Opinion for the Court filed by Circuit Judge WALD.
WALD, Circuit Judge:
The National Lime Association (NLA), representing ninety percent of this country's commercial producers of lime and lime hydrate (the industry), challenges the new source performance standards (NSPS) for lime manufacturing plants issued by the Environmental Protection Agency (EPA, Administrator or Agency) under § 111 of the Clean Air Act (the Act), 42 U.S.C. § 7411 (Supp. I 1977). The standards limit the mass of particulate that may be emitted in the exhaust gas from all lime-hydrating and from certain lime-manufacturing facilities and limit the permitted visibility of exhaust gas emissions from some facilities manufacturing lime. We find inadequate support in the administrative record for the standards promulgated and therefore remand to the Administrator.
I. RELEVANT PARTICULARS OF THE LIMESTONE INDUSTRY
A. The Industry
In sheer size and weight of production, the limestone industry ranks among the largest in this country. Limestone production in the United States ranks second only to sand and gravel in commodity tonnage and exceeds petroleum, coal and iron ore in volume produced. Limestone deposits can be found beneath an estimated fifteen to twenty percent of the surface of the United States and occur in every state. Total national production approximates twenty-two million tons annually and derives from plants in over forty states.
The recent development of two important industrial uses for lime
B. The Production of Lime From Limestone
The process by which commercially valuable lime is produced is relatively simple. Limestone is quarried, crushed, sized and fed into a kiln where it is subjected to high temperatures (1100°C/2000°F). By a process
Almost ninety percent of total United States lime production is processed in rotary kilns.
C. The Production of Hydrated Lime
A comparatively small amount (ten percent) of all lime produced is further processed into hydrated or slaked lime. This is done by adding water to lime and introducing the mixture into an agitated hydrator. An exothermic reaction occurs and a fluffy, dry, white powder, known as hydrated lime, is the result.
D. Emissions Control in the Production of Lime
Rotary kilns here and abroad have employed several different methods of emissions controls including the fabric filter baghouse, the electrostatic precipitator (ESP), the high energy scrubber, and the gravel bed filter.
EPA has identified baghouses, ESPs and scrubbers as "best systems" of emissions control for rotary lime kilns.
The operation of baghouses and electrostatic precipitators was briefly explained in our initial review of EPA's performance standards for portland cement plants, Portland Cement Association v. Ruckelshaus, 486 F.2d 375, 390-91 (D.C.Cir. 1973), cert. denied, 417 U.S. 921, 94 S.Ct. 2628, 41 L.Ed.2d 226 (1974) [hereinafter cited as Portland Cement I]. The baghouse method employs fabric filters ("bags"), situated within an enclosed area (a "house"), to remove particulate from the kiln exhaust gas which is channeled through the house.
As the exhaust gas passes through, a dust cake forms on the filters. The cake itself improves filtration efficiency, but from time to time the filters must be cleaned. This is done by forcing a reverse gas flow through the fabric, thus releasing the cake for disposal.
EPA acknowledges that fabric filter effectiveness is primarily a function of kiln exhaust particle size distribution, fabric type, fabric age and maintenance history.
Under this method, "dust particles are charged [by discharge electrodes] and pass through an electrical field [collector plates] of the opposite charge, thus causing the dust to be precipitated out of the exhaust gas . . .." Portland Cement I, 486 F.2d at 390. Two basic criteria must be met before an ESP can be utilized: (1) the suspended particle must be able to accept an electric charge; and (2) the particle must then pass through an electric field of sufficient strength to ensure removal of the particulate from the gas stream at the desired efficiency.
Precipitability is a function of the chemical composition of the dust particles, and will vary with the different kinds of material that make up the kiln exhaust dust (limestone, quicklime, fly ash, calcium sulfate, etc.).
Scrubbers operate on the principle that wet particles are easier to control than dry. High pressure (or high energy) scrubbers of the type EPA considers capable of meeting the promulgated standards are those which because of their design increase the likelihood of contact between particle and water.
The most common high pressure drop scrubber used for controlling emissions from rotary lime kilns is the venturi scrubber. This scrubber operates by accelerating the velocity of the exhaust gas through a narrow venturi-shaped throat, where it is then brought into contact at great force with a spray of water. The particles thus dampened coalesce to form a slurry that can then be collected by a comparatively simple water-gas separation device. The separated gas is then released into the atmosphere.
The efficiency of particulate removal is a direct function of energy input, measured by pressure drop across the venturi throat.
E. Emissions Control in the Production of Hydrated Lime
Hydration emissions have been shown to be most effectively controlled by wet scrubbers and they are the only system of emission reduction considered by EPA for lime hydrators.
The most common type of scrubber used on lime hydrators is the wetted fan type with centrifugal separation. In this scrubber water is sprayed into the center of a draft fan where it is forced to mix with the exhaust gas. More water is sprayed just after the fan into the duct carrying this gas-water mixture. The dust laden slurry water is then removed from the cleaned gas stream by centrifugal separation and the "scrubbed" gas is then vented to the atmosphere.
Slurry water is returned immediately to the hydrator for reuse; the hydration process requires the addition of water and the captured dust seems to contribute to, rather than interfere with, the production of hydrate. Recycling the slurry water eliminates the settling ponds and waste sludge disposal problems usually associated with particulate scrubbers.
II. PROCEDURAL HISTORY
Section 111 of the Clean Air Act, formerly 42 U.S.C. § 1857c-6 (1976) (repealed 1977), now 42 U.S.C. § 7411 (Supp. I 1977), authorizes the Administrator to limit the air pollutants that can lawfully be emitted from newly constructed
On May 3, 1977, EPA added lime manufacturing plants to the list of sources that "may contribute significantly to air pollution which causes or contributes to the endangerment of public health or welfare" pursuant to section 111(b) of the Clean Air Act, 42 U.S.C. § 1857c-6(b)(1)(A) (1976) (repealed 1977).
Although lime plants were determined to be sources of nitrogen oxides, carbon monoxide and sulfur dioxide as well as particulates, standards of performance were proposed and ultimately promulgated only with respect to particulate matter.
The standard proposed and promulgated for lime hydrators limits emissions to 0.075 kilogram of particulate matter per megagram of lime feed (0.15 pound per ton). No opacity standard was set.
The standards promulgated for particulate emissions are considerably stricter than the average applicable state regulations already in effect. Plants conforming to the NSPS here would—in the case of rotary kilns—be required to emit less than one-third the particulate permitted under average state regulations and—in the case of hydrators—less than one-sixth the particulate permitted by these regulations. See SSEIS 4-15.
Evidently, EPA had engaged in a dialogue with the NLA concerning the anticipated NSPS for at least a year before the standards were proposed.
III. PREVIOUS REVIEW UNDER SECTION 111
As amended in 1977, section 111 of the Clean Air Act requires the Administrator to prescribe standards of performance for new statutory sources that reflect
42 U.S.C. § 7411(a) (Supp. I 1977).
These decisions, viewed independently, have established a rigorous standard of review under section 111. We have not deviated from the approach applied to the first NSPS to reach this court. In that case, Portland Cement I, we acknowledged that
486 F.2d at 402 (citations omitted).
In Essex Chemical we reiterated this concept of the court's role in examining the basis for section 111 standards:
486 F.2d at 434. The search for reasoned decisionmaking in a world of technical expertise must continue if judicial review is to have any meaning in the statutory scheme.
Section 111 requires that the emissions control system considered able to meet the standard be "adequately demonstrated" and the standard itself "achievable." 42 U.S.C. § 7411(a) (Supp. I 1977). We have in the past remanded section 111 standards for the "seeming refusal of the agency to respond to what seem to be legitimate problems with the methodology of the [ ] tests," Portland Cement I, 486 F.2d at 392; and the limited relevance and reliability of the tests relied upon in support of the standard. Id. at 396, 401. In Essex Chemical as well as Portland Cement I we expressed concern that the standards set might not have been achievable in periods of abnormal operation, e. g., during the "startup, shutdown and [equipment] malfunction" periods that occur in plant operation; and we remanded for further consideration of this issue. Portland Cement I at 398-99; Essex Chemical, 486 F.2d at 433. We have also questioned the significance of tests conducted for purposes of standard development under conditions different from those specified by the regulations for enforcement. Essex Chemical at 436. In analogous review proceedings under other sections of the Clean Air Act and under the Federal Water Pollution Control Act, 33 U.S.C. § 1251 et seq. (1976), this court and other courts have evinced a similarly rigorous approach.
However, we think it serves little purpose to elaborate on the standard of review as applied before we explain how, under the general approach required by statute and our earlier decisions, we have evaluated petitioner's and respondents' contentions.
The issue presented here is primarily one of the adequacy of EPA's test data on which the industry standards are based. NLA disagrees with EPA's conclusion that the standards are achievable under the "best technological system of continuous emission reduction which . . . the Administrator determines has been adequately demonstrated." Specifically, NLA claims that the test data underlying the development of the standards do not support the Administrator's conclusion that the promulgated emission levels are in fact "achievable" on a continuous basis. Promulgation of standards based upon inadequate proof of achievability would defy the Administrative Procedure Act's mandate against action that is "arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." 5 U.S.C. § 706 (1976).
IV. ASSESSMENT OF THE OBJECTIONS RAISED BY THE INDUSTRY
Our review has led us to conclude that the record does not support the "achievability" of the promulgated standards for the industry as a whole.
Bearing this initial burden will involve first, identifying and verifying as relevant or irrelevant specific variable conditions that may contribute substantially to the amount of emissions, or otherwise affect the efficiency of the emissions control systems considered. And second, where test results are relied upon, it should involve the selection or use of test results in a manner which provides some assurance of the achievability of the standard for the industry as a whole, given the range of variable factors found relevant to the standards' achievability.
EPA itself acknowledged in this case that "standards of performance . . . must . . . meet these conditions for all variations of operating conditions being considered anywhere in the country." SSEIS 2-6 (emphasis supplied). As set forth in the standards support statement, EPA's guidelines require data to be assessed with consideration of the "representativeness" of the source tested, including the "feedstock, operation, size and age" of the source. SSEIS at 2-7. Furthermore, the record strongly suggests other factors that may affect the particulate emissions from lime plants. Yet at no point does EPA evaluate the relevance or irrelevance of such factors to regulable emissions; nor does the Agency explain how such factors might have been taken into account in choosing test plant sites or in analyzing the data from the sites it chose.
The critical question presented here is whether the regulated industry, through its trade association, should have borne the entire burden of demonstrating the unreliability for the industry as a whole of the conclusions drawn by the EPA. In this connection we are candidly troubled by the industry's failure to respond, at a crucial juncture in the standards development process, to the Agency's invitation to submit data supporting a fundamental industry objection to the achievability of the standard.
The showing we require does not mean that EPA must perform repeated
We must remand to the Agency for a more adequate explanation or, if necessary, for supplementary data to justify the standard in terms of the "representativeness" of the sources tested. The specific doubts generated by our review of the record in light of the lime industry's attack on the standard are more fully explained below.
A. The Particulate Emission Standards
1. Rotary Kilns
EPA tested emissions at six plants
Our doubts about the representativeness of the data relied upon are grouped under three subheadings below: Variations in Quantity of Particulate Generated in the Kiln ; Variations in Controllability of Particulate Generated ; and Explanation of Discarded Data from Plants A and F. Under the subheading Variations in Quantity of Particulate Generated in the Kiln, we discuss the possible impact on the standard's achievability of composite dust levels generated by the tested plants and two factors (feedstock variations and gas velocity) that may contribute to composite dust levels. Under the subheading Variations in Controllability of Particulate Generated, we discuss two factors—apart from sheer quantity of dust—that may affect emissions control: coal usage and particulate size. Finally under the subheading Explanation of Discarded Data from Plants A and F, we discuss the EPA's handling of the results of two tested plants that were unable to meet the standards proposed.
a. Variations in Quantity of Particulate Generated in the Kiln
That the quantity of dust produced in the kilns would affect the controllability of emissions and the achievability of the standards
(1) Feedstock Variations
For example, the record suggests that the size and chemical composition of the limestone feedstock used will affect the amount of dust produced.
The MRI Report, prepared for EPA as a prelude to proposal of the particulate emission standards and an important background document considered in developing the proposed standards,
The same theme was struck by NLA's comments on the proposed standard: "No consideration has been given by EPA to variations produced in stone size or preparation, or to the physical characteristics of the stone feed and lime produced, with the resultant variations in the quantity of flue dust to be handled." R. 103, 10.
The EPA did note in its SSEIS that "[r]otary kilns can handle a range of stone feed sizes between 1/4 inch and 2½ inches," SSEIS 3-6, and that larger feed size generally results in lower dusting in the kiln. See SSEIS 3-14.
(2) Gas Velocity and Operation Levels
According to the MRI Report, quoted above, dust generation is in part a function of gas velocity in the kiln. Gas velocity appears in turn to depend on several factors, including the percentage of capacity at which the kiln is operating. The MRI Report stated that kiln gas velocity has "the most [apparent] effect [on dust generation] when the kiln is operated close to 100 percent of design capacity," and noted that in one plant studied an increase in production—from 100% to 135% of design capacity—resulted in double the rate of emissions where a reduction from 100% to 75% resulted in only an eight percent reduction. R. 8, 2-3.
Both in this court and at the administrative level the industry has addressed the possible atypicality of the production level of some of the test plants, which it alleges were not tested at full capacity
Data on the production level and air flow rate (velocity) at the tested plants were included in the support document filed in this case.
Having stated that much, however, the Agency did not explain how the range of test results fully takes account of any significant differences in operating conditions in the industry. The support document is totally devoid of analysis of the relevance or irrelevance of operating level or gas velocity to the achievability of the standard, notwithstanding assertions in the EPA's own contracted-for report
(3) Dust Levels at the Tested Plants
The SSEIS asserts, without explaining how the conclusion was reached, that Kilns A, B and E each generated dust at a rate of twenty-two to twenty-five percent (pounds of dust collected per pound of lime produced),
As laypersons it seems entirely logical to us to suppose that dust generation levels would directly affect emissions controllability, viz., the higher the dust generation, the more difficult the achievability of the standard by the technological control device. But the exact relationship between volume of dust generated and the efficiency of the emissions control systems is never clearly stated or explained by the Agency. Instead, the Agency sends us several mixed signals.
On the one hand, the Agency suggests both directly and indirectly that more dust means a more difficult control problem. The direct suggestion is made in the Agency's rationale for the standard, which states that the two baghouse-controlled test kilns generated "higher [dust levels] than the industry reported average and therefore represent difficult control situations" SSEIS 8-17 (emphasis supplied). The indirect suggestion is made by the standard itself, which permits higher levels of emissions when larger quantities of feed are being burned, a circumstance under which the production of more dust would be expected.
On the other hand, the Agency asserts that the amount of dust generated is irrelevant to the efficiency of at least one control method and therefore to the achievability of the standard. In correspondence with the NLA antedating the standard's proposal, EPA stated,
R. 8, 10 (emphasis supplied). However, the MRI Report does not indicate whether long term heavy dust loading or extremely heavy short term dust loading would impair the efficiency of the control system; nor does the report indicate what manufacturers consider to be a heavy or short term dust loading; nor does it indicate on what basis the manufacturers' opinion is predicated.
Our examination of the record thus yields a conflict: while in one breath EPA appears to acknowledge the relevance of dust generation levels to the proposed standard, in another breath the relevance is denied. In our view, the conflict is not adequately explained, nor is the industrywide achievability of the standard adequately justified, in light of the acknowledged possibility that heavy dusting creates a more difficult control problem. From what appears in the record, both variations in dust volume produced and its contributing factors received inadequate attention from the Agency in the development and explanation of this standard.
b. Variations in Controllability of Particulate Generated
The record points to other variables which were also given short shrift in the stated rationale: the use of coal to fuel the kiln (as it relates to controllability of emissions); and variations in size of emitted particles. The record strongly supports the relevance of coal usage to the efficiency of at least the ESP control method and it also suggests a relationship between particle size and the efficiency of both the ESP and the baghouse control method. Nothing indicates how—if at all—variations in these factors were considered in proposing an "achievable" standard.
(1) Coal Usage
It is clear that the trend in the industry is not only toward coal, but toward high sulfur coal, as other energy sources become scarcer. EPA estimates that by 1986, fifty percent of the lime plant new capacity will have high sulfur coal as the only fuel available. SSEIS 3-5. One-half of all coal used will be between one and four percent sulfur content; the average, as high as three percent. SSEIS 6-6. Moreover, conversion to coal is expected to be a major "modification" that will bring old plants into the regulatory orbit under section 111. SSEIS 5-2-5-3, 8-23. Finally, Congress was especially concerned in passing the 1977 Clean Air Act Amendments that the increased use
However, the impact of high sulfur coal usage on the controllability of particulate emissions under any of the three "best" emissions control systems was not clearly or closely examined by EPA in the development of this standard.
With respect to the ESP system, for example, EPA acknowledged that "precipitability [or efficiency of the ESP method] is a function of the chemical composition of the dust particles and will vary with the different kinds of material that make up the kiln exhaust dust (limestone, quicklime, flyash, calcium sulfate, etc.)." SSEIS 4-6. However, neither of the two ESP plants burned coal, the burning of which will affect the chemical composition of the dust and hence the "precipitability" of emissions.
The support document acknowledged:
SSEIS 8-12. EPA does not, however, explain the basis for its optimistic judgment that an ESP could meet the standard on a coal burning kiln.
In still other ways the critical influence of coal, particularly high sulfur coal, was not adequately taken into account. For example, EPA acknowledges that conversion to coal will "cause an increase in particulate emissions in the kiln." SSEIS 5-3.
In addition, the record reflects little consideration of the impact of variations in the sulfur content of coal used. For example, the sulfur content at the coal burning plants tested was considerably smaller than the average projected sulfur content (3 percent) for all new lime plants in the near
It is certainly plausible that the use of high sulfur coal will result in a greater increase in uncontrolled or difficult-to-control particulate emissions. (The standards support statement suggests that sulfur content may affect particulate weight. SSEIS D-7.) Yet EPA did not state whether the one coal-converted plant which showed no increase in controlled emissions used high or low sulfur coal.
These little bits of information about the impact of coal usage on the controllability of particulate emissions are left for us to piece together. This obvious and important trend at least deserves to be discussed in a coherent fashion.
Given the high emphasis in the 1977 Clean Air Act Amendments on coal— especially high sulfur coal—as the fuel of choice,
(2) Particle Size
Although there is (a) considerable evidence in the record that the efficiency of available control technology varies with emitted particle size and (b) that lime dust particle size varies regionally (probably due to feedstock variation), the EPA (c) undertook no analysis of the impact of particle size distribution on the achievability of its standard. Each of these points is discussed under separate subheadings below.
(a) The relationship of particle size to efficiency of control methods
That particle size affects the efficiency of at least two of the three "best" technological control systems seems clear.
With respect to the baghouse method of emissions control, the support statement itself states that "[f]abric filter effectiveness is primarily a function of kiln exhaust particle size distribution, fabric type, fabric age and maintenance history." SSEIS 4-2 (emphasis supplied).
With respect to the ESP method, EPA acknowledges that ESPs experience a "relatively low collecting efficiency on submicron particles." SSEIS 4-7. Furthermore, EPA has made a similar acknowledgment with respect to both the ESP and the baghouse method on remand from this court's decision in Portland Cement I. In a document prepared in response to the remand, EPA stated: "These collectors, fabric filters or electrostatic precipitators, are more effective in removing coarse particles than fine particles." EPA, Response to Remand Ordered by U.S. Court of Appeals for the District of Columbia in Portland Cement Association v. Ruckelshaus (486 F.2d 375, [D.C.Cir.] June 29, 1973), EPA 450/2-74-023, 113 (1945) [hereinafter cited as EPA, Response to Remand].
(b) Regional variations in particle size
Two early studies on which EPA relies in support of its standard strongly suggest regional or temporal variations in lime particle size. First, the Study of Technical and Cost Information noted: "The size analysis of the [lime] dust being discharged from the kiln may contain as much as 30 percent below 5 microns and 10 percent below 2 microns." R. 1, 35. Second, the Vulcan Report included a table showing that in a typical rotary kiln in Ohio, 12.7% of particulate did not exceed 4.4 microns and 23.8% was smaller than 7.7 microns. Id. 20. The report also cautioned that there was "a significant percentage of `large' particles (larger than thirty-two microns) in this distribution," id. 19, and that "the various percentages associated with [ ] particle size distribution . . . may change from state to state depending on the characteristics of the respective limestone deposit." Finally, at an April 30, 1976 meeting between industry and Agency representatives, an industry spokesman made the challenge directly. According to EPA's file memorandum summarizing the meeting, the industry representative
R. 118, 1. The EPA's response at the meeting was noteworthy:
Id. At the same meting another industry representative suggested:
This promising but aborted exchange dramatically illustrates our dilemma in this case. When particle size was identified as a potentially important variable, both the Agency and the industry failed to pick up the ball.
(c) EPA's lack of analysis
As far as we can tell the Agency gathered no data on particle size distribution at the tested plants or in the industry generally, either before or after the industry meeting which focused on this factor. Whether the EPA took particle size into account in developing and promulgating its proposed standard cannot be determined from this record.
In this respect, we believe that the industry's comments, concerning particle size distribution, when viewed in light of the material contained in EPA's own support statement and in light of the background documents on which it relied, met a "threshold requirement of materiality,"
c. Explanation of discarded Data From Plants A and F
Finally (with respect to the rotary kiln particulate emission standard), a few words should be devoted to the mysterious Plant A and the plant controlled by a low-pressure venturi scrubber (Plant F.). Test results obtained at Plant A were excluded from consideration and those obtained at Plant F were discounted (if not excluded entirely from consideration) in the rationale for the proposed standard. This was because after testing it was concluded these plants did not represent best technology. SSEIS 8-17, 8-18. At both plants the measured particulate emissions had significantly exceeded the proposed standard.
E) that were source tested in conjunction with this study.
It would appear that EPA's observation of "large quantities of dilution air" at this plant is related to its measurement of high oxygen levels in the effluent.
If, for unexplained reasons, one-third of the test plants initially chosen by EPA for their well-controlled systems fail to meet the standard, the conclusion is just as plausible that the standard is not achievable as that the plants chosen did not have well-controlled systems. It is up to EPA to dispel such doubts, and they have not done so here.
Of course, the fact that Plant A did not meet the proposed standard does not itself prove the standard is unachievable. However, ignoring the Plant A results merely because they were not satisfactory would suggest that the process by which the standard was promulgated was an arbitrary one. This is especially true where the results excluded are those obtained from one of only three plants tested which utilized the existing technology (baghouse) "that approximately 80 percent of the new and modified facilities subject to the proposed standards would use . . . ." SSEIS 8-13.
EPA's handling of the Plant F (scrubber) results does not seem as troubling, primarily because neither the trend in the industry nor this standard favor the use of scrubbers for rotary kilns. It was, however, the only scrubber-controlled plant tested and it did not meet the standard. EPA attributed the poor results to the low pressure employed by the Plant F scrubber and hypothesized that a higher pressure scrubber could meet the standard proposed. In support of this hypothesis EPA relied upon a non-EPA-conducted test reported in the literature, although the conditions under which that test was conducted were not mentioned. SSEIS 8-12. Were the venturi scrubber projected to be in use for any sizable number of new or modified lime plants, we would be considerably less comfortable with the Agency's conclusion that "EPA['s] . . . source test . . . show that all [three control devices] are capable of meeting the particulate emission level of 0.15 kilogram per megagram . . . ." SSEIS 8-12.
Since EPA has already agreed to a remand of the standard for "pressure" hydrators, we consider the standard only as it relates to "atmospheric" hydrators.
However, in reviewing the record in light of the industry's attack, we have encountered the same problem with the hydrator standard as with the rotary kiln standard. There is record evidence substantial enough to raise a real question in our minds whether adequate account was taken of significant variables relevant to the standard's achievability.
Material submitted by the NLA at its June 1977 meeting with EPA suggests that lime hydrators (like rotary kilns) produce particles of different size and surface area.
Since the efficiency of the wet scrubber method of emissions control apparently depends on the probability that dust particles will collide with and be captured by small water droplets which are sprayed into an area through which the effluent must pass,
All the record reflects is that both hydrators utilized calcitic (rather than dolomitic) lime, again with no explanation of the relevance of that item of information to the achievability of the proposed standard on an industry-wide basis. Since the comments submitted by NLA in connection with the rotary kiln standard suggest that particle size in calcination is affected by the chemical composition of the material used, a similar effect might therefore be anticipated in the hydration process; but the EPA does not address this possibility either through assumptions, tests performed, data collected and reported, or analysis of results. We are asked to conclude that the projection of an achievable standard for the industry as a whole based on tests conducted at two hydrator plants using calcitic
Because we remand, the Agency will have the opportunity to consider the hydrator standard more fully in light of the additional material and more elaborate arguments relating to the achievability of the standard for hydrators that were first submitted by the industry when the matter was brought to this court.
B. The Opacity Standard and Continuous Monitoring Requirement
1. The Opacity Standard
"Opacity" is defined by regulation to mean "the degree to which emissions reduce the transmission of light and obscure the view of an object in the background." 40 C.F.R. § 60.2(j) (1979). EPA explains that "[t]he opacity level of visible emissions is an indication of the mass concentration of a particular pollutant" and that "[v]arious studies have shown that opacity varies directly with mass concentrations of particulate matter." SSEIS 8-19. EPA considers opacity standards to be "a necessary supplement to particulate mass emission standards" basically because "[o]pacity test methods are quicker, easier to apply, and less costly than concentration/mass tests for particulate matter." SSEIS 8-19.
The performance standards prescribed by EPA for rotary lime kilns consist of both a mass emission standard (grams of particulate emission per gram of feed) and an opacity standard (ten percent). 43 Fed.Reg. 9453 (1978). Only those kilns using dry methods of emissions control are subject to the ten percent opacity standard. As previously noted,
We have considered the various arguments made by the NLA and conclude that EPA's apparent failure to consider in this case some variables which were (1) given more careful consideration in the promulgation of earlier opacity standards and (2) given inadequate consideration in the companion mass emission standard requires us to remand the opacity standard to the Administrator for additional explanation or for revision.
a. Variables Considered in the Promulgation of Earlier Opacity Standards
On remand from Portland Cement I, 486 F.2d 375, the Administrator undertook extensive reconsideration of both the opacity standard proposed for portland cement plants and the methodology (EPA's "Method 9," 40 C.F.R. Part 60, App. A (1979)) of
The impact of variations in particle size and shape were also considered by EPA in evaluating an opacity standard for asphalt concrete plants.
b. Variables Inadequately Considered in Mass Emission Standard
Opacity standards are intended to operate in tandem with mass emission standards, notwithstanding their independent enforceability. Ideally, a violation of an opacity standard should indicate a violation of a mass emission standard. See SSEIS 8-19. For this reason the Agency relies on data from the same test plants to support both the opacity and the mass emission standard; but for this reason when the representativeness of data relied upon for one standard is inadequately shown, the representativeness of data relied upon for the other standard is drawn in question.
As discussed above, the Agency failed to consider the representativeness of the particle size produced at its tested plants. This failure is particularly striking in connection with the opacity standard because variations in particle size have been given careful consideration in the development of earlier opacity standards.
We have already noted that the emissions control systems favored by the standards and by prevailing economic and technological trends may operate more efficiently when the predominant size of particulate emissions is large. As it happens, large particulate is also likely to appear less opaque. Thus, it is possible that a plant would meet both standards only because the particles emitted are uniformly large and we cannot ascertain how the plants tested here "measure up."
c. EPA's Arguments
Both in this court and at the administrative level EPA emphasizes the overwhelming extent to which the plants tested were able to meet the ten percent opacity standard.
EPA has committed itself to take the possibility of inaccurate opacity measurement into account in the enforcement of the standard.
The Agency relies upon the flexibility built into the regulatory scheme to support the rationality of its standards.
We recognize the usefulness of opacity standards as an enforcement tool.
2. Continuous Monitoring
On the opacity monitoring requirement, the petitioner's argument is simple: there is no adequately demonstrated technology for monitoring opacity.
EPA answers that the continuous monitoring data would not be used to determine compliance with the opacity standard but "to keep a check on the operation and maintenance of the control equipment," and to trigger performance checks by trained observers. Brief for Respondents at 12-13, citing SSEIS 8-24 and standard as proposed (42 Fed.Reg. 22506, 22509 (1977)). The Agency argues that if the equipment gives any "indication" of changed opacity it is enough to justify a continuous monitoring requirement. Brief for Respondents at 29. It dismisses the industry's contention that reliable monitoring equipment is not available to perform this limited a function and shifts the burden to the industry to show "by supporting data," SSEIS II, 13, that it is not.
EPA states that it now routinely requires continuous monitoring of opacity in new source performance standards.
The industry itself admits there is some value to a continuous monitoring requirement. Dow Chemical took a critical stance (adopted by NLA, Brief for Petitioner at 52) but also acknowledged that monitoring equipment "gives an indication of whether the opacity is increasing or decreasing." R. 148, 2, App. 328. Given this concession, we cannot find the continuous monitoring requirement arbitrary as an adjunct to a non-arbitrary, non-capricious opacity standard. We have today remanded the opacity standard for lime plants. If on remand an opacity standard is retained, EPA may continue to require continuous monitoring.
V. THE STANDARD OF REVIEW AS APPLIED
Our requirement that the EPA consider the representativeness of the test data relied upon in the development and justification of its standard does not presage any new or more stringent standard of judicial review. The rigorousness of the review in which this court has engaged in previous NSPS decisions—known to some as the "hard look" standard
We think these decisions amply support our conclusion that a remand is appropriate in this case. Both decisions reviewing the NSPS and those reviewing other administrative determinations under the Clean Air Act evince a concern that variables be accounted for,
Our opinion should not suggest the necessity of "ninety-five percent certainty"
With respect to the standard's achievability we are thus not presented with the question how much deference is owed a judgment predicated on limited evidence when additional evidence cannot be adduced or adduced in the near future.
A systematic approach may not necessarily require a conclusion grounded in actual test results. We do not intend to bridle the Agency's discretion to make wellfounded assumptions even where the assumption could be replaced by valid test results, but we think first, the assumption should be stated and second, where test data could have verified the assumption, a reason for not testing or relying on such data should be given.
We recognize, for example, that the finding of facts, especially through elaborate testing, is costly
To ensure that the Agency has engaged in reasoned decisionmaking, we remand. We have outlined our substantive misgivings; the Agency may choose the appropriate method of response.
Other exhaust emissions resulting from the processing of lime and limestone include carbon monoxide and nitrogen oxides. SSEIS 8-4.
The increased use of coal, particularly high sulfur coal, can be expected to affect emissions. Use of high sulfur coal can result in "significant" SO
The standards at issue here, however, expressly limit only particulate emissions. No standard has been set for emissions of sulfur dioxide in the lime industry.
42 U.S.C. § 7411(a)(2) (Supp. I 1977); 42 U.S.C. § 1857c-6(a)(2) (1976) (repealed 1977) (same).
42 U.S.C. § 7411(a)(4) (Supp. I 1977); 42 U.S.C. § 1857c-6(a)(4) (1976) (repealed 1977) (same). See 40 C.F.R. § 60.14 (1979) (governing "modification" of stationary sources).
Conversion of a kiln from natural gas or fuel oil to coal firing may constitute a "modification," triggering application of the NSPS here promulgated. See SSEIS 5-3.
SSEIS 8-9 (footnote omitted).
42 Fed.Reg. 22508 (1977). See also SSEIS 8-22 ("EPA . . . is excluding rotary lime kilns controlled with scrubbers from the proposed opacity standard.")
Compare 42 U.S.C. § 7411(a)(1) (Supp. I 1977) with 42 U.S.C. § 1857c-6(a)(1) (1976) (repealed 1977). In addition, the 1977 Amendments require the promulgation of NSPS with respect to "fossil fuel fired sources" which reflect not only the degree of emission limitation achievable, but also the "percentage reduction" achievable under the best systems. 42 U.S.C. § 7411(a)(1) (Supp. I 1977). H.R.Conf.Rep.No. 564, 95th Cong., 1st Sess. 130 (1977), reprinted in 3 Senate Comm. on Environment and Public Works, 95th Cong.2d Sess., A Legislative History of the Clean Air Act Amendments of 1977, at 510 (1978) [hereinafter cited as Legislative History], U.S.Code Cong. & Admin.News 1977, p. 1077.
Except as otherwise expressly provided, the Clean Air Act Amendments of 1977 (the "Amendments") became effective August 7, 1977, the date of enactment. Pub.L.No.95-95, § 406(d), 91 Stat. 797 (1977). The effective date of a new subsection concerning Agency rulemaking procedures, 42 U.S.C. § 7607 (Supp. I 1977), was expressly delayed by the Amendments. Id. § 7607(d)(11). See also text following note 126, infra. But no such delay was provided for the substantive amendments to the NSPS provisions.
A "savings" clause did perpetuate "rules, regulations, orders, determinations . . . or other actions [already] duly issued, made or taken," Pub.L.No.95-95, § 406(b), 91 Stat. 796 (1977); but as the standards challenged here were not "duly issued" until finally promulgated in March 1978, 43 Fed.Reg. 9452 (1978), the substantive aspects of the finally promulgated standards are governed by the 1977 provisions. See Alabama Power Co. v. Costle, No. 78-1006, slip op. at 34 n.79, (D.C.Cir. Dec. 14, 1979).
There is no suggestion in the record that the Agency gave any consideration to the substantive impact of the 1977 Amendments on the standard it had proposed. We think that the Agency should not be required to withhold the promulgation of a proposed standard while it considers the development of newly authorized and severable aspects of that standard; and we consider the requirement of "percentage reduction" for fossil-fuel fired sources one such severable aspect.
However, with respect to aspects of the 1977 Amendments which may operate at cross-purposes or in fact inconsistently with prior law, we think the Agency's standard should reflect the new law. The new requirements that the standard be achievable by an emission reduction system which is both "technological" and "continuous" are two such aspects to which the Agency ought to have given some consideration before the standard here was finally promulgated. Our concerns in this regard are set forth below, note 54 (systems of continuous emission reduction) and text at note 77 and note 77 (technological systems).
The last new requirement, that the Administrator take into account the nonair quality health and environmental impact and energy requirements, was already a part of the case law developed under section 111. Portland Cement I, 486 F.2d at 385. The Administrator did, in fact, take these factors into account in proposing the NSPS for lime plants. SSEIS 6-1-6-30.
This is the first challenge to a new source performance standard since passage of the 1977 Amendments. Consequently, we are surprised that neither party in discussing the applicable standard of law so much as mentioned the fact of this major legislative effort.
The statutory standard is one of achievability, given costs. Some aspects of "achievability" cannot be divorced from consideration of "costs." Typically one associates "costs" with the capital requirements of new technology. See e. g., AFL-CIO v. Marshall, 617 F.2d 636, 659 (D.C.Cir.1979). However, certain "costs" (e. g., frequent systemic shutdown to service emissions control systems or use of feedstock of a certain size or composition in order to meet the new emissions standards) are more intimately intertwined with "achievability" than are the capital costs of new technology. In this case the lime industry attacks the standards as "unachievable." When questioned at oral argument, counsel for petitioner disclaimed any attack upon the expense of implementation, stating that he attacked the achievability of the standard "on any reliably repetitive basis," "because of the very variables in the production of lime." This necessarily asserts that a standard which does not account for certain routine variations in conditions is "unachievable." We agree, where, as here, there is no evidence in the record that the "costs" of adjusting for such routine variations (assuming such adjustments be possible) were considered by the Agency in promulgating its standard.
The EPA has expressly built some flexibility into the enforcement end of the new source performance standards, 40 C.F.R. § 60.8(c) (1979) (relating to startup, shutdown and malfunction) and is vested with a more general enforcement discretion, but the flexibility appropriate to enforcement will not render "achievable" a standard which cannot be achieved on a regular basis, either for the reasons expressly taken into account in compliance determination regulations (here startup, shutdown and malfunction), or otherwise. Cf. Portland Cement I, 486 F.2d at 398 n.91 and see discussion infra text at notes 111-15. In this connection the Congress' new concern that emissions control systems operate continuously, see 42 U.S.C. § 7411(a)(1) (Supp. I 1977) and discussion infra, note 54, is pertinent.
Because we remand for the development of a more adequate rationale for the promulgated standards we do not now specify the kinds of variations in conditions—not accounted for in the Agency's cost analysis—which might render a uniform standard "unachievable" or so "unachievable" as to represent an arbitrary or capricious exercise of the Administrator's discretion under the Act.
EPA considers the significant production of particulate emissions itself to cause or contribute to air pollution (which may reasonably be anticipated to endanger public health or welfare). The Agency has made this determination for purposes of establishing national primary and secondary ambient air quality standards under § 109 of the Clean Air Act, now codified at 42 U.S.C. § 7408 (Supp. I 1977), and without regard to the harmful or beneficial effect of the material of which the particulate is composed. 36 Fed.Reg. 1502, 8137, 8138 (1971). When ambient air quality standards for particulate were first proposed, the Agency described some of the health effects of particulate matter:
36 Fed.Reg. 1502 (1971). See generally II Midwest Research Institute, Particulate Pollutant System Study—Fine Particulate Emissions (Aug. 1, 1971) (on file in EPA library) (health hazards of fine particulate); U.S. Dep't of Health, Education and Welfare, National Air Pollution Control Admin., Air Quality Criteria for Particulate Matter, AP-49 (1969) (health hazards of particulate).
The MRI Report, considered by EPA in developing the proposed standard, observes that lime dust can raise the pH of water bodies. MRI Report 22. However, EPA does not appear to have relied on this effect of the lime emissions in support of its standard. It focused instead on the sheer quantity of dust generated by lime plants. 42 Fed.Reg. 22507 ("A study performed for EPA in 1975 by the Research Corporation of New England ranked the lime industry twenty-fifth on a list of 112 stationary sources categories which are emitters of particulate matter"); SSEIS 8-2 ("In a study performed for EPA by Argonne National Laboratory in 1975, the lime industry ranked seventh on a list of the 56 largest particulate source categories in the U.S.").
The industry's argument rests on the asserted nontoxicity of lime dust.
R. 139, 18, App. 200. See also R. 140, 56, App. 301. NLA argues the innocuousness or even benign effect of lime emissions and concludes that "the statement that lime endangers health should be stricken from this EPA document." R. 139, 19, App. 201. The fact that lime dust reacts with and traps SO2 emissions (see notes 2 and 27, supra) leads NLA to continue, "A more plausible case could be made that the presence of a low concentration of lime particles in the air could actually be beneficial in minimizing so-called acid rains, neutralizing molecules of airborn acid gases, like SO[x] and NO[x] into harmless compounds." R. 139, 19, App. 201.
We think the danger of particulate emissions' effect on health has been sufficiently supported in the Agency's (and its predecessor's) previous determinations to provide a rational basis for the Administrator's finding in this case. See Air Quality Criteria for Particulate Matter, supra. Moreover, whatever its impact on public health, we cannot say that a dust "nuisance" has no impact on public welfare. Congress has provided that with respect to the Clean Air Act:
42 U.S.C. § 7602(h) (Supp. I 1977); 42 U.S.C. § 1857h(h) (1976) (repealed 1977) (same). Thus, we could not say that the Administrator's determination is arbitrary, even if the dust were shown innocuous to public health.
The Administrator's assessment of a pollutant's danger to public health or welfare
Nat'l Asphalt, 539 F.2d at 783-84. Our conclusion in Nat'l Asphalt is equally applicable here:
Id. at 784.
There are some indications that the 1977 Amendments were intended to prohibit all averaging to determine compliance where continuous emission reduction systems were specified. See H.R.Rep. No. 294, 95th Cong., 1st Sess. 92, reprinted in 4 Legislative History at 2559, U.S.Code Cong. & Admin.News 1977, p. 1170 ("Any emission limitation under the Clean Air Act, therefore must be met on a constant basis, not on an `averaging' basis . . . . The `averaging' method is not allowable, precisely because it cannot provide assurances that the emission limitation will be met at all times."); 123 Cong.Rec. H8662, H8664 (daily ed. Aug. 4, 1977) (statement of intent with respect to Conference Committee substitute, referring to NSPS for fossil-fuel fired boilers) ("No averaging in fuel content or in emissions content or levels [will be] allowed in determining whether the prescribed performance standard will be met by a source.").
Whether the 1977 Amendments have effectively repealed the regulations permitting flexibility to account for startups, shutdowns and malfunctions—regulations applauded by this court in Portland Cement I, 486 F.2d at 398-99 —is certainly unclear. Such variations, unlike the kinds of "intermittent" reductions which concerned Congress, are less within the industry's control. The impact of the 1977 Amendments on EPA's compliance-testing methodology, which relies on average readings both for mass emission and opacity standards, 40 C.F.R. § 60.8(f) (1979); 40 C.F.R. Part 60, App. A, § 2.5 (1979), is equally unclear. It may be that a reasonable construction of the statutory language would leave these regulations intact.
However, we think the perplexing implications of Congress' new requirement of systems of continuous emission reduction should first be addressed by the Administrator and there is no evidence in the record that the Agency considered or reconsidered its proposed standard in light of this or other aspects of Congressional intent in the 1977 Clean Air Act Amendments.
The tests were conducted under EPA's "Method 5" for the measurement of particulate emissions. Method 5 consists of withdrawal of sample emissions by means of a probe inserted into the wall of a smokestack, through which sample emissions are withdrawn by means of a pump set to correspond to the velocity of the air within the stack. 40 C.F.R. Part 60, App. A (1979).
Unfortunately, the industry did not make clear whether it was more concerned with the validity of the test results—which because of the difficulties in accurate measurement under such conditions may be questionable—or with EPA's reliance on less than capacity results, even if valid, to project an "achievable" standard for capacity operations.
Like "feedstock," "operation" was listed by the EPA as one criterion of "representativeness" for which data on emissions are assessed before standards are proposed. SSEIS 207. We take consideration of the "representativeness" of operation to include consideration of the percentage of capacity of operation.
An incorrect assumption of this sort would not necessarily taint the proceeding, whose purpose is to state an "achievable" standard under any "adequately demonstrated" system. However, the incorrect assumption would probably have been reflected in the Agency's cost analysis, viz., the Agency would have assumed that a broader choice of control methods was available to the industry than in fact was available. To the extent that the cost analysis depends on an incorrect assumption like this one, the rationale for the standard may be flawed. Cf. Portland Cement I, 486 F.2d at 396 (noting no substantiation of achievability of standard for kilns employing alternate mode of processing feed) ("We are not here considering a regulation that was issued in the contemplation that all new cement plants will be dryprocess . . . .").
R. 153, 3 (letter dated July 5, 1977 from Deputy Assistant Secretary of Interior to Goodwin of EPA).
R. 139, 8, App. 190. See also R. 140, 38, App. 283 (NLA spokesman orally reiterating this concession).
486 F.2d at 394. See 42 U.S.C. § 7607(d)(6)(B) (Supp. I 1977) (response required to "significant comments"). See also Vermont Yankee Nuclear Power Corp. v. Natural Resources Defense Council, Inc., 435 U.S. 519, 553-55, 98 S.Ct. 1197, 1216-17, 55 L.Ed.2d 460 (1978).
R. 139, 13, App. 195 (footnotes omitted).
Our conclusion to remand the standard derives in part from our examination of the materials drawn to our attention by the industry in connection with the first two prongs of the industry's attack and in part from our conclusion with respect to the mass emission standard above.
We reject the third prong of the industry's attack—EPA's failure to abide by its own "Method 9" in obtaining the test results on which the standard is based. The articles concerning opacity testing submitted by the NLA themselves demonstrate that in most cases the alleged failure to abide by the standards would have had the effect of overestimating rather than underestimating opacity. That is, EPA's mistakes would have laid the basis for a standard which was easier, not harder, to achieve by the industry.
Id. (emphasis supplied). Having conceded this principle, EPA supported its standard as follows:
Id. at 113 (footnotes omitted).
Variations in particle size were thus considered and found not to warrant a change in the opacity standard. Whether such variations were attributable to different feed composition is not clear.
(The opacity standard for asphalt concrete plants, originally promulgated in March 1974, 39 Fed.Reg. 9307 (1974), was affirmed by this court in Nat'l Asphalt, 539 F.2d 775 (1976).)
Portland Cement I, 486 F.2d at 389-90.
39 Fed.Reg. 39872-73 (1974).
SSEIS D-8. Equipment and installation costs for visible emissions monitoring were estimated at $18,000 to $20,000 per site. Id. Annual operating costs, including recording of data, were estimated at $8,000 to $9,000 per site. Id.
The phrase "hard look" derives from Judge Leventhal's opinions in Greater Boston Television Corp. v. FCC, 444 F.2d 841 (D.C.Cir.1970), cert. denied, 403 U.S. 923, 91 S.Ct. 2229, 29 L.Ed.2d 701 (1971), and Pike's Peak Broadcasting Co. v. FCC, 422 F.2d 671 (D.C.Cir.), cert. denied, 395 U.S. 979, 89 S.Ct. 2134, 23 L.Ed.2d 767 (1969). As originally articulated the words "hard look" described the agency's responsibility and not the court's. However, the phrase subsequently evolved to connote the rigorous standard of judicial review applied to increasingly utilized informal rulemaking proceedings or to other decisions made upon less than a full trial-type record. Judge Leventhal himself used the phrase in this sense in Maryland-Nat'l Capital Park and Planning Comm'n v. United States Postal Serv., 487 F.2d 1029, 1037-38 and n.4 (D.C.Cir.1973).
The etymological evolution of the phrase "hard look" and of other capsule descriptions of standards stated on judicial review of administrative decisions is in no small part attributable to the shifting meaning of "informal rulemaking." The transformation in informal rulemaking proceedings in turn can be traced to the more rigorous standards of review applied.
As originally conceived, "notice and comment" rulemaking provided a scant "record" for review. The statutorily required rationale consisted merely in "a concise general statement of [the rule's] basis and purpose." 5 U.S.C. § 553(c) (1976). The cumbersomeness of rulemaking "on the record" and its attendant delays prompted increased provision for the more flexible and expedient "notice and comment" rules in areas in urgent need of regulation. See Pedersen, Formal Records and Informal Rulemaking, 85 Yale L.J. 38, 39 (1975) [hereinafter cited as Pedersen].
The sheer massiveness of impact of the urgent regulations issued under the new rulemaking provisions and the diffidence of judges in the face of highly technical regulatory schemes prompted the courts to require the agencies to develop a more complete record and a more clearly articulated rationale to facilitate review for arbitrariness and caprice. See Kennecott Copper Corp. v. EPA, 462 F.2d 846, 849-50 (D.C.Cir.1972) (remand of national secondary ambient air quality standards to EPA for additional rationale); K. Davis, Administrative Law of the Seventies, § 29.01-6 (1976); Stewart, Vermont Yankee and the Evolution of Administrative Procedure, 91 Harv.L.Rev. 1805, 1812-13 (1978); Nathanson, Probing the Mind of the Administrator: Hearing Variations and Standards of Judicial Review Under the Administrative Procedure Act and Other Federal Statutes, 75 Colum.L.Rev. 721, 746-70 (1975). (Indeed, a section of the Clean Air Act Amendments of 1977 not applicable to the instant proceedings expressly codified much of prior law and the suggestions made in Pedersen concerning the "formalization" of records in informal rulemaking. 42 U.S.C. § 7607(d) (Supp. I 1977); H.R. Rep.No.294, 95th Cong., 1st Sess. 320 (1977), reprinted in 4 Legislative History at 2787.)
As these newly-required records and rationales became more routinely available, the "hard look" taken began to appear more judicial than administrative, blurring the original meaning of that phrase. The availability for judicial review of substantial administrative records has also generated both confusion and controversy over the applicable standard of review under the Administrative Procedure Act. See generally DeLong, Informal Rulemaking and the Integration of Law and Policy, 65 Va.L.Rev. 257, 284-89 (1979); Auerbach, Informal Rulemaking: A Proposed Relationship Between Administrative Procedures and Judicial Review, 72 Nw.U.L.Rev. 15 (1977); Pedersen, at 46-49.
The conferees also recognized the convergence in practice of the "substantial evidence" and the "arbitrary and capricious" standards of review. Id. (reinstating "arbitrary and capricious" standard of review):
Congress has authorized the Administrator to "distinguish among classes, types and sizes within categories of new sources for the purpose and establishing . . . standards [under § 7411]," 42 U.S.C. § 7411(b)(2) (Supp. I 1977). But the Administrator has not availed himself of the discretion to account for variations in conditions covered by the standard here. Compare the extensive exercise of analogous discretion (with respect to existing facilities) under the Federal Water Pollution Control Act, 33 U.S.C. § 1251 et seq. (Supp. I 1977). Weyerhaeuser Co. v. Costle, 590 F.2d at 1053 (300 pulp and paper plants classified into 16 subcategories and 66 subdivisions, with different limitations for each subdivision). See also Judge Leventhal's concurring opinion in ASARCO, Inc. v. EPA, 578 F.2d 319, 330 (D.C. Cir. 1978) (noting the Administrator's discretion to classify under § 111 of the Clean Air Act).
quoting Int'l Harvester Co. v. Ruckelshaus, 478 F.2d at 647.
(footnote omitted) (citing Amoco Oil Co. v. EPA, 501 F.2d 722 (D.C. Cir.1974)).