Differences in the Way Air Assessments are Conducted in Ontario
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It may seem unusual but air assessments are carried out in different ways depending on the purpose. The main differences are between air assessments conducted for permit applications (Environmental Compliance Approvals [ECAs] or Environmental Activity Sector Registrations [EASRs]) versus air assessments for Environmental Assessments (EAs) and Land Use Compatibility Assessments (LUCAs; the latter two are, or should be, similar in terms of techniques used).
Air assessments for EAs and LUCAs are complete studies in that they involved all project-related sources, require conservative inputs and full assessment of fugitive dusts, as well as requiring consideration of baseline air quality. DiGiSci Environmental Consulting is the leading air quality assessment consulting company in Ontario, and is providing this blog as part of our client outreach and education.
We will now delve into these main sources of differences and, where possible, try to explain why those differences occur.
1. Vehicle emissions
It is well known that on-road (cars, trucks usually travelling on public roads) and off-road vehicles (bulldozers, scrapers, forklifts, etc.) emit airborne contaminants from (i) their exhaust pipes, as well as, (ii) raise road dust from wheel travel over paved and unpaved roads.
Common tailpipe emissions include CO, NOx, various organics and very fine soot (assessed as “PM2.5” or diesel particulate matter, if the fuel used is diesel; the particles are too small to be seen by the naked eye). Road dust is classified by (i) size of the dust particles (the very fine PM2.5 particles being those of most human health concern), but, (ii) also by type (crystalline silica is a common mineral in road dusts, and is a carcinogen if inhaled at high enough levels for long enough).
For EAs, it is standard to include both on-road and off-road vehicle emissions, both on the subject site and off-site but associated with the project in question. For example, an intermodal hub, used to transfer containers between rail and road, will have vehicles on-site (trains, forklifts, tractor-trailers). Trains and trucks, associated with the hub will also operate, and emit contaminants outside of the boundaries of the hub. Sometimes, those off-site emissions can occur very close to sensitive receptors (e.g., houses near roads) and so potentially cause high air quality impacts. When these impacts are combined with on-site emissions, this produces a complete picture of air emissions of the hub and their impacts.
For LUCAs, assessments should include on-site operation of all vehicles. There is some controversy over whether off-site, but related, vehicular emissions should be accounted for as the LUCA process is a very “site-boundary”-related process. Part of the reason for this may be that off-site activities, related to the subject site (let’s use our example intermodal hub) are essentially part of the supply chain serving that hub. It then raises the question of how far up or downstream of the supply chain should we consider impacts. For example, how far away from the hub do we track truck traffic and train traffic before they merge into the background milieu of transportation sources generally operating in a region? Do we account for the other operations in region, or far off-site, that support the off-site truck and train traffic (manufacturing facilities, maintenance depots, etc.). These are not easy questions to answer in strict technical terms. These questions also apply to air quality assessments for EAs.
For permit applications, however, vehicular air emissions are explicitly exempt, as stated in the Ontario Environmental Protection Act (EPA):
(3) Subsection (1) does not apply to,
(f) any motor or motor vehicle that is subject to Part III. R.S.O. 1990, c. E.19, s. 9 (3).
……..so, permit applications under s.9 of the EPA do not require assessment of emissions of contaminants.
The confusing part is that the Ontario Ministry of the Environment, Conservation, and Parks (MECP), the Ministry with responsibility for operating the permitting system in Ontario, actively requires assessment for the emissions of vehicle noise (sound emissions are classified as “contaminants” under the EPA), but only while the vehicle is on the site for which a permit is being applied for. As soon as the vehicle crosses the property boundary, onto a public road, those noise emissions are exempt. The reason for exempting vehicle air emissions, at least while the vehicles are on public roads, is perhaps one of jurisdiction, in that the Federal government in Canada sets vehicle air emission standards. Just to add another layer of confusion, we have been involved in a permit application where air emissions, from on-site, idling, truck traffic were required to be assessed.
2. Fugitive Dusts
Fugitive dusts are dust clouds that arise from sources where there is no definite emission point, vent of stack. Commonly these occur with open-air activities, such as road dust raised from paved and unpaved roads, and handling of dusty materials outdoors, e.g., stacking of gravel, mineral piles, conveyor belt drops, size sorting, front-end loader drops, etc.
Both EAs and LUCAs should require both types of classification (and subsequent assessment) for the different size class of dusts and their compositional breakdown. This is because the different size classes of dust cause different adverse effects; all sizes combined can cause visibility issues, whereas it is only the finer size fractions (particularly PM2.5) that can cause serious respiratory health concerns for humans. The compositional breakdown of fugitive dust emissions is also important to assessment as there may be components that have own particular health impacts (again, the example of crystalline silica, which is very common in fugitive dusts; micas are another example).
However, permit applications do not normally consider the different size fractions of dusts, they only consider all size fractionations added together as Total Suspended Particulate (TSP); the health-impacting finer size fractions (i.e., PM2.5) are not normally considered. Having said that, however, we have experienced a permit application where the MECP did demand assessment of PM10 and PM2.5 size fractions. It is unknown why the MECP required the assessment in that case, but not in other cases; all we can say is that the MECP may occasionally demand size fractionation, but it is not common.
In terms of compositional fractionation, the A-10 Guide for permit applications does require explicit compositional analysis for metals in certain cases, but also where “particulate contains significant quantities of contaminants that contribute to a ministry POI Limit that may cause a health effect (e.g., metals or other health-based ministry POI limits).” Unfortunately, this has often been misinterpreted to mean that only metals are of concern, and not other components of dust. Again the example of crystalline silica being a common element of fugitive dusts, and so the fugitive dust should be analyzed, perhaps for metals (if the facility falls within the list of those designated for metals analysis) but certainly analyzed mineralologically for minerals that may have their own health impact concerns. The reason for this misinterpretation is unknown.
The metals analysis of fugitive dusts will be the subject of a more detailed future blog.
3. The Use of the Conservative Principle
When attempting to predict the air pollution emissions, especially of a facility that is yet to be built, or yet to be changed or expanded, it is almost invariably the case that some information required to predict air pollution emissions is not available, and estimates of that information must be made instead. These estimates must be made in a “conservative” fashion; that is, they must (for sure) not lead to an underestimate of potential air quality impacts. This is a principle required (in theory) for air quality assessments conducted for permitting, but certainly for EA and LUCA assessments.
For example, in trying to estimate the emissions of road dust from unpaved roads in a proposed gravel pit, normal practise is to use an “emission factor” to estimate that emission rate. The most widely used source of emission factors (at least in North America) are the US EPA AP-42 equations. The emission factor equation for dust emissions from vehicles driving over unpaved roads is:
(AP-42, Ch. 13.2.2-4) where:
E = the resultant emission factor in lb/VMT,
k, a and b are empirical constants specific to certain dust size fractions,
s = is the surface material silt content (%; a measure of road dustiness quantifying the “fines” in road dust), and,
W = mean vehicle weight (tons)
Once the calculation is complete, the emission factor, E, is then multiplied by the value of “VMT.” VMT stands for “Vehicle Miles Travelled” (along that segment of road) and itself is derived by multiplying the length of the road segment (in miles) and the number of trucks that use that road segment in, say, 24 hours (if it is a 24 hour standard we are assessing). The result of E x VMT will provide the lbs of dust emitted over a 24 hour period; this is the emission rate used to input into the appropriate dispersion model and ultimately to predict airborne dust levels beyond the borders of the proposed gravel pit from that source.
For example, if gravel trucks exited an aggregate pit along a certain planned road, and it was known that their maximum loaded weight will be 40 tons, and we were interested in estimating PM2.5 emissions, the values we would use would be:
W = 40 tons
k = 0.15 (lb/ton)
a = 0.9
b = 0.45
………we would still be left with determining the silt content of a non-existent road. The AP-42 chapter providing this equation indicates some values for surface silt content that have been measured at other roads in the US. For example, Table 13.2.2-1 of AP-42 Ch 13.2.2 summarizes measured silt values for industrial unpaved roads. It should be noted that the ranges of silt content vary over two orders of magnitude. Therefore, the use of data from this table can potentially introduce considerable error. The US EPA indicates that “use of this data is strongly discouraged when it is feasible to obtain locally gathered data.” The top part of this table is reproduced below.
If the operation we are assessing is a proposed sand and gravel extraction facility then, examining the table for plant roads indicates a data spread of 4.1 – 6.0 % (but based on only 3 samples at one location), with a mean of 4.8%. If we have no other information available then the principle of conservatism dictates that we’d pick the upper limit or 6.0%. On the other hand, we may have information about the planned site (when compared to the site that the US EPA had obtained their data from) and we may be able to argue that the mean value is more accurate at our proposed site. The difference in emission factor between using s variable set at 4.8 and 6.0 is:
With other factors remaining the same, the difference between the two emission factors is 0.258-0.211 = 0.05 lbs, or 22% higher emissions than using the average value. In cases where plant roads can be a dominant source of dust emissions this can make quite a difference to dust impacts on the surrounding community. Just to add another layer of complication, available evidence (e.g., size fractionation of sample drill cores for the proposed gravel site, may suggest silt content values even higher than the values listed in the AP-42 chapter; there is no particular reason you site may be “better”, or the same as those sites used in the AP-42 chapter.
Since, in environmental studies, the onus is on the proponent to demonstrate that their emissions do not cause a problem, the onus would be on the proponent to prove values are conservative.
In the case of existing roads, of course, the proponent can measure silt level on-site, alleviating the need to estimate silt levels (since you’ll have measurements), and there is no need to appeal to the principle of conservatism in this case. In reality, proponents may have to use conservative values, and plan for any mitigation necessary, until the road is built; once in-use, on-site measurements can then be used instead of conservative values.
With the MECP, for permitting air quality assessments, however, it has been our experience that average values, presented in appropriate chapters of AP-42 are accepted without question. It would seem that the MECP does not necessarily require conservative estimates. However, estimates for input values must be made on a conservative basis when conducting air quality assessments for EAs and LUCAs. Reasons for these differences are unknown.
4. Baseline Air Quality
The air we breathe is not completely free of trace contaminants. These pollutants come from many sources we encounter in our everyday lives. For example, most areas of the GTHA experience annual values of PM2.5 fine particulate of about 10 micrograms per cubic metre of air (10 µg m-3); there can be higher values closer to major sources (e.g., highways) and lower values far away from major sources (for example, in suburban and rural areas).
The most common “baseline” air quality pollutants consist of the so-called criteria contaminants, which include oxides of nitrogen (NOx), CO, SO2, volatile organics, particulate matter, and ammonia. Most of these contaminants are at levels which do not present a danger to human health, but some can be generally present at levels above safe concentrations (e.g., Benzo(a)pyrene and benzene).
Regardless, when a new facility is introduced to an area, or an existing facility expands or modifies it operations, those new contaminants emitted (or increases in emissions) will add to levels of the same contaminants that already exist. In other words the new emissions cumulate with the pre-existing, “baseline” air quality levels, and increase them to new levels.
Of course, to provide a complete air quality assessment practitioners must account for pre-existing baseline air quality to ensure that they are providing data on the total exposure that the public are facing or that the environment is facing. This is a fairly obvious concept and is adopted by air practitioners for Environmental Assessments, and by some (but not all) for LUCAs (see my other blogs on LUCAs for a discussion of why cumulative air quality levels should be done for compatibility assessments).
However, for permit applications in Ontario (ECAs and EASRs) cumulative air quality level assessments are not required by the MECP. Instead, just the incremental air levels, caused by the new facility or modified facility are compared to air quality standard for compliance under permitting schemes. Having said that, we are aware of a few instances where the MECP have asked for cumulative air quality assessments for permit applications; the reasons for those particular demands are unknown.
It should be mentioned that the MECP are beginning to assess cumulative air quality in certain areas of Ontario where air quality is particularly poor, mainly due to industrial sources. These areas include Hamilton, Sarnia, and Sudbury. In these areas, facilities, as part of their application process for ECAs (but not EASRs) are required to submit additional information and possibly commit to additional emissions mitigation. However, this MECP scheme only applies to emissions of benzo(a)pyrene and benzene. So, if your facilities are in one of the three areas AND you emit those contaminants, special procedures would apply to you.