Environmentalists argue that wrapping, sealing and burying ash removed from unlined ponds to be a better solution, although not much is known about the long-term ramifications.

Charlotte state officials said they were investigating a plan to take millions of tons of coal ash from the retired Riverbend Steam station on Mountain Island Lake – Charlotte’s source of drinking water– and burying it in lined, covered enclosures at the airport.

There, it would be used to grade land for construction projects, saving the airport millions.

But officials haven’t said where the ash would be buried and how the Catawba River shed and Lake Wylie would be protected.

There are concerns that without proper management, toxic chemicals found in coal ash will make its way into the Catawba River shed.

At Ashville airport, contractor Charah and Duke Energy have installed groundwater-monitoring wells on the site.

The water is tested quarterly and thus far, each assessment has met water-quality standards.

Duke and Charah have moved 3 million tons of coal ash from the power plant to the airport.

Asheville Regional has saved $US12 million ($A13.2million) on the cost of fill dirt it might have otherwise bought.

Asheville officials said no projects had been built yet on the graded land.

Documents released by the City of Charlotte said Charlotte Douglas airport could save up to $US30 million if it used 4 million pounds (1814 tonnes) of Duke’s ash to fill in land for future construction projects.

Coal ash is not regulated as a hazardous material, although the Environmental Protection Agency is expected to issue tougher standards later this year.