In 1970, the United States Environmental Protection Agency (EPA) estimated that 85% of water pollution came from point sources, with the other 15% coming from non-point sources. With the passage of the Clean Water Act (CWA) those figures have been reversed; by 2010 point sources accounted for only 15% of pollution, with non-point sources making up the other 85%.2
Stormwater is the water from precipitation events such as rain and snow, including snowmelt. While it's easy to assume that stormwater is a natural process of the water cycle, many of its deleterious effects on the environment are man-made. Stormwater runoff occurs when precipitation from rain and snowmelt is not naturally absorbed into the ground.3 Impervious surfaces (i.e., streets, parking lots, rooftops) preclude the natural absorption of stormwater as it instead accumulates debris, chemicals, sediments and other pollutants until it is ultimately discharged as runoff into a water system, thereby negatively affecting water quality.
While the CWA provides regulations and requirements for stormwater management, it is often left to the stormwater designer and/or facility as to the exact means and methods to achieve compliance and performance. New technologies and philosophies of green infrastructure are proving to be effective in not only the control of runoff but also providing a cost effective alternative to conventional stormwater controls.
This paper provides a brief overview of the stormwater measures within the CWA along with an introduction to green infrastructure controls. Stormwater issues and controls are site and area specific and this overview provides EHS Professionals a summary of potential requirements along with possible considerations for control measures.