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9110 Thornton Road, Stockton, California September 30, 1993 <br /> The Southland Corporation Page 3 <br /> SOIL CONTAMINATION <br /> As requested, a more comprehensive summary of soil quality data is included in Attachment 2, Table 1. <br /> Photoionization detector (PID) readings were recorded for many of the soil samples collected during the <br /> Installation of the monitoring wells, but laboratory analytical results are limited (Table 2). <br /> SOIL VAPOR EXTRACTION RADIUS OF INFLUENCE <br /> Field notes describing the soil vapor extraction test performed (on MW-3) on April 28, 1989 indicate <br /> anisotropic pneumatic character of the vadose zone materials, and a radius of influence between 30 and <br /> 50 feet. The total applied vacuum at the maximum power of the 1.5 hp (127 cfm) Rotron blower was <br /> approximately 30 inches of water and the flow rate was approximately 70 cfm. From previous <br /> experience of geologically similar sites, these pressure/flow rate values generally reflect radii of influence <br /> In excess of 60 feet. <br /> The four blowers used during the 13-month period of soil vapor extraction by Vapor Extraction <br /> Technology, Inc. (VET), were larger (160 cfm) than the blower used during the test (127 cfm capacity); <br /> therefore, the radii of influence were probably well in excess of the 30 to 50 feet estimated during the <br /> test. Induced vacuum pressures in vadose monitoring wells were not reported by VET. <br /> It is unclear as to where additional soil confirmation sampling should be implemented based on the <br /> PHS/EHD letter. Hopefully, the data presented in this letter will help clarify the issue. Groundwater <br /> Technology on behalf of The Southland Corporation will contact the PHS/EHD shortly after receipt of <br /> this letter to request a meeting with the PHS/EHD and the Central Valley-Regional Water Quality Control <br /> Board (CVRWQCB) to discuss closure requirements for this site. <br /> If you have any questions or comments, please do not hesitate to contact our West Sacramento office at <br /> (916) 372-4700. <br /> Sincerely, <br /> Groundwater Technology, Inc. Groundwater Technology, Inc. <br /> Written/Submitted by Reviewed/Approved by �f <br /> ,p.EEDGkaL <br /> kED)k 0 <br /> 04P J'2'`sa <br /> BRUCE H. EPPLER E. K. SIMONIS, R.G. O <br /> Environmental Geologist Senior Environmenta G @gis <br /> ht).4422 <br /> Project Manager * ,� <br /> BHE/EKS:rz N'� 0R�lti <br /> cc: Mr. Bob Vasquez -The Southland Corporation d�'CALIF <br /> Ms. Beth Thayar- CRWQCB-CVR <br /> 71 GROUNDWATER <br /> TECHNOLOGY <br />