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Groundwater Protection in Selected Countries

4. Groundwater Protection

4.1 General strategy

The GPP document

The Environment Agency has published the document "Policy and Practice for The Protection of Groundwater" (GPP) which is composed of 3 key elements:

1. a series of statement on policy with respect to protection of groundwater
2. a classification of groundwater vulnerability to assist in the protection of aquifers as a whole
3. the delineation of groundwater protection zones in connection with specific major water supplies.

The GPP is perhaps the single most important tool used in England for the protection of groundwater from point source contamination. It is, however, non-statutory in nature and is therefore used only in a consultative manner. The Environment Agency makes use of the GPP in carrying out its own areas of statutory authorisation as well as in attempting to influence decisions of other regulatory bodies as well as parties with interest in or influence on groundwater.

Statutory information

In addition to this non-statutory tool, groundwater protection is effected through the following Acts and Regulations:

	EC Directive on the Protection of Groundwater Against Certain Dangerous Substances (80/68/EEC)
	Environmental Protection Act 1990
	Town and Country Planning Act 1990
	Water Resources Act 1991
	Water Industry Act 1991
	Environment Act 1995
	Groundwater Regulations 1998

Control is also exerted through the planning development process enacted by the Town and Country Planning Acts. In the following sections, the key elements in the GPP will be described.

4.2 Policy statements

Objectives

The GPP sets out a number of policy objectives of the Agency (Environment Agency, 1998). These objectives are divided into 8 groups as follows:

	control of groundwater abstractions
	physical disturbance of aquifers and groundwater flow
	waste disposal to land
	land contamination
	disposal of liquid effluent, sludges and slurries to land
	discharges to underground strata
	diffuse pollution of groundwater
	additional activities or developments which pose a threat to groundwater quality

Policy statements

Of special interest to this report are the policy statements with respect to waste disposal to land (9 policy statements) and land contamination (8 policy statements). Examples of policy statements with respect to these two groups are:

"The Environment Agency will liaise with Planning Authorities and others to entourage the location of new landfill sites in areas where groundwater is least vulnerable to pollution."

"The Environment Agency will encourage the implementation of effective remedial measures to prevent pollution of groundwater by existing direct or indirect discharges from any contaminated site. Where pollution occurs the Agency will prosecute in appropriate cases under Section 85 of the Water Resources Act 1991."

4.3 Vulnerability maps

In connection with implementation of the GPP, groundwater vulnerability maps on a scale of 1:100,000 have been prepared for the whole of England and Wales (National Rivers Authority, 1995a). The purpose of these maps is to aid developers planning new activities and planners assessing new proposals to make more informed judgements. The maps also have a use in the prioritising of investigations and subsequent remedial actions in locations where contamination has occurred. In this way, the vulnerability maps relate to the protection of the groundwater resource as a whole.

The maps have been prepared by the Soil Survey and Land Research Centre and the British Geological Survey and are overlayed on regular Ordnance Survey maps. They are based on the two major parameters, geological classification and soil classification.

Geological classification

The geological classification defines 3 categories as follows and refers to the unsaturated zone between the soil and the water table where leaching of contaminants to the groundwater may occur:

Major aquifer: Formations with a high primary permeability and a known or probable presence of significant fracturing. These formations may be able to support large water abstractions.

Minor aquifer: Formations which are fractured or potentially fractured but which do not have a high primary permeability. These formations are important for local water abstractions and supplying base flow to rivers.

Non-aquifer: Formations which are generally regarded as containing insignificant quantities of groundwater.

Leaching potential

Each of the 700 soil series (types) which have been established in England have been assigned a leaching potential based on texture, structure, soil water regime and the presence of distinctive layers such as raw peaty topsoil and rock or gravel at shallow depth. The soil classification subdivides areas with major and minor aquifers into 3 categories as follows. Areas designated as non-aquifers are not subdivided.

High leaching potential: Soils with little ability to attenuate diffuse source pollutants and in which non-adsorbed diffuse source pollutants and liquid discharges have the potential to move rapidly to underlying strata or to shallow groundwater.

Intermediate leaching potential: Soils which have a moderate ability to attenuate diffuse source pollutants or in which it is possible that some non-adsorbed diffuse source pollutants and liquid discharges could penetrate the soil layer.

Low leaching potential: Soils in which pollutants are unlikely to penetrate the soil layer because either water movement is largely horizontal, or they have the ability to attenuate diffuse pollutants.

Mapping practices

These two major parameters result in 7 different categories, each of which has been assigned a separate colour. The 3 soil leaching potential categories described above are further subdivided into subclasses (3 for high leaching potential, 2 for intermediate, and no subclasses for low leaching potential). These subclasses are denoted on the maps by means of closed curves with encircle the subclass number.

The final piece of information on the maps is the presence or absence of low permeability drift deposits (unconsolidated superficial deposits such as fluvioglacial and alluvium) overlying major and minor aquifers. These deposits are denoted on the maps by means of a stipple ornament.

4.4 Groundwater protection zones

In order to allow a sensible balance to be struck between the protection of the groundwater resource as a whole and the protection of specific water supplies, an additional tool of groundwater source protection zones has also been prepared (National Rivers Authority, 1995b). The primary use of these zones is to signal that within specified areas there are likely to be particular risks to groundwater quality should certain land use activities take place. Delineating these zones can therefore influence land use practices and prioritise investigations according to the greatest risk.

It is estimated that protection zones will be necessary for over 2,000 water supplies, where as it will not be practicable or efficient to define zones around 76,000 smaller sources due to lack of data.

3 concentric zones

The Environment Agency has adopted a tripartite zonation in which 3 generally concentric zones are defined. These zones are described below.

Inner Zone I is related to the decay of bacterial contamination. It includes the area immediately around the wellhead which is subject to especially strict controls. It is defined by a 50 day travel time, though minimum 50 meters from the source. This zone is usually not defined for confined aquifers.

Outer Zone II is based on the delay, dilution and attenuation of slowly degrading pollutants. It includes the area around the wellhead which is within a 400 day travel time (or 25% of the source catchment area, whichever is larger). This zone is usually not defined for confined aquifers.

Source Catchment Zone III is simply defined as the area needed to support a certain yield with long-term groundwater recharge. For confined aquifers, this zone may be located some distance from the actual abstraction.

Zone delineation

Delineation of the zones can be carried out using a variety of techniques depending on the quality of data available, the operational importance of the source concerned and the human and financial resources available. The simplest technique is to define circular protection zones based on the recharge area required to support the abstraction. Where data is available, mathematical models have been used including a semi-analytical model WHPA, a 2D steady-state numerical flow model FLOWPATH and the well-known MODFLOW/MODPATH. In the case of Karstic aquifers, the assumption of regional darcian flow is unlikely to be valid and computer simulation of groundwater flow based on standard models is inappropriate.

4.5 Criteria

No Criteria

In England, no "trigger or target values" for soil, groundwater or soil gas have been established because of the need to take a site-specific approach.

ConSim software

The intention is to use the newly developed software "Contamination Impact on Groundwater: Simulation by Monte Carlo Method" (ConSim), which has been developed on behalf of the Environment Agency and will be sold commercially, starting in 1999. Issues which may be addressed using ConSim include the following (ConSim Manual, 1999).:

	to help assess the plausibility of a significant pollutant linkage existing for a site with respect to its potential to cause pollution of controlled waters
	to assess whether or not the collection of additional site investigation data is required in order to quantify the risk to groundwater posed by the land contamination
	to determine the extent of remediation that is required in order to reduce the risk of contamination of controlled waters to an acceptable level
	to compare the viability of various remedial techniques to successfully reduce the risk of pollution to controlled waters.

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