The Puget Sound Air Pollution Control Agency (PSAPCA) and the State of Washington by and through the Department of Ecology (DOE) appeal a superior court judgment reversing the Pollution Control Hearings Board's affirmance of an assessment of a civil penalty by PSAPCA1 against ASARCO for emitting smoke plumes in violation of PSAPCA's Regulation I, section 9.03(b)(1) and DOE's WAC 173-400-040(1). The Superior Court, concluding that the regulations were beyond the purview of the agencies' statutory authority,2 declared the regulations invalid. We disagree and reverse.
ASARCO, Inc., owned and operated a copper smelter in Tacoma. On December 28, 1983, a PSAPCA inspector saw ASARCO employees dumping molten slag, a by-product of the copper smelting process, in a disposal area. The inspector observed plumes of blue-white smoke rising into the air. Utilizing the Ringelmann method, a standard technique for measuring the opacity of smoke, the inspector determined that the opacity of the smoke from two emissions exceeded 20 percent for 16 Vi minutes within a 1-hour period. During this 1-hour period the opacity of the smoke was measured at 100 percent for a total of 1 minute, 60 percent for a total of 1 minute and at no less than 35 percent for "the remaining time necessary to exceed a total of three minutes." *51PSAPCA assessed a civil penalty of $2503 against ASARCO for violation of PSAPCA. Regulation I, § 9.03(b)(1) and DOE's WAC 173-400-040(1). PSAPCA Reg. I, § 9.03(b)(1) in pertinent part provides:
(b) . . . it shall be unlawful for any person to cause or allow the emission of any air contaminant for a period or periods aggregating more than three (3) minutes in any one hour which is:
(1) Darker in shade than that designated as No. 1 (20% density) on the Ringelmann Chart, as published by the United States Bureau of Mines. . . .
WAC 173-400-040(1) promulgated by DOE states:
(1) Visible emissions. No person shall cause or permit the emission for more than three minutes, in any one hour, of an air contaminant from any emissions unit which at the emission point, or within a reasonable distance of the emission point, exceeds twenty percent opacity . . .
On ASARCO's appeal, the Pollution Control Hearings Board affirmed the penalty. ASARCO then appealed to the Superior Court.
The Superior Court, indicating that it was relying on principles enunciated in Kaiser Aluminum & Chem. Corp. v. Pollution Control Hearings Bd., 33 Wn. App. 352, 654 P.2d 723 (1982),4 held the regulations invalid and reversed the Pollution Control Hearings Board. ASARCO argues, and the court below agreed, that the regulations merely penalize the emission into the outdoor atmosphere of contaminants causing opacity of a certain degree and duration without regard to whether the emitted contaminants are or are likely to be injurious in some manner, or interfere unreasonably with the enjoyment of life and property, so as *52to amount to air pollution as defined by RCW 70.94.030(2) and made unlawful by RCW 70.94.040.
Judicial review of the decision of the Pollution Control Hearings Board (the Board) after a formal hearing, as here, is governed by RCW 34.04.1305 and .140 of the administrative procedure act. RCW 43.21B.180. Our review of an administrative decision is on the record of the administrative tribunal itself, not that of the superior court. Franklin Cy. Sheriffs Office v. Sellers, 97 Wn.2d 317, 323, 646 P.2d 113 (1982), cert. denied, 459 U.S. 1106 (1983).
Because the facts are undisputed, the court reviews the Board's decision de novo under the error of law standard. Whether the Board committed an error of law turns on whether it properly interpreted the validity of the regulations of PSAPCA and DOE. At issue, then, is the scope of the rulemaking authority of PSAPCA and DOE and whether that authority was exceeded in the adoption and promulgation of the regulations before us. Our review of this issue is limited. We simply must ascertain whether the rules are reasonably consistent with the statutes they purport to implement.
The following principles enunciated in Green River Comm'ty College v. Higher Educ. Personnel Bd., 95 Wn.2d 108, 112, 117, 118, 622 P.2d 826 (1980), adhered to as modified, 95 Wn.2d 962, 633 P.2d 1324 (1981) are particularly appropriate to the task before us:
*53Certain well settled principles govern the scope of an administrative agency's rule-making authority. First, an agency has only those powers either expressly granted or necessarily implied from statutory grants of authority. Anderson, Leach & Morse, Inc. v. State Liquor Control Bd., 89 Wn.2d 688, 694, 575 P.2d 221 (1978). Second, an agency does not have the power to promulgate rules that amend or change legislative enactments. Fahn v. Cowlitz County, 93 Wn.2d 368, 383, 610 P.2d 857 (1980). Third, rules may "'fill in the gaps"' in legislation if such rules are "necessary to the effectuation of a general statutory scheme." Hama Hama Co. v. Shorelines Hearings Bd., 85 Wn.2d 441, 448, 536 P.2d 157 (1975). Fourth, administrative rules adopted pursuant to a legislative grant of authority are presumed to be valid and should be upheld on judicial review if they are reasonably consistent with the statute being implemented. Fahn, at 374. Fifth, a party attacking the validity of an administrative rule has the burden of showing compelling reasons that the rule is in conflict with the intent and purpose of the legislation. Weyerhaeuser Co. v. Department of Ecology, 86 Wn.2d 310, 314-17, 545 P.2d 5 (1976).
The Washington Clean Air Act (RCW 70.94) was enacted in 1967 (Laws of 1967, ch. 238). Its purpose is to secure and maintain beneficial levels of air quality in this state and to comply with the federal clean air act. RCW 70.94.011. Asarco, Inc. v. Air Quality Coalition, 92 Wn.2d 685, 709, 601 P.2d 501 (1979).
RCW 70.94.040 provides:
Except where specified in a variance permit, as provided in RCW 70.94.181, it shall be unlawful for any person to cause air pollution or permit it to be caused in violation of this chapter, or of any ordinance, resolution, rule or regulation validly promulgated hereunder.
RCW 70.94.030(2) defines air pollution as follows:
"Air pollution" is presence in the outdoor atmosphere of one or more air contaminants in sufficient quantities and of such characteristics and duration as is, or is likely to be, injurious to human health, plant or animal life, or property, or which unreasonably interfere with enjoyment of life and property.
(Italics ours.) RCW 70.94.030(1) states that:
*54"Air contaminant" means dust, fumes, mist, smoke, other particulate matter, vapor, gas, odorous substance, or any combination thereof.
DOE administers the act on a statewide basis. Regional authorities, such as PSAPCA, administer the act within their respective geographical areas. RCW 70.94.053; RCW 70.94.211. DOE and PSAPCA are authorized to adopt implementing resolutions, rules and regulations so long as they are consistent with the act. RCW 70.94.141; RCW 70.94.331(1).
DOE is specifically authorized to adopt "air quality standards and emission standards for the control or prohibition of emissions to the outdoor atmosphere of radionuclides, dust, fumes, mist, smoke, other particulate matter, vapor, gas, odorous substances, or any combination thereof", RCW 70.94.331(2)(c), which is another way of saying it is authorized to control the emission of air contaminants into the outdoor atmosphere. See RCW 70.94.030(1). An air quality standard is defined as "an established concentration, exposure time and frequency of occurrence of a contaminant or multiple contaminants in the ambient air which shall not be exceeded." Former RCW 70.94.030(13). PSAPCA's rules may be more stringent than DOE's, but they may not be less stringent. RCW 70.94.380. As one of the means of enforcing the act, a person who violates the act or any rule or regulation of DOE or PSAPCA is subject to a civil penalty. RCW 70.94.431.
ASARCO concedes, and indeed stipulated before the Board, that the plumes of smoke observed on its premises contained "air contaminants" as that term is defined in RCW 70.94.030(1). It nevertheless argues that air contaminants creating a degree of opacity proscribed by the regulation does not amount to air pollution.
Two sets of factors, defining air pollution, are set forth in the statutory definition of the term. Air contaminants of sufficient quantities, characteristics, and duration as to be harmful or potentially harmful to humans, etc., amount to air pollution when emitted into the outdoor *55atmosphere. However, there may be air pollution in the absence of such harm or potential for harm. The emission into the outdoors of air contaminants neither harmful nor potentially harmful may still amount to air pollution if the air contaminants unreasonably interfere "with enjoyment of life and property." This dual concept of air pollution is reinforced by the statutory scheme of the Washington Clean Air Act.
The penalties for causing air pollution may be avoided by obtaining a variance permit. RCW 70.94.040. However, a variance permit is not allowed for emission of air contaminants that endanger health or safety. RCW 70.94.181(l)(a). There is no need to obtain a variance permit if one is not causing air pollution.6 Consequently, air pollution must embrace conduct much broader than emitting into the outdoor atmosphere harmful or potentially harmful air contaminants. Otherwise, one could never qualify for a variance. Air pollution, then, also embraces the emission of air contaminants which, though not harmful to persons or property, do unreasonably interfere with the enjoyment of life and property.
There was no evidence before the Board that emissions of contaminants with an opacity of 20 percent for a duration of 3 minutes within 1 hour, without more, were harmful, or potentially so, or that such emissions unreasonably interfere with the enjoyment of life and property. However, there was evidence of a correlation between opacity in general (without relation to any degree or duration) and its harmful effects or its capacity to affect one's enjoyment of life and property. The document entitled EPA's Guidelines for Evaluation of Visible Emission; Certification, Field Procedures, Legal Aspects, and Background Material, EPA-340/1-75-007 (Apr. 1975) (the Guidelines) was *56admitted in evidence. The Guidelines provides scientific evidence of a correlation between opacity and harm to health and property, as well as a correlation between opacity and a diminished enjoyment of life and property (each chapter is supported by a bibliography of scientific studies). Section 9.5 of the Guidelines states that particles from 0.5 to 1 micron in size do the greatest damage in the alveolar region of the lungs, and are also the most significant cause of opacity because they are the same size as the wavelengths of light, thus tending to scatter light. Section 9.5 concludes: "There is then a correlation between the plume opacity, as determined by the observer in the field, and the amount of lung-damaging particulate being emitted." Section 8.1(7) states: "Although it is usually not possible to accurately quantify the reduction in mass emissions by visual observations, there is a definite relationship between reducing visible emissions and improvements in particulate air quality." The Guidelines also concludes that water vapor (another cause of opacity) "can have adverse effects on the environment," section 5.1, and can cause fog, ice, and reduced visibility, creating safety hazards for automobiles, aircraft and shipping. Section 5.2.
No one can seriously dispute that the emission into the outdoors of air contaminants causing opacity of any amount will result in some sort of interference with one's enjoyment of life or property. One may question what degree and duration of opacity amounts to an unreasonable interference. The appropriate agencies have determined that limit. Our capacity to question the validity of the opacity test as an air pollution test is quite limited. The agencies' scientific expertise is entitled to great deference. " [T]he court is not free to substitute its judgment as to the desirability or wisdom of the rule, for the legislative body, by its delegation to the agency, has committed those questions to administrative judgment and not to judicial judgment." Weyerhaeuser Co. v. Department of Ecology, 86 Wn.2d 310, 314, 545 P.2d 5 (1976) (quoting 1 K. Davis, Administrative Law § 5.05, at 315 (1958)).
*57The Legislature itself has acknowledged that an opacity standard is an appropriate measure of at least one form of air pollution. In 1984 the Legislature increased the maximum civil penalty for violation of the act and its implementing rules and regulations. Thé maximum penalty was raised to $1,000 per day for each violation. At the same time, the Legislature placed a lower limit for a violation of opacity standards by providing, "Notwithstanding any other provisions of this chapter, no penalty may be levied for the violation of any opacity standard in an amount exceeding four hundred dollars per day." (Italics ours.) Former RCW 70.94.431(3) (Laws of 1984, ch. 255, § 2).
While we do not believe the statute is ambiguous, one might argue otherwise. Arguably one might claim there exists a conflict between the definition of the term air pollution, which is clearly proscribed, and declaring it unlawful to violate rules and regulations establishing air quality standards without explicitly requiring that the violation of the standards results in some harm or unnecessarily interferes with the enjoyment of life or property. Assuming an ambiguity exists, the agencies' construction of the statute is of considerable importance in determining its meaning.
The validity of an administrative rule may also be tested by the construction placed on the authorizing statute by the administrative agency. Washington Water Power Co. v. State Human Rights Comm'n, 91 Wn.2d 62, 68-69, 586 P.2d 1149 (1978). Moreover, an administrative construction nearly contemporaneous with the passage of the statute, especially when the legislature fails to repudiate the contemporaneous construction, is entitled to great weight. Morin v. Johnson, 49 Wn.2d 275, 279, 300 P.2d 569 (1956). Finally, a contemporaneous construction by the department charged with administering an ambiguous statute is even more persuasive if the legislature not only fails to repudiate the construction, but also amends the statute in some other particular without disturbing the administrative interpretation. Bradley v. Department of Labor & Indus., 52 Wn.2d 780, 786-87, 329 P.2d 196 (1958).
*58Green River Comm'ty College v. Higher Educ. Personnel Bd., 95 Wn.2d 108, 117-18, 622 P.2d 826 (1980), adhered to as modified, 95 Wn.2d 962, 633 P.2d 1324 (1981).
The Washington Clean Air Act was adopted in 1967. PSAPCA's regulation was promulgated the following year. See Asarco, Inc. v. Air Quality Coalition, 92 Wn.2d 685, 702-03, 601 P.2d 501 (1979). In 1970, the Washington State Air Pollution Control Board, DOE's predecessor under the act, by regulation established emission standards for primary aluminum plants, which, inter alia, prohibited visible emissions from all sources with opacity of 20 percent density or more on the Ringelmann Chart for more than 3 minutes in any hour. 7 DOE, starting in 1972, has adopted regulations limiting emissions from all sources of air contaminants with various shadings of opacity and duration.8
PSAPCA's regulation was adopted as nearly contemporaneously with the adoption of the act as one can expect. DOE's predecessor, shortly after the act was adopted, promulgated a similar opacity standard to control pollution as it was authorized to do by the act. The Legislature has amended the act numerous times but has never disturbed the construction of the act by the agencies created to administer it.9 This is persuasive authority upholding the *59validity of the agencies' construction of the act. We are satisfied that ASARCO has failed to meet its burden of showing that the regulations under review are in conflict with the intent and purpose of the Washington Clean Air Act. Recognizing the presumption of validity, as we must, we are satisfied that the regulations under review are reasonably consistent with the act and therefore are valid.
The Superior Court's judgment is reversed and the Board's affirmance of the civil penalty is affirmed.
Alexander, A.C.J., concurs.
PSAPCA is a local authority authorized to enforce state regulations dealing with air quality and emissions standards, as well as its own regulations on these matters, provided its regulations are no less stringent than the state regulation, RCW 70.94.211 and 70.94.331(2)(b). No one denies that PSAPCA's regulation is as stringent as DOE's. The issue before this court is the validity of both regulations.
The Washington Clean Air Act, RCW 70.94.
The $250 assessment was the maximum civil assessment then allowable by former RCW 70.94.430. Laws of 1984, ch. 255, § 1, increased the maximum allowable assessment per violation to $1,000.
Kaiser invalidated a regulation of PSAPCA which proscribed the discharge of particulate matter onto property of another and upheld a different regulation which proscribed the emission of air contaminants harmful to persons or which causes damage to property or business. It did not address the validity of the regulations now under review.
RCW 34.04.130(6) states:
"The court may affirm the decision of the agency or remand the case for further proceedings; or it may reverse the decision if the substantial rights of the petitioners may have been prejudiced because the administrative findings, inferences, conclusions, or decisions are:
" (a) in violation of constitutional provisions; or
" (b) in excess of the statutory authority or jurisdiction of the agency; or
"(c) made upon unlawful procedure; or
” (d) affected by other error of law; or
" (e) clearly erroneous in view of the entire record as submitted and the public policy contained in the act of the legislature authorizing the decision or order; or
" (f) arbitrary or capricious."
We note with interest that in 1975 ASARCO sought a variance from the strictures of PSAPCA's Regulation I, section 9.03(b)(1), the same same regulation it challenges in these proceedings. See Asarco, Inc. o. Air Quality Coalition, 92 Wn.2d 685, 601 P.2d 501 (1979).
Washington State Air Pollution Control Board Order 14 amending WAC 18-52-030 adopted May 20, 1970.
DOE Order 72-6 adopting WAC 18-04-040 (Jan. 24, 1972) (limiting emissions exceeding 40 percent opacity for more than 3 minutes in the hour); DOE Order 72-29 amending WAC 18-04-040 (Jan. 22, 1973) (limiting emissions exceeding 40 percent opacity for more than 3 minutes in the hour); DOE Order 76-38 adopting WAC 173-400-040(1) (Dec. 21, 1976) (limiting emissions exceeding 20 percent opacity for more than 3 minutes in the hour); DOE Order 78-21 amending WAC 173-400-040 (Apr. 27, 1979) (emission standards same as in DOE Order 76-38); DOE Order 80-14 amending WAC 173-400-040 (adopted July 28, 1980) (emission standards same as in DOE Order 76-38); DOE Order 83-13 amending WAC 173-400-040 (adopted Mar. 30, 1983) (emission standards same as in DOE's Order 76-38).
Laws of 1980, ch. 175; Laws of 1979, ch. 141; Laws of 1975, 1st Ex. Sess., ch. 106; Laws of 1973, 1st Ex. Sess., ch. 193; Laws of 1969, 1st Ex. Sess., ch. 168.