Interstate 80, Just West of The California State Line
May 22, 2007 this hillside above Interstate 80 was on fire. The firefighters would eventually contain the Highway Fire at 850 acres, but their job was complicated from the beginning by the steep, unstable terrain.
Not only did it mean dragging hose and equipment up these steep inclines, it also meant dodging falling rocks and flaming debris which kept starting spot fires downhill.
Fire typically makes unstable slopes all the more so.
"The root structure that would have held the the soil together goes away with the plants that were burned off," says District Ranger Joanne Roubique of the Tahoe National Forest.
"So, if we don't get plants regrowing on that slope sometimes if you'll get rain on it too early you'll see erosion starting to happen."
And that's just what we saw yesterday--in spades. Rocks and debris were once again flowing down the mountain, in this case spreading mud all over the roadway.
It forced the closing of the Interstate for a time, backing up or diverting traffic on the busy freeway.
The damage from the fire six years ago played a role, but its not uncommon for these slopes to send rocks down onto the roadway in all kinds of weather.
Fire and the freeze-thaw cycle in the winter can loosen rocks. Add a lot of rain to the equation and you can get mudslides.
A CALTRANS spokeswoman tells us with the amount of rain falling here a mudslide was likely in any case.
"CALTRANS does have a problem," says Roubique. "We've seen lots of rocks and lots of soil come down during those rain events and I know they struggle with keeping the highway safe."
In fact, CALTRANS has posted monitors along the Truckee Canyon for the next few days. They say if they see any movement on the slopes above them, they may shut down the highway in a proactive move to protect the driving public.