Highways Agency - Safe roads, Reliable journeys, Informed travellers

Related pages

• Summary
• 1 introduction
• 2 traffic, congestion and safety issues
• 3 geotechnical issues
• 4 environmental constraints
• 5 option development
• 6 options considered further
• 7 engineering comparison of options
• 8 economic comparison of options
• 9 environmental appraisal of options
• 10 waste management
• 11 public open day
• 12 responses from statutory and non-statutory consultees
• 13 conclusions
• 14 recommendations
• Environmental study findings
• Environmental study findings
• Environmental study findings
• Environmental study findings
• Environmental study findings

A417 Cowley to Brockworth Bypass Improvement

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:

• environment;
• safety;
• economy;
• accessibility; and
• integration.

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:

• Noise;
• local air quality;
• greenhouse gases;
• landscape;
• townscape;
• heritage of historic resources;
• biodiversity;
• water environment;
• physical fitness; and
• journey ambience.

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:

• As part of the signalised roundabout, mitigation in the form of woodland planting (mostly beech), in conjunction with ground modelling, would be appropriate and in character with the landscape of the escarpment. Such mitigation measures at this location would reduce the visual impact from Moderate Adverse to Slight Adverse.
• Between the Air Balloon Roundabout and Parson's Pitch, mitigation could include ground modelling or false cutting, where appropriate, to help assimilate the route corridor into the landscape. New tree and hedgerow planting would also be appropriate, provided that the open, expansive character of the plateau landscape was not compromised. New planting would need to be designed to ensure that it could be successfully integrated with the local vegetation pattern and did not emphasise the line of the road. Mitigation at this locality is assessed as resulting in a change in visual impact for this section from No Change to Slight Beneficial and a change to the impact for pattern from Neutral to Slight Beneficial.
• To the east of Parson's Pitch, the impact of the embankment to the north of Nettleton would be difficult to mitigate. Gentle grading out of the embankment is unlikely to successfully mitigate the impact on landform, and may not be possible due to the level of landtake necessary. Furthermore, tree and hedgerow planting in this location, while helping to screen views of traffic, would not be in character with the valley, which is mostly devoid of vegetation.
• Either side of Nettleton Valley, mitigation would be more successful. Tree planting to the north/north-east of Birdlip Quarry could be linked to existing woodland and would therefore be appropriate. The use of false cutting at key locations could also be considered, especially if this would increase the cutting depth sufficiently to screen lorries.

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:

• The possibility of buried archaeology sealed under landslip deposits at Crickley Hill.
• The area to the west of the Air Balloon has not previously been subject to archaeological field evaluation.
• The proximity of the works at Air Balloon roundabout to Emma's Grove round barrows and their effect on their setting (SM 32381).
• The effect of the Air Balloon roundabout works on the setting of Crickley Hill (SM 40).
• The new underpass and access from Birdlip involves works in very close proximity to Barrow Wake Iron Age cemetery (SMR Glos 3807) and a possible round barrow site (SMR Glos 3806). Further evaluation would probably be required in this area.
• The widening of the Birdlip bypass intrudes upon an area of known prehistoric and Romano-British activity partly excavated in advance of the construction of the existing road (SMR Glos 7185; Parry 1998)
• The new road line between Nettleton and Stockwell passes through a dense area of archaeological deposits of all periods including the Birdlip Quarry Neolithic site and Roman settlement (part excavated under the Cowley roundabout in 1997, Mudd et. al 1999), and close to other known sites of archaeological significance including the Stockwell DMV (SMR Glos 5758).
• The link from the Cowley roundabout to the historic road line may affect parts of the Birdlip Quarry Neolithic site and Roman settlement not excavated in 1997 and the historic road line is that of the Roman Ermin Street (SMR Glos 7542).
• 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.

9.51 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:

• Use of sustainable drainage systems for surface water run-off - measures such as the use of swales and ditches to filter water prior to discharge to soakaways, balancing ponds to control inflows into local streams (to control erosion and scouring), porous surfaces for hardstandings etc.
• Provision of pollution control technologies/accidental release control technologies - this might include oil/grit interceptors, pollution control valves, reed bed technology and polishing/balancing ponds. The provision of these technologies would be different for different parts of the proposed scheme.

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:

• The possibility of buried archaeology sealed under landslip deposits at Crickley Hill.
• Any road widening at Crickley Hill may damage archaeological deposits.
• The effect of the works on the Listed Building at Crickley Hill Farm is dependant on the engineering decisions taken.
• The area to the west of the Air Balloon has not been subject to archaeological field evaluation.
• The removal of the 18th century Air Balloon public house and the possibility of earlier buildings on the site would need to be investigated if options involving demolition are pursued (SMR Glos 13040).
• The area east of the Air Balloon roundabout has not been subject to archaeological field evaluation.
• The proximity of the A436 links to Emma's Grove barrows and the effect on their setting (SM 32381).
• The effect of the grade separation works on the setting of Crickley Hill (SM 40).
• If the removal of the 18th century Air Balloon public house is necessary, the possibility of earlier buildings on the site would need to be investigated (SMR Glos 13040).
• The new underpass and access from Birdlip involves works in very close proximity to Barrow Wake Iron Age cemetery (SMR Glos 3807) and a possible round barrow site (SMR Glos 3806). Further evaluation would probably be required in this area.
• The widening of the Birdlip bypass intrudes upon an area of known prehistoric and Romano-British activity partly excavated in advance of the construction of the existing road (SMR Glos 7185; Parry 1998)
• The new road line between Nettleton and Stockwell passes through a dense area of archaeological deposits of all periods including the Birdlip Quarry Neolithic site and Roman settlement (part excavated under the Cowley roundabout in 1997, Mudd et. al 1999), and close to other known sites of archaeological significance including the Stockwell DMV (SMR Glos 5758).
• The link from the Cowley roundabout to the historic road line may affect parts of the Birdlip Quarry Neolithic site and Roman settlement not excavated in 1997 and the historic road line is that of the Roman Ermin Street (SMR Glos 7542).

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:

• Use of sustainable drainage systems for surface water run-off - measures such as the use of swales and ditches to filter water prior to discharge to soakaways, balancing ponds to control flows into local rivers and streams (to control erosion and scour), use of porous surfaces where possible.
• Provision of pollution control technologies - this might include oil/grit interceptors, pollution control valves and balancing/polishing ponds and reed bed technology. The technology used would be finalised during detailed design, but would be consequent on the level of risk to the local environment, volumes of runoff to be controlled and existing water management systems on the existing highway.

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:

• The possibility of buried archaeology sealed under landslip deposits at Crickley Hill.
• The area to the south and west of Crickley Hill Farm may need further evaluation.
• The mouth of the tunnel and new road line at Nettleton and Stockwell may affect a dense area of archaeological deposits of all periods including the Birdlip Quarry Neolithic site and Roman settlement (part excavated under the Cowley roundabout in 1997, Mudd et. al 1999).
• The link from the Cowley roundabout to the historic road line may affect parts of the Birdlip Quarry Neolithic site and Roman settlement not excavated in 1997 and the historic road line is that of the Roman Ermin Street (SMR Glos 7542).
• 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.

9.161 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:

• Use of sustainable drainage systems for surface water run-off Use of porous surfaces for some of the adjacent hardstandings (e.g. around the control buildings),
• Re-use of some collected and treated waters for groundwater recharge, ecological enhancement, top-up of stored fire water, use in the control buildings etc
• Provision of pollution control technologies - this would include oil interceptors and stop valves along the length of the tunnel and the provision of storage tanks at the bottom of the hill to collect pollutants (and for possible on-site treatment such as oxidation) prior to disposal. This would apply particularly in the event of a major incident, e.g. chemical spill or fire, within the tunnel.

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.

• Download Table: Table 9-7 Environmental Impacts: Comparison of Options (11KB PDF)