   1) We suggest that some clarification is needed with respect to statements in the rule regarding the date on which the Tailoring Rule will take effect.  On page 11, the first sentence of the first full paragraph states:  "The effect of EPA narrowing its approval in this manner is that there will be no federally-approved title V program that requires permits for sources due to emissions of GHG below the final Tailoring Rule threshold of 100,000 tpy CO2e (and 100 tpy mass basis), which takes effect on July 1, 2011."   

The first phase of the Tailoring Rule, however, takes effect for both PSD and Title V on January 2, 2011 (although the second phase takes effect on July 1, 2011).  See, e.g., 75 Fed. Reg. at 31,516/2, 31,523/2.  EPA should clarify why July 1, 2011 is the appropriate date.  We also note that the July 1, 2011 date appears elsewhere in the Rule -- for example on page 9, line 1.

   2) Page 1:  Throughout the text, consider replacing "limit" with "revise" (or "narrow") because the word "limit" carries an unnecessary negative connotation and, in this context, may be interpreted to broadly mean more SIPs than EPA intended, which could potentially confuse readers.  The rest of the sentence on page 1 in the summary does a good job of explaining this rule's purpose.

   3) Page 11: For clarity, suggest qualifying the statement "[s]tates affected by this rule will not be required to take any action as a result of this rule" by explaining that states need not take any further action under the federal Clean Air Act as a result of this rule. Also, suggest referring the reader to the passages in "Limitation of Approval of Prevention of Significant Deterioration Provisions Concerning Greenhouse Gas Emitting-Sources in State Implementation Plans" where EPA urges states to amend state law to align with the Tailoring Rule.

   4) Page 15:  It might be helpful to add a citation to the first sentence of the first full paragraph to support the statement that CAA § 301(a) "incorporates the authority of an agency to reconsider its actions."

   5) Page 25:  First sentence of the first full paragraph is redundant as a similar statement appears on the previous page, which could potentially confuse readers. Suggest deleting second instance on page 25.

   6) Page 34:  In the middle of the page, it might be helpful to provide a citation for the statement "Reconsidering prior rulemakings, when necessary, is part of `[EPA's] functions' under the CAA ."   

