Black Hills seeks approval for third Pueblo Airport gas unit

Black Hills/Colorado Electric Utility Co. LP d/b/a Black Hills Energy applied April 30 at the Public Utilities Commission of Colorado for a Certificate of Public Convenience and Necessity (CPCN) to develop and own a new, 40-MW gas-fired unit.

This would be an additional unit at the Pueblo Airport Generating Station (PAGS). This proposed facility is primarily intended to replace a coal-fired facility (the Clark Station) under the state’s Clean Air-Clean Jobs Act (CACJA), with Clark due to be retired by the end of 2013.

“A new LM6000 turbine installed at the existing PAGS is appropriate for Black Hills’ develop-and-own rights under the CACJA,” the application noted. This would be a third unit using a natural gas-fired turbine at PAGS.

The LM6000 is an aeroderivative combustion turbine generator (CTG), which will be equipped to burn only natural gas with a chiller system installed on the inlet air for use at higher ambient temperatures. The power plant will use infrastructure currently installed for the two existing LMS100 units (shared facilities) including the onsite 115-kV switchyard, the water supply line connection to the Pueblo municipal system, a stormwater drainage pond, a wastewater treatment facility, gas pipeline interconnections, and other infrastructure.

The LM6000 has a designed net power output capacity of 40 MW based on Pueblo’s altitude above sea level of approximately 5,000 feet. The designed net power output capacity during the summer months at 100% load is estimated to be 38.5 MW per turbine, and during the winter months at 100% load is estimated to be 40.5 MW. Actual capacity will vary based upon actual ambient and operating conditions since a gas turbine generator is designed to produce a specific output with a specific heat rate for a given set of ambient and operating conditions.

Air permit would need to be altered to allow for new turbine design

The existing air permit for PAGS includes a planned third LMS100 unit with an identified construction commencement deadline of April 13, 2015. Black Hills will apply for a modification of the air permit to substitute an LM6000 in place of the third LMS100 unit, which will result in a revised construction commencement deadline. The revised deadline will be either within 18 months after issuance of the permit modification or within 18 months of the date on which the construction is scheduled to commence in the modified permit, whichever is later.

The construction of the LM6000 will commence after the issuance of a CPCN. The LM6000 can be delivered within 14 months of its ordered date. The construction period is expected to take 12 months and will be completed in time for the generating unit to be in-service in January 2017.

There was 42 MW of replacement capacity for Clark Station that has been found by the commission to be necessary and in the public interest. The replacement capacity for Clark Station is 42 MW as referenced in Black Hills’ Clean Air-Clean Jobs Act Plan. The actual replacement capacity is now 40 MW because one set of cables was removed from each phase of Clark Station Unit 1 in 2011, reducing the unit’s capability from 18 MW to 16 MW.

While Black Hills has proposed replacement alternatives in two prior dockets, there has been no final decision. In this proceeding, Black Hills is asking the commission to:

  • issue a CPCN permitting Black Hills to develop and own a new LM6000 generating unit at PAGS;
  • find that the LM6000 is in the public interest;
  • find that the retail rate impact is reasonable; and
  • approve Black Hills’ use of a Point Cost Cap and associated incentive-sharing mechanism.

The LM6000 turbine can be delivered within 14 months after it is ordered as confirmed by a General Electric proposal dated March 5, 2013. Black & Veatch has conducted a preliminary study of this project and prepared a plot plan drawing. Additional preliminary engineering has been completed, including electrical one line diagrams, piping and instrument drawings, general arrangement drawings, the water balance, and equipment and procurement lists.

Clark coal plant not retired yet, but it’s already pretty much history

The Clark Station coal units were placed in economic shutdown in August 2012 and have not operated since. The company is in the process of obtaining bids for their decommissioning, noted Fredric Stoffel, employed by Black Hills Utility Holdings Inc., a wholly-owned subsidiary of Black Hills Corp. He is Director of Regulatory Services, Colorado.

Eric Egge, employed by Black Hills Utility Holdings as Director of Electric Transmission Services, said the transmission impacts of this third PAGS turbine have already been accounted for.

“In November 2010, the Company submitted a Large Generator Interconnection Request for additional resources located at the PAGS facility for evaluation,” Egge noted. “The subsequent technical studies indicated some slight, negative impacts due to the requested resource addition. Transmission upgrades identified to facilitate the interconnection included rebuilding approximately 2 miles of 115 kV line and increasing the size of entrance and exit conductors at one substation. These upgrades are estimated to cost $2 million. These upgrades will be required within the next three years in any event to address identified future reliability issues on the network. The upgrades were filed in the Company’s Annual Rule 3206 Report in 2011 as the ‘Baculite Mesa-Overton 115 kV Line Upgrade Project’ with a $2 million cost. In Decision C11-0749 the Commission found this project to be in the ordinary course of business. The costs associated with the network upgrades will be assigned to the transmission provider not the generator.”

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.