ENCINITAS — The drive down Lone Jack Road is one of the more scenic routes you’ll find in Encinitas.
Horses trot on pathways on a pepper tree-lined side of the road, all as cars jaunt up and down and to and from large, gated equestrian estates.
But this week, the road to paradise was closed. Orange detour signs routed motorists through one of the estates whose gates are usually closed to everyone except for homeowners and visitors.
And at the center of the closure, two large steel plates cover the reason for the street closure.
City public works crews call it a “pavement failure,” one likened it to a smaller-scale version of an underground landslide that occurred 30 years ago in Norway.
The road failure could cost the city more than $100,000 to repair and take weeks to fix, city staff said.
“It isn’t something that we see everyday around here,” City Deputy Public Works Director Ed Deane said.
The problems with the street were discovered in the early morning hours of March 1, when a dump truck driving along the road began to sink into the roadway just south of Fortuna Ranch Road.
Crews discovered that it wasn’t the asphalt, but the material below, that keeps the street in tact, had basically turned into pudding, causing the asphalt above to shift and slide out of place.
It’s an event known by geologists as liquefaction, and occurs when groundwater rises and mixes with the soil, causing it to become increasingly fluid until the ground above it begins to move.
Deane compared what was occurring to the quick clay slide at Rissa, Norway, which occurred in 1978, when the groundwater rose and caused an entire movement of earth that devastated the Norwegian coastal community. There’s a Youtube video that explains the event in detail.
“Obviously we are talking on a much smaller scale, but that is basically what is going on over on Lone Jack,” Deane said.
Deane said the area affected by the rising groundwater could be as large as 20 feet and as deep as three to four feet.
This type of failure will take time and a lot of money to fix, Deane explained.
“It definitely is something that requires a lot of time, effort and money, and we appreciate the public’s patience,” Deane said.
Crews will begin pumping out the groundwater — the toughest task of the fix — later this week. Once the water table has dropped, the city will fill the affected area with new layers of aggregate, a permeable base of gravel and cement, and then asphalt.
Finally, they will install a new drainage system on both sides of the road that will intercept rainwater and keep it from raising the water table in the future.
At least one resident said that the closure of the road might be a blessing in disguise, as the road had fallen into disrepair in recent years and had accelerated as a result of the rains.
“The road was in bad shape,” said Niki Morrison, as she walked her dog along Fortuna Ranch Road. “With all the rain, there were big potholes, my husband blew out a tire on one of them, and you have to drive slow on the road to keep debris from flying and hitting your windshield.
“Maybe the closure will allow for the street to get repaired,” Morrison said.
That section of Lone Jack Road was last resurfaced in 2004 and the city rated its condition as a 60 on its one-to-100 pavement condition index, which is a “fair” rating.
Deane, however, said that the problems that caused the failure were not a result of what was happening at the surface.
“First off, water is bad for asphalt, it degrades the asphalt and accelerates its deterioration, which is why our roads in California hold up better than in other places because there is less rain and precipitation,” Deane said. “But this issue is caused by stuff occurring underneath the roadway. It is not a top-down, but a bottom-up situation.”
The “bottom up” solution, which could take two weeks, possibly longer, Deane said, will require Lone Jack to remain closed. In the meantime, the city arranged with Wildflower Estates, a nearby gated community, to provide a detour route.
City officials are working out an arrangement to fairly compensate the private community for any damage the increased traffic might have on its roads.
“We want to be good neighbors to them and we realize this is an imposition on them,” Deane said.