This is a suit for injunction, brought under the aegis of the Michigan Environmental Protection Act, MCLA 691.1201 et seq.; MSA 14.528(201) et seq. Following a nine-day trial that began on November 23, 1976, plaintiff Wayne County Health Department, Air Pollution Control Division, (hereafter, "the Division”), secured a decree from the lower court directing defendant Olsonite Corporation to adopt within a stated period "a specific supplemental odor control system” capable of achieving emission limits set by the court.
The Division, empowered to investigate, prevent and abate causes of air pollution within Wayne County and to enforce the Wayne County Air Pollution Control Regulation, (hereafter, "the Regulation”),1 filed the present suit on October 12, 1973. Its complaint alleged that Olsonite, a domestic corporation located at 8801 Conant Avenue, *673Hamtramck, Michigan, "has discharged and continues to discharge” into the ambient air "obnoxious and foul odors” which threaten to pollute, impair or destroy the atmosphere and which endanger the health, welfare and safety of residents in the vicinity.
Olsonite, situated amid other industrial facilities and bordering residential areas to the east, north and south, manufactures molded plastic toilet seats, steering wheel inserts and various flexible plastic parts used by the automotive industry. Of these items, only the flexible plastic parts require painting at Olsonite’s plant on Conant. The parties do not dispute that, as an incident of the painting process, certain pungent odors are produced which, if unrestrained, are then emitted into the atmosphere and carried off by prevailing winds. The crux of the controversy, however, centers on the effectiveness of Olsonite’s present method of restraining its paint fumes from entering the atmosphere.
The painting operation, conducted weekdays on a single shift from 7 a.m. to 3:30 p.m., employs an overhead conveyor system by which parts to be painted are passed through a series of four paint spray booths, a flash-off chamber and a bake oven. In addition, Olsonite uses a chain-on-edge conveyor which carries parts through an enclosed painting machine. Necessary finishing is then performed in two separate paint spray booths. In all, according to defendant, there are ten potential sources from which odor may emanate.
Paint is electrostatically applied by automatic spray equipment located in front of the booths. The paint, specified by Olsonite’s customers, is a proprietary urethane enamel produced by PPG, Inc. In addition to certain known solvents that are *674part of PPG’s paint formula, Olsonite is required to add other solvents in connection with the painting process. Originally Olsonite utilized a solvent blend of Toluol and Xylol as recommended by PPG. During 1973, however, because of the energy crisis, these solvents became unavailable and Olsonite allegedly was required to switch to a blend containing solvents with lower odor thresholds (and thus higher odor potential) than those in the original Toluol-Xylol blend. In February 1975, the original blend became available again and has been used by Olsonite since that time. These solvent blends, it should be noted, are not water soluble.
Each of the paint spray booths is equipped with devices which form a curtain of water designed, primarily, to trap wayward particles of paint and, secondarily, to prevent the emission of odors into the atmosphere. The water curtain is maintained by a system drawing recirculated water from a tank at the base of each spray booth through a pipe to a manifold at the top of the booth. The manifold contains a number of uplifted nozzles which discharge water against and over a series of baffles controlling the flow and splash of water to form, when fully functional, a continuous curtain of water. Owing to the use of recirculated water, the nozzles at times become clogged by accumulations of paint, causing breaks in the curtain. Through these breaks, paint particles, solvents and exhaust materials escape into the stacks and thence into the ambient air. Olsonite has from time to time modified its operation in an effort to improve the water curtains by adding more baffles, using additional weirs in the water tanks, purchasing extra manifolds to replace those that become clogged and installing (four to five weeks prior to *675trial) a filtration system that skims excess particles from the recirculated water. In addition, Olsonite has established a procedure for periodic inspection and maintenance of its painting operations.2
At the trial, the Division presented the following evidence to establish its prima facie case: 1. Five field inspectors, employed by the Division, testified regarding inspections and surveillance they conducted at or near the Olsonite facility from 1972 to the time of trial. According to their testimony, the inspectors, although not formally enrolled in odor-detection courses, did receive instruction and training on the subject. One of the inspectors, witness Zabick, described the nature of the orientation available to the Division’s inspectors:
"Q. [Mr. Donald A. Campbell, Assistant Prosecuting Attorney] I would like you to tell the Court specifically, if you can, the type of material which is contained, for instance, in the EPA [i.e., the United States Environmental Protection Agency] manuals? For instance, do they talk about technique? I mean, you said you have read manuals which deal with odor, is that correct?
"A. That is right.
*676"Q. Can you be a little more specific' as to what specifically you read about concerning odors?
"A. Sources of different types - of odors right from rendering plants to paint making operations to odors in steel making, types of control devices, methods of detecting it, various type charts to use to detect levels of odors, numerical system of evaluating them, methods of positioning yourself, making a complete around-the-source surveillance, up wind, down wind, the complainant’s role in determining the severity of an odor.
"THE COURT: I think that is fine, Mr. Zabik [sic]. Are these manuals available to all the inspection staff of the agency?
"THE WITNESS: Yes.”
The testimony of the inspectors essentially revealed that on frequent instances from 1973 to the date of trial they had been summoned, often by radio run and almost invariably at the behest of complaining citizens, to verify alleged odors issuing from Olsonite’s plant. The voluminous inspection reports and violation notices, entered at trial to show defendant’s knowledge that complaints had arisen, describe the alleged odors either in narrative fashion (e.g., "very high”, "very pronounced”, "pungent”, "slight odor”) or by means of a Division-adopted Odor Detection Chart,3 a variant of the US EPA Odor Detection Chart.4 *677Each of these detection charts employs a numerical rating system designed to eliminate the ambiguity inherent in narrative descriptions of odor intensity.
The inspectors’ testimony, backed by their reports, discloses many instances where odors specifically attributable to Olsonite’s painting process were assigned a numerical value of "2” or "2+” and, on fewer occasions, "3”. Although these odors abated at times, especially after February, 1975, when Olsonite returned to use of the Toluol-Xylol blend, the reports indicate that inspectors Gribbs, Krawiec and Zabick frequently noted in 1975 and 1976 detectable paint odors emitted by Olsonite.
2. The lower court admitted office records of the Division which indicate that the Division received 59 citizen complaints against Olsonite in 1973, 38 in 1974, 24 in 1975, and 13 as of August 31, 1976.
3. Thirteen citizens, living north, east and south of the Olsonite complex, testified at trial. These witnesses relayed to the court complaints they registered with the Division and with Olsonite concerning odors, generally characterized as paint-like, very distinctive, unpleasant and offensive, emanating from the Olsonite complex. According to the largely unrebutted testimony of the citizens, the odors caused nausea, burning eyes, headaches, loss of sleep and a reduction in appetite; in addition, the fumes penetrated their homes and were particularly obnoxious during periods of warm weather.
In instances when inspectors and citizens had been asked whether they could distinguish between odors attributable to Olsonite and those of *678other neighboring industries, the witnesses stated that they had no difficulty in differentiating the various smells. One inspector did mention, however, that the paint odors ascribed to Olsonite and those issuing from a nearby Chrysler facility "were somewhat similar, but there are generally differences between one type of odor from one operation to the other” that a person "very familiar with the different plants” would detect.
4. Dr. Peter Warner, the Division’s laboratory supervisor and an expert on odors and odor measurement, testified regarding various field samplings and laboratory analyses of gases emitted from Olsonite’s stacks; these tests began in November, 1972, and continued sporadically up to March, 1976.
During his testimony, Dr. Warner explained the method utilized to retrieve a sample of Olsonite’s stack effluent5 and then described the manner in which the relative concentration of an odor is determined in the laboratory. This latter task employs a five-member odor panel consisting of odor-sensitive individuals capable of distinguishing between three odors at successively lower concentrations. Once selected, each odor panelist is subjected to varying concentrations of stack effluent diluted with clean air and a determination is made regarding the lowest concentration at which over 50 percent of the panel can detect any odor from *679the samples. Thus, the greater the number of dilutions required, the more intense is the odor under scrutiny. Once the lowest concentration of stack effluent, discernible by over half of the panel, is ascertained, calculations are then made to express the concentration in odor units per cubic foot of air.
In analyzing the results of this testing, the Division has established certain recommended guidelines similar to those employed by "a number of agencies and states”;6 the Division’s guidelines describe odor emission levels which, if not exceeded, are "acceptable”7 to the Division: 150 odor units per cubic foot or one million odor units per minute (i.e., odor units per cubic foot times cubic feet of exhaust gas per minute).
The November, 1972, stack tests conducted at Olsonite by the Division showed that of the two potential emission sources tested, viz., the drying *680oven and flash-off chamber, both fell well within the Division’s guidelines; the report on the November tests concluded: "it is unlikely that the above source represents any appreciable community odor problems.”
Stack tests conducted in October, 1973, measuring emissions from seven sources (five paint spray booths, the flash-off chamber and drying oven) disclosed levels far exceeding the Division’s guidelines for both odor concentration and odor emission rate.8 These results coincided with the change in solvents necessitated by the energy crisis.
Stack testing performed in August, 1974, found odor levels in excess of the Division’s guidelines in the three spray booths tested, while the flash-off chamber and drying oven emission levels fell below the guidelines.9
No testing occurred in 1975.
In March, Í976, stack tests conducted at Olsonite’s request, measuring emissions from spray booth number two, revealed odor levels (i.e., in odor units per cubic foot) below the Division’s *681guidelines, but emission rates (i.ein odor units per minute) slightly above the guidelines in two of four samples tested.10 Olsonite had requested the *682March tests to measure the effectiveness of using aqueous potassium permanganate as a pollution abatement technique. The tests, conducted on two occasions in March, first measured the effectiveness of the water curtain alone and then with the addition of the permanganate. Prior to the initial test, certain changes in the spray booth had been effected:
"1. Redistribution of the total paint sprayed per day to relieve the loading on the booth No. 2 stack and to more equally distribute the rate of spray to other booths which were formerly used to apply lighter coats to parts.
"2. Cleaning and improvement of the water curtain plumbing and pumping system.
"3. Installation of a baffle to reduce the water travel distance at the throat of the water curtain.” Trial Exhibit 12, p 16.
In his report on the March tests, Dr. Warner discounted the effectiveness of permanganate as an additive and noted an "apparent measured improvement” in the utility of the tested water curtain as an odor suppressant; however, he reserved judgment on the system as a whole:
"[I]t is necessary to determine any change in the odor output of the other adjacent booths and stacks, as odor sources, as a result of changes in the operation of booth No. 2, before any claim is made to an overall condition of odor abatement.” Trial Exhibit 12, p 18.
Moreover, Dr. Warner observed a deterioration in water-curtain efficiency from the first March test to the second attributable to plugged nozzles which thus "allowed an estimated 15 to 35% of the solvent mist to enter the booth No. 2 stack untreated”. Id. at 19. Nonetheless, he concluded:
*683"[I]n view of the apparent effectiveness achievable by water curtain improvements coupled with techniques in redistribution of solvent, this approach should be explored further by the company.” Trial Exhibit 12, p 19.
Dr. Warner amplified the point in his testimony by stating that an improved water curtain "would certainly be an excellent approach to a solution” but the reliability of the curtain "is the only unknown factor. Our experience with reliability has been very poor”. The court then asked Dr. Warner to indicate other odor abatement techniques potentially available to Olsonite. With the qualification that he was not an engineer, Dr. Warner listed the following: fume incineration (afterburners); a scrubbing system combined with a packed tower containing fragments of absorptive material; and carbon adsorption.
Following Dr. Warner’s testimony, plaintiff rested. Olsonite then moved for a directed verdict but the court denied the motion.
The first defense witness, Mr. Gerald Eggers, Olsonite’s manager of industrial engineering, described his duties, the painting process at Olsonite, the various modifications undertaken to improve the water curtain, and efforts made to obtain a positive pollution-control system for the company. According to Mr. Eggers, each of these systems— (a) odor masking agents, (b) odor counteractants, (c) scrubbers and chemical absorption systems, (d) catalytic converters, (e) afterburners, (f) tall stacks, (g) recuperative combustion devices, (h) refrigeration and, (i) activated carbon adsorption — has drawbacks that make its use unacceptable for the company.
For example, he testified that masking agents, which merely camouflage the odor, are unacceptable to the Division; that odor counteractants tested *684by Olsonite proved erratic and at times created additional odor; that systems based on carbon adsorption or catalytic conversion are ineffective because the paint used by Olsonite will contaminate the carbon or catalyst used in these systems, and, further, that catalytic converters pose an inherent risk of explosion; that tall stacks erected at a cost of $417,000 by Ford Motor Company for its Utica painting operation still draw citizen complaints; and that chemical absorption, using ozone, presents potential dangers created by ozone. Mr. Eggers also conveyed budgetary quotes he received for certain methods of odor control.11 On cross-examination, the witness often exhibited lapses of memory when questioned on the extent of his investigations into alternate odor control systems and on the identities of persons he contacted in this quest. He acknowledged, however, that no pilot tests or engineering drawings had been commissioned by defendant; that no efforts had been made to negotiate reductions in the quoted costs or *685to ascertain whether less expensive equipment might be used on Olsonite’s less offensive odor sources; and that he had never submitted to management a "formal capital appropriation request” for any of the proposed systems. Further, he maintained that while the companies submitting budgetary quotes promised odor reductions of 95 to 97 percent, none would guarantee the elimination of all odors.
Three additional defense witnesses followed Mr. Eggers to the stand. Mr. Edmund Szajna, defendant’s director of manufacturing, explained maintenance procedures covering Olsonite’s painting operation. Mr. Arthur W. Sempliner, Olsonite’s first vice-president, described Olsonite’s products, gave financial and employment data on Olsonite,12 explained an odor sampling technique conducted by Olsonite’s employees in 1976, noted the possibility that expensive odor abatement methods might entail a shutdown of the entire plant and stated that on his way to work he occasionally smells a paint odor, indistinguishable from Olsonite’s, emanating from a nearby Chrysler plant. Mr. Sempliner also offered the view that no prudent or feasible alternative to the water curtain exists which could solve Olsonite’s problem of odorous *686emissions. Lastly, Mr. Henry Wojtaszek, the director of Olsonite’s central staff, testified regarding defendant’s painting process, the nature of the paint and solvents employed, Ford’s limited success with tall stacks and Olsonite’s recent experimentation with spray applicators which may be able to reduce the amounts of solvent and paint used from 25 to 50 percent.
Following closing arguments, the lower court requested and received proposed findings of fact and conclusions of law from the parties. On December 15, 1976, the court issued an opinion finding, inter alia, that:
1) the "complaints [of the citizen witnesses] were justified”;
2) "the odors came from defendant’s plant”;
3) "[t]he inspection reports established the existence of a number two odor on repeated occasions throughout the period in question, and on some occasions a number three odor”;
4) "an acceptable level of odor strength is an emission of less than 150 odor units per cubic foot or a total of one million odor units per minute”;
5) "[t]he [October] 1973 tests conclusively established that defendant polluted the air contrary to the Act”;
6) the March, 1976 tests revealed "two samples out of four that exceeded acceptable levels and polluted the air”; and
7) "the use of water curtains, baffles and filters, no matter how well cleaned and maintained, is not sufficient to prevent air odor pollution.”
From the foregoing, the trial court concluded that plaintiff had "established its prima facie case”. See MCLA 691.1203(1); MSA 14.528(203X1). Next, concluding that defendant had failed to rebut plaintiff’s prima facie case, the court ruled:
*687"the tests [conducted] by company employees * * * are of the most self serving nature and in no way rebut the convincing testimony of the inspectors, the residents of the neighborhood, and the scientific tests of Dr. Warner. Furthermore, it is significant that not one of the company employees who conducted the tests was called to testify, subject to cross examination.” Wayne County Department of Health, Air Pollution Control Division v Olsonite Corporation, Wayne County Circuit Court No. 73-252680-CE, issued December 15, 1976, pp 7-8.
The court then surveyed existing methods of pollution control available to defendant, along with their attendant costs, and cited Olsonite’s employment and revenue figures, noted supra, in concluding that any one "of the suggested methods is economically feasible and prudent”.
Thus the court found:
"There are a variety of odor control techniques available, some of which have been listed. Defendant has failed to establish that there is no feasible or prudent alternative to the continued pollution. In fact, except for some work with the water curtain system and some minor tests with counteractants, defendant has failed to try any method and has failed in its affirmative defense to show that there is no feasible and prudent alternative.
"It is also clear that the conduct of defendant is not consistent with the promotion of the public health, safety and welfare in light of the state’s paramount concern for the protection of its natural resources from pollution. In fact, defendant throughout, although appearing to cooperate and treat complaints with sympathy and seriousness, has failed to take any effective means to control or attempt to control the air pollution it has created. The defendant has been well aware of the pollution problem for many years, and although many solutions were potentially available, defendant failed to employ any of them except to attempt to clean up the water curtains.
*688"Defendant contends that it has taken affirmative action in planning a new system that will reduce the amount of paint used and involving the water curtain device. The fact remains, however, that there is no showing that these plans will solve the continuing pollution problem.” Wayne County, supra at 9-10.
Lastly, the trial court ended its opinion by making conclusions of law and ordering injunctive relief:
"IV CONCLUSIONS OF LAW
"The Court having found that plaintiff has established its prima facie case affirmatively, that defendant has failed to rebut plaintiff’s prima facie case, and that the defendant has failed to establish as an affirmative defense that there is no feasible and prudent alternative to his conduct and that the conduct is consistent with the promotion of the public health, safety and welfare, it must follow as a matter of law that plaintiff is entitled to relief.
"Defendant argues, however, that even in the face of the statute, the Court must consider the character, quality and nature of the locality where defendant operates.
"The arguments of defendant state many propositions of general nuisance law, all of which were enunciated prior to the enactment of the Environmental Protection Act of 1970. By this statute, the Legislature defined the standards to be used and the method to be determined by the Court in deciding cases where there is a claim of environmental pollution. The standards set out in the statute are clear and unequivocable, and to the extent that the prior law relating to nuisance varies from the statute, the statute must control. Plaintiff has established its prima facie case, which has not been rebutted, and defendant has failed in its affirmative defense.
"But even if general nuisance law were to be applied, plaintiff still would have to prevail. It has established by both objective and subjective standards, conduct *689which has polluted the air. It has established that there are feasible methods to control the pollution. And defendant has failed to rebut plaintiff’s case. It therefore follows that the plaintiff is entitled to relief.
"V RELIEF ORDERED
"It is obvious that an order must be entered enjoining the defendant from continuing to pollute the air. At the same time defendant must be given a reasonable time to reach full complaince [sic].
"To accomplish this, it is ordered that defendant forthwith at its own expense conduct pilot testing of prototype odor control systems to compile operating and odor control data. Such tests shall be monitored by representatives of plaintiff and be completed by March 1, 1977. The results shall be made available to the Court at that time.
"On or before April 1, 1977, defendant shall select a specific supplemental odor control system and timetable for its installation and completion. This system shall achieve odor emission limits of no more than 150 odor units per cubic foot and no more than one million odor units per minute under odor evaluation tests to be approved by plaintiff. Defendant shall submit to the Court its timetable for installation and completion, which shall be approved by the Court after hearing.
"If after installation of the equipment on or before a date approved by the Court, defendant at any time emits more than 150 odor units per cubic foot or one million odor units per minute under odor evaluation tests run in accordance with procedure outlined by plaintiff, plaintiff may move this Court for supplemental injunctive relief.
"The Court will retain jurisdiction of the case. Costs to plaintiff.” Wayne County, supra at 11-14.
On defendant’s motion, a panel of this Court stayed enforcement of the injunction by an order dated February 7, 1977.
In its appellate brief, defendant seeks review of four issues. The first is whether the trial court correctly ruled that the Environmental Protection *690Act (EPA) supplants prior doctrines of common law nuisance to the extent these doctrines conflict with the act.
Two Michigan Supreme Court cases offer insight on the issue. In Ray v Mason County Drain Commissioner, 393 Mich 294; 224 NW2d 883 (1975), Justice Williams, writing for a nearly unanimous Court, recognized the EPA as the Legislature’s response to the mandate of Const 1963, art 4, § 52:13
"The Legislature in establishing environmental rights set the parameters for the standard of environmental quality but did not attempt to set forth an elaborate scheme of detailed provisions designed to cover every conceivable type of environmental pollution or impairment. Rather the Legislature spoke as precisely as the subject matter permits and in its wisdom left to the courts the important task of giving substance to the standard by developing a common law of environmental quality. The act allows the courts to fashion standards in the context of actual problems as they arise in individual cases and to take into consideration changes in technology which the Legislature at the time of the act’s passage could not hope to foresee.” 393 Mich at 306-307. (Footnote omitted; emphasis supplied.)
In a note accompanying the foregoing passage, the Court observed:
"While the language of the statute paints the standard for environmental quality with a rather broad stroke of the brush, the language used is neither illusive nor vague. 'Pollution’, 'impairment’ and 'destruc*691tion’ are taken directly from the constitutional provision which sets forth this state’s commitment to preserve the quality of our environment. In addition these and other terms used in establishing the standard have acquired meaning in Michigan jurisprudence. The development of a common law of environmental quality under the EPA is no different from the development of the common law in other areas such as nuisance or torts in general, and we see no valid reason to block the evolution of this new area of common law.” 393 Mich at 307, fn 10.
Similarly, see State Highway Commission v Vanderkloot, 392 Mich 159, 184; 220 NW2d 416 (1974), opinion of Williams, J.;
"It is most important to note that EPA does not, as both parties imply, merely provide a separate procedural route for protection of environmental quality, it also is a source of supplementary substantive environmental law. See Sax and Conner, Michigan’s Environmental Protection Act of 1970: A Progress Report, 70 Mich L Rev 1004, 1054-1064 (1972).” (Emphasis in Vanderkloot.)
Defendant gleans from the cited cases a requirement that the EPA be interpreted in harmony with existing Michigan law. In further support of its argument, defendant cites Crandall v Biergans, Clinton County Circuit Court No. 844, 3 ERC 1827 (1972), and an analysis of that case coauthored by Professor Sax, the initial draftsman of the EPA. See Sax and Conner, supra at 1066-1067.
In Crandall, a two-count odor-pollution suit alleging nuisance and an EPA violation, the court refused to enjoin defendant’s operation of a hog farm or to order relocation of defendant’s barn,
"so long as defendants continue their operation in a careful and husbandlike manner and use such odor *692control products or devices as are from time to time available and developed and are economically feasible. In short, it is the opinion of the Court that on balance the equities are in favor of defendants and that they are not maintaining a nuisance.” 3 ERC at 1830.
Turning to the EPA, the court in Crandall recognized that no standards regulating porcine odors had yet been established, see MCLA 691.1202(2); MSA 14.528(202)(2),14 and, disclaiming an ability to set standards on its own, interpreted § 3 of the act as "in effect saying that some balance has to be maintained between absolutely no pollution and the carrying on of activities necessary to human existence”. 3 ERC at 1831. The court then indicated that if defendants hold "the odor entering the atmosphere * * * to a practical minimum” they will have established an affirmative defense under the EPA, id.; see MCLA 691.1203(1); MSA 14.528(203X1). The court cautioned, however, that a balancing of interests on a case by case basis would be appropriate "[ujnless there are definite standards set”. 3 ERC at 1831-1832.
In commenting on the Crandall decision, Professors Sax and Conner remarked that the court apparently adopted common law standards on odor control,
"where none previously existed in legislation or administrative rules; and * * * the judge enforced those *693standards by finding that the defendants had complied with the policy of the EPA, a policy that is largely coextensive with the law of nuisance as he applied it in this case”. Michigan’s Environmental Protection Act of 1970: A Progress Report, 70 Mich L Rev 1004, 1067. (Emphasis supplied.)
We need not disagree with either Crandall or the Sax-Conner analysis of that case in order to reject defendant’s contention that traditional principles of nuisance law must always control in an EPA action. Crandall, unlike the present case, resorted to nuisance law because no definitive standards had been established. Here, however, the lower court, presumably on the authority of MCLA 691.1202(2); MSA 14.528(202)(2), adopted odor emission standards set by the Division.
In our view, MCLA 691.1202(2); MSA 14.528(202)(2) serves as a legislative recognition that unforeseen "changes in technology”, Ray, supra at 307, may permit the judicial adoption of standards more precise, and perhaps more exacting, than those previously required under the generalized language of the common law of nuisance. Surely, it is not unreasonable for the Legislature to have concluded that plaintiffs and defendants alike would prefer explicit but attainable standards of conduct in place of the uncertainties attending a balancing-of-the-equities analysis under the law of nuisance.
Moreover, to hold, as defendant urges, that the standards of conduct required by the EPA are coterminous with those imposed by the common law of nuisance would eviscerate the substantive facets of the act, Ray, supra at 306, and condemn as mere surplusage all but its procedural remedies. Given our state’s "paramount concern for the protection of its natural resources from pollution, *694impairment or destruction”,15 we believe the Legislature intended the EPA to supersede the common law of nuisance to the extent these respective bodies of law conflict.16
Defendant also assails as erroneous and unsupported by the evidence various factual findings of the trial court. Although an appellate court reviews chancery suits de novo, we apply the "clearly erroneous” standard of GCR 1963, 517.1. See 2 Honigman & Hawkins, Michigan Court Rules Annotated (2d ed), p 596. Compare Causley v LaFreniere, 78 Mich App 250, 254-255, fn 2; 259 NW2d 445 (1977), and Miller v Magline, Inc, 76 Mich App 284, 293-294; 256 NW2d 761 (1977).17 Under this test, a finding is clearly erroneous when, although there is evidence to support it, the reviewing court on the entire evidence is left with the definite and firm conviction that a mistake has been made. Tuttle v Department of State Highways, 397 Mich 44; 243 NW2d 244 (1976). For convenience, our examination of the trial court’s assertedly erroneous findings will track the statute.
Prima Facie Case of Pollution
Initially it should be noted that probable as well *695as actual degradation of the environment may be considered in deciding whether plaintiff has made a prima facie showing of pollution. Ray, supra at 309. Moreover, the evidence necessary to establish a prima facie case "will vary with the nature of the alleged environmental degradation involved”. Id.
Defendant cites four trial court findings as clearly erroneous:
"1. The Trial Court found that there have been innumerable complaints by citizens of the area as to odors of an unpleasant nature coming from the Olsonite Plant.” (Appellant’s Brief at 38.)
"2. The Trial Court found that the [Division’s] inspection reports established the existence of a No. 2 odor on repeated occasions, and on some occasions a No. 3 odor and that repeated violation notices have been served on defendants.” (Id. at 39.)
"3. The Trial Court found the 1976 [Division] laboratory tests based upon stack samples exceeded acceptable levels and polluted the air.” (Id. at 41.)
"4. The Trial Court found that the effectiveness of the water curtain to control odorous solvent emissions is very doubtful and that it is clear that the use of water curtains, baffles and filters, no matter how well cleaned and maintained, is not sufficient to prevent odor pollution.” (Id. at 42.)
Regarding the first finding, defendant asserts that the record demonstrated "serious problems of [odor] attribution and identification”; defendant notes 1) the similarity of Olsonite’s alleged odor to that of other industrial concerns, 2) the failure to detect any number 4 odors and only a single number 3 odor in the two years prior to trial, 3) the absence of violation notices since April, 1975, and 4) the absence of scientific or medical evidence showing the harmfulness of Olsonite’s odors.
*696We do not find the judge’s initial finding to be clearly erroneous. The great majority of citizens and inspectors who testified remained firm in attributing the recurrent odors as emanating from Olsonite’s factory. That the intensity of the odors may have diminished in the two years preceding trial does not refute the probable environmental degradation established at trial by citizen witnesses who complained of serious physical symptoms caused by Olsonite’s odors in 1975 and 1976. Plaintiff was not obliged to offer scientific or medical evidence of health impairment, for the judge believed the "convincing testimony” of the citizens. Moreover, the absence of violation notices is explained by the inspectors’ testimony that the Division had directed them to cease issuing such notices because of Olsonite’s failure to respond affirmatively to previous notices.18
Nor is the second finding clearly erroneous. Although the judge characterized a number 2 odor as "distinctly unpleasant” whereas the Division’s *697odor intensity schedule characterizes a number 2 odor as distinct, definite and clearly detectable, the testimony of two inspectors discloses that the Division staff did not limit the number 2 intensity to the recognition threshold as defendant asserts, but gave it a range starting at the clearly detectable level up to an odor level just short of a number 3 intensity. Since defendant does not suggest that the distinct, clearly detectable odor of its paint and solvents is by any means fragrant and since the inspectors’ reports were entered merely to show the existence of citizen complaints, we do not find the lower court’s slight misdescription to constitute clear error.
Turning to the third finding, i.e., stack samples exceeding acceptable levels and polluting the air, again we do not discern clear error in the judge’s finding that stack samples tested by Dr. Warner had exceeded and continued to exceed odor emission levels denominated "acceptable” by the Division. We are disturbed, however, by what appears to be a premature adoption of standards governing odor emissions, viz., 150 odor units per cubic foot or one million odor units per minute.
Under MCLA 691.1202(2)(a); MSA 14.528(202)(2)(a), a court may adopt an agency-approved standard after having assessed "the validity, applicability and reasonableness of the standard”. As noted, supra, Dr. Warner’s testimony relative to the Division’s standards did not clearly disclose whether other states had adopted the identical standards employed by the agency; rather, he indicated, without adequate citation, that "quite a number of agencies and states have adopted regulations which specify the emission limits of sources to a given number of odor units per cubic foot * * * [and that] [o]ther states have *698adopted various responses to odor problems”. Moreover, we note that the Division’s laboratory guidelines are neither officially compiled nor mentioned in the Regulation; that the guidelines do not guage the cumulative effect of multiple emission sources from a single plant;19 and that no showing has been made explaining why a pattern of citizen complaints is unlikely to appear at a given emission level. Without an examination of the above factors, the lower court could not have determined "the validity, applicability and reasonableness of the standard”. Thus, the judge acted prematurely in adopting the Division’s guidelines.
This holding does not, however, suggest either that the Division’s standards are indeed "deficient”, MCLA 691.1202(2)(b); MSA 14.528(202)(2)(b), or that plaintiff has failed to establish a prima facie case of pollution. The former must await further inquiry by the trial court and the latter is to be decided, infra, by this panel.
Defendant’s fourth allegation of a clearly erroneous factual finding involves the effectiveness of the water curtain as a pollution-control device. Despite the improvements in water filtration and paint spray application, the maintenance procedures employed, and the reports by Dr. Warner suggesting some improvement in water-curtain efficiency, we do not believe the lower court clearly erred in finding that the water curtains are not sufficient to prevent odor pollution. Adequate evidence supported the court’s finding: 1) many of the solvents employed are not water soluble; 2) the second test in March, 1976, conducted at Olsonite’s request under optimal maintenance procedures, revealed a deterioration of the water curtain from 15 to 35 percent since the previous test three days *699earlier; and 3) the March tests measured emissions from a single spray booth rather than from the system under normal operations. Thus, we do not share defendant’s definite and firm conviction that the court erred in finding the water curtain to be unreliable.
Accordingly, we hold that plaintiff satisfactorily established by preponderating evidence a prima facie case of actual and probable environmental degradation.
Rebuttal By Defendant of Plaintiff’s Prima Facie Case
Defendant challenges two trial court findings: 1) that the trial court improperly discounted the odor tests conducted by Olsonite in 1976; and 2) that "defendant has failed to rebut the existence of community odor problems in the past or present, or demonstrate that such problems will not continue into the future”. (Opinion, p 8.)
We agree with the trial court’s assessment of the weight he attached to Olsonite’s employee-conducted odor tests. The reports were prepared after institution of the present suit by employees untrained in odor detection. These self serving tests in no way measure up to the kind of "empirical studies” which are "necessary when the impact upon the environment resulting from defendant’s conduct cannot be ascertained with any degree of reasonable certainty”. Ray v Mason County Drain Commissioner, 393 Mich 294, 311; 224 NW2d 883 (1975).
To counter the court’s second finding defendant argues principally that the judge failed to note that the number of citizen complaints appeared to wane in direct relation to Olsonite’s reinstitution *700in February, 1975, of its Toluol-Xylol blend of solvents. This argument disregards the presence of continuing complaints in 1975 and 1976 and it presumes, somewhat myopically, that the energy shortages which necessitated the switch to higher odor-producing solvents will not recur. Given defendant’s misconceptions, we hold the trial court did not err in concluding that defendant had failed to rebut plaintiffs prima facie case.
As the present suit illustrates, then, in the absence of properly approved standards, MCLA 691.1202(2); MSA 14.528(202)(2), a case of actual and probable environmental degradation is nonetheless established where 1) numerous citizens complain over a lengthy period that foul odors, recurrently emitted from defendant’s plant, penetrate their homes and cause such adverse physical reactions as nausea, burning eyes, headaches, loss of sleep and reduction of appetite; 2) inspectors of the local health agency verify the citizen complaints; 3) defendant fails to produce the necessary empirical evidence in rebuttal; and 4) the trial court gives credence to the plaintiffs evidence while disbelieving that of defendant. In that event, unless defendant asserts and wins success on the statutory affirmative defense, the trial court, in the exercise of discretion, may order injunctive relief.
Feasible, Prudent Alternatives and Conduct Consistent With the Promotion of Public Health, Safety and Welfare
In relevant part, § 3(1) of the EPA states:
"The defendant may also show, by way of an affirmative defense, that there is no feasible and prudent alternative to defendant’s conduct and that such con*701duct is consistent with the promotion of the public health, safety and welfare in light of the state’s paramount concern for the protection of its natural resources from pollution, impairment or destruction. Except as to the affirmative defense, the principles of burden of proof and weight of the evidence generally applicable in civil actions in the circuit courts shall apply to actions brought under this act.” MCLA 691.1203(1); MSA 14.528(203X1). (Emphasis added.)
We interpret the language italicized above to say that the normally applicable rules on burden of proof and weight of the evidence, requiring plaintiff to carry the burden of proving its case by preponderating evidence, Ray, supra at 309-311, shall not apply where an affirmative defense is asserted. See Haynes, Michigan’s Environmental Protection Act in its Sixth Year: Substantive Environmental Law from Citizen Suits, 53 Journal of Urban Law 589, 599 (1976) ("[0]nce a plaintiff in a MEPA lawsuit demonstrates that a defendant’s actions harm, or are likely to harm, the environment, the defendant carries a heavy burden of environmental justiffcation. This burden requires a defendant to prove that no feasible and prudent alternatives to his actions exist and that he is acting in the public interest.” [Emphasis added; footnote omitted.])
If "the private citizen [is to have] a sizable share of the initiative for environmental law enforcement”, Eyde v Michigan, 393 Mich 453, 454; 225 NW2d 1 (1975), then the only reasonable construction20 of the statute is to place the burden of proof *702not on a citizenry largely unschooled in the intricacies of environmental technology, but on a defendant who "has the underlying data and documentation upon which his choice of a given course of action is based”. Pierce, Sax and Irwin, Responses to "Thoughts on H. B. 3055”, at 4, March 20, 1970 (unpublished manuscript in the files of Professor Sax, University of Michigan Law School), quoted in Note, Michigan Environmental Protection Act: Political Background, 4 U Mich J L Ref 358, 367 fn 36 (1970). Thus we hold that a defendant asserting the statutory affirmative defense of § 3(1) of the EPA has the burden of proving same by a preponderance of the evidence.
In the present case, defendant alleges the trial court mistakenly concluded that defendant had failed to establish its affirmative defense. On reflection, we side with the trial judge.
The testimony of Dr. Warner described three examples of "known technology” which offer "solutions to odor abatement”. Moreover, defense witness Eggers acknowledged that certain companies offered to reduce Olsonite’s odorous emissions by 95 to 97 percent; indeed one company, contrary to Eggers’ testimony, offered Olsonite a thermal oxidation system backed by "an odor free guarantee [that] can be made * * * without any extensive tests”.
But defendant wants more. It asks the Division to recommend a system guaranteed to eliminate all citizen complaints. This position expects more than reality can offer and it forgets that one sense of the word feasible comprehends an approach which "is likely to work out or be put into effect successfully”.21
*703The Division clearly does not expect perfection; rather, it requires defendant to keep its emitted fumes to a "practical minimum”. Crandall v Biergans, Clinton County Circuit Court No. 844, 3 ERC 1827 (1972). As we have found, defendant has not succeeded in minimizing its odors. Relying almost exclusively on an undependable water curtain, Olsonite has done little more than make preliminary inquiries which ceased as soon as it encountered obstacles seemingly preventing adoption of an alternative odor-abatement program. As noted, Olsonite never sought a reduction in the quoted cost of these systems, never ascertained whether less expensive abatement techniques might be used on its less egregious emission sources and never instituted pilot studies or commissioned engineering drawings. Thus, we are convinced that the lower court did not clearly err — indeed did not err at all — in finding the technical feasibility of alternative controls on odor.
With respect to the economic feasibility of alternative pollution controls, we adopt the test employed in an analogous setting under the Occupational Safety and Health Act of 1970, 29 USC 651 et seq. (OSHA). See Industrial Union Department, AFL-CIO v Hodgson, 162 US App DC 331; 499 F2d 467 (1974).
In Hodgson, the Court of Appeals for the District of Columbia Circuit, interpreting the term "feasible” as used in § 655(b)(5)22 of OSHA, observed:
"There can be no question that OSHA represents a decision to require safeguards for the health of em*704ployees even if such measures substantially increase production costs. This is not, however, the same thing as saying that Congress intended to require immediate implementation of all protective measures technologically achievable without regard for their economic impact. To the contrary, it would comport with common usage to say that a standard that is prohibitively expensive is not 'feasible.’
"[Practical considerations can temper protective requirements. Congress does not appear to have intended to protect employees by putting their employers out of business — either by requiring protective devices unavailable under existing technology or by making financial viability generally impossible.
"This qualification is not intended to provide a route by which recalcitrant employers or industries may avoid the reforms contemplated by the Act. Standards may be economically feasible even though, from the standpoint of employers, they are ñnancially burdensome and affect proñt margins adversely. Nor does the concept of economic feasibility necessarily guarantee the continued existence of individual employers. It would appear to be consistent with the purposes of the Act to envisage the economic demise of an employer who has lagged behind the rest of the industry in protecting the health and safety of employees and is consequently ñnancially unable to comply with new standards as quickly as other employers.” 499 F2d at 477-478. (Footnotes omitted. Emphasis added.)
Accord: United States v Reserve Mining Company, 380 F Supp 11 (DC Minn, 1974), applying the above interpretation to the Minnesota Environmental Rights Act, a statute modeled generally after Michigan’s EPA.
Concerning the requirement that the alternative to a polluter’s conduct be "prudent”, we approve of the interpretation advanced in Citizens to Preserve Overton Park, Inc v Volpe, 401 US 402; 91 S Ct 814; 28 L Ed 2d 136 (1971). There the Supreme *705Court examined the term "prudent alternative” in § 4(f) of the Department of Transportation Act of 1966, 49 USC 1653(f), and in § 18(a) of the Federal Aid Highway Act of 1968, 23 USC 138, which prohibit the Secretary of Transportation from authorizing the use of Federal funds to finance highway construction through public parks if a "feasible and prudent alternative” route exists. In unequivocal language, the Court rejected the contention that the phrase "prudent alternative” requires a comprehensive balancing of competing interests:
"[N]o such wide-ranging endeavor was intended. It is obvious that in most cases considerations of cost, directness of route, and community disruption will indicate that parkland should be used for highway construction whenever possible.
"Congress clearly did not intend that cost and disruption of the community were to be ignored by the Secretary. But the very existence of the statutes indicates that protection of parkland was to be given paramount importance. The few green havens that are public parks were not to be lost unless there were truly unusual factors present in a particular case or the cost of community disruption resulting from alternative routes reached extraordinary magnitudes. If the statutes are to have any meaning, the Secretary cannot approve the destruction of parkland unless he finds that alternative routes present unique problems.” 401 US at 411; 91 S Ct at 821; 28 L Ed 2d at 151. (Emphasis supplied.)
Similarly, see County of Freeborn v Bryson, — Minn —; 243 NW2d 316, 318 (1976).
This interpretation of "prudent alternative” is bolstered by recognition that the Legislature rejected an amendment which would have inserted the phrase, "considering all relevant surrounding circumstances and factors” before the "feasible and prudent” language of § 3(1). See, Note, Michi *706 gan’s Environmental Protection Act: Political Background, 4 U Mich J L Ref 358, 363 (1970), and Thibodeau, Michigan’s Environmental Protection Act of 1970: Panacea or Pandora’s Box, 48 Journal of Urban Law 579, 586 (1971).
Applying the cited cases to the facts at hand, we conclude that the defendant has failed to show the technical, economic infeasibility and the imprudence of alternatives to defendant’s conduct. Although the adoption of additional pollution controls may financially burden Olsonite and adversely affect its profit margin, Hodgson, supra, we believe, in light of the revenue data noted, supra, that the company is fully able to finance the added cost of restraining odorous emissions. The costs involved do not approach "extraordinary magnitude” and no "truly unusual factors”, Overton Park, supra, refute the demonstrated prudence of alternative systems. We believe that a reasonable, cost-effective solution to Olsonite’s odor problem can be achieved if an earnest examination of other abatement methods is made. Defendant’s conduct, then, will no longer be inconsistent with the promotion of public health, safety and welfare in light of Michigan’s paramount concern for the natural resources of the state.
In its final claim of error, Olsonite decries as too drastic the injunctive relief ordered by the trial court and asserts that the judge erred in failing to recognize and exercise his discretion before issuing an injunction.
We disagree.
The trial court’s decree has been narrowly drafted. It awards relief to plaintiff while permitting defendant a reasonable time to comply and affording it an opportunity for further hearing. Although the court expressed the need for injunction in mandatory terms, we are certain the *707learned judge, having studiously followed the commands of Ray, supra, clearly understood that the granting of equitable relief is a discretionary decision under MCLA 691.1204(1); MSA 14.528(204)(1). Ray, supra at 305.
Accordingly, the trial court is directed to conduct, as soon as practicable, a new hearing consistent with the requirements of MCLA 691.1202(2); MSA 14.528(202)(2), as outlined previously. In its discretion, the court may then 1) specify an appropriate standard (which may be the same, more strict or possibly, but improbably, less strict than that previously approved) governing odor emissions, 2) incorporate the chosen standard into its decree, and 3) set new compliance dates for the selection, installation and completion of a specific supplemental odor control system ultimately selected by defendant.
In the meantime, defendant is ordered to begin forthwith at its own expense the comprehensive examination of alternative odor restraints that should have occurred months and years ago. This effort shall be monitored by knowledgeable representatives of plaintiff and both parties shall prepare reports for submission to the trial court on a date set by that court. This date may be the same or different than the hearing date above. GCR 1963, 820.1(7).
Nothing in the foregoing order shall prevent defendant from seeking to further improve the efficiency of its water curtain or to investigate paint spray applicators which reduce the amount of paint or solvents utilized in its painting process.23
Affirmed in part and remanded for proceedings consistent with this opinion.
No costs, a public question being involved.