For over a century, Washington, D.C. and its surrounding community have relied on the Northwest Boundary Trunk Sewer (NWBTS) to safely transport both stormwater and sanitary sewage. During an inspection, missing bricks were discovered in the crown of a junction where the sewer connects with two other effluent pipes.  Several years later, a follow-up inspection revealed further brick deterioration, and a LIDAR survey identified 470 cubic feet of missing soil. To protect public safety and restore this critical infrastructure, DC Water collaborated with STRUCTURAL and other trusted partners to design and implement a long-term repair solution.

The repair site was in a congested area near active public spaces, adding complexity to the project. To meet the urgency of the situation, a Design-Build approach was adopted to accelerate project delivery. After evaluating multiple repair strategies, reinforced shotcrete with geopolymer was selected as the optimal solution, balancing site constraints with the need to keep the pipeline operational.

The project was executed in two phases: the first focused on stabilizing the soil and installing steel reinforcement around the initial void, while the second addressed proactive repairs to other vulnerable sections of the aging pipeline.

Through rapid mobilization, innovative strategies, and a coordinated effort, this critical pipeline was restored safely restored ahead of schedule and under budget.