Geo Inspection

Vasquez Rocks Park in Agua Dulce

What is a GEO?

“Geo” is short for Geological Inspection. Geo Inspections are done by Geologists who evaluates the risk, from a geological standpoint, of buying a home in escrow. Geologists rate risk on a scale of low, medium/average, or high.

The steeper the slope- the greater the force of Gravity

I always recommend to get a Geological Inspection for hillside properties. Hillside properties have gravity working against them, so it is important to ensure that the geological conditions of the lot are stable. A house is only as good as the foundation it is built on, and a foundation is only as good as the bedrock it rests on top of.

If the property has or has had a geological problem in the past like a Landslide, Slope Failure, Erosion, Creep, Collapsed Retaining wall, etc, these are expensive and can cost in the $100,000’s of dollars and could make the property unmarketable!

A GEO inspection protects you from buying a property with a known or observable Geological defect. 

GEO inspections have two parts:

(1) Site Visit: the geologist and visual inspection of the property.

(2) Research: the geologist reviews city records and reports including building permits, previous soils tests, grading reports, historic landslide information, proximity to active faults, and geological bedrock survey maps.

At the end of the inspection, the geologist will write a report that summarizes all of their findings.

Geological Inspections do not include testing. The purpose of a GEO is to satisfy the buyer’s due diligence during escrow and not to be used for obtaining approval of building plans. No testing keeps cost down- a GEO inspection is 1/3 to 1/5 of the cost of a Soils test.

How do I tell if my property is Hillside?

You can usually tell just by looking around. Hillside properties are in the mountains, so if you see any big hills or slopes, you are probably in a hillside area.

Hillside Areas Are Shaded

Los Angeles has a special zoning designation for Hillside properties. You can look up the zoning information on the city’s zoning website ZIMAS. The main characteristic that defines a hillside property is slope.

The definition of a Slope (LABC 7003)

SLOPE. An inclined ground surface the inclination of which is expressed as a ratio of horizontal distance to vertical distance. Slope greater than 10% shall be considered as a sloping surface.

What does a GEO inspection Cover?

The GEO covers several different topics that relate to the hillside: Drainage, Grading, Soil/Bedrock, Seismicity, Landcaping, and Foundation

-Drainage

Controlling stormwater runoff is the most important thing to keep your hill safe. Good drainage also protects your foundation from deterioration. Los Angeles doesn’t get much rain, but the occasional heavy rainstorm can dump 5 to 10 inches quickly, which can lead to landslides and slope failures if your property doesn’t have proper drainage.

Soil naturally absorbs water, so having some open areas on the lot that can absorb runoff and not all concrete pavement will help drainage. For excess water, the best place to drain is in the streets that are connected to the city’s stormwater system and empty into the ocean.

Sometimes on hillside lots, you can’t drain to the street. If you can’t connect to the stormwater system, then an onsite drainage system such as a dispersion wall, sump pump, swale, or cross-lot drainage easement can be built to direct the runoff to an approved location. 

It is illegal to send your stormwater runoff into the sewer system, which is a different system altogether. If everybody drained their storm water into the sewers, they would overflow. Storm surges can move 10 billion gallons of water in just 1 day. In addition, it is very costly to treat sewer water, whereas stormwater is not treated.

Grading

Grading is flattening the land by moving topsoil. Hillsides are sloped. You need a flat pad to build on. Grading sculpts the land to prepare it for building.

Grading Diagram

When you remove soil- this is called a “cut”. When you add soil- that is called a “fill”. Depending on the soil composition, sometimes you can use your cut from the same site as fill.

Fill is where you sometimes run into trouble. Prior to the enactment of the Grading Code in 1963, fill was not generally well compacted, which lead to an excessive amount of settlement, landslides, and erosion. If your Geological inspection reveals that the lot has fill prior to 1963- be extra careful.

Just like you have setbacks for the front yard, backyard, and side yards, of your house- you have required setbacks from the hillside of your lot. There are two reasons for the hill setback- 1) the more flat land between the foundation and slope, the more bearing capacity of the soil and 2) if there is a rockfall or a mudslide you house has a better chance of being a safe distance away from it. The amount of the hill setback varies. 

Soil/Bedrock Conditions

Geologists study rocks and dirt. When you start learning about Geology, it’s actually pretty cool! The first rocks on Earth formed about 4 billion years ago. Since that time the surface of the Earth has changed quite dramatically- and it’s still changing. Los Angeles is moving towards San Fransisco along the San Andreas Fault at the rate of a few inches each year which means that in about 15 million years these two cities will be connected!  

 
The Geologist will visually inspect the soil conditions and estimate the composition.
 

Sand- Water drains quickly through sand

Silt/Loam- Just the right amount of sand and clay and organic materials, basically dirt. 

Clay- Clay absorbs water, and expands and contracts. Too much clay in the soil can create expansive soils. 

Bedrock 

 There are 4 main types of Bedrock in Los Angeles Area:
 
Basalt
 
Granite
 
Shale
 
Slate
 
 

 

 
 
and estimate how far below the surface the bedrock is. The closer to the surface the bedrock is, the better.
 
Bedrock is what you anchor your foundation to and what gives it strength. Bedrock 5 – 10 below the surface is close to the surface, 20-30 feet below the surface is average, and 40 feet or more means the bedrock is very far from the surface and it can be very costly to anchor the foundation with caissons. 
 
Types of Bedrock:
 

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2 comments

  • Chris Caparro
    July 27, 2016 at 9:14 pm

    Hi came in contact with James by simply searching the internet. I found this blog post of his on geo-inspections that was extremely helpful. I had some additional questions and he was more than happy to help. I learned a lot from our conversation as he seems to know a lot about real estate, especially real estate inspections.


  • Chris
    November 16, 2016 at 4:02 pm

    Great post on geotechnical inspections. I came across this post by just doing some local research and spoke directly with James who was very helpful and knowledgeable about these types of issues. Thank you James!


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