Drivers in rural southwest Shawnee County will soon see a five-month construction project to replace a deteriorating 78-year-old bridge.

"This is an emergency repair project, an emergency bridge replacement," said Curt Niehaus, the county's public works director.

The S.W. 61st Street bridge spans Six Mile Creek, located about 800 feet west of S.W. Auburn Road. The 61st and Auburn intersection is about 3 miles north of Auburn and about 3 miles west of Washburn Rural High School.

The stonework bridge was built in 1943.

"This was the one with the metal culverts with the vertical faces made of rock, and we were losing the rock," Niehous said. "So we were losing what was containing the fill above the culverts. So that's why we classified this as an emergency repair."

Biennial inspections revealed the bridge had deteriorated after previously being rated in fair condition.

In February, the commission spent about $102,000 to have Finney & Turnipseed Transportation and Civil Engineering carry out design and construction engineering work.

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Considering the bridge repair to be an emergency allowed the county to bypass its normal process for selecting contractors, speeding up the process.

"In 10 months, we (will) have designed and constructed a bridge," Niehous said. "We don't like to do things this fast because it takes a lot of luck. Things just fell together, things worked out, and we were able to get this done. Normally, these bridge projects take a minimum of two and a half to three years."

The contract calls for work to start Aug. 1, with the bridge substantially completed by Dec. 9 and completed by Dec. 16. Delays may result in deductions from the final payment.

If the bridge isn't done on time, winter weather and asphalt plant shutdowns could prevent final completion until springtime.

The contractor's bid to replace the bridge combined with previous engineering and design costs will approach $1 million.

Commissioners Bill Riphahn and Kevin Cook on Thursday approved the contract with King Construction, of Hesston. Commissioner Aaron Mays was absent.

The bridge replacement will cost about $864,000. Funding comes from the half-cent sales tax approved by voters in 2014 in part to finance infrastructure work, including bridge replacements.

The engineering estimate had been about $915,000, and the other bid was about $984,000 from Paola's Bryan-Ohlmeier Construction.

This bridge replacement meant that "other bridges had to move back a little bit" during budget talks, Niehous said.

Bridge inspection data show 58 of the 563 bridges in Shawnee County are in need of repair or corrective action. The U.S. Department of Transportation rates 14 as poor; 16 are structurally deficient.

More:See the results of Shawnee County bridge inspections

Project costs have risen substantially over the past 18 months, Niehous said.

The bridge will be exactly the same as one the county recently replaced on Glick Road near Silver Lake, though the Six Mile Creek bridge is slightly wider, requires more channel work and is being built on an accelerated construction schedule.

Still, attempts to account for those factors to compare cost ratios on the bridges indicates this new bridge will be roughly $174,000 more than could have previously been expected.

"This isn't an exact apples to apples thing. ... Nevertheless, I think it's a valuable lesson in what project costs are doing for us," Niehous said.

Construction cost inflation is typically higher than the general inflation rate, he said, "but what we're seeing now is extraordinary." The cost of labor and materials, as well as uncertainty around supply availability, are feeding the higher prices.

"I'm a little concerned about projects we may have already estimated and have in the works now," Riphahn said.

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Jason Tidd is a statehouse reporter for the Topeka Capital-Journal. He can be reached by email at jtidd@gannett.com. Follow him on Twitter @Jason_Tidd.