Grants Help Finance Use of New Device to Remove Floating Debris From Storm Water

By James W. Maxell
Deputy Commissioner of Public Works
City of New Rochelle, New York

Heeding the voices of environmental groups along with federal and state agencies concerned about the water quality in Long Island Sound, the City of New Rochelle, New York, it taking steps to eliminate much of the floating debris from its storm-water runoff.

New Rochelle is a city of 67,000 residents with 10 miles of shoreline, including city and county parks, tidal marshland, several marinas and beach clubs, as well as residences with direct access to the water. Thus, keeping the water clean and suitable for recreational use is of prime importance.

Government and private environmental groups alike have identified non-point source pollutants as a contributing risk to the water quality of Long Island Sound. Floating debris in particular is seen as a significant pollutant as well as an unsightly nuisance. The most common source of this debris comes from storm water outfalls, which carry discarded trash from streets directly into the bays and backwaters of Long Island Sound.

In addition to putting catch basin cleaning on a maximum three-year cycle and providing regularly-scheduled street sweeping, the city is employing the use of an apparatus known as a "stream floatable debris collection device." This device has been installed at a major storm water outfall, which empties into Echo Bay and Long Island Sound.

The installation was made possible through grant monies made available by the New York State Department of Environmental Conservation through the Nonpoint Source Pollution Prevention Program. Grant funds were provided on a 50-50 matching basis to municipalities to develop both ordinary and innovative programs.

In-kind services helped meet city's financial obligation to grant

The completed grant application totaled $ 58,000 with $ 29,000 in grant monies coming from the State of New York and $ 29,000 contributed by the city, much in the form of in-kind personnel services. These in-kind services were for the design of the device, construction oversight and maintenance of the device for the project period.

An educational effort to inform residents of the need to control nonpoint source pollution was also a required component of the grant.

Having already installed a stream floatable debris collection device in a shallow river under different circumstances, it seemed logical to the city that a similar device could be adapted to collect debris under conditions of tidal action. The concept, though simple in design, required the use of a proprietary device initially developed to control oil spills along shorelines and around leaking vessels.

When installed, the device consists of orange boom sheeting suspended from foam-filled floats equally spaced the entire length of the boom. The boom extends approximately 8 inches below the water and 12 inches above the water and is anchored at the upstream far shoreline by a 20 food long galvanized steel post driven into the creek bed.

The boom is attached to a sliding mechanism on the post, allowing it to rise and fall with the tide, which could change as much as 8 feet during its cycle. The boom is stretched across the creek to the downstream side on a 45-degree angle where the collection basket is set.

The 8 x 10-foot galvanized steel collection basket is set within a large galvanized steel framework which is suspended from foam-filled floats. These, too, rise and fall with the tide on four galvanized steel posts, 20-feet long and driven into the creek bed.

The open mesh basket has a water level capacity of just under 3 cubic yards and is designed to be set immediately adjacent to the downstream bank.

The offset stream channel, which has its deepest cross section near the westerly shoreline, necessitated a field modification to the device. The device was set away from the westerly bank of the creek and a short section of boom was installed from the basket to the downstream shoreline, thus providing a V-shaped collection area rather than the original straight-line configuration of the boom. An additional anchor post was set upstream from the collection basket so that in the event of heavy weather, which could damage the device, the boom could be removed easily and quickly from across the waterway.

City removes debris from collection basket on routing basis

It took approximately 6 hours to install the device and associated components. The maintenance aspect of the program calls for staff from the city's Bureau of Sewers and Drains to visually inspect the device daily and to make any necessary repairs. During periods when there is no rain, approximately 6 cubic feet of material is removed from the collection basket every three days. When heavy rains occur, debris is removed as often as twice a day and has a volume of approximately 6 cubic yards. Debris removal from the device requires the lifting of the 8 x 10-foot basket with a backhoe, usually at high tide. When full, the combined weight of the basket and debris can be as much as 1,500 pounds.

Debris collected is shoveled into a graduated container and broken down into categories of glass, metal, plastic woody products, and other. A comprehensive spreadsheet is kept on a daily basis of debris collected, required personnel, equipment usage, and costs incurred. The data on debris collected will be tabulated and forwarded to the New York State Department of Environmental Conservation for evaluation of the device's effectiveness. Also, data on personnel utilization and equipment usage is used as verification of in-kind matching funds expended.

Device has added bonus of quickly containing oil spills

The device has an added feature not previously recognized during the design phase of the project. In the event of an oil spill within the storm water drainage system, the debris collection basket can be isolated from the boom so that complete containment of spilled product can be accomplished within the boom area in a matter of minutes.

Continually looking for ways to improve water quality, the city applied for and has received two other grants under the New York State 1996 Clean Water / Clean Air Bond Act. One grant will provide for aquatic plantings around city lakes for shoreline stabilization to prevent erosion. The other involves retrofitting storm water manholes with a device designed to increase retention of suspended solids so that they do not enter the waters of Long Island Sound.

Information concerning the debris collection device can be obtained by contracting the author at the City of New Rochelle Department of Public Works at 914-654-2130.

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