SITE INFORMATION AND CORRESPONDENCE

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P. 5 Andrew Bema-Hicks Page 2 of 2 February 18, 2003 INTRODUCTION On November 20, 2002, General Dynamics submitted a report written by Chow Engineering, titled "November 2002, Corrective Studies Measures, Solid Waste Management Unit No. 21, Follow Up Report,"(Follow Up Report), The Follow Up Report described the field methodology and analytical results of an April 2002 investigation at the facility, and recommended additional work to delineate the horizontal and vertical extent of petroleum hydrocarbons in the vicinity of SWMU #21. In a memorandum dated January 7, 2003, GSU concurred with the Follow Up Report while recommending some minor alterations, primarily with the intent of clarifying the planned field work. Subsequently, General Dynamics submitted the current Workplan, dated January-31, 2003, addressing the recommendations made by GSU. COMMENTS AND RECOMMENDATIONS GSU concurs with the current Workplan as written,with the exception of the proposed methodology for collecting a grab groundwater sample adjacent to boring BH-4. Although GSU concurred with the initial groundwater sample collection methodology proposed in the Follow Up Report, General Dynamics subsequently changed the groundwater sample collection methodology in the text of the current Workplan. In the November 2002 Follow Up Report,General Dynamics proposed to collect a grab groundwater sample from an 8-inch temporary boring. In the text of the current workplan, General Dynamics proposes to collect a grab groundwater sample by installing a temporary well using two-inch schedule 40 polyvinyl chloride (PVC) plastic, a filter pack, and an annular seal consisting of two feet of hydrated bentonite pellets, and then destroying the well. In Appendix B-2 of the current Workplan, however, a more traditional approach for collecting a grab groundwater sample through a temporary boring is described. In a subsequent telephone discussion between GSU and Chow Engineering on February 14, 2003, Chow Engineering explained that they were proposing to install a temporary monitoring well instead of collecting a more traditional grab groundwater sample in order to address concerns expressed by the San Joaquin County- Environmental Health Department. After additional discussion between GSU and the San Joaquin County-Environmental Health Department, as well as GSU and Chow Engineering, all parties concerned agreed that it is appropriate at this site to collect a grab groundwater sample by installing -a emporarylToflng as desenloeclin Appendix B-2 of the curve or an ra er than by installing a temporary we . enera ynamics s ou a aware, owever, wa i the boring is not immediately and properly abandoned following the collection of the grab groundwater sample,the San Joaquin County-Environmental Health Department will view the boring as an inadequately installed monitoring well and thus not in compliance with San Joaquin County well regulations. General Dynamics has adequately described the additional investigative work planned for the facility, and GSU concurs with the proposed field investigation. Thus, further workplan submittals are not required at this time and GSU recommends that the field work take place on March C>�� of2003, as scheduled.