| Certification |
Leak
rate of 0.1 gph with PD = 100% and PFA = 1.6%. |
| Leak
Threshold |
A
tank system should not be declared tight when an acoustic
signal is detected above the background or baseline noise
by a computer data acquisition system, or when water ingress
is detected by the water sensor. |
| Applicability |
Gasoline,
diesel, aviation fuel, fuel oil #4, fuel oil #6, solvents,
and waste oil.
Other liquids may be tested after consultation with the
manufacturer. |
|
Tank
Capacity
|
Maximum
of 30,000 gallons.
Evaluated at product levels between 8%* and 91% full.
Maximum of 30,000 gallons per tank for manifolded tank
systems. If isolation cannot be performed, the tanks can
be tested simultaneously using two sondes (sound amplifier
modules) or else they must be pressurized simultaneously
and tested separately, depressurizing between tests. |
|
Waiting
Time
|
None
between delivery and testing. |
|
Test
Period
|
When
groundwater level in tank excavation backfill is below
bottom of tank: After the Vacuum conditions are established
on the tank, the data collection times are very short,
typically one minute or less.
When groundwater level in tank excavation backfill is
above bottom of tank or when the groundwater level in
the tank excavation backfill has not been determined:
The time it takes for water ingress to increase the water
level in the tank to allow the water sensor to detect
the "minimum detectable change in water level"
(see "Water Sensor" section below).
Test period based on water ingress is dependent on tank
size. For example, the test period is 0.97 hours for a
10,000 gallon (96” dia x319” lg) tank.
The correct test period is always determined from the
field calibration on each specific tank.
Before starting test, water sensor must be calibrated
to "minimum detectable water level" (see "Water
Sensor" section below) according to manufacturer's
instructions.
There must be no dispensing or delivery during test. |
|
Test
Pressure
|
A
vacuum of 60 inches of water or –2.16 psig must be used. |
|
Temperature
|
Acoustic
signal is independent of product temperature. |
| Water
Sensor |
Conductivity water sensor must be used to detect water
ingress and must be calibrated for every test when groundwater
level in tank excavation backfill is above bottom of tank
or when the groundwater level in the tank excavation backfill
has not been determined.
Minimum detectable change in water level is 0.016 inch.
Minimum water level in tank must be adjusted to at least
0.14 inch (sensor’s minimum detectable water level) before
calibrating sensor and starting test. |
|
Groundwater
|
Per
California regulations, depth to groundwater in tank excavation
backfill must be determined.
Groundwater level in tank excavation backfill must be
determined by observation well or soil probe in tank excavation
backfill.
If groundwater level in tank excavation backfill is above
bottom of tank or the groundwater level in the tank excavation
backfill has not been determined, water sensor must be
used and test time extended to ensure water ingress detection
during test. |
|
Comments
|
*Although
not evaluated using empty tanks, a third party acoustics
specialist has certified the device is equally effective
when tanks are empty as when tanks contain product.
Test may be inconclusive if there is high background noise.
Vacuum test method may not be effective in some tank excavation
backfill (such as clay) because it may plug holes in tank.
If free product is present in tank excavation backfill,
a leak in the free product zone may not be detected by
a vacuum test method.
An observation well or soil probe in tank excavation backfill
may help determine backfill material, water level in tank
excavation backfill, and presence of free product. Manufacturer
must certify test operator at least every 2 years.
More than 4 psi pressure differential across the tank
wall at any location in the tank could damage tank.
|
