Sutter Bypass East Levee Geotechnical Borings

Sutter Bypass East Levee Geotechnical Borings

The proposed project involves installation of piezometers - groundwater observation wells and sensors - on and adjacent to the east levee of Sutter Bypass. Twelve water pressure sensor/loggers will be installed. Seven of these will be in observation wells and five will be surface water sensors. The seven observation wells will be bored into the soil on or adjacent to the levee using a drill rig. Standard drilling procedures will be followed using a combination of hollow-stem auger and rotary wash drilling methods. The borings will be approximately 6 inches in diameter and a maximum of 65 feet deep. The observation wells will be constructed of schedule 40 PVC well screen and casing, a sand filter pack, a bentonite transition seal, and bentonite-cement grout near the ground surface to prevent water from seeping into the well. The surface water sensors will be installed in the ditches adjacent to the levee by hand using a sledge hammer and will consist of a perforated steel casing, 2-4" in diameter, with the pressure transducer sensor inside the pipe. The distance of the collection ditches from the land side levee toe varies from 0 to 25 feet. The borrow canal on the water side of the levee is approximately 20 feet from the levee toe. The purpose of the project is to gather information essential to assessing causes and possible solutions to under seepage affecting the Sutter Bypass' east levee. Residents and landowners protected by the Sacramento River flood control project and California taxpayers are the ultimate beneficiaries of this work. The project will take place after May 1, 2007 but no later than October 1, 2007 with a total work period of approximately two weeks.

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