UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION IX 75 Hawthorne Street San Francisco, CA 94105-3901 

# MAY 02 2016

Ms. Karen Magliano Chief, Air Quality Planning and Science Division California AirResources Board 1001 I Street, P.O
. Box 2815 Sacramento, California 95812 DearMs. Magliano: This letter provides the U
.S
. Environmental Protection Agency's (EPA's) review and approval for the California AirResources Board's (CARB's) relocation ofthe ozone (03 ) State/Local AirMonitoring Station (SLAMS) monitor at the Arvin -BearMountain site (Air Quality System (AQS) Site ID: 06-029- 5001) to the proposed Arvin- DiGiorgio site (AQS Site ID: 06-029-5002) in Kern County, California. On April 29, 2016, CARB sent a letter to EPA with a description ofthis network change
. In this letter, CARB explained the need to relocate the Arvin

- Bear Mountain 0 3monitor due to logistics beyond the state's control (i
.e., expiration ofthe property lease). Per 40 CFR 58.14, monitoring agencies are required to obtain EPA approval for the relocation ofSLAMS monitors
. EPA has reviewed CARB's relocation request for the Arvin

- BearMountain site against criteria contained in 40 CFR 58.14(c)(6) and approves this request as described below
. Overview ofArvin

- Bear Mountain Relocation History In July 2009, the Arvin-Edison Water Storage District notified CARB that it was letting the lease that allowed CARB to operate the Arvin

- Bear Mountain site on the Water District's property expire on August 31 , 2009. The Water District directed CARB to remove its equipment from the site by that date, despite efforts by both CARB and San Joaquin Valley Air Pollution Control District (SJVAPCD) to negotiate with the Water District to keep the Arvin- Bear Mountain site in operation. CARB immediately initiated a search process for potential replacement site locations that were as nearby as practical considerations allowed, which is described in detail in their request letter, but generally included: selecting the criteria that would be used to evaluate an appropriate replacement site, identifying potential sites, conducting parallel monitoring, analyzing subsequent data, and preparing the site relocation package for submittal to EPA. In August 2009, CARB began the search for potential sites to evaluate as a suitable relocation site. As part ofCARB's search process, CARB reviewed adherence to EPA relocation criteria, generated meteorological and air quality statistics, and reviewed satellite image maps to characterize the Arvin

- BearMountain site
. Several other factors were considered such as the local topography and land uses, nearby traffic counts, lack ofimpact from local NOxand other urban sources, and the predominant wind direction coinciding with high 1-hour 0 3concentrations using monitoring data from the most recent complete (May through October 2008) 0 3season. Logistics were also considered, including limiting the search to public property to ensure lease longevity, general site access, existing infrastructure, and adequate power supply
. The initial search resulted in 31 possible replacement sites located within five miles ofthe Arvin

- BearMountain site. CARB then refined the search with more specific search criteria
.

Printed 011 I00% P ostcon sumer Recycled Pa pe1: Process C hlori11e Free.CARB's refined search concluded with two potential replacement sites that met all search criteria, both located on Di Giorgio Elementary School property. The Di Giorgio Elementary School property at 19405 BuenaVista Blvd, Arvin, California 93203 was chosen as a potential replacement site because this location was the closest site in proximity to the Arvin

- BearMountain site (approximately 2.2 miles northwest ofthe Arvin- BearMountain site) that met all search criteria, was minimally impacted by local NOx sources, immediately available, and had electricity. Adjacent land uses are similar to those at the Arvin- BearMountain site, with vineyards to the west and north, orchards to the east and southwest, and light urban use to the southeast. Local topography is flat, withpredominant wind direction and nearby traffic counts similar to the Arvin

- BearMountain site. Although the lease ended on August 31, 2009, SN APCD negotiated with the Water District to continue operation ofthe Arvin- BearMountain site through October 31, 2010. This additional time allowed CARB to conduct parallel monitoring with the potential Arvin

- Di Giorgio replacement site, which began temporary operation on November 16, 2009. The Arvin- BearMountain and Arvin- DiGiorgio sites operated in parallel from November 16, 2009 through October 31, 2010, when the Arvin- BearMountain site was permanently shut down, allowing for almost a year ofparallel 

### 03 monitoring at the two sites. As described in CARB's relocation request, 

### 03 concentrations between May and October were generally 6-7 ppb lower at the Arvin

- Di Giorgio site compared to the Arvin

- BearMountain site and showed a strong correlation between 

### 03 data at these two sites. Priorto completion ofCARB's relocation request, a potential site was identified on Tejon Ranch Conservancyproperty approximately 0.3 mi east ofthe Arvin- BearMountain site, which would have been closerthan the Arvin- Di Giorgio site to the Arvin- BearMountain site. To ensure that the most suitable replacement site was selected, CARB requested access to the Tejon Ranch Conservancy land for a short-term study of

### 03 concentrations and potential long-term monitoring site operation (see Attachment 1in CARB's relocation request). Access to this location for purposes ofestablishing an air monitoring site was denied by the Tejon Ranch Conservancy Board (See Attachment 2 in CARB's relocation request). Regulatory Requirements According to certified data submitted to AQS, 8-hour and 1-hour daily maximum 

### 03 concentrations at the Arvin

- Bear Mountain 

### 03 monitor were among the highest levels in the Bakersfield Metropolitan Statistical Area (MSA) at the time ofits discontinuation onNovember 1, 2010 and the site was therefore considered to represent the maximum concentration site for the MSA. EPA regulations (40 CPR part 58) require, among otherthings, that at least one 

### 03 site for each MSA must be designated to record the maximum concentration for that area. The closure ofthe Arvin

- BearMountain site without subsequent approval ofa replacement site prevented the designation ofa maximum concentration 

### 03 site for the Bakersfield MSA. 40 CPR 58.14(c)(6) describes the relocation requirements ifa SLAMS monitor is not eligible for removal under the criteria in 40 CPR 58.14 (c)(l) through (c)(5) and states that, "[a] SLAMS monitor.
..may be moved to a nearby location with the same scale ofrepresentation iflogistical problems beyond the State's control make it impossible to continue operation at its current site." As described above, the land uses and sources for 

### 03 near the Arvin

- Di Giorgio site are similarto the Arvin

- BearMountain site. Given the logistical constraints and factors considered by CARB, the Arvin

- Di Giorgio site provides the most similar concentrations from similar sources to the original Arvin

- BearMountain site, thus fulfilling the requirement that the replacement site is at a nearby location with the same scale ofrepresentation. Furthermore, relocation ofthis monitoring will not prevent SJVAPCD from meeting 40 CPR 58, Appendix D requirements, including that for a maximum concentration 

### 03 site in the Bakersfield MSA.Conclusion Based on the above assessment of

### 03 concentrations, land use, and nearby sources, EPA approves CARB's relocation ofthe Arvin

- BearMountain 

### 03 SLAMS monitorto the Arvin

- Di Giorgio site. As this is a relocation, the data from the old and new sites will be combined to form one continuous data record for design value calculations. Please note this in the AQS comment field for both the old and new AQS sites. Please attach this approval letter and update the relevant monitor and site information in your next Ambient Air QualityMonitoring Network Plan. Ifthere are any questions regarding this letter, please feel free to contact me at (415) 947-4534 or Dena Vallano ofmy staffat 415-972-3134.

cc (via email): RaviRamalingam, CARB Gayle Sweigert, CARB Greg Gilani, CARB Seyed Sadredin, SN APCD Jon Klassen, SN APCD Sincerely, ,



# ci/L~~. Meredith Kurpius,



# Mana~r 

# V Air Quality Analysis Office