The last piece of the Anacostia sewage tunnel system is halfway completed, so in a matter of less than three years the Anacostia will be the cleanest river to take a swim in after a rainstorm in the metro area. Citizens need to understand what this is all about and how it happened that nearly all the cities in the country that date back to the 19th century ended up with the problem of sewage overflowing into their rivers in a rainstorm.
Back then, engineers planning sewer systems in cities determined that the best way to keep sanitary sewage moving through the system was to combine it with the storm sewers so that runoff from the streets would occasionally flush the sewer lines. So “combined sewers” became the practice and provided a solution until paving all the streets and putting up large buildings left too little open ground to absorb the stormwater. So the combined sewers became overloaded. There had to be a better solution than letting them back up into everyone’s homes and businesses, so the idea was formed to discharge the “combined sewer overflow” or CSO into each city’s streams and rivers.
While this was at first thought to be a solution for occasional use, as cities grew and got denser and more paved, the frequency of CSO events went up. In the Anacostia, there were eventually 14 CSO locations and an average of 20 overflows of the combined sewage each year—more in wet years. For comparison, the Potomac has 10 CSO outfalls and an average of 77 overflows each year, and Rock Creek has 23 outfalls and 33 events. This is from DC Water data and estimates. In addition to the loadings of high levels of bacteria in the water as a danger to humans, the overflows harm fish, shellfish, and underwater grass habitat with bacteria, sediment and low oxygen levels. Each overflow impacts the receiving waters from one to three days, depending on the severity of the rain event.
As far as improvements are concerned, we in the Anacostia will be getting the most thorough reductions because we were first and our improvement plan uses the most extensive system of tunnels to achieve a 98 percent drop in overflows. Part of this is due to the inclusion of a tunnel to the north end of the combined sewer area along Rhode Island Avenue to reduce flooding and standing contaminated water in neighborhoods in near northeast and northwest DC.
The tunnels are deep and large – slightly bigger than Metro tunnels – in order to handle the volume and store it underground until it can be treated by the Blue Plains Advanced Wastewater Treatment Plant along the Potomac. Some have asked why the alternative has not been considered to simply replace the combined sewer areas with separate sewer lines as are used in the newer parts of the metro area. The answer is two part: First, such an approach would require extensive excavation and restoration along all the streets and other public areas, whereas the tunnels can be drilled deep underground with little surface disruption to where the connections can be dropped straight down. Second, the tunnels store both sanitary and stormwater; separation would mean that the stormwater would go directly to the River and increase flooding, floating trash and erosion. By using the tunnels, disruption is less and the River is protected from a major influx.
The waterfront tunnels are complete and operational, including from RFK stadium along the River and across it above the Navy Yard to connect with the existing tunnel to Blue Plains under the Poplar Point area of Anacostia. Improvements in the water quality during and after storm events have already been observed because these tunnels are capturing large amounts of combined sewage that would have entered the River through the overflows.
The last tunnel is the segment to Rhode Island Avenue, called the Northeast Boundary Tunnel, which has reached the half-way point in its journey from the connection on the River, north to the edge of the National Arboretum, then northwest to join Rhode Island Avenue at about 10th St NE and then west on Rhode Island to 6th and R Streets, NW. It is on time for completion in the summer of 2021. There will then be a period to make the flood-control improvements in the area and connect the CSO lines to the tunnel. Completion date for the entire project is 2023.
Construction on this tunnel segment is being carried out by DC Water 24 hours a day, five days a week. The tunnel boring machine operates at the rate of 4 inches a minute and stops every six feet to place a linear ring segment comprised of 7 interlocking pieces. There are other innovative parts of the tunnel effort. Businesses at street level are being assisted with programs to enhance their access and front appearance to overcome any negative effects of the construction access sites. The access site fences are wrapped in large works of art produced by students at Howard University, as shown in the photo. The hiring goals of DC Water are that 51% of the workforce is DC residents and that 60% of all new jobs associated with the CSO reduction program go to DC residents.
When completed, the entire Anacostia River Tunnel System will be 13.1 miles long, and send 98% of combined sewage direct to Blue Plains Treatment Plant. Anticipated overflows to the Anacostia are estimated at 1 or 2 per year, and those will be at times the River is so full that whatever is added will move quickly into the Potomac. For more information, check dcwater.com/cleanrivers. You may also contact the DC Water Office of Marketing and Communications at 202-787-2200.
Just remember, it won’t be long before you will be able to call up your friends in Georgetown and Northwest DC and invite them to come swim with you in the cleanest river around – the Anacostia!
Bill Matuszeski is a member of the Mayor’s Leadership Council for a Cleaner Anacostia River, and the retired Director of the Chesapeake Bay Program. He also serves on the board of Friends of the National Arboretum and on Citizen Advisory Committees for the Chesapeake and the Anacostia.