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26 December 1995 AGE-NC Project No. 95-0118 } Page 2 of 6 grade (bsg). TPH-g and BTE&X were detected in all four soil samples from B-1. The highest concentration of gasoline was detected in B-1 at a depth of 30 feet at 3,200 ppm. During drilling, ground water was encountered at 36 feet bsg. On 30 August 1994, three additional borings were drilled at the site to depths of 49 feet and completed as 2-inch ground water monitoring wells MW-1, MW-2 and MW-3. A total of 13 soil r>a samples were analyzed for TPH as gasoline and BTE&X. Laboratory analyses detected TPH-g in 6 of the 13 samples analyzed. TPH-g and BTE&X were detected in two samples from MW-3; toluene was detected in one sample from MW-2; and xylenes were detected in three samples from MW-2,. . No petroleum hydrocarbons were detected in samples from MW-1. 2.4. GROUND WATER MONITORING The ground water monitoring wells were initially monitored and sampled in September 1994.7 he hydraulic gradient was calculated to be 0.0029 ft/ft(0.17°) flowing to the southeast. .,. Results of the ground water samples indicated that TPH-g was detected in MW-1, MW-2 and MW-3 = _ at concentrations of 280 pgA(parts per billion: ppb), 9,500 ppb and 1,200 ppb, respectively. BTE&X were detected in samples from MW-2 and MW-3 at concentrations of up to 1,600 ppb (toluene, MW- 2). No BTE&X were detected in MW-1. The analytical results of all ground water samples are summarized in Table 2. ! ' 3.0. PROCEDURES 3.1. MONITORING WELL INSTALLATION J On 31 August, 1995,three borings were drilled at the site to depths of 49 feet bsg and completed as V. ground water monitoring wells MW-4, MW-5 and MW-6. The locations of the borings are shown on Figure 2. .3 Each boring was drilled using a truck-mounted CME 75-HT drill rig. The drill rig and two-man crew were supplied by Mitchell Drilling Environmental(NIDE) of Rancho Cordova, California. Samples were collected at five-foot intervals in each boring using a split tube sampler loaded with three clean, 2-by 6-inch brass sleeves. A 140-pound hammer was used to advance the sampler 18 inches;the number of blows required to advance the sampler in 6-inch increments was recorded on the boring logs. All sampling equipment was washed in an Alconox solution and rinsed twice with water prior to each sampling run.