5 Reasons for a Subsurface Soil Investigation

So, you’re getting ready to start a new construction project, and you’ve been told that you need to test your soil using a subsurface soil investigation (also known as a drill report). They sound pretty expensive. You’re probably asking yourself, “Why do I need one of those?” Here are 5 reasons why soil testing is worth the cost.

1) They’re required.

Whether required by the local building department before they’ll issue a permit or by the geotechnical engineering firm to develop design parameters, your construction project likely won’t be allowed to proceed until you have had the necessary subsurface soil investigation(s) performed which may include some drilling.

2) They can help identify significant challenges presented by your site.

The soil conditions underlying the Colorado Front Range are highly variable and can present significant challenges to construction. A subsurface soil investigation can identify these challenges early in the process, and provide the information necessary to plan and budget for the necessary mitigations. In some cases, they may even identify challenges so costly to mitigate that you decide to sell the site and build somewhere else. While nobody wants to receive that kind of news, it’s better to find out before you invest significant time, energy, and resources into developing that site.

3) They provide necessary foundation design information.

One of the primary purposes of a geotechnical investigation is to provide foundation design parameters to the structural engineer. Without these parameters, the structural engineer can’t finalize a foundation design. While the foundation could be designed based on preliminary (assumed) design parameters, those parameters would need to be verified by having a geotechnical engineer perform an excavation observation (after excavation, but before the foundation is constructed). If the final design parameters are different from those preliminary (assumed) parameters, the foundation would need to be revised. This typically results in significant costs (both in money and in delays to the project).

4) They provide additional information necessary for contractor estimates.

In addition to the foundation type and associated design parameters, the subsurface soil investigation also provides additional recommendations relating to site grading and drainage, floor systems (particularly slabs placed directly atop soil), foundation drains, earthwork and excavation operations, etc. Without this information, contractors would have to make assumptions on what they think will be required later, which can lead to high variability in estimates from one potential contractor to another, as well as costly change orders later.

5) Peace of mind.

Construction of a new building (whatever its size) is a significant investment, both in time and money. No matter how much money you spend on the building itself, it won’t last unless it’s supported by a stable foundation. Likewise, the foundation won’t be stable unless it’s adequately supported by the underlying soil. An understanding of the subsurface soil conditions and their behavior is essential in selecting, designing, and building a stable foundation. Having a subsurface soil investigation performed at the beginning of the project gives you peace of mind in knowing that your investment will be supported atop a solid, stable and enduring foundation.