St. Clair Power Plant

Saint Clair Power Plant
Company type	Subsidiary
Industry	Electric power generation
Founded	1953
Defunct	2022
Fate	Retired
Headquarters	St. Clair County, United States
Area served	Michigan
Products	Electricity generation (coal- and oil-fired)
Owner	DTE Electric (DTE Energy)
Number of employees	300

The Saint Clair Power Plant was a prominent coal- and oil-powered electricity generation facility owned by DTE Electric, a branch of DTE Energy. Situated in St. Clair County, Michigan along the western shore of the St. Clair River, it was positioned directly across from the newer Belle River Power Plant in East China, Michigan. The initial four generating units were established between 1953 and 1954, with an additional three units incorporated subsequently. The plant’s cumulative output capacity reached 1,982 megawatts, ranking it as Detroit Edison’s second-largest energy producer. Employing roughly 300 personnel, the facility played a vital role in supporting the regional economy. Operations were discontinued in May 2022.

Units

St. Clair housed seven coal-fired boilers, with six units operational until closure.

Units 1 – 4

Units 1 – 4 consisted of 163 MW boilers manufactured by Babcock & Wilcox, each connected to GE and Allis-Chalmers steam turbines. These foundational units formed the base load for St. Clair, commonly operating at maximum capacity. Exhaust gases were discharged via a southern stack installed in the late 1970s alongside new electrostatic precipitators; originally, each unit had an individual short stack. Unit 4 was retired in 2017 due to mechanical complications, followed by Unit 1’s retirement in March 2019.

Unit 5

Unit 5, a 300 MW cyclone boiler, was taken out of service in 1979 after experiencing mechanical failure. Its associated stack was dismantled in 2012.

Unit 6

Unit 6 is a tangentially fired dual furnace boiler supplied by Combustion Engineering, paired with a Westinghouse turbine. Commissioned in 1961, it delivered an output of 321 MW.

Unit 7

Unit 7, also utilizing tangential firing technology from Combustion Engineering, is equipped with a Westinghouse steam turbine. Commissioned in 1969, this unit generated 451 MW (initially exceeding 500 MW). As St. Clair’s largest unit, it featured a relatively small electrostatic precipitator, which led to opacity challenges when burning western coal varieties.

Other units

An oil-powered gas turbine designated Unit 11, rated at 18.5 MWe, was installed in 1968. Additionally, two smaller oil-fueled internal combustion generators (units 12A and 12B) with a combined capacity of 5.4 MWe were added in 1970.

History

Operations at St. Clair Power Plant commenced in August 1953, marking it as the largest facility within the DTE Energy system at that time with a capacity of 652 MW. To accommodate increasing demand across the Metro Detroit area, Units 5, 6, and 7 were subsequently introduced, expanding total capacity to 1,571 MW. Upon completion of Unit 7 in 1969, St. Clair became the world’s largest coal-fired power station. During the mid-to-late 1970s, the plant transitioned to using Western subbituminous coal, which resulted in reduced power ratings per unit and necessitated larger electrostatic precipitators on Units 1–4 and Unit 6, as well as construction of a new stack for Units 1–4. All units were upgraded with low NOx burners and overfire air ports.

On August 11, 2016, a fire incident forced a complete shutdown of St. Clair; fortunately, there were no injuries reported. The blaze required approximately fifteen hours to be fully extinguished, with firefighting efforts supported by local and regional departments including teams from Detroit and Canada.

Following the commissioning of the Blue Water Energy Center, DTE announced plans to retire St. Clair Power Plant in 2022.

Coal mixture employed

St. Clair utilizes a combination of low-sulfur coal from Western sources (specifically the Decker and Spring Creek mines in Montana) and high-sulfur Eastern coal from the Pittsburgh seam. This mixture is prepared within the coal yard using feeders with adjustable speeds. Generally, the blend consists of approximately 85% Western coal and 15% Eastern coal; however, this ratio fluctuates depending on factors such as demand, coal pricing, inventory levels, and unit operational status. During summer months, Units 6 and 7 adjust to a 70/30 Western-to-Eastern coal ratio to boost power generation by incorporating more Eastern coal, which possesses a higher heating value. The increased sulfur content also assists in mitigating opacity challenges encountered by the electrostatic precipitator on Unit 7.

Logistics and inventory management

Western coal is transported via unit trains to Superior, Wisconsin, then shipped by barge aboard vessels capable of carrying 60,000 tons to St. Clair. Due to the Great Lakes shipping freeze from late December through late March, the facility maintains a winter stockpile ranging between 2.1 and 2.4 million tons. Eastern coal arrives at the plant through rail deliveries to a dedicated unloading terminal. With declining production levels, the seasonal stockpile of Eastern coal was reduced significantly—from around 140,000 tons down to between 20,000 and 30,000 tons by 2004.

Operational metrics

Functioning primarily as a baseload facility, St. Clair is dispatched subsequent to DTE Energy’s Fermi 2 nuclear plant and the nearby Belle River coal station. Between 1999 and 2003, the plant recorded an average capacity factor of 57%, maintained a heat rate averaging 10,449 Btu per kWh (equivalent to roughly 32% efficiency), and experienced a forced outage rate of 18%.

Grid interconnections

The facility interfaces with the electrical grid through two double-circuit 345 kV transmission lines alongside five 120 kV lines managed by ITC Transmission. It also features one 345 kV line (St. Clair-Lambton #1) and one 230 kV line (St. Clair-Lambton #2) that connect with Hydro One in Ontario, Canada. Additionally, one conductor of a 345 kV line feeds into a substation located at the Belle River Power Plant.

Environmental considerations

Both the St. Clair and Belle River complexes hold ISO 14001 certification for environmental management.

Sulfur dioxide emissions

Despite having units originating in the 1950s, St. Clair was ranked 74th among U.S. power plants for sulfur dioxide emissions per megawatt-hour in 2006. Emission reductions could be achieved through installing flue-gas desulfurization systems ("scrubbers"), akin to those employed at Lambton Generating Station across the river. DTE Energy is currently implementing scrubber technology at Monroe Power Plant and may consider similar upgrades for St. Clair in future plans.

Wastewater handling

The plant discharges all its waste heat—approximately double its electrical output—into the St. Clair River. This water serves as cooling medium for steam condensers before undergoing treatment, filtration, and being returned to the river system. Additional water used for boiler cleaning and turbine maintenance is processed through settling ponds that remove ash and particulates prior to purification and recirculation. The collected solid waste is transported to a nearby ash landfill shared by St. Clair and Belle River facilities.

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