material, e.g. a clay plug, to ensure that no preferential drainage pathways are created;


 A site investigation will be undertaken to determine the type of fill material, depth of fill, presence/condition of groundwater within landfill, presence of any lining system. The information obtained during site investigation will inform appropriate design of trenching to prevent creation of pollution pathways;


 Storage of oils and fuel within designated areas in impervious storage bunds with a minimum of 110% capacity to contain any leaks or spills;


 Oil, water and silt separators will be used where applicable on construction compound sites;


 Limit refuelling activities to designated, impermeably surfaced areas and use drip traps where possible;


 Check and maintain equipment regularly to ensure that leakages do not occur;  Have spill kits available on site at all times;  The process of HDD involves the use of bentonite (used as a lubricating agent and grout); in order to reduce the risk of pollution of surface waters and / or break out in the river bed the use of these materials should be carefully controlled; and


 In order to reduce the likelihood of pollution from bentonite and / or grout when working near rivers, hydrophobic (water repelling) grout and quick setting mixes should be used.


99.


Following implementation of the mitigation measures described above, the overall significance of the impacts to groundwater is considered to be minor.


21.6.1.4 Impact 4: Impacts to Surface Water 100. The construction activities listed in section 21.6 have the potential to affect surface water and watercourses in the following ways:


 Increase sediment loading;  Disturbance and transmission of contaminated sediments;  Change in water quality through spills and leaks;


 Flow and quality, therefore, impacting the licensed surface water abstraction points; and


 Changes in final bed level.


21.6.1.4.1 Landfall 101. There are no watercourses at the landfall and therefore there would be no impacts.


21.6.1.4.2Onshore cable route


Scenario 1: Pre-installed ducts 102. All watercourses would be crossed and ducted prior to cable installation under this scenario, therefore there would be no impact.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm


Chapter 21 Water Resource and Flood Risk Page 37


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