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THE DESIGNATED LEVEL METHODOLOGY FOR WASTE CLASSIFICATION AND CLEANUP LEVEL DETERMINATION EXECUTIVE SU NEVL RY Improper waste disposal practices and sites which have been contaminated with toxic substances pose significant threats to the quality of California's useable ground and surface water resources This report shows,from a water quality perspective, l) how to classify various wastes so that appropriate disposal practices may be selected, and 2)how to determine the degree to which a contaminated site should be cleaned or to which remedial action is necessary ("how clean is clean"),and 3)how these two decision-making processes are related. ' In California, the classification of wastes and the establishment of cleanup levels for sites t which have been contaminated with toxic chemicals are performed by two separate State agencies with separate regulatory authority. The Department of Health Services (DHS) classifies wastes as 'hazardous' or 'restricted hazardous' and sets site cleanup/mitigation criteria based on a direct threat of these wastes or sites to public health. The State Water Resources Control Board together with the nine Regional Water Quality Control Boards VA classify wastes as 'designated', 'nonhazardous solid' or 'inert' and determine cleanup levels based on the threat that wastes and contaminated sites pose to the beneficial uses of waters of the State,as required by the Porter-Cologne Water Quality Control Act (contained in Division 7 of the California Water Code). Regulations administered by these agencies clearly state,using detailed criteria,how wastes are to be classified with the exception of the'designated waste' category. The Iower {boundary of this category is described only as the limit above which a waste could impair watenquality=at-the site of discharge.This-boundary can be more clearly defined=by -= — establishing "Designated Levels" for specific constituents of a waste which provide a site- T^ specific indication of the water quality impairment potential of the waste. This report provides a methodology for calculating such levels. Designated Levels are calculated by t -first determining the bodies of water that may be affected by a waste and the present and probable future beneficial uses of these waters. Next, site-specific "water quality goals" are selected, based on background water quality or accepted criteria and standards,to protect those beneficial uses. Finally, these water quality goals are multiplied by factors which account for environmental attenuation and leachability. The result is a set of Soluble and_ Total Designated Levels which are applicable to a particular waste and disposal site and _ which, if not exceeded, should protect the beneficial uses of waters of the State. Wastes having constituent concentrations in excess of these Designated Levels are assumed to pose a threat to water quality and are, therefore, classified as-designated wastes' and directed to waste management units which isolate these wastes from the environment. In 1986, DHS released a document entitled The California Site Mih ahon Decision Tree Manual'which presents a detailed methodology for determining cleanup/mitigation levels for sites contaminated with toxic substances. The object of this methodology is to r r Designated Level Methodology Page 3