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'.d CONDOR EARTH TECHNOLOGIES INC t 188 Frank West Circle Suite I Stockton CA 95206 Phone 209.234.0518 3 0 2043 FAX 209.234.0538 CONDOR MAI www.condorearth.com ENVaRoR pumlISERVICES May 9,2003 Ms. Donna Heran San Joaquin County Environmental Health Department 304 E. Weber Avenue, 3'd Floor Stockton, CA 95202 Re: Work Plan for Groundwater Monitor Well Sampling and Groundwater Investigation, Pilkington North America,500 East Louise,Lathrop,San Joaquin County,California Condor Project No.3151J Dear Ms.Heran: Condor Earth Technologies, Inc. (Condor) is submitting this work plan in response to your April 11, 2003 letter to Mr. Mike Bowles, formerly with Pilkington North America (PNA), regarding the above- referenced facility (Figure 1, attached). Your letter requested the submittal of this work plan by June 1, 2003 to describe monitor well sampling at the site associated with the 1986 and 1987 underground storage tank (UST) removals (Figure 2, attached) and groundwater investigation at the site associated with the 1997 UST removal (Figure 3, attached). This work plan includes project background information and a description of proposed field and analytical methods for conducting the required work. Project Background The project background information provided in this work plan is based solely on documents prepared by PNA, Woodward Clyde Consultants (WCC), and the San Joaquin County Environmental Health Department (SJCEHD) reviewed by Condor during a SJCEHD file review. According to WCC reports, a 550-gallon UST was removed in 1986 and a 5,000-gallon UST was removed in 1987 from a single location. Both USTs formerly contained gasoline. Soil and groundwater samples collected during the UST removals and during subsequent soil over-excavation activities indicated the presence of gasoline contamination. The soil over-excavation activities did not successfully remove all soil contamination in the source area because of site structures (loading dock). Two monitor wells (MW-17 and MW-18) were installed in the suspected down-gradient direction from the contamination source area. At least two groundwater sampling events were conducted by WCC using the two monitor wells. WCC indicated that, based on the results of the sampling, some gasoline contamination was present in groundwater at the location of the immediate down-gradient monitor well (MW-17), but the further down-gradient monitor well(MW-18)was apparently not impacted. PNA and SJCEHD documents indicate that one 5,000-gallon gasoline UST was removed from a second site location in 1997. Laboratory analysis of the four soil samples collected from the tank excavation sidewalls and the two soil samples collected from the soil removed from the excavation (soil stockpile) indicated that total petroleum hydrocarbons quantified as gasoline (TPH-G)was not detected in any of the samples at or above the laboratory reported detection limit of 1.0 milligram per kilogram (mg/kg).