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Chapter 3 THE DESIGNATED LEVEL METHODOLOGY Existing California regulations dearly define how wastes are to be classified; and detailed guidance is provided for the implementing agencies to set all but one of the boundaries between the five major waste classes (see Figure 1) The one significant boundary not clearly delineated is the lower end of the 'designated waste' classification. Wastes above this boundary— 'designated wastes' and 'hazardous wastes'—have the potential to significantly degrade water quality and must be discharged to waste management units (Class H and Class I) which isolate them from the surrounding environment(see Figure 2). Wastes below this boundary— 'nonhazardous solid wastes'and 'inert wastes' may be discharged to units (Class III and unclassified) that do not provide this isolation. Thus, failure to classify a waste as 'designated'or 'hazardous' permits its discharge to waste management units that have little or no natural or engineered controls to prevent the release of waste constituents to the environment(most Class III and unclassified units are not required to have liners nor leachate collection and removal systems). How are the regulatory agencies and the regulated community to determine whether a waste discharged to one of these waste management units poses a threat to beneficial uses of water? The following discussion presents a methodology which may be used to determine whether a waste has the potential to degrade water quality if discharged to a waste management unit that provides less than Class II containment The methodology defines the lower boundary of the 'designated waste' classification (as well as the criteria which may be used to grant §2520(x)(1)variances under Subchapter 15)by establishing "Designated Levels" (see Figure 1). These levels are concentrations of waste constituents above which a waste is presumed to pose a threat to water quality at the site being considered. Designated Levels are derived from numerical "water quality goals",limits or levels of water quality constituents which are established to protect the beneficial uses of water. Wastes whose constituent concentrations exceed the sif& p dffic Designated Levels T should be classified as`designated wastes' with-respect_to that site, and-the site should-be-required to provide Class H containment under Subchapter 15. r IThe Designated bevel Methodology is adapted from a procedure used by DHS to calculate`hazardous' STLCs and MCs from dnnlung water standards,which is presented in the document"Final Statement of Reasons for Proposed Regulations,'Criteria for Identification of Hazardous and Extremely Hazardous Wastes"'in Title 22(CAM SOR),adopted by DHS in February 1984.31 t 3.1 Determining Available Concentrations of Waste Constituents ' In order to determine the threat posed to water quality by a particular waste it is first necessary to ascertain the quantity of each constituent of concern in the waste that is available to migrate to waters of the State. 3.1.1 Liquid Wastes The quantity of chemical constituents that is available to migrate from liquid wastes is . dependent on the expected migration route. Only the dissolved concentrations of waste Designated Level Methodology Page 19