Waste Management

An important aspect of environmental stewardship is properly transporting and disposing of the by-products from our generation facilities. The primary by-product we manage is coal combustion residuals (CCR). The American Coal Ash Association estimates that the electric utility industry generated 110 million tons of CCR in 2017. CCR consists of the ash left over from burning coal along with any additive that may have been inserted into the flue gas for emissions control.

In 2018 we invested approximately $4.5 million to retrofit the Big Stone Plant bottom ash handling system and permanently remove CCR from two areas. These upgrades will help to ensure Big Stone Plant is well-positioned to properly manage CCR in the future and to comply with Environmental Protection Agency regulations. We spent $3.4 million in 2019 to perform a similar set of projects at Coyote Station. Completion of the Coyote Station project was the last step in the transition to dry CCR handling systems at all of our facilities.

We look for opportunities to responsibly reuse our CCR in useful and appropriate applications. Beneficial reuse saves landfill space and conserves natural resources by substituting CCR for a material that would have to be mined and processed. The demand for CCR in beneficial use applications is largely market-driven, but we do what we can to identify opportunities. During the last five years we’ve beneficially used an average of 26% of our boiler slag, which is a type of CCR. In 2018 we beneficially used 28% of our boiler slag.

2018 Waste Disposal

 

Disposal

Tons

HOOT LAKE PLANT

Fly ash

On-site landfills

5,033

Bottom ash

On-site landfills

2,157

Other materials (recovered historic ashes)

On-site landfills

0

BIG STONE PLANT

FGD product

On-site landfills

56,569

Boiler slag

On-site landfills

30,970

Other materials

(pond waste, construction or remodeling debris)

On-site landfills

3,003

Volume beneficially used

Donated or sold

23,963

Other non-coal wastes

Incineration

27

COYOTE STATION

FGD product

On-site landfills

162,810

Boiler slag

On-site landfills

122,080

Other materials (construction or remodeling debris)

On-site landfills

76

Volume beneficially used

Donated or sold

42,239

Management of PCB Materials

Electricity distribution systems require oil-containing transformers. Although we’ve taken steps to remove polychlorinated biphenyl (PCB) oil from our larger substation transformers and regulators, a small percentage of electrical equipment within our distribution system does contain PCBs. When old equipment is retired, we test for PCBs and dispose of them properly. In 2018 we disposed of 2,672 pounds of PCB material. Should a leak or release occur from a unit potentially containing PCBs, it’s our policy to test the released material for the presence of PCBs and promptly clean up and dispose of any contamination according to state and federal standards.

Spills, Fines, and Sanctions

Despite our commitment to sound environmental stewardship, rare mistakes and uncontrollable events occur. When they do, we correct them as quickly as possible. Our Environmental Services Department ensures compliance with our environmental permits and regulations. In the event of noncompliance, we work with regulators to mitigate the instance and adjust processes. We train our employees to be aware of our environmental permit requirements and the steps they need to take to stay in compliance.

Spills

Equipment failures caused minor oil spills. The most significant one involved approximately 150 gallons of non-polychlorinated biphenyl (non-PCB) transformer oil that spilled after a bushing failed in Casselton, North Dakota, in April 2018. The spill impacted the parking lot, entrance, and landscaping of a residential apartment complex. We promptly reported the spill to the appropriate authorities and hired a contractor to restore the area to its original condition.

Fines and sanctions

In 2019 we were fined for one environmental permit violation that occurred in 2018. Big Stone Plant operates under the conditions of a Title V Air Permit, which regulates the rates at which the plant can emit certain pollutants into the air. In August 2018 the plant emitted a higher level of particulate matter than was allowed in our permit, resulting in a Notice of Violation being issued by the South Dakota Department of Environment and Natural Resources. To mitigate the violation, we paid a monetary penalty of approximately $5,000, replaced fabric filter bags used to control particulate matter emissions, and updated our Operation, Maintenance, and Monitoring Plan.

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