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GROUND WATER MONITORING WORK PLAN DREDGE MATERIAL DISPOSAL SITE 1,ROBERTS ISLAND,PORT OF STOCKTON Based on prior boring logs, dredge materials are anticipated to range in thickness in Area A from 10 feet to 20 feet thick and in Area B from 3 feet to 8 feet thick. There have been no borings yet advanced in Area C, but the thickness of dredge materials may be similar to that in Area B due to a history of similar use. 2.2 PLACEMENT OF SEDIMENT AT DMD1 DMD1 has historically received dredge materials from maintenance dredging activities performed by the United States Army Corps of Engineers (USACE) in the Stockton Deep Water Channel. DMD1 also received dredge materials generated from the Port's West Complex. USACE anticipates that similar maintenance dredging activities within Stockton Deep Water Channel will place dredge materials at DMD1. The Port anticipates sediment dredging to deepen the draft available at the West Complex docks will place materials at DMD1. One of the early steps in the dredge planning process is the collection of samples, analytical data, and filing of a Notice of Intent (NOI) to dredge. Samples of the sediments proposed to be dredged are collected and analyzed for various physical and chemical properties in accordance with the RWQCB's current WDR. Pursuant to the recent WDRs, data collected by USACE include: sediment grain size, total metals, dissolved metals resulting from the California Waste Extraction Test modified using distilled water (DI-WET) and from the effluent elutriate test (EET), acid generation potential (AGP), neutralization potential (NP), hardness, biological oxygen demand, chemical oxygen demand, ammonia and ammonium, total suspended solids, and organic chemicals including pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs). The data are evaluated to estimate potential risks posed to the environment from the proposed dredging activity. With respect to the proposed placement of the dredge materials at a DMD, the data are evaluated to identify potential threats to ground water quality. For example, results from the DI-WET are compared with water quality criteria and estimated attenuation capacity provided by underlying soils, or foundation soils, beneath the DMD. In addition, the neutralization potential of the sediments must be at least three times greater than the acid generation potential. Based on the NOI, the RWQCB reviews the data and if appropriate, approves the proposed dredging activity in a Notice of Applicability (NOA). 2.3 GEOLOGIC AND HYDROGEOLOGIC SETTING 2.3.1 Regional Setting Unconsolidated Deltaic Deposits underlie the island to a depth of approximately 1,500 feet below ground surface (bgs). These Pliocene, Pleistocene, and recently deposited deltaic January 2005 Page 3 Environmental Risk Services,Corp.