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Crews use explosives to blast boulders plugging creeks in Montecito

Caltrans crews are using explosive charges to fracture massive sandstone boulders in Montecito. Crews drill 1 ½ inch holes into the boulder and insert charges filled with ammonium nitrate and nitro methane. They then detonate the blast on the other end of a 250-foot long cable as they stand safely behind heavy equipment, vehicles or other barriers.

Micah Gammons, a licensed blaster with Caltrans, has gotten a lot of practice blowing up boulders recently.

Last year, there were the 300-ton granite boulders that rolled onto Highway 1 in San Luis Obispo County. Now, he’s busting sandstone boulders bigger than an SUV in Montecito.

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“We usually do one to three blasts a year,” said Gammons, the District 5 maintenance superintendent for the California Department of Transportation. “This year … we’ve done well over 30.”

A dozen of those explosions have been in Montecito, where a Jan. 9 storm dumped 25% of its water in a single five-minute span. The deluge turned fire-ravaged hillsides into rivers of mud, trees and massive sandstone rocks.

Boulders, some measuring 12 feet in diameter, rumbled down neighborhood creeks and plugged outlets. Gammons was called in because the rocks are too big to move in one piece.

Over two days last week, Gammons’ team blasted 12 boulders clogging Toro Canyon Creek at Highway 192. The shards then were pulled out of the creek bed.

Workers carefully cross the Ashley Road Bridge over Montecito Creek as crews clear debris, attempt to restore power and reopen roadways.
Workers carefully cross the Ashley Road Bridge over Montecito Creek as crews clear debris, attempt to restore power and reopen roadways. (Al Seib / Los Angeles Times)

The rocks are fractured using a one-third-pound explosive that’s a mix of ammonium nitrate and nitromethane — commonly known as a fertilizer bomb.

Crews use a rock drill to bore a 1½-inch-diameter hole deep in the boulder and fill the void with explosives. The hole is then packed with angular rock, “like one of those Chinese finger-cuffs that keeps it from rifling out,” Gammons said.

A 250-foot-long detonation cord is then added, and Gammons and his team take position behind heavy equipment, a vehicle or some type of barrier that is within sight of the boulder.

Then, with spotters stationed in all directions where people could enter the area, the countdown begins with a five-minute warning from an air horn, followed by another when the explosion is one minute away.

The team then does a 20-second countdown before Gammons sets off the bomb.

The blast fractures the boulder but doesn’t send pieces flying in all directions, Gammons said. Sandstone absorbs the blow better than granite, limiting the concussion felt by people nearby.

In one instance, the team connected four huge boulders with one line and blasted them all simultaneously. In areas near gas lines where explosions are too dangerous — particularly in creeks to the west — contractors are using an expanding gel that is injected into a hole drilled in the rock. Hours later, the expansion forces the rock to fracture.

Gammons, who has been with Caltrans for 12 years, said this was the first time he’s had to do this kind of work in a community.

“I’ve worked mudslides on Highway 1 a lot, but it’s just a highway,” he said. “But dealing with houses and neighborhoods … the pictures on the news don’t do it justice.”

The job of clearing out the creeks and debris basins is a massive undertaking. At a community meeting Tuesday night, Santa Barbara County Sheriff Bill Brown said just one basin had 100,000 cubic yards of debris that need to be cleared. The trucks coming in to transport that debris can take out only 10 to 20 cubic yards at a time.

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"So you can imagine how many large trucks are needed to complete this massive task," he said.

A caravan of firetrucks, emergency vehicles, large dump trucks and utility vehicles have been driving through the heart of Montecito at Coast Village and Olive Mill roads as buried sections of town are cleared and repaired.

“It looks like Grand Central Station,” Brown said. “This is constantly happening throughout the day.”

Crews are working around the clock in Cold Springs Creek, using excavators to dig out the mud and rocks piled more than 12 feet high along the creek bed.

During last week’s powerful storm, the creek transformed into a highway of destruction, draining a large 2,500-acre watershed that extends up into the steep slopes of the Santa Ynez Mountains.

The massive Thomas fire had left slopes in that area scorched and barren: 77% of the watershed is burned and stripped of the alder trees, willows and cattails that could have soaked up the rain.

The fire burned so hot and thoroughly that a waxy film developed over the dirt and repelled rain, sending a slurry of ash, water, mud and boulders racing down the creek, tearing away whatever stood in its path.

"It is like an ice cream scooper came through here and scraped the earth down to bedrock," said Tom Fayram, deputy public works director for Santa Barbara County.

On Wednesday, just a trickle of water flowed through as Santa Barbara County officials toured the damage and workers used an excavator fitted with a powerful hydraulic hammer to break rocks apart.

County officials don't expect Friday morning’s forecasted light rain to cause problems. But in time, heavy rain will come back, so a thorough cleanup is crucial.

Workers have cleared about half of the debris from the massive basin along East Mountain Drive that acts as a dam, stopping some of the thick muck from continuing down Cold Springs Creek to where it eventually joins Montecito Creek and slices through a dense patch of homes.

The debris dam, built in 1964 after the Coyote fire burned more than 60,000 acres in the creek's watershed, couldn’t stop the massive mudflow, but it did slow it down and hold back many boulders.

Even so, a group of homes along Hot Springs Road was destroyed.

Upstream, the mudflow had taken out Mountain Drive, leaving behind strands of rebar and scattered pavement. Fencing was wrapped around a tree. A boulder a few feet high sat underneath a house on a hill near a bend in the creek.

Clint Greene and Kathy Espino, two doctorate students at UC Santa Barbara, hiked through the debris Wednesday, taking in the sight.

Greene, who used to frequent Cold Springs Trail, couldn't believe this was the same place.

"There used to be trees here, everywhere," he said. "You could hear frogs."

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