Dealing With Deluges
Getting ready for a rainy day has become a top priority for many U.S. cities. Once considered a backwater issue, stormwater management has become an important matter to municipal officials as a result of the enactment in recent years of the National Pollutant Discharge Elimination System (NPDES) permitting program under the Clean Water Act that addresses stormwater discharges.
Published in 1990, Phase I of the NPDES stormwater regulations pertains to operators of large and medium municipal separate storm sewer systems (MS4s). Under the Phase I rules, large MS4s that serve a population of 250,000 or more or medium MS4s that serve a population of 100,000 or more, but less than 250,000, are required to obtain NPDES permits and manage their stormwater discharges. In 1999, Phase II regulations were enacted that require certain regulated small MS4s, which serve populations of less than 100,000, and construction sites that disturb 1 to 5 acres, to obtain stormwater management permits. For more information on the U.S. Environmental Protection Agency's (EPA) NPDES regulations, go to www.epa.gov/npdes/stormwater.
Stormwater discharges are generated by runoff from land and impenetrable areas, such as paved streets, parking lots, and building rooftops, during rainfall and snow events. Under the NPDES program, most stormwater events are considered point sources and therefore require coverage by an NPDES permit. Stormwater events have two main components that municipalities have to address: the increased volume and rate of runoff from impervious surfaces and the concentration of pollutants in the runoff. According to EPA officials, both components are directly related to development in urban areas. Together, these components cause changes in hydrology and water quality that result in a variety problems, including habitat modification and loss, increased flooding, decreased aquatic biological diversity, and increased sedimentation and erosion.
Typically, cities have several main goals related to stormwater management: reducing pollutant loads, maintaining groundwater recharge and quality, protecting stream channels, and safely conveying extreme floods. As well, effective stormwater management offers a multitude of other possible benefits, including protection of wetlands and aquatic ecosystems, improved quality of receiving water bodies, conservation of water resources, and protection of public health
One of EPA's new priorities related to stormwater management is encouraging municipalities to promote low impact development (LID), a new comprehensive land-planning and engineering-design approach created to maintain and enhance the pre-development hydrologic state of urban and developing watersheds. EPA's position is that, through LID approaches, stormwater runoff can be controlled while development objectives are achieved. An important aspect of a municipal LID program is public outreach. When successfully implemented, LID education and awareness programs can establish a marketing tool that allows developers to attract environmentally conscious buyers, create more landscaped areas, educate property owners on effective pollution prevention measures, and inform commercial property owners of potential cost savings from using LID approaches. Additional information about EPA's LID policies can be found at http://cfpub2.epa.gov/npdes/stormwater/menuofbmps/edu_7.cfm.
Several organizations are also working to promote LID principals. For example, the Low Impact Development Center ( www.lowimpactdevelopment.org) is a nonprofit organization dedicated to the advancement of LID techniques. The group provides research, training, planning, sustainable infrastructure design, municipal ordinance development, prototype design, and monitoring.
Another pro-LID group that is concerned about the negative environmental impacts of runaway development in the United States is Smart Growth America ( www.smartgrowthamerica.com). It is a coalition of national, state, and local organizations working to improve the way we Americans plan and build our towns, cities, and metro areas. According to Smart Growth America, abundant research suggests that when impervious surfaces cover more than 10 percent of a watershed, the water bodies they surround become degraded. The group further points out that if current urban growth trends continue, many healthy watersheds will develop serious problems over the next 25 years and our country will experience sharp and irreversible declines in the health of our coastal areas.
Increasingly, the road to ecological hell is paved not with good intentions, but with asphalt. Urban sprawl is starting to have a devastating impact on our environment and the expansion of nonporous pavement and parking lots is a big part of the problem. Our cities need to take aggressive action now to promote LID both for future growth and for redevelopment projects. If strongly promoted by both our public and private sectors, LID policies can have a high impact on the long-term protection of our nation's watersheds.