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'i San JoagWn County Environmental Health Department DIRECTOR }. '_, ' ' •.o Donna Heran, REHS a p Nit 600 East Main Street v. -'�' Stockton , California 952023029 PROGRAM COORDINATORS U% �� Robert McClellon, REHS Jeff Carruesco, REHS, RDI • :. . ,:p > Kasey Foley, REHS 9 � rFo'R�� Website: www.Sigov. org/ehd Linda Turkatte, REHS Phone: (209) 468-3420 Fax: (209) 464=0138 June 28, 2011 Mr. David Atwater I Van De Pol Enterprises, Incorporated Post Office Box 1107 Stockton, California 95201 Subject: Pacific Pride - South EI Dorado Street 3147 South EI Dorado Street Stockton, CA 95206 Dear Mr. Atwater: The San Joaquin County Environmental Health Department (EHD) has received and reviewed Dual Phase Extraction Pilot Test Report - February 2011 (report), dated 13 May 2011 , prepared by your consulting firm, Advanced GeoEnvironmental, Inc. (AGE), on your behalf for the above-referenced site. In the report, AGE documents the results from a 24-hour dual phase extraction (DPE) pilot test involving the simultaneous extraction of groundwater and soil vapor from monitoring well MW-7 located approximately 31 feet down-gradient of the former underground storage tank area . AGE describes how soil vapor and groundwater samples were collected and analyzed for chemicals of concern at designated times throughout the pilot test. note that high concentrations of TPH-g and TPH-d were detected in soil samples collected from P- 1 at 20 feet below surface grade (bsg) and high soil gas concentrations were detected in P-7 . AGE induced and sustained a cone of groundwater depression of 38.5 feet below surface grade (bsg) at MW-7, noting that the static water level measured from MW-7 prior to the DPE test was approximately 24 bsg . AGE monitored wells MWA , MW-2, MW-4, MW-6, and VW-1 through-VW_-3-for induced-groundwater_draw-down levels-while extracting groundwater fmrr MW-7 at a rate of approximately 1 .8 gallons per minute; the maximum induced groundwater drawn-down was 0.32 feet measured from MW-1 . A total of 2,592 gallons of water were extracted between 01 and 02 February 2011 , and approximately 0. 1 pounds (equivalent to 0.012 gallons) of total petroleum hydrocarbons as gasoline (TPH-g) were removed over the 24-hour period . Once the water level was sustained at 38.5 feet bsg in MW-7, AGE induced a vacuum in the vadose zone and monitored VWA through VW-3 and MW-4. The greatest induced vacuum measurement was 0.23 inches of water measured from VW-2 located 32 feet from extraction well MW-7. The effective radius of influence was projected to be approximately 53 feet at a vacuum potential of 0 . 1 inches of water. AGE calculated the mass and volume of soil vapor hydrocarbons extracted during the DPE pilot test to be approximately 15. 1 pounds of gasoline (equivalent to 2.4 gallons of gasoline).