Top Plant: Plum Point Energy Station Mississippi County, Arkansas

Owners: Plum Point Energy Associates, Missouri Joint Municipal Electric Utility Commission, Empire District Electric Co., East Texas Electric Cooperative, and Municipal Energy Agency of Mississippi Operator: NAES Corp.

The new 665-MW Plum Point Energy Station is energizing the Arkansas Delta, an area that is ready to supplement its farming heritage by promoting new jobs that offer residents a higher standard of living. But first, the plant’s construction team had to overcome a number of significant challenges related to building a facility in the New Madrid fault zone.

Courtesy: Black & Veatch

Mississippi County, Ark., has long been known for agriculture and the hard-scrabble lives of many of its residents. The county is part of the First Congressional District in Arkansas, which has been ranked as the poorest congressional district in the U.S.

On May 31, 2006, at the groundbreaking ceremony for the Plum Point Energy Station, then U.S. Congressman Marion Berry commented on the impact the new plant located in Osceola would have on the community: “I would submit to you today that the Delta is moving forward like it hasn’t since cotton seed was first unloaded here,” he said. “It’s like we just discovered the Mississippi River and all the wonderful things it brings and businesses just discovered it, too.”

One of the key accomplishments of the Plum Point Energy Station, which began commercial operation in August 2010, is that it is helping to transform this delta blues region into the center of the new delta “boom.” The power plant has already brought additional jobs to the region and is now providing reliable electricity to support a growing number of new businesses.

Roger Lenertz, director of major projects in Black & Veatch’s global energy business, told POWER in August how construction of the Plum Point Energy Station has affected the region. “The economic impact of an investment exceeding $1 billion reaches and benefits a very large population,” he said. “The project has had a very marked and positive impact on the local community.”

The mayor of Osceola was a key driver in developing the project and helped shepherd the local business community’s interactions with the project’s management.

Big Construction Challenge: Fault Line

A number of significant construction obstacles made building the plant a challenge, according to Lenertz. Most were related to geological and civil engineering aspects of the location. “The New Madrid fault line lies directly below the plant,” he said. “The design seismic acceleration factors are greater than any in California.”

The site is adjacent to the Mississippi River in an area with about 900 feet (deep) of silty, clayey soil (muck). The water table is less than 10 feet below the surface. Lenertz emphasized that “whenever one opens an excavation, you are working in water and in a difficult soil composition.” It should be no surprise that dewatering the construction area was very challenging.

Lenertz explained that a large power plant requires deep, massive foundations. The rotary car dumper required a substructure that extended 85 feet below the surface for the handling equipment.

“Any large power plant represents a complex project. This one provided some additional unique challenges,” he said. “The project team used some very specialized engineering and construction techniques to overcome these challenges.”

For example, the use of the buckling resistant brace at the plant serves as a structural shock absorber. This brace substantially reduced the amount of steel required to protect the facility from high seismic acceleration and helps limit potential damage to the energy station from an earthquake over the next 50 years.

1. From the bottom up. A worker stands beneath the header where the downcomers terminate at the bottom of Plum Point’s pulverized coal boiler. Courtesy: Black & Veatch

People Power

The construction team had to meet the various regulatory environmental restrictions governing construction. For example, they took extraordinary measures during construction to reduce volatile organic compound emissions (by using a high-solids siloxane paint) and to minimize groundwater disruption during construction. The owners brought in their environmental specialists very early in the project and exercised diligent monitoring and control over its environmental aspects. Black & Veatch’s design engineers and the owners’ professionals worked together to make sure prudent measures were always in place.

This project employed many local workers. Site construction staff peaked at more than 1,600 people, and the work took place over the course of about four years. Many craft workers received training, as new craft workers were beginning their construction careers. This sizeable construction project meant a lot to the local area’s economy and helped generate a major growth spurt for businesses.

Plant Profile

The plant’s performance test demonstrated a heat rate that was lower than 9,100 Btu/kWh, Lenertz explained. The unit’s actual generating capacity exceeded the guaranteed value of 665 MW by more than 2%. The data were generated under test conditions just before commercial operation began in August 2010.

Flue gas treatment performance test results show the facility’s emissions control systems are exceeding guaranteed removal rates. These technologies include:

• A selective catalytic reduction system for nitrogen oxides control.
• A dry flue gas desulfurization system (scrubber) for sulfur dioxide removal.
• A carbon injection system for mercury removal.
• A fabric filtration system (baghouse) for particulate material removal.

Toshiba manufactured the steam turbines and shipped them to Osceola from Tokyo. The steam generator was also manufactured by a Japanese company, IHI, which has utilized manufacturing facilities in a number of areas in Southeast Asia. Alstom provided the air quality control system scrubber and the baghouse. Thermal Engineering Inc. manufactured the condenser, which was shipped from Missouri. The transformers were manufactured in Korea by Hyundai Heavy Industries, a major supplier to the power industry. Emerson provided its state-of-the-art Ovation distributed control system. Black & Veatch utilized its global procurement system to select and procure the plant’s equipment.

Equipment installed at the new plant includes:

• Geomembrane liners (ESI)
• Continuous emissions monitoring systems (Forney)
• Compressed air system (Ingersoll Rand)
• Cooling tower (GEA Cooling Technologies)
• Steam turbine generator (Toshiba)
• Condensers (Thermal Engineering)
• Deaerators (Ecodyne)
• Feedwater heaters (Thermal Engineering)
• Fly and bottom ash handling system (United Conveyor Corp.)
• Wastewater treatment equipment (Siemens Water Technology)

The owners contracted NAES Corp. to operate the plant, and it has been doing so from the start of its commercial operation. The operations and maintenance staff includes more than 80 permanent staff members on site, plus some contract personnel. In addition, temporary workers are brought in for plant outages or key maintenance periods.

Regional Economic Impact

“Having low-cost, reliable power is paramount to any economy in today’s world,” Lenertz said. “Can you think of any economic activity or even personal life activities that do not require electrical power?”

The U.S. is retiring many coal-fired power plants because they are at the end of their operating lives, do not have high efficiency, and do not have the necessary environmental controls to meet the new standards, he pointed out. However, “lost power must be replaced, or the strong supply that we have enjoyed over the decades will be disrupted.” The Plum Point Energy Station is a major, baseload unit that helps fill that need.

The city of Osceola actually owns a small piece of the plant as an investor. The electrical power gets distributed to a number of other states, where others members of the plant ownership group sell it to their respective customers.

“The Plum Point Energy Station has become a fixture in the local area, and the people in the area are proud of its place in their community,” Lenertz said. “The revenues from employment, ongoing operational needs, etc. will continue to contribute to the local area’s economic well-being over the long-term life of the plant.”

— Angela Neville, JD, is POWER’s senior editor.