PLACING SOUTH CAROLINA's LARGEST SEWER IN SERVICE GO WITH THE FLOW — IT ALL RUNS DOWNHILL ANYWAY

Western Carolina Regional Sewer Authority (WCRSA) is in the final stage of construction of South Carolina's largest wet-weather sewer project. The 45 million Reedy River and Brushy Creek Sewer System will convey 160 mgd and includes ten miles of deep trunk sewer up to 96 inches in diameter. This project has been ongoing for more than eight years, including initial study phase, design, and construction of sewers in two phases.The new Reedy River Trunk Sewer replaces a 36-inch sewer constructed in 1927. The existing 48-inch Reedy River Sewer will remain in service and will operate in parallel with the new trunk sewer to convey flow to the Mauldin Road Wastewater Treatment Plant (WWTP). This expanded Reedy River Trunk Sewer System is designed to convey wet-weather flows during a two-year storm event to the plant without sewer system overflows (SSOs).The new PVC-lined reinforced concrete pipe (RCP) trunk sewer had to be installed, tested, and accepted by the design engineer, Camp Dresser & McKee (CDM), WCRSA, and South Carolina Department of Health and Environmental Control (SCDHEC) before any flow could be diverted from existing collection sewers. The old 36-inch sewer was then removed from service and replaced with smaller sewers to interconnect existing collector sewers along the route. Continuous sewer service was maintained through sequential upstream-to-downstream flow diversions to unload the 36-inch sewer. Various construction techniques included installing smaller sewers inside the 36-inch sewer, replacing the 36-inch sewer with new, small-diameter sewers in the same trench, and in some instances abandonment of the existing sewer. Also, several existing manholes were rehabilitated to minimize disturbance in the Greenville Zoo. Diversions and interconnections were completed under the constant threat of high infiltration and inflow and river flooding. Throughout this process, State and Sewer Subdistrict coordination was critical to successfully manage existing flows.This paper focuses on the final stage of construction, including:Construction sequencing to ensure that a high level of sewer service was continuously maintainedCoordination with start-up of the new Mauldin Road WWTP influent pump stationTesting and certification of the large Reedy River Trunk SewerSequential flow diversions and sewer interconnections required to remove the 36-inch sewer from service and place the new trunk sewer in operation