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How to Test Oil Tanks & Groundwater

Underground storage tanks (UST) and aboveground storage tanks (AST), including those for oil, gasoline and other petroleum hydrocarbons, as well as any associated soils and groundwater resources, must be tested by a professional engineer on a regular basis to ensure environmental compliance and to protect public health and safety. You can reduce your risk for liability, while providing good environmental stewardship for your petroleum product storage tanks by inspecting and testing them more frequently than the law requires. Learn to perform some standard tests in-house to avert potential environmental disasters, to reduce liability, and to prevent exorbitant damage control and clean-up expenses.

Things You'll Need

  • Notebook
  • Camera
  • Soil auger
  • Plastic tubing
  • Plastic zip bag
  • Air compressor
  • Extra oil storage tank cap
  • Pressure gauge in PSI
  • (with 1/2-inch fitting and gasket)
  • Tire air valve (1/2-inch base)
  • Soapy water (1:40 solution)
  • Paint brush
  • Drill with 1/2-inch bit
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Instructions

  1. How to Test Oil Tanks & Groundwater

    • 1

      Keep a notebook of all documents and activities affecting your oil storage tank, including any original plans, diagrams, blueprints, specifications, warranties, certifications, invoices, professional inspections, in-house inspections, samples taken, test results, photographs, maintenance records, and filling and draining volumes for inventory control purposes.

    • 2

      Visually inspect your oil tank on a monthly basis to check for any evidence of leakage, corrosion or damage. Carefully examine all surfaces and especially seams and tank bottoms for any signs of leakage or corrosion. Keep your tank clean and freshly painted so that any evidence of leakage or corrosion will be easy to spot. Take photographs and record your observations. Visual inspection of the underground portions of underground tanks will not, of course, be possible.

    • 3

      Construct a pressure-testing cap for your oil tank using a spare oil tank cap, a one-half-inch base tire valve, and a pressure gauge with a one-half-inch fitting and gasket. Drill two one-inch holes in the cap several inches apart, if possible. Install the tire valve in one hole and the pressure gauge in the other hole. New oil tanks are tested at the factory at five to seven PSI (pounds per square inch).

    • 4

      Test your tank when it is empty by installing the test cap, plugging all outlets, closing all valves and using the air compressor to fill the tank to no more than 15 PSI. Excessive pressure could damage the tank. Note the date, time, beginning and ending pressures in your notebook. Allow the pressure to remain for one hour while you check all seams, fittings, plugs, and caps (including your test cap) for leaks with a soap solution and a paintbrush. Any leaks will be revealed by a flow of bubbles from the leak or a loss in air pressure indicated by the gauge. If the tank leaks, it will need to be professionally repaired or replaced.

    • 5

      Auger a test boring in the soil a few feet away from the tank. Collect a few soil samples as your auger brings soil to the surface. Invert a plastic zip bag over your hand and grab a fistful of soil from each foot of soil augured. Perform olfactory analysis by sniffing each bagged sample for any evidence of petroleum vapors. If you smell petroleum, your soil is contaminated and will require professional clean-up. Send soil samples to your local environmental testing facility to identify the contamination, which may or may not be from from your tank.

    • 6

      Continue auguring to reach the water table. Once water accumulates in the test borehole, insert a piece of plastic tubing into the groundwater. Place your finger tightly over the upper end of the tubing and withdraw the tubing from the hole. Release the water sample into a plastic zip bag and tightly seal the bag immediately.

    • 7

      Take several water samples, if possible. Send these to your local environmental testing facility to test for the presence of hydrocarbons. Send along a sample of your tank's oil to test whether the contamination is from your oil or from another source. If your groundwater sample contains hydrocarbons, you will need to have the source definitively identified and the contamination professionally cleaned up. Keep records of all these activities in case you are required to answer questions later, and to ensure your good faith compliance with any and all environmental regulations.

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