CLINTON — Ameren, with help from the Illinois Environmental Protection Agency, in September will begin clean up of the former Illinois Power site, located in the 200 block of N. Monroe St. The work will begin with the demolition of the empty IP building, which once housed local offices.

The IP property was the site of a manufactured gas plant. The plant produced gas for Clinton street lamps and for gas lighting in some homes from 1904 until 1941.

Ameren has been working to clean up a number of such sites in Illinois and Missouri. The process to clean up the Clinton site began in November 2009.

Demolition of the building is scheduled for September, with work to dig up residue on the property to start in October, said Steven Burns, consulting environmental scientist for Ameren.

Residue created from the gas manufacturing process has not posed a health risk to local inhabitants, Burns said in November. This is mostly due to the tar-like consistency of the residue and the fact that the material is buried in clay, which helps prevent “leaching.”

Once the building is razed, the site will be covered by an enclosure, a tent, and negative air pressure will be applied to prevent air inside the tent from leaking out. “We will suck the air out from inside of the tent, because there might be volatile organic chemicals that would be emitted into the atmosphere,” Burns said.

The air from inside the tent would then go through a filtration system. An independent company will monitor the emissions from the air-handling units. “We’ll also have four different air monitoring stations that operate 24-hours-a-day for the whole time we’re doing our remediation,” Burns said.

A wall will be constructed separating the property from the alley to the south, and then a tent will arch over the site. Workers will dig down to approximately 25 feet at the deepest point, and shallower levels of excavation will radiate beyond that on the site. The wall will protect service lines, such as sewer, water and other utilities by preventing the deepest part of the excavation from collapsing.

“The tent will run in a north-south direction …and then on the east and west sides, we’ll have vertical walls, called gable walls,” Burns said. Equipment traffic will enter through an overhead door on the Madison St. side of the site, be loaded, and then exit on the Monroe St. side. The tent will cover about two-thirds of the site.

Burns said the plan was to return the site to residential standards and to sell the property once that was established.

The public will be notified about an open house that Ameren and the IEPA will conduct before work begins.