September 13, 2012

Reply to Attn Of: OEA-095

MEMORANDUM

SUBJECT: Sandpoint PM 10 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 PM 10 Nonattainment Area (NAA). Based on statisti cal analysis I have found the Sandpoint PM 10 NAA to be meeting the attainment and design value cr iteria necessary to qualify for the Limited Maintenance Plan option i

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Background On December 14, 2011, the State (Idaho DEQ or IDEQ) submitted to EPA for approval the Sandpoint PM 10 LMP and requested that EPA re-designa te the Sandpoint NAA to attainment for the PM 10 NAAQS.

To qualify for the LMP option th e NAA must be attaining the PM 10 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 annual ii PM 10 standards iii (98 μ g/m 3 and 40 μ g/m 3 respectively). Utilizing data through December 31, 2008, IDEQ show ed that the NAA had been attaining the PM 10 NAAQS and that the 24-hr and annual ADVs for Sandpoint were below the 24-hr and annual LMP defined DVs (71 μ g/m 3 and 17 μ g/m 3 respectively).

The 2001 Lydia Wegman LMP memo i requires that the most recent five years of data be used to determine LMP eligibility. Theref ore the purpose of this review is to determine if the Sandpoint PM 10 NAA attains the PM 10 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 perfo rmed and found that both the Division Street and the Ontario Street PM 10 samplers met or exceeded specifie d criteria in 40 CFR 58 for bias, verifications checks and audits iv . Based on these results the Division/Ontario PM 10 data has been deemed to be of appropriate quality for dete rmining NAAQS attainment for years 2009-11 and LMP eligibility for the 2007-11 timeframe.

Data Completeness In the 2 nd quarter of 2007, and in the 4 th quarter of 2010, the Sandpoint PM 10 data did not meet the Part 50 Appendix K minimum complete ness criteria of 75%. In the 2 nd quarter of 2007, data completeness was 64% with 33 out of 91 sample days missing for the Division Street site. In the 4 th quarter of 2010, data completeness was 53% w ith 43 out of 92 sample days missing for the Ontario Street site.

To show NAAQS attain ment EPA regulation v allows for substitution in quarters with less than 75% but greater than 50% data completeness if approved by the Regi onal Administrator and following EPA guidance vi . 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 prefer ably from a collocated monitor but as neither the Division Street nor the Ontario Street sites had a collocated monitor fo r years 2007-11 this is not an available substitution option. The opti on used was to substitute the highest recorded value for the missing data points. This high s ubstitution value can be from any of the years within the data set of interest but mu st be from the same quarter (i.e., 3 rd quarter 2007, 2008, 2009, 2010, or 2011).

For the 2 nd quarter of 2007 the highest subst itute value was found to be 65 μ g/m 3 recorded on June 1, 2009. This value of 65 μ g/m 3 was substituted for each of the 33 missing days in the 2 nd quarter of 2007, in computing the 24-hr and annual LMP DVs for 2007-11.

For the 4 th quarter of 2010, the highest subs titute value was found to be 46 μ g/m 3 recorded on December 6, 2009. This value of 46 μ g/m 3 was substituted for each of the 43 missing days in the 4 th 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 PM 10 standard was revoked effectiv e December 18, 2006, this document discusses only attainment for the 24-hour PM 10 standard. To show attainment for the 24-hour PM 10 NAAQS the 3 most recent years of data must be below 1.0 Expected number of Exceedances (EE) per the criteria establishe d in Appendix K to 40 CFR Part 50. Three consecutive years of complete data is needed to make an affirm ative 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 Stre et and the Ontario Street sites met this completeness requirement with the exception of 4 th quarter 2010. One exceedance of the 24- hour standard was recorded on August 26, 2010. By substitution 46 μ g/m 3 for the 43 missingdays 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 Sa ndpoint NAA is not violating the PM 10 NAAQS over the most recent 3 years.

LMP Design Value Computation Results

24 Hour PM 10 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 convinc ing evidence that an area is ei ther meeting or exceeding the 24-hr LMP defined DV. For purpos es 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 st atistical approach only takes into account the high 10% concentration values which are the most important when determining an ADV. The advantage of the Tabul ar Estimation method is that it does not require any data computations. Both methods allow for data substitution wh ich 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 fo r computing these two ADV statistics.

– Upper 10% Tail Distribution This method is a straight st atistical equation derived by EP A/OAQPS and only uses the high 10% of data values.

Equation 1: ADV = X 90 + 3.612(U 90 - X 90 ), where for the Sandpoint sites X 90 = 90 th percentile value = value 169 = 29.0 μ g/m 3

U 90 = mean of the upper 10% of values = 40.5 μ g/m 3 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 μ g/m 3

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– 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 ValueUtilizing the Tabular Estimation table above a nd based on a total of 1759 data points the 2007- 2011 DV value would be the si xth highest value or 65 μ g/m 3 (see below).

Monitor ID A rithmetic Mean Collection Date Ran k 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 PM 10 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 aver age concentration, incl uding substitution on 76 days, is 16 μ g/m 3 for Sandpoint. This ADV is well below the LMP defined upper limit of 40

μ g/m 3

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Summary In summary each computational method de scribed above shows that the 2007-11 PM 10 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 μ g/m 3

. Based on the data quality and statistical results, the Sandpoint NAA meets the attainment and design value crit eria to qualify for the LMP option.

i Memorandum from Lydia Wegman, Director AQSSD ‘LMP Option for Moderate PM 10 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 canno t meet these basic CDV criteria by meeting the sitespecific CDV. Determination of the site-specifi c CDVs was not necessary for this LMP analysis.

iv Region 10 also determined that the PM 10 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.