Ref: 8P-AR 

MEMORANDUM 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 8 

1595 Wynkoop Street 

Denver, CO 80202-1129 

Phone 800-227-8917 

http://www.epa.gov/region08 

SUBJECT: Element G, Emergency Powers, Adequate Contingency Plans. 

FROM: Abby Fulton, Environmental Protection Specialist 

Air Program, Air Quality Planning Unit 

TO: Docket File No. EPA-R08-0AR-2011-0725 

NOV 2 5 2014 

In the Emergency powers, Section 110(a)(2)(G) discussion of EPA's Promulgation of State 

Implementation Plan Revisions; Infrastructure Requirements for the 1997 and 2006 PM2.s, 2008 

Lead, 2008 Ozone, and 2010 N02 National Ambient Air Quality Standards; South Dakota, 

proposed rule notice, we briefly discussed the events surrounding an elevated monitored level of 

24-hour PM2.s on September 4, 2009. Below is a detailed description of the events ofthe date in 

question and our reasoning for approval of Element G. 

For approval of Element G, states must meet the requirements of subpart H of 40 CFR Part 51 

which requires states to classify regions and to develop contingency plans (also known as 

emergency episode plans) after ambient concentrations of certain criteria pollutants in an area 

have exceeded specified levels. For example, if ambient concentrations of nitrogen dioxide in an 

area have exceeded 0.06 parts per million (annual arithmetic mean), then the area is classified as 

a Priority I region, and the state must develop a contingency plan that meets the requirements of 

sections 51.151 and 51.152. However, Subpart H does not currently address requirements for the 

24-hour PM2.s standard. 

In 2009, EPA issued a guidance memorandum that, among other things, recommended an 

approach for states to address the contingency plan requirements of 11 O(a)(2)(G) with respect to 

the 2006 PM2.s NAAQS. 1 The guidance, in Attachment A, suggested that states develop a 

contingency plan if, based on the most recent three calendar years of data, an area within the 

state had monitored and recorded a 24-hour PM2.s level greater than 140.4 micrograms per cubic 

meter (!lglm\ For states that were to develop a contingency plan, the guidance recommended 

states set priority and emergency levels consistent with requirements of 40 CFR 51.150 through 

51.153. EPA notes that section 51.153 requires periodic reevaluation of priority classifications 

based on the three most recent years of air quality data. 

1 Memorandum from William T. Harnett, Director, Air Quality Policy Division, to Regional Air Division Directors, 

Guidance on SIP Elements Required under Sections 11 O(a)(l) and (2) for the 2006 24-Hour Fine Particle (PM2 5) 

Standards (NAAQS), at 6-7 (Sep. 25, 2009). 
On September 4, 2009, a continuous PM2.s air monitor operated by the State of South Dakota in 

Wind Cave National Park registered a 24-hour level of303.6 Jlg/m3• Data for this monitor is 

contained within this docket. The monitor in question was a special purpose Federal Equivalent 

Method monitor collocated with a Federal Reference Method (FRM) State and Local Air 

Monitoring Stations (SLAMS) monitor. The SLAMS FRM was designated as the primary 

monitor at the site, and recorded 120.5 Jlg/m3 as the official regulatory value for the monitoring 

station that day. In order for EPA to determine if, as suggested by the guidance, it is appropriate 

to interpret section 110(a)(2)(G) as requiring South Dakota to develop a contingency plan, it is 

necessary to provide details surrounding the recorded value and air quality in South Dakota in 

general. On the day the secondary monitor recorded a value of 303.6 Jlg/m3, the National Park 

Service conducted a prescribed burn in the Park. 

The Park is adjacent to the Black Hills National Forest and lies entirely within rural Custer 

County (population 8,216, 2010 census). The closest major town to the monitor is Hot Springs 

(population 3,711, 2010 census), 8 miles south ofthe monitor. The closest city is Rapid City 

(population 67,956,2010 census), 40 miles away. On the day ofthe prescribed burn, PM2.s 

monitors elsewhere in the state recorded 24-hour levels from 4.3 Jlg/m3 to 20.8 Jlglm3, well 

below the 24-hour primary and secondary standard of35 Jlg/m3.

2 The highest levels were in 

Sioux Falls and adjoining Union County, in the far southeastern part of the State. The two closest 

monitors to the Park, in Rapid City, recorded levels of 9 and 10.5 Jlg/ m3

• 

Generally, air quality in South Dakota with respect to PM2.s is good. No PM2.s monitor in South 

Dakota has ever recorded a violation of any PM2.s NAAQS, and the entire state, including Custer 

County, is designated unclassifiable/attainment for the 2006 PM2.s NAAQS. For monitors with 

complete data for any given year, the highest ever 98th percentile 24-hr PM2.s value was 29.7 

Jlg/m3 at the Union County site (30 miles NE of Sioux City, Iowa) in 2010. The highest ever 

annual mean3 PM2.s value (complete monitoring year) was 11.0 Jlg/m3 at Watertown in 2012. 

Since 1999, PM2.s monitors in South Dakota record exceedances of the 24-hour PM2.s standard 

only once every four or five years, on average. The top three exceedances, other than the one on 

September 4, 2009, also occurred at the Wind Cave National Park monitor during prescribed 

burns; those recorded values ranged from 112.6 Jlg/m3 to 121.8 Jlg/m3

. After those, the next 

highest exceedance, 62 Jlg/m3

, was recorded in Rapid City. Furthermore, South Dakota has 

recorded no levels of ambient air concentrations in the three most recent complete calendar 

years-2011, 2012, and 20134-that exceed the 2009 guidance memorandum5 recommended 

levels for states to develop a contingency plan for PM2.s. 

Given this data, the unique circumstances ofthe prescribed burn, and the fact that the official 

2 A table containing the monitoring data is in the docket. 3 See 40 CFR Part 50, Appendix N, 4.3(a) for rounding requirements. 4 A table containing the monitoring data is in the docket. 5 Memorandum from William T. Harnett, Director, Air Quality Policy Division, to Regional Air Division Directors, 

Guidance on SIP Elements Required under Sections llO(a)(l) and (2) for the 2006 24-Hour Fine Particle (PMzs) 

Standards (NAAQS), at p. 6-7 (Sep. 25, 2009). 

2 
regulatory value from the SLAMS FRM on the day of the prescribed bum fell below the 140.4 

ug/m3 threshold recommended in the 2009 guidance memorandum, EPA finds it appropriate in 

these circumstances to interpret section 110(a)(2)(G) ofthe Act as not requiring the state to 

develop a contingency plan for PM2.s. However, this does not imply that other, future 

circumstances in the state cannot trigger this requirement. 

3