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v 111RICU�-UHUR Mr. Charles Leubner 6 February 1998 Page 2 total petroleum hydrocarbons as gasoline (TPH-G) and benzene, toluene, ethylbenzene, and total xylenes (BTEX). One groundwater sample was collected from the boring located directly over the former underground tank location. This sample was submitted for analysis of TPH-G, BTEX, methyl tertiary butyl ether(MTBE), and ethylene dibromide (EDB). The results of these analyses are presented in Table 2. After presenting the results of the soil investigation to PHS/EHD in the Helmick and Lerner Inc. report entitled Preliminary Site Investigation- Stagg High School dated 23 September 1997, the County requested the installation of a monitoring well to evaluate the presence of the gasoline constituents in groundwater. SCOPE OF WORK Task 1 —Install Monitoring Well A monitoring well (MW-1) is proposed at the location on Figure 2. It will be constructed using the hollow stem auger flight drilling method. Drilling activities will be conducted according to San Joaquin County regulations and permitting requirements. Drilling and Samplinu Drilling will be performed by hollow-stem auger drilling techniques using a truck-mounted drill rig equipped with 8-inch outside diameter hollow-stem augers. Augers and associated drilling and soil sampling equipment will be cleaned with a high pressure hot water washer before drilling each boring. The sampling equipment and brass tubes will be cleaned with an Alconox or trisodium phosphate wash and rinsed with distilled water prior to collecting each soil sample. Drilling and sampling will be performed according to ASTM Method D 1452-80, "Soil Investigation and Sampling by Auger Borings." Soil samples will be collected by placing the drill rig above the desired sampling depth and then driving a modified California split-spoon sampler lined with three brass tubes into the undisturbed soil. The sampler will be driven by a 140-1b hammer with a 30-inch drop (or an automatic hammer system with an equivalent force) according to ASTM Methods D 1586-84 "Split Barrel Sampling of Soil." Blow counts will be recorded in six-inch intervals after every sampling event. The ends of the middle of the three brass tubes filled at each sampled depth will be sealed using Teflon sheeting secured by tight fitting plastic caps. Soil samples will be collected at 5-foot intervals starting at a depth of 5 feet below ground surface.