Chapter 9: Road drainage and the water environment

M1 Junction 19 Improvement 

Environmental Statement 

Volume 2 

Chapter 9 – Road Drainage and the 

Water Environment 

Final

M1 JUNCTION 19 IMPROVEMENT 

ENVIRONMENTAL STATEMENT VOLUME 2 

CHAPTER 9 – ROAD DRAINAGE AND THE WATER ENVIRONMENT 

REPORT CONTROL SHEET 

PROJECT NAME: 

REPORT TITLE: 

REPORT REFERENCE: 

M1 Junction 19 Improvement 

Environmental Statement 

Chapter 9 – Road Drainage and the Water 

Environment 

B0531000/ID/70 

Version Detail Prepared By: 

Date 

Checked By: 

Date 

Reviewed By: 

Date 

Approved by: 

Date 

Draft Rev 0 Sharon Woodruff 

10/11/09 

Barry Moore 

16/11/09 

Andy Drake 

19/11/09 

Tim Worrall 

19/11/09 

Final Rev 1 Sharon Woodruff 

02/12/09 

Barry Moore 

02/12/09 

Stephen Taylor 

03/12/09 

Tim Worrall 

03/12/09 

Final Rev 2 Sharon Woodruff 

8/01/10 

Barry Moore 

11/01/10 

Susan Moore 

11/01/10 


12/01/10 

Final Rev 3 Robert Peatfield 

19/01/10 

Andrew Drake 

19/01/10 


19/01/10 


19/01/10 

Final Rev 4 Robert Peatfield 

03/02/10 

Andrew Drake 

03/02/10 

Tim Worrall 

03/02/10 

Tim Worrall 

03/02/10




Page Not Used




CONTENTS 

9.1 INTRODUCTION .................................................................................................................. 1 

Objectives ............................................................................................................................. 1 

Study Area ............................................................................................................................ 2 

The Project............................................................................................................................ 2 

Interaction ............................................................................................................................. 2 

9.2 METHODOLOGY.................................................................................................................. 3 

9.3 LEGISLATION AND POLICY FRAMEWORK....................................................................... 9 

UK and EC Legislation.......................................................................................................... 9 

Regional Planning Policy .................................................................................................... 11 

Local Authority Planning Policy........................................................................................... 11 

9.4 BASELINE CONDITIONS................................................................................................... 13 

Surface Water ..................................................................................................................... 13 

Groundwater ....................................................................................................................... 16 

Surface Water Flows and Flood Risk.................................................................................. 18 

Sensitivity Assessment of Receptors.................................................................................. 18 

9.5 MITIGATION ....................................................................................................................... 21 

Potential Impacts ................................................................................................................ 21 

Construction Environmental Management Plan.................................................................. 21 

Permanent Drainage........................................................................................................... 22 

Flood Compensation........................................................................................................... 24 

River Channel Regrading.................................................................................................... 24 

9.6 ENVIRONMENTAL IMPACT .............................................................................................. 27 

Catthorpe Viaduct Replacement ......................................................................................... 27 

Surface Waters ................................................................................................................... 28 

Groundwater ....................................................................................................................... 32 

Flood Risk........................................................................................................................... 33 

Implications for Planning Policies ....................................................................................... 34 

9.7 SIGNIFICANCE OF EFFECTS ........................................................................................... 37 

Construction........................................................................................................................ 37 

Operation ............................................................................................................................ 37 

Overall Effect ...................................................................................................................... 37 

9.8 INDICATION OF DIFFICULTIES ENCOUNTERED ........................................................... 45 

9.9 SUMMARY.......................................................................................................................... 47 

9.10 REFERENCES ................................................................................................................... 49 

TABLES 

Table 9.1: Estimating the Importance of Water Environmental Attributes ........................................ 5 

Table 9.2: Criteria for Determining Magnitude of Impact .................................................................. 6 

Table 9.3: Criteria for Estimating the Significance of Potential Effects ............................................. 6 

Table 9.4: Overall Assessment Scoring............................................................................................ 8 

Table 9.5: Relevant UK and EC Legislation...................................................................................... 9 

Table 9.6: Summary Details of Existing Highway Drainage............................................................ 13 

Table 9.7: Water Environment Features Summary......................................................................... 18 

Table 9.8: Summary Details of Proposed Highway Drainage......................................................... 29 

Table 9.9: Summary Results of Simple Assessment of Pollution Impacts from Routine Runoff 

(DMRB Method A) ...................................................................................................... 30 

Table 9.10: Summary Results of Detailed Assessment of Pollution Impacts from Routine Runoff 

(DMRB Method B) ...................................................................................................... 30 

Table 9.11: Summary Results of Assessment of Pollution Impacts from Accidental Spillages 

(DMRB Method D)...................................................................................................... 31 

Table 9.12: M1 Junction 19 Water Environment Features Summary: Construction Effects ........... 38 

Page i




Table 9.13: M1 Junction 19 Water Environment Features Summary: Operation Effects................ 41 

FIGURES 

Figure 9.1 

Figure 9.2 

Figure 9.3 

Figure 9.4 

Figure 3.13 

Existing Hydrological Features 

Existing Drainage Zones 

Proposed Drainage Zones 

Typical Pond Layout 

River Avon Flood Compensation and Otter Mitigation 

APPENDICES 

Appendix A 

Appendix B 

Appendix C 

Pollution and Spillage Risk Calculations 

Glossary of Technical Terms 

Flood Risk Assessment 

Page ii




9.1 INTRODUCTION 

9.1.1 This chapter is an assessment of the potential environmental effects of the proposed M1 

Junction 19 Improvement on road drainage and the water environment. It comprises the 

environmental assessment of surface water, groundwater and flood risk during both 

construction and operation of the scheme. It includes calculations in line with the Design 

Manual for Roads and Bridges (DMRB) Volume 11, Section 3, Part 10, Annex 1. The 

chapter also provides recommendations for best practice and mitigation based on the 

outcomes of the assessment. 

9.1.2 In common with other Chapters, the Road Drainage and the Water Environment 

assessment recognises that the Catthorpe Viaduct, which carries the M6 to M1 

Southbound link over the M1, is being replaced as a maintenance project. The scope of 

this work includes the replacement of the bridge on a new alignment immediately to the 

south west of the existing. It also requires the creation of new approach embankments 

either side of the M1. The work is programmed to begin in June 2010, for completion in 

November 2011. 

9.1.3 The bridge and earthworks either side of the M1 would be retained in the proposed layout 

for the M1 Junction 19 Improvement, as would the alignment of the M6 to M1 Southbound 

link east of the M1. To the west of M1 this link would have to be amended to accommodate 

the proposed M6 to A14 link. 

9.1.4 A separate environmental assessment 49 has been carried out for the bridge replacement as 

a stand alone maintenance project. 

9.1.5 This ES for the M1 Junction 19 Improvement takes into account the new bridge both:- 

• As part of the existing junction, assuming the M1 Junction 19 Improvement is not built; 

the ‘do-minimum’ scenario 

• As part of the completed M1 Junction 19 Improvement; the ‘do-something’ scenario. 

9.1.6 In terms of road drainage and the water environment, the proposals for the viaduct 

replacement will be to match the existing drainage arrangements as far as possible, with 

only negligible differences in the locations of pipes and gulleys. There will also be some 

reduction in the highway area to be drained as the replacement viaduct will be narrower 

than the existing. 

9.1.7 These issues are dealt with in Section 9.6 Environmental Impact. 

Objectives 

9.1.8 The objectives for the road drainage and water environment assessment are:- 

• To protect the water environment 

• To reduce the risk of pollution and flooding 

9.1.9 In addition, there is a general scheme objective that the impact on the natural and built 

environment should be minimised. It is also considered that appropriate measures should 

be taken and best practice followed during and after construction, by the use of sustainable 

drainage techniques. 

B0531000_ID_70-EIA Vol 2 Chap 9 Road Drainage and the Water Environment Final Rev 4.doc Page 1




Study Area 

9.1.10 The Study Area consists of all of the surface water and groundwater resources likely to be 

directly or indirectly affected including, in particular, the River Avon and its tributaries. 

9.1.11 Sensitive surface water and groundwater features within the study area are identified and 

the potential impacts arising from the construction and operation of the scheme are 

assessed. The extent of the study area and features identified are illustrated on Figure 9.1. 

A glossary of technical terms used in this Chapter is at Appendix B. 

The Project 

9.1.12 Junction 19 of the M1 currently forms an interchange between the M1, M6 and A14 Trunk 

Road. In addition, it provides access to two minor roads, Rugby Road to Swinford and 

Swinford Road to Catthorpe, both of which connect to the A14 Trunk Road. 

9.1.13 A Comparative Environmental Assessment published in 2008 considered the potential 

impacts of five different options for the junction and the local road network. Following that 

assessment, the Red Junction and Orange Local Road Network was announced as the 

Preferred Route. 

9.1.14 The project is illustrated by a series of plans bound into a separate Appendix 1 to Volume 1 

of the ES as follows:- 

Interaction 

• Figure A : Location Plan 

• Figure B : Environmental Master Plan 

• Figure C : Environmental Resources Plan 

• Figure G : Areas Required During Construction 

• Figure H : Cross Sections 

9.1.15 There are interactions between this chapter and other chapters as follows:- 

• Chapter 3, Ecology and Nature Conservation, sets out the value of water features, and 

potential impacts upon them, as wildlife habitats. 

• Chapter 5, Materials, interacts with the groundwater element of this chapter. 

9.1.16 Care has been taken to avoid significant overlap or double counting of adverse impacts or 

benefits resulting from the proposals. 





9.2 METHODOLOGY 

9.2.1 This assessment has been carried out in accordance with the requirements of DMRB 

Volume 11, Section 3, Part 10, HA216/06 2006 2 . It should be noted that in November 2009, 

HA216/06 was replaced with HA45/09. However, this new guidance document was issued 

after the assessment reported in this chapter had been completed. For this reason, all 

references to Volume 11, Section 3, Part 10 of DMRB within this chapter are references to 

HA216/06, which was current at the time of the assessment. 

9.2.2 Baseline information has been compiled from documentary research, site reconnaissance, 

and liaison with appropriate organisations. Reference to specific sources is made as 

appropriate within the chapter. In addition to the Environment Agency,(EA), the following 

principal sources were consulted:- 

• Ordnance Survey (OS) maps 

• British Geological Survey (BGS) maps and memoirs 

• Previous site investigations 

9.2.3 A Scoping Report for the Environmental Assessment was produced in March 2009 3 , and a 

copy was sent to the EA. A consultation meeting was held with the EA on 24 th March 2009, 

and a written response was sent from the EA to the Highways Agency on 26 th May 2009. A 

further consultation meeting was held on 2 nd July 2009. 

9.2.4 The EA’s written comments included the following:- 

• A Flood Risk Assessment is required in accordance with PPS25. The Flood Risk 

Assessment 48 is at Appendix C. 

• Surface water should be managed in a sustainable manner. 

• The opportunity should be taken to improve on the existing situation to reduce the 

overall flood risk. 

• The Environmental Statement should assess the potential effects on the water 

environment during the construction phase and the operational phase. 

• Mitigation measures and residual impacts should be detailed within the Environmental 

Statement. 

9.2.5 The assessment has been undertaken within the framework of national and local planning 

policies, environmental guidance and legislation. These are set out in Section 9.3 below. 

The methodology follows that of DMRB 2 . Tables 9.1 to 9.4 summarise the DMRB grading 

(importance) of water features. 

9.2.6 Prediction of the nature and magnitude of the potential environmental impacts is based on 

knowledge of the proposed development (both construction phase and subsequent 

operation) and the environmental resources of the area, by identifying the different ways in 

which particular aspects of the development could affect particular aspects of the 

environment. This includes the size of the impact, for instance an increase in pollutant 

concentrations above threshold levels. 

9.2.7 The assessment of the significance of environmental effects of an action is determined by 

combining the magnitude of the impact with the environmental importance of the water 

resource, resulting in the prediction of the significance of the effects on that receptor. Table 

9.1 below sets out criteria for estimating the importance of water resources or ‘attributes’. 

Table 9.2 sets out the criteria for determining the magnitude of impact and the matrix in 

Table 9.3 combines the two to determine the significance of effect. Table 9.4 provides 





further guidance on the overall assessment of significance. Effects can be direct, indirect, 

secondary or cumulative, and can be permanent or temporary. Prediction also takes into 

account mitigation measures which have already been incorporated into the design, such 

as drainage design measures, or proposals for phasing parts of the development to restrict 

operations to a limited part of the year or day. Judgement may be made on the likelihood of 

an impact occurring. 

9.2.8 Prediction of the magnitude of impacts should not be confused with evaluation of their 

significance. The significance of an effect is the product of the magnitude and the 

sensitivity / importance / quality of the environmental resource which is affected. 





Table 9.1: Estimating the Importance of Water Environmental Attributes 

(Reproduced from DMRB Volume 11, section 3, Part 10, table 5.3) 2 

Importance Criteria Typical Examples 

Very High 

Attribute has a high 

quality and rarity on 

regional or national scale 

Surface Water: EC Salmonid/Cyprinid fishery; 

RQO River Ecosystem Class RE1 Site protected 

under EU or UK wildlife legislation (SAC, SPA, 

SSSI, Ramsar Site) 

Groundwater: Major aquifer providing a 

regionally important resource or supporting site 

protected under wildlife legislation; SPZ I 

Flood Risk: Flood Plain or defence protecting 

more than 100 residential properties from 

High 

Medium 

Low 

Notes : 

Attribute has a high 

quality and rarity on local 

scale 

Attribute has a medium 


scale 

Attribute has a low 


scale 

flooding 

Surface Water: RQO River Ecosystem Class 

RE2; Major Cyprinid Fishery; Species protected 

under EU or UK wildlife legislation 

Groundwater: Major aquifer providing locally 

important resource or supporting river ecosystem; 

SPZ II 

Flood Risk: Flood plain or defence protecting 

between 1 and 100 residential properties or 

industrial premises from flooding 


RE3 or RE4 

Groundwater: Aquifer providing water for 

agricultural or industrial use with limited 

connection to surface water; SPZ III 

Flood Risk: Flood plain or defence protecting 10 

or fewer industrial properties from flooding 


RE5 

Groundwater: Non-aquifer 

Flood Risk: Floodplain with limited constraints 

and a low probability of flooding of residential and 

industrial properties 

EC : European Community 

Salmonid : Fish species including salmon and trout 

Cyprinid : A family of soft finned mainly freshwater fish including carp, tench, rudd and 

dace 

RQO : River Quality Objective, set by the EA 

RE : River Ecosystem, set by the EA 

EU : European Union 

SAC : Special Area of Conservation. European designated wildlife site. 

SPA : Special Protection Area. European designated wildlife site 

Ramsar : European designated wildlife site. 

SPZ : Source Protection Zone 





Table 9.2: Criteria for Determining Magnitude of Impact 

(Based on DMRB, Volume 11, section 3, Part 10, table 5.4) 2 

Magnitude Criteria Example 

Major 

Adverse 

Loss of attribute and/or quality 

and integrity of attribute 

High risk of surface water pollution and potential 

failure of total zinc and dissolved copper, 

extensive change to a fishery or nature 

conservation site, loss of an aquifer or high risk of 

groundwater pollution, 100mm increase in flood 

Moderate 

Adverse 

Minor 

Adverse 

Negligible 

Minor 

Beneficial 

Moderate 

Beneficial 

Major 

Beneficial 

Effect on integrity of attribute 

or loss of part of attribute 

Measurable change in 

attribute’s quality or integrity 

Effects of insufficient 

magnitude to affect the 

attribute’s use or integrity 

Some beneficial effect or 

reduced risk of negative effect 

Moderate improvement to 

attribute quality 

Major improvement to attribute 

quality 

peak level (1% annual probability) 

High risk of surface water pollution and potential 

failure of either total zinc or dissolved copper, 

partial loss in productivity of a fishery, partial loss 

or change to an aquifer, medium risk of 

groundwater pollution, greater than 50mm 

increase in flood peak level (1% annual 

probability) 

High risk of surface water pollution but no change 

in total zinc and dissolved copper, low risk of 

pollution to groundwater, greater than 10mm 

increase in flood peak level (1% annual 

probability) 

Unlikely to affect the integrity of the water 

environment 

Table 9.3 Criteria for Estimating the Significance of Potential Effects 

(Based on DMRB Volume 11, section 3, Part 10, table 5.5) 2 

Reduction in spillage risk by 50% or more (where 

existing risk is less than 1% per annum), greater 

than 10mm reduction in flood peak level (1% 

annual probability) 

Reduction in spillage risk by 50% or more (where 

existing risk is greater than 1% per annum), 

greater than 50mm reduction in flood peak level 

(1% annual probability) 

Removal of existing polluting discharge or of 

existing potential polluting discharge, recharge of 

an aquifer, greater than 100mm reduction in flood 

peak level (1% annual probability) 

Criteria for Estimating the Significance of Potential Effects 

Magnitude of Importance 

potential impact Very High High Medium Low 

Major VERY LARGE LARGE / VERY 

LARGE 

LARGE SLIGHT / 

MODERATE 

Moderate 

LARGE / VERY MODERATE / MODERATE SLIGHT 

LARGE LARGE 

Minor MODERATE / SLIGHT / SLIGHT NEUTRAL 

LARGE MODERATE 

Negligible NEUTRAL NEUTRAL NEUTRAL NEUTRAL 





9.2.9 Significance should be assigned after consideration of proposed mitigation. In some cases, 

two alternatives are given for significance. In such cases, a reasoned judgement should be 

used to decide on a single description of significance. 

9.2.10 Potential effects can either be beneficial or adverse. 





Table 9.4 Overall Assessment Scoring 

(Based on DMRB, Volume 11, Section 3, Part 10, Table 5.6) 

Criteria Overall Score Predicted Outcome / Comment 

Very significant potential adverse impact on one or several water attributes. 

Very Large Degradation of water environment 

Adverse Effect 

At least one highly significant potential adverse impact, and/or 

Large Adverse Degradation of water environment 

significant potential adverse impacts on several water attributes 

Effect 

Moderate adverse impact on at least one water attribute 

Moderate Degradation of water environment 

Adverse Effect 

Slight adverse impact on one or more water attributes 

Slight Adverse Degradation of water environment 

Impact 

No appreciable effects on water attributes Neutral Generally impacts slight or 

moderate, possible but more 

difficult to balance more diverse 

adverse / beneficial impacts 

Proposal provides an opportunity to enhance the water environment or provide an 

improved level of protection for a water attribute 

Slight 

Beneficial 

Enhancement opportunity 

Proposal provides an opportunity to enhance the water environment, with a 

moderate improvement to a water attribute 

Effect 

Moderate 

Beneficial 

Effect 

Improvement opportunity 

(improvements should greatly 

outweigh negative impacts) 

At least one very significant /highly significant potential beneficial impact, and 

all potential adverse impacts insignificant 

Large 

Beneficial 

Effect 

Unlikely for major road scheme 





9.3 LEGISLATION AND POLICY FRAMEWORK 

UK and EC Legislation 

9.3.1 Relevant legislation comprises UK Acts and Regulations (many of the latter represent the 

incorporation of specific EC Directives into UK law), EC Directives and regulatory guidance. 

These are listed below in Table 9.5. The EA as statutory / regulatory authority applies these 

various forms of legislation to support the EA’s role to maintain and improve water quality 

within England and Wales. 

Table 9.5 Relevant UK and EC Legislation 

Title Water Feature Summary 

Water Resources Act 

1991 4 All waters, but 

specifically main 

rivers and 

groundwater 

abstraction 

Consolidates previous water legislation in respect 

of both the quality and quantity of water 

resources. Sets statutory objectives, giving the 

Government and the EA a legal duty to ensure 

that they are achieved. Gives EA power to grant 

licences for groundwater abstraction. Covers 

works in, over or under main river, control of 

pollution of waters, including discharge consents 

UK Town and 

Country Planning Act 

1990 5 Flood Protection Enables local authorities to enter into agreements 

with developers about how their land and flood 

defences should be managed. 

Land Drainage Act Ordinary (i.e. 

1991 6 not main) Rivers 

Gives local authorities powers to undertake flood 

defence works on watercourses which have not 

been designated as "main" and which are not 

within internal drainage board areas. Covers 

works within the river channel including discharge 

consents 

Environment Act 

1995 7 Main Rivers Establishment of the EA, and introduction of 

measures to enhance protection of the 

environment, including further powers for the 

prevention and remediation of water pollution. 

Control of Pollution 

Act 1974 8 

Surface waters 

and 

groundwater 

The Water 

Integrated river 

Environment (Water basin 

Framework Directive) management of 

(England and Wales) all surface 

Regulations 2003 9 , waters, 

and EC Water transitional 

Framework Directive waters and 

2000 (2000/60/EC) 10 coastal waters 

in England and 

Wales 

The Surface Water 

(River Ecosystem) 

Regulations 1994 11 

Makes it an offence for anyone to cause or 

knowingly permit any poisonous, noxious or 

polluting matter to enter any stream or controlled 

waters or any specified underground waters. 

The directive sets out environmental objectives 

for water status based on parameters of 

monitoring and assessment strategies, and sets a 

Programme of Measures in order to meet the 

objectives. The Regulations transpose the 

directive and deal with the responsibility and 

timescales for setting up River Basin Districts, 

characterisation, economic analysis of water use, 

bodies of water used for abstraction for drinking 

water, register of protected areas etc. leading to 

the development of River Basin Management 

Plans 

Sets out River Ecosystem Classification system 

used as River Quality Objectives by the EA. 





Title Water Feature Summary 

The Groundwater 

Regulations 1998 12 

and EC Groundwater 

Directive 1980 

(80/68/EEC) 13 Groundwater Gives the EA powers to issue notices to control 

activities other than licensed disposal, where 

these are likely to result in an indirect or direct 

discharge of a listed substance to groundwater. 

Surface Waters 

(Dangerous 

Substances) 

Regulations 1992, 

1997 and 1998 14 ; and 

Surface Water 

(Classification) 

Regulations 1989 15 , 

and EC Dangerous 

Substances Directive 

(76/464/EEC) 16 Surface Waters Addresses specific hazardous substances such 

as mercury, cadmium and chloroform that may be 

discharged into surface waters and sets limit 

values for discharges and Environmental Quality 

Objectives (EQOs) for receiving waters. 

The Surface Waters 

(Abstraction for 

Drinking Water) 



and EC Surface 

Water Abstraction 

Directive 

(75/440/EEC) 18 

Potable 

Abstraction from 

surface waters 

Sets quality objectives for the surface water 

sources from which drinking water is taken 

The Surface Waters 

(Fishlife) 



the Surface Waters 

(Fishlife) 


(Amendment) 

Regulations 2003 and 

EC Freshwater Fish 

Directive 

2006(2006/44/EC) 20 Fisheries Protection of the health of freshwater fish and 

shellfish populations, by designating waters in 

need of protection and setting quality standards 

for those waters. 

Salmon and 

Fisheries In England and Wales, it aims to prevent the 

Act 1975 21 to fisheries or their habitat. 

Freshwater Fisheries 

spread of fish diseases and to minimise damage 

Environment Agency Pollution Prevention Guidelines 

9.3.2 The proposed scheme would also need to take note of the EA’s Pollution Prevention 

Guidelines (PPGs) 22 , which provide advice on statutory responsibilities and good 

environmental practice. The following PPGs are considered to be relevant to the scheme:- 

• PPG1 – General guide to the prevention of pollution of controlled waters 

• PPG3 – The use and design of oil separators 

• PPG5 – Works in, near or liable to affect watercourses 

• PPG6 – Working at construction or demolition sites 

• PPG8 – Safe storage and disposal of used oils 





• PPG21 – Pollution incident response planning 

• PPG22 – Dealing with spillages on highways 

UK Planning Policy Guidance 

9.3.3 The Department for Communities and Local Government (DCLG) provides guidance in the 

form of Planning Policy Statements (PPSs) and Planning Policy Guidance Notes (PPGs). 

Relevant PPSs and PPGs are as follows:- 

• PPS 25 Development and Flood Risk, 2006 23 . This provides guidance on the protection 

of development to ensure public safety and prevent damage to property as a result of 

flooding. A Flood Risk Assessment 48 carried out in accordance with PPS25 is at 

Appendix C. 

• PPS23 Planning and Pollution Control, 2004 24 . This provides guidance on the protection 

of the environment and humans from pollution from development in England. 

• PPG13 Transport, 2001 25 . This provides guidance to local authorities and others on 

transport and land use planning. 

Regional Planning Policy 

West Midlands Regional Spatial Strategy (2008) 26 

9.3.4 The Regional Spatial Strategy for the West Midlands was adopted in 2008 and includes 

provisions for the protection and improvement of water quality and the reduction of flood 

risk. These aims can be found in policies CC1: Climate Change and QE9: The Water 

Environment. 

East Midlands Regional Plan (2009) 27 

9.3.5 The East Midlands Regional Plan was adopted in 2009 and includes the provision of up-todate 

policies which cover drainage and the water environment. In particular policy 32: A 

Regional Approach to Water Resources and Water Quality covers the protection and 

improvement of water quality and seeks to insure that development does not increase the 

risk of pollution to vulnerable water resources. Policy 35: A Regional Approach to 

Managing Flood Risk aims to ensure that development does not increase the risk of 

flooding. 

Local Authority Planning Policy 

Daventry District Council Local Plan (1997) 28 

9.3.6 The Daventry District Council Local Plan was adopted in 1997. In September 2007 any 

policies not “saved” expired, among these expired policies were all policies relating to 

drainage and the water environment. 

9.3.7 These policies are to be eventually replaced with emerging policies under the Local 

Development Framework (LDF). Daventry are producing a joint Core Strategy as part of 

the LDF which is the West Northamptonshire Joint Core Strategy (2007) 29 which is 

currently at the Issues and Options Stage. This means that any policies are currently only 

in draft form. As the Core Strategy is currently at Issues and Options Stage there are not 

yet any policies, but the strategy does set out Strategic Objectives which will inform the 

basis of future policies. Strategic Objective 8 of the Core Strategy aims to ensure that 

development is sensitive to its environment. 





Harborough District Council Local Plan (2001) 30 

9.3.8 The Harborough District Local Plan was adopted in 2001 and all policies that were not 

formally saved expired in September 2007. There are no saved policies which relate to 

drainage and the water environment. 

9.3.9 Harborough are in the process of producing their Core Strategy which is currently at the 

Final Draft stage. Within this document (2009), Potential Strategy ST1 states that all 

development must help mitigate and adapt to climate change and that development in 

areas liable to be at risk of flooding will therefore be avoided. 

Rugby Borough Council Local Plan (2006) 31 

9.3.10 The Rugby Borough Local Plan was adopted in 2006 and contains a number of saved 

policies. Policies GP10: Flooding and Surface Water Drainage and GP11: Pollution Control 

of the local plan cover issues relating to drainage and the water environment. Policy GP10 

aims to ensure that development does not increase the risk of flooding and that all 

developments should incorporate sustainable drainage systems. Policy GP11 requires 

development proposals to show that there would not be any resulting pollution to surface or 

ground water. 

9.3.11 In addition to the saved policies in the Local Plan, the emerging Core Strategy for Rugby is 

currently at the Proposed Submission Draft Stage. Within the Draft Submission Core 

Strategy Document (2009), there are no specific policies which relate to drainage or the 

water environment. 

North Northamptonshire Core Strategy (2008) 32 

9.3.12 The North Northamptonshire Core Strategy was adopted in 2008 and is a joint Core 

Strategy covering the areas of Corby, Kettering, Wellingborough and East 

Northamptonshire. Within this document Policy 13: General Sustainable Development 

Principles covers issues relating to the protection of ground water and surface water from 

pollution, as well as ensuring that the development does not increase flood risk. In addition 

to these requirements it also states that development should incorporate sustainable 

drainage systems. 





9.4 BASELINE CONDITIONS 

Surface Water 

9.4.1 The existing distribution of surface waters in the area is shown on Figure 9.1. Junction 19 

of the M1 lies within the upper catchment of the River Avon. The River Avon flows in a 

broadly south-westerly direction; it is crossed by the eastern extent of the A14 Trunk Road 

within the study area, and is also crossed further downstream by the southern extent of the 

M1 within the study area. 

9.4.2 There are a number of tributaries in the vicinity of the junction which predominantly flow 

southwards / south-westwards / south-eastwards to the River Avon. These include the 

Swinford Lodge Brook, which is located to the north east of the junction and flows beneath 

the eastern extent of the A14 Trunk Road. Another tributary, the Clay Coton Yelvertoft 

Brook, is located to the south east of the junction and flows westwards, converging with the 

River Avon adjacent to and east of the M1. 

9.4.3 The River Avon and Clay Coton Yelvertoft Brook are classified as ‘main’ rivers. All others 

are ‘ordinary’ watercourses. 

9.4.4 A network of drains and ditches currently collects highway runoff from the M1, M6 and A14 

Trunk Road, which is then discharged at some 11 locations to the adjacent watercourses 

(as shown on Figure 9.2). Summary details of the drainage areas or ‘zones’ and their 

discharge points to the receiving watercourses are shown in Table 9.6 below. The areas 

quoted in the table are those within the limits of the scheme as illustrated on Figure 9.2. 

The drainage of highways outside the scheme limits as noted on Figure 9.2 has not been 

included in the assessment. In some areas, land and highway drainage are combined prior 

to discharge, which is sometimes direct, to the various receiving watercourses. Water 

courses are currently culverted at three locations within the scheme area, beneath the M1, 

M6 and A14 Trunk Road. There are two bridges over the River Avon. 

Table 9.6 Summary Details of Existing Highway Drainage 

Drainage Highway Sections 

Area Receiving Water Course 

Zone 

(m 2 ) 

1 Northern extent of M1 8209 Tributary of Swinford Lodge 

Brook 

2 Majority section of M1 54064 Swinford Lodge Brook 

between Zone 1 and north of 

interchange including various 

slip roads 

3 M1 south of Zone 2 extending 61383 River Avon 

southwards to just north of 

River Avon 

4 South of Zone 3, section of 8753 River Avon 

M1 over River Avon 

5 South of Zone 4, comprising 20800 Clay Coton Yelvertoft Brook 

most of remaining southern 

extent of M1 

6 Mostly westbound section M6, 

west of interchange including 

various slip roads, between 

Zones 1, 3 and 9 

32421 Tributary of River Avon (name 

unknown) 





Drainage Highway Sections 

Zone 

7 Majority section of A14, south 

of Zone 2 

8 Western extent of M6, west of 

Zones 1 and 7 

9 Eastern extent of A14, east of 

Zone 8 

Area Receiving Water Course 

(m 2 ) 

21614 Swinford Lodge Brook 

11492 Tributary of River Avon (name 

unknown) 

1174 River Avon 

9.4.5 A number of ponds exist within the vicinity of the junction, of which some 16 are within 100 

metres of the highway edge. These vary in size from small field ponds to an ornamental 

lake within the grounds of Catthorpe Manor. Figure 9.1 shows the distribution of ponds. 

Ponds are described in more detail in Chapter 4 Ecology and Nature Conservation. 

Surface Water Abstractions 

9.4.6 There are three surface water abstractions, licensed by the EA, within 1km of the proposed 

junction improvement. These abstractions are from an un-named brook to the north west of 

the junction, and are for general farming and domestic purposes. There are no licensed 

surface water abstractions within 500 metres of the proposed scheme. 

9.4.7 Severn Trent Water Ltd. abstracts water from the River Avon for public supply some 7km 

downstream of the junction, at Brownsover Mill, Rugby. 

Fisheries 

9.4.8 The EA has stated that the River Avon at Ryton (some 17km west-south-west of Junction 

19) is a ‘prime coarse fishing river containing most coarse fish species and a prime 

spawning area for Chubb, Barbell and Dace’, and the stretch of the River Avon 

downstream of Rugby (some 5km south-west of Junction 19) to Tewkesbury is considered 

one of the most important river coarse fisheries in the West Midlands. 

9.4.9 The EC Freshwater Fish Directive (2006/44/EC) seeks to protect those water bodies 

identified by Member States as waters suitable for sustaining fish populations. Under the 

Surface Waters (Fishlife) (Classification) Regulations 1997, and the Surface Waters 

(Fishlife) (Classification) (Amendment) Regulations 2003 19 , a number of cyprinid fisheries 

are designated along the River Avon. 

Surface Water Quality 

9.4.10 The EA uses the General Quality Assessment (GQA), based on the chemical parameters 

of dissolved oxygen, biochemical oxygen demand and ammonia, to measure the water 

quality characteristics of water bodies. 

9.4.11 The EA takes samples of water quality in the River Avon at Welford, approximately 11 

kilometres upstream of Junction 19. The water chemistry was consistently at Grade A (very 

good) between 1999 and 2007. No more recent data is available. Grade A rivers have 

natural ecosystems and may be used for any type of abstractions including potable supply. 

Nitrate levels in 2007 at this location were Grade 3 (moderately low), and Phosphate levels 

were Grade 2 (low). Nitrates and Phosphates are both indicators of nutrient loading, often 

resulting from the run off of agricultural fertilisers. As indicated by the grading system, low 

levels are considered to be better in terms of water quality. 





9.4.12 The EA also takes samples on the River Avon at the confluence with Clifton Brook, 

approximately seven kilometres downstream of Junction 19. The water chemistry at this 

location in 2007 (the most recent available data) was Grade B (good), and has varied 

between Grades B and C (fairly good) over recent years. Nitrate levels in 2007 at this 

location were Grade 3 (moderately low), but Phosphate levels were Grade 4 (high). At this 

downstream location, the EA also measures the biological quality of the water samples by 

taking into account the number and diversity of macro-invertebrates present. The biological 

water quality at this location is Grade C (fairly good). 

9.4.13 EA water quality sampling data is also available for the Clay Coton Yelvertoft Brook 

immediately before its confluence with the River Avon. However, the most recent available 

data for this location is from 2005. The water chemistry varied between Grade B (good) in 

2002 and Grade D (fair) in 2004 at this location. Data from 2005 shows that nitrate and 

phosphate nutrient levels were very high. 

9.4.14 River Ecosystem Classifications were introduced under the Surface Water (River 

Ecosystem) (Classification) Regulations 1994. For each River Ecosystem (RE) Class, River 

Quality Objectives (RQOs) are set. These relate directly to measured GQA parameters. As 

the River Avon upstream of the proposed junction improvements is of GQA Grade A, it is 

understood be of RE Class 1. 

9.4.15 Hardness, dissolved copper, total zinc and pH values have been recorded in the River 

Avon, both at Welford (upstream of Junction 19) and at the confluence with Clifton Brook 

(downstream of Junction 19). The most recent available data is from 2006. At Welford, the 

average hardness was 322 milligrammes per litre (mg/l) CaCO 3 , average dissolved copper 

was 2.52 micrograms per litre (µg/l), average total zinc was 1.99 µg/l, and the pH was 7.88. 

At Clifton Brook, the average hardness was 368 mg/l CaCO 3 , average dissolved copper 

was 1.46 µg/l, average total zinc was 3.95 µg/l, and the pH was 7.91. 

9.4.16 The potential impact of discharges from the highway runoff on water quality in the receiving 

watercourses has been estimated for the do minimum scenario (i.e. the situation without 

the scheme in place) for 2029 for dissolved copper and total zinc, in accordance with 

DMRB guidance (see Appendix A). This indicates that, for most drainage zones, the risk of 

pollution from routine runoff from all drainage zones combined is low. However, the risk in 

two areas was higher, and required further assessment using Method B. These were 

drainage zones 2 and 6. The Method B assessment found that no mitigation would be 

needed for the discharge from the existing drainage zone 2, but that the discharge from the 

existing drainage zone 6 would require mitigation if it were to be designed in line with 

current guidance. 

Pollution Incidents Affecting Surface Water 

9.4.17 In addition to routine highway discharges, there have been a number of pollution incidents 

associated with the road traffic network recorded by the EA. These have not been 

comprehensively listed here but include spillage of cattle slurry at M1 Junction 19 in 

September 1997, spillage of 500 litres of caustic soda at M1 Junction 19 in November 1997 

and diesel spillage from a traffic accident between M1 Junction 19 and Junction 20 in April 

1999. One diesel spillage at the Junction in 1995 affected public water supply abstraction 

from the River Avon. 

9.4.18 The pollution risk is expressed as the probability of an incident in any one year. In most 

circumstances, the acceptable risk of a serious pollution incident occurring will be where 

the annual probability is predicted to be less than 1%. Using the DMRB methodology, the 

assessment indicated that, for the do-minimum scenario for 2029, the accident probability 





would be below 1% for each drainage zone, and would be 0.5% for all drainage zones 

combined. This means that the do-minimum scenario would present an acceptable risk of a 

pollution incident occurring. 

Surface Water Discharges 

9.4.19 In addition to the highway discharges described earlier, which are currently exempt from 

licensing, there are a number of consented discharges to the various watercourses in the 

area. The majority comprise treated sewage / storm effluent from both water companies 

and private residences. There are also a few site drainage trade effluent discharges. 

Groundwater 

9.4.20 Published geological and ground investigation information form the basis of the geological 

baseline conditions. The geology is described in more detail in Chapter 5 Materials. 

9.4.21 The general geological sequence is of Glacial Till overlying Jurassic Lower Lias Group 

mudstones, which has been dissected by the River Avon and its tributaries causing erosion 

and removal of the Glacial Till cover in places and deposition of overlying younger river 

terrace gravels and alluvium. Thus there are small outcrops of Glacial Till along the 

western extent of the M6, the most northern and southern extents of the M1 (although the 

cuttings have exposed the underlying solid strata in places) and also beneath part of the 

area of the Junction. Extensive deposits of river terrace gravels and alluvium are 

associated with the River Avon and Clay Coton Yelvertoft Brook. There are lesser fluvial / 

alluvial deposits associated with the Swinford Lodge Brook and tributary and also some unnamed 

watercourses which are crossed by the M6. 

9.4.22 There are some areas of made ground (described in more detail in Chapter 5 Materials), 

mainly associated with borrow pits from various earlier phases of road construction, which 

appear to have been infilled with ‘inert’ construction waste. There is a former Cleanaway 

landfill site (Catthorpe Landfill, NGR SP 553 787) located adjacent to the south of the M6, 

which was licensed between 1977 and 1986 to receive domestic and industrial wastes. 

9.4.23 The alluvium generally comprises soft to firm alluvial clay and silt up to about 5m deep in 

the vicinity of the River Avon. The river terrace gravels comprise interbedded very gravelly 

clay, gravelly sand, and gravel (mainly of flint) between about 1 to 3m thickness. The 

Glacial Till, varying between gravelly clay to firm to still clay is up to 10m thick. The Lower 

Lias strata comprise a sequence of horizontal to sub-horizontal, predominantly ‘hard’ clays 

/ mudstones with occasional thin limestone and (separate) ironstone bands. The Lower 

Lias is between 140-170m thick. 

9.4.24 The river terrace and fluvio-glacial / alluvial deposits are classified as minor aquifers. The 

distribution of the minor aquifer is shown on Figure 9.1. Minor aquifers are usually of only 

local importance for supporting abstractions or providing baseflow to surface waters. The 

Lower Lias strata and Glacial Till deposits are generally classified as non-aquifers, 

although specific units within the former can have minor aquifer status. Non-aquifers 

usually do not support any abstractions or provide significant baseflow to surface waters. 

However, some of the thin limestones within the Lias can yield significant quantities of 

water. The proportion of water-bearing limestones increases towards the base of the Lower 

Lias Group, forming the Blue Lias or Scunthorpe Mudstone Formation, which can be 

classified as a minor aquifer. On the basis of interpretation of the published geological map, 

the strata below the proposed scheme are towards the top of the Lower Lias Group 

sequence, and therefore would indicate non-aquifer status. 





Groundwater Abstractions and Source Protection Zones 

Private Supplies 

9.4.25 Abstractions below 20m 3 /day (with a number of exceptions) do not require a licence from 

the EA; these private supplies are registered with the relevant Local Authority. There is one 

private well (NGR SP 5610 7775) within 1km radius of the proposed scheme, registered 

with Harborough District Council, located at Station House, Lilbourne, 250m west of the 

M1. On the basis of location, it would appear to be sourced by groundwater within the river 

terrace gravels / alluvial deposits. 

Licensed Abstractions and Source Protection Zones 

9.4.26 The Envirocheck Report for the site, dated March 2009, shows two abstractions from 

groundwater within 500 metres of the proposed junction improvement. These abstractions 

are for general farming and domestic use. In addition, there are 26 abstractions from 

groundwater between 500m and 1km from the site. Of these, 21 are for mineral washing / 

mineral products at Gibbett Quarry in Shawell, to the north west of the Junction, and six are 

for general farming and domestic use at other locations. 

9.4.27 No groundwater source protection zones (SPZs) are shown on the EA website records 

within 1km of the proposed scheme. The nearest SPZs are approximately 7km to the north 

east, near to Welford and North Kilworth. 

Groundwater Levels and Flow 

9.4.28 No published hydrogeological map exists for the area. It is understood that the nearest EA 

observation borehole information is located some 3km to the north-west of the scheme. 

However, a number of ground investigations have been undertaken within the area and 

monthly groundwater monitoring was carried out between April 2004 and August 2006. 

There is little / no groundwater information near the northern section of the M1 and east 

along the A14. Groundwater level and monitoring data was recorded within the underlying 

Lower Lias bedrock and also in the localized Alluvium, River Terrace Deposits and Glacial 

Till. Analysis of the data indicates that groundwater is in hydraulic continuity across the 

geological strata; however, shallow perched groundwater may be present within highly 

permeable lenses in the superficial deposits. 

9.4.29 Monitoring data shows groundwater levels fall from 112.5m AOD along the M6 in the west 

to 110m AOD in the vicinity of the interchange, 108.5m AOD along the A14 to the east and 

93.5m AOD to the south along the M1. Groundwater levels therefore appear to fall to the 

south and east, towards local surface waters and broadly ‘shadowing’ topography. Hence, 

surface waters are likely to be in hydraulic continuity with the underlying aquifer. 

Groundwater Vulnerability 

9.4.30 The Environment Agency’s Groundwater Vulnerability Map, Sheet 30, 1996, shows soils of 

low leaching potential over the minor aquifer. This means that pollutants are unlikely to 

travel through the soil layer into the groundwater, and the groundwater vulnerability is 

therefore low. The non-aquifer is of negligible vulnerability. 

9.4.31 At the time of writing, further Ground Investigation works are underway which will provide 

further data on ground water levels. However, as the data is not currently available, it 

cannot be taken into account in this assessment. 





Surface Water Flows and Flood Risk 

9.4.32 The EA previously supplied flow summary statistical data from the gauging station at 

Lilbourne for the River Avon. This indicated Q 95 flows (95 percentile flows taken as 

equivalent to ‘dry weather or low flow’, i.e. flow rate which is exceeded 95% of the time) of 

0.474m 3 /s (1963-2002). The Comparative Assessment Report 1 noted that there were 

considerable discrepancies between these values and those estimated for verification 

purposes using the Flood Estimation Handbook Volume 4 – Institute of Hydrology, 1999, 

Flood Studies Report Rainfall Runoff Method (FEH method) 33 . The EA values were 

significantly lower. The FEH method estimated Q 95 flow of 0.71m 3 /s for the River Avon 

where it is crossed by the M1. 

9.4.33 Following discussion with the EA, it was ascertained that there was ‘low confidence in the 

accuracy of the data supplied’, and the FEH method was therefore used to estimate flows, 

as would be necessary for the majority of the watercourses where flow monitoring is not 

routinely carried out. 

9.4.34 The floodplain of the River Avon and the Clay Coton Yelvertoft Brook is crossed by the A14 

Trunk Road to the east of the junction and the M1 to the south. The indicative floodplain is 

shown on Figure 9.1. The indicative floodplain is interpreted as the flood risk area based on 

an event with a 1% chance or occurring in any given year, otherwise described as a 1 in 

100 year flood event. Figure 9.1 also indicates the floodplain with a 0.1% chance of 

occurrence in any given year, i.e. a 1 in 1,000 year flood event. 

Sensitivity Assessment of Receptors 

9.4.35 Table 9.7 summarises the importance of the various features using the criteria set out in 

Table 9.1. 

Table 9.7 – Water Environment Features Summary 

Feature & 

Attribute / Service 

Surface Water 

River: 

Water supply 

Transport & dilution of 

waste products 

Quality 

Indicator 

Chemical 

water quality 

Scale A , Details and 

Grading 

Regional / Local: River 

Avon RE1 

Regional / Local: Clay 

Coton Yelvertoft Brook 

RE2 

Importance 

Very High 

High 

Local: Status of other 

water courses not recorded 

(assumed) 

Medium - Low 

Non potable 

abstraction 

Local: No abstractions 

within 2 km downstream: 

Low 

Drinking water 

supply 

National / Regional: River 

Avon drinking water supply 

downstream of 

development. 

High 





Feature & 


River: 

Biodiversity B 

River: 

Conveyance of flow and 

material 

Still Waters: 

Biodiversity 


Groundwater: 

Water supply 

Transport and dilution of 

waste products 

Quality 

Indicator 

Biological 


Fisheries 

quality 

Nature of 

watercourses 

Non potable 

abstraction 


supply 

Vulnerability 


Grading 


Avon GQA C (monitored 

downstream of site) 


water courses not recorded 

Regional: River Avon 

designated cyprinid fishery 


watercourses not recorded, 

assumed undesignated / 

non fishery 


Avon and Clay Coton 

Yelvertoft Brook both main 

rivers assumed




Feature & 


Flood Risk 

Floodplain: 

Conveyance of flood 

flows 

Quality 

Indicator 


Grading 

Local: Minor alluvial & river 

terrace gravel deposits 

aquifer with low leaching 

soils 

Local: Non aquifer Lower 

Lias Group strata & Glacial 

Till 

Surface waters Regional / Local: Proposed 

Development within River 


Yelvertoft Brook 1:100 year 

indicative floodplain 

Groundwater Local: Alluvial and river 


with water table in places 

below 1m 

Local: Clay soils 

Importance 

Low 

Low 

Medium 

Medium 

Low 

A 

The majority of features are deemed to be of ‘local’ scale. Regional / national status has been 

afforded to important main rivers, public water supplies, major aquifers etc. 

B Conservation value is not included; this is covered within Chapter 3 Ecology and Nature 

Conservation 





9.5 MITIGATION 

9.5.1 During the construction and subsequent operation of the junction improvement, there would 

be a number of activities which have the potential to impact upon controlled waters, as 

described below. 

Potential Impacts 

Construction 

9.5.2 The following potential impacts could occur during construction:- 

Operation 

• Generation of surface runoff containing high suspended solids arising from various 

activities including soil stripping and landscaping, demolition, excavation, infilling, 

embankments, importation and exportation of soil or fill material, storage and 

stockpiling, dust suppression, wheel washes, etc. 

• Spillages of oil, fuel or other construction chemicals 

• Piling for any of the larger structures 

• Watercourse crossings and diversions 

• Works within the floodplain 

• Disturbance of contaminated land, such as the former landfill 

• Dewatering 

• Creation and removal of ponds, diversion and culverting of existing watercourses 

• Development within the floodplain 

9.5.3 The operational phase covers the use of the junction once construction has been 

completed. The following potential impacts could occur over the long term:- 

• Highway runoff discharges including spillages of predominantly oil/fuel and de-icing 

• Piled foundations providing pathways for migration 

• Changes to land drainage, surface runoff and water quality 

Construction Environmental Management Plan 

9.5.4 A Construction Environmental Management Plan (CEMP) is being developed for the 

junction improvement. An outline CEMP 34 has been prepared and is reported in Volume 1 

of this ES. This identifies potential areas and / or activities which may lead to water 

pollution or other adverse consequences, and sets out good site practice and management 

which would avoid or minimise such outcomes while also providing instruction on 

emergency response procedures to be adopted following a specific incident. The outline 

CEMP sets out the key measures that would be implemented on the site to manage water 

resources on the site throughout the construction works. 

9.5.5 Proposed environmental protection measures relevant to protection of the water 

environment would include:- 

• First construction activities would be the construction of drainage ponds, and the 

extension of the drainage outfall culvert and ditch system 

• Fuel storage: All fuel would be stored, in accordance with the Control of Pollution (Oil 

Storage) Regulations 2001 35 , away from watercourses, drains and other sensitive 

receptors. Emergency spillage clean up kits would be provided at all refuelling points 





and strategic points around the work site. Emergency grab packs would be provided in 

site vehicles. Fuel storage points would be located in the site compound. Refuelling 

would be carried out by trained operatives. Regular checks would be carried out on fuel 

storage areas. 

• Drainage: An effective temporary drainage system would be maintained for the duration 

of the works. In general, the permanent drainage ponds providing attenuation, pollution 

control and water treatment shown on Figure 9.3 would be constructed early in the 

works to enable these pollution control measures to be utilised during the construction 

phase. The operation of these ponds is described under drainage below. Where the 

permanent locations of the ponds would conflict with ongoing construction operations, 

for example pond 2b shown on Figure 9.3, then temporary ponds would be provided. 

Mobile settlement tanks and temporary oil interceptors (in the compound area) would 

be used to control and treat all water produced during the construction process. Where 

necessary, the features would be reinstated to their full design standard before 

completion of the project. 

• Dewatering: Where small volumes of water would be required to be removed from an 

excavation, water would, where possible (and with appropriate EA consent) be pumped 

to a local soakaway point to return to the underlying groundwater. 

• The flood compensation areas required as a consequence of the scheme, described 

under flood compensation below, would be constructed at an early phase of the project. 

• A site environmental management team would be employed to oversee implementation 

and monitoring of the CEMP. 

• Site Compound: The setting up procedures would include installation of temporary 

drainage and material storage areas, including fuel storage. Environmental measures 

taken to minimise impacts would include: fuel storage (double bunded tank 

arrangement, pollution control measures and a site based emergency response team, 

all in accordance with the fuel storage regulations) and drainage (temporary foul and 

surface water drainage system would be installed, and the surface water system would 

include interceptors. These interceptors would be emptied regularly and following any 

spills). 

9.5.6 Similar measures, where appropriate, will also apply to the Catthorpe Viaduct Replacement 

which will be provided as a maintenance project in advance of the junction improvement. 

No flood compensation will be required for these works. 

Permanent Drainage 

9.5.7 The permanent solution for the drainage of the M1 Junction 19 Improvement would 

maintain the existing drainage patterns, with improved pollution control and reduced overall 

discharge rates compared with the existing situation. 

9.5.8 Figure 9.3 shows the proposed drainage arrangements for the junction improvement. They 

include mitigation measures for ‘normal’ runoff and pollution incidents for the main road 

network. 

9.5.9 Water quality treatment and pollution incident control would be provided by ponds for 

drainage catchments 2a, 3b, 2c, 3b, 3c, 3d, 7a, 7b and 7c. Figure 9.4 shows the plan and 

section of a typical drainage pond designed to attenuate or reduce the flow of highway runoff, 

to provide pollution control in the event of a spillage and to treat the water by removing 

pollutants. The plan and section are diagrammatic, intended to illustrate in principle the 

functional design of the system. Actual outlines are illustrated on Figure B, the 

Environmental Master Plan. The typical design includes a two pond system to collect 

sediment and pollutants, with the majority of sediment settlement occurring in the first 





pond, and vegetation within the second pond enabling ‘polishing’ of the flow prior to 

discharge to the receiving water courses. The first pond is designed to take the first flush of 

water from the drainage network, which would carry the heaviest pollution load. If a storm 

event continues, cleaner water would then bypass the first pond and go direct into the 

second pond. A baffle between the two ponds would also trap any floating oils in the first 

pond. The ponds would be lined so that there would be no discharges to groundwater. A 

system of penstocks and baffles would be designed to isolate any pollution incident spillage 

that may enter the drainage network. 

9.5.10 Fixtures known as booming eyes would be included to enable the emergency services to fit 

temporary booms to catch contaminants in the event of a pollution incident. The emergency 

services would also be made aware of the location of the ponds, their access points and 

penstock operation and specific signs would be erected to show how best to access the 

systems. A small spillage could be contained within the first pond, and the second pond 

could also be used where necessary. The drainage ponds would be incorporated into a 

maintenance and management programme in order that the ponds would continue to 

function effectively as designed. For this reason the drainage ponds have been included in 

the Compulsory Purchase Order for the project and would be retained by the Highways 

Agency for permanent management. Access roads have been provided as illustrated on 

Figure B for maintenance vehicles. 

9.5.11 Catchments 1, 3a, 4, 5, 8 and 9 would be retained without any modifications to the highway 

drainage network. The impermeable area draining to 3a, 4 and 5 would not change, and 

the impermeable areas of catchments 1, 8 and 9 would increase only slightly. Therefore, 

attenuation ponds are not proposed for these catchments. The EA have asked for pollution 

control measures to be provided for all outfalls within the scheme limits, including those 

that discharge water collected from catchments which extend beyond the scheme area. In 

response, pollution control measures are proposed as follows: 

• For Catchment 1, a petrol interceptor and penstock would be installed, subject to 

detailed surveys 

• For Catchment 3a, a penstock would be installed to contain pollution spillage incidents 

• For Catchments 4 and 5, no pollution controls are proposed. The only work to the 

highway proposed within these catchments is white-lining. There would be no increase 

in the impermeable area draining to these outfalls. 

• For Catchments 8 and 9, more surveys are required during the detailed design. As a 

minimum, the aim is to include penstocks to control pollution incidents. 

9.5.12 In terms of run-off discharge rates, the ponds have been designed in accordance with EA 

requirements. The EA have requested that, in accordance with PPS 25, the improvement 

scheme should reduce the net discharge rate from the existing sections of motorway within 

the limits of the scheme (21.99 hectares in extent) by at least 20% to allow for the effect of 

climate change. The proposed discharge rates from the ponds have been designed to 

achieve this net reduction in discharge flow with an allowance being made for a greenfield 

run-off rate of five litres per second per hectare plus an additional allowance of 20% for 

climate change, as agreed with the EA, for the new sections of carriageway within the limits 

of the scheme (5.70 hectares in total). The scheme limits are defined on Figures 9.2 and 

9.3. The storage volume of the ponds is designed to achieve these proposed discharge 

rates based on the run-off from a 1 in 100 year storm event. 

9.5.13 Drainage from the local road network is not included in these arrangements. Over-the-edge 

drainage into adjacent ditches is proposed for the local road network when at ground level 

or on embankment. 





9.5.14 Where the local roads are in cutting, kerb and gully drainage is proposed on the low side of 

the carriageway to drain the carriageway run-off, and filter drainage is proposed on the high 

side of the carriageway to collect the run-off from the earthworks slopes. The water from 

these areas would drain into the treatment ponds. Swinford Road would be in a particularly 

deep cutting beneath the M6. This water would therefore be incorporated into the mainline 

drainage for the M6-A14 via deep pipes, and would outfall via drainage pond 7. 

9.5.15 As set out in the introduction the proposals for Catthorpe Viaduct Replacement will be to 

match the existing drainage arrangements as far as possible, with only negligible 

differences to the locations of pipes and gulleys. There will also be some reduction in the 

highway area to be drained as the replacement viaduct will be narrower than the existing. 

9.5.16 No provision of drainage ponds or petrol interceptors as described for the junction 

improvement above is included for the viaduct replacement works. 

9.5.17 There will be some widening as a precautionary measure of approximately 400 metres of 

an existing drainage ditch along the eastern side of M1 to the north of the River Avon. 

Mitigation measures will be used to minimise the risk of any suspended solids reaching the 

River Avon, including phasing the regrading to reduce the duration of disturbance. 

Flood Compensation 

9.5.18 Proposed works to widen the A14 embankments would displace part of the floodplain of the 

River Avon, and thereby reduce flood storage capacity. In addition, two bridleway bridges 

would be built in the floodplain, and would also reduce the capacity. To mitigate these 

impacts, several flood compensation areas would be excavated to provide 587m 3 of 

additional flood storage capacity. The locations are illustrated on Figure 3.13. 

9.5.19 As set out in Development and Flood Risk – Guidance for the Construction Industry Report 

C624 by CIRIA 36 , compensatory flood storage must become effective at the same point in a 

flood event as the lost storage would have done. It therefore has to provide the same 

volume and be at the same level relative to flood level as the lost storage. This requirement 

is often referred to as “level for level” or “direct” compensation. 

9.5.20 The various areas shown on Figure 3.13 have been selected to be at the appropriate level. 

Some of the proposed compensation areas would be returned to agricultural use. Others 

have been sited to coincide with proposals for habitat creation and these are described in 

detail in Chapter 3 Ecology and Nature Conservation. 

9.5.21 Unlike the drainage ponds described above, the Highways Agency does not intend to take 

permanent title to the areas required for flood compensation. The intention is to hand them 

back to the original landowners on completion of the works. However, as a precaution the 

areas will be included in the CPO to ensure certainty that they can be provided. Upon 

completion the areas would become part of the flood plain regulated by the EA. 

River Channel Regrading 

9.5.22 Figure 3.13 also shows sections of the river bank between the A14 and M1 which would be 

graded to a shallower profile. The objective of these works is not hydrological but 

ecological, and the measure is described in more detail in Chapter 3 Ecology and Nature 

Conservation. Enlarging the channel would not provide any direct flood compensation. The 

locations have been agreed with the EA and the intention of the regrading is to encourage 

the development of marginal vegetation to provide greater cover for otters and to improve 





their habitat. The regrading is proposed on the inside of river meanders to complement the 

flow pattern of the river and to minimise the risk of erosion. The measures are in mitigation 

of the potential disturbance to otters arising from the provision of a new bridleway 

alongside the river, also shown on Figure 3.13. The proposal is to leave the existing bed of 

the river undisturbed, though precautions would need to be taken during the regrading 

works to avoid silt being carried downstream. Care would be taken to phase the regrading 

works to minimise the duration of disturbance to the banks, perhaps by beginning the 

excavations from the landward side, and breaking through the bank as late as possible. 

Material arising from the regrading would not be left within the flood plain. As indicated on 

Figure 3.13, the bridleway would be sited at least 8 metres from the top of the river bank as 

required by the EA to enable long term maintenance of the river channel. 

9.5.23 Figure 3.13 also illustrates the proposed realignment of the Swinford Lodge Brook, a 

tributary of the River Avon. The existing line of the brook would be affected by the works to 

the A14 and a new section replicating a narrow meandering channel is proposed, 

integrated with flood compensation and habitat creation. 





Page Not Used 





9.6 ENVIRONMENTAL IMPACT 

9.6.1 The potential impacts of both the construction and operation of the junction improvement 

are considered for surface waters and groundwaters respectively below, together with 

proposed mitigation measures where necessary. 

9.6.2 Highway runoff and accidental spillages present the most significant risk. The Design 

Manual for Roads and Bridges (DMRB), Volume 11, Section 3, Part 10 2 identifies ranges of 

pollutant concentrations in highway runoff. It lists 39 different pollutants which may arise in 

road runoff. DMRB states that, in broad terms, metals and hydrocarbons affect water 

quality and impair biological functions, and sediments affect aquatic habitat by smothering 

feeding and breeding grounds and by physically altering the habitat. 

9.6.3 Potential impacts on flood risk are also dealt with below, and in more detail in the Flood 

Risk Assessment. 

Catthorpe Viaduct Replacement 

9.6.4 As set out in the introduction, there are proposals to replace the Catthorpe Viaduct in 

advance of the junction improvement. 

Surface Water 

9.6.5 During construction EA Pollution Prevention Guidelines (PPG’s) 22 will be followed and 

control measures included in a project CEMP similar to the junction improvement as set out 

under Section 9.5 Mitigation above. The main concern at this stage will be run-off 

containing high concentrations of suspended solids into the River Avon and temporary silt 

traps may be required to prevent this. If a pollution event were to occur to the River Avon, 

despite the measures in place, it would have a Moderate Adverse impact. 

9.6.6 In operation any impacts will be Negligible compared with the existing junction. There will 

be some reduction in the amount of run-off as the surface area of highway will be reduced. 


9.6.7 The viaduct replacement is over an area of non-aquifer and there is no known source of 

contaminated land, although there is always a risk of leaks and spills during construction. 

This would be controlled by the CEMP. The risk of adverse impacts is considered to be 

Negligible. 

9.6.8 During operation there would be no change in risks to groundwater compared with the 

existing road. Run-off from the carriageway would not be discharged to groundwater. 

Flood Risk 

9.6.9 The viaduct replacement is not within a flood zone. There would be a reduction in the 

quantity of surface run-off. 

Summary for Catthorpe Viaduct 

9.6.10 At construction there would be a risk of a Moderate Adverse effect. In operation, the 

drainage measures will match the existing arrangements as far as possible resulting in a 

Neutral effect. 





9.6.11 These comments consider the viaduct replacement as a stand alone project, and reference 

should be made to the Catthorpe Viaduct Replacement Environmental Assessment 49 . 

9.6.12 The detailed assessment that follows includes the viaduct replacement as part of the 

completed M1 Junction 19 Improvement. 

Surface Waters 

9.6.13 Surface water resources can be impacted either by changes in levels / flows or by changes 

in quality. Changes in water quality and flows can significantly impact on flora and fauna 

supported by surface water. Changes in quality and flows can also affect abstractions. 

Construction 

9.6.14 Leaks and spills of hydrocarbons or other pollutants could cause localised pollution of 

surface waters. The surface waters which flow through the study area are of good quality, 

and such pollution incidents would have serious effects on water quality downstream, if 

they were allowed to occur. These can be avoided through good site practice and 

management in line with the CEMP as described in the preceding section, and through the 

additional measures outlined in this section. In particular, measures have been described 

above to safeguard water resources from the effects of the proposed site compound. The 

location of the site compound is shown on Figure G Areas Required During Construction 

included in Appendix 1 to Volume 1 of the ES. 

9.6.15 EA Pollution Prevention Guidelines (PPGs) 22 would be followed. Precautionary measures 

for the protection of surface waters during site works would be agreed with advice from the 

EA, including authorisation of any consented discharges. 

9.6.16 The effects of spillage events associated with construction are likely to be temporary. By 

definition, any such occurrence would be accidental, and its precise nature and scale could 

not be precisely predicted. 

9.6.17 The main concern during construction, as for most construction works, would be discharge 

of runoff containing high concentrations of suspended solids into nearby watercourses. Of 

most concern are the main rivers and any existing ponds. Potential impacts would include 

increased sediment accumulation (blanketing of the stream bed, directly destroying aquatic 

life and indirectly removing part of the food chain), turbidity, discolouration and possible 

nutrient enrichment. Similar impacts can arise during earthworks, culverting, diversion or 

channel regrading works. In order to mitigate the impacts of silt-laden runoff during rain 

events, standard precautions (good site practice) would be necessary. Typical measures, 

in addition to the early provision of drainage ponds already described, include temporary 

run-off drainage, suitable location of stockpiles, etc. Such measures are outlined in the EA 

PPGs. The main risks are during conditions of comparatively low flow. In addition, the River 

Avon, as a designated cyprinid fishery, is vulnerable during the fish spawning season, from 

October to January. Temporary silt traps may be required for site works drainage to 

prevent silt-laden discharges. Other measures include maintaining / retaining as much of 

the vegetation and ground cover as possible along the margins of the works as a buffer to 

surface drainage from the site. In addition, surface vegetation alongside any watercourse 

should be retained wherever possible in order to obtain benefits in terms of runoff 

retardation and filtration / deposition of suspended materials. These measures would mean 

that the risk of siltation incidents would be very low. 

9.6.18 During construction there would be a number of temporary haulage road crossings required 

across various watercourses. The locations of these are shown on Figure G. These are 





likely to require the temporary placement of pipe, geotextile membrane and gravel backfill 

within the smaller watercourses. The placement of these structures would cause temporary 

increases in suspended solids downstream and would also cause an in-river obstruction 

which would remain as long as the haulage route was required, potentially for the whole 

duration of the construction period. These structures would result in a short-to-medium 

term change to the form of the river channel and temporary smothering of small sections of 

the water course bed. 

9.6.19 There would be extension and/or modification of existing culverts, together with 

decommissioning of others. Such works could potentially cause deterioration in water 

quality due to sediment mobilisation from the disturbance of the river banks and riverbed, 

breaking up of structures, generation of silty runoff, spillages / release of materials. 

Precautions and procedures would be followed. Depending on the nature and location of 

an incident, the impact could migrate through the new surface water network. Works on 

culverts would be in accordance with legislation. Diversion, culverting and bridge 

arrangements would be agreed with the EA as required. 

9.6.20 Existing ponds in the vicinity of the junction improvement are not expected to be affected 

by runoff or spillages, as runoff would be collected within the surface water management 

system and disposed of as appropriate. 

9.6.21 Water levels in all rivers, except very locally in the River Avon, are not predicted to change 

during the works. The impact on water levels in the River Avon due to dewatering 

operations during construction is considered in the groundwater section. 

Operation 

9.6.22 The main risk to surface waters is from runoff discharges and accidental spillages with the 

potential impact(s) as described for the construction works. Summary details of the 

drainage areas or ‘zones’ and discharge points are shown in Table 9.8. Their locations are 

illustrated on Figure 9.3. 

Table 9.8 Summary Details of Proposed Highway Drainage 

Drainage Zone Area (m 2 ) Receiving Watercourse 

1 10048 Tributary of Swinford 

Lodge Brook 

2 38080* Swinford Lodge Brook 

3 63875 River Avon 


5 20795 Clay Coton Yelvertoft 

Brook 

6 29795 Tributary of River Avon 

(name unknown) 

7 87928* Swinford Lodge Brook 

8 12760* Tributary of River Avon 

(name unknown) 


*Drainage zones 2, 7 and 8 include drainage from some of the local road network. 

9.6.23 Increases in highway area and traffic have the potential to lead to increased pollutant 

loading within the runoff. The potential impact of the proposed discharges from the highway 





runoff on water quality in the receiving watercourses has been estimated (see Appendix A) 

for dissolved copper and total zinc, in accordance with DMRB guidance 2 . Copper and zinc 

are two of the most important pollutants present in soluble form, and have been selected as 

a proxy for other dissolved pollutants, serving as an indicator of whether there is sufficient 

dispersion and dilution within the receiving water. 

9.6.24 As set out in the DMRB, the simple assessment (method A) is used to determine whether 

the routine runoff is likely to have an impact on the receiving surface watercourses. If it 

shows that an impact is possible, further assessment is required using the detailed 

assessment (method B). Where two or more outfalls discharge to the same reach or 

adjacent reaches, their runoff volumes are combined for the purposes of assessment. 

9.6.25 The results are summarised in tables 9.10 and 9.11. More detailed results are shown in 

Appendix A, Pollution and Spillage Risk Calculations. 

Table 9.9 Summary Results of Simple Assessment of Pollution Impacts from Routine Runoff 

(DMRB Method A) 

Junction Option Drainage Zones 

1 and 2 

combined 

3, 4 and 5 

combined 


combined 


combined 

All zones 

combined 

2029 Do Minimum X X 

2029 Do 

Something 

X X X 

= DMRB Method A calculations show that required dilution is achieved 

X = DMRB Method A calculations show that detailed assessment (Method B) is required 

Drainage zones are combined according to the location of the relevant discharge points – see 

Figures 9.2 and 9.3 

Table 9.10 Summary Results of Detailed Assessment of Pollution Impacts from Routine 

Runoff (DMRB Method B) 


combined 

Zones 3, 4 and 

5 combined 


combined 


combined 

All zones 

combined 

2029 Do Minimum 2029 Do Something 

Downstream Downstream 

Zinc (µg/l) Copper (µg/l) 

(EQS < 200 (EQS < 22 

µg/l) 

µg/l) 

µg/l) 

Downstream 

Copper (µg/l) 

(EQS < 22 

µg/l) 

Downstream 

Zinc (µg/l) 

(EQS < 200 

24 94 21 81 

n/a n/a 6 18 

35 143 32 131 

n/a n/a 6 18 

n/a n/a 13 45 





9.6.26 The estimations indicate that the discharges from the proposed junction improvement 

would cause the concentration of copper in an un-named tributary of the River Avon to 

exceed the EQS. This watercourse would receive runoff from drainage zones 6 and 8. All 

other receiving watercourses would continue to meet the standards for copper and zinc. 

Under the do minimum scenario in 2029, the EQS for copper would also be exceeded in 

the tributary receiving runoff from drainage zones 6 and 8. In addition, under the do 

minimum scenario for 2029, Swinford Lodge Brook, receiving discharges from drainage 

zones 1 and 2, would fail to meet the EQS for copper. 

9.6.27 The routine runoff estimations are conservative as they do not include for mitigation 

measures. The proposed arrangement of treatment ponds and other precautionary 

pollution prevention measures, including penstocks and petrol interceptors, would further 

reduce the potential for pollution from surface water discharges. Given that there is little 

treatment available for the existing discharges, there is potential for the water quality to 

improve within the receiving watercourses. 

9.6.28 The probability of pollution from an accidental spillage reaching a receiving watercourse 

has been assessed for the proposed junction improvement, using DMRB methodology 

(method D). The pollution risk is expressed as the probability of an incident in any one 

year. The acceptable risk of a serious pollution incident occurring is where the annual 

probability is predicted to be less than 1%. 

9.6.29 The results are summarised in Table 9.11 below. More detailed results are shown in 

Appendix A. 

Table 9.11 Summary Results of Assessment of Pollution Impacts from Accidental Spillages 

(DMRB Method D) 

Annual Probability of Pollution Incident (%) 

Drainage Zones 2029 Do Minimum 2029 Do Something 

Zones 1 and 2 combined 0.29 0.06 


0.13 0.27 

combined 



All zones combined 0.55 0.68 

9.6.30 Where two or more outfalls discharge to the same reach (section of river) or adjacent 

reaches, their runoff volumes are combined for the purposes of assessment – see Figures 

9.2 and 9.3. 

9.6.31 The calculations indicate that, for all drainage zones, both for the do minimum scenario and 

for the proposed junction improvement, the annual probability of a serious pollution incident 

is less than 1%. Therefore, the risk of pollution is assessed as being acceptable. 

9.6.32 While the serious spillage calculations assume some risk reduction due to emergency 

response (use of booms, absorbent pads etc), the initial calculations do not take into 

account the mitigation measures of the proposed treatment and attenuation ponds. DMRB 

guidance states that the inclusion of ponds within a scheme can reduce the pollution 

incident risk by 50%. 






9.6.33 Groundwater resources can be affected by changes in groundwater elevations / flows or 

quality. Changes in quality and flows can affect abstractions. 

Construction 

9.6.34 Leaks and spills of hydrocarbons or other pollutants could cause localised pollution of 

groundwater anywhere within the extent of the works where such incidents could occur. 

The main contaminants of concern are List 1 substances under the 1998 Groundwater 

Regulations 12 , and should be prevented from discharge, direct or indirect, to groundwater. 

List 1 substances are defined on the basis of toxicity, persistence and bio-accumulation via 

the aquatic environment, and include organohalogen, organophosphorus and organotin 

compounds, substances with carcinogenic, mutagenic or teratogenic properties, mercury 

and cadmium and their compounds, mineral oils and hydrocarbons, and cyanides. Some 

299 specific compounds have currently been determined as List 1 substances by the 

Environment Agency. 

9.6.35 Although much of the study area is underlain by a minor aquifer, it is designated of low 

vulnerability and therefore groundwater should not be particularly susceptible to pollution. 

The site compound and re-fuelling depot would be located partly over the minor aquifer. A 

pollution incident could lead to pollution of the minor aquifer. Remediation of groundwater is 

usually difficult and rarely totally effective. Furthermore, it is likely that the alluvial / fluvial 

minor aquifer provides baseflow to surface waters, so such a pollution incident could also 

lead to pollution of a surface water. 

9.6.36 The majority of the proposed drainage ponds, and the flood compensation areas, would be 

located over the minor aquifer. It is not expected that the excavation of these structures 

would be below the water table and therefore there should be no requirement for 

dewatering. The proposed drainage arrangements are shown on Figure 9.3. Flood 

compensation is discussed further in the next section. 

9.6.37 The risk of encountering groundwater during the construction of both the Swinford Road 

Cutting and the A14-M6 link is considered to be high, although the volume of groundwater 

seepage into the cuttings is likely to be slow (around 1-2m 3 per hour) as a result of the 

presence of glacial till and clay, through which water flow is restricted. Groundwater 

seepage is to be taken into account during the detailed design of the drainage system. 

9.6.38 The majority of the road widening or realignment over the minor aquifer would be on 

embankments, constructed using clay obtained from excavating the cuttings. There would 

also be areas of embankments over the non-aquifer. The breaking out of existing structures 

is unlikely to require deep excavations and associated dewatering operations. Foundations 

for some of the larger structures, such as the overbridges, may require deeper excavations 

and therefore there may be localised areas where dewatering operations may be required. 

The majority of these structures are located within the non-aquifer, but there may be some 

deeper excavations within the minor aquifer in places. 

9.6.39 Two small groundwater abstractions are located within 1km of the proposed works; a 

private assumed potable supply (Station House, Lilbourne) some 250m west of the M1, 

and a licensed agricultural and domestic supply (Swinford Lodge), some 400m east of the 

M1. The private supply is located relatively close to the river Avon and may be affected by 

any localised groundwater lowering. The licensed supply is too distant to be affected by 

localised groundwater lowering. Both supplies could potentially be affected by a pollution 





incident, although the licensed supply is probably too distant to receive any impact. 

Groundwater within the non-aquifer in the study area is still potentially at risk from pollution, 

although the consequence of such pollution is considerably reduced compared to the minor 

aquifer. 

9.6.40 Another source of potential contamination is remobilisation of contaminated land. The only 

known source on site is the area of the former Cleanaway landfill site. However, the 

junction improvement has been designed to avoid the area. Thus the risk of groundwater 

pollution by disturbance is negligible. Chapter 5, Materials, deals with this issue in more 

detail. 

Operation 

9.6.41 A system of ditches and filter drains exists to intercept and divert groundwater at the 

existing highway boundary, and it is proposed to maintain and supplement this system as 

appropriate to control groundwater levels as necessary along the highway. Filter drains 

would be used at the base of embankments. Minor levels of infiltration to groundwater may 

occur. However, no significant change to groundwater levels or discharges is likely to arise 

from the operation of any of the junction options. 

9.6.42 Carriageway runoff is to be collected in drainage ponds and discharged to surface water. It 

is proposed that the ponds would be lined to prevent potentially contaminated water 

migrating down to the underlying groundwater. Operational drainage is not anticipated to 

pose a significant pollution threat to groundwater; therefore a quantitative discharge to 

groundwater assessment has not been undertaken. However, potential contaminants 

include List 1 substances such as herbicides from verges / embankment vegetation control 

applications in addition to oil and fuel. 

9.6.43 Recharge to groundwater would be reduced due to the increase in highway area and 

associated interception of incident rainfall, and subsequent drainage to surface waters. The 

overall reduction in recharge of groundwater is not considered to result in significant 

impacts because the increase in road area on the minor aquifer, as a proportion, is 

negligible. However, as good practice, reduction in infiltration should be limited wherever 

possible. Figure 9.1 shows the extent of the minor aquifer and non-aquifer in the vicinity of 

the junction. 

9.6.44 Some works, such as bridges, would involve piled foundations through areas of the minor 

aquifer. These piled foundations may cause localised changes to groundwater flow and 

provide a potential downward migration pathway. ‘Contaminated’ land should not be piled 

through, and the type of pile may also be chosen to restrict downward migration. There is 

no piling proposed in the vicinity of the former Cleanaway landfill site. 

Flood Risk 

9.6.45 The A14 part of the site is situated in Flood Zone 3a High Probability, as defined by 

Planning Policy Statement 25 (PPS 25). The widening of the A14 would displace the 

existing floodplain, and would be mitigated by introducing floodplain compensation areas, 

as described in Section 9.5 and illustrated on Figure 3.13. With the compensation in place, 

there would be no increase in flood risk. A Flood Risk Assessment 48 has been carried out in 

accordance with PPS 25 and is at Appendix C. 

9.6.46 Two bridleway crossings over the River Avon would be constructed within the 1 in 100 year 

floodplain. These structures would be at risk of flooding, and would not be passable during 

flood events. They have been allowed for in assessing the flood compensation required. 





9.6.47 The increased highway area would result in a net increase in highway runoff. To ensure 

that there is no increase in runoff to the surface watercourses, a system of attenuation 

ponds has been designed. As described in Section 9.5 discharge rates would be equivalent 

to at least a 20% reduction for existing carriageways retained by the project. For new 

sections of highway run-off would be attenuated to a green field rate of 5 litres per second 

per hectare as agreed with the EA, less an additional allowance of 20% for climate change. 

9.6.48 To mitigate against the risk of groundwater seepage in cuttings, filter drains and slope 

drainage would be used. 

9.6.49 In summary, all flood risks associated with the junction improvement could be successfully 

managed. 

Implications for Planning Policies 

Regional Policy 

9.6.50 Policy CC1 from the West Midlands Regional Spatial Strategy promotes the enhancement 

and extension of natural habitats, so that the opportunities for species migration are not 

precluded and biodiversity can adapt to climate change and hence help to mitigate its 

affects by absorbing flood water. This policy also requires all new development to minimise 

resource demand and encourage the efficient use of resources, especially water, avoid 

development in areas at risk of flooding and promote the use of sustainable drainage 

techniques. 

9.6.51 Policy QE9 from the West Midlands Regional Spatial Strategy aims to protect or improve 

water quality and where necessary significantly reduce the risk of pollution, particularly 

regarding wetland species and habitats subject to local biodiversity partnerships. Where 

possible, the implementation of sustainable drainage systems should be considered. 

Development that poses an unacceptable risk to the quality of groundwater or surface 

water should therefore be avoided. The proposed development would accord with the 

Regional Policy objectives for the West Midlands where possible and would therefore have 

a Neutral/Beneficial Impact on these objectives. 

9.6.52 Policies 32 and 35 from the East Midlands Regional Plan regarding Water Quality and 

Flood Risk, seek to promote improvements in water efficiency in new development, 

improve water quality, reduce the risk of pollution and flood risk. The most sustainable 

solutions should take account of climate change and use sustainable drainage techniques. 

9.6.53 Development would not be permitted if, alone or in conjunction with other new 

development, it would be at unacceptable risk from flooding or create such an 

unacceptable risk elsewhere. However, adequate measures to mitigate negative effects, 

including provision for the maintenance and enhancement of biodiversity may be 

considered in accordance with the flood management regime for the region. As the 

proposed development would take drainage and sustainability into account where possible 

it would have a Neutral/Beneficial Impact on East Midlands Regional policy objectives. 

Local Policy 

9.6.54 Strategic Objective 8 of the Joint Core Strategy for West Northamptonshire Issues and 

Options document aims to ensure that development is sensitive to its environment as it 

states that development should be locally distinctive and of a high quality design, using 

sustainable construction methods. 





9.6.55 Potential Strategy ST1 from the Harborough District Core Spatial Strategy Final Draft 

Document states that all development must help mitigate and adapt to climate change; 

development in areas liable to be at risk of flooding will therefore be avoided. The 

promotion of sustainable drainage measures that do not compromise the function of 

watercourses and value of river corridors in providing natural floodplains is also promoted. 

9.6.56 Policy GP10 from the Rugby Borough Local Plan regarding Flooding and Surface Water 

Drainage which states that Planning Permission will be granted for development that does 

not reduce the capacity of the floodplain to store water or otherwise exacerbate, or give rise 

to, the risk of flooding. Any necessary flood protection and mitigation measures, to ensure 

that the risk of flooding and damage to buildings and related areas is reduced to an 

acceptable level for the lifetime of the development, should be incorporated where 

possible. The use of mitigation measures is also promoted, including Sustainable Drainage 

Systems to provide for the disposal of surface water and provide for the re-use and 

recycling of such water within the development. 

9.6.57 Policy GP11: Pollution Control from the Rugby Local Plan covers issues relating to 

drainage and the water environment, requires development proposals to show that there 

would not be any resulting pollution to surface or ground water. This is supported by Policy 

CS17 from the Rugby Borough Core Strategy Proposed Submission Draft document, 

regarding sustainable design and construction, which states that developments should be 

designed to reduce the use of non-renewable resources and take into account the impact 

of climate change over the lifetime of the development, through the implementation of 

methods such as Sustainable Drainage Systems. 

9.6.58 Policy 13: General Sustainable Development Principles from the North Northamptonshire 

Core Strategy states that development should not cause a risk to (and where possible 

enhance) the quality of the underlying groundwater or surface water, nor increase the risk 

of flooding on the site or elsewhere, and where possible incorporate Sustainable Drainage 

Systems. 

9.6.59 Overall, it is not considered that the proposed improvement to Junction 19 would negatively 

impact on Regional or Local policy principles and objectives, providing that sustainable 

measures such as Sustainable Drainage techniques and other mitigation measures to 

minimise the potential for pollution and flooding are implemented where possible 

throughout the scheme. 





Page Not Used 





9.7 SIGNIFICANCE OF EFFECTS 

9.7.1 This description of the significance of effects includes Catthorpe Viaduct Replacement as 

part of the completed M1 Junction 19 Improvement. An assessment of the viaduct 

replacement as a separate project is summarised in Section 9.6 above. 

9.7.2 It is assumed that good site practice would be followed during the construction phase and 

that maintenance would be undertaken as necessary during operation. 

9.7.3 The main potential impact of the proposed junction improvement is pollution of surface 

waters. Mitigation measures have been proposed within this chapter to reduce the potential 

for pollution and other impacts to surface waters. 

9.7.4 With respect to groundwater, the potential impacts are more minor in comparison and 

therefore fewer mitigation measures have been proposed. 

9.7.5 The significance of residual effects with mitigation in place is set out in Tables 9.12 

(construction) and 9.13 (operation). 

Construction 

9.7.6 Summary Assessment: Moderate Adverse effect. 

9.7.7 The effect is conservative due to two Moderate/Large Adverse effects relating to potential 

pollution of the River Avon drinking water supply and designated fishery which is of Very 

High importance. However, the risk associated with these impacts is temporary and of very 

short potential duration as the treatment ponds would be constructed early, providing 

mitigation for accidental spillage. 

Operation 

9.7.8 Summary Assessment: Slight Beneficial effect 

9.7.9 There would be beneficial effects associated with improvements in water quality as a result 

of the treatment provided by the drainage ponds, and by penstocks and oil interceptors and 

improved signing of these systems for emergency personnel. In most cases, these 

beneficial effects would be Slight, although there would be a Moderate Beneficial effect on 

chemical water quality in the River Avon. There would be a Slight Adverse effect on the 

nature of the watercourses due to the addition of permanent structures in and over them. 

All other effects would be Neutral. 

Overall Effect 

9.7.10 Summary Assessment: Neutral 

9.7.11 The construction impacts would be of limited duration compared with the operation, and the 

negative scoring for the construction reflects the risk of incidents occurring prior to 

implementation of mitigation measures. During operation, the effective operation of the 

highway drainage system and emergency procedures should ensure that there would be a 

Slight Beneficial effect on the water environment. 





Table 9.12 M1 Junction 19 Water Environment Features Summary: Construction Effects 

Feature & 

Attribute / 

Service 

Surface Water 

River: 

Water supply 

Transport & 

dilution of waste 

products 

River: 

Biodiversity 

Quality 

Indicator 

Chemical water 

quality 

Non potable 

abstraction 


supply 

Biological water 

quality 

Fisheries 

quality 

Scale 1 , Details and 

Grading 


Avon RE1 



RE2 


water courses not 

recorded 



National / Regional: 

River Avon drinking 

water supply 

downstream of 

development 






recorded 


designated cyprinid 

fishery 


watercourses not 

recorded, assumed 

undesignated / non 

fishery 

Importance Potential Impact Magnitude 

without 

Mitigation 

Very High 

High 

(assumed) 

Medium - 

Low 

Pollution: Local works in, over and 

in the vicinity of watercourses 

Magnitude 

with 

Mitigation 

Minor 

adverse 

Minor 

adverse 

Minor 

adverse 

Significance 

of Effect 

Moderate / 

Large adverse 

Slight / 

Moderate 

adverse 

Neutral 

Low None (Negligible) Neutral 

High 

Medium 

(assumed) 

Medium 

High 

Medium 







Unknown 

Unknown 

Unknown 

Moderate 

adverse 

Minor 

adverse 

Minor 

adverse 

Moderate 

adverse 

Minor 

adverse 

Moderate / 

Large adverse 

Slight adverse 

Neutral 

Moderate / 

Large adverse 

Slight adverse 





Feature & 

Attribute / 

Service 

River: 

Conveyance of 

flow and material 

Still Waters: 

Biodiversity 



Water supply 

Transport and 


products 

Quality 

Indicator 

Nature of 


Non potable 

abstraction 


supply 


Grading 



Yelvertoft Brook both 

main rivers assumed 




Feature & 

Attribute / 

Service 

Flood Risk 

Floodplain: 

Conveyance of 

flood flows 

Quality 

Indicator 

Vulnerability 




Grading 

Local: Two licensed 

abstractions within 500 

metres of the Junction 

and five licensed 

abstractions up to 1km 

away include domestic 

use. 

Private water supply at 

Station House, Lilbourne, 

assumed to be




Table 9.13 M1 Junction 19 Water Environment Features Summary: Operation Effects 

Feature & 

ATTRIBUTE / 

SERVICE 

Surface Water 

River: 

Water supply 

Transport & 


products 

River: 

Biodiversity 

Quality 

Indicator 

Chemical water 

quality 

Non potable 

abstraction 


supply 

Biological 



Grading 


Avon RE1 



RE2 



recorded 



National / Regional: River 

Avon drinking water 

supply downstream of 

development, assumed 

DW3 and within critical 

travel time 





without 

Mitigation 

Magnitude 

with 

Mitigation 

Very High Increased routine runoff to 

watercourses. Pollutant 

Negligible Minor 

beneficial 

High concentrations within acceptable Negligible Minor 

limits. Slight increase in pollution 

beneficial 

incident risk. The introduction of 

(assumed) treatment ponds and other Negligible Minor 

Medium - pollution prevention measures 

beneficial 

Low 

offer an improvement in the quality 

of discharges to receiving waters, 

compared with the do minimum 

scenario. 

Significance 

of Effect 

Moderate 

beneficial 

Slight beneficial 


Low None (Negligible) (Negligible) (Neutral) 

High 

Medium 

Increased routine runoff to 


concentrations within acceptable 

limits. Slight increase in pollution 

incident risk. The introduction of 

treatment ponds and other 

pollution prevention measures 

offer an improvement in the quality 

of discharges to receiving waters, 

compared with the do minimum 

scenario. 

Increased routine runoff to 


concentrations within acceptable 

Negligible 

Negligible 

Minor 

beneficial 

Minor 

beneficial 







Feature & 

ATTRIBUTE / 

SERVICE 

River: 

Conveyance of 

flow and material 

Still Waters: 

Biodiversity 

Quality 

Indicator 

Fisheries 

quality 

Nature of 



Grading 



recorded 


designated cyprinid 

fishery 


watercourses not 

recorded, assumed 

undesignated / non 

fishery 



Yelvertoft Brook both 

main rivers assumed 




Feature & 

ATTRIBUTE / 

SERVICE 



Water supply 

Transport and 


products 

Quality 

Indicator 

Non potable 

abstraction 


supply 

Vulnerability 


Grading 

4 Ecology and Nature 

Conservation) 




include agricultural use. 

Other abstractions up to 

1km away, but assumed 

to be outside of zone of 

influence 

National / Regional: No 

public supplies 




and five licensed 

abstractions up to 1km 

away include domestic 

use. 

Private water supply at 

Station House, Lilbourne, 

assumed to be




Feature & 

ATTRIBUTE / 

SERVICE 

Flood Risk 

Floodplain: 

Conveyance of 

flood flows 

Quality 

Indicator 




Grading 

Regional / Local: 

Proposed Development 

within River Avon and 

Clay Coton Yelvertoft 

Brook 1:100 year 

indicative floodplain 

Local: Alluvial and river 


with water table in places 


without 

Mitigation 

Medium 

Medium 

Potential increase in flood peak 

due to construction within flood 

plain 

Change in road runoff rates 

Residual loss of deposits during 

construction phase 

Minor 

adverse 

Minor 

adverse 

Magnitude 

with 

Mitigation 

(Negligible) 

Minor 

beneficial 

Significance 

of Effect 

(Neutral) 

Negligible Negligible Neutral 


below 1m 

Local: Clay soils Low None (Negligible) (Negligible) (Neutral) 

1 Assume that quality and rarity of the same grading and that all features of limited substitutability 





9.8 INDICATION OF DIFFICULTIES ENCOUNTERED 

9.8.1 Water quality data is not available for some of the tributaries of the River Avon in the study 

area. For these watercourses, it has been assumed that the quality is of the same high 

standard as the River Avon upstream of the junction, thus ensuring that a precautionary 

approach has been taken during the assessment. 





Page Not Used 





9.9 SUMMARY 

9.9.1 An assessment of the effects of the proposed junction improvement, in relation to surface 

water, groundwater and flood risk, has been undertaken following DMRB methodology, 

specifically developed for the assessment of the impacts of highway schemes, and based 

on advice from the EA. Impacts for the Catthorpe Viaduct have been indicated separately 

and included in combination with an overall assessment of the junction improvement. 

9.9.2 Baseline conditions have been reviewed. The site is underlain by a mixture of non-aquifer 

and minor aquifers. The distribution of the latter are associated with the location of the 

various surface watercourses. The site lies within the catchment of the River Avon, a main 

river, and the highway crosses the River Avon at a number of locations. There is one other 

main river, the Clay Coton Yelvertoft Brook. There are numerous other ordinary 

watercourses / drainage ditches and ponds. 

9.9.3 There are some groundwater abstractions, including private potable supply, located within 

1km of the highway, presumed to be sourced from the minor aquifer. There are no surface 

water abstractions, although there is an important public water supply abstraction some 

seven kilometres downstream on the River Avon. 

9.9.4 The main rivers are of good water quality. However, the existing highway drainage 

undergoes little treatment prior to discharge and, in addition, these receiving watercourses 

are very vulnerable to pollution incidents. 

9.9.5 Without mitigation, construction work has the potential to adversely impact the water 

environment. The main potential impact is pollution of surface waters. It is assumed that 

good site practice as incorporated within and fundamental to the CEMP would be followed 

during the construction phase. The overall assessment score for the construction phase is 

of a Moderate Adverse effect – however, this is considered to be conservative as it reflects 

the inclusion of potential pollution of the River Avon drinking water supply. This would be a 

temporary risk, and of very short potential duration as the treatment ponds would be 

constructed early, providing mitigation for accidental spillage. 

9.9.6 For the proposed junction improvement, the drainage scheme for the highway operation 

would upgrade the existing arrangements with spillage containment, water treatment and 

attenuation where required. It is assumed that maintenance and management of the 

operational scheme would be undertaken as necessary. The overall assessment score for 

the operational phase is of a Slight Beneficial effect. 

9.9.7 With respect to groundwater, there is a potential for construction of cuttings to lead to a 

lowering of the water table within the minor aquifer. However, this effect would be localised 

and of Neutral significance. Other impacts on groundwater are relatively insignificant, and 

few mitigation measures are proposed or required. This results in the residual impact being 

little changed from the current situation. 

9.9.8 In terms of flood risk, the widening of the A14 embankments and the creation of two 

bridleway bridges would reduce the storage capacity in the River Avon floodplain. 

However, flood compensation would be provided and so there would be no net loss of flood 

storage. Attenuation ponds would reduce the discharge rate for highway runoff across the 

scheme by at least 20%, and would therefore have a Slight Beneficial effect on flood risk. 

9.9.9 The junction improvement would satisfy the requirements of DMRB for routine runoff and 

pollution incidents from accidental spillages. Details of the DMRB calculations are included 

in Appendix A. 





9.9.10 The proposals meet the objectives set out in the introduction to protect the water 

environment and to reduce the risk of pollution and flooding. 





9.10 REFERENCES 

1 M1 Junction 19 Improvement Comparative Environmental Assessment, Chapter 10, Road 

Drainage and the Water Environment. Highways Agency, 2008 

2 Road Drainage and The Water Environment, DMRB Volume 11, Section 3, Part 10, HA 

216/06, 2006. 

3 M1 Junction 19 EIA Scoping Report, March 2009, Highways Agency 

4 Water Resources Act 1991 

5 UK Town and Country Planning Act 1990 

6 Land Drainage Act 1991 

7 Environment Act 1995 

8 Control of Pollution Act 1974 

9 The Water Environment (Water Framework Directive) (England and Wales) Regulations 

2003 

10 EC Water Framework Directive 2000 (2000/60/EC) 

11 The Surface Water (River Ecosystem) Regulations 1994 

12 The Groundwater Regulations 1998 

13 EC Groundwater Directive 1980 (80/68/EEC) 

14 Surface Waters (Dangerous Substances) Regulations 1992, 1997 and 1998 

15 Surface Water (Classification) Regulations 1989 

16 EC Dangerous Substances Directive (76/464/EEC) 

17 The Surface Waters (Abstraction for Drinking Water) (Classification) Regulations 1996 

18 EC Surface Water Abstraction Directive (75/440/EEC) 

19 The Surface Waters (Fishlife) (Classification) Regulations 1997, as amended 

20 EC Freshwater Fisheries Directive 2006 (2006/44/EC) 

21 Salmon and Freshwater Fisheries Act 1975 

22 Environment Agency Pollution Prevention Guidelines. Various 

23 Planning Policy Statement 25 (PPS25) Development and Flood Risk. Department of 

Communities and Local Government, 2006. 

24 Planning Policy Statement 23 (PPS23) Planning and Pollution Control, Office of the Deputy 

Prime Minister, 2004 

25 Planning Policy Guidance 13: Transport, Department of the Environment, Transport and the 

Regions, 2001 

26 West Midlands Regional Spatial Strategy, 2008 

27 East Midlands Regional Plan, 2009 

28 Daventry District Council Local Plan, 1997 

29 West Northamptonshire Joint Core Strategy, 2007 

30 Harborough District Council Local Plan 

31 Rugby Borough Council Local Plan 

32 North Northamptonshire Core Strategy, 2008 

33 Flood Estimation Handbook Volume 4, Institute of Hydrology, 1999 

34 M1 Junction 19 Improvements Construction Environmental Management Plan, Highways 

Agency, 2009 

35 Control of Pollution (Oil Storage) (England and Wales) Regulations, 2001 

36 CIRIA, Development and Flood Risk 

37 Geological Map, Sheet 170 (solid & drift), Market Harborough, scale 1:63360, British 

Geological Survey (BGS), 1969 

38 Geological Map, Sheet 185, (solid & drift), Northampton, scale 1:50000, BGS, 1980 

39 Geology of the Country around Market Harborough, BGS memoir for Sheet 170, 1968 

40 The physical properties of minor aquifers in England and Wales, BGS Technical Report 

WD/00/04 (Environment Agency R&D 68), 2000 

41 Policy and Practice for the Protection of Groundwater (2 nd Edition), Environment Agency, 

1998 and Regional Appendix Severn Trent Region, National Rivers Authority 1991 





42 Groundwater Vulnerability of Leicestershire, Sheet 23, scale 1:100000, Environment 

Agency, 1996 

43 Groundwater Vulnerability of Northern Cotswolds, Sheet 30, scale 1:100000, Environment 

Agency, 1996 

44 M1 Junction 19 Improvement, Contractor’s Proposals for Drainage, November 2009, 

prepared by Skanska & Jacobs for the Highway Agency 

45 Flood Risk Assessment: Final Report, July 2005 (updated October 2005), JBA Consulting 

46 Control of pollution from highway drainage discharges, CIRIA report 142, 1994. 

47 Junction 19 M1 Addendum to Flood Risk Assessment, JBA Consulting, May 2007. 

48 M1 Junction 19 Improvement Flood Risk Assessment, Jacobs, 2009 

49 Catthorpe Viaduct Replacement Environmental Assessment, Highways Agency. January 

2010. 





FIGURES 

Figure 9.1: Existing Hydrological Features 

Figure 9.2: Existing Drainage Zones 

Figure 9.3: Proposed Drainage Zones 

Figure 9.4: Typical Pond Layout 

Figure 3.13: River Avon Flood Compensation and Otter Mitigation



CHAPTER 9 – ROAD DRAINAGE AND THE WATER ENVIRONMENT

Swinford Road 

# 

FIGURE 9.1 

Catthorpe Road 

Shawell Road 

SWINFORD 

Legend 

M1 J19 Junction Location 

# Groundwater Abstractions 

Watercourse 

Caves Inn Pits SSSI 

Ponds In Close Proximity To Junction Improvement 

Minor Aquifer Overlain by Soils of Intermediate 

Leaching Potential 

Minor Aquifer Overlain by Soils of Low Leaching 

Potential 

Non Aquifer 

Flood Zone (1 in 100y) 

Swinford Lodge Brook 

Flood Zone (1 in 1000y) 

M6 

Shawell Lane 


CATTHORPE 

A14(T) 

River Avon 

# 

A5(T) 

River Avon 

M1 

Clay Coton Yelvertoft Brook 

/ 

River Avon 

This map is reproduced from Ordnance Survey material with the permission 

of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office 

© Crown copyright. Unauthorised reproduction infringes Crown copyright and may 

lead to prosecution or civil proceedings. 0100018928 (2010). 

LILBOURNE 

Rugby Road 

Project 

Title 

M1 Junction 19 

Environmental Statement Volume 2 

Chapter 9 Road Drainage and the Water Environment 

Existing Hydrological Features 

Scale 

Drawn 

1:12500 (A3) Date Nov 2009 Ref. B0531000_E_09_01 

AD Checked SW Approved LB




APPENDICES 

Appendix A – Pollution and Spillage Risk Calculations




Appendix A – Pollution and Spillage Risk Calculations 

Method A – Simple Assessment of Pollution Impacts from Routine Runoff 

Drainage Zones 

Road Area 

Run-off co 

efficient 

Rainfall Depth 

Run-Off 

Volume (Vh) 

Daily River Flow 

(Vr) 

Dilution 

Relevant AADT 

(m2) (m/day) (m3/day) (m3) 

Existing layout 

Drainage zone 1 8209 0.5 0.0085 34.89 864 24.76 124400 Low 

Drainage zone 2 54064 0.5 0.0085 229.77 2992 13.02 124400 High 




Drainage zone 6 32421 0.5 0.0085 137.79 1382 10.03 97600 High 




All zones combined 219910 0.5 0.0085 934.62 31968 34.20 221800 Low 

Proposed 2029 - Do Something 

Drainage zone 1 10048 0.5 0.0085 42.70 864 20.23 135400 high 


Total zones 1 and 2 combined 48128 0.5 0.0085 204.54 2992 14.63 135400 high 

Drainage zone 3 63875 0.5 0.0085 271.47 29376 108.21 159000 low 



Total zones 3,4 and 5 combined 93428 0.5 0.0085 397.07 29376 73.98 159000 low 



Total zones 6 and 8 combined 42555 0.5 0.0085 180.86 1382 7.64 123600 high 



Total zones 7 and 9 combined 92710 0.5 0.0085 394.02 29376 74.56 100100 low 

Combined drainage zones 276821 0.5 0.0085 1176.49 31968 27.17 259100 high 

Assessed 

Risk

Method B - Detailed Assessment of Pollution Impacts from Routine Runoff 

Method B results for those drainage zones highlighted by Method A as high risk and therefore requiring detailed assessment: 

RE Classification = 1 

EQS for copper = < 22µg/l 

EQS for zinc = < 200µg/l 


River 

flow (m 3 ) 

Existing Layout 


combined 


combined 

Proposed 2029 – Do Something 


combined 


combined 


combined 


combined 

All zones 

combined 

Runoff 

volume (m3) 

Upstream 

Copper 

(µg/l) 

Dissolved 

copper 5- 

day build up 

(kg) 

Downstream 

copper 

(µg/l) 

Upstream 

Zinc (µg/l) 

Dissolved 

zinc 5-day 

build up (kg) 

Downstream 

zinc(µg/l) 

2992 265 2.52 0.070 24 1.99 0.301 94 No 

1382 180.86 2.52 0.052 35 1.99 0.220 143 Yes 

2992 204.54 2.52 0.059 21 1.99 0.253 81 No 

31968 397.07 2.52 0.121 6 1.99 0.518 18 No 

1382 180.86 2.52 0.047 32 1.99 0.202 131 Yes 

29376 394.01 2.52 0.110 6 1.99 0.464 18 No 

31968 1176.49 2.52 0.338 13 1.99 1.437 45 No 

Mitigation 

Required?

Method D – Assessment of Pollution Impacts from Accidental Spillages 

Maximum acceptable annual probability = 1% 


Annual 

Accident 

Probability 

(Pacc) 

Pollution 

Probability 

Factor 

(Ppol) 

Annual 

Probability 

of Pollution 

Incident 

Pollution 

Incident 

Return 

Period 

(years) 

Annual 

Probability 

(%) 

Do Minimum 

Zones 1 and 2 combined 0.00483 0.6 0.0029 345 0.29 

Zones 3, 4 and 5 combined 0.00214 0.6 0.0013 778 0.13 



All zones combined 0.00913 0.6 0.0055 183 0.55 

Do Something 


Zones 3, 4 and 5 combined 0.00454 0.6 0.0027 367 0.27 



All zones combined 0.00973 0.6 0.0058 171 0.58 

Please note that the AADT traffic figures used in Methods A, B and D are taken from the individual link flows extracted from SATURN and may differ 

slightly from those presented elsewhere in the Traffic Forecasting Report (Ref:- B0531000/OD/108)




Appendix B – Glossary of Technical Terms




Glossary of Technical Terms 

Abstraction 

Alluvial Deposits 

Aquifer 

Attenuation 

Base Flow 

Bio-accumulation 

Biochemical Oxygen 

Demand. 

CaCO 3 

Carcinogenic 

Catchment 

Coarse fish 

Contaminated Land 

Cyprinid 

De-watering: 

DMRB: 

Earthworks: 

Embankment: 

Environmental Impact 

Assessment: 

Flood Plain 

Fluvial 

Fluvio-glacial Deposits 

Glacial Till 

Ground Investigation: 

Removal of water from a groundwater or surface water 

body- usually by means of a pump. Groundwater is water 

that is contained in porous rocks underground. 

Soil Sediments deposited by the action of rivers 

A porous body of rock capable of holding quantities of water 

that can be abstracted for human use 

Reduction. The term is used in drainage design to indicate a 

reduction in the rate of flow or flooding risk, for example by 

means of a pond to hold back water. 

Normal water flow rate in the absence of significant run-off 

or precipitation. 

The accumulation of substances within living organisms 

A chemical procedure for determining the uptake rate of 

dissolved oxygen by biological organisms in water. 

Calcium carbonate. An indicator of water hardness 

Causing or tending to cause cancer 

The area of land which drains into a specific watercourse or 

river. 

Fish species such as cyprinids, pike and eel 

Defined in Section 78 2A of the Environmental Protection 

Act 1990 as 

“any land which appears to the local Authority in whose area 

it is situated to be in such a condition, by reason of 

substances in, on or under the land, that:- 

a) significant harm is being caused or there is a significant 

possibility of such harm being caused; or 

b) pollution of controlled waters is being, or is likely to be 

caused.” 

A family of soft finned mainly freshwater fish including carp, 

tench, rudd and dace 

Removal of water during construction with implications for 

pollution of surface water and changes to ground water. 

The Department for Transport’s Design Manual for Roads 

and Bridges, a multi-volume work that gives guidance on all 

matters relating to highway construction. Volume 11 relates 

to Environmental Impact Assessment. 

In construction, this means any operations involved in 

moving, loosening, depositing, shaping, compacting and 

stabilising soil and rock. In archaeology, it means any 

archaeological features that are visible as slopes, mounds, 

banks or depressions in the ground surface. 

An elongated mound of soil deliberately placed to form a 

raised area, sometimes built to elevate a highway surface 

above the surrounding ground. 

A systematic process for assessing a project’s likely 

significant environmental effects so that they can be taken 

into account in decision-making about the project. 

Area of land prone to flooding and protected against 

development. 

Affected by rivers and streams 

Material deposited by water from a melting glacier 

The mixture of rocks, stones and soils left behind when a 

glacier melts 

Survey incorporating boreholes and pits to investigate the


Hydrocarbons 

Hydrogeology 

Lower Lias 

Macro-invertebrate 

Made Ground: 

Mitigation: 

Mutagenic 

Organohalogen 

Organophosphorus 

Organotin 

PH 

Piling: 

Planning Policy Guidance 

(PPG): 

Potable water 

Ramsar 

River Terrace 

Run-off: 

SAC 

Salmonid 

Sediment: 

Siltation: 

Source Protection Zones 

(SPZ): 

SPA 

Surface Water: 

Suspended Solids 

Teratogenic 

Turbidity 

nature and strength of soils below the ground. 

Water held underground within porous rocks. 

Organic compounds made of hydrogen and carbon, often 

found in fuels. 

The study of groundwater. 

A period of geological time towards the end of the early 

Jurassic, ie. from about 195 – 180 million years ago. 

An animal without a backbone large enough to be seen 

without magnification. 

Land which has been infilled or built up above original 

ground level. 

Measures, including any process, activity or design to avoid, 

reduce, remedy or compensate for adverse effects of a 

development project. 

Causing genetic mutation. 

Organic compounds including fluorine, chlorine, bromine or 

iodine. 

Common natural compound, but also the basis of many 

insecticides and herbicides 

Highly toxic organic compounds combined with tin, used as 

anti-foulant paint for boats 

A measure of relative acidity or alkalinity 

The act of driving ‘piles’ (supports) into the ground. 

A series of government documents that provide guidance, 

principally to Local Planning Authorities, about various 

aspects of government policy in relation to the planning 

system. 

Water suitable for human consumption. 

European Designated wildlife site 

A flat platform of land created alongside a river. 

Water which is not absorbed by the soil and flows to lower 

ground, eventually draining into a stream, river, or other 

body of water. 

Special Area of Conservation. European designated wildlife 

site. 

Fish species such as salmon and trout 

Particulate matter that can be carried by water flow and 

eventually deposited as a layer of solid particles on the bed 

or bottom of a body of water. Sedimentation is the 

deposition by settling of a suspended material. 

The deposition or accumulation on the bottom of a body of 

water of fine or intermediate sized mineral particles known 

as ‘silt’. 

A defined zone surrounding a groundwater abstraction point 

(e.g. a well or a spring), within which certain activities are 

restricted to prevent contamination of the groundwater. 

Special Protection Area. European designated wildlife site. 

Watercourses, ponds or lakes that run or lie on the surface 

of the land 

Small solid particles which remain in suspension in water. 

Causing birth or embryo defects 

Muddiness created by stirring up sediment.




Appendix C – Flood Risk Assessment 

Please note that Appendix B to the Flood Risk Assessment 

The Contractor’s Proposals for Drainage, November 2009, Skanska Jacobs 44 

Is not included




Skanska Construction UK/Highways Agency 

M1 Junction 19 Improvements Scheme 

Flood Risk Assessment 

Project No: 0531000 

Task Code: E700 

September 2009 

Report Ref. B0531000/FRA/F01 

Jacobs UK Limited, Fairbairn House, Ashton Lane, Sale, Manchester, M33 6WP 

Registered Office: 95 Bothwell Street, Glasgow, G2 7HX

Non Technical Summary 

Skanska Construction UK is currently leading the development of the M1 

Junction 19 Improvements Scheme. The aim of the scheme is to relieve 

congestion at the junction, make the roads safer and reduce journey times, whilst 

minimising any environmental effects. 

Jacobs UK Limited has been commissioned by Skanska Construction UK to 

provide a Flood Risk Assessment (FRA) for the M1 Junction 19 scheme. The 

purpose of the FRA is to ensure that flood risk and its management have been a 

material consideration in the planning of this scheme, in accordance with the 

Department of Communities and Local Government’s Planning Policy Statement 

25: Development and Flood Risk (PPS25Planning Policy. 

This specific FRA relates to the proposed M1 Junction 19 Improvements 

Scheme. During the course of the FRA, the site has been investigated to 

determine the risk from all significant sources of flooding and the impact they 

could have on flood risk elsewhere. The key findings from the FRA are: 

• The site is at risk from fluvial flooding. Part of the site (the A14 road) is 

situated in Flood Zone 3a High Probability as defined by PPS25. The 

proposed land use is classified as essential infrastructure therefore 

passes the PPS25 Sequential and Exception Test. The proposed scheme 

will displace the existing floodplain, this will be mitigated by introducing 

floodplain compensation. 

• Two bridleway crossings will be constructed below the Q100 flood 

levels. The structures will be at risk from fluvial flooding, furthermore the 

bridges will not be passable during high flows. Signage is recommended 

to inform users of the risks of attempting to use the bridge during high 

flows. 

• The scheme will result in a net increase in highway runoff. To 

mitigate against the effect of increased runoff in the River Avon a system 

of attenuation ponds have been proposed and designed in consultation 

with the Environment Agency. 

• There is evidence of high groundwater tables relative to the 

proposed finished road levels. This may result in groundwater seepage. 

To mitigate against this risk extra filter drains and slope drainage is being 

investigated by the contractor. 

In summary, it is considered that if the proposed M1 Junction 19 improvements 

are planned and designed in-line with the recommendations of this FRA all 

associated flood risks can be successfully managed. The development will 

therefore meet the requirements of the PPS25 Sequential Test and Exception 

Test.

Page left blank intentionally

Contents 

1 Introduction 1 

1.1 Overview 1 

1.2 Proposed Development Details 1 

1.3 Previous FRA’s 2 

2 Policy Review 3 

2.1 Planning Context 3 

2.2 Planning Policy Statement 25 (PPS25) 3 

2.3 Harborough Strategic Flood Risk Assessment 5 

3 Flood Risk to the Proposed Development 7 

3.1 Fluvial Flooding – Main River 7 

3.2 Fluvial Flooding – Ordinary Watercourses (Non-Main River) 9 

3.3 Coastal and Tidally Influenced Flooding 9 

3.4 Groundwater Flooding 9 

3.5 Surface Water Runoff 10 

3.6 Flooding from Artificial Drainage Systems 12 

3.7 Flooding from Infrastructure Failure 13 

3.8 Climate Change 14 

3.9 Summary of Risks to Site 15 

4 Impacts of the Proposed Development on Flood Risk 

Elsewhere 17 

4.1 Impacts on Fluvial Flood Risk 17 

4.2 Impacts on Groundwater Flooding 17 

4.3 Impacts on Flood Risk from Surface Water Runoff 18 

4.4 Impacts on Flooding from Artificial Drainage Systems 18 

4.5 Impacts on Flooding from Infrastructure Failure 18 

4.6 Summary of Flood Impacts from Development 19 

5 Proposed Mitigation Measures 20 

5.1 Mitigation of Impacts on Fluvial Flooding 21 

5.2 Mitigation of Groundwater Flood Risks 22 

5.3 Mitigation of Surface Water Runoff (Overland Flows) 23 

5.4 Mitigation of Flood Risks from Artificial Drainage Systems 23 

5.5 Mitigation of Flood Risks from Infrastructure Failure 24 

5.6 Incidental Mitigation Measures 24 

5.7 Summary of Recommended Mitigation Measures 25 

6 Residual Risks 27 

7 PPS25 Sequential and Exception Test 29 

7.1 The Sequential Test 29 

7.2 The Exception Test 29 

7.3 Summary 30 

8 Conclusion 31

Appendices 

Appendix A – Existing Layout and Environmental Masterplan 

Appendix B – Contractor’s Proposal for Drainage 

Appendix C – Hydrogeological Assessment 

Appendix D – Elevation Distribution for Flood Compensation

1 Introduction 

1.1 Overview 

Jacobs UK Limited has been appointed by Skanska Construction UK/Highways 

Agency to undertake a Flood Risk Assessments (FRA) for a proposed road 

improvements scheme. 

Junction 19 of the M1 forms the intersection between three major parts of the 

motorway and trunk road network - the M1 and M6 motorways and A14 Trunk 

Road. The A14/M6 corridor also forms part of the Ireland/UK/Benelux Trans 

European Network or TEN. It is therefore a key node for both north/south and 

east/west movements. The Location Plan, Figure A (Appendix A), shows the 

current layout. 

The existing junction 19 on the M1 gives rise to the following problems: 

• congestion, delays and long queues 

• accidents sometimes resulting in serious injuries and fatalities 

• conflicts between local and longer distance traffic 

• presents a barrier to pedestrian, cyclist and horse rider movements 

The proposed improvement, illustrated by Figure B (Appendix B) aims to relieve 

congestion at the junction, making the roads safer and decreasing journey times, 

whilst minimising the environmental impacts of the scheme. 

According to Planning Policy Statement 25: Development and Flood Risk, a FRA 

is required to support the planning application because: 

• There will be new areas of development within an area identified as being 

at risk of flooding (from the River Avon). 

• The area of the development is greater than 1 hectare. 

] 

1.2 Proposed Development Details 

The proposed junction would be constructed on three levels and would be similar 

in height to the existing junction. It would involve the construction of new free flow 

links, A14 to M1 northbound, M1 southbound to A14 and M6 to A14 in both 

directions. The existing link between M6 to M1 southbound would be 

reconstructed, and that from M1 northbound to M6 modified. The M1 motorway 

through the junction would be retained on its current alignment. 

The improvement would require several new structures, including viaducts on the 

higher level links. There would also be changes to existing lighting and gantry 

provision. The above works would all be constructed to motorway standard, dual 

two lane carriageways for the M6 to A14 link and single two lane carriageways for 

the remainder, all with hardshoulders. 

Facilities would be provided for vulnerable users, pedestrians, cyclists and horse 

riders, both as part of the local road network to provide direct utility links, and in 

the form of new and diverted field paths to provide recreational links, including a 

new bridleway. The proposed bridleway would require two crossings of the 

1

watercourse, one of which would replace an existing rudimentary crossing north 

of the A14, the other would be a new crossing between the A14 and M1. 

A public consultation was held between June and September 2008 seeking the 

views of the public on three junction options and three local road network options. 

There was support for an improvement scheme, with the Red Junction the most 

favoured. Of the three local road network options, the Orange Local Road 

Network was the most favoured. 

The outline preferred option is shown below in Figure 1. 

Orange Local Road 

Network 

Red Junction Option 

Figure 1: The preferred route: The Red Junction and Orange Local Road Network 

1.3 Previous FRA’s 

Throughout the evolving design process a number of flood risk assessments 

have been performed. A list of previous flood risk assessments is given below: 

• Flood Risk Assessment completed by (JBA Consulting, July 2005) 

• Addendum to stage 3 flood risk assessment – flood plain compensation 

(JBA, October 2005) 

• Addendum to Flood Risk Assessment produced to fulfil PPS 25 

requirements (JBA, May 2007 ) 

This FRA seeks to take the re-design as an opportunity to produce a new standalone 

FRA which will draw together all relevant information in a format which is 

more suitable for the current planning environment. 

2

2 Policy Review 

2.1 Planning Context 

The strategic case for the M1 Junction 19 scheme is set by:- 

• HM Treasury Public Service Agreement 5 – Deliver reliable and efficient 

transport networks that support economic growth 

• Towards a Sustainable Transport System, Supporting Economic Growth 

in a Low Carbon World. Department of Transport, October 2007 

• Department of Transport Business Plan 2008-0998 

2.2 Planning Policy Statement 25 (PPS25) 

PPS25 sets out the national policy for land use planning in relation to flood risk. The 

policy statement contains the planning and development framework which should be 

adhered to be Regional Government, Local Planning Authorities and developers. It 

was produced by the Department for Communities and Local Government in 

December 2006. 

2.2.1 Policy Aims 

PPS25 states; 

“The aims of planning policy on development and flood risk are to ensure that 

flood risk is taken into account at all stages of the planning process to avoid 

inappropriate development, and to direct development away from areas at 

highest flood risk. Where new development is, exceptionally, necessary, the 

policy aims to mitigate the flood risk without increasing the flood risk elsewhere.” 1 

2.2.2 PPS25 Requirements 

In order to meet its aim, PPS25 requires that a site-specific FRA is undertaken to 

assess the risks of all forms of flooding to and from development taking climate 

change into account. The FRA is then used to inform the application of the PPS25 

Sequential Test. 

1 Planning Policy Statement 25: Development and Flood Risk, page 2, paragraph 5 

3

2.2.3 PPS25 Sequential Test 

The Sequential Test is used to examine the possibility of relocating development in 

areas found to be at medium and high probability of flooding from rivers and the sea 

to areas of low probability. The definition of low, medium and high probability flood 

risk areas is determined in PPS25 and is shown below Table 1. 

Flood Zone 1 

Flood Zone 2 

Flood Zone 3a 

Flood Zone 3b 

Low 

Probability 

Medium 

Probability 

High 

Probability 

The 

Functional 

Floodplain 

This zone comprises land assessed as having 

less than 1 in 1000 annual probability of river or 

sea flooding in any year (1% AEP) or a 1 in 200 or greater 

annual probability of flooding from the sea (>0.5% 

AEP) in any year. 

This zone comprises land where water has to flow 

or be stored in times of flood. Strategic Flood 

Risk Assessments (SFRA) should identify this 

Flood Zone (land which would flood with an 

annual probability of 1 in 20 (5% AEP) or greater 

in any year or is designed to flood in an extreme 

(0.1% AEP) flood or at another probability to be 

agreed between the LPA and the Environment 

Agency, including water conveyance routes). 

Table 1: Definition of Flood Zones (from PPS25 Table D1) 

If areas at lower flood risk are not available or appropriate, then vulnerability of the 

proposed development to the effects of flooding are considered. Within PPS25, the 

vulnerability of different types of development is given. These are shown in the table 

below: 

Essential 

Infrastructure 

Highly 

Vulnerable 

More 

Vulnerable 

Less 

Vulnerable 

Water 

Compatible 

Essential transport infrastructure (including mass evacuation routes) 

that has to cross the area at risk, and strategic utility infrastructure, 

including electricity generating power stations and grid and primary 

substations. 

Police stations, ambulance stations and fire stations and command 

centres and telecommunications installations required to be operational 

during flooding; emergency dispersal points; basement dwellings; 

caravans, mobile homes and park homes intended for permanent 

residential use; installations requiring hazardous substances consent. 

Hospitals; residential institutions; dwelling houses; pubs, clubs, hotels; 

health centres, nurseries, schools; landfill and sites for hazardous 

waste; sites used for holiday, short let caravans and camping. 

Retail, offices, warehouses, workshops, leisure; agriculture; nonhazardous 

waste treatment; mineral working; water treatment plants; 

sewage treatment plants. 

Flood control infrastructure; water transmission infrastructure; docks, 

marinas, wharves; navigation facilities; MOD defence installations; ship 

building; water based recreation; lifeguard stations; amenity open 

spaces and sand and gravel workings. 

Table 2: Development Vulnerability (as defined in PPS25 Table D2) 

2 AEP: Annual Exceedance Probability 

4

When the both the ‘Flood Zone’ and ‘flood vulnerability’ of flooding have been 

identified, compatibility of the proposed development is confirmed in-line with Table 

3 (Table D3 in PPS25). The requirements of the Exception Test are as follows: 

a) it must be demonstrated that the development provides wider sustainability 

benefits to the community that outweigh flood risk, informed by a SFRA 

where one has been prepared. If the Development Plan Document (DPD) has 

reached the ‘submission’ stage the benefits of the development should 

contribute to the Core Strategy‘s Sustainability Appraisal; 

b) the development should be on developable previously-developed land or, if it 

is not on previously developed land, that there are no reasonable alternative 

sites on developable previously-developed land; 

c) a FRA must demonstrate that the development will be safe, without 

increasing flood risk elsewhere, and, where possible, will reduce flood risk 

overall. 

Flood Risk 

Vulnerability 

Classification 

Zone 1 

Essential 


Water 

Compatible 

Highly 

Vulnerable 

More 

Vulnerable 

Less 

Vulnerable 

 

 

Flood Zone 

Zone 2 

Zone 3a 

 

Exception 

Test required 

 

 

Exception 

Test required 

 

 

Exception 

Test required 

 

 

Zone 3b 

Exception 

Test required 

 

 

Development is appropriate Development should not be permitted 

Table 3: Flood Risk Vulnerability and Flood Zone ‘Compatibility’ (Table D3 in 

PPS25). 

2.3 Harborough Strategic Flood Risk Assessment 

In accordance with PPS25, Harborough District Council commissioned Scott 

Wilson to undertake a Strategic Flood Risk Assessment (SFRA) to inform the 

LDF. 

At the time of writing the Harborough SFRA was still in preparation and had not 

been issued. The recommendations and aspirations of the SFRA will therefore 

not be considered in this FRA. 

5

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6

3 Flood Risk to the Proposed Development 

3.1 Fluvial Flooding – Main River 

Fluvial flooding refers to flooding from rivers, streams and other inland natural 

watercourses. It is usually caused by prolonged or intense rainfall, generating 

high rates of runoff which overwhelm the capacity of the river or channel. When 

this occurs, excess water will spill onto low-lying areas of land adjacent to the 

channel. This area is known as the floodplain. 

In England, the term ‘Main River’ is given to strategically important waterways 

that drain a catchment. They are defined by lines drawn on a statutory map held 

by the government (Defra). 

Main Rivers are not always the biggest rivers in a catchment but they are 

hydraulically important to how water drains from a catchment. Consequently, they 

also tend to be associated with the greatest flood risks. 

The Environment Agency has permissive powers, but not a duty, to carry out 

flood defence works on Main Rivers. 

3.1.1 Initial Investigation 

The nearest Main River is the River Avon, which flows from east to west. It 

passes under the A14 via a formal bridge crossing. 

The widening of the A14 slip roads will require embankments which encroach on 

flood zone 3a (see Figure 2 and Figure 8 in Appendix B). The embankments will 

therefore experience flooding in the 1 in 100 (1%) annual probability event, 

however since the A14 road level is significantly above the 1 in 100 (1%) annual 

probability level the consequence of flooding is thought to be minimal i.e. does 

not represent a tangible risk to road users. Flood risk to the A14 embankments 

(shoulders) from the Main River is considered low. 

The river continues to the west between the A14 and the M1 where it passes 

under the M1 under a formal bridge crossing. There is no proposal to change the 

existing highway bridge crossings therefore the water levels will remain the same. 

The M1 and A14 are both significantly elevated (5.2m and 1.4m respectively) 

above the River Avon 1 in 100 (1%) annual probability levels therefore the flood 

risk to the M1 and A14 highways from the Main River is considered very 

low. 

Upstream of the A14 and between the A14 and the M1 there are proposed 

bridleway crossings shown in Figure 2. The proposed bridleway bridges 

upstream of the A14 will be replacing an existing bridge of simple timber 

construction. Whilst the bridleway bridge between the A14 and M1 will be a new 

bridge. The deck level and approach ramps of the proposed bridges will be below 

the 1 in 100 (1%) annual probability flood level. This design has been agreed with 

the Environment Agency. The structure will be at risk from flooding, furthermore 

users of the bridge will be at risk from flooding. Flood risk to this bridleway 

bridge is therefore considered to be high and some degree of mitigation 

will be required (see Section 5). 

7

M1 

A14 

Figure 2: River Avon flowing under the A14 and M1, position of proposed bridleway bridges 

are shown 

8

3.2 Fluvial Flooding – Ordinary Watercourses (Non-Main River) 

Ordinary watercourses are described as all watercourses that are not Main River, 

such as streams, drainage ditches (whether dry or not), ponds, culverts, drains, 

pipes and any other passage through which water may flow. However, for the 

purposes of this part of the FRA, only ordinary watercourses such as small 

streams and brooks are considered. Drainage pipes and ditches are addressed 

later on in Section 3.6. 

Swinford Lodge Brook (see Figure 2) runs under the A14 close to the River Avon 

crossing, continuing alongside the existing A14 embankment and joins the River 

Avon downstream of the A14 bridge crossing. The brook is thought to run dry for 

parts of the year and as such acts as a land drain. The proposal at this location is 

to widen the road and supporting embankments. The proposal for Swinford 

Lodge Brook is to move this laterally out of the footprint of the proposed 

embankments. The channel section dimensions and levels will be maintained 

where feasible. The A14 is significantly elevated (approximately 1.4m above the 

1 in 100 (1%) annual probability level of the River Avon downstream) above the 

watercourse at this location, the watercourse is not considered to pose a risk to 

the A14. Flood risk presented by diverting Swinford Lodge Brook to the 

scheme is therefore considered to be low. 

3.3 Coastal and Tidally Influenced Flooding 

There is no coastal flood risk. The scheme is located inland, and all watercourses 

are unaffected by tidal variations. 

3.4 Groundwater Flooding 

Increased groundwater levels caused by prolonged periods of rainfall can result 

in flooding. Generally, groundwater flooding may be a problem where 

developments are underlain by permeable soils or rocks, known as aquifers. 

Aquifers often have an extensive capacity to receive and store water from rainfall. 

This level of storage means that in many cases heavy rainfall can be absorbed 

without resultant flooding. 

However, if above average rainfall persists for extended periods, groundwater 

levels may raise to the surface. This can cause seepage into basements, ponding 

of water in low-lying areas and the re-emergence of normally dry groundwater 

springs and ephemeral watercourses. 

3.4.1 Hydrogeological assessment 

A hydrogeological assessment has been performed by Jacobs (July 2009, see 

Appendix C for full report) to assess the impact of groundwater on the scheme. 

The main areas of concern are the proposed Swinford Road Cutting under the 

M6 and the A14 –M6 link beneath the M1. 

The solid geology underlying the site comprises Lower Lias strata, this is overlain 

in areas by a combination of glacial till, River Terrace Deposits and alluvium. 

Groundwater strike and monitoring data indicates that groundwater is in hydraulic 

continuity across the geological strata and above the lowest road levels for the 

9

two locations of interest. The results of groundwater monitoring are summarised 

below: 

Location 

Average 

Ground 

water level 

(mAOD) 

Lowest Proposed 

road level (mAOD) 

Difference 

(m) 


Cutting 

111.5 108.1 3.4 

A14-M6 link 109.6 107 2.6 

Table 4: Ground water levels and proposed finish road level for Swinford Road Cutting and 

A14-M6 link 

The likeliness of groundwater flooding at these locations is high (probable). 

However the hydraulic conductivity of the ground is relatively low thus seepage 

volumes are likely to be low. Any seepage would be intercepted by the proposed 

highway drainage system and may therefore not present a risk to vehicles using 

this stretch of the scheme. It may be precautionary, however, to consider 

mitigation measures so that these seepage volumes do not surface (see Section 

5). Flood risk presented by groundwater to the scheme therefore is 

considered to be low. 

3.5 Surface Water Runoff 

Surface water runoff is defined as water flowing over the ground that has not yet 

entered a drainage channel or artificial drainage system. It usually occurs as a 

result of an intense period of rainfall, which exceeds the capacity of the ground to 

soak up the water. 

Typically, runoff occurs on sloping land and where the ground surface is relatively 

impermeable. The ground can be impermeable, either naturally through the soil 

type/geology or due to development which places a large area of impervious 

material over the ground surface (i.e. paving and roads). 

The flow path taken by surface water runoff is strongly influenced by the local 

topography and the built form. Runoff will gravitate towards the lowest areas. The 

places at greatest risk from surface water runoff are usually situated in 

topographical low spots where water will pond or within the flow path for the 

runoff. 

3.5.1 Initial assessment of surface water run-off 

A review of the topographical data provided on the 1:50,000 scale Ordnance 

Survey maps allows surface water pathways to be inferred. These are shown 

below: 

10

Major earthworks 

affecting surface 

water pathways 

Surface water 

flow path 

Figure 3: Surface water pathways inferred from contours 

According to the hydrogeology assessment the drift geology is River Terrace 

deposits and alluvium. The alluvium is described as soft sand clay with some 

organic material, therefore, rainfall falling onto the site may generate significant 

volumes of surface water runoff. Surface water runoff is thought to find is way into 

the many existing land drains and ditches in place to assist in draining 

surrounding farmland. Surface water runoff is not considered to present a risk to 

the scheme due to the elevated nature of the highways. In the proposed scheme 

the raised embankment shown in Figure 3 has the potential to change the 

surface water runoff flow path. However, this water will flow from the earthworks 

and the highways into the proposed drainage system. 

Flood risk presented by surface water to the scheme therefore is 


11

3.6 Flooding from Artificial Drainage Systems 

Artificial drainage systems are those which have been installed into an area 

during development to manage runoff or effluent discharges. They include pipes, 

land drains, sewers and drainage channels. 

Sites currently or previously used for agricultural purposes may additionally have 

systems of land drains as well as open ditches and watercourses. 

The main risk from this source of flooding occurs during periods of heavy rain 

when the capacity of the system is exceeded. Debris and sediment can often get 

trapped in these systems causing a reduction in the capacity of the network. 

3.6.1 Assessment of highways runoff and land drains 

There are no known issues with regards to the highway drainage system 

currently. The existing drains are maintained regularly and thus the likeliness of 

the highways flooding due to highway runoff is thought to be low. 

The proposed development will increase the total impermeable area contributing 

to highway runoff. Without a commensurate improvement in the proposed 

drainage system the flood risk from highway runoff will increase. The 

consequence of flooding on the highway would be significant as it would present 

a significant risk to vehicles and drivers. Mitigation measures will therefore be 

required to maintain the existing low level of flood risk. 

Flood risk presented by highway runoff to the proposed development 

(vehicles and drivers) is considered to be high. 

There are a number of culverts (see Figure 4 in Section 5.4) which convey small 

unnamed watercourses within the limits of the scheme. Where embankments are 

being widened these culverts will be lengthened. Lengthening the culverts will 

have the effect of increasing friction (marginally for the lengths being considered) 

and thus reducing the conveyance of the culverts. There are no known issues of 

under capacity, blockage or flooding from the existing culverts. Mitigation 

measures will be required to maintain or reduce the level of flood risk. 

Flood risks presented by the culverts to the proposed development is 


12

3.7 Flooding from Infrastructure Failure 

This type of flooding occurs as result of the failure of infrastructure which exists to 

retain, transmit or control the flow of water. The failure can be caused by 

structural, hydraulic, mechanical, geotechnical or operation problems. 

The risk of flooding comes from infrastructure such as canals, dams, water 

mains, flood defences, pumping station and blockages of pipes. 

Investigations of the Severn Trent infrastructure suggest that there are water 

supply pipes that pass directly through the site. Inspection of the OS background 

indicates that there is a reservoir upstream of the site. 

(a) Reservoir Failure 

From Ordnance Survey data it is observed that Stanford reservoir lies 

approximately 4km upstream of the site and feeds the River Avon at the 

upstream limit. 

Severn Trent has a comprehensive and ongoing mandatory inspection and 

maintenance regime of their reservoirs under the Reservoirs Act. Any structural 

problems with this reservoir would be identified by this regime and rectified. A 

sudden failure of the reservoir is considered to be a very low probability event. 

A dam break analysis has been performed for Stanford Reservoir, and an 

inundation map was produced as part of this. Severn Trent’s reservoir 

supervising engineer 3 has stated that the M1/M6 junction was part of the detailed 

analysis and the report concludes that "The M1/M6 motorway junction and wide 

bridge opening across the valley between the dam and the disused railway 

embankment, at 4.8 km downstream, would have a negligible effect on the flood 

wave". The remainder of the dam break information is considered a confidential 

nature at present. 

A request for the inundation map has been made but has not at the time of 

writing been made available. 

(b) Water Supply and Sewage Infrastructure Failure 

The existing data obtained from Severn Trent does not indicate the size of the 

pipes, depth of the pipes or what they convey. The designers should ensure that 

the water supplier (Severn Trent) is contacted and details of the pipes obtained. 

Where necessary an application for diversions will have to be made. 

The failure of any of these pipes during construction may lead to overland flows 

towards the low spots such as Swinford Road crossing and the A14-M1 link. The 

water supply pipes are unlikely to represent a serious risk to the scheme or 

highway users. The flow rates are likely to be low and the water would be 

intercepted by the drainage network. 

The risk of flooding from identified infrastructure failure is considered to be 

low. 

3 Email (13/07/09) from Mr. Francis Simba Chigara, Reservoir Supervising Engineer, Severn 

Trent. email: francis.chigara@severntrent.co.uk 

13

3.8 Climate Change 

The impacts of climate change are uncertain. Modelling carried out by the Hadley 

Centre (Met Office) has looked at a number of different scenarios. These models 

suggest that winters will become wetter over the whole of the UK, by as much as 

20 per cent by the 2050’s. 

A shift in the seasonal pattern of rainfall is also expected, with summer and 

autumn becoming much drier than at present. However, the intensity of the 

rainfall during summer storms is predicted to be much greater. So even though 

the overall amount of rain in the summer will be less, there will be more 

occurrences of heavy rainfall. 

Once constructed, the development is expected to be there for at least 100 years. 

(This is generally considered an appropriate time horizon for Developers to have 

to accommodate.) 

However, once an area has become developed, it is more likely to remain 

developed in some form or another beyond this life-span. This should be taken 

into account in longer-term strategies for the area. 

Therefore, climate change will present a Future Risk to the site in the form of 

greater volumes of surface water runoff from the surrounding area and from the 

site itself. 

In making an assessment of the impacts of climate change Table 5 shows the 

precautionary allowances that should be considered for the parameters relevant 

to this site. 

Parameter 

1990 to 

2025 

2025 to 

2055 

2055 to 

2085 

2085 to 

2115 

Peak rainfall intensity +5% +10% +20% +30% 

Peak river flow +10% +20% 

Table 5: Recommended national precautionary sensitivity ranges 4 

4 PPS25 – Table B2 

14

3.9 Summary of Risks to Site 

Table 6 contains a summary of the risks to the site. Mitigation measures to 

address identified risks are discussed in Section 0. 

Flood Risk 

Level of 

Risk 

Actions Required 5 

A14 

Embankments 

Low 

None 

Fluvial - Main 

River 

Highways Low None 

Bridleway 

Crossing 

Fluvial – Ordinary Watercourse 

Sea/Tidal 

High 

Low 

None 

identified 

Mitigation measures 

Ensure culvert capacities are 

assessed/designed based on 

DMRB methodology. 

None 

Groundwater Medium Mitigation measures 

Surface Water Runoff Low Mitigation measures 

Artificial Drainage Systems 

Potentially 

High 

Further investigation – visual 

assessment planned by 

drainage design team. 

Infrastructure Failure Low None 

Table 6: Summary of risks to the M1 Junction 19 

5 See Section 5 for further details. 

15


16

4 Impacts of the Proposed Development on Flood Risk 

Elsewhere 

4.1 Impacts on Fluvial Flood Risk 

The effect of the M1 Junction 19 improvements proposal on fluvial flood risk can 

be summarised as follows: 

• The expansion in impermeable area will result in a net increase in the 

volume of highway runoff and also in the peak runoff flow rate. If this 

runoff is allowed to discharge freely into the adjacent land drains and 

ditches (and subsequently into the River Avon) it would have the effect of 

increasing fluvial flood risk. 

• The widening of the embankments along the A14 will have the effect of 

displacing the floodplain and reducing the total volume of storage 

available to the river in times of spate. This would have the effect of 

increasing water levels and therefore increasing fluvial flood risk. 

Therefore, it is important that any increases in flow volumes and displacement of 

the floodplain are carefully managed in line with Environment Agency 

requirements (discussed in Section 0, Proposed Mitigation Measures). 

Limited information regarding the bridleway bridge crossings is available at this 

time. A simplified Manning’s assessment of the bridges based on an assumed 

rectangular cross section measuring 5m wide and 1.5m deep indicates that the 

bridge will be surcharged at low return period flows i.e. approximately 1 in 2 yr or 

less. The low deck height of the bridleway bridge is required due to the proposed 

use of the bridge (a low gradient is required to improve accessibility to all users).If 

the bridge was to be raised out above the 1 in 100 (1%) annual probability flood 

levels, the height required would be significant. This would also require large 

lengths of the bridleway to also be raised which would have a greater impact on 

flood risk than the bridge alone. 

The impact of bridges will be to reduce the conveyance of the river channel 

sections at these two locations. This may have an impact of backing up flows and 

raising water levels upstream of the bridges. However, as the bridges will remain 

low this impact will be minimised. The bridges may have the effect of flooding the 

adjacent fields more frequently, and therefore increasing the risk to farmland 

marginally. At higher return period events the bridge and approach ramps will be 

overtopped and bypassed. 

4.2 Impacts on Groundwater Flooding 

The scheme proposals include provision for deep excavation below the adjacent 

ground water level for the Swinford Road underpass and the A14-M6 link. Slope 

face drainage has been proposed in the Contractor’s Drainage Report to control 

groundwater seepage. Such a system of drains will have the effect of lowering 

groundwater levels locally, with a decreasing effect further away from the 

scheme. At this broad level of assessment it is not thought that the scheme will 

increase the groundwater levels or the groundwater flood risk elsewhere. 

17

Mitigation measures to reduce the impact of groundwater flooding locally (on the 

scheme) are given in Section 0: Proposed Mitigation Measures. 

4.3 Impacts on Flood Risk from Surface Water Runoff 

The scheme involves some major earthworks particularly in the construction of 

the M6-A14 link and the M1–A14 link, this is shown in Figure 3. The impact of the 

proposal will be to reduce the total area contributing to surface water runoff which 

would ordinarily have found its way into land drains and subsequently into the 

River Avon. The existing proposal of cuttings, embankments and highways will 

divert this surface water runoff into the proposed drainage system. Therefore the 

scheme will have an effect of reducing the surface water runoff and the 

associated risk. However, it is noted that this surface water will be managed 

differently in the current proposal i.e. transferred to the artificial drainage system, 

this is considered in the following section. 

4.4 Impacts on Flooding from Artificial Drainage Systems 

The volume of runoff picked up by the artificial drainage system is set to increase 

following the proposed scheme because it will: 

• collect groundwater for the substantial cuttings 

• collect surface water which would have ordinarily infiltrated or have been 

intercepted by land drains 

• collect from a larger impermeable area 

The runoff from the existing drainage system discharges into nearby water 

courses which subsequently flow into the River Avon. The impact of the 

increased volume of runoff from various sources conveyed by the artificial 

drainage system may increase peak flow and thus flood risk in the River Avon. 

Arguably the time of concentrations from a catchment wide event would be very 

different between the natural catchment and the impermeable catchment. Despite 

this, mitigation measures should be considered (see Section 5). 

4.5 Impacts on Flooding from Infrastructure Failure 

Construction of the scheme (particularly around the Swinford Road cutting and 

A14-M1 link) may damage the water supply pipelines through the site. Damage to 

these pipes could cause overland flows towards the site. Whilst, this flooding is 

not likely to cause a risk to highway users or the scheme in general, it could 

cause short term nuisance. Mitigation will be required on site to avoid any 

damage to these pipes. 

18

4.6 Summary of Flood Impacts from Development 

Table 7 contains a summary of the potential impacts of the development on flood 

risk elsewhere. Proposed mitigation measures are discussed in Section 5. 

Flood Risk Impact on Risk Actions Required 6 

Fluvial - 

Main River 

Fluvial – 

Ordinary 

Watercourse 

Medium 

Low 



Sea/Tidal None identified None 

Groundwater Low Mitigation measures 

Surface 

Water Runoff 

Artificial 

Drainage 

Systems 


Failure 

Low 

Low 

Low 




Table 7: Potential impacts of the development on Flood Risk. 

6 See Section 5 

19


20

5 Proposed Mitigation Measures 

5.1 Mitigation of Impacts on Fluvial Flooding 

Sections 3.1 and 4.1 have identified that the site is at direct and indirect risk from 

fluvial flooding. The direct risk is that some of the proposed embankments are 

within Flood Zone 3. The indirect risk is that the scheme would result in 

increasing the rate and volume of surface water runoff into the receiving 

watercourses. 

5.1.1 Mitigation for Loss of Floodplain 

The EA have stipulated in their communication 7 regarding the scheme that: 

1. Details on any loss of flood plain (Flood Zone 3), and resulting flood plain 

compensation proposals. The proposed fill and compensation areas assessment 

should be undertaken on a like for like level basis in 200mm slices, from (below) 

the modelled 100 year flood event level, and presented in plan and tabular form. 

The floodplain of the River Avon is defined by 1 in 100 (1%) annual probability 

event design water levels from the Environment Agency’s hydraulic model of the 

River Avon. The floodplain level at the sites of interest vary and ar given in the 

table below. 

Calculations have been performed in AutoCAD to identify the volume loss per 

200mm level interval for all affected sections within the flood zone. There are 

three distinct areas where flood plain loss occurs shown in the table below. 

Area of Flood Plain 

Loss 

River Avon Crossing 1 

(North of A14) 

A14 embankment 

widening 

River Avon Crossing 2 

(Southeast quadrant) 

100 yr flood level 

(mAOD) 

Volume loss of flood 

plain (m 3 ) 

- floodplain 

compensation 

required 

98.2 83 

97.6 405 

96.6 99 

Table 8: Summary of sites flood plain loss 

The distribution of volumes and locations for floodplain compensation areas for 

construction purposes are given in Appendix D. 

7 EA letter ref: LT/2009/107833/01-L01 (26 th May 2009) 

21

5.1.2 Mitigation for Increased Runoff Volumes and Rates 

In order to deal with increase runoff from the highways without increasing the 

discharge to the neighbouring watercourse, namely the River Avon, five 

attenuation ponds have been proposed. 

The Environment Agency was consulted in the development of the Contractors 

drainage proposal. The EA design parameters adopted at this stage of design are 

as follows: 

• Where attenuation is to be provided the proposed discharge rate is to be 

limited to 60% of existing (existing discharge rates based on a 2 year 

design storm 30 minute rainfall event). This parameter has been adopted 

to achieve the EA objective to reduce the total existing discharge flow 

within the limits of the scheme by a minimum of 20%. It also provides a 

conservative basis from which to determine land take and allows for 

further design development during PCF Stage 5 (Construction 

Preparation). 

• Existing greenfield run-off rates are to be restricted to 5l/s/ha 

• Attenuation ponds are to be designed to accommodate a 100 year design 

storm plus an additional 20% for possible climate change 

Furthermore, the highways drainage system has been designed in accordance 

with the Design Manual for Roads and Bridges (DMRB) to the following criteria: 

• Carrier drains have been designed to accommodate a 1 year design 

storm in bore and checked to ensure no flooding in a 5 year storm 

• Filter drains have been designed to accommodate a 1 year design storm 

in-bore and checked to ensure no surcharging above formation level or 

sub-formation level in a 5 year storm 

• Networks have been designed to accommodate an additional 20% 

increase in rainfall intensity for possible climate change without flooding in 

a 5 year design storm. 

Additionally, the attenuation ponds will require a regular maintenance regime to 

maintain the effectiveness of the attenuation ponds. This is described in detail in 

the Contractor’s Drainage Proposal (see Appendix B). 

5.1.3 Further Mitigation Requirements 

The above describes the measures required to mitigate against increasing flood 

risk from the development. It should also be noted that the embankments, 

bridleways and approach ramps are at fluvial flood risk and as such should be 

designed with the relevant design scenarios in mind (e.g. rapid drawdown, scour, 

hydrostatic loading etc.). Furthermore, the bridleway crossings and approach 

ramps will be submerged during high flows. The bridge and approaches should 

be designed to minimise the obstruction to the flow. Additionally, signage should 

be considered to inform users that the crossing is impassable during high flows. 

5.2 Mitigation of Groundwater Flood Risks 

Certain parts of the proposed road infrastructure are below existing ground levels 

and have been identified as being at risk of groundwater flooding. 

22

The extents of this problem are currently being investigated by the design team in 

the form of additional ground investigation planned for August 2009. Once the 

level of risk has been clarified, mitigation measures will be put in place to prevent 

flooding from this source. At present, the proposed method of mitigation is to 

control groundwater levels by installing a system of ditches and filter drains at the 

highway boundary. Slope face drainage is also being considered to control water 

seepages in deeper cuttings. All groundwater discharges will be managed and 

released in a manner which will not increase flood risk elsewhere in accordance 

with PPS25. 

5.3 Mitigation of Surface Water Runoff (Overland Flows) 

The impact of the scheme will be to reduce the total amount of surface runoff as 

described in Section 3.4. No mitigation measures are therefore required. 

5.4 Mitigation of Flood Risks from Artificial Drainage Systems 

There are a number of culverts which convey small unnamed watercourses within 

the limits of the scheme. Where embankments are being widened these culverts 

will be lengthened. The design approach to these modifications is being carried 

out as per DMRB methodology (106/04) for the design of culverts. A summary of 

the culverts are given below: 

Figure 4: Culverts within the scheme which require modification 

23

Table 9: Summary of proposed works to culverts ( Contractors Proposal for 

Drainage, 2009) 

From Table 9 above it can be seen that 6 of the 7 culverts will require 

modifications. Culvert C/5 will be replaced with a smaller (existing = 1200mm 

diameter, proposed = 900mm diameter) culvert since this will be conveying land 

drainage only and not highway runoff as was the case for the existing 

configuration. 

The design team plan to perform a survey on the drainage system. It is 

recommended that this includes a visual assessment of the culverts described 

above to identify any issues and mitigate against them. 

The complete drainage proposal therefore provides an acceptable 

mitigation against increasing flood risk. 

5.5 Mitigation of Flood Risks from Infrastructure Failure 

The level of risk as a result of infrastructure failure is considered to be low. 

However, it is suggested that more details of the assets shown on the Severn 

Trent service layouts are obtained. Further ground investigation/trial pits may be 

required to identify the nature and location of Severn Trent’s assets which conflict 

with the location of the proposed scheme. Diversion of Severn Trent’s assets 

may be required. 

5.6 Incidental Mitigation Measures 

Due to environmental concerns the river banks of the Avon will be widened to 

create habitat for otters. The extents of the widening has is not confirmed at this 

stage of the project. The effect of the river widening, though not the purpose, will 

be to increase the conveyance and storage capacity of the river channel, in turn 

lowering flood levels and flood risk. 

24

5.7 Summary of Recommended Mitigation Measures 

Table 10 contains a summary of the recommended mitigation measures for the 

Carleton developments. 

Flood Risk 

Scheme may increase 

fluvial flood risk in 

downstream watercourses 

Scheme may be at risk of 

groundwater flooding 

Flooding to the site as 

result of failure of Artificial 

Drainage Systems 

Infrastructure Failure 

Recommended Mitigation 

• Reduce the runoff rates to 60% of existing 

values by introduction of attenuation ponds 

• Introduce flood plain compensation for 

locations where proposed development is 

within Flood Zone 3a 

• Consider signage at bridleway crossings to 

inform users of the risk of flooding 

• Introduce filter drains and slope face 

drainage where necessary to control 

groundwater levels 

• Perform more detailed drainage survey to 

identify existing issues with the drainage 

system and culverts 

• Regular maintenance of drainage system 

and culverts 

• Pursue Severn Trent for more details of 

their assets in the area, including Stamford 

reservoir upstream of scheme and potential 

water supply pipes which run through the 

site 

Table 10: Summary of recommended mitigation measures. 

25


26

6 Residual Risks 

The level of flood risk to the M1 Junction 19 has been investigated at an 

appropriate level of detail. Suitable mitigation measures have been identified for 

these risks. 

Consequently, the flood risk to the development, if the recommended mitigation 

measures are followed, will be low. 

However, there is always a residual risk that an event will occur that exceeds the 

design criteria. 

Table 11 identifies what are considered to be the residual risks to the site: 

Risk Impacts Potential Further 

Mitigation Measures 

Extreme rainfall event 

greater than drainage 

system design event. 

Failure of to maintain 

artificial drainage 

systems (i.e. highway 

drainage, land drains). 

Failure of 3 rd parties to 

maintain essential 

infrastructure (i.e. 

reservoirs, water supply 

network). 

• Water build up on 

highway 

• Water built up on 

highways 

• Impounding of water 

against highway 

embankment 

• Water flow along 

highways 

• Consider alternative 

drainage routes 

based on road 

camber/topography 

only 

• Consider alternative 

drainage routes 

based on 

road/camber 

topography only 

• Regular inspection of 

culverts, 

implementation of 

trash screens 

• Pursue Severn Trent 

for more details of 

their assets in the 

area, including 

Stamford reservoir 

upstream of scheme 

and potential water 

supply pipes which 

run through the site 

Table 11: Potential residual risks to site 

27


28

7 PPS25 Sequential and Exception Test 

In this section, the suitability of the scheme in relation to the requirements of 

PPS25 has been considered. 

The widening of the A14 slip roads and proposals for the bridleway crossings will 

require embankments (approach ramps) which encroach into the Flood Zone 3a 

as defined by PPS25. The proposed development is classified as essential 

transport infrastructure and therefore is only permitted in Zone 3a if a FRA and 

the Sequential Test and Exception Test are completed. 

7.1 The Sequential Test 

The Sequential Test should be applied to demonstrate that there are no 

alternative sites within the area with a lower probability of flooding that could be 

used for the development. In this case, the A14 crosses the River Avon and the 

existing junction is close to the watercourse, it is not possible to relocate the 

development outside of the floodplain. 

Since the development is regarded as Essential Infrastructure and falls within 

Flood Zone 3a (refer to to Table 3) the Exception Test will need to be performed. 

7.2 The Exception Test 

For the Exception Test to be passed: 

a) It must be demonstrated that the development provides wider sustainability 

benefits to the community that outweigh flood risk, informed by the SFRA where 

one has been prepared. 

Response: 

There are known, high profile, congestion and safety problems with the M1 / 

A14 junction. The improvements to the junction will therefore reduce the 

stress associated with travelling across Junction 19, increase safety for 

vehicle drivers and reduce travel times. 

b) The development must be on developable previously developed land or, if it is 

not on previously developed land, that there are no reasonable alternative sites 

on developable previously developed land. 

Response: 

Due to the existing location of Junction 19 and the River Avon, it is not 

possible to locate the development elsewhere. 

c) A FRA must demonstrate that the development will be safe, without increasing 

flood risk elsewhere, and, where possible, will reduce flood risk overall. 

Response: 

In this case the proposals include floodplain compensation storage for the 

areas of the floodplain required for embankments and bridge approach 

ramps. The existing drainage alongside the M1 and existing carriageway 

drainage will be maintained and improved in accordance with consultation 

with the EA. 

29

The increase in storm runoff from the additional carriageway area will be 

attenuated to reduce the existing discharge to the river using attenuation 

ponds. All of the attenuation ponds are located outside the floodplain area 

and therefore will not impact on the floodplain. These measures will maintain 

the existing drainage into the River Avon and therefore the flood risk 

elsewhere will not be increased. The proposed level of the A14 and M1 slip 

roads is above the level of the floodplain and therefore the development itself 

is not at risk of flooding, access along the A14 and M1 will not be impaired 

during a flood event. 

7.3 Summary 

It is considered that the proposed M1 Junction 19 improvement scheme is 

compliant with PPS25 and that it meets the requirements of the Sequential Test 

and the Exception Test. 

30

8 Conclusion 

The M1 Junction 19 Improvements scheme is considered to be at risk of fluvial 

flooding as parts of the scheme are located within flood zone 3a, the 1 in 100 

(1%) annual probability flood extents. 

The proposed development is classified as essential transport infrastructure and 

is only permitted in zone 3a if the Exceptions Test is satisfied. 

Due to the location of the existing junction it is not possible to relocate this 

development outside of the floodplain. 

The Exception Test (PPS 25) has been completed for the development. The 

development has been shown to have wider sustainability benefits by reducing 

the stress, risk and travel time associated with driving between the M1 and A14. 

The specific locations at fluvial risk are: 

• The A14 on the eastern part of the scheme, specifically the embankment 

shoulders, the highway deck is unaffected 

• Bridleway Crossing 1 north of the A14 over the River Avon will be totally 

submerged in the 1 in 100 year event 

• Bridleway Crossing 2 between the M1 and A14 (southeast quadrant) will 

be totally submerged in the 1 in 100 year event 

To mitigate against the risk of increasing flooding downstream flood 

compensation areas have been proposed. Dimensions of the compensation 

areas can be found in Appendix D. 

There will be a net total increase in impermeable area associated with the 

scheme and thus a commensurate increase in highway runoff. To mitigate 

against the effect of increased runoff in the River Avon, five attenuation ponds 

have been proposed. The design has been developed in consultation with the 

EA. Details of the attenuation ponds can be found in Appendix B. 

It is recommended signage is incorporated at the bridleway crossing to inform 

users of the risk of flooding 

The scheme will involve deep cuttings for the Swinford Road underpass and the 

A14-M1 link. This may result in groundwater seepage. To mitigate against this 

risk filter drains and slope drainage are being considered by the contractor. 

It is recommended that Severn Trent is pursued by the designers in respect of 

their assets (water supply) which appear to pass through the site. 

It is anticipated that the level of residual risk to the site, following the 

implementation of all identified mitigation measures, will fully satisfy the 

requirements of PSS 25. 

. 

31


32

Appendix A 

Existing Layout, Environmental Masterplan and 

Environmental Resources Plan


Appendix B 

Contractor’s Proposals for Drainage


Appendix C 

Hydrogeological Assessment


Memorandum 

Fairbairn House, Ashton Lane 

Sale, Manchester, UK 

M33 6WP 

+44.(0)161.962.1214 Fax +44.(0)161.905.5855 

Date 02/07/2009 

To 

From 

Subject 

cc 

Ref 

Sharon Woodruff 

Rachael Nieuwoudt 

M1 Junction 19 - Hydrogeological Assessment 

Peter Dupen; Tim Worrall; Anna Firth 

B0531000 

1. Introduction 

The Highways team in Leeds is designing the new Junction 19 for the M1 and has raised a concern that 

the proposed Swinford Road Cutting under the M6 (area around S9) and the A14–M6 link beneath the M1 

(area around S1) could be at a level close to the saturated zone. As a result a hydrogeological review has 

been undertaken in order to provide a brief assessment of the risk of encountering groundwater during the 

construction of these particular elements of the scheme. 

2. Data Source 

The report is based on information provided by Tim Worrall, Anna Firth and other members of the project 

team. The following data has been reviewed in the course of producing this report: 

• British Geological Survey (1969), Market Harborough, Sheet 170, Solid Edition, 1:50,000; 

• British Geological Survey (1968), Geology of the Country around Market Harborough, Memoir 

170; 

• Envirocheck Report (dated 06/03/2009); 

• BH logs (from site investigations undertaken between 1965 and 2005); 

• Jacobs design drawings and plans; 

• Jacobs groundwater monitoring data (between 04/2004 and 08/2006), and; 

• Background reports held by Jacobs. 

3. Geology 

Published geological information and ground investigation data form the basis of the geological baseline 

conditions. The scheme has been the focus of a number of ground investigations dating from 1965 to 

2005. Geological cross sections A-A’ and B-B’ (attached) show the geology in the areas of interest around 

the Swinford Road Cutting and the A14-M6 Link respectively. The solid geology underlying the site 

comprises Lower Lias strata, this is overlain in areas by a combination of glacial till, River Terrace 

Deposits and alluvium. 

River Terrace Deposits and Alluvium 

The Alluvium and River Terrace Deposits are found in bands across the site in association with the River 

Avon and its tributaries. The alluvium is described as soft sandy clay with some organic material; 

however, it is likely that the Alluvium will have been removed from site during the first stages of road 

constructions as it is an unsuitable founding strata for embankment material. The River Terrace Deposits 

are likely to comprise firm to stiff sandy clay and loose silty sand. The geological memoir describes the 

strata as thin deposits of gravely loam about 0.9 m thick. 

Glacial Till 

Glacial Till is found on higher ground and may vary from soft to very stiff gravely sandy clay with 

numerous flint and quartzite. 

Jacobs Engineering U.K. Limited 

Registered Office: Jacobs House, 427 London Road, Reading, Berkshire, RG6 1BL, UK 

Registered in England and Wales No. 2594504 

Jacobs_MemoA4.doc


(Continued) 

Page 2 of 6 

Lower Lias Clay 

The solid geology comprises Lower Lias Clay of varying strength from stiff to hard. This material is likely 

to comprise of closely fissured bluish grey clay with fossil fragments. Within this strata, bands of 

mudstone and limestone bands are common. 

4. Groundwater Data 

River Terrace Deposits and Alluvium 

The River Terrace Deposits and Alluvium are classified as minor aquifers usually only of local importance 

for supporting abstractions or providing baseflow to surface waters. 

Lower Lias Clay and Glacial Till 

The Lower Lias strata and Glacial Till deposits are generally classified as non aquifers, however, there is 

potential for groundwater flow through fissures and rock inclusions within the solid deposits. Also, specific 

units within the Lower Lias Clay can have minor aquifer status as some of the thin limestones within the 

strata can yield significant quantities of water. 

The proportion of water bearing limestones increases towards the base of the Lower Lias Group, forming 

the Blue Lias or Scunthorpe Mudstone Formation, which is classified as a minor aquifer. 

On the basis of interpretation of the published geological map, the strata below the proposed scheme are 

towards the top of the Lower Lias Group sequence, and therefore would indicate non-aquifer status. 

Correspondence from the EA (2003) indicates that the underlying geology is a minor aquifer, but it is not 

specific with respect to the various geological formations being referred to. An earlier EA /National River 

Authority publication classifies the Lias Group as a non-aquifer which is also in accordance with the 

Envirocheck report and published groundwater vulnerability mapping. 

The geological memoir notes a cutting for the M1 located approximately 30 m south of the proposed A14- 

M6 Link at NGR [56137858], where 1.5 m of Glacial Till is underlain by 3m of Lower Lias Clay overlying 6 

m of Mudstone. At the foot of the cutting a 15 m limestone band was encountered, described as yielding 

large quantities of water. 

Groundwater Abstractions 

Abstractions below 20 m 3 /day (with a number of exceptions) do not require a licence from the EA; these 

private supplies are registered with the relevant Local Authority. There is one private well (NGR SP 5610 

7775), located at Station House, Lilbourne, approximately 1 km south of the A14-M6 Link. No other 

information is available. On the basis of location, it would appear to be sourced by groundwater within the 

river terrace gravels /alluvial deposits. 

There is one licensed abstraction for 2 wells (NGR SP 5621 798) located approximately 1 km northeast of 

the A14-M6 Link at Swinford Lodge. The license is for general farming and domestic use all year round 

but for a relatively small annual volume of 1637 m 3 (and maximum daily rate of 5.5 m 3 ). 

Groundwater Monitoring 

Exploratory holes relevant to the Swinford Road Cutting and A14-M6 Link are listed in Table 4.1, including 

groundwater strikes and other pertinent information. Monthly groundwater monitoring data collected 

between April 2004 and August 2006 is summarised in Figures 4.1 and 4.2 with average groundwater 

levels recorded in Table 4.1. 


Jacobs_MemoA4.doc


(Continued) 

Page 3 of 6 

Table 4.1 Groundwater Data 

Underpass 

Swinford 

Road Cutting 

Exploratory 

Hole 


Strike 

Comments 

Response Zone 

( mAOD) 

BH216 (04) - - 

91.8-89.8 

Lower Lias 

BH3009 (87) - - - - 

BH1389 (65) 110 Strike within Glacial Till - - 

BH1390 (65) 111.3 Strike within Made Ground - - 

BH212 (04) 111.3 

BH323 (05) 108.5 

Strike within Made Ground, 

BH dry from 109 mAOD 

Strike within River Terrace 

Deposits, BH dry from 

106.3 mAOD 

100.6-98.6 

Lower Lias 

106.5-107.8 

River Terrace 

Deposits 

Average 


Level (mAOD) 

113.3 

111.9 

110.8 

A14-M6 Link 

BH217 (04) - - - - 

BH210 (04) - - 

104.6-102.6 

Lower Lias 

BH22 (04) 97.35 

BH102A (04) - 

BH24 (04) 103.79 

BH25 (04) - - 

BH201 (04) 109.65 

BH103(04) 110.71 

BH322s (05) 

BH322d (05) 

BH203 (04) 111.55 

BH321s (05) 

BH32d (05) 

- 

- 

Strike within Lower Lias 

Mudstone band at base of 

borehole 

Damp within Made Ground 

at 114.25 and Lower Lias 

Clay 85.25 mAOD 

Groundwater not apparent 

during boring but entered 

borehole over night 


Clay, groundwater present 

for remainder of boring 


Clay, BH dry from 

109.7 mAOD 


Clay, groundwater present 

for remainder of boring 


Clay, BH dry from 

107 mAOD 

BH dry with slight seepage 

within Lower Lias Clay at 

106.9, 101.7 & 

92.7 mAOD 

94.35-93.35 

Lower Lias 

101.25-100.25 

Lower Lias 

87.89-86.59 

Lower Lias 

87.43-85.93 

Lower Lias 

92.65-90.65 

Lower Lias 

110.71-109.71 

Lower Lias 

118.72-115.72 

Lower Lias 

114.72-100.22 

Lower Lias 

114.55-107.25 

Lower Lias 

108.79-106.68 

Lower Lias 

105.68-89.68 

Lower Lias 

109.4 

105.5 

110.2 

109.5 

108.7 

108.1 

110.8 

Dry 

110.3 

110.8 

108.3 

107.6 


Jacobs_MemoA4.doc


(Continued) 

Page 4 of 6 

Figure 4.1 Groundwater Monitoring - Swinford Road Cutting 

114 

112 

110 

g/w level (m AOD) 

108 

106 

104 

102 

BH212 

BH216 

BH323 

100 

98 

1/8/04 

9/11/04 

17/2/05 

28/5/05 

5/9/05 

14/12/05 

24/3/06 

2/7/06 

10/10/06 

Date 

120 

Figure 4.2 Groundwater Monitoring - A14-M6 Link 

115 

BH24 

g/w level (m AOD) 

110 

105 

100 

95 

BH25 

BH103 

BH201 

BH203 

BH321s 

BH321d 

BH322d 

BH210 

BH22 

BH102 

90 

14/01/04 

23/04/04 

01/08/04 

09/11/04 

17/02/05 

28/05/05 

05/09/05 

14/12/05 

24/03/06 

02/07/06 

10/10/06 

Date 


Jacobs_MemoA4.doc


(Continued) 

Page 5 of 6 

5. Groundwater Assessment 

Swinford Road Cutting (area around S9) 

Ground investigation data is limited with only six boreholes within the vicinity of the proposed cutting, the 

majority of which are over 100 m from the underpass. Three groundwater monitoring installations are 

located in BH216, BH212 and BH323 (as shown in Table 4.1). BH216 and BH212 have been monitored 

on a monthly basis between April 2004 and August 2006. BH323 has been monitored monthly between 

August 2005 and August 2006. Screened response zones are installed at varying depths within the Lower 

Lias Clay (BH216 & BH212) and River Terrace Deposits (BH323). 

Cross Section A-A’ (attached) indicates the area is underlain by up to 4.5 m of Glacial Till underlain by 

Lower Lias Clay with River Terrace Deposits situated to the northeast. The underpass is likely to cut 

through the Glacial Till into the Lower Lias Clay during the construction phase. Both strata will also be 

exposed in the 1:3.5 cut slopes. 

Groundwater strike and monitoring data indicates that groundwater is in hydraulic continuity across the 

geological strata with an average head of 111.5 mAOD. Proposed finished road level is around 

108.1 mAOD at its deepest point, therefore the risk of encountering groundwater during the construction 

of this particular element of the scheme is high. 

A14 – M6 Link (area around S1) 

Cross Section B-B’ (attached) and the BGS geological map indicate that the proposed A14-M6 Link is 

underlain by Lower Lias Clay with an area of Glacial Till up to 4m in thickness situated immediately west 

of the underpass. 

Nine borehole logs and nine groundwater monitoring installations are available in the assessment of the 

groundwater regime (as listed in Table 4.1). Response zones are installed at depths within the Lower Lias 

Clay between 85.93 mAOD and 118.32 mAOD. 

Groundwater monitoring data indicates that groundwater is in hydraulic continuity across area with an 

average head of 109.6 mAOD. Proposed finished road level is approximately 107 mAOD at its deepest 

point in the region of the underpass, however this drops to the east to tie in with existing ground levels. 

The risk of encountering groundwater during the construction of this particular element of the scheme is 

therefore considered high. 

Further hydrogeological assessment 

Although there is a high risk of encountering groundwater at both locations during construction, the 

hydraulic conductivity of the Glacial Till and Lower Lias Clay is thought to be relatively low. The geological 

memoir states that the Lower Lias deposits are predominantly argillaceous (very fine-grained) in nature. In 

several localities boreholes to depths of over 60 m have not encountered groundwater in these 

formations. At best they are reportedly capable of yielding around 1-2 m 3 per hour, generally from thin 

bands of fissured Limestone within the shales and clays. 

A number of the GI borehole logs indicate that no groundwater was encountered during boring, however 

groundwater is reported to have entered the exploratory hole overnight or following installation of the 

standpipe. This suggest that even though the intercepted strata is saturated (i.e. lies below the water 

table), the hydraulic conductivity of the Glacial Till and Lower Lias Clay is so low that the bores take a 

significant period to fill to the standing water level. Based on this and the published data referred to above, 

the volume of groundwater seepage into the cuttings is likely to be relatively slow. 

6. Conclusions & recommendations 

The risk of encountering groundwater during the construction of both the Swinford Road Cutting and the 

A14-M6 Link is considered to be high based on the available information. However, the hydraulic 

conductivity of the Glacial Till and Lower Lias Clay is relatively low; therefore the volume of groundwater 

seepage into the cuttings is likely to be slow (around 1-2m 3 per hour). 


Jacobs_MemoA4.doc


(Continued) 

Page 6 of 6 

Geological and hydrogeological data is limited across this site, especially in the area of the proposed 

Swinford Road cutting. An additional ground investigation is due to commence on site in August 2009, it is 

recommended that a Hydrogeologist has input into the design of the ground investigation and is consulted 

during site works. The investigations should include pump testing to enable an accurate estimate both of 

the rate of inflow into the cuttings and also the likely impacts on the local water table and potential for 

impacts on local water users and ecologically sensitive sites (if any). 

The volume of groundwater seepage from the 1:3.5 cut slopes upon completion of the scheme is 

predicted to be relatively low. Nonetheless, it is recommended that groundwater seepage will need to be 

taken into account during drainage design. 

The interception and permanent lowering of the water table around the Swinford Road cutting and A14- 

M6 Link may impact upon adjacent farmland and ecologically sensitive receptors (if any), and on local 

private or public water supplies. It may also increase the risk of providing a pollutant pathway from a 

nearby landfill to controlled waters. It is recommended that further hydrological and hydrogeological 

assessment be undertaken to determine the risk to local water supplies and controlled waters. 


Jacobs_MemoA4.doc

Appendix D 

Volume Distribution for Flood Compensation


Floodplain compensation area – elevation distribution for the three sites are 

provided in the table below. 

Volume required (m 3 ) 

Elevation 

(mAOD) 

A14 

embankment 

widening. 

River Avon 

Crossing 1 

North of A14 

River Avon 

Crossing 2 

(South East 

Quadrant) 

Total volume 

per slice 

95.500 - 95.600 0.60 0.00 10.28 10.87 

95.600 - 95.800 3.61 0.00 20.40 24.01 

95.800 - 96.000 26.50 0.00 14.84 41.33 

96.000 - 96.200 24.08 0.00 21.70 45.78 

96.200 - 96.400 32.26 0.00 21.33 53.60 

96.400 - 96.600 38.44 0.00 10.73 49.17 

96.600 - 96.800 30.96 0.00 0.00 30.96 

96.800 - 97.000 29.48 0.00 0.00 29.48 

97.000 - 97.200 37.14 18.50 0.00 55.64 

97.200 - 97.400 71.38 26.05 0.00 97.43 

97.400 - 97.600 110.72 25.10 0.00 135.82 

97.600 - 97.800 0.00 13.26 0.00 13.26 

97.800 - 98.000 0.00 0.00 0.00 0.00 

98.000 - 98.200 0.00 0.00 0.00 0.00 

95.500 - 95.600 0.60 0.00 10.28 10.87 

95.600 - 95.800 3.61 0.00 20.40 24.01 

95.800 - 96.000 26.50 0.00 14.84 41.33 

Total 405 83 99 587 

100 yr flood 

level (mAOD) 

97.6 98.2 96.6


Depth Bands (m) 

TOTAL 

(m³) 

Area Required 

(m²) 

95.500 - 95.600 10.87 54.37 

95.600 - 95.800 24.01 120.05 

95.800 - 96.000 41.33 206.67 

96.000 - 96.200 45.78 228.90 

96.200 - 96.400 53.60 267.99 

96.400 - 96.600 49.17 245.84 

96.600 - 96.800 30.96 154.78 

96.800 - 97.000 29.48 147.40 

97.000 - 97.200 55.64 278.18 

97.200 - 97.400 97.43 487.17 

97.400 - 97.600 135.82 679.11 

97.600 - 97.800 13.26 66.31 

97.800 - 98.000 0.00 0.00 

98.000 - 98.200 0.00 0.00

Chapter 9: Road drainage and the water environment

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