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TYLIN NITERNATIONAL July 11, 2011 Mr. Joshua Pack Senior Transportation Engineer City of Pleasanton Community Development Department Traffic Division 200 Old Bernal Avenue Pleasanton, CA 94566 Subject: 1-580 / Foothill Interchange Improvement Project Amendment 1 Request— Retaining Wall Design, Additional ADL Testing, Traffic Analysis, and NES Report Pleasanton PSA: 10-663C TYLI Project Number: 320126.1T Dear Mr. Pack: This letter is our formal request for a contract amendment to cover the cost of designing a retaining wall on piles along the westbound Foothill off ramp, performing additional traffic forecasting as required by Caltrans, and preparation of an updated NES as required by Caltrans. Retaining Wall Design The 1-580 / Foothill Interchange Improvement Project includes filling a portion of the drainage channel along the westbound Foothill off ramp adjacent to the hotel parking lot and constructing a standard Caltrans retaining wall with spread footing. Our original scope of work and project fee includes the preparation of a retaining wall layout plan and elevation for this wall. We assumed that we would need to prepare a retaining wall plan showing the horizontal alignment (layout) and elevation for the retaining wall along the eastbound off ramp. This plan would indicate that the retaining wall was to be built using a Caltrans standard plan sheet retaining wall design (a Type 1 retaining wall with spread footing). The geotechnical investigation and report for the 1-580 / Foothill Interchange Project has been complete. The findings from the investigation indicate that due to the poor soils and high groundwater a standard Caltrans Type 1 retaining wall with spread footing cannot be used for the area along the westbound Foothill off ramp adjacent to the hotel parking lot.