MEMORANDUM 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

RESEARCH TRIANGLE PARK, NC 27711 

TO: Docket No. EPA-R09-0AR-2014-0708 

OFFICE OF 

AIR QUALITY PLANNING 

AND STANDARDS 

Clean Data Determination for 1997 PM2.5 Standards; California - South Coast; 

Applicability of Clean Air Act Requirements 

FROM: Richard A. Wayland, Director?~ ,4. tt/~ Air Quality Assessment Division, Office of Air Quality Planning and Standards 

SUBJECT: Data Handling for the Proposed Clean Data Determination for the South Coast 

Air Basin Nonattainment Area for the 1997 Annual and 24-hour PM2.5 National 

Ambient Air Quality Standards 

The Environmental Protection Agency (EPA) is proposing a clean data determination for the 

South Coast Air Basin Nonattainment Area (Area) for the 1997 Annual and 24-hour PM2.5 

National Ambient Air Quality Standards (NAAQS). EPA Region 9 proposes that the data used in 

this determination have followed the data handling procedures in 40 CFR 50 Appendix N. While 

we understand that data from one monitoring site in the Area, Pasadena (AQS ID: 06-037-2005), 

does not meet the completeness requirements or the maximum quarterly value data substitution 

test procedure discussed in 40 CFR 50 Appendix N, Sections 4.1(d) and 4.2(d) further state that: 

an annual [or 24-hour] PM2.5 NAAQS DV [design value] based on data that do not meet 

the completeness criteria stated in 4(b) and also do not satisfy the test conditions 

specified in section 4( c), may also be considered valid with the approval of, or at the 

initiative of, the EPA Administrator, who may consider factors such as monitoring site 

closures/moves, monitoring diligence, the consistency and levels of the daily values that 

are ·available, and nearby concentrations in determining whether to use such data. 

Therefore, EPA Region 9 has provided additional analysis of the data from the Pasadena monitor 

to assess whether the data should be considered valid for the proposed attainment determination 

based on these additional criteria. 

EPA Region 91 reviewed the data collected by the South Coast Air Quality Management District 

(SCAQMD) for the most recent three-year period (2011-2013) for completeness, and determined 

that the data collected from the Pasadena monitoring site is not eligible for the maximum 

1 Analysis conducted by Michael Flagg, Air Quality Analysis Office, EPA Region 9 

Internet Address (URL) • http://www.epa.gov 

Recycled/Recyclable • Printed wHh Vegetable Oil Based Inks on Recycled Paper (Minimum 25% Postconsumer) 
quarterly value data substitution test due to four quarters (quarter 1 2011, quarter 4 2012, quarter 

1 2013 and quarter 2 2013) having less than 50% completeness. 40 CFR 50, Appendix N, 

Sections 4.1 ( c )(ii) and 4.2( c )(ii) both state that if any quarter has less than 50% data capture then 

the substitution test cannot be used. 

The Pasadena monitoring site had 4 7% completeness in quarter 1 2011 due to poor quality 

assurance results and sampler operational issues, 47% completeness in quarter 4 2012 due to site 

repairs (i.e: SCAQMD was working to replace the monitoring site shelter from mid-November 

2012 until the beginning of June 2013), 0% completeness in quarter 1 2013 due to site repairs, 

and 19% completeness in quarter 2 2013 due to site repairs. Additionally, quarter 3 2012 had 

71% completeness due to multiple different sampler operational issues and site operator error. 

Per 40 CFR 50, Appendix N, Sections 4.1(d) and 4.2(d), EPA Region 9 evaluated the location of 

the Pasadena monitoring site relative to the historical design value site for the area, the historical 

annual and 24-hour PM2.5 design values trends over the past 12 years at nearby monitoring sites, 

and causes· of incomplete data when determining whether the 2011-2013 design value at the 

Pasadena monitoring site could be considered valid for the purposes of this action. 

First, the Pasadena monitoring site is not located near the previous and current design value sites 

for the area. Historically, the Rubidoux (AQS ID: 06-065-8001) and the Mira Lorna (Van Buren) 

(AQS ID: 06-065-8005) monitoring sites have been the design value sites for the area for both 

the annual and 24-hour PM2.5 NAAQS. The Rubidoux monitoring site was the design value site 

for both thy annual and 24-hour PM2.5 NAAQS from 2001 to 2006, while the Mira Lorna (Van 

Buren) monitoring site was the design value site for both the annual and 24-hour PM2.5 NAAQS 

from 2006 to 2013. The Pasadena monitoring site is located in the center of Los Angeles County, 

while the Rubidoux and Mira Lorna (Van Buren) monitoring sites are located approximately 38 

miles to the east in Riverside County where higher values are typically measured. See Figure 1. 

Second, an assessment of the long term trends at the Pasadena monitoring site and nearby 

monitoring sites shows nearby sites have design values below both the annual and 24-hour 1997 

PM2.5 NAAQS and the Pasadena monitoring site has the lowest design value compared to these 

nearby sites. See Figures 2 and 3. For example, during the 2001 to 2013 period, the Pasadena 

monitoring site has consistently measured lower design values for both the annual and 24-hour 

PM2.5 NAAQS than the Azusa (AQD ID: 06-037-0002), Burbank (AQS ID: 06-037-1002), Pica 

Rivera (AQS ID: 06-037-1601), Pico Rivera #2 (AQS ID: 06-037-1602), and Los Angeles (Main 

St.) (AQS ID: 06-037-1103) monitoring sites, which are all located within an approximately 12 

mile radius from the Pasadena monitoring site. These four sites all have complete annual and 24-

hour design values below the 1997 NAAQS for the 2011-2013 period and provide appropriate 

characterization of air quality for the area surrounding the Pasadena monitoring site. 

Based on the location of the Pasadena monitoring site, the historical design value concentrations 

relative to both the annual and 24-hour 1997 PM2.5 NAAQS at the site and nearby locations, 

EPA Region 9 concluded that the PM2.5 data set for the 2011-2013 period from the Pasadena 

monitor should be considered valid for the proposed attainment determination. OAQPS agrees 

with this a~sessment and concurs that this data should be considered valid for the purposes of this 

proposed action. 
Figure 1 - South Coast Air Basin Nonattainment Area Monitor Locations
Figure 2 – 1997 Annual PM2.5 NAAQS Design Value Trends
Figure 3 - 1997 24-Hour PM2.5 NAAQS Design Value Trends