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PARS S <br /> W Parsons Engineering Science,Inc. A Unit of Parsons Infrastructure&Technoloc. <br /> 2101 Webster Street • Suite 700 • Oakland. California 94612 • (510)891-9085 • Fax(510)835-4355 <br /> October 29, 1999 <br /> Ref: 729801 <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 3443 Routier Road, Suite A <br /> Sacramento, California 95827-3098 <br /> Attention: Mr. Philip S. Isorena <br /> Subject: Amendment to Remedial Action Work Plan <br /> Applied Aerospace Structures Corporation Facility <br /> Stockton, California <br /> Dear Mr. Isorena: <br /> This letter responds to requirements of your letter to BP Oil Company dated September <br /> 16, 1999 and is submitted by Parsons Engineering Science, Inc. (Parsons) on behalf of <br /> BP Amoco Company. The site Remedial Action Work Plan (Parsons 1998) is hereby <br /> modified to include implementation of the changes described in the following sections. <br /> Expansion of the GWETS <br /> The groundwater extraction and treatment system (GWETS) will be expanded to include <br /> three additional groundwater extraction wells in the northeastern portion of the Applied <br /> Aerospace Structures Corporation (AASC) property (Alternative B in the Remedial <br /> Alternatives Evaluation [Parsons 1999a]). The proposed well locations are shown on <br /> Figure 1. <br /> The groundwater extraction wells will be installed and developed according to the <br /> procedures in the Phase 11 RI Work Plan (Parsons 1997). Extraction wells will be 4-inch <br /> diameter PVC construction with 10- to 20-foot screened intervals. Observation wells will <br /> be 2-inch diameter PVC. The planned total depths of the wells are GW-4 and GW-6 = <br /> approximately 65 feet and GW-5 = 80 feet. <br /> Analyses of soil samples in remedial investigation soil borings yielded no detections of <br /> HVOCs in this portion of the site. Therefore, no chemical analyses of soil are planned. <br /> Soil sample headspace vapor concentrations will be screened in the field with a PID. <br /> Grab groundwater samples will be collected from the wells for analysis. <br /> Placement of extraction wells at various downgradient well locations was evaluated by <br /> three-dimensional groundwater flow field modeling with the program MODFLOW <br /> AMEND3WP.DOC <br /> E PARSONS <br />