Clean Water Act Section 316(b)


Alden has historically played, and continues to play an active role in providing technical comments to UWAG and EPRI during the 316(b) rule-making. 

As the Rule was being developed, Alden was selected by EPA as the recognized expert in the field of alternative fish protection technologies to participate at public meetings. The Alden team is comprised of engineers, fisheries scientists, and modeling personnel. 

Our multidisciplinary approach combines expertise in intake design and operational engineering, biology, economics, hydraulics and hydrology, and environmental restoration.  


Alden’s philosophy is simple. We use a sensible approach that minimizes the costs associated with compliance.


When studies are required by the agencies, we excel at maximizing biological benefits through the development of flexible and cost-effective technology, restoration, and/or flow reduction alternatives. 

Detailed Review of Section 316(b) of the Clean Water Act

The U.S. Environmental Protection Agency provided long-awaited guidance on fish protection at cooling water intake structures (CWIS) on May 19, 2014. The final Rule issued under Section 316(b) of the Clean Water Act applies to facilities that withdraw at least two million gallons per day (MGD) of cooling water from Waters of the U.S. The requirements set forth in the final Rule will be implemented through the National Pollutant Discharge Elimination System (NPDES) permitting process.

The final Rule provides greater compliance flexibility than earlier drafts.  In the draft Rule, there were only two compliance alternatives for meeting impingement mortality reduction standards (required of all facilities withdrawing greater than 2 MGD): installation of traveling water screens (TWS) with fish protection features; or, installation of a technology that is designed not to exceed 0.5 ft/sec through-screen velocity.  The TWS option would have required extensive biological monitoring to demonstrate that total impingement mortality was no greater than 12% (annual average) and 31% (monthly average). 

The final Rule provides seven options for reducing impingement impacts at water withdrawals: 1) closed cycle cooling; 2) 0.5 ft/sec through-screen velocity (by design); 3) 0.5 ft/sec through-screen velocity (measured); 4) existing offshore velocity cap; 5) modified TWS; 6) a suite of technologies determined by the Director (permit writer) to be best technology available (BTA); or 7) any technology that results in an annual impingement mortality below 24%. 

As with the draft Rule, the final Rule would impose entrainment reduction requirements on a case-by-case basis.  

In both the draft and final Rules, facilities with an actual intake flow (AIF) greater than 125 MGD would be required to provide more detailed information to support the determination of entrainment reduction requirements.  EPA clarified the definition of AIF to allow days of zero flow to be included. 

The final Rule addresses many of the concerns industry had with the draft Rule and provided additional clarification.  

For example, EPA removed a requirement that facilities on estuaries must install barrier nets (or their equivalent) to protect shellfish from impingement.  Meeting this requirement was seen by many water users as difficult or even impossible to implement because of waves, debris, biofouling, and navigational issues.  In the draft Rule, there was considerable ambiguity about which of the newer modified TWS designs would meet Rule requirements.  

In the final Rule EPA expanded the definition to encompass all of the available TWS types, including: through-flow, dual-flow, center-flow, rotary-disc, and vacuum systems. 

In the final Rule, EPA reduced the level of biological monitoring required after the installation of a technology.  In the draft Rule, impingement mortality sampling was required at least on a monthly basis for the life of the facility.  In the final Rule, those facilities complying with modified TWS or a suite of technologies (compliance alternatives 5 and 6) would be required to conduct a 2-year optimization study.  During the study, operational components could be varied and the impact to survival evaluated.  The design and operation features identified as optimal for fish survival would be incorporated into a facility’s NPDES permit.  Perhaps most importantly, EPA addressed a scheduling conflict between compliance with entrainment and impingement requirements.  

The draft Rule required impingement to be addressed prior to entrainment.  Under such a scenario, it would be possible for a facility to install fish protection technologies to address impingement and at a later date find these technologies incompatible with those technologies or operational measures necessary to reduce entrainment.