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Development of a System to Maintain Satisfactory Dissolved Oxygen Levels in Gowanus Canal, New York City

New York City Department of Environmental Protection
New York City, New York

Upcoming construction work related to facilities upgrades will require a shut down of the Gowanus Flushing Tunnel for approximately 26 months. During this time, DO levels in the Canal are expected to drop to unsatisfactory levels. To address this problem, an interim system was developed to maintain satisfactory DO levels throughout Gowanus Canal at all times during a typical year. This centralized oxygenation system would withdraw Canal water at a rate of approximately 0.43 m3/s, oxygenate it to between 16 mg/L and 40 mg/L (as necessary to maintain desired ambient oxygen levels), and then discharge it via a diffuser system featuring 51 nozzles: one at the head end to support DO levels there, and 50 spaced 12 to 15 m apart between Sackett Street and the 4th Street turning basin—a reach of the upper Canal with minimal boat traffic and water depths of at least 1.2 m at mean low tide. The diffuser system is expected to achieve mixing across the width of the Canal without disturbing bottom sediments as long as the discharge ports can be placed at least 0.6 m below the surface and 0.6 m above the bottom at MLW. In a typical year, the system would need to operate from April through November. With the system discharging about 1,500 kg/d of oxygen (discharge concentration about 40 mg/L), the results show that DO levels of 3.0 mg/L would be maintained throughout the length of the Canal continuously throughout a typical year. Reducing the discharge to 40 percent of that level (600 kg/d of oxygen, or a discharge concentration of 16 mg/L) is projected to maintain satisfactory DO levels throughout most of the year and minimum DO levels of at least 1 mg/L throughout the Canal at all times. Source: WEFTEC 2009 Proceedings


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Posted: August 27th, 2010 | Filed under: Uncategorized | Tags: , | No Comments »