It is a mystery how or precisely when the Grand Boulevard bridge over Interstate 670 became a hazard.
“It just broke,” is all that Brian Kidwell can figure.
“My hunch is a very heavy load went over it. It could have been a totally legal load” but more weight than the 140-foot-long overpass could handle, said Kidwell, an assistant engineer for the local district of the Missouri Department of Transportation.
“I don’t know if I’ve ever seen one fail this way … like, overnight.”
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Unusual things are happening around the interstate loop downtown, which is entering its second half century of existence. Engineers worry about funding for infrastructure repairs in the short term, while some planners talk about eliminating entire stretches over the long term.
All over the loop, including the I-670 stretch, more than 40 overpasses built in the 1950s and ’60s are needing attention. MoDOT says they’re structurally sound enough to pass inspections every two years. But that was also true of the Grand Boulevard bridge when inspectors just eight months ago deemed it adequate.
Then it broke.
“A significant failure,” Kidwell called it.
Kidwell was standing on the eastbound I-670 shoulder, where chunks of concrete the size of pork chops had fallen from the underside of the Grand bridge above. Steel studs were raced to the site earlier in the month to brace an area of the span that was sagging an inch.
On the west face of the overpass, below Grand’s southbound lanes, he pointed to an S-shaped crack that had crept 20 feet since the inspection in September.
Bridge engineer Rick Kingery had been keeping an eye on the 53-year-old structure in the months since. Driving underneath in April, he saw the crack forming.
“It was tight then,” he said, “not something you could stick your arm in.” But the S-shape would be open to that point when he checked again on the morning of May 6.
He phoned Kidwell within minutes.
“You need to get out here,” Kingery said. “I want to close this bridge.” And state inspectors did that very day, shutting down the overpass lanes and even the sidewalks.
Orange netting and striped barricades now block entrances where 9,300 vehicles had passed through daily.
The state hopes to replace the bridge by December at a cost of about $5 million, which will come out of the budgets of other road projects on the books. The city would like to see MoDOT broaden at least one sidewalk and add more baffling to reduce freeway noise, which could up the price.
And what of those other bridges around the sunken I- 670/70/35 loop — 64 bridges in all by MoDOT’s count, most of which have stood for half a century or more?
“We believe that the remaining bridges in the downtown loop are safe,” the department said in a statement Thursday.
It continued: “All of our employees observe the highway system as we travel around our region, both on and off the clock.”
MoDOT also relies on the eyes of law enforcement, local public works officials and the traveling public.
On the south loop alone, between Charlotte Street and Broadway, MoDOT records show six spans over I-670 were completed between 1961 and 1966, all running north and south. Construction began in 1963 on the widest, Grand’s four-lane bridge, which opened to traffic the following year.
(In the past decade, the McGee Street bridge was removed and the others, including Grand’s, have been enhanced with guardrails and more accessible walkways. The Main Street bridge was rebuilt to accommodate the new streetcar line.)
The north loop features at least 10 bridges built in the 1950s.
Their future may require more than Band-Aid repairs, engineers and regional planners say.
“If you were designing the loop from scratch, it wouldn’t look as it does today,” said Ron Achelpohl, director of transportation and environment at the Mid-America Regional Council. He cited too many access points close together, forcing vehicles to weave and dodge.
“Back then the premise was, for Kansas City to remain competitive, the downtown core had to be very accessible to automobiles,” he said. “The thinking was that the future (of residential living) was not there. It was in the suburbs.”
Now downtown dwellers are coming back.
The boldest of recent ideas imagines the oldest part of the freeway loop, the north side, being torn out for good.
Little wonder that proponents call this the Big Bang Plan. Start by decommissioning the milelong ditch of speeding traffic dividing the Central Business District and the River Market. Develop the property into something attractive to, say, a major corporate headquarters looking for a campus that could bring 12,000 or more new jobs downtown.
At the request of city leadership and the Mid-America Regional Council, a panel overseen by the area branch of the Urban Land Institute outlined the idea in a February report.
“This is just the start of what will end up being a lengthy planning process,” said Achelpohl. Officials first must decide whether to replace or just repair the Broadway bridge, which opened in the late 1950s.
“For now, it remains to be seen if it’s a feasible strategy” to remove and renovate the north-loop strip,” he said.
Rerouting some 70,000 daily vehicles now on the north freeway to the three other sides of the loop could improve “connectivity,” enhance the pedestrian experience and bring new development downtown, the thinking goes. The excavated roadbed could be converted to two or three levels of underground parking.
Connectivity — a more aesthetic integration of streets, sidewalks, bike trails and parks — is a concept gaining traction in other cities carved up and bridged over by the post-World War II rush into the freeway age.
“It’s true across the board. We operate differently as a culture than we did 50 years ago,” said Kansas City public works spokesman Sean Demory. “We have different goals of what makes an ideal commute” and a desirable downtown landscape.
An executive summary written by the group studying the north loop touched on a variety of private and public funding options, all totaling hundreds of millions of dollars just to redevelop the property on top of the existing freeway site.
MoDOT, which owns most of the loop, said it is open to the suggestion of one day decommissioning the north stretch. But for now, a projected $142 million replacement of the Broadway bridge tops the state’s priority list for highways in the area.
And that job could be five or more years down the road, said engineer Kidwell.
“We just don’t have the money to fix everything we have to fix,” he said. He noted that the state’s fuel tax to fund road construction hasn’t been raised in 20 years.
The downtown loop “was a huge investment our parents made that has been with us our whole lives,” said the middle-age Kidwell. “We just got our driver’s licenses and started using it. We took it for granted.
“Now as this stuff starts to wear out, it might be time for folks to reimagine” how they want to travel through and around downtown.
Reimagine, for sure: At least one plan in 2010 pictured all traffic in the loop heading in the same direction, as if navigating a giant roundabout.
Prior to that idea, a study headed by the architectural firm HNTB proposed putting a lid over the I-670 south loop. Soil, landscaping, flat roadways and trails would go on top, making for a pleasing plaza with freeway traffic rumbling below, out of sight.
HNTB issued its last report on the “South Loop Link” in 2009 after years of discussion. The proposals have gone dormant in the midst of stressed federal and state coffers.
“It’s an impressive idea,” said Demory. “And it would be incredibly expensive,” priced at $175 million or so.
What we now call I-670 or the south loop began as the “Crosstown freeway,” ultimately linking I-70 and U.S. 71 to the east with I-35 to the west.
Eight lanes wide and less than nine-tenths of a mile long, it cost roughly $30 million in 1965 dollars, the equivalent of not quite $230 million today. It took most of the 1960s to complete.
The first overpasses appeared on the east end, and construction generally moved west.
The Star marveled at the freeway work in progress a few months before the opening of the Grand bridge:
“They have dug into forgotten underground rooms and cisterns, wrestled with unyielding limestone formations, gone through the whole archaeology of Kansas City in digging a canyon through the downtown area.”
At the lowest level of the Crosstown freeway, around Walnut Street, a crew cracked into a rock wall and water gushed out at a rate of 220 gallons a minute.
“The Crosstown freeway was opened for a few blocks this week and already motorists can tell the difference,” The Star reported in July 1967. By then, the work had been “going on for so many years it is difficult to recall exactly what that area was like before it began.”
And yet the end of the Grand bridge may have happened on a single day, according to MoDOT. And maybe recently, as the concrete that fell in the past month near the I-670 median appeared clean.
That doesn’t mean the overpass hadn’t been deteriorating. I-670 motorists could see exposed rebar on the undercarriage and sides, in addition to that S-shaped gouge on the west face.
That bridge and a few others around the loop are of a “sonovoid” design. Empty cylinders were built into the deck with concrete poured around them, making the span less heavy. It’s possible that autumn and winter rains seeped below the pavement and froze, weakening the cylinders.
The state needs to further investigate the cause of the failure, said Andy Hermann, past president of the American Society of Civil Engineers.
“It’s the first time I’ve heard of this happening to a sonovoid bridge, so maybe it’s an isolated case,” Hermann said. “But could it be something more chronic? The (Missouri) department is going to have to look into that.”
The damage that MoDOT says occurred after the September inspection is a block southeast from where a massive crane and other equipment are parked to erect the Two Light high-rise.
Kidwell and Kingery wondered whether the luxury apartment project somehow contributed to stress on the west side of the bridge. Could a large truck passing the site have caused the span to sag and bust below the pavement, unbeknown to the motorists above?
Kidwell said he had no way of knowing.
But he acknowledged that with some busy bridges older than 50 years, the cause of irreparable damage can be likened to “the straw that broke the camel’s back.”