Owners and operators of
regulated underground
storage tanks (USTs) on tribal
lands must comply with
federal UST regulations.
This compliance assistance
brochure highlights best
management practices
for overfill prevention.
Note: This document is a
resource to promote
compliance and does not
replace the federal UST
regulations.
EPA developed this
brochure to help UST
owners and operators in
Indian country comply with
the federal UST regulations.
This brochure is one in a
series of EPA compliance
assistance brochures
designed to help owners and
operators comply with UST
regulations.
Other brochures focus on
spill buckets;
recordkeeping and
notification; financial
responsibility, insurance, tank
release detection, and piping
release detection.
www.eoa. aov/oust/ou bs
Effective through
October 12, 2018
Visit
https://www.epa.gov/ust/managing-
your-usts-indian-country
Maintain
vvEPA
Office of Underground Storage Tanks
www.epa.aov/oust
July 2012
EPA-510-F-12-003
Compliance Assistance in
Indian Country

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OVERFILL PREVENTION
Overfill prevention is required for every
underground storage tank (LIST) filled with
more than 25 gallons of product at one time.
It is installed inside your tank to stop product
flow, reduce product flow, or alert the delivery
person during delivery before the tank
becomes full.
There are three common types of overfill
protection, as shown below:
Overfill alarm	Automatic shutoff Flow restrictor
device	(ball float valve)
(flapper valve)
If a tank is overfilled, product could be forced
through the vent line and other loose tank
fittings, potentially resulting in a damaging
and costly release into the environment.
Properly functioning overfill prevention will
significantly reduce the chance of an overfill
release.
What can you do to prevent
an overfill?
Repair or replace improperly functioning
overfill alarms
^ Alarms alert the
delivery driver that
product is
reaching a certain
level in the tank.
They also give the
delivery driver
enough time to
shut off product
flow to avoid a
potential release.
Alarms must be located
where the delivery
driver can see or hear
them easily.
If you hear the alarm,
ensure the delivery
person has stopped tiie
flow of fuel to the tank.
Repair or replace improperly functioning
automatic shutoff devices
Automatic shutoff devices stop the flow of
product when the product reaches a certain
level in the tank during delivery.
Automatic shutoff device
with damaged float
Looking down the fill pipe
at the flapper valve
The automatic shutoff device is located in the
drop tube within the fill pipe riser.
A qualified UST contractor can check to make
sure that all float components are functioning
properly, and the float arm is not obstructed and
can move freely.
Keep the automatic shutoff valve free and
unobstructed. A disabled automatic shutoff
prevents the valve from closing to prevent an
overfill.
A dip stick is in the drop tube
preventing the shutoff device
from closing.
Periodically inspect the
automatic shutoff device
to make sure it has not
been tampered with,
disabled, or removed
from the fill pipe and there
are no obstructions in the
drop tube that will prevent
the device from operating.
Monitor product deliveries and transfers
w" Pay close attention before, during, and after
product delivery to help the delivery person
avoid overfilling your UST.
Immediately report spills to your
implementing agency.
Replace improperly functioning ball float valves
Ball float valves slow product flow by
preventing vapors from leaving the tank when
product reaches a certain level in the tank.
The restricted flow alerts the driver to stop the
delivery. The top of the tank must be tight
during deliveries so that vapors can not
escape.
A qualified UST contractor can check
to make sure the ball float operates
properly and moves freely, Ihe cage is
intact, and the ball float air hole is not
plugged.
Ball float valves should not be installed
on tanks with: suction piping, pumped
delivery, coaxial Stage I vapor recov-
ery, remote fill pipes with gauge open-
ings, or when shutoff valves are used
for overfill prevention.
The top of the tank must be tight during
deliveries so that vapors can not
escape.
Ball float
valve with
ball out of
the cage
Order the appropriate amount of product
Order only the quantity of product that wiii fill
90 percent of the tank.
X	\
The formula for determining the maximum amount *
of gasoline to order is:
(Tank capacity in gallons X 90%) -
volume of product currently in tank = maximum
amount of fuel to order
Example: (10,000 gallons X 0.9 ) -
2,000 gallons = 7,000 gallon maximum amount to
order	i
For recommended inspection guidelines,
checklists, and best management practices
for your UST system overfill prevention, see
EPA's Operating and Maintaining
Underground Storage Tank Systems at
www.epa.gov/oust/pubs/ommanual.htm or
order a free copy by calling (800) 490-9198.
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