The EPA is crafting new rules that would impose more severe stormwater retention requirements on newly developed urban sites than those applied to redevelopment projects. The different approaches are meant to further encourage a recent trend favoring urban redevelopment over new construction.

The Environmental Protection Agency will propose regulations requiring new developments to construct greater stormwater retention ability than redeveloped sites, an agency official said April 30.

The new rules would be employed to reduce the volume of stormwater runoff that transports pollutants into nearby groundwater. Retaining some rainfall on these sites through performance standards, either via green infrastructure or natural features, would "basically eliminate the discharge of any pollutants for that particular volume," said Christopher Kloss, green infrastructure and stormwater coordinator in the EPA Office of Water, during a webinar on stormwater regulations.

More stringent standards for stormwater at newly developed sites versus less taxing standards at redeveloped sites may create an incentive for businesses to invest in urban redevelopment projects, he explained.

The post-construction stormwater rule would apply to developed and redeveloped sites inside cities and towns with municipal separate storm sewer systems, but not to cities with combined sewer systems for both stormwater and wastewater, Kloss said.

Kloss said EPA is considering performance standards to retain stormwater discharges at sites between one and five acres, and the agency has yet to decide on a threshold for performance standards. He also expects the agency will set at least a 90-day period for comments because of the complex nature of the rulemaking.

Local governments will have flexibility in meeting EPA's performance requirements to retain stormwater on site, Kloss said. A locality could comply with national standards if it already has a mix of green infrastructure, he said, such as porous pavements and grassy swales, and gray infrastructure practices that retain stormwater.

EPA is under a 2010 consent agreement with the Chesapeake Bay Foundation to propose a post-construction stormwater rule by June 10 and to finalize the rule by Dec. 10, 2014 (Fowler v. EPA, D.D.C., No. 1:09-cv-5, 5/11/10). The U.S. Water Alliance, the Mayors Innovation Project, and the Clean Water for Healthy Communities Coalition organized the webinar.