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14 <br /> 6E T r' L- E-R' R YA N hi C. <br /> , April 29, 1999 <br /> Mr Ed Ralston <br /> Tosco Marketing Company <br /> Environmental Compliance Department <br /> 1380 Lead Hill Road, Suite 120 <br /> Roseville, CA 95661 <br /> c <br /> Subject First Quarter 1999 VES Report,Tosco 76 Branded Station No 6981.,4707 Pacific Avenue,Stockton, <br /> California <br /> Mr Ralston <br /> This report summarizes the sampling'and operational data for the vapor extraction system,(VES) at the subject site from <br /> January through March, 1999 The VES operates under San Joaquin Valley Unified Air Pollution Control District Permit <br /> N-3335-2-0 Location of the subject site is shown on Figure I The current station configuration is shown on Figure 2 <br /> Gettler-Ryan Inc (GR)'sampling procedures are attached <br /> Continuous VES operation was stopped on November 3, 1998,due to low influent concentrations, but has operated in"pulse" <br /> mode since Between January 4 and March 26, 1999, the VES operated approximately 374 hours (14 5 days), or 17 9% <br /> of the time GR monitored the system and collected influent and effluent vapor stream samples on January 27, February 1, <br /> s . February 24, March 1, March 22, and March 26, 1999 On March 22, 1999, only the influent sample was collected On <br /> March 26, 1999, the effluent sample bag deflated during transport to the laboratory Samples were analyzed for TPHg and <br /> BTEX at Sequoia Analytical (FLAP#1210 and#1271) Copies of the laboratory reports and chain-of-custody documents <br /> are attached <br /> Soil vapor was extracted from all vapor wells during the first quarter 1999 Hydrocarbons were detected in all effluent <br /> airstream samples Effluent concentrations of TPHg ranged from 5 to 14 parts per million vapor However, during the <br /> January and February 1999 operational periods, the VES operated within the permit requirement of 95% or greater <br /> destruction efficiency or G 2 pounds TPHg per day(lb /day)emission rate VES destruction efficiencies during this period <br /> ranged from 51 82% to 96 47% Emission rates for TPHg ranged from 0 3 to 0 7 lb /day It was not possible to evaluate <br /> the destruction efficiency or emission rate for the March 1999 operational period since the effluent samples could not be <br /> analyzed However, influent concentrations during the March-1999 operational period were below those concentrations <br /> detected in the January or February 1999 samples, suggesting that the system operated within permit conditions during > <br /> March <br /> During the first quarter 1999, the VES extracted and treated approximately 42 pounds of TPHg and 1 pound of benzene <br /> Since installation in September 1994, the VES has extracted and treated approximately 14,409 pounds of TPHg and 176 <br /> pounds of benzene VES analytical data for the quarter are summarized in Table 1, and operational data are summarized <br /> in Table 2 , <br /> GR also evaluated the VES radius of influence(ROI)during the March 1999 sampling event The VES extracted from well <br /> VW-5 far 4 days Vacuum readings were then collected from wells VW-1, VW-2, VW-4 and VW-6 (Table 3) Based on <br /> these observations the VES ROI was calculated at approximately 55 feet (Figure 3) <br /> r <br /> 140124 04 <br /> 6747 Sierra Court ; Suite J Qu'blin , California 94568 ( 925 ) 551 - 7555 <br />