A concrete bridge in downtown San Anselmo upon which a closely used public plaza has been situated is unsafe and requires instant repairs, Marin County public works officers mentioned.
In a report submitted to the general public works division on Sept. 12, Michael Watkins, one among a number of engineers the county employed to look at the bridge, wrote that the construction is liable to “catastrophic failure.”
“If an earthquake happens when a big exercise is in progress on the deck,” Watkins wrote, “a structural collapse may happen which might lead to many critical accidents.”
Watkins beneficial that repairs be carried out as quickly as doable. In any other case, he wrote, “I like to recommend that the construction be declared unsafe and all exercise on the construction terminated.”
On Thursday, county Public Works Director Rosemarie Gaglione mentioned, “We’re planning on closing off the bridge in an abundance of warning.”
She mentioned fencing, barricades and indicators might be erected to maintain folks out of the realm. The bridge spans San Anselmo Creek.
The construction, estimated to be between 80 and 120 years outdated, used to have a constructing on it with actual property and optometry places of work, a restaurant and a salon. The constructing was eliminated in 2020 as a part of a $20 million flood management venture.
San Anselmo Mayor Brian Colbert mentioned that since picnic tables and wooden chips changed the constructing, the realm has change into a well-liked group house.
“It’s change into a gathering place, very very similar to Grand Central Station in New York Metropolis,” Colbert mentioned. “You see folks studying, working, simply hanging out. It's in use from solar as much as solar down.”
The flood management plan additionally known as for the removing of the concrete bridge slab on which the constructing sat so the water in San Anselmo Creek may circulation extra freely. This would cut back the chance of flooding within the downtown and upstream.
That plan needed to be placed on maintain, nevertheless. The Federal Emergency Administration Company has mandated the bridge should stay in place till work is accomplished to mitigate the extra flooding that the bridge’s removing would trigger to about 20 downstream properties.
It's unclear how lengthy county officers have been conscious of the magnitude of the bridge’s structural injury.
At a gathering on July 19, Liz Lewis, water assets supervisor for the Marin County Flood Management and Water Conservation District, briefed county supervisors on the monkey wrench that the FEMA edict had thrown into the flood management plan.
Lewis’ presentation was a part of a routine annual report on a storm water drainage payment that funds the trouble. Lewis made no point out of issues that the bridge is perhaps unsafe.
Lewis, nevertheless, instructed supervisors that public works engineers have been proposing to switch the bridge with a concrete baffle at a value of $200,000. She didn’t clarify what that will accomplish, for the reason that baffle would finally should be eliminated.
Lewis offered the identical choice to the San Anselmo City Council on June 14, as soon as once more making no point out of any structural issues with the bridge.
Lewis did add, nevertheless, that if a call was made to depart the bridge in place, legal responsibility for the bridge can be transferred again to San Anselmo. The county flood district bought the construction for $1.75 million in 2018 as a part of the flood management venture.
The Impartial Journal submitted a request to the general public works division on July 25 requesting copies of any studies associated to the security and structural integrity of the bridge.
Gaglione mentioned Thursday that it was after receiving the newspaper’s request that she obtained a ultimate report from Martin/Martin Consulting Engineers outlining structural issues with the bridge and recommending repairs. She mentioned quickly after that the county employed MGE Engineering for a second opinion on the bridge’s situation.
Gaglione mentioned the sooner suggestion to switch the bridge with a concrete baffle had nothing to do with issues concerning the construction’s security. She mentioned the purpose of the baffle was to take away the bridge in time to entry grant funding that is because of expire in June 2028.
Her division didn't provide copies of the preliminary studies submitted by Martin/Martin and MGE Engineering. As a substitute, on Sept. 12, it shared a second report submitted by MGE Engineering on Sept. 9 and one other analysis submitted by Martin/Martin on Sept. 12.
The Martin/Martin report, nevertheless, signifies that the agency despatched an evaluation of the bridge to the county lengthy earlier than July 2022. It states that draft variations “have been despatched to the county for preliminary evaluation on July 28 and August 16 in 2021.”
Gaglione mentioned she by no means noticed these drafts. She mentioned neither Martin/Martin nor MGE Engineering may state with any diploma of certainty how protected the bridge was as a result of that they had no details about its situation previous to restore work performed in 2002, when the bridge was owned privately.
Gaglione mentioned it was solely after Watkins examined the bridge on Sept. 12 that she was in a position to confirm that the bridge was unsafe. Watkins’ agency, Ballard and Watkins, oversaw the 2002 restore and supplied a subsequent analysis of the bridge to its personal proprietor in 2006.
Watkins reported on Sept. 12 that “substantial horizontal cracking of the middle wall had occurred for the reason that earlier restore initiatives have been accomplished.”
Watkins wrote that the middle wall of the bridge was bowing and that positioned stress on the reinforcing metal inside it.
“Ought to this metal yield, it's doable that the joint the place the crack is seen on the middle wall will unzip like a zipper,” he wrote. “This might result in a catastrophic failure on this construction.”
“This dialogue focuses on the results of gravity on masses on this construction and has not but launched issues of lateral masses which is perhaps launched throughout an earthquake,” Watkins wrote. “The degradation of this construction absolutely has resulted within the discount of the power to outlive an earthquake.”
Gaglione mentioned, “We’re nonetheless in talks with San Anselmo and FEMA about demolishing the bridge.”
She mentioned repairing the bridge isn’t possible as a result of estimated value and the uncertainty of the outcomes.
Relating to repairs he beneficial, Watkins wrote in a Sept. 13 letter to Gaglione, “There is no such thing as a method to make sure that they'll categorically eradicate the potential of a collapse. The lack of life or accidents which could happen on account of even a partial collapse throughout a group occasion can be troublesome to justify.”
Gaglione mentioned FEMA isn’t the one impediment to eradicating the bridge.
“There are a sequence of occasions that must happen,” she mentioned.
Gaglione mentioned whether it is doable to take away the bridge earlier than Oct. 15, when the wet season usually begins, one thing should be performed to duplicate the bridge’s impact on the creek’s circulation.
“If we take this bridge out,” Gaglione mentioned, “we will’t simply take it out and go away the waterway vast open due to these downstream properties.”
Doug Ryan, who has lived in a home downstream of the property for 18 years, mentioned, “In the event that they’re going to take away that bridge they should do the mitigation that they’ve identified they should do for 5 years. They've already begun work within the creek, so if my home floods, I’m suing folks. I’ve been very clear about that.”
Gaglione mentioned it's too late within the season to switch the bridge with the concrete baffle. She mentioned as an alternative some massive rocks lined with soil and netting is perhaps used. She mentioned the county has a hydrologist evaluating the probabilities.
If the bridge can’t be eliminated earlier than Oct. 15, Gaglione mentioned, the bridge will stay closed by the winter.