Stormwater poses challenges to urban areas in the form of combined sewer overflows (CSOs) and flooding. Impervious surfaces such as driveways, sidewalks, streets, parking lots, and rooftops prevent stormwater from naturally soaking into the ground. This water also carries bacteria and other pollutants into nearby bodies of water. Waterways are especially vulnerable in cities that have combined sewer systems, which discharge a mixture of sewage and stormwater runoff when these systems overwhelm their designated treatment plants. After a waterway has been degraded, it is difficult and expensive to restore it to a healthy condition. Prevention is the way to go, and urban communities across the country are turning to “Green Infrastructure (GI)” as a cost-effective, environmentally friendly solution to stormwater management.
The U.S. Environmental Protection Agency defines GI as the use of “vegetables, soils and natural processes to manage water and create healthier urban environments.” In its 2013 Green Infrastructure Strategic Agenda, the EPA states that, “Green infrastructure reduces the volume of stormwater discharges by managing rainwater close to where it falls and removes many of the pollutants present in runoff, making it an effective strategy for addressing wet weather pollution and improving water quality.” GI includes bioswales, tree planting, green roofs, rain gardens, rain barrels, low-maintenance native planting, and permeable pavements that capture and infiltrate rain water into the ground before it enters the sewer system. In addition to reducing the volume of storm water, GI reduces the pollution loads on treatment plants. Chief among these pollutants is the nitrogen released from fertilizers, a major cause of waterbody degradation and very expensive to remove at the treatment plant.
GI demonstration projects and high-profile programs have been instituted in many communities to meet mandated stormwater regulations. As part of its $2.6 billion Clean Rivers Project, DC Water in Washington, DC is including GI investments to reduce CSOs in the Rock Creek and Potomac River drainage areas. In September 2010, New York City released its Green Infrastructure Plan, which integrates GI with traditional infrastructure. The New York City Department of Design and Construction (NYCDDC), for example, employs sustainable design principles when designing and building in a watershed area, an initiative referred to as Best Management Practices (BMP). BMPs minimize the environmental impacts of urban stormwater runoff affecting natural wetland systems. The agency also emphasizes strategies that mitigate heat absorption.
At HAKS, our objective is to assist clients with programs that improve the urban ecology and restore the natural hydrologic cycle. Our early work in this area involved resident engineering inspection (REI) for a pioneering stormwater control and treatment program—an $18.7 million stormwater management project utilizing both structural and non-structural BMPs for Lenevar Avenue in Staten Island for the NYCDDC. Since then, our projects include:
- Assistance to the New York City Department of Parks and Recreation with the design of greenstreets and right-of-way bioswales for sites within the Bronx River and Flushing River Sewersheds
- Provision of REI for the NYCDDC’s $38 million stormwater BMP project for North Railroad Street in Staten Island, part of the overall Staten Island Bluebelt Program, which is one of the largest applications of stormwater BMPs in the United States
- Ongoing construction management services to DC Water’s Clean Rivers Project, which will reduce CSO discharges by 96% in the Washington metropolitan area
- Surveying, design and construction support to the New York City Department of Environmental Protection (NYCDEP) for a relief sewer at Newtown Creek to reduce CSO discharges
- Surveying services for the NYCDEP’s CSO Long-Term Control Plan for Alley Creek, Coney Island Creek, Hutchinson River, Flushing Creek, the Bronx River, the Gowanus Canal, Jamaica Tributaries and Bay, Westchester Creek, Flushing Bay and Newtown Creek
- Implementation of bioswales as part of the Atlantic Avenue Trunk Water Main Installation for NYCDDC
- Topographic surveys to calculate runoff rates in the New Creek and Oakwood Beach Watersheds for the NYCDDC
- Environmental permitting, design and construction management as part of a BMP project that constructed subsurface gravel wetlands to improve water quality for runoff that discharges into the Barnegat Bay for Ocean County, New Jersey
- Construction management/inspection for an NYCDEP project involving new plantings and remediated wetlands to help absorb stormwater runoff and thereby improve the overall ecology and water quality of Alley Creek in Queens, New York
- Implementation of a stormwater collection and treatment system, including hydrodynamic separator, and wetlands restoration, including retention ponds, drainage structures, and planting of more than 2,400 trees and shrubs as part of our CM services for the New Canaan Highway Maintenance Facility for ConnDOT
GI practices continue to be evaluated, modified and improved upon. As more and more communities adopt these technologies, it is hoped that benefits beyond stormwater management will result.