Chapter 9: Road drainage and the water environment

More documents

Recommendations

Info

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
Page 1:
M1 Junction 19 Improvement Environm
Page 4 and 5:
M1 JUNCTION 19 IMPROVEMENT ENVIRONM
Page 6 and 7:
Page 8 and 9:
Page 10 and 11:
Page 12 and 13:
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21:
Page 22 and 23:
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 30 and 31:
Page 32 and 33:
Page 34 and 35:
Page 36 and 37:
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 44 and 45: M1 JUNCTION 19 IMPROVEMENT ENVIRONM
Page 71 and 72: Appendix A - Pollution and Spillage
Page 73: Method D - Assessment of Pollution
Page 78 and 79: Groundwater: Hydrocarbons Hydrogeol
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: 3 Flood Risk to the Proposed Develo
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 and 134: Memorandum (Continued) Page 3 of 6
Page 135 and 136: Memorandum (Continued) Page 5 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
show all

Chapter 9: Road drainage and the water environment

Create successful ePaper yourself

Delete template?

Save as template?