20
11.3.2. The tank’s venting system must be adequately sized to
ensure that atmospheric pressure is maintained at all times,
including during filling and emptying of tank.
11.3.3. Whenever installing overfill protection, such as alarms,
automatic shut-off devices (“flapper valves”) or vent-restriction
devices (“ball-float valves”), follow the instructions provided by
the manufacturer of the overfill-protection device and consult the
authority having jurisdiction to determine the level at which the
overfill protection should operate.
Overfill protection, such as automatic shut-off devices or
vent-restriction devices, should not be installed if
owner/operator will allow pump or pressure filling of the
tank. Failure to follow this instruction could cause tank
failure, and result in death or serious injury.
11.4. VENTING INTERSTITIAL SPACE
All reservoirs must be vented for proper operation.
11.4.1. When the tank’s interstitial space is filled with a
monitoring fluid, the space must be vented. It is sufficient to drill
a 1/4-inch-diameter hole in the side or cap of the reservoir
standpipe as supplied by the installer. If the groundwater level
could be high enough to enter a drilled vent hole, install a vent
line from the standpipe to above high-water level.
11.4.2. When the interstitial space is dry, it is not necessary to
vent the space to atmosphere.
12. FILLING TANK
12.1. GENERAL
12.1.1. Xerxes recommends only gravity filling of tanks.
12.1.2.
See SECTION 18, Operating Guidelines.
13. BACKFILLING TO GRADE
13.1. GENERAL
13.1.1. Continue to take safety measures (such as placing
barricades) around the excavation site until installation is
completed.
13.1.2. When the tank has been set, tested and backfilled, and
all piping and venting has been completed, add the balance of
the backfill material.
13.1.3. The backfill must be free of debris, ice or snow. Any
blocks or bricks used as support material during piping must be
removed prior to completion of backfilling.
13.1.4. The backfill material
specified in SECTION 4
must be
used to completely fill excavation.
13.1.5. Be sure that the installation meets all of the require-
ments of minimum cover as
specified in SECTION 5.
13.1.6. When the tank has been backfilled to subgrade (before
placement of asphalt or concrete), take a measurement of the
internal diameter of the tank.
(See SECTION 14 of the
Installation Manual
for instructions on taking diameter
measurements.)Record this measurement as Final Internal
Diameter on the Tank Installation Checklist, Section 4.
13.1.7. Complete the Tank Installation Checklist.
14. DEFLECTION MEASUREMENT
14.1. GENERAL
14.1.1. Obtain the deflection measurement by taking a minimun
of two measurements of the internal diameter of the tank.
14.1.2. Two methods of measuring the internal diameter of the
tank are described here. Both methods use a dipstick. (Similar
methods can be used, such as with a tape measure, etc.)
14.1.3. The deflection measurement can be obtained by using
either method twice or by using each method once. Each will be
described here as if that method were being used twice.
14.1.4. Take the initial internal-diameter measurement before
backfilling the tank.
(See Point 8.2.8.)
In a wet-hole installation,
take this measurement before the tank is placed in the
excavation hole.
(See Point 8.3.1.1.)
14.1.5. Take other diameter measurements during the backfilling
process to determine whether vertical deflection continues to be
within the limits specified by Xerxes.
(See Point 6.4.6 and
Point 9.1.1.)
14.1.6. Take the final internal-diameter measurement when the
tank has been backfilled to subgrade.
(See Point 13.1.6.)
14.1.7. For both methods, drive a small-headed, nonsparking
nail (for example, brass) halfway into a wooden dipstick 1 inch
above its base.
14.2. INTERNAL-DIAMETER MEASUREMENT WITHOUT A
STANDPIPE
14.2.1. Place the dipstick into a service fitting.
14.2.2. Measure and record the distance from the tank bottom to
the top of the fitting.
14.2.3. Pull the dipstick up until the exposed nail catches on the
inside top of the tank.
14.2.4. Measure the distance from the tank top (inside) to the
top of the fitting. Subtract 1 inch from this measurement and
record the distance.
14.2.5. Subtract the second distance (inside tank top to top of
fitting) from the first distance (tank bottom to top of fitting).
Record this measurement as Initial Internal Diameter
on the
Tank Installation Checklist, Section 4.
14.2.6. For subsequent measurements of the internal diameter,
repeat Points 14.2.1. through 14.2.5. When the measurement is
