UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION IX

75 Hawthorne Street San Francisco, CA 94105

November 1, 2010

Mr. Eric Stevenson

Director of Technical Services Bay Area Air Quality Management District

939 Ellis Street San Francisco, C A 9 4109

Dear M r. Stevenson :

Thank you for your submission of the 2009 Air Monitoring Network Review for the Bay Area Air Quality Management District ( BA AQMD)

, July 1, 2010

. We h a ve reviewed the

submitted document and have found that the plan is complete, i nformative, very detailed and meets all of the requirements for annual network plans as required by our regulations set forth

under 40 CFR P art 58 .10

. We also approve the closure of the Fremont site as requested in BAAQMD’s September 22, 2010 letter. As discussed in the September correspondence, Fremont has not measured exceedances of the NAAQS over the past 5 years. The Livermore station, also i n Alameda County, measures the same pollutants and shows similar or higher concentrations for all four polluta nts. BAAQMD will still exceed minimum monitoring requirements even without Fremont. There is therefore no monitoring regulatory requirement for monitoring at Fremont , and EPA approves discontinuation of monitoring activities at Fremont

. Additional futur e system modifications will require separate EPA approval, and w e will continue to work with your district to review system changes as they proceed.

We also want to thank you for your timely submission of the 2010 Air Monitoring Five

Year Assessment for t he Bay Area AQMD , as required under 40 CFR Part 58.10. We recognize that preparing the network assessment was a significant project and we appreciate your effort. We plan on providing feedback to all agencies on network assessments during the winter 2011

.

If you have any questions regarding this letter or the enclosed comments , please feel free to contact me at (415) 9 72

- 3851 or Gwen Yoshimura at (415) 9 47

- 4134

.

Sincerely,

/s/

Matthew Lakin, Manager Air Quality Analysis Off

ice

Air Division

Enclosure

cc: Glen Colwell, BAAQMDComments on 2009 Network Plan for Bay Area AQMD

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

- Minimum Monitoring Requirements: Minimum monitoring requiremen ts per 40 CFR 58 Appendix D are calculated based on MSA population and monitored values (design values, maximum monitored values) for the MSA. Future plans should show the highest monitored values for each MSA regardless of who operates the monitor, and list the resulting minimum monitoring requirements. Listing only monitoring data from monitors operated by BAAQMD results in confusion as to what minimum requirements apply. For example, Table 3 (page 12) lists Vallejo

- Fairfield with a population of
407, 234, a design value of 67 ppb, and 2 required monitors. 40 CFR 58 Appendix D,

Table D

- 2, indicates that areas with a population between 350,000 and 4 million require 1 monitor if the design value is less than 68 ppb, and 2 monitors if the design value is equal to or greater than 68 ppb. It is unclear whether Bay Area has listed a higher number of required monitors because a Yolo

- Solano

- operated monitor has a design value of 68 or over, or if Vallejo

- Fairfield in fact only requires 1 ozone monitor.

Perfor mance Evaluations: Livermore’s last annual performance evaluation (gaseous) is listed as 7/29/2008 (page 42). Point Richmond’s last performance evaluation is listed as 10/02/2008 (page 58). Please ensure that performance evaluations are conducted

annual ly for all sites and that the most current information is reflected in the network plan.

Changes Within the Next 18 Months: Monitor information for San Pablo (page 77) states that there will be changes within the next 18 months. There is no change descr ibed in the narrative. Please contact EPA for approval of any future changes to be made at this site.

PM2.5 Monitor Sampling Frequencies: At sites such as Concord (page 30), the sampling frequency of the primary and collocated PM2.5 monitors varies acco rding to the month, but the primary and collocated do not shift sampling frequency at the same time. Please explain why this is the case in your next network plan.

Monitoring Objective and Spatial Scale: Please explain why Oakland West (page 55) is

desc ribed as source impact, urban scale, for SO2.