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Site Background Information: Thater Property (former Tucker Construction)
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<br /> detected at a concentration of 16,000 µg/1; total lead was detected at a concentration of
<br /> 110 µg/1.
<br /> • On 24 April 2001, ground water in monitoring well MW-1 was sampled by Central Valley
<br /> Regional Water Quality Control Board(CVRWQCB)personnel and analyzed by California
<br /> Laboratory Services (CLS) for petroleum hydrocarbon constituents. BTEX compounds were
<br /> detected at concentrations of 49 µg/1 benzene,540 µg/l toluene,590 µg/1 ethylbenzene,and
<br /> 2,300 µg/1 xylenes. 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, isopropylbenzene,
<br /> naphthalene,n-propylbenzene,p-isopropyltoluene, and sec-butylbenzene were detected at
<br /> concentrations of 520 µg/l, 400 µg/1, 34 µg/1, 180 µg/1, 85 µg/1, 13 gg/l, and 390 µg/1,
<br /> respectively.
<br /> • On 18 and 19 April 2005, three additional ground water monitoring wells (MW-2 through
<br /> MW-4) were installed at the site by AGE. Pilot borings MW-2 through MW-4 were
<br /> completed as ground water monitoring wells of the same designations using 2-inch diameter,
<br /> Schedule 40 PVC casing with a 0.020-inch slotted screen installed from 45 feet to 65 feet
<br /> bsg.A total of sixteen soil samples were analyzed for petroleum hydrocarbon constituents;
<br /> no analytes were detected at or above laboratory detection limits.
<br /> • On 14 July 2006,vapor extraction well VW-I was installed at the site. The 2-inch diameter
<br /> well was completed with a 40-foot screen interval(10 feet to 50 feet bsg).No soil samples
<br /> were collected during installation.
<br /> • On 19 and 20 July 2006, three soil probe borings (B 1 through 133)were advanced to a total
<br /> depth of 55 feet bsg utilizing a van-mounted Geoprobe 5400 direct-push probing unit. Total
<br /> petroleum hydrocarbons quantified as gasoline (TPH-g), BTEX, and 1,2-dichloroethane
<br /> (1,2-DCA)were detected in soil samples collected from B 1 at concentrations of 670 mg/kg
<br /> TPH-g, 0.30 mg/kg benzene, 4.8 mg/kg toluene, 6.7 mg/kg ethylbenzene, 21.4 mg/kg total
<br /> xylenes, and 0.018 mg/kg 1,2-DCA. A grab ground water sample was collected from each
<br /> boring at approximately 55 feet bsg. TPH-g and BTEX compounds were detected in the
<br /> samples from borings B1 and B3 at maximum concentrations of 1,700 µg/1 TPH-g, 66 µg/l
<br /> toluene, 69 µg/1 ethylbenzene, and 860 µg/1 xylenes.
<br /> • On 27 July 2006,an 8-hour SVE pilot test was conducted at the site using vapor well VW-I
<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 firther
<br /> changes in vacuum pressure were observed.As expected,the highest vacuum was measured
<br /> in the observation point nearest the extraction well (MW-1); the lowest vacuum was
<br /> measured in MW-3,located approximately 64.8 feet southeast of the extraction point.Based
<br /> upon a vacuum of 0.1 inches of water, the extrapolated radius of influence (ROI)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/l
<br /> to 2,000 gg/l;BTEX compounds were detected at concentrations as high as 9.0µg/l benzene,
<br /> 74 µg/1 toluene, 17 µg/1 ethylbenzene, and 78 µg/l total xylenes.
<br /> Advanced GeoEnvironmental,Inc.
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