filling stations. The Agency now believes, however, that by allowing variable or recurring flow, but
limiting this exclusion to production processes, this concern is no longer relevant. Tanks that do form a
part of a production process are often operated in a batch fashion, where inflow and outflow are periodic
rather than steady or uninterrupted. EPA believes that the inclusion of such tanks is consistent with the
intent of this exclusion, which is to preclude regulation of tanks that form an integral part of a production
process.
Under the same rationale, EPA agrees with commenters that tanks that hold intermediates may be an
integral part of a production process. Accordingly, tanks that store intermediates as part of a production
process are flow-through process tanks. Similarly, the Agency agrees with the commenter who suggested
that holding tanks, pulse tanks, feed tanks, mixing tanks, tanks that hold material being cut in
concentration, and other tanks in the process stream are flow-through process tanks.
The Agency does not agree, however, that wastewater treatment tanks, including oil-water separators, are
flow-through process tanks. These tanks do not form an integral part of a production process. Wastewater
treatment tanks typically follow the production process, and in no way contribute to the production itself.
Many of these treatment tanks, however, fall within the regulatory exclusion for tanks that are subject to
CWA requirements or are excluded because they contain de minimis concentrations of regulated
substances; wastewater treatment tanks that are not excluded are deferred from these regulations (see
section IV.A.3.). For the same reasons, hydraulic lifts and electrical equipment, which commenters
suggested should be defined as flow-through process tanks, are not. Hydraulic lift tanks and electrical
equipment do not form part of a production process.
One commenter requested clarification on whether processes in service industries, specifically the dry
cleaning industry, would qualify as "production processes." In the dry cleaning industry, the main
"product," the cleaning of garments, is really a service. As stated above, EPA does not intend to restrict
the phrase "production process" solely to industries where a tangible good is produced. Tanks that contain
regulated substances that are integral to the dry cleaning process are eligible for consideration as flow-
through process tanks. The tanks in dry cleaning machines, however, store regulated substances prior to
their introduction to the cleaning process. Thus, these tanks are not flow-through process tanks.
(8) Liquid Traps or Gathering Lines Related to Oil or Gas Production and Gathering Operations. The
eighth exclusion covers "liquid traps or associated gathering lines directly related to oil or gas production
and gathering operations." The liquid trap exclusion refers to sumps, well cellars, and other traps used in
association with oil and gas production, gathering, and extraction operations (including gas production
plants), for the purpose of collecting oil, water and other liquids. Such liquid traps may temporarily
collect liquids for subsequent disposition or reinjection into a production or pipeline stream, or may
collect and separate liquids from a gas stream.
This exclusion applies only to traps and gathering lines, and does not include other storage tanks at oil
and gas production sites. Similarly, although liquid traps are often used in activities other than oil and gas
production, the only liquid traps excluded from UST jurisdiction under this provision are liquid traps used
for the purpose of separating oil and gas liquids from water at oil and gas production facilities. Liquid
traps used in conjunction with landfill methane gas production facilities are within this exclusion and
would not be subject to UST jurisdiction. Liquid traps such as grease and oil traps at gas stations,
however, are not within this exclusion.
PREAMBLE--40 CFR Part 280 71