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Technical Support Document

Monitors with Incomplete Data in the St. Louis Nonattainment Area for the  

2007‐2009 Monitoring Period

EPA has reviewed whether the St. Louis Nonattainment Area (the area) is meeting the 1997 fine

particulate matter (PM2.5) annual National Ambient Air Quality Standard (NAAQS).  The St. Louis area consists of

the counties of Franklin, Jefferson, St. Charles, and St. Louis, along with the City of St. Louis in Missouri and the

Illinois counties of Madison, St. Clair, and Monroe and a portion of Randolph County (Baldwin Township).  

According to regulations at 40 CFR §50.7 the 1997 annual primary and secondary PM2.5 standards are met when

the annual arithmetic mean concentration, as determined in accordance with 40 CFR Part 50, Appendix N, is less

than or equal to 15.0 μg/m3

.  The NAAQS is based on a 3‐year average of annual averages measured at a

monitoring site.  EPA’s review focused on the most recent three years of complete, quality‐assured data, i.e., 2007

to 2009.  For these years, a complete design value could not be generated for a number of sites in the area.  These

sites lacked three complete years of data for this period, since the State discontinued five monitoring sites and

started operating four monitoring sites during this period.  The Missouri monitors with incomplete data are located

in St. Louis County, the City of St. Louis, Jefferson County, and St. Charles County and the Illinois monitor with

incomplete data was located in Madison County. This technical support document discusses the reasons these

monitors did not record complete data during the 2007‐2009 monitoring period, their monitoring history, and how

this information supports the monitors with complete data in showing that the area is attaining the 1997 annual

PM2.5 standard.  In determining whether the area has attained the standard from 2007‐2009, EPA is thus proposing

to consider the history and recent data from monitors with incomplete data for this period as well as the monitors

having complete data.    

Data handling conventions and computations necessary for determining whether areas have met the

PM2.5 NAAQS, including requirements for data completeness, are listed in Appendix N of 40 CFR Part 50.  Data for a

monitor meet data completeness requirements when at least 75 percent of the scheduled sampling days for each

quarter of the calendar year have valid data.  The use of less than complete data is subject to the approval of the

EPA, which may consider factors such as monitoring site closures/moves, monitoring diligence and nearby

concentrations in determining whether to use such data as set forth at 40 CFR Part 50, Appendix N section 4.1(c).   

Although, as noted, certain monitors in the St. Louis area do not have complete data for the 2007‐2009 monitoring

period, EPA has reviewed historical certified data recorded both at discontinued monitors and at monitors that

started operation during the 2007‐2009 monitoring period and has found that the data and EPA’s evaluation of

monitoring history and monitoring diligence support its determination that the St. Louis area has attained the 1997

annual PM2.5 NAAQS.  Table 1 provides a list of monitors in the area that, for a variety of reasons, did not have

complete data for the 2007‐2009 monitoring period.

Table 1.  Monitors with incomplete data for the 2007‐2009 monitoring period

State County AQS ID Site Name Last 3 years of complete data

Illinois Madison 171190024 2100 Madison Ave. new site, started 07/01/2007

Missouri Jefferson 290990012 Arnold 2005‐2007

Missouri Jefferson 290990019 Arnold West new site, started 3/01/2008

Missouri Saint Charles 291831002 West Alton 2005‐2007
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Missouri Saint Louis 291892003 Clayton 2006‐2008

Missouri Saint Louis 291893001 Ladue new site, started 07/01/2009

Missouri St. Louis City 295100086 Margaretta 2004‐2006

Missouri St. Louis City 295100087 Mound St. 2006‐2008

Missouri St. Louis City 295100093 Branch St. new site, started 07/16/2007

   

As shown in Table 1, the Madison Ave. site (located in Illinois) as well as the Arnold West, Ladue , Oakville

and Branch St. sites (located in Missouri) could not be considered to have complete data, for purposes of

calculating a design value, because the monitors started operation after the beginning  of the 2007‐2009

monitoring period.  Even though a design value cannot be determined for each of these monitors, a review of each

of the monitors’ annual averages (given in Table 2) for the years that the monitors have been in operation (and

have complete data for those years) shows that the monitors are recording values consistent with attainment of

the 1997 annual PM2.5 NAAQS.  

Table 2.  Monitoring sites with incomplete date due to start‐up

State County AQS ID Site Name

Annual

Average

2007

Annual

Average

2008

Annual

Average

2009

Illinois Madison 171190024 2100 Madison Ave. NA 14.4 11.4

Missouri Jefferson 290990019 Arnold West NA 11.4 10.7

Missouri Saint Louis 291893001 Ladue NA NA 11.1

Missouri St. Louis City 295100093 Branch St. NA 13.4 12.0

The Arnold, West Alton, Clayton, Margaretta and Mound St. monitoring sites (all located in Missouri)

could not be considered to have complete data, for purposes of calculating a design value, since the monitors

discontinued operation during the 2007‐2009 monitoring period.  Even though a design value cannot be

determined for each of these monitors, a review of each of the monitors’ annual averages (Table 3) for the years

that the monitors had been in operation (and had complete data for those years) shows that the monitors were

recording values consistent with attainment of the 1997 annual PM2.5 NAAQS.  

Table 3. Monitoring sites with incomplete data due to discontinuance

State County AQS ID Site Name

Annual

Average

2007

Annual

Average

2008

Annual

Average

2009

Missouri Jefferson 290990012 Arnold   13.8 NA NA

Missouri Saint Charles 291831002 West Alton 13.2 NA NA

Missouri Saint Louis 291892003 Clayton 13.1 12.0 NA

Missouri St. Louis City 295100086 Margaretta NA NA NA

Missouri St. Louis City 295100087 Mound St. 14.3 12.7 NA

EPA’s review of historical data from these discontinued monitors showed that these monitors, with the

exception of the Mound Street monitor, had all recorded annual values in compliance with the NAAQS until the
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monitors were discontinued.  Table 4 provides the annual averages and the design values for each of these

monitors from 2001 until their discontinuance.  All values meet the 1997 annual PM2.5 NAAQS with the exception

of the Mound Street site.  The Mound Street monitor has met the standard with every three‐year design value

since 2001‐2003.  

Table 4.  2001‐2009 Annual average and 3‐year design values of discontinued monitors

Annual Average 3‐year Design Value

Site Name 2001 2002 2003 2004 2005 2006 2007 2008 2009

2001‐

2003

2002‐

2004

2003‐

2005

2004‐

2006

2005‐

2007

2006‐

2008

2007‐

2009

Arnold 14.5 15.1 13.9 12.6 15.4 12.6 13.8 NA NA 14.5 13.9 14 13.5 13.9 12.6 NA

West Alton 15 14 14 11.9 15.2 11.6 13.2 NA NA 14.3 13.3 13.7 12.9 13.3 NA NA

Clayton 13.9 14.6 13.6 12.2 15.5 11.8 13.1 12 NA 14 13.5 13.8 13.2 13.4 12.3 NA

Margaretta 14.2 14.3 13.5 12.1 15.3 12.5 NA NA NA 14 13.3 13.6 13.3 NA NA NA

Mound St. 15.4 15.8 14.7 13.6 15.9 13.7 14.3 12.7 NA 15.2 14.7 14.7 14.4 14.6 13.5 NA

According to 40 CFR § 58.14(c)(1) any PM2.5 State Local Air Monitoring Station (SLAMS) monitor that has

shown attainment during the previous five years, that has a probability of less than 10 percent of exceeding 80

percent of the applicable NAAQS during the next three years based on the levels, trends, and variability observed

in the past, and which is not specifically required by an attainment plan or maintenance plan may be discontinued

with EPA approval.  During the monitoring period from 2001‐2003, the Mound Street monitor recorded a violation

of the 1997 annual PM2.5 NAAQS.  Subsequent years of monitoring data (provided in Table 4), however, show

attainment of the standard until the monitor was discontinued in April 2008.  Although at the time of

discontinuance the Mound Street monitor had recorded values in excess of 80 percent of the 1997 annual PM2.5

NAAQS, the EPA’s review of the historical data recorded at the site indicated that monitor was not in jeopardy of

exceeding the standard, and thus EPA has determined that its discontinuance is appropriate.

Appendix E of 40 CFR Part 58 identifies the siting criteria requirements for PM2.5 SLAMS. The State of

Missouri determined that the Arnold, West Alton, and Margaretta sites no longer met the monitor siting criteria

requirements as listed in that appendix. According to 40 CFR §58.14(c)(4) a PM2.5 SLAMS monitor, which EPA has

determined cannot be compared to the relevant NAAQS because of the siting of the monitor in accordance with 40

C.F.R.§58.301

, may be discontinued.  The Arnold monitoring site was discontinued October 2007,  in accordance

with the provisions of 40 CFR §58.14(c)(4) due to excessive vegetative growth impeding airflow at the site causing

the site to no longer comply with the siting requirements outlined in 40 CFR Part 58 Appendix E.  A review of

                                                           

1 40 C.F.R. § 58.30   Special considerations for data comparisons to the NAAQS. (a) Comparability of PM 2.5 data. (1) There are two forms of the PM2.5NAAQS

described in part 50 of this chapter.  The PM2.5monitoring site characteristics (see appendix D to this part, section 4.7.1) impact how the resulting PM2.5 data can be

compared to the annual PM2.5NAAQS form.  PM2.5 data that are representative, not of area wide but rather, of relatively unique population‐oriented microscale, or

localized hot spot, or unique population‐oriented middle‐scale impact sites are only eligible for comparison to the 24‐hour PM2.5NAAQS.  For example, if the PM2.5

monitoring site is adjacent to a unique dominating local PM2.5 source or can be shown to have average 24‐hour concentrations representative of a smaller than

neighborhood spatial scale, then data from a monitor at the site would only be eligible for comparison to the 24‐hour PM2.5NAAQS. (2) There are cases where

certain population‐oriented microscale or middle scale PM2.5monitoring sites are determined by the Regional Administrator to collectively identify a larger region of

localized high ambient PM2.5 concentrations.  In those cases, data from these population‐oriented sites would be eligible for comparison to the annual PM2.5NAAQS.

(b) [Reserved]
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historical data recorded at the Arnold site showed that the monitor had recorded values meeting the NAAQS and

that its discontinuance was appropriate.

The West Alton site was discontinued, February 2008, in accordance with the provisions of 40 CFR

§58.14(c)(4), due to persistent flooding at the monitoring site causing the site to no longer comply with the siting

requirements outlined in 40 CFR Part 58 Appendix E.   A review of historical data recorded at the West Alton site

showed that the monitor had recorded values meeting the NAAQS and that its discontinuance was appropriate.

The Margaretta site was discontinued, June 2007,  in accordance with the provisions of 40 CFR

§58.14(c)(4) due excessive tree growth causing the site to no longer comply with the siting criteria requirements of

40 CFR Part 58 Appendix E. A review of historical data recorded at the Margaretta site showed that the monitor

had recorded values meeting the NAAQS and that its discontinuance was appropriate.

An allowance is made by 40 CFR §58.14(c)(6) for the discontinuance of a monitor, and moving it to a

nearby location (with the same scale of representation), if the monitor is not eligible for discontinuance under any

of the other criteria of 40 CFR §58.14 (c)(1) through (c)(5) and if logistical problems, beyond the State's control,

make it impossible to continue operation at its current site.  Due to the sale of the property where the Clayton site

was located (77 Hunter Avenue), the State of Missouri was forced to discontinue its operation in June 2009.  

However, in July 2009, the State of Missouri was able to initiate monitoring at the Ladue site (55 Hunter Avenue).  

The Ladue site is located approximately 100 meters from the previous location of the Clayton site and is

representative of the same scale. A review of historical data recorded at the Clayton site showed that the monitor

had recorded values meeting the NAAQS and that its discontinuance was appropriate.

EPA has found that the State of Missouri and the State of Illinois PM2.5 monitoring networks meet the

design criteria established at 40 CFR Part 58 Appendix D.  Appendix D requires each State to operate the minimum

number of required PM2.5SLAMS sites as listed in Table 5.   The required monitoring sites must be sited to

represent community‐wide air quality. The St. Louis area has a population of over one million people and a design

value over 85 percent of the annual PM2.5 NAAQS.  Based on the population estimate, and the design value for the

St. Louis area, Appendix D requires that a minimum of three monitoring sites be operated in the area.  The St. Louis

area has eight monitoring sites with complete data for the 2007‐2009 monitoring period so it exceeds the

minimum number of required monitoring sites. The States of Missouri and Illinois provide for adequate, diligent

monitoring of PM2.5 in the St. Louis area.

40 CFR Part §58.10 (a)(1) requires each State, by July 1 of each year, to adopt and submit to the Regional

Administrator an annual monitoring network plan which provides for the establishment and maintenance of an air

quality surveillance system that consists of a network of monitoring stations.   The plans are to include a statement

of purpose for each monitor and evidence that siting and operation of each monitor meets the requirements of

appendices A, C, D, and E of 40 CFR Part 58 where applicable. Regional Administrator Karl Brooks (Region 7)

approved the State of Missouri’s 2009 Annual Network Plan on September 23, 2010, and the State of Missouri’s

2010 Annual Network Plan on October 27, 2010 (http://www.epa.gov/region07/air/quality/quality.htm).  Loretta

Lehrman, Region 5 Air Monitoring and Analysis Section Chief, approved the Illinois 2008 Annual Network Plan on

March 4, 2008, and the Illinois 2010 Annual Network Plan on January 5, 2010.  

Table 5. PM2.5minimum monitoring requirements

MSA population2,3 Most recent 3‐year design value ≥85% of Most recent 3‐year design value <85% of

                                                           

2 Minimum monitoring requirements apply to the Metropolitan statistical area (MSA). 
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any PM2.5NAAQS4 any PM2.5NAAQS4,5

>1,000,000 3 2

500,000–1,000,000 2 1

50,000–<500,0006 1 0

The EPA evaluated air quality data from the St. Louis area and is proposing to determine that the area has

attained the 1997 annual PM2.5 NAAQS.  This determination is based upon complete, quality assured, quality

controlled, and certified ambient air quality data from the 2007‐2009 monitoring period.  This data shows that the

St. Louis area has monitored attainment of the 1997 annual PM2.5 NAAQS.  The EPA finds, based on its analysis of

data from monitors in the area that have incomplete data along with a review of preliminary 2010 data (which is

not yet certified), that the data supports the EPA’s determination that the St. Louis area monitors air quality in

attainment of the 1997 annual PM2.5 NAAQS.   

The EPA’s consideration of the incomplete data for the St. Louis area is consistent with 40 CFR Appendix N

section 4.1(c) and the requirements of 40 CFR Part 58.  After its review, the EPA determined that each of the

monitor discontinuances, relocations, and start‐ups is appropriate.  The EPA concludes that the incomplete data,

as described in this document, supports the EPA’s determination that area monitors air quality in attainment of

the standard.   

                                                                                                                                                                                               

3 Population based on latest available census figures. 

4 The PM2.5 National Ambient Air Quality Standards (NAAQS) levels and forms are defined in 40 CFR part 50. 5 These minimum monitoring requirements apply in the absence of a design value. 

6 Metropolitan statistical areas (MSA) must contain an urbanized area of 50,000 or more population