UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX

75 Hawthorne Street

San Francisco, CA 94105

December 1, 2011

Eric Massey, Director

Air Quality Division

Arizona Department of Environmental Quality

1110 W. Washington St.

Phoenix, A rizona 85007

Dear Mr. Massey :

Thank you for your timely submission of the State of Arizona Air Monitoring Network Plan: For the

Year 2011 . We have reviewed the submitted document and have found that it is complete, informative,

very detailed and meets all of the requirements for annua l network plans as required by our regulations

set forth under 40 CFR Part 58.10. We specifically acknowledge the discontinuation of the Bethune

Elementary School PM 10 SPM per 40 CFR Part 58.20 (f). While this letter serves as official approval of

the annu al network plan, it does not constitute approval of the system modifications that are proposed in

the plan for the future. We will continue to work with your district to review system changes as they

proceed.

If you have any questions regarding this lett er or enclosed comments , please feel free to contact me at

(415) 972

- 3851 or Michael Flagg at (415) 9 72

- 3372

.

Sincerely,

/s/

Matthew Lakin, Manager

Air Quality Analysis Office

Air Division

Enclosure

cc: Theresa Rigney

, ADEQComments on 2011 State of Arizona Air Monitoring Network Plan

Please update next year’s annual network plan to reflect the following comments:

In order to better show that minimum monitoring requirements are being met, it would be

beneficial for Section 4.0 to contain a table summarizing the number of monitors required in

each of the six MSAs for each pollutant and the number of monitors operating within them

. The plan should discuss the monitoring delegation to other agencies in the State when assessing

PM 2.5 and PM 10 minimum monitoring requirements in the Phoenix

- Mesa

- Scottsdale and Tucson

MSAs.

Section 4.1: PM 2.5 Monitoring Network Requirements discusses the required sampling frequency

for all ADEQ

- operated PM 2.5 SLAMS sites. The information presented suggests numerous sites

throughout the State are not sampling at the required frequency. ADEQ sh ould implement the

required sampling schedules at the following sites: Douglas Red Cross, Flagstaff Middle School,

Nogales Post Office, Prescott Valley, and Yuma Supersite.

Section 4.2: PM 10 Monitoring Network Requirements discusses the required sampling f requency for all ADEQ PM 10 sites. The sampling frequency of PM 10 monitors should be based on the

“relative level of that monitoring site concentration ” , rather than the number of estimated

exceedances (40 CFR 58.12 (3)(e))

. EPA has interpreted this concent ration to be the design

concentration

, as discussed in Section 6.3 of the PM 10 SIP Development Guidance (EPA

- 450/2

- 86

- 001). The assessment of the required sampling frequency was performed with the appropriate

concentration levels in Table 4.2

- 2 of the 2010 network plan. ADEQ should reassess the required

sampling frequency for all PM 10 monitors using the appropriate methodology

. The NPAP and PEP audit monitor columns in Appendix C for O 3 and PM 2.5 , respectively, should

be updated to reflect current audit requirements (i.e. all SLAMS are required to participate in

PEP and NPAP).