COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

-7�;616s Work Plan — Highway 12 Crossing and Cord Road 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 '12 (see attached air photo plan) using trenchless methods. One of the borings planned to support the design for this crossing will be performed within private property immediately southwest of the highway at its intersection with Cord Road, and a piezometer will be installed in this boring (B-68). In addition, a second piezometer will be installed in a boring performed within the same private property along the west side of Cord Road a short distance to the south (B-69). This second boring will be performed just north of a northern tributary to Bear Creek. Materials to be encountered are anticipated to consist of predominantly granular alluvium of the Modesto-Riverbank formation. The piezometers will be installed 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 and 25 feet, for Borings B-68 and B-69, respectively. The alluvial 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 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 extending from the bottom of the boring 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. 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 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 a groundwater sampling wells. Groundwater samples will not be obtained from the piezometers. A schedule for abandonment of the piezometers has not been established.