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Work Plan — Mokelumne River Crossing Fugro is performing a geotechnical design study for East Bay Municipal Utility District (EBMUD) who will be constructing a new 66-inch diameter water conveyance pipeline. As part of this project, the pipeline will pass under the Mokelumne River within EBMUD property (see attached air photo plan) using trenchless methods. Four borings, two at each side of the river (B-61 through B-64), are planned to support the design of the trenchless crossing. Materials to be encountered are anticipated to include about 25 to 35 feet of recent alluvium and tailings from previous mining operations. These materials are underlain by variably consolidated rock units of the Mehrten formation, likely consisting of sandstone, siltstone and conglomerate at this location. Piezometers will be installed in three of the four borings (B-62 through B-64) to allow recording of the piezometric head and phreatic surface on a periodic basis leading up to construction. To gather the information needed to support the design, wire-line drilling methods will be utilized that allow continuous coring of the rock materials underlying the overburden materials (alluvium and tailings) in borings that will extend to 100 feet. The overburden soils would be sampled with 2.0- and 3.0-inch outside diameter split spoon samplers, with and without liners. Standard geotechnical laboratory testing would be performed on the materials recovered, including unconfined compression testing of rock materials and corrosivity testing of alluvial soils. These borings would be tremie-grouted under a separate permit and three additional holes will be drilled using wet-rotary drilling methods with a 6-inch diameter tri-cone bit specifically for installation of the piezometers. We propose to use 2-inch diameter, flush-joint, Schedule 40, PVC pipe material for construction of open-standpipe piezometers. A 20-foot screened interval is anticipated for two of the borings and a 10-foot screened interval will be installed in the third (80 to 100 feet, 40 to 60 feet, and 20 to 30 feet, respectively). The factory slotted pipe will have 0.020-inch slots, and the filter pack will consist of Monterey #3 sand that will extend a minimum of 2 feet above the slotted zone. Above the sand, 3/8—inch diameter bentonite pellets will be used to provide the two to three-foot seal above the filter pack. Portland cement grout, with a low water to cement ratio, will be placed above the seal by the tremie method, and extend to the ground surface. Vented slip caps will be provided for the standpipes. After topping off the grout, traffic-rated Christy boxes will be installed in concrete to protect the installations. The non-hazardous drilling fluids and cuttings will be drummed and transported to a designated storage area to be later removed from the project site. The piezometers will not be developed into a groundwater sampling wells. Groundwater samples will not be obtained from the piezometers. A schedule for abandonment of the piezometers has not been established.