Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/548151
Dust Control Best Practices OPERATIONS D ust control touches every part of an aggregate op- eration, from productivity, effi ciency, and product quality to compliance, safety, and good neighbor relations. According to Mark Kestner, Ph.D., president and CEO of National Environmental Ser- vice Co. (NESCO), "My philosophy has always been that good dust control is good process control. If your stone isn't spilling on the ground or going up in the air, it's going across a scale and into a truck, railcar, or barge to make money." Dust in aggregate operations comes from three major source categories: roads, stockpiles, and processing operations. The most signifi cant causes of dust from an operations standpoint include mobile equipment on unpaved roads, crush- er discharge, screen discharge, con- veyor transfer points, and stacking conveyor discharge, says Clif Morris, general manager of aggregates for Tilcon New York. Engineered controls that are em- ployed to contain dust and spillage should be an integral part of plant design, Kestner says. "Any owner/ operator of a new mine is required by federal and state laws to obtain permits to construct, install, and operate the facility. As part of the permitting process, the mine must specify the dust controls it will use and must demonstrate that it is able to comply with NSPS (New Source Performance Standards)." As part of the design, transfer points should be enclosed on three sides, covered, fi tted with a dust curtain, and properly skirted. Load points should have suffi cient idler support to prevent sagging between idlers that leads to visible dust and spillage. "I see more and more plants using impact beds to maintain uniform seals at load points and dual skirting at impact crusher discharg- es," Kestner notes. Kestner and Morris agree that the following steps are required when developing a dust control plan: 1. Conduct a site survey to identify all the sources of dust on the property. 2. Estimate "uncontrolled" dust emis- sions from these sources using EPA AP-42 emission factors; this provides a baseline to evaluate the performance of controls. 3. Specify Reasonably Available Con- trol Measures (RACM) for each dust source. 4. Estimate "controlled" emissions using control effi ciency ratings es- tablished by federal or state EPAs. 5. Establish a budget to purchase and install dust controls. 6. Implement the control plan. 7. Monitor the performance of the control plan and modify as neces- sary to maintain compliance. Companies that ignore engineered controls to reduce the costs of new plant construction will pay for it later in time and labor to clean up dust and spillage. Additionally, when la- borers have to sweep, shovel, or use a skid steer to remove spillage out from under screens, conveyors, and crushers, they are at their greatest risk for exposure to respirable dust. AGGREGATES MANAGER The fi rst step in taking control of dust is to conduct a site survey to identify all sources of dust on the property. Plant operations produce dust from three major sourc- es: roads, stockpiles, and processing operations. After identifying sources of dust emissions, producers should specify Reasonably Available Control Measures (RACMs) for each source and implement a control plan. Stockpiles are often a source of dust within the plant, starting with the stacking conveyor discharge. Stock- piles that are too high or that are situated within the fl ow of predominant winds can also lead to excess dust. Producers should minimize stockpile heights and consider spraying stockpiles to control dust. Loader operators should avoid overfi lling buckets and spilling material when loading from stockpiles. 1 Conduct a site survey 4 Control dust from stockpiles