|Area watersheds. Image: DC Water|
The sea change in the city's 20-year timeline for cleaning up area rivers will happen only if DC Water can renegotiate a 2005 federal decree to build the full tunnel system. That consent decree from the Environmental Protection Agency emerged out of a lawsuit over DC's management of runoff in which several environmental groups were plaintiffs.
A decision on the future flow of the city's $4.6 billion Clean Rivers Project could come in the next week or so, a spokeswoman with the city's water authority, The District of Columbia Water and Sewer Authority, or DC Water, told DCMud this week.
"It might shift to a more green solution, or it might be a hybrid of the two: green and gray," DC Water spokeswoman Pamela Mooring told DCMud. Green infrastructure, here, refers to infrastructure that absorbs or uses water before it enters the sewer system in the first place. Gray solutions refer to engineering to deal with runoff after it happens - in this case, a massive tunnel infrastructure project to build underground storage tanks for overflow.
The water authority is making efforts to re-focus the Clean Rivers Project for an eight-year pilot "Low-Impact Development" program. The proposal could emphasize infrastructure like rain barrels and rain gardens instead of pipes that have been the mainstay of water channelling. DC Water says that approach - if it proves successful - could render two future pipelines, planned to keep run-off out of the Rock Creek and Potomac waters, obsolete, possibly saving millions of dollars. It notes that other cities including Kansas City and St. Louis have already experimented with similar versions of green infrastructure.
|Blue Plains Treatment Plant. Image: DC Water|
Old System, Old Problem
Regardless, consensus holds that the city must do something about its dirty water problem. About one third of DC's water system was built in the 1800's, before pipe systems separated storm water, or run-off from non-permeable surfaces, from sewage. That part of the system is called a combined sewer system (CSS), and when heavy rains like those from Hurricane Sandy hit the low-lying city, the CSS can't handle all the water and dumps it - along with sewage - into area watersheds, reducing water oxygen levels and killing wildlife at 53 documented places.
A portion of the pipeline system planned for the Anacostia River is already under construction. In 2011, DC Water awarded a $330 million contract to a joint proposal from Traylor brothers-Skanska-JayDee (TSJD) to build the first part of the system. The pipe, 23 feet in diameter, would be laid 100 feet underground and extend 12,500 feet from southwest DC, along the Potomac and under the Anacostia to about RFK Stadium. Slated for completion in January, 2018, the massive system will hold dirty water from the CSS until it can be piped to the Blue Plains Treatment Plant for processing in dryer weather. Of the scale of the project, DC Water General Manager George Hawkins called it "absolutely huge." "The machine our teams will use to build these tunnels is the size of a football field," and needs to be assembled underground.
|Image: courtesy Mike Bolinder, @AnacostiaRrkper on Twitter|
Riparian Repair - "Not a Zero Sum Game"
Although he supports a low-impact development approach, Anacostia Riverkeeper Mike Bolinder said it's an approach that he supports in combination with the full, planned tunnel system. "In general I love the idea of green infrastructure, but there is a consent decree in place."
Bolinder said yearly sewage overflow into all three DC watersheds amounts to 2.5 billion gallons.
On the money question, Bolinder said the CSS under the city was built in the time of Abraham Lincoln, so it makes sense that replacing it will cost some money. There is also the cost of maintaining and monitoring the efficacy of low-impact development. "If they don't maintain rain gardens, they stop retaining stormwater," Bolinder said. "Then we have the same system that we had beforehand, with a couple of rain gardens."
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