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High Bridge Combined Cycle Project
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High Bridge plant before MERP
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High Bridge plant after MERP - artist's rendition
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click any image to see a larger version
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The High Bridge generating plant has been a fixture and visible presence in St. Paul since 1923, and it remains a critical source of electricity for downtown St. Paul and the surrounding community. The High Bridge MERP project involves replacing our existing coal-powered facility with a natural gas-fired combined-cycle unit.
A natural gas-fired, combined-cycle plant produces electricity from two sources of energy instead of one. Natural gas is used as a fuel in a combustion turbine, similar to a jet engine. Exhaust from the combustion turbine also is used to make steam in a heat recovery steam generator. Both sources of energy then drive turbines and electric generators to produce electricity. Integrating combustion turbine and steam turbine technology provides an extremely efficient electricity production process. Combined cycle is about 30 percent more efficient than a traditional steam plant. The new unit will include two combustion turbines, corresponding heat recovery steam generators and a new steam turbine to be installed in a new building on the existing site.
The new unit will operate more cleanly and efficiently than the existing coal-powered units. As a result, air emissions will be significantly reduced: sulfur dioxide, nitrogen oxides and particulate matter will be reduced by more than 90 percent, while mercury will be completely eliminated — please see the fact sheet (181K PDF) for more details. At the same time, electricity output from the High Bridge site will be increased by 270-280 megawatts — enough electricity to supply almost 300,000 typical homes.
General project schedule
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January – August 2005
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Secure necessary permits
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July – September 2005
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Award major contracts
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August – December 2005
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Preliminary site preparation
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February 2006
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Mobilize turnkey contractor
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February – October 2006
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Earthwork and equipment foundations
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June 2006 – June 2007
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Major equipment delivery
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Spring 2006 – Fall 2007
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Install mechanical equipment
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September 2007 – March 2008
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Startup and testing
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May 2008
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Commercial operation
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June 2008 – December 2009
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Demolition and removal of old plant
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High Bridge project FAQ
Why are you converting High Bridge from coal to natural gas?
We’re repowering the plant with natural gas because of the environmental and energy supply benefits. The High Bridge conversion is part of a bold and visionary plan called the Minnesota Metro Emissions Reduction Project (MERP), which calls for improvements at three Twin Cities coal-powered plants to significantly reduce air emissions while increasing the amount of electricity they can produce.
Although natural gas prices have increased, this conversion makes sense for the long term. The gas market is subject to short-term volatility, but the plants will operate for another 30 years so it’s the long-term projections that are most important.
What kind of impact will these projects have on natural gas supply and prices?
Currently, about 8% of the electricity we provide our customers is fueled by natural gas. After MERP is completed, that will increase to about 12%. The conversion of High Bridge and our Riverside plant in Minneapolis will not affect the local supply or cost of natural gas for home heating because the gas usage at these plants represents only an incremental increase in demand, and the majority of the operating hours at these plants will occur during the summer months.
Minnesota has great access to natural gas supplies in the U.S. and Canada.
How will the cost of the MERP projects affect my electric bill?
Customers will see a gradual increase in their electric rates starting in 2006 that recover the cost of the three MERP projects. This charge will be a separate line item in the monthly bill. There will be a 1.8% increase starting Jan 2006, increasing to about 11.8% by 2010.
Close to half of the increase is attributable to the additional 300 megawatts of electrical generating capacity that will result from these projects, which is necessary to meet customers’ growing needs regardless of the conversion of these plants to natural gas.
What can the surrounding neighborhoods expect during construction in terms of noise and traffic?
There will be more noise and traffic during construction; however, the project team is taking steps to mitigate these impacts. If you have questions or concerns during construction, contact Plant Director Ron Brevig, 651-223-6904.
Will there be any new transmission lines or natural gas lines associated with this project?
Existing transmission lines from the plant will be upgraded and some towers relocated, but there is no need for new transmission.
A new natural gas pipeline will be built to supply the needs of the plant.
What happens to the old power plant?
Plans are for it to be demolished after the new plant is fully operational. Demolition will most likely start in 2008 and continue through 2009.
What kind of noise can we expect from the new plant?
The new facility will operate in compliance with the City of St. Paul’s noise ordinance. Most of the equipment will be in an enclosed building and sound mitigation measures will be incorporated into the plant design.
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