Maryland Court Upholds “Maximum Extent Practicable” Standard for MS4 Permits Under the Clean Water Act

On April 2, 2015, a Maryland appellate court issued a significant decision in a case involving a stormwater permit issued for a municipal separate storm sewer system (“MS4”) that may have significance beyond the borders of Maryland.

In Maryland Department of Environmental Protection v. Anacostia River Keeper, et. al., the court addressed the issue of whether the Clean Water Act’s “maximum extent practicable” standard for MS4s require strict compliance with water quality standards. Under Section 1311 of the Clean Water Act, “point sources” of pollutants are required to comply with technology-based discharge limitations, including certain numeric criteria necessary to meet water quality standards. Stormwater discharges have been treated as point sources since a 1987 amendment to the Clean Water Act, which amendment states that permits for discharges from municipal stormwater sewers include “controls to reduce the discharge of pollutants to the maximum extent practicable.”

In this case, the local and regional environmental groups challenging the MS4 permit argued that the permit is subject to the technology-based limitations of Section 1311 in addition to any more stringent limitations necessary to assure compliance with applicable water quality standards. However, the Maryland court rejected this argument and reaffirmed prior federal and state court decisions finding that the “maximum extent practicable” standard for MS4s does not require the MS4s to achieve strict compliance with water quality standards, but rather comply with those requirements in the aforementioned 1987 amendment to the Clean Water Act.

Notwithstanding the court’s finding that MS4s are not required to strictly comply with water quality standards, the court addressed other issues with the challenged MS4 permit that should be reviewed by MS4 permitees or permit holders. For example, the court found problematic the lack of clear “benchmarks” to determine compliance with MS4 permits, and further found that the MS4 permit lacked the necessary clarity for attaining TMDL requirements. Despite the court’s reaffirmation of the “maximum extent practicable” standard under the Clean Water Act, municipal entities must nevertheless be cognizant of the court’s other findings, which may be a point of challenge by groups in the future to their MS4 permit.