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constituent of a solid waste,expressed in milligrams SOLUBLE DESIGNATED LEVEL FOR per liter(mg/1)of WET extract,is equal to the water A CONSTITUENT OF A SOLID WASTE quality goal times the environmental attenuation factor divided by the ten-fold dilution of the test. [Due to DOMESTIC WATER UNLINED LANDFILL OR WASTE PILE differences in the test methods,a 20-fold dilution factor WELL is used in calculations based on TCLP results.] For the o oos X n mg soluble As/kg waste , ur Figure 7 example,the Soluble Designated Level for o oos,X n mg A5/ kter of extreot 10 i from the WET arsenic is equal to(0.005 x n=10)mg/l of WET extract. Concentrations of constituents in landfill leachate should not be con-fusedmg Arsenic with concentrations of constitu- (o.00s«n) ,per ofe ents in extract from the Waste Extraction Test or the leachate Toxicity Characteristic Leaching Procedure. They are not the same. Concentrations of constituents in leachate are the result of the accumulation of constitu- n — FOLD ents from the waste as moisture migrates through a ATTENUATION landfill or waste pile. The ratio of liquid-to-solids is not expected to be large within a landfill. Concentra- tions of constituents in the extract from the WET or the Water TCLP are the result of specific laboratory procedures - Table where waste constituents are extracted from a solid. waste by an extract solution under a large liquid-to- 0.005 mg Arsenic/liter of water GROUND g q (Proposition 65 regulatory level) �j ATE solids ratio necessary to ease sample handling. The FLOW extract from the WET or the TCLP is,therefore;not a simulation of leachate,but a means to measure the Figure 7 amounts of waste constituents that may be leached from the waste in a landfill. As stated above,actual landfill Therefore,The Designated Level Methodology can be used leachate is expected to have considerably higher pollut- to calculate Designated Levels for site contaminants ant concentrations than WET or TCLP extracts due which,if exceeded,indicate a threat to the beneficial mainly to this difference in liquid-to-solids ratio. uses of nearby ground or surface waters. California's CONTAMINATED SITE ASSESSMENT water quality standards(from the applicable Water Quality Control Plans)are used to select water quality DTSC has prepared guidance materials which con- goals which protect the beneficial uses of waters which tain procedures for performing risk assessments and could be adversely impacted by site contaminants. At- determining cleanup/mitigation levels for sites con- tenuation factors are estimated based upon site hydro- taminated with toxic substances. The object of these geologic data and information on the contaminants procedures is to prevent toxicologic impacts on hu- themselves. Soluble Designated Levels are then calcu- mans and other potential"biological receptors of con- lated by multiplying the water quality goals by the cern". While sufficient to cover DTSC's concerns attenuation factors and dividing by the ten-fold dilu- regarding site assessment and cleanup,the procedures tion of the WET or the 20-fold dilution of the TCLP(for in these documents are not designed to fully protect volatile contaminants). The results are expressed as water resources that may be adversely impacted by site milligrams of soluble constituent per liter of extract. contaminants,as required by the Porter-Cologne Water Soil samples from the site are subjected to the WET Quality Control Act. Therefore,another methodology and/or TCLP procedure and results are compared with must be used by the State and Regional Water Boards these site-and constituent-specific Soluble Designated to fulfill this need. Levels. Cleanup or mitigation would be required for Comparison of Figures 7 and 8 reveals that the soils having extractable concentrations which exceed threat posed to water quality by contaminated soils is Soluble Designated Levels. For this type of site assess- similar to that posed by wastes in an unlined landfill. ment,the WET procedure is often modified to account Central Valley Regional Water Quality Control Board Page 7