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<br />. <br />.. <br /> <br />Moffatt & Nichol <br />Redwood Shores / San Carlos Airport Levee, San Mateo County <br />PROPOSAL FOR LEVEE CERTIFICATION SERVICES <br /> <br />8585.oo0.0Ql <br />June 26, 2009 <br />Page 3 <br /> <br />very general assumptions regarding these two critical parameters in order to perform our <br />analyses. The additional exploration locations will allow for the confirmation in assumptions <br />made regarding shear strength and consolidation of the site soil in addition to evaluating the <br />potential hazards associated with the portions of the levee which appear to have been constructed <br />over previous natural drainage channels. The associated tasks for Phase 1 include the following: <br /> <br />1. Prior to drilling, ENGEO will obtain the required drilling permit from the County of <br />San Mateo (County) and complete the appropriate Underground Service Alert (USA) <br />notifications. We have assumed that San Mateo County will waive their permit fee through <br />their relationship with the City. All field work will be coordinated with the City of Redwood <br />City at least 48 hours in advance. <br /> <br />2. We propose to advance four rotary wash soil borings through the crest of the existing levee. <br />Each of the proposed exploration locations will extend to the bottom of the Young Bay Mud <br />we expect to underlay the site; we anticipate borings will be approximately 40 to 50 feet <br />below existing grades. In addition, three additional borings will be drilled at select locations <br />adjacent to the proposed soil borings for in-situ Vane Shear Testing (VST). The borings will <br />be completed using a truck-mounted drill rig from the crest of the existing levee system. <br />Borings will be backfilled on the day of drilling following County requirements comprising <br />neat cement grout. <br /> <br />3. During the subsurface exploration, an ENGEO geologist or engineer will observe the <br />sampling operations and log the samples recovered. Soil samples will be recovered at <br />frequent intervals for visual classification and laboratory testing. Soil samples will be <br />collected by driving or pushing split-spoon (California type or Standard Penetration Test) or <br />Shelby tube samplers, respectively, at locations selected in coordination with the design <br />team. These samples will be used to determine strength and consolidation properties of the <br />soil deposits, as appropriate. In addition, in-situ Vane Shear Testing will be perfonned in <br />additional borings at select locations adjacent to the proposed soil boring locations. The <br />Vane Shear Testing will be performed in the Young Bay Mud deposits to assess in-place <br />shear strength of the soft deposits anticipated below the levees. <br /> <br />4. The samples will be reexamined in our laboratory to verify field classifications and will be <br />tested for moisture content, dry unit weight, Plasticity Index, shear strength, consolidation, <br />and other physical properties as appropriate. <br /> <br />5. Based on the geological and geotechnical data gathered, we will prepare a supplemental <br />exploration letter documenting our services and addressing the following: <br /> <br />· Discussion of the field operations and laboratory testing completed for this scope of <br />services. <br />