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BACKGROUND The City of Dublin completed a Project Report and Environmental Documents for improvements to the I-580/Foothill Road — San Ramon Road interchange in 2002. The improvements were designed to provide increased capacity and improve operations and safety. Required documentation for a Categorical Exemption for CEQA compliance and Categorical Exclusion for NEPA clearance were completed at that time. The City of Dublin began work on the north side interchange improvements in 2003. At that time the City of Pleasanton deferred the construction of improvements on the south side of the interchange. In July 2010 the City Council approved a contract with T.Y. Lin International to prepare project plans, specifications and estimates (PS&E) and environmental documentation for the I-580/Foothill Road Interchange for the not-to-exceed amount of $372,638. DISCUSSION Retaining Wall The original scope of work and project fee included the preparation of a standard Caltrans retaining wall design. A geotechnical report indicated that poor soils and high groundwater could not support a standard Caltrans retaining wall. A special retaining wall with a pile foundation is required at this location. This additional work requires detailed design calculations and design sheets not accounted for in the original scope of services. The high groundwater results from the presence of a nearby drainage channel. Additional water quality sampling and testing is required to determine if the ground water can be discharged to the nearby drainage system or if it needs to be treated before disposal. Additional Traffic Analysis In 2009 the City completed an updated interchange traffic study that included traffic forecasts and Level-of-Service (LOS) analysis at surrounding intersections. The study identified a preferred preliminary design and alignment similar to the original design but included design elements that significantly improved vehicle, bicycle and pedestrian circulation throughout the project limits. This study included traffic forecasts during existing and future buildout (2025) conditions in line with the original 2002 Project Report. At a May 10, 2011 meeting Caltrans asked the City to update the traffic study by utilizing updated regional land use projections available after the 2009 traffic study. A supplemental technical memorandum will be prepared to ensure that improvements identified in the original Project Report and updated traffic study will operate acceptably during future buildout (year 2035) traffic forecasts. Page 2 of 3