What you need to know about Geotechnical Engineering on the Central Coast
Real estate in our region often lends itself to large acreage parcels or lots without availability to a municipal sewer system. These conditions require septic systems and independent drainage solutions. Also, due to the diverse and frequently varying soil types and geological formations, local county and city building officials call for geotechnical engineering studies to be performed for almost every new structure or remodel project.
Percolation Report:
Septic systems are necessary when your proposed building or remodel location does not have convenient access to a municipal sewer source. To begin this process, a percolation study is required in order to determine the rate that the septic system’s effluence will percolate into the a fields. Typically, the project Civil Engineer will use the percolation values we determine in our study to design the septic system.
Geotechnical Engineering Report:
A geotechnical engineering report, also commonly referred to as a soils report, is the result of a study of the project site’s soil types and characteristics. Specifically, grading procedures and foundation recommendations are outlined so that the project design engineers and contractors will be able to construct a pad suitable to support the structure’s foundation. Recommendations are site specific and account for various local soils conditions including loose native material, expansive clay, slope stability, and liquefaction.
Field Testing:
Once your project is ready to begin grading, have your grading/excavation contractor contact us so that we can make sure they fully understand your site’s specific grading requirements. We will typically need to visit your job site at each stage of the grading process in order to provide the necessary inspections and certification reports. These reports will be used to show your local building official that your pad has been certified and is suitable to support the designed foundation.
In addition to performing the inspections to your building pad, it is recommended that we perform grading observations and inspections on your driveway area as well, in order to ensure that the finished road material is being placed over competent sub-grade.
Expansion Index Test:
Although an expansion index test is an important part of our geotechnical engineering process, unlike a geotechnical engineering report, it does not evaluate sub-surface soil conditions for suitability in the development process. A full geotechnical engineering report includes a discussion of geotechnical conditions such as total and differential settlement, bearing capacity, soil expansion or collapse, etc. In addition, a soils report provides design criteria for grading, foundations, retaining walls, slabs and other improvements.
An expansion index test provides a method of evaluating a soil’s potential for expansion when exposed to saturated or moist conditions. Typically, soils with higher clay content will have a greater potential for expansion, while sandy soils may expand very little. The structural design professional that provides the foundation engineering will use the results of the expansion index test in the foundation design process.
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