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Subject:Remedial investigation Work Plan-Addendum Reference.Facility Site Code:2371 February 8;2008 Page 3 of 7 groundwater quality in the approximate 45-59 bgs zone depending on the depth in.which the saturated flowing sand'is encountered. Well MW-2D'would be placed adjacent to MW-2 within the former UST excavation to monitor the-groundwater quality at the deeper zone of the source:area. MW 3D would be placed adjacent to well MW-3to monitor the groundwater quality at the deeper zone up-gradient of boring C8 and slightly up .and'cross-gradient of borings C6 and C7. 'MW-5D .would be placed at the northeastern property boundary to monitor the'groundwater quality at the deeper zone cross-gradient of borings C6 and C7 and up-gradient of C8. Details concerning drilling, soil sampling; groundwater monitoring wellinstallation, and post-installation procedures are described in the Work Plan. Each groundwater monitoring well will be constructed using 2-inch diameter Schedule 40 PVC casing. The monitoring wells are expected to be installed to no more than 59-60 feet deep bgs with screened intervals being no more than 10 feet in length. Final well construction details, including the screened intervals and the slot size used in the screened portion of each well will be determined based upon hydrogeologic data obtained during drilling.- An inspector from SJCEHD will observe and approve the grouting procedures. Following installation activities, a DWR 188 Well Completion Report will be prepared for each monitoring well' and submitted to SJCEHD and DWR. Additional Information Identified The location for wells MW3D and MW-5D is also based on evaluating up-gradient and cross-gradient residual contamination versus a possible contamination source from the adjacent auto body shop. Upon completing the first phase of this remedialinvestigation to identify residual contamination, PSC' subcontracted PIS Surveys, Inc. (PLS) to perform a property boundary survey to specifically identify the northern property line. Identifying the northern property line was necessary to ensure that the installation of additional wells were within the Site's boundary. In addition, during a utility locate for the remedial investigation.SubDynamic Utility Detection Services, Inc. (SubDynamic) identified a metallic anomaly in front of the auto body shop. The metallic anomaly appears.to be an underground storage tank. PSC also ordered the survey to determine if the potential UST'was on the auto body shop property or the Site's property. In addition, PSC's subcontractor ETIC.performed title searches and registered UST.searches. None of the searches reported the registration or identification of an UST being,installed for either of the two properties.. Boring and/or well locations cannot be placed further north of boring'C8 towards the -potential UST, due to overhead and underground utilities. Thus, well MW-5D is located in the northeastern corner of the Site close to the anomaly-, but clear of utilities. The location of the potential off-site UST has been noted on Figures 2 and 3. Copies of the PLS survey and various title and UST searches will be presented in the .subsequent report to be submitted upon completion of this. phase of the investigation. PHILIP ENVIRONMENTAL SERVICES CORPORATION 210 West Sand Bank Road,Columbia,IL 62236 (618)281-1543 Fax(618)281-7020 JR