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, Arizona 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 annual 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 PM10 SPM per 40 CFR Part 58.20 (f). While this letter serves as official approval of 

the annual 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 letter or enclosed comments, please feel free to contact me at 

(415) 972-3851 or Michael Flagg at (415) 972-3372.

Sincerely,

/s/

Matthew Lakin, Manager

Air Quality Analysis Office

Air Division

Enclosure

cc: Theresa Rigney, ADEQ
Comments 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 

PM2.5 and PM10 minimum monitoring requirements in the Phoenix-Mesa-Scottsdale and Tucson 

MSAs. 

Section 4.1: PM2.5 Monitoring Network Requirements discusses the required sampling frequency 

for all ADEQ-operated PM2.5 SLAMS sites. The information presented suggests numerous sites 

throughout the State are not sampling at the required frequency. ADEQ should 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: PM10 Monitoring Network Requirements discusses the required sampling frequency 

for all ADEQ PM10 sites. The sampling frequency of PM10 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 concentration to be the design 

concentration, as discussed in Section 6.3 of the PM10 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 PM10 monitors using the appropriate methodology. 

The NPAP and PEP audit monitor columns in Appendix C for O3 and PM2.5, respectively, should 

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

PEP and NPAP).