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06 October 2006
<br /> AGE-NC Project No. 04-1207
<br /> Page 3 of 9
<br /> • On 24 April 2001, ground water in monitoring well MW-1 was sampled by CVRWQCB
<br /> personnel. BTEX compounds were detected at concentrations of 49 µg/1 benzene, 540 µg/1
<br /> toluene, 590 µg/1 ethylbenzene, and 2,300 µg/l xylenes. 1,2,4-trimethylbenzene, 1,3,5-
<br /> trimethylbenzene,isopropylbenzene,naphthalene,n-propylbenzene,p-isopropyltoluene,and
<br /> sec-butylbenzene were detected at concentrations of 520 µg/1, 400 µg/1, 34 µg/1, 180 µg/1,
<br /> 85 µg/1, 13 gg/1, and 390 µg/1, respectively.
<br /> • On 18 and 19 April 2005, three additional ground water monitoring wells (MW-2 through
<br /> MW-4; Figure 2) were installed at the site by AGE. A total of sixteen soil samples were
<br /> analyzed for petroleum hydrocarbon constituents; no analytes were detected at or above
<br /> laboratory detection limits.
<br /> • On 14 July 2006, vapor extraction well VW-1 was installed at the site for use in an 8-hour
<br /> SVE pilot test. The 2-inch diameter well was completed with a 40-foot screen interval
<br /> (10 feet to 50 feet bsg).No soil samples were collected during installation.
<br /> • On 19 and 20 July 2006,three soil probe borings(B1 through B3)were advanced to a total
<br /> depth of 55 feet bsg utilizing a van-mounted Geoprobe 5400 direct-push probing unit.
<br /> TPH-g, BTEX, and 1,2-dichloroethane (1,2-DCA)were detected in soil samples collected
<br /> from B 1 at maximum concentrations of 670 mg/kg TPH-g,0.30 mg/kg benzene,4.8 mg/kg
<br /> toluene, 6.7 mg/kg ethylbenzene, 21.4 mg/kg total xylenes, and 0.018 mg/kg 1,2-DCA. A
<br /> grab ground water sample was collected from each boring at approximately 55 feet bsg.
<br /> TPH-g and BTEX compounds were detected in the samples from borings B1 and B3 at
<br /> maximum concentrations of 1,700 µg/1 TPH-g, 66 µg/1 toluene, 69 µg/1 ethylbenzene, and
<br /> 860 µg/1 xylenes.
<br /> • On 27 July 2006,an 8-hour SVE pilot test was conducted at the site using vapor well VW-1
<br /> as the extraction well.The vacuum pressure at all observation points(MW-1 through MW-4)
<br /> stabilized after 5 hours, and the pilot test was terminated after 7 hours after no further
<br /> changes in the vacuum pressures were observed. As expected, the highest vacuum was
<br /> measured in the observation point nearest the extraction well (MW-1); the lowest vacuum
<br /> was measured in MW-3, located approximately 64.8 feet southeast of the extraction point.
<br /> Based upon a vacuum of 0.1 inches of water,the extrapolated radius of influence at the site
<br /> was calculated to be approximately 108 feet. Vapor samples were collected at 2-hour
<br /> intervals during the pilot test.TPH-g was detected at concentrations ranging from 1,800µg/1
<br /> to 2,000µg11;BTEX compounds were detected at concentrations as high as 9.0µg/1 benzene,
<br /> 74 µg/1 toluene, 17 µg/1 ethylbenzene, and 78 gg/1 total xylenes.
<br /> • On 28 July 2006,a variable-rate ground water aquifer pumping test was performed to assess
<br /> the general ground water aquifer characteristics and to assess aquifer response to ground
<br /> water extraction. During the test, a maximum ground water draw-down of approximately
<br /> 11.07 feet was observed in extraction well MW-1 following 6 hours of pumping operation;
<br /> in addition, ground water draw-down was observed in observation wells MW-2 through
<br /> Advanced GeoEnvironmental,Inc.
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