment of the A417. This section of the route corridor passes through the elevated, flat and exposed plateau landscape, the scale of which helps to absorb the impact of the road on the landform and landscape pattern. This section of the route corridor would give rise to a Neutral Impact on Pattern.

9.26 To the east of Parson's Pitch, the route corridor moves off-line and would enter into cutting to the south of Stockwell before crossing the small valley to the north of Nettleton on embankment. Nettleton Valley is steep-sided and open with little tree cover. An embankment at this location would both truncate the valley and be incongruous with the local landform. This section of the route corridor would give rise to a Moderate Adverse Impact on Pattern. Landscape mitigation measures may be able to reduce impacts but can only be assessed at the detailed design stage.

9.27 The route corridor as a whole would give rise to a Moderate Adverse Impact on Pattern.

Impact on Tranquillity

9.28 The sense of remoteness and isolation within the landscape of the Study Area is currently significantly adversely affected by views of, and the noise generated by, traffic on the A417. Many of the footpaths and public areas in the Study Area, including Crickley Hill Country Park, Barrow Wake and the Gloucestershire and Cotswold Ways, are currently adversely affected.

9.29 Because the route corridor follows the existing alignment of the A417, for the most part, the impact on the tranquillity of the landscape of the Study Area would remain as the baseline. However, there would be an adverse impact on the tranquillity of the Study Area, to the north of Nettleton, where the off-line section of the route corridor would have a localised impact on the tranquillity of the valley. This adverse impact would, in part, be off-set by an improvement to the same valley directly south of Nettleton.

9.30 This route corridor as a whole would give rise to a Slight Adverse Impact on Tranquillity.

Impact on Cultural Context

9.31 Signage and lighting proposed as part of the signalised roundabout would impinge slightly on the setting of Emma's Grove (a Scheduled Monument), and the eastern edge of Crickley Hill Country Park. This section of the route corridor would give rise to a Slight Adverse Impact on Cultural Context.

9.32 Between the Air Balloon and Parson's Pitch, the route corridor is not assessed as having any discernible impact on landscape elements that contribute to cultural importance of the landscape. Potential physical impacts to Sites of Archaeological Interest are discussed under Archaeology and Cultural Heritage. This section of the route corridor would give rise to a Neutral Impact on Cultural Context.

9.33 To the east of Parson's Pitch, the route corridor is situated off-line to the north of Nettleton. The setting of the Golden Hart Inn, a Grade II Listed Building, is currently significantly affected by traffic on the A417. The removal of traffic off the A417 to the new route corridor further north would have a beneficial impact on the setting of the Golden Hart Inn. The setting of the listed milestone, located on the A417 further west, would also be improved. Potential physical impacts to Sites of Archaeological Interest arising from construction of the new route corridor are discussed under Archaeology and Cultural Heritage. This section of the route corridor would give rise to a Slight Beneficial Impact on Cultural Context.

9.34 The setting of Brimpsfield Conservation Area and the Listed Buildings contained therein would remain unaffected.

9.35 The route corridor as a whole would give rise to a Slight Adverse Impact on Cultural Context.

Impact on Landcover

9.36 The Study Area comprises primarily of farmland. The fabric of this farmland, namely the field pattern, size and boundary treatment would remain largely unaffected in the Study Area. A localised impact would occur to the north of Nettleton, where the new route corridor would segment existing fields into smaller plots. The fields located between the new route corridor and the A417 are likely to become unviable as agricultural land. Two local footpaths would also be severed in this location.

9.37 Semi-natural habitats constitute the other major landcover. Important woodland areas, namely the beech woodlands that clothe the upper slopes of the escarpment and ancient semi-natural woodland, would remain unaffected. Potential impacts on Sites of Special Scientific Interest and County Wildlife Sites are assessed under Biodiversity.

9.38 The route corridor as a whole would give rise to a Slight Adverse Impact on Landcover.

Visual Impact

9.39 A Slight Adverse Visual Impact to viewpoints in the locality of the signalised junction has been identified. Views from the property known as Crickley Lodge would experience a Moderate Adverse Impact resulting from the construction of the sliproad to the south of the Air Balloon Inn.

9.40 Potential visual impacts associated with the route corridor between the Air Balloon Roundabout and Parson's Pitch are assessed as No Change because widening at this location has not been identified as increasing the visibility of road, or the traffic on it, when compared to the baseline.

9.41 The off-line section of the route corridor would be in cutting either side of Nettleton, thereby reducing the visibility of the road in the adjacent landscape. At Nettleton Bottom, the route corridor would cross the valley on embankment, resulting in a Moderate Adverse Impact to local viewpoints. The property known as The Rise is situated to the south of Stockwell and would look directly over the new route corridor. There would be a Substantial Adverse Visual Impact on views from this property.

9.42 The route corridor as a whole would give rise to a Moderate Adverse Visual Impact.

Mitigation

9.43 Mitigation measures have not been developed in detail for any of the route corridors at this stage of the Environmental Assessment. However, intrinsic mitigation which is likely to form part of this route corridor has been considered below. Where mitigation is considered to alter the scale of impact assessed for each of the landscape features, it has been noted:

Summary of Character

9.44 The whole of the Study Area is designated as an Area of Outstanding Natural Beauty, which reflects the National Importance of the landscape. The escarpment, which is characterised by its dramatic topography is recognised as being of particular high scenic quality.

9.45 The main impact on the landscape associated with the route corridor would occur as a result of the off-line section to the east of Parson's Pitch, especially where the route corridor crosses Nettleton Valley on embankment. Impacts attributed to this section of the route corridor include a Moderate Adverse Impact on Pattern and Moderate Adverse Visual Impacts.

9.46 Following the GOMMMS methodology, the overall impact on the landscape of the Study Area is assessed as Moderate Adverse. This overall score reflects the level of impact attributed to the off-line section of the route corridor at Nettleton.

Townscape

9.47 The scheme is within a rural area and therefore the townscape would not be affected.

Heritage of Historic Resources

9.48 The current assessment has been based primarily on a desk study and consideration of the potential impacts of the proposed road alignment changes. No field surveys have been carried out at this stage. It is certain that the local planning authorities would require detailed desk based assessment of the entire route, including the areas of ancillary works and work compounds, which may need to be followed by geophysical survey or other forms of field evaluation of any identified sites of archaeological interest, including the areas listed in the bullet points below. The issue of how best to evaluate areas buried under landslip would need to be addressed.

9.49 Mitigation strategies which may include the raising of levels, revisions to alignments and working methods that minimise damage to archaeological deposits, would need to be considered at the design stage.

9.50 Archaeological excavation may be required in advance of construction where archaeological deposits cannot be preserved in situ. Watching briefs and further programmes of archaeological recording are likely to be required during the construction phases. Summary of potential archaeological issues, from north-west to south-east:

9.51 The overall assessment of this option is considered to be Moderate Adverse.

Biodiversity

9.52 There are seven designated sites within close proximity to the proposed improvements, four of national importance and three of regional importance. Other areas of ecological importance include habitats suitable for protected reptiles, bats and breeding birds. For most ecological features within the route corridor, there would be little or no impact as the majority of the construction works would take place within the existing highway boundary where habitats are already disrupted or degraded. However, this option would sever an area of mature beech woodland to the north of Birdlip Disused Quarry and remove habitats suitable for protected species. Additional landscaping and other measures would have to be considered in the detailed design stage.

9.53 Further detailed surveys would be required to detail the exact location and extent of habitats for breeding birds, bats and reptiles. Whilst the magnitude of impact would most likely be intermediate negative, this assessment has erred on the side of caution subject to further detail.

9.54 Existing drainage ditches would be affected along the route corridor but the construction of culverts would maintain a link and thereby, reduce any adverse effect. The existing road verges would be affected, which would reduce their value as habitat link features.

9.55 The proposed tunnel would create additional disturbance including noise, dust and human. Construction workers would disturb wildlife, mainly birds usually accustomed to minimal disturbance associated with moving traffic along the A417. The timescale of this additional disturbance would be short-term.

9.56 The overall assessment of impacts is considered to be Serious Adverse.

Water Environment

9.57 Under Option 1, most of the improvements would be within the existing highway boundary. Between the Air Balloon and Cowley roundabouts, road widening would take place to the east of the existing road. Earthworks associated with this would not involve deep excavations and would therefore not impact on any springs or the underlying Major Aquifer. The latter feeds into the River Churn which is a major abstraction point for drinking water supplies.

9.58 The short offline section around Nettleton would require construction of an earth embankment and associated excavation. The embankment would cross a small valley through which surface water naturally drains. The embankment has the slight potential to disrupt water flow which is believed to feed into the springs that feed two water-fed SSSIs mitigation measures can be designed to minimise any adverse impact.

9.59 On Crickley Hill, road widening would be undertaken within the existing highway boundary. A number of springs are found on the hillside and previous highway works have experienced difficulties with water flows. Some retaining structures and drainage systems would be required to stabilise the new downhill carriageway which may disrupt the natural flow of water.

9.60 Mitigation measures could be put in place to minimise the impacts. These would include the following:

9.61 The overall assessment of impacts on the water environment is therefore considered to be Slight Adverse.

Physical Fitness

9.62 The Air Balloon Roundabout is the cross over point for the Cotswold Way and Gloucestershire Way long distance footpaths. It is unknown at the time of writing how many walkers use these routes. At present, pedestrians, cyclists and equestrians have to cross the existing road at grade. No crossing facilities are supplied and crossing movements are not segregated from vehicles. However, a safe crossing point would be provided for these users at the Air Balloon roundabout which would result in a Slight Benefit assessment for the scheme.

Journey Ambience

9.63 Improvements in carriageway alignment and approaches to the Air Balloon Roundabout would improve driver visibility. The provision of traffic signals would ease congestion during peak periods. Additional speed and route signage would improve information available to drivers whilst the provision of crossing points for pedestrians (particularly those using the National Trails) would improve accessibility at this difficult junction. The overall assessment of Option 1 on journey ambience is considered to be Slight Beneficial.

OPTION 2 - Dualling of A417, grade separated junction at the Air Balloon, and an additional two lanes down Crickley Hill

9.64 A plan showing the indicative road layout and alignment is provided in Figure 5.2.

OBJECTIVE : ENVIRONMENT

Noise

9.65 The change in alignment for the A417 to the north of Cowley Roundabout would bring the carriageway closer to one dwelling (with a resulting potential increase in noise levels) but further away from 4 other dwellings (with a resulting potential decrease in noise levels).

9.66 The new slip roads at the Air Balloon Roundabout would bring traffic closer to one dwelling, with a resulting potential increase in noise levels. Placing the new link roads between the A417 and A436 in cutting would lead to lower noise levels at two dwellings (Air Balloon cottages). However, this would be partially offset if sound reflecting retaining structures (walls) are used.

9.67 The widened carriageways between the Air Balloon and Cowley Roundabouts could cause elevated noise levels at 3 other dwellings that lie within 300m of the road.

9.68 The additional downhill lanes on Crickley Hill would bring the carriageway closer to 4 dwellings, with a resulting increase in noise levels. In addition to these 4 properties, the remaining 23 dwellings at Crickley Hill would also be affected by increased noise levels due to an increase in average traffic speeds on the eastbound (uphill) carriageway on Crickley Hill.

9.69 Other noise sensitive locations (e.g. Birdlip County Primary School and Crickley Hill Country Park) would be likely to remain relatively unaffected. However, the Gloucestershire Way and other paths might experience an increase in noise levels due to the widened carriageways.

9.70 A comparison of the number of properties that would be likely to experience a net benefit / disbenefit under Option 2 is shown in Table 9-3.

Table 9-3 Number of properties likely to experience a change in noise levels for Option 2
Option 2: Online (grade separation) Number of Properties/People Within 300m
Likely number of properties/people that would experience an increase in noise levels 32/77
Likely number of properties/people that would experience a reduction in noise levels 6/14
Likely number of properties/people that would be relatively unaffected 10/24

Local Air Quality

9.71 For the assessment of the changes in air quality along the existing route for Option 2 no traffic data were provided for the existing section at Nettleton, where the proposed changes to the route would become offline. The existing road would only be used for access to properties. By doing this, the assessment is very worst-case but it would still provide an indication as to the change in air pollution properties along the existing route would experience as a result of the proposed alignment of the A417.

9.72 The total scores for each pollutant calculated in the assessment is given below in Table 9-4. These scores have been calculated on the assumption that maximum retaining structures would be constructed.

Table 9-4 Air quality assessment score for Option 2
Route Option PM10 NO2
Option 2 (Online with grade separated junction at Air Balloon) 63 1398

9.73 Table 9-4 shows that for Option 2 the scores are positive numbers indicating that the proposed route would generate an increase in air pollution or exposure of properties to air pollution.

9.74 If minimal retaining structures were used there would be no change in the overall scores for both pollutants as there would be the same number of properties affected. The scores would, however, be lower if earth embankments were used as there would be fewer properties - the Air Balloon pub and the two cottages adjacent to the existing roundabout would be lost.

9.75 In terms of the number of properties affected by air pollution, Option 2 would result in approximately 8 properties experiencing a reduction in air pollution (principally those at Nettleton), whilst approximately 6 properties would experience an increase in air pollution. This is essentially the same as for Option 1.

Greenhouse Gases

9.76 The results for this part of the air quality assessment have been used to compare the concentrations of CO2 for each option with the amount produced by the existing alignment both in 2002 and in 2012.

9.77 These results indicate that the existing route option would produce an increase in CO2 of approximately 3117 tonnes per annum between the present year and 2012. Under Option 2, there would be a decrease of approximately 1530 tonnes per annum in 2012 compared to the 2012 'do minimum'. As with Option 1, this is due to a reduction in congestion and consequent increase in traffic speeds along the dualled sections although the reduction in CO2 is greater under this option because of the free-flowing junction at the Air Balloon.

Landscape

9.78 The route corridor for Option Two is identical to Option One from the Air Balloon Roundabout to Cowley Roundabout. The impact on landscape described for Option One would therefore be the same for this section of the route. Option Two differs to Option One at the western end of the route corridor. A description of this part of the option corridor and the associated impacts on landscape are provided in the following sections. For clarity, for each landscape feature, an overall assessment for the whole route corridor has also been given.

9.79 At the western end, this option follows the existing alignment of the A417 as it climbs Crickley Hill. Widening of the road to five lanes (three up and two down) would take place along the southern boundary of the existing A417. Along the northern boundary of the A417, the route corridor remains within the existing highway boundary.

9.80 At the Air Balloon Roundabout, a grade separated junction is proposed. The A417 through roads would be at grade with the link roads to/from the A436 passing beneath through cuttings. The Air Balloon Roundabout is retained, but relocated further along the A436 to the junction with the Leckhampton Road.

Impact on Pattern

9.81 The A417 currently follows the valley profile as it climbs Crickley Hill and fits well with the landscape pattern. Widening to the south up Crickley Hill, on the down slope of the valley profile, would have a localised adverse impact on the landform. In several locations, embankment, or some form of retaining structure, would be required, thereby increasing the potential impact on the valley profile. Existing vegetation along the southern boundary of the A417 would be lost. Towards the top of Crickley Hill, the existing A417 reaches the head of the valley, before passing into a steep cutting. Widening to the south at this location would increase the width and scale of the cutting, especially as the rock is unstable and therefore is likely to require some form of benching. At the Air Balloon Roundabout, the scale of the proposed grade separated junction would be at odds with the local landform and pattern. The junctions fit into the landscape would be further compromised by the extensive retaining structures either side of the A436 link roads (some up to 7.5m high where the road passes beneath the A417 through roads). Gantries (if used) and signage would also be intrusive. This section of the route corridor would give rise to a Large Adverse Impact on Pattern.

9.82 The route corridor as a whole would give rise to a Large Adverse Impact on Pattern.

Impact on Tranquillity

9.83 As for Option One, the route corridor follows the existing alignment of the A417, thereby minimising potential impacts to tranquillity when compared to the baseline.

9.84 Loss of vegetation along the southern edge of the A417 as it climbs Crickley Hill, and the grade separated junction at the Air Balloon would result in an increase in the visibility of this section of the route corridor from viewpoints in the landscape currently unaffected, or not significantly affected by the A417. At these viewpoints, the sense of tranquillity would be degraded.

9.85 The route corridor as a whole would give rise to a Slight Adverse Impact on Tranquillity.

Impact on Cultural Context

9.86 At the western end of the route corridor, widening to the south up Crickley Hill would result in the loss of vegetation by Crickley Hill Farm, thereby affecting the setting of this Grade II Listed Building. Crickley Hill Country Park, which includes an area of Common Land and several Scheduled Monuments, would not be physically affected. The new roundabout would require a small amount of landtake from the cricket ground, adjacent to the Leckhampton junction. Loss of trees at this location would increase the visibility of the road from the cricket ground and from Crickley Hill Country Park. Gantries (if used) and signage would be visible from Emma's Grove round barrow. The setting of all three features, which are important cultural elements in the landscape, would be adversely affected. This section of the route corridor would give rise to a Moderate Adverse Impact on Cultural Context.

9.87 The route corridor as a whole would give rise to a Moderate Adverse Impact on Cultural Context.

Impact on Landcover

9.88 Widening up Crickley Hill would result in the loss of a intermittent belt of trees along the southern edge of the A417. These trees are of varying quality and are more important in terms of providing a screen to traffic as it climbs Crickley Hill. The impact on the landcover is assessed as Slight Adverse.

9.89 At the Air Balloon Roundabout, the northern edge of the fine group of mature trees located on the boundary of the Cricket Ground with the existing Air Balloon Roundabout, would be physically affected. It is estimated that between five and seven trees would be lost. These trees contribute to the visual amenity of the area and provide an important visual buffer to the Cricket Ground and Crickley Hill Country Park.

9.90 To the south of Emma's Grove, nine mature beech trees that are located within the highway boundary would be lost, although it is considered that this potential impact may be able to be avoided during the development of this option. This section would result in a Moderate Adverse Impact on Landcover.

9.91 This route corridor as a whole would give rise to an overall Moderate Adverse Impact on Landcover.

Visual Impact

9.92 Traffic on the existing A417 is well screened by existing vegetation as it climbs Crickley Hill. Loss of a significant amount of visually important vegetation along this section of the route corridor would increase the visibility of traffic when viewed from surrounding countryside, including distant views from the Cotswold Way and Barrow Wake. From local viewpoints overlooking this section of the route corridor, including nearby properties to the south, there would be a Moderate Adverse Visual Impact.

9.93 Views of the grade separated junction would be mostly confined to the locality. By constructing the new road junction at grade, or below grade, potential views from the escarpment landscape would be largely avoided, although traffic and the gantries may be visible at one or two locations. Views from Crickley Hill Country Park, the Cricket Ground and local footpaths (including the Cotswold/Gloucestershire Way) would overlook the junction. A number of these viewpoints are elevated and would look down over the junction, with the retaining walls clearly visible. Loss of some of the trees at the Cricket Ground would increase the visibility of traffic from views to the north. Tree loss to the south of Emma's Grove would not affect views, as woodland to the east would continue to screen this section of the road. The property known as Crickley Lodge would experience a Substantial Adverse Impact. This section would give rise to a Substantial Adverse Visual Impact.

9.94 No discernible change to the Zone of Visual Influence has been assessed.

9.95 Overall, this route corridor would give rise to Substantial Adverse Visual Impact.

Mitigation

9.96 Intrinsic mitigation which is likely to be considered for the section of the route corridor between Crickley Hill and Air Balloon could include:

9.97 Loss of trees up Crickley Hill could be mitigated by new planting of locally indigenous species. Where retaining structures were used, tree planting along the southern boundary may not be possible, although subtle ground modelling would also be appropriate in this location. These measures would improve the visual impact to viewpoints that overlook this section of the route, but within the timescale of the assessment (15 years) there would be no change to the scale of visual impact, which would remain at Moderate Adverse.

9.98 At the grade separated junction, mitigation could include ground modelling, and extensive tree planting (mostly of beech). The planting of beech woodland on the upper slope of the escarpment would be in character with the landscape of the area. Sightlines have been considered and would not significantly reduce the area available for planting. Retaining walls either side of the below grade section of the A436 would need to be carefully designed. It has been assumed that they would be faced with local stone to help assimilate these structures into the landscape. Trees that have been lost at the Cricket Ground and by Emma's Grove could be replanted. Mitigation measures, as described above, are considered to reduce the impact attributed to Pattern from Large to Moderate and the visual impact from Substantial to Moderate.

9.99 Mitigation measures for the remainder of the route corridor would be the same as designed for Option One.

Summary of Character

9.100 The whole of the Study Area is designated as an Area of Outstanding Natural Beauty, which reflects the National Importance of the landscape. The escarpment, which is characterised by its dramatic topography is recognised as being of particular high scenic quality.

9.101 The main impact on landscape associated with this route corridor would occur as a result of widening to five lanes up Crickley Hill, the grade separated junction at Air Balloon Roundabout and the off-line section to the east of Parson's Pitch, especially where the route corridor crosses Nettleton Valley on embankment. Mitigation measures would reduce the impact attributed to widening up Crickley Hill and the grade separated junction.

9.102 While there are no Large Adverse Impacts attributed to this option once mitigation has been taken into account, it is considered that the cumulative effect of the Moderate Adverse Impacts determines that the overall impact on the landscape of the Study Area is Large Adverse.

Townscape

9.103 The scheme is within a rural area and therefore the townscape would not be affected.

Heritage of Historic Resources

9.104 A particular concern with this option are the settings of the Scheduled Monuments at Crickley Hill and Emma's Grove. It is essential that the views of English Heritage are sought regarding the matter. Estimates of the likely location, height and visibility of the superstructure of any proposed flyovers and the depth and extent of any cuttings including details of retaining structures and embankments would be required before English Heritage would give a detailed opinion.

9.105 The extent of cuttings, embankments and retaining structures has yet to be determined, but obviously the larger the area excavated or otherwise disturbed, the greater the possibility that archaeological deposits are damaged. It is therefore probable that building retaining structures would be likely to damage fewer archaeological deposits than embanked cuttings, although the extent to which this is the case would be dependant on the archaeology present in specific areas and on the engineering designs chosen.

9.106 It is certain that the local planning authorities would require detailed desk based assessment of the entire route, including the areas of ancillary works and work compounds, which may need to be followed by geophysical survey or other forms of field evaluation of any identified sites of archaeological interest, including the areas listed in the bullet points below. The issue of how best to evaluate areas buried under landslip would need to be addressed. Mitigation strategies which may include the raising of levels, revisions to alignments and working methods that minimise damage to archaeological deposits, would need to be considered at the design stage.

9.107 Archaeological excavation may be required in advance of construction where archaeological deposits cannot be preserved in situ. Watching briefs and further programmes of archaeological recording are likely to be required during the construction phases. Summary of potential archaeological issues, from north-west to south-east:

9.108 The new access/exit link road near Highgate House appears to pass through the Iron Age enclosures partly excavated in 1997 (Mudd et. al 1999), but mostly preserved in situ.

9.109 The overall assessment of this option is considered to be Moderate Adverse.

Biodiversity

9.110 The impacts associated with Option 2 would essentially be the same as for Option 1 due to the broadly similar route alignment. Additional loss of vegetation down Crickley Hill would, however, occur to make way for the additional two lanes.

9.111 The overall assessment of this option is therefore considered to be Serious Adverse.

Water Environment

9.112 The impacts associated with Option 2 would be essentially the same as for Option 1 as much of the construction would be within or immediately adjacent to the existing highway boundary.

9.113 On Crickley Hill, construction of the two additional downhill lanes would involve extending outwards on the southern side of the existing road but at a lower level for part of the route. The carriageway could be constructed either on embankments or piled structures. The final design would depend on further consideration of geotechnical and hydrological issues. Construction of embankments could potentially disrupt some of the springs and hence water flow in the numerous streams and result in significant release of groundwater (as previously occurred during the last widening works on the road). Knowledge of this problem allows a drainage solution to be put in place that may allow the re-introduction of water into spring beds to maintain the status quo.

9.114 Mitigation measures could be put in place to minimise potential impacts. These would include the following:

9.115 The overall assessment of impacts on the water environmental is therefore considered to be Slight Adverse.

Physical Fitness

9.116 The Air Balloon Roundabout is the cross over point for the Cotswold Way and Gloucestershire Way long distance footpaths. It is unknown at the time of writing how many walkers use these routes. At present, pedestrians, cyclists and equestrians have to cross the existing road at grade. No crossing facilities are supplied and crossing movements are not segregated from vehicles. However, safe crossing points (possibly underpasses) would be provided for these users at the Air Balloon roundabout which would result in a Slight Beneficial assessment for the scheme.

Journey Ambience

9.117 Improvements in carriageway alignment and approaches to the Air Balloon grade separated junction would improve driver visibility. The free-flow junction would reduce congestion providing a less stressful journey along this stretch of the A417. Additional speed and route signage would improve information available to drivers. However, the scheme would result in the loss of the Air Balloon public house and hence a service area that currently provides rest, food and toilet facilities. The overall assessment of this option on journey ambience is therefore considered to be Neutral.

OPTION 3 - Tunnel between Nettleton and the bottom of Crickley Hill. Old A417 would be de-trunked

9.118 A plan showing the indicative road layout and alignment is provided in Figure 5.3.

OBJECTIVE : ENVIRONMENT

Noise

9.119 All dwellings along the A417 between Air Balloon and Cowley Roundabout would be likely to experience a reduction in noise levels due to lower traffic flows along the existing A417 and rerouting of the A417 through the tunnel. All dwellings along the A417 Crickley Hill between the Air Balloon Roundabout and Crickley Court would also benefit.

9.120 There are 12 properties at Holly Brae (at the bottom of Crickley Hill) that lie within 100m of the tunnel portal at the north-western end. All of these properties could experience an increase in noise level.

9.121 Other noise sensitive locations (e.g. Birdlip County Primary School, Crickley Hill Country Park and the Gloucestershire Way) would be likely to experience a decrease in noise levels due to lower traffic flows along the existing A417 and re-routing of the A417 through the tunnel.

9.122 A comparison of the number of properties that would be likely to experience a net benefit / disbenefit with Option 3 is shown in Table 9-5.

Table 9-5 Number of properties likely to experience a change in noise levels for Option 3
Option 3: Tunnel Number of Properties/People Within 300m
Likely number of properties/people that would experience an increase in noise levels 12/29
Likely number of properties/people that would experience a reduction in noise levels 41/89
Likely number of properties/people that would be relatively unaffected 0

Local Air Quality

9.123 As much of the route for Option 3 is under ground property counts were carried out from both entrances/exits of the tunnel until the proposed route meets the existing road. In addition to this the counts were carried out, again in 50 metre bands, up to 200 metres back from each end of the tunnel portal. This was undertaken so as to take into account dispersion of pollution form the portals by the wind in all directions.

9.124 The total score Option 3 is given below in Table 9-6.

Table 9-6 Air quality assessment score for Option 3
Route Option PM10 NO2
Option 3 (Tunnel) -63 -968

9.125 Table 9-6 shows that for Option 3 the score is negative for both pollutants as this proposed option has been predicted to cause a reduction in air pollution. The primary reason for this is that much of the A417 would be under ground in this option and therefore there is no exposure of air pollution along the majority of the route. It is only at the portals that vehicle emissions are vented to the atmosphere.

9.126 In terms of the number of properties affected by air pollution, Option 3 would result in approximately 91 properties experiencing a reduction in air pollution and none experiencing an increase. Again, this is due to the fact that the majority of the new road would be underground with air pollution concentrated around the tunnel portals. Both are located away from properties. Furthermore, the existing A417 would experience a significant reduction in traffic flows (approximately 70%) which would result in an improvement in air quality along the route. Since the majority of properties are located adjacent to or in close proximity of the existing road, they would all benefit from the reduced traffic flows and concomitant reduction in air pollution.

Greenhouse Gases

9.127 The results for this part of the air quality assessment have been used to compare the concentrations of CO2 for each option with the amount produced by the existing alignment both in 2002 and in 2012.

9.128 These results indicate that the existing route option would produce an increase in CO2 of approximately 3117 tonnes per annum between the present year and 2012. Under Option 3, there would be a decrease of approximately 10,574 tonnes per annum in 2012 compared to the 2012 'do minimum'. This equates to a 50% reduction. This is primarily because the volume of traffic using the tunnel would be lower than the total volume that would use the existing A417. Approximately 70% of the traffic flow would be diverted through the tunnel.

Landscape

9.129 The alignment and length of the proposed tunnel is illustrated on Figure 5.3. Each carriageway would be duelled and located in separate tunnels running parallel and approximately 15m apart. The portals to the tunnels are, for the purpose of this assessment, assumed to be 50m wide by 20m high and faced with local stone.

9.130 The western portal would be located to the west of Crickley Hill Farm at the foot of the escarpment. Access from the old A417 onto the Brockworth Bypass would be maintained by a single lane road passing to the south of Crickley Hill Farm. A permanent Maintenance Building with parking facilities would be located near to the portal.

9.131 The portal at the eastern end would be sited within Nettleton Bottom. Cowley Roundabout would be removed, and a new junction provided onto the old A417. The approaches to both tunnel portals would be well lit.

9.132 The existing A417 would remain in place, although approximately two thirds of the existing traffic would be removed.

Impact on Pattern

9.133 Although the siting of the western portal at the base of the escarpment helps to limit potential impacts on the landform of the escarpment, considerable remodelling of the landform in the vicinity of the portals would be required.

9.134 A new single lane road is required to the south of Crickley Hill Farm and the western portal, to maintain access to the old A417. The alignment of the road is assessed as having an adverse impact on the pattern of the escarpment. The complexity of the landform in this area is likely to result in both cutting and embankment being required, especially where the new road crosses the valley to the south of the existing A417. A number of mature trees and hedgerows would be lost although this would be limited. The western portal and associated structures/roads would give rise to a Large Adverse Impact on Pattern. Mitigation measures may be possible.

9.135 The eastern portal would be sited with Birdlip Quarry, thereby minimising potential impacts on the landform. The section of new dual carriageway between the portal entrance and the A417 would require minor cut into the landform. The Slight Adverse Impact on Pattern is assessed.

9.136 This option would give rise to an overall Large Adverse Impact on Pattern.

Impact on Tranquillity

9.137 A Slight Adverse Impact to the tranquillity of the landscape in the vicinity of the portals is assessed. However, the main impact to the tranquillity of the Study Area would be beneficial due to a 70% reduction of traffic on the existing A417. The removal of the majority of heavy vehicles from Crickley Hill would result in a significant improvement to the surrounding countryside and to the escarpment landscape. An overall Large Beneficial Impact to the tranquillity of the Study Area has been assessed for this option.

Impact on Cultural

9.138 The western portal and associated structures/roads would adversely affect the setting of Crickley Hill Farm, a Grade II Listed Building.

9.139 At the eastern portal, potential impacts to Sites of Archaeological Interest are likely. These impacts are discussed under Archaeology and Cultural Heritage.

9.140 Reduction in traffic along the old A417 would result in an improvement to the setting of culturally important landscape features which are currently adversely affected by the A417. This would include Crickley Hill Cricket Ground, Barrow Wake Common and Emma's Grove. The setting of the Golden Hart Inn, a Grade II Listed Building, would also improve.

9.141 Overall, this option is assessed as having a Neutral Impact on Cultural Context.

Impact on Landcover

9.142 Loss of hedgerows and a stand of mature beech trees could occur as part of the construction of the new road lane to the south of Crickley Hill Farm. The new lane would also result in the severance of three public rights of way, although this impact would be off-set by considerable improvements to access along existing footpaths elsewhere in the Study Area where they cross the A417.

9.143 The construction of the tunnel would require dewatering of the bed rock. This would result in both short and long-term impacts on the water resources of the Study Area, although the degree of impact has not been possible to determine at this stage. Potential indirect adverse impacts on the landcover may occur as a result of changes to the water resources. In particular, Bushley Muzzard and Brimpsfield Bog, both sites of Special Scientific Interest, could be adversely affected. This potential impact is discussed and assessed under Biodiversity.

9.144 Dewatering of the area could also affect a number of the springs in the area, possibly resulting in them drying up. This could impact on the landcover in the vicinity of the springs.

9.145 An overall Slight Adverse Impact on the landcover has been assessed for this option.

Visual Impact

9.146 The siting of the eastern portal in Birdlip Quarry would reduce the visibility of this structure. A Slight Adverse Impact to viewpoints in the locality is assessed.

9.147 The western portal, and its associated structures/lanes would be highly visible from the surrounding area. In views from the west, the tunnel portals would be an alien feature, these together with the new lane to the south of Crickley Hill Farm, would be seen against the landscape of the escarpment and would be visually intrusive. There would be a Substantial Adverse Visual Impact on views from nearby properties and footpaths. The new portal and associated structures/lanes would also be visible in medium/long distant views from the east, including Barrow Wake and Crickley Hill Country Park. Lighting at both portals would adversely affect night-time views in these areas.

9.148 Reduction of traffic on the A417 would result in an improvement to views overlooking this road.

9.149 Due to the importance of the escarpment landscape, this option would give rise to an overall Substantial Adverse Visual Impact.

Mitigation

9.150 As for corridor Options One and Two, mitigation measures associated with the tunnel option have not been developed in detail at this stage of the Environmental Assessment. The detailed design of the portals and associated mitigation measures would be important in determining how successfully these structures could be assimilated into the landscape.

9.151 At both of the portal entrances, extensive tree and hedgerow planting would be appropriate to help reduce visual impact. Remodelling of the landform could also be considered, although this would need to be carefully handled at the western portal where unsympathetic mounding could impact further on the landform and character of the Vale and Scarp landscapes.

9.152 The impact of the new road lane to the south of Crickley Hill Farm could be mitigated by hedgerow and tree planting along the boundary, although any cuttings or embankment are likely to still be intrusive 15 years after construction.

9.153 Some local views overlooking the portal would be improved by mitigation, but a number of key views from the surrounding landscape would continue to be subject to Substantial Adverse Visual Impact.

9.154 Mitigation measures along the existing A417, especially between the Air Balloon Roundabout and Parson's Pitch, could result in improvement in visual impact when compared to the baseline.

Summary of Character

9.155 The western portal and associated structures would result in the Moderate Adverse Impact on the pattern. Views from nearby properties and footpaths, would be affected by a Large Adverse

Visual Impact.

9.156 The eastern portal is assessed as resulting in a slight impact on the landscape.

9.157 Reduction in traffic along the existing A417 would result in some beneficial impacts to the landscape of the Study Area, mostly noticeable on tranquillity. However, the scale of adverse impacts on the escarpment landscape resulting from the western portal would give rise to an overall Large Adverse Impact on the landscape of the Study Area.

Townscape

9.158 The scheme is within a rural area and therefore the townscape would not be affected.

Heritage of Historic Resources

9.159 The engineering options chosen are crucial to the effect of tunnel construction on archaeological deposits. For instance, construction using the cut and cover method or requiring ventilation shafts would be entirely destructive of archaeological deposits in the areas affected.

9.160 As with Options 1 and 2, it is certain that the local planning authorities would require detailed desk based assessment any areas where the ground surface may be disturbed, including the areas of ancillary works such as the reservoir, spoil storage and work compounds, which may need to be followed by geophysical survey or other forms of field evaluation of any identified sites of archaeological interest, including the areas listed in the bullet points below. The issue of how best to evaluate areas buried under landslip would also need to be addressed. Summary of potential archaeological issues, from north-west to south-east:

9.161 The overall assessment of this option is considered to be Slight Adverse.

Biodiversity

9.162 There is one nationally designated site within close proximity of the proposed scheme. Other areas of ecological importance include habitats suitable for reptiles, bats and breeding birds. This option would potentially have an impact on a major aquifer and in turn could indirectly affect Bushley Muzzard (Brimpsfield Bog) and Watercombe Marsh SSSI's. This option would also sever an area of mature beech woodland to the north of Birdlip Disused Quarry remove habitats suitable for protected species.

9.163 Existing drainage ditches would be affected along the route corridor but the construction of culverts would maintain a link and thereby, reduce any adverse effect. The existing road verges would be affected, which would reduce their value as habitat link features.

9.164 The proposed tunnel construction would create additional disturbance including noise, dust and human. Construction workers would disturb wildlife, mainly birds usually accustomed to minimal disturbance associated with moving traffic along the A417. The timescale of this additional disturbance would be short-term.

9.165 The overall assessment of impacts on biodiversity is considered to be Very Serious Adverse.

Water Environment

9.166 Construction of the tunnel would involve tunnelling through the Major Aquifer that extends across the top of the escarpment and to the east towards the River Churn. The geological conditions in the upper parts of the (fissured limestone) are such that groundwater flows are difficult to predict. It is possible that the tunnel could cause significant changes in the volume and direction of flows.

9.167 As stated in 9.57, this aquifer feeds the River Churn, and which also supplies drinking water. The Churn is the largest river within the Study Area and runs roughly north-south to the east of the existing A417. The river is spring fed and this is confirmed by the river hydrographs. The river is recognised by the Environment Agency as one being susceptible to low flows during summer months. A low flow action plan for the river has been drawn up and is in operation (funding was approved for 2000). It is proposed that abstractions from the major aquifer would be reduced starting in 2003/4 to alleviate low flows in the Churn.

9.168 In the past, sections of the river have dried up during summer months. The most notable example of this was 1995 when the river upstream of Siddington Bridge dried up and a major fish rescue had to take place. Surveying the following winter was also compromised by low flows in the river. Ecology of the river was severely affected by the low flow situations and surveys in 1997 indicated that fish stocks were recovering but had been eradicated during the drought in 1995.

9.169 The river is classified as an "ordinary river" within the study area (i.e. not a "main" river).

9.170 Approximately one third of the tunnel (approx. 0.9km) would pass through the aquifer. Localised dewatering would be required to facilitate construction which could potentially have a large adverse impact on groundwater. Post-construction, there would continue to be some disruption to groundwater flows, particularly to the west of the tunnel bores.

9.171 On the lower slopes of the escarpment, a thin layer of unstable landslip material is present and is highly permeated by water from natural springs. Construction of the tunnel at the lower end would again require localised dewatering to stabilise the ground. This would result in short to medium term disruption/diversion of water flows. This could potentially impact on the Minor Aquifer located in the Vale of Gloucester to the west.

9.172 Post-construction, water could be redirected into streams and other watercourses which would lessen the overall magnitude of impact.

9.173 Mitigation measures could be put in place to minimise some of the impacts. These would include the following:

9.174 On the basis of the information available on the likely design and construction of the tunnel, the overall assessment of impacts from this option is considered to be Large Adverse. Significant amounts of additional site investigation and assessment would have to be undertaken on this option such that the actual potential for impact can be identified and suitable mitigation measures designed, if possible.

Physical Fitness

9.175 The Air Balloon Roundabout is the cross over point for the Cotswold Way and Gloucestershire Way long distance footpaths. It is unknown at the time of writing how many walkers use these routes. At present, pedestrians, cyclists and equestrians have to cross the existing road at grade. Construction of the tunnel would divert about 70% of traffic off the existing road at this location although safe crossing points would still be required to improve the safety of the current arrangements. This would result in a Large Beneficial impact.

Journey Ambience

9.176 The tunnel would provide a direct link between Cowley and the Brockworth bypass avoiding a number of junctions including the Air Balloon Roundabout. Additional speed and route signage would improve information available to drivers. However, as most of the new road would be within the tunnel travellers views to the surrounding high quality environment would be restricted. The overall assessment is therefore considered to be Slight Beneficial.

SUMMARY COMPARISON OF OPTIONS

9.177 Each of the options has been assessed individually with GOMMMS Appraisal Summary Tables produced for each. Table 9-7 presents a summary of the AST scores for each GOMMMS objective showing the overall comparison of the options.

9.178 There is no defined means of combining individual scores within the AST to give an overall score or rating for a given option. This is because the weightings applied to individual components e.g. landscape, economics, safety etc. are not directly comparable. However, a very simple indication of the overall acceptability or otherwise of a series of options can be gained by looking at the number of adverse, neutral and beneficial scores. In Table 9-7, the scores for each environmental objective in each option have been shaded to highlight which option is better or worse. Bold text in a box with heavy border shading indicates a comparatively poor score, bold text a fair score and normal text a good score.


9 environmental appraisal of options

10 waste management

10 WASTE MANAGEMENT

10.1 All three options would generate excess material, which would be required to be removed off site for re-use, recycling or disposal. The following text discusses the potential amounts that may be generated. These figures are preliminary at this stage and would be modified as detailed design is undertaken.

Option 2 -On-Line with Grade Separated Junction at Air Balloon

10.2 Initial considerations of earthworks for this option indicate the following:

10.3 Overall, the scheme would generate a surplus of excavated geological materials that would be classified as waste if they are not used on the scheme. Much of this material would have a commercial value, but whether suitable uses are available at the same time as the material is unknown and the effect on other local businesses quarrying or selling stone would have to be assessed. Local Authorities have pointed to the Cotswold Water Park and their requirement for surplus material for quarry restoration. It is possible that restoration of one of these quarries using excavated materials would be exempt from Waste Licensing Regulations (see restrictions on exemptions in Table 10-1). The amount of fill allowed would depend upon the end-use. If the quarry site were to be restored to agriculture, then a layer up to 2m deep could be deposited under the exemption. if buildings or other end-uses were considered, the volumes exempt would be unlimited for inert waste. Discussions with the Cotswold Water Park Society have indicated that it is likely that local mineral operators could accept the waste so long as the material meets certain criteria, and that transport routes could be agreed with local authorities. The acceptance criteria on wastes to be deposited are imposed by the Environment Agency. They include that the material should be highly permeable (so that it does not affect groundwater flow or recharge, and that it should be clean. The majority of surplus material generated in Option 2 should meet these criteria.

10.4 At present it is not possible to confirm if such a route would be available for the re-use of waste materials produced on the scheme at the time it arises. If it were, then disposal costs would be significantly reduced and would then comprise mainly transportation costs (in the order of £15-£20 per cubic metre at 2002 prices). It is recommended to re-visit this possibility at a later date when the time that wastes would be generated is better understood and when planning for the Cotswold Water Park is more defined.

Option 1 - On-line with Signalised Junction at Air Balloon

10.5 The change in junction type at Air Balloon Roundabout would have very little difference in terms of the wastes produced over Option 2. The re-arrangement of the existing roundabout would mainly be at grade with only a small requirement for levelling to be undertaken.

10.6 As with Option 2, there would be a small requirement for material to widen the Birdlip bypass. This would be provided from the material cut from the new Birdlip access slips and from the Nettleton (Cowley) cutting.

10.7 As with Option 2 the proposed new Nettleton bypass would pass through cutting. The design of this element of the scheme is identical to Option 2. This element would generate a large surplus of high quality limestone's which would have to be disposed of or sold commercially. The discussion in option 1 on possible other re-use options also applies to this option.

Option 3 - Tunnel Option

10.8 The tunnel option would generate significant additional volumes of waste materials over Options 1 and 2. These would be generated from the excavation of the two tunnel bores, the 27 interconnections between the bores, and the creation of two portal faces. Initial calculations have indicated that approximately 950,000 m3of material would be excavated during the construction of the tunnels. The upper 34% of the tunnel length would be through hard limestone (329,500 m3). This material would be mined, and the majority can be re-used. For the purposes of this study it has been assumed that 90% can be re-used, either on the site or sold for off site use. Uses on-site 90 include as aggregate in construction, road base or mixed with concrete to enable the portal faces to "mature" or weather with age. In addition, this material can be used in landscaping and for dry stone walling to define field boundaries where this fits in with the local landscape. The remaining 10% would be treated as waste material. Further geotechnical investigation, however, may show that some of this material may have a commercial use. Such commercial uses could be:

10.9 The lower 66% of the tunnel length passes through clays and a mixture of slip material (619,560 m3). The use of this material on the scheme would be limited due to the small areas available for landforming and landscaping and for the creation of the header reservoir to hold fire water. For the purposes of this study it has been assumed that 25% can be re-used, although this figure would have to be confirmed once a detailed engineering and landscape design and a detailed geotechnical survey has been completed. The remaining material would be classified as waste, even if alternative uses off-site are identified. Such re-use or recycling could be undertaken so long as appropriate schemes are occurring at the same time, as the material becomes available. Such re-use schemes would have to take into account the nature and physico-chemical properties of the materials, and some uses may only be possible following processing and re-use. Re-use options could include:

10.10 The likelihood for such uses being available at the time of generation cannot be confirmed at present. It is highly likely that a proportion of this material can be re-used on other sites given that certain business sectors have a constant need for such material. The longer period over which materials are generated during tunnel construction (when compared with on-line options) would assist in this respect, as the local market for such materials would be less likely to be swamped with such material. It would be important to use local re-use schemes rather than transport the material over great distances. The Cotswold Water Park may be one such opportunity. Discussions with the Cotswold Water Park Society have indicated that it is likely that local mineral operators could accept the waste so long as the material meets certain criteria, and that transport routes could be agreed with local authorities. Acceptance criteria are placed on wastes to be deposited and these are imposed by the Environment Agency. As discussed previously, they include that the material should be highly permeable (so that it does not affect groundwater flow or recharge, and that it should be clean.

10.11 In addition to the material generated by the excavation of the tunnel, Option 3 also includes the first half of the Nettleton (Cowley) cutting as discussed in Options 1 and 2. This potentially could generate over 150,000m3of material. However, the potential for re-use on the scheme is smaller than in either option 1 or 2 as the requirement for the widening of the Birdlip bypass is removed. The majority of this material would, therefore have to be sold or disposed of.

10.12 As for Options 1 and 2 the potential for material to be used in local remediation activities exists. Local Authorities have pointed to the Cotswold Water Park and the requirement for surplus material for quarry restoration. It is possible that restoration of one of these quarries using excavated materials would be exempt from Waste Licensing. The amount of fill requiring disposal would be considerably larger than in Options 1 and 2, and the amount allowed to be re-used would depend upon the end-use. Discussions have indicated that this may be a potential route for disposal of the permeable material generated (the limestones). However, the clays in the lower 66% of the tunnel are unlikely to meet the Environment Agency acceptance criteria, and therefore would still have to be removed for disposal elsewhere. At present it is not possible to confirm if the Water Park is a route available for the re-use of some of the waste materials produced on the scheme, especially given the greater quantities generated over Options 1 and 2. If it were, then disposal costs would be significantly reduced. It is recommended to re-visit this possibility at a later date when the time when wastes would be generated is better understood.

10.13 Without re-use, disposal costs could be in the order of £30-50 per cubic metre (2002 prices) assuming local disposal locations are available. With re-use, the disposal costs would only involve the transport element of the cost. This could be in the range of £15-20 per cubic metre (2002 prices) depending on the bulking factor achieved and the distance travelled. These costs would have to be revised once the timing of arisings is better defined, more information on the waste materials is gathered, and the availability of disposal options known.

10.14 Transport of the waste material off-site also potentially causes problems. Initial estimates, based on a construction period of one year, suggest that up to 1,000 truck loads per week would be required to transport surplus material off-site. Taking into account vehicle movements to the site, this would result in up to 2,000 HGV movements per week, all of which would have to use the existing A417. The potential for increased congestion is thus not insignificant. Taken over a longer period, say 3 years, this would still generate in the order of 650-700 HGV movements per week.

10.15 Depending on the availability of disposal sites to take the material, it is likely that there would be a need for storage compounds on-site which could be substantial in size. These would generate their own environmental impacts including landscape and visual, as well as the potential for surface water run-off to nearby streams and to groundwater. These impacts would need to be assessed once the likely phasing of construction are known.


10 waste management

11 public open day

11 PUBLIC OPEN DAY

11.1 In order to inform the public and interested parties of the study purpose and the results of the study, Public Open Days were held on 15th/16th February 2002 at Birdlip Village Hall, Gloucestershire.

Information Presented

11.2 Information on the study was presented on nine display panels. These are identified in Table 11-1.

Table 11-1 Public Open Day Panels
Public Open Day Panels
  • Welcome
  • Study Purpose
  • Environmental Issues
  • Environmental Constraints
  • Water and Geology
  • Options Considered
  • Option Assessment
  • What Happens Next

11.3 Members of the project team from WSP and the Highways Agency were present on both days to answer questions from the public and discuss issues and concerns raised.

11.4 On 15th February the public viewing session was from 12:00 noon until 8:00pm. Between 11:00am and 12:00 noon there was a preview session for invited guests, Councillors, local MPs and the media. The open day was from 10:00am and 4:00pm on 16th February.

11.5 Total attendance was a total of 224 people visiting over the two days.

11.6 The first day was the best attended with 143 people. This includes the invited guests for the preview session. The second day attracted only 81 visitors.

11.7 Over the two days representatives of local authorities and statutory/non-statutory bodies visited the display. These are detailed in Table 11-2.

Table 11-2 Local Authorities and Non-Statutory Bodies Visiting the Public Open Day
Local Authorities and Non-Statutory Bodies Visiting the Public Open Day
  • Elkstone Parish Council
  • Coberley Parish Council
  • Winstone Parish Council
  • Great Whitcombe Parish Council
  • Churchdown Parish Council
  • Shurdington Parish Council
  • Caudle Green Parish Council
  • Badgeworth Parish Council
  • Gloucestershire County Council
  • Tewkesbury Borough Council
  • Cotswold District Council
  • Environment Agency
  • Countryside Agency
  • Cheltenham Borough Council
  • Cotswold Way National Trail
  • CPRE Gloucestershire
  • Cotswold Archaeological Trust
  • Cheltenham Ramblers Association
  • South West Transport Network
  • National Trust Severn Region

Issues Raised

Rat-Running

11.8 Concern was raised by a number of people about rat-running through the villages e.g. Elkstone, Winstone and Brimpsfield. One member of the public provided a schedule of the traffic numbers passing through Brimpsfield during a peak period i.e. Friday afternoon/evening. Another visitor suggested that the people most concerned about the current situation are those who have moved to the Cotswolds from London and elsewhere in search of a rural idyll and are now unhappy to see cars on country roads.

Access

11.9 Concern was expressed by a number of local residents regarding the safety issues associated with access to Cold Slad Lane. Options 1 and 2 increase the number of lanes on Crickley Hill. These were considered by residents as making the situation worse unless a safe junction could be provided.

The Tunnel Option

11.10 Few people attending the open day openly expressed a preference for the tunnel option. Most people expressing an view felt that it was unrealistic and too costly. Some felt that this was simply a case of "out of sight, out of mind" as objectors wanted to see less traffic on the road. It should be noted, however, that most of the responses received following the Open Day have been pro-tunnel.

11.11 Several people suggested that the "Option Assessment" display panel was biased against the tunnel option. They felt that the issue of impacts on the underlying aquifer and the need for dewatering the escarpment slope were not as important as suggested and that with enough money, these could be overcome. Others could not understand why the assessment for the tunnel concluded a Severe Adverse Impact on the AONB.

11.12 Those who did express support for the tunnel pointed out that a reduction in the gradient compared to that on Crickley Hill would be an advantage and there would be benefits in times of severe weather (snow) as the A417 has had to be closed in the past due to snow drifts.

Corridor Options

11.13 In general, most support appeared to be for the re-modelling of the existing A417 with improvements at the junctions. Most people seemed in favour of dualling the road and felt that it was better to widen the existing road rather than building new roads.

11.14 Concern was expressed by the resident of The Rise at Stockwell about that potential noise and visual impacts related to the offline section around Nettleton.

11.15 The recent improvements at Birdlip Junction were commented on by a number of people. Whilst some felt this had improved the situation, others felt it was now even more difficult to negotiate and the road markings are confusing.

11.16 Several visitors felt that the proposed changes under Options 1 and 2 would do nothing to improve the situation.

11.17 This was not a formal public consultation exercise and hence, there were no questionnaires or other means of obtaining detailed feedback from the public. However, on the basis of the discussions held with team members, there appeared to be general support for the corridor options rather than the tunnel. Nonetheless, this should not be viewed as an endorsement of any particular option. The tunnel concept does have the support of 11 parish councils and two local authorities.

11.18 Since the open days, WSP and the HA have received letters from various Parish Councils and members of the public expressing their views. These have been replied to and included in a report on the Public Open Day. A summary of the views expressed is given in Table 11-3. They are mostly pro-tunnel. The issue mentioned most often is the suggestion that the open day was too biased against the tunnel option. The second was pollution (and noise) issues related to surface options (Options 1 and 2).

Table 11-3 Summary of views expressed on the Public Open days
View Expressed/Issue Raised Number of Organisations/individuals Expressing View
Bias against the Tunnel Option 4/11
Bias Towards Option 2 0/1
Support for the tunnel option 4/16
Impact on footpaths 0/1
Noise from above ground options 1/2
Pollution from above ground options 1/6
Visual Impact of above ground options 0/1
Unacceptable visual impact of Option 2 on Crickley Hill 1/2
Safety concerns over the slope of Crickley Hill (options 1 and 2) 2/3
300° turn for A417 at Air Balloon-Safety Issues 1/0
Impact of slow moving traffic up Crickley Hill on local residents/environment 1/0
Visual Impact of widening/modifying lanes on Crickley Hill 1/0
All options Unacceptable 3/0
Adverse impact from Option 3 1/0
Impact on A436 insufficiently considered 0/1
Alternative Option Provided 1/3
Issues with weather on Crickley Hill 0/3
Safety at Birdlip junction 0/1
Concern over safety of a tunnel 2/0
Safety of additional lanes on Crickley Hill 0/1
Support for Option 2 1/0

11 public open day

12 responses from statutory and non-statutory consultees

12 RESPONSES FROM STATUTORY AND NON-STATUTORY CONSULTEES

12.1 This chapter presents responses received from the environmental statutory consultees and key non-statutory bodies. Formal responses (where received) are provided in Appendix E.

Responses From Statutory Consultees

Countryside Agency

12.2 The Countryside Agency (CA) does not, at this stage, rule out any of the options being taken forward for further consideration. They do, however, have some concerns and have requested more information on certain issues. Their views are summarised below:

12.3 On a general note, the CA would like to see more details of the access arrangements for pedestrians, cyclists and other non-motorised users. They believe there is potential for significant gains.

12.4 Their final comment is on the potential impact of de-trunking the A40 and upgrading the A436 which, they believe, is likely to increase traffic at the Air Balloon junction. They have sought assurances that this has been taken into account as part of the current assessment.

English Nature

12.5 On a general note, English Nature highlight the proximity of SSSIs to the three options and the fact as a public body, the Highways Agency has a duty to take reasonable steps to further the conservation and enhancement of SSSI's when exercising their functions. They also note that as all the options could lead to loss or fragmentation of non-SSSI habitats and features. They would expect to see appropriate mitigation and habitat creation.

12.6 On the specific options, their comments are as follows:

English Heritage

12.7 English Heritage recognise the need for a long term improvement scheme on this stretch of the A417 and accept that any scheme is likely to have some environmental impact. They have no objection in principle to any of the three options being considered but do have some concerns. These are summarised below:

12.8 EH are content with the assessment carried out to date and generally agree with the findings. From their perspective, a tunnel would have the least impact on historic resources by virtue of the fact that the majority of it will be well below ground.

Environment Agency

12.9 Throughout discussions held with the Environment Agency which have been based on the available information, they have expressed serious concerns over the potential impact of dewatering for the tunnel option on the Major and Minor Aquifers underlying the study area. They consider that a considerable amount of further investigation and detailed design would be required for them to reconsider the potential 'high risks' of a tunnel option.

12.10 They continue to maintain their objection to the tunnel option because of the potential impact on water resources and nature conservation interests.

12.11 A summary of their views on all of the options is given below.

The Agency therefore objects to the tunnel pending further information on the short and long term impacts on:

12.12 In addition to the above issues, the EA have provided general guidance on various issues including the need for appropriate pollution control equipment to be provided and consent requirements for different works.

Responses from Non-Statutory Consultees

National Trust

12.13 The Trust is concerned not only with impacts on land owned by them but also on the wider environment and would seek to ensure there is an overall environmental benefit from 'doing something' as opposed to leaving things as they are. Their overall opinion is that all three options could be taken forward for more detailed design and assessment.

12.14 With respect to the individual options, their main comments are as follows:

Gloucestershire Fire & Rescue Service

12.15 The general view of the fire and rescue service is that Options 1 and 2 would still have accident, fire and rescue issues whilst the tunnel option would be unacceptable. In order to provide adequate fire and rescue services a dedicated fire station would be necessary at the tunnel with rescue vehicles located at each end. They believed that this would add to their already stretched capabilities and that without Government funding they would be unable to provide and maintain such a dedicated service. Given the choice between a tunnel and leaving the road as it is, they would prefer the latter.

Gloucestershire Constabulary

12.16 Similar concerns to the fire and rescue service were raised. For options 1 and 2, they felt these had merits as they are 'open air' roads and as such could be policed using conventional methods and resources. However, they did have concerns about tight radius turns on the grade separated junction and were uneasy about the provision of additional lanes down Crickley Hill.

12.17 With regard to the tunnel option, they expressed serious concerns particularly over the need to provide a dedicated service in conjunction with the Fire and Rescue Service. Despite the reduction in gradient, they felt that breakdowns would still be common (particularly HGVs) and rescue and recovery services within the confines of a tunnel would be very difficult. The potential for a large number of vehicles to continue using the existing A417 instead of the tunnel due to perceived safety concerns by drivers was cited as another concern.

12.18 Finally, it was stated that unless Central Government provided funding up front for the maintenance of the service, then the burden on local taxpayers would likely outweigh the benefits. The tunnel would "become an immense 'millstone' around the necks of the emergency services, both financially and operationally."

Gloucestershire County Council (GCC)

12.19 Gloucestershire County Council have indicated support for all options to be taken forward for further consideration. They agree that a long term solution to the "Missing Link" is necessary but that any scheme must be deliverable.

12.20 They do have concerns about the effectiveness of Option 1 as it represents only a short term improvement. It also performs poorly on safety. GCC have expressed real concerns over the deliverability of a tunnel given the total cost of the scheme and the very low cost-benefit ratio. Other concerns relate to the potential impact of a tunnel on the Major Aquifer and the waterfed SSSI.

12.21 Option 2 is generally seen as a more deliverable long term solution although concerns have been raised over the potential visual impact of adding the two new lanes down Crickley Hill. GCC have asked if this option would remain viable if one lane were added down Crickley Hill (retaining the two lanes up) as in Option 1.

Cheltenham Borough Council (CBC)

12.22 CBC's views on the 3 options were similar to Gloucestershire County Council in supporting the need to consider all of them further.

Tewkesbury Borough Council (TBC)

12.23 TBC has resolved to support a tunnel option for this stretch of the A417. In the view of TBC officers, the current assessment reinforces their position in view of the comparative impacts on the local communities and the Cotswold landscape. They feel that Option 1 is of questionable value given the short time period predicted by which it would reach its design capacity. TBC are also concerned as to what evidence has been provided of the potential adverse impact of a tunnel on the aquifer as they understand this has been challenged by other parties. It is also noted that there is continued concern among TBC Members about the potential impact of proposals to de-trunk the A40 which is likely to direct additional traffic onto the A436 and down to the Air Balloon roundabout.

Cotswold District Council (CDC)

12.24 CDC strongly support a tunnel and see it as the only option to solve all the problems associated with this stretch of the A417. Whilst agreeing with a number of the key issues identified during this study, they have questioned whether or not the potential impacts would be as significant as suggested. Issues related to the potential impact on the Major Aquifer and the re-use/disposal of excavated material are considered by CDC to be relatively simple to resolve. The high construction cost of approximately £200 million is not considered to be a problem if the tunnel would ease congestion and improve safety on the A417.

Cotswold AONB Partnership

12.25 The AONB Partnership have highlighted concerns over the potential visual impact of any scheme and reiterated the need to maintain the integrity of the Cotswold AONB.

Parish Councils/Missing Link Action Group

12.26 Eleven local Parish Councils have formed a group known as the "Missing Link Action Group" to campaign for a tunnel. They see a tunnel as being the only viable solution. The Highways Agency and WSP have met the group on two occasions (November 2001 and March 2002) to discuss the potential options and concerns they have. One of their main concerns has been the problem of 'rat-running' through the villages by vehicles trying to avoid congestion at Nettleton and the Air Balloon. In their view, on-line options would not resolve this problem.


12 responses from statutory and non-statutory consultees

13 conclusions

13 CONCLUSIONS

13.1 A process of option development and assessment has been undertaken for the remaining section of single carriageway road on the A417 between Cowley roundabout and the Brockworth bypass.

13.2 This has included technical reviews and discussions with statutory environmental consultees, non-statutory bodies, local interest groups, Parish Councils and others. From this process three possible improvement options have been identified. These are:

13.3 All statutory and non-statutory bodies consulted agreed that doing nothing is not viable and that the current road needs improvement. There has also been general agreement that the current situation has had an adverse impact on the local economy.

13.4 The Study Area contains:

13.5 All three options are buildable. Option 3 would cause the least disruption during construction as the majority of the work would be undertaken offline. Of the two surface options, Option 2 would cause less disruption to vehicle flows up Crickley Hill. However, remodelling of the Air Balloon roundabout under both Options 1 and 2 would cause major disruption to vehicle flows during construction.

13.6 Retention of carriageways on Crickley Hill in Options 1 and 2 would mean that the existing steep gradients (in the order of 10%) would remain. The tunnel would have an average gradient of 4.4%.

13.7 Option 1 would require departures from standards, however, there are safety concerns with the signalised junction which cannot be overcome by careful detailed design and for this reason Option 1 is not considered viable. Departures from standards would be required on Option 2 but safety would not be compromised. Option 3 would not require departure from standards.

13.8 Temporary contractor camps would be required for all three options, although these would be larger for Option 3. Option 1 would take less than 2 years to construct, Option 2 would take approximately 2.5 years, and Option 3 more than 3 years (depending on hydraulic conditions encountered).

13.9 It is anticipated that only Option 2 would have a severe impact on properties.

13.10 Both the fire service and police have concerns over Option 3.

13.11 Waste material from excavation work would be generated by all three options, with Options 1 and 2 generating in excess of 300,000 m3 and Option 3 over 1.1 Mm3. Under Options 1 and 2, a large proportion of the material could be re-used within the scheme for landscaping, fill and/or embankments. For Option 3, re-use of waste material within the scheme would be very limited and restricted to the areas around the tunnel portals. The majority would need to be disposed of off-site. It is possible that re-use options may be available e.g. for quarry restoration at the Cotswold Water Park, although quantities would be small because of the restrictions placed on material suitability by the Environment Agency. This issue would have to be considered in more detail in the detailed design phase.

13.12 The preliminary economic assessment undertaken has identified that all options provide positive Net Present Values (NPV's) on the high growth scenarios. In addition, Options 1 and 2 shown positive NPV's for low growth scenarios. Under the low growth scenario, Option 3, the tunnel option, exhibits a negative NPV and under this scenario it would not be viable.

13.13 All three options contribute timesavings and accident reductions. With Option 1 the accident reductions are suppressed because they do not reflect the safety concerns on certain aspects of the layout.

13.14 Option 1 would be the least expensive option at approximately £40 million, but has the least benefits and would only represent a short to medium term improvement for congestion relief. Option 2 represents best value for money as it has the highest NPV's and Benefit/Cost Ratio. This option would cost in the region of £60 million. Option 3 has the highest benefits but is also the most expensive at approximately £200 million.

13.15 Geotechnical and hydrogeological issues are important and affect all three options. Particular issues include the underlying Major Aquifer and the presence of landslipped material along the escarpment slopes and valley sides. Detailed geotechnical site investigations and groundwater modelling would likely be required in the next stage of the project.

13.16 The in-situ soils and rocks over this section of the study area are masked by a mantle of landslipped and soliflucted materials derived from the underlying lithologies.

13.17 The hydrogeology of the route is complex and would be dominated by the variations in natural strata together with the history of slope failures along the escarpment slope. A number of springs and areas of artesian or near-artesian groundwater pressure are recorded within the area reflecting the impact of both topography and the previous landslipping.

13.18 For on-line widening, existing slope angles should be employed, wherever possible.

13.19 Toward the eastern end of the route, the presence of the Crickley Hill SSSI restricts the widening options to the north of the existing carriageway. To maintain existing slopes benching details would require the removal of a large part of the slope. Widening is, therefore, likely to be restricted to an anchored wall over the lower parts of the slope.

13.20 Environmental and geotechnical constraints limit what can be achieved on Crickley Hill under Options 1 and 2. Widening to the south of the existing carriageway, using a series of retaining measures, over the section beneath Crickley Hill SSSI would alleviate the need to cut into the toe of the slope to the north of the carriageway. The use of a split-level carriageway in Option 2 would reduce loading on slopes and, therefore, reduce any destabilising effects of the widening works. Further culverting or realignment of the stream would be required should a southern widening option be taken forward. As a result of the recorded artesian groundwater pressures in this area, a drainage blanket (together with other slope drainage measures) would be required beneath any earthworks to ensure dissipation is achieved.

13.21 The slopes below the escarpment have been demonstrated to be only marginally stable. Preliminary analysis would suggest that maximum cut slopes of 1 in 3 are required for slopes less that 2 metres high and flatter slopes are required for cut slopes greater than 2 metres high. A reinforced soil slope or use of soil nailing may provide a suitable solution for cut slopes greater than, say 2.5 metres. However, a detailed ground investigation would be required in order to check that the cut would not reactivate historic failure of a slope.

13.22 It is anticipated that, in their present condition, the Crickley Hill colluvial deposits would be unsuitable for re-use as structural engineering fill without some form of improvement. However, where fill materials derived from the colluvial deposits are to be used, maximum side slopes of 1 in 3 should be assumed for preliminary design purposes for embankments greater than 2m high. Using imported fill materials embankment side slopes of 1 in 2 would appear suitable up to a maximum height of 2 metres. For embankment slopes greater that 2 metres in height, slope reinforcement would be required. However, this is dependent upon the founding material and would require a detailed ground investigation. Partial removal and replacement of materials together with deep drainage measures may provide a more stable design. The use of lightweight fill, such as PFA or even polystyrene, may be considered to increase embankment heights. However, the environmental implications of using PFA should be considered at preliminary design stage together with implications of using polystyrene adjacent to the stream.

13.23 It is likely that cut slopes would require drainage in the form of deep toe or counterfort drains and embankments may require drainage blankets together with reworking of shear zones. The use of strengthened basal zones to embankments may also be considered.

13.24 Environment Agency approval would be required for the culverting of the stream where the off-line options are carried on embankment across the valley. A low bridge / viaduct may need to be considered depending upon the Environment Agency's response, together with consideration of the most cost effective engineering solution in order to ensure adequate performance of the earthwork.

13.25 Various improvement options are available for the section of the route below the escarpment, although these are constrained by existing slopes close to the Air Balloon Roundabout. Each option would affect the valley slopes to a varying degree by cutting and/or filling. At this stage and in light of the uncertainties regarding depth of potential failure surfaces, groundwater pressures and soil properties, further investigation would be required to geotechnically assess the feasibility of each option.

13.26 Towards the base of the valley it would be advantageous for any route to use low embankment wherever possible in this 'near toe' situation avoiding cutting into previously unstable ground. However, for widening works on the higher valley slopes, embankments may have a less beneficial effect and may possibly be destabilising. Careful assessment of proposed horizontal and vertical alignments would, therefore, be necessary to optimise the performance of new earthworks.

13.27 An environmental appraisal of the three options has been undertaken using the GOMMMS methodologies.

13.28 In terms of landscape, Option 1 would have a moderate adverse impact on the AONB and landscape character, whilst both Options 2 and 3 have large adverse impacts, the latter due to the link roads and portals.

13.29 Cultural and archaeological resources within the study area are very important. Options 1 and 3 are predicted to have slight adverse impacts whilst Option 2 is predicted to have a moderate adverse impact, mainly due to its affect on the context of Crickley Hill.

13.30 The two surface options largely avoid nationally and locally designated ecological sites. However, dewatering for the tunnel may potentially severely affect Bushley Muzzard SSSI which relies on spring water. It is possible that mitigation measures could be designed to minimise impact. However, given the high level of risk, a very serious adverse impact has been predicted for Option 3.

13.31 Water is a major issue in the study area and has had a major impact on previous schemes in the study area. Options 1 and 2 are such that mitigation measures could be added so that the long term impact on the ground and surface water regime would be slight adverse. However, considerably more doubt exists about the potential impact of the tunnel and the Environment Agency have serious concerns. The tunnel option, therefore, has a large adverse impact score.

13.32 Options 1 and 3 are anticipated to slightly improve journey ambience whilst loss of facilities in Option 2 lead to a neutral impact prediction. In terms of physical fitness, Options 1 and 2 are scored as slight beneficial whilst Option 3 is scored as large beneficial.

13.33 In terms of local air quality, Options 1and 2 lead to increases in localised air pollution. Under Option 3 overall local air quality would improve, although the pollutants would be concentrated at the tunnel portals. Both Options 1 and 2 also lead to an increase in the release of greenhouse gasses, whilst the tunnel option leads to a decrease in greenhouse gas emissions.

13.34 Up to 29 properties would experience an increase in noise levels under Option 1 and 4 properties would experience a decrease in noise levels. Under Option 2 up to 32 properties would experience an increase and 6 a decrease in noise levels. Under Option 3, 12 properties would experience an increase in noise and 37 a decrease.

13.35 A summary of the overall scores for each option is shown in Table 13-1.


13 conclusions

14 recommendations

14 RECOMMENDATIONS

14.1 Discussions with statutory and non-statutory bodies in the area have shown there is a need to improve the single carriageway section of the A417 trunk road. The study has been a pre-investment study which has aimed to identify if there are route improvement options which can be developed which do not have unacceptable environmental consequences and which can be supported by statutory environmental bodies. This study has been completed and three options have emerged from the process. Each has passed through an initial screening and "optioneering" process. This identified in broad terms that they met the study criteria and merited further assessment. This assessment has considered whether the options:

14.2 In environmental terms all three exhibit a mixture of potentially beneficial and adverse impacts. This is to be expected given the environmental sensitivity of the area, and the history of proposed improvements on this section of trunk road.

14.3 All three options need further design (vertical and horizontal alignments) and for more detailed traffic modelling to be undertaken. Results of this Stage 2 assessment would identify a preferred route. The recommendations which follow identify which of the options should be taken forward and identify where specialist environmental or geotechnical assessments will have to be undertaken.

14.4 Discussions with statutory environmental consultees have confirmed that all three options could proceed to the next stage in planning and design, albeit with a recognition that all of them require additional, more detailed, design and environmental assessment.

14.5 However, whilst no 'environmental showstoppers' have been identified for Options 1 and 2, there has been for Option 3, the tunnel. Discussions with the Environment Agency, English Nature and other bodies have identified serious concerns about Option 3, the tunnel, and the potential impact on the groundwater regime. At this stage the available information indicates that further detailed assessment of this option is unlikely to provide sufficiently conclusive data regarding the risks to the groundwater regime to permit the Environment Agency to remove their existing objection. At this stage it is sufficient reason not to take this option forward.

Option 1

14.6 Whilst it is recognised that this option is buildable, economic and provides some congestion relief, it does not provide a long term solution for road borne traffic within the study area due to limited capacity at the Air Balloon junction. In addition, there are serious concerns over safety on certain aspects of the layout which could not be overcome by careful detailed design. Although this option would improve the majority of the route the Air Balloon junction would continue to be a bottleneck and present safety problems. Whilst detailed design and modelling may be able to extend this congestion-free period by a few years, it is unlikely to provide a long term solution or overcome the safety concerns This option therefore fails to meet 2 of the main tenets of this study.

14.7 Of the options considered, Option 1 would result in the least environmental impact, would be quickest and cheapest to construct but also would provide the least benefit.

14.8 From the discussions held with the statutory environmental consultees, it was evident that further consideration of certain aspects would be required. In particular, the impact of the restructured Air Balloon Junction, the link roads on Crickley Hill and the proposed bypass of Nettleton were identified by the Countryside Agency and National Trust as being of importance. Lighting and landscape proposals would need significant input at these locations.

Recommendation

14.9 Consideration of the safety concerns, the limited lifetime of the scheme and the limited environmental benefits mean that Option 1 is not recommended to be taken forward for further design and assessment.

Option 2

14.10 Work completed to date indicates that this option is viable and provides a long-term safety and capacity improvement for road based traffic within the study area. It also offers the opportunity to provide improvements to non-motorised users in terms of access across the road particularly for the National Trails.

14.11 The pre-investment assessments have identified potential environmental impacts could occur and discussions with statutory environmental consultees have identified similar issues to Option 1 with regard to Crickley Hill, the Air Balloon and Nettleton. However, it has been recognised that relocation of the Air Balloon roundabout and grade separation offers potential opportunities to reduce the existing lighting impact at Air Balloon, especially with regard to Crickley Hill and the top of the scarp slope. The anticipated impacts can only be defined after a sensitive design is developed and agreed with key stakeholders in the process.

14.12 The bypass around Nettleton would also require sensitive design and assessment if unacceptable impacts on the AONB are to be avoided. Landscaping will be the key issue at this location.

14.13 Impacts on local air quality and noise and land-take issues will have to be addressed and mitigation measures designed if these are to be acceptable to local residents. However, it is believed that some of these can be reduced during detailed design and suitable mitigation measures designed once the type and quantum of impact are fully identified.

Recommendation

14.14 Discussions with statutory environmental bodies have confirmed that subject to further work this option can be taken forward for more detailed design and assessment. It is therefore recommended that this option be taken forward.

14.15 Options 1 and 2, as tested in this report, are either ends of a spectrum with regard to Crickley Hill and Air Balloon roundabout. Option 1 endeavours to maximise the utilisation of land within the existing highway boundary for the improved carriageways and involves the re-alignment of the existing lanes up Crickley Hill to provide two lanes up and two lanes down the hill. Option 2 is the opposite end of the spectrum requiring minimal interference with the existing carriageway and the provision of two new downhill lanes on Crickley Hill allowing a "three up and two down" option. The "two-up and two down" option with the grade separated roundabout option has also been considered and shown to work, therefore it is recommended that this alternative to Option 2 should also be tested using a detailed traffic model in the next stage.

Option 3

14.16 The assessment carried out to date on this option indicates that it is buildable, relieves the pressure on Crickley Hill and the Air Balloon roundabout and provides long term local safety and environmental improvements. Tunnel costs, however, cancel out the economic benefits so that it is on the border line of a viable scheme. Also, discussions with the environmental statutory bodies, and the Environment Agency in particular, have raised serious concerns about the potential impact on the underlying major aquifer. Both the police and fire services have raised additional safety concerns.

Recommendation

14.17 Whilst concerns have been raised by all the statutory consultees, the Environment Agency has entered a holding objection to the tunnel, pending provision of more detailed information on the potential impacts on the local (and potentially regional) groundwater regime. All the statutory bodies are content that the option be assessed further but, to overcome their concerns, significant further work would be required.

14.18 The additional information required by the Environment Agency would involve a phased risk assessment, and potentially computer modelling, to more accurately assess the risks of tunnel construction on the major aquifer, groundwater abstractions in the area, the impact on the Baunton source and the River Churn and the numerous springs along the scarp.

14.19 Given the nature of the underlying geology, there is a real possibility that to accurately define and model the groundwater regime over such a wide area will prove so difficult and problematic that, even after completion of the significant additional work, it may not be possible to be definitive about the impact of the tunnel. It is uncertain that even following this additional work the risks to the aquifer could be reduced to a level that would be acceptable to the Environment Agency, and for them to remove their objection. In these circumstances, the Environment Agency would be unlikely to withdraw their objection and would hold the Highways Agency legally responsible should environmental problems arise during construction and operation of the tunnel The Highways Agency could not accept such a condition.

14.20 It is recommended that at this stage no further assessment of this option is carried out.


14 recommendations

Environmental study findings

Environmental Study Findings

BACKGROUND

Known locally as the 'missing link', the 3 mile stretch of the A417 from the Cowley roundabout near Nettleton Bottom to the eastern end of Brockworth Bypass has a poor safety record and queues occur regularly at peak periods. It is the only remaining single carriageway section on the A417/A419 route between the M4 (Jnc.15) and M5 (Jnc.11a) and carries over 30,000 vehicles per day, of which 14% are heavy goods vehicles.

This section of the trunk road lies in an area of particularly high environmental sensitivity and importance, being within the Cotswold Area of Outstanding Natural Beauty, with Sites of Special Scientific Interest and Scheduled Monuments close by. In August 2001, Ministers asked the Highways Agency to carry out an environmental study and examine the environmental effects of possible plans to improve the A417 between Cowley and Brockworth Bypass.

PUBLIC OPEN DAY

200 people attended the public open days held in Birdlip Village Hall in February last year, to view a display of the study findings and discuss them with the Highways Agency and WSP, the consultants appointed to carry out the study.

The open days indicated strong support for a major road improvement, and many local people expressed a preference for a tunnel.

PURPOSE OF THE BROCHURE

This brochure explains why Ministers have chosen to take forward an on-line improvement scheme (Option 2), and why it has been decided not to do any further work on Option 1 (on-line) or on a tunnel.

map

Environmental study findings

Environmental study findings

Environmental Study Findings

ILLUSTRATIVE TUNNEL CROSS SECTION

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View larger image

Environmental study findings

Environmental study findings

Environmental Study Findings

COMPARISON OF OPTIONS

Option 1

Between Cowley roundabout and the Air Balloon roundabout, the road would be widened to dual carriageway with a new section of road bypassing Nettleton Bottom. A modified junction at Birdlip would also be included.

Option 1 would modify the Air Balloon roundabout with traffic signals and provide an additional lane down Crickley Hill. This option has been discarded because:there are serious concerns about the safety of the proposed traffic signals on the Air Balloon roundabout.

Tunnel Option

A 2.8km tunnel from Nettleton Bottom to the bottom of Crickley Hill.

A tunnel would remove between 70% and 80% of vehicles from the existing trunk road, and overall the noise and air quality effects on adjacent properties would be improved. However, the existing road would have to be retained to maintain access to County roads and to provide an alternative route should the tunnel be closed in an emergency.

A tunnel would have a number of major drawbacks; it would:

There are so many disadvantages that it has been decided not to pursue a tunnel option further at this stage.

Option 2

Between Cowley roundabout and Air Balloon, the proposed improvements to the A417 are the same as Option 1. In Option 2, the A417 west of Air Balloon would be widened to provide three lanes up Crickley Hill and two lanes down it. The Air Balloon roundabout would be replaced with a two-level free-flow junction. The scheme cost is estimated at £60M.

Option 2 would provide a dual carriageway solution that would overcome the congestion and safety problems on this section of the A417. No unacceptable environmental effects have been identified, it provides good value for money and is deliverable. For these reasons, this option is to be developed further.

Detailed information about the Environmental Study is available in the Study Report.


Environmental study findings

Environmental study findings

Environmental Study Findings

WHAT HAPPENS NEXT

Following this announcement, work will begin to develop the design of Option 2 and undertake a more detailed assessment of the likely impact. The next key stage will be a public consultation later in the year to provide residents, other interested parties and organisations and members of the public with the opportunity to comment on more detailed proposals. Results of the public consultation will be detailed in a report which will be made available for the public. In deciding on the preferred route, the Minister will take into account all the views from the consultation. The announcement of the preferred route would be followed by the appointment of a contractor who will be responsible for the design process leading to the publication of detailed proposals in the form of draft statutory Orders and an environmental statement.


Environmental study findings

Environmental study findings

Environmental Study Findings

FURTHER INFORMATION

Further copies of this brochure are available from:

Jayne Arberry HighwaysAgency Temple Quay House Temple Quay Bristol, BS1 6HA Telephone (0117) 3728043 e-mail : jayne.arberry@highways.gsi.gov.uk

Hard copies of the A417 Cowley to Brockworth Bypass Improvement Study Report are available on request from Jayne Arberry at a cost of £15.00 to cover printing and processing.


Environmental study findings