SITE INFORMATION AND CORRESPONDENCE FILE 2

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ENVIRONMENTAL HEALTH DEPARTMENT SAN JOAQUIN COUNTY coo Unit Supervisors = 2 Donna K. Heran, R.E.H.S. Q' 304 East Weber Avenue, Third Floor cart Born,Borgman, .H.S ., R. a. � Director Mike Huggins, R E.H.S ., R.D. T. = ' Al Olsen, R.E.H.S. Stockton, California 95202-2708 Douglas W. Wilson, R.E.H.S. o _ , {P • Program Maaager Telephone: (209) 468-3420 - Margaret Lagorio, R.E.H.S. 46 -F-6o Laurie A. Man Ba Co R.E.H.S. Fax: (209) 464-0138 Robert clellon, R.E.H.S. Program Manager Mark Barcellos, R.E.H.S.. RODGER LISTON APR 1 6 2004 DARPETRO INC USA SERVICE STATION 3450 EL CAMINO CERES CA 95307 RE : DARPETRO, INC Site Code: 1060 749 E CHARTER WAY STOCKTON, CA 9520 San Joaquin County Environmental Health Department (EHD) visited the 749 E . Charter Way site during the second quarter 2004 ground water monitoring event conducted by your consultant California Geophysical Group, Inc. (CGG) . During the quarterly monitoring event (QM), EHD noted several problems with the monitoring procedures that must be addressed to ensure that the data collected is representative of aquifer conditions . During the QM , EHD noted that decontamination procedures were not adequate to. minimize data degradation due to possible cross-contamination from equipment introduced into the well . The decontamination procedure for the pump consisted of immersing the pumping unit into a detergent solution of Simple Green and pumping approximately 1 to 1 . 5 gallons of the soapy solution into another bucket. After this , approximately 1 gallon of tap water was pumped into the bucket. While this decontamination procedure may provide minimal decontamination of the pump and hose interior, it did not address the upper pump exterior or the hose exterior. This creates the potential to introduce contaminants into the next well when the pump and hose are inserted . The pump and hose exterior should be well washed , even scrubbed if appropriate, to minimize the potential to introduce contaminants from one well into another. The PVC sampling bailer was not decontaminated at all and the field technician had no brushes to attempt to decontaminant the bailer. The field technician informed EHD that he had been instructed that decontamination of the PVC sampling bailer was not necessary and that the bailer had not been decontaminated during any of the preceding quarterly monitoring events in which he was a participant. This is not an accepted procedure and is a potential source of cross contamination for samples collected from all the wells. This problem is not adequately mitigated by sampling the wells in order from the least-impacted to the most-impacted well as the contaminant concentrations and species may change unpredictably over time in the wells. At the very least, all the reports for monitoring events this technician participated in that state that the ground water samples were collected with a decontaminated bailer are incorrect. All the chemical analysis data collected during these events are suspect and may be inaccurate. If your consultant will provide EHD with authoritative references or guidance