Residual Designation Authority: Will It Drive the Future of Stormwater Regulation?

Residual Designation Authority: Will It Drive the Future of Stormwater Regulation?

The Long Creek watershed in southern Maine includes a shopping mall, big box and smaller retail stores, the Portland Jetport, and a section of Interstate 95. While it appears similar to many urban retail districts in the United States, this watershed is one of the few locations where the EPA has exercised its residual designation authority (RDA) to require a National Pollutant Discharge Elimination System (NPDES) permit for stormwater discharge from private and non-industrial sources.

States and the EPA are required by the Clean Water Act (CWA) to monitor and identify all water resources that are threatened or impaired by pollution. Since the inception of the CWA, the EPA has focused its efforts on regulating discharges from industrial and municipal point sources, such as wastewater treatment plants, through NPDES permits with the objective of improving water quality. In addition, they must determine the total maximum daily load (TMDL) of any pollutant discharged from any source into receiving waterbodies.

Regulating Non-Point Sources

The EPA’s efforts have generally not included permits for stormwater from non-point sources that discharges from private property, even though the stormwater that flows from parking lots, roofs, and lawns carries oil, fertilizer, and toxic chemicals. Municipal Separate Storm Sewer Systems (MS4s) that convey and discharge polluted stormwater through municipally-owned collection systems require NPDES permits, but stormwater pollution from something like a parking lot that flows directly into a local pond isn’t as simple to monitor and treat as municipally owned end-of-pipe stormwater or wastewater discharges. Yet the EPA notes that the pollution from non-point sources is likely the “leading remaining cause of water quality problems.”

The CWA does include criteria in section 402(p) for defining and regulating non-point discharges through residual designation. David Owen, an associate professor at the University of Maine School of Law, described the RDA as an “obscure,” “catch-all provision” that delegates to the EPA or state’s NPDES permitting authority for any significant contributor of pollutants to receiving waters. In addition, any person can file a petition to force the EPA or state to exercise this authority. However, Owen notes the RDA “cannot be invoked without a watershed-specific evidentiary basis” that stormwater discharge is a significant contributor of pollutants to a waterbody.

The fact that direct evidence is required has made it difficult for regulators to issue a NPDES permit or TMDL standard for stormwater that flows from a non-point source such as a rooftop or parking lot into a creek. It’s challenging and expensive to pinpoint where stormwater is flowing, what specific pollutants are present, and to what extent it is creating a negative impact. Furthermore, NPDES permits require the implementation of best management practices (BMPs) that include engineered and educational measures to control pollution. BMPs are easier to implement on public land and through municipal funding and more complex to coordinate and fund through private subsidy and on private property.

The RDA Is Invoked to Clean Up Long Creek

In 1998, the Long Creek watershed was listed as an impaired watershed by the Maine DEP. Scientific studies determined that stormwater from the 640 acres of impervious surface in the watershed contributed to the environmental degradation of the creek. When watersheds exceed 8-10% impervious area, stream health begins to decline. The impervious area in the Long Creek watershed far exceeds that percentage, and the high water temperature and lack of brook trout and other native species was indicative of the creek’s poor condition.

Ten years after the MDEP’s designation of Long Creek as impaired, the Conservation Law Foundation petitioned the EPA and MDEP to use its RDA and require area businesses to comply with a NPDES permit for stormwater discharges. The agencies agreed. The MDEP required permits for discharges from parcels in the Long Creek watershed with at least 1 acre of impervious cover. Owners have the option to work with the MDEP through an individual permit, but most are working through a general permit in a collaborative entity organized by businesses and area stakeholders called the Long Creek Watershed Management District.

The Portland Press Herald reported that the restoration plan is estimated to take 10 years and cost $14 million. Still, by focusing on mitigation measures that offer the greatest environmental return for the lowest cost and through economy of scale, the cost to implement the Long Creek Management plan is roughly one third of what the total would be through an individual landowner approach. The plan and the district are nationally recognized as a model program for addressing non-point source pollution through shared costs.

Several BMPs have been employed in the Long Creek watershed to address polluted runoff. For example, stormwater collection areas with filtration systems have been installed in shopping mall parking lots and in nearby vacant lots, which will significantly reduce the flow of oil, grease, and toxic chemicals from urban runoff into the creek. In our work on several of the Management District’s projects, including the evaluation and design of road, curb, and gutter retrofits in South Portland, we have seen that these BMPs, which use the latest concepts in media filtration, improve drainage conditions and cost less than conventional design.

The Future of Stormwater Regulation

A 2004 EPA study found that urban stormwater discharge is the source of impairment in:

  • 22,559 miles of impaired rivers and streams;
  • 701,024 acres of impaired lakes; and
  • 867 square miles of impaired estuaries.

The National Research Council describes the EPA’s current approach to regulating stormwater as “unlikely to produce an accurate or complete picture of the extent of the problem, nor is it likely to adequately control stormwater’s contribution to waterbody impairment.” The reality of impaired waters coupled with uncertainty in regulatory controls will likely lead to an increase in the use of RDA to address stormwater issues. In July of 2013, the Conservation Law Foundation and other environmental groups petitioned several EPA regions to again exercise their RDA and require all unregulated stormwater discharges to impaired water bodies to be subject NPDES permits. The EPA has asked for more time to submit their response.

The RDA will survive well after the EPA’s National Stormwater Rule is ultimately finalized. Through some measure, municipalities and property owners will be compelled to collectively or independently implement control measures to reduce pollutant loading or defend the status quo.

Paul Hogan, a Senior Water Resources, Regulatory and Compliance Specialist at Woodard & Curran, contributed significantly to this article. Mr. Hogan brings over 35 years of experience as a regulator and water resources expert and has been involved with all aspects of environmental quality as it relates to surface water discharge. He has worked with the U.S. Environmental Protection Agency on a regular basis, as well as the New England Interstate Water Pollution Control Commission and other New England states on water quality, permitting, and other regulatory matters.

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