from landfills or other potentially contaminated land to become connected to watercourses the impact is considered of high magnitude.
107. All surface water abstraction points along the line of the onshore electrical transmission works are for spray irrigation and therefore considered to be of low sensitivity. Of the eight registered abstractions, six lie within the footprint of the onshore electrical transmission works and are likely to be affected by the works, the remaining two lie either upstream of the works or relate to abstraction from a spring and will not be affected. Impact on the flow and quality of the abstraction is probable during the period of diversion and reinstatement of flow, however, over pumping will be undertaken to ensure that the flow downstream is not significantly changed in addition to preventing flooding upstream of the trenching. The works will be temporary and are considered to be of low magnitude.
108. In accordance with the embedded mitigation the storage of potentially contaminative materials would be away from the edge of any watercourses and compliant with Environment Agency Pollution Prevention Guidance series and the Outline CoCP (refer to section 21.3.3 for further details). The use of machinery and cement based products, such as concrete and grout which are highly alkaline, should be monitored and maintained to reduce the risk of spillage within the dammed watercourse. The impact from spills and leaks is considered to be temporary and of low magnitude.
109. The placement of the cable and its surround will be placed at a suitable depth beneath the active bed of the watercourses to ensure no long term impact on water flow or erosion. The magnitude of the impact of the cable placement is negligible.
110. In general it is considered that works would result in a temporary low magnitude impact on the watercourses with aminor adverse significance. Where potentially contaminative sites or landfills will be crossed the magnitude of effect is high and so the significance is considered to bemoderate or major adverse. Additional mitigation to reduce the impact significance is described below in Table 21.15.
Table 21.15Mitigation measures for impact to surface water Scenario 2 Mitigation measures
In order to reduce the impacts to surface water quality from the creation of permanent contamination pathways along the cables, ducting and granular surround, the following activities should be undertaken: The use of pollution control measures will be adopted (as outlined in PPGs and the Outline CoCP for East Anglia ONE) to reduce sediment run-off entering any watercourses or surface water drains;
Periods of low flow will be chosen to carry out construction works wherever practicable. This will result in a quicker deposition from the water column of any sediment released;
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 21 Water Resource and Flood Risk Page 39
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58