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<br /> CONESTOGA-ROVERS Ms. Victoria McCartney
<br /> &ASSOCIATES October 1,2007
<br /> Groundwater beneath the site historically ranges from approximately 2ir to 35 fbg. Historical groundwater
<br /> elevation data infers a consistent flow direction toward the�s°u�west at an approximate gradient of 0.001 feet per
<br /> foot(ft/ft). Th southwest ow direction is consistent with other sites in the vicinity.``
<br /> 1995 UST Removal: On September 27, 1995, Chevron removed four USTs, including two 10,000-gallon
<br /> gasoline tanks, one 5,000-gallon gasoline tank, and one 1,000-gallon waste-oil tank. Three 12,000-gallon
<br /> gasoline USTs were installed northwest of the former UST complex. Chevron also removed and replaced the
<br /> dispenser islands and product lines. Touchstone Developments was present during UST removal to conduct soil
<br /> sampling activities. Total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel
<br /> (TPHd), benzene, and methyl tertiary-butyl ether (MTBE) were detected at maximum concentrations of 260
<br /> milligrams per kilogram-(Ug/kg), 1.1 mg/kg, 0.03 mg/kg, and 0.1 mg/kg. An estimated 315 cubic yards of soil
<br /> were removed from the site. �-
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<br /> 1996 Well Installation: On January 10, 1996,xPacific Environmental Group, Inc. oversaw advancement of soil
<br /> borings B-1 through B-4 in the vicinity of the former USTs, and installation of groundwater monitoring wells
<br /> MW-1 through MW-4. The only hydrocarbons detected in soil were 1.3 mg/kg TPHd in B-2 at �fbg and 0.18
<br /> mg/kg MTBE inB-1 at 11 feet fbg. x}/So G1�lk-� / d"'�� 60lp)-e4t
<br /> al- iG 1 bis n rYIW 4 10 '"'
<br /> 1997 Closure Request: A closure request was submitted in June 1997. At the time of the closure request, no
<br /> TPHd, TPHg, benzene, toluene, ethylbenzene, xylenes (BTEX), or MTBE were detected in groundwater from
<br /> monitoring wells MW-1 through MW-4. Groundwater flow was consistently to the southwest at gradients
<br /> ranging from 0.0002 to 0.003 ft/ft from Febr ary 1996 to October 1997. The request for closure was denied due
<br /> to no monitoring wells being located directly d n-ggradient of the current and former USTs.
<br /> 6 — MW-Z CS 24 -19 13z -O,64ullL j T4. i.S,Uj/L ; X -0,?3
<br /> 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
<br /> line test, leak detector test, and monitoring system certification conducted by Tanknology. On September 28,
<br /> 2001, all three USTs passed a leak detector test and monitoring system certification conducted by Tanknology.
<br /> On November 11, 2001, all three USTs passed a tank interstitial test, a piping interstitial test, and a sump test
<br /> conducted by Tanknology. On September 16, 2002, UST number 3 (regular unleaded), and UST number 2
<br /> (unleaded plus) failed a leak detector test conducted by Tanknology. While no actual leak was detected,
<br /> according to the report comments,the PLLDs were not calibrated to detect leaks at 3 gallons per hour(GPH). On
<br /> January 15, 2003, monitoring systems were tested by Tanknology and all USTs passed monitoring system
<br /> certification, including testing calibration to detect leaks at 3 GPH.
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