Gowanus Canal Flushing Tunnel, Brooklyn

Alert reader Elizabeth Barry wrote:

so i've been wondering about the path of the engineered watercourse that allegedly runs beneath Brooklyn carrying water from the East River to the Gowanus Canal. Common knowledge about the "Flushing Tunnel" is that its purpose is to flush out the stagnant water at the top of gowanus canal, the remnant of a pre-red hook tidal wetlands. I've heard that the tunnel and pump has been revived in the past 10 years or so, with some work done by Hydroqual.  Its path under BK is not self-evident - I'd like to find out where the inlet is from the East River, and the course it takes.....

The Flushing Tunnel flushes water between New York Harbor and the Gowanus Canal in Brooklyn, to help reduce stagnation in the heavily polluted canal. It was created in 1911 using a steam-driven propeller to drive the water; it broke in the 1960s, and was repaired finally in 1999. The city offers a press release from 1999 telling about the canal:
http://www.nyc.gov/html/dep/html/press_releases/99-28pr.shtml

Below is a very basic map of the tunnel, taken from gothamist, which in turn apparently got it from the DEP:

The Gowanus Dredgers Canoe Club has an excellent history of the canal and neighborhood:
http://www.waterfrontmuseum.org/dredger/history.html

Other links:
http://en.wikipedia.org/wiki/Gowanus_Canal
http://www.brooklyncb6.org/neighborhoods/?a=detail&content_id=58
http://gothamist.com/2007/04/09/gowanus_flushin.php
http://home2.nyc.gov/html/dep/html/press_releases/05-07pr.shtml

A nice map showing the location of the pumping station at the head of the canal:
http://www.communitywalk.com/view/172018#00046gIi