A great deal of the many wonderful things we build at Naturescape are retaining walls. In case you have not noticed, San Diego is filled with slopes, hills, and valleys, and of all the many reasons we build walls, the most frequently used reason is to maximize ridiculously tight spaces, or add usable space to a property.
Our team has been NCMA (National Concrete Masons Association) certified, and we continue our education on walls and structures as often as there are classes available to take.
In the case of the wall pictured, the homeowner wanted more space added to the area where their kids could play, so, they had us build this 14' tall by 200' long wall of of Keystone Century Wall. As written, the job sounds like a simple procedure, and if you think that, you more so than anyone reading this blog need to absorb the next part of the post.
WE began by excavating a trench to accommodate the bottom course of the wall. As a standard rule of thumb, there has to be 1" of wall buried for every 1' in elevation the wall is above grade. As we dug in, water began bubbling from the ground in a spot where no water should have been....It turned out that the swimming pool had been leaking since it was installed 8 years prior. to add more difficulty to the job, it was leaking at a fitting right in the center of the spa, just under the gunite. After we tunneled into the hill, the repair was made. We then had the arduous task of drying the earth so we could use it to fill behind the wall.
Along with the DG based soil, we also use class 2 roadbase for fill, and topped the job off with 2' of growers mix. While the wall was being built, Geo-Grid, an earth stabilization product, was placed every 3rd course of wall, 12' back into the slope. This was, if the earth got wet, and the soil got heavy, the grids would hold the wall from falling over on it's nose. Soil was compacted to 95% proctor scale, and tested by a soils engineer for each 2' of earth we brought in. A gravel layer, 1' thinks was used behind the wall, and perforated pipe placed in the gravel, with a discharge pipe under the footing to take the water to the street.
Permits are required for any wall over 3' in elevation, and in many cases around the county, soils tests and a grading plan is required before the building department will approve the wall.
In recent months, I'm sure you have heard of the Mount Soledad land slide, (2007, LaJolla) along with the Arroyo street landslide in Oceanside (2004) and Bluebird Canyon in Laguna Nigel.
Still, with all these wall and earth failures, there are people who are hell bent on building that wall without permits. In one extreme case, a homeowner in Solana Beach was told by the city not to build a wall....He thought he was going to save money by using illegal aliens and untested back fill to make his project. Dozens of truckloads of dirt, and Keystone wall were used, only to have them fall down in 2004 during a wet winter. The repair is just about completed as of this writing, and to save several thousand dollars of cost, this homeowner has spent nearly $600,000 in soil nails and shoring.
Retaining walls are a necessary structure in San Diego, however, they are also one of the most expensive items you can build. Before going out and making a mess of things, or causing bodily injury to someone who might be in the way when the wall fails, call a pro in. Call Naturescape.
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