Officials are scrambling to stabilize the crumbling Del Mar bluffs, with four collapses having occurred since August.
Emergency efforts to reinforce the eroding cliffs, atop which Amtrak and Coaster trains run daily, have been in the works for nearly a year. Now officials say they hope to break ground on a number of key projects by summer.
In the meantime, transportation officials have said the trains are safe to ride, barring a major earthquake.
“We inspect the tracks twice a week, and in addition, anytime we have any failure or erosion event we inspect to make sure it’s safe for train traffic,” said Stephen Fordham, director of rail engineering for the North County Transit District.
For now, the landslides pose more danger to those walking on or beneath bluffs than to train operations, according to officials. Though warning signs are posted around the cliffs, pedestrians routinely ignore them.
The latest collapse occurred on Monday morning, when a section of the cliff roughly 25 feet wide and 4 feet deep fell near 9th and 10th streets. Officials halted train traffic for a safety assessment, restarting operations within a few hours.
The event follows several other similar landslides on Oct. 5, Sept. 27 and Aug. 22. In one case, a section of rock that broke loose was reportedly 50 feet wide.
Following the collapse in August, the transit district announced plans to erect fencing around sections of the tracks to prevent trespassers from trampling vegetation that helps stabilize the cliffs. Community members protested, launching an online petition.
Officials have said the main reason the bluffs are failing is that urban runoff seeps into the ground when residents and businesses irrigate their property. Coastal erosion from waves and wind also plays a significant role.
“The city can’t do much about the water coming off,” said Del Mar Mayor Dave Druker, who also sits on the North County Transit District board. “This is irrigation. It’s not runoff from rain. It’s about the water that people are putting in the ground.
“Eventually an earthquake will happen and the bluff will be done,” he added.
More than 100 inches of water a year wash through the bluffs, largely from such urban irrigation, according to officials with the San Diego Assn. of Governments (SANDAG). Under natural conditions the area would be subjected to about 12 inches annually.
The bluffs have historically been reinforced using 3-foot-thick concrete and steel columns, known as soldier piles, which are dropped into 50-foot holes and secured with concrete. At the same time, urban runoff is funneled through drainage pipes to limit erosion from rain and residential irrigation.
Despite such efforts, the bluffs erode at an average rate of about six inches a year, Fordham with North County Transit District said.
“We have a drought, and then it rains, and we have these fits and starts of erosion events,” he said. “Walking below is always a concern. We have technical people analyze these bluffs, but there’s always more areas where we want additional soldier piles as a result of the natural retreat.”
Parts of the bluffs are made of robust mudstone, while others are more precarious, such as those that were filled with materials when the railroad was first constructed, according to SANDAG officials.
The North County Transit District and San Diego Assn. of Governments have performed three bluff stabilizations, as well as various drainage improvements, since 1998, costing a total of about $5 million. A new round of projects through 2050 are now underway, with an estimated price tag of around $90 million.
As part of that, a $3-million emergency stabilization program is now underway. Expected to break ground by summer, the effort includes adding soldier piles, repairing aging drainage structures and reinforcing wooden sea walls.
Repairs will focus on areas of concerns around 7th Street and Anderson Canyon, north of Torrey Pines State Beach.
Transportation officials have said that in the long term, the two-mile section of train track that runs through Del Mar will have to be relocated.
The San Diego Assn. of Governments is in the process of double-tracking nearly all of the coastal rail line by 2035. These plans call for moving the rail line off the bluffs and into a tunnel under Del Mar or Del Mar Heights by 2050.
However, that project could cost as much as $3.5 billion and is currently unfunded.
Terry Sinnott, SANDAG board chair and former Del Mar mayor, said the project has been delayed due to cost for too long.
“It’s been postponed and postponed because it’s expensive,” he said. “Every time anything’s observed, North County Transit inspects everything and halts the trains for a period of time, but there’s still a safety concern that we have to always be addressing.”