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Harding Lawson Associates September 24, 1996 363712 Ms. Margaret Lagario San Joaquin County Public Health Services Environmental Health Division Page 2 The lowermost tube from each sample interval will be removed from the sampler and immediately capped with Teflon-lined plastic end caps, labeled, and placed in an ice-chilled cooler for transport to a State-certified analytical laboratory. Samples will be recorded on a standard HLA chain-of- custody form to document sample identification and handling. The remaining soil sample from each interval will be checked for hydrocarbon stains and monitored for VOC vapors using a photoionization detector(PID) which is calibrated daily. The PID will be equipped with a 10.2 electron-volt lamp and calibrated to a 100 part per million(ppm)isobutylene standard. The soils will be visually classified using the Unified Soil Classification System (USCS); soil classifications and other field observations are recorded on standard HLA field logging forms. After drilling is terminated, the borings will be tremie grouted with neat cement in accordance with San Joaquin County Environmental Health Department(SJCEHD) requirements. Soil cuttings and decontamination water generated during drilling activities will be stockpiled on and covered with visqueen. The cuttings will be retained on site pending analytical results after analytical results are received,the cuttings will be disposed in an appropriate manner. Task 2 -Analytical Program One to three soil samples from each boring will be analyzed for total petroleum hydrocarbons as gasoline (TPHg) and total petroleum hydrocarbons as diesel (TPH-d)by Environmental Protection Agency(EPA) Method 8015M and for benzene, toluene, ethylbenzene, and total xylenes(BTEX) with EPA Method 8020. Task 3 -Awicultural Mixing Areas To evaluate the potential presence of agricultural chemicals in soils in the vicinity of the concrete water boxes, one composite surface soil sample will be collected. This sample will be composited from individual soil samples collected from each of the concrete water boxes onsite. The composite sample will be analyzed for organochlorine pesticides(EPA 8080), organophosphorus pesticides (EPA Method 8140), chlorinated herbicides (EPA Method 8150), carbamate and urea pesticides(EPA Method 632), and nitrate. Task 4 -Report Preparation HLA will prepare a letter transmitting the results of the investigation. The letter will include the boring logs, analytical test results, maps showing sampling locations, and conclusions. SCHEDULE Field investigation activities are currently scheduled to occur on October 2, 1996. Assuming a two week turn-around-time for laboratory analyses, the letter transmitting the results of the investigation will be completed by October 23, 1996.