Ask a Pro: What should I know about existing soils before building?
Question: What should I know about existing soils before building?
Answer: Before buying a piece of property, find out if a geotechnical evaluation has been completed to identify potential defects with the existing soils. These defects can make development more expensive than expected, to the point where it is no longer practical.
A common problem developers face is the presence of existing fill. There should be documentation on the placement of the existing fill soils on the site. This would also include confirmation that all topsoil and vegetation were removed, because they will decompose and cause settlement. During construction, if existing fill soils are present without appropriate documentation, the site development budget should then include costs to remove and replace the fill so that it is reliable. This new fill should be tested for compaction both vertically and horizontally. If not thoroughly compacted, it will compress under the weight of new fill, a new building, or traffic. Also, careful moisture conditioning of the soil must be conducted during fill placement or it could collapse/swell with changes in the moisture content.
Braun Intertec has experienced geotechnical engineers and scientists that can assist during the early stages of property selection and can quickly check the documentation available on existing fill at a site. For more information, please reach out to Wes Dickhut in our Bismarck, North Dakota office.