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Preliminary Environmental Assessment Report Pittman Elementary School,Stockton,CA December 10,2003 Page 6 • Groundwater samples were collected using a push-type groundwater sampler. The sampler was equipped with a sealed, retrievable stainless steel screen. The sampler was pushed in a closed position in the borings to groundwater. The sampler push rod was then retracted exposing approximately four feet of intake screen. Groundwater flowed hydrostatically from the formation into the intake screen. A groundwater sample was retrieved from within the screen with a length of clean, 3/8-inch diameter polytygon tubing equipped with a check valve at the bottom. The tubing was moved up and down by hand to draw groundwater up inside the tubing. The groundwater samples were discharged directly from the tubing into laboratory supplied sample containers. All groundwater sample containers were sealed, labeled, and placed in a cooler chilled with Blue Ica. The soil vapor and groundwater samples were analyzed for volatile organic compounds (VOCs). The soil gas samples were shipped under chain-of-custody procedures via overnight carrier to Air Toxics Ltd. in Folsom, California, for analyses. The groundwater samples were shipped in a cooler chilled with Blue Ice® under chain-of-custody procedures via courier to Argon Laboratories in Ceres, California, for analyses. Upon completion of the drilling and sampling, the borings were grouted with cement slurry containing three to five percent bentonite. The sampling equipment was cleaned prior to collecting each sample. The cleaning procedures consisted of washing in a solution of laboratory-grade, non-phosphate detergent and deionized water, and double rinsing with deionized water. 5.5 NORTHERN FORMER UNDERGROUND STORAGE TANKS SITE SAMPLES Soil vapor borings were installed at four locations along the northern site boundary. The borings were completed to groundwater, approximately 40 feet bgs. Soil vapor samples were collected at depths of 10 • and 20 feet bgs in each boring for a total of eight soil vapor samples. Groundwater samples were also collected from the borings. Sample locations are indicated on Figure 5,Appendix A. The borings were advanced and samples collected using direct push technology. The borings were advanced using a Geoprobe percussion hammer driven sampler equipped with a two-inch outside diameter, four-foot long core barrel. Soil gas samples were collected from each direct push boring from a sample barrel fitted with a three-inch long, screened, expendable air sampling tip. The soil gas sampling tip was advanced to the target depth, opened, and the sample tubing purged of ambient air with a vacuum pump. Six-liter Summa canisters were checked for vacuum seal integrity, then connected to the purged sampling tube with a 10-micron filter and a soil gas sample was collected. The Summa canisters were checked for appropriate vacuum pressure after sample collection. Each Summa canister was labeled for sample identification. Groundwater samples were collected using a push-type groundwater sampler. The sampler was equipped with a sealed, retrievable stainless steel screen. The sampler was pushed in a closed position in the borings to groundwater. The sampler push rod was then retracted exposing approximately four feet of intake screen. Groundwater flowed hydrostatically from the formation into the intake screen. A groundwater sample was retrieved from within the screen with a length of clean, 3/8-inch diameter polytygon tubing equipped with a check valve at the bottom. The tubing was moved up and down by hand to draw groundwater up inside the tubing. The groundwater samples were discharged directly from the tubing into laboratory supplied sample containers. All groundwater sample containers were sealed, labeled, and placed in a cooler chilled with Blue Ice® and delivered under chain-of-custody procedures to Argon Laboratories in Ceres, California. . • R is CONDOR