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,7 Work Plan — Highway 88 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 Caltrans right-of-way at Highway 88 (see attached air photo plan) using trenchless methods. Two of the borings (B-55 and B-55A) planned to support the design for this crossing will be performed within private property immediately southeast of the highway. Materials to be encountered are anticipated to include a thin veneer of dense older alluvium (less than 10 feet) underlain by variably consolidated rock units of the Mehrten formation that likely consist of sandstone, siltstone and minor conglomerate at this location. Although we don't anticipate that groundwater will be encountered at this location, piezometers will be installed in the borings to allow recording of the phreatic surface on a periodic basis leading up to construction. To gather the information needed to support the design, wet rotary drilling methods will be employed to advance the borings with a 6-inch diameter tri-cone bit to a maximum depth of 40 feet. The overburden soils would be sampled with 2.0- and 3.0-inch outside diameter split spoon samplers, with and without liners, and a conventional core barrel would be used to obtain core samples of the Mehrten formation materials. Standard geotechnical laboratory testing would be performed on the materials recovered, including unconfined compression testing of rock materials and corrosivity testing of alluvial soils. We propose to use 2-inch diameter, flush-joint, Schedule 40, PVC pipe material for construction of the open-standpipe piezometers in the 6-inch diameter holes. A 10-foot screened interval (between a depth of 30 to 40 feet) is anticipated that will consist of factory slotted pipe with 0.020-inch slots. The filter pack will consist of Monterey #3 sand that will extend a minimum of 2 feet above the slotted zone, and 3/8—inch diameter bentonite pellets will be used for 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. A vented slip cap 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 either be disposed of onsite, or be drummed and transported to a designated storage area to be later removed from the project site. The piezometers will not be developed into groundwater sampling wells. Groundwater samples will not be obtained from the piezometers. A schedule for abandonment of the piezometers has not been established.