On January 8, 2025, the U.S. Army Corps of Engineers (USACE) and the Environmental Protection Agency (EPA) released the Final National Ordinary High Water Mark (OHWM) Field Delineation Manual for Rivers and Streams. This manual is a valuable technical resource designed to assist professionals in the identification and delineation of the ordinary high water mark (OHWM) across the nation. Although non-mandatory, it provides a standardized framework that enhances consistency, reliability, and defensibility in water resource assessments.
Understanding the Role of the OHWM in Federal Regulations
The OHWM serves as a crucial boundary marker for defining the lateral limits of federal jurisdiction under several key laws, including the Clean Water Act (CWA) and the Rivers and Harbors Act (RHA) of 1899. Specifically:
- Clean Water Act (CWA): For non-tidal waters, the OHWM delineates where federal jurisdiction begins, extending further when adjacent wetlands are present.
- Rivers and Harbors Act (RHA): The OHWM marks the lateral extent of federal oversight for navigable waters.
By delineating the OHWM accurately, stakeholders can ensure compliance with federal regulations, streamline permitting processes, and avoid costly violations.
Key Features and Updates in the Final OHWM Manual
The Final National OHWM Manual builds on feedback collected during a comprehensive review process that included public, state, tribal, and local government input. Here are some notable updates and improvements in the final version:
- Enhanced Datasheet Clarity and Efficiency: The datasheet and manual sections have been reorganized to align for seamless field use.
- Clearer Instructions: Revisions to the weight of evidence method and additional field procedure chapters make the manual easier to use as a reference.
- Executive Summary: A new executive summary outlines the purpose and scope of the manual, enhancing accessibility for new users.
- New Definitions and Indicators: Terms such as “top of bank,” “break in slope,” and “valley bottom” have been added, ensuring greater precision.
- Additional Visuals: Updated figures and illustrations help users visualize the procedures and data collection methods more effectively.
Moreover, the manual now includes a checkbox for instances where an OHWM is not found, making the documentation process more transparent.
No Regulatory Changes—A Non-Mandatory Resource
It is important to note that the use of the Final OHWM Manual does not introduce any regulatory changes or alter existing definitions of the OHWM or Waters of the U.S. (WOTUS). This manual provides guidance for delineating OHWMs rather than establishing new rules or regulations. For this reason, it was not published in the Federal Register, which is reserved for regulatory announcements and rulemaking notices. Instead, the manual offers a scientifically grounded, consistent methodology for fieldwork that complements existing regulatory frameworks without imposing new legal obligations.
Implications for Waters of the United States (WOTUS) Determinations
The release of the Final OHWM Manual is particularly significant in light of recent regulatory changes surrounding WOTUS. Determining WOTUS boundaries is critical for assessing federal jurisdiction over various water bodies and wetlands. The OHWM plays a pivotal role in this process, particularly for non-tidal streams and rivers.
Here’s how the manual can be leveraged for WOTUS determinations:
- Standardization of Procedures: By following the uniform framework provided in the manual, environmental consultants, regulators, and project developers can ensure consistency in delineating water bodies.
- Defensible Documentation: The standardized datasheets and methodologies improve the defensibility of OHWM delineations during regulatory reviews and legal challenges.
- Informed Decision-Making: The manual’s scientifically validated approach enhances the accuracy of WOTUS assessments, reducing the risk of erroneous jurisdictional claims.
- Public Transparency: The inclusion of public feedback during the manual’s development underscores the agencies’ commitment to transparency and ensures that the latest scientific methods inform policy decisions.
Practical Applications in Wetland and Stream Permitting
Professionals working on projects that involve potential impacts to wetlands and streams can benefit from using the Final OHWM Manual in the following ways:
- Jurisdictional Determinations: The manual aids in determining whether a particular stream or river segment falls within federal jurisdiction, which is essential for Section 404 permitting under the CWA.
- Mitigation Planning: Accurate OHWM delineation helps define the extent of required mitigation measures, particularly for stream and wetland restoration projects.
- Compliance Audits: Environmental compliance teams can use the manual to audit and verify delineations conducted by third parties.
Conclusion
The Final National OHWM Field Delineation Manual represents a significant step forward in ensuring consistent and science-based delineation of ordinary high water marks. Its comprehensive guidance provides critical support for accurate WOTUS determinations and reinforces federal, state, and local efforts to protect aquatic resources. By adopting the methods outlined in this manual, stakeholders can enhance regulatory compliance, improve project outcomes, and contribute to the sustainable management of rivers and streams across the nation.
For further details, you can access the full manual and supporting documents on the official USACE website: https://www.erdc.usace.army.mil/ohwm.