Felix C. Davis Wastewater Treatment Plant Emergency Rehabilitation for the North Charleston Sewer District

The case study describes the emergency repair of large-diameter drains at the North Charleston Sewer District's (NCSD) Felix C. Davis Wastewater Treatment Plant (WWTP). In January 2024, two large sinkholes opened adjacent to Primary Clarifier No. 4. The drain line from the clarifier had collapsed. The drains from Primary Clarifiers No. 3 and 4 each begin as 48-in. prestressed concrete cylinder pipe (PCCP) that enlarge into 60-in. drains before combining at a wye into a single 60-in. drain. The first collapse occurred in the 48-in. drain, just downstream of the effluent box. The second collapse occurred, where the drain enlarges eccentrically to the 60-in. drain. Inspection videos of the drains revealed the poor condition of both drains to the point of imminent collapse. The NCSD initiated emergency repair of the drains. The rehabilitations were made utilizing cured-in-place pipe (CIPP) methodology and geopolymer concrete repairs. The project was completed in October 2024.