The Bay Park Conveyance Project, being designed to divert up to 75 million gallons per day (MGD) of treated effluent from the South Shore Water Reclamation Facility in Nassau County to an existing ocean outfall, will improve water quality and storm resilience.
The project involves design and construction 3.6 miles of micro-tunnel force main; 14 shafts for micro-tunneling constructed using secant piles, soil-mixing and jet-grout; rehabilitation and slip-lining of 7.3 miles of existing pipeline; a new 75 MGD effluent diversion pump station; and replacement of pumps at an existing pump station. The water will be conveyed to the Cedar Creek Water Pollution Control Plant (WPCP) outfall, which discharges and diffuses treated water three miles offshore in the Atlantic Ocean.
The project involves a variety of challenges, including accommodating changes in tunnel alignment and slip-lining an existing 100-year-old pipe.
WSP and Nassau County recognized the property acquisition process would need to commence before the project proposals were received to meet eminent domain law timelines. However, innovations in shaft siting and micro-tunnel alignments were anticipated to be major cost and schedule savings opportunities. To address this conundrum, our team created an Alternative Technical Concept (ATC) process that enabled proposers to identify ATCs early, so the project owner could engage with affected property owners and other stakeholders as soon as possible. The process resulted in the winning proposer eliminating a shaft and introducing a curved tunnel alignment.
A key innovation on the project was repurposing a 100-year-old water supply pipe to convey treated effluent. WSP carefully reviewed previous inspections of the pipe — including videos, steel samples and survey data. Various relining methodologies were considered and a slip-lining method was ultimately specified, which will effectively create a new pipe that does not rely on the structural integrity of the existing pipe. The selected fiberglass reinforced mortar pipe will be durable for 100 years.