1

Brown, Kelly

Subject: FW: Follow-up on questions from mtg (email 1 of 2)

Attachments: 2015 03 17 Ozone NAAQS Proposal Cmts ALA AMC CBD CAC EJ EDF NPCA NRDC 

SC.pdf; Ex 12 - Summary 2002-2014 3-Yr Max Max.xlsx; Ozone Powerpoint 5.4.15 

OAQPS.pdf

From: Joshua Berman [mailto:josh.berman@sierraclub.org] 

Sent: Tuesday, May 12, 2015 10:17 AM 

To: Wayland, Richard; Page, Steve; Mathias, Scott; Stone, Susan; Scavo, Kimber; Keating, Martha; Zimny, James 

Cc: Josh Stebbins; David Baron 

Subject: Follow-up on questions from mtg (email 1 of 2) 

I wanted to provide a quick note following up regarding a few technical questions that were raised during last 

week's meeting. I hope these clarifications are useful and I would be happy to provide any additional

information. 

First, with regard to the slide depicting frequency of 8-hour ozone levels of 75 ppb or higher in cities with 

design values between 71 and 75 ppb (Slide 19), a question was raised about how far in excess of the standard 

these days were. The underlying data are described in greater detail at pages 156-58 of our comments on the 

proposal (reattached for your convenience). As that discussion illustrates, many of these cities experienced 6 to 

10 occurrences of 8-hour levels of 80 ppb or higher in a single ozone season while still attaining the 75 ppb 

standard. To be clear, however, the point of Slide 19 was not about how far over the standard each day was, but 

rather to illustrate that, given the form of the NAAQS, areas attaining the standard (with no additional emission 

reduction obligations) frequently experience numerous days at or above the standard in a single ozone season. 

Consequently, to the extent EPA is concerned about multiple exposures to levels of 70 ppb or above, setting the 

standard at 70 ppb would not be expected to eliminate instances of multiple exposures. 

Second, there appeared to be some confusion regarding the data used for the analyses of variability/stability of 

the 1st versus 2nd versus 4th highest 3-year average 8-hour daily max alternative forms of the standard (Slides 

17-18). The data were all provided to EPA in Exhibits 8 and 12 of our comments and are re-attached to this and 

a subsequent email. The purpose of the analysis was to illustrate that using a 3-year average of 4th highest 

rather than 1st or 2nd highest 8-hour daily maximums provides limited incremental stability benefit but has a 

dramatic effect on level by cutting off, on average, 7.2 to 8.1 ppb from the design value. Consequently, if EPA 

retains the current 4th highest form of the standard, it is critical that the level be adjusted downward to account 

for the fact that the 1st and 2nd highest values consistently average at least 7.2 ppb and 3.5 ppb higher than the 

4th highest. 

Third, because the analysis of differences between the 1st, 2nd and 4th highest forms looked at design values 

for all CBSAs and took a national average, a question was raised about whether the results held for the most 

important metropolitan areas (Slide 17). As illustrated in Tables 15 and 16 of our comments (pages 141-43), 

the difference between the 1st, 2nd and 4th highest levels in EPA's HREA study areas is actually far greater 

than the national average indicating that the national averages understate the impact of using the 4th highest 

form. 

Finally, there was a discussion regarding the slides depicting over- and under-representation of different 

populations in counties with nonattaining monitors (Slides 26-30). I wanted to be clear that the data were for 

only those counties with nonattaining monitors, not for counties designated nonattainment that either lack a 

monitor or have a monitor showing attainment. 
2

Again, I hope these clarifications are useful and don't hesitate to let me know if you have any follow-up 

questions. 

Best regards, 

Josh 

-- 

Joshua Berman 

Staff Attorney 

Sierra Club Environmental Law Program 

50 F St. NW, 8th Floor 

Washington, DC 20001 

Tel: (202) 650-6062

Fax: (202) 547-6009