Swimming pools must be designed to withstand any force that will be exerted upon the structure. These forces are called "surcharges." The leading surcharge on an in-ground pool are the soils surrounding the pool itself.
The soils must be able to support the structure and prevent movement. Soil conditions can very from lot to lot in the same subdivision.
For example, these soils can be expansive, non-supportive, prone to sliding or vertical uplift or subject to liquifaction.
One cannot ascertain the characteristics of the underlying soils by looking at the top soil. That is unless they are Superman with x-ray vision.
Structural Engineer needs a soils report
A structural engineer cannot design the structure, without knowing the characteristics of the underlying soils.
Therefore, they need a soils report to tell them what site conditions are present.
Required by Law (Building Codes)
The 2012 International Swimming Pool and Spa Code states:
802.1 Materials of components and accessories.
The materials of components and accessories used for permanent inground residential swimming pools shall be suitable for the environment in which they are installed. The materials shall be capable of fulfilling the design, installation and the intended use requirements in the International Residential Code.
802.2 Structural design.
The structural design and materials shall be in accordance with the International Residential Code.
The International Residential Code goes into further depth as to the requirement for project specific engineering, soils reports, minimum concrete strengths, foundation requirements, shotcrete strengths, rebar installation, special inspectors, laboratory testing, etc.
Since the 2012 International Swimming Pool and Spa Code has been incorporated into the International Building Code, which is THE building code for the entire United States... it has defacto become the swimming pool code for the United States.
The Swimming Pool Code's counter reference to the IBC and IRC places a lot of additional minimum specifications and requirements on the construction of a concrete swimming pool or spa (gunite/shotcrete).
It helps to know the law.
Aquatic Artist, Watershape Consultant, Expert Witness
"Creating water as art."™
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