On August 15, 2014, as part of the Clean Water Act, the U.S. Environmental Protection Agency (EPA)  issued final regulations for existing cooling water intakes—known to those in the industry as the “§316(b) Rule." This rule advises facilities on how to implement or improve their fish screening  technology at cooling water intakes. While these regulations are meant to provide guidance to facilities, many operators still struggle with understanding how to move forward, particularly when it comes to compliance measures, alternatives, and optimization studies.   

If your facility is considering a compliance alternative that requires an optimization study, our experts can help you make sense of it all. Read on to learn more.   

The 316(b) Rule and Compliance

The 316b rule of the Clean Water Act includes a body of regulations that apply to all facilities that use more than 2 million gallons per day (MGD) and at least 25 percent of the water withdrawn is used exclusively for cooling purposes. Facilities that meet these criteria are required to use the best technology available (BTA) for reducing fish entrainment and impingement at their facility. As part of 316b rule, the § 122.21(r)(6) application requirement is intended to determine if the chosen compliance method will reduce impingement mortality (IM) at the cooling water intake structure (CWIS). Seven compliance alternatives for meeting the IM BTA standard were laid out by the EPA and include two alternatives that require optimization studies to confirm compliance.

Compliance Alternative 5

Facilities operating a modified traveling screen (BTA) that the Director determines meets the definition at § 125.92(s) and that the Director determines is the best technology available for impingement reduction must show favorable results via an optimization study. 

Compliance Alternative 6

A two year biological demonstration is needed if a facility operates any other combination of technologies, management practices and operational measures that the Director determines is the best technology available for impingement reduction

What Are Optimization Studies?

Once an impingement mortality BTA is chosen and installed at a facility, a two year optimization study must be conducted. During this two year period, the facility will conduct monthly impingement data collection, during which the facility will seek to optimize the technology performance to minimize impingement and/or impingement mortality.

In accordance with the rule, an optimization study must include a description of the sampling approach, taxonomic identification of all organisms sampled, identification of moribund organisms, and a description of latent mortality during holding periods. These studies would involve developing sampling protocols and a study plan, setting up fish holding facilities to evaluate latent mortality, and conducting the monthly sampling which can be conducted by the facility or with the help of an outside consulting company.

A fish holding facility that is used as part of an optimization study is set up onsite to aid in evaluating latent mortality of fish at a facility with a cooling water intake structure. 

Optimization studies are intended to determine the optimal configuration and operating conditions of the IM BTA so that it is consistently protective of aquatic organisms. During an optimization study, interim results will be used to identify and make appropriate changes to the design and/or operation of the IM BTA to maximize its biological performance.

Once the optimization study is complete and the IM BTA is operating in the optimized manner, design and operating parameters will be developed to ensure long term success. There parameters will serves as observable and enforceable permit conditions. After completion of the optimization study, no further biological data collection will be needed to demonstrate IM compliance.

Alden's Experience

Alden staff have been involved in all aspects of the §316(b) Rule for fish screening at cooling water intakes, including rulemaking development, research, design, evaluation, installation of intake technologies, and the completion of the studies needed to demonstrate fish screen compliance. We use an integrated approach in developing compliance strategies for intake structures. With our familiarity with intake screen technology involving close cooperation between engineers and scientists, we can ensure that a design will be biologically effective, as well as feasible to construct, operate and maintain. We strive to make these regulatory requirements as cost-effective as possible. 

As for our experience with fish screening technologies, our scientists and engineers have been thoroughly involved with the research and development, evaluation, and design of fish screening facilities at water withdrawals. Through hydraulic model studies and both laboratory and field biological evaluations, Alden has been part of the development of state-of-the-art fish protection facilities that are in use throughout North America.

Some of the various types of fish screens that have either been developed or tested at Alden, include

  • Coarse- and fine-mesh modified traveling screens (Ristroph-type collection screens with fish lifting buckets)
  • Fixed and traveling fish diversion screens
  • Cylindrical wedgewire screens
  • Rotary drum screens 
  • Fish return systems.

In addition, Alden's scientists and engineers have conducted extensive research on the effectiveness of behavioral barriers for preventing fish impingement that have included technologies like strobe lights, sound deterrent systems, infrasound, air bubble curtains, hanging chains, electric deterrents, and water jet barriers.

We have also developed, along with EPRI, manuals that describe the components of a modified traveling water screen and fish returns that can be optimized, including both design and operational considerations (EPRI 2015, 2020). These manuals were created to provide further knowledge of the new fish protection component requirements and a better understanding of the optimization process. (Links are provided below for your convenience.)

Ways Alden Can Help with §316(b) and Optimization Studies

We have completed water intake systems alternative technology design and costs assessments for over 170 water intake structures throughout the U.S. Alden has completed the 122.21(r)(2-8) and (10) studies for a clients across the country and for all major waterbody types. We can use our detailed understanding of §316(b) and intake technologies to help you with: 

  • Preparation of 121(r)(2-8) Studies
  • Analysis and selection of impingement mortality best technology available compliance alternatives as part of the 122.21(r)(6) Study
  • Technical feasibility assessment and costs of fine-mesh technologies as part of the 122.21(r)(10) Study
  • Selection of appropriate screens and mesh along with the development of screen vendor specifications for both IM &E compliance
  • Design of screen installation and fish return system
  • Technical support during the bidding and construction of a BTA
  • Preparation of optimization study design and standard operating procedures (SOPs)
  • Design, fabrication and setup of fish collection and holding systems
  • Training, oversight and collection of monthly biological sampling
  • Collection of data, including analysis and reporting
  • NPDES Permitting Support and Agency Consultation

We are available to help with any questions you may have about §316(b) and the optimization study process, so let's talk. Contact us now to get the conversation started. 

Helpful Links

EPRI Optimization manuals

EPRI TWS Optimization Manual: https://www.epri.com/research/products/000000003002013687

EPRI Fish Return Guidelines: https://www.epri.com/research/products/3002001422


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