New Source Performance Standards, Subpart OOO
EPA promulgated its New Source Performance Standard (NSPS), 40 CFR Part 60, established under Section 111 of the Clean Air Act on December 16, 1975 (40 FR 58416) as means to regulate stationary sources of particulate matter (PM) emissions. Subpart OOO of the NSPS standard covers nonmetallic mineral processing, which includes regulations for emissions from operating equipment that was manufactured, modified or reconstructed after August 31, 1983. NSPS Subpart 000 was further revised on April 28, 2009. Processing equipment regulated under Subpart OOO affecting the crushed stone, sand and gravel industry includes crushers, grinding mills, screens, bucket elevators, bagging operations, storage bins, enclosed truck and railcars and transfer points on belt conveyors.
Under Subpart OOO, aggregate facilities are required to conduct performance testing on stationary equipment in accordance with EPA Reference Method 9. Method 9 is a visual emissions test that determines opacity or the percentage of the light that is prevented from passing through a plume or fugitive emission. Individuals performing the opacity readings are required to be trained and certified in accordance with the method. EPA has set specific limits for the aggregates industry based on opacity readings designated to various processing equipment ranging from 7-12 percent (%). Among the requirements of Method 9 is determining the average of twenty-four average readings over a six-minute period for a total of 30 minutes for each piece of equipment that falls under the purview of NSPS.
Compliance with the National Ambient Air Quality Standard for particulate matter measured at the property line is a much more accurate indicator of overall facility compliance as well as giving the general public a measurable sense of environmental protection from both a health and welfare perspective. Relying on a subjective visual determination and analysis of an emission rate from individual sources based on opacity is neither a scientifically sound nor legally defensible compliance strategy. Maintaining an antiquated requirement to maintain compliance with a visual opacity standard does nothing to further environmental protection, facility compliance or general public safety.
Current EPA Reference Method 9 Under Subpart OOO and NSSGA Position
EPA in its Final Rule, “Standards of Performance for New Stationary Sources: Nonmetallic Mineral Processing Plants (50 FR 31328, August 1, 1985), justifies its determination to include nonmetallic mineral processing plants under the purview of NSPS, because, “as a category [aggregate industry] contribute significantly to particulate matter air pollution, and that such pollution may reasonably be anticipated to endanger public health and welfare”. However, industry derived emission factor testing conducted continuously since 1991 and approved by the EPA has demonstrated that aggregate facilities emit significantly less particulate matter than was once believed at the time when the rule was promulgated. Furthermore, opacity is an optical property that bears no relationship to the current National Ambient Air Quality Standard (NAAQS), which sets concentration limits for ambient air.
We believe by these references alone that the subjective Method 9 testing required under Subpart OOO has become outdated and renders no substantive value to the agencies for determining ambient concentrations or contributions of PM emissions to the ambient air.
Therefore, NSSGA believes the EPA Reference Method 9 should no longer be used as a viable means for determining ambient concentrations of PM for the following reasons:
- Method 9 opacity testing is a completely subjective test that determines optical properties based on the inherent inequities of calibrating each individual’s eyes to the plume in question, and has no relationship to the current NAAQS
- Emission standards for aggregate facilities should be based solely on National Ambient Air Quality Standards (NAAQS) due to the formation, composition and deposition of particulate matter emissions generated from aggregate operations
- Capture efficiencies of control equipment have vastly improved since the inception of the NSPS rule, thereby reducing the fugitive emissions generated by aggregate operations
- Implementation of engineering controls at aggregate facilities is widely adopted as a best available control technology (BACT)
- Resources required to train and certify personnel, conduct the testing, document and report testing results are unnecessary and burdensome.
Irrelevance and Inaccuracies of the EPA Reference Method 9
EPA’s Reference Method 9 test has been scrutinized since its inception, due in part that opacity is an optical property that bears no relationship to quantifiable mass or concentrations of emissions that is currently addressed by the NAAQS. Opacity evaluation was first used as an indicator of inefficient combustion, but has evolved as a determination of PM emissions when adopted by the EPA. Method 9 relies solely on the discretion and the accuracy of the individual performing the test. Of major concern with the reliability of this testing method is that many industry experts believe that the human eye cannot be not calibrated enough to distinguish between 5, 7, 10 or even 15% opacity. Many have also stated that Reference Method 9 is only an estimation technique accurate to plus or minus 7.5% opacity. There is also no direct correlation between the results of a visual opacity test and a measured or monitored concentration at a fence line. Reliance on the NAAQS is a much better and more accurate determination of facility compliance.
NSSGA PM Emissions Testing for the Aggregate Industry
NSSGA has been conducting air quality studies to accurately characterize particulate emission data that is representative of the aggregate industry. Emission data and pollution estimates for the aggregates industry generated by EPA, prior to the promulgation of NSPS Subpart OOO, grossly overestimated and mischaracterized the amount of particulate matter emitted by these sources. In fact, since 1991, EPA has adopted and revised AP-42 Section 11.19.2 - Crushed Stone Processing - based on more recent and accurate empirical data generated and submitted by NSSGA three times.
Numerous NSSGA studies have demonstrated that stone crushing facilities are not a major source of fine particulates [aerodynamic diameter less than 2.5 micrograms per cubic meter (ug/m3)] and have negligible impact on ambient levels quantified within this diameter range. Results from a 2000 NSSGA study entitled, “PM2.5 PM10 and TSP Formation, Composition and Deposition at a Stone Crushing Plant”, indicated an observed decrease in the concentrations of total suspended particulates (TSP) and PM10 as a function of downwind distance confirmed that there is a rapid loss of PM in the coarse and supercoarse size ranges. Furthermore, the results suggest that EPA’s emission inventories were significantly biased high due to the failure to account for rapid removal of large particles from the atmosphere.
This essentially means the settling velocities, or the speed at which particles dissipate from ambient conditions due to gravitational forces, of the particle sizes indicative of aggregate processing equipment, usually settle out of ambient atmospheric conditions before they reach a facility’s boundary.
PM emissions that do extend beyond the boundary of an aggregate facility would be better quantified by Air monitoring and modeling.
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