When coal is burned to produce electricity, it generates several byproducts. Coal combustion residuals, or CCRs, are generically referred to as “coal ash.” There are two types of coal ash produced at the Rawhide Energy Station–flyash and bottom ash. Both are considered to be non-hazardous materials by the U.S. Environmental Protection Agency (EPA).


Flyash

Flyash is a powdery material and the main byproduct of coal combustion. It is transported from the boiler by the flue gas and trapped within Teflon®-coated fiberglass bag filters contained in Rawhide’s baghouses.

Most of the flyash and bottom ash produced at Rawhide is disposed of in a State of Colorado-approved monofill located on the 4,560 acre plant site. The monofill is underlain by naturally occurring highly impermeable clay and shale strata.

The monofill is inspected regularly by the Colorado Department of Public Health and Environment and the Larimer County Department of Health and Environment. Inspection results have been consistently excellent. Flyash is taken from a special silo located adjacent to Rawhide’s baghouses and transferred to the monofill in large trucks.

With goals of avoiding disposal costs and saving natural resources, Platte River works to find beneficial uses for Rawhide flyash.

Bottom Ash

Bottom ash is coarser material that settles to the bottom of the boiler. It is removed from the boiler and sluiced through pipes to one of two temporary storage transfer ponds. The transfer ponds were constructed by excavating below existing grade and lined with 18 inches of impervious clay to prevent seepage. When one pond is two-thirds to three-quarters full, the water in the pond is allowed to evaporate while the other pond receives bottom ash. When the bottom ash in the first pond is dry, it is dredged and trucked to the monofill.

At the monofill, flyash and bottom ash are compacted, contoured to match the surrounding topography, covered with two feet of soil, and seeded with native plants.

There has never been a release of ash from Rawhide’s monofill or bottom ash transfer ponds. Also, a number of monitoring wells are used at the monofill and the bottom ash transfer ponds. There has been no evidence that anything contained in the ash has leached into ground or surface water.


Regulation of Disposal

The EPA regulates the disposal of coal ash under the Coal Combustion Residuals Rule, published in April 2015. Information that Platte River is required to provide under the new rule can be found at CCR Rule Compliance Data and Information.

Beneficial Uses for Flyash

Flyash is a non-hazardous powdery material that is a byproduct of the coal combustion process at the Rawhide Energy Station. Most of the flyash produced at Rawhide is disposed of in a State of Colorado-approved monofill located on the plant site.

With goals of avoiding disposal costs and saving natural resources, Platte River works to find beneficial uses for Rawhide flyash. There has, historically, been little or no use for Rawhide’s flyash due to changes in its chemical properties caused by the sulfur dioxide (SO2) removal process at the plant. Flyash from coal-fired plants that do not remove SO2 upstream from the particulate removal system in their exhaust streams can be used in a number of construction and industrial processes.

Platte River Monofill

However, since 2006, Platte River has had success supplying a portion of the Rawhide flyash to manufacturers of architectural block and operators of liquid waste disposal facilities.

Block makers reduce costs by substituting Rawhide flyash for a portion of their cement. Lower demand for cement reduces the amount of CO2 released into the atmosphere (approximately one ton of CO2 is emitted during the production of one ton of cement). Liquid waste solidification—Waste management and oil field services companies utilize Rawhide flyash to solidify liquid waste, allowing it to be disposed of with minimal hazard to land and ground water.

Contact ash@prpa.org for more information about the availability of Rawhide flyash for beneficial uses.

Platte River Ash Block