Facility Upgrade Gowanus Canal Flushing Tunnel and Pumping Station

Posted on July 8, 2014

Client: New York City Department of Environmental Protection
Location: Gowanus Canal
Project Period: 2011-Present
Project Cost: $141,000,000

Major Components

  • Tunnel Repairs
  • Concrete Repairs
  • Pump Station
  • Force Main
  • Sewer Reconstruction
  • Crew Quarters
  • CSO Screening
  • Compatibility with Historical Buildings

Project Description


The Gowanus Canal was originally constructed in the early 1860’s to improve industrial commerce in the area but became heavily polluted due to unregulated sewage and industrial discharges to its waters. To alleviate this problem, a Flushing Tunnel, along with a propeller pump building and gate house, were constructed in 1911 at the head of the Canal between Douglas and Butler Streets, to increase the flushing of cleaner, higher oxygenated water from Buttermilk Channel, through the Canal.

In the late 1960’s, the Flushing Tunnel system failed and was not immediately rehabilitated. In the mid-1980’s, the Gowanus Pumping Station was upgraded and a new 36-inch force main was constructed inside the tunnel. However, due to repeated force main failures beginning in 1991, the NYCDEP decided to abandon this force main and divert the flow back to the Bond/Lorraine Street sewer system. This operational change resulted in increased wet weather overflows to the Canal due to the capacity limitations of the sewer system.

Present Project

D&B Engineers and Architects, P.C. is leading the Gowanus Facilities Design Team, which includes the new tunnel access shafts, structural rehabilitation of the 6,000 foot long, 12-foot diameter brick tunnel, tunnel leak repair, Flushing Tunnel Pumping System (300 MGD design capacity); Flushing Tunnel Pump Building and Gate House; the Gowanus Pumping Station (30 MGD design capacity) serving the combined sewer system and screening of CSO while creating limited back-ups in the sewer system. In addition, planning and design is being performed for bio-retention, stormwater best management practices (BMPs). The improvements must be completed on a site which is less than two-acres, and be compatible with local historical buildings.

Issues to be investigated include, the following:

CSO Screenings

Project included one of the first installations of a horizontal rake screening system used to remove CSO flotatables. Capacity of screens is 200 mgd.
Design also included the ability to tip 650 MGD of flow without backing up the sewer system.


New access shafts, structural rehabilitation of the 6,000 foot long, 12-foot diameter brick tunnel using chemical grouting, replacement of damaged or missing bricks, repair of deteriorated motor joints, restoration of damaged or missing shotcrete lining and installation of new shotcrete lining. Concrete repair of existing tunnel shafts and chambers.

Sewage Pumping Station

Influent grinders followed by 4 submersible pumps having a total capacity of 30 MGD. Concrete repair of existing wet well.

Force Main

6,300 L.F. of FRPM pipe installed within a 100 year old 12 ft. Dia. brick sewer which also supplies the flushing water for the canal.

Project also involved microtunneling of several hundred linear feet under Columbia Street.

Flushing Tunnel Pumping System

The proposed upgrade to the Gowanus Canal Flushing System will involve the removal of the existing pump and the installation of three (3) vertical, submersible, axial flow pumps arranged parallel within the existing Power House. The three (3) submersible axial flow pumps will improve the reliability of the Flushing System and increase the peak capacity of the system from 192 mgd to approximately 252 mgd at mean high tide.

Stormwater BMP

Design of bio-retention stormwater BMP utilizing principles of low impact development and “green” design.

Temporary/Bypass Pumping

D&B designed a temporary pumping scheme for maintaining 20 mgd of sanitary flow during the 2 year construction period.


  • Facilities Planning
  • Hydraulic Modeling
  • Detailed Design
  • Stormwater Bio-retention Design
  • Presentation to Art Commission
  • Environmental Review and Permitting
  • Cost Estimates
  • Construction Services

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