2005/08/24 Council Agenda Packet

EXHIBIT A-2 t) SCOPE OF WORK 1. Modifications to the Existing Pile Supported Design— Consider various changes or modifications that might be implemented to reduce the cost of the original elevated pile supported pipe design. Such changes or modifications may include the following: • Elimination of battered piling and use of vertical piling. • Use of sliding saddle supports to reduce the impact of seismic forces on the piling. • Use of all fixed end connections at the pile caps for all piles. • Reduction of horizontal deflection angles at horizontal bends. • Possible deletion of third pipeline from the design criteria (last option). • Eliminate or extend in-water construction window based on either construction constraints during high tide periods or use of bubble curtains around pile driving to protect juvenile fish. • Leaving temporary steel pipe piles in place rather that removal. • Use of less costly alternative grating materials for walkways. • Incorporate steel price escalation clause into specifications to reduce contractor risk. • Provision of an access route to the pipeline corridor from Homeacres Road via a new north/south elevated access adjacent to the pedestrian bridge for both the west and east segments of Phase 6. • Other concepts that may be identified from interviews conducted with Contractors. 2. At-Grade Road — Consider use of an extended at-grade road at the east and west ends of Phase 6 project to the extent practical, as a possible method for material supply and/or for construction access in association with the original elevated pile supported pipe design. This alternative would also include coordination with WSDOT regarding the construction schedule for the future State Route 2 Seismic Upgrade Project and possible use of the existing rock access work pad for access to the work site located east of the Snohomish River. 3. Buried Pipeline Located Along South Side of Dike — Consider use of a buried pipeline along the south side of the dike as an alternative to the original elevated pile supported pipe design. 4. Horizontal Directional Drilling. - Consider use of horizontal directional drilling (HDD) as a trenchless technology for installation of two new replacement pipelines as an alternative to the original elevated pile supported pipe design. In addition to the above four alternatives, consider a possible combination consisting of possible "leap frogging" of a crane on the piling to install piles with a lighter weight at- grade road for material supply and subsequent pipeline construction and demolition. In preparation for the alternatives/constructibility workshop, develop sketches, plans and sections, design approach, and a preliminary matrix evaluation summary. Evaluation criteria will be similar to those used in the original preliminary design analysis. MWH Page 5 EVERETT PHASE 6-Supplemental Agreement No 2 8/5/05 EXHIBIT A-2—SCOPE OF WORK 34