A preliminary report by two consultants has concluded that a resident's proposal to fight the Flying Triangle landslide by means of a massive canyon landfill probably would not work. But the City Council has asked the two to analyze more information about the slide and report back in two weeks. At that time, a study of the proposal by the Los Angeles County Public Works Department also is expected to be in the council's hands.
Frederic W. Hartwig, an engineer and long-time Flying Triangle resident, proposed two months ago that Klondike Canyon be filled with 224,000 cubic yards of compacted soil dumped by contractors, who would pay fees. The 6-year-old slide, which already has destroyed five expensive homes, is moving into both Klondike and Paintbrush canyons, and Hartwig said his landfill concept could be applied to both. He contends that the fill would "stop the toe of the slide" and that, in turn, would halt land movement above it.
However, civil engineer Sam W. Peterson and geotechnical engineer E. Douglas Schwantes Jr., who were retained by the city to analyze the proposal, said that too little is known about the full extent of the slide and that a detailed geotechnical study is needed to see if there are "any feasible methods of stabilizing and redeveloping the area."
As to the Hartwig proposal, the consultants said that though it might stabilize one or two lots, it "is likely to do little or no good considering the greatly expanded area of the landslide movement," and actually "could accelerate the movement." They said that an effective earth buttress might require a large area that "would bury many southern lots" in the Flying Triangle. Hartwig's home, which he has put up on heavy steel beams that shift with the moving land, is near Klondike Canyon.
Peterson and Schwantes said their conclusions were based on a review of a 1981 county study of the original 10-acre slide, the Hartwig proposal and a walking tour of the slide area. Schwantes said the slide has accelerated and now covers "10 times the area mapped by the county in 1981."
Councilwoman Ginny Leeuwenburgh took issue with the consultants for not considering a series of county reports that monitored the ever-widening landslide during 1984 and 1985. "I am concerned about your information," Leeuwenburgh said.
City Manager Terrence L. Belanger responded by saying that the two were asked to focus their attention on the Klondike Canyon portion of the slide and not the larger area. The council went on to ask the consultants to broaden the scope of their study.
Peterson and Schwantes also said that "there is a strong possibility that the Flying Triangle landslide is directly related to the Portuguese Bend landslide" in neighboring Rancho Palos Verdes because of the proximity of the two slides. They said, however, that there is no hard evidence of this connection.
Rancho Palos Verdes, which is planning a $2-million project to stabilize the Portuguese Bend slide, contends that the slides are separate. In a telephone interview, county geologist Arthur G. Keene, who has monitored the Flying Triangle slide for several years, said the two slides "are not related at all." He also reiterated his statement that Paintbrush and Klondike canyons should be "filled as a buttress, and the sooner the better."
For his part, Hartwig said this week's council session offered "nothing definitive one way or the other" on his landfill plan. He disagreed with Peterson's conclusions that the project could cost $1.5 million and that it is commercially unfeasible because of poor access to the canyon and the availability of more convenient landfills, including the Chandler quarry in Rolling Hills Estates.
Hartwig said two private engineers support his cost figures of $253,500 for the entire Klondike Canyon project, adding, "We have had contractors ask if they could count on our price" of $1.50 per cubic yard to dump soil in the landfill.