Air emissions associated with mining and preparation processes can include dust, emissions from combustion of fuels including vehicle exhaust, and release of naturally occurring gases from the geologic strata during the mining process.
Potential dust sources include vehicle traffic on unpaved mine roads, dumping and loading activities, material crushing, storage, and — at certain sites — blasting.
Arch’s subsidiary operations use an array of methods and tools to protect air quality, including water sprays, enclosures and dust suppressants.
A variety of methods are used to prevent or limit the generation of fugitive and non-fugitive dust emissions. The primary means is to limit those activities that create the potential for generating airborne dust. These may include strategically positioning equipment and routing vehicle traffic patterns for shortened haul ways as well as surfacing long-term roads with stone.
While operations are underway, specific engineering controls are designed into the process equipment for the sole purpose of minimizing the generation of airborne particulates. Examples of these engineering controls include enclosures on coal and refuse conveyance devices, water sprays at material transfer points, the application of dust suppressants on road surfaces and coal storage piles, and the use of baghouse filter systems to capture particulates during material transfers of bulk loads of fine-grained process materials, to mention only a few. These engineering controls are designed and built into the permitted and approved designs of each of our operations.
The teams at each operation understand and maintain compliance with the requirements of air quality permits and perform regular self-inspections to monitor for visible emissions and conduct performance tests on air quality control devices in order to ensure proper operation. Our fully compliant systems operations and their controls are inspected by state regulators on a regular basis.
Interaction with communities near or adjacent to our facilities led one Arch subsidiary operation to launch initiatives recently to control fugitive emissions from coal stockpiles. During high-wind events, excess coal dust can become airborne. To prevent the release of particulates, and to preserve valuable product, the West Elk mine in Colorado developed efficient methods to apply a non-hazardous surface crusting agent to coal piles, using a combination of truck-mounted water cannons and a dozer-mounted applicator, in order to solidify the surface of the pile. These crusting agents are applied in lieu of traditional water applications, which tend to have limited utility once the water evaporates. The crusting agents remain in place for as long as the pile remains undisturbed.
Arch’s subsidiary operations deemed to have the potential to exceed certain emissions thresholds for so-called “criteria pollutants” — including particulate matter, carbon monoxide, sulfur oxides and nitrogen oxides — operate under air program permits issued by their respective states. In instances when these permits establish limits on emissions of these pollutants, Arch’s subsidiary operations are required to report their actual emissions to the state air regulators on a permit-specified interval — typically annually.
Emissions of Four Criteria Pollutants
(for Arch and its operating subsidiaries, in tons)