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Fugitive Dust: Opacity and Nuisance

The heat of summer calls to mind dust. Dust in recycling operations, especially fugitive dust, calls to mind two things: opacity and nuisance. Both of these have regulatory requirements, usually by the state or locality, and can become larger problems if not adequately addressed.

Opacity is probably the easier one to tackle because it is mainly an on-site air issue and has fairly well-defined metrics. For instance, according to a Michigan DEQ document on fugitive dust, visible emissions of particulate matter (PM) shall not exceed “[a] (6) minute average of 20 percent opacity with one allowance of a 27 percent opacity reading per (6) minute average per hour” or a more-stringent limit specified by a permit. In Michigan, fugitive is defined as “particulate matter which is generated from indoor processes, activities, or operations and which is emitted into the outer air through building openings and general exhaust ventilation, except stacks. The term also means particulate matter which is emitted into the outer air from outdoor processes, activities, or operations due to the forces of the wind or human activity.” In New York, the limit is slightly different: “an opacity equal to or greater than 20 percent (six minute average) except for one continuous six-minute period per hour of not more than 57 percent opacity.”

Due to such variations, operators should check with their state and local authorities to know their requirements for dust and opacity. For instance, Chicago has specific rules for material susceptible to becoming windborne, including “reasonable precautions to minimize windborne particulate matter” for material storage and handling and “dust control measures to ensure that no visible dust or dirt from material piles migrates off the site.” Also, operators “shall ensure that mud, dirt, and other debris is not tracked onto the public way” and may be required “to employ a street sweeper, water truck, truck wash, or other device to control the track out”. In the case of outdoor fugitive emissions from vehicular traffic, material loading, unloading, and handling, and processing operations, regular sweeping and judicious application of water via water truck with manifold or wide-area misting devices may be effective for limiting dust emissions and opacity, but perhaps more importantly off-site migration of dust.

Off-site migration of visible dust, which might itself constitute a violation, has the potential to create or contribute to nuisance. (This potential also applies to off-site stormwater runoff, as well as lighting, noise, odor, and vibration which are not, strictly speaking, “environmental”.) Unlike opacity, nuisance is subjective because it is defined by the perceiver. Nuisance is essentially determined by complaints. California’s South Coast Air Quality Management District has brought these issues together in its compliance and inspection discussion, “Visible Emissions, Public Nuisance & Fugitive Dust”: “Public nuisance violations can occur when a considerable number of individuals complain to AQMD of odors, paint overspray, or other bothersome conditions that appear to be related to the operation of a business in the neighboring vicinity. An AQMD Inspector may be dispatched to investigate such complaints … Fugitive dust violations occur when significant (>20 percent opacity) dust emission [sic] are generated… a violation can also occur when the dust is visible past the property line of the emission source or when dirt/mud is tracked out onto the public roads for [sic] more than 25 feet.”

Because of nuisance’s subjectivity, it is important for recyclers to minimize potential adverse offsite impacts of their operations and to be responsive to complaints. Good will from neighbors is highly valuable, but can be lost very quickly. Complaints have led to a significant study of off-site air quality near certain metal recyclers in Houston (still on-going) and also to new risk-based air quality regulations in Oregon (not because of metal recycling operations). Fugitive dust is just one potential cause. ISRI is here to help members to address these issues.

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