Agmt 2003 Philip Williams & Associates Ltd

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EXHIBIT A SCOPE OF SERVICES The is a supplement agreement to the previous contract with Philip Williams and Associate, LTD. This work involves additional review services required for the completion of the project. At this time, PWA has completed the scope of services as included in the original contract. Completed tasks include: • Task 1. Project Initiation/Data Collection. PWA visited the site several times to conduct field reconnaissance of both on-site and off-site conditions. Site visits were required to determine existing site conditions and to visually confirm the existence of, and state of, relevant infrastructure (such as inlets/outlets to storm drains). Data collection included the compilation of local and regional hydraulic and hydrologic studies of the area, maps of site topography and storm drain design plans. • Task 2. Assessment of Proposed Drainage Plan. FWA reviewed the proposed site drainage plan, and the existing hydraulic analysis of the proposed development. PWA also met with the County to verify the appropriate design criteria. Our results indicated that the proposed site drainage plan did not comply with the appropriate county criteria, and that there were also potential unaddressed CEQA impacts from the project. The inability to comply with County standards results from existing conditions (combination of high tides and existing stormwater flow). As such, we recommended that the development include comparable storage to existing conditions to prevent any future flood impacts. To address the potential project impacts, PWA conducted two assessments: 1. Calculation of the loss of usable, on-site flood storage; and 2. Change to rainfall-runoff conditions expected as a result of the site development. To address item 2, PWA created a hydrologic rainfall/runoff model of the site (using the ACOE code HEC-HMS with ACFCD methodology to the extent possible) to evaluate the impact of development and decreasing surface permeability on subsurface storage volumes. Increasing impervious surface area reduces the amount of rainfall infiltrating into the soil during a storm event. These findings were summarized in PWA, April 17, 2003 memo. Additionally, storage is lost as a result of fill placed on the site to raise the new buildings above the design flood. PWA calculated estimates of onsite detention lost with water inundation to elevation 6.9 feet. These findings are summarized in PWA, Apri17, 2003 memo. • Task 3. Snmmary of Findings/Recommendations. As described above, PWA has detailed our key findings and calculations in 2 memos. During meetings with the City, Gounty and the Developer's staff we have suggested several potential measures to mitigate the potential project impacts resulting from decreased flood storage and increases in onsite runoff. The next steps in this process are for the developer team to propose an appropriate mitigation plan to compensate for the impacts described above (with input from PWA as requested), PWA to review the proposed plan, and provide guidance to the City regarding the adequacy of the revised plan. The additional scope of services is outlined below: Contractual Services Agreement-supplement Tract 7382 Hydraulic Analysis Consultant Page 3 of 3 Revised 5-02