Owners and operators of
   regulated underground
storage tanks (USTs) on tribal
   lands must comply with
  federal LIST 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 LIST
    EPA developed this
  compliance assistance
   brochure to help LIST
  owners and operators in
 Indian country comply with
the federal LIST regulations.

  This brochure is one in a
 series of EPA compliance
   assistance brochures
  designed to help owners
 and operators comply with
     LIST regulations.

 Other brochures focus on
       spill buckets;
    recordkeeping and
  notification; and tank and
  piping release detection.
                                        Office of Underground Storage Tanks
                                        July 2012
                                           Compliance Assistance in
                                               Indian Country


Overfill prevention is required for every
underground storage tank (UST) 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

What can you do to prevent
an overfill?

Repair or replace improperly functioning
overfill alarms          x	
^ 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 driv-
er can see or hear them

If you hear the alarm,
ensure the delivery
person has stopped the
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
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, i
Monitor product deliveries and transfers
^  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
                                                                    A qualified UST contractor can check ^
                                                                    to make sure the ball float operates
                                                                    properly and moves freely, the cage is
                                                                    intact, and the ball float air hole is not
                                                                    Note: Recommended practices say
                                                                    ball float valves should not be installed
                                                                    on tanks with: suction piping, pumped
                                                                    delivery, coaxial Stage I vapor
                                                                    recovery, remote fill pipes with gauge
                                                                    openings, or when shutoff valves are
                                                                    used for overfill prevention.
                                                                                                               Ball float valve
                                                                                                               with ball out of
                                                                                                               the cage
                                                                                       Order the appropriate amount of product
                                                                                       ^  Order only the quantity of product that will fill
                                                                                           90 percent of the tank.
                                                          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                                     ,
                                  For recommended inspection
                                  guidelines, checklists, and best
                                  management practices for your
                                  UST system overfill prevention, see
                                  EPA's manual, Operating and
                                  Maintaining Underground Storage
                                  Tank Systems at
                                                                                         http://www.epa.gov/oust/pubs/ommanual.htm or order a
                                                                                       . free copy by calling (800) 490-9198.