Opinion ID: 785093
Heading Depth: 4
Heading Rank: 1

Heading: The 90 percent threshold

Text: 18 By requiring a standard based on the best technology available, the Clean Water Act appears to contemplate a single level of performance applicable to all facilities. The Environmental Petitioners contend that Track II violates this aspect of section 316(b) by allowing facilities to demonstrate only 90 percent of the reduction in impingement and entrainment that Track I would accomplish, instead of requiring an equivalent reduction in impingement and entrainment. 19 The EPA agrees that Tracks I and II must reflect the same standard, but it contends that 10 percent is an acceptable margin of error for measuring reductions in impingement and entrainment. As it wrote in the preamble to the Rule: 20 EPA does not consider this requirement to mandate exactly the same level of reduction in impingement and entrainment as would be achieved under Track I. Rather, given the numerous factors that must be considered to determine the required level of reduction in impingement and entrainment for Track II and the complexity inherent in assessing the level of performance of different control technologies, EPA believes it is appropriate for a new facility following Track II to achieve reductions in impingement and entrainment that are 90 percent or greater of the levels achieved under Track I. 21 Final Rule, 66 Fed.Reg. at 65,279. 15 Measurements of organism impingement and entrainment are necessarily inexact estimates based on available data as well as certain assumptions. Id. The EPA can only predict the effect of a proposed Track II approach at a new facility based on empirical results at other facilities, but the data on which the EPA relies in reaching those estimates comes from a variety of sources ( e.g., studies at multiple plants using different methods at different periods of time, interviews, on-site visits, literature searches), and the underlying studies themselves contain only estimates of technological performance that is bound to vary according to site-specific conditions. See Eng'g & Analysis Div., U.S. Envtl. Prot. Agency, Technical Development Document for the Final Regulations Addressing Cooling Water Intake Structures for New Facilities, Pub. No. EPA-821-R-01-036, at 5-1 to 5-2, 5-5 (2001) [hereinafter TDD ]. Sampling errors and natural fluctuations in animal populations further skew the results: The number of fish impinged at the same intake points at the same plants, withdrawing the same amount of water at the same speed, will not be equal on any two days, see, e.g., Carole D. Goodyear, U.S. Fish & Wildlife Serv., Evaluation of 316(b) Demonstration: Detroit Edison's Monroe Power Plant, Admin. Rep. No. 83-3, at 11, 13-16, 28 (1978), and animal populations in the water surrounding the intake point will oscillate from year to year for a variety of reasons unrelated to the intake structure, see Eugene P. Odum, Fundamentals of Ecology 188-95 (3d ed.1971). As a result, when predicting whether one approach will have the same effect in reducing impingement and entrainment as Track I's capacity and velocity limits, the EPA must necessarily account for all of those variables. 22 The Environmental Petitioners do not contend that 10 percent is an unreasonable margin of error to use in measuring compliance. Rather, they argue that the EPA should not have accounted for any measurement error by adjusting the underlying standard to 90 percent. The logic of their position suggests that they would not object if the EPA required equivalent (instead of comparable) reductions in impingement and entrainment in Track II but indicated elsewhere in the Rule that a facility could demonstrate such equivalence within (plus or minus) 10 percent. The distinction between those two options is lost on us, however, for we discern no significance in the location of the 10 percent provision in the Rule, or whether the Rule requires 90 percent compliance instead of allowing a 10 percent margin of error. We recognize that the EPA, consistent with Congress's intention that there be a national standard governing the discharge of pollutants, must promulgate precise effluent limitations under sections 301 and 306, for example, 40 milligrams of suspended solids per liter, or 30,000 parts per million of toxic pollutants. See Natural Res. Def. Council, Inc. v. U.S. EPA, 863 F.2d 1420, 1431-32 (9th Cir.1988); Cal. & Hawaiian Sugar, 553 F.2d at 285; Hooker, 537 F.2d at 623-24, 630. But Congress did not intend the EPA to leave industry with only one means of reducing adverse environmental impact, viz. reducing capacity and velocity, just as it did not intend to bind industry's hand by requiring particular types of effluent reducing technology. Because impingement and entrainment, unlike pollutant concentration and the velocity and volume of water, cannot always be measured directly and with mathematical precision, the use of any alternative technologies would require the EPA to make a judgment call as to whether those technologies yield results equivalent to Track I's. We think it was reasonable for the EPA to make clear in the regulation how much ambiguity it is willing to tolerate in measuring compliance and what it considers a reasonable margin of error in comparing the performance of different technologies. 16 23