Reconstructing the washout at Rat Creek: How’d they do it?

Posted at 8:01 AM, Jun 07, 2021
and last updated 2021-06-07 17:15:51-04

The January 28th washout on Highway 1 at Rat Creek closed the well-traveled thoroughfare for nearly three months. Some may be wondering how they opened the road so quickly after such a massive natural disaster. KSBY Daybreak anchor, Neil Hebert, took an in-depth look at how the state, along with a local construction company, got traffic on the 1 flowing smoothly once again.

“Everything aligned. It was the perfect storm,” said Randy Anderson, a project manager with Papich Construction in Arroyo Grande.

A combination of the Dolan Fire burn scar, 17 inches of rain, and tons of debris flow barreling its way through the 6.5-foot culvert, built in the 1930s, brought traffic to a screeching halt for months. So what all goes into repairing such a massive washout?

“Cleared it out, processed the bottom, got a good key started, dumped material in it, compacted it as we came up, to completion. Put base and asphalt on the road and turned traffic loose-,” said Anderson.

While the explanation from Anderson seems simple enough, there’s much more to it. The Arroyo Grande-based construction company entered into an emergency contract with Caltrans to start clearing the organic debris flow and constructing the base with new material below Highway 1.

The first thing needed to be done was to clear 70,000 cubic yards of debris, which likely weighed close to 150 million pounds; truckload upon truckload, hauling it out.

“Once we got the main debris flow out, we went down and cleaned this out and started our fill clear down at the bottom,” said Anderson. “You have to work up on a level platform. We just kept dumping material, which we got from another site up the road. Perfect material. Granular size was less than an inch and a half, perfect for compaction.”

That perfect compaction is part of the reason this section of the 1 will be sturdy for generations to come. To add to that, this stretch of highway only had one, 6.5-foot culvert, nearly 100 years old, when the hillside gave way. There is now a 5-foot culvert and two, 24-inch culverts in-place, with the main line of defense currently under construction.

“We’re creating a backboard for the boring machine that’s going to push the pipe through this fill,” said Anderson.

Papich Construction is in the process of boring a culvert that’s 10 feet in diameter into the side of the fill, all the way to the ocean, that will allow for sufficient flow of any natural phenomenon that occurs.

“In any extreme weather condition that might come upon us in the next 100 years, we’ve got these redundant culverts, which are able to accept both a higher volume of debris and water,” said Kevin Drabinski, a public information officer for Caltrans. “Even if something were to happen to the 10-foot one, we’ve got these redundant ones at highway grade. It makes the highway more resilient to any extreme weather conditions we might see in the future.”

Once the machine reaches the ocean, the dirt will have to be removed from the shore. The plan is to bring a helicopter in to carry the excess to a separate location.

A lot of the work to prevent washouts like this from happening is done before the fire and rain seasons begin, clearing any kind of debris that comes down the hill. Caltrans has implemented debris catches inland that stop big pieces of debris, with the last line of defense being the culverts.

Drabinski and Anderson said that Highway 1 is completely safe to travel across. The hope is for the project to be completely finished by the end of July. Until then, expect a lot of commotion and heavy equipment travelling in that area.