Current through February 27, 2024
(a)
General
requirements. Each method of release detection for tanks that is used to
meet the requirements of
18 AAC 78.060 must meet the
requirements of this section.
(b)
Inventory control.Inventory control must be capable of detecting a
release of at least 1.0 percent of flow-through plus 130 gallons monthly.
Inventory control must be conducted monthly as follows:
(1) inventory volume measurements are
recorded each operating day for petroleum
(A)
inputs;
(B) withdrawals;
and
(C) amount remaining in the
tank;
(2) the equipment
used is capable of measuring the level of petroleum over the full range of the
tank's height to the nearest one-eighth of an inch;
(3) at the time of delivery, inputs of
petroleum are reconciled with delivery receipts, by measurement of the tank
inventory volume before and after delivery;
(4) deliveries are made through a drop tube
that extends to within one foot of the tank bottom;
(5) dispensing is metered and recorded within
state standards for meter calibration;
(6) at least once a month, the measurement of
any water level in the bottom of the tank is made to the nearest one-eighth of
an inch; and
(7) the information
generated under this subsection must be reviewed analyzed, and certified by
signature monthly by the owner or operator; and
(8) to meet the requirements of this
subsection, an owner or operator shall ensure that one of the following are
used:
(A) practices described in the American
Petroleum Institute Recommended Practice RP 1621, Bulk liquid Stock Control at
Retail Outlets, Fifth Edition, May 1993, adopted by reference; or
(B) another procedure, code, or standard that
is no less protective of human health and safety and the environment and
approved by the department.
(c)Manual tank gauging. Manual
tank gauging must meet the following requirements:
(1) tank liquid level measurements must be
taken at the beginning and end of a period, using the appropriate minimum
duration of test value in Tab le A of this subsection, during which no liquid
is added to or removed from the tank;
(2) level measurements must be based on an
average of two consecutive stick readings at both the beginning and ending of
the period;
(3) the equipment used
must be capable of measuring the level of product over the full range of the
tank's height to the nearest one-eighth of an inch;
(4) testing must be conducted at least once
each week, and the four weekly results must be averaged to obtain a monthly
result; a release is suspected and subject to the requirements of
18 AAC 78.200 -
18 AAC 78.280 if the variation
between beginning and ending measurements exceeds the weekly or monthly
standards in Table A of th is subsection; and
(5) owners and operators of tanks with a
nominal capacity of 550 gallons or less, and owners and operators of tanks with
a nominal capacity of 551 to 1,000 gallons and a tank diameter of 48 or 64
inches may use the method in this subsection as the sole method of release
detection; owners and operators of all other tanks with a nominal capacity of
551 to 2,000 gallons may use the method in this subsection in combination with
periodic tank tightness testing in place of inventory control in (b) of this
section; owners and operators of tanks with a nominal capacity greater than
2,000 gallons may not use the method in this subsection to meet the
requirements of this section.
TABLE A
|
Nominal tank capacity
|
Minimum duration of test
|
Weekly standard (one test)
|
Monthly
standard (four test average)
|
|
550 gallons or less
|
36 hours
|
10 gallons
|
5 gallons
|
|
551-1,000 gallons, when tank diameter is 64
inches
|
44 hours
|
9 gallons
|
4 gallons
|
|
551 - 1,000 gallons, when tank diameter is 48
inches
|
58 hours
|
12 gallons
|
6 gallons
|
|
551 - 1,000 gallons, when tank diameter is
not
48 or 64 inches
|
36 hours
|
13 gallons
|
7 gallons
|
|
1,001 - 2,000 gallons
|
36 hours
|
26 gallons
|
13 gallons
|
(d)
Tank tightness testing. Tank
tightness testing, or another test of equal performance, must be capable of
detecting a 0.1 gallon per hour leak rate from any part of a tank, including
the associated piping, that routinely contains petroleum, while accounting for
the effects of thermal expansion or contraction of the petroleum, vapor
pockets, tank deformation, evaporation or condensation, and the location of the
water table. To satisfy the requirements of this subsection,
(1) the owner or operator may use only tank
tightness tests that have been developed and reviewed by a nationally
recognized association or third-party testing laboratory and that meet or
exceed the criteria for the detection of leaks set out in the United States
Environmental Protection Agency's manuals Standard Test Procedures for
Evaluating Leak Detection Methods: Volumetric Tank Tightness Testing Methods,
March 1990 (EPA/530/UST- 90/004), and Standard Test Procedures for Evaluating
Leak Detection Methods: Nonvolumetric Tank Tightness Testing Methods, March
1990 (EP A/530/UST-90/005), the provisions of which are adopted by
reference;
(2) the tests required
under this sub section must be performed by a person certified under this
chapter;
(3) the owner or operator
shall submit to the department a certified copy of the evaluation results
indicating that the criteria have been met or exceeded and a copy of the
manufacturer's test protocol;
(4)
an owner or operator may use tank tightness testing only if
(A) the UST meets the performance standards
set out in
18 AAC 78.025 or
18 AAC 78.030; and
(B) the owner or operator complies with the
monthly inventory control requirements set out in (b) of this section or the
manual tank gauging requirements set out in (c) of this section;
(5) if tank tightness testing is
used, the test must be conducted every five years for 10 years after the tank
is installed or upgraded, whichever is later;
(6) the combination of tank tightness testing
and either inventory control or manual tank gauging is a temporary release
detection method and may not be used for more than the period of time indicated
in 18 AAC
78.060(e)(1)(A); after that period, a
permanent monthly release detection method must be used; and
(7) the department may disapprove a tank
tightness test or testing system under this subsection if the
(A) test or testing system fails to disclose
leaks that fall within the boundaries of the criteria stated in this
subsection; or
(B) tester is not
certified by the manufacturer of the test or testing system.
(e)
Automatic
tank gauging. Equipment for automatic tank gauging that tests for the
loss of petroleum and conducts inventory control must meet the following
requirements:
(1) the automatic product level
monitor test must be able to detect a 0.2 gallon per hour leak rate from any
part of the tank that routinely contains petroleum and a release of 150 gallons
within a 30-day period;
(2) the
automatic tank gauging equipment must meet the inventory control, or other test
of equivalent performance, requirements of (b)(6) of this section;
and
(3) the test must be performed
with the system operating in one of the following modes:
(A) in-tank static testing conducted at least
once every 30 days; or
(B)
continuous in-tank leak detection operating on an uninterrupted basis or
operating within a process that allows the system to gather incremental
measurements to determine the leak status of the tank at least once every 30
days.
(f)
Soil gas vapor monitoring.Vapor monitoring may be used only at
certain sites and only with department approval. The department will, in its
discretion, approve the testing or monitoring of soil gas vapors in the
excavation zone if the following requirements are met:
(1) material used as backfill is sufficiently
porous to readily allow diffusion of vapors from a release into the excavation
area; for purposes of this paragraph, gravel, sand, or crushed rock are
"sufficiently porous" materials;
(2) the stored petroleum, or a tracer
compound placed in the tank system, is sufficiently volatile to result in a
vapor level that is detectable by the monitoring devices located in the
excavation zone if a release from the tank occurs; for purposes of this
paragraph, gasoline is "sufficiently volatile;"
(3) the measurement of vapors by the
monitoring device is not rendered inoperative by groundwater, rainfall, soil
moisture, other local climatological, geologic, or hydrogeologic conditions, or
other known interference so that a release could go undetected for more than 30
days;
(4) the level of background
contamination in the excavation zone will not interfere with the method used to
detect a release from the tank;
(5)
the vapor monitors are designed and operated to detect any significant increase
in concentration above background of
(A)
petroleum stored in the tank system;
(B) a component or components of the
petroleum; or
(C) a tracer compound
placed in the tank system;
(6) the UST excavation zone is assessed as
required by
18 AAC 78.090 to
(A) ensure compliance with (1) - (4) of this
subsection; and
(B) establish the
number and positioning of observation wells that will detect a release within
the excavation zone from any part of a tank that routinely contains petroleum;
and
(7) observation
wells are clearly marked and secured to avoid unauthorized access and
tampering.
(g)
Groundwater monitoring. Groundwater monitoring may be used with
department approval. Testing or monitoring for liquids in the groundwater must
meet the following requirements:
(1) the
petroleum stored must be immiscible in water and must have a specific gravity
of less than one;
(2) groundwater
may not be, at any point, more than 20 feet from the ground surface and the
hydraulic conductivity of the soil between the UST and the monitoring wells or
devices may not be less than 0.01 centimeters per second;
(3) the slotted portion of the monitoring
well casing must be designed to prevent migration of natural soils or filter
pack into the well and to allow entry of petroleum on the water table into the
well under both high and low ground water conditions;
(4) monitoring wells must be sealed from the
ground surface to the top of the filter pack;
(5) monitoring wells or devices must
intercept the excavation zone or be as close to it as is technically
feasible;
(6) the continuous
monitoring devices or manual methods used must be able to detect the presence
of at least one-eighth of an inch of free product on top of the groundwater in
the monitoring wells;
(7) within
and immediately below the UST excavation zone, the site must be assessed to
ensure compliance with the requirements in (1) - (5) of this subsection and to
establish the number and positioning of monitoring wells or devices that will
detect releases from any portion of the tank that routinely contains product;
and
(8) monitoring wells must be
clearly marked and secured to avoid unauthorized access and
tampering.
(h)
Interstitial monitoring.Interstitial monitoring between the UST or
pipe and a secondary barrier immediately around or beneath the UST or pipe may
be used only if the system
(1) is designed,
constructed, and installed to detect a leak from any part of a tank or pipe
that routinely contains petroleum; and
(2) meets one of the following requirements:
(A) for a double-walled UST, including
piping, the sampling or testing method is capable of detecting a release
through the inner wall in any part of a tank or pipe that routinely contains
petroleum;
(B) for a UST with a
secondary barrier within the excavation zone, the sampling or testing method
used is capable of detecting a release between the UST and the secondary
barrier as follows:
(i) the secondary barrier
around or beneath the UST consists of artificially constructed material that is
sufficiently thick and impermeable to direct a release to the monitoring point
and permit its detection; for purposes of this clause, "sufficiently thick and
impermeable" means have a permeability of at least 10-6 cm/sec for the
petroleum stored;
(ii) the
barrier is compatible with the petroleum stored so that a release from the UST
will not cause a deterioration of the barrier and allow a release to pass
through undetected;
(iii) for a
cathodically protected tank, the secondary barrier must be installed so that it
does not interfere with proper operation of the cathodic protection
system;
(iv) groundwater, soil
moisture, or rainfall will not render the testing or sampling method
inoperative so that a release could go undetected for more than 30
days;
(v) the site is assessed to
ensure that the secondary barrier is always above the groundwater and not in a
25-year floodplain, unless the barrier and monitoring designs are for use under
those conditions; and
(vi)
monitoring wells are clearly marked and secured to avoid unauthorized access
and tampering; or
(C)
for a tank with an internally fitted liner, an automated device is capable of
detecting a release between the inner wall of the tank and the liner, and the
liner is compatible with the substance stored.
(i)
Statistical inventory
reconciliation. Third-party reviewed and certified release detection
methods based on the application of statistical principles to inventory data
similar to those described in (b) of this section must meet the following
requirements:
(1) the release detection
methods must be capable of detecting a leak rate of 0.2 gallons per hour or a
release of 150 gallons not later than 30 clays;
(2) the release detection methods must use a
threshold that does not exceed one-half the minimum detectible leak rate;
and
(3) the release detection
methods must report a quantitative result with a calculated leak
rate.
(j)
Other
methods.Any other type of release detection method, or combination of
such other methods, may be used with prior approval, if the method or
combination of methods can, for volumetric release detection methods, detect a
0.2 gallon per hour leak rate or a release of 150 gallons in a 30-day period
with a probability of detection of 95 percent and a probability of a false
alarm of five percent. For non-volumetric release detection methods, the
department may approve another method of release detection not described in (d)
- (i) of this section, if the owner or operator shows that the method can
detect a release as effectively as any of the methods allowed in (d) - (i) of
this section. In comparing methods, the department will consider the size of
release that the method can detect and the frequency and reliability with which
it can be detected. If the method is approved, the owner or operator shall
comply with any conditions imposed by the department on its use to ensure the
protection of human health and safety and the environment.
(k)
Certification of performance
standards.The National Work Group on Leak Detection Evaluations'
List of Leak Detection Evaluations for Storage Tank Systems,
17th Edition, January 11, 2010 shall be used to determine compliance with the
applicable performance standards for automatic tank gauging, statistical
inventory reconciliation, tightness testing, electronic interstitial
monitoring, and automatic line leak detectors. The List of Leak
Detection Evaluations for Storage Tank Systems, 17th Edition, January
11, 2010, is adopted by reference.
1. The American Petroleum Institute Recommended Practice
162 1, Bulk liquid Stock Control at Retail Outlets, Fifth Edition, May 1993 ,
adopted by reference in 18 AAC 78.065(b), may be reviewed at the Department of
Environmental Conservation's office in Anchorage.
2. The provisions outlined in the Steel Tank Institute's
Standard for Dual Wall Underground Steel Storage Tanks, F841, revised January
2006, may be used as guidance for aspects of the design and construction of
underground steel double-walled tanks as described in (h)(2)(A) of this
section.
3. The National Work Group on Leak Detection Evaluations'
List of Leak Detection Evaluations for Storage Tank Systems, 17th Edition,
January 11, 2010, adopted by reference in 18 AAC 78.065, may be reviewed at the
Department of Environmental Conservation's office in Anchorage or may be
obtained on the Internet at http://www.nwglde.org.
4. The tank tightness documents referred to in Notes 1 and
2 may be reviewed at the Department of Environmental Conservation's office in
Anchorage or may be obtained from the publisher at the address listed in the
editor's note at
18 AAC 78.025.
5. The United States Environmental Protection Agency tank
tightness testing documents referred to in 18 AAC 78.065(d) may be reviewed at
the Department of Environmental Conservation's office in Anchorage or may be
obtained from:
United States Environmental Protection Agency (EPA), Office
of Underground Storage Tanks, 1200 Pennsylvania Ave., NW, Mail Code 5401P,
Washington, D.C. 20460; telephone (703) 603-9900; Internet address:
http://www.epa.gov/oust;
United States Government Bookstore, 717 North Capitol St.
NW, Washington D.C. 20401; telephone: (866) 512-1800; facsimile: (202)
512-2104; Internet address: http://bookstore.gpo.gov/.
Authority:AS
46.03.020
AS
46.03.365
AS
46.03.375
