Last month, the Maryland Court of Appeals issued a comprehensive opinion affirming water pollution (“NPDES”) permits issued to authorize discharges from two municipal separate storm sewer systems (“MS4s”) to the Chesapeake Bay watershed. Md. Dep’t of the Envt. v. County Comm’rs of Carroll County, Nos. 5 & 7, Sept. Term 2018 (Md. Aug. 6, 2019). The court held that state permits issued by the Maryland Department of the Environment (MDE) are required to conform to the Chesapeake Bay Total Maximum Daily Load (TMDL) issued by the federal Environmental Protection Agency and the Maryland Watershed Implementation Plan (WIP) promulgated by MDE and approved by EPA. The permittee may not challenge permit conditions necessary to meet the requirements of the TMDL or the WIP through judicial review of the permit, but instead must have already sought review in federal court of the TMDL. Moreover, EPA’s interpretation of the TMDL is entitled to Chevron deference.

The dispute addressed here provided occasion for Maryland’s highest court to opine (for 99 pages) about the Clean Water Act permitting scheme and “cooperative federalism” generally. Therefore, one can expect this opinion to provide guidance across a wide range of permitting issues. The specific issues, however, arose from the regulation of stormwater discharges.

When the Clean Water Act requires control of stormwater discharges, the discharger typically must implement control practices and technologies. NPDES permits for MS4s in particular do not rely primarily on numerical effluent limitations. They would be impractical for stormwater. In general, MS4s must control pollutants in stormwater “to the maximum extent practicable.” 33 U.S.C. § 1342(p)(3)(B)(iii) (the “MEP” standard). That control, however, may not suffice – and EPA and the Chesapeake Bay states have concluded will not suffice – to achieve water quality standards in the Bay. Accordingly, the permits here required Carroll and Frederick Counties to “restore” 20% of the impervious surfaces in each county not already “restored” under prior permits calling for control to the MEP standard. Impervious surface is “restored” if it is made pervious or otherwise managed to reduce rapid runoff without infiltration.

Frederick County had submitted a report showing that restoration of that proportion of the impervious surface in the county was not practicable. The court held that MDE had properly imposed the condition nevertheless because it was in the nature of a water-quality-based effluent limitation imposed over and above the technology-based MEP standard.

The counties also complained that MDE had improperly imposed the restoration obligation on 20% of all the impervious surface in each county, not just the impervious surface that drained to the MS4. Again, the requirement was necessary in order to meet the TMDL and therefore upheld.

The court considered certain further objections to the permits. Of interest, it held that MDE did not have to allow pollutant trading in these permits because Maryland has not adopted comprehensive pollutant trading regulations.

Looking beyond Maryland, one may wish to note that on August 27, Pennsylvania issued its Phase 3 Watershed Implementation Plan for the Chesapeake Bay TMDL.