Last week’s rains sent some rocks skittering down the hillside at Mud Creek, where a massive slide has kept Highway 1 closed for nearly 10 months. Still, the road remains on track to reopen as scheduled late this summer, resident engineer Rick Silva said Thursday.
If the weather holds.
Silva and construction inspector Garret Hilton provided a tour of the site Thursday, exactly two months after a previous visit. Plenty has changed in those two months. Here are five ways the highway is closer to completion than it was then ... even though, in some places, it may not look like it.
In January, workers had cleared a makeshift dirt-and-gravel road that connected the paved highway at either end of the slide. Portions of that road near the north end are now buried under rock and debris.
This isn’t a setback, though. It’s by design. A piece of equipment called a “spider” is working on the hillside above the roadway, helping to dislodge loose material that then descends onto the road. That debris, Hilton said, will be either trucked away or used for fill elsewhere on the site.
The spider, designed for use on steep inclines, is also installing anchors that will be used to hold protective netting when the project is complete. It’s the same kind of netting visible on other steep slide areas along the highway. It isn’t designed to stop rocks from falling, but so that “when they fall, they have something to fall against,” Hilton said. “The rocks collect at the bottom of the net” in what he called “a controlled fall.”
Although a portion of that temporary road is now covered in debris, Silva said, “We always knew the road was going to be shut down” intermittently.
In the meantime, surveyors are working to find the proper elevation and location for the actual highway when it’s installed.
Hilton expects the temporary road to be alternately cleared and covered with debris at various times until then. He and Silva stressed that the makeshift road (whatever its status) is not open to public access.
Caltrans and its contractors have received a big boost from the dry winter weather in their quest to complete the project on time.
But that advantage could turn into a challenge if more rains come.
Rains that fell March 1 have already affected the project. Silva estimated the site got 4.5 inches of rain from that storm and said rainfall totals there are often comparable to those at Rocky Butte, the wettest spot in San Luis Obispo County. The rains, he said, had slowed work on the northern slope above the temporary road.
Hilton pointed to a dark spot near the top of the mountain as evidence that more water had gathered beneath the surface. That’s what created the instability that led to the massive slide May 20 of last year.
“We’re always looking for wet spots showing up randomly, because that’s an indication that there’s water flowing through the mountain,” Hilton said.
And there were more signs of instability on the surface, as well. Silva played a video taken March 2 that showed small rocks tumbling down the slide area.
How much do rains delay the project?
“It all depends on the amount of rain,” Hilton said. “If it’s a small amount of rain, sometimes we continue to work. Anything more than a half-inch, we have to get out of the area to make sure it’s safe.”
A geologist must go in and re-evaluate the area after a heavy rain to assess the extent of the damage and weigh safety risks, Silva said.
Crews will be keeping an eye on the weather forecast, which could bring several days of rain in the coming week.
The waters from Mud Creek aren’t actually flowing on the surface, but their presence is clearly marked a canyon cleft in the hillside far above Highway 1. It’s easy to follow the creek’s path from there, as it descends and eventually passes between a pair of smaller hillsides just above the road.
A huge pipe has been installed to carry water from the creek down to the ocean during rainy periods. A portion of the pipe, which Silva said measures about 54 inches in diameter, can be seen protruding from the surface right beside the temporary road. Another section is visible just above ground farther down the hillside.
Silva and Hilton joked that the pipe’s so big you could use it as a waterslide. If you weren’t afraid of the dark. And if there wasn’t a danger of getting stuck.
The pipe is designed to help shield the hillside from further erosion.
A short distance above the pipe, on the south side of the Mud Creek ravine, workers are using heavy equipment to create one of two earthen platforms Hilton refers to as “baskets.”
A new access road leads to the platform, which is enclosed by a tall wire fence. It’s being built in front of a catchment area, which is designed to collect rocks and debris that continue to fall from the mountainside.
The basket itself serves two purposes:
- To shield the road from the debris that accumulates there
- To provide a platform from which heavy equipment can reach down into the catchment area and clear out that debris
Work has yet to begin on a second basket, which will be installed on the north side of the ravine.
The rock wall
Perhaps the most visible evidence of progress on the site is at the seashore, where a rock seawall is between 75 and 80 percent complete.
The wall rises 36 feet above sea level — or 10 feet higher than originally planned. Silva explained that the additional height was required because the site was being hit by “more wave activity” than initially predicted.
Augie Wilhite of John Madonna Construction estimated that 165,000 tons of rock had been placed in the embankment as of Thursday, with another 30,000 to 40,000 still to come. At 1,000 tons a day, that leaves 30 or 40 more days before that portion of the project is complete.
(That 30- to 40-day estimate “doesn’t include any rain,” Hilton said, “because we might be able to bring the material to the site, but we won’t be able to bring it down here” to the seawall.)
Workers are placing the rocks atop a layer of GT-110, a thick and sturdy material that Hilton calls “filter fabric,” which keeps the rocks separate from the dirt underneath them.
With the excavation already complete, Hilton said, work on the wall is speeding up. On Thursday, a CAT 972M and other wheel loaders transported rocks down the hillside to the embankment, where a CAT 349F hydraulic excavator picked them up and placed them strategically atop the wall.
The rocks are being brought to the site at a rate of 46 to 50 truckloads a day, Wilhite said, from Cambria and Porterville. Cambria’s Winsor Construction has played a major role in this part of the process from the outset.
In contrast to the road, which is further along at the southern end of the slide, the wall’s northern half is complete, while work continues on the southern half.
The Mud Creek slide is 8.9 miles north of the Monterey County line and is one of three major storm-damaged sites on Highway 1.
Paul’s Slide, almost 12 miles farther road, remains a geologically active slide. A temporary guardrail is in place at the center line, and the site is open to one-way, alternating traffic, controlled by a signal, Caltrans said Monday.
Also, final work is progressing on the new Pfeiffer Canyon Bridge in Big Sur, which opened in the fall to replace a failing structure. Roadwork there, according to Caltrans, consists of “alternating lane closures from 7 a.m. to 4 p.m. Mondays through Thursdays and 7 a.m. to 2 p.m. Fridays until work is complete.”
All work on the bridge is scheduled for completion by the end of March, Caltrans said, with the ever-present caveat “weather permitting.”