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T1, uf 1 a Standard Operating Procedures GROUNDWATER LEVEL MEASURING, PURGING AND SAMPLING Prior to groundwater sampling,static water level measurements are recorded for each well using a battery-powered sounder with a precision of plus or minus 0.01 feet. All measurements are recorded as depth-to-water from the surveyed measuring point at the top-of-casing. Depth-to-water readings are converted to water level elevations referenced to the USGS mean sea level datum. Thzn each well is purged by evacuating a minimum of three to five well casing volumes of groundwater using either adedicated polyvinyl chloride(PVC)bailer, sterile disposable bailer or a stainless steel pump. During the purging of each well and prior to sampling,discharge water temperature,specific conductivity,and pH measurements are recorded and are allowed to stabilize. Stabilized measurements indicate that formation water has entered the well. The groundwater sample is _ taken when the water level in the well recovers to 80%of its static level. Following purging,a groundwater sample is collected in accordance with California Regional Water Quality Control Board(RWQCB)procedures described in the Leaking Underground Fuel Tank(LUPI}Field Marural,the Tri-Regional Board Staff Recommendarimu for Preliminary Evaluation and Investigation of Underground Tank Sites,and local regulatory guidelines. A groundwater sample is first collected and checked for;he presence of free p,-oduct in the sampling bailer. Thickness of possible free product is measured using an electronic interface probe with a plus or minus 0.01 foot detection limit. Groundwater samples are collected using a pre-cleaned teflon or stainless steel bailer equipped with a ball-check valve,and sample containers are filled directly from the bailer as soon after purging as possible. Agitation is minimized during sample retrieval and sample transfer to laboratory prepared sample containers in order to minimize sample aeration. Groundwater samples to be analyzed are carefully decanted into laboratory-prepared,40- milliliter volatile organic analysis(VOA)vials. The VOA vials are fulled completely,leaving no headspace,and are capped and.sealed with Teflon-lined lids. Additional groundwater samples may be collected in 1 liter bottles. A11 s-mples are labeled and stored in an ice chest with crushed ice to maintain a constant temperature of 4 degrees Celsius. A thermometer is kept in the ice chest to ensure that the proper temperature is maintained- The samples are then delivered under chain-of-custody to a state-cerdfied hazardous materials testing laboratory. Monitor well purge water is properly stored on-site pending off-site disposal. Parker Environmental Services, 4185 Rialto Court, Pittsburg, CA 94555-6116 Phone (415) 439-1024 Fax (415) 439-2566 � mi�e�we� �o1,7f�A