### January 16, 2015 CarlDaly USEPA,RegionVIII (8P-AR) 1595 Wynkoop St. Denver, Colorado 80202-1129 

### RE: RequestforYellowstone County (part) S02

### NonattainmentArea CleanData Determination DearMr. Daly: TheU.S. EnvironmentalProtectionAgency (EPA) ftnalized andpublished 

### Guidance for 1-Hour502 

### NonattainmentAreaSIPSubmissions (Guidance) onApril23,2014, includingprovisions outliningthe use ofEPA's CleanDataPolicytoinitiate arearedesignations underthe 2010revised National AmbientAir Quality Standards for sulfur dioxide (standard). Theguidance specifically states: "...to demonstrate that it is meeting the standards, a nonattainment area which was designated based on air 

### quality monitoring data would first need to have 3 consecutive years of air quality monitoring data which show that the area is meeting the standard. The data would need to be complete and quality-assured, consistent with 40 CFR part 58 requirements, and other relevant EPA guidance, andproperlysubmittedto theAQS database oftheEPA'sAerometric Information RetrievalSystem (AIRS)." Usingthe 2009-2011 designvalue of79 parts perbillion (ppb) collected atthe CoburnRoad SLAMS orState orLocalAirMonitoringStation, onAugust 5, 2013 EPApublishedits final "nonattainment"designation forYellowstone County (part) in 78 FR47191. This designation became effective October 3, 2013. InaccordancewiththeClean DataPolicy, Montanais nowpleasedto presentthe2012-2014design value demonstratingtheareahas attainedthe standard (see table below). The2012-2014datahas beenquality-assured and submittedtoAQS. CoburnRoadAmbient 1-hrS02

### MonitoredConcentrations (ppb)
Annual99thPercentile 2013 DesignValue 2012 70 2013 48 2014 93 70

Steve Bullock, Governor I Tom Livers, Director I P.O. Box 200901 I Helena, MT 59620-0901 I (406) 444-2544 I www.deq.mt.gov

### The Guidancegoes onto state,inrelevantpart: "The EPA will determine whether or not an S02 

### nonattainment area has attained the NAAQS based on air quality monitoring data (when available), air quality dispersion modeling for the affected area, and/or a demonstration that the control strategy in the SIP has been fully implemented... In addition, if EPA determines that the air quality monitors located in the affected area are located atthe area ofmaximumconcentration, the EPAmay be able to use the data from thesemonitors to make the determination ofattainmentwithoutthe use ofairquality modelingdata." S02

### has beenmonitoredintheBillings areain one form oranotherfor morethan four decades. Theattached documenttided

### Billings-LaurelHistoricalAmbient502

### MonitoringReport, completedby BisonEngineering, Inc., details thehistory ofS02 

### monitoringintheBillings airshed. This significanthistory ofS02

### monitoring, whichinmany cases useddispersion modelingto determine maximumconcentrationsites tobemonitored, strongly supportsMontana's position thatthe CoburnRoad SLAMS is in factlocatedin the area ofmaximumambientS02 

### concentration. Also, inestablishingandlimitingtheextentofthenonattainmentarea, EPAuseddatacollectedat four separateindustrialsource-operated

# so2monitorsinthe area, all ofwhich demonstrate compliance with the standard. EPA's nonattainmentareaboundaryincludes onlythe CoburnRoadSLAMS; therefore, accordingtothe Guidance, EPA mayuse CoburnRoadSLAMS datato make a determination ofattainmentwithoutrequiringtheuse ofair qualitymodelingfor suchpurposes. InSummary, theYellowstone County (part) nonattainmentareahas attainedthe standardwellin advance ofthe October2018 attainmentdate. Infact, the areahas attainedthe standardin advance oftheApril2015 attainmentplandue date. Further,Montanahas suppliedalltherequired documentation andsupportinginformationto qualify for a determination of"attainment" underthe S02

### CleanDataPolicy. I lookforward toyourresponseto this request. If

### youhave anyquestions regardingthis action, please contactM. EricMerchant, the Department'sAir QualityPolicyandPlanning Supervisor, by telephone at (406) 444-1457 orby email atemerchant@mt.gov.

DavidL. 

### Kle p AirResource ManagementBureauChief Enclosures cc: MonicaMorales,Air QualityPlanningChief, US EPA Region 8 TomLivers, Director,DepartmentofEnvironmental Quality M. EricMerchant,AirResources ManagementBureau

### January 16, 2015 ShaunMcGrath RegionalAdministrator US EPARegion 8 1595Wynkoop Street Denver, CO 80202-1129
DearMr. McGrath, Please accept this letter as the Montana Department of Environmental Quality's (MTDEQ's) certification ofits 2014 ambient air monitoring data for the Coburn Road 1-hour and maximum 5- minute sulfur dioxide parameters and the Libby 1-hour particulate matter with an aerodynamic diameter of 2.5 microns or less (PM2.5) parameter as required by Tide 40 Code of Federal Regulations Part 58.15. As summarized in the attached reports (AQS AMP600 andAMP450NC), MTDEQ's ambient air 

### concentration and quality assurance data for the time period ofJanuary 1, 2014, through December 31, 2014, are completely submitted to AQS. The concentration data are accurate to thebestofmyknowledge, takinginto considerationthequality assurance findings. Please be advised that MTDEQ will certify the remaining ambient air quality data as part of the required annualairmonitoring data certification schedule onorbeforeMay 1, 2015. Digital copies ofthis letterand the attachedreports are being senttoJoshua Rickard atthe office of EPA . 8.

BureauChief AirResources ManagementBureau 406-444-0286 dklemp@mt.gov

Steve Bullock, Governor I Tom Livers, Director I P.O. Box 200901 I Helena, MT 59620-0901 I (406) 444-2544 I www.deq.mt.govr

r-\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY User ID: DCXUENZLI CERTIFICATION EVALUATION AND CONCURRENCE Report .Request ID: 1286861 Report Code: AMP600 **GBOGRAPHIC,SELEC~IONS** Tribal Code State County Site Parameter POC City AQCR. 'CAR 30 111 0066 30 PROTOCOL SELECTIONS Parameter Classification CRITERIA CRITERIA Parameter Method 42401 88101

053 Duration 0018 I **AGEN~~IONS** -·--] Mt Dept Of Environmental Quality, Air Quality Division ---·

-- **~l** SELECTED OPTIONS I__ Option Type
Option Value MERGE PDF FILES

YES AGENCY ROLE CERTIFYING I DATE CRITERIA

I Start Date End Oat: 2014 2014 Selection Criteria Page
1 CBSA CSA EPA Region

**~** Jan. 15, 2015--,

"-" Data Evaluation and **C~urrence** Report Summary Jan. ,JOlS

Certification Year: 2014 Certifying Agency (CA): Mt Dept Of Environmental Quality, Air Quality Division (0730)
Pollutants in Report: Monitors Monitors Recommended for Monitors NOT Recommended

Parameter Name **~** Evaluated Concurrence by AQS for Concurrence by AQS

PM2.5 - Local Conditions Sulfur dioxide PQAOs In Report: PQAO Name 88101 42401

Mt Dept Of Environmental Quality, Air Quality Division Summary of 'N' flags for all pollutants: AQS Parameter PQAO Code AQS Site·ID POC

- - 1 1 1 1 PQAO Code TSA Date 0 0 Reason for AQS Recommendation

Signature of Monitoring Organization Representative: **7f'A>~~~~0...;-'7' ?2~~~=-----------------** 

Page 1 of 1 IData Evaluation and Concurrence Report for Gaseous Pollutants

Certifying Year Certifying Agency Code NPAP Audit Summary: 2014 Mt Dept Of Environmental Quality, Air Quality Division (0730)

Sulfur dioxide Mt Dept Of Environmental Quality, Air Quality Division (0730) 05/03/2013 Number of Valid Audits NPAP Bias Criteria Met

0

POC Monitor I Mean Min Max

ID Type 11-0066 1 SLAMS **~** u **~ ~**  \'-"' ,_;

Data Evaluation and Concurrence Report for Particulate Matter

Certifying Year:2014 Certifying Agency: Mt Dept Of Environmental Quality, Air Quality Division {0730}
PM2.5- Local Conditions {88101}

, .. ...,6u .. Name: Mt Dept Of Environmental Quality, Air Quality Division {0730}

Assurance Project Plan Approval Date: 05/03/2013 Collocation Summary PEP Summary #Sites #Sites % cv Criteria # #Audited #PEP #PEP % Criteria

Method # Sites !!!g Collocated Collocated §!! **~** Met? Methods Methods Required Submitted Complete i!!! M!!!

170 9 1 2 -15.51 16.49 y 2 0 8 0 0 y

183 6 1 1 8.65 10.47 y Routine Data (ug/m3) Monitor Exceed.Outller % %

I"'--_, ... ·- POCMethod 1m! !.!!!1 Min J!!! **~ ~**  Completej Bias Completej CV Complete Crit Mefrit. **Me~** &!P!:.j .E1!9. fl!s. ConcuG

8 3 170 SLAMS 9.35 -5.0 98.4 0 y s

I"C 

# " CD 

### ..J


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**~** 

## t:: 0 Q. 

# & c 0 

# ·- 1G :::s



# ~ 

# ) w "C 

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# )\__, User ID: DCKCENZLI Report Request ID: 1286873 Tribal Code PROTOCOL SELECTIONS State County 30 053 30 lll Parameter Classification Parameter Method Duration **~------------------~--------------~** 42406

88101 42401
ALL CRITERIA CRITERIA· UNITED STATES **ENVI~NTAL** PROTECTION AGENCY

Site 0018 0066 QUICKLOOK ALL PARAMETERS Report Code : AMP450NC GEOGRAPHIC SELECTIONS Parameter POC City AQCR UAR

I AGENCY **SELECT~-n--u** J

Mt Dept Of Environmental Quality, Air

Quality Division CBSA CSA EPA Region

I SELECTED OPTIONS II='' ---· SORT ORDER I

Option Type Option **Value~ Colu~** 

MERGE PDF FILES YES 1 STATE_CODE

EVENTS PROCESSING

AGENCY ROLE INCLUDE EVENTS PQAO 2 3 4 5 6 7 COtJNTY_CODE SITE_ID PARAMETER_CODE POC DATES EDT_ID **~I** Jan. 15, 2015

DATE CRITERIA j
Start Date End Date __ l APPLICABLE STANDARDS l Standard Description

2014 2014 Selection Criteria Page 1 PM25 24-hour 2013 S02 1-hour 2010**~** UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

AIR QUALITY SYSTEM QUICKLOOK ALL PARAMETERS EXCEPTIONAL DATA TYPES

[iDT -· DiSciiPTioN - I

0 NO EVENTS

1 EVENTS EXCLUDED

2 EVENTS INCLUDED

5 EVENTS WITH CONCURRENCE EXCLUDED ,-' \

\-.._/ Jan. 15, 2015 ,__;"---' Parameter Site ID: 30-053-0018 City: Libby
88101 PM2.5 - Local Conditions 88101 PM2.5 - Local Conditions **·-_~** UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

AIR QtmLITY SYSTEM QUICKLOOK ALL PARAMETERS

p

0 #

Cbs 1st Max 2nd Max 3rd Max

Unit c PQAO Year Meth Value Value value

County: Lincoln Address: 418 Mineral Ave Micrograms/cubic meter 3 0730 2014 170 8681 98.4 75.7 72.7

(LC)

Micrograms/cubic meter 3 0730 2014 170 365 48.6 39.1 28.2

(LC)

Site ID: 30-111-0066 City: Not in a city County: Yellowstone Address: CO:B'ORN HILL ROAD

42401 Sulfur dioxide 42406 S02 max s-min avg Parts per billion Parts per billion

Note: The * indicates that the mean does not satisfy summary criteria. l 0730 2014 100

1 0730 2014 100 7953 8197 Page 2 of 5 130.0 250.0 105.0 239.0 100.0 230.0 4th Max value 65.2 27.9 93.0 212.0 Arith. Mean 9.35 9.30 **·~** Jan. 15, 2015 Cert& @g

Duration Eval >i

1 HOUR s 2 24-HR :BLK s 2 AVG 16.45 l HOUR 7.85 1 HOUR s 0 s 0·-·· ..•......•. •·•··· .... ·-····· . - ---- ..... ······•••• .. - • **-···-······.-'-'>."--~·""'-"'-"="** ....... ----- ... -··--·-···--·····--·-·-

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

AIR QUALITY SYSTEM QUICKLOOK ALL PARAMETERS METHODS USED IN THIS REPORT

METHOD **~---- ~ARAMETER**  CODE COLLECTION METHOD **~YSIS** METHOD I

42401 100 INSTROMENTAL ULTRAVIOLET FLUORESCENCE

42406 100 INSTRUMENTAL ULTRAVIOLET FLUORESCENCE

88101 170 Met One BAM-1020 Mass Monitor w/VSCC Beta Attenuation

Note: The * indicates that the mean does not satisfy summary criteria. Page 3 of 5

''-"' \.._/ Jan. 15, 2015 -.._.)**~** UNITED STATES **ENVI~AL** PROTECTION AGENCY

AIR **Q~ITY** SYSTEM QUICI<LOOK ALL PARAMETERS PQAOS USED IN THIS REPORT

I'""" -= DSSORIPHOS I

0730 Mt Dept Of Environmental Quality, Air Quality Division

Note: The * indicates that the mean does not satisfy summary criteria. Page 4 of 5 0 Jan. 15, 2015

rUNITED STATES ENVIRONMENTAL PROTECTION AGENCY

AIR QUALITY SYSTEM QUICKLOOK ALL PARAMETERS CERTIFICATION **~UATION** AND CONCURRENCE FLAG MEANINGS Jan. 15, 2015

I FLAG MEANING I

M The monitoring organization has revised data from this monitor since the

most recent certification letter received from the state.

N The certifying agency has submitted the certification letter and required

summary reports, but the certifying agency and/or EPA has determined

that issues regarding the quality of the ambient concentration data cannot

be resolved due to data completeness, the lack of performed quality
assurance checks or the results of uncertainty statistics shown in the

AMP255 report or the certification and quality assurance report.

s The certifying agency has submitted the certification letter and required

summary reports. A value of "S" conveys no Regional assessment regarding

data quality per se. This flag will remain until the Region provides an "N" or

"Y" concurrence flag.

u Uncertified. The certifying agency did not submit a required certification

letter and summary reports for this monitor even though the due date has

passed, or the state's certification letter specifically did not apply the certification to this monitor.

X Certification is not required by 40 CFR 58.15 and no conditions apply to be

the basis for assigning another flag value

Y The certifying agency has submitted a certification letter, and EPA has no

unresolved reservations about data quality (after reviewing the letter, the

attached summary reports, the amount of quality assurance data
submitted to AQS, the quality statistics, and the highest reported concentrations) . Note: The * indicates that the mean does not satisfy summary criteria. \_.,.- **/-~** -..._./ Page 5 of 5 \.__,.1**~** UNITED STATES ENVIRm"-jAL PROTECTION AGENCY

User ID: SCG DESIGN VALUE REPORT

Report Request ID: 1286778 Report Code: AMP480 GEOGRAPHIC SELECTIONS

Tribal Code State County Site Parameter POC City AQCR

30 111 0066 PROTOCOL SELECTIONS Parameter Classification Parameter Method Duration
DESIGN VALUE 42401 SELECTED OPTIONS Option Type SINGLE EVENT PROCESSING WORKFILE DELIMITER USER SITE METADATA MERGE PDF FILES QUARTERLY DATA IN WORKFILE AGENCY ROLE DATE CRITERIA Start Date End Date
2014 2014 Option Value EXCLUDE REGIONALLY CONCURRED EVENTS STREET ADDRESS YES NO PQAO Selection Criteria Page 1 UAR CBSA CSA EPA Region APPLICABLE STANDARDS Standard Description S02 1-hour 2010 \ 0 Jan. 15, 2015UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

AIR QUALITY SYSTEM PRELIMINARY DESIGN VALUE REPORT

**~** 1. computed design values are a snapshot of the data at the time the report was run (may not be all data for year). Report Date: Jan. 15, 2015

2. Some PM2.5 24-hour DVs for incomplete data that are marked invalid here may be marked valid in the Official report due to additional analysis.

3. Annual Values not meeting completeness criteria are marked with an asterisk ('*'). Page 1 of 3

\_.., \._) v'-" \._I UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

AIR QUALITY SYSTEM PRELIMINARY DESIGN VALUE REPORT Design Value Year: 2014 .'---" Report Date: Jan. 15, 2015

Pollutant: Sulfur dioxide(42401) Standard Units: Parts per billion(OOB)
NAAQS Standard: S02 1-hour 2010 REPORT EXCLUDES MEASUREMENTS WITH REGIONALLY CONCURRED EVENT FLAGS.

Statistic: Annual 99th Percentile Level: 75 State Name: Montana

2014 I 2013 I 2012 3-Year

I

Comp. 99th Cert& I Comp. 99th Cert& 1 Comp. 99th Cert& I Design Valid

Site ID STREET ADDRESS I Qrtrs Percentile Eval 1 Qrtrs Percentile Eval 1 Qrtrs Percentile Eval I Value Ind.

30-111-0066 COBURN HILL ROAD 4 93 s 4 48 y 4 70 y 70 y

**~** 1. Computed design values are a snapshot of the data at the time the report was run (may not be all data for year).

2. Some PM2.5 24-hour DVs for incomplete data that are marked invalid here may be marked valid in the Official report due to additional analysis.

3. Annual Values not meeting completeness criteria are marked with an asterisk ('*'). Page 2 of 3FLAG MEANING UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

AIR QUALITY SYSTEM

PRELIMINARY DESIGN VALUE REPORT CERTIFICATION EVALUATION AND CONCURRENCE FLAG MEANINGS

M The monitoring organization has revised data from this monitor since the

most recent certification letter received from the state.

N The certifying agency has submitted the certification letter and required

summary reports, but the certifying agency and/or EPA has determined

that issues regarding the quality of the ambient concentration data cannot

be resolved due to data completeness, the lack of performed quality
assurance checks or the results of uncertainty statistics shown in the

AMP255 report or the certification and quality assurance report.

S The certifying agency has submitted the certification letter and required

summary reports. A value of "S" conveys no Regional assessment regarding

data quality per se. This flag will remain until the Region provides an "N" or

"Y" concurrence flag.

u Uncertified. The certifying agency did not submit a required certification

letter and summary reports for this monitor even though the due date has

passed, or the state's certification letter specifically did not apply the

certification to this monitor.

X Certification is not required by 40 CFR 58.15 and no conditions apply to be

the basis for assigning another flag value

Y The certifying agency has submitted a certification letter, and EPA has no

unresolved reservations about data quality (after reviewing the letter, the

attached summary reports, the amount of quality assurance data

submitted to AQS, the quality statistics, and the highest reported

concentrations) . Notes: 1. Computed design values are a snapshot of the data at the time the report was run (may not be all data for year). Report Date: Jan. 15, 2015

2. Some PM2.5 24-hour DVs for incomplete data that are marked invalid here may be marked valid in the Official report due to additional analysis.

3. Annual Values not meeting completeness criteria are marked with an asterisk ('*'). Page 3 of 3

"---'.

**~** ·-._/

# A Summaryof HistoricalAmbient

# S02 MonitoringintheBillingsArea
For 

# Billings-LaurelAirQualityTechnicalCommittee (BLAQTC) 700ExxonMobilRoad P.O. Box 1163 Billings, Montana59103

Preparedby: 

## BisonEngineering,Inc. 1400 11th

## Avenue Helena, MT 59601 (406)442-5768 www.bison-eng.com

February9, 2013

# EXECUTIVE SUMMARY
A review of the historical ambient air quality monitoring for sulfur dioxide (S02) in the Billings-Laurel area indicates a wealth of monitoring sites and data. Continuous monitoring for sulfur dioxide was established in the early 1970s and continues on today. The area has been heavily monitored over the past 4+ decades and has extended over a large geographical area (see Figure 2). Approximately 31 locations have been monitored over the years in this airshed. The monitoring overtime has served two purposes: 1) Measure concentrations within population areas; and 2) Establish and measure areas of high concentration Sulfur dioxide monitoring has been conducted at many sites throughout Billings, Laurel, and Lockwood targeting populous or population sensitive areas. At one time or another, S02 monitoring has been conducted at or near public schools, local businesses, major street intersections, city parks, county fairgrounds, etc. The preponderance of S02monitoring throughout the Billings/Laurel valley has targeted areas of high S02concentrations. Consistently and historically, the Coburn Road site has yielded the highest S02concentrations in the monitoring networks. Although the record is notwell documented, the Coburn Road site was chosen based on asulfation plate study (an objective screening method) and a general belief that areas abovethe valley floor, and near major industrial facilities, would be a prospective location for high concentrations. Dispersion modeling was also used to evaluate areas for high S02concentrations, but dispersion modeling has not proven to be a useful tool to predict high S02concentration. For example, the model did not predict Coburn Road as the highest S02concentration area. Sites that were established primarily based on dispersion modeling such as Sacrifice Cliff, Lower Coburn Board and Johnson Lane yielded lower concentrations than Coburn Road. Thus, Coburn Road appears to be the appropriate site to represent the highest concentrations in the airshed. The results of the entire monitoring effort, with one exception in the 1970s, indicate no violations of the National Ambient Air Quality Standards (NAAQS) as they have existed for the past 39 years (i.e., prior to the new 2010 1-hr S02 ambient standard). However, values were recorded in excess of the more stringent Montana Ambient Air Quality Standards (MAAQS). These values were resolved during the mid-1980s. No exceedances ofthese standards have been recorded since.

A Summary of Historical Ambient 802 Monitoring in the Billings Area Page 2 2/9/2013 

# )

)

# 1.0 INTRODUCTION The Billings-Laurel Air Quality Technical Committee (BLAQTC) has asked Bison Engineering, Inc. (Bison) to conduct a historical review of the 802 ambient air quality stations in the Billings/Laurel area. The purpose of the study will be to create a history that describes the ambient monitoring that has been conducted in Billings over the past 30+ 

### years. In particular, the study will further attempt to decipher the reasoning and rationale for the selection of some of the monitoring sites, especially sites targeting concentration areas. The Coburn Road site is selected for review to evaluate why this site is the appropriate 'high concentration' site forthis area. This compendium will provide evidence to the public, to the Montana Department of Environmental.Quality (MDEQ) and to the Environmental Protection Agency (EPA) asto why the Coburn Road site, and others, is most appropriately sited at a high 802 

### concentration area. The information is germane to the ongoing designation process before EPAforYellowstone County and Montana as a whole.

ASummaryof Historical Ambient 802 

### Monitoring in the Billings Area Page 3 2/9/2013

# 2.0 REFERENCEDOCUMENTS The following is a list of documents and information sources reviewed for this report. Copies of all of the referenced documents can be found in the Bison Engineering files. Other documents may exist in the files of MDEQ; however, they are stored off-site from MDEQ and are thoughtto be incomplete and difficult to access.
c STATE OF MONTANA- 2010 AIR MONITORING NETWORKASSESSMENT 

### ct MONTANAAIR MONITORING NETWORK REVIEW 2001 c MONTANAAIR MONITORING NETWORK REVIEW FOR 1996 o MONTANA 1986 NETWORK REVIEW e STATE OF MONTANA- AIR QUALITY CONTROL IMPLEMENTATION PLAN, 1979 c BILLINGS S02 

### STUDY- DATA ANALYSIS, MODEL VALIDATION AND SOURCE DETERMINATION, 1984 c MONTANAAIR QUALITY DATA & 

### INFORMATION SUMMARY FOR: 0 

### 1979-1980 0 

### 1982 0 

### 1983 0 

### 1984 0 

### 1985 0 

### 1986 0 

### 1987 0 

### 1988 & 

### 1999 o MONTANAAIR POLLUTION STUDY FINAL REPORT JUNE 1981 c Phone Interview: Mike Machler: Formerly of the Air Quality Bureau of MDEQ1 , 

### GeoResearch Inc., and Bison Engineering, Inc. 

### ct Phone Interview: Steve Duganz, formerly of Yellowstone County Health Department c Phone Interview, Bob Jeffrey, formerly of MDEQ, Air Quality Section 

### ct Phone Interview, Hoby Rash, MDEQ Air Quality Monitoring Section 

## n Personal Interview, Hal Robbins, formerly Air Quality Bureau Chief of MDEQ2, 

### currently at Bison Engineering, Inc.

1 The agencywas known as the Department of Health and Environmental Sciences atthis time. It was laterto becomethe Department of Environmental Quality. 2 1bid. A Summary of Historical Ambient S02 Monitoring in the Billings Area Page4 2/9/2013

# 3.0 EARLYS02MONITORINGHISTORY (UPTO
- 1980) There appears to be little surviving written information surrounding early S02 monitoring efforts (pre-1975). Brief oral histories were taken from people involved in these activities and were used in this reportto fill in some gaps. The surviving written history of S02 monitoring in Yellowstone County starts about 1974-75. The earlier written accounts have very little detail or resulting data collected. As time progresses, the available written reports become more detail oriented. The 1979 State of Montana Air Quality Control Implementation Plan reports 802 monitoring stations3 

### were installed and operating in Billings on January 1, 1972. The Plan also shows three S02bubblers operating in the Billings/Laurel area in 1975 (City Hall, Laurel and "Refinery Area"). The results from the monitoring showed compliance with the National Ambient Air Quality Standards (NAAQS), although problems were identified in Laurel, about 15 miles west-southwest of downtown Billings. The Plan also shows one continuous analyzer in operation in 1975, at "Sewage Treatment Plant E. on road to Fairgrounds, Billings."4 

### In addition, the Montana Department of Health and Environmental Sciences (the predecessorto MDEQ}, Yellowstone County and the Crow Tribe operated an extensive network of sulfation plates throughout the Billings-Laurel area.5 

### Although MDEQ knew thatthe sulfation plates were not "exact", airquality officials knew the plates provided an objective measurement of relative levels and trends of ambient S02 at many locations throughoutthe valley. In fact, there was a Montana Ambient Air Quality Standard for this pollutant during this time period. The standard was known as "Reactive Sulfur."6 

### These sulfation plates could be easily deployed and thus create a geographical picture of local trends. Little information was found on the time frames of operation, or results of the
3 The sampling methodology at that time used what was referred to as a "bubbler" sampler. This method was the official S02 reference method (per 40 CFR 50, Appendix A) until only a few years ago. The method bubbles ambient air through a liquid solution of potassium tetrachloromercurate (0.4 M) for typically 24 hours. The solution is then analyzed to determine ambient S02 concentrations. This method is sometimes referred to as the "Pararosaniline Method." 4 Although the document provides no details, it is assumed (from a past MDEQ employee) that this continuous analyzer operated on the principal of coulimetric titration and was manufactured by Beckman (Model 906A).
. 5 These "sulfation plates" are usually referred to as the "Huey Sulfation Plates." These plates, as far as can be determined, were invented by Norm Huey who was an air quality engineer who worked for EPA in the Region 8 office in Denver. These are static samplers in which a plastic petri dish was coated with a layer of PbO. The device was mounted outdoors and allowed to react with ambient S02to form PbS04• The samplerswere usually exposed to the atmosphere for about a month and then analyzed for S02 . More information may be obtained from the following publications: N. 

### A. Huey "The lead dioxide estimation of sulfur dioxide pollution," J. Air Poll. ControlAssoc. 18:610 (1968) and Paul E. Rider et at. "Studies of Huey Sulfation Plates at High Ambient S02Concentrations," J. AirPoll. ControlAssoc, 27:10, 1011-1013 (1977). 6 The standard was codified in 16-2.14(1)-S14040 (as was the rule structure at that time). A Summary of Historical Ambient S02Monitoring in the Billings Area Page 5 2/9/2013

## ,---\ sulfation plate network. Figure 

## 1 shows the network of sulfation plates in 

## 1986. From ) vague references, it appears that the sulfation plates operated from approximately 

## 1970 through 

## 1990. In 

## 1978, the Montana Air Pollution Study (MAPS) implemented an S02 monitoring network. The network consisted of four continuous analyzers which operated from 

## 1978-1980. The locations were Central Park, Lockwood School, 27'h and Montana, and Laurel Farm east of CHS (formerly Cenex). The Laurel site recorded exceedances of the NAAQS. This data, combined with previous analyzer data, resulted in a portion of the Laurel area (1 kilometer circle) being designated as non-attainment for 802 in 

## 1978.7 

### During this time period, no violations of the NAAQS were found at any other site. It 

### is worth noting that in accordance with a 

## 1977 stipulation8 

### between valley industries and MDEQ (DHES at that time); Cenex implemented some corrective measures aimed at bringing the area below the NAAQS. Once these efforts were concluded, no further violations of the NAAQS have been recorded. Starting in 

## 1980, better written accounts of S02 monitoring history have been made by the MDEQ. Section 4 provides more detail on this monitoring.

7 43 FR 8964 (3/3/78) and 43 FR 40427 (9/11/78) 8 This is reference to what is commonly referred to asthe "1977 Stipulation"which was between the major industries (CHS, Phillips 66, Western Sugar, ExxonMobil, MontanaSulphur & Chemical Co., and PPL) and MDEQ. A Summaryof Historical Ambient S02 Monitoring in the Billings Area Page 6 2/9/2013 

# )

' 

# ). .-·- (

-163- 

## Figure 1: SulfationPlateNetwork- 1986
A Summaryof Historical Ambient S02 Monitoring in the Billings Area Cl 0 0**~~** u 0:: 00**~~** _, UJ UJ :z: N 0:: o.n ::> UJ <CI- UJ -'<C 0:: .......

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Page 7 2/9/2013

# 4.0 MDEQBILLINGSMONITORINGHISTORY (-1978) The following history is a collection of excerpts from the STATE OF MONTANA - 

### 2010 AIR MONITORING NETWORK ASSESSMENT, and the MONTANA AIR MONITORING NETWORK REVIEW FOR 1996. Bob Jeffrey recounted specifically compiling the monitoring network histories for the state, as he thought they would be useful as a historical reference. The following paragraphs are taken from these reports, and specifically deal with S02monitoring in Yellowstone County. In preparing this "Summary of Historical Ambient S02 Monitoring in the Billings Area" document various comments and annotations are made as appropriate. "Yellowstone County The Billings/Laurelarea in Yellowstone Countyhas dealt with 

### 802issues forseveraldecades dating backto the beginning oflocalandMontana airqualityprograms in the 1960s. There is a long history of

### 802monitoring in the cities ofBillings and Laurel which are located in the Yellowstone River Valley, which runs southwest to northeast and has a major influence on the airflowin the area. To the west nearLaurel, the valley is approximately 12 miles wide but heading east the valley narrows and on the east edge of Billings, the sandstone cliffs or rimrocks result in a constriction that is approximately one mile wide and which channels the airflows. The majorindustrial

### 802sources are alllocatedin the Billings/Laurelarea along the river valley and, as a result, the nearby elevated terrain is often higher than the tallest smokestacks. ' 8 "Wind roses for the area reflect the orientation of the Yellowstone River Valley. The predominant winddirection is from the southwestandthe secondmostpredominantdirection is from the northeast; i.e., the wind flows up anddown the rivervalley. As with manyareas in Montana, the area experiences inversions in the fall and winter months which causes pollutants to become trappedand concentrated. The breakup ofthe temperature inversions rightaftersunrise can force those concentratedlayers of

### 802to the ground, resulting in high 

### 802concentrations beingmeasuredatthe groundlevelmonitoringstations." 

### While the observation offered by MDEQ has some validity, it seems that more recent data, at least, offers an equally valid alternative explanation. A review of the wind speeds and directions during periods of observed high concentrations at Coburn indicates that the high concentrations are more likely the result of convective air movement with perhaps some accumulation (but not always) from inversions or stable air masses aloft. 10 

### The reasoning is that if, indeed, inversion (thermal) breakups were the cause of some of these relatively higher concentrations (after sunrise) then such events would likely be accompanied by low wind speeds. A typical inversion break-up (associated with sunrise) is typically caused by the sun heating the ground. This causes some vertical movement in the atmosphere which brings concentrations of S02 in the

9 Notethat this is especiallytrue forthe Coburn site, the primarysubject of this report, and the Sacrifice Cliff site which is discussed later in this document. 10This is technically breaking upan inversion, but not in the moretraditional sense when coupling it with an assumed sunrise (solar heating). A Summary of Historical Ambient S02 Monitoring in the Billings Area Page 8 2/9/2013 

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# /) upper atmosphere (a few hundred vertical feet) down to the ground and thus breaks up the inversion. 11 

### Observed high concentrations at Coburn are almost always associated with medium strength wind speeds; between 8 and 12 mph. Such an event will, of course, break up an inversion, but it does so by moving the air from one location to another and mixing the air in the interim (from turbulence). Other times during relatively higher 

## 802 

### concentrations observed at Coburn Road, the wind was also blowing at a steady 8-12 mph from approximately 240 degrees. The Coburn Road 

## 802 

### monitor routinely records higher 

## 802 

### concentrations during this steady southwest wind pattern. That issue aside, MDEQ continues with their discussion of ambient monitoring. "There are seven major S02 sources in the Billings/Laurel area. In Billings, these include ExxonMobil (oil refinery), Phillips 66 (oil refinery), PPL-MT Corette (coal-fired electricpower generating facility), Western Sugar (coal-fired sugar beet factory), Yellowstone Energy LimitedPartnership (coke-fired cogeneration powerplant}, andMontana Sulphur& 

### Chemical (sulfur recovery facility). In Laurel, the majorsource is the Cenex Harvest States (CHS - oil refinery). Allofthese sources combinedcontribute to the S02in the Billings/Laurelairshed. In March 1978, 

### based on ambient air monitoring data, the Laurel area was designated nonattainment for S02. 12 In anticipation of the pending nonattainment designation, the Billings/Laurelindustries andthe State signeda stipulation requiring the industries to employ various controloptions in December 1977. 

### This stipulation was incorporatedinto the SIP, and it provided the framework to bring the area into compliance. The 1977 

### stipulation also commissioned the Department (with industrial funding) to conduct an ambient air quality study to more fully describe the magnitude and geographical extent of the S02 concentrations. Another major goal of the study was to identify the relative source contributions from each industrialsource." 

### Another related goal of the study was to investigate the validity of computer modeling in predicting concentrations at relevant sites. "In 1981-82, 

### the Department (through a cooperative effort with the industries) designedand installeda localS02 monitoring network. The networkconsisted ofeightS02 monitoringsites with meteorologicalmonitoring thatincludedupperairmeasurements from acousticradarand pilot balloons. Six of the S02 sites were in Billings and two were in Laurel. Using the monitoring data, the Department attempted to validate a mathematical modet 3 

### that could predict concentrations from the various S02 sources. The model failed for the following reasons:14 •a lackofgoodemissions data;

11 As the air mixes vertically, temperature no longer increases with increasing elevation and thus an inversion no longer exists. 12 The "area" referred to by MDEQ consisted only of a 1 kilometer circle around Tank 26 atthe CHS refinery. 13 This was, in fact, a "Gaussian" model. 14 The reader is reminded that these are MDEQconclusions. A Summary of Historical Ambient 

### 802 Monitoring in the Billings Area Page9 2/9/2013•high concentrations causedbyinversion breakup15anddirectplume impact which the modelcouldnothandle; •over-prediction ofplume rise bythe model; and •smallchanges in winddirection couldcause large differences inpredictedversus actual concentrations atreceptors locatedclose to the sources." 

### The reader is reminded that the conclusions above are those of MDEQ only and not the authors of this document.**·~** novel approach was developed using directional analysis and mass em1ss1ons to characterize source contributions to the annual average at the worst-case receptor (highest estimatedground-level S02 concentration). This was useful but could not be applied as a predictive toolforshort-term averages oratotherreceptors in the valley. Following the 1981-82 study, the S02 monitoring network was scaleddown in various stages until it reached a minimum early in 1987. As mentioned previously, eight S02 monitoring stations were in operation in 1982 during the S02 study. Following the conclusion of that study, the network was scaleddown to foursites in 1983. These included Coburn Road (30- 111-0066), Lockwood Park (30-111-0065), North Johnson Lane (30-111-0064} and Taft School (30-111-0064). Itshouldbe noted thatno sites were keptin the Laurelarea since the two sites In the 1981-82 study showed compliance with the NAAQS and MAAQS. The Department felt that greater emphasis was needed in the Billings/Lockwood area. In December 1983, the Taft School site was shut down to reduce the operator's workload in Billings. The network ofthree continued untilJune 1986 when a leasingproblem caused the Departmentto shutdown the North Johnson Lane site. In January 1987, the Departmentshut down its LockwoodParksite due to furthercutbacks ofpersonnelin the Billings office. Atthat time the network was reducedto a single site, Coburn Road, which has been the backbone of the network." 

### The Coburn Road site was chosen as what MDEQ describes as the "backbone of the network" because, based on opinion and experience Coburn was "the" monitoring site that yielded the most information for regulatory purposes. MDEQ clearly had an interest in monitoring in the Billings area for many reasons including population exposure. However, it was believed that if one continues to monitor at the "highest" reporting station and that station was reporting concentrations below the ambient standards, then it was reasonable to assume that the rest of the County was also below the ambient standard. "Following the 1987 Legislature session, a committee of the Billings/Laurel industries, the local chamberofcommerce, and airpollution professionals united to monitorand report on the area's air quality. The Billings/Laurel Air Quality Technical Committee (BLAQTC) was formed in the spring of 1987. The Department was a non-paying member ofBLAQTC and worked with the group on site selection, qualityassurance, andambientmonitoring. BLAQTC hireda contractor, purchased equipmentandinstalled three S02monitoring stations. Two of the sites were in Billings: Lockwood Park (30-111-1065) and Coulson Road (30-111-2004),

15 MDEQ believed that these high concentrations were caused by inversion break-up, but this was not necessarily a known fact. A Summary of Historical Ambient 

### 802 Monitoring in the Billings Area Page 10 2/9/2013 

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( 

# )

)and one in Laurel: Laurei-BLAQTC (30-111-00 16). By the end of 1987 the combined Department-BLAQTCnetworkconsistedoffive sites. 

### This organization known as "BLAQTC" continues today. Over time, the group has become a loose organization that primarily consists of six of the seven industrial facilities in the Billings/Laurel airshed. "The layout of the monitoring network remained the same until October 1989. Upon agreement between the Department and BLAQTC, the Scottish Rites site was moved to Ponderosa School (30-111-0076) and the Coulson Road site was moved to Brickyard Lane (30-111-2005). The group felt that the oldsites hadservedtheirpurpose andthathigherS02 concentrations might be found at the new sites. The EPA approved all of these sites in a letterdatedMay 14, 1990. On June 30, 1992, the Ponderosa Schoolsite was shutdown due to low readings. EPA approved this action in a letter dated June 22, 1992. The monitoring shelterfrom Ponderosa was movedandreplacedthe agingshelterat Coburn Road. Due to interest from EPA and environmental groups, in November 1988 the Department began collectingpeak5-minute S02 averages for each validhourofdata. 16Ata meeting with the Department and BLAQTC in February 1990, EPA offered two S02 analyzers to conduct peak monitoring in the range from 1 to 5 ppm. In September 1990, the Department and BLAQTC installed these monitors at the Coburn Road and Lockwood Park sites. These monitors collectedpeak 5-minute data for 6 months until March 1991. Peak data was also collectedatthe otherthree sites with analyzers in the range of0 to 1ppm. Aftercompletion of the study, an EPA contractor reviewed and analyzed the data but the results were not conclusive. The Departmentcontinued to collectpeak5-minute S02 data through 2003, but none was collected at the industry sites. It's worth noting that for calendaryear2002, the Departmentcollectedandreportednotjust the maximum 5-minute value in each hour, butall ofthe 5-minute values in each hour. In 1990, 

### E. H. Pechan andAssociates (Pechan) developedan S02 emission inventoryforthe Billings/Laurelarea. The final report, submitted to EPA in 1991, indicated a large difference between actual and potential S02 emissions for most sources. Also in 1990, the City of Billings contracted with GeoResearch Inc. to conduct an S02 dispersion modeling study for the Billings area utilizing recentlygatheredmeteorologicaldata andthe Pechan S02 emission inventory. The dispersion modeling results predicted violations ofthe S02NAAQSatboth the potentialto emitandmaximum actualemission rates." 

### The purpose of the study commissioned by the City of Billings was to identify areas in the city and its environs where new or expanding industry might be sited successfully. Given the use of emission rates (from the Pechan study) far beyond those reported in actual use, the study, not surprisingly, predicted ambient concentrations well beyond those actually observed at the monitoring sites. "The Department reviewed and refined the results of those latest modeling studies 17 and concluded additional S02 monitoring sites were needed. At the location of the modeled maximum S02 "hot-spot" the Department installed an S02 monitor. That max site, Sacrifice Cliff (30-111-0080), was approved by EPA effective May 19, 1993, and sampling began.
16 MDEQ does not mention in this summarythat the industries themselves, via BLAQTC, also participated in the collection of short-term (5 minute) data. 17 MDEQ is primarily referring to dispersion modeling studies conducted bythe "YELP-BGI"facility in support of its airquality permit application (1991 ). A Summary of Historical Ambient 

### S02 Monitoring in the Billings Area Page 11 2/9/2013Also, as a result ofthe permittingprocess, YELP-BGI was required to operate S02monitors at two other modeled "hot-spots" at Johnson Lane (30-111-2006) and Pine Hills (30-111- 2007). EPA approvedboth sites on March 

### 7, 1994, with data collection starting on November 2, 1993. Through 1996, the Sacrifice Cliffsite measuredthe highestS02concentrations in the Billings/Laurel monitoring network but a change to low sulfur coal at the YELP-BGI faciliti8 resulted in a dramatic drop in ambientS02concentrations. After the fuel switch, the Sacrifice Cliffsite consistently measuredlowerconcentrations than the values atCoburn Roadandthe Sacrifice Cliffsite was shutdown in June2001. 

### There are two items of note regarding DEQ's comments above. First, the agency states that the S02 concentration**drop~ed** 

### as a result of a fuel switch (to lower sulfur coal) at PPL-Montana's Corette station. 1 

### While indeed PPL emissions were reduced during this period, it is equally true that emissions from other industries also reduced their emissions as well. The emissions from the major nearby facilities during the same period (3 year average prior to 1996 versus the 3-year average beginning in 1996) were as follows: Emissions and Ambient Comparison 1993-1995 vs. 1996- 1998 

## Emissions a



### ·**~PL(Qqrett~)·** 

### ExxonMobil PhiUips66 CHS yYestern.Sugar MSCC 

# YSI:...Fl· Ambient Data b
Notes: 

## ··•·· GobtlrnRa·ad Sacrifice Cliff 1993-1995 725o··

__

## , ,-- 

### 10,300

1,800 5,100

470 3,500



## n/a··.• >.87 

### 61 1996-1998 

## 2 570

__:___

## ,
__ -.--, 

### 5,600 1,090. 3,150 140 

### 3,700 

## 2000·

. . 

## '

a. Emission values are in tons/year and are rounded for convenience 

### Difference 

# .;-65%

-46% -40% -39% 

### -70% +8%



# . !"l/a. -54% -46%
b. Ambient data units= ppb c. Ambient data averaging period= 2"d high 24-hourvalue (3-year average); consistent with one of the averaging period of the NAAQS at that time. d. Emission values are rounded for convenience e. YELP began operation in late 1995. 

### Second, a review of the dataduring this period shows that the Sacrifice Cliff data indeed yielded among the highest concentrations in the valley. On the other hand, the pre-1996 values were nearly identical to that of Coburn Road. Some statistics indicated pre-1996

18 This is an apparent error onMDEO's part. YELP-BGI does not combust coal. It is assumed that MDEQ was, orshould have been, referring to the Corette plant. 19 See footnote 

### above. MDEQ mistakenly refers to YELP-BGI when it should have stated PPL. A Summary of Historical Ambient S02 Monitoring in the Billings Area Page 12 2/9/2013 

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### Sacrifice Cliff as the highest concentration while others show that Coburn ranks higher. Regardless, the S02 concentrations at Sacrifice Cliff, after a short time, were reduced and thus the site no longer served its purpose. The site was no longer the highestreporting site and it (and Coburn Road) failed to show any values in excess of the ambient airquality standards. In order to characterize population exposure, BLAQTC installed an S02 analyzer at the Mount Olive site in late 1995. This was an already established air monitoring site that was measuring continuous carbon monoxide values. The site was located near the corner of 

## 241 h

### and Central Avenue, two majorthoroughfares in Billings. At about the same time, another station was started at Senior High School. This site was also established for population measurement coverage. The Senior High site included carbon monoxide and meteorological parameters (wind speed, wind direction and temperature). Due to measured concentrations well below the ambient air quality standards and values below Coburn Road, both sites were discontinued in 1997. Another monitoring site was installed near the Coburn Road site in 1999 in an attempt to find yet-higher reporting monitoring values than Coburn Road itself. The site was chosen, in part, from dispersion modeling data. This newsite was located about%miles from the Coburn site, at an elevation well below Coburn, but elevated from the valley floor. This became known as the Lower Coburn site. Monitoring continued here for about three years. Again, monitoring was discontinued since no exceedances of any ambient air quality standards were observed and.the monitored values were well below those measured at Coburn Road. MDEQ describes the next few years of monitoring below. As before, none of these sites, despite their geographical and population intent, yield ambient air quality values above ambient standards. All results remain well belowthose found at Coburn Road. (from DEQ) 

### 'To better document population exposure and monitor trends in the growing west end of Billings, the Mount Olive site (30-111-0079) was reopenedandmonitoringbegun forS02and CO in October2001. In July2001, S02monitoring was addedto the BridalShop CO site (30- 111-0082). The results from Mount Olive showed a substantial reduction in ambient S02 concentrations in the west endofBillings as compared to the earliermonitoring results from the late 1990s, so the Mount Olive site was shutdown in September2004. At the same time, a review ofthe S02 results from the Bridal Shop site indicated very low concentrations with the occasional elevated reading only when winds were blowing directly from the ConocoPhillips refinery, so the BridalShop site was shutdown in June2004. Since the 1980s, there has been substantial residentialandcommercialdevelopment on the high bench located above and northeast ofdowntown Billings. As the population in Billings Heights increased so did the number of complaints about air pollution. The "Heights" is locatedjust north ofseveral S02-emitting industrialsources in the Lockwood Park area, and given the frequency ofsouth winds during the summer months, the Department decided to A Summaryof Historical Ambient 

### 802 Monitoring in the Billings Area Page 13 2/9/2013installa newairmonitoring site to investigate thepublic's airpollution complaints. As a result, the Beartooth Elementarysite (30-111-0084) began collecting SOzdata in August2003. Over the next 3years, the site did monitora fewperiods ofelevated SOzbut they were ofshort duration and veryinfrequent, so the site was shutdown in December2006.20 As ofthis writinif1
, there are sixSOzmonitoringsites in the Billings/Laurelarea; two operated due to permit requirements (Johnson Lane and Pine Hills), three by BLATQC (Brickyard Lane, Lockwood Park, Laurel), and one by the Department (Coburn Road). Over the years, SOzhas been monitoredat31 locations in the Billings/Laurelarea. In summary, those sites, theirAIRScodes andyears ofoperation are as follows: •LockwoodSchoolBillings (30-111-0006), 1975-81 •LaureiBN(30-111-0015), 1981-82 •LaurelBLAQTC (30-111-0016), 1987-present • Hi-Ball Trucking (30-111-0035), 1974-75 •Division & Grand(30-111-0052), 1975 •2fh& Montana (30-111-0053), 1975-78 • CentralParkBillings (30-111-0059), 1978-81 •Metra ParkBillings (30-111-0061), 1981-82 • TaftSchoolBillings (30-111-0062), 1980-83 • Shawnee ParkBillings (30-111-0063), 1982 •North Johnson Lane DHES (30-111-0064), 1982-86 •LockwoodCountyParkDHES (30-111-0065), 1981-87 • Coburn Road(30-111-0066), 1981-present • Scottish Rites Billings (30-111-0073), 1987-89 •Ponderosa School(30-111-0076), 1989-92 •Mount Olive Billings (30-111-0079), 1995-97&2001-04 • Sacrifice Cliff(30-111-0080), 1993-2001 •BridalShop (30-111-0081), 2001-04 • LowerCoburn Road(30-111-0083), 1999-2003 •Beartooth Elementary (30-111-0084), 2003-06 •LaurelJr. High (30-111-1001), 1973 •Laurel WaterPlant(30-111-1005), 1976 •EastLaurel(30-111-1008), 1973-76 • LaurelEastFarm Cenex (30-111-1009), 1976-80 •LaurelNewFarm (30-111-1014), 1980-82

20 A cursory review ofthe data indicates that values at this site were about

### Ya ofthe values recorded at Coburn. Since Coburn was, itself, below the ambient air qualitystandards, the results did notjustify continued monitoring. 21 

### 2010. A Summary of Historical Ambient S02 Monitoring in the Billings Area Page 14 

### 2/9/2013 

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J • LockwoodParkBLAQTC (30-111-1065), 1987-present ·Coulson RoadBLAQTC (30-111-2004), 1987-89 • BrickyardLane BLAQTC (30-111-2005), 1989 -present •Johnson Lane YELP (30-111-2006), 1993-present • Pine Hills YELP (30-111-2007), 1993 -present • SeniorHigh (30-111-2008}, 1995-97 

### A map depicting the locations of all 31 monitoring stations is included here as Figure 2. The reader will observe that continuous ambient sampling for 

## S02 has occurred throughout the Billings-Laurel-Lockwood area. The sampling includes not only a wide geographical area; it also includes locations of high population density, public interest (schools), industrial activity, road intersections, and various elevations.

A Summary of Historical Ambient 802 Monitoring in the Billings Area Page 15 2/9/2013,.,,, l ,I • Hf.Boll **Truc~lng**

;1

I I .$

''---" - ... **--~** '" .·

It 'AiiiiJJt,

**~'** ·#- . ,. .. # f!'''"""' \._/ .. . **~:~~~** Ro,BEQ ,( . **;;,~** ··;;, l ·.··· **P~.!JMorrtana** . ,··· .. ·. ;·· .· **~ ~**  **~liff;''** .' v ..

. r· . **J.~** Sugar'''''; .,J,. ·· J ........

. ·:· .. **~** ' #' **·~--.** #'' ;.,,, **I,~** ; tl /, • J ..........

:- **~ Jr;.·\~**  ..,,..., • . ·i
./ . **~~** ........... - ''M . I

, I Figure 2

... Major Industries CUrrent S02 **Mon~ors**

• Historic S02 Monitors Monitoring Site Locations **~BISON** ENGINEERING; INC Sept2012 in the Billings/Laurel Area

0 0.5 2 Scale in Miles

1 inch= 1 mile Projection: UTM Zone 12, NAD83 /•\ 0 3

# 5.0 HISTORY OF COBURN ROAD MONITOR The written records of Billings ambient monitoring, Coburn Road in particular, have been reviewed. The records indicate an extensive effort by MDEQ, the county and the industrial sector to pick ambient monitoring stations that represented a plethora of purposes. Those purposes ranged from health study investigations such as the 1981 Montana Air Pollution Study, population exposure, special requests and peak impacts. A total of 31 sites, other than sulfation plate studies, have been monitoring since the early 1970s. The Coburn Road continuous S02analyzer was installed in 1981. In various forms, an ambient S02 analyzer has been operating atthat site ever since. Based on the review of the data no specific written record was found that describes the specific logic behind the location of the Coburn Road monitoring station. However, interviews from a number of persons who were involved, in one form or another, with eitherthe original site selection or its operation yielded some common recollections. Bob Jeffreyand Steve Duganz had similar recollections in their interviews, as follows: The sulfation plate network, previously described, was used to locate a station at Coburn Road. This was based, in part, on the fact that this location routinely recorded among the highest sulfation rates. In addition, the site also had three other attributes that are required to establish an ambient monitoring station: a cooperative landowner, (easy) access, and available power. In addition to the sulfation plate information, the site also represented an area above the valley floor. This site seemed intuitive to MDEQ since it was suspected that the prevailing southwest wind would yield elevated S02 concentrations from upwind industrial facilities. Bob Jeffrey recalled that the Coburn Road site was moved several times, and received new shelters several times. None of the moves was more than 100 yards from the current site. Some selected text from the MDEQ 1986 MONTANA NETWORK REVIEW about the Coburn Road site is copied here forfurther information. "8. The Coburn Road site is located on the top of a ridge which separates the city of Billings from the Lockwood area. The Conoco oil refinery, the Montana Power Co. Corette Plant, and the Western Sugar refinery are sulfur dioxide sources which are located on the Billings side of the ridge within two miles of the monitoring site. On the other side of the ridge in Lockwood are the Exxon oil refinery and the Montana Sulphur and Chemical Company. Both of these sulfur dioxide sources are approximately two miles northeast of the Coburn Road site. The site is at an elevation of 3380 feet MSLor approximately 280 feet above the surface of the Yellowstone Valley. Wind patterns at the Coburn Road site are somewhat different than at the other sites located within the valley. In general, the wind speed is 0.5 to 1.0 meter per second faster with a much
A Summary of Historical Ambient S02 Monitoring in the Billings Area Page 17 2/4/2013greater predominance from the west-southwest. Apparently, terrain features have much less effect on wind atthe Coburn Road site." "1

### 0. The department suspects that the Coburn Road site is located at an optimum elevation, so that during periods of multiple layered inversions, the plumes of the various sources are trapped in a layer at the same height. This might explain why sulfur dioxide concentrations at Coburn Road are generally higher and often do not follow the concentrations atthe othervalley locations. 11
. Since Coburn Road consistently records high sulfur dioxide concentrations, the department intends to continue to monitor sulfur dioxide at this location. In addition, the site will be the key site in determining the amount of sulfur dioxide control necessary at each plant." 

### In addition to those comments directly from MDEQ, Hal Robbins22 

### offered some of his thoughts and recollections of this site. He recalls reviewing and discussing the selection of the site with various agency staff. In particular he recalls that there were two primary factors that led to the selection of this site (beyond site access, power availability, etc.). The first, and most important, was the results of the sulfation network previously described in this document. The sulfation network included a large geographical area which helped narrow where the ideal maximum concentration site might be located. The sulfation network indicated that the Coburn Road area consistently showed either the highest or nearthe highest concentrations of measured ambient 802• 

### The second factorwas elevation. It was thought at the time that monitoring efforts in the valley may be useful, relative to population exposures and the geographical extent of the network, but the valley monitoring may not characterize the peak impacts. (MDEQ wanted, consistent with EPA policy, to be sure that the monitoring network included areas with the maximum concentration.) A site that was above the valley floor, and thus closer to stack height, coupled with high sulfation plate readings was thought to be a prudent location. Hal also recalls working with David (Dave) Maughan during this time period. Dave was in charge of special projects and conducted a number of investigations into the extent and nature of ambient readings. This included fluoride studies in Butte-Anaconda, 

## S02 

### mapping in Anaconda, lead (Pb) snow-deposition studies in East Helena, etc. Dave was involved in the sulfation plate analysis and selection discussions. The Yellowstone County Health Department played an important role in these discussions as well.

22 Hal was the Bureau Chief of the Montana Air Quality Bureau from 1980through 1987, worked in the air monitoring and dispersion modeling section ofthe agencyfrom 1975 to 1980, and was directly involved in the selection of Coburn as a high concentration site.
A Summaryof Historical Ambient S02 Monitoring in the Billings Area Page 18 2/4/2013 

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# 6.0 SUMMARYAND CONCLUSIONS This document has reviewed the historical ambientair quality monitoring for S02 in the Billings-Laurel area. The review has indicated a large number of monitoring sites have been in place over the past 40 years. The sites have included places on high terrain, low terrain, near schools, adjacent to major intersections, high population areas, low population areas, and near major industrial facilities. With one exception in the late 1970s, none of these monitoring sites yielded ambient concentrations above the National Ambient Air Quality Standards (NAAQS) as they existed priorto 2010. The siting of these stations was typically driven by a desire to capture the location that produces the highest concentration. However, in some cases, the monitoring was established to ascertain population exposure orfor aspecific study or request. As it regards siting a station at an area of highest concentration, a combination of passive monitoring (sulfation plate studies), professional judgment and dispersion modeling were employed. In retrospect, the sulfation plate study along with some professional judgment appears to have been the most successful means of achieving that goal. On a consistency basis, the Coburn site has recorded, and continues to record, the highest concentrations of S02 in the Billings airshed since it was installed in 1981; 32 years ago. This observation remains despite the fact that dispersion modeling has indicated other locations which should, according to the model, record higher concentrations. Modeling was used to site additional samplers (Lower Coburn, Sacrifice Cliff and others), but those stations did not record values higherthan Coburn Road. The geographical distribution (see Figures 1 and 2) coupled with the length of the monitoring periods has well characterized the concentration of S02 in the Billings-Laurel airshed.

A Summaryof Historical Ambient S02 Monitoring in the Billings Area Page 19 2/4/2013