Coastsiders' worst nightmare almost came true Monday night as a warning sign activated on Devil's Slide, advising drivers to turn back because the mountainside had supposedly begun slipping toward the ocean once again.
The lights were on for several hours. Some motorists heeded the warning signs on Monday, making U-turns on the highway in the rain and almost getting into accidents as a result.
Half Moon Bay City Councilman Jerry Donovan said his wife's car was almost rear-ended when she attempted to turn back.
But the California Department of Transportation later said it believes that the monitoring system was vandalized, not that the road has started to slide again.
CalTrans initially thought the lights were triggered by rocks falling into netting above the roadway and had geologists checking out the slide on Tuesday. But a spokesman said it now appears that a plug to one of the monitors in an unlocked box was pulled out of its connection, tripping the caution sign. A Sheriff's Office spokesman said the incident had not been reported, however.
Last year a 750-foot stretch of the road fell more than five feet, closing Highway 1 for six months.
"On the surface it seems like a false alarm," said CalTrans spokesman Jeff Weiss.
Monday's problem, combined with heavy rains over the past several weeks served as a reminder of the coast's fragile link to the north with the rest of the world. Weiss offered a glimmer of hope to those whose nerves may be fraying at the prospect of another slide that the road will hold.
Two weeks ago the water level below the road was between one and five feet short of where it was at the same time last year, he said. But Weiss also cautioned that the water level is only one factor that can cause the slide plain to become unstable and that CalTrans engineers are still testing various hypotheses about why the road slipped in heavy rains last year and in 1982, but did not in 1984.
He emphasized that unlike last year, Devil's Slide has a newly installed system of steel beams criss-crossing the slide plain to support the roadbed. New drainage pipes were also installed to prevent undue amounts of water from seeping into the slide plain.
However, Weiss added, CalTrans engineers cannot predict whether the road will ultimately hold.
"It's anybody's guess," he said.
As of Tuesday, 23.83 inches of rain had fallen in Half Moon Bay this season compared to 24.6 inches at this time last year.
In another slide-related matter, at the midway point in its signature-gathering campaign, tunnel initiative supporters said they have collected 15,000 signatures - about two-thirds of the number needed to qualify for the November ballot.
The initiative would ask voters countywide to amend the Local Coastal Plan to make a tunnel the preferred alternative to permanently repair Highway 1 through Devil's Slide.
The second half of the campaign will prove tougher because volunteers will come up against more people who have already signed the petition. But supporters expressed confidence that they will easily meet the necessary 22,000 required signatures of registered voters and come close to their goal of 32,000 signatures for a margin of safety.