Municipal Storm Water Permits - Why Numeric Limits Don't Fit

Alexandra Dapolito Dunn
Association of Metropolitan Sewage Agencies

"Storm water discharge is highly variable both as to flow and pollutant type and concentrations, and storm water permits are issued on a system-wide basis, thus rendering it largely incompatible with numeric effluent calculation methodologies." EPA Environmental Appeals Board, NPDES Appeal No. 00-18, July 16, 2001 (citing EPA's 1996 Storm Water Regulation Guidance, 61 Fed. Reg. 57, 425)

An important Clean Water Act (CWA) permitting trend that municipal wastewater treatment agencies are watching closely is a relatively steady stream of environmental group petitions seeking numeric effluent limits in urban storm water National Pollutant Discharge Elimination System (NPDES) permits. These petitions continue even after the Ninth Circuit confirmed in the August 1999 Defenders of Wildlife v. Browner decision that Congress did not intend for municipal storm sewer discharges to comply strictly with state water quality standards. See 191 F.3d 1159 (9th Cir. 1999). The Defenders court found unambiguous the CWA's plain language that municipal storm sewer discharge controls should "reduce the discharge of pollutants to the maximum extent practicable (MEP), including management practices, control techniques and system, design and engineering methods, and such other provisions as the Administrator or the State determines appropriate for the control of such pollutants." CWA § 02(p)(3)(B)(iii). Despite this clear endorsement of the MEP approach to address municipal storm water in lieu of strict compliance with water quality standards, these petitions - coupled with the ever increasing focus on total maximum daily loads (TMDLs) and continuing difficulty across the nation achieving water quality - are bringing pressure to bear on state permitting entities to include numeric requirements.

On May 21, 2001, the U.S. District Court in Oregon dismissed for the second time on procedural grounds a storm water case raising this very issue, Tualatin Riverkeepers v. Browner (No. CV-00-793 BR). In Tualatin, an environmental group asserted that EPA violated the CWA when it approved a municipal storm water permit without numeric effluent limits because the permit "[would] not, in any way whatsoever, ensure that the permitted discharges will comply with the current TMDLs for the Tualatin River" and "NPDES permits (including storm water discharge permits) must ensure that the permitted discharges are in compliance with the CWA, and any other limitations, including TMDLs, necessary to implement the applicable water quality standards." While this one case is effectively ended, it is likely that the same issue will resurface soon in another federal case.

This same issue also is arising in state courts. For example, on July 31, 2001 the Minnesota Court of Appeals reviewed an environmental group challenge to storm water permits issued to Minneapolis and St. Paul. Mississippi River Revival, Inc. v. Minnesota Pollution Control Agency, 2001 Minn. App. LEXIS 855 (Minn. Ct. App. July 31, 2001) (unpublished opinion not for citation). The permits allowed the cities to use best management practices (BMPs) to control storm water pollutants. The environmental challengers argued the permits were illegal because they did not impose numeric effluent limitations to ensure compliance with Minnesota's water quality standards. Relying on the Defenders decision, the Minnesota court found that under both federal law and the parallel state law BMPs are appropriate in lieu of effluent limitations given the nature and variability of storm water discharges. The environmental group appealed the case to the Minnesota Supreme Court, but the court denied review on October 16, 2001 (No. C1-01-23).

In addition to activity on this matter in federal and state courts, the quest for numeric limitations in municipal storm water permits also is arising in permit appeals before the Environmental Protection Agency's (EPA's) Environmental Appeals Board (EAB). Shortly after the Defenders of Wildlife decision, the EAB endorsed the Ninth Circuit's analysis that municipal storm water permits do not require strict compliance with water quality standards. See Storm Water Discharge Permit for the Municipal Separate Storm Sewer System of Anchorage, Alaska, NPDES Permit No. AKS 05255-8, NPDES Appeal No. 99-1 (Nov. 23, 1999). Staying true to its original agreement with the Defenders court's conclusion, on July 16, 2001 EAB issued an opinion in the City of Irving, Texas' appeal of its storm water permit. Although the EAB rejected many of the City's arguments on jurisdictional grounds, the opinion includes a comprehensive overview of the history of the storm water program, and a careful discussion of the reasons storm water discharges do not easily lend themselves to numeric effluent calculation methodologies. The City of Irving EAB opinion can be obtained at http://www.epa.gov/boarddec/orders/new.htm.

A future test case for this important issue could be EarthJustice Legal Defense Fund v. EPA,Appeal No. 00-14, a case submitted to EAB and ripe for acceptance for review in EAB's discretion. In EarthJustice, the environmental group appealed the District of Columbia Water and Sewer Authority's storm water permit - which already contains a numeric effluent limit for oil and grease - because EPA did not include similar limits for all of the City's storm water outfalls or place numeric limits on all potential storm water pollutants. The environmental group asserts that the Defenders of Wildlife endorsement of the MEP approach for municipal storm water was wrong and should not be followed by the EAB. The results of this permit appeal could further solidify - or mark a change in - the EAB's approach on the numeric limitations issue.

The state permitting context is yet one further area where the question of numeric limits in municipal storm water permits continues to arise, particularly in California. For example, an ongoing appeal of the NPDES permit issued by the California Regional Water Quality Control Board to the City of San Diego asserts that language in the permit in effect requires strict compliance with water quality objectives through the application of numeric effluent limitations. The San Diego permit and various appeal documents discussing this issue are available at http://www.swrcb.ca.gov/rwqcb9/Programs/Storm_Water/storm_water.html.

The question of whether numeric effluent limitations are appropriate in municipal storm water permits is likely to continue as various stakeholders seek to make progress toward our nation's water quality goals. However, it is important to remember that selecting the right tool to address each water quality challenge is a critical step in the process. Given the case law acknowledging the realities of storm water - the variable nature of the discharge both regarding flow and pollutant type and concentrations, and the system-wide issuance of storm water permits - BMPs, not numeric effluent limitations, are the right tool for the job.