Conditions of Alexandria's Combined Sewer  System - Learn more.

Frequently Asked Questions About RiverRenew

General

RiverRenew is a major initiative being undertaken in response to a 2017 Virginia law that was passed thelp achieve cleaner, healthier waterways in Alexandria. The project features a new network of deep tunnels and sewers that will connect to four outfalls in Alexandria that currently pollute our waterways on rainy days. The new tunnel system will capture millions of gallons of sewage mixed with rainwater for treatment at AlexRenew, and the cleaned water will be returned to the Potomac River.  

Portions of the City of Alexandria use a combined sewer system (CSS) that allows sewage to mix with rainwater on rainy daysSewage mixed with rainwater is called “combined sewage.” In a CSS, only one pipe is designated for transporting both sewage and rainwater. When it’s not raining, these pipes transport sewage for treatment at AlexRenew.  

 

On rainy days, the capacity of these combined sewer pipes is often exceeded. Instead of being transported and treated at AlexRenew, combined sewage overflows into Alexandria’s waterways via four outfalls. Currently, these overflow events occur approximately 70 times a year, resulting in bacteria, trash and other pollutants flowing into local waterways, including Hooffs Run, Hunting Creek and the Potomac River.  

In April 2017, Virginia passed a law requiring Alexandria to remediate all four of its combined sewer outfalls. The law, Senate Bill 898, introduced by Senator Richard H. Stuart (District 28), requires Alexandria’s combined sewer outfalls to be brought into compliance with state and federal law by July 1, 2025.

RiverRenew is the name of the solution to Alexandria’s combined sewer issue. RiverRenew includes the following major components:  

  • A two-mile-long, approximately 100-foot-deep tunnel 
  • New sewer infrastructure 
  • Upgrades to AlexRenew’s wastewater treatment plant 

Together, these components will allow for the capture, storage and treatment of millions of gallons of combined sewage, instead of overflowing into Alexandria’s waterways.  

RiverRenew will prevent millions of gallons of combined sewage from contaminating our waterwaysThreduction in the frequency and volume of combined sewage will reduce the amount of bacteria, trash, and other pollutants flowing into Hooffs Run, Hunting Creek, and the Potomac River. Through RiverRenew, we can achieve safer waterways for our community, a healthier environment for our wildlife, and cleaner waterways for future generations. 

Led by a five-member citizen board, AlexRenew is a special-purpose authority that has been serving the City of Alexandria and parts of Fairfax County for the last 60 years. AlexRenew treats an average of 35 million gallons of wastewater per day from more than 300,000 people at its water resource recovery facility, located in Alexandria’s southwest quadrant.

In keeping with our water protection mission, AlexRenew, with support from the City of Alexandria, will lead the planning and construction of RiverRenew to ensure its implementation by 2025. AlexRenew has demonstrated success in building and operating large-scale infrastructure. AlexRenew’s facility will serve as the main construction site for the proposed tunnel system to minimize community impact. Additionally, the combined sewer flows collected by the tunnel system will be delivered to AlexRenew for treatment.

Construction related to RiverRenew is estimated to cost between $465 million up to $596 million.

RiverRenew will be funded primarily by sewer rate increases. These rate increases will help pay down the debt from the loans acquired to keep RiverRenew on track and meet the mandated deadline of July 1, 2025. AlexRenew and the City of Alexandria have secured preliminary commitments for low interest loans through state and federal programs. In April 2019, the Virginia General Assembly appropriated $25 million in grant funding for RiverRenew. The Commonwealth has a long-standing policy of financial partnership with localities dedicated to infrastructure projects, like RiverRenew, that benefit local waterways.

In May 2019, AlexRenew Board of Directors approved rate increases to start funding RiverRenew. The first increase of 13% went into effect on July 1, 2019. A second increase of 11% was approved to start on July 1, 2020.

In June 2020, AlexRenew approved an updated Fiscal Year 2021 budget which will lower the previously approved rate increase of 11% to 6.6%. This updated rate increase equates to an average increase of about $3 per month for the average homeowner and will go into effect on July 1, 2020.

AlexRenew anticipates that the next rate increase to fund RiverRenew will occur in July 2021. The amount of this rate increase has not yet been determined. Overall sewer rate increases for RiverRenew are estimated to total between $20 and $40 per month on top of current sewer bills.

Planning and Design

Existing combined sewers will be connected to the new tunnel system through new infrastructure called diversion facilities. Diversion facilities are concrete structures that consist of three main components: 

  • Diversion chamber to divert flows from the existing combined sewer; 
  • Drop shaft to “drop” captured flows 100-feet down to the tunnel; and 
  • Ventilation control vault to regulate air into and out of the tunnel. 

Diversion Facility 3-D Graphic

Diversion Facility Model (Click to Enlarge)

Check out this video of our scale-model drop shaft to see this process in action.

To build the new tunnel system, RiverRenew will use a state-of-the-art tunnel boring machine (TBM) that will: 

  • Erect the tunnel 100 feet below ground without digging up major portions of the city; 
  • Excavate soil and install a new concrete tunnel in the void that is created; and 
  • Remove soil through the TBM and along the newly created tunnel, then lift it to the surface at AlexRenew. 

Check out this page to take a guided tour of a TBM. 

AlexRenew, with cooperation from the National Park Service, completed an Environmental Assessment to evaluate potential impacts of RiverRenew on the environment, community and cultural resources. The Environmental Assessment process solicited significant feedback from the community to establish a preferred alternative for the tunnel system that includes: 

  • Waterfront Tunnel: 12-foot-diameter tunnel that features an east-west alignment largely under Church Street, a north turn under Jones Point Park, and routing under the Potomac River until reaching Oronoco Bay. 
  • Outfall 001 Diversion Facility: located on the northeast corner of the Robinson Terminal North site.
  • Outfall 002 Diversion Facility: located at Royal Street, just south of the entrance to Jones Point Park. 
  • Hooffs Run Interceptor: 6-foot diameter open-cut sewer along Hooffs Run. 

 

Outfall 001 Diversion Facility

 

Outfall 002 Diversion Facility

 

Hooffs Run Interceptor

Combined sewage captured by the tunnel will flow by gravity to AlexRenew’s water resource recovery facility, where it will be pumped to the surface and treated before being returned to the Potomac River at Hunting Creek 

Odors associated with the tunnel system operation are not anticipated to be an issueThe tunnel system will feature built-in measures to mitigate the potential for odors. These include components to regulate the air flow in/out of the tunnel and odor control units that will filter potentially odorous air. 

RiverRenew is collecting soil samples and environmental data at select locations within the City of Alexandria. These subsurface explorations are called borings, and the data collected help us understand the conditions below ground to design and build solutions best suited to our local geology. You can learn more about these borings and our drill rigs here.

The impacts of climate change on the RiverRenew tunnel system, in the form of increased rainfall and sea level rise, have been consideredThe performance of the proposed infrastructure under year 2100 climate conditions was analyzed and summarized in this informational flyer. 

Construction

In August 2019, construction began at AlexRenew’s water resource recovery facility to upgrade existing infrastructure and prepare for the tunnel system construction. Construction of the tunnel system is anticipated to begin in 2021.   

To comply with Virginia law, RiverRenew must be operational by July 1, 2025. 

The tunnel will be built deep below ground – approximately 100 feet  using a state-of-the-art tunnel boring machine that stabilizes the external soil and groundwater as they move. This technology significantly minimizes the potential for ground movement, resulting in no disruption at the surface. 

A Documentary Study was prepared for RiverRenew to identify existing historic structures and assess potential archeological resources within the proposed surface disturbance areas.  A thorough Protection-of-Structures program will be implemented to minimize the potential impacts to historic structures in construction areas.

AlexRenew is also coordinating with federal and state agencies, as well as Alexandria Archeological Commission, to determine the scope of additional pre-construction archeological investigations and monitoring requirements during construction.   

Yes. Some of the locations where RiverRenew facilities will be constructed are within urban fill and/or located near former industrial facilities. RiverRenew is currently conducting an environmental exploration and characterization program to identify and analyze concentrations of potential contaminants in the areas of proposed ground disturbance. When working in areas with contaminated soils and groundwater, exposure pathways to workers and the public will be minimized utilizing best management practices and other methods approved by the VDEQ. 

The risk of exposure to the general public is negligible. Work sites will be fenced, securedscreened, and will use dust mitigation techniques. Trucks transporting excavated soils will be equipped with tied-down tarps to ensure materials leaving the site are fully contained. Trucks leaving the construction sites will also pass through wheel washes and be inspected prior to entering City streets. Additionally, street sweeping along proposed haul routes and adjacent to the construction sites will be conducted on a regular basis. Any impacted groundwater will be pre-treated on site before entering the sewer system for further treatment at AlexRenew 

Haul routes are at the discretion of the City of Alexandria Department of Transportation and Environmental Services (T&ES). Based on coordination to date between AlexRenew and T&ES, potential haul routes are depicted in the figure below. 

Construction hours are at the discretion of the City of Alexandria Department of Transportation and Environmental Services (T&ES). Based on coordination to date between AlexRenew and T&ES, anticipated work hours will take place during the hours of 7:00 a.m. – 6:00 p.m., Monday – Friday. 

Construction activities related to RiverRenew are not anticipated to impact private properties. 

Learn More

X