EPA approves lower SO2 limit for Inver Hills plant of Northern States Power

The U.S. Environmental Protection Agency is approving a revision to the Minnesota SO2 State Implementation Plan (SIP) for Northern States Power‘s Inver Hills Generating Plant, located in Inver Grove Heights, Minnesota.

The revision, submitted by the Minnesota Pollution Control Agency (MPCA) in May 2015, incorporates a more stringent limit for the sulfur content of the fuel used at the facility, and modifies the fuel analysis requirements to meet the more stringent limit, said EPA in a notice to be published in the Jan. 28 Federal Register. This rule is effective 60 days after the date of publication in the Federal Register, unless EPA receives adverse written comments within 30 days after. If EPA receives adverse comments, EPA will publish a timely withdrawal of the rule in the Federal Register and inform the public that the rule will not take effect.

Northern States Power is a unit of Xcel Energy (NYSE: XEL). The Inver Hills facility is a 440-MW peak demand generation plant. The plant has six generation units, turbines EU 001-EU 006, which can burn both natural gas and distillate fuel oil.

In 1980, Inver Hills was identified by the state of Minnesota as a culpable source in the Pine Bend portion of the Minneapolis-St. Paul SO2 nonattainment area in Dakota County. In 1992, MPCA issued an administrative order for Inver Hills to address the source’s contribution to the nonattainment problem. The SIP revision containing the administrative order was approved by EPA in 1994. The area was subsequently in 1997 redesignated to attainment of the SO2 National Ambient Air Quality Standards (NAAQS), and is now a maintenance area for SO2.

In 2004, EPA approved a Minnesota SO2 SIP revision, replacing the administrative order with Title I conditions for the Inver Hills facility. In addition, in 2007, EPA approved a Minnesota SO2 SIP revision, updating the Title I conditions for the Inver Hills facility.

On May 1, 2015, MPCA submitted a request to EPA to revise the Title I SIP conditions in the SO2 SIP for the six turbines at the Inver Hills facility. The SIP revision reduces the allowable sulfur content limit for all fuels delivered to the facility from 0.48% by weight to 0.005% by weight. In addition, the SIP revision updates the requirements necessary to demonstrate compliance with this more stringent fuel limit.

The Inver Hills SIP revision contains two methods for determining compliance with the sulfur limit for fuel oil.

  • Method A requires Inver Hills to sample the fuel upon delivery to demonstrate compliance with the new lower fuel sulfur limit of 0.005% by weight.
  • Method B requires the fuel supplier to provide a guarantee that the fuel oil has a sulfur content below a specific limit. If the fuel oil supplier provides that guarantee, Inver Hills is not required to conduct any additional sampling or analysis of the fuel oil. Since no sampling is required, the SIP revision reduces the sulfur content limit under Method B from 0.10% by weight to 0.0015% by weight.

A modeling analysis was not conducted for the Inver Hills because the SIP revision imposes more stringent SO2 emission limits at the facility, resulting in a decrease in SO2 emissions. Because the revision strengthens the existing SO2 SIP for Inver Hills, EPA deems the submittal approvable. “We are publishing this action without prior proposal because we view this as a noncontroversial amendment and anticipate no adverse comments,” said EPA.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.