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Ms. Victoria McCartney
<br /> May 27, 2008
<br /> CONESTO"A-ROVERS
<br /> &ASSOCIATES
<br /> PREVIOUS INVSTIGATIONS
<br /> 1995 UST Removal: On September 27, 1995, Chevron removed four USTs, including two 10,000-gallon gasoline
<br /> tanks,one 5,000-gallon gasoline tank,and one 1,000-gallon waste-oil tank. Three 12,000-gallon gasoline USTs were
<br /> installed northwest of the former UST complex. Chevron also removed and replaced the dispenser islands and product
<br /> lines. Touchstone Developments was present during UST removal to conduct soil sampling activities. Total petroleum
<br /> hydrocarbons as gasoline(TPHg),total petroleum hydrocarbons as diesel(TPHd), benzene,and methyl tertiary-butyl
<br /> ether(MTBE) were detected at maximum concentrations of 260 milligrams per kilogram (mg/kg), 1.1 mg/kg, 0.03
<br /> mg/kg, and 0.1 mg/kg. An estimated 315 cubic yards of soil were removed from the site.
<br /> 1996 Well Installation: On January 10, 1996,Pacific Environmental Group,Inc.oversaw advancement of soil borings
<br /> B-1 through B-4 in the vicinity of the former USTs,and installation of groundwater monitoring wells MW-1 through
<br /> MW-4. The only hydrocarbons detected in soil were 1.3 mg/kg TPHd in B-2 at 16 fbg and 0.18 mg/kg MTBE in B-1 at
<br /> 11 feet fbg.
<br /> 1997 Closure Request: A closure request was submitted in June 1997. At the time of the closure request,no TPHd,
<br /> TPHg, benzene, toluene, ethylbenzene, xylenes (BTEX), or MTBE were detected in groundwater from monitoring
<br /> wells MW-1 through MW-4. Groundwater flow was consistently to the southwest at gradients ranging from 0.0002 to
<br /> 0.003 ft/ft from February 1996 to October 1997. The request for closure was denied due to no monitoring wells being
<br /> located directly down-gradient of the current and former USTs.
<br /> 1998 Tank Testing and Leak/Spill Information: On December 29, 1998, all three 12,000-gallon gasoline USTs
<br /> passed a line test conducted by Tanknology of Austin, Texas. On September 27, 2000, all three USTs passed a line
<br /> test, leak detector test,and monitoring system certification conducted by Tanknology. On September 28,2001,all three
<br /> USTs passed a leak detector test and monitoring system certification conducted by Tanknology. On November 11,
<br /> 2001,all three USTs passed a tank interstitial test,a piping interstitial test,and a sump test conducted by Tanknology.
<br /> On September 16,2002,UST number 3 (regular unleaded),and UST number 2(unleaded plus)failed a leak detector
<br /> test conducted by Tanknology. While no actual leak was detected,according to the report comments,the PLLDs were
<br /> not calibrated to detect leaks at 3 gallons per hour(GPH). On January 15, 2003, monitoring systems were tested by
<br /> Tanknology and all USTs passed monitoring system certification,including testing calibration to detect leaks at 3 GPH.
<br /> 2001 Geoprobe Soil and Groundwater Sampling Activities: On July 26,2001,SECOR supervised Gregg Drilling and
<br /> Testing, Inc. of Martinez,California(Gregg)advance Geoprobe soil borings GP-1 through GP-3 to approximately 40
<br /> fbg,along the southwest edge of the property. Two soil samples and one grab-groundwater sample were collected from
<br /> each boring and submitted for chemical analysis. The grab-groundwater samples were collected between 36 and 38
<br /> fbg. MTBE was detected in one soil sample(GP-2 at 32 fbg)at 0.19 rng/kg. No other hydrocarbons were detected in
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