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• , GROUND WATER MONITORING WORK PLAN DREDGE MATERIAL DISPOSAL SITE 1,ROBERTS ISLAND,PORT OF STOCKTON 3.2 PHASE 2 -MONITOR WELL INSTALLATION AND QUARTERLY GROUND WATER MONITORING The following details the specific tasks resulting in the construction of monitor wells at DMD1 and their subsequent quarterly monitoring and reporting. 3.2.1 Task 5- Utility Location, Permitting, and Health and Safety Plan This task will be implemented as described above in Task 1. 3.2.2 Task 6 -Monitor Well Installation Monitor wells will be installed at the seven locations shown on Figure 5. The purpose of the monitor wells is to enable collection of ground water samples from the shallow aquifer. The monitor well design proposed herein is based on the current hydrogeologic model that is schematically depicted on Figure 3. Actual monitor well design will be based on the improved understanding of the local shallow hydrogeologic system resulting from the implementation of Phase 1. The rationale for monitor well locations and general construction details are provided below. ■ MW-1 -is located upgradient from the dredge materials to characterize background ground water quality near the zone of recharge. ■ MW-2-is located within the primary dredge materials disposal area and will consist of three adjacent monitor wells. An earthen mound consisting of dredge materials will be constructed to protect the monitor wells during dredge placement activities. The three wells will be constructed to enable monitoring of the water within the: • Dredge materials-this well will be screened from the base of the dredge materials to two feet above the highest expected water elevation,based on observations in Phase 1 and historical data from the four existing monitor wells. • Peat underlying DMD1 -this well will be screened across the entire thickness of the peat, or the upper ten feet of the peat layer, whichever is less. • Shallow sandy aquifer. ■ MW-3, MW-4, MW-5-are located to monitor potential impacts to shallow ground water immediately downgradient of DMD1 January 2005 Page 17 Environmental Risk Services,Corp.