Waste deposit influences on groundwater quality as a tool for waste type and site selection for final storage quality

Abstract

Leachates from deposits of wastes may, in the long run, adversely influence groundwater quality. Since tipping still constitutes the most important form of waste disposal, strategies must be developed which are capable of protecting groundwater against contamination from leachates. In the first instance such protective measures must provide for a minimization of contamination by setting up optimal barriers. Since it would seem difficult to reach this goal in a forseeable future, the avoidance of substances with a high potential for groundwater hazards has to be attributed much importance.

In former times, little attention was given to impermeability or avoidance of substances with a high potential for groundwater hazards contained in wastes. Therefore, results of the investigation of groundwater near abandoned sites can be used to optimize groundwater protection on future tipping sites. In the present study, the results of chemical investigation of groundwater from the vicinity of 92 waste disposal sites in the Federal Republic of Germany are presented and the changes in groundwater quality owing to the penetration of leachates are discussed separately for inorganic and organic contaminants.

The level of the contamination factor may serve to estimate the potential of a substance to become mobilized from wastes. Also the detection frequency of substances in groundwater permits the recognition of this potential. Substances characterized by a high contamination factor and/or a high detection frequency are defined as main contaminants. A comparison with similar studies made in the USA shows a good coincidence of results and in particular a predominance of volatiles in groundwater.

The contamination factor and the detection frequency are closely related to mobility, persistence and accumulation potential of substances which can be described by their physico-chemical properties, and they describe the groundwater currency of a substance. The potential groundwater hazard is not known before an additional evaluation of the toxicity and hygienic relevance of the substance has been made. Substances involving a high potential groundwater hazard are defined as priority pollutants. In the future, priority should be given to reduce their presence in wastes to be disposed. According to present knowledge, this refers to arsenic, cadmium, lead, chromium and nickel from the number of inorganic substances, and to tetrachloroethene, trichloroethene, cis-1,2-dichloroethene, benzene, vinyl chloride, trichloromethane, 1,1,1-trichloroethane, xylenes, trans-1,2-dichloroethene, toluene, ethylbenzene, dichloromethane, dichlorobenzenes, chlorobenzene and tetrachloromethane from the organic ones.

Since, for a variety of reasons as e.g. heterogenity of material, control of tipping, it does not appear to be possible to avoid completely these substances in wastes, there should be an additional protection of groundwater by a suitable selection of future sites, taking into account present and future uses of the groundwater in this area, as well as by an optimal sealing of tips.