#904 - WEST DUWAMISH WET WEATHER STORAGE

The West Duamish Wet Weather Facility Storage Project scope of work includes:

• A buried cast-in-place concrete West Duwamish Combined Sewage Storage Tank that includes drain pumps, a tipping bucket system, and mechanical piping.

• CSO Control Structure built adjacent to the West Duwamish Combined Sewage Storage Tank. This CSO Control Structure includes an overflow weir to the existing West Michigan Outfall and an outfall tide flap gate.

• Drain pumps in the tank and drain piping to convey stored flow to the existing 15-inch-diameter Seattle Public Utilities sewer located in SW Michigan Street.

• Tipping buckets and utility water system.

• Aboveground facility building, including electrical room housing electrical and I&C equipment, C2 pump room housing utility water system and associated equipment, standby generator room housing standby generator and instrument air system, storage area, communication room, and restroom.

• Odor control area consisting of carbon scrubber, odor control fans, and associated odor control equipment in outdoor area.

• Piping revisions to the existing 36-inch-diameter sanitary sewer (previously referred to as the West Michigan Outfall) to convey flow into the CSO Control Structure and to convey flow from the CSO Control Structure to the existing West Michigan Outfall.

• Piping to convey flow from the CSO Control Structure to the West Duwamish Combined Sewage Storage Tank.

• West Duwamish Interceptor Diversion Structure constructed over the existing West Duwamish Interceptor and the existing 36-inch-diameter sanitary sewer (previously referred to as the West Michigan Outfall) located near the intersection of West Marginal Way SW and Highland Park Way SW.

• Modifications to the existing Terminal 115 Overflow Structure.

• Improvements to the existing mechanical, electrical, and I&C systems at the W Michigan St. RS, including a new standby generator.

• New water distribution line within 2nd Avenue SW to provide water service to the West Duwamish CSO Control Facility.

• Deep soil mixing underneath West Duwamish Combined Sewage Storage Tank and adjacent structures (CSO Control Structure, Force Main Discharge Maintenance Hole, Flow Meter Vault, Drain Pump Valve Vault, and associated piping).