Shale Rests at Root of Construction Problems

For many Northwest Arkansas developers, their real estate investments have gone to shale.

While residential projects face the most common foundation problems, developers and commercial contractors deal with everything from shale to expanding clays and faults.

And when developers are forced to drill deep for a secure foundation, they’re also forced to dig deeper into their pockets.

If a commercial construction project has to have piers drilled rather than a simple shallow foundation, the developer can expect a 35-50 percent increase in cost of the foundation. A foundation typically constitutes 5-10 percent of the overall cost of the building, so for a $1 million project, tens of thousands of dollars would be at stake.

“The culprit in all of this is the Fayetteville shale,” said Walter Manger, professor of geology at the University of Arkansas. “Shale expands and contracts, caused from the clay’s weathering.”

Manger said the Springfield Plateau (see map) that covers Benton County and the northernmost part of Washington County is generally limestone and flint. But the Boston Mountain Plateau, the geological province that encompasses Fayetteville, is generally sandstone and shale.

The Salem Plateau that covers north central Arkansas is considered better than both the Springfield and Boston Mountain plateaus.

“Boston Mountain is just not very good,” Manger said. “Limestone is good. Shale is bad.”

Fayetteville’s Foundation Woes

Many Fayetteville homes have suffered because of poor planning on the front end. One contractor told the Northwest Arkansas Business Journal that in most cases in which foundations have been damaged, developers failed to consult a geotechnical engineer. And many owners failed to pay attention to such detail when purchasing the home.

Companies such as Gintonio Foundation and Stabilization Inc. of Springdale are called in to rescue a damaged home. They’re not cheap, but they are necessary once foundation shifts occur.

Manger said he has heard that as many as 70 percent of all structures in Fayetteville have foundation problems.

Commercial contractors must adhere to stricter guidelines on the front end than residential contractors. However, that doesn’t mean foundation problems won’t arise later.

Matt Bodisbaugh, vice president of Nabholz Construction Corp. in Rogers, said that when Nabholz needs pier drilling done to a project, it subcontracts the job to another company.

“That company will come in and drill a hole,” Bodisbaugh said. “Then, a geotechnical engineer will come out and inspect the bottom. Once it’s verified that the hole has reached rock, Nabholz lowers a steel rebar cage. That reinforces the concrete pier. It’s not cheap because you can’t do very many in a day.”

Bodisbaugh recalled an amazing sight during a visit to a warehouse in Hope. He saw a concrete pier 24 inches in diameter and 18 feet deep that had been moved so violently by the expanding and contracting clays that it had been shoved through a six-inch thick concrete slab.

Bodisbaugh said southwest Arkansas actually may be even more difficult for contractors because the local earth is home to some very expansive clays.

Shale is a sedimentary rock composed mainly of clay particles. It is formed by the “lithification” of clay with silt. Shales composed predominantly of clay minerals easily split into parallel flat plates or sheets. And it erodes much faster than most other sedimentary rocks.

As for prospective new home owners, Manger offered some advice in avoiding foundation problems.

“I tell people when they’re looking at buying a house or about to build one to just look at the trees,” Manger said. “If the trees are straight up and down, there’s no problem. But if the trees are tilting, you’ve got a problem. That’s the shale moving down the slope, and the trees are getting heavier pressure so they start leaning. That’s when you need to get someone to design the footing on the house. You do it now rather than 12 or 15 years down the line when it will cost you much more.”

Jay Huneycutt of the UA’s Physical Plant said it was “standard practice” for the UA to put reinforcement piers in almost all of its larger construction projects. Reynolds Razorback Stadium had about 50-60 piers drilled some 30-50 feet deep when it was renovated to 72,000 seats.

Ben Israel, owner of Dixie Development Co. in Springdale, has been very busy in the last year with several commercial projects, including Commerce Center in Fayetteville and Signature Square in Springdale. But Israel said his company has been lucky and has not faced many foundation obstacles.

“We just go to the engineers and basically do what they say,” Israel said. “They do soil borings and determine what’s down there. From those, we determine if we need piers or just bridge over with red dirt.”

Manger said the sandstone in Fayetteville makes for a good foundation, but only if veins of shale don’t alternate with the sandstone’s mix.

“Fayetteville’s got rocks that are real old, but the landscaping is fairly young,” Manger said.

Eventually, the collapsed shale won’t be a problem, but Manger added, “Not in anybody’s lifetime that’s here.”

“It’s going to get better, but it’s going to get worse before it gets better.”

It was only 35 years ago that Fayetteville’s north edge was where Fiesta Square now sits.

A prime example of the problems shale can cause is Interstate 540, which only opened in 1998, yet it already has deteriorated severely in some areas. The pavement has been fracturing and sinking around the Chester area in Crawford county.

Trains Keep on Rollin’

Fayetteville has very little limestone. And its premium limestone location may be under the Northwest Arkansas Mall. That’s good news for the Mall, but with ready-mix concrete plants already forced to import sand from outlying areas, the financial effect is felt everywhere from the large commercial projects down to the home owner.

“Fayetteville is a very unique development in that there is no source of sand in Northwest Arkansas,” Manger said. “That’s why the railroad is still running. They have to load up the sand and bring it back to the ready-mix plants. Limestone is fairly limited, too. And if you’re going to make concrete, you have to have sand and rocks that can be crushed into small enough pieces.

“Products at a quarry are of high volume and low cost. The most expensive stuff they sell is about $6 per ton. But if they have to haul it more than about 10 miles away, they have to double the price. From West Fork to Bella Vista is a strip city, where everything is built right up to the city limit lines. No one wants to live by a quarry, so they’re pushing these quarries farther and farther out. There’s a very limited area to produce it around. There hasn’t been a whole lot of planning going on if you ask me.”

The closest rock quarries to Fayetteville now are in Springdale on the Benton County line, West Fork and near Hickory Creek. And some companies have to bring sand in from as far away as Fort Smith.

Manger suggests that Fayetteville planners missed the ball with the mall’s location. Nearby Zero Mountain is an old underground quarry operation. And Manger said the mall would have been better sited at another site.

“We could’ve used [the mall’s] site for a quarry location,” Manger said.

“The irony of the development of Fayetteville is that the place has no sand. And there’s not much limestone. But it’s one of the growth centers in the nation, not just Arkansas. People don’t realize just how deficient it is of sand and limestone.”