SOUTH DAKOTA Department of
Environment & Natural Resources

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Air Quality

Natural Events Action Plan

Introduction

Purpose

Area of Implementation

Identification of Contributing Sources

Development and Implementation of BACM

Public Education and Notification of High Wind Events

Particulate Matter Background History


Introduction

In a memo dated May 30, 1996, by Mary D. Nichols, Assistant Administrator for the Office of Air and Radiation, the Environmental Protection Agency (EPA) established a Natural Events Policy to address National Ambient Air Quality Standards for PM10 (particulate matter less than 10 microns) violations or exceedances that occurred during natural events. One of the three natural events identified in the memo was high winds.

Rapid City experiences PM10 exceedances that could lead to violations of the National Ambient Air Quality Standard.  Past history has shown that the majority of these exceedances occur during high wind events. In 1997, the South Dakota Department of Environment and Natural Resources began to develop a Natural Events Action Plan, which is the compliance mechanism to the Natural Events Policy.  A coordinated effort between the department, the Pennington County Air Quality Board, the City of Rapid City, Pennington County, and the industries in the Northwest Industrial Complex was undertaken to complete the plan.  The plan was finalized on July 1, 1998. 

To download the Natural Events Action Plan in Adobe Acrobat format click here.

To download the NEAP 5 year review click here.

To download the NEAP Appendices click here.

 

Purpose

The purpose of the plan was to identify the Natural Events that have resulted in past PM10 exceedances and to develop or identify controls for PM10 sources to reduce or eliminate future PM10 exceedances in West Rapid City during high wind events. If the proposed Best Available Control Measures and public notice of an event are implemented, any future exceedance occurring during a high wind event, as defined in the plan, would not be counted towards a violation.

Area of Implementation

This plan will be implemented in West Rapid City where the PM10 exceedances have occurred. West Rapid City lies in the middle of the geological formation termed the limestone racetrack that surrounds the Black Hills National Forest. It is bordered on the west and south by the Black Hills and on the east by a series of hogback hills, creating a bowl-like formation ideal for air pollution problems. The city’s main industrial and mining complex is located in this section of the city. The area of implementation for this plan will be between a line extending north and south from the "Gap" to 5 miles west of the city's western city limit.  The "Gap" is a geographic marker that is drainage for Rapid Creek out of the Black Hills that runs through Rapid City. Click here to view a map of the NEAP Control Area.  Click here to view air quality monitoring locations in Rapid City.

Identification of Contributing Sources

It is stated in the Natural Events Policy that all sources contributing to a PM10 violation are required to have Best Available Control Measures implemented. This plan identifies fugitive dust sources within the industrial complex as the main contributors to the PM10 exceedances. It also identifies the proposed Best Available Control Measures for these sources and the process of implementation.

Other sources having the potential to contribute to the exceedances include point sources in the area, street sanding operations, construction activities, paved and unpaved parking lots/alleys, woodburning, and open burning. Best Available Control Measures have already been implemented for these sources because of past particulate pollution problems in other sections of the city. They are desscribed in the plan. Since the implementation of these measures, particulate pollution problems in other areas in the city have been significantly reduced or eliminated.

Development and Implementation of BACM

The 1996 policy stipulates that Best Available Control Measures must be federally enforceable. The controls for industrial fugitive dust sources are implemented through the industrial sources’ state air pollution permits. These are either in the state’s Part 70 permit or minor permit, both of which are federally enforceable through South Dakota's State Implementation Plan (SIP). Controls for other sources contributing to the violation, such as reentrained street dust, unpaved parking lots/alleys, woodburning, construction activity, and open burning, have been established either under state regulations or the local Pennington County Air Quality Ordinance #12.

Public Education and Notification of High Wind Events

A review of meetings held to notify the public of high concentrations and to discuss the Natural Events Action Plan is provided in the plan along with the process for calling high wind dust alerts for future high wind events.

Particulate Matter Background History

Historically, the Rapid City area has had problems with high particulate levels. Due to recorded exceedances, Rapid City was classified as nonattainment for total suspended particulate (TSP) in 1978. In 1986, the dust standard was changed to PM10. With the change in standards, Rapid City became designated "unclassifiable" for PM10. Rapid City met the new standard for several years.

In October 1992, two samples collected at Jaehn’s Business Supply site in West Rapid City violated the PM10 standard and triggered the nonattainment process with EPA. The department submitted information to EPA requesting the samples be flagged as exceptional events under 40 CFR Part 50 Appendix K as a result of abnormally dry conditions coupled with high winds. It was stated these samples should not be used to determine the air quality status of Rapid City. The department made several appeals to EPA for a favorable ruling.

In a letter from EPA to Governor Janklow dated July 19, 1995, EPA did not agree with the department’s position and planned to go forward with the nonattainment designation. EPA based their decision on the belief that high wind events are recurring. However, the department convinced EPA the designation would be counterproductive to all the work the city, county, industry, and state had done to improve the air quality. EPA decided to suspend the designation if the following conditions were met:

DENR established some fugitive dust controls in the sources’ permits, but the controls were not implemented in all the permits due to the then recent development of the Part 70 permitting program and the Natural Events Policy.

In January, February, and December 1996 and May 1997, four exceedances of the daily PM10 standard occurred at the Family Thrift Center site in Rapid City. The department flagged these exceedances as exceptional events in the Aeromatic Information Retrieval System (AIRS) database. Although the four exceedances occurred on high wind days, the exceedances could not be considered exceptional events under 40 CFR Part 50 Appendix K because, according to EPA, the conditions could recur.

On May 30, 1996, EPA issued its Natural Events Policy to address PM10 violations that occur during natural events. The policy covered natural events such as wildfire, volcanoes, and high wind with the requirement that best available control measures be applied to sources contributing to the PM10 violation even if the event could recur. On August 7, 1997, the department notified EPA that the policy would be applied to the three exceedances and any future exceedances caused by high wind events to the Natural Events Action Plan the department developed for Rapid City.  The plan was reviewed by EPA and accepted by them on July 1, 1998. 

The department submitted its first high wind exceedance (May 6, 1999) to EPA for exclusion under the Natural Events Action Plan.  In a letter dated December 20, 1999, to the department, EPA acknowledged the exceedance as a high wind event that would not be counted towards a violation under the Natural Events Action Plan.

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