Technical Support Document

For 

Determination of Attainment and Redesignation 

of the

Mammoth Lakes PM10 Nonattainment Area:

Analyses Addressing 2012 Incomplete Data

Environmental Protection Agency – Region 9

Air Quality Analysis Office

Jennifer Williams and Gwen Yoshimura

April 30, 2015
Mammoth Lakes PM10 Data Analysis Addressing Incomplete Data for Redesignation Purposes

Within the Mammoth Lakes Planning area there are two PM10 monitors which are both located at the Mammoth Lakes 

site (06-051-0001). One of the monitors is a Federal Reference Method (FRM) manual monitor (POC 5) run at a sampling 

frequency of once every three days. The other monitor is a Federal Equivalent Method (FEM) continuous monitor (POC 

6) run at a daily sampling frequency. Below are the 2014 Design Values (DVs) and DV validity for each monitor:

06-051-0001 POC 5: 0.0 expected exceedances, Valid

06-051-0001 POC 6: 0.7 expected exceedances, Invalid

Each monitor produces its own data stream, and the data from the two monitors produce separate design values. As 

such, the highest 2014 DV for the Mammoth Lakes Planning Area is 0.7, as measured by the POC 6 monitor, but this is an 

invalid DV due to completeness issues with the data. The following analysis examines what this invalid DV may mean for 

the attainment status of the area.

To demonstrate attainment of the PM10 NAAQS, three years of data with 75% of the scheduled PM10 samples per 

quarter collected is required per 40 CFR Part 50, Appendix K, section 2.3(b). The POC 6 monitor at the Mammoth Lakes 

site did not meet the 75% completeness requirement in quarter 3 (Q3) of 2012, therefore its 2014 DV, which uses data 

from 2012, 2013, and 2014, is considered to be invalid. For 2012 Q3, the POC 6 monitor’s data completeness is 61% with 

a total of 36 missing days from August to September. The majority of the missing data is shown in EPA’s Air Quality 

System (AQS) database as invalid due to “Shelter Temperature Outside Limits” (AQS null data qualifier code “AE”). Since 

the DV is invalid, further analysis is needed to determine whether the missing data could reasonably have an effect on 

the DV, specifically, whether it could have changed the DV from attaining to violating. 

Two monitors operate at this site. As previously described, the POC 5 monitor runs every-third day, while the POC 6 

monitor is scheduled to collect data continuously. A correlation graph showing results of a statistical analysis comparing 

the two monitors with one another is included below. Looking at data from both monitors from 2009 to 2014, the R2

value for the simple linear regression is 0.9773 (n=680), indicating that the data from the two monitors are wellcorrelated. For purposes of this analysis, this indicates that the POC 5 data, for the days that it collected data, well

represents what the POC 6 data would have recorded. During the time period POC 6 did not collect valid samples, POC 5 

measured values between 9 and 17 μg/m3, well below the level of the PM10 NAAQS. 

However, since the POC 5 monitor does not sample daily, it is possible that there could have been exceedances during

POC 5 non-sample days which POC 6, operating every day, would have captured had it measured valid samples on those 

days. In order to determine whether it is reasonable to assume that exceedances did not occur in the missing time 
period on POC 5 non-sample days, identification of the high PM10 season is useful. The first through fifth highest PM10

concentrations from 2009-2014 measured by POC 6 occurred in the months of July or August. Of these highest 

concentrations, only the July 28, 2013 and July 29, 2013 concentrations were exceedances of the 150 μg/m3standard. 

The next highest concentration, 133 μg/m3, occurred on August 1, 2014 and was not an exceedance of the standard. 

While winter months do exhibit consistently elevated concentrations at Mammoth Lakes, over the past six years the 

highest PM10 values were measured during the summer months. The time series graph below shows data from 2012-

2014 from both POC 5 and POC 6, and indicates the missing data period circled in red in 2012 as well as the maximum 

values measured in years 2013 and 2014. 

For data from 2009 through 2014, the only two exceedances measured at Mammoth Lakes are flagged as wildfire 

exceptional events in AQS. While a demonstration package was not submitted for the dates, the Aspen Wildfire 

(http://calfire.blogspot.com/2013/07/ca-snf-aspen-wildlandfire-50-acres.html) occurred in the Mammoth Lakes area 

during the exceedance days. 

While the late summer season appears to represent the maximum PM10 concentrations at the site, since the only two 

exceedances in the last 6 years were due to a wildfire exceptional event, it is reasonable to conclude that the missing 

data would not reasonably have an effect on the DV.