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2.3 Monitoring Well Installation In a letter dated October 2, 1992, the San Joaquin County Public Health Services - Environmental Health Division (PHS/EHD) stated that a groundwater investigation of the site would be required Subsequently, on February 3, 1993, one 2-inch diameter groundwater ' monitoring well (MW-1) was installed at the site The well was initially sampled on February 9, 1993 Low concentrations of TPH as diesel and benzene were detected in the initial water sample A second groundwater sample was ' collected in May, 1993 No petroleum hydrocarbons or volatile aromatics were detected A third water sample was collected on August 16, 1993 TPH as diesel and benzene were ' detected 3.0 PROCEDURES 3.1 Drilling and Sampling ' On January 27, 1995, two soil borings (MW-2 and MW-3) were drilled at the site Each boring was drilled using a ti uck-mounted CME 75-HT di 111 rig The dr ill ii- and two-plan crew were supplied by Soils Exploration Seiviees (SES) of Benecla, Callfolnia One boring ' (MW-2) was di filled south of the farmer underground storage tanks (USTs), a second boring (MW-3) was dillled on the west side of the building ori a line with MW-1 and the city municipal well Both borings were advanced to depths of 30 feet The borings were completed as 2-inch groundwater monitoring wells The locations of the borings are shown on Figure 2 ' Dui ing drilling, samples were collected at five-foot intervals u1 each boi Ing using a split tube sampler loaded with three clean, 2 by 6-inch Wass sleeves A 140-pound hanlriler was used to advance the sampler 18 inches, the number of blows required to advance the sampler in ' 6-In(h ineienients was accorded ori the boirng logs All sa111pling eclllipineiit was washed in an Alconox solution and rinsed twice with water prior to each sampling run tFor each sample, both ends of the lead tube were covered with nilln1111u1n sheets, capped and sealed with tape The samples wc,re then stoied ori tee and tiansported undel chalrl-of- custody to McCampbell Analytical, lnu (Rl-\i) 1n Pacheco, CA i During drilling, auger returns were monilmed for the presence of organic vapors using a photo-ionization detector (11113 `I twimo Environmental 580A, 100 eV, calibrated to isobutylene) Auger returns were tlic.rr pl iced on plastic sheeting incl stored on-site ' 3.2 Logging Soil was extruded from the second bifiss tube and screened for the presence of organic vapors, using a PID, and the readin s N%eie lecoided ort the boring logs Tile soil was then Ooobynl AudSeevaew Cae ,t ' W W—i PIER Q5W..1995 `'�