Near the spot where smokestacks once belched toxins over the South Side, two companies soon will begin turning trash into something better.

The Solid Waste Authority of Central Ohio announced an agreement today that will allow an Arizona building-supplies maker and a northeastern Ohio landscaping company to begin operations at the site of Columbus' former trash-burning power plant.

Rastra Inc., of Scottsdale, Ariz., recycles landfill-bound Styrofoam as a component of concrete building forms. Its first Midwest plant will employ as many as 50 people.

Kurtz Brothers Inc., headquartered in the Cleveland suburb of Independence, plans to put an anaerobic digester on the site to turn yard waste and other organic material into compost and energy.

SWACO spokesman John Remy said groundbreaking will take place this fall.

The agreement announced today is to raise the level of 10 acres at the SWACO site that are prone to flooding.

The Shelly Co., a road-building and mining company based in Thornsville, will do that work, valued at $4 million, in exchange for mining rights on another part of the property.

Shelly already has a limestone mine nearby.

Remy said Shelly will pay royalties for rock mined on SWACO land. The payments, estimated at about $1.5 million, will pay down the agency's debt on the trash-burning plant, which operated from 1983 to 1994. The plant was torn down in 2005.