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San Joaquin County DIRECTOR <br /> O Pp,wiry C Donna Heran,REHS <br /> Environmental Health Department <br /> ASSISTANT DIRECTOR <br /> 600 East Main Street Laurie Cotulla,REHS <br /> �iTP Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Carl Borgman, REHS <br /> • r .�-��.. �c Mike Huggins, REHS, RDI <br /> 4 F6R Website: www.sjgov.org/ehd Margaret Lagorio,REHS <br /> Phone: (209) 468-3420 Robert McClellon,REHS <br /> Fax: (209) 464-0138 Jeff Carruesco,REHS, RDI <br /> Kasey Foley,REHS <br /> JAY MCILRATH OCT 1 2 2007 >,o°' <br /> JC & M MCILRATH , <br /> PO BOX 326 �7 <br /> STOCKTON CA 95201 }v, <br /> e � <br /> w <br /> RE: JAMAR Service SITE CODE: 1667 <br /> 4075 Main Street <br /> Stockton CA 95212 <br /> San Joaquin County Environmental Health Department (SJC/EHD) has reviewed Well <br /> Installation Work Plan (Work Plan) dated August 9, 2007, submitted on your behalf by ATC <br /> Associates Inc. (ATC) and has the following comments. <br /> In correspondence dated July 23, 2007, SJC/EHD directed you to submit a work plan to <br /> investigate the lateral and vertical extent of the offsite contaminant plume moving down- <br /> gradient from your site, and to expand the onsite ozone remediation. The Work Plan <br /> proposes the installation onsite of three additional groundwater monitoring wells, two ozone <br /> infusion point clusters, and up to five groundwater extraction wells/clusters. <br /> ATC has proposed to install three additional groundwater monitoring wells onsite with <br /> screen intervals of up to 55 feet in length. Screen intervals of this length in groundwater <br /> monitoring wells are not appropriate or acceptable as they greatly increase the potential for <br /> crossing confining or semi-confining units and spreading the contamination vertically. The <br /> maximum accepted length of screen interval for a shallow groundwater monitoring well is <br /> 20 feet. Deep monitoring wells designed to monitor discrete water-bearing units should <br /> have short (5-10 feet) screen intervals targeted specifically to intercept those water-bearing <br /> units. SJC/EHD does not approve the installation of additional groundwater monitoring <br /> wells onsite, with the exception of one shallow well at the location proposed cross-gradient <br /> to MW-2 (labeled MW-12 on figure 2). Maximum approved screen interval for this well, <br /> targeted to monitor the shallow groundwater contamination, is 20 feet. The vertical extent <br /> of groundwater contamination onsite has been delineated by monitoring well MW-8. . <br /> SJC/EHD does not approve the installation of the proposed shallow groundwater extraction <br /> wells. The pumping test conducted on extraction well EW-1 showed pumping influence <br /> extended to MW-1, MW-4 and MW-2; a technical justification for the proposed location of <br /> EW-2, approximately 5 feet from EW-1, was not provided. SJC/EHD does not approve the <br /> installation of extraction wells in to what ATC refers to as `Zone B-C' to conduct pumping <br /> and aquifer tests at this depth. Groundwater contamination has not been documented at <br /> this depth onsite, and the operation of two remediation technologies, both directed at the <br /> shallow groundwater contamination at one site, has not been justified. <br />