National Association of Metal Finishers, Electroplaters of York, Inc. And Pioneer Metal Finishing, Inc. v. Environmental Protection Agency, the Institute for Interconnecting and Packaging Electronic Circuits v. Environmental Protection Agency, Ford Motor Company, Inc. v. United States Environmental Protection Agency and Douglas M. Costle, Administrator, United States Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. National Association of Metal Finishers and Institute for Interconnecting and Packaging Electronic Circuits v. Environmental Protection Agency, General Motors Corporation v. United States Environmental Protection Agency and Walter Barber, Acting Administrator, United States Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. Natural Resources Defense Council, Inc. v. U.S. Environmental Protection Agency, Douglas M. Costle, Administrator, U.S. Environmental Protection Agency, Chemical Manufacturers Association, American Cyanamid Company, Fmc Corporation, Union Carbide Corporation, Intervenors. United States Brewers Association v. Administrator, Environmental Protection Agency, and Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. Manufacturing Chemists Association, American Paper Institute, National Forest Products Association, National Paint and Coatings Association, Synthetic Organic Chemical Manufacturers Association, Air Products and Chemicals, Inc., American Cyanamid Company, Fmc Corporation, Hercules Incorporated, Shell Oil Company, and Union Carbide Corporation v. Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. Association of Metropolitan Sewerage Agencies v. United States Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. National Association of Metal Finishers v. Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. Chemical Manufacturers Association, American Cyanamid Company, Fmc Corporation, Union Carbide Corporation v. Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. American Paper Institute and National Forest Products Association v. Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor. Natural Resources Defense Council, Inc. v. U.S. Environmental Protection Agency, Chemical Manufacturers Association, American Cyanamid Company, Fmc Corporation, Union Carbide Corporation, Intervenors. Metal Finishing Association of Southern California v. Environmental Protection Agency, Interlake, Inc., Republic Steel Corporation and United States Steel Corporation v. United States Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor, American Iron & Steel Institute, Rouge Steel Co., Intervenors. Chicago Association of Commerce and Industry, Illinois Manufacturers' Association, and Mid-American Legal Foundation v. United States Environmental Protection Agency, Natural Resources Defense Council, Inc., Intervenor

Michael K. Glenn, Gary R. Feulner, Chadbourne, Parke, Whiteside & Wolff, Washington, D.C., for American Paper Institute and The National Forest Products Ass'n.

Donald T. Bliss, David T. Beddow, O'Melveny & Myers, Washington, D.C., and Mark R. Steinberg, O'Melveny & Myers, Los Angeles, Cal., for Metal Finishing Ass'n of Southern California.

Barry S. Neuman (argued), Michael Steinberg (argued), George E. Henderson, Lee R. Tyner, Carol E. Dinkins, Asst. Atty. Gen., Jose R. Allen, Acting Chief, Environmental Defense Section, Lloyd S. Guerci, Joan Z. Bernstein, Anthony Z. Roisman, Ellen Maldonado, James W. Moorman, Donald W. Stever, Michael W. Stein, U.S. Dept. of Justice, Michael Dworkin (argued), Michael Murchison, Ellen Siegler, Daniel J. Berry, Environmental Protection Agency, Washington, D.C., for EPA; Of Counsel: Robert M. Perry, Associate Administrator and Gen. Counsel, Susan G. Lepow, Asst. Gen. Counsel Environmental Protection Agency, Washington, D.C., of counsel.

A. The Definitions of "Interference" and "Pass

Through"

B. Definition of "New Source"

AISI                 American Iron and Steel Institute
BAT                  Best Available Technology Economically
                      Achievable
BDT                  Best available Demonstrated Control
                      Technology
BPT                  Best Practicable Control Technology
                      Currently Available
CACI                 Chicago Association of Commerce and
                      Industry
CMA                  Chemical Manufacturing Association
EPA                  Environmental Protection Agency
FDF                  Fundamentally Different Factor
GM                   General Motors Corp.
IIPEC                Institute for Interconnecting and
                      Packaging Electronic Circuits
J. App.              Joint Appendix
Legis.  Hist.         Legislative History
Me degrees           Regulated Metal in Influent
MFASC                Metal Finishing Association of Southern
                      California
NAMF                 National Association of Metal Finishers
NPDES                National Pollutant Discharge
                      Elimination System
NRDC                 Natural Resources Defense Council
PM                   Precipitable Metals in Influent
POTW                 Publicly Operated Treatment Works
R. Add.              Addendum of Respondent
TSS                  Total Suspended Solids
TTO                  Total Toxic Organics
USBA                 United States Brewers Association
Xme                  Ratio of Me degrees to PM

Before: GIBBONS, HUNTER and BECKER, Circuit Judges.

Section 307 of the Clean Water Act1 directs the Administrator of the Environmental Protection Agency ("EPA") to promulgate regulations requiring industrial facilities to pretreat the pollutants that they discharge into public sewage treatment systems. The Administrator has promulgated both general pretreatment regulations2 and regulations establishing categorical pretreatment standards for existing electroplating sources.3 The petitioners in these consolidated cases seek review of the Administrator's actions in promulgating certain provisions of those regulations. Under section 509 of the Clean Water Act4 we have jurisdiction to exercise a limited review of the Administrator's actions. We may overturn those actions only if they are arbitrary, capricious or otherwise contrary to law.5 Under that standard of review, we find invalid certain provisions of the general pretreatment regulations. Because it is not for us to rewrite those provisions, we will remand them to the Administrator.

In 1972 Congress amended the Federal Water Pollution Control Act ("the Act" or "the Clean Water Act"),6 setting as a national goal the elimination, by 1985, of the discharge of pollutants into navigable waters, 33 U.S.C. Sec. 1251(a)(1) (1976). To reach that goal the Act directed the Administrator of EPA to promulgate regulations setting limits on the pollution that can be discharged by three general types of "point sources," see id. Sec. 1362(14) (1976 & Supp. I 1977).

First, the Administrator was to establish effluent limitations for point sources which discharge pollutants directly into navigable waters ("direct dischargers"). The Administrator had to define effluent limitations for categories or classes of point sources which would require existing direct dischargers to employ by 1977 the best practicable control technology currently available ("BPT"), id. Secs. 1311(b)(1)(A), 1314(b)(1) (1976), and to use by 1983-87 the best available technology economically achievable ("BAT"), id. Secs. 1311(b)(2) (1976 & Supp. I 1977), 1314(b)(2) (1976). For newly-constructed direct dischargers the Administrator had until 1974 to establish "new source" performance standards requiring the application of the best available demonstrated control technology ("BDT"). Id. Sec. 1316. The Administrator had to set the BPT, BAT, and BDT limitations by considering the factors specified in sections 304(b) and 306(b) of the Act, id. Secs. 1314(b), 1316(b). He was to apply those limitations to individual direct dischargers through the National Pollutant Discharge Elimination System ("NPDES") permit issued to the discharger under section 402 of the Act, id. Sec. 1342 (1976 & Supp. I 1977).

Second, the Act mandated that the Administrator set effluent limitations for publicly owned treatment works ("POTWs") engaged in the treatment of municipal sewage or industrial wastewater. See id. Sec. 1292(2) (1976 & Supp. I 1977). Under the Act the Administrator had to establish effluent limitations, based on "secondary treatment," which POTWs had to meet by 1977. Id. Secs. 1311(b)(1)(B), (C), 1314(d)(1) (1976). The limitations thus established were to be applied to each individual POTW through its NPDES permit. Id. Sec. 1342 (1976 & Supp. I 1977).

Third, section 307 of the Act addressed the "indirect dischargers," point sources which discharged their pollutants not directly into navigable waters but into POTWs. Congress recognized that the pollutants which some indirect dischargers release into POTWs could interfere with the operation of the POTWs, or could pass through the POTWs without adequate treatment. To prevent such discharges by existing sources, Congress directed in section 307(b)(1) of the Act:

(b)(1) The Administrator shall ... publish proposed regulations establishing pretreatment standards for introduction of pollutants into [POTWs] for those pollutants which are determined not to be susceptible for treatment by such treatment works or which would interfere with the operation of such treatment works.... Pretreatment standards under this subsection ... shall be established to prevent the discharge of any pollutant through [POTWs], which pollutant interferes with, passes through or otherwise is incompatible with such works.

33 U.S.C. Sec. 1317(b)(1) (1976); see also id. Sec. 1314(g) (Supp. I 1977). The Administrator had to designate the categories of existing sources to which each such standard would apply, promulgate the standards by 1973, and revise the standards as control technologies and industrial processes changed. Id. Sec. 1317(b). For newly-constructed indirect dischargers the Act directed that by 1974 the Administrator had to promulgate pretreatment standards for each category of new sources which "shall prevent the discharge of any pollutant into such treatment works, which pollutant may interfere with, pass through, or otherwise be incompatible with such works." Id. Sec. 1317(c). New and existing indirect dischargers did not need to obtain NPDES permits, but instead had pretreatment standards imposed directly upon them.

In 1977 Congress amended the Act by passing the Clean Water Act of 1977, Pub.L. No. 95-217, 91 Stat. 1566 ("the 1977 Amendments"). Section 54 of the 1977 Amendments added a sentence to section 307(b)(1) permitting a POTW to modify the pretreatment requirement of an existing indirect discharger if the POTW could successfully remove all or part of the toxic pollutants released by that discharger. Id. Sec. 54(a), 91 Stat. 1591 (amending 33 U.S.C. Sec. 1317(b)(1) (Supp. I 1977)).

The Administrator elaborated his regulatory approach to indirect dischargers in his National Pretreatment Strategy, 43 Fed.Reg. 27,759 (1978), and in the consent decree in NRDC v. Train, 8 Env't Rep.Cas. (BNA) 2110 (D.D.C.1976), modified sub nom. NRDC v. Costle, 12 Env't Rep.Cas. (BNA) 1833 (D.D.C.1979), aff'd in part sub nom. Environmental Defense Fund v. Costle, 636 F.2d 1229 (D.C.Cir.1980), modified on remand sub nom. NRDC v. Gorsuch, Nos. 2153-73 et al. (D.D.C. Oct. 26, 1982). The Administrator announced that he would promulgate two types of pretreatment standards.

The first type, "categorical" pretreatment standards, would establish numerical limits on the discharge, by twenty-one specific categories of industrial sources, of particular toxic pollutants which could cause interference with or pass through POTWs. 43 Fed.Reg. 27,760, 27,771-73 (1978); NRDC v. Train, 8 Env't Rep.Cas. (BNA) at 2130-36. Categorical pretreatment standards would be set to require the application of similar levels of control technology as the Act mandated for direct dischargers. 43 Fed.Reg. 27,760-63 (1978); 42 Fed.Reg. 6480 (1977). The Administrator agreed to promulgate categorical pretreatment standards "generally analogous to best practicable control technology currently available" (BPT) for eight industries by May 15, 1977. NRDC v. Train, 8 Env't Rep.Cas. (BNA) at 2128 p 13. For all twenty-one industrial categories the Administrator would then promulgate categorical pretreatment standards based on BAT for existing sources and BDT for new sources. 43 Fed.Reg. 27,760 (1978); see NRDC v. Gorsuch; NRDC v. Train, 8 Env't Rep.Cas. (BNA) at 2123-26.

The second type of pretreatment standard, the "prohibited discharge" standard, would not set numerical limits on the discharge of particular pollutants by specified sources. 43 Fed.Reg. 27,759-60 (1978). Rather, the prohibited discharge standard would establish a general prohibition on the release of any pollutants by any nondomestic source if those pollutants interfere with or pass through a POTW. Id.

The General Pretreatment Regulations for Existing and New Sources of Pollution, 40 C.F.R. Sec. 403.1.-16 (1982), serve to implement the two types of pretreatment standards. First, the general pretreatment regulations themselves contain the prohibited discharge standard generally forbidding interference and pass through, id. Sec. 403.5, and define the terms "interference" and "pass through," id. Sec. 403.3(i), (n). Second, the general pretreatment regulations establish the mechanisms and procedures governing the separately promulgated categorical pretreatment standards. The general regulations define whether a source is a "new source" under the standards. Id. Sec. 403.3(k). The general regulations contain a mechanism through which the existing industrial user of a POTW can obtain a variance from a categorical discharge limit if the user can show that during the development of the standard EPA had considered "fundamentally different" factors than those relating to the user's operation ("the FDF variance provision"). Id. Sec. 403.13. The regulations set up the procedure by which a POTW can revise an industrial user's categorical discharge limit to reflect the POTW's removal of the user's pollutants ("the removal credit provision"). Id. Sec. 403.7. Finally, the regulations provide a formula to calculate an adjusted categorical discharge limit where the industrial user mixes the effluent from the regulated process with other wastewaters prior to pretreatment ("the combined wastestream formula"). Id. Sec. 403.6(e).

The Administrator first proposed the general pretreatment regulations on February 2, 1977. 42 Fed.Reg. 6476 (1977). He promulgated the regulations on June 26, 1978. 43 Fed.Reg. 27,736 (1978). On October 29, 1979, the Administrator proposed amendments to the regulations, 44 Fed.Reg. 62,260 (1979), which he promulgated on January 28, 1981, 46 Fed.Reg. 9404 (1981). The Administrator then attempted to postpone indefinitely the effective date of first all and later part of the general pretreatment regulations. 47 Fed.Reg. 4518 (1982); 46 Fed.Reg. 19,936, 50,502, 50,503 (1981). After we declared that indefinite postponement invalid in NRDC v. EPA, 683 F.2d 752 (3d Cir.1982), the Administrator reinstated the regulations' effective date of March 30, 1981. 47 Fed.Reg. 42,688 (1982); see 46 Fed.Reg. 11,971 (1981). On October 4, 1982, we granted the petitioners' unopposed motion to extend the regulations' effective date until June 30, 1981. 48 Fed.Reg. 2774 (1983).

The categorical pretreatment standards for the Electroplating Point Source Category, 40 C.F.R. Secs. 413.01.-84 (1982), are BPT-level pretreatment standards set pursuant to the NRDC v. Train consent decree. 44 Fed.Reg. 52,592, 52,608 (1978); see 8 Env't Rep.Cas. (BNA) at 2128 p 13(b). The categorical electroplating standards cover 7752 existing firms with electroplating operations, the firms falling in three broad groups: independent "job shops," firms performing electroplating as their primary line of business; independent manufacturers of printed circuit board; and "captive operations," electroplating sections of firms which perform electroplating as part of their manufacture of another product. See 44 Fed.Reg. 52,593 (1979); 43 Fed.Reg. 6561-62 (1978). The electroplating standards divide those firms into seven subcategories, based on the electroplating process employed.7 For each subcategory the standards, inter alia, set numerical limits on the dischargeable concentrations of cyanide and several metals (e.g., cadmium, chromium, copper, lead, nickel, and zinc). 40 C.F.R. Secs. 413.14.-84 (1982). Electroplating sources discharging less than 10,000 gallons per day of electroplating process wastewater have to meet limits for only lead, cadmium and amenable cyanide. Id. "Integrated" facilities, which combine the process wastestream from their captive electroplating operations with other wastewaters prior to pretreatment, are instructed to adjust their discharge limits using the combined wastestream formula. Id. Sec. 413.04; see id. Sec. 413.02(h).

The Administrator proposed the categorical electroplating standards on February 14, 1978, 43 Fed.Reg. 6560 (1978), and promulgated them on September 7, 1979, 44 Fed.Reg. 52,590 (1979), corrected, id. at 56,360. Following promulgation petitioners National Association of Metal Finishers and Institute for Interconnecting and Packaging Electronic Circuits filed petitions for review in this court. Nos. 79-2256, 79-2443. On March 7, 1980, those parties and EPA reached a settlement agreement ("the NAMF Settlement Agreement"). Addendum to Respondent's Brief at D-1 [hereinafter cited as "R.Add."]. Pursuant to that agreement the Administrator on July 3, 1980, proposed several amendments to the 1979 electroplating standards. 45 Fed.Reg. 45,322 (1980). In response to the petition for review of Ford Motor Co., No. 80-1008, EPA proposed other changes, 45 Fed.Reg. 19,245 (1980). Ford later filed a petition for reconsideration of the 1979 standards. J.App. at 2082. On January 28, 1981, the Administrator denied Ford's petition for reconsideration, 46 Fed.Reg. 9476 (1981), and promulgated the amendments to the electroplating standards, id. at 9462, corrected, id. at 30,625. The deadline for compliance with the electroplating standards for integrated facilities was set at three years from the effective date of the combined wastestream formula,8 while non-integrated facilities had a compliance date of May 12, 1982, 46 Fed.Reg. 9462 (1981), later modified to April 27, 1984, 48 Fed.Reg. 2775 (1983); 46 Fed.Reg. 43,973 (1982).

On August 31, 1982, the Administrator published the proposed Metal Finishing regulations, which established BAT pretreatment standards for most of the indirect dischargers presently covered by the electroplating standards. 47 Fed.Reg. 38,462-63 (1982). Only existing job shops and printed circuit board manufacturers would remain under the electroplating standards, which would be amended to restrict the discharge of toxic organic pollutants. Id. at 38,464, 38,468. On July 15, 1983, the Administrator promulgated the Metal Finishing regulations. 48 Fed.Reg. 32,462 (1983) (to be codified at 40 C.F.R. Sec. 433.10.-17).

As noted above, National Association for Metal Finishers ("NAMF"), Institute for Interconnecting and Packaging Electronic Circuits ("IIPEC"), and Ford Motor Co. ("Ford") filed petitions for review of the 1979 electroplating standards. Nos. 79-2256, 79-2443, 80-1008. Ford, NAMF, General Motors Corp. ("GM"), and Metal Finishing Association of Southern California ("MFASC") petition for review of the 1981 electroplating amendments. Nos. 81-1279, 81-1351, 81-1712, 81-2119. Ford also petitions for review of the Administrator's denial of its petitions for review of the Administrator's denial of its petition for reconsideration of the 1979 electroplating standards, No. 81-1214. We address that appeal in Ford Motor Co. v. EPA, 718 F.2d 55 (3d Cir.1983).

Petitioners Natural Resources Defense Council ("NRDC"), United States Brewers Association ("USBA"), and Chemical Manufacturing Association ("CMA") petition for review of the 1978 general pretreatment regulations. Nos. 81-1977, 81-1978, 81-1979. Petitioners Ford, NAMF, CMA, NRDC, Interlake, Chicago Association of Commerce and Industry ("CACI") and others seek review of the 1981 general pretreatment regulations. Nos. 81-1210, 81-1981, 81-1982, 81-1983, 81-1984, 81-1985, 81-2150, 81-2151.

Consideration of the cases was necessarily held pending our resolution in NRDC v. EPA of the challenge to the Administrator's indefinite postponement of the 1981 general pretreatment amendments. Judge Becker of this Court then presided over a series of conferences in which he consolidated the cases, set a briefing schedule, and, on October 29, 1982, limited the subjects of briefing.9

Under section 10(e) of the Administrative Procedure Act, we may not invalidate agency actions unless we find them to be "arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." 5 U.S.C. Sec. 706(2)(A) (1976). This standard sets the level of deference with which we must review the agency's actions for their statutory authority, substantive validity and procedural regularity. See Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1024 (D.C.Cir.1978).

We must extend "great deference to the interpretation given the statute by the officers or agency charged with its administration." EPA v. National Crushed Stone Association, 449 U.S. 64, 83, 101 S.Ct. 295, 307, 66 L.Ed.2d 268 (1980) (quoting Udall v. Tallman, 380 U.S. 1, 16, 85 S.Ct. 792, 801, 13 L.Ed.2d 616 (1965)); American Iron & Steel Institute v. EPA ("AISI I"), 526 F.2d 1027, 1041-42 (3d Cir.1975), mandate recalled in part, 560 F.2d 589 (3d Cir.1977), cert. denied, 435 U.S. 914, 98 S.Ct. 1467, 55 L.Ed.2d 505 (1978). If an act is susceptible to more than one reasonable interpretation, we must accept any reasonable interpretation chosen by the agency. Udall v. Tallman, 380 U.S. 1, 16, 85 S.Ct. 792, 801, 13 L.Ed.2d 616 (1965); see NRDC v. Train, 421 U.S. 60, 75, 95 S.Ct. 1470, 1479, 43 L.Ed.2d 731 (1975). If the agency rejects the reasonable interpretation of the statute, however, we must "honor the clear meaning of a statute, as revealed by its language, purpose and history." International Brotherhood of Teamsters v. Daniel, 439 U.S. 551, 556 n. 20, 99 S.Ct. 790, 800 n. 20, 58 L.Ed.2d 808 (1979); see FEC v. Democratic Senatorial Campaign Committee, 454 U.S. 27, 32, 37, 102 S.Ct. 38, 42-45, 70 L.Ed.2d 23 (1981).

Our inquiry into the substantive basis for the agency's actions must be searching and careful, but our review is a narrow one. As the Supreme Court has recently stated:

The scope of review under the arbitrary and capricious standard is narrow and a court is not to substitute its judgment for that of the agency. Nevertheless, the agency must examine the relevant data and articulate a satisfactory explanation for its action including a "rational connection between the facts found and the choice made." Burlington Truck Lines v. United States, 371 U.S. 156, 168 [83 S.Ct. 239, 246, 9 L.Ed.2d 207] (1962). In reviewing that explanation, we must "consider whether the decision was based on a consideration of the relevant factors and whether there has been a clear error of judgment." Bowman Transp. Inc. v. Arkansas-Best Freight System, [419 U.S. 281, 285, 95 S.Ct. 438, 442, 42 L.Ed.2d 447 (1974) ], Citizens to Preserve Overton Park v. Volpe, [401 U.S. 402, 416, 91 S.Ct. 814, 823, 28 L.Ed.2d 136 (1971) ]. Normally, an agency rule would be arbitrary and capricious if the agency has relied on factors which Congress has not intended it to consider, entirely failed to consider an important aspect of the problem, offered an explanation for its decision that runs counter to the evidence before the agency, or is so implausible that it could not be ascribed to a difference in view or the product of agency expertise. The reviewing court should not attempt itself to make up for such deficiencies: "We may not supply a reasoned basis for the agency's action that the agency itself has not given." SEC v. Chenery Corp., 332 U.S. 194, 196 [67 S.Ct. 1575, 1577, 91 L.Ed. 1995] (1947). We will, however, "uphold a decision of less than ideal clarity if the agency's path may reasonably be discerned." Bowman Transp. Inc. v. Arkansas-Best Freight Systems, [419 U.S. at] 286 [95 S.Ct. at 442].

Motor Vehicle Manufacturers Association v. State Farm Mutual Automobile Insurance Company, --- U.S. ----, ---- - ----, 103 S.Ct. 2856, 2865-66, 77 L.Ed.2d 443 (1983).

Our review of an agency's "observance of procedure required by law," 5 U.S.C. Sec. 706(2)(D) (1976), is more exacting. NRDC v. EPA, 683 F.2d 752, 760 (3d Cir.1982); see Weyerhaeuser, 590 F.2d at 1027-28. Under section 4 of the Administrative Procedure Act, an agency initiating informal rulemaking must first publish a general notice which includes "either the terms or substance of the proposed rule or a description of the subjects and issues involved." 5 U.S.C. Sec. 553(b)(3) (1976). Such notice must "fairly apprise interested persons" of the subjects and issues dealt with in the rule ultimately promulgated. American Iron & Steel Institute v. EPA ("AISI II"), 568 F.2d 284, 290-93 (3d Cir.1977); see Ethyl Corp. v. EPA, 541 F.2d 1, 48 (D.C.Cir.1976) (en banc), cert. denied, 426 U.S. 941, 96 S.Ct. 2663, 49 L.Ed.2d 394 (1976). The agency must then give interested persons an opportunity to participate in the rulemaking through the submission of written comments. 5 U.S.C. Sec. 553(c) (1976). After considering the relevant comments submitted, the agency must incorporate in the promulgated rules "a concise general statement of their basis and purpose." Id. To ensure meaningful judicial review, the agency in that statement and in its supporting materials must articulate the rational basis for the choices it has made; however, as stated above, we "should not reverse an agency's decision that is not fully articulated where we can reasonably discern the basis for the agency's action." AISI I, 526 F.2d at 1047; see AISI II, 568 F.2d at 295-96.

Finally, we note that the Administrator's actions are entitled to a presumption of regularity. Citizens to Preserve Overton Park v. Volpe, 401 U.S. 402, 415, 91 S.Ct. 814, 823, 28 L.Ed.2d 136 (1971). A party petitioning for review of an agency's regulations bears the burden of overcoming that presumption. Lewes Dairy v. Freeman, 401 F.2d 308, 316 (3d Cir.1968), cert. denied, 394 U.S. 929, 89 S.Ct. 1187, 22 L.Ed.2d 455 (1969); accord Environmental Defense Fund v. Costle, 657 F.2d 275, 283 n. 28 (D.C.Cir.1981). If after adequate notice and opportunity to comment a petitioner claims on appeal that the agency overlooked technical, factual and policy issues not raised in comments before the agency, that petitioner will have less latitude in its complaints, Weyerhaeuser, 590 F.2d at 1028 n. 15, or in special circumstances will be barred altogether, AISI I, 526 F.2d at 1050; see American Frozen Food Institute v. Train, 539 F.2d 107, 134 (D.C.Cir.1976).

NRDC and all the other petitioners ("industrial petitioners") raise challenges to several provisions of the general pretreatment regulations, 40 C.F.R. Secs. 403.1.-16 (1982). We consider those challenges in the following order: (A) the definitions of "interference" and "pass through;" (B) the definition of "new sources;" (C) the FDF variance provision; (D) the removal credits provision; and (E) the combined wastestream formula.

A. The Definitions of "Interference" and "Pass Through"