Over time, the Cross Town Tunnel developed leakage where it passed beneath Rock Creek near the access shaft at 25th & N Streets, NW.
Corman installed a 75 in. steel liner within the tunnel that spans the leakage points.
The lower end site at Foxhall and Massachusetts Avenues was used for ventilation, dewatering, structure modifications and valve installations.
The main work site at 25th & N Streets was used to access the tunnel for pipe installation and structure modifications.
Sites were next to urban buildings up to 10 stories high and busy streets.
To initiate construction, the tunnel’s water supply was disconnected, the tunnel was isolated from the inflow of water by installing two 72 in. gate valves weighing 50,000 lbs. in the lines leading to the tunnel, and 3.5 million gallons of water were pumped, de-chlorinated and discharged to the C & O Canal nearby.
After shaft excavation, a mine shaft personnel/material elevator was erected on the shaft wall for entering/exiting the tunnel during pipe installation.
The 75 in. steel liner was installed within the tunnel using a Corman-designed pipe carrier. Procedures for joining the pipe, end bulkheads and bracing mechanisms were developed in-house by Corman.