Trench Backfilling: Methods Explained

If you’re comparing possible trench backfilling options, there are a few different methods that might be a good fit for your project. Below are some of the most common methods and some information about their usefulness for trenching projects:


Compacting typically involves using the existing soil and organic materials in a trench and applying a jumping jack, compactor, or excavator to produce a coarse, wet material or slightly saturated, fine material that is level and used to secure pavement over a trench. This is one of the most common and effective methods.


This involves backfilling a trench with flowable fill, which is a cement mix, using a cement truck that’s brought directly to the site. This method generally works well but can cause issues if the flowable fill covers any pipe too snugly. It’s best to cover pipe with protective material before filling. Additionally, it’s best to block off sections of the trench if the fill needs to be applied in multiple batches. Otherwise, it will spread to other areas and won’t be as level.


This method involves filling the trench with a material that isn’t compacted. The contractor then comes back to the trench later in the project and applies pressurized water to the trench. Unfortunately, after several years, the pavement over the trench often dips or is compromised when this method is used. It’s not the best method for the long-term.


This is one of the more recently developed methods of backfilling. It involves backfilling a trench with open-graded coarse aggregate materials instead of compacting. This method has not been as time-tested as others and poses risks including soil that migrates in holes in the aggregate materials. This method is best used with caution.

While we’re on the subject of trenching, have you taken a look at our trench boxes?