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,N.. <br /> San Joaquin County <br /> 0. .� Environmental Health Department DIRECTOR <br /> Donna Heran, REHS <br /> 600 East Main Street <br /> 1< PROGRAM COORDINATORS <br /> Stockton, California 95202-3029 <br /> �. Robert McClellon, REHS <br /> -- —_-- - <br /> Jeff Carruesco, REHS, RDI <br /> cq��.-.. ��P Website: www.sjgov.org/ehd Kasey Foley, REHS <br /> FOR Phone: (209) 468-3420 Linda Turkatte, REHS <br /> Fax: (209) 464-0138 <br /> March 29, 2012 <br /> Mr. Weldon Church Ms. Lacey N. Skelton <br /> 1958 Yosemite Road 25969 South Corral Hollow Road <br /> Berkeley, California 94707 Tracy, California 95376-9108 <br /> Subject: Weldon Church Property <br /> 104 West Beverly Place <br /> Tracy, California 95376 <br /> Dear Mr. Church: <br /> The San Joaquin County Environmental Health Department (EHD) has received and reviewed <br /> Vapor Intrusion Mitigation System Work Plan (work plan), dated 08 February 2012, submitted <br /> by your consulting firm, Advanced Geo Environmental, Inc. (AGE) on your behalf for the <br /> above-referenced site. By letter dated 22 November 2011, the EHD had directed the <br /> submittal of a work plan for installation of a vapor intrusion mitigation system to abate <br /> hydrocarbon-impacted soil gas intruding into the crawl space beneath the home at this site. <br /> In the work plan, AGE proposed to install a sub-slab depressurization (SSD) system designed <br /> by Terra-Petra Environmental Engineering (Terra-Petra) in the crawl space to create a lower <br /> pressure within the crawl space than within the home. Terra-Petra's design includes installing <br /> four-inch diameter schedule 40 perforated polyvinylchloride (PVC) piping (header pipe) <br /> attached to the underside of the structure's floor and extending approximately 28 feet oriented <br /> east-west beneath the home. _ Perpendicular and intersecting the header pipe are three <br /> parallel sets of piping oriented north-south. Terra-Petra proposes to connect the header pipe <br /> to a vertical PVC riser attached to the outside of the residency on the east side of the <br /> structure. A Fantech fan located at the base of the vertical vent riser is proposed to generate <br /> the lower pressure within the crawl space. <br /> The EHD approves the vapor intrusion mitigation system designed by Terra-Petra as <br /> proposed in the work plan. Please have the system in operation by 09 May 2012. <br /> In addition, AGE had proposed to collect three ambient, three crawl space, and two indoor air <br /> samples prior to the start-up of the vapor intrusion mitigation system. On March 12, 2012, <br /> these samples were collected. AGE further proposed to collect indoor air samples and <br /> ambient air samples every six months after the start-up of the vapor intrusion mitigation <br /> system to determine how effective the vapor intrusion mitigation system is for abating the <br /> hydrocarbon-impacted soil gas in the crawl space. The EHD concurs with the <br /> recommendation by AGE to collect ambient and indoor air samples every six months after the <br /> start-up of the mitigation system as presented in the work plan. <br />