From: Chuck French/RTP/USEPA/US

To: "King, Heidi R." < Heidi_R._King@omb.eop.gov >

Cc: "Raymond, Gabrielle" < graymond@rti.org >; VanLare.Paula@epamail.epa. gov ; "Marinshaw, Richard" < rjmarinshaw@rti.org >;

Date: 12/15/2010 12:57 PM

Subject: RE: EO 12866 Interagency Review comments on Gold Mine Draft Final

Hi Heidi,

Attached is a slightly revised document to address the one remaining question.

Thanks.

Chuck

(See attached file: Summary of Interagency Working Comments_Gold Mines Final_2010_12_8

- EPA

- responses

- revised.doc)Summary of Interagency Working Comments on Draft Language under EO12866 Interagency Review. Subject to Further Policy Review.

1

. The Cost Analysis page 13 mentions an increase in electricity consumption and an increase in carbon generation. Can we be more specific?

Response: The additional electricity consumption and increase in carbon generation is from

facilities that will have to add a carbon adsorber to their units to meet the MACT standards. We

have add ed this description to the impacts document.

2

. The Cost Analysis lists the facilitie s by name and number, the MACT F loor document uses names but the preamble uses A

- Z lettering

. Could the preamble switch to numbers that are consistent with the support documents, or simply, to be most transparent use the facility names (at most only 9 facilities are presented in each table) ? The goal is to allow a reader to cross

walk the docume nts.

Response: We added the letters used in the preamble/rule to the MACT floor document to keep

consistent. The numbers in the impacts document are not used as facility identifiers, but just as a listing the number of facilities.

3

. MACT F loor TSD page 2 states that there are 10 facilities for carbon processes with mercury retorts. This is consistent with table 2 in the document. However in the preamble (table 3) only lists 9 facilities.

Response: We clarified this in the preamble.

4

. MACT Floor TSD: C ould EPA provide the number of tests used to calculate the average for each source in Tables 1, 2, 3, and 4?

Response: Yes, we will add the number of tests or runs used for each facility used in those tables

in the MACT floor document.

5

. What comments di d EPA receive (formally or informally) regarding the cost of emissions reductions? In particular, on the capital cost for additional controls in the MACT Floor TSD?

Response: Industry said that we underestimated the capital and total annualized costs o f the

carbon adsorbers on the autoclaves. Barrick provided new estimates of capital and TAC that we used in our analysis. We will send you a separate document that described these.

6

. MACT Floor TSD P age 8 mentions invalidated emissions tests from 2007 and 2008 but the reationale for invalidation is very vague. It would be helpful if EPA could provide more details on this. In addition, the preamble should then reference this discussion in the TSD.

Response: The document showing all of NDEP’s invalidations is in the docket as EPA

- HQ

OAR

- 2010

- 0239

- 0061, can add this to the preamble. Some of the rationale are: failure to comply with federal reference method, failure to comply with established test protocol, possible sample contamination, etc. We will add mo re rationale to the MACT document.Summary of Interagency Working Comments on Draft Language under EO12866 Interagency Review. Subject to Further Policy Review.

7

. MACT Floor TSD. Regarding variance calculation, could EPA provide reference for the adopted method , assumed distribution of the variance, etc ? In particular, is the adopted method appropriate for small sample size ( n=2 or n=10)

Here is a reference for the UPL method:

Neter, J, Wasserman W. and Kutner M. H. 1989. Applied Linear Regression Models, Second Edition. Richard D. Irwin, Inc. p.246

.

As for the appropriateness of using it for small sample sizes, we believ e it is fine for small sample sizes if the distribution is normal

.

8

. MACT Floor TSD page 13, table 5 show s results for a 70% reduction. Why 70%? S ome text to explain this, for the bey ond the floor analysis, would be helpful

.

Response: We used 70% reducti ons from carbon adsorbers on autoclaves because that was what Twin Creeks proposed in their Phase 2 applications. We used 70% reductions for the carbon adsorbers on the ore preheaters/dryers to be consistent with percent reductions we said that the

carbon adsorbers on the autoclaves were getting. We will add some text to the MACT floor document to clarify this.