Date: Thu, 03 Jul 2014 18:39:30 -0400
From: mark <whitroth at 5-cent.us>
To: undisclosed-recipients:;
Subject: [WSFA] Inside D.C.'s Massive Tunnel Project
Reply-To: WSFA members <WSFAlist at KeithLynch.net>

Excerpt:
The new tunnel is a central piece of D.C.'s $2.6 billion Clean Rivers
Project, a 20-year effort spanning 2005 to 2025. The goal is to get the
Potomac and Anacostia rivers swimmable and fishable again, says Ray. (See
"Fishing the Forgotten River in the Nation's Capital.")

Storm water collected in drains off city streets will be channeled into
the new 13-mile (21-kilometer) tunnel, which will run parallel to the
rivers and empty into the soon-to-be expanded Blue Plains water treatment
plant.

The new excavations correct a problem that dates from the 19th century,
when the city was fitted with a "combined sewer overflow" system. A
combined system means storm water and sewage are channeled into the same
pipes. About 750 communities around the country still use this system,
notes Ray.

On dry days, the pipes are big enough to move that combined flow to local
water treatment plants. But if the city gets more than a quarter inch of
rain at one time, the system is overwhelmed, and engineers have to divert
the entire flow\342\200\224sewage and all\342\200\224directly into the local rivers.

Washington has been diverting three billion gallons of raw sewage into the
rivers on an annual basis, says Ray. The Anacostia takes the brunt of that
flow, which is especially bad for its water quality because impurities
tend to linger in slower and shallower rivers.

In 1987, Congress passed an amendment to the 1972 Clean Water Act that
required major cities to address pollution from combined sewer overflows.
However, many cities struggled with the financial burden of fixing their
aging infrastructure.
--- end excerpt ---

<http://news.nationalgeographic.com/news/2014/07/140703-combined-sewer-overflow-washington-storm-water-tunnel/>

        mark