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GROUND WATER MONITORING WORK PO • DREDGE MATERIAL DISPOSAL SITE 1,ROBERTS ISLAND,PORT OF STOCKTON 1. INTRODUCTION Environmental Risk Services, Corporation (ERS) has prepared this Ground Water Monitoring Work Plan (Work Plan) on behalf of the Port of Stockton (Port). This Work Plan was prepared pursuant to the Regional Water Quality Control Board-Central Valley Region (RWQCB) Waste Discharge Requirements (WDR) R5-2004-0137 Provision 6. This Work Plan is focused on Dredge Material Disposal Site 1 (DMD1), which is located on Roberts Island, and has been referred to as Roberts Island No. 1 and Dredge Placement Site 1. The location of DMD1 is shown on Figure 1. The purpose of this Work Plan is to comply with the requirements in WDR Provision 6. Pursuant to WDR Provision 6, the objectives of this Work Plan are to: • include "the items listed in the first section of Attachment E: Monitoring Well Workplan and Monitoring Well Installation Report Guidance." • "describe a groundwater monitoring network of at least five new groundwater monitoring wells specifically designed to ensure that background water quality (upgradient and out of the influence of waste management activity at the site) is adequately characterized and any potential water quality impacts from the discharge are detected." • describe methods "designed to yield samples representative of the uppermost portion of the first aquifer underlying the site." The primary objective of this Work Plan is to evaluate if the dredge materials placed at DMD1 have significantly impacted ground water quality. Accordingly, the ground water quality beneath DMD1 must be evaluated relative to background ground water quality and the geochemistry of the sediment in DMD1. Therefore, this Work Plan also proposes a significant effort to characterize the sediments in DMD1 and the geologic materials underlying and adjacent to DMD1. We request the RWQCB to consider that the effort proposed herein is also adequate to characterize the dredge materials consistent with the requirements in WDR Provision 9 for the"existing dredge spoils in the DMD site." Ground water monitoring within four monitor wells at DMD1 has been performed since 2001 and an investigation of background ground water quality was performed in 2004. However, significant questions remain regarding the structure, hydrology, and geochemistry of the local hydrogeologic system. Therefore, prior to constructing monitor wells, a thorough investigation of the hydrogeologic system is proposed to be implemented first. January 2005 Page 1 Environmental Risk Services,Corp.