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6 <br /> to determine if the data collected during the original plant construction could be compared with <br /> the geotechnical data collected during the current design. <br /> Many methods of site stabilization were evaluated, and several meetings were held with City <br /> staff and/or specialty geotechnical construction firms to determine the most appropriate means <br /> of construction. The recommended method is to utilize a combination of both stone columns and <br /> jet grouting beneath Clearwell No. 2, the CFDS, and portions of the 84-inch diameter piping in <br /> areas of complex piping. The latter soil stabilization is recommended in those areas where there <br /> are complex pipe crossings, with the intent of providing protection to simplify needed repairs <br /> against future seismic events. <br /> Redesign of the Existing Backwash Pump Station <br /> During the development of the design, the design team was authorized an additional design <br /> task to determine the feasibility of replacing the existing pumps in the existing backwash pump <br /> station (BWPS). Ultimately, the entire existing BWPS was rehabilitated, with replacement of <br /> both backwash pumps and one surface wash pump; a new electrical room, requiring the <br /> relocation and replacement of all electrical equipment while keeping the pump station on line; an <br /> entirely new building structure with associated architectural and structural drawings, requiring <br /> demolition of the existing building and replacement with a new structure; and other <br /> modifications. In addition,on-line water quality monitoring was moved from the Operations <br /> Building to the BWPS, with plant analyzers and sample pumps mounted in the BWPS. In effect, <br /> the entire structural, mechanical, electrical and instrumentation and control (1&C) infrastructure <br /> was replaced and expanded. <br /> Clearwell Flow Distribution Structure (CFDS) <br /> The original plant design did not provide facilities for flow splitting between the original plant <br /> clearwell and a new clearwell for a future plant expansion. Due to the critical design criteria of <br /> providing equal flow split between clearwells, and the necessity of keeping plant shutdowns <br /> limited in duration to a maximum of four hours, it became necessary to design a flow distribution <br /> structure that would provide a location for equal flow split and non-mechanical mixing chemical <br /> addition. Due to the complexity of the 84-inch piping installed during the original plant design <br /> and the construction of Finished Water Pump Station No. 2, the resultant CFDS is a large, <br /> complex structure(approximately 27 by 44-foot footprint, 35 feet deep, with the bottom of the <br /> slab 13 feet below the groundwater). This structure was not included in the original design fee <br /> estimate. <br /> CFDS Bypass Pipeline and Hot Tap <br /> Through the 90% design submittal, the project design assumed that the CFDS would be <br /> constructed around the existing 84-inch diameter pipe connecting the filters to Clearwell No. 1. It <br /> H:\Client\Everett_SEA\Contracts\7094A10-Clearwell dgdn\Amend 1 Apr 2007\EXHIBIT A.doc A-2 <br />