Current through September 21, 2024
Petroleum USTs with a capacity of more than 2,000 gallons
shall be monitored at least every thirty (30) days for releases using one or
more of the following methods:
(a)
Inventory control. Inventory control is never acceptable as a
leak detection method except when it is combined with another method. Product
inventory control (or another test of equivalent performance) shall be
conducted monthly to detect a release of at least 1.0 percent (1%) of
throughput plus one hundred thirty (130) gallons in the following manner:
(i) Inventory volume measurements for
regulated substance inputs, withdrawals, and the amount still remaining in the
UST shall be recorded each operating day;
(ii) The equipment used shall be capable of
measuring the depth of regulated substance over the full range of the USTs
height to the nearest one-eighth (1/8) of an inch;
(iii) The regulated substance inputs shall be
reconciled with delivery receipts by measurement of the UST inventory volume
before and after delivery;
(iv)
Deliveries shall be made through a drop tube that extends to within six (6)
inches of the Storage Tank bottom;
(v) Dispensing of regulated substances shall
be metered and recorded within the local standards for meter calibration or an
accuracy of six (6) cubic inches for every five (5) gallons of regulated
substance withdrawn; and
(vi) Water
in the bottom of the UST shall be measured to the nearest one-eighth (1/8) of
an inch at least once a month.
(vii)
Owners and/or operators using inventory control may combine this method with
tank tightness testing at least every five (5) years until December 22, 2008,
or until ten (10) years after the UST itself first met the requirements of
Section 6(a), whichever is sooner;
(viii) Owners and/or operators using
inventory control shall report a suspected release under Section 19(c) of this
chapter whenever:
(A) The inventory control
fails to balance within 1.0 percent (1%) of total throughput plus one hundred
thirty (130) gallons for the second consecutive month;
(B) More than 20 daily readings are either
positive or negative for the second consecutive month; or
(C) A graph of the daily over/short readings
shows a consistent non-zero trend for two (2) consecutive
months.
(ix) The following
methods are methods of equivalent performance to inventory control:
(A) Vapor Monitoring conducted in accordance
with section 16(d) of this chapter;
(B) Groundwater Monitoring conducted in
accordance with section 16(e) of this chapter;
(C) Interstitial Monitoring conducted in
accordance with Section 16(f) of this chapter;
(D) Statistical Inventory Reconciliation
conducted in accordance with Section 16(g) of this chapter;
(E) Tracer Surveys conducted in accordance
with Section 16(h) of this chapter;
(F) Passive Acoustical Sensing conducted in
accordance with Section 16(k) of this chapter; and
(G) Other methods approved under Section
16(j) of this chapter, providing that the approval of the method specifically
states that the method is of equivalent performance to inventory
control.
(b)
Tank tightness testing. Tank tightness testing shall be
capable of detecting a 0.1 gallon per hour leak rate from any portion of the
UST that routinely contains regulated substance while accounting for the
effects of thermal expansion or contraction of the regulated substance, vapor
pockets, tank deformation, evaporation or condensation, and the facility of the
water table. Whenever a tank tightness test shows a failing result, the owner
and/or operator shall report a suspected release and follow Section 20(a)(i)
and (ii) of this chapter.
(c)
Automatic tank gauging (ATG). Equipment for automatic tank
gauging that tests for the loss of a regulated substance shall detect a 0.2
gallon per hour leak rate from any portion of the tank that routinely contains
a regulated substance. Owners and/or operators using automatic tank gauging
shall also:
(i) conduct inventory control in
conformance with paragraph (a) of this section, unless:
(A) the regulated substance is placed in the
UST in batches of twenty-five (25) gallons or less;
(B) the tank is used only to fuel an
emergency power generator;
(C) a
passing result is obtained monthly from the Automatic Tank Gauge with the tank
at least 85% full;
(D) the automatic
tank gauge itself reconciles the inventory to the same levels as required by
paragraph (a)(i) of this section; or
(E) a method of equivalent performance to
inventory control is also used.
(ii) report a suspected release and follow
the requirements of Section 19(c) of this chapter whenever:
(A) Any calendar month goes by when a passing
result cannot be obtained from the ATG sometime during the month; or
(B) A pattern becomes evident that the ATG
produces a failing result whenever the level of a regulated substance in the
tank is high, even if passing results can be obtained when the level is
low.
(C) Inventory control fails for
the second consecutive month.
(d)
Vapor Monitoring. Testing or
monitoring for vapors within the soil gas of the excavation zone shall 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
zone;
(ii) The stored regulated
substance, or a tracer compound placed in the UST system, is sufficiently
volatile 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 groundwater,
rainfall, or soil moisture or other known interferences so that a release could
go undetected for more than thirty (30) days;
(iv) The soil and backfill material
immediately surrounding the UST system shall not be contaminated with the
regulated product in such a way as to interfere with the method used to detect
releases from the UST system;
(v)
The vapor monitors shall be designed and operated to detect any significant
increase in concentration above background of the regulated substance stored in
the UST system, a component or components of that substance, or a tracer
compound placed in the UST system;
(vi) In the UST excavation zone , the site is
assessed to ensure compliance with the requirements in this section and to
establish the number and positioning of vapor monitoring wells that will detect
releases within the excavation from any portion of the tank that routinely
contains regulated substance; and
(vii) Vapor monitoring wells shall be clearly
marked for identification and secured to avoid unauthorized access and
tampering.
(viii) Owners and/or
operators using vapor monitoring wells for leak detection shall report a
suspected release under Section 19(c) of this chapter whenever a vapor
monitoring device detects a leak and cannot be made to reset within forty-eight
(48) hours.
(ix) After the effective
date of these regulations, no new UST facility shall be installed using vapor
monitoring as the only leak detection method. Owners and/or operators may
install vapor monitoring wells as a secondary method. In the event that vapor
monitoring wells are installed in the backfill, a permit to construct under
Chapter 3, Wyoming Water Quality Rules and Regulations is not
required.
(e)
Groundwater monitoring. Testing or monitoring for liquids on
the groundwater shall meet the following requirements:
(i) The regulated substance stored is
immiscible in water and has a specific gravity of less than one (1);
(ii) Groundwater is never more than twenty
(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, coarse silts or other permeable materials);
(iii) The slotted portion of the monitoring
well casing or well screen shall 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 groundwater
conditions;
(iv) Monitoring wells
shall be sealed from the ground surface to the top of the filter pack with
hydrated bentonite and concrete;
(v)
Monitoring wells or devices shall intercept the excavation zone or are as close
to it as is technically feasible;
(vi) The continuous monitoring devices or
manual methods used shall be capable of detecting the presence of at least
one-eighth (1/8) of an inch of free product on top of the groundwater in the
monitoring wells;
(vii) Within and
immediately below the UST excavation zone, the site shall be assessed to ensure
compliance with the requirements in Section 16(e)(i) through (v) and to
establish the number and positioning of monitoring wells or devices that will
detect releases from any portion of the UST system that routinely contains a
regulated substance;
(viii)
Monitoring wells shall be clearly marked for identification and secured to
avoid unauthorized access and tampering; and
(ix) Groundwater monitoring shall not be used
when the ambient groundwater is already contaminated with the regulated
substance being stored in the UST system.
(x) Owners and/or operators using groundwater
monitoring shall report a suspected release and follow the requirements of
Section 19(c) and (d) of this chapter whenever any regulated substance is
observed in any monitor well at any level whatsoever.
(xi) After the effective date of these
regulations, no new UST facility shall be installed using groundwater
monitoring as the only leak detection method. Owners and/or operators may
install groundwater monitoring wells as a secondary method. In the event that
groundwater monitoring wells are installed in the backfill, a permit to
construct under Chapter 3, Wyoming Water Quality Rules and Regulations is not
required.
(f)
Interstitial monitoring. 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 a regulated substance
and also meets one of the following requirements:
(i) For double-walled UST systems, the
sampling or testing method shall be capable of detecting a release through the
inner wall in any portion of the tank that routinely contains a regulated
substance;
(ii) For UST systems
with a secondary barrier within the excavation zone, the sampling or testing
method used shall be capable of detecting a release between the UST system and
the secondary barrier;
(A) The secondary
barrier around or beneath the UST system shall consist of artificially
constructed material that is sufficiently thick and impermeable to direct a
release to the monitoring point and permit its detection. The permeability of
this barrier to the regulated substance stored shall be no more than
10-6 cm/sec;
(B) The barrier shall be compatible with the
regulated substance stored so that a release from the UST system will not cause
a deterioration of the barrier allowing a release to pass through
undetected;
(C) For cathodically
protected USTs, the secondary barrier shall be installed so that it does not
interfere with the proper operation of the CP system;
(D) Groundwater, soil moisture, or rainfall
shall not render the testing or sampling method used inoperative so that a
release could go undetected for more than thirty (30) days;
(E) The site shall be assessed to ensure that
the secondary barrier is always above the groundwater and not in a 25-year
flood plain, unless the barrier and monitoring designs are for use under such
conditions; and
(F) Monitoring wells
shall be clearly marked for identification and secured to avoid unauthorized
access and tampering.
(iii) For USTs with internally fitted liners,
an automated device shall be capable of detecting a release between the inner
wall of the UST and the liner. The liner shall also be compatible with the
regulated substance stored.
(iv)
Owners and/or operators using interstitial monitoring shall report a suspected
release and follow the requirements of Section 19(c) of this chapter whenever
any monitoring device indicates a leak and the device itself cannot be shown to
be defective within forty-eight (48) hours of the initial
alarm.
(g)
Statistical Inventory Reconciliation (SIR). All SIR methods
shall:
(i) meet the requirements found in
Section 16(a) for inventory control
(ii) be capable of detecting a 0.2 gallon per
hour leak rate or a release of one hundred fifty (150) gallons within a month
with a probability of detection of at least 0.95 and a probability of false
alarm of no more than 0.05; and
(iii) be approved, in writing, by the
department prior to use.
(iv) All
"inconclusive" results shall be investigated by the owner and/or operator as
soon as they are reported by the SIR company, including a complete audit of all
input data. The owner and/or operator shall make every effort to resolve all
"inconclusive" results as soon as they are reported. If the inventory for an
entire month fails to balance within two thousand (2,000) gallons, that month
shall be treated as inconclusive. A month with an un-resolved inconclusive
result is a month when no valid leak detection was provided.
(v) Owners and/or operators using SIR shall
report a suspected release and follow the requirements of Section 19(c) of this
chapter whenever:
(A) Any single month is
reported as a failure for the UST system by the SIR company;
(B) Any month is reported by the SIR company
as "inconclusive" unless that inconclusive result has been resolved by
re-submission of audited inventory numbers to the SIR
company.
(vi) UST Systems
with a throughput of more than 500,000 gallons per month in any single system
shall not be monitored using SIR as the only release detection
method.
(h)
Tracer Surveys. Owners and/or operators may use tracer surveys
as an approved monthly monitoring technique if:
(i) The tracer method can detect a 0.2 gallon
per hour leak rate or a release of one hundred fifty (150) gallons within a
month with a probability of detection of 0.95 and a probability of false alarm
of 0.05; and
(ii) The tanks are
inoculated with the same tracer each month;
(iii) The tanks are inoculated each month
before the 10th day of the month;
(iv) The Tracer Survey is completed before
the 25th day of each month;
(v) The
report for each month includes the calculations of the amount of tracer needed,
the amount actually added to each tank, and the calculated leak detection limit
in gallons per day; and
(vi) The
report for each test clearly states that the tank(s) either passed or failed
the test.
(vii) Any failing test
using tracer surveys shall be treated as a suspected release under Section 24
or 25.
(i)
Passive Acoustic Sensing. Owners and/or operators of Storage
Tanks using this method shall be equipped with a continuous sensing system
capable of detecting a release of 0.2 gallons per hour or a release of 150
gallons per month with a probability of detection of 0.95 and a probability of
false alarm of 0.05. All passive acoustic sensing systems shall produce a
written record showing that the system is on and operable. All passive acoustic
sensing systems shall be calibrated annually;
(j)
Other technology. With prior
department authorization, pursuant to Section 33, other types of release
detection methods, or combination of methods, may be used if:
(i) The method can detect a 0.2 gallon per
hour leak rate or a release of one hundred fifty (150) gallons within a month
with a probability of detection of 0.95 and a probability of false alarm of
0.05; or
(ii) The owner and/or
operator can demonstrate that the method can detect a release as effectively as
any of the methods allowed in Section 16(b) through (h). In comparing methods,
the department shall 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 and/or operator shall comply with any conditions imposed
by the department to ensure the protection of human health and the
environment.
(k)
Multiple Methods. Whenever these regulations require the use
of more than one leak detection method, the owners and/or operators shall meet
all of the requirements for all of the leak detection methods
required.
