| Certification |
Leak rate of 0.005 gph with PD = 97.6% and PFA = 0%. |
| Leak Threshold |
A tank should not be declared tight when the chemical marker detected exceeds the background level outside of the tank. |
| Applicability |
Gasoline, diesel, aviation fuel, fuel oil #4, fuel oil #6 (if between 60 to 150 degrees F), solvents, waste oil, liquefied petroleum gas, natural gas.
Other fluids which are compatible and soluble with an acceptable chemical marker may be tested after consultation with the manufacturer. |
| Tank Capacity |
Not limited by capacity. |
| Waiting Time |
A range from 5 to 31 days after the chemical marker is mixed throughout the tank to be tested.
The waiting period may be adjusted below or above this range when supported by "Controlled Leak Points" as described below.
The waiting time or test period begins once the chemical marker has been mixed and distributed throughout the tank system(s) to be tested. |
Controlled
Leak Points |
"Controlled Leak Point" is a port where chemical marker is injected directly into the soil surrounding the tank to confirm the adjusted leak rate and the rate at which the chemical marker migrates through the backfill. It can be used to demonstrate that the metered amount of chemical marker will migrate through the soil to a detection point in a documented amount of time, as described in manufacturer's procedures. |
Chemical
Marker Dosage |
Dosage of the chemical marker, either liquid, vapor or both is based on tank volume and the duration of time the inoculated product will remain within the tank.
Tanks are typically tested in an in-service operating condition; tanks that are out of service are tested at working pressure. Chemical marker concentration and sampling points are adjusted to meet the test specifications. |
Soil
Permeability |
Soil permeability must readily allow chemical marker movement through the excavation backfill (greater than 1 Darcy) or the use of a controlled leak point is required. |
| Sampling Port |
Radius of influence of each chemical marker sampling port is maximum 16 feet.
Tank must be accurately located to ensure that all tank surfaces are within the zone of influence of a sampling port.
Sampling ports must be installed per manufacturer's guidelines.
Horizontal sampling probes may be installed in manufactured backfill during the initial tank installation. These probes must be installed per manufacturer's guidelines. |
| Groundwater |
The method was not evaluated with groundwater above the bottom of the tank.
Depth to groundwater in tank excavation backfill must determined.
When the interior hydrostatic pressure of the tank being tested is less than the exterior hydrostatic pressure, the use of other test method(s) such as water ingress measurements must be incorporated for that portion of the tank below water.
At the discretion of the regulator agency, water ingress measuring devices may be used to supplement test method in high groundwater conditions.
When the regulatory agency allows testing to be performed with groundwater above the bottom of tanks containing water based or water soluble products, the product must be removed from the tank prior to testing and tested with a non-water soluble product or a vapor chemical marker.
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| Comments |
This method can be used to test single-walled and double-walled components for leakage to soil by sampling in the backfill or to test the primary containment integrity of a double-wall component by sampling in the interstitial space.
Evaluator indicates that the detectable leak rate can be adjusted by controlling test variables such as chemical marker concentration and test duration.
The tester may determine that pre or post testing is needed to establish the background level of chemical marker in the soil.
For shorter/longer test periods, for different sampling port spacing, or in soil conditions that are uniquely different from standard engineered backfill, such as water saturated frozen soil, a controlled leak point shall be installed to document the chemical marker migration period. |
