The abundance of shale rock found near Pleasant Grove Hill south of Lawrence will shift the path there of the new four-lane U.S. Highway 59 farther to the east than planned.
The project is part of an expansion from Lawrence to Ottawa.
Bob Henthorne, the Kansas Department of Transportation's chief geologist, above, said that portion of the new highway would now run through the middle of a smaller hill to the east of Pleasant Grove Hill.
Originally, construction would have put the new road on the west side of the smaller hill.
Construction crews will still have to cut 72 feet into the hill, and when work begins, the shale rock will be exposed for one year so it will break down.
State officials have said the project in Douglas County would not be complete until 2011.
Known as "Lawrence shale," it can absorb moisture, expand and break down, which would have damaged a finished road, Henthorne said.
Henthorne also said the adjustment has increased the project's cost in Douglas County by $5 million, but the rock would have done $30 million in damage to a finished project.