IS4 – Phase 2 (Construction of Storm Sewer Lift Station)

The IS4 Phase 2 project involves construction of a storm sewer lift station consisting of a concrete cast in place underground vault with three 185 hp submersible Flygt pumps at the NE corner of 92nd Ave/SR 532 intersection in the City of Stanwood. Discharge from the pumps will be through a 24-inch diameter restrained joint DI force main that will couple with a fusion welded 24-inch diameter HDPE pipe just south of SR 532 and connecting to the existing outfall. The 24-inch discharge force main will be sleeved through the existing 36-inch cmp drainage discharge pipe under SR 532, so an open cut across the state highway to install the discharge force main will not be needed. Included in the station will be all electrical equipment including an electrical component FRP enclosure. Electrical equipment shall include but not be limited to VFD starter panels, supply panels, a disconnect for a portable city owned generator and setting of supply power vaults for power serviced. Storm conveyance piping into the pump vault will be large diameter SD pipe with catch basins and a jellyfish filter treatment system. The treatment system will have a flow splitter upstream of treatment to allow for larger flows to bypass the filter. There is a large (72-inch) Corrugated metal storm pipe 14-feet under the sidewalk along the east side of 92nd that will need to be partially removed to allow for the vault to be constructed. With the vault being approximately 24-feet deep and groundwater at 5-feet, dewatering and shoring will be needed. Layback of the trench sides is not an option due to tight site constraints. Coordination with SnoPUD will be required as a few of the power poles are to be relocated.