Ashley Interceptor Phase 8, North Charleston, SC

NSCD's 42-inch Ashley Interceptor extends for 7.4 miles within lowlands and marsh associated with the Ashley River and is therefore highly susceptible to inflow and infiltration. This project included rehabilitation of 4,650 LF of reinforced-concrete-pipe gravity sewer originally constructed during the late 1960's. An inspection in 2010 found deterioration due to hydrogen sulfide/sulfuric acid attack. Fourteen manholes and the force main receiving junction box at the upstream end were also rehabilitated. Service and main laterals were reinstated in the interceptor after curing the new pipe.

To accomplish the bypass a connection was made to the 24-inch force main just upstream of the receiving junction box. This allowed flow to be bypassed without utilizing rented diesel pumps. The entire length of the project was bypassed in a 24-inch high-density polyethylene pipeline. The peak bypass capacity was 7,000 GPM (10 MGD), and normal day flow are 4.3 MGD. The setup included six secondary bypasses for lateral sewers manifolded into the primary bypass, with several service laterals tied in as well.

The route of the interceptor passed beneath the docks of high-value residences along the riverfront and along the middle of the roads. These site conditions imposed additional challenges with tight working quarters and few laydown areas. Prior to the commencement of construction, the NCSD, WK Dickson, and the contractor presented the project scope to the neighborhood residents to build goodwill and share project information. Their understanding of the necessity of the project facilitated their patience with the disruptions.