When a construction project requires too little material, it can end up in a situation where they are having to rush to get a new order when they were already in the middle of a job. Ordering too much can waste the budget and may also leave unused sand on the site. Several interdependent factors need to be understood to correctly estimate volume of sand you will need for your bank.
Correct volume estimation is good for the contractor and good for the property owner as there is no need for over ordering of material which must now be managed, or under ordering which causes inefficiency.
The importance of the trench dimensions to the calculations of backfill.
The volume of material to be put in the backfill for the utility trench depends on an accurate calculation of the length, width and depth of the trench that is to be backfilled below the point where the bedding material or utilities occupy space. The multiplication of these dimensions will give a good indication of the volume, although usually adjustments are made based on the compaction that is expected.
Some of the critical measurements that affect the volume calculations of backfills are:
- Overall amount of trench throughout the project
- The width of the trench per excavation equipment used.
- Space for backfill over utilities installed
- Adjustments to the volume of settled material based on the compaction factor of the material.
When a grading project uses a different method of calculating, you should make sure to understand how it is calculated.
When using this method for site leveling and grading applications, a different calculation method is needed, as it is normally applied to a larger, irregularly shaped area of the site to raise the elevation rather than fill a consistent, linear trench shape as is the case for trench backfill. Current vs. target elevation data from surveys aids in determining the accurate volume requirements for these uses.
This is why the compaction factors impact the final numbers:
Bank sand delivery is not compacted and is more expansive than it would be in its final place. This typically requires some adjustment of the calculated raw volume from the dimensions of the trench or the grading to account for this compaction when ordering material to reach the real volume that has been specified.
Typical compaction factors can be used with experienced contractors and suppliers, which can be used to help translate the raw calculated volumes into realistic volumes that can be ordered, taking into account this settling effect.
A Practical Estimation Checklist
There are a few practical steps that will aid in getting an accurate estimation before ordering products:
- Take accurate measurements or surveys of the area needing fill material
- Use these measurements to calculate the baseline volume.
- Use the correct compaction factors for bank sand (specifically)
- Include reasonable contingencies for minor variations in measurements
Why Discussing Estimates With Suppliers Helps
A bank sand supplier with extensive experience in similar sand supply projects should have some idea if an estimated volume of sand for a given application is reasonable or not. This conversation can help to identify if there are any possible miscalculations that could happen before the delivery is received and it might turn into an ordering error that costs a lot of money.
Suppliers who have experience with the various types of projects commonly encountered in Houston can typically offer a general estimate of volume for a project that they have completed in the past, which can be very helpful to check against independently derived estimates.
What happens when there are large estimation errors?
Under ordering generally leads to more negative effects, as it involves having to schedule a follow up delivery while equipment may be idle waiting for more material. While not as immediately disruptive, over ordering can cause a waste of budget and cause contractors to be inundated with excess material that has to be stored or eventually removed from the site.
Final Thoughts
The accurate volume estimation keeps the project budget and schedule from being ineffectively wasted by estimating, rather than estimating sand requirements. Measure carefully, take into consideration compaction, and take the time to ask some experienced suppliers will increase the likelihood of getting it right the first time.