Laserfiche WebLink
a division of <br /> ENVIRONMENTAL SOL �I ep6wa& I EM <br /> con <br /> ' '. <br /> H +,FP 20 Pig I: 05 <br /> April 8, 1998 <br /> Project 20805-146.010 <br /> Mr. Ron Rowe <br /> San Joaquin County Public Health Department <br /> Environmental Health Division <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> Re: Results of Soil Vapor Extraction Assessment, Former ARCO Service Station No. <br /> 2168, located at 441 West Charter Way, Stockton, California <br /> Dear Mr. Rowe: <br /> EMCON has prepared this letter on behalf of ARCO Products Company (ARCO) <br /> presenting the results from the evaluation of the soil vapor extraction (SVE) system <br /> performance at the Former ARCO Service Station No. 2168, located at 441 West Charter <br /> Way, Stockton, California. The work performed in this letter is based on our telephone <br /> conversation and letter dated January 27, 1998 and February 2, 1998, respectively. <br /> As outlined in our February 2, 1998 letter, EMCON shut off the soil vapor extraction <br /> (SVE) system for a three week period to allow for soil vapor concentrations to rebound. <br /> Commonly, during SVE activities at a site, the concentrations continue to decline during <br /> SVE operation only to rebound during non-operational periods. EMCON has been <br /> operating the system at the site over the past few quarters in an intermittent pulse mode to <br /> account for and treat these episodes of higher concentrations. The purpose of this <br /> evaluation was to (1) quantify the amount. of any rebound and if present, (2) assess the <br /> length of time required for it to decline back to pre-shutdown levels. <br /> Previous Operational Data <br /> Prior to shutting down the SVE system to evaluate the response of petroleum hydrocarbon <br /> concentrations in the vadose zone, EMCON collected background influent samples at the <br /> site in January 1998. The analytical results indicated that influent concentrations were <br /> 1,200 part-per-million by volume (ppmv) for total petroleum hydrocarbons as gasoline <br /> (TPHG) and 2.8 ppmv for benzene. Table 1 presents the analytical data for the pre- and <br /> post pulse sampling events. <br /> SACC:\FILES\AtCO\2168\RO WE2.DOC-951mtt:1 <br /> 3939 Cambridge Road,SuBe 220 Cameron Park,California 95682 (530)676-6884 (530)676-6885 Fax <br />