Opinion ID: 4538714
Heading Depth: 3
Heading Rank: 2

Heading: Toxic Emissions

Text: Petitioners raise two arguments concerning the Weymouth station's emissions of toxic air pollutants. According to DEP, the Weymouth station's SoLoNOx turbine may emit up to 0.91 tons of toxic pollutants (combined) per year, with up to 0.41 tons of that being attributable to formaldehyde emissions. Formaldehyde is a genotoxic carcinogenic chemical that can form from incomplete combustion of natural gas. Incomplete combustion can occur at lower temperatures, so formaldehyde can be a particular problem for Dry Low NOx turbines. Since the 1980s, DEP has handled air toxics through Allowable Ambient Limits (AAL) and Threshold Effects Exposure Limits (TEL).17 See DEP Office of Research & Standards, Methodology for Updating Air Guidelines: Allowable Ambient Limits (AALS) and Threshold Effects Exposure Limits (TELS) 1–2 (2011); see also DEP, Ambient Air Toxics Guidelines, https://www.mass.gov/files/ documents/2017/11/07/Ambient%20Air%20Toxics%20Guidelines.pdf. TEL 17 For context, EPA regulates air toxics at the federal level through the National Emission Standards for Hazardous Air Pollutants (NESHAP). See 42 U.S.C. § 7412. Petitioners do not argue that the Weymouth station will exceed or in any way implicate the NESHAP for formaldehyde or any other pollutant. - 31 - is a 24-hour-based measurement reflecting toxic concentrations at a low-enough level that no health effects at all, even noncarcinogenic effects like eye irritation, are expected in the population, including sensitive populations, over a lifetime of continuous exposure. In common parlance, the record labels the risk at these levels de minimis; i.e., the added risk is so small that it makes no meaningful difference. AAL is an annual measurement focused on risks of cancer in humans and is determined by the lower of the TEL and the Non-Threshold Effects Exposure Limits (NTEL). For certain air toxics, scientists consider any non-zero concentration in the air to produce some risk of cancer in humans, see Brookline II, 497 N.E.2d at 11, so NTEL represents a de minimis cancer risk rather than no risk at all. We turn now to each of the petitioners' arguments concerning AAL and TEL.
Petitioners claim that DEP violated the Massachusetts CAA and associated regulations because it failed to account for background levels of air toxics near the Weymouth station when considering AAL and TEL. They point to three chemicals: formaldehyde, benzene, and acrolein. They accept, for purposes of this argument, but see infra section II(B)(2)(b), that the marginal emissions from the Weymouth station for each of these air toxics fall below the AAL and TEL, but they contend that the - 32 - Weymouth emissions plus the already-existing background concentrations exceed those values. In fact, even without the Weymouth emissions, background levels from other sources in that area already exceed the AAL and TEL for these three air toxics, such that any additional emissions would, as petitioners argue, contribute to an exceedance. Since Algonquin and DEP ignored this cumulative effect and only compared the marginal increase to the AAL and TEL, petitioners claim the air permit violates Massachusetts law. In support of their position, petitioners point us to two Massachusetts regulations. First, they point us to the definition of air pollution, which says in full: AIR POLLUTION means the presence in the ambient air space of one or more air contaminants or combinations thereof in such concentrations and of such duration as to:

current information, potentially injurious to human or animal life, to vegetation, or to property; or
comfortable enjoyment of life and property or the conduct of business. 310 Mass. Code Regs. § 7.00 (second emphasis added). Second, the General Regulations to Prevent Air Pollution state: No person owning, leasing, or controlling the operation of any air contamination source shall willfully, negligently, or through failure to provide necessary equipment or to take necessary precautions, permit any emission for said air contamination source or - 33 - sources of such quantities of air contaminants which will cause, by themselves or in conjunction with other air contaminants, a condition of air pollution. Id. § 7.01(1) (emphasis added). Because these regulations contemplate combinations of air contaminants, or contaminants in conjunction with one another, petitioners say that DEP is mandated to consider background levels of air toxics. DEP responds that its longstanding policy is to compare only emissions from the new source to the applicable AAL and TEL, without regard to background levels. According to its 1989 policy statement, DEP requires new or modified sources of air contaminants to assess, through computer modeling, the ambient concentrations caused solely by that source's emissions, and [t]hese modelled concentrations are then compared to the AALs to determine whether there may be potentially unacceptable risks associated with that particular source. DEP Div. of Air Quality Control, Air Toxics Implementation Update 2 (1989) [hereinafter 1989 Air Toxics Update] (emphasis added). DEP calls the AAL and TEL screening guidelines, whereby new sources that exceed these values are subject to further evaluation and new sources below these values receive no further scrutiny. And, DEP points out, most states have a similar two-step approach to air toxics, whereby - 34 - step one (here AAL and TEL comparison) is for screening purposes only.18 Petitioners argue, in substance, that to interpret the regulation's in conjunction with language as not requiring an assessment of the cumulative level of background and proposed new emissions would be to adopt an irrational or absurd interpretation of the regulation. We disagree, finding it perfectly rational to use a low threshold to identify those instances in which additional, cumulative impacts need be examined. Consider, for the sake of analogy, a baking hobbyist who plans on making a pie for a family reunion. The baker knows he has sugar, but he is not certain how much, and he may not even have the full cup needed for the recipe. Before he can start baking, his neighbor knocks on his door and asks to borrow some sugar. And, to make this analogy more like this case, imagine that measuring the baker's current supply of sugar would be resource intensive for the baker and his neighbor at that particular moment when the neighbor needs the sugar. It would be a perfectly reasonable response in this scenario for the baker to ask his neighbor how much sugar he needs. If the neighbor wants only a teaspoon, the baker might simply give 18 In practice, it appears, that applicants regard surviving step-one screening as essential, given that DEP Air Quality Section Chief Thomas Cushing could recall no instance in which DEP received an application for a project that exceeded an AAL or TEL. - 35 - it to the neighbor without first measuring his own supply. A teaspoon is likely too little to make a difference between having and not having a cup, and even if it would, the practical effect will not be noticeable. But if the neighbor wants a quarter cup, then the baker might decide to spend the resources to measure his supply before agreeing to the neighbor's request. This is in essence the purpose of AAL and TEL. Before deciding whether to require that the resources be spent to measure the current cumulative amount of air toxics, DEP asks whether the amount to be produced by the new source is like the teaspoon or like the quarter cup. If it is like the teaspoon, DEP decides that it is unlikely to make a practical difference. And here DEP's case is perhaps even stronger than the pie example, because petitioners have not pointed us to any other cap on how much pollutant is too much cumulatively (other than NESHAP, see supra note 17, and petitioners do not allege that the Weymouth station is even close to violating that standard). In other words, it would be as if the pie recipe said roughly one cup, depending on how sweet you want it. Petitioners, for their own analogy, point us to California's rules for automobile tailpipe emissions. See Motor Vehicle Mfrs. Ass'n of U.S., Inc. v. N.Y. Dep't of Envtl. Conservation, 17 F.3d 521, 524–25 (2d Cir. 1994) (explaining California's unique exemption from federal preemption over mobile- - 36 - source regulations). [P]rior to the creation of California's stringent air pollution regulations, petitioners tell us, daily emissions from millions of . . . vehicles resulted in a chronic condition of air pollution -- smog -- in the City of Los Angeles . . . even though the incremental emissions from each of those individual vehicles undoubtedly represented a tiny contribution to the overall problem, and a de minimis risk to human health. The tailpipe example would be like our hypothetical example if the baker had twelve neighbors at his door all asking for sugar. In that case, he might want to measure his supply even if each neighbor wanted only a teaspoon. But surely there are not millions of proposed stationary sources of formaldehyde, benzene, and acrolein around Weymouth. It is completely rational for DEP to treat this limited number of sources differently for screening purposes than California treats personal automobiles. Cf. 310 Mass. Code Regs. § 7.02(2)(b)(7) (excluding stationary sources not capable of emitting one ton or more of any pollutant from the air-permit requirement). Moreover, there are plenty of other examples of air-pollution regulatory schemes that similarly screen out de minimis sources. In addition to other states' rules on air toxics, DEP points us to the Significant Impact Limits (SILs) used by EPA when assessing compliance with the National Ambient Air Quality Standards (NAAQS). See Sierra Club v. EPA, - 37 - 705 F.3d 458, 461 (D.C. Cir. 2013) (explaining SILs); see also Sierra Club v. EPA, 955 F.3d 56, 58–60 (D.C. Cir. 2020); 40 C.F.R. § 51.166(b)(23)(i) (setting net-emissions-increase levels deemed [s]ignficant for purposes of Prevention of Significant Deterioration (PSD)). The fact that some regulatory programs take a different approach does not make these programs irrational. Of course, the fact that DEP's two-step approach is rational does not dispense with petitioners' argument that the Massachusetts regulations compel consideration of background levels. Nevertheless, we defer to the agency's interpretation. The regulations to which petitioners point us, 310 Mass. Code Regs. §§ 7.00, 7.01(1), are broad regulations concerning all air pollution generally, not just air toxics. See Town of Brookline v. Comm'r of Dep't of Envtl. Quality Eng'g (Brookline I), 439 N.E.2d 792, 799 (Mass. 1982) (giving DEP discretion to interpret 310 Mass. Code Regs. § 7.01); see also Brookline II, 497 N.E.2d at 13 (The Legislature has granted [DEP] broad authority.). And we do not think that the language from those general regulations unambiguously forecloses DEP's approach to air toxics. The phrases in conjunction with other air contaminants, 310 Mass. Code Regs. §§ 7.01(1), and combinations thereof, id. § 7.00, might mean, as petitioners argue, that DEP should consider background levels of a given pollutant. Or they might reasonably be read as referring to situations where two different air pollutants produce a chemical - 38 - reaction in the air, as with ozone precursors, see Ill. State Chamber of Commerce v. EPA, 775 F.2d 1141, 1143 & n.3 (7th Cir. 1985), in which case the regulations do not compel petitioners' approach. Since the text is ambiguous, and traditional tools of construction do not resolve that ambiguity, we defer to DEP's reasonable interpretation. See Kisor, 139 S. Ct. at 2414–18; Brookline II, 497 N.E.2d at 15.
Petitioners also argue that the formaldehyde emissions solely from the Weymouth station will, in fact, exceed the applicable AAL and TEL. They argue that Algonquin's air-dispersion model, which showed that formaldehyde emissions would be no more than 70% of the AAL, underestimated the actual emission rate because it did not include emissions during intermittent startup events. The proposed SoLoNOx turbine will not run continuously. Instead, it will be shut down and restarted up to 416 times per year. Normally, the turbine will employ an oxidation catalyst to reduce formaldehyde emissions, but during the time it takes the turbine to start up, this catalyst will not be fully operational, meaning formaldehyde emissions will be higher. Algonquin estimates that startups will usually last only nine minutes, though the time may be longer if a startup fails initially. - 39 - The air permit as initially drafted by DEP staff allowed for startup times up to thirty minutes. Petitioners opposed the allowed startup period before the Presiding Officer. Their witness, John Hinckley, performed his own dispersion modeling that, unlike Algonquin's initial modeling,19 accounted for startup emissions -- one model representing thirty-minute startups, and another representing nine-minute startups. Hinckley's thirtyminute model showed that formaldehyde emissions from the Weymouth station would exceed the AAL and TEL when measured at the property line as required by DEP guidance. See 1 DEP, The Chemical Health Effects Assessment Methodology and the Method to Derive Allowable Ambient Limits 21 (1990). Hinckley's nine-minute model showed an exceedance of the AAL, but not the TEL, at the property line. In response, Algonquin's witness, Justin Fickas, put together a model representing eighteen-minute startups, which also showed an exceedance of the AAL. The Presiding Officer acknowledged that EPA's guidance does not require modeling of intermittent startups at all, but nevertheless expressed concern over the modeled exceedances. As 19 DEP policy requires an applicant to model emissions of air toxics only for sources subject to PSD, plus a few other types of facilities. See 1989 Air Toxics Update, supra, at 3. The Weymouth Station does not meet any of these criteria, but DEP exercised its discretion to request that Algonquin perform this modeling. See 310 Mass. Code Regs. § 7.02(5)(c)(6) (requiring applicants to furnish air-dispersion modeling upon request by DEP). - 40 - such, she recommended reducing the allowable startup time from thirty minutes to eighteen minutes, and the Commissioner adopted this recommendation. As to the fact that even the eighteen-minute model showed a concentration above the AAL, the Presiding Officer stated that [t]he slight exceedance shown in the revised modeling beyond the fence line . . . does not, in my opinion, justify denying the permit. Petitioners' main argument before us is straightforward: the Weymouth station will, even under the revised air permit, create an exceedance of the AAL for formaldehyde, and so the permit should have been denied, and we should vacate DEP's contrary decision as arbitrary and capricious. As its name suggests, AAL is meant to be a limit, petitioners argue, so an exceedance should not be allowed, no matter how slight. DEP counters that under the applicable policy, there was no exceedance here. EPA's guidance explains that the intermittent nature of the actual emissions associated with . . . startup/shutdown [operations] in many cases, when coupled with the probabilistic form of the standard, could result in modeled impacts being significantly higher than actual impacts would realistically be expected to be for these emission scenarios. Memorandum from Tyler Fox, Leader, Air Quality Modeling Grp., EPA, to Reg'l Air Div. Dirs., Additional Clarification Regarding Application of Appendix W Modeling Guidance for the 1-Hour NO2 National Ambient - 41 - Air Quality Standard 8 (Mar. 1, 2011), https://www.epa.gov/sites/ production/files/2015-07/documents/appwno2_2.pdf. EPA thus advises against using startup modeling. See id. at 9–10; see also DEP, Modeling Guidance for Significant Stationary Sources of Air Pollution 1 (2011) (noting that DEP generally follows EPA's guidance on air modeling); cf. 40 C.F.R. § 60.8(c) (Operations during periods of startup, shutdown, and malfunction shall not constitute representative conditions for the purpose of a performance test . . . .). DEP relied on this guidance in not requiring Algonquin to account for startups in its application, and petitioners have not pointed to anything in DEP policy requiring a contrary rule. Although Algonquin provided additional (non-mandatory) modeling to explore the effects of startup events, such models have not been adopted into official department policy or regulations. Thus, DEP acted within its discretion when it relied on a model excluding startup emissions to find, without further evaluation, that there was no exceedance of AAL or TEL.