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Groundwater Protection in Selected Countries

4. Groundwater Protection

In the following sections, measures which are used in Denmark for the protection of groundwater are given. To improve the overview, these measures are divided into measures which can be utilised to prevent contamination from happening (prevention) and measures which are used to tackle existing contamination problems (remediation).

4.1 Prevention

4.1.1 Well field protection zones

A number of protection zones around individual supply wells or well fields have been set for a variety of types of contamination. These zones are not intended to be used with respect to prioritising the remediation of contaminated sites, but are listed below since they are related to point sources.

	A physical protection area with a 10 m radius around individual supply wells is described by the Environmental Protection Act (Miljøstyrelsen, 1988). Within this area, only supply related activities are permitted.
	A hygiene protective area with a radius of 300 m is described by the Environmental Protection Act. Within this area, discharge of wastewater via leach fields is not allowed. The size and shape of this area can be altered, depending on the local geological conditions.
	A code of practice (Normstyrelsen, 1988) lists recommended distances between water supply wells and various potential sources of contamination.

Detailed zoning

A more detailed zoning is currently under preparation. A guidance document specifying this detailed zoning is under preparation by the Danish EPA (Miljøstyrelsen, 1999).

In this draft guidance document, it is suggested that the hygiene protective area should be redefined as an area in which any form for pollution should be avoided, if possible.

4.1.2 Aquifer protection zones

Particularly valuable areas

According to the government’s 10- point plan from 1994, particularly valuable water abstraction areas must be designated. A later guidance document prepared by the Danish EPA (Miljøstyrelsen, 1998a) specifies that all groundwater in Denmark must be divided into 3 categories: particularly valuable areas, valuable areas, and abstraction areas of limited value. This designation was carried out by the regional authorities and was completed in 1997.

In order to designate these areas, assessments in the following areas were carried out:

	amount, quality and natural protection of the groundwater resource
	estimation of the future water supply needs
	point sources
	current water supply structure
	effect on surface water bodies
	potential land use conflicts

Finally, a political assessment was carried out and the particularly valuable water abstraction areas were designated. In the actual designation, the aim was to designate large cohesive areas such that significant portions of the regional demand could be covered and such that entire water sheds were included.

Detailed zoning

A more detailed zoning is currently under preparation. A guidance document specifying this detailed zoning is under preparation by the Danish EPA (Miljøstyrelsen, 1999).

In this draft guidance document it is suggested that 2 zones be designated on the basis of existing knowledge. These zones are:

	Sensitive Source Water Areas, which are especially sensitive to one or more types of contamination. Primarily, it is suggested to designate areas, which are sensitive to nitrate.
	Response-Demand Areas, in which it is necessary to actively respond to the threat of a contamination source.

Vulnerability

In addition, it is suggested that vulnerable zones are designated, but only after detailed mapping has been performed. The methods for detailed mapping and the procedure for the following designation of the vulnerable zones is outlined.

Presently, detailed mapping which leads to the designation of vulnerable zones has been implemented in very few areas. It is intended that detailed mapping should be performed within a period of 10 years.

4.1.3 Costs

The costs of detailed mapping is assessed to about DKK 54,000 pr. km². Including the designation of zones this amounts to a total of about DKK 92 mill. for mapping and zoning of all particularly valuable areas (Miljø- og Energiministeriet, 1998b).

The costs of making agreements to diminished agricultural impacts on groundwater is assessed to be about DKK 1,000 pr. ha. On this basis, it is assessed that the total yearly costs for diminishing the agricultural impacts will be about DKK 600 mill.

4.2 Remediation

4.2.1 Prioritising contaminated sites

When discussing the prioritisation of contaminated sites, it is important to define what type of prioritisation is meant. For example, contaminated sites can be prioritised according to various geographical scales such as a regional prioritisation or a national prioritisation. Point sources can also be prioritised for a specific phase of work. For example, one prioritisation could be for which sites are to be investigated first and another prioritisation could be for which sites are to remediated first.

In this section, prioritising means the determination of an order for remediation on a national scale.

As described earlier, there are currently 6 distinct programmes regarding remediation of contaminated sites in Denmark. The method of prioritising varies with these programmes. Each method is described briefly below.

Prioritising and remediation of contaminated sites under this act are responsibilities of the regional authorities. Therefore, a number of differences due occur. Guidelines, however, have been prepared by the national authorities.

In 1992, guidelines were prepared which identified threats to groundwater, land use and surface water recipients as the major problems which require remediation. Of these, groundwater and land use are to be treated as parallel in importance, while surface water recipients takes a secondary role (Miljøstyrelsen, 1992). As previously mentioned, guidelines on identifying particularly valuable water abstraction areas were made in 1995 (Miljøstyrelsen, 1995). Of the contaminated sites that threaten groundwater, these guidelines prioritise those that lie within the particularly valuable areas.

The most recent results show that 822 sites were remediated due to groundwater threats, 360 due to land use threats and 203 due to both.

A ranking system for prioritising contaminated sites within each risk group (groundwater, land use and surface water recipients) has been developed (Miljøstyrelsen, 1995). With respect to groundwater, the system takes the following into account: vulnerability, exposure, contaminant hazard, site specific conditions, and landfill gas risks. This system, however, does not have advisory or statutory status and is not in widespread use.

OM-programme

Sites within the competence of the OM-programme are prioritised nationally by a specially formed Environmental Council of the Association for Remediation of Retail Sites. Here, a ranking systems has been developed. Threat to groundwater and threat to land use are each scored on a point scale of 1, 2, 4, 7, 11. If the contaminated site lies in a particularly valuable area, 7 additional points are awarded. The sum of these 3 subjects is totalled to give the ranking. A maximum of 22 points is awarded. The tie is broken for all sites which are awarded 22 points by carrying them through a second step. The second step includes 3 subjects, each of which gives a score of 1 to 5 points. These subjects are: 1) distance to a supply well, 2) distance to a surface water recipient, and 3) probability of the site being contaminated.

The Defence Construction Service and The Railway Agency prepare action plans and clean-up plans respectively, which involve the prioritising of sites. In both cases, these plans are prepared with the co-operation of the regional authorities to ensure an overall co-ordination.

The Lost Value Act appropriates money on a first come, first served basis. In principle, newer contamination within the competence of the Environmental Protection Act must all be remediated, as the responsible party can be required to finance the clean-up. No system of prioritising is therefore required.

4.2.2 Criteria

Soil

In Denmark, so-called "soil quality criteria" have been set, for use at contaminated sites in which the soil contamination presents a threat to the intended land use through direct exposure (skin contact, ingestion of soil or breathing of dust). Here, the soil quality criteria have been set low enough to ensure that even very sensitive land-use (for example gardening and children’s play grounds) will not present a toxicological problem with regard to land use.

In addition to the soil quality criteria, a limited number of cut-off criteria, which refers to values which, when exceed, should result in remedial activities which cut off the exposure pathway. The reason for setting more than one soil criteria is that large areas in cities have soil concentrations which exceed the soil quality criteria due to diffuse contamination (such as lead contamination from traffic). Higher criteria are thought admissible if certain recommendations (such as avoiding growing vegetables, direct contact with bare soil, and dust) are followed (Miljøstyrelsen, 1998b).

According to the Danish EPA, however, these soil quality criteria and cut-off criteria are not intended to be used for assessing the risk for groundwater contamination since they are based on exposure in the case of very sensitive land-use. Leaching and mobility in relation to the groundwater resource are not built into the criteria.

Instead of using these soil criteria, the Danish EPA recommends applying a risk assessment that relates groundwater concentrations to soil concentrations. The Danish EPA has developed a 3-stage risk assessment, with each stage requiring additional data. A risk assessment is site specific and should include the following elements:

	results of site investigations
	assessment of the contaminants present
	assessment of contaminant transport and exposure pathways

A risk assessment can estimate whether existing soil concentrations present a threat to the groundwater. In this way, a risk assessment can be used to determine trigger/intervention values. In addition, these same values can be used as clean-up/target values for a remediation. In Danish terminology, these values are referred to as the "acceptable" level of contamination

The soil quality criteria and cut off criteria are included in Appendix 1 (Miljøstyrelsen, 1998a).

Groundwater

In Denmark, groundwater criteria have been established which ensure that groundwater can be used for drinking water after a traditional water treatment comprised of aeration and filtration. These criteria are therefore closely related to drinking water criteria.

The groundwater quality criteria are not to be exceeded in aquifers which may be exploited for water supply purposes nor in shallow aquifers (with only secondary importance with respect to water supply), if this may cause exploitable aquifers to exceed the quality criteria. In general, groundwater quality criteria must not be exceeded at the source of contamination. When carrying out a risk assessment, however, it may be exceed at a distance of up to one-year’s groundwater travel (though a maximum of 100 meters).

The multifunctionality of groundwater is considered to be maintained if the groundwater quality criteria are not exceeded. Appendix 2 lists these criteria (Miljøstyrelsen 1998a). It may be noted that no separate pore water criteria have been set.

Soil gas

As in the case of soil criteria, soil gas criteria which would ensure the protection of the groundwater resource would be practical. Soil gas criteria for this purpose, however, have not been set at the present time.

So-called "air quality criteria" have been set, however, for use at contaminated sites in which contaminated soil gas presents a threat to indoor air quality in buildings or outdoor air quality in open areas.

Even though these air quality criteria are not intended in theory for use in groundwater protection from point sources, the criteria have been included in Appendix 3 (Miljøstyrelsen, 1998a).

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