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RES 07100
City of Pleasanton
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RES 07100
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3/30/2007 4:11:15 PM
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3/30/2007 4:09:03 PM
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CITY CLERK
CITY CLERK - TYPE
RESOLUTIONS
DOCUMENT DATE
3/20/2007
DOCUMENT NO
RES 07100
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Pnnlic•o Drive Turnout rnu/ Pipeline Project Litvironmentnl Clrec•k/ist <br />a-iii) Less than Significant. Liquefaction is a soil behavior in which a soil undergoes a rapid <br />loss in effective strength due to the development of high excess pore water pressure <br />generated by earthquake ground shaking. Soils that are most susceptible to liquefaction <br />are clean, loose, uniforn~ly graded, saturated, fine-grained sands or saturated soft to firm <br />low plasticity silts that lie near to the ground surface, depth usually considered to be less <br />than 50 feet. 1'he geotechnical study commissioned for the project (DCM Engineering <br />2005) concluded that, while the regional mapping of liquefaction hazard levels by others <br />shows that the liquefaction hazard to be moderate to high along the pipeline alignment, <br />based upon exploratory borings taken along the pipeline alignments that did not <br />encounter any layers of saturated silts or sands of low to medium density, the risk of <br />liquefaction is considered to be low. Therefore, this would be less than significant. <br />a-iv) No Impact. The site is generally flat and no landslides are present within the project site <br />and pipeline alignment (DCM Engineering 2005). Therefore, this would be no impact. <br />b, c, and d) Less than Significant. There will be limited grading and excavation activities <br />associated with construction of the fluoridation building and the two facility vaults over a <br />relatively small area of approximately 2,450 square feet or less than 0.06 acres. The <br />pipeline will be installed with open trenching and the spoil material trucked off site. <br />There will be no large scale mass grading activities that will disturb the ground surface <br />over an extensive area. Implementation of the erosion control Best Management <br />Practices (BMP's), as discussed in the Project Description and Section VIII, Hydrology <br />and Water Quality will reduce erosion and loss of soil in the limited areas of dishirbance <br />during constniction. Construction will be in conformance with all storm water <br />management and discharge control provisions contained in Chapter 9.14 of the City of <br />Plcasanton's Municipal Code and the National Pollutant Discharge Elimination System <br />Permit (NPDES) for construction activities. As described in the Project Description, the <br />City of Pleasanton standard specifications include development of a Storm Water <br />Pollution Prevention Plan (SWPPP) for construction. "The SWPPP will identify Best <br />Management Practices necessary to control erosion and sedimentation during <br />construction. The SWPPP will require that the measures applied to prevent and control <br />erosion arc inspected and kept in working order throughout project construction. Grading <br />will be prohibited from October 15 to April Ito reduce city-wide impacts. These <br />measures will mitigate off-site erosion during construction and will decrease hazards of <br />strong ground shaking and reduce impacts to less than significant. <br />The project area and adjacent areas are located in flat terrain and would not be subject to <br />landslides. <br />Excavations of the pipeline trench will be in soils classed according to Ca]/OSHA as <br />Type C in the upper 3.5 feet, overlain with clayey and sandy fill soils and with depth <br />medium to stiff to stiff saturated native lean clay and fat clay "type B soils. Groundwater <br />is anticipated to occur in some portions of the pipeline trench. Based upon the <br />geotechnical investigation recommendations, shoring will be required so that the trench <br />walls do not collapse affecting personnel who enter the trench, adjacent existing utilities, <br />pavements and structures and resist effects from adjacent vehicular traffic, construction <br />City of Pleasanton 29 Winzler & Kelly <br />Draft Initial Study/Proposed Negative Declaration August 2006 <br />04263501 <br />
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