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DDD <br /> C E DDD <br /> T AUG 0 2 2002 <br /> CONDOR EARTH TECHNOLOGIES INC. ENVIRONMENT HEALTH <br /> PERfl4lT,4aEP v; V <br /> 188 Frank West Circle <br /> July 30, 2002 Suite I <br /> Stockton , CA 95206 <br /> (209) 234-0518 <br /> FAX (209) 234-0538 <br /> Jeffrey C. F . Wong <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E. Weber Avenue, Third Floor <br /> Stockton, California 95202 <br /> Re: Canepa' s Car Wash, 6230 Pacific Avenue, Stockton, CA <br /> Site Code: 1225; Condor Project No. 1707B <br /> Dear Mr. Wong: <br /> The purpose of this letter is to request authorization to temporarily suspend soil vapor extraction (SVE) at <br /> the above referenced site because of its limited effectiveness and to allow its relocation as part of the <br /> additional development of the site planned by the property owner. As described below, the SVE system <br /> is at best minimally effective in its current configuration. Condor anticipates restarting SVE operations at <br /> the site in a different configuration, potentially in tandem with air-sparging and/or groundwater pump and <br /> treatment, once approval of a comprehensive remedial approach for the site is approved. The remedial <br /> system to be recommended in the Corrective Action Plan Condor is currently preparing will be designed <br /> to greatly enhance the contaminant treatment at the site. After you have had an opportunity to review this <br /> letter, we would like to have a telephone meeting to discuss this issue. <br /> The soil vapor extraction system operated by Condor was started in March 1999 . Initial inlet <br /> concentrations were between 125 and 288 parts per million by volume (ppm) during the first week of <br /> operation. Over the course of 4 months, the vapor concentrations grew to 1280 ppm. After five additional <br /> months of operation, we saw a significant decline to less than 200 ppm. In general, concentrations <br /> remained between 100 ppm and 200 ppm for the remainder of 1999 and throughout 2000 . In 20015 the _ <br /> concentrations dropped below 100 ppm, and the therma! oxidation unit was no longer efficient. <br /> As the thermal oxidizer could not meet the efficiency requirements of the air discharge permit, we <br /> AJW <br /> changed the air treatment system to carbon adsorption. The reconfigured unit began operation in March <br /> 2002 and initial inlet concentrations were over 100 ppm. Since the beginning of operation, we have seen a <br /> continuous and consistent decline in inlet concentrations (see attached spread sheet and graph) to current <br /> concentrations of about 34 ppm, with 100 percent efficiency. Furthermore, the laboratory analysis of the <br /> influent indicates the influent air contains primarily ethyl benzene and xylenes, with no detectable <br /> benzene or MTBE. <br /> Condor' s contention is that the system is no longer cost effective because the extraction is occurring in <br /> present day vadose zone that contains soil vapor only in very low concentrations. Once dewatering of the <br /> saturated zone (via pump and treat) and/or air-sparging of the saturated zone commences, the SVE system <br /> ENVIRONMENTAL GEOLOGICAL ENGINEERING GEOTECHNICAL <br /> http://www.condorearth.com <br />