| (A) Manual tank gauging in accordance with this subparagraph
may be used as the sole method of tank release detection only for
petroleum substance tanks having a nominal capacity of 1,000 gallons
or less.
(B) The use of manual tank gauging shall not be considered
an acceptable method for meeting the release detection requirements
of this section for any tanks with a nominal capacity greater than
1,000 gallons.
(C) When used for compliance with the release detection
requirements of this section, the procedures and requirements in the
following clauses shall be applicable.
(i) For purposes of this subparagraph only, the following
definitions are applicable.
(I) Level measurement--The average of two consecutive
liquid level readings from a tank gauge, measuring stick, or other
measuring equipment.
(II) Gauging period--A weekly period during which no
substance is added to or removed from the tank. The duration of the
gauging period is dependent upon tank volume and diameter, as specified
in clause (v) of this subparagraph.
(III) Weekly deviation--The variation between the level
measurements taken at the beginning and the end of one gauging period,
converted to and expressed as gallons.
(IV) Monthly deviation--The arithmetic average of four
consecutive weekly deviations, expressed as gallons.
(ii) Any measuring equipment shall be capable of measuring
the level of stored substance over the full range of the tank's height
to the nearest 1/8 inch.
(iii) Separate liquid level measurements in the tank
shall be taken weekly at the beginning and the ending of the gauging
period, and the weekly deviation shall be determined from such level
measurements.
(iv) Once each month, after four consecutive weekly
deviations are determined, a monthly deviation shall be calculated.
(v) For the purposes of the manual tank gauging method
of release detection, a release shall be indicated when either the
weekly deviation or the monthly deviation exceeds the maximum allowable
standards indicated in the following subclauses:
(I) for a tank with a capacity of 550 gallons or less
(any tank diameter): minimum duration of gauging period = 36 hours;
weekly standard = ten gallons; monthly standard = five gallons;
(II) for a tank with a capacity of 551 gallons to 1,000
gallons (when tank diameter is 64 inches): minimum duration of gauging
period = 44 hours; weekly standard = nine gallons; monthly standard
= four gallons; and
(III) for a tank with a capacity of 551 gallons to
1,000 gallons (when tank diameter is 48 inches): minimum duration
of gauging period = 58 hours; weekly standard = 12 gallons; monthly
standard = six gallons.
(vi) When either the weekly standard or the monthly
standard is exceeded and a suspected release is thereby indicated,
the owner or operator shall comply with the applicable release reporting,
investigation, and corrective action requirements of Subchapter D
of this chapter.
(3) Monthly (every 30 days) tank gauging. Monthly tank
gauging may be used as a tank release detection method, subject to
the following limitations and requirements.
(A) Monthly tank gauging in accordance with this paragraph
may be used as the sole method of tank release detection only for
emergency generator tanks.
(B) The use of monthly tank gauging shall not be considered
an acceptable method for meeting the release detection requirements
of this section for any tanks other than emergency generator tanks.
(C) When used for compliance with the release detection
requirements of this section, the procedures and requirements in the
following clauses shall be applicable.
(i) For purposes of this subparagraph only, the following
definitions are applicable.
(I) Level measurement--The average of two consecutive
liquid level readings from a tank gauge, measuring stick, or other
manual or automatic measuring equipment.
(II) Gauging period--A period of at least 36 hours
during which no substance is added to or removed from the tank.
(III) Monthly deviation--The variation between the
level measurements taken at the beginning and the end of one gauging
30-day period, converted to and expressed as gallons.
(ii) Any measuring equipment (whether operated manually
or automatically) shall be capable of measuring the level of a stored
substance over the full range of the tank's height to the nearest
1/8 inch.
(iii) Separate liquid level measurements in the tank
shall be taken at least once every 30 days at the beginning and the
ending of the gauging period, and the monthly deviation shall be determined
from such level measurements.
(iv) For the purposes of the 30-day tank gauging method
of release detection, a release shall be indicated when the monthly
deviation exceeds the maximum allowable standards indicated in the
following subclauses:
(I) for a tank with a capacity of 550 gallons or less:
monthly standard = five gallons;
(II) for a tank with a capacity of 551 gallons to 1,000
gallons: monthly standard = seven gallons;
(III) for a tank with a capacity of 1,001 gallons to
2,000 gallons: monthly standard = 13 gallons; and
(IV) for a tank with a capacity greater than 2,000
gallons: monthly standard = 1.0% of the total tank capacity.
(v) When the monthly standard is exceeded and a suspected
release is thereby indicated, the owner or operator shall comply with
the applicable release reporting, investigation, and corrective action
requirements of Subchapter D of this chapter.
(4) Automatic tank gauging in combination with inventory
control.
(A) A combination of automatic tank gauging and inventory
control may be used as a tank release detection method, subject to
the following requirements.
(i) Inventory control procedures shall be in compliance
with paragraph (1)(B) of this subsection.
(ii) The automatic tank gauging equipment shall be
capable of:
(I) automatically monitoring the in-tank liquid levels,
conducting automatic tests for substance loss, and collecting data
for inventory control purposes; and
(II) performing an automatic test for substance loss
that can detect a release of 0.2 gallon per hour from any portion
of the tank which contains regulated substances.
(iii) The automatic tank gauge testing must be performed
with the system operating in one of the following modes:
(I) in-tank static testing conducted at least once
every 30 days; or
(II) 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.
(B) For emergency generator tanks and used oil tanks
only, automatic tank gauging may be used as a tank release detection
method without inventory control, provided that the automatic tank
gauging equipment shall be capable of:
(i) automatically monitoring the in-tank liquid levels;
(ii) conducting continuous automatic tests for substance
loss during the periods when the emergency generator engine is not
in operation;
(iii) performing an automatic test for substance loss
that can detect a release of 0.2 gallon per hour from any portion
of the tank which contains regulated substances; and
(iv) measuring the water level at the bottom of the
tank to the nearest 1/8 of an inch at least once every 30 days.
(5) Vapor monitoring. Equipment and procedures designed
to test or monitor for the presence of vapors from the regulated substance
(or from a related tracer substance) in the soil gas of the backfilled
excavation zone may be used, subject to the following limitations
and requirements.
(A) The bedding and backfill materials in the excavation
zone shall be sufficiently porous to allow vapors from any released
regulated substance (or related tracer substance) to rapidly diffuse
through the excavation zone (e.g., gravel, sand, crushed rock).
(B) The stored regulated substance, or any tracer substance
placed in the tank system, shall be sufficiently volatile so that,
in the event of a substance release from the UST system, vapors will
develop to a level that can be readily detected by the monitoring
devices located in the excavation zone.
(C) The capability of the monitoring device to detect
vapors from the stored regulated substance shall not be adversely
affected by the presence of any groundwater, rainfall, and/or soil
moisture in a manner that would allow a release to remain undetected
for more than 30 days.
Cont'd... |
