Engineer Told Bosses of Thin Asphalt
PIKEVILLE — Wendi Johnson, a Department of Transportation engineer, warned department officials in 2003 and 2004 that the 5.2 inches of asphalt they planned to use on Interstate 795 would be too thin — and too weak.
Cracks and potholes sprouted in northern Wayne County near Pikeville last spring, just 16 months after traffic started rolling down the new four-lane freeway between I-95 at Wilson and U.S. 70 at Goldsboro.
The asphalt was expected to bear cars and trucks for 15 years. Now DOT officials are weighing repairs for I-795 that could cost between $1.6 million and $10 million. They have not determined the extent of I-795′s pavement failure or found its cause, but they have tentatively agreed on a remedy:
Thicker asphalt.
The two-year-old pavement on North Carolina’s newest interstate is deeply fractured in some places. Core samples of asphalt cracked apart Thursday morning when test lab engineers pulled them out and laid them gently on the roadway.
Johnson, a DOT engineer since 1989, monitored their work closely. She has overseen road construction for DOT Division 4 in Wayne and five other counties for the past eight years. She has seen other new roads that needed pavement repair years earlier than expected — including U.S. 64 near Rocky Mount and U.S. 264 near Wilson — because the original asphalt wasn’t thick enough.
"The division has had failure of pavement in the past with the thin design," Johnson wrote from her Wilson office on Aug. 23, 2003, to Clark Morrison, who heads DOT’s pavement design unit in Raleigh. It would be cheaper to add sufficient pavement while the freeway was being built than to come back later for big repairs, she said.
Her plea for three more inches of asphalt on 17 miles of I-795 would have added $2.8 million to the project’s $196 million pricetag.
DOT officials said it was too expensive. They said the thinner design would suffice for a freeway projected by 2024 to carry 40,800 cars and trucks each day. (The latest count is about 7,000 daily vehicles.)
Johnson watched Thursday as engineers from two DOT labs drilled 4-inch and 6-inch core samples and lifted 24-square-foot asphalt slabs out of the damaged roadway.
She was too much the team player, and too much the dispassionate engineer, to declare that she was right and DOT officials in Raleigh were wrong to reject her call for thicker pavement on I-795. Fiscal pressures forced DOT administrators to trim project costs wherever they could, and they believed their calculations a few years ago supported the decision, she said.
"Obviously, it would be wonderful to be able to thicken up the pavement on every new highway, to make it as stout as possible, so they would all last longer and our maintenance costs would be lower," Johnson said. "But there has to be some mindfulness about construction costs."
DOT has had embarrassing, expensive problems with bad pavement before.
Last year, the department spent $22.4 million to rip out a three-inch layer of almost-new concrete — four lanes wide and 10.4 miles long — on I-40 in Durham County. Mistakes in design and lapses in construction oversight were blamed for a botched paving job that caused the new concrete to deteriorate.
The I-40 blunders led to the resignation of DOT’s chief roadbuilder. It helped spark a $3.6 million initiative that is supposed to make DOT a more efficient, businesslike and accountable agency.
Judith Corley-Lay, DOT’s chief pavement engineer, told Johnson in a Dec. 6 memo that months of tests had pointed to a fix for the problem on I-795 but not to its cause. She recommended replacing 2.5 inches of damaged asphalt along about 2.8 miles of I-795 near Pikeville, and topping it with another 1.5 inches, for $1.6 million.
"While these analyses do not answer the question of exactly what failed this pavement, it does demonstrate that additional quality thickness is needed," Corley-Lay wrote.
A departmental committee ordered more extensive tests Friday along the entire 17-mile stretch that was built with the 5.2-inch asphalt layer, Corley-Lay said in an interview.
If more problems are found, DOT could spend up to $10 million to make repairs and add 1.5 inches of asphalt on 17 miles where — under Johnson’s original recommendation — $2.8 million would have paid for twice as much.
Corley-Lay said it was not yet clear whether DOT erred in its original pavement design. Some tests suggest the two top layers of asphalt on I-795 are separating from each other, a problem that might be unrelated to the overall pavement thickness.
"We have built that exact same pavement design on more than 130 projects around North Carolina," Corley-Lay said. "That design has not had a record of performing badly."
While Johnson was not ready to say "I told you so," her former boss was less guarded in his assessment of the I-795 pavement failure.
"It was preventable, absolutely," Jim Trogdon, who was DOT’s supervising engineer for Division 4 until 2005, said in an interview.
Trogdon now works as a transportation expert on the General Assembly staff, and he also serves as a brigadier general in the National Guard.
He said DOT did not really save money when it rejected Johnson’s recommendation to spend $2.8 million for more asphalt.
"It’s a false savings if you have to come back later and do substantial repairs after you open it to traffic," Trogdon said. "Those are not the kinds of savings we look for."
bruce.siceloff@newsobserver.com or (919) 829-4527
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