SOUTH DAKOTA Department of
Environment & Natural Resources

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Pierre, SD 57501
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Air Quality

NEAP Controls

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

    Crusher Controls

    Unpaved Road Control

    Paved Roads and Parking Area Controls

    Track-out Area Controls

    Reclamation Plan

    Front-end Loader Controls

    Open Storage Pile Controls

    Waste Pit Control

    Blasting Controls

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:

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:

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:

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:

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 Control

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:

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:

Waste pits are defined as areas where waste particulate matter from process equipment or pollution control units are deposited or disposed.

Blasting Controls

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
(605) 773-3151