GREENBUSH – Maine Department of Transportation officials knew the 30-foot rock wall along U.S. Route 2 would tumble – they just didn’t know when.

It turned out to be Thursday.

The fall of the wall is a setback for the DOT in its attempt to fix Route 2. The wall constructed last week faltered, as predicted. No one was injured.

State crews built the wall using tons of granite rock, but because of the soft soil of the area the design was expected to fail. As a result, some granite rocks went into the Penobscot River.

“There was an even chance it would happen,” DOT official Jerry Waldo said Thursday afternoon as he viewed the site. “The weight of the rock overloaded the soil.”

A crew was at the site Thursday afternoon building a ledge with small rocks and dirt. Workers will continue Friday to rebuild the wall.

Soft soil underneath the rocks is blamed for the rockslide. It is the same soil condition that caused the road to slide, creating the Route 2 mess two weeks ago. Last week’s rain had little to do with the slide, Waldo said.

The design of the rock wall is looked at to be a permanent fix to the problem, but Waldo said he expected that the DOT will have to return to the site.

“Next spring, when the river rises, it may take some more soil and rock, and we will have to replace it again,” Waldo admitted.

In fact, the new rock wall to be built over the next week isn’t expected to hold either.

“Fill it, let it fail, then fill it again. It takes time,” Waldo said of the process of reconstructing Route 2.

The lumber put in place between I-beams also was knocked out when the rock wall slid.

The DOT plans to keep building a new wall each time one fails until it creates a balance with the subsoil under the ground, allowing the structure to stabilize. No one knows how much weight the soil can take, but the amount used for the first wall is what is needed to stop the road from sliding anymore, so the DOT will not use less rock, Waldo said.

“It’s a little bit of a crapshoot,” he said earlier Thursday in an interview.

There is no safe way to keep the rock wall in place, nor is there a cost-effective design that would prevent the DOT from having to return to the Greenbush site.

“We are working within our means the best we can,” the DOT official said.

Waldo added that the unforeseen crack and unexpected slide of Route 2 prevented the DOT from designing a better fix.

Unstable soil and clay sent the road into the Penobscot River, and the tons of gray rocks from the wall had only one place to go: the river.

A white residue has formed on the top of the Penobscot where rock and soil have entered the river. The current of the river dodges this area, possibly because the granite rocks are blocking the flow.

The fall of the Route 2 wall is an event Waldo called a good thing to happen while crews are still on scene.

“The public now realizes this is a dangerous situation,” he said.

The fall set crews back a week, leading Waldo to predict the road will open back up the second week of August, but with the wall expected to fail again, that estimate could change.

“Mother Earth is controlling the situation,” he said.