Willits Bypass: 150 foot bypass span collapses

Willits News: 1/29/15

By Adrian Baumann

A 150-foot long span of the viaduct being poured for the Willits Bypass collapsed completely Thursday with workers on top and around the site. Two men were trapped in the debris. One freed himself while the other was extracted by Little Lake Fire Department; several workers were injured, three were taken to Frank R, Howard Hospital and one was airlifted directly to Santa Rosa. No one was killed. The three admitted to Howard Hospital were released that evening, while the man sent to Santa Rosa remains in the hospital.

The collapsed occurred at about 2:15 p.m. on Thursday Jan. 22, just north of where the viaduct crosses East Valley St. (Center Valley Rd.) and directly above where it spans Haehl Creek. The falsework for this span of the viaduct, the timber and I-beam scaffolding that supports the concrete forms, has been up for months. Earlier Jan. 22 crews from Flatiron, a CalTrans subcontractor, were pouring concrete for the final box girders, which make up the long spans of the viaduct.

Several workers were atop the structure when it collapsed. Workers described running for their lives as the structure swayed and buckled beneath them. One man, clearly shaken, pointed out that his hardhat was still sitting on the pile of debris.

Little Lake Fire Department responded with two chief officers, heavy rescue, two engines, and 17 total personnel. They initially requested heavy rescue from Brooktrails, and four advanced life support ambulances and an air ambulance.

Little Lake Fire Chief Carl Magann described the situation upon arriving:

“We identified that we had one person that was entrapped in the collapse. One individual was partially entrapped, self-extricated when we got on-scene. He got himself out. And then the one patient, we assisted Flatiron in getting him out from entrapment. He was pinned in by the structure itself, so we worked with flat-iron and we got him out, got him stabilized and transported to CalStar 4, and got him out. He was talking to us, but he was hurt, I don’t know what the extent of the injuries were.”

He continued, “Basically it was just getting the lumber and debris out from where he was. We wound up using a circle saw to get in there and cut some of the debris out. But we didn’t have to use any of our specialized equipment for that.”

A large portion of the debris fell directly into Haehl Creek, poisoning the water and endangering wildlife. The debris fell into Haehl Creek just upstream of where it meets Baechtel Creek. Wayne Briley of REHIT, the Mendocino County department responsible for hazardous materials response, explained that wet concrete is extremely alkaline, with a pH of up to 13 or 14. Meters, which are in the creek at all times measured a brief spike in pH up to 11, but relatively few dead fish were eventually found, and the quick work of game wardens and Flatiron minimized environmental damage.

Game Warden Steve White of California Department of Fish and Wildlife worked with Flatiron to install earthen dams upstream and downstream of the debris in Haehl Creek and diverted water around the rubble.

LATEST UPDATE

Clean up began over the weekend on the wreckage of the spilled concrete, bent rebar, broken falsework and shattered formwork that had been slated to become the newest span of the viaduct section of the Willits Bypass. The nearly 950 cubic yards of fluid concrete, and many more tons of steel I-beams and heavy timbers that make up the falsework came tumbling down on Thursday afternoon, the cause of the collapse remains unclear.

WORKER INJURIES

According to Little Lake Fire Chief Carl Magann five people were injured in the accident, one declined treatment, two were sent by ambulance to Howard Hospital, another was driven in a private vehicle, with the fifth flown to Santa Rosa; neither CalTrans, nor the primary contractor Flatiron, would make any comment about the workers’ condition except to say that they suffered “non-life threatening injuries.” Three of the men hospitalized worked for Flatiron, with another working for AECOM, another CalTrans contractor.

A California Occupational Safety and Health Administration spokesperson said three workers were injured, two seriously.

As for how many workers were actually on top of and around the span when it collapsed, we may have to wait for the OSHA report to know for sure. Frisbie says that, “Based on the current information it appears there were 4 above and 2 below.” While the official report put out by Magann states that, “It was estimated that 18-20 workers were on the section prior to collapse, most workers successfully running onto the still standing portions of the new freeway.” It is unclear why the discrepancy exists.

Magann’s report also states, “We witnessed one of the Flat-Iron workers self-extricate from the collapsed structure, covered in wet concrete, but denying any injuries. Several workers rode the section down to the ground with several reported injuries.”

In the moments after the arrival of the fire department a headcount was done by the workers, determining that only one man was missing. In the report Magann praises the workers from Flatiron for aiding in freeing their trapped coworker, at personal risk.

Once the injured people had been transported the fire fighters ordered a shut down of all machinery and total silence to listen for anyone else trapped in the rubble, they then used their thermal imaging cameras to search for anyone else who was trapped, finding no one.

CALOSHA INVESTIGATION

In serious mishaps the site is temporarily taken over by CalOSHA, which conducts an investigation of the site, to ensure worker safety and to try to figure out what went wrong. CALOSHA finished their preliminary investigation of the site over the weekend, clearing the way for the primary contractor on this section of the job, Flatiron Construction, to begin clearing the debris.

CalOSHA will now conduct interviews with the workers, and continue to inspect and monitor the site. They were informed of the collapse soon after it happened, but because they are based in Sacramento could not begin their inspection till the following day. By law CalOSHA has six months to complete the investigation.

Spokesman Peter Milton explained, “Basically they have asked for documentation which I don’t believe they’ve received yet…One of the things that they did was they gave parties the ok to begin taking the rubble apart, clear the site so the engineers can inspect it…and we don’t know what it was yet, but that’s what the investigation is trying to find out.”

COST AND SCHEDULE

CalTrans expected to be done with clean up by the end of the Jan. 30. Structural work on the viaduct and other bridges, which had been suspended, resumed across the project. Work on the collapsed span, however, will not resume until engineers have determined the extent of the damage and conduct tests. It’s very likely that the sections near the collapsed portion were also damaged, and the columns at the site were clearly tilted. Engineers will need to test and examine the whole area, understand what went wrong, and if the nearby structures were damaged, before reconstruction can begin.

CalTrans maintains that, because the dry weather has allowed work to continue through the winter, this collapse will not actually significantly delay completion of the bypass.

The cost of that section of the viaduct, also known as “frame 1,” is roughly $3 million dollars according to CalTrans spokesman Phil Frisbie. However, CalTrans confirmed that the additional costs incurred by clean up, delays, and reconstruction will apparently not fall to CalTrans or the taxpayer, but will covered by Flatiron, likely through their insurance.

FALSEWORK 

Not to be confused with scaffolding, which are temporary platforms for workers to stand on, falsework supports the bridge itself while it’s being constructed. Built like temporary bridges, out of big timber posts and steel I-beams girders, and thoroughly cross-braced, the falsework holds up the forms into which the concrete will eventually be poured.

During the pour the falsework must support the full weight of the concrete as it hardens. In fact, the spans are not self supporting until they are “stressed.” Concrete is strongest when it is under tension—after the concrete has hardened long cables placed inside the walls of the box-girders are tensioned.

This means that the falsework must be capable of holding up many tons of concrete while it sets up. Though the weight of concrete varies depending on kind, for 950 cubic yards roughly 1,700 tons is a good estimate. And in addition to the weight of the concrete, there is the weight of the falsework itself.

While the official investigation into the cause of the collapse gets started rumors and pet theories abound in the community. One idea now repeated several times is that the ground beneath the falsework gave out, perhaps as a result of the December flood, or that the ground in which the columns were placed were unstable.

CalTrans provided some details in response to these theories: work on the falsework began in April 2014, finishing up in Jan. 2015; the footings of the falsework are anchored to piles driven into the ground.

Frisbie described the system for double checking the falsework as, “redundant inspections,” which he said were done by CalTrans and contractors, “during erection, during final adjustments, immediately prior to placement of concrete, and continuously during concrete placement.” Frisbie also maintains that at least one inspection was preformed after the December flood.

FLATIRON

Flatiron which is based in Colorado, with several divisions across the United States and Canada, has been building bridges for CalTrans since 1991. They are one of CalTrans biggest contractors.

In July 2007 Flatiron, which at that time was called FCI Constructors, suffered another bridge falsework collapse, in Oroville. A 50 foot high span over Highway 149 came crashing down while workers were atop. Carpenter Jeffrey Doll rode the collapsing bridge down and was severely injured. Rob Sylvester, a FedEx contract driver, was also badly hurt when debris from the collapse crashed down on his truck. He was pinned inside for hours, and in 2010 settled out of court with Flatiron. He did not say how much he won, but did donate $25,000 to local firefighters.

After an investigation CalOSHA eventually fined Flatiron $6,750.

FISH KILL

The California Department of Fish and Wildlife (CDFW) had Flatiron installed dams and pumps by the evening of the collapse, routing the water flowing in Haehl creek around the debris, and isolating the wet concrete from the flow of the creek.

The dams and diversions in Haehl Creek will be maintained by CDFW until the debris can be cleared and the creek bed remediated. However, CDFW spokesman Andrew Hughan, said that with only 14 dead fish found, none of which were steelhead, the damage was surprisingly minor, “So we’re pleased—we got lucky and we’re pleased with how the effort’s gone so far, and we’re also satisfied that CalTrans and the contractor are doing what they need to do in regards to the fish and the creek.”

He also pointed out that contractors had laid down plastic over the entire area before the pour as a protective measure. When the bridge collapsed the plastic helped contain the wet concrete, acting as a barrier with the creek bed, and minimizing the amount that actually got mixed into the fish habitat.

Steelhead are an endangered species, which is one of the main reason’s for CDFW quick involvement. Said Hughan, “There are several dozen fish in the creek there, waiting to go back to sea, and now with the blockage they are now stuck. Now that being said, Steve [White, the game warden] is confident that CalTrans will build a diversion or get that concrete out of the creek in plenty of time for those steelhead to migrate to the ocean.”

Adding, “As far as the department of Fish and Wildlife is concerned the condition in the creek is stable for now and we can live with the conditions that exist in the creek right now, the most important thing is to find out why it happened and that it does happen again.”

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