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i ENVIRONMENTAL HEALTH DEPARTMENT ` SAN.JOAQUIN COUNTY �; Donna K:Reran,RIK H.S. Unit Supervisors l .Df rector 304 East Weber Avenue, Third Floor Carl Bergman,R.E.H.S. • _ ,v Olsen,R:E.H.S. Stockton, California '95202-2708 Mike Huggins,R.E.H.S.,R.D.I. Program Manager Douglas W.Wilson,R.E.H.S. N 4f F o¢ Laurie A..�,Cotulla,RE.HTelephone: (209)468-3420 � .S. garet I,agorio,R.E.H.S. Program Manager Pari (209)464' 38 Robeit McClellon,R.E.H.S. {� Mark Barcellos,RX-H.S. WILLIAM BLRGVALL MAY O 5 205 2977 YGNACZO' VALLEY RD WALNUT CREEK CA ` 94598 3 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 Monitoring Report dated March 3, 2005, and Additional 1,2- DCA Investigation and Site Conceptual Model and Second�uarter 2004 GroundwaterMonitoring Report dated Februaty,18,.2005 (the reports)prepared by your consultant,URS Corporation Americas (URS) for the above-referenced sate: Four quarterly samplings have.been conducted to investigate the site since the installation of the two monitoring wells DMW-8 r and DMW-9 in March 2004. 1,2-Dichloroethane (1,2-DCA) has been consistently detected in the groundarater samples of DMW-5,DMW-6, and DMW-9,which is rhe furthest down- gradient (north`,northeast) monitoring weRat the site. With the exception of Se tembe.r P P. 2004, 1,2-DCA"has not been detected in'the deepest monitoring well DMW-8 screened at 80 •r feet below sui ice 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 alt 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#low. 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 'EHD is not actively looking for any chemicals that conclusion UAS presented at this time. '. 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 requiting 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.