DC Water New Jersey B Street 12-to-18-Foot Diameter Trunk Sewer Geopolymer Rehabilitation during Live Dry Weather Flow

The Washington, DC, sewer system is managed by DC Water. As part of its capital improvement program, DC Water is performing rehabilitation on their New Jersey B Street (NJB Street) trunk line sewer. This project is 4,434 linear feet of a 12-to-18-foot-wide arched CSO masonry sewer tunnel composed of brick and unreinforced concrete. The spring line to spring line crown of the pipe is being lined with geopolymer spray on mortar. No bypass is utilized, so all construction is during active dry weather flow conditions. The cross section of the pipe contains a large deep cunette which concentrates the dry weather flow at the invert of the pipe. A portable work platform/scaffolding system is utilized to spray the crown above the dry weather flow. This project traverses through the heart of the tourist district and runs under the National Mall. Construction started fall 2018 and will be completed by September 2019. Construction takes place at off peak rush hours from 7:30 pm to 5:30 am. This minimizes traffic and tourist disturbance and flow is typically lower during the night. The general contractor (GC) is utilizing a geopolymer mortar to provide a corrosion resistant composite structural enhancement to the tunnel crown. This paper focuses on the initial condition site assessment, finite element analysis (FEA) design of a geopolymer liner solution, construction challenges, and lessons learned.