The U.S. Environmental Protection Agency (EPA) has proposed new Clean Water Act section 316(b) regulations for once-through cooling water intake structures. Comments on the proposed rules closed in August, and a final rule is expected mid-2012. The EPA estimates that at least half of the power plants using once-through cooling will be required to implement a best technology available solution in coming years. That typically means barriers and screens, but you may want to consider other options.
The U.S. Environmental Protection Agency (EPA) recently proposed regulations, under section 316(b) of the Clean Water Act (CWA), designed to reduce the mortality of fish and other aquatic life entering cooling water intake structures of existing power plants. CWA 316(b) “requires that the location, design, construction, and capacity of cooling water intake structures for facilities having NPDES [National Pollutant Discharge Elimination System] permits reflect the best technology available (BTA) for minimizing adverse environmental impact.” An NPDES permit, which requires compliance with CWA 316(b), is required for any “point source” discharge into the “navigable waters” of the U.S. Most states are authorized to issue State Pollutant Discharge Elimination System permits.
The proposed rule covers “roughly 1,260 existing facilities that each withdraw at least 2 million gallons per day of cooling water,” according to the EPA. The agency estimates that this rule will affect about 670 power plants. Comments on the proposed rulemaking closed on August 18, 2011, and a final rule is expected in July 2012. The current rulemaking process will be interesting to watch. Twice, prior CWA 316(b) rulemakings (2004 and 2006) were successfully challenged in federal court and were remanded for corrections.
The proposed rule comes in three parts. First, existing facilities that withdraw at least 25% of their water from an adjacent water body used exclusively for cooling purposes and that have a design intake flow of greater than 2 million gallons per day would be subject to an upper limit on the number of fish killed by “impingement” against intake screens or other parts at the facility. Impingement occurs when fish and other organisms “are trapped against screens when water is drawn into [a] facility’s cooling system,” according to the EPA.
The owner of the facility will be required to select a technology to reduce those organism deaths, including reducing “its intake velocity to 0.5 feet per second.” Fish can swim away from the structure in water flowing at this velocity. This rule no longer allows restoration of a facility as a compliance alternative.
The second component of the new rule pertains to large users of once-through cooling water, at least 125 million gallons per day, which probably means all power plants using once-through cooling, whether it is ocean, river, or lake water. Those users must conduct studies that will determine site-specific technology alternatives, including conversion to the use of closed-cycle cooling (cooling towers), that will reduce aquatic organism mortality. The BTA option selected for use at a particular facility will be determined on a case-by-case basis.
The third and last requirement states that new units constructed at existing plants will be “required to reduce intake flow to a level similar to a closed cycle, recirculation system.” In essence, new units must use cooling towers to handle the additional load, or the equivalent.
The EPA requires BTA compliance within eight years of the new rule’s effective date. Also, the EPA estimates that more than half of the facilities affected by the rule already use technologies that will likely put them into compliance, although the EPA estimates covered all industrial plants, not just power plants. The rule does not apply to “new facilities,” defined as those plants that began construction after January 17, 2002.
Today’s Technology Options
Many plants continue to move forward and implement voluntary plans to meet the original guidelines set by the EPA’s 2004 Phase II Rule, specifically aimed at large power plants, which was suspended in July 2007. That rule required many existing facilities that were withdrawing their cooling water from rivers, oceans, and the Great Lakes to reduce their entrainment and impingement of aquatic organisms by an estimated 60% to 90%.
There are a number of technology options that can be used to comply with the Phase II Rule and BTA as defined by the pending rule. BTA is usually a combination of physical or nonphysical barriers: fine mesh intake traveling or passive screens, modification of existing screens for fish collection and return, special angled or louvered bar racks, or the addition of behavioral modification for fish guidance or deterrence.
Recent studies and field-testing of each option have produced positive results that are close to the desired levels previously set by the EPA. Each technology offers its own set of challenges and advantages. However, in our experience, deploying a combination of two or more technologies has proven to be the most effective approach to reaching a plant’s fish mortality reduction goals.
The use of physical barriers such as fish gates or rock barriers is the least desirable method because such barriers create an obstacle to waterway navigation and require frequent maintenance. Passive screens can be effective, but they have limited applications. The use of fine mesh screens will result in velocities greater than those set by the EPA, and high debris loading on the screen will reduce its effectiveness.
Impinged fish often come in a wide variety, often 50 to 100 species of juvenile and adult fish. Delicate pelagic (silver) fish such as shads, smelts, and herring are often the bulk of the impinged fish. These smaller, weaker swimming fish are unable to escape the intake current and are drawn in to the intake screen.
Technologies growing in favor are those that use behavioral modification, a system that uses stimuli such as electricity, sound, light, and air bubbles. The results obtained at several power stations and other water intakes over the past 10 years have proven such technologies to be effective in protecting many of the juvenile or mature fish species.
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