WILLISTON (AP) - Work is being done to fill abandoned coal mines along an oft-traveled Williams County road to keep it from collapsing.

More than $1 million is slated to spent through 2009 along Williams County No. 9, where many coal mines were prominent between 1910 and the 1940s. The 2 miles of work is funded through the Public Service Commission's Abandoned Mine Land Division. The program is funded by a production fee on lignite coal mined in North Dakota.

Theim Drilling of Williston is the lead contractor. S&S Drilling of Williston and Grigsby Drilling of Glendive, Mont., have been hired as subcontractors.

"We're drilling holes for the Public Service Commission to try and find the underground old coal mines," said Kevin Sorenson of S&S Drilling. "When we find mines, we install plastic pipe, and the grouting contractor pumps the voids in."

Sorenson said they use maps to help find the voids. But he said they are not always complete.

Bill Dodd, assistant director of the Abandoned Mine Land Division of the PSC, said projects like the one along County No. 9 have been done since 1981, at a cost of about $30 million.

Dodd said filling in the mine orifices is a slow process.

"Sometimes it takes days or weeks to fill up one location," he said. "Mine caverns can accept a lot of grout. We can be at a single hole for several days, and then move forward a few feet."

Dodd said 9,625 tons of grout will be used this year.

Exploratory drilling along the road began in 1993 to find the voids. Backfilling began last year.

Dodd said a similar project also is being done this year in the Columbus area, in northwestern North Dakota.