It is not uncommon for an earthwork contractor to order for clean fill to improve construction site elevation only to find out later that the material delivery contained some contaminants.
This contamination may come in various forms, from volatile organic solvents to heavy metals, which make the material unsafe. This in turn can expose the contractor to litigation from his client, given that it is the contractor's job to ensure that fill material is actually clean before using it on a construction site. The following are tips to help you avoid such scenarios in your career as an earthwork contractor:
1. Comprehensive contracting
The contract must stipulate exactly what should be delivered, instead of relying on blanket description terms. Remember that whenever a client finds out the fill material is not as clean as they want, the contractor is liable for litigation as well as site clean-up costs.
In addition, see if your supplier can insure you against any liability arising from contaminated fill. Because the strength of indemnity relies on the financial abilities of the supplier, confirm that your supplier can finance this indemnity before entering into contract with them.
2. Visual inspection
Carry out visual inspection of materials on delivery and during unloading to make sure that clean fill material 'looks' clean. You should be able to see contaminants like petroleum products and by-products since they cause soil discolouration. Look out for lumber, asphalt, painted materials, concrete, bricks and other easily visible materials.
3. Request for sample analysis
If you are not sourcing your clean fill from a reputable and known site, request for an analysis of the fill material. They should check for both organic and inorganic compounds, including heavy metals. If the materials have already been analysed, ask for a copy of the report and then decide whether or not they are acceptable for your purposes.
4. Analyse yourself
In truth, if the owner doesn't usually analyse their fill material, they will not consent to a sample analysis even at your request. As such, you will have to inspect and analyse the material yourself. Start by using an Organic Vapour Analyser or Photo-ionizing Detector, tools which can detect presence of certain contaminants. Bear in mind that these won't give exact measures or detect heavy metals, but they can give you an idea of whether or not the fill is really clean. Train your personnel to use these devices as well.
5. Audit clean fill suppliers
If you routinely accept clean fill from a handful of suppliers, conduct regular audits of the site/facility. Ask to see their permit status, eco-management plans, site security, operations, analysis procedures, onsite tanks and waste management among others. This is a hassle-less procedure that gives you an idea about the supplier's practices and whether you can trust their products.
6. Verify material origins
This is the most important part, and it won't cost you anything. As part of your supplier audits and for each consignment delivered, verify the origin of the fill material. Knowing from whom and where clean fill originated will tell you exactly what to test for and whether or not the sample is likely to be clean, even before you see it. This also applies to stockpiled soil/dirt – ensure you know the source.