Technicians Work from the Ground Up : Soil Tests Help Builders Stay Step Ahead of Mother Nature
There are Southern Californians who have gone to bed in a modish California Ranch house and awakened in a battered split-level.
If they didn’t know what soils engineering is before that happened, it’s a good bet they do now. And also that they realize the old saying is wrong--what you don’t know can hurt you.
There is a lot one cannot know about the ground underfoot as, to pick a spectacular and fairly recent example, the residents of Bluebird Canyon in Laguna Beach found out on Oct. 2, 1978.
And it can hurt you. There were no deaths on that date but 3 1/2 acres of ground slid downhill, a matter of more than 500,000 tons of earth. In the final total, 24 homes were destroyed by the slide or had to be demolished later, streets were torn open or pushed away, gas and water lines were broken; the final damage total was estimated at $15.5 million.
“No geotechnical work was done (when Bluebird Canyon was developed in 1925),” said Michael J. Miller, president of San Diego Soils Engineering Inc. “If there had been, there probably wouldn’t have been a Bluebird Canyon.”
It wasn’t clear whether he meant there wouldn’t have been a development or wouldn’t have been a disaster but his present concern at Rancho San Clemente, in the hills behind that coastal city, is to see to it that there is a development but no disaster.
As developments go, it’s a big one, even for Southern California. Encompassing 1,200 acres, it is master planned for 2,931 dwelling units--single-family detached homes, cluster town houses, condominiums and apartments--with a 10-acre neighborhood commercial center, a neighborhood park and an elementary school.
Also in the master plan are a 299-acre business park, eight acres of additional commercial facilities and a community sports park. The business park will contain offices and facilities for light manufacturing and research and development.
About half the acreage will be left as natural open space, preserving the coastal hills and ridges.
The developer is Irvine-based Western Properties Service Corp., an arm of Western Savings. Site preparation is being performed by McCoy Construction Co. of Woodland Hills and San Diego Soils Engineering of San Diego, a subsidiary of the Irvine-based Irvine Consulting Group Inc., is supervising site preparation and providing geotechnical, soils engineering and other related services.
“It’s one of the biggest dirt-moving projects I’ve ever seen in California,” Miller said. “It’s the largest single dirt-moving project in Southern California, both in the total square yards and the number moved each day.”
When the whole project is completed, probably in three to four years, McCoy will have moved about 40 million cubic yards of earth. The company is moving 130,000 cubic yards a day and when the first phase of site preparation is completed, scheduled for early March, 21 million cubic yards will have been moved.
The machinery used for that sort of work is elephantine. One of the big track-laying earth-movers was called a “Triple 6" by McCoy’s general superintendent, Gerald L. Snyder. Weighing 140,000 pounds, it can carry 45 cubic yards of earth at one time, a total weight, machine and cargo, of nearly 150 tons.
Another gigantic machine is called a D-10 Ripper; a San Diego Soils spokesman said they “move dirt around by the tons but drive like Cadillacs.”
(While a visitor found, during a short ride, that the cabs are enclosed and air conditioned, to say they “offer almost all the comforts of freeway driving,” according to a spokesman, is an exaggeration.)
The planning for this enormous job was done by four representatives of four specialties: the land planner, the civil engineer, the geotechnical engineer and the developer (“he pays the bills”).
Speaking for the third of these specialties, Miller explained that the first thing to be done is to get full information about the site. This is accomplished in three ways: by aerial photography, by “walking the site,” officially “field reconnaissance,” and by subsurface exploration.
“This site (Rancho San Clemente) is one of the most geotechnically complex ones, because of the number of old landslides--probably more per acre than any other this company has helped develop--and the number of quake faults, all inactive,” he said.
What’s “inactive?” “No activity in the past 11,000 years.”
Making an old landslide safe, so it won’t slip again, usually consists of cutting a huge trench across the slide and inserting a sort of wall of heavy material, highly compacted. It could be compared to a retaining wall on a home site, though it could be 50 feet high or even higher and several hundred yards long, or to a dam across a stream.
Compaction is not only necessary for such uses as nailing down old landslides but for roadbeds, building sites, just about everywhere. The basic tool is a huge sheepsfoot roller, as much bigger than the one you use on your lawn as the D-10 Ripper is bigger than your wheelbarrow.
One of the many ultramodern scientific devices San Diego Soils uses is a nuclear density gauge to test compaction of the soil. It replaces older methods that were, in essence, taking a core sample in somewhat the way you core an apple, then measuring how much it slumps in how much time.
The nuclear device, whose probe has a “source pellet” inside, can make 15 to 18 measurements and store them in a computer memory to be worked up later.
The company has a complete field laboratory on the site.
San Diego Soils Engineering is the soils engineer/geologist, McCoy Construction the earth-moving contractor, and Western Properties Service Corp. the developer.
Others on the development team include Corbin/Yamafuji & Partners Inc., architect-planner; Haworth & Anderson Inc., planner; Psomas & Associates, civil engineer; Closson & Closson, landscape architect, and Market Profiles, marketing research.
Irving Consulting Group, headed by Neil H. Durkee Jr., chairman and chief executive officer, is a 10-year-old firm and the parent of San Diego Soils Engineering. Miller was appointed president of the latter group in January, from his position as vice president and general manager.
San Diego Soils specializes in geotechnical and materials testing work for high-rise, commercial and residential development and also has expertise in the fields of hazardous waste research and geological instrumentation.
Among San Diego Soils’ other commissions are the geotechnical investigation for the first-phase commercial and industrial portions of the 3,000-acre, mixed-use East Lake community in eastern Chula Vista, proposed as a master-planned community to include single and multifamily housing along with commercial, industrial and recreational elements.
The engineering company has completed its field explorations and laboratory analyses; grading of the project is expected to begin sometime in the first half of this year.
San Diego Soils is also the geotechnical investigator for a $16-million, 300-unit housing project at Camp Pendleton, where Turnkey Design & Construction Co. will build 28 officers’ units and 272 units for senior enlisted personnel. Grading is in progress and completion is expected late this year near the Marine base’s north gate at Basilone Road.
If anyone in any of these developments--or any of the others San Diego Soils Engineering and the others have a hand in--wakes up in a sudden split-level, it will be because of a convulsion of nature that even these specialists can’t handle.