How Do Different Soils React to Fuel Oil?

Various soil types react differently to the introduction of oil, but oil always takes the path of least resistance.

Soft Clay

Depending on the density of the clay, oil tends to slowly seep through this type of material over time.  If the oil has leaked into the soil, usually the soil would react to the hydrocarbons by transforming into a blue colour and/or having an oily odor.

Hard Clay/Hardpan

Hardpan is a dense material that usually slows down the absorption and the dispersal of oil.  It will still have the typical signs of contamination visually and through odor; however, it definitely has the highest probability of containing contamination.


Sand is porous and offers the least amount of resistance. Due to its high permeability sand can be tricky to assess, as it can show or not show the typical visual and odour indicators that are usually quite obvious in clay.  As the water table transports the oil throughout the sand, the path of the oil may take unpredictable routes if the conditions are not consistent.

Fractured Tills

Fractured tills are a combination of fine-grained silt veins throughout clay.  Although clay has reasonably low permeability, the combination of the two materials can greatly increase the distance that the oil travels.  Since silt is porous and highly permeable, the oil follows the path of least resistance through silt within the fractures of the hard pan and contaminates the hard pan on its way.  As the same with sand or silt, this type of material can be unpredictable and may not always exhibit the same contaminated characteristics as clay.

For examples of contaminated properties, please visit our gallery and check out some pictures of Remediation.