Sasha Fahme
CHC Panel Presentation: The Staten Island Bluebelt System
WHAT IS IT AND WHY DOES IT EXIST?
The Staten Island Bluebelt is a system of streams, ponds, and wetlands managed by the New York City Department of Environmental Protection NYCDEP for stormwater management. A watershed is a geographic area that contributes water to a particular stream or water body. The Bluebelt system drains 15 watersheds clustered at the southern end of the Island, in addition to the Richmond Creek watershed, with land acquisitions totaling over 250 acres of natural waterways, and a watershed area in excess of 12,000 acres. The area where this exists has the last major strand of freshwater wetlands in New York City, and was one of the last parts of the city that lacked decent stormwater and sanitary drainage systems, which affected the natural resources of the area (sewer overflowing into streams and ponds), as well as the residents of the area, who experienced flooding and degraded water quality.
Because of these reasons, the NYCDEP implemented the Storm Water and Sanitary Drainage Management Plan for this area, which uses and preserves the area’s natural drainage system (Bluebelts), of streams, ponds, marshes, and wetlands to the greatest extent possible. These methods of nontraditional stormwater management and sanitary sewer management include a series of storm sewers, which collect and convey street runoff to the existing streams, which provide natural drainage corridors for stormwater. To control storm water discharges, DEP has built Bluebelt facilities called Best Management Practices or BMPs, at the sites where storm sewers meet the natural areas. These BMPs minimize the negative impacts of the storm sewer discharges on those areas by storing and channeling stormwater before it is discharged into a receiving water body. Their main purpose is to reduce the impact of stormwater runoff discharge on the streams, and so the BMPs attenuate peak flow and reduce pollutant load into the streams, while simultaneously minimizing erosion and flooding, as well as improving water quality. This network of BMPs is the one of the largest in the nation and is the only one to operate on a large scale in New York City.
HISTORY
In the 1970s, New York City’s City Planning Commission conducted a study for a comprehensive land-use plan for the South Richmond area, which revealed vast areas still in their natural state that had open-space value in the zoned landscape. It was decided that it was important to preserve and protect them for long-range land use and quality-of-life concerns, and the commission decided it was best to do it by implementing a zoning component. This was the first time it became suggested that these natural areas containing water courses and wetlands could be used for stormwater conveyance.
The zoning component was implemented in the form of the: Designated Open Space (DOS) system, which captured the network of existing, naturally occurring lakes, ponds, streams, and wetlands, as well as a significant amount of public owned property and kept it from being sold. It then prohibited development in those areas and kept the natural features protected. These areas were arranged to connect to mapped parks, creating a comprehensive drainage corridor for the natural water-course system, setting the framework for the later-to-come Bluebelt program which would incorporate additional lands abutting and within the system.
THE SETUP
The incorporation of stormwater BMPs like retention basins, provides significant flood attenuation and water-quality benefits. Flow was stored or retained and released gradually to the downstream areas. Existing wetlands were restored and, in certain cases, preceded by a stormwater treatment system to remove sediments. For example, a long flow path through a constructed wetland (channeling) can aid in pollutant removal and stormwater attenuation. To decide which BMPs should be used, extensive hydrologic, hydraulic, water-quality modeling of the streams occurred, along with wetland evaluation and analysis, sanitary/storm sewer system layout, and topographic surveys. There was a screening process that limited the number of BMP designed, narrowing it down from more than 100 used nationally. Effective use of the criteria in this selection process allowed for a more precise listing of BMPs suitable to the watershed. Suitable retrofit sites were identified after the selection of appropriate BMPs. Some retrofit techniques include:
a. Retrofit Existing Older Stormwater Management Facilities: involves converting existing detention facilities into multifunctional stormwater BMPs. This is easy because stormwater is already managed in a distinct location, and modifying existing facilities usually involves minimal impacts to secondary environmental resources such as wetlands and forest cover. Excavation of the pond bottom results in additional storage for extended detention. The use of baffles, earthen berms, and pod microtopography all result in enhanced pollutant removal. The BMP known as RC-4 at Richmond Creek has this type of retrofit technique, which uses a pocket wetland with a marsh and a combination of a forebay and micropool to enhance pollutant removal from the stormwater flows before these waters enter the creek via the natural wetland. At Lighthouse Avenue in this area, an undersized culvert was constantly flooding into regulated wetland. It was enlarged to maximize its capacity for stormwater, and hence had the potential to drain the adjacent natural wetland—however, the construction of a BMP preserved the wetland. The BMP design uses pocket wetlands to attenuate small storms and provide pollutant removal; the pocket wetlands then drain into the existing wetland and replace the loss of water caused by the redesign of the culvert.
b. Construction of New BMPs at Storm Drainage Pipe Outfalls: This type of retrofit entails constructing a BMP at the immediate terminus of the storm drainage system. Flow splitters can be used to convey water-quality treatment volumes to a BMP. The BMP RC-5 at Richmond Creek watershed uses a constructed wetland with a marsh and a forebay and a micropool to attenuate peak flows, reduce pollutant loading to the creek, and diversify and enhance the impacted wetlands. This is larger than a pocket wetland and can handle larger flows—the extended detention provides the ability to control larger flows while the marshes provide pollutant removal capacities.
c. Instream Practices in Channels: Previously channelized streams can be sites for small instream detention structures. These structures consist of small weir walls or check dams placed within the channels. A small ponding area is provided upstream of the structures for establishing wetland areas. This method is very easy to install and can provide moderate pollutant removal benefits but can have potentially adverse impacts on the floodplain. Careful analysis of existing floodplain levels compared to those with the BMPs in place are important in planning this construction.
CONSTRUCTION: TECHNOLOGICAL AND AESTHETIC FACTORS
The completed project within the Richmond Creek Bluebelt included extensive landscaping and specialized construction techniques not typically used for sewer projects. The BMPs include shallow marsh wetlands to filter stormwater, retention basins to reduce water velocity before the water discharges into the stream, and sand filters to remove pollutants. Constructing these BMPs involved soil excavation, pipe installation, site work, grading, and implementing planting plans. Natural products, native plants, and stone facing were used to enhance the BMPs and also to add to the aesthetic nature of the site. The installation of coconut fiber rolls along the stream’s edges to anchor plants, and the planting of at least 25 species of trees, shrubs, and ground cover were a few of the main features adopted to enhance the aesthetic quality of the constructed elements. Carefully planned landscape zones were designed and implemented, all areas were diversely vegetated to maintain biodiversity and support a wide variety of wildlife.
EROSION CONTROL
Soil erosion and sediment control plans were developed to protect adjacent natural areas like streams and wetlands from the effects of soil erosion and sediment accumulation during construction. The plans aimed to minimize runoff into the wetlands and reduce the amount of sediment accumulation that might occur, which reduces the carrying capacity of streams and reduces the stormwater storage capacity of wetlands and ponds. This plan included: reinforced slit fencing, surface-water collectors, portable sediment tanks, and crushed-stone-lined sediment traps. The sediment tanks treat the water pumped from construction trenches, which passes through sediment-trapping baffles within these tanks, and then continues into the adjacent pit lined with crushed stone where the water then permeates the ground. Turbidity levels are mentioned and if they exceed the established limit, the discharge undergoes further treatment or is disposed of off-site. All the soil and sediment control features and temporary and must be removed prior to the end of the project.
STREAMBANK STABILIZATION
The urbanization of watersheds causes flood peaks to be quicker, higher, and more frequent, and base flows to be generally lower than before urbanization. To regulate these levels, streambank stabilization techniques have been employed to minimize erosion, sediment transport, and flooding. To minimize erosion, the maximum allowable stream velocity is restricted to 3-5 ft./sec. If the rate exceeds this, then there are methods that can either reduce this velocity or protect the streambank from erosion. The use of riprap is employed to protect the streambank from high velocity water—most effective method when velocity cannot be reduced. Another technique is undercut stabilization, where a small amount of rirap is placed at the water line along the edge of the stream, and a coconut-fiber roll is staked above it. The area behind the roll is backfilled to meet the existing grade, and then the area is planted. The riprap and roll absorb much of the erosive energy from the storm, allowing the streambank vegetation to survive and reducing erosion.
COMMUNITY PARTICIPATION
NYCDEP has a strong partnership with the community to educate people about the nature of the program and keep them informed of progressive developments. The NYCDEP implemented a comprehensive public participation program that maintains dialog regarding the projects purpose and objectives and involves citizens in the decision-making process. There is the Citizens’ Advisory Committee, which is a group of approximately 30 citizens representing diverse interests that range from environmental, civic, and homeowners associations to builders’ organizations. The CAC’s role is to act as a liaison to the broader community and to assist the NYCDEP in developing an effective program.
CONCLUDING THOUGHTS AND FUTURE BLUEBELTS
Because of the success of the Bluebelt system, more are being developed, such as the New Creek Bluebelt, draining a watershed of 1,700 acres which is being acquired currently by the DEP, in addition to bluebelts in South Beach and Oakwood Beach. The Bluebelt Program saves tens of millions of dollars in infrastructure costs when compared to just conventional storm ewers for the same lad area, demonstrating how wetland preservation can be economically prudent and environmentally responsible. In addition to restoring formerly degraded wetlands, it creates enhanced natural areas that inspire community pride, which leads to volunteers organizing cleanup campaigns.
AWARDS
• 1996, American Rivers, Urban River Restoration Award for Staten Island Bluebelt Project
• 1997, New York Association of Consulting Engineers, Platinum Award for Richmond Creek Drainage Plan
• 2003, American Council of Consulting Engineers, National Recognition Award
• 2003, American Academy of Environmental Engineers, Honor Award
• 2003, New York Association of Consulting Engineers, Diamond Award for Blue Heron Drainage Plan
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