PURCELL – Cursed by the continuing emergence of unpredictable cracks, state Transportation Department officials Monday abandoned an ambitious goal of completing emergency repairs and reopening the Lexington-Purcell bridge to passenger car traffic within 45 days.
Officials now want all repair and reinforcement work done before reopening the bridge to anyone — a process projected to take 120 days from Feb. 14, when repair work began. The new target date is June 14.
At that point, the bridge will be safe for heavy trucks, as well as cars and pedestrians, said Casey Shell, the Oklahoma Transportation Department’s chief engineer.
“We’d rather stand here before you today and say, ‘We’re going to close this and we’re going to make life miserable for people,’ than stand before you four months later and say, ‘We’re so sorry, 10 people got injured or died,’” said Terri Angier, Transportation Department spokeswoman.
Shell said he feels terrible about the delay — personally having seen the “shock and fear” on the faces of Lexington and Purcell residents when transportation officials discussed the bridge’s closure at town meetings. Resident after resident told about the extreme hardships created by the bridge’s Jan. 31 closure, which turned a short jaunt over the Canadian River that links the two communities into a 40-mile trip.
State transportation officials say they feel even worse because they inadvertently created the current crisis by failing to recognize and tell a Sapulpa contractor who did renovation work on the bridge last year that a few members of one truss were made out of a rare manganese alloy steel.
The contractor welded on brackets that were intended to strengthen the bridge. But welding on manganese alloy steel weakens the material and makes it subject to cracking under stress, Shell said.
Cracks have appeared around last year’s welds.
“That’s the part that I feel horrible about,” Shell said. “It could have been avoided had we known. ... We don’t have a single crack that isn’t associated with a weld out there.”
But the thing that would make transportation officials feel much worse is if the bridge were to collapse. That’s a real danger with fracture-critical bridges like the 76-year-old bridge that joins Purcell and Lexington, because there are not load-bearing redundancies built into the design, Shell said.
“When this one fails, it’s going to be no warning,” he said. “It’s going to break, and that’s going to be the end of it.”
Concerns of more cracking
Ten crack locations had appeared on critical bridge trusses by Feb. 14 when the Transportation Department awarded a two-tiered, incentive-laden $10.8 million repair contract to Manhattan Road & Bridge Co. of Muskogee.
The number of crack locations since has grown to 41 — something transportation engineers say they didn’t expect and fear could grow, especially if traffic is reintroduced to the bridge before all 264 areas weakened by welding have been addressed.
Manhattan’s repair contract called for the construction company to make emergency repairs to the 10 crack-damaged areas within 45 days so the bridge could reopen to passenger car traffic.
The contractor was then to continue reinforcing all 264 areas on the trusses weakened by welding, with an ultimate goal of reopening the bridge to all traffic within 120 days of the start of work.
When the repair project was designed, engineers thought the 10 original crack locations were tension cracks caused by tightening bolts attached to rods that stretched between brackets across weakened areas, Shell said. The location of the cracks made that the logical conclusion.
Engineers thought that by halting those cracks, bolting plates across the damaged areas and loosening all tension bolts put on during the previous renovation, they could prevent further cracking and allow traffic back on the bridge while other preventive renovation work was being done, Shell said.
The most recent unpleasant surprise has been that additional cracks have appeared around other welds, even after the bolts were loosened to remove tension, he said.
Engineers now think those cracks are being caused by the weakened metal expanding and contracting during Oklahoma’s dramatic temperature swings, Shell said.
Engineers fear that fixing the 41 crack locations they know about currently won’t be enough to protect the public.
“Once we get these all addressed — if we can ever catch up with them all — there’s no assurance that it’s not going to continue to crack,” Shell said.
“We can address the ones we know are there, but it’s the ones that continually pop up. You can’t do a pre-emptive strike, because you don’t know which one to go to.”
Angier said, “The information is changing for us by the hour. It’s developing as we speak.”
Shell said officials feared that if they continued to push for the early reopening, they would be creating a scenario where the bridge would have to be ordered closed and reopened again on an irregular and unpredictable basis as new cracks appeared.
“I really didn’t want to subject the people to that, because I think that’s more torturous than knowing that it’s closed and you deal with it until it’s opened continually,” Shell said.
Transportation Department Executive Director Mike Patterson said the good news is that the repair contractor is making great progress, with work going faster than expected.
By eliminating the 45-day early reopening goal, the department has freed up the contractor to do the repairs in the most efficient order possible, which could quicken the overall time necessary to complete the project, Shell said.
Repairs must be made from lifts that operate beneath the bridge, because of weight restrictions on the bridge itself. If heavy rains were to cause the Canadian River to rise, that could delay the project.
By eliminating the 45-day goal for completing work on locations where cracks have formed, the contractor is free to start at the river and work his way outward, which eliminates some of that weather delay risk, Shell said.
Shell said even though the bridge will not reopen to passenger traffic after the initial 10 crack locations are fixed, the $2,500-an-hour incentive or punishment to the bridge contractor for beating or missing the 45-day target for initial repairs will remain, as well as the $1,500-an-hour incentive or punishment for beating or missing the 120-day target for total completion.
Shell said he is “fully confident” that the bridge will be safe once all 264 weakened areas have been addressed.
“I’m driving on it first,” Patterson said.