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TSRIA Document 3: 

Upwind Sources Other Than PPL Do Not Significantly Influence 

High Coburn Road Ambient Concentrations 

(Supplements Charts 4a and 4b from February 27, 2014, TSRIA Presentation) 

Chart 4c: Emissions from all upwind sources: Coburn 2010 produces an 

exceptional number of high outlier readings. 

This chart is similar to Chart 4a from the TSRIA presentation of February 27, 2014, 

except: 

 Results are limited to a southwest (SW) wind direction (wind direction of 210 to 

250 degrees) 

 Emission rate = PPL + Western Sugar + Phillips 66 + CHS, when PPL is 

operating 

 The green line represents an updated visual outlier boundary for ambient 

readings. The updated outlier line provides a better fit for the data 

distribution of all upwind sources than the yellow line from Chart 4a, 

separating those ambient readings that have no nearby readings without 

QA problems (the blue diamonds). 
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Chart 4d: Emissions from all upwind sources with 2010 removed. Removing 

Coburn 2010 greatly reduces outlier readings. 

This chart is similar to Chart 4b from the TSRIA presentation of February 27, 2014, 

except: 

 Results are limited to a SW wind direction (wind direction of 210 to 250 degrees) 

 Emission rate = PPL + Western Sugar + Phillips 66 + CHS, when PPL is 

operating 

 The same green line as Chart 4c represents an updated visual outlier 

boundary for ambient readings. The updated outlier line provides a better 

fit for the data distribution than the yellow line from Chart 4b. 

Updated Chart 4c and 4d Comments: 

It has been previously noted that all elevated readings at Coburn Road, relative to the 

standard, are associated with winds from the southwest, and that all such readings are 

also associated with periods of PPL-Corette operation (see TSD at 13-14). This 
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granular analysis, therefore, focuses on those conditions. The measured hourly 

emissions rates from major facilities generally upwind from the Coburn Road monitor 

were summed and compared to the recorded SO2 concentrations at the Coburn Road 

monitor during periods when the wind was from this southwest direction. The prevailing 

wind direction at the Coburn Road monitor is also from the west-southwest; therefore, 

thousands of points were evaluated. Facilities located in this upwind direction include 

the PPL–Corette, Western Sugar, Phillips 66, and the much more distant Cenex 

Harvest States (CHS) facilities. The purpose of this evaluation was to determine if 

emissions from any major sources in addition to the PPL-Corette facility could rationally 

explain higher readings recorded at Coburn Road. 

The analysis found no significant difference between Coburn Road readings as a 

function of total upwind sources’ emissions by hour, versus as a function of emissions 

from PPL alone. (See Chart 4a from the February 27, 2014 TSRIA Presentation for 

PPL- alone analysis.) The present analysis also found no cases where summed upwind 

hourly emissions explained high readings observed during periods of lower PPL 

emissions, nor did we find cases where summed hourly emissions explained suspect / 

outlier readings that were almost always associated with QA failures in 2010 or other 

years (see Chart 5 from the February 27, 2014 TSRIA Presentation). The data 

associated with QA-failures are identified by date on the charts. This analysis 

demonstrates that the non-PPL upwind emission sources did not have a significant 

influence on, and do not explain, the high readings recorded at Coburn Road during the 

2009 – 2013 observation period. 

As discussed elsewhere, plume-rise variations also do not correlate with or explain the 

elevated readings. The weight of evidence suggests that the elevated readings are 

suspect, and that the readings are best explained as inaccurate due to their QA-failures.