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ENVIRONMENTAL HEALTH DEPARTMENT SAN JOAQUIN COUNTY iUntt Supervisors � Donna K Henan,R.E H S K Director 304 East Weber Avenue, Third Floor Carl Borgman,R E H S z Al Olsen,R E H S Stockton, California 95202-2708 Mike Huggms,R E H S,R D I Douglas W Wilson,R E H S one o ��P Program Manager Telephone 209 468-3420 Laurie A.Cotulla,RE H S P { ) Margaret Lagorio,R E H S Program Manager Fax (209) 464-0138 Robert McClellon,R E H S Mark Barcellos,R E H S WILLIAM BERGVALL MAY 0 5 2005 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 the Third and Fourth quarter 2004 Groundwater Monitonng Report dated March 3, 2005, and Ad�tional 1,2- DC-4 Invertzgation and Sate Conceptual Model and SecondQmarter 2004 GroundwaterMomtonng Deport dated February 18, 2005 (the reports) prepared by your consultant, URS Corporation Americas (URS) for the above-referenced site Four quarterly samplings have been conducted to investigate the site since the installation of the two monitoring wells DMW-8 and DMW-9 in March 2004 1,2-Dichloroethane (1,2-DCA) has been consistently detected in the groundwater samples of DMW-5,DMW-6, and DMW-9,which is the furthest down- gradient (north-northeast) monitoring well at the site With the exception of September 2004, 1,2-DCA has not been detected in the deepest monitoring well DMW-8 screened at 80 feet below surface grade (bsg) Tetrachloroethene (PCE) has also been detected in DMW-9, but has not been detected in any other wells Total petroleum hydrocarbons as diesel (TPH- d) has decreased to non-detect level in all wells EHD does not agree with URS'request for site closure The lateral extent of 1,2-DCA contamination plume has not been defined, especially in the down-gradient direction of the groundwater flow Additional investigation of the groundwater contamination plume is required Submit a work plan to EHD that will define the extent of the groundwater contamination plume by June 15,2005 URS has concluded that because PCE has been found only in DMW-9 groundwater samples, the origin of the PCE release may not be on-site EHD has no comment on the conclusion URS presented at flus time EHD is not actively looking for any chemicals that can not be traced to underground storage tanks (UST) as the source of release In a telephone conversation on May 3, 2005,California Regional Water Quality Control Board (RWQCB) concurred with EHD that PCE should continue to be reported only to fulfill the "report all peaks" of the 8260B analyses requirement EHD is not requiring further investigation of the PCE found in DMW-9 samples at this time, but PCE and other peaks in 8260B analyses should continue to be reported