Highways Agency

• 1. Introduction
• 2. Existing Conditions
• 3. Scheme Proposals
• 4. Engineering Assessment
• 5. Environmental Assessment - 1
• 5. Environmental Assessment - 2
• 5. Environmental Assessment - 3
• 5. Environmental Assessment -4
• 5. Environmental Assessment - 5
• 5. Environmental Assessment - 6
• 5. Environmental Assessment -7
• 5. Environmental Assessment -8
• 5. Environmental Assessment -9
• 5. Environmental Assessment -10
• 5. Environmental Assessment -11
• 5. Environmental Assessment -12
• 5. Environmental Assessment -13
• 5. Environmental Assessment -14
• 5. Environmental Assessment -15
• 5. Environmental Assessment -16
• 5. Environmental Assessment -17
• 5. Environmental Assessment -18
• 5. Environmental Assessment -19
• 6. Traffic and Economic Assessment

5. Environmental Assessment -14

5. Environmental Assessment (continued)

5.14 Water Quality and Drainage

5.14.1 Introduction

New roads can have an impact on the movement and quality of nearby surface andground waters, both during the construction phase and once the road isoperational. This section of the report addresses the issues, associated with thewater environment, which will need to be considered during the construction andoperation of the proposed road improvements.

5.14.2 Study Area

The study area for the water environment consists of surface watercourses (andassociated flood plains) that are crossed or receive drainage from the proposedimproved route and groundwater in the vicinity of the improvements.

5.14.3 Method of Assessment

There is a raft of legislation and guidance relevant to the potential impact of roadconstruction and operation on the quality and quantity of water within nearbysurface and ground water environments. Some of the most relevant are identifiedand described in this section.

The Transport Analysis Guidance (TAG) sets out the framework in which to assessthe attributes of the existing water environment and their importance, along with thepotential impacts of a new road and their magnitude and significance. This beginsby identifying relevant features and their attributes. For this scheme the featuresare the main rivers, such as the River Great Ouse, the wider flood plain and theassociated network of tributaries and drainage ditches, groundwater and anydesignated sites associated with the water environment. The attributes includewater supply, transport and dilution of wastewater, biodiversity, aesthetics,recreation, value to economy and conveyancing of flow and flood waters.

Within the TAG framework, the potential impacts on water quality were assessedusing the established methodologies for routine runoff and spillage risk outlined inthe Design Manual for Roads and Bridges Volume 11 Section 3 Part 10 (DMRB11.3.10). The methodology for routine runoff involves tests to predict futureconcentrations of zinc and copper in receiving watercourses. The spillage riskassessment methodology provides the return period of a serious accident based onroad length, presence of junctions, annual average daily traffic (AADT), percentageof heavy goods vehicles (%HGV), serious spillage rates, emergency servicesresponse time and River Ecosystem (RE) Target of the receiving watercourse.

The potential influence of road development on flow regimes in the flood plain isaddressed in Advice Note HA 71 The Effects of Highway Construction on FloodPlains (DMRB 4.2.1). In addition, The Department for Transport, LocalGovernment and the Regions (DTLR) has introduced the Planning Policy GuidanceNote 25 (PPG 25) in July 2001 to prescribe how flood risk should be consideredduring all stages of the planning and development process to reduce future damage to property andloss of life. This guidance is particularly relevant to any new development in theflood plain, where there are potentially acute impacts for flooding both for the newdevelopment itself and elsewhere.

Water quality in rivers and canals within England and Wales is monitored by theEnvironment Agency through the General Quality Assessment scheme (GQA),which is designed to provide an accurate and consistent assessment of the state ofwater quality and changes in this state over time. As part of this scheme; chemical,biological, nutrient and aesthetic quality are assessed. The chemical and biologicalparts of the GQA scheme are scored from Grade A, which represents water of Verygood quality, through to Grade F, which represents water of Bad quality (Tables5.48 and 5.49). Chemical quality is assessed through concentrations of ammonia,biochemical oxygen demand (BOD) and dissolved oxygen (DO), and biologicalquality determined from the range of macro-invertebrate species found in thewatercourse.

• * Provided other standards are met
• ** Where the grade is caused by discharges of organic pollution

Additionally, River Quality Objects (RQOs) are used in England and Wales astargets for water quality under The Surface Water (River Ecosystem)(Classification) Regulations 1994. As part of this, seven parameters (DissolvedOxygen (DO), Biochemical Oxygen Demand (BOD), total ammonia, un-ionisedammonia, pH, dissolved copper and total zinc) have been grouped to form theRiver Ecosystem Classification (RE). The RE Classification system is a useorientatedscheme of environmental objectives, the targets from which specify theuses for which a particular river should be able to provide (Table 5.50).

The monitoring and protection of water quality within surface waters are part of theduties the Environment Agency has for 'controlled waters' under the WaterResources Act (1991). Controlled waters are essentially all waters, either above orbelow ground, which are neither in the drinking water supply pipe nor the seweragenetwork.

Water within the ground, particularly in aquifers, is important as it providesbaseflow to many rivers and provides approximately 35% of all drinking water inEngland and Wales. Once contaminated, groundwater is extremely difficult torehabilitate, so discharges to ground are strictly controlled, most notably throughthe Groundwater Directive (80/68/EEC), which is enshrined in UK law in theGroundwater Regulations 1998. Furthermore, the "Policy and Practice for theProtection of Groundwater" introduced by the National Rivers Authority (NRA) (aprecursor to the Environment Agency) in 1992, established Source ProtectionZones (SPZs) to control land use and activities close to abstraction sources(springs, wells, boreholes) in order to protect vulnerable aquifer resources (Table5.51).

The monitoring and protection of water quality within surface waters are part of theduties the Environment Agency has for 'controlled waters' under the WaterResources Act (1991). Controlled waters are essentially all waters, either above orbelow ground, which are neither in the drinking water supply pipe nor the seweragenetwork.

Water within the ground, particularly in aquifers, is important as it providesbaseflow to many rivers and provides approximately 35% of all drinking water inEngland and Wales. Once contaminated, groundwater is extremely difficult torehabilitate, so discharges to ground are strictly controlled, most notably throughthe Groundwater Directive (80/68/EEC), which is enshrined in UK law in theGroundwater Regulations 1998. Furthermore, the "Policy and Practice for theProtection of Groundwater" introduced by the National Rivers Authority (NRA) (aprecursor to the Environment Agency) in 1992, established Source ProtectionZones (SPZs) to control land use and activities close to abstraction sources(springs, wells, boreholes) in order to protect vulnerable aquifer resources (Table5.51).

• Description of the three Source Protection Zones (SPZs)

The data used to assess the existing nature of the water environment within thestudy area have been obtained through a combination of desk studies, literaturereview, consultation and site visits.

5.14.4 Criteria for Magnitude and Significance of Impacts

Under the TAG framework, the attributes of the water environment are evaluatedon the basis of quality, scale, rarity and substitutability, giving an overallimportance. The operational effect of the new road is assessed using criteria fordetermining impact magnitude, for example 'loss of attribute'. The significance ofthe impact (Table 5.52) is estimated by considering both the importance of theattribute and the predicted impact magnitude.

Specific criteria were used for assessing the magnitude and significance of theoperational impacts of the road on water quality, and whether mitigation measureswere required. If soluble copper or total zinc concentrations are predicted to behigher than the Environmental Quality Standard for the receiving watercourse, thenthe need for mitigation is determined by more detailed modelling. If the spillagerisk return period is less than 1 in 50 years, then mitigation is necessary. Both ofthese assessments consider the effects of the road in the context of the existingenvironment (i.e. current use of water and RE Target).

5.14.5 Existing Conditions

SURFACE WATER RESOURCES

There are five gauging stations pertinent to the proposed improvements identifiedby the National River Flow Archive (NRFA) maintained by the Centre for Ecologyand Hydrology (CEH):

• Great Ouse at Offord (Stn. 33026) NGR TL 216669 (1970)
• Great Ouse at Offord (Stn. 33026) NGR TL 216669 (1970-)
• Alconbury Brook at Brampton (Stn. 33020) NGR TL 208717 (1963-)
• Great Ouse at Brownshill Staunch (Stn. 33001) NGR TL 369727 (1936-1962)
• Cam at Jesus Lock (Stn. 33016) NGR TL 450593 (1959-1983)
• Cam at Bottisham (Stn. 33003) NGR TL 508657 (1936-1987)

Data available for these gauging stations, from the NRFA website, pertinent to theflow regime of these watercourses are displayed in Table 5.54.

N.B. The data were obtained from the National River Flow Archive (NRFA) website, which is maintained by the Centre for Ecology and Hydrology (CEH).

In addition, there are a number of stageboards on the River Great Ouse and theRiver Cam that are used by the Environment Agency, which would provide a waterlevel data set. On the Great Ouse, the most pertinent are at: Brampton Sluice,Garkies Mill, Godmanchester Sluice, Houghton Mill, Hemmingford Sluice, St. IvesSluice, Webb's Hole Sluice, Brownhill Staunch and Earith, and on the River Camat: Jesus Lock and Baits Bite.

Details of abstraction licences were provided by the Environment Agency for fourgeographical areas, which broadly represent the area of study associated with theproposed improvements. The four areas are defined by the following national gridreferences (NGRs): Area 1 - SW TL 110650, NE TL 190770; Area 2 - SW TL190620, NE TL 330750; Area 3 - SW TL 330580, NE TL 400720; and Area 4 - SWTL 400560, NE TL 540670.

Within the overall area, there are 65 licensed surface water abstractions. Of these,55 are for agricultural spray irrigation, five are for industrial, commercial or publicservices, one is for general agricultural or domestic use, one is of private watersupply (non-potable) and three are for public water supply (Table 5.55). Surfacewater is mainly abstracted from drains, but the licensed abstractions include: 12from the Great Ouse, three from the Cam, one from Elsworth Brook, one fromDiddington Brook and one from Swavesey Drain. The public water supplyabstractions consist of the potable water abstraction from Grafham Water licensedto Anglian Water Services for an annual quantity of 120000000 m3 at NGR TL170671 and two transfers between sources licensed to Anglian Water Servicesfrom the Great Ouse at Offord (NGR TL 214661) for annual quantities of167588290 m3 and 9436710 m3.

GROUNDWATER RESOURCES

The area within which all of the proposed offline improvement routes and themajority of the online improvements lie is covered entirely by the one-inchGeological Sheet 187 (Huntingdon), which was originally surveyed on the one-inchscale between 1864 and 1882 and most recently reprinted at the 1:50000 scale in1975 (BGS, 1975). An additional part of the online improvement and the whole ofthe proposed Cambridge Northern Bypass are covered by the one-inch GeologicalSheet 188 (Cambridge), which was surveyed on the six-inch scale between 1936and 1953 and most recently reprinted at the 1:50000 scale in 1981 (BGS, 1981).

Regional dips in the geology are to the east or east-south-east and are generallyless than 2° and as a result, the outcropping Solid Geology tends to decrease inage from Jurassic to Cretaceous in this direction also.

To the north-west of Hilton, the uppermost layer of the Solid Geology is dominatedby Oxford Clay, whilst between Hilton and Boxworth the uppermost layer of theSolid Geology is dominated by the Ampthill Clay (and to a lesser extent Clays andlimestones including Elsworth Rock) of the Coralain Beds. Around Boxworth itself,it is the Kimmeridge Clay that largely forms the uppermost layer of the SolidGeology. Large areas of these are overlain by Boulder Clay deposits, whilst alongthe major watercourses (River Ouse, Ellington Brook and Alconbury Brook) theBoulder Clay is overlain by River Gravels. It has been noted that between St Neotsand Huntingdon much of the terrace gravel is underlain by Boulder Clay, whichappears to fill an irregular hollow in the Oxford Clay³.

To the south and east of Boxworth, the Drift deposits grade out and the bedrock(Solid Geology) forms the surface geology; the uppermost layer of which is formedinitially of Lower Greensand, then the Gault and subsequently Lower Chalk in thedirection of Cambridge. Similarly to the major watercourses in the northern area,the Solid Geology along the River Cam is overlain by River Gravels.

The Lower Chalk is considered by the BGS and Environment Agency to be a MajorAquifer, whilst the Lower Greensand is generally considered to be a Minor Aquifer.

There are 165 groundwater abstractions within the overall search area, defined forthe surface water abstractions (above). Of these, 101 are for general agriculturalor domestic groundwater remediation purposes (Table 5.56). The abstractions foruse, 26 are for industrial, commercial or public services, 25 are for agriculturalspray irrigation, six are for other agricultural purposes, three for private watersupply, three for public water supply and one for g public supply are licensed to theCambridge Water Company and are located at Fenstanton (NGR TL 314699), St.Ives (NGR TL 306698) and Fulbourn (NGR TL 511565) for annual quantities of159110 m3, 590993 m3 and 2046000 m3, respectively. These abstractions havesource protection zones associated with them, as defined by the EnvironmentAgency. Of which, those at Fenstanton and St. Ives are closest to the proposedimprovements, being directly north (1-2 km) of the existing A14 trunk road.

'NB includes abstractions for horticultural watering

SURFACE WATER QUALITY

Data were obtained for the RE and GQA scored watercourses directly from theEnvironment Agency and also through its website. Only data for the three watercourses in the study area that are likely to be directly impacted by theimprovements included in this report.

The period of record from the data obtained directly from the Environment Agencywas, generally, 1985 to 2002 for the chemical GQA and 1990 to 2002 for thebiological GQA, whilst from the Environment Agency website, the period of recordfor chemical quality was: 1990 and 1993 to 2001 (inclusive), and for biologicalquality: 1990, 1995 and 2000. The following assessment is based upon thesedata.

RIVER GREAT OUSE

There are four reaches of the Great Ouse that are most likely to be affected by theproposed route, for which data are available: Offord Darcy to Brampton, Bramptonto Marina and Marina to Hemingford Grey Mill, which are sampled at the samepoint, and Hemingford Grey Mill to Holywell. Currently all these reaches have a RETarget of 3, which is classified as 'water of fair quality and suitable for high classcoarse fish populations'. Data for Offord Darcy to Brampton and Brampton toMarina showed that the target was met in all years from 1993 to 2001, althoughthere were only marginal passes in 1993 and 2001 for Offord Darcy to Bramptonand Brampton to Marina, respectively.

Offord Darcy to Brampton (Sampled at Offord Intake - NGR TL 214662)

The chemical GQA from 1985 to 2002 varied between Grade D (Fair) and Grade B(Good). Most recently, it was Grade B in 1999 and 2000, and Grade C (Fairlygood) in 2001 and 2002. Between 1990 and 1995, the biological GQA variedbetween Grade C (Fairly good) and Grade B (Good), but since 1996 it has beenconsistently Grade B. Recent phosphate and nitrate GQA assessments between2000 and 2002 have indicated that concentrations were Very high and High,respectively, over the period, except in 2000 when nitrate concentrations were alsoVery high.

Brampton to Hemingford Grey Mill (Sampled at Black Bridge - NGR TL278716)

Between 1985 and 1990 the chemical GQA was Grade D (Fair) except for in 1989when it was Grade C (Fairly good). From 1991 to 2000 it was Grade C, butreturned to Grade D in 2001 and 2002. The biological GQA varied between GradeB (Good) and Grade A (Very good) from 1990 to 1998, but since 1999 it has beenconsistently Grade A. Recent phosphate and nitrate GQA assessments, between2000 and 2002, have indicated that concentrations were Very high and High,respectively, over the period.

Hemingford Grey Mill to Holywell (Sampled at St. Ives Rd. Br. - NGR TL403706)

The chemical GQA was Grade F (Bad) from 1985 to 1988 and Grade E (Poor) from1989 to 2000. Since then, the GQA has improved to Grade D (Fair) in 2001 andGrade C (Fairly good) in 2002. Between 1990 and 2002, the biological GQA hasbeen Grade C (Fairly good), except for 2000 when it was Grade D (Fair). Recentphosphate and nitrate GQA assessments, between 2000 and 2002, have indicatedthat concentrations were Very high and High, respectively, over the period.

ELLINGTON BROOK

The reach of the Ellington Brook from Spaldwick to the confluence with AlconburyBrook has a RE target of 4, which is classified as 'water of fair quality and suitablefor coarse fish populations'. The watercourse passed this target in all years from1993 to 2001.

During this period, the GQA for chemical quality varied from Grade E (Poor) toGrade C, with Grade E recorded in 1993, 1994 and 1995, Grade D recorded in1996, 1997, 1998 and 2000, and Grade C recorded in 1999 and 2001. The GQAfor biological quality, meanwhile, was Grade C in 1990 and 1995 and Grade B in2000.

RIVER CAM

The River Cam is monitored by the Agency for water quality, close to where it iscrossed currently by the existing A14(T), in the reaches from Church to the A45road Bridge and from the A45 road Bridge to Clayhithe. This section of the A14 willbe subject to widening under the proposed improvements. Both reaches have aRE target of 3, which was consistently passed by the former, during the period1993 to 2001 and by the latter in 1996 and 2001. The target was not met in theA45 road Bridge to Clayhithe reach in 1993 and there were only marginal passes in1994, 1995, 1997, 1998, 1999 and 2000.

In the Church to A45 road Bridge reach, the GQA chemical quality was Grade Cfrom 1993 to 1996 and 1998 to 1999, Grade B in 1997 and 2000 and Grade A(Very good) in 2001 and 2002. In contrast, in the A45 road Bridge to Clayhithereach, the GQA chemical quality was Grade D in 1994 and 1995 and from 1997 to2000, but Grade E in 1993. In 1997 and 2001 the quality was rated as Grade C,whilst in 2002 it was rated as Grade B.

The GQA biological quality of the two reaches is in contrast to the chemical quality,with the Church to A45 road Bridge reach recorded as Grade D in 1990, Grade C in1995 and Grade B in 2000 and the A45 road Bridge to Clayhithe reach recorded asGrade C in 1990 and 1995 and Grade A (Very good) in 2000.

5.14.6 Water Quality Monitoring

Owing to the scale of the proposed improvements, there are a number ofwatercourses that will potentially receive drainage from the improved road that arenot currently monitored by the Environment Agency. To address this datashortage, a monitoring programme was instigated in April 2004, which wouldprovide water quality data pertinent to the DMRB 11.3.10 Annex III routine runoffand spillage risk assessments, amongst other information relevant to the waterenvironment within these watercourses. This monitoring programme is scheduledto run from April through to August 2004.

5.14.7 Discharge Consents

According to Environment Agency records, there are 456 current licenseddischarge consents in the area of the proposed improvements, defined by arectangle of co-ordinates: NGR TL 159717 (NW) and NGR TL 483605 (SE). Themajority of these are to surface water and include: 60 to the Great Ouse and 45 tothe River Cam.

FLOOD RISK

The worst flood event on record across this area is the 1947 event, whichcorrelates to a 1 in 100 year event in some areas and to a 1 in 140 year event inothers. These events have been used by the Environment Agency to createindicative flood plain maps, which are used by the Environment Agency to evaluatethe feasibility of various types of development within the flood plain. By overlayingthe proposed improvement options on the indicative flood plain map, it is clear thatflood plain is crossed, by at least one of the route options, in three main areas(refer to the Planning Constraints drawings).

• South-east of Brampton
• North of Hilton
• North-east of Conington

In addition, the indicative flood plain of Ellington Brook, to the east of Ellington, iscrossed where the proposed routes intersect with the existing A14 route (EllingtonJunction) and the structure of the existing crossing of the River Cam may need tobe altered to accommodate a widened A14 as part of the Cambridge NorthernBypass, which may impact upon the flood plain in this location. Developmentacross watercourses and their associated flood plain has the potential to alter theexisting flow regime and thus alter the flood risk either up or downstream of thedevelopment. Owing to the risk of loss of life or property associated with anincrease in flood risk, the potential for alteration of flow regime needs carefulconsideration prior to the detailed design being completed and construction workcommencing. Further consideration of the flood risk associated with EllingtonBrook, River Great Ouse and West Brook/Hall Green Brook is provided in thefollowing sub-sections, the information in which is taken largely from previousAtkins reports.⁴

ELLINGTON BROOK

The Ellington Brook is a sub-tributary of the River Great Ouse. It flows in aneasterly direction through the villages of Spaldwick and Ellington before joining theAlconbury Brook near Brampton Race Course. The Great Ouse Catchment ispredominantly underlain by clays resulting in a high percentage of surface run-offand sudden peaks in river flow in response to rainfall. The Ellington Brook isgenerally slow flowing and meandering with a deep channel. The reachimmediately upstream and downstream of Thrapston Road Bridge is shallower,faster flowing and has a number of riffles. The construction of the existing A14(T)has affected the character and structure of the brook in the vicinity of Ellington, withsections straightened and the banks artificially raised.

Residential and commercial properties in Spaldwick and Ellington, outlyingbuildings and a section of the A14 were inundated by floodwaters from the EllingtonBrook during Easter 1998; an event with a return period of approximately 30 years.Hydraulic modelling indicates that 35 residential and 20 commercial properties arethreatened by a 1 in 100 year event.

The river's physical characteristics are affected by periodic maintenance for floodprotection, including obstruction removal, grass and weed cutting and bushclearance. Dredging is undertaken infrequently on an "as-needs" basis.

RIVER GREAT OUSE

The Bedford Ouse/River Great Ouse is a substantial river system draining acatchment of over 3500 km² Originating in the Northamptonshire Uplands it flows ina north-easterly direction through five counties before discharging to the North Sea,via the Wash, near King's Lynn. Upstream of the study area, major tributaries to theriver include the River's Twin, Tove, Ouzel, Ivel and Kym, and, within the studyarea, Alconbury Brook.

Because of its size, the River Great Ouse can also exert an influence on itstributaries during flood events, which can exacerbate flooding within these. Forexample, hydraulic modelling has shown that the Great Ouse has a considerableinfluence up the Hall Green Brook from even relatively low flood return periodevents. This work has shown that flood levels in the Great Ouse start to back upalong Hall Green Brook at around the 1 in 5 year level in the vicinity of Fenstanton.

WEST BROOK/HALL GREEN BROOK

The West Brook/Hall Green Brook watercourse is a lesser tributary of the RiverGreat Ouse. Rising to the south of the village of Papworth St Agnes(Cambridgeshire), it flows in a northerly direction around the village of Hilton beforecontinuing downstream to join the Hall Green Brook approximately 800 m upstreamof the existing Cambridge to Huntingdon A14(T) road in the village of Fenstanton.The downstream reach of the watercourse continues as Hall Green Brook alongthe western edge of the village of Fenstanton, crossing some 2 km of the GreatOuse flood plain before joining the River Great Ouse downstream of the town of StIves. From recent flood events (Easter 1998, October 2001 and January 2003), thiswatercourse has been identified as potentially being at risk from flooding.

Whilst there are no formal flood defences along the Hall Green Brook or WestBrook. an earth embankment has been constructed along the left bank of HallGreen Brook from the location of Turnpike Bridge in Fenstanton (NGR TL 313686)downstream to the confluence with the Great Ouse (NGR TL 321698), possibly bya predecessor of the Environment Agency, and also along the left bank of HallGreen Brook upstream of the A14 (T) road to the confluence with West Brook,probably to prevent inundation of the former sand and gravel workings during floodevents.

Local public perception of the embankment that stretches downstream fromFenstanton is that, during flood conditions along Hall Green Brook, it acts toprevent water from flooding across the left bank flood plain thereby increasingwater levels in Hall Green Brook along the right bank and within the village ofFenstanton itself. Flood levels produced by the Great Ouse River Model also showthat the left bank embankment is drowned out at the 1 in 5 year flood level alongthe lower length of Hall Green Brook. The length of embankment adjacent toFenstanton has a slightly higher elevation, and when compared against the GreatOuse flood level, is not drowned out until approximately a 1 in 15 year flood event.

The Environment Agency undertakes general maintenance along the WestBrook/Hall Green Brook which includes the following actions: annual weed andgrass cutting, obstacle removal and channel dredging.

DESIGNATED SITES

There are three designated sites, directly associated with the water environment,within the local area of the proposed off-line route options and two designated sitesclose to the eastern terminus of the proposed Cambridge Northern Bypass at FenDitton. None of these, however, lie directly upon the line of any of the proposedimprovement options.

To the north of the proposed improvements (and 1.5 to 2.5 km downstream of theproposed Great Ouse crossing points) is Portholme (NCR TL 238708), which is thelargest surviving traditionally-managed meadow in the UK, with an area of 104 haof alluvial flood meadow (7% of the total UK resource). Because the site supportsfeatures of national and international importance, it has been designated as a Siteof Special Scientific Interest (SSSI) and Special Area of Conservation (SAC), andwas also classified as a Grade 2 site in the Nature Conservation Review. Thefeatures for which the site has been designated are partly attributable to the site'sinundation by floodwaters in winter and early spring from the surrounding channelsof the Great Ouse, which helps maintain the diversity of the natural plantcommunities. In addition to the Portholme site, The Great Ouse and AlconburyBrook, close by, provide habitats for dragonflies and, in particular, the dragonflyLibellula fulva, which has a nationally restricted distribution. The features for whichthis site has been designated would be potentially vulnerable to any change in theflood regime associated with a new crossing of the Great Ouse and also to adecline in the quality of water entering the system.

On the western bank of the Great Ouse, approximately 3 km upstream of theclosest proposed Great Ouse crossing point (Orange Route), is Little Paxton Pits(NGR TL 200637); a series of flooded gravel pits that are of national importance forwintering wildfowl and an important stopping point for migrants. In addition, the sitesupports a diverse vegetation structure and an extremely rich diversity ofinvertebrate fauna, including a number of national rarities. As a result of thesefeatures, the site was designated as a SSSI in 1986. It is less likely that LittlePaxton Pits would be affected by a new river crossing (or additional drainage) thanPortholme as it is upstream of the proposed improvement options. Should flowwithin the Great Ouse be restricted by the new crossing, however, there may besome effect on the site.

Approximately 3 km to the south and west of the Ellington Junction to A1BramptonInterchange section of the proposed improvements is Grafham Water (NGR TL150680), a 680 ha reservoir that is designated as a SSSI largely because of thewintering and breeding wetland birds it supports. Whilst the reservoir is supportedby the transfer of water from the Great Ouse at Offord (NGR TL 214661), theabstractions are at Offord, approximately 2 km upstream of the closest proposedGreat Ouse crossing point. Like Little Paxton Pits, it is less likely that this site wouldbe impacted by the proposed improvements than Portholme as it is upstream.

Further removed from the proposed improvements are the Ouse Washes, whichare a half mile by twenty mile washland lying between the parallel banks of the OldBedford River / River Delph and the New Bedford River or One Hundred Foot Draindownstream (NGRs TL 393747 to TL 571987), which is designated as a RamsarSite, SAC, Special Protection Area (SPA) and SSSI. The site represents one of thefew remaining areas of washland habitat in the country, which is recognized for thelarge numbers of wildfowl and waders that it supports and generally for therichness of the aquatic fauna and flora within the associated watercourse, inparticular for the presence of the Spined Loach Cobitis taenia. The Ouse Washesplay a major land drainage role as a flood water storage area and the washland isthus subject to regular winter flooding. As a result, the features for which this sitehas been designated are intrinsically linked to the flow regime within the GreatOuse and also the quality of water within it. The Ouse Washes are, however,approximately 20 km downstream of the closest proposed crossing point over theGreat Ouse.

There have are already been concerns raised about the integrity of this site, towhich any changes in the flow regime within the Great Ouse would be particularlyrelevant. The latest report on the SSSI area by English Nature (12th January 2004)stated that whilst 17.74% of the area was 'favourable', 83.26% of the area was'unfavourable with no change'. This means that, for a large area of the SSSI unit,the special interest is not being conserved and will not reach favourable conditionunless there are changes to the site management or external pressures. Thelonger the SSSI unit remains in this poor condition, the more difficult it will be, ingeneral, to achieve recovery. In addition, according to the report on the OuseWashes by the Ramsar Advisory Mission No. 49, there are two main, but interlinked,issues that appear to be affecting the features of importance: 1) an increasein the incidence of summer flooding over the last 25 years, as well as high waterlevels in winter, and 2) a decline in water quality affecting the communities ofhigher plants within the rivers and ditches of the Ouse Washes.

Approximately 2 km upstream from the Ouse Washes is the washland habitat ofBerry Fen (NGR TL 378745), which was first designated as a SSSI in 1971. Theproximity of this site to the Ouse Washes influences the use of Berry Fen bywintering wildfowl, especially when the Washes are too deeply flooded. Inparticular, the Bewick's swan numbers reach nationally significant levels. As withthe Ouse Washes, adverse changes to the quantity or quality of water reaching thissite could have a negative impact, potentially, on the features for which it has beendesignated.

To the east of Fen Ditton are Stow Cum Quy Fen SSSI (NGR TL 515627) andWilbraham Fens SSSI (NGR TL 520590), both of which have features relevant tothe water environment. Stow Cum Quy has a number of pools formed on ChalkMarl, so there may be some continuity between these and the underlyinggroundwater. The pools have a good range of emergent and aquatic living plantsand are particularly attractive to dragonflies and damselflies including the emperorAjax imperator. Wilbraham Fens, meanwhile, has a number of drainage ditchesthat run through the site, which are relatively unpolluted and thus provide a habitatfor emergent plants, along with insect and bird communities.

There are two stretches of the Great Ouse that are designated as a FreshwaterFish (Cyprinid) Stretch under the Freshwater Fish Directive (78/659/EEC) in thestudy area. The closer stretch to the improvements extends 16.5 km fromGodmanchester (NGR TL 244712) to Brownhills Staunch (NGR TL 369727), whilstthe other extends 26.5 km from Brownshill Staunch (NGR TL 369727), to WelneyBridge (NGR TL 535928). The former stretch is monitored at Brownshill Staunch.

SITE SURVEYS

River Crossing Points

A site visit was conducted on 06/08/03 to assess the crossing points of flood plainand major watercourses associated with the proposed road improvements.

Drainage Assessment Surveys

To assess the nature of watercourses that have been designed to accept drainagefrom the proposed improvements, in order to provide a preliminary assessment asto their suitability for this function, drainage assessment surveys were alsoconducted. A summary of the findings is presented below.

SUMMARY

Many of the watercourses that would receive drainage from the new routes arerelatively small drains that provide drainage to the agricultural land that dominatesland use within the study area. The maintenance of which is largely conducted byDistrict Councils or Internal Drainage Boards, generally on an ad-hoc basis relatedto the importance (in terms of drainage) of the watercourse. The majority of thedrains surveyed would seem suitable, in their present state, to provide thisdrainage function, assuming appropriate attenuation is provided and regularmaintenance is provided. However, a more detailed assessment of the capacity ofsome of the smaller drains maybe required to assess whether they would need tobe re-profiled to ensure that they would have sufficient capacity to accept thedrainage. In addition, current issues with flooding have been noted for the ditchtributary to West Brook (Site 14), which will need further consideration during thedetailed drainage design.

These drains flow ultimately into the Main Rivers that have been identified in thestudy area, which are maintained by the Environment Agency. It is anticipated thatdrainage will enter three of these Main Rivers (Ellington Brook, West Brook/HallGreen Brook and Oakington Brook) directly, following appropriate attenuation.Whilst these watercourses are maintained on or more formal basis than the NonmainRiver watercourses, two of these (Ellington Brook and West Brook/Hall GreenBrook) are known to have on-going issues related to flooding and as such themethod and scale of attenuation will need to be carefully considered to ensure thatthis is not exacerbated.

5.14.8 Assessment of Proposed Routes

The water environment is important in terms of water supply, transport and dilutionof wastewater, biodiversity, aesthetics, recreation, value to economy andconveyancing of flow and flood waters. The predicted impacts, and theirsignificance, to these attributes of the water environment, for each of the mainroute options, will be formally summarized in the appropriate TAG Worksheets andAppraisal Summary Tables (ASTs), following the completion of the water qualitymonitoring, when the potential impacts to water quality have been modelled. A briefqualitative assessment of each of the Optimum Junction Strategies and LimitedJunction Strategies is provided below.

MAINLINE ALIGNMENTS WITH JUNCTION A STRATEGY (ENHANCED JUNCTIONSTRATEGY)

Blue Route

Advantages

• The alignment to the north of Buckden North Landfill Site, which has an engineered containment system, reduces the potential for leachate to migrate into the water environment during construction activities, such as piling work.

Disadvantages

• The crossing of the Great Ouse is further north than that of the Orange Route, which increases the risk of adverse impacts to Portholme SSSI, SAC, during construction and from changes to flow regime during operation.
• Whilst there is an engineered containment system within the Buckden North Landfill Site, should this be damaged during construction activities, such as piling work, it is likely that the leachate will be acetogenic and therefore potentially extremely harmful to the water environment should there be an accidental release during construction activities, such as piling work.
• Some of the drainage from this route would enter a drainage ditch that anecdotal evidence suggests already floods regularly, inundating surrounding agricultural land and Hilton Road.

Orange Route

Advantages

• The crossing of the Great Ouse is further south than that of the Blue and Purple Route, which decreases the risk of adverse impacts to Portholme SSSI, SAC, during construction and from changes to flow regime during operation.
• The route alignment passes close to the south of the completed and restored Buckden South Landfill. Owing to the age of this part of the landfill, it is likely that the leachate is methanogenic and therefore less harmful to the water environment than the newer acetogenic leachate should there be an accidental release during construction activities, such as piling work.

Disadvantages

• The Orange Route drainage scheme inputs drainage directly into the Great Ouse. Whilst DMRB modelling shows that there would be no significant adverse impact from routine runoff, the predicted return period of a serious pollution incident resulting from a serious accident is relatively low (6 years). This increases the risk of significant adverse impacts to Portholme SSSI, SAC, during operation compared to other routes.
• This route crosses the flood plain of West Brook closest to the village of Hilton, which is already considered to be at risk from flooding from this watercourse.
• The route alignment passes close to the south of the completed and restored Buckden South Landfill. Owing to the age of the landfill (operational from the 1930's until 1994) it is likely that there is no (or limited) engineered containment system, which increases the risk of leachate migrating to the water environment as a result of construction activities, such as piling work.
• Some of the drainage from this route would enter a drainage ditch that anecdotal evidence suggests already floods regularly, inundating surrounding agricultural land and Hilton Road.

Many of the identified differences in impacts to the water environment between theroutes can be reduced or eliminated through the use of appropriate mitigationmeasures. The early identification of potential impacts is important so that thecorrect mitigation techniques can be taken into account as the project progressesfrom design to implementation.

Orange/Blue Route

Advantages

The crossing of the Great Ouse is further south than that of the Blue Route, whichdecreases the risk of adverse impacts to Portholme SSSI, SAC, during constructionand from changes to flow regime during operation.

The route alignment passes close to the south of the completed and restoredBuckden South Landfill. Owing to the age of this part of the landfill, it is likely thatthe leachate is methanogenic and therefore less harmful to the water environmentthan newer acetogenic leachate should there be an accidental release duringconstruction activities, such as piling work.

Disadvantages

The Orange Route drainage scheme inputs drainage directly into the Great Ouse.Whilst DMRB modelling shows that there would be no significant adverse impactfrom routine runoff, the predicted return period of a serious pollution incidentresulting from a serious accident is relatively low (6 years). This increases the riskof significant adverse impacts to Portholme SSSI, SAC, during operation comparedto other routes.

The Orange route alignment passes close to the south of the completed andrestored Buckden South Landfill. Owing to the age of the landfill (operational fromthe 1930's until 1994) it is likely that there is no (or limited) engineered containmentsystem, which increases the risk of leachate migrating to the water environment asa result of construction activities, such as piling work.

5.14.9 Limited Junction Strategy - Blue and Orange Route Alignments

Blue Route (Limited Junction Option)

• The number of watercourses crossed by the Limited Junction Option is the same as for the Reference Option so there is no advantage, to the water environment, in this respect.
• It is assumed that crossing structures and culverts, along with land take within flood plains, is the same as for the Reference Option, so potential impacts to flood risk, without mitigation, will be the same.
• It is assumed that the drainage design is the same as for the Reference Option, so potential impacts to flow and water quality within receiving watercourses, without mitigation, will be the same.
• DMRB spillage risk assessment modelling shows that there would be no significant reduction in the risk of a serious pollution incident compared to the Reference Option.

Orange Route (Limited Junction Option)

• The number of watercourses crossed by the Limited Junction Option is the same as for the Reference Option so there is no advantage, to the water environment, in this respect.
• It is assumed that crossing structures and culverts, along with land take within flood plains, is the same as for the Reference Option, so potential impacts to flood risk, without mitigation, will be the same.
• It is assumed that the drainage design is the same as for the Reference Option, so potential impacts to flow and water quality within receiving watercourses, without mitigation, will be the same.
• DMRB spillage risk assessment modelling shows that there would be no significant reduction in the risk of a serious pollution incident compared to the Reference Option.

Purple Route

Advantages

• This route has the smallest chainage of road off the alignment of the existing A14(T). This decreases the number of additional watercourses that will be crossed by the improvements, reducing the potential risks from changes to flow conveyance.
• The flood plain of West Brook/Hall Green Brook is crossed along the alignment of the existing A14(T). As a result, the risk of potential adverse impacts to flow conveyance to this watercourse, already identified as being at risk from flooding, are reduced compared to the other options.
• The alignment to the north of Buckden North Landfill Site, which has an engineered containment system, reduces the potential for leachate to migrate into the water environment during construction activities, such as piling work.

Disadvantages

• The crossing of the Great Ouse is further north than that of the Orange Route, which increases the risk of adverse impacts to Portholme SSSI, SAC, during construction and from changes to flow regime during operation.
• Whilst there is an engineered containment system within the Buckden North Landfill Site, should this be damaged during construction activities, such as piling works, it is likely that the leachate will be acetogenic and therefore potentially extremely harmful to the water environment should there be an accidental release during construction activities, such as piling work.
• This route alignment is closest to the completed and restored Conington Landfill Site and Hemingford Grey Landfill Site (unknown status). This potentially increases the risk of leachate migrating to the water environment as a result of construction activities, such as piling work.
• The route alignment is closest to the groundwater abstraction for public water supply at Fenstanton operated by Cambridge Water Company. This increases the risk, compared to the other routes, of impacting this water source during construction or operation.

Orange/Purple Route

Advantages

The crossing of the Great Ouse is further south than that of the Purple Route,which decreases the risk of adverse impacts to Portholme SSSI, SAC, duringconstruction and from changes to flow regime during operation.

The route alignment passes close to the south of the completed and restoredBuckden South Landfill. Owing to the age of this part of the landfill, it is likely thatthe leachate is methanogenic and therefore less harmful to the water environmentthan newer acetogenic leachate should there be an accidental release duringconstruction activities, such as piling work.

Disadvantages

The Orange Route drainage scheme inputs drainage directly into the Great Ouse.Whilst DMRB modelling shows that there would be no significant adverse impactfrom routine runoff, the predicted return period of a serious pollution incidentresulting from a serious accident is relatively low (6 years). This increases the riskof significant adverse impacts to Portholme SSSI, SAC, during operation comparedto other routes.

The Orange route alignment passes close to the south of the completed andrestored Buckden South Landfill. Owing to the age of the landfill (operational fromthe 1930's until 1994) it is likely that there is no (or limited) engineered containmentsystem, which increases the risk of leachate migrating to the water environment asa result of construction activities, such as piling work.

5.14.10 Predicted Impacts and Significance

DURING CONSTRUCTION

With any construction work undertaken close to a watercourse there is an inherentrisk of adverse impacts to surface and ground water. Potential contaminantsinclude fuel oils from mechanical plant, dirty water runoff from the site, cement, sitedisturbance within the river channel and general debris from the construction site.The deliberate or accidental discharge of polluting material into controlled waters isan offence under the Water Resource Act 1991, if undertaken without consent, andcould lead to impacts of major adverse significance without mitigation.

The significance of potential impacts to surface waters associated with theseimprovements is enhanced by the proximity of conservation sites of internationalimportance (Portholme SAC and Ouse Washes SAC, SPA and Ramsar Site)downstream of proposed construction activities. In particular, each of the proposednew routes contains a major crossing of the Great Ouse and thus all theimprovement options have the potential to negatively impact upon these sitesduring construction. The crossing of the Blue and Purple routes is, however,approximately 1 km closer to Portholme than the crossing of the Orange route,which slightly increases the risk from these options. In addition to the Great Ousecrossing, the improvement routes also cross a number of other watercourses thatultimately drain into the Great Ouse upstream of the Ouse Washes. As a result,pollutants (particularly dissolved solutes e.g. metals and substances less densethan water e.g. oil and diesel) entering these watercourses have the potential to betransported to the Ouse Washes.

Impacts associated with contaminants entering groundwater are likely to berelatively isolated compared to impacts associated with surface waters; however,once impacted groundwater is relatively difficult to remediate and contaminants canbe relatively persistent. Whilst none of the proposed routes cross source protectionzones, there are a relatively large number of licensed abstractions in the local area,many for general agricultural and domestic use, but two for public water supply andone for private water supply. The release of pollutants into groundwater close tothese abstractions would potentially enhance the significance of any impactsassociated with the contravention of the Water Resources Act (1991). In addition,close to the terminus of the Cambridge Northern Bypass is the Stow Cum Quy FenSSSI, which has a number of pools formed on Chalk Marl. These may be incontinuity with groundwater in the underlying Chalk and therefore contaminantsreleased into the Chalk could migrate into these and potentially affect a number offeatures for which the site has been designated.

The Environment Agency has stated that it anticipates the main source of impact towater resources, during the period of construction, to be associated withdewatering works, e.g. for the construction of bridge foundations. Whilst dewateringactivities are exempt from control, in accordance with Section 29 of the WaterResources Act 1991, as no abstraction licence is required, the EnvironmentAgency may wish to issue a Conservation Notice outlining measures to be taken totaken to protect existing sources under Section 30 of the Water Resources Act1991.

In addition, the Environment Agency will expect that the impact of any dewateringworks on water resources is assessed, probably at the detailed design stage. It isanticipated that this will include submission to the Environment Agency of details ofthe proposed works, the geological and hydrogeological situation, the predictedabstraction quantities, the predicted drawdown of the groundwater table and theestimated area of influence. As dewatering activities may impact upon nearbydomestic and licensed groundwater sources and other water features, a waterfeatures survey will be required to identify these.

All the new routes associated with the proposed improvement options cross theRiver Great Ouse and a number of other minor watercourses, including a numberdrains and ditches. In addition, the structure of the existing crossing of the RiverCam may need to be altered to accommodate a widened A14 as part of theCambridge Northern Bypass. During the construction of these crossings, there is apotential that flow within the watercourse could be affected or that the channel mayneed to be temporarily blocked, which could increase the flood potential, locally,within the catchment. The potential impact of this would depend upon the size ofthe watercourse and the land-use of the affected area, but it is anticipated that thiswould be of minor to moderate adverse significance without mitigation.

DURING OPERATION

It is likely, however, that the greatest impact to the water environment, withoutmitigation, will be from the crossing of watercourses and associated flood plains,and the volume of drainage entering watercourses from the new impermeable roadsurface. The potential impacts of these to the flow regime can have implications forchannel stability, aquatic habitats and flooding. Where the movement of anyexisting channels is required, this may also affect the local hydrological regime.

To assess the potential impacts of such processes on the existing watercoursesmore fully, Flood Risk Assessments (FRAs) will need to be undertaken, whichshould encompass the general requirements established in Planning PolicyGuidance Note 25 (PPG 25) and will require consultation with the EnvironmentAgency, and Local Councils and Drainage Authorities where appropriate.

Under Section 89(5) of the Water Resources Act (1991), the Highways Agency isexempt from needing to apply for discharge consents for highway runoff. It does,however, have a responsibility to ensure that highway discharges comply withcurrent pollution legislation. Water quality is potentially effected by pollutants inrunoff and spray including heavy metals (such as zinc and copper), suspendedsolids, chloride ions, organics and hydrocarbons. These are derived from routineroad surface and vehicle wear, exhaust emissions, oil, de-icing salts and rubbish,and also from accidents. Contamination can affect surface waters and alsogroundwater, potentially causing longer-term problems. A change in water qualitycan affect existing uses of the water for amenity, water abstraction and habitats.

The potential impacts from road runoff, in the form of soluble copper and total zincconcentrations, have been assessed in accordance with the method outlined inDMRB 11.3.10 Annex Ill. The analysis has been conducted for all watercoursesthat would receive highway drainage for which copper and zinc concentrations aremonitored by the Environment Agency in addition to watercourses for whichmonitoring is being conducted currently.

In addition to the routine runoff assessment, the risk of a serious pollution incidentoccurring from an accidental spillage occurring on the carriageway has beenassessed in accordance with the method outlined in DMRB 11.3.10 Annex Ill. Thespillage risk assessment was conducted using the predicted traffic density for asingle design year and information on the nature of the road and receivingwatercourse.

5.14.11 Potential Mitigation Measures

DURING CONSTRUCTION

The risk of pollution can be reduced by the adoption of good working practices andstrict adherence to the Environment Agency's Pollution Prevention Guidance,particularly to the following guidance notes:

• PPG01 General guide to the prevention of water pollution
• PPG05 Works in near or liable to affect watercourses
• PPG06 Working at construction and demolition sites
• PPG22 Dealing with spillages on highways
• PPG23 Maintenance of structures over water
• Guidance on silt pollution and how to avoid it

During construction it is possible that surface water run-off from construction areasmay have a relatively high content of suspended sediment, along with elevatedconcentrations of heavy metals and hydrocarbons. Where construction work mayinvolve discharges into local receiving watercourses, early consultation with theEnvironment Agency will be necessary in order to determine the most appropriatemitigation measures that will be required to control any impacts. Discharges togroundwater will not be permitted by the Environment Agency and particular carewilt be required during construction to protect this resource.

As a minimum, the following mitigation measures should be considered duringconstruction:

• On-site availability of fuel oil spill clean up equipment including absorbent material and inflatable booms for use in the event of a fuel oil spill or leak;
• Use of dip trays under mobile plant;
• Sediment trapping matting installed downstream of any construction activities adjacent to or over watercourses;
• Preparation of incident response plans, prior to construction, which should be present on site throughout construction to inform contractors of required actions in the event of a pollution incident;
• Timing of works close to watercourses should be such that they do not interfere with spawning fish;
• Construction materials brought to site should be free from contaminated material, so as to avoid any potential contamination of the watercourse; and
• Care should be taken to ensure that wet cement does not come into contact with river water. Cement should be poured in dry and consideration should be given to using fast-drying cement.

In addition to these measures, consideration should be given to the potentialimpact of runoff and foul flow entering watercourses from construction compounds,under licence, on the flow within the watercourse. This is of particular importanceduring high flows when additional water entering the watercourse could increasethe potential flood risk. To mitigate against this, evaluation of this additional watershould be a part of any flood risk assessments that are undertaken.

The potential impacts from an alteration of the flow regime associated with inchannelworks are explicitly addressed in the requirement of formal consent fromthe relevant authority prior to the works being undertaken. Any work that affects theflow of a watercourse, such as culverting, will require a Land Drainage Consentfrom the Environment Agency under the Land Drainage Act 1991/Water ResourcesAct 1991; although the Environment Agency seeks to avoid culverting and itsconsent for such works will not normally be granted, except as a means of access.Furthermore, appropriate flood defence consents will need to be gained fortemporary works (construction) and permanent works under the Water ResourcesAct 1991 and Land Drainage Byelaws; with prior written consent required from theAgency for proposed works or structures in, under, over or within 9m of the top ofthe bank of Main Rivers within the study area.

In addition, consent would be required from the body responsible for thewatercourse for the construction of any road drainage outfall that enters it. Theapplication process for, and issue of, formal consent should allow potential impactsfrom the restriction of flows to be assessed formally for their significance, and, as aresult, the formal consent may impose conditions that aim to minimise thesepotential impacts. In any case, consideration should be given to the timing of anyin-channel works such that potential increases to flood risk are kept to a minimum.

Provided correct working procedures and practices are adopted, as outline above,and care is taken to avoid pollution, it is anticipated that impacts on the waterenvironment during construction will be of negligible significance.

DURING OPERATION

A number of different treatment options are available for normal road runoff, inorder to improve the quality of the discharge to the watercourse from roaddrainage. Recently guidance has been produced with regard to the use of naturaltreatment systems. This formal guidance is contained in Volume 4 of the DMRB(HA 103/01 - Vegetative Treatment Systems for Highway Runoff). There are 3 maintreatment systems that could be considered for the treatment of highway runoff:swales, petrol interceptors or constructed wetlands. It is important that the practicalconstruction and maintenance related issues, of each of these options, areconsidered during the design phase.

There is always a certain risk that a serious accidental spillage may occur on a newsection of road, which could lead to a serious pollution incident in one of the localwatercourses. Where the risk of this happening is found to be high (using the testsfrom DMRB), it will be recommended to include some form of mitigation thatprovides spillage containment. High risk sites include roads with very high trafficdensities, outfalls draining to sensitive watercourses or at roundabouts/junctionswhere risk of accidents is higher.

The treatment options should also be designed to ensure that potential impacts togroundwater are also minimized, as these impacts would potentially be moredifficult to remediate than impacts to surface waters. Should these mitigationmeasures be implemented successfully, it is anticipated that the residual impact onthese aspects of the water environment, from the operation of the new route, wouldbe of negligible significance.

Impacts associated with changes to flow conveyance are likely to have the greatestimpact on the water environment, without mitigation. In particular, the potentialimpacts associated with the crossing of the River Great Ouse and its flood plain,which include the potential for increased flood risk and adverse effects to theintegrity of conservation sites of international importance (Portholme SAC, andOuse Washes SAC, SPA and Ramsar site). Increased flood risk is also a potentialimpact for smaller watercourses that would be crossed or would receive drainage;with the influence of channel alterations (such as culverts) or additional drainagepotentially more important, relatively, than for larger watercourses such as theGreat Ouse. Owing to potential severity of the effects associated with increasedflood risk, the Environment Agency has already stipulated a number of mitigationmeasures that will need to be utilised in order to reduce this potential impact:

• Compensation for any loss of flood plain;
• Attenuation of runoff from all hardstanding areas and embankments > 30° so that it does not exceed the equivalent Greenfield rate (3 litres/second/hectare); and
• Appropriate design of the river crossing such that any support pillars, or other support structures, to be positioned within a watercourse are most hydraulically efficient to reduce impact on flow conveyance.

To reduce the flood risk, IDBs may also require attenuation, to reduce the input ofwater to manageable quantities. The Ely Group of IDBs, responsible for the OldWest Internal Drainage District and the Swaffham Internal Drainage District, hasstated that 'their surface water receiving systems have no residual capacity toaccept any increased flows' and that 'all discharges of surface water will berequired to be attenuated prior to entering either Internal Drainage District'.Similarly, the Middle Level Commissioners, responsible for the Swavesey 1DB, hasstated that it 'is not prepared to accept any 'foreign' water into its system and that'any surface run off... should be attenuated to the equivalent greenfield rate of runoff'.

A similar position has been adopted by Huntingdonshire District Council (HDC) forAwarded Watercourses within its administrative boundaries, with its assessmentthat 'there is currently no additional capacity for water within the existing drainagenetwork'. However, drainage would be allowed provided appropriate attenuationwas provided prior to the water entering the drainage network. SouthCambridgeshire District Council (SCDC) has also stated that it was likely that noadditional water would be allowed into its drainage network, without appropriateattenuation.

In addition to these requirements, for some watercourses the potential impacts onflow conveyance will need to be assessed through the completion of an appropriateflood risk assessment (FRA), which will inform the detailed design process andassess the potential effectiveness of mitigation measures. Owing to the numberand scale of watercourses that will potentially be affected by these proposed roaddevelopments, the issue of flood risk assessment is discussed in more detail in thefollowing section.

WATER RESOURCES

The Environment Agency has stated that the long-term impacts on water resourcescaused by structures remaining within underlying aquifers or by the operation of thenew road scheme will need to be assessed. It is anticipated that this assessmentwould need to be conducted at the detailed design stage and would be based onthe geological and hydrogeological situation. During the assessment it will need tobe demonstrated that there is no negative impact on water resources caused bylong term changes in groundwater levels and groundwater flow directions, or bychanges in surface water levels and flows.

Mitigation and monitoring measures to assess the potential long-term impact onwater resources may need to be conducted well in advance of the commencementof any construction works in order to a baseline to which future assessments canbe referenced. This may involve the design, installation and operation of anadequate monitoring system, including boreholes and gauge boards.

FLOOD RISK ASSESSMENT

In recognition of PPG 25, the Environment Agency stated, at an early stage, thatthere would be a requirement to demonstrate that the proposed improvements willhave no impact on the hydrological regime (peak flow and levels) of any mainrivers, either by crossing of the watercourse (or flood plain) or through the receipt ofdrainage. In particular, it was stated that a model of the River Great Ouse (thelargest floodplain that is crossed by the proposed route) would be required to showinterested parties that the improvements will not have a detrimental effect on theexisting flow regime. This is of particular importance owing to the proximity ofrelatively large numbers of dwellings and conservation sites of internationalimportance.

In addition to the main rivers, there is also a requirement to undertake a FRA fornon- main rivers and other watercourses (such as 'Awarded Watercourses') whenappropriate. In particular, Internal Drainage Boards (IDBs) require FRAs for all newdevelopments that meet any of the following criteria:

• adjacent to a Board's drain or Commissioners' watercourse
• within an area known to have an existing flooding problem
• any development having an impermeable area greater than 500 m².

The adoption of these criteria is at the discretion of the individual IDB, however,and is not always enforced. For example, the Alconbury & Ellington IDB, has statedthat there is no particular requirement for FRAs, for water entering itswatercourses, as long as the other requirements of the IDB can be met.

District Councils have similar obligations for Awarded Watercourses within theiradministrative boundaries, but enforcement is largely at the discretion of eachindividual Council. Huntingdonshire District Council (HDC) has stated that it doesnot have any specific requirements for FRAs to be conducted for water entering itswatercourses, although it does expect that the Environment Agency will requireFRAs and that the output of these would be passed on to HDC. In contrast, SouthCambridgeshire District Council (SCDC) specifically requires ERAs to demonstratethat water entering Awarded watercourses will not increase the flood risk elsewherein the catchment.

FLOOD RISK MODELLING

It is common for complex flood risk assessments to comprise an element ofmodelling in order that quantifiable predictions can be made on the potentialinfluence on flood risk. The requirement for modelling, for the A14 Improvementworks, was confirmed in a meeting between Atkins and the Environment Agency on22/08/03, in which it was also stated that modelling would be required for any mainrivers for which there was an existing hydraulic/hydrological model. In particular,models of the main rivers will need to examine pre- and post-developmentscenarios, in which the impact of structures and drainage is examined. These willbe required to show that there is no increase to the flood in either the active orpassive flood plains. The river will need to be modelled to 1 in 100 year event andthe effects of global warming would need to be taken into account, with theallowance of + 20% for climate change. The models will have to show that theproposed alignment of the new road will not impede flood flows nor increase theflood risk elsewhere.

In addition, the Environment Agency stated that catchment analysis would berequired for ordinary watercourses that will receive additional drainage from theroad improvements. This should be Flood Estimation Handbook (FEH) based andwill need to demonstrate that the flow regime of the receiving watercourse (and anyassociated balancing ponds) will not be adversely impacted by the additionaldrainage and that water will not be transferred between catchments.

The output from the flood risk assessments should aid the determination of whichdesigns are most suitable for crossings and drainage in order that the hydrologicalregime is unaltered, as specified by the Environment Agency. In particular, thehydraulic/hydrological model of the Great Ouse, which has already beenconstructed by Atkins for the Environment Agency, should be used to inform thedetailed design of the River Great Ouse Viaduct. Following the successfulimplementation of any recommendations from the flood risk assessments, it isanticipated that there will be no significant impact to flood risk from the proposedimprovements.

5.14.12 Summary

New roads can have an impact on the movement and quality of nearby surface andground waters, both during the construction phase and once the road isoperational. This report addresses the issues, associated with the waterenvironment, which will need to be considered during the construction andoperation phases of the proposed A14 improvement.

In particular, the proposed new road has potential implications for the flow andquality of water within the River Great Ouse and its associated tributaries, mostnotably: Ellington, Alconbury, Stonyhill, Longmarsh/Lake, and West/Hall GreenBrooks. In addition, there are also possible consequences for flood plainsassociated with these watercourses, but in particular for the Great Ouse, EllingtonBrook and West Brook, the flood plains of which are crossed by the proposedroute. These watercourses are classified as Main River and are therefore theresponsibility of, and are maintained by, the Environment Agency.

In addition to these Main Rivers, there are numerous natural and man-made ditchesand drains that either cross, or run close to, the proposed route, in particular thedrains near Conington and Hilton, and the Swavesey Drain that have flood plainassociated with them. These Awarded watercourses are the responsibility of eitherInternal Drainage Boards (IDBs) or Local Authorities.

Widening of the current A14 trunk road to the north of Cambridge up to Fen Dittonhas potential implications for the flow and quality of water within Beck Brook andWashpit Brook, and the River Cam, which is crossed currently at NGR 54842616.There are also possible consequences for the flood plain of the Cam, if the currentstructure that conveys the road over it requires alteration to accommodate thewidened carriageway. The River Cam is classified as Main River and is thereforemaintained by the Environment Agency.

Within the study area, there a number of geological strata with differenthydrogeological properties. The Lower Chalk is considered by the BGS andEnvironment Agency to be a Major Aquifer, whilst the Lower Greensand isgenerally considered to be a Minor Aquifer. There have been 3 abstractions forpublic supply identified at Fenstanton, St. lves and Fulbourn, which have sourceprotection zones associated with them, as defined by the Environment Agency.

Whilst some of the potential impacts are generic to either surface or ground watersas a result of road construction or operation, some impacts have been identifiedthat are particular to a single route alignment or there is a greater risk of an impactassociated with a particular alignment. Having identified these, however, many ofthe differences can be reduced or eliminated through the use of appropriatemitigation measures. The early identification of potential impacts is important sothat the correct mitigation techniques can be taken into account as the projectprogresses from detailed design through to implementation.

3. Horton, A (1970) The drift sequence and sub-glacial topography in parts of the Ouse and Nene basis, Rep. Inst. Geol. Sci., 70(9), 30 pp back [3]
4. WS Atkins (2002) Spaldwick & Ellington Flood Defence Improvements - Environmental Appraisal (Final) REF: AK2795/72/DG/013.
   Atkins (2004) Spaldwick & Ellington Flood Defence Improvements - Addendum to Environmental Appraisal Report (Draft) REF. 4132795/721DG
   Atkins (2003) ARTS2c Regionwide Modelling Project, Bedford Ouse Catchment Block - Data Review (Final) REF. 5010336/61 /DG/45 lssue.doc.
   Atkins (2003) Southern Catchment, Central Area SoP/PF Studies - Fenstanton Village Flood Defence Standard of Protection Study (Final) REF. 5008521/68/DG/011.
   Atkins (2004) Southern Catchment, Central Area SoP/PF Studies - Hilton Village Flood Defence Standard of Protection Study (Final). REF 5008582/71/DG/016 back [4]