February 12, 2013

VIA ELECTRONIC MAIL

Andra Juniel

Air Assessment Section Arizona Department of Environmental Quality 1110 W. Washington Street, 3415-A Phoenix, AZ 85007.

RE: Response to ADEQ January 2013 Reque st For Public Comments on E xceptional

Events In The Greater Phoenix Area

Dear Ms. Juniel:

We submit the following comm ents regarding the exceptional event de monstrations for September 11 & 12, 2011 and June 16; June 27; Ju ly 11; August 11; August 14; and September 6, 2012. With respect to these demonstrations, we incorporate by reference the general observations

included in our letter of Janua ry 1, 2013 regarding the December 2012 demonstrations. We provide the following additional comments in light of ADEQ’s responses to those earlier comments.

In our earlier comment letter, we expressed the opinion that th e demonstrations should be tested by modeling. Specifically, we stated that the modeling should be used to support assumptions made by ADEQ and its consultants rega rding the cause and imp acts of the particular

events. We indicated that we were in th e process of modeling th ese exceptional event demonstrations and would be making the model re sults available online for public review. We are moving forward with that effo rt and anticipate having some of the initial results available as soon as next week. We will, of course, provi de notice to ADEQ when the model results are

available.

In response to our comment, Mr. Eric Massey wrote that because “the exceptional event demonstrations rely upon actual me asured values,...[t]he addition of model derived data into the analysis would not provide additio nal benefit in characterizing the events.” Letter dated Jan. 28, 2013 to Joy E. Herr-Cardillo from Erik C. Masse y, p. 3, Comment 2. We disagree. We realize that air quality analysis should rely upon actual measured data wh enever possible; however, air monitoring data is geographically and temporally limited. That is where air quality modeling can fill the gaps. Air quality modeling is a met hod that has been supported by the Clean Air Act and its implementing Federal Regulations sin ce their inception. The EPA Exception Events guidance recommends a number of analytical methods that ca n only be done by the use of models (i.e. source contribution analysis, comprehe nsive controls analysis, spatial and temporalComment Letter re Exceptiona l Events February 12, 2013 Page 2 of 2

relationship between event, sour ces and transport of emissions , etc.) Modeling would not only fill in the gaps and test the assumptions, it woul d also provide important information about what, if any, additional controls could be implemented to prevent future ev ents so as to better protect the public health.

Notably, in its concurrence letter of September 6, 2012 (rega rding the demonstration for the July 3 – 8 events) ADEQ noted, “the in formation and analyses presented in ADEQ's submittal do not represent all possible evidence for exceptional event packages, and additional or alternate evidence may be necessary to make an exceptional event determination in other instances or for other types of events.” Le tter dated September 6, 2012 To Erik Massey from Jared Blumenfeld. We believe that back trajec tory analysis (using WRF as input) would provide the information necessary to answer the critical questions: 1) where was the storm? 2) did it lift dust? 3) did that dust reach the exceeding m onitor? and 4) was the dust controllable?

In sum, we believe incorporating modeling in to the analysis would not only improve the quality of the demonstration, but would also provide ADEQ with important information that would allow it to address the problem of high wi nd events, which appear to be occurring with increasing frequency to the detrim ent of the area’s air quality

We are also concerned with the statement in the demonstrations that the events were caused by “winds transporting dust from de sert areas of Pima and Pinal Count ies” or “desert area outside of

the Phoenix PM10 nonattainme nt area” without furthe r addressing the source of that dust. The EPA

Draft Guidance on th e Preparation of Demonstrations in Suppo rt of Requests to Exclude Ambient Air Quality Data Affected by High Wi nds under the Excep tional Events Rule (June 2012) states that “all upwind areas of disturbed so il to be considered po tential contributing source s.” (6.3.2.3 Basic controls analysis). Further, “[a] basic controls analysis should identify all contri buting emission sources in upwind areas and provide evidence that those sources were reasonably controlled, whether anthropogenic or natural. ” (6.3.2.3 Basic controls an alysis) and “inspection re ports and/or notices of violations (NOVs) in upwi nd areas should be submitted, if avai lable.” None of th e demonstrations provide evidence that control measures outside of Maricopa County we re even evaluated.

Under the Clean Air Act, the EP A generally considers a state ( not including ar eas of Indian country) to be a single respon sible actor. Accordingly, neither the EPA nor the Exceptional Events Rule provides special considerations for intrastate scenarios when an event in one county affects air quality in another county in the same state, assuming that the event occurs on land subject to state authority (versus tribal government authority). EP A response to 6.4. Reasonabl e controls for sources outside of state/local/tribal jurisd iction. Because ADEQ is the single responsible acto r for air quality control in Arizona, it should address whether Agricu ltural Best Management Practice inspectors were

sent to Pima and Pinal Countie s during any of the five-day du st control fore cast periods.

We appreciate the opp ortunity to comment on the demonstrations.

Sincerely,

Joy E. Herr-Cardillo