From Mandate to Milestone: Implementing a Major CSO Program in 7 years

The City of Alexandria is a nationally designated historic district founded in 1749 with more than 900 acres of parks and dedicated public space. Like many older cities in the United States, the City is served by combined sewers, which discharge excess flows into local waterways via four permitted CSO outfalls. In April 2017, the Virginia General Assembly passed a new law requiring an accelerated schedule to address the discharge of combined sewage to the Potomac River and its tributaries. In response to the law, Alexandria Renew Enterprises (AlexRenew), with support from the City of Alexandria, developed the RiverRenew Program to meet strict regulatory requirements and aggressive timeline.

RiverRenew is the largest infrastructure initiative in the history of Alexandria, VA with an estimated capital cost of $615 million. The Program encompasses four major projects: a storage and conveyance tunnel system, upgrades to AlexRenew’s primary pumping capacity at its wastewater plant, relocation of facilities and decommissioning of AlexRenew’s former administrative building, and wet weather treatment.

The schedule stipulated by the 2017 law requires the tunnel system – the largest of the four projects – and other controls to be in place by July 1, 2025. AlexRenew worked expeditiously on parallel tracks to advance conceptual-level designs, comply with the National Environmental Policy Act through the development of an Environmental Assessment with the National Park Service, and acquire the necessary permits and agreements needed to build the tunnel system. In addition, AlexRenew simultaneously developed and implemented a design-build procurement approach for the tunnel system, analyzing potential impacts on the community and cultural and environmental resources, mitigating risks, and evaluating innovative construction techniques to minimize costs.

Construction of the tunnel system began in December 2020 to meet the legislative mandate and is currently ongoing at all project sites. Design is anticipated to be complete in early 2023, with 37 of 54 design packages already finalized. The over two-mile-long, 14-month journey of the tunnel boring machine began in October 2022. Overall, the Project is 34 percent complete, on-track to meet the mandate and bring healthier waterways to Alexandria.