UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX

75 Hawthorne Street

San Francisco, CA 94105

November 1, 2011

Donald Gabrielson, Director

Pinal County Department of Development Services

Air Quality Control District

P.O. Box 987

Florence, A rizona 85232

Dear Mr. Gabrielson:

Thank you for your timely submission of the Pinal County 2011 Annual Monitoring Network Plan and

2010 Data Summary . We have reviewed the submitted document and have found that it is complete,

informative, very detailed and meets all of the requirements fo r annual network plans as required by our

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

Maricopa County Complex Ozone and Combs School Ozone SPM s per 40 CFR Part 58. 2 0 (f). While

this letter serves a s official approval of the annual network plan, it does not constitute approval of

system modifications that may take place in the future. Also, approval of the Riverside Maintenance

Yard and Mammoth County Complex PM 10 monitor shutdowns will be addressed in separate

correspondence. 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) 9 72

- 3372

.

Sincerely,

/s/

Matthew Lakin, Manager

Air Quality Analysis Office

Air Division

Enclosure

cc: Mike Sundblom , PCAQCD

Kale Walch , PCAQCDComments on 2011 Annual Monitoring Network Plan and 2010 Data Summary

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

T he sampling frequency for the Cowtown PM 2.5 monitor should be included in Table 3.9: PM 2.5 Sampling Frequency. The plan indicates that the Cowtown monitor, which determines the design

value for the area, is not meeting the monitoring frequency requirements of 40 CFR Part 58.12

(d)(1). While the plan discusses the possibility of maintaining an FDMS TEOM to measure daily

PM 10 and PM 2.5 in the future, changes to the sampling frequency should be made as soon as

possible in order to ensure compliance with 40 CFR Part 58.12 (d)(1).

While 40 CFR Part 58.20 states that SPM monitors may not be used to show compliance with the

minimum monitoring requirements, SPM monitors should be included in the assessment of the

number of minimum monitors that are required. For example, the Cowtown PM 2.5 design value

should be included in the analysis in Table 3.8: Minimum Monitoring Requirements for PM 2.5 , as

data from thi s monitor are valid for comparison to the PM 2.5 NAAQS per 40 CFR 58.20 (c).

Similarly, PM 10 SPMs operating more than 24 months should also be considered in assessing

minimum PM 10 monitoring requirements.

The Casa Grande Downtown information in Appendix B s hould be updated to match recent

changes to the network that were identified in Section 5.0: Proposed Changes to the Network

Specifically, the method code (126) and classification (SPM) need to be updated to 079 and

SLAMS, respectively.

It would be helpful and very informative if the site descriptions in Appendix B indentified the

POC number for each instrument.