4.1.2. Using other than approved bedding and backfill materials
without prior written authorization from Xerxes will void the tank
warranty.
Use of unapproved backfill material could cause tank
failure and result in death or serious injury.
4.1.3. Approved backfill material must meet the following specifi-
cations:
4.1.3.1. The material is washed, free-flowing, and free of ice,
snow and debris.
4.1.3.2. The material conforms to the specification of ASTM
C-33, par. 9.1, size numbers 6 through 8 of Table 2.
4.1.3.3. When using pea gravel, the material is to be a mix of
rounded particles, sizes between 1/8 inch and 3/4 inch.
(See
FIGURE 4-1.)
FIGURE 4-1
4.1.3.4. When using crushed stone, the material is to be a mix of
angular particles, sizes between 1/8 inch and 1/2 inch.
(See
FIGURE 4-2.)
FIGURE 4-2
4.1.3.5. No more than 5% (by weight) of the material may pass
through a #8 sieve.
4.1.3.6. It is recommended that the materials supplier certifies
that the material conforms to ASTM C-33 and any other
applicable specifications.
1/8”
1/2”
1/8”
3/4”
11
4.1.4. For additional information, refer to the Xerxes document,
Fiberglass Tank Backfill Guidelines.
4.1.5. If material which meets these specifications is not
available, contact technical support at Xerxes Minneapolis for
information on alternate materials and the process for approval.
5. EXCAVATION PARAMETERS
Follow OSHA regulations for tank excavations. Collapse of
excavation walls could result in death or serious injury.
5.1. GENERAL
5.1.1. The installing contractor must take all precautions
necessary to protect employees working in or near a tank
excavation. These precautions should include, but are not
limited to the following:
5.1.1.1. Locate and protect any utility installations near the
excavation before opening the excavation.
5.1.1.2. Secure the walls of the excavation.
5.1.1.3. Prevent exposure of employees to hazardous fumes
from the excavation.
5.1.1.4. Protect employees from hazards associated with water
accumulation in the excavation.
5.1.1.5. Erect barricades, etc., to prevent unauthorized vehicle
or pedestrian traffic.
5.1.1.6. Inspect, a minimum of once a day, the excavation and
surrounding area.
5.1.2. For additional information on excavation, trenching and
shoring safety practices, consult OSHA’s Standard, Part 1926,
Subpart P(Excavations), 650-652; and “Fall Protection Rules
and Regulations.”
5.1.3. The minimum depth of the excavation is normally
determined by the presence or absence of groundwater and the
presence or absence of traffic at the site. These dimensions are
critical to the successful installation of a tank and are often
regulated by code.
5.1.4. For additional requirements and specifications, refer to
federal, state and local codes; NFPA 30, 30A and 31; API RP
1615; PEI RP100; and
FIGURE 5-1 and FIGURE 5-2
.
5.1.5. In all cases, the depths of cover given in 5.1.5.1. and
in 5.1.5.2. are minimums.
5.1.5.1. Tanks subjected to traffic loads (H-20 loads) must have
a cover depth of at least 36 inches of backfill [48 inches for
12-foot-diameter tanks], or 18 inches of backfill [36 inches for
