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Now LM ° ENVIRONMENTAL HEALTH DEPARTMENT ppU.�N SAN JOAQUIN COUNTY Unit Supervisors 1+ ? — Carl Borgman,R.E.H.S. Donna K.Reran,R.E.H.S. 304 East Weber Avenue, Third Floor Director Mike Huggins,R.E.H.S.,R.D.I. �: ... Al Olsen,R.E.H.S. Stockton, California 95202-270 Douglas W.Wilson,R.E.H-s. ti,., P• Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E-H.S. • cit;F-eo Laurie A.Cotulla,R.E.H.S. Fax. (209) 464-0138 Robert McCiellon,R.E.H.S. Program Manager Mark Sareellos,R.E.H.S. ,., APR 6 2003 WILLIAM BERGVALL 2977 YGNACIO VALLEY RD WALNUT CREEK CA 94598 ►• RE: FORMER AMERICAN FOREST PRODUCT 2801 WEST LANE STOCKTON CA San Joaquin County Environmental Health Department (EHD) has reviewed Closurr Request Addendum Report, 1, 2-DCA Investigation (the report) dated July 22,2002 prepared by URS Group,Inc. (URS). Five direct-push strataprobes were advanced at the site and six grab groundwater samples were collected in May 2002. Analytical results of the grab groundwater sample from soil boring HP-1 were 170 micrograms per liter (µg/1) 1,2- �" dicholorethane (1,2-DCA) at 50 feet below surface grade (bsg), 130 µg/l 1,2-DCA at 65 feet below surface grade (bsg); 4.0 µg/11,2-DCA-from HP-2 at 52 feet bsg, 2.3 pg/1 tetrachloroethene (PCE) from HP-6 at 50 feet bsg, 4.9 pg/l PCE from HP-7 at 50 feet bsg, and 4.4 µg/l PCE from HP-8 at 52 feet bsg. The report included a recommendation for site closure. During a telephone conversation on March 27,2003,Central Valley Region Water Quality Control Board (CVRWQCB) and EHD concurred that the closure request should be denied Lo at this time. The vertical and horizontal extent of the 1,2-DCA in groundwater has not been fully delineated. California Department of Health Services (DHS) has established a Maximum Contaminant Level (MCL) for 1,2-DCA in drinking water at 0.5 µg/l. The rV concentration of 1,2-DCA in the current grab water samples as well as in the previous quarterly monitoring well samples exceeded the MCL. Additional investigation is needed to delineate the lateral and vertical extent of 1,2-DCA. L Historical groundwater Iow in the area has been 80 feet bsg according to San Joaquin County Flood Control and Water Conservation District publication Lines of Equal Depth to L Groundwater for 1993. DMW-2 was screened from 60 feet to 80 feet bsg. Analytical results of DMW-2 samples were 9.7 µg/11,2-DCA in August 2000, 5.5 pg/I in November 2000, and 1.4 lig/l in December 2001. Minimum sampling depth to address the vertical delineation of the 1,2-DCA contamination at this site has been 80 feet bsg. EHD had previously approved Work Plan_for 1,2-DCA Investigation dated April 2, 2002 prepared by URS } on the condition that CPT hydro-punch technology be used to collect grab groundwater IL. ' f k..