This portion of the plan discusses the air pollution controls that were required to be implemented by the industrial facilities. The controls are referred to as Best Available Control Measures (BACM).
Identifying Why Existing Controls Failed
BACM for Particulate Emissions
BACM Determination for Industrial Fugitive Dust Sources
Unpaved Road Control
Paved Roads and Parking Area Controls
Track-out Area Controls
Front-end Loader Controls
Open Storage Pile Controls
Waste Pit Control
Comments or Proposed New Controls
Identifying why existing controls failed
The Natural Events Action Plan describes the weather conditions in Rapid City which contributed to the PM10 exceedances. Following is a discussion of the reasons why existing controls for fugitive dust emissions can fail under these conditions.
Hourly Wind Speed: When winds exceed 20 mph (hourly average), the soil or dust crust covering stockpiles, waste dust pits, land, and haul roads deteriorates. This allows the dust to become airborne. It has been identified that PM10 concentrations increase from 100 ug/m3 per hour up to 900 ug/m3 when average hourly winds are greater than 20 mph. Conversely, the concentrations drop below 100 ug/m3 when hourly average wind speeds decrease below 20 mph.
Peak Wind Speed: When peak winds exceed 40 mph (one minute average), the soil or dust crust deteriorates at a faster rate, and the dust becomes airborne. These wind speeds also reduce the effectiveness of any water control practices because the strength of the wind makes it difficult to apply the water where needed.
Soil Moisture Content: It has been documented in studies that soil erosion caused by wind can begin at 13.4 mph and is highly accelerated at winds of up to 50 mph. These studies were conducted on agricultural, construction and industrial soils in separate studies by W.G. Nickling, J.A. Gilles, D.W. Fryrear, D.A. Gillete, J. Adams, A. Endo, D. Smith, R. Kihl, L.D. Stetler, K.E. Saxton. The parameters established in this plan are consistent with these wind rates. Soil moisture content is also a vital component in the rate of wind erosion, although there are no data available discussing the relationship between soil moisture, wind speeds and PM10 concentrations for this area.
Consecutive Days of No Precipitation: Three or more days of little or no precipitation also results in conditions favorable to generating dust. First, when there is no precipitation for several consecutive days, there is no creation of a natural crust on fugitive dust sources. Second, the moisture content in the existing crust evaporates, leaving the dust vulnerable to reentrainment. There is also a new buildup of dust from the industrial processes during this time period. Long-term dry periods reduce vegetative cover and cause fugitive dust to become airborne during high winds, even in reclaimed quarry areas.
Temperature: When the temperature is below 32 degrees F., the industrial sources do not apply water, which was the main source of dust control. Water is not applied during freezing periods because it has the potential to cause unsafe working conditions. Equipment used to apply the water (water trucks or crusher spray bars) can also freeze. The freezing and thawing effect also increases the erodibility of the crustal surfaces, contributing to high PM10 concentrations on windy days.
BACM Determination for Industrial Fugitive Dust Sources
The Best Available Control Measures determination was based on finding controls that could provide the best and economically feasible control of fugitive dust during high winds and freezing conditions. The search began with reviewing Best Available Control Technologies (BACT) implemented in PM10 nonattainment areas with similar air pollution problems as Rapid City. Nonattainment area controls in Reno and Las Vegas, Nevada, Spokane and Puget Sound, Washington, and South Coast, California were reviewed. The search indicated accepted controls of chemical application on fugitive dust sources such as haul roads, stockpiles, and waste pits with enclosures and installation of pollution control devices on limestone rock crushing and processing. Water for dust suppression was an accepted control in milder climates; however this type of control would not always be effective in Rapid City’s colder winter months when water is not used due to safety and mechanical problems associated with freezing.
The department also reviewed EPA’s "Best Available Control Technologies for Fugitive Dust Sources." The review indicated the BACM developed by the department for sources in West Rapid City were comparable to the controls in EPA’s document. This book did not provide controls for crushing operations. Therefore, a search for Best Available Control Measures for rock crushing was conducted in EPA’s "RACT/BACT/LAER Clearinghouse." The clearinghouse identifies acceptable level of controls for new and modified sources that have to comply with requirements in nonattainment areas as well as EPA’s New Source Review and Prevention of Significant Deterioration rules. The results of this search indicated water spray bars are the accepted control for rock crushing operations processing aggregate other than limestone. Limestone crushing operations are required to enclose the operation and install a pollution collection device. Again, because of the colder seasons, water spray control systems are not acceptable in the Rapid City area except for a wet scrubber system, which is considered a pollution control collection device.
To conclude the search on fugitive dust controls and to determine if the controls were economically feasible to implement, a review of controls already implemented by similar industries in the Rapid City area was conducted. A couple of the industries were implementing most of the proposed fugitive dust and crushing controls, but the majority of industries were implementing only a few of the proposed controls. Many of the proposed controls were implemented within the last three to four years. The implementation of these controls is reflected in the reduction of days with greater than 100 ug/m3 of PM10 per year.
BACM for Particulate Emissions
The following Best Available Control Measures, based upon the review described above, were developed for fugitive dust sources in the industrial complex in West Rapid City. The Best Available Control Measures have been reviewed by EPA’s Region VIII and Headquarters, the Rapid City industries, the Pennington County Air Quality Board, and the department.
The Best Available Control Measures apply to the following industries and to any new industry locating in West Rapid City:
- Birdsall Sand and Gravel;
- Black Hills Power and Light Company;
- Dakota Block Company;
- Fisher Sand and Gravel;
- Hills Materials Company;
- J.E. Simon Construction;
- Pete Lien and Sons, Inc.; and
- South Dakota Cement.
Standard of Control
Best Available Control Measures for particulate matter sources are techniques and/or controls that achieve the maximum degree of emission reduction from a source as determined on a case-by-case basis considering technological and economic feasibility. (59 FR 42010, August 16, 1994).
Alternative Techniques and Controls
The owner or operator shall have the option to implement other techniques and/or controls that are as efficient in reducing or eliminating particulate matter as the controls listed. If the owner or operator decides to pursue other alternative techniques and/or controls, the owner or operator shall notify the department in writing of the alternative technique and/or controls. The notification shall include an explanation as to what the owner or operator proposes, testing results, emission projections, and a timeline for installing the control measure. The department shall review the proposal and notify the owner or operator in writing within 30 days of receiving the proposal, that the owner or operator may proceed as proposed or with changes outlined in the department’s written response. The department shall be receptive of proposals that are as efficient as existing techniques and/or controls. Failure of the department to notify the owner or operator within 30 days shall be deemed to be acceptance of the owner or operator’s alternative techniques and/or controls.
Crusher Control Options
The owner or operator shall enclose any primary, secondary or tertiary rock crusher along with the associated screens, transfer points and load-outs (from hoppers or conveyors to other than stockpiles). Any captured particulate matter shall be disposed of in a manner that will not allow the captured particulate matter to become reentrained into the ambient air.
The term "enclosure" shall be defined to be either a complete enclosure around one or more pieces of equipment or an enclosure of those points on the equipment from which particulates are emitted. To qualify as an enclosure, the enclosure shall be:
Constructed of materials impermeable to air. The actual shell of a piece of equipment may be considered as the enclosure or part of the enclosure.
Designed and constructed to minimize the number and size of openings through which air may enter or exit the building or enclosure. Openings shall be covered by a curtain or other method to minimize the opening to the size reasonably needed for the movement of materials, equipment, personnel, and air necessary for operation and ventilation of occupied areas.
Designed and constructed so that the discharge of air from the building or enclosed structure on the unit associated with movement of materials shall be minimized as much as is reasonably possible.
Include a method of control, either (1) treating, capturing or removing particulate matter emissions generated from the material being processed with wet suppression, baghouse or wet scrubber for complete enclosed buildings, and/or (2) capturing or removing particulate emissions generated with a baghouse or wet scrubber for an enclosure of an emission point. Wet suppression may not be used as a control for option (2). At least one control method shall be used when equipment is operated.
Whenever reasonably possible, the control shall have a negative pressure.
Designed and constructed together with the controls to allow for the removal of particulate emissions which have settled out of the air inside the enclosure or have been removed from the air by controls.
Air emissions from the enclosure shall be subject to the 20 percent opacity emission limit or the applicable New Source Performance Standards. Limitations in sealing off enclosures from airflow that will impact worker safety and health standards for indoor particulate emission limits will be considered when reviewing the plans.
Unpaved Roads Controls
For Unpaved Road Controls the owner or operator shall implement one of the following:
- Apply a chemical stabilizer to all main haul roads in sufficient quantity and frequency to suppress particulate matter generation to comply with opacity standards as identified in the plan, and apply a chemical stabilizer or water to all secondary haul roads that have daily vehicular traffic at a frequency to suppress particulate matter generation to comply with opacity standards identified in the plan; or
- Pave main haul roads and secondary haul roads with tack seal, asphalt, recycled asphalt or concrete.
Main haul roads are defined as passageways between the mining area and the processing facility or between the processing facility and the storage area in which material is transferred on a road.
Secondary haul roads are defined as passageways in which there is daily vehicular traffic on normal work days other than the main haul roads.
Chemical stabilizers include magnesium chloride, calcium chloride, or on-specification used oil as defined in ARSD 74:28 that is applied to a scarified road surface. To receive approval for an additional chemical stabilizer, the owner or operator shall submit a written proposal to the department demonstrating the proposed chemical will not violate surface or ground water standards upon run-off or leaching and is equivalent to the approved chemical stabilizer for controlling particulate matter. Delays for application of chemical stabilizers up to 30 days will be allowed during freezing conditions or when conditions are not favorable for application.
Paved Roads and Parking Area Control
The owner or operator shall sweep and water flush or vacuum and water flush all paved roads and parking areas to remove particulate matter that has the potential to be resuspended. The frequency of cleaning will be on an as needed basis to comply with opacity standards.
Track Out Area Control
For Track Out Area Controls the owner or operator shall implement one of the following:
- Pave (asphalt or concrete) a track out area to maintain a stabilized surface starting from the point of intersection with the public paved surface into the facility boundary for a total distance of at least 100 feet and a width of at least 20 feet; or
- Install a wash station and require all haul truck vehicles leaving the facility to remove track out materials through the use of water.
For temporary track out areas (in use for less than 60 days in a calendar year), techniques and/or controls shall be implemented so as to prevent particulate matter from becoming entrained in violation of the opacity standard identified in the plan. The controls and/or techniques shall require DENR approval unless it is a control or technique approved in this section.
Track out areas are defined as driving surfaces from the owner or operator’s facility to public roadways upon which particulate matter has been deposited by transport vehicles.
- Reclamation Plan: The owner or operator shall submit to the department for approval, a plan to reclaim lands that have a wind erosion potential within 90 days of the issuance of the Part 70 Operating Permit. Upon approval of the plan by the department, the plan shall remain in effect as the BACM for lands with wind erosion potential, until reclamation has been completed at the facility and approved by the department. The department will approve a plan that makes reasonable progress toward reclaiming land with a wind erosion potential.
- Plan Approval: The department shall notify the owner or operator within 90 days after issuance of the owner or operator’s operating permit if the plan is approved or, in the alternative, which portions are not approved and the reason why the portions have not been approved. The owner or operator shall resubmit a revised plan within 90 days of notification. When the department finds the owner or operator’s plan or revised plan to be acceptable, it shall provide written notice to the owner or operator. The accepted plan shall remain in effect until further modification.
- Plan Modification: The owner or operator may propose further modification of an approved plan by written notice to the department. The department shall respond in writing within 90 days of the owner or operator’s proposed modification.
- Reclaimed Lands: Lands which have been successfully reclaimed, as approved by the department, shall no longer be subject to the approved plan requirements, as long as they remain reclaimed.
Reclaimed land is defined as an area which meets the requirements for reclamation in SDCL 45-6 for licensed mining operations or established in the reclamation plan of a mining operation permitted under SDCL 45-6B.
Lands with a wind erosion potential are all areas within the facility except those that have a hard rock surface, are paved (concrete or asphalt), have a building structure over it, the working face of the quarry, or have been reclaimed.
Front-end Loader Control
Control Development: Controls for particulate matter generated by front-end loader operations are being researched. At the time a control is determined and agreed upon, it will be placed in each permit as necessary.
Open Storage Pile Control
For open storage pile controls the owner or operator shall implement one of the following:
- Apply chemical stabilizer in a sufficient quantity and frequency to suppress particulate matter generation to comply with the opacity standard identified in the plan; or
- Apply water to the surface area of all open storage piles on an as needed basis to comply with the opacity standard between May 1 to October 1; or
- Install at least a two-sided enclosure with walls which extend, at a minimum, to the top of the pile to comply with the opacity standard.
Open storage piles are defined as a storage pile with a silt content of four percent or greater, has a height of three feet or more, and a total surface area of 150 square feet or more. Silt content will be determined by sampling and analysis in accordance with the ASTM C-136 or other equivalent methods approved by the department. Silt is defined as any material with a particulate size less than 74 micrometers in diameter and passes through a number 200 sieve.
Chemical stabilizer delays - Delays for application, up to 30 days, will be allowed during freezing conditions or when conditions are not favorable for application.
Waste Pit Control
For waste pit areas, the owner or operator shall implement one of the following:
- Apply a soil cement or similar application that is approved by the department between October 1 and March 31 and apply a water spray to adequately create a crusted surface over the entire waste pit area to adequately control particulate matter between April 1 and September 30; or
- Implement a combination of wind protection (wind-fence, wind-screen, three wall enclosure) and water spray application on an annual basis; or
- Eliminate the waste pit by developing a market for the waste.
Waste pits are defined as areas where waste particulate matter from process equipment or pollution control units are deposited or disposed.
No blasting shall be allowed when a high wind air quality alert is in effect. The only exception is if the detonation charges have been set in the blasting holes prior to being notified of the high wind air quality alert. This exception is allowed for safety reasons and Mining Safety and Health Administration blasting requirements.
Comments and Proposed Controls:
Comments on the controls or suggestions on new controls are always welcome. To submit comments or proposed new controls, please call or write the department at the address and phone number below or send an email to the state contact:
Brad Schultz, Environmental Senior Scientist
Air Quality Program
523 E. Capitol
Pierre, South Dakota 57501