UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION IX 

75 Hawthorne Street 

San Francisco, CA 94105-3901 

MAY 0 2 2016 

Ms. Karen Magliano 

Chief, Air Quality Planning and Science Division 

California Air Resources Board 

1001 I Street, P.O. Box 2815 

Sacramento, California 95812 

Dear Ms. Magliano: 

This letter provides the U.S. Environmental Protection Agency's (EPA's) review and approval for the 

California Air Resources Board's (CARB's) relocation of the ozone (03) State/Local Air Monitoring 

Station (SLAMS) monitor at the Arvin -Bear Mountain 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 of this network change. In this letter, 

CARB explained the need to relocate the Arvin - Bear Mountain 0 3 monitor due to logistics beyond the 

state's control (i.e., expiration of the property lease). Per 40 CFR 58.14, monitoring agencies are required 

to obtain EPA approval for the relocation of SLAMS monitors. EPA has reviewed CARB 's relocation 

request for the Arvin - Bear Mountain site against criteria contained in 40 CFR 58 .14( c)( 6) and approves 

this request as described below. 

Overview of Arvin - 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 (SJV APCD) 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 -

Bear Mountain site. Several other factors were considered such as the local topography and land uses, 

nearby traffic counts, lack of impact from local NOx and other urban sources, and the predominant wind 

direction coinciding with high 1-hour 0 3 concentrations using monitoring data from the most recent 

complete (May through October 2008) 0 3 season. 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 of the Arvin - Bear Mountain site. CARB then refined the search with more specific search criteria. 

Printed 011 I 00% Postconsumer Recycled Pape1: Process Chlori11 e 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 Buena Vista Blvd, Arvin, California 93203 was 

chosen as a potential replacement site because this location was the closest site in proximity to the Arvin -

Bear Mountain site (approximately 2.2 miles northwest of the Arvin- Bear Mountain 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- Bear Mountain 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, 

with predominant wind direction and nearby traffic counts similar to the Arvin - Bear Mountain site. 

Although the lease ended on August 31, 2009, SN APCD negotiated with the Water District to continue 

operation of the Arvin- Bear Mountain 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- Bear Mountain and Arvin- DiGiorgio sites 

operated in parallel from November 16, 2009 through October 31, 2010, when the Arvin- Bear Mountain 

site was permanently shut down, allowing for almost a year of parallel 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 - Bear Mountain site and showed a strong 

correlation between 03 data at these two sites. 

Prior to completion ofCARB's relocation request, a potential site was identified on Tejon Ranch 

Conservancy property approximately 0.3 mi east of the Arvin- Bear Mountain site, which would have 

been closer than the Arvin- Di Giorgio site to the Arvin- Bear Mountain 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 

1 in CARB's relocation request). Access to this location for purposes of establishing 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 of its discontinuation on November 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 other things, that at least one 03 site for each MSA must be designated to record the 

maximum concentration for that area. The closure of the Arvin - Bear Mountain site without subsequent 

approval of a replacement site prevented the designation of a maximum concentration 03 site for the 

Bakersfield MSA. 

40 CPR 58.14(c)(6) describes the relocation requirements if a 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 of representation 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 similar to the Arvin - Bear Mountain 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 - Bear Mountain site, thus fulfilling the 

requirement that the replacement site is at a nearby location with the same scale of representation. 

Furthermore, relocation of this monitoring will not prevent SJV APCD 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 of the Arvin - Bear Mountain 03 SLAMS monitor to 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 Quality Monitoring Network Plan. 

If there are any questions regarding this letter, please feel free to contact me at ( 415) 94 7-4534 or Dena 

Vallano of my staff at 415-972-3134. 

cc (via email): Ravi Ramalingam, 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