In order to reduce chronic flooding and restore the water quality of Washington DC’s scenic rivers, DC Water is undertaking the $2.7 billion Clean Rivers Project. This program comprises 18 miles of new sewer tunnels to increase Washington’s sewer system capacity and reduce combined sewer overflow (CSO) discharges. The Northeast Boundary Tunnel (NEBT), a new 5.1-mile, 23-foot-diameter reinforced concrete tunnel, connects with previously completed program tunnels, reducing CSO discharges to the Anacostia River by 98 percent.

As a member of the design-build team, EnTech led the geotechnical instrumentation and monitoring program, which entailed installing, monitoring, and reporting the results of thousands of instruments and sensors to measure displacement at ground level and in the tunnel. The geotechnical monitoring program was essential to maintaining the safety of aboveground structures and protecting workers underground. In addition to monitoring the tunnel excavation, EnTech monitored the construction of deep shafts, ventilation control facilities, diversion facilities, and green infrastructure installations.

For each construction area, EnTech configured an Automated Data Acquisition system, a geotechnical instrumentation monitoring system, and an alert notification system to provide stakeholders with real-time notifications when instruments recorded deformations or other movements over acceptable limits. The monitoring team was an integral part of the design-build process, and EnTech continually adjusted the instrumentation work plan as necessitated by the advancing design.