NEW YORK — New York City Department of Environmental Protection (DEP) Commissioner Carter Strickland announced a pilot program to remotely measure the frequency and volume of combined sewer overflows (CSO) at five outfalls, which will be used to guide DEP’s green and grey capital infrastructure investments. Under the NYC Green Infrastructure Plan, launched by Mayor Bloomberg in 2010, DEP will invest more than $187 million over the next three years and an estimated $2.4 billion of public and private funds by 2030 to reduce CSOs by capturing stormwater before it enters the city’s combined sewer system. The goal of the pilot sensor program is to collect accurate real-time data which will be used for many purposes, including guiding the future installation of traditional gray, as well as green, infrastructure.
“This technology will help us develop the most cost-effective long-term plans to further reduce CSOs,” said Commissioner Strickland. “By collecting real-time data on the location and volume of overflows and cross-referencing it with highly localized rainfall totals and land use patterns, we will be able to focus our infrastructure upgrades to achieve the greatest possible reduction in CSOs. This project delivers on a key element of the NYC Green Infrastructure Plan to research and implement cutting edge technology to measure CSOs.”
Like other older urban areas, New York City is largely serviced by a combined sewer system where stormwater and wastewater are carried through a single pipe. During heavy rain storms, the system can exceed its capacity and must discharge a mix of stormwater and wastewater into New York Harbor. Since 2002, New York City has invested approximately $10 billion to reduce CSOs and upgrade wastewater treatment plants to increase capacity. Capital investments have included the construction of four CSO storage facilities with the capacity to hold approximately 120 million gallons of wastewater until it can be properly treated. These storage facilities reduce CSOs by more than 2.7 billion gallons annually. DEP will monitor how accurately the new sensors measure the volume of CSO released at each outfall, and determine whether they can reliably transmit data instantaneously.
The new sensors will complement the 108 sensors currently installed at combined sewer outfall locations. The current sensors cannot detect the direction or rate of flow making it difficult for DEP to measure the volume of CSO or to distinguish between discharges and tidal inflows. The goal of the new sensors is to measure wastewater elevation and both the direction and rate of flow. This will allow DEP to improve its development of long term plans to reduce CSOs and to consider enhancements to the system that alerts the public when they occur.
The five real-time monitoring sensors have been installed at the following combined sewer outfalls:
• Near the Navy Yard, which empties into the East River
• In Dutch Kills, which ultimately feeds into Newtown Creek
• At the Gowanus Canal
• Near Soundview Park, which empties into the Bronx River
• Near Gravesend Bay
DEP is also planning to add three additional monitoring sites at outfalls leading into the Hudson River, the upper East River and Jamaica Bay.
In addition to guiding efforts to reduce CSOs, if the sensors prove reliable they may be integrated into DEP’s public notification system. In recent years, DEP has taken numerous steps to expand public access to information about harbor water quality:
• In February 2011, DEP finished replacing combined sewer outfall signs at a cost of $1 million. The new signs not only meet the requirements of the New York State Department of Environmental Conservation, but are easier to read from a distance, have clearer warnings of wet weather events, and have graphic images that convey unambiguous warnings about recreational use to English and non-English speakers alike.
• In September 2011, DEP, for the first time, began posting weekly harbor water quality data online, available at www.nyc.gov/dep.
• Last year, DEP partnered with the New York City Office of Emergency Management to announce that Notify NYC, New York City’s official notification system, will now issue advisories when heavy rain is likely to cause untreated wastewater discharges into the city’s waterways.