OV

, 

W

990

July 11, 2011

Shawn M. Garvin (3RAOO)

Regional Administrator

United States Environmental Protection Agency

Region III

1650 Arch Street

Philadelphia, PA 19103-2029Dear Mr. Garvin:In late July and August 2010, fallen trees caused complete power loss and significant down-time at

the Delaware Brandywine air monitoring station (AQS ID 10-003-10 10). An extended power outage

resulted in no valid data being collected from July 21 through August 20, 2010. Other miscellaneous

issues resulted in smaller data loss on individual days in May and June 2010. The resulting total

valid data capture for 2010 at Brandywine was 85%. Previous year’s data capture was 95% for 2008and 79% for 2009, for a three year average 2008-2010 of 86%.

Section 2.3(b) of Appendix Ito 40 CFR Part 50 requires three consecutive years of data with data

availability of at least 90% on average, with a minimum data completeness in any one year of at least

75%. Furthermore, this section also states:

“... When computing whether the minimum data completeness requirements have been met,

meteorological or ambient data may be sufficient to demonstrate that meteorologicalconditions on missing days were not conducive to concentrations above the level ofthe

standard. Missing days assumed less than the level ofthe standard are countedfor the

purpose ofmeeting the data completeness requirement, subject to the approval ofthe

appropriate Regional Administrator.”Because the missing data occurred largely during mid-summer with associated high daily average

temperatures, meteorological data alone were not sufficient to estimate missing data below the

NAAQS. Delaware therefore performed a correlation analysis between the Brandywine site and

other local regional ozone monitors to demonstrate that a suitable linear regression equation with ahigh coefficient of determination could be used to generate estimated daily 8-hour ozone maxima for

the missing days in 2010.

The Delaware DNREC Division of Air Quality (DAQ) therefore determined that the use ofthe nulldata code, “BG”, for the following 26 days in 2010 is appropriate:

p

(

) 

Fax No.: (302) 739- 3106

RECEIVED

JUL 222011

Division Director (3APOO)

Printed on

Recycled Paper
5/27 1

5/30-31 2

6/14 1

7/25—7/27 3

7/29—8/9 12

8/12—8/16 5

8/18 1

TOTAL 26

Adding the 26 days to the Brandywine data results in a data capture percentage of 97% for 2010.

In July 2010, Delaware had performed a missing data analysis for 2009 data from the Brandywinesite (Data Substitution Analysis, 2009 Ozone, Brandywine AQS Site ID 10-003-1010, DE DNREC,

Division of Air Quality, July 15, 2010). Further review ofthe 2009 ozone monitoring data for the

Brandywine site and nearby regional sites indicated that there were a significant number of additionalmissing days likely to be below the NAAQS. To supplement the earlier analysis, Delaware expanded

the meteorological assessment for additional missing days in 2009.For 2009, analysis of meteorological conditions, precipitation records, and regional ozone maps

showed that 16 days were likely to represent low ozone concentrations for missing days at the

Brandywine monitoring site. In reviewing all the primary and supplemental information, 16 days arebeing proposed by Delaware as appropriate for the use ofthe null data code “BG” as listed below.

2009 Dates proposed for use of “BG”

5/14/2009

6/23/20096/30/2009

7/3/20097/4/2009

7/23/2009

8/6/2009

8/7/2009

8/13/20098/28/20098/29/2009

8/31/2009

9/1/2009

10/7/2009

10/9/2009

10/21/2009
—2010 for Brandywine would be 93%. This meets the minimum requirement of 90% as stated in 40

CFR Part 50 Appendix I Section 2.3(b).

Delaware DAQ has discussed this process and data review with Andrew Hass of EPA Region III.The data substitution analysis report and raw data on CD are attached. A revised 2009 and 2010

Delaware Data Certification package for the updated ozone data will also be submitted to EPARegion III.

Please feel free to contact Betsy Frey at 302-323-4542 if you have any questions.

Sincerely,

‘Au Mirza halili, P.E.

DirectorEnclosure

cc: Arnie Howell, EPA Region III

Walter Wilkie, EPA Region III

Andrew Hass, EPA Region IIIPauline Devose, EPA Region IIIDavid Lutz, Data Certification Contact, EPA (Mail Code C304-06)Ron Amirikian, DAQ

Betsy Frey, DAQJoe Martini, DAQ