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May 24, 1996 Quarterly Monitoring Report Chapin Brothers Automobile Repair Facility Stockton, California :k 2.0 SAMPLING PROTOCOL Lush Geosciences conducted a quarterly monitoring event on March 20, 1996. The work consisted of: LI I. Measuring the depth to water and checking for the presence of free product in each of the wells (no free product was enco,untered); 2. Purging groundwater from the wells and collecting and analyzing groundwater samples Lfrom each of the monitoring wells; k 3. Preparing a groundwater potentiometric surface map indicating the direction of groundwater flow at the time of sampling; and 4. Preparing this report. The following sections summarize field methods used in association with the collection of groundwater samples at the site. 2.1 Subjective Inspection Prior to purging or sampling, the wellheads were inspected and found to be in good condition. Water was present in all of the well boxes due to infiltration of surface water through the wellhead covers. A disposable plastic bailer was lowered to the groundwater surface, retrieved, and inspected for floating product or other subjective evidence of contamination. No �k floating product was present. An electronic water level indicator was used to measure the depth to groundwater and the total depth of each well relative to a surveyed mark on the wellhead. The thickness of the water column was then used to calculate the volume of water in the well and thus to arrive at a calculated minimum purge volume. 2.2 Well Purging Prior to sample collection, each'well was purged of 30 to 50 gals of groundwater using a r1.5-in diameter decontaminated submersible electric pump. The volumes purged correspond to a LL�p.• minimum of three well volumes (easing and gravel pack volume). Table 1 lists the date of sampling, depth to water, and field measurements of pH, temperature and electrical conductivity. _ h 530-001 w - 3 - LUSx GEOSCIENCES