thresholds are potential concerns regarding public perception of ambient benzene concentrations reported to be
above EPA’s fence-line monitoring action level at individual
locations. While EPA classifies the fence-line monitoring requirement as a “work practice standard” (vs. a type of emissions limit), the distinction that the benzene concentration
threshold of 9 μg/cu m ( 2. 8 ppbv) serves as an action level
rather than an emissions limit may not be fully recognized
or understood when EPA makes monitoring data publicly
available. Plant owner-operators also should expect the public to make a variety of comparisons among refineries and
petrochemical sources as a group as well as between individual plants.
While operators can defer reporting refinery fence-line
monitoring data to EPA until 12 months of data have been
collected, data from the initial and all subsequent sampling
periods must be reported. Consequently, publicly available
data will document high benzene concentrations from any
issue resulting in high benzene emissions from a petrochemical source, even if that issue was identified and corrected soon after the monitoring compliance date.
Unless a specific, recent change can be identified as a
cause of the high benzene concentration, the presumption
likely will be that the condition was a long-standing one, entailing all enforcement and potential legal implications that
normally accompany that presumption.
To avert potential problems that could arise from discovery of high benzene concentrations at a refinery’s
fence-line, many refiners are conducting benzene
fence-line monitoring studies to identify potential issues and take corrective action this year,
ahead of EPA’s Jan. 30, 2018, data-collection compliance date. Several more have conducted benzene fence-line monitoring studies in the past.
It is advisable for petrochemical plants operating near a refinery to initiate discussions with
the neighboring refinery to determine whether
benzene emissions from the petrochemical operations could be implicated as a contributor to a high benzene concentration at the refinery’s fence line. Depending
on whether the refinery has performed an ambient benzene
monitoring study, what the data indicate, and how much information the refinery is willing to share with the nearby
petrochemical plant, it also may be advisable for the petrochemical operator to conduct its own ambient benzene
monitoring study to determine whether the site could be implicated as a cause for a high ambient benzene concentration
reported by the refinery in the future.
Seasonal and even day-to-day variations in wind direc-
tion as well as a petrochemical plant’s benzene emissions
can affect the extent to which a neighboring plant’s emis-
sions would impact a refinery’s fence-line benzene concen-
the site’s emissions were accurately represented in air quality
permit applications. Since refineries’ fence-line monitoring
data will be publicly available, environmental groups, media
outlets, and the public seeking some context for the reported
benzene concentrations also likely will use ambient benzene
thresholds from state air toxics programs as a convenient
Some states’ ambient benzene thresholds are close to
EPA’s fence-line monitoring action level of 9 μg/cu m ( 2. 8
ppbv). For example, Louisiana and Texas—two states with a
high concentration of refineries—have annual benzene ambient thresholds easily comparable to fence-line monitoring
The Louisiana Toxic Air Pollutant (LTAP) standard for
ambient benzene is 12.00 μg/cu m (annual basis). 20 The Texas Commission on Environmental Quality’s (TCEQ) Effects
Screening Level (ESL) for benzene of 4. 5 μg/cu m (annual
average), 21 meanwhile, is half of EPA’s 9-μg/cu m fence-line
monitoring action level.
The accompanying table compares the federal, Louisiana,
and Texas action levels for ambient benzene concentrations.
In Texas, reported ambient concentrations that fall well
below the federal fence-line monitoring action level could
still garner attention if they simply exceed the state’s ESL. As
a result, petrochemical sources contributing to those ambient concentrations also may find themselves under heightened scrutiny.
Even if the cause of a high benzene concentration is
found to be a source in compliance with all applicable state
and federal control technology (e.g., MACT) standards,
enforcement actions could
result if that concentration
exceeded air permit emission limits and representations submitted as part of
an air quality permit application, including air dispersion modeling submittals.
EPA or state agency en-
forcement actions under the refinery RTR rule could include
• Financial penalties.
• Additional emissions controls.
• Additional permit (e.g., operational) limitations or requirements.
• Inconvenience and cost of having to update air quality
permit emission rates.
Increased scrutiny resulting from the fence-line monitoring program also could lead to discovery of compliance issues that may have otherwise been unknown to the plant’s
owner-operator but will nonetheless require additional investments of time, labor, and money to remedy.
Alongside issues associated with state ambient benzene
ACTION LEVELS FOR
EPA refnery RTR rule 9.00
LTAP standard 12.00
TCEQ ESL 4. 50