A judge in a Maryland Circuit Court ruled in a decision released earlier this month that the state of Maryland must regulate air pollution from poultry operations under the state’s implementation of the Clean Water Act (“CWA”). According to the court, Maryland has broadened the scope of protection offered by the CWA in such a way that the state is capable of regulating multiple categories of pollutants under its CWA authority, including any “gaseous” substance. Following the ruling, animal feeding operations in Maryland may be subject to limitations on ammonia through their CWA permits.

CWA Permitting Authority & States

Permitting programs are one of the main tools employed by the CWA to help limit water pollution in the United States. Of the permitting programs administered under the CWA, the National Pollutant Discharge Elimination System (“NPDES”) is perhaps the most well-known. The NPDES program helps to address water pollution by regulating discharge of pollutants from point sources into waters of the United States. Any such discharge that occurs without a NPDES permit is a violation of the CWA, and the NPDES permits themselves contain terms that permit-holders must follow in order to remain in compliance with the law.

The Environmental Protection Agency (“EPA”) is the federal agency tasked with implementing the NPDES program. Typically, anyone looking to apply for a NPDES permit will go through EPA. However, under the CWA, states can apply to EPA for authorization to implement some or all of the NPDES program within their borders. In other words, EPA can delegate some or all of its NPDES permitting authority to individual states. In order to gain NPDES permitting authority, there are a variety of things state must have in place, including a description of the proposed permitting program, underlying laws and regulations to carry out the program, and a Memorandum of Agreement with EPA. Once EPA approves the program, the state takes on permitting authority. From that point on, applications for new NPDES permits would go through the state where the permitted discharge would be taking place.

States that have been authorized to issue NPDES permits must comply with the text and regulations of the CWA. However, meeting federal regulations is the minimum threshold that states must comply with. Authorized states also have the option of broadening the scope of protection granted by the CWA.

Maryland CWA Authority

The state of Maryland has been authorized to assume NPDES permitting authority since 1974. Under its NPDES permitting authority, the Maryland Department of the Environment (“MDE”) is responsible for the issuance of all NPDES permits in the state, including general permits. This means that MDE issues NPDES permits both for individual dischargers, and to cover multiple dischargers with similar operations and types of discharges.

In addition, Maryland’s statutory scheme has defined several key CWA terms more broadly than the federal statute. For example, Maryland state law defines “pollutant” to include any “gaseous [. . .] substance,” while the CWA limits its definition of “pollutant” to solid and liquid wastes. MD. CODE. ANN. ENVIR. § 9-101; 33 U.S.C. § 1362(6). Maryland has also expanded what types of dischargers require NPDES permits. Under the CWA, concentrated animal feeding operations (“CAFOs”) are regulated as point sources if they discharge pollutants directly into a protected water. Discharges of pollutants from CAFOs into protected waters require NPDES permits. In Maryland, the state has created an additional category of regulated livestock operations separate from CAFOs to help ensure that all possible point sources are subject to permitting requirements. These operations are referred to as Maryland Animal Feeding Operations (“MAFOs”), and meet the same size requirements as CAFOs but do not discharge pollutants directly into surface waters. Maryland requires MAFOs to be regulated under MDE’s General Discharge Permit for Animal Feeding Operations (“GD Permit”).

Current Lawsuit

The recent court decision in In re Petition of Assateague Coastal Trust, No. 482915-V (Cir. Ct. Md. March 12, 2021) stems from issues involving poultry operations located near the Chesapeake Bay. The operations are typically designated as either CAFOs or MAFOs, capable of producing a significant amount of manure each year. The plaintiffs claim that the manure generated by the poultry operations creates “gaseous ammonia” that is blown away from the operations by industrial fans, ultimately causing pollution in the Chesapeake Bay.

The MDE regulates the discharge of waste from CAFOs and MAFOs into the Chesapeake Bay through the GD Permit, however the discharge of gaseous ammonia is not addressed in the GD Permit. In 2020, when the MDE last reissued the five-year permit, the Department made the decision not to include limitations on gaseous ammonia. Plaintiffs filed suit, arguing that the GD Permit is deficient under both state and federal law due to its lack of restrictions on the ability of CAFOs and MAFOs to discharge ammonia into the Chesapeake Bay. According to the plaintiffs, MDE’s conclusion that regulating gaseous ammonia fell outside the scope of the CWA was contrary to law. They argue that several statutory definitions within both the CWA and the state law of Maryland supported regulating gaseous ammonia under the GD Permit.

The judge agreed with the plaintiff, concluding that Maryland’s expansion of the CWA clearly includes the ability to regulate gaseous ammonia through MDE’s implementation of the NPDES program. To support this conclusion, the court noted that Maryland’s water pollution control laws broadened the definitions of several key CWA terms. Specifically, the court noted that the term “pollutant” has been defined in Maryland as “any liquid, gaseous, solid, or other substance that will pollute any waters of this State.” MD. CODE. ANN. ENVIR. § 9-101. Additionally, the term “discharge” has been defined by Maryland state law as “the addition, introduction, leaking, spilling, or emitting of a pollutant into the waters of this State.” MD. CODE. ANN. ENVIR. § 9-101. According to the court, this statutory language demonstrates a “clear intent” to expand the scope of the CWA and to require MDE to regulate ammonia as a water pollutant.

Finally, the court addressed the argument from MDE that regulating gaseous ammonia under its NPDES permitting authority would be too broad an application of the CWA. The court disagreed with that argument, concluding that neither Congress or the Maryland General Assembly had enabled CAFOs and MAFOs to dump ammonia into the Chesapeake Bay. Instead, Maryland decided to strengthen the CWA by broadening the key definitions of “pollutant” and “discharge.” Because there was no other federal or state law explicitly allowing the CAFOs and MAFOs to discharge ammonia, and because Maryland is legally allowed to regulate beyond the minimum requirements of the CWA, requiring MDE to regulate gaseous ammonia through the GD Permit is not beyond the scope of the CWA.


After reaching its conclusion, the court determined to reverse MDE’s final GD Permit decision and sent the permit back to the Department to set limits for gaseous ammonia. Anyone operating a CAFO or MAFO in Maryland should be aware that future limitations on discharges of gaseous ammonia may be forthcoming.

The court’s decision is applicable only in Maryland. It is an interpretation of Maryland state law, and MDE’s adoption of CWA permitting authority. However, it is possible that other state courts could look to this decision for guidance if a similar issue arose. Currently, it is unclear whether MDE will attempt to appeal that decision through the Maryland state court system.


To read the decision in In re Petition of Assateague Coastal Trust, click here.

To read the text of the CWA, click here.

To read the relevant Maryland state law, click here.

For additional CWA resources from the National Agricultural Law Center, click here.