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New EPA report documents green infrastructure savings
The U.S. Environmental Protection Agency (EPA) released a report that found green infrastructure can be a cost effective solution to controlling storm water while providing numerous economic benefits. Using the city of Lancaster, Pa., as a case study, EPA sought to quantify the economic benefits associated with utilizing green infrastructure for controlling wet weather pollution.
The report estimated that within the combined sewer system (CSS) area, Lancaster’s green infrastructure plan will reduce gray infrastructure capital costs by $121.7 million and reduce wastewater pumping and treatment costs by $661,000 per year. It will also provide approximately $2.8 million in energy, air quality and climate-related benefits annually.
These benefits exceed the costs of implementing green infrastructure, which were estimated to range from $51.6 million if green infrastructure projects were integrated into already planned improvements to $94.5 million if green infrastructure projects were implemented independently.
Unlike single-purpose gray storm water infrastructure, which uses pipes to dispose of rainwater, green infrastructure uses vegetation and soil to manage rainwater where it falls. By weaving natural processes into the built environment, green infrastructure provides not only storm water management, but also flood mitigation, air quality management, and community revitalization.
In 2011, the city of Lancaster released its comprehensive green infrastructure plan. Developed with the assistance of city, county, and state agencies, the plan identified opportunities for adding green infrastructure throughout the city within five-year and 25-year timeframes; estimated the water quality benefits and articulated a series of policy, outreach, and technical recommendations for implementing green infrastructure in the city.
Because of the plan and the city’s interest in understanding the added benefits of green infrastructure, EPA selected the city of Lancaster to serve as a case study for calculating the additional environmental, social and economic benefits.
Lancaster, like hundreds of other cities across the country, has both a combined sewer system (CSS) and a municipal separate storm sewer system (MS4). While the CSS collects both sewage and storm water and conveys flows to a wastewater treatment plant, the MS4 collects only storm water runoff and discharges flow directly to receiving streams.
The report summarized how installing green infrastructure in the CSS area could reduce gray infrastructure capital investments and associated wastewater pumping and treatment costs; as well as how installing green infrastructure in both the CSS and MS4 areas could produce a range of environmental benefits across the city.