City calls Mother Nature’s bluff with landslide project
After a landslide destroyed several homes and closed a vital highway, the seaside town of Dana Point, Calif., led the two-year effort to rebuild and strengthen the collapsed bluff, reopen the road and safeguard the area’s coastal beauty.
Dana Point, Calif., got an unwelcome addition to its property base in 1993 when five ocean-view homes from the neighboring city of San Clemente came crashing down an eroded bluff along with 44,000 tons of earth, blocking a major highway and railroad line in the city limits. The homes had been evacuated prior to the massive slide, which occurred after several days of heavy winter rains saturated and destabilized a section of the bluff.
The bluffs collapse was one of the first major tests under fire for Dana Point, a south Orange County community that had incorporated only four years earlier, partly in an effort to separate itself from the reaches of San Clemente. Just as the newborn city, with a population of around 36,000 people, was getting on its feet, Mother Nature reminded residents and officials that she often does not respect the municipal boundaries they draw.
Still, despite its youth, Dana Point responded to the slide so well that its erosion control efforts have become a national model both for dealing with slides, as well as for community relations and cooperation among governmental agencies at all levels.
As the lead city in the effort to shore up and restore the bluff, Dana Point has been racking up kudos for its work, including a Judges Award of Distinction from the American Public Work Association’s 1996 Public Works Project of the Year award program. The city has also been receiving dozens of phone calls from local officials throughout the country who are interested in the project.
So, what is all the fuss about? According to Mort August, Dana Point’s Director of Public Works and Engineering Services, the individual steps in the erosion control effort are not as noteworthy as their combined use in a single project.
“There is nothing particularly unique about what we did, other than to put all these things together in one package,” he says.
This package included:
* rebuilding the collapsed bluff and strengthening it with dozens of large tie-back anchors;
* applying a shot-crete surface to further strengthen the bluff;
* installing an extensive drainage system in the bluff face;
* utilizing a latex mold of rock, sculpted concrete surfaces, stain and landscaped groundcover to hide the construction and replicate the bluff’s natural face;
* working with a variety of local, state and federal agencies as well as a private group to permit and finance the project; and
* keeping affected residents informed of the details and progress of the bluff restoration through open houses and periodic newsletters.
BLUFF FACE RESTORED AS REAL-TO-LIFE AS POSSIBLE
Much of the first year after the landslide was spent arguing responsibility for the bluff’s erosion and collapse, as well as options and funding for its restoration. A flurry of lawsuits was filed against Dana Point by property owners who lost homes and those with abutting land who claimed a loss in their property values.
In the meantime, a vital road remained blocked, threatening local businesses and causing major headaches for drivers. Coast Highway — formerly State Highway 1 — serves as the main link between Dana Point and San Clemente, and the road’s designation as the primary evacuation route from the nearby San Onofre nuclear power plant was an added twist to the situation.
Finally, the various interests agreed, without settling all their differences, on a plan to rebuild the eroded bluff. The cities chose the more complicated route over simply constructing a 25-foot-high steel-and-wood retaining wall along the highway to intercept any future slides, since such a wall would not have stabilized the bluff, restored lost property or addressed the aesthetic damage caused by the slide.
“It was to everyone’s benefit to compromise and agree to disagree on the causes [of the landslide], and to let the lawyers and judges decide that on down the road,” August says.
With the truce in place, the private contractor hired by Dana Point began work in July 1994. Minor demolition at the top of the bluff to prevent further uncontrolled slides during construction and protect workers’ safety was the initial step. The mound of eroded earth was then graded to form a ramp to the bluff’s top, enabling the project to proceed from the top down.
Once the earthen ramp was complete and workers had access to the bluff face, they began the essential job of reinforcing the bluff. The first reinforcement was done on the edges of the slide area, to prevent further damage to adjacent property. Nail-like tieback anchors, epoxy-coated rebar and shot-crete were all used to stake the 600-foot section of cliffside in place.
To create the anchors, the contractor drilled six-inch-diameter holes into the bluff face and extended stainless steel cables into the holes. A total of 165 anchors were installed to a depth of 75 feet.
The anchor holes were then pressure-grouted, and concrete pads, four feet wide, eight feet long and two feet thick, were poured at the end of the anchors. The 30-degree angle of the anchors creates tension and pulls them against the bluff’s slope.
To further strengthen the bluff, a network of salt-resistant rebar was woven among the anchor pilings, and a layer of shot-crete was applied at various heights.
An extensive drainage system, designed to replicate natural seepage by piping and draining off water throughout the rock surface, was also installed within the bluff to deal with future saturation during heavy rains.
As the reinforcement and drainage systems were going in, workers were clearing debris from Coast Highway down below. The road was finally reopened in April 1995, restoring a major lifeline in the area’s tourism-dependent economy.
The remediation project was also designed to recreate the bluff’s natural appearance, since the coastal beauty of Dana Point and San Clemente is a major draw for tourists. The goal was to make the repairs to the bluff as unnoticeable as possible.
Thus, a subcontractor hired to create an artificial bluff face used a latex mold of nearby rock outcroppings to actually “sculpt” the concrete facing, along with concrete imprinting and a clear stain that reflects brown and black tones. A landscaped cover of native plants was also used to further camouflage the project. Altogether, the rebuilt bluff would most likely impress even the movie-set builders in nearby Hollywood.
COOPERATION AND COMMUNITY RELATIONS BUILD MOMENTUM
By the time they celebrated the project’s completion at a reopening ceremony in April of 1995, residents and officials from the cities and other agencies knew one another well. Along with the requisite placing of blame, there had also been essential cooperation for more than two years to keep the bluff restoration on track.
Dana Point was largely responsible for stoking the project’s momentum, both during preliminary engineering and the actual construction. One of the city’s keys to success was its effort to treat everyone as a stakeholder in the project and to keep these stakeholders involved and informed throughout the process.
In the first year after the slide, Dana Point officials held several meetings with officials and staff from San Clemente, as well as with property owners, to negotiate agreements on the basic restoration plans. Eight affected owners signed waivers to release Dana Point from liability if any further sliding occurred during construction to restore the bluff.
Before the start of construction, city officials invited residents to an open house at City Hall, where they were able to meet and ask questions of the project manager, contractor and inspection team. Open houses were also held during construction, and the city sent out newsletters to give project updates to about 100 people.
“Everyone has a fear of the unknown,” August says. “People tend to go to the worst case scenario; they get their defenses up. [But] by going through this, we demonstrated that we were responsible and sensitive to [residents’] concerns.
“We spent a great deal of time in letting people know every step of the way what we were doing,” he says. “People accommodated changes in the construction because they knew who to contact and how things were going. There were no surprises, so when there were problems, we didn’t have people running to the newspaper or to the city council [members] or their congressman.
“The bottom line is that we developed the communities’ trust in what we were doing and how we were going about it and faith in what the end result would be,” he says.
The city’s goal was to make it as easy as possible for stakeholders to agree with decisions, according to August. People would thus feel like part of the solution, as opposed to feeling as if a solution had been imposed upon them.
Additionally, Dana Point officials and staff kept in mind that several agencies had a vested interest in the project’s outcome and tried to give as much personal attention as possible to those agencies. The California Coastal Commission, the state Office of Emergency Services (OES), the state department of transportation (Caltrans) and the Federal Highway Administration (FHWA) all had permitting authority and major input in the project.
Caltrans was significantly involved because the landslide had blocked a vital highway. In dealing with the department, Dana Point representatives hand-delivered various proposals to six different offices, rather than leaving them with someone at the agency who would then distribute copies to the appropriate people. The chances were thus reduced that key department officials would not receive and understand the proposals.
These efforts to foster cooperation and provide personal attention helped the city secure both public and private funding for the bluff restoration. In fact, Dana Point’s costs were limited to staff time for overall management of the project.
FHWA paid the biggest chunk — around $2.7 million of the total engineering and construction costs of $3.5 million. The state OES provided $583,745, and a group of San Clemente homeowners affected by the slide contributed another $200,000.
It was money well spent. The young city of Dana Point now has a well-stabilized bluff and a share of national renown. Plus, of the 42 lawsuits originally filed against Dana Point after the landslide, only five are still being pursued, according to August.
Just to the south, San Clemente has undertaken a similar reinforcement of a cliffside in danger of sliding. As surely as the forces of water and wind remain, erosion problems will most likely continue, but the two coastal communities can tackle them with improved knowledge of the techniques, negotiation and long-term planning required for success.
Soil erosion and siltation build-up have been significant problems at many of the city parks in Phoenix. The city has in the past used concrete channels, soil stabilizers, soil cements, culverts and concrete spillways to combat these problems, but only with partial success.
“Many of our parks are detention basins,” says Terry Mills, parks supervisor for the city’s northeast district. “They’re designed for high stormwater flows one day, and needed for safe public use the next.”
To make that possible, in several areas, Phoenix installed a monolithic, cast-in-place concrete reinforced with steel mesh, manufactured by Bomanite, Madera, Calif., and installed by locally based Progressive Concrete Works. Prior to pouring concrete, hollow formers were placed on prepared subgrades and removed after the concrete was sufficiently hardened. The void left by the formers was filled with a loose mixture of topsoil and sand.
“[This step] has been very effective for erosion control in high visibility park areas, such as Venturoso, Sereno, Sand Piper and Crossed Arrow, where heavy stormwater inflows affect soccer field and baseball field usage,” Mills says.
For example, Venturoso Park, located at the headwaters of Indian Bend Wash, was the site of erosion problems in 1990. A 66-inch storm drain outfalls into the park, entering a 60-square-foot concrete box that has an existing 36-inch low-flow pipe.
During significant storms, when runoff exceeds pipe capacity, water flows out of the top of the outfall box into the park. In the early `90s, a six-foot fountain of water shot from the box during heavy storms and eroded a four- to five-foot deep crater around the box.
Phoenix considered plain concrete to solve the problem in Venturoso Park, but concerns that it might attract skateboarders and graffiti led the city to install 196 square yards of monolithic, cast-in-place concrete around the outfall box. Grass completely covered this reinforced concrete slab, and no signs of erosion were found in subsequent storms.
The city has also used the monolithic, spaced concrete in Crossed Arrow Park to provide access to areas of siltation caused by stormwater flows. Tractor operators can better use the concrete’s finished grade as a platform while regarding the silt, since this concrete is not likely to settle unevenly and thus be lifted out during this grading.