RiverRenew: Alexandria's Biggest Ever Public Works Project
RiverRenew: Alexandria's Biggest Ever Public Works Project
AlexRenew board members Jim Beall and John Hill describe the massive tunnel project designed to remedy the city's rainwater and sewage overflows.
RiverRenew: Addressing Alexandria’s Combined Sewer Overflow Problem
RiverRenew is a $615 million water quality improvement project implemented by Alexandria Renew Enterprises (AlexRenew.) Established in 1952, AlexRenew is the independent authority that manages water treatment for over 300,000 customers in Alexandria and parts of Fairfax County.
RiverRenew is the biggest public works project in Alexandria’s history. You can find out more than you might want to know about AlexRenew and RiverRenew
RiverRenew is designed to eliminate the annual discharge of over 140 million gallons of combined rainwater and sewage in local streams and the Potomac River from the 60-70 rain-caused overflows every year. These overflows originate from areas in or near Old Town that date from the 1800’s where the storm and sanitary sewers are combined. A moderately heavy rain causes pipes (which would otherwise carry water to AlexRenew’s water treatment plant on Holland Lane) to overflow into the Potomac at four outfall sites.
AlexRenew’s service area, four pumping stations, four combined sewer outfalls, 20 miles of interceptors, and the location of the combined sewer system are shown below. An interceptor receives sewer flows from smaller sanitary sewer lines. It is essentially a main “artery” or “trunk” that brings sanitary sewer flows to the wastewater treatment plant.
In 2017, the Virginia General Assembly passed a law mandating that Alexandria solve its combined sewer overflow problem by 2025. Accordingly, the city government, and everyone interested in the Potomac River’s health, have a significant stake in RiverRenew.
How AlexRenew Operates
AlexRenew is governed by a five-member board of directors appointed by the City Council. The board consists of Adriana Caldarelli, Bill Dickinson, John Hill and Jim Beall. A vacancy on the board is expected to be filled soon. Beall describes his colleagues as a “board of nerds” interested in the details of public infrastructure engineering and finance.
Hill marvels at the number of opportunities for Alexandrians to participate on the city’s boards and commissions. He has been active in city affairs for years, including serving on the city’s Budget and Fiscal Affairs Advisory Committee. He said that in 2014 the former Alexandria Sanitation Authority rebranded itself as AlexRenew “out of necessity” when the water company declined to include sewer bills on its customer invoices.
Beall, a civil engineer, was recruited for the AlexRenew board by a former board member who was leaving the city. He said of his involvement, “It was probably a desire to put engineering to work for the city.”
Hill said, of the combined sewer system overflows, “Alexandria is not unique in this problem.” Hill said that the District of Columbia is building 22 miles of tunnels that are 20 feet in diameter.
Beall said, “We were late to this party. I think everybody—Council, city engineers, City Manager, AlexRenew—realized that we really did need to take care of this. It has probably been in the back of everybody’s mind for 10 to 15 years…there is a solution to it, but it’s not cheap.”
“The fact that we have a river that big running through a major city and high school kids can row on it—it’s a gift,” Hill said, “The water we [AlexRenew] return to the Potomac is cleaner than the water that’s there.”
How RiverRenew is Funded
RiverRenew will be paid for through financing package that includes low-interest loans from the Environmental Protection Agency’s Water Infrastructure Improvement and Innovation Act (WIFIA) and Virginia’s Clean Water Revolving Loan Fund (VCWRLF), federal and state grants, and sewer rate increases.
AlexRenew signed loan agreements in early 2021 for a 40-year $321 million loan from the WIFIA program at 1.88% interest and a 30-year loan from Virginia’s VCWRLF program for $185 million at 1.35% interest. Hill said, “The real story is the loans. I think it [RiverRenew’s relatively low cost of capital] is really to the credit of AlexRenew’s finance team.”
AlexRenew also received $140 million in state grants and federal American Rescue Plan Funds to help offset sewer rate impacts.
In July 2021, AlexRenew adopted a two-year sewer rate adjustment to fund RiverRenew and support upgrades at its wastewater treatment facility. The two-year rate adjustment increased sewer rates by 6.5% on July 1, 2021 and July 1, 2022. An average residential customer is expected to pay an increase of about $3 per month or $36 per year.
Hill said, “Our rate strategy was a gradual, predictable increase in rates over a 5-year period instead of a big jump at the end and a big jump at the beginning.”
Why A Massive Tunnel is Required
Beall said three possible approaches to the combined sewer problem were considered: 1) digging up most of the streets in Old Town to put in separate sewers (a disruptive and costly option), 2) building a huge storage tank in Oronoco Park and pumping water to AlexRenew’s plant through the existing pipes, and 3) two tunnels, one in Old Town and one to deal with water going to the Duke Street outfalls.
The ultimate decision was to construct a single tunnel along the waterfront to AlexRenew’s water treatment plant which is positioned between the end of the new tunnel and the new Hooffs Run Interceptor. The Hooffs Run Interceptor is not a storm water pipe, nor does it collect stream flows from Hooffs Run—it is designed to collect separate sanitary and combined sewage. It is so named because of its location along Hooffs Run.
The tunnel will also connect to diversion facilities that will collect flows at each outfall to the tunnel direct them to the water treatment plant. Here is a graphic representation of a diversion facility.
The two mile tunnel, 12 feet in diameter, will capture sanitary sewer and rainwater flows that currently enter local streams and the Potomac when it rains. The tunnel will run from the Oronoco Bay Park outfall to AlexRenew’s water treatment plant at the end of Holland Lane.
Hazel: An Underground Space Ship
One of key technologies critical to RiverRenew is Hazel, a massive tunnel boring machine (TBM.) Hazel was made in Schwanau, Germany by Herrenknecht AG, a leading TBM manufacturer. Hazel is about to start underground work on RiverRenew. Hazel’s 380 tons of components were shipped to Alexandria by freighter, barge and truck. Anyone interested in acquiring a TBM can learn more about Herrenknecht AG
According to AlexRenew’s General Manager, Karen Pallansch, it cost $24 million to have Hazel built and delivered to Alexandria.
Hazel is named for Hazel Johnson who devoted her life to fighting negative ecological effects in her Chicago community. Johnson founded People for Community Recovery and was posthumously awarded the Congressional Gold Medal.
There were 97 boring samples taken to assess the mix of clay and alluvial soil that Hazel will tunnel through. Hazel took months to build and does more than just chew through dirt with its giant cutterhead (think of a huge mechanical lamprey.)
This is a graphic cross-section showing Hazel’s complex operating system. The best way to understand how Hazel works is to click on the cross-section and save it as a JPEG file. You should then be able to expand the image.
RiverRenew and the Future of the Potomac River
Beall said that a common misperception is that RiverRenew will solve the city’s persistent flooding problems. RiverRenew is a water quality project, not a flood control initiative.
RiverRenew’s ultimate success depends on regional cooperation, especially because Alexandria is downstream from the District of Columbia. If the District of Columbia and AlexRenew can substantially reduce or eliminate combined sewer outflows Alexandria may realize Beall’s dream of “a fishable and swimmable Potomac.”
Helpful explanation, thank you. The fish in the tank are striped bass, I believe. The small ones that grow up in the Potomac we fishers call "schoolies." With cleaner water there will be more, I hope!