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The stage was set, a crowd had gathered and cameras were rolling but the Antlers Bridge, after faithfully carrying Interstate 5 travelers across the Sacramento arm of Shasta Lake for three-quarters of a century, declined on Tuesday to take its final bow.
The 1,330-foot-long cantilevered span, which has already been replaced, had been stripped of its deck and rigged with 700 pounds of C4 plastic explosive and was scheduled for a carefully choreographed demolition at 9 a.m.
As a steady rain fell, the California Highway Patrol stopped traffic on I-5 at both ends of the new bridge and Shasta County Sheriff’s Department boats patrolled the lake to keep any curious onlookers a thousand feet from the blast site.
Project supervisors, contractors, Caltrans workers and officials with Tulsa, Okla.-based Dykon Blasting joined a gaggle of reporters, photographers and umbrella-toting bystanders at the Lakeshore Inn & RV to await the all-clear signal and the countdown to detonation.
The piercing bray of an air horn alerted the audience that the button would be pushed in one minute; it was shortly followed by a Dykon employee barking out a countdown that ended with a throaty “fire in the hole!”
As advertised, a rapid series of explosions raced across the bridge, north to south, and a loud boom echoed across the lake, followed by a concussive blast of air. Large sections of the green steel trusses shrieked, folded and plunged into Shasta Lake, yet when the smoke cleared, a lengthy section of the superstructure remained in place at the southern end.
Eric Akana, a structural engineer and the Caltrans project manager for the Antlers Bridge project, was initially at a loss to explain how the southern span remained aloft after the detonation. Dykon employees, who are under contract for the demolition and removal of the decommissioned bridge, would have to analyze the situation and determine the safest way to go forward, Akana said.
Four of the five spans laced with explosives collapsed in the demolition. Akana said Dykon workers are prepared to use divers, a barge and a crane to retrieve the trusses and truck them to a salvage yard.
Later on Tuesday, Caltrans spokeswoman Trisha Coder said engineers were able to inspect the remaining span and determined that the pounding rain had compromised the explosive charges. The soggy C4 is being removed and replaced with fresh charges that are now scheduled for detonation on Saturday.
“It will be much less dramatic than today,” Coder said. In the meantime, boating is prohibited on the Sacramento arm of the lake near the bridge and the Antlers boat ramp will remain closed. The CHP will again close I-5 for the Saturday demolition, “hopefully for about 20 minutes,” Coder said.
Traffic on southbound I-5 was restricted to one lane on Tuesday while engineers inspected the rain-dampened charges.
–Tutor Saliba Corp., the principal bridge contractor, deployed silt curtains to collect any debris from the blast and had workers in skiffs standing by to skim any floating debris.
–The steel superstructure has an undercoating of lead-based primer that is covered by green paint. An analysis by Geocon Consultants indicates dissolved lead levels may reach 1.07 parts-per-billion (PPB). State and federal standards for drinking water allow for a maximum lead level of 15 PPB.
–The demolition project received approvals from the Central Valley Regional Water Quality Control Board, the Environmental Protection Agency and the U.S. Forest Service.
–The concrete piers will be removed at a later date using special wire saws and a crane.
The new bridge
The new Antlers Bridge was a $125 million project that started in 2009 and was expected to take five years to complete. It opened in September. It is 1,942 feet long and 104 feet wide. Designed for a 100-year life, the bridge is composed of 13 million pounds of steel and 36,000 cubic yards of concrete.
The bridge is supported by massive piers that rise to 120 feet above the lake surface and extend as much as 100 feet to the lake bottom. The piers include 16 bat houses and two large bass motifs (read about the bass art work here).
JAN. 12 UPDATE: Caltrans District 2 will temporarily close Interstate 5 in order to allow contractors to demolish the fifth span of the Old Antlers Bridge.
WHEN: Saturday, January 14, 2017 at 8:45 a.m.
WHERE: Lake Shasta, Lakehead
NOTES: There will be no specified media-staging area for this demolition. The California Highway Patrol will hold traffic on I-5 from approximately 8:45 a.m. until 9:15 a.m. The channel under the bridge and the Antlers Boat Ramp will be closed through Sunday. Due to the safety of the public and our workers, the public is asked to not travel to the demolition site during the blast.
Photos and video by Jon Lewis.