Phase 5 will begin when the Phase 4 contractor has completed their work and has demobilized from the site. Due to the footprint of the pump station being directly over the wetwell which is being construction as part of Phase 4, the work must be completed sequentially and not concurrently. Due to the long lead time in manufacturing of the main stormwater pumps, procurement will begin in early 2020 so they are ready for installation at the appropriate time during Phase 5 construction. It is expected that construction of the pump station will begin in summer of 2022 when the Phase 4 contractor has completed their work and be complete by the end of 2023.
Project Phase Overview
The final phase of the US17 Spring/Fishburne Drainage Improvement Project will be the main stormwater pumps, diesel engines, and pump station structure that is designed to significantly reduce the frequency, severity, and duration of the flooding in the Spring St and Fishburne St drainage basins which include US17 (the Septima Clark Parkway) which spans the Charleston Peninsula. Phase 5 includes:
Three main stormwater pumps each capable of pumping in excess of 120,000 gallons per minute (gpm) or 267 cubic feet per second (cfs)
Three 850 h.p. diesel engines to power the main stormwater pumps which will allow them to operate even if electrical power is lost
The pump station structure to house the equipment and protect it from the elements
The pump station has been designed to accommodate a 10% (10-yr) storm event. This means that all lanes of US17 will remain passable during the 10% event. When the city experiences an event that exceeds the design event, some ponding of water may occur on US17, however, it is expected that the depth and duration of that flooding will be significantly less than the current conditions.
The pump station is designed to quickly and efficiently remove stormwater (runoff from rain events) from the drainage basins. In the event of a tropical system with a storm surge that may inundate the deep tunnel system, the pump station will be temporarily brought offline until the storm surge subsides. Even without electrical power, the pump station can be brought back online to remove any water that remains in the drainage basins to mitigate damage and speed recovery efforts.