Chapter 9: Road drainage and the water environment

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Memorandum (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 Engineering U.K. Limited Jacobs_MemoA4.doc
Memorandum (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 Engineering U.K. Limited Jacobs_MemoA4.doc
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M1 Junction 19 Improvement Environm
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M1 JUNCTION 19 IMPROVEMENT ENVIRONM
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Appendix A - Pollution and Spillage
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Method D - Assessment of Pollution
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Groundwater: Hydrocarbons Hydrogeol
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Page 83 and 84: Non Technical Summary Skanska Const
Page 85 and 86: Contents 1 Introduction 1 1.1 Overv
Page 87 and 88: 1 Introduction 1.1 Overview Jacobs
Page 89 and 90: 2 Policy Review 2.1 Planning Contex
Page 91 and 92: When the both the ‘Flood Zone’
Page 93 and 94: 3 Flood Risk to the Proposed Develo
Page 95 and 96: 3.2 Fluvial Flooding - Ordinary Wat
Page 97 and 98: Major earthworks affecting surface
Page 99 and 100: 3.7 Flooding from Infrastructure Fa
Page 101 and 102: 3.9 Summary of Risks to Site Table
Page 103 and 104: 4 Impacts of the Proposed Developme
Page 105 and 106: 4.6 Summary of Flood Impacts from D
Page 107 and 108: 5 Proposed Mitigation Measures 5.1
Page 109 and 110: The extents of this problem are cur
Page 111 and 112: 5.7 Summary of Recommended Mitigati
Page 113 and 114: 6 Residual Risks The level of flood
Page 115 and 116: 7 PPS25 Sequential and Exception Te
Page 117 and 118: 8 Conclusion The M1 Junction 19 Imp
Page 119 and 120: Appendix A Existing Layout, Environ
Page 127 and 128: Appendix B Contractor’s Proposals
Page 129 and 130: Appendix C Hydrogeological Assessme
Page 131 and 132: Memorandum Fairbairn House, Ashton
Page 133: Memorandum (Continued) Page 3 of 6
Page 141 and 142: Appendix D Volume Distribution for
Page 143 and 144: Floodplain compensation area - elev
Page 145: Depth Bands (m) TOTAL (m³) Area Re
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Chapter 9: Road drainage and the water environment

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