RiverRenew Project Nearing the Finish Line

The RiverRenew Tunnel System Project in Alexandria, VA, the largest infrastructure project in the city’s history, includes an approximately 2.2-mile-long, 12-ft-wide tunnel, shafts, and other sewer infrastructure that will help prevent about 130 million gallons of sewage from polluting local waterways each year. The project will solve a sewer issue dating back to the mid-19th century.

AlexRenew, the wastewater authority for Alexandria and parts of neighboring Fairfax County, oversees the RiverRenew program, and began implementing the project in 2018 in response to a Virginia law requiring remediation of outfalls.
The RiverRenew tunnel system consists of:

• Four new diversion structures on existing outfalls surrounding Old Town Alexandria, Virginia
• Four shafts ranging from 35- to 65-ft inside diameter (ID) and up to 130 ft in depth
• A 12-ft ID tunnel in soft ground that is 11,500 ft in length located 115 to 160 ft below ground surface (Waterfront Tunnel)
• 2,500 lf of new 72-in. diameter interceptor pipeline (Hooffs Run Interceptor)
• A new Tunnel Dewatering and Wet Weather Pumping Station with a capacity for 20-mgd tunnel dewatering and 180-mdg wet weather pumping
• A relocated outfall and other near surface structures
  Traylor-Shea was awarded a $454.4 million contract to complete the final design and construct the Tunnel System Project. NTP was issued Dec. 1, 2020. The Traylor-Shea design-build team consists of Traylor Bros, Inc., and J.F. Shea Co., a joint venture, with support from Jacobs Engineering and Corman Kokosing Construction Co.

The Herrenknecht tunnel boring machine (TBM) achieved completion of the factory acceptance test on April 29, 2022, and arrived onsite in July 2022, with assembly starting in August, and boring beginning on Nov. 1. Boring of the Waterfront Tunnel was completed on March 13, 2024, as the TBM broke through into the Pendleton Street shaft, completing its 16-month journey.

The breakthrough occurred in a 100-ft-deep shaft immediately south of Oronoco Bay. This shaft will collect combined sewage overflows from an existing outfall and direct these flows to AlexRenew through the new 12-ft wide, 100-ft deep tunnel. The newly completed tunnel signifies a crucial connection point, as it marks the integration of AlexRenew’s wastewater plant with all four of Alexandria’s combined sewer outfalls that date back to the 1860s.

To complete the Waterfront Tunnel, more than 15,000 concrete segments were used and nearly 78,000 cubic yards of soil were removed.

The project also includes the 2,300 lf Hooffs Run Interceptor. The RiverRenew team announced in December 2024 that the interceptor has begun accepting flows. The commissioning of this piece of infrastructure will reduce the number of overflow events from Outfall 4 from 45 to less than 4. A portion of the interceptor was excavated using a Herrenknecht 76-in. MTBM.

“The completion of the Waterfront Tunnel and Hooffs Run Interceptor in 2024 marked tremendous milestones for our team and the community,” explains AlexRenew’s Director of Communication Matt Robertson. “As crews continue to make progress on the remaining components of the RiverRenew program, we’re closer each day to delivering healthier waterways to the region — it’s really exciting to witness.”