4
FINAL BACKFILL FOR BASIN SYSTEMS
Backfill
Instructions
The authority having
jurisdiction has the right to
require alternative materials or
procedures for backfilling the
installation.
Failure to properly backfill
may result in damage to the
basin which could cause leaks
or structural failure. Failure to
follow these backfill instructions
during the installation of the
basin voids the basin warranty.
In freezing conditions the
backfill must be dry and free
of ice. Do not use other backfill
materials. Failure to use the
recommended bed and backfill
materials during the installation
of the basin voids the basin
warranty.
Risk of electrical shock or
electrocution. May result in
serious injury or death or fire
hazard. Failure to properly
support electrical conduit, lines
and connections may result in
structural failure. Electrical
connections may be damaged,
exposing live electrical
connections.
Step 1
Obtain proper backfill material.
The backfill material provides
as much as 90% of the basin’s
support under certain stress
conditions. The installer must
be positive that correct bed and
backfill materials are used per
instructions as follows:
A. Gravel – clean and free
flowing with particle size not
less than 1/8" or more than
3/4" in diameter. Use this
description when ordering or
specifying as material varies
upon geographical location.
This material is commonly
known as “pea gravel”.
B. Stone or gravel crushings with
angular particle size of not
less than 1/8" or more than
1/2" diameter, washed and
free flowing, is acceptable as
an alternative material.
Step 2
At least a 4 inch wide band of
compacted aggregate must be
placed in successive layers (6"
lifts) around the entire periphery
of the basin. Carefully compact
aggregate under all piping and
electrical lines. Cover grade
should slope down 3" to the
normal surrounding grade. Care
must be taken to prevent damage
to any influent, discharge, or
electrical connections made to
the basin.