Gowanus Facilities Upgrade Named CMAA Metro NY/NJ Honorable Mention Project of the Year

The construction of the Service Building, CSO Screening System, Wastewater Pumping Station and Flushing Tunnel Building required an extensive amount of subsurface and foundation work.

The new Flushing Tunnel Pumping System was upgraded by replacing the existing 7-foot diameter propeller with an average flow of 154 mgd with three axial flow pumps and new intake/discharge chamber capable of pumping at a rate of up to 252 mgd from the Buttermilk Channel (East River) to Gowanus Canal.

The new Service Building was constructed in the footprint of the existing crew quarters building, housing the electrical systems required to operate the facility.

As part of this project, the tunnel section underneath the Flushing Tunnel Building was demolished and new Flushing Tunnel intake and discharge chambers were constructed. This involved an extensive subsurface planning and monitoring effort to install the excavation support system underneath the 100-year old brick masonry building while ensuring the foundation and superstructure were not compromised.

The 12-foot diameter tunnel was shutdown and dewatered for the duration of construction to facilitate the installation of the new 33-inch force main within the tunnel, several access structures, and tunnel brick repairs.

(NEW YORK, NY – May 8, 2017) – The Gowanus Facilities Upgrade – Flushing Tunnel Modernization and Wastewater Pump Station Reconstruction project was selected as the CMAA Metro New York/New Jersey Honorable Mention Project of the Year (Category 4 – Projects Greater than $100 Million).

The main objectives of this project were:
• Improve water quality in the Gowanus Canal,
• Reduce Combined Sewage Overflow (CSO) events and
• Upgrade the Gowanus Wastewater Pumping Station.

Hazen and Sawyer provided construction management services to help the NYCDEP achieve these important goals and consistently meet NYSDEC water quality standards in the canal.

To modernize and increase the capacity and reliability of the Gowanus Flushing Tunnel, the new Flushing Tunnel Pumping System was upgraded by replacing the existing 7-foot diameter propeller with an average flow of 154 mgd (million gallons per day) with three axial flow pumps and new intake/discharge chamber capable of pumping at a rate of up to 252 mgd.

The 12-foot diameter tunnel was dewatered for the duration of the construction to facilitate the characterization, cleaning and disposal of approximately 6,000 linear feet of biological film on the tunnel walls, repair of concrete and brick sections of the tunnel including utilizing shotcrete for concrete rehabilitation, repairs to several leaks within the tunnel, installation of the new 33-inch force main within the tunnel, and construction of several access structures along the tunnel.

The wastewater pump station upgrade from 22 mgd to 30 mgd required the installation of a new CSO Screenings and Level Control System upstream of the pump station. This system consisted of six hydraulically-actuated bending weirs, continuously raked uptake bar screens (hydraulically-actuated), oscillating baffles, and a new CSO overflow extension. This extension was constructed next to the influent sewer and then connected by saw cutting the existing sewer wall. The CSO overflow area had consisted of four existing wooden timber tide gates to prevent canal water from flooding the sewer system, which were replaced with four new stainless steel 12-foot tide gates.

The 24th Annual CMAA Metro New York/New Jersey Awards Banquet will be held at the Yale Club on Friday, June 9, 2017.

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