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be equal to"n". The Designated Level for arsenic in differences in the test methods,a 20-fold dilution factor leachate at this site would be equal to(0.005 x n) is used in calculations based on TCLP results.] For the milligrams arsenic per liter of leachate. Figure 7 example,the Soluble Designated Level for arsenic is equal to(0.005 x n + 10)mg/1 of WET The goal in calculating Designated Levels for a solid extract. waste is to determine concentrations of soluble con- stituents in the waste above which leachate may carry Concentrations of constituents in landfill leachate them to ground or surface waters in amounts that should not be confused with concentrations of constitu- could cause water quality goals to be exceeded. There- ents in extract from the Waste Extraction Test or the fore, the next step in the methodology is to convert the Toxicity Characteristic Leaching Procedure. They are Designated Level for leachate into one which may be not the same. Concentrations of constituents in applied to leachable concentrations of constituents in a leachate are the result of the accumulation of constitu- solid waste prior to disposal. Rationale presented by ents from the waste as moisture migrates through a DTSC in the 1984 Statement of Reasons for the Hazardous landfill or waste pile. The ratio of liquid-to-solids is Waste Identification Regulations indicates that the not expected to be large within a landfill. Concentra- concentrations of constituents in leachate could either tions of constituents in the extract from the WET or the be numerically higher or lower than the soluble TCLP are the result of specific laboratory procedures constituent concentrations in the solid waste prior to where waste constituents are extracted from a solid leaching. In the calculation of Designated Levels, these waste by an extract solution under a large liquid-to- concentrations are assumed to be numerically equal,as solids ratio necessary to ease sample handling. The in DTSC's Statement of Reasons. Therefore, the Soluble extract from the WET or the TCLP is, therefore,not a Designated Level for a constituent in a solid waste is simulation of leachate,but a means to measure the numerically the same as the Designated Level for the amounts of waste constituents that may be leached from same constituent in leachate which forms at the base of the waste in a landfill. As stated above,actual landfill the landfill—the water quality goal times the environ- leachate is expected to have considerably higher mental attenuation factor. In the example of Figure 7, pollutant concentrations than WET or TCLP extracts the Soluble Designated Level for arsenic in the solid due mainly to this difference in liquid-to-solids ratio. waste is(0.005 x n)milligrams of soluble arsenic per kilogram of waste. CONTAMINATED SrrE AssEssmurr Soluble concentrations of constituents in solid wastes are determined by performing the Waste Extraction DTSC has prepared guidance materials which contain Test(WET)from Title 22 of CCR,Division 45,Chapter procedures for performing risk assessments and 11,Appendix II,or a variation of this test. (The Toxic- determining cleanup/mitigation levels for sites con- itv Characteristic Leaching Procedure(TCLP) from taminated with toxic substances. The object of these Title 22 of CCR,Division 45,Chapter 18,Appendix 1,is procedures is to prevent toxicologic impacts on hu- used for volatile waste constituents.] The WET in- trans and other potential'biological receptors of volves a ten-fold dilution of solid waste into an extract concern". While sufficient to cover DTSC's concerns solution,agitation for 48 hours,followed by filtration regarding site assessment and cleanup,the procedures and analysis of the liquid phase. Results are expressed in these documents are not designed to fully protect in milligrams of extractable constituent per liter of water resources that may be adversely impacted by site extract solution. Therefore,the WET extract is ex- contaminants,as required by the Porter-Cologne Water pected to be ten-times more dilute than actual landfill Quality Control Act. Therefore,another methodology leachate. The Soluble Designated Level for a constitu- must be used by the State and Regional Water Boards ent of a solid waste,expressed in milligrams per liter to fulfill this need. (mg/1)of WET extract,is equal to the water quality goal times the environmental attenuation factor Comparison of Figures 7 and 8 reveals that the threat divided by the ten-fold dilution of the test. [Due to posed to water quality by contaminated soils is similar Page 14 California's Water Quality Standards