Groundwater and Fluid Filled Cables

Transcription

1 Groundwater and Fluid Filled Cables Jenny Thomas Groundwater Quality Technical Specialist, Thames 8 th June 2010 EDF Energy EA Joint FFC Workshop, Bidder Street, London

2 Groundwater What is groundwater? Why is groundwater important? Risk from fluid-filled cables Legislation Groundwater Protection Policy

3 Groundwater any water below the water table in direct contact with the ground or subsoil - as defined in the Water Framework Directive forms part of the natural water cycle present in underground strata - aquifers - everywhere beneath our feet

4 World water distribution

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6 Importance of Groundwater provides a high proportion of water supply and the base flow in rivers aquifers store large volumes of high quality water, widely available at low cost, requiring limited treatment however, all too frequently: out-of-sight and out-of-mind polluted groundwater is difficult, if not impossible to rehabilitate

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8 Groundwater is valuable Strategic significance Licensed groundwater abstractions 4.5 billion m 3 per year Cost of abstraction replacement estimated at 1 million per m 3 but only where there is spare resource available Therefore groundwater protection and pollution prevention is crucial

9 Status of groundwater resources

10 Conceptual Migration and Partitioning of oil from a Leaking cable Housing Water Supply Borehole Cable Water Table Floating Product Groundwater Flow Dissolved Contaminant Plume Bedrock

11 Pollution direct or indirect introduction which may be harmful to human health or the quality of aquatic ecosystems or terrestrial ecosystems directly depending on aquatic ecosystems

12 Remediation and Risk Assessment - carry out in parallel, where possible Ex-situ treatment Excavation of soil Pumping of groundwater In-situ treatment Estimate loss Assess local geological conditions Soil sampling Groundwater sampling purpose-drilled boreholes normally SPEED IS IMPORTANT!

13 LEGISLATION - The Environmental Permitting Regs (E&W) 2010 Incorporates Gw Regs and WRA 1991 Section12(1) A person must not: (b) cause or knowingly permit a water discharge activity or groundwater activity Section 38(1) It is an offence to contravene regulation 12(1)

14 Groundwater Activity - discharge that might lead to the direct or indirect input of a pollutant to groundwater EA may determine it is not a groundwater activity if the input of the pollutant is: the consequence of an accident or exceptional circumstances of natural cause that could not reasonably have been foreseen, avoided or mitigated; of a quantity and concentration so small as to obviate any present or future danger of deterioration in the quality of the receiving groundwater; or incapable, for technical reasons, of being prevented or limited without using measures that would increase risks to health or environment EA must keep a record of all determinations

15 LEGISLATION - The Environmental Permitting Regs (E&W) 2010 Schedule 22 Groundwater activities Hazardous substance toxic, persistent and liable to bio-accumulate includes mineral oils, hydrocarbons, certain solvents and pesticides etc Non-hazardous pollutant any other pollutant generally harmful, may degrade or attenuate are tolerable below certain concentrations

16 after the event - does not prevent pollution but. Environment Act 1995 Amendment of Section 161 of the Water Resources Act 1991 Agency can require works to be done to control actual or potential pollution through Works Notices (WN)

17 Groundwater Protection: Policy and Practice -GP3 Part 1 - Overview Part 2 - framework for groundwater information and policy Part 3 - targeted modules for decision makers, technical, developers, industry, planners, consultants and companies Part 4 - policy statements and legislation Part 1 Overview Our overall position at the Environment Agency on the management and protection of groundwater. An overview that identifies our goals. Part 2 Technical Framework A basic introduction to groundwater and its place in the water cycle. Key principles and concepts. Description of the threats from human activities. Part 3 - Tools A brief overview of the use and application of each tool and where to obtain it. Introduction to the tools available for analysing and assessing the risks to groundwater. Currently being revised/updated Part 4 Legislation and policy Key groundwater legislation and how we interpret it. Policies on activities that pose a risk to groundwater and how we plan to deal with them.

18 GP3 Policies reflected in operating code P1-3 We expect developers and operators to assess the area of influence of their activities and to take account of the uses of groundwater during planning and operation P1-6 If necessary we will use our powers to serve notices to prevent or limit unacceptable releases to groundwater P2-1 We will use SPZs as initial screening tools to show areas where we would object in principle to certain activities, and areas where additional controls or restrictions on activities may be needed to protect water abstracted for human consumption. P9-1 We require those who cause new contamination to quickly and effectively remediate the effects to ensure groundwater quality is protected and where necessary, restored.

19 WFD reclassification of aquifers Based on geology Major Minor Non Non Principal Secondary Secondary - if capable of supporting abstractions of 10m 3 /d Unproductive strata

20 Groundwater Vulnerability

21 Fissured aquifer - Chalk

22 Source Protection Zones - What are they? CatchmentBoundary Source Protection Zones around a borehole used for human consumption 1 Inner Zone (50 day) 2 Outer Zone (400 day) 3 Total Catchment Direction of groundwater flow

23 Groundwater risk map Principal aquifers Key Principal aquifers Secondary and unproductive aquifers Source Protection Zones 1 and 2 Source Protection Zones 3 and 4 Secondary aquifers and unproductive strata Source Protection Zones (SPZ)

24 QUESTIONS? The most common occurrences of groundwater at the surface are at springs or through the sinking of wells or boreholes. However, outflow (discharge) from aquifers also helps to maintain baseflow in rivers and conserve important habitats like wetlands. A reduction in either the quantity or the quality of contributing groundwater can significantly influence surface water and associated ecosystems. Groundwater is also used to augment the flow of rivers during prolonged dry periods. This is important to rivers that are used as a source for local water supplies or that support important habitats.