Chapter 9: Road drainage and the water environment

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M1 JUNCTION 19 IMPROVEMENT ENVIRONMENTAL STATEMENT VOLUME 2 CHAPTER 9 – ROAD DRAINAGE AND THE WATER ENVIRONMENT 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. B0531000_ID_70-EIA Vol 2 Chap 9 Road Drainage and the Water Environment Final Rev 4.doc Page 16
M1 JUNCTION 19 IMPROVEMENT ENVIRONMENTAL STATEMENT VOLUME 2 CHAPTER 9 – ROAD DRAINAGE AND THE WATER ENVIRONMENT 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. B0531000_ID_70-EIA Vol 2 Chap 9 Road Drainage and the Water Environment Final Rev 4.doc Page 17
Page 1: M1 Junction 19 Improvement Environm
Page 4 and 5: M1 JUNCTION 19 IMPROVEMENT ENVIRONM
Page 71 and 72: Appendix A - Pollution and Spillage
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Method D - Assessment of Pollution
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M1 JUNCTION 19 IMPROVEMENT ENVIRONM
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Groundwater: Hydrocarbons Hydrogeol
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M1 JUNCTION 19 IMPROVEMENT ENVIRONM
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Non Technical Summary Skanska Const
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Contents 1 Introduction 1 1.1 Overv
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1 Introduction 1.1 Overview Jacobs
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2 Policy Review 2.1 Planning Contex
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When the both the ‘Flood Zone’
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3 Flood Risk to the Proposed Develo
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3.2 Fluvial Flooding - Ordinary Wat
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Major earthworks affecting surface
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3.7 Flooding from Infrastructure Fa
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3.9 Summary of Risks to Site Table
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4 Impacts of the Proposed Developme
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4.6 Summary of Flood Impacts from D
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5 Proposed Mitigation Measures 5.1
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The extents of this problem are cur
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5.7 Summary of Recommended Mitigati
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6 Residual Risks The level of flood
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7 PPS25 Sequential and Exception Te
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8 Conclusion The M1 Junction 19 Imp
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Appendix A Existing Layout, Environ
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Appendix B Contractor’s Proposals
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Appendix C Hydrogeological Assessme
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Memorandum Fairbairn House, Ashton
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Memorandum (Continued) Page 3 of 6
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Memorandum (Continued) Page 5 of 6
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Appendix D Volume Distribution for
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Floodplain compensation area - elev
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Depth Bands (m) TOTAL (m³) Area Re
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Chapter 9: Road drainage and the water environment

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