When It Rains, It Floods

For years, rains have caused such severe flooding and erosion at San Ramon Canyon that it threatened two vital roadways and more than 250 senior citizens’ homes at the bottom of the hill. 

San Ramon is “one of the most daunting problems facing our city,” said councilman Douglas Stern, and last night the council approved the first steps toward designing a permanent solution at a public workshop held at Hesse Park.

The council approved a recommendation by the city's Public Works Department to design a $19.2 million project that will divert water runoff from the top of the canyon down a 1,900-foot tunnel that passes beneath the threatened roadways, Palos Verdes Drive East and 25th Street.

The tunnel, which will be 80 inches in diameter and run 60 feet below ground, then connects to a 1,700-foot surface pipe leading to a cliff, where a 300-foot slant pipe will drop the water to the beach below.

The tunnel project will greatly reduce the amount of rainwater runoff that courses down the canyon and slams up against 25th Street, where the existing drainage system is too small to handle the load.

Years of hard runoff has deposited so much heavy debris against the roadway that it's starting to bend, Director of Public Works Ray Holland said.

Plans also call for laying a pipeline along the streambed leading to 25th Street. The canyon would be filled with 30 feet of compacted earth to further slow the amount and velocity of runoff water going into to the existing drainage system.

The need to find a solution to the flooding and erosion was continually brought up by council members and city staff. 

“There’s a growing sense of urgency every time there’s a rainstorm,” said council member Stefan Wolowicz.

Much of the story is familiar to residents. Every rainy season, flooding down San Ramon Canyon and onto 25th Street below slows down or cuts off traffic — including emergency response vehicles — on the main link between RPV and San Pedro.

Worse, every year increases the threat to 500 senior citizens who live in trailer homes on the downhill side of 25th Street.

The erosion problems are also growing more critical. Near the canyon’s top, the Terapaca landslide continues to collapse the east wall of the canyon and push the streambed closer and closer to the west wall. That causes constant water erosion of the west wall, which is moving toward a switchback curve on Palos Verdes Drive East.

The bank is now within 86 feet of the roadway, and it’s eroding quickly. If the roadway collapses, said a public works report, “reconstruction may be impossible.”  And if that happens, residents and emergency vehicles lose a primary route to the area.

Public Works officials selected the tunnel solution as the best of five alternatives presented by contractor Harris and Associates under a $1.2 million project study. Public Works officials were at first skeptical about the safety of tunneling, said Holland, but geological studies showed it was viable. 

Another advantage is, unlike other proposed solutions, this project would be built entirely on RPV land, minimizing easement and rights-of-way requests for the pipeline. It would also do away with time-consuming  negotiations with other jurisdictions — namely L.A. City and L.A. County, which control property at the lower end of the canyon and across 25th Street, where the senior housing lies.

However, a new complexity was introduced at last night’s public workshop that added even more urgency to the situation. Public Works officials recently discovered an 8-inch sewer line that lies between the crumbling canyon wall and the section of Palos Verdes Drive East that it is threatened by erosion.

“Going into this, we just didn’t know the sewer was at such risk,” Holland said.  “The last thing we want is that pipeline to be undercut and start spilling sewage down into canyon and into the ocean. There will stiff fines for us if that ever happens. “

In response, the council also approved a plan to relocate the sewer line farther away from the crumbling canyon wall. 

That relocation plan would fit into another plan the council approved in March 2010 for a fast-action, interim solution that could be adopted if erosion near Palos Verdes Drive East moves faster than anticipated.

Public Works is 70 percent done with the design for an emergency plan to strengthen the land supporting the threatened section of roadway with a series of concrete caissons, Holland said, which is similar to a solution just completed by the city of Palos Verdes Estates to shore up the crumbling cliffs at Bluff Cove.

If put into action, the $2 million, 3-month project involves drilling deep holes, filling them with concrete and tying them together to keep the soil in place. The sewer line would be relocated behind the caissons.

Building the caissons depends on how fast erosion proceeds toward P.V. Drive East. Aiding the council in that decision are seven land movement monitors that Public Works is installing throughout the San Ramon area. Holland pledged that his department will regularly report monitoring data to the council and public. 

If erosion proceeds more slowly, the caisson project might never be initiated — and if the tunnel project could be completed first, the caissons aren’t needed. 

But finishing the tunnel project could take years, according to estimates from Public Works.

Holland told the council that getting a detailed design and producing bid-ready documents could take anywhere from 18 months to 33 months, depending on the difficulty of obtaining environmental approvals. 

The bid and award process would take about four months, according to a public works official, and actual construction would take another 9 months to 13 months, depending on the availability of needed materials.

That puts completion of the tunnel project anywhere between 31 months and 50 months from now — and that’s a lot of rainy seasons.

Cost and time considerations were intertwined at the workshop. The city will campaign for $10 million in federal funding for the tunnel project.

The rest of the tunnel project cost would have to come from state grants or the city itself, said City Manager Carolyn Lehr, adding that would be “quite challenging.”

Wolowicz expressed frustration with the time it’s taking the federal government to act on the city’s requests for funding for the project.

“We’re not talking about some roadway with potholes or a beautification program,” he said. “Were talking about a situation where if there’s a failure, a lot of water will likely run right through some homes. 

“When Mother Nature steps in, she’s not waiting for committees or bills.”