How to Estimate Oil Spills on Soil

Oil contamination in soil can be determined from the loss of oil at its source. A 250-gallon fuel tank that has lost half its content would yield a 125-gallon loss or spill. A stain on the ground where a car had its oil changed would be a spill of around 1 gallon. However, most oil spills in soil occur with little knowledge of the source or of the migration pattern through the soil. Portable screening instruments are used to take samples to determine the extent of contamination. These measurements are performed at the surface and at various depths using boreholes.

Things You'll Need

• Organic vapor analyzer with photoionization dectector
• Clean glass screw top jars
• Aluminum foil
• Soil scoops
• Borehole sampler
• Sample-removing tools

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Instructions

• 1

  Take two sample jars half full of contaminated soil. Cover immediately with aluminum foil, and screw the lids on tight. Let the samples stand 10 minutes for head space to develop. Shake vigorously at the beginning and end of the head space development period. Remove the lid and insert the organic vapor analyzer probe tip through the foil seal about half way into the soil. Record the maximum reading, which should occur in 2 to 5 seconds. Perform a similar test procedure on the second jar. Replicate values should be +/- 20 percent. Record readings for calibration data and sensitivity. Continue doing surface tests and mapping test locations until the instrument reading drops below the limit of detectability. This map will define the surface of your spill.

• 2

  Take borings at depths from the locations with the highest surface area readings. Perform jar tests on bore samples at various depths, and check levels of contamination. This will give you a profile of the contamination below ground. When combined with the surface information, your profile will be in three dimensions and will delineate the area that is subject to remediation.

• 3

  This is an initial screening test. It can be followed up with other tests using other instruments depending on the target compounds of interest. Other considerations include detection limits, required data quality, moisture content and method applicability. These instruments include an organic vapor analyzer and a portable gas chromatograph with any of three detectors: flame ionization, photoionization and electrolytic conductivity.

• 4

  A pipeline break or a major holding tank rupture may require a more sophisticated model or imagery. Passive microwave or infrared scanning can be used to determine the depth of the spill. Oil spills are not stationary. They move through the soil to infiltrate groundwater and can remain in place for many years.