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i . • <br /> r, California Regional Water Quality Control Board " �1 <br /> Central Valley Region <br /> Robert Schneider,Chair Gray Davis <br /> Governor <br /> Winston H.Hickox Sacramento Main Office <br /> secretaryfor D <br /> Environmental intemet Address: http://www.swrcb.ca.gov/rwgcb5 (((I���r'''I�,, <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 `��� �� , <br /> Phone(916)255-3000•FAX(916)255-3015 JAN 2 5 2002 <br /> ENP RMI�T/SERVICES HEALTHENT <br /> 24 January 2002 <br /> Mr. W.T.Nickerson <br /> UNOCAL Asset Management Group <br /> 8788 Elk Grove Blvd,Bldg 3, Suite 15 <br /> Elk Grove, CA 95624 <br /> DESIGNATED LEVELS FOR SOIL CONSTITUENTS, WESTERN FARM <br /> SERVICE, STOCKTON, SAN JOAQUIN COUNTY <br /> UNOCAL is preparing a feasibility study for the Western Fane Service site at 1905 North <br /> Broadway Avenue in Stockton. On 19 December 2001,your consultant,Mr. Eric Chase <br /> of Sierra-Pacific Group, telephoned to advise me that you had not yet received designated <br /> levels from our office that define soil cleanup goals that are protective of groundwater <br /> quality. Cleanup levels that are protective of human health are presently under evaluation <br /> with the Office of Environmental Health Hazard Assessment. <br /> In response to Mr. Chase's inquiry,the enclosed Table 1 identifies the Water Quality <br /> Goal and the corresponding designated levels for soil at the Broadway site. Designated <br /> levels are developed from the water quality goal which is multiplied by an Attenuation <br /> Factor and a Leachibility Factor to obtain the designated level. Attenuation Factors <br /> incorporate environmental influences that provide capacity for the soil to retain <br /> constituents. These include depth to groundwater, soil type, climate, compound <br /> characteristics and uncertainty. The Leachibility Factors account for the fraction of the <br /> compound that is mobile and available to migrate. These procedures are described in <br /> California Regional Water Quality Control Board, Central Valley Region's October 1986 <br /> (Updated June 1989)Designated Level Methodology for Waste Classification and <br /> Cleanup Level Determination,which is available on our website at <br /> www.swreb.ca.gov/rwqcb5. <br /> The Leachibility Factors are conservative estimates since leachibility data for these <br /> constituents are not yet available. If UNOCAL wishes to perform at least four waste <br /> extraction tests using de-ionized water as the extractant(DI-WET)with on-site soils, <br /> more accurate leachibility factors could be developed. <br /> California Environmental Protection Agency <br /> pa Recycled Paper <br /> The energy challenge facing California is real. Every Califomian needs to take immediate action to reduce energy consumption. For <br /> a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.sy r b.ca.gov/mgcb5 <br />