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 CA C 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; Sto ne, Susan; Scavo, Kimber; Keating, Martha; Zimny, Ja mes

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 regar ding a few technical questions that were raised dur ing last week's meeting. I hope these clarifications are us eful 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 citi es with design values between 71 and 75 ppb (Slide 19), a q uestion was raised about how far in excess of the s tandard 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 tha t discussion illustrates, many of these cities expe rienced 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 NA AQS, areas attaining the standard (with no addition al emission reduction obligations) frequently experience numero us 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, se tting the standard at 70 ppb would not be expected to elimina te instances of multiple exposures.

Second, there appeared to be some confusion regardi ng the data used for the analyses of variability/st ability of the 1st versus 2nd versus 4th highest 3-year averag e 8-hour daily max alternative forms of the standar d (Slides 17-18). The data were all provided to EPA in Exhib its 8 and 12 of our comments and are re- attached to this and a subsequent email. The purpose of the analysis wa s to illustrate that using a 3-year average of 4th highest rather than 1st or 2nd highest 8-hour daily maximum s provides limited incremental stability benefit bu t has a dramatic effect on level by cutting off, on average , 7.2 to 8.1 ppb from the design value. Consequentl y, if EPA retains the current 4th highest form of the standar d, it is critical that the level be adjusted downwa rd to account for the fact that the 1st and 2nd highest values co nsistently average at least 7.2 ppb and 3.5 ppb hig her 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 questi on was raised about whether the results held for th e most important metropolitan areas (Slide 17). As illust rated in Tables 15 and 16 of our comments (pages 14 1-43), the difference between the 1st, 2nd and 4th highest levels in EPA's HREA study areas is actually far g reater than the national average indicating that the natio nal averages understate the impact of using the 4th highest

form.

Finally, there was a discussion regarding the slide s depicting over- and under-representation of diffe rent 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 d on'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