Oil & Gas Journal - April 03, 2017

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.

Immediate considerations

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
reference point.

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 results.

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
the following:
• 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.