What is known about the below-ground support structure for the 16th Street viaduct substructure doesn’t look good, and what is unknown may be even scarier.
That was the opinion of Anthony Siahpush, president of Engineering Specialists Inc. of Omaha, whose firm recently completed a forensic evaluation about the 85-year-old structure.
Siahpush provided a presentation about the evaluation and accompanying 260-page report during the Hastings City Council’s regular meeting Monday. He was joined by ESI associate Paul Douglas.
The viaduct has been closed since May 2019 because of concern about its deteriorating condition. Many Hastings residents have expressed interest in having the structure repaired and reopened, and the council is planning to put the issue to a vote of the people in the November general election.
Both Siahpush and Douglas stated the structure can’t be repaired and would have to be replaced.
“We can comfortably say that pier one, possibly two and three have some kind of a surprise under the surface,” Siahpush said. “However, the rest of them are still unknown. They are still 85 years old. The life expectancy of treated timber for piles is 75 years.”
ESI’s report includes more than 200 photographs, many of which show crumbling concrete, exposed rebar, and rusted and corroded rollers that have eliminated seasonal expansion and contraction.
Monday’s presentation didn’t require any immediate action by the council, but the election ballot language concerning the viaduct’s future needs to be approved by Sept. 1.
According to ESI’s report, the estimated cost for a replacement for the existing 570-foot long, 26-foot-wide, two-lane bridge with a 590-foot-long, 38-foot-wide, four-lane bridge would be between $6.838 million and $7.062 million.
Including engineering and architectural design of $512,857 to $529,672.50 — based on a 7.5% fee for the total cost of construction — ESI estimates the project would cost around $7.5 million.
That amount doesn’t include the costs associated with working with the Union Pacific Railroad on the project.
Siahpush said the support piles are built more than 70 feet into the ground.
The report states it is ESI’s determination that the condition is unknown for the subsurface foundation concrete pile caps and related steel reinforcement, treated timber and steel piles. That condition can’t be definitively confirmed without causing distress or damages, nor is it economically feasible.
“The critical element here is below the surface,” he said. “We can’t see below grade.”
He was asked if it would be feasible to repair the structure’s piers and preserve the existing deck.
“If we were to renovate and repair the piers we have to remove the superstructure to the deck,” he said. “If you were to touch the superstructure the state of Nebraska may require the width of the bridge to come in compliance with the current code.”
That requirement is for a width of 38 feet.
The piles have shown evidence of damage and deterioration, so the piles would need to be removed.
“To remove the pier and remove the pile, you’ll end up with a new bridge,” Siahpush said.
ESI estimates the cost to demolish the structure would be $1.452 million, which is similar to the $1.46 million demolition estimate from Olsson.
It was pointed out Monday that amount doesn’t include funds for work on adjacent streets affected by the demolition of the viaduct, however. That additional cost has been estimated to be around $1 million.
Siahpush estimated demolition could take about two weeks, done in a certain sequence and in conjunction with railroad.
He said reconstruction would take 90-120 days.
While there are still a lot of unknowns, especially when it comes to working with Union Pacific, Mayor Corey Stutte said ESI’s forensic study of the viaduct already has given the city a better idea of what the project may cost.
“We were talking about a not-to-exceed of $5 million,” he said. “We didn’t want to be Lucy with the football and pull it out from under the voters after they did work to pass a $5 million ballot measure and then say, ‘Hold on. This is a $7 million project.’ “
Also during the meeting, the council honored 22 city employees who celebrated service anniversaries from April to July.
The council recognizes milestone anniversaries for employees each month but was unable to while holding remote meetings.
In other business, the council:
— Voted 6-0 to approve a resolution approving the application of Boys 3 MCP Inc. doing business as Coach’s Corner Convenience Store for a Class “D” Liquor License at 3212 Osborne Drive East. Council members Jeniffer Beahm and Matt Fong were absent.
— Unanimously approved the manager application of Leah S. Ratzlaff in connection with the Coach’s Corner Convenience Store application.
— Unanimously approved awarding the $98,795 contract to Precision Sprinklers of Hastings for boring and installing fiber innerducts from the Bypass Substation to the North Denver Station.
— Unanimously approved sending a letter to the Nebraska congressional delegation in support of a loan program for public power utilities and electric cooperatives as a result of the effects of the novel coronavirus disease, COVID-19.
— Unanimously approved reappointing several members to city boards: Robert Parker was reappointed to the Civil Service Commission, Dan Schwartzkopf was reappointed to the Board of Adjustments, Tom Krueger was appointed to the Board of Adjustments, Jake Smidt was reappointed to the electrical board, and Dave Bierman was reappointed to the library board.