UST Inventory Control
And Manual Tank Gauging
Procedures And Forms
United States Environmental Protection Agency
Region 8
Underground Storage Tank Program
April 1993
-------
EpA 13-ni
327
If you use inventory control or manual tank
gauging as your underground storage tank leak detec-
tion method, you are not alone! Currently, over 50% of
UST facilities in the United States use either one of
these leak detection methods for their tanks.
Historically, inventory control has been standard oper-
ating procedure at most UST facilitiesand it's a sure
bet that you have your own particular way of sticking
your tanks and keeping track of your product.
However, EPA has new requirements which
regulate when and how to stick your tank and how to
keep track of your inventory so that you can discover a
leak and prevent it from becoming a big problem.
This booklet discusses two of the eight
methods currently accepted by EPA that tank owners
may use to comply with leak detection requirements:
inventory control and manual tank gauging. While
you are not required to use the forms in this booklet,
you are required to document specific information. You
may choose any format you like to keep track of this
information. For information on the other accepted
leak detection methods, you should consult with your
federal or state UST office.
1
-------
Inventory Control
The inventory control leak detection method
consists of two parts: monthly inventory control recon-
ciliation and tank tightness testing. You must do both
to be in compliance with the leak detection regulations
for the inventory control method.
Inventory control is a leak detection method
whereby product in each tank is physically measured
each operating day and is compared to the records of
the volumes delivered to and then sold from those
tanks.
Tank tightness testing is a precision test that
must be done annually if the tank has not been
upgraded or every five years if the tank has been
upgraded. (An upgrade includes cathodic protection
and/or tank lining and spill and overfill protection.)
To Properly Conduct Inventory Control
You Must:
¦ Have proper equipment
¦ Stick the tank each operating day
¦ Reconcile fuel deliveries
¦ Reconcile inventory monthly
¦ Check for water monthly
¦ Document and save records for all
items listed above
3
-------
Inventory Control
Proper Equipment:
Minimum equipment needed includes:
¦ a non-sparking dipstick that can be read in l/8th-
inch increments and is not warped or worn at the
bottom,
¦ a calibration chart that converts gauge stick (dipstick)
readings to gallons for your specific tank type and size,
¦ water indicator paste for monthly water measure-
ments,
¦ a calibrated meter/pump assembly that is accurate to
within six (6) cubic inches per five (5) gallons of
product (approximately 1/3 cup per 5 gallons), and
¦ a drop tube located inside the fill pipe that extends to
within one (1) foot of the tank bottom.
Stick readings each operating day
Product in the tank must be measured each oper-
ating day (or at least 7 times a month). The more
consistent the stick readings are, the more accurate the
inventory will be. This means that product level should
be read at the same time each day, by the same person,
using the same stick and the same tank calibration chart.
Consistency is vital!
Delivery reconciliation
The tank product inventory must be read (using
your gauge stick) before and after each fuel delivery.
Relying on the accuracy of invoice readinqs from the
delivery company is not adequate.
Monthly reconciliation
Your daily inventory balances (overages and
shortages) must be reconciled monthly. To do this, add
all of the daily dispersements for each tank, then take
1% of that figure and add 130 gallons. This is your allow-
able standard which product overage or shortage may
not exceed. If you are over or short more than the allow-
able standard then you may have a leak. If this happens,
keep careful inventory for another month. If the
NOTE: Under no
circumstances should
you attempt to
artificially adjust
numbers to make daily
over/short numbers
come out to zero (0).
This would defeat the
whole purpose of inven-
tory control and could
4
-------
Inventory Control
standard is exceeded again, this is considered a
confirmed release and you must contact your federal or
state UST implementing agency.
Water measurements
Water must be checked on a monthly basis. Do
this by using water paste or another method that will
provide accurate results.
Documentation
You must keep documentation of all monitoring
for at least one year. This includes monthly inventory
records (including water measurements), fuel delivery
records, the latest tank tightness test results, and
current dispenser calibration results.
Steps To Follow For Using
Monthly Inventory Control Record Sheet:
1 Stick tank - the opening stick reading is either from the
previous night or from the next morning of operation. This
reading indicates how much product you actually have in the
tank.
2 Convert stick reading from inches to gallons using the correct
tank calibration chart.
3 Add deliveries (after reconciling the delivery-see page 4).
4 Subtract the sales or outputs (totalizer reading).
5 Compute book inventory (what you should have in the tank).
6 Compare what you should have in the tank with what you
actually have in the tank (based on end of day or next
morning's stick reading). This comparison provides you with
an overage or shortage figure.
7 Reconcile the tank by taking 1% of sales or outputs plus 130
gallons. Compare this figure with your overage/shortage figure
and see which is larger. If the overage/shortage figure is larger,
then watch the inventory carefully for another 30 days. If the
trend continues, contact your federal or state UST imple-
menting agency.
5
-------
si
MONTHLY INVENTORY RECORD
MONTH/YEAR : _ j/f3
FACILITY NAME
TANK CONTENTS
Ed's AiTclS
dJtS&I
DATE OF THIS MONTH'S WATER LEVEL CHECK: <2-*2! AMOUNT OF WATER (INCHES): O
DATE
START STICK , GALLONS _
GALLONS _
PUMPED
BOOK
INVENTORY
END STICK INVENTORY
DAILY OVER
OR
MITIALS
INCHES
GALLONS
1
4*47
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TOTAL GALLONS PUMPED:
(<>293
TOTAL GALLONS OVER OR SHORT:
<74>
TOTAL GALLONS PUMPED
LEAK CHECK: K b2. 93 > x -01 + 130 = J 93
TOTAL OF "DAILY OVER OR SHORT" IS LARGER THAN THE "LEAK CHECK" RESULT: YES £NP> (circle one)
IF ANSWER IS "YES" TWO MONTHS IN A ROW, NOTIFY REGULATORY AGENCY
KEEP THIS PIECE OF PAPER ON FILE FOR AT LEAST ONE YEAR
REGION 8 VERSION 1 - MARCH 93
-------
MONTHLY INVENTORY RECORD
MONTH/YEAR :
FACILITY NAME:
TANK CONTENTS:
DATE OF THIS MONTH'S WATER LEVEL CHECK: AMOUNT OF WATER (INCHES):
DATE
START STICK , GALLONS GALLONS _ BOOK
END STICK INVENTORY
DAILY OVER
OR
INITIALS
INCHES
GALLONS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
2 5
26
27
28
29
30
31
TOTAL GALLONS PUMPED:
TOTAL GALLONS OVER OR SHORT:
TOTAL GALLONS PUMPED
LEAK CHECK: ( ) X .01 + 130 =
TOTAL OF "DAILY OVER OR SHORT IS LARGER THAN THE 'LEAK CHECK1 RESULT: YES NO (circle one)
IF ANSWER IS "YES" TWO MONTHS IN A ROW, NOTIFY REGULATORY AGENCY
KEEP THIS PIECE OF PAPER ON FILE FOR AT LEAST ONE YEAR
REGION 8 - VERSION 1 - MARCH 93
-------
DAILY SALES RECORD
FACILITY NAME:
DATE:
TYPE OF FUEL / TANK
Totalizer Reading
Totalizer Reading
Totalizer Reading
Totalizer Reading
Totalizer Reading
Totalizer Reading
Today's Sum of Totalizers
Yesterday's Sum of Totalizers
AMOUNT PUMPED TODAY
REGION 8 - VERSION 1 - MARCH 93
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FUEL DELIVERY RECORD
FACILITY NAME:
DATE OF DELIVERY:
DELIVERY C<
DM PAN Y:
TYPE OF FUEL
INCHES
GALLONS
INCHES
GALLONS
INCHES
GALLONS
FUEL BEFORE DELIVERY
FUEL AFTER DELIVERY
GALLONS DELIVERED
(STICK)
GROSS GALLONS DELIVERED
(RECEIPT)
DATE OF DELIVERY:
DELIVERY C<
DMPANY:
TYPE OF FUEL
INCHES
GALLONS
INCHES
GALLONS
INCHES
GALLONS
FUEL BEFORE DELIVERY
FUEL AFTER DELIVERY
GALLONS DELIVERED
(STICK)
GROSS GALLONS DELIVERED
(RECEIPT)
DATE OF DELIVERY:
| DELIVERY C<
DMPANY:
TYPE OF FUEL
INCHES
GALLONS
INCHES
GALLONS
INCHES
GALLONS
FUEL BEFORE DELIVERY
FUEL AFTER DELIVERY
GALLONS DELIVERED
(STICK)
GROSS GALLONS DELIVERED
(RECEIPT)
KEEP THIS PIECE OF PAPER ON FILE FOR AT LEAST ONE YEAR
REGION 8 - VERSION 1 - MARCH 93
-------
Manual Tank Gauging
This leak detection method can be used for tanks
2,000 gallons and smaller only. Manual tank gauging
may be used without tank tightness testing on tanks
1,000 gallons or smaller. Manual tank gauging must be
used in combination with tank tightness testing for
1,000- to 2,000-gallon tanks.
Manual tank gauging consists of measuring
product in the tank before and after a "rest period."
Product input or output may not occur during the rest
period. Two measurements, from which you will take
an average, are required before and after each rest
period. The chart on page 13 will tell you the length of
the rest periods and the allowable product loss/gain
standard for your tank's size and dimension.
To Properly Conduct Manual Tank Gauging
You Must:
¦ Have proper equipment
¦ Stick the tank before and after the rest
period
¦ Reconcile inventory weekly and
monthly
¦ Document & save records for all items
listed above
11
-------
Manual Tank Gauging
Proper Equipment
Minimum equipment needed includes:
a non-sparking gauge stick (dipstick) that can be
read in l/8th-inch increments and is not warped or
worn at the bottom,
a calibration chart that converts gauge stick readings
to gallons for your specific tank type and size
Stick readings before and after each "rest period"
The tank inventory must be measured twice and
averaged before and after each "rest period." The more
consistent the stick readings are, the more accurate the
inventory will be. This means that product level should
be read by the same person using the same stick and
the same tank calibration chart. Consistency is vital!
Weekly and monthly reconciliation
NOTE: Under no
circumstances should
you attempt to artifi-
cially adjust numbers to
make daily over/short
numbers come out to
zero (0). This would
defeat the whole
purpose of inventory
control and could mask
aleak.
Inventory readings must be reconciled weekly
and monthly. (The chart on page 13 shows the recon-
ciliation standard per week and per month.) The
standard for allowable product loss or gain depends on
the tank capacity and dimension. If you are short or
over more than either the allowable weekly or monthly
standard, you may have a leak. If this happens, care-
fully monitor your inventory for another month. If
either of the standards are exceeded again, contact your
federal or state UST agency.
Documentation
You must keep documentation of all monitoring
for at least one year. This includes monthly manual
tank gauging records and the latest tank tightness test
results (if required).
12
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Manual Tank Gauging
Tank Capacity
(gallons)
Tank Dimensions
Weekly/Monthly
Standard (gallons)
Minimum Rest
Period Duration
550
N/A
10/5
36 hours
551 -1,000
N/A
9/7
36 hours
1,000
64"(diameter) X
73 (length)
9/4
44 hours
1,000
48"(diameter) x
128"(length)
12/6
58 hours
1,001 - 2,000
N/A
26/13
36 hours
Steps To Follow For Using
Manual Tank Gauging Record Sheet.
1 Stick the tank twice before the rest period and average the
readings.
2 Allow no product input or withdrawal during the rest period,
which is a specific time period based on your tank's size and
dimension (see chart on page 11).
3 At the end of the rest period, stick the tank twice and average
the readings.
4 Reconcile the stick readings on both a weekly and monthly
basis and compare overages/shortages to the allowable ranges
on the chart. If the overage/shortage figure exceeds the allow-
able range, carefully watch the inventory for another 30 days. If
the trend continues, contact your UST implementing agency.
13
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MANUAL TANK GAUGING RECORD
^ FACILITY NAME £d 5 /ke/HlUM AtXTOS
^ TANK CONTENTS dl'Se.l
^ JT^ TANK CAPACITY /$60 fig/ZonS
MINIMUM TEST LENGTH AeUtS
TO PASS THE WEEKLY TEST THE WEEKLY CHANGE IN VOLUME MUST BE LESS THAN GALLONS.
TO PASS THE MONTHLY TEST THE FOUR WEEK AVERAGE CHANGE IN VOLUME MUST BE LESS THAN /3 GALLONS.
YEAR: 93
START DATE
(MONTH/DAY)
LENGTH
OF TEST
START
END
CHANGE IN
VOLUME
(WEEKLY)
PASS
WEEKLY
TEST
CHANGE IN
VOLUME
(MONTHLY
AVERAGE)
PASS
MONTHLY
TEST
(HOURS)
AVG
INCH
GAL
AVG
INCH
GAL
vs
// N
(XN
v?
n
99
h
1/
/P
($) N
a-/s
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/So
JO
ISO
0
<$) N
a -23.
vt
3,6
9t>*>
906,
o
(5> N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
IF YOU DO NOT PASS ANY OF THE WEEKLY OR MONTHLY TESTS, YOU MUST REPORT A SUSPECTED
LEAK TO YOUR REGULATORY AGENCY
KEEP THIS PIECE OF PAPER ON FILE FOR AT LEAST ONE YEAR
REGION 8 - VERSION 1 - MARCH 93
-------
MANUAL TANK GAUGING RECORD
FACILITY NAME
TANK CONTENTS
TANK CAPACITY
MINIMUM TEST LENGTH
TO PASS THE
TO PASS
MONTHLY
THE WEEKLY TEST TH
TEST THE FOUR WEEK
E WEEKLY CHANGE IN
AVERAGE CHANGE IN
VOLUME MUS
VOLUME MUS
T BE LESS
T BE LESS
THAN
THAN
GALLONS.
GALLONS.
YEAR:
START DATE
(MONTH/DAY)
LENGTH
OF TEST
(HOURS)
START
END
CHANGE IN
VOLUME
(WEEKLY)
PASS
WEEKLY
TEST
CHANGE IN
VOLUME
(MONTHLY
AVERAGE)
PASS
MONTHLY
TEST
AVG
INCH
GAL
AVG
INCH
GAL
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
Y N
IF YOU DO NOT PASS ANY OF THE WEEKLY OR MONTHLY TESTS, YOU MUST REPORT A SUSPECTED
LEAK TO YOUR REGULATORY AGENCY
KEEP THIS PIECE OF PAPER ON FILE FOR AT LEAST ONE YEAR
REGION 8 - VERSION 1 - MARCH 93
-------
MANUAL TANK GAUGING WORKSHEET
MONTH/YEAR
FACILITY NAME
TANK CONTENTS
TANK CAPACITY
WEEK #1
DATE
TIME
STICK READING #1
STICK READING #2
AVERAGE OF #1 AND #2
BEGINNING
ENDING
WEEK #2
DATE
TIME
STICK READING #1
STICK READING #2
AVERAGE OF #1 AND #2 |
BEGINNING
ENDING
I
WEEK #3
DATE
TIME
STICK READING #1
STICK READING #2
AVERAGE OF #1 AND #2
BEGINNING
ENDING
WEEK #4
DATE
TIME
STICK READING #1
STICK READING #2
AVERAGE OF #1 AND #2
BEGINNING
ENDING
SUMMARY OF MANUAL TANK GAUGING REGULATORY REQUIREMENTS
TANK SIZE
(CAPACITY/DIAMETER)
TEST LENGTH
(HOURS)
WEEKLY TEST
STANDARD
(GALLONS)
MONTHLY TEST
STANDARD
(GALLONS)
TIGHTNESS
TEST REQUIRED
VALID UNTIL
550 GAL
36
10
5
NO
TANK REMOVED
1,000 GAL/64"
44
9
4
NO
TANK REMOVED
1,000 GAL/48"
58
12
6
NO
TANK REMOVED
551 GAL TO 1,000 GAL
36
9
7
YES
1998 OR 10 YRS
1,001 GAL TO 2,000 GAL
36
26
13
YES
1998 OR 10 YRS
2,001+GAL
<<<<<<< NOT ALLOWED >>>>>>>
KEEP THIS PIECE OF PAPER ON FILE FOR AT LEAST ONE YEAR
REGION 8 VERSION 1 MARCH 93
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