US EPA Delaware River Water Quality Standards Praised By Environmental Leaders As Being Guided By Good Science

​Big Win For the Clean Water Act, the Delaware Riverkeeper Network & Endangered Atlantic Sturgeon

Today, the United States Environmental Protection Agency (US EPA) finalized the rule revising outdated water quality standards for the 38 miles of the Delaware River between Philadelphia and Wilmington. The new rule was developed and released in response to a legal petition, and subsequent litigation, led by the Delaware Riverkeeper Network. The new standards recognize the importance of good quality water, including oxygen, for aquatic life in the river, including the genetically unique population of sturgeon that live there, and the new standards recognize that a healthy Delaware River is a driver of economic value to our region.

Maya K. van Rossum, the Delaware Riverkeeper praised the new proposal, saying, “the new proposed standards are a dramatic improvement for the quality of the Delaware River, aquatic life, and the many communities that depend upon a healthy River. Among the many benefits of these new standards, will be to protect the Delaware River’s genetically unique population of Atlantic Sturgeon from being driven to extinction by too much pollution and a lack of needed oxygen to both survive and thrive as a species. We are pleased to see that the EPA allowed their decision to be guided by science.”

Delaware Riverkeeper Maya van Rossum adds, “when we first filed the Clean Water Act petition requesting that the EPA take on the leadership role in developing these new standards, a petition that was later backed by legal action, we did so because of the need for science-driven decisionmaking; and we were not seeing that kind of leadership out of the states of Pennsylvania and New Jersey, or the regional Delaware River Basin Commission. We felt we had to turn to the US EPA to secure a science-driven process and outcome, rather than one that was being driven by politics or industry. I am pleased to see that we seem to be getting what we were striving for and hoping for … a good quality decision.”

Kacy Manahan, Senior Attorney at Delaware Riverkeeper Network and lead legal counsel on the case says “Today’s rulemaking proved that the Clean Water Act is still a powerful tool to secure critical protection for aquatic life. We look forward to the day that Atlantic Sturgeon are abundant in their Delaware River home once again.”

This decision comes on the heels of an over 10 year battle led by Delaware Riverkeeper Network to have the water quality criteria upgraded for the Delaware Estuary from Zones 3 through 6. Additionally, the Delaware Riverkeeper Network has defended the genetically unique population of Atlantic Sturgeon, found only in the Delaware River. For over a decade the Delaware Riverkeeper Network has advocated for the designation of the Delaware River population of Atlantic Sturgeon as endangered and have brought multiple legal actions to ensure that federal and state agencies uphold their obligations to protect this prehistoric species. There are less than 250 spawning adults left of this genetically unique population of Atlantic Sturgeon. Other recent efforts include legal challenges to prevent illegal by-catch and take of the Atlantic Sturgeon of the Delaware River.

Adds van Rossum, “While today’s decision was a win for water quality and was guided by good, sound science, the Atlantic Sturgeon still have an uphill battle against extinction which these revised rules have not resolved but we are taking on.”

In 2013, the Delaware Riverkeeper Network originally petitioned the Delaware River Basin Commission to issue upgraded water quality criteria for the Delaware Estuary from Zones 3 through 6.

In April 2022, the Delaware Riverkeeper Network and partners filed a legal petition pursuant to the federal Clean Water Act and Administrative Procedure Act urging the federal government to promptly initiate the rulemaking necessary to protect aquatic life in the Delaware Estuary and to revise the current water quality standards set by the Delaware River Basin Commission, a regional authority, which was failing to use their authority to protect the health of the Delaware River Estuary after decades of requests from Delaware Riverkeeper Network and partners.

On December 1, 2022, the EPA granted the Delaware Riverkeeper Network petition and exercised its Clean Water Act Section 303(c)(4)(B) authority, determining that revised water quality standards for the Delaware River estuary are necessary to meet the requirements of the Clean Water Act. EPA’s determination letter stated “ . . . the currently applicable dissolved oxygen criterion for these zones is not sufficient to protect propagation [of fish and other aquatic life]....”

In December 2023, the EPA published proposed higher standards which includes dissolved oxygen requirements as high as 74% saturation or 6.0 mg/L. The higher standards would better protect aquatic life in the Delaware River, including the oxygen-sensitive Atlantic Sturgeon . A 60-day public comment period followed and closed on February 20, 2024.

In October 2024, the Delaware Riverkeeper Network filed suit in the U.S. District Court for the Eastern District of Pennsylvania because the EPA had not yet published final water quality standards within the 90 day window required by the Clean Water Act.

On April 1, 2025 EPA announced that it would “finalize a rule revising outdated water quality standards for 38 miles of the Delaware River between Philadelphia and Wilmington” and that the final rule would “prioritize clean water to support aquatic life and benefit those living, working and recreating in Delaware, New Jersey and Pennsylvania.” The announcement by the EPA confirmed that the dissolved oxygen standards will be issued in a delayed but still timely fashion. In July 2025, Delaware Riverkeeper Network and EPA entered a stipulated judgment in Delaware Riverkeeper Network’s legal challenge requiring EPA to sign its final rule by September 22, 2025.