United States Department of the Interior 

OFFICE OF THE SECRETARY 

Washingron, DC 20240 

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Mr. Bharat Mathur 

Acting Regio�al Administrator 

U.S. Environmental Protection Agency, Region 5 

77 West Jackson Boulevard 

Chicago, Illinois 60604-3507 

Dear Mr. Mathur: 

Exhibit A 

On September 3, 2009, the National Parks Conservation Association (NPCA), Minnesota Center 

for Environmental Advocacy, Friends of the Boundary Waters Wilderness, and Voyageurs 

National Park Association petitioned the Department of the Interior (DOI) to certify to the 

Minnesota Pollution Control Agency (MPCA) that a portion of the visibility impairment in 

Voyageurs and Isle Royale National Parks is reasonably attributable to pollution emissions from 

Xcel Energy's Sherburne County Generating Plant (Sherco) in central Minnesota. 1 have 

enclosed a copy of this petition for your review. Under 40 C.F.R. § 51.302(c)(l), "[t]he affected 

Federal Land Manager may certify to the State, at any time, that there exists reasonably 

attributable impairment of visibility in any mandatory Class I Federal area." In this case, 

because the Environmental Protection Agency (EPA) currently administers the 1980 Visibility 

Protection Rules for the State of Minnesota through a Federal Implementation Plan, any such 

visibility impairment certification should be directed to the EPA, not the MPCA. For the reasons 

discussed below, I am granting the NPCA's request, and hereby certify that there exists 

reasonably attributable impairment of visibility at Voyageurs and Isle Royale due to emissions 

from the Sherco facility. 

Background 

On November 30, 1979, the DOl identified Voyageurs and Isle Royale as Class I areas where 

visibility is an important value. On November 14, 1985, the DOl certified to the EPA that 

visibility impairment existed in Voyageurs and Isle Royale, and all other Class I areas in its 

jurisdiction in the lower 48 States. 

Sherco consists of three coal-fired units with a total plant electrical output rating of 2,25 5 

megawatts. The plant is located in Becker, Minnesota, and based on Xcel Energy's analyses, its 

emissions impact visibility at Voyageurs and Isle Royale, both mandatory Class I Federal areas 

administered by the National Park Service (NPS). According to EPA's Clean Air Markets 

Database, in 2008, out of 1,228 power plants in the United States, Sherco ranked number 101 in 

sulfur dioxide emissions at 23,419 tons and number 33 for nitrogen oxides (NOx) emissions at 

17,713 tons. Only Sherco Units 1 and 2 are suhject to the Best Available Retrofit Technology 

(BART) provisions of the Regional Haze Rule. Xcel Energy initially proposed to install 

Selective Catalytic Reduction (SCR) at Sherco Units 1 and 2 to control NOx emissions from 

those units. However, for reasons unclear to us, Xcel Energy later withdrew its SCR proposal in 

favor of the existing combustion controls for Sherco Units 1 and 2. On June 26,2009, and then 
Exhibit1\ 

again on September 3, 2009, the NPS submitted extensive comments in support of its position 

that SCR is indeed BART for Sherco Units 1 and 2 (copy enclosed). Despite our comments, and 

the fact that the MPCA determined that SCR was BART for the smaller Minnesota Power 

Boswell Unit 3 and Xcel Energy King Units I and 2, the MPCA agreed with Xcel Energy that 

the existing combustion controls were BART for Sherco Units I and 2. 

Sherco's Air Quality Impacts at Voyageurs and Isle Royale 

According to the EPA's BART guidelines, a single source that is responsib�e for a 0.5 deciview 

(dv) or more change in visibility should be considered to "contribute to" visibility impairment. 

Xcel Energy's regional haze modeling submitted to the MPCA in October 2006, showed that, for 

the 2002-2004 modeling period, combined impacts from Sherco Units I and 2 were above the 

EPA 0.5 dv threshold on 165 days at Voyageurs and I 59 days at Isle Royale, with maximum 

impacts of 2.34 dv and 1.79 dv respectively. 

Conclusion 

Based on Xcel Energy's modeling results, a portion of the existing visibility impairment in 

Voyageurs and Isle Royale is reasonably attributable to pollution emissions from Sherco Units 1 

and 2. As noted in our previous comments on MPCA's proposed regional haze rules, we believe 

that SCR at 0.06 pounds per million British thermal units heat input (30-day rolling average) is 

BART for the Sherco facility. Applying SCR would reduce NOx emissions from the facility by 

80 percent, or more than l 0,000 tons per year. 

We would be happy to discuss our concerns directly with you and the MPCA. Please direct any 

questions you have regarding this matter to Chris Holbeck, Natural Resource Program Manager, 

Midwest Region, NPS, at 402/66l-I864. By working together, I am confident that we can reach 

a solution that will preserve the visibility at Voyageurs and Isle Royale for the enjoyment of 

future generations. 

Sincerely, 

Thomas L. Strickland 

Assistant Secretary for Fish and Wildlife and Parks 

Enclosure 

cc: 

Secretary Tom Vilsack, Department of Agriculture, 1400 Independence Avenue, S.W., 

Washington, District of Columbia 20250 

Mr. Paul Eger, Commissioner, Minnesota Pollution Control Agency, 520 Lafayette Road North, 

St. Paul, Minnesota 55155-4194 

Mr. Ernest Quintana, Regional Director, Midwest Region, National Park Service, 601 Riverfront 

Drive, Omaha, Nebraska 68102