What Is A Soils Report?

Understanding the Importance of a Soils Report in Construction Projects

What exactly is a soils report? Most of us are familiar with the concept of sales reports, but why are soils reports equally crucial? How are they prepared, and what should you look for? In this blog, we will discuss the importance of soils reports, how they are made, and some tips to ensure they are relevant and effective for your planning process.

Why You Need a Soils Report

One key challenge I see when working with project teams during the early planning stages is the lack of sufficient information from the soils report. Often, project sites, particularly larger ones, don’t have enough boreholes (which are drilled into the ground to investigate soil or rock conditions) to give an accurate representation of the soil at various depths. This lack of data can lead to problems when making decisions about the site’s structural foundations.

What is a Borehole in Construction?

A borehole is a hole drilled into the ground to extract samples of soil or rock for analysis at various depths. Boreholes provide crucial data on subsurface conditions where a new building or project is planned. 

The drilling process involves specialized equipment, such as drill rigs, augers, or coring tools. As the subsurface is exposed, the soil or rock is analyzed for its composition, density, moisture content, strength, permeability, and other essential characteristics.

Strategically placed boreholes provide data that influences decisions about foundation design, slope stability, and groundwater assessments. However, one of the biggest issues is not having enough boreholes drilled throughout the site, leading to incomplete or misleading data.

Why More Boreholes Matter

Imagine this: one borehole on your site indicates sandy soil, while another borehole just a few hundred feet away shows stable soil that doesn’t require any stabilization. How do you plan for foundations in such conditions? 

Without enough boreholes, you may need to account for potential risks, or even request additional boreholes to ensure the soil data is accurate. While getting more boreholes is often difficult, the critical data they provide can significantly influence the design of your structural foundations.

What is a Soils Report?

A soils report is a document prepared by a geotechnical engineer that provides detailed information about the soil conditions at a construction site. This report helps engineers and designers make informed decisions about the structural design of buildings, roads, bridges, and retaining walls. For instance, the report will specify whether you need to over-excavate, how to construct your foundations, and whether scarification or re-compaction of the site is necessary.

Real-World Example: The Impact of Soils on Construction

In Texas, I encountered an issue with expansive clay. The soils report indicated that under the foundations, void form—a waxed cardboard-like material—needed to be placed beneath the footings.

 As the expansive clay underneath expanded, this void form dissolved, preventing the building from being pushed up by the soil. This is just one example of how a soils report can influence the construction process, making it essential to thoroughly read and understand the report.

Key Information in a Soils Report

The soils report will include a site description, field investigation data, laboratory testing results, and a soil classification. Here’s why this is important:

1. Risk Identification: Knowing the soil composition helps prevent costly surprises. For instance, if you encounter sandy soil that needs to be stabilized with slurry, it could significantly increase the project cost.
2. Construction Planning: The report will tell you if you need to haul off unsuitable material or bring in fill, both of which affect your construction timelines and budget.
3. Site Preparation: The report explains what needs to be done to prepare the site for construction, such as scarification, re-compaction, over-excavation, or building retaining walls.
4. Soil Classification: Under OSHA regulations, soil is classified as Type A, B, or C, with Type C being the least stable. If your site has Type C soil, it requires special planning, such as sloping the sides of trenches to ensure worker safety.

Final Thoughts

A soils report offers essential design recommendations and construction parameters that should never be overlooked. While your structural drawings may not specify how to prepare the soil for foundations, the soils report will fill in those crucial details.

 Reading and understanding every aspect of the soils report, particularly the recommendations and design parameters, can save your project from unexpected delays and budget overruns.

Challenge Yourself: Dig Into Your Soils Report

I challenge you to read your soils report thoroughly. Highlight the key recommendations, and communicate this information to your team. The report offers critical insights that will help you plan more effectively, manage your budget, and keep your project on schedule. The more familiar you become with soils reports, the more valuable they will be in your construction planning process.

Make sure you reference your soils report at every stage of your project. You’ll be surprised by how much it can affect not only your building’s design but also your safety planning and scheduling efforts. By understanding the subsurface conditions, you can ensure a smoother, safer, and more cost-effective construction process.