The Chadron Airport runway paving project that won the Nebraska Concrete Paving Association’s Best Airport Project award for 2000 doesn’t look as praiseworthy in 2012, and will have to be replaced at an estimated cost of $6.4 million.
That news was delivered to the Chadron City Council Tuesday, Jan. 15, by Public Works Director Milo Rust, who said cracking problems with the 6,000 foot long concrete runway came to light last summer and are due to a chemical reaction with the silica sand used in the cement mix.
“We had hoped it would last for 40 or 50 years,” Rust said of the concrete on the airport’s main runway, known as 02/20 for its compass orientation. “When we were doing the (lighting) project this summer, we found... the concrete had horizontal cracking,” said Rust.
The problem is serious enough that the Federal Aviation Administration (FAA), which paid 93 percent of the cost of the 2000 project, has already allocated funds to have the concrete replaced, said Rust. The agency will again stand most of the cost, but the city will have to pay 5 percent, or about $320,000, he said.
The concrete used in the project in 2000 was the standard 47B mix specified by the state of Nebraska for all of its highway projects at the time, and it met all of the required tests after it was laid, according to Rust. “It was a Nebraska specification being used by everybody,” he said.
The 47B specification was developed by the Nebraska Dept. of Roads in 1947 and specifies the percentages of cement, coarse and fine aggregate, and water, to be used in concrete, according to a The Birds Nest, a blog dedicated to information about concrete (nebraskconcrete.blogspot.com).
In a phone interview Thursday, Rust said that city officials and FAA representatives noticed a spiderweb effect on the surface of the runway during an annual inspection a couple of years ago and attributed it to Alkali-Silica Reaction (ASR) in the concrete that stems from the type of aggregate used in the mixture.
The problem wasn’t viewed as serious, however, until last summer when work on another project revealed that the six-inch-thick concrete had developed horizontal cracks about two to three inches below the surface.
The full extent of the problem isn’t yet known, and the first step of the repair process will be testing to see if how much of the concrete and base may have to be replaced, said Rust.
Chadron is apparently not the only place where similar runway problems have occurred, according to Rust. He said Nebraska Dept. of Aviation officials have told him about instances in several other places, including one in Nebraska and one in Kansas.
In Chadron the problem is limited to runway 02/20 and two taxiways, but hasn’t been found in runway 11/29, according to Rust. That concrete in that runway was laid about four years later, and apparently a different mixture was used then, he said.
The state now tests the aggregate used in concrete mixtures to avoid ASR problems, according to Rust.
Initial reaction to the news from council members was to question if the city has any way to take action against the contractor for the 2000 project. “Did you check the a lawyer if we had any recourse at all?” asked vice-mayor Levi Grant. “There is some liability somewhere.”
The chances of taking action against anyone for the problem appear slim, according to Rust, but the city hasn’t asked a lawyer to look at the situation. The concrete met project specifications and pressure tests, and the warranty was only for two years, he noted.
City Manager Wayne Anderson said he doubts there is any way to take legal action for the problem. “It had a two-year guarantee and we are beyond that. There is nobody to hold accountable,” he said.
Grant said he is grateful to the FAA for putting the repair work on ‘fast track’ but still is concerned about the city’s expenses for the airport. “Every time we turn around we spend money on that airport,” he said. “I’d feel better if an attorney looked at it and tells me there is nothing we can do.”
The city has contacted Olsson Associates, its approved airport engineering firm, about the project, and should plan to do the project in 2014-15 in order to take advantage of the FAA funding that has been made available, said Rust.
Council action will be needed to proceed with the project, but Rust did not say when the matter would appear on the agenda for a decision.
Source: http://rapidcityjournal.com
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment