September 13, 2012 

Reply to 

Attn Of: OEA-095 

MEMORANDUM

SUBJECT: Sandpoint PM10 NAAQS and LMP Determination 

FROM: Chris Hall 

 ECU Air Data Analyst, OEA 

TO: Kristin Hall 

 STAPU Air Planning Team, OAWT 

At the request of the Air Planning Team in OAWT, I have conducted both a NAAQS attainment 

determination and a Limited Maintenance Plan (LMP) review for the Sandpoint PM10 Nonattainment Area (NAA). Based on statistical analysis I have found the Sandpoint PM10 NAA to 

be meeting the attainment and design value criteria necessary to qualify for the Limited 

Maintenance Plan optioni

. 

 

Background 

On December 14, 2011, the State (Idaho DEQ or IDEQ) submitted to EPA for approval the 

Sandpoint PM10 LMP and requested that EPA re-designate the Sandpoint NAA to attainment for 

the PM10 NAAQS. 

To qualify for the LMP option the NAA must be attaining the PM10 NAAQS, and in the 

simplistic case, the Average Design Value (ADV) must be below the LMP defined design value 

(DV) for both the 24-hr and annualii PM10 standardsiii (98 μg/m3

 and 40 μg/m3 respectively). 

Utilizing data through December 31, 2008, IDEQ showed that the NAA had been attaining the 

PM10 NAAQS and that the 24-hr and annual ADVs for Sandpoint were below the 24-hr and 

annual LMP defined DVs (71 μg/m3

 and 17 μg/m3 respectively). 

The 2001 Lydia Wegman LMP memoi requires that the most recent five years of data be used to 

determine LMP eligibility. Therefore the purpose of this review is to determine if the Sandpoint 

PM10 NAA attains the PM10 NAAQS for 2009-11 and to determine if the LMP option is an 

available option for IDEQ based on a DV analysis for years 2007 through 2011. 
Data Quality Review 

A data quality review of the 2007-11 data was performed and found that both the Division Street 

and the Ontario Street PM10 samplers met or exceeded specified criteria in 40 CFR 58 for bias, 

verifications checks and auditsiv. Based on these results the Division/Ontario PM10 data has been 

deemed to be of appropriate quality for determining NAAQS attainment for years 2009-11 and 

LMP eligibility for the 2007-11 timeframe. 

Data Completeness 

In the 2nd quarter of 2007, and in the 4th quarter of 2010, the Sandpoint PM10 data did not meet 

the Part 50 Appendix K minimum completeness criteria of 75%. In the 2nd quarter of 2007, data 

completeness was 64% with 33 out of 91 sample days missing for the Division Street site. In the 

4th quarter of 2010, data completeness was 53% with 43 out of 92 sample days missing for the 

Ontario Street site. 

To show NAAQS attainment EPA regulationv

 allows for substitution in quarters with less than 

75% but greater than 50% data completeness if approved by the Regional Administrator and 

following EPA guidancevi. For this review data substitution was utilized to compute the 24-hour 

NAAQS DV and the 24-hr and annual LMP ADV. 

The optimal source for data substitution is preferably from a collocated monitor but as neither 

the Division Street nor the Ontario Street sites had a collocated monitor for years 2007-11 this is 

not an available substitution option. The option used was to substitute the highest recorded 

value for the missing data points. This high substitution value can be from any of the years 

within the data set of interest but must be from the same quarter (i.e., 3rd quarter 2007, 2008, 

2009, 2010, or 2011). 

For the 2nd quarter of 2007 the highest substitute value was found to be 65 μg/m3 recorded on 

June 1, 2009. This value of 65 μg/m3

 was substituted for each of the 33 missing days in the 2nd

quarter of 2007, in computing the 24-hr and annual LMP DVs for 2007-11. 

For the 4th quarter of 2010, the highest substitute value was found to be 46 μg/m3

 recorded on 

December 6, 2009. This value of 46 μg/m3

 was substituted for each of the 43 missing days in the 

4th quarter of 2010, for computing both the NAAQS expected number of exceedances for 2009-

11 and the 24-hr and annual LMP ADVs for 2007-11. 

NAAQS Attainment 

Because the annual PM10 standard was revoked effective December 18, 2006, this document 

discusses only attainment for the 24-hour PM10 standard. To show attainment for the 24-hour 

PM10 NAAQS the 3 most recent years of data must be below 1.0 Expected number of 

Exceedances (EE) per the criteria established in Appendix K to 40 CFR Part 50. Three 

consecutive years of complete data is needed to make an affirmative attainment determination. 

A year is deemed complete if each of the four quarters has at least 75% data completeness. 

For calendar years 2009 through 2011, the Division Street and the Ontario Street sites met this 

completeness requirement with the exception of 4th quarter 2010. One exceedance of the 24-

hour standard was recorded on August 26, 2010. By substitution 46 μg/m3 for the 43 missing 
days in 2010, the Sandpoint EE for 2009-11 is computed to be 0.33 for the 2009-11 timeframe. 

As the EE value is below 1.0 the Sandpoint NAA is not violating the PM10 NAAQS over the 

most recent 3 years. 

LMP Design Value Computation Results 

24 Hour PM10 NAAQS 

There are multiple DV determination methods provided in the EPA ‘PM10 SIP Development 

Guideline’, EPA-450/2-86-001, June 1987. Each method has value and drawbacks individually 

and as a group can provide convincing evidence that an area is either meeting or exceeding the 

24-hr LMP defined DV. For purposes of this analysis the Upper 10% Tail Distribution method 

and the Tabular Estimation methods are utilized. 

The advantage of the Upper 10% Tail Distribution method is that this statistical approach only 

takes into account the high 10% concentration values which are the most important when 

determining an ADV. The advantage of the Tabular Estimation method is that it does not require 

any data computations. Both methods allow for data substitution which is necessary for 

incomplete data sets. 

The 24-hr and annual ADV computations provided below utilize data from the full five years 

rather than a running average of the three 3-yr DV averaging periods. Using the full five years 

provides a larger and more robust data set for computing these two ADV statistics. 

– Upper 10% Tail Distribution 

This method is a straight statistical equation derived by EPA/OAQPS and only uses the high 

10% of data values. 

Equation 1: ADV = X90 + 3.612(U90 - X90), where for the Sandpoint sites 

X90 = 90th percentile value = value 169 = 29.0 μg/m3

U90 = mean of the upper 10% of values = 40.5 μg/m3

Total Data points = 1759 including 76 substituted values for missing days 

Solving equation 1 with the provided values yields a 24-hr ADV of 72 μg/m3

. 

– Tabular Estimation Method 

The Tabular Estimation method is simply a table which tells you which data value to use as your 

ADV and is dependent on the total number of data values in your data set. 

No. of Daily Values Rank of Upper 

Bound 

Rank of Lower 

Bound Value Used for LMP DV 

≤ 347 - 1 Highest Value 

348 to 695 1 2 Second Highest Value 

696 to 1042 2 3 Third Highest Value 

1043 to 1390 3 4 Fourth Highest Value 

1391 to 1738 4 5 Fifth Highest Value 

1739 to 2086 5 6 Sixth Highest Value 
Utilizing the Tabular Estimation table above and based on a total of 1759 data points the 2007-

2011 DV value would be the sixth highest value or 65 μg/m3 (see below). 

Monitor ID Arithmetic Mean Collection Date Rank

16-017-0005- 166 26-Aug-2010 1

16-017-0005- 132 19-Aug-2009 2

16-017-0004- 78 18-Aug-2008 3

16-017-0005- 72 3-Aug-2009 4

16-017-0005- 65 27-Jul-2009 5

16-017-0005- 65 1-Jun-2009 6

Annual PM10 NAAQS 

The ADV for the annual standard is simply the arithmetic mean of all the daily values within the 

data set. For the 2007-11 timeframe the average concentration, including substitution on 76 

days, is 16 μg/m3 for Sandpoint. This ADV is well below the LMP defined upper limit of 40 

μg/m3

. 

Summary 

In summary each computational method described above shows that the 2007-11 PM10 ADVs for 

the Sandpoint NAA are well below the annual and 24-hr LMP defined DVs. Using the most 

conservative approach the 24-hour ADV was found to be 72 ug/m3, and the annual ADV was 

found to be 16 μg/m3. Based on the data quality and statistical results, the Sandpoint NAA meets 

the attainment and design value criteria to qualify for the LMP option. 

 

i

 Memorandum from Lydia Wegman, Director AQSSD ‘LMP Option for Moderate PM10 Non-attainment Areas’, 

August 9, 2001. 

ii Subsequent to the issuance of the 2001 LMP Option memo, EPA revoked the annual PM10 standard. 71 Fed. Reg. 

61,114 (Oct. 17, 2006). 

iii An area may still qualify for the LMP option if it cannot meet these basic CDV criteria by meeting the sitespecific CDV. Determination of the site-specific CDVs was not necessary for this LMP analysis. 

iv Region 10 also determined that the PM10 data from the Sandpoint monitors met quality criteria through December 

31, 2009 in the NAAQS attainment determination rulemaking dated June 22, 2010 (75 FR 35302). 

v

 See 40 CFR Part 50, Appendix K, §2.3(b) 

vi In this case we follow the EPA ‘Guideline on Exceptions to Data Requirements for Determining Attainment of 

Particulate Matter Standards’ EPA 450/4-87/005, April 1987.