Current through Register Vol. 41, No. 3, September 23, 2024
Owners and operators must obtain a permit and the required
inspections in accordance with
9VAC25-580-50
or
9VAC25-580-60
for the installation of certain release detection equipment contained in
subdivisions 4 through 9 of this section.
Each method of release detection for tanks used to meet the
requirements of
9VAC25-580-140
must be conducted in accordance with the following and be designed to detect
releases at the earliest possible time for the specific method chosen:
1. Inventory control. 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:
a.
Inventory volume measurements for regulated substance inputs, withdrawals, and
the amount still remaining in the tank are recorded each operating
day;
b. The equipment used is
capable of measuring the level of product over the full range of the tank's
height to the nearest 1/8 of an inch;
c. The regulated substance inputs are
reconciled with delivery receipts by measurement of the tank inventory volume
before and after delivery;
d.
Deliveries are made through a drop tube that extends to within one foot of the
tank bottom;
e. Product dispensing
is metered and recorded according to regulations of the Bureau of Weights and
Measures of the Virginia Department of Agriculture and Consumer Services for
meter calibration within their jurisdiction; for all other product dispensing
meter calibration, an accuracy of six cubic inches for every five gallons of
product withdrawn is required; and
f. The measurement of any water level in the
bottom of the tank is made to the nearest 1/8 of an inch at least once a month.
NOTE: Practices described in the American Petroleum
Institute Recommended Practice RP 1621 Bulk Liquid Stock Control at Retail
Outlets, may be used, where applicable, as guidance in meeting the requirements
of this subsection.
2. Manual tank gauging. Manual tank gauging
must meet the following requirements:
a. Tank
liquid level measurements are taken at the beginning and ending of a period
using the appropriate minimum duration of test value in the table below during
which no liquid is added to or removed from the tank;
b. Level measurements are based on an average
of two consecutive stick readings at both the beginning and ending of the
period;
c. The equipment used is
capable of measuring the level of product over the full range of the tank's
height to the nearest 1/8 of an inch;
d. A release is suspected and subject to the
requirements of Part V (9VAC25-580-190
et seq.) 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
|
|
1001 - 2,000 gallons
(also requires periodic tank tightness
testing)
|
36 hours
|
26 gallons
|
13 gallons
|
e.
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 the table in
subdivision 2 d of this section may use this 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 subdivision 1 of this section.
Tanks of greater than 2,000 gallons nominal capacity may not use this method to
meet the requirements of this part.
3. Tank tightness testing. 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.
4. Automatic tank gauging. Equipment for
automatic tank gauging that tests for the loss of product and conducts
inventory control must meet the following requirements:
a. The automatic product level monitor test
can detect a 0.2 gallon per hour leak rate from any portion of the tank that
routinely contains product;
b. The
automatic tank gauging equipment must meet the inventory control (or other test
of equivalent performance) requirements of subdivision 1 of this section;
and
c. The test must be performed
with the system operating in one of the following modes:
(1) In-tank static testing conducted at least
once every 30 days; or
(2)
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.
5.
Vapor monitoring. Testing or monitoring for vapors within the soil gas of the
excavation zone must meet the following requirements:
a. 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;
b. 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;
c. 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 30 days;
d. The level of background contamination in
the excavation zone will not interfere with the method used to detect releases
from the tank;
e. 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;
f. In
the UST excavation zone, the site is assessed to ensure compliance with the
requirements in subdivisions a through d of this subdivision 5 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; and
g. Monitoring wells
are clearly marked and secured to avoid unauthorized access and
tampering.
6.
Groundwater monitoring. Testing or monitoring for liquids on the groundwater
must meet the following requirements:
a. The
regulated substance stored is not readily miscible in water and has a specific
gravity of less than one;
b.
Groundwater is never more than 20 feet from the ground surface and the
hydraulic conductivity of the soils 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);
c. 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 groundwater
conditions;
d. Monitoring wells
shall be sealed from the ground surface to the top of the filter
pack;
e. Monitoring wells or
devices intercept the excavation zone or are as close to it as is technically
feasible;
f. The continuous
monitoring devices or manual methods used can detect the presence of at least
1/8 of an inch of free product on top of the groundwater in the monitoring
wells;
g. Within and immediately
below the UST system excavation zone, the site is assessed to ensure compliance
with the requirements in subdivisions a through e of this subdivision 6 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
h. Monitoring wells are clearly
marked and secured to avoid unauthorized access and tampering.
7. 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 product and also meets one of the following
requirements:
a. For double-walled UST
systems, the sampling or testing method can detect a leak through the inner
wall in any portion of the tank that routinely contains product;
b. 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:
(1) 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;
(2)
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;
(3) 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;
(4) The groundwater, 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;
(5) The site is 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
(6) Monitoring
wells are clearly marked and secured to avoid unauthorized access and
tampering.
c. 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.
8.
Statistical inventory reconciliation. Release detection methods based on the
application of statistical principles to inventory data similar to those
described in subdivision 1 of this section must meet the following
requirements:
a. Report a quantitative result
with a calculated leak rate;
b. Be
capable of detecting a leak rate of 0.2 gallon per hour or a release of 150
gallons within 30 days; and
c. Use
a threshold that does not exceed one-half the minimum detectible leak
rate.
9. Other methods.
Any other type of release detection method, or combination of methods, can be
used if:
a. It can detect a 0.2 gallon per
hour leak rate or a release of 150 gallons within a month with a probability of
detection of 0.95 and a probability of false alarm of 0.05; or
b. The department may approve another method
if the owner and operator can demonstrate that the method can detect a release
as effectively as any of the methods allowed in subdivisions 3 through 8 of
this section. 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 operator must
comply with any conditions imposed by the department on its use to ensure the
protection of human health and the environment.
Statutory Authority: §§ 62.1-44.15 and
62.1-44.34:9 of the Code of Virginia;
42 USC §
6901 et seq.; 40 CFR Parts 280 and
281.
