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15.3. TANK WITH A DRY INTERSTITIAL SPACE
15.3.1. The monitoring system and method is the responsibility
of the tank owner and/or operator.
15.3.2. A safe electronic or mechanical system should be used
to detect either product or incoming water.
15.3.3. The monitoring system should detect leakage near the
bottom of the tank.
15.3.4. Monitoring can be done through the monitor fitting
provided.
15.3.5. If a double-wall tank is sloped, the monitor should be at
the low end.
15.4. TANK WITH A WET INTERSTITIAL SPACE
15.4.1. GENERAL
15.4.1.1. In a monitoring system filled with monitoring fluid, the
interstitial space is typically filled with monitoring fluid at the
point of manufacture.
Monitoring fluid should not be present in the standpipe
except during a TRUCHEK
®
test. (See the Xerxes
TRUCHEK
®
brochure.) Monitoring fluid in the standpipe
may create excessive pressure on the interstitial space and
may result in tank damage.
15.4.1.2. All wet interstitial spaces must be vented to
atmosphere.
(See SECTION 11.4.)
15.4.1.3. The system enables the owner to have continuous
monitoring or to conduct a tank-tightness test, TRUCHEK
®
,
which meets the EPA criteria for tank-tightness testing.
(See the
Xerxes TRUCHEK
®
brochure.)
15.4.1.4. The level of the monitoring fluid in the reservoir is set
at the plant to a predetermined position, approximately 3 inches
above the top of the tank. When the tank is delivered, check the
monitoring-fluid level and record it on the shipping/receiving
paperwork and Tank Installation Checklist.
(See FIGURE 15-1.)
FIGURE 15-1
Label
Reservoir
Monitoring-Fluid
Level
the final diameter measurement, record this measurement as
Final Internal-Diameter
on the Tank Installation Checklist,
Section 4.
14.3. INTERNAL DIAMETER MEASUREMENT WITH
A STANDPIPE
14.3.1. Place the dipstick into a service fitting with a standpipe.
14.3.2. Measure and record the distance from the tank bottom to
the top of the standpipe.
14.3.3. Pull the dipstick up until the nail catches on the inside
top of the tank.
14.3.4. Measure the distance from the tank top (inside) to the
top of the standpipe. Subtract 1 inch from this measurement and
record the distance.
14.3.5. Subtract the second distance (inside tank top to top of
standpipe) from the first distance (tank bottom to top of
standpipe). Record this measurement as Initial Internal
Diameter on the Tank Installation Checklist, Section 4.
14.3.6. For subsequent measurements of the internal diameter,
repeat Points 14.3.1. through 14.3.5. When the measurement is
the final diameter measurement, record this measurement as
Final Internal Diameter
on the Tank Installation Checklist,
Section 4.
14.4. CALCULATION AND COMPARISON
14.4.1. To get the deflection measurement at any time, subtract
the current internal-diameter measurement from the initial
internal-diameter measurement.
14.4.2. Compare this measurement to the allowable deflections
shown in the table on the Tank Installation Checklist, Section 4.
14.4.3. Vertical deflection in excess of this measurement
indicates improper installation and voids the tank warranty.
15. MONITORING
15.1. SINGLE-WALL TANK
15.1.1. Single-wall tank installations may require release
detection monitoring, which can include inventory control,
automatic tank gauging, vapor monitoring or groundwater
monitoring.
15.1.2. Check with federal, state and local officials for require-
ments in your area.
15.2. DOUBLE-WALL TANK
15.2.1. A Xerxes double-wall tank has an interstitial space
between the wall of the primary (internal) tank and the wall of
the secondary (external) tank for the containment and detection
of leaked product from the primary tank.
15.2.2. The tank, as supplied, will have a minimum of one
monitor fitting that provides access into the interstitial space.
