Oct 5 - Knight Ridder/Tribune Business News - Jeff Tucker The Pueblo Chieftain, Colo.

The same hardening properties that made Xcel Energy's fly ash useful for cement will keep the waste from going airborne when put in a dump, the company said.

Last week, Xcel, as part of its planned expansion of its Comanche plant, won approval from the city to store the leftover coal ash on a 235-acre site next to the plant. The need for a dump arose because upgraded pollution controls will require chemicals that may make the ash less attractive to cement makers.

Previously almost all of the ash was sold to cement makers.

"We have stored ash there before but it's been miniscule," Xcel spokesman Mark Stutz said "Maybe 5 to 10 percent of the product was stored out there, usually in down periods like the winter when there wasn't as much demand for cement."

The ash can easily be compacted and kept from becoming airborne, thanks to the properties that make it useful in cement aggregates, Stutz said. "When the ash is put down, we spray it with water until we get a very hard shell," Stutz said. "It's not quite the consistency of concrete, but it won't get kicked up by wind."

Stutz said Xcel plans to store the ash in eight cells over a period of 50 years.

The cells will be shallow pits on the site.

Once a cell is full, Xcel will put topsoil over the ash and replant native grasses on the site, Stutz said. The finished cells will look like natural hills or berms, Stutz said.

It is the same process that has been followed by Xcel for the small portions of ash now stored. The same approach has also been used at a number of other power plants, Stutz said.

The agreement reached last week with the city of Pueblo's zoning board of appeals was one of the last regulatory hurdles the company needed to clear before starting its $1 billion expansion.

Construction on the new plant and pollution-control upgrades to the existing units is expected to last three to four years. Xcel hopes to break ground in January.