January 3, 2002

N3615 (2350)

Mr. S. William Becker

Executive Director

STAPPA /ALAPCO

444 North Capitol St. NW

Washington, D.C. 20001

Dear Mr. Becker:

The National Park Service (NPS) and U.S. Fish and Wildlife Service (FWS) have

developed a Deposition Analysis Threshold (DAT) for sulfur deposition within NPS and

FWS Class I air quality areas. The DAT for sulfur follows the development of a DAT for

nitrogen, which was presented in an August 1, 2001, letter to you. Both DATs were

developed in response to requests by permitting authorities and permit applicants to

develop consistent, predictable permit review processes. Through this letter and the

enclosed guidance document, we seek to inform you of this refinement in our permit

review process. The nitrogen and sulfur DATs will also be used in reviewing National

Environmental Policy Act and other relevant documents. We would appreciate your

sharing this document with your members so that they can incorporate the use of these

DATs into state and local planning, guidance, and permit review processes.

The final Federal Land Manager’s Air Quality Related Values Work Group (FLAG)

report states that State agencies and others who intend to use the FLAG information

“deserve further guidance and implementation assistance, provided through established

formal and informal links between FLMs, States, EPA, and others.” (page 151). This

DAT and guidance document are a continuation of this ongoing commitment. By

developing DATs, the NPS and FWS seek to improve the review process by providing a

quantitative value with which to evaluate nitrogen and sulfur deposition in Class I areas.

By providing applicants, permitting authorities, and the FLMs with a specific value with

which to evaluate potential impacts, we believe that the use of DATs will help to expedite

the permit review process when NPS and FWS Class I areas are involved. The U.S.

Forest Service (USFS), a collaborator in the FLAG process, currently uses separate

deposition thresholds, and the DATs may not apply to USFS Class I air quality areas.

Enclosed please find a copy of Guidance on Deposition Analysis Thresholds. This

document discusses both the nitrogen DAT as well as the new sulfur DAT. We are

providing this single guidance document so that interested parties will have a clear

understanding of the DAT development process and how it will be utilized by the NPS

and FWS. This document will also be made available at the following web addresses: 

http://www.aqd.nps.gov/ard/flagfree

http://www.aqd.nps.gov/ard/whnew.htm
2

Please notify your member states, local agencies, and other interested parties as to the

availability of this document. We understand that it may take some time to incorporate

this guidance into the permit review process. 

We would welcome any questions that you may have regarding the DATs or guidance

document. Please contact Don Codding (303-969-2076) or Tamara Blett (303-969-2011)

of the NPS, or Ellen Porter of the FWS at (303) 969-2617.

Sincerely, Sincerely,

Christine L. Shaver Sandra V. Silva

Chief, Air Resources Division Chief, Air Quality Branch

National Park Service U.S. Fish and Wildlife Service

Enclosure

cc:

Bob Hodanbosi

STAPPA Permitting Committee Chair

c/o Ohio Environmental Protection Agency

Division of Air Pollution Control

P.O. Box 1049

Columbus, OH 43216-1049

WESTAR Council

1001 Southwest Fifth Ave., Suite 1100

Portland, OR 97204-1127

NESCAUM

129 Portland St., Suite 501

Boston, MA 02114

bcc: 

Regional and Park Air Resource Coordinators

ARD: All Staff, Reading and Project File

ARD: Dcodding:dc:01/03/02:2076:SDAT-STAPPA.ltr