Current through Register Vol. 6, March 22, 2024
(1) Each method of release detection for
tanks used to meet the requirements of ARM
17.56.402
must be conducted in accordance with the following:
(a) product inventory control (or another
test of equivalent performance) must be conducted monthly to detect a release
of at least 1.0% of flow-through plus 130 gallons on a monthly basis in the
following manner:
(i) inventory volume
measurements for regulated substance inputs, withdrawals, and the amount still
remaining in the tank are recorded each operating day;
(ii) the equipment used is capable of
measuring the level of product over the full range of the tank's height to the
nearest one-eighth of an inch;
(iii) the regulated substance inputs are
reconciled with delivery receipts by measurement of the tank inventory volume
before and after delivery;
(iv)
deliveries are made through a drop tube that extends to within one foot of the
tank bottom;
(v) product
dispensing is metered and recorded within for an accuracy of six cubic inches
for every five gallons of product withdrawn; and
(vi) the measurement of any water level in
the bottom of the tank is made to the nearest one-eighth of an inch at least
once a month;
(b) manual
tank gauging must meet the following requirements:
(i) tank liquid level measurements are taken
at the beginning and ending of a period of at least 36 hours during which no
liquid is added to or removed from the tank;
(ii) level measurements are based on an
average of two consecutive stick readings at both the beginning and ending of
the period;
(iii) the equipment
used is capable of measuring the level of product over the full range of the
tank's height to the nearest one-eighth of an inch;
(iv) a release is suspected and subject to
the requirements of ARM Title 17, chapter 56, subchapter 5 if the variation
between beginning and ending measurements exceeds the weekly or monthly
standards in the following table:
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 (also requires periodic tank
tightness testing) |
36 hours |
13 gallons |
7 gallons |
1,001 - 2,000 gallons (also requires periodic tank
tightness testing) |
36 hours |
26 gallons |
13 gallons |
(v)
tanks of 550 gallons or less nominal capacity and tanks with a nominal capacity
of 551 to 1,000 gallons that meet the tank diameter criteria in Table 1 may use
this method as the sole method of release detection. All other tanks with a
nominal capacity of 551 to 2,000 gallons may use the method in place of
inventory control in (1)(a). Tanks of greater than 2,000 gallons nominal
capacity may not use this method to meet the requirements of this subchapter;
and
(vi) tanks listed in ARM
17.56.402(1)(a)(iv)
may use this method of release detection as the sole method of annual tank
tightness testing;
(c)
tank tightness testing (or another test of equivalent performance) must be
capable of detecting a 0.1 gallon per hour leak rate from any portion of the
tank that routinely contains product while accounting for the effects of
thermal expansion or contraction of the product, vapor pockets, tank
deformation, evaporation or condensation, and the location of the water
table;
(d) equipment for automatic
tank gauging that tests for the loss of product or conducts inventory control
must meet the following requirements:
(i) the
automatic product level monitor test can detect a 0.2 gallon per hour (gph)
leak rate from any portion of the tank that routinely contains
product;
(ii) after December 31,
2010, if the automatic tank gauging equipment has the capability, the leak
detection console must be set to temporarily disable the pumping system after a
failed 0.2 gph leak test. The owner or operator may not restart the pumping
system until:
(A) an investigation of the UST
system alarm condition is conducted in accordance with the leak detection
equipment manufacturer's requirements and ARM Title 17, chapter 56, subchapter
5; and
(B) the owner or operator
determines that a release to the environment has not occurred;
(iii) inventory control (or
another test of equivalent performance) is conducted in accordance with the
requirements of (1)(a); and
(iv)
the test must be performed with the system operating in one of the following
modes:
(A) in-tank static testing is
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.
(e) testing or monitoring for vapors within
the soil gas of the excavation zone may only be used as a leak detection method
until October 13, 2023, to meet the requirements of ARM
17.56.402
and must meet the following requirements:
(i)
the materials used as backfill are sufficiently porous (e.g., gravel, sand,
crushed rock) to readily allow diffusion of vapors from releases into the
excavation area;
(ii) the stored
regulated substance, or a tracer compound placed in the tank system, is
sufficiently volatile (e.g., gasoline) to result in a vapor level that is
detectable by the monitoring devices located in the excavation zone in the
event of a release from the tank;
(iii) the measurement of vapors by the
monitoring device is not rendered inoperative by the ground water, rainfall, or
soil moisture or other known interferences so that a release could go
undetected for more than 30 days;
(iv) the level of background contamination in
the excavation zone will not interfere with the method used to detect releases
from the tank;
(v) the vapor
monitors are designed and operated to detect any significant increase in
concentration above background of the regulated substance stored in the tank
system, a component or components of that substance, or a tracer compound
placed in the tank system;
(vi) in
the UST excavation zone, the site is assessed to ensure compliance with the
requirements in (1)(e)(i) through (iv) and to establish the number and
positioning of monitoring wells that will detect releases within the excavation
zone from any portion of the tank that routinely contains product;
(vii) monitoring wells are clearly marked and
secured to avoid unauthorized access and tampering; and
(viii) after December 31, 2010, if the vapor
monitoring equipment has the capability, the leak detection console must be set
to temporarily disable the pumping system after a failed leak test. The owner
or operator may not restart the pumping system until:
(A) an investigation of the UST system alarm
condition is conducted in accordance with the leak detection equipment
manufacturer's requirements and ARM Title 17, chapter 56, subchapter 5;
and
(B) the owner or operator
determines that a release to the environment has not
occurred;
(f)
testing or monitoring for liquids on the ground water may only be used as a
leak detection method until October 13, 2023, to meet the requirements of ARM
17.56.402
and must meet the following requirements:
(i)
the regulated substance stored is immiscible in water and has a specific
gravity of less than one;
(ii)
ground water is never more than 20 feet from the ground surface and the
hydraulic conductivity of the soil(s) between the UST system and the monitoring
wells or devices is not less than 0.01 cm/sec (e.g., the soil should consist of
gravels, coarse to medium sands, course silts, or other permeable materials);
(iii) 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 regulated substance on the
water table into the well under both high and low ground water conditions, as
well as all conditions between the high and low ground water conditions;
(iv) monitoring wells shall be
sealed from the ground surface to the top of the filter pack;
(v) monitoring wells or devices intercept the
excavation zone or are as close to it as is technically feasible;
(vi) the continuous monitoring devices or
manual methods used can detect the presence of at least one-eighth of an inch
of free product on top of the ground water in the monitoring wells;
(vii) within and immediately below the UST
system excavation zone, the site is assessed to ensure compliance with the
requirements in (1)(f)(i) through (v) 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;
(viii) monitoring wells are clearly marked
and secured to avoid unauthorized access and tampering;
(ix) monitoring wells must be accessible for
the sampling purposes of ARM
17.56.503;
and
(x) after December 31, 2010, if
the ground water monitoring equipment has the capability, the leak detection
console must be set to temporarily disable the pumping system after a failed
leak test. The owner or operator may not restart the pumping system until:
(A) an investigation of the UST system alarm
condition is conducted in accordance with the leak detection equipment
manufacturer's requirements and ARM Title 17, chapter 56, subchapter 5; and
(B) the owner or operator
determines that a release to the environment has not occurred;
(g) interstitial
monitoring between the UST system and a secondary barrier immediately around or
beneath it may be used, but only if the system is designed, constructed, and
installed to detect a leak from any portion of the tank that routinely contains
product and also meets one of the following requirements:
(i) for double-walled UST systems:
(A) the sampling or testing method can detect
a release through the inner wall in any portion of the tank that routinely
contains product; and
(B) after
December 31, 2010, if the interstitial monitoring equipment has the capability,
the leak detection console must be set to temporarily disable the pumping
system after a failed leak test. The owner or operator may not restart the
pumping system until:
(I) an investigation of
the UST system alarm condition is conducted in accordance with the leak
detection equipment manufacturer's requirements and ARM Title 17, chapter 56,
subchapter 5; and
(II) the owner
or operator determines that a release to the environment has not
occurred
(ii)
for UST systems with a secondary barrier within the excavation zone, the
sampling or testing method used can detect a leak between the UST system and
the secondary barrier;
(A) the secondary
barrier around or beneath the UST system consists of artificially constructed
material that is sufficiently thick and impermeable (at least
10-6 cm/sec for the regulated substance stored) to
direct a leak to the monitoring point and permit its detection;
(B) the barrier is compatible with the
regulated substance stored so that a leak from the UST system will not cause a
deterioration of the barrier allowing a release to pass through
undetected;
(C) for cathodically
protected tanks, the secondary barrier must be installed so that it does not
interfere with the proper operation of the cathodic protection system;
(D) the ground water, soil
moisture, or rainfall will not render the testing or sampling method used
inoperative so that a release could go undetected for more than 30 days;
(E) the site is assessed to ensure
that the secondary barrier is always above the ground water and not in a
25-year flood plain, unless the barrier and monitoring designs are for use
under such conditions; and
(F)
monitoring wells are clearly marked and secured to avoid unauthorized access
and tampering; and
(iii)
for tanks with an internally fitted liner, an automated device can detect a
leak between the inner wall of the tank and the liner, and the liner is
compatible with the substance stored; and
(h) release detection methods based on the
application of statistical principles to inventory data must meet the following
requirements:
(i) report a quantitative
result with a calculated leak rate;
(ii) be capable of detecting a leak rate of
0.2 gallon per hour or a release of 150 gallons within 30 days; and
(iii) use a threshold that does not exceed
one-half the minimum detectible leak rate.
(i) any other type of release detection
method, or combination of methods, can be used if it can detect a 0.2 gallon
per hour leak rate or a release of 150 gallons within 30 days with a
probability of detection of 0.95 and a probability of false alarm of
0.05.
(2) UST systems
installed, modified, or replaced after November 26, 2009, must employ
interstitial monitoring and meet the requirements in [17.56.306 ](3), ARM
17.56.204,
and applicable recordkeeping requirements in ARM
17.56.409.