July 2 3 , 2012

Reply to

Attn Of: OEA

- 095

MEMORANDUM

SUBJECT: Mendenhall Valley PM 10 Limited Maintenance Plan Determination

FROM: Chris Hall

ECU Air Data Analyst , OEA

TO: Keith Rose

STAPU Air Planning Team, OAWT

Claudia Vaupel STAPU Air Planning Team, OAWT

Introduction At the request of the Air Planning Team in OAWT, I have conducted a Limited Maintenance Plan (LMP) review for the Mendenhall Valley PM 10 Non

- attainment Area ( NAA ) for calendar years 2007 through 2011. Based on a data quality and statistical analysis I have found that th e Mendenhall Valley PM 10 NAA meets the attainment and design value criteria necessary to qualify for the Limited Maintenance Plan option i

.

Background On September 16, 2010, EPA determined that the Mendenhall Valley PM 10 N AA attained the

PM 1 0 NAAQS as of December 31, 1995. Supporting this decision w ere data through December 31, 2009 , which show ed no exceedances of the standard

. I n order for EPA to re

- designate this

area to attainment there must be an approved Maintenance Plan in place. For the Mendenhall Valley A laska DEC i ntends to submit a Limited Maintenance Plan (LMP)

. To qualify for the LMP option the NAA in question must be attaining the PM 10 NAAQS

, and in the most simplistic

case, that the a verage Design Value ( A DV) must be below the LMP defined design value ( DV)

for both the 24

- hr and annual PM 10 standards ii

.

In February 2009, ADEC submitted to EPA a L MP for the Mendenhall Valley. U til izing data through December 31, 200 4, ADEC show ed that the NAA had been attaining the PM 10 NAAQS

and that the 24

- hr and annual A DV s were below the 24

- hr and annual LMP defined DV s. OAWT recently initiated a review of this submittal and

, bas e d on the 2001 LMP memo
,determined that the most recent five y ears of data needed to be used to calculate the annual and

24

- hr ADVs . Therefore the purpose of this review is to determine if the Menden hall Valley

PM 10 NAA would qualify for the LMP option based on a review of the most recent five years of

data

. Subsequent to the issuance of the 2001 LMP option memo, EPA revoked the annual PM 10 standard. 71 Fed. Reg. 61,114 (Oct. 17, 2006).

Data Requi rements

Se ction IV of the 2001 LMP guidance memo states that to qualify for the LMP option the area should be attaining the PM 10 NAAQS , the 24

- hr ADV must be below the 98 μ g/m 3 , and the

annual ADV must be below the 40 μ g/m 3

. As mentioned above EPA determined that the Mendenhall Valley NAA attained the PM 10 NAAQS based on data from the Floyd Dryden site as of December 31, 199 5.

Data Quality Review

PM 10 data through 2009 was previously reviewed for data quality to support the OAWT July 16, 2010, attainment determination for the Mendenhall Valley NAA . A data quality review of the most recent two years of data has a lso been performed and i s summarized here to support the LMP analysis

.

ADEC certified to EPA that the PM 10 data from these monitors in the AQS database is accurate. Data completeness was 97% and 100% for calendar years 2010 and 2011 respectively. In

addition each of the eight quarters had greater than 75% data completeness , thus the data meets

the completen ess criteria specified in §2.3(b) of 40 CFR 50, Appendix K.

Precision results met quality objectives where variation between the collocated PM10 samplers

was less than 10% in both 2010 and 2011. Monthly flow rate verification results showed that

both PM 10 samplers operated within the required specifications for these two years

. Quarterly audits were performed by ADEC QA staff with passing results.

Based on these quality control results the PM 10 data is of appropriate quality and is usable for

determini ng LMP eligibility for the 2007

- 11 timeframe.

Data Substitution

In the 2 nd quarter of 2008 data completeness was 73% with 4 missing sample days for the Floyd Dryden site. In the 3 rd quarter of 2009 PM 10 data completeness was much lower with 14 missing

da ys. For this LMP review, data substitution, following EPA regulation iii and guidance iv was utilized to determine a 24

- hr and annual ADV to compare to the respective LMP defined DVs.

The optimal source for data substitution is from a collocated monitor but as ADEC did not begin operation of a collocated PM 10 monitor at Floyd Dryden until October 2010, this is not a viable substitution option. The second option is to substitute the highest recorded value from the same quarter for the missing data points. T his high substitution value can be from any of the years within the data set of interest (i.e., 3 rd quarter 2007, 2008, 2009, 2010, or 2011).

For the 2 nd quarter 2008 the highest substitute value found was 27 μ g/m 3 which was recorded on May 20, 2010. For 3 rd quarter 2009 the highest substitute value found was 27 μ g/m 3 which wasrecorded on September 17, 2010. Substituting this value for the 4 missing days in 2008, and the

14 missing days in 2009, still yields an ADV of 45 μ g/m 3 for 2007

- 2011.

LMP De sign Value Computation Results

24 Hour PM 10 NAAQS

Four DV determination methods are provided within this section. Each method has value and

drawbacks individually , but as a group they can provide convincing evidence that an area is

either meeting or exceeding the 24

- hr LMP defined DV

. These methods are outlined in the EPA

‘ PM10 SIP Development Guideline ’, EPA

- 450/2

- 86

- 001, June 1987.

For calendar years 2007 through 2011 there are a total of 299 valid 24

- hr average data values.

The DV estimations provided below are for the totality of these five years rather than an average

of the three 3

- yr DV averaging periods. This approach was used due to the limited amount of data points over this 5 year timeframe.

Method 1

– E xponential Distribu tion The following equation is used to determine the A DV and is based on a fitted trend line plotted on a semi logarithmic graph for the data points of interest :

Equation 1:

Where a = slope of the line

e = 2.71828

Y = 1/365 = 0.00274

b = y intercept

x = Average Design Value (i data points) = A DV i

By solving E quation 1 for ‘x’ we get the following equation:

Equation 2: A DV i =

Equation 2 can now be used to determine a design value if the slope and y intercept are known.

The f ollowing are two similar A DV determinations for the Mendenhall Valley PM 10 data sets. The first determination uses all available data from 2007 through 2011 (299 data points). The

second determi nation uses only the top 10% of data points ( i.e. , the 30 highest concentration data points).

Chart 1 is the semi log graph of all 299 data points. The equation of the line, as auto determined by Excel, provides the needed slope and intercept values (a = 1.2662, b =

- 0.147). Substituting these into equation 2 gives us the following equation and A DV result.

Equation 3 : A DV 299 = = 41.74 = 42 μ g/m 3Chart 1

– 2007

- 11 Design Value Computation, 299 data points

Similarly using the values provided in Chart 2 we are able to determine the A DV for the upper 10% of data points (30 data points)

.

Equation 4 : A DV 30 = = 41.41 = 41 μ g/m 3

Chart 2

- 2007

- 11 Design Value Computation, 30 d ata points

Method 2

– Graphical Estimation

The second method provided in the 1987 PM10 SIP Development Guideline is the graphical

estimation method. This is a visual method that estimates the A DV by determining the intersection point of the data trend line and the 1/365 line. The intersection points and A DV estimates are provided in both charts by the red lines. In both charts the A DV is very close to 42

μ g/m 3

. Note that the determination of the slope of the trend line is subjective to a certain degree and as such leads to slightly varying A DV determinations. For the 2007

- 11 Mendenhall PM 10 data set these variations are inconsequential as the values are less t han have the LMP limit

.Method 3

– Upper 10% Tail Distribution

This method is a straight equation and only uses the high 10% of data values.

Equation 5: A DV = X 90 + 3.61828(U 90 - X 90 )

Where

X 90 = 90 th percentile value

U 90 = mean of the upper 10% of value s

For our data set X 90 = 17 and U 90 = 22.67. Solving the equation yields a n A DV of 38 μ g/m 3

.

Method 4

– Tab ular Estimation Method Lastly the fourth and the most straight forward A DV determination method is the T a bular

Estimation method (see table below)

. The Tab ular Estimation method is particularly useful in that it is the only method that allows for data substitution without sk ewing A DV results for the Mendenhall Valley.

No. of Daily Values Rank of Upper

Bound Rank of Lower

Bound Value Used for A 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

The Mendenhall Valley 2007

- 2011 PM 10 data set contains less than 347 data points therefore t he

A DV value is the highest data value using the Tabular Estimation method

. For Mendenhall Valley the highest value is 45 μ g/m 3

.

Annual PM 10 NAAQS

The A DV 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 is 8 μ g/m 3 , which is well below

the LMP defined DV of 40 μ g/m 3 . Substituting 27 μ g/m 3 for the 1 8 missing sample days for

2008 and 2009 raises this A DV to 9 μ g/m 3

.

Summary In summary each computational analysis described above show s that the 2007

- 11 PM 10 A DVs

for the Mendenhall Valley are well below the annual and 24

- hr LMP defined DVs

. Using the most conservative approach the 24

- hour A DV was found to be 45 ug/m3, and the annual A DV

was found to be 9 μ g/m 3

. Based on the data quality and statistical result s
, it has been shown that

the Mendenhall Valley NAA attains the PM 10 NAAQS for 2007

- 2011, and the design value for that period qualif

ies the Mendenhall Valley NAA for the LMP opti on

.

i ‘ LMP Option for Moderate PM 10 Non

- attainment Areas ’, August 9, 2001, as approved by Lydia Wegman designee,

ii An area may still qualify for the LMP option if it cannot meet these basic CDV criteria by meeting the site

- specific

CDV. Determination of the site

- specific CDVs was not necessary for this LMP analysis.

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

iv In thi s 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.