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GROUND WATER MONITORING WORK PLAN DREDGE MATERIAL DISPOSAL SITE 1,ROBERTS ISLAND,PORT OF STOCKTON This Work Plan is divided into two phases. Phase 1 proposes to first characterize the sediments, soil, and hydrogeologic system at, beneath, and adjacent to DMD1. Consistent with the WDR requirements, Phase 2 proposes monitor well locations. However, the additional insight gained from Phase 1 may provide a basis for recommending changes to the monitor well locations and/or construction details proposed herein. 2. BACKGROUND Roberts Island is located along the eastern margin of the Sacramento-San Joaquin Delta (Delta) formed by the confluence of several rivers, including the San Joaquin, Sacramento, Mokelumne, Calaveras, and Consumnes Rivers (Figure 1). The island was originally a marshy grassland. The Swamp and Overflow Land Act in 1850 initiated the development of the Delta by conveying ownership of all swamp and Delta marshes from the federal government to the State of California (DWR, 1995). The State Board of Swamp and Overflowed Land was created in 1861 to manage reclamation projects funded by the sale of swamp and marsh lands. The management authority was transferred to the local county level in 1866, and by 1871 most of California's swamp land was in private ownership. Beginning in the 1870s, early settlers built a system of perimeter levees and interior drainage channels to prevent flooding and make the land suitable for farming. These levees remain vital today by maintaining the integrity of the Delta islands and maintaining historically low salinity levels in surface water. 2.1 OPERATION OF DMD1 DMD1 is located on the south side of the San Joaquin River and is bounded to the west (down river), east, and south by agricultural lands (Figure 2). DMD1 is located approximately 3 miles northwest of the Port of Stockton East Complex and approximately 2 miles due west of Interstate Highway 5. Nearby roads include House Road to the west and Burns Cutoff Road to the southeast. Immediately southeast of DMD1 lies a complex of buried petroleum pipelines. Burns Cutoff lies approximately 700 feet southeast of DMD1. DMD1 extends approximately 7,400 feet parallel to the San Joaquin River and is at most approximately 1,700 feet wide. Dredging activities in the Stockton Deep Water Channel typically utilize cutterhead dredging techniques that generate approximately 85 percent to 90 percent water and 10 percent to 15 percent sediment. Of the approximately 163-acre DMD1 site, approximately 46 acres are utilized for the primary placement and management of dredge materials, labeled as Area A on Figure 2. The remaining acres are utilized primarily for the management and settlement of decant water. Area B is approximately 80 acres and Area C covers approximately 37 acres. As needed, internal dikes are built up, relocated, and cut to manage sediments and decant water. January 2005 Page 2 Environmental Risk Services,Corp.