Cooling water systems face compliance eddies

Susan Metzger

Thomas Englert

John Matousek

Glenn Piehler

Lawler, Matusky & Skelly Engineers LLP

Few people outside the utilities industry or the U.S. Environmental Protection Agency (EPA) have heard of Section 316(b) or the Clean Water Act (CWA), but revisions to that section, which are currently being undertaken by EPA, could have a massive impact on any company with a cooling water intake.

Section 316(b) affects any industry which uses surface waters as a source of non-contact cooling water (electric utilities, non-utility power producers, and certain large manufacturing operations). The Act states that “the location, design, construction and capacity of cooling water intake structures reflect the best technology available (BTA) for minimizing adverse environmental impact (AEI).” The impacts of concern are related to the effects of entrainment of early life history stages through the circulating cooling water system (CWS) of power plants and/or impingement of juveniles and adults on the intake screens protecting the CWS.

Evolution of Section 316(b)

EPA issued final rules in 1976, in conjunction with a BTA “Development Document,” followed in 1977 with “Guidance for Evaluating the Adverse Impact of Cooling Water Intake Structures on the Aquatic Environment.” In 1977 the rules were challenged by Appalachian Power Co. and ultimately suspended by the 4th Circuit Court. Thus there was no requirement for the application of the rules or associated documentation. The procedural challenges were related to EPA leaving the determinations of impact and BTA to regional staff, based on staff site-specific knowledge and professional judgement.

In the 1977 draft guidance manual for implementing Section 316(b), EPA stated, “The exact point at which adverse aquatic impact occurs at any given plant site or waterbody segment is highly speculative and can only be estimated on a case-by-case basis.”

To this end, utilities-generally on an EPA regional basis-funded studies to demonstrate that their plant`s intakes reflected BTA relative to the local aquatic populations and communities. This resulted in a host of innovative intake designs, as well as a new generation of mathematical models for estimating impacts on aquatic populations. Nevertheless, although there was some agreement about locating intakes outside of the spawning areas for important fish species, and designing new intakes to have low approach velocities (greater than 0.5 ft/sec), neither AEI definitions nor BTA decisions were uniformly implemented.

In 1993, the Hudson Riverkeeper and others sued EPA, demanding that the agency develop rules for implementing Section 316(b) regulations. The case was settled in 1995, with EPA agreeing to develop proposed rules by July 1999 and final rules by August 2001. Since then, EPA has conducted a screening level survey of selected utility companies and held two public hearings. EPA scheduled detailed questionnaires to be sent out in early 1999, but the Office of Management and Budget (OMB) rejected these pursuant to the Paperwork Reduction Act. The questionnaires, which are now expected to be distributed in July 1999, will require utilities to provide data on technical and financial aspects of their plants and operations. The financial data is required in order for the agency to conduct economic analyses of their rulemaking, including socio-economic impacts and cost-benefit analyses.

EPA`s next step following its review of the history of Section 316(b), reviewing existing intake studies, impact estimation techniques and conclusions, and the range of applicable CWS parameters is to develop a definition of AEI. As might be imagined there are widely divergent opinions on this important definition. To some, AEI is equivalent to the death of a single organism, which is fairly easy to measure. To others, it is the reduction of economically or ecologically important populations of species that matters, which is costly in both time and money and subject to debate over assumptions and precision of mathematical end-points. To yet another group, adverse impacts are reflected in the community of organisms rather than a single species.

In consideration of comments from industry and organizations such as EPRI and the Utility Water Act Group (UWAG), and the cost-effectiveness of various approaches, EPA has been developing a tiered approach to revisiting AEI assessment and BTA evaluations. Under the current approach, Tier 1 is a prescreening step wherein plants would first be prioritized on the basis of operational parameters like intake screen type and approach velocity. In Tier 2, some measure of overall waterbody or intake area “stress” would be examined using relatively quick and standardized methods such as the Rapid Bioassessment Procedures (RBPs). These techniques produce metrics that estimate community health like the Index of Biological Integrity (IBI) or the Reservoir Fish Assemblage Index (RFAI) being developed by the Tennessee Valley Authority. Still others are promoting use of population-and ecosystem-level risk analyses to evaluate impacts or impact potential. Nonetheless, EPA`s stated intent for Tier 2 is to focus on what has changed. If no change is indicated, the third tier-quantitative studies to determine impact and demonstrations of BTA-could be less rigorous. If a new source is proposed, EPA would require more extensive studies and BTA evaluations.

Evaluating options

First, although oil, pulp and paper, and a few other industrial operations involve CWS, steam electric plants have more intakes, and use more cooling water than all the rest combined. Second, since some environmental action groups push to equate cooling towers with BTA (based on the ultimate flow reduction technology), utilities could collectively be faced with retrofits costing tens of billions of dollars. Third, EPA estimated completion of the detailed questionnaire will involve 160 person-hours; however, the final questionnaire approved by OMB presumably will be less time-consuming. Fourth, utilities may want to start evaluating their situations sooner rather than later.

The first option is to determine whether facilities have a CWS that is BTA. Secondly determine whether or not, based on available intake and waterbody monitoring data, it can be demonstrated that adverse environmental impacts are not occurring as a result of operation. Recognize that some mitigation like substitution of a fish return for a trash basket and increasing screen rotation frequencies, might enhance the chance of obtaining a Section 316(b) variance. If this option appears questionable, and cooling tower retrofit or intake relocation is not acceptable to achieve BTA, evaluate technologies that can reduce entrainment and/or impingement rates or mortality in or around the structure. Figure 1 identifies intake technologies, grouped into those that prevent aquatic populations from entering the CWS (exclusion system) and those that separate and remove the organisms at some point within the CWS (separation and removal system). The primary advantages of exclusion systems are that organisms are not handled (stressed), while separation and removal systems generally require both removal and return handling. Physical exclusion systems are the only technologies that have the capability of substantially reducing entrainment impacts; however, several guidance systems can potentially reduce entrainment. Some of the more successful intake technologies are the Ristroph intake screen modification, which results in lower post-impingement mortality, underwater sound deterrent systems and exclusion barrier systems like the “Gunderboom” currently being evaluated on the Hudson River. Though usually a last resort, changes in plant operation such as seasonal flow reductions to reduce involvement of vulnerable stages of important species by lessening CWS capacity (numbers of pumps operating) and screen approach velocity may be considered. Finally, while frowned upon by many environmentalists who have urged EPA not to consider it a legitimate form of BTA, offsets may be considered (s

Early planning pays off

There is already a resurgence in interest in Section 316(b) in terms of hearings, workshops and conferences. EPRI sponsored an invitation-only workshop in September 1998 and an open conference in April of this year, and the authors conducted a short course on the subject in October 1998, partnering with the Stevens Institute of Technology in New Jersey. Attendance at these types of meetings and awareness of EPA`s actions by following their Internet news site ( owm/316b.htm) are two ways to begin preparation. Training for staff who were not part of the process during the 316(b) heyday in the `70s and early `80s may be helpful. Begin locating and reviewing previous Environmental Reports, 316s, and operational-monitoring data for any involved plants. It is also helpful to review gray literature, Edison Electric Institute and EPRI publications, conference proceedings and published literature to refresh institutional memory. And, it might not be a bad idea, in the case of plants located on marine or estuarine systems, to check-out the latest National Marine Fisheries Service Fishery Management Plans to get a feel for whether one should be thinking about simple approaches and approximations like “Equivalent Adult Losses” or more detailed models of natural, fishing, and plant-induced rates of mortality. The bottom line: do not ignore the planning process.

For more information on the status of Section 316(b), contact the authors at (888) 567-4080, or e-mail

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