Inflatable Dams Check Harbor H20

Devices Will Retain The Overflow From Sewers

Department of Environmental Protection (DEP) Commissioner Carter Strickland announced the completion of a $15.7 million project to reduce pollution by installing two inflatable dams within existing large sewer lines that will temporarily store a mix of stormwater and wastewater that might otherwise be discharged as combined sewer overflow (CSO) into New York Harbor.

At left, an inflatable dam that will be used to help keep New York Harbor clean. At right are sensors designed to monitor the discharge of sewer overflow into the harbor.

The two inflatable dams are attached to the base of the sewers and have a controlled mechanism with automated sensors that cause the dam to inflate during rain events. Once the storm subsides, the rubber dams have the ability to deflate quickly and allow the stored flow to reach one of two wastewater treatment plants for treatment.

The dams are monitored remotely by the Newtown Creek and Red Hook wastewater treatment plants where the retained CSO is conveyed. The inflatable dams are part of the strategy to improve the New York City sewer system to better manage flows, a component of the NYC Green Infrastructure Plan, which calls for investing $2.4 billion over the next 20 years to help reduce combined sewer overflows.

Each dam can retain more than two million gallons of wastewater per rain event and will help avoid up to 100 million gallons of combined sewer overflows into the harbor every year.

This is the first time this technology is being used in New York City to help upgrade the water quality in the city’s waterbodies.

“We are using all available technology to keep New York City Harbor the cleanest it has ever been in the last 100 years,” said Strickland. “Investments like this show the city’s and Mayor [Michael] Bloomberg’s commitment to bring innovative ways to upgrade critical infrastructure. The inflatable dams will give us the opportunity to retain and treat more combined sewer overflow before it reaches the harbor, opening up waterfront development and recreational opportunities to the benefit of all New Yorkers.”

The inflatable dams are located entirely underground at two different locations in Brooklyn. One facility is located at Kent Avenue and South Fifth Street in Williamsburg and is controlled by the Newtown Creek Wastewater Treatment Plant. The other dam is at Gold and Plymouth Streets in Red Hook and is controlled by the Red Hook Wastewater Treatment Plant.

Inflatable dams are long, cylindrical flexible rubber structures anchored to a concrete base. The rubber dams require relatively little maintenance, do not corrode or require painting and are durable under ex- temperature or harsh conditions.

The inflatable dams are part of the city’s efforts to optimize the sewer system-an element of the NYC Green Infrastructure Plan. In addition to system optimization and traditional grey infrastructure investments, the plan proposes a total investment of $2.4 billion over the next 20 years in green infrastructure to improve harbor water quality by capturing and retaining stormwater runoff to help reduce CSOs into the harbor.

Of the $2.4 billion, $900 million is expected to be funded through regulations on new developments that were adopted on Jan. 4. The DEP’s most recent 10-year capital plan dedicates $735 million to building green infrastructure.

Most green infrastructure includes vegetated features such as bioswales and green roofs, or structural aspects such as porous pavement, and sewer reconfigurations, which can absorb and retain stormwater. These projects effectively increase stormwater retention times and allow more efficient treatment of CSOs at wastewater treatment plants.

Two-thirds of New York City has a combined sewer system that collects wastewater and stormwater runoff together in the same pipe from properties and streets. Upgrades to the DEP’s plants and sewers have allowed the agency to capture a greater amount of overall flow, from about 30 percent in the 1980s to over 72 percent today.

Overflows are also more dilute, with the percentage of sanitary waste decreasing from 30 percent to about 12 percent today.

In addition to green infrastructure investments, the DEP is planning $1.7 billion in addition traditional or grey infrastructure investments from 2012 through 2021 to improve water quality. These investments will build on the progress made by the approximately $1.6 billion in Combined Sewer Overflow and other related projects that were funded since 2002, including the Flushing Bay, Spring Creek, Paerdegat and Alley Creek Combined Sewer Overflow Retention Facilities now in operation.

Clean harbor water and CSO control plans are outlined in Strategy 2011-2014, a plan that lays out 100 distinct initiatives to make DEP the safest, most efficient, cost-effective, and transparent water utility in the nation. The new plan, the product of nearly one year of analysis and outreach, builds on PlaNYC, Mayor Bloomberg’s sustainability blueprint for New York City. The plan is available on DEP’s website, www.nyc.gov/dep.

For more information, visit the DEP’s Facebook page at www.facebook.com/nycwater, or follow the agency on Twitter at www.twitter.com/nycwater.