Dartmouth College has temporarily halted work on a new $200 million building after construction workers dug and braced a 70-foot deep hole that was 10 feet away from its intended layout. (Valley News - Jennifer Hauck) Copyright Valley News. May not be reprinted or used online without permission. Send requests to permission@vnews.com.

HANOVER — Dartmouth College has halted work on a new $200 million building for its engineering school after construction workers dug and braced a 70-foot-deep hole that differed from the intended layout.

All foundation work on the new Center for Engineering and Computer Science, which includes a 340 vehicle parking garage, has been temporarily suspended, Dartmouth said on Thursday, as the college considers its options.

“The northern soil retention structure at the Thayer/Computer Science building site has been placed 10 feet south of the intended location. The college has informed the town and is working with Turner Construction and outside design professionals to evaluate our options,” Dartmouth spokeswoman Diana Lawrence said via email. “There are no safety issues related to the matter.”

The project on the so-called “west end” of campus is to include a new building housing the Thayer School of Engineering as well as computer sciences for Dartmouth. It also is to include the Magnuson Center for Entrepreneurship and Dartmouth’s electron microscope facility.

Work began on the 160,000-square-foot building this winter, and Turner Construction Co., a national firm based in New York City, discovered the mistake as it prepared to install a tower crane at the worksite, Dartmouth said on its website.

Lawrence said the hole is the right size, but placed 10 feet too far to the south. She said Dartmouth is taking steps to “ensure the financial impact to Dartmouth is minimized” and hopes to have a better sense of the costs and effect on the project schedule in the coming weeks.

“We are in the process of investigating how the error occurred. We have assembled a core group of internal and external representatives with design, project management and legal expertise and will know more in the coming weeks,” she said.

Emails and a phone message sent to Turner’s national headquarters on Thursday were not returned.

The error puts the excavated area farther than intended from the adjacent MacLean Engineering Sciences Center. Dartmouth’s plans include changing that portion of nearby Engineering Drive to a roadway only accessible to pedestrians, emergency vehicles and students as they move in and move out.

Lawrence said the college’s options “could include additional excavation work to place the building as originally intended or a change in building location to fit the area already excavated.”

But both come with caveats.

Robert Houseman, Hanover’s director of planning, zoning and codes, said Dartmouth officials talked about possible options but had not said what they might do.

Houseman said he didn’t want to speculate but a different footprint for the building could require Dartmouth to resubmit plans to the Planning Board.

“If a building were to move in a way that alters the lighting, the road-drive grading, the proximity to neighborhoods, all of that would be subject to Planning Board approval,” Houseman said.

Hanover’s Planning Board has a meeting scheduled for mid-July, and then under its summer routine wouldn’t meet again until Aug. 27.

Meanwhile, trying to adjust the size of the excavated area, which is currently held in place by interlocking sheet piling, could be costly.

Frank “Jay” Barrett, an architect in White River Junction, said site work on major projects “has become extraordinarily expensive” and complex over the years, and he said fixing the error could “get into seven-digit figures.”

Because of the depth of the hole, which will house the three-level parking garage, the steel sheet piling is holding back “a tremendous amount of soil pressure,” and trying to move it would be no small feat, said Barrett, who grew up in Hanover and lives in Fairlee.

“It’s not just ‘OK, we need to dig the hole a little bit bigger,’ ” said Barrett, who has worked on smaller projects for Dartmouth in the past but is not involved in this one. “There’s no simple way to deal with this thing.”

Dartmouth’s website includes a link to a time-lapse camera showing much of the excavation work.

John P. Gregg can be reached at jgregg@vnews.com or 603-727-3217.