easily as neighboring petrochemical operations by the monitoring program.
Fence-line monitoring provisions
The RTR rule’s fence-line monitoring provisions require
sampling conducted in accordance with Methods 325A and
325B or an approved alternative test method. 9 Method 325A
includes instructions for how to set up the sampling network
as well as placement and collection of sample tubes. Method
325B is the companion laboratory analysis method.
This article is based on using Methods 325A and 325B for
fence-line monitoring because the refinery RTR regulatory
package explicitly details requirements for both methods.
Monitoring results from an approved alternative test method
would have to be deemed equivalent and likely would have
similar implications for nearby petrochemical plants.
Key aspects of Refinery MACT 1’s fence-line monitoring
provisions are as follows:
• Benzene is the target analyte. 10
• The number of monitoring locations and their placement are determined by Method 325A procedures based on
the refinery’s size (either acreage or perimeter length) and
configuration, including shape of the refinery property and
whether “known sources of volatile organic compounds”
(defined as a wastewater treatment unit, process unit, or any
emission source requiring control according to the requirements of 40 CFR Part 63, Subpart CC, including marine vessel loading operations) are near the property boundary. 11
• Pursuant to Method 325A, passive collection of the
target analyte is accomplished with diffusive sorbent tubes
placed under weather protectors.
• The sampling period is 14 days unless a shorter sampling period is deemed necessary under a site-specific monitoring plan or a root-cause analysis triggered by the rule’s
benzene concentration-based action level. 12
• For each sampling period, a benzene concentration,
Δc, is determined using either the default procedure for cal-
culating Δc (as the difference between the highest and low-
est benzene concentrations from the samples collected) or a
site-specific monitoring plan. 13
• For each sampling period, a new annual average Δc is
calculated from the 26 most recent sampling-period Δc values. 14
• An action level of 9 μg/cu m ( 2. 8 parts per billion by
volume, ppbv), on an annual average basis, triggers the rule’s
root-cause analysis and corrective action procedure. 15
• After collecting the first 12 months of fence-line monitoring data, the refinery submits the initial and all subsequent data on a quarterly basis to EPA’s Compliance and
Emissions Data Reporting Interface (CEDRI), through the
agency’s Central Data Exchange (CDX). 16
While listed refinery fence-line monitoring provisions do
not apply directly to the petrochemical industry, the refinery
fence-line monitoring sampling results have both near-term
and potentially long-term implications for petrochemical
sources.
The accompanying box lists immediate recommendations for owners-operators of petrochemical sites to consider ahead of the refinery fence-line monitoring compliance
deadline.
Near-term concerns
If the refinery owner or operator believes an off-site upwind source or an on-site source excluded under 40 CFR
63.640(g) (e.g., ethylene processes or HON processes and
emission points) may influence the benzene measurements,
fence-line monitoring requirements provide for collection of
background samples through a site-specific monitoring plan
developed and submitted by the refinery owner or operator
to EPA for approval. 17
The refinery fence-line monitoring reporting provisions
require the refiner to submit individual “sample results for
each monitor for each sampling period” to ensure the total
ambient benzene concentration measured at each sampling
location will be reported for each 14-day sampling period. 18
Since EPA requires refiners to identify NFSs in their site-specific monitoring plans, 19 on-site and off-site petrochemical sources contributing to high ambient benzene concentrations will be implicated.
Many states have air toxics programs with ambient benzene concentration thresholds in either regulatory or policy form. Because air quality permit representations can be
binding, regulators and environmental interest groups can
compare ambient benzene concentrations attributed to petrochemical operations under the RTR rule’s fence-line monitoring program to required air dispersion modeling results
previously submitted to state air toxics programs. If the measured ambient concentrations exceed the modeled ambient
concentrations, a petrochemical plant’s owner-operator, at a
minimum, may be subject to intensified scrutiny by local,
state, or federal regulators or other interested parties, and
could face EPA enforcement actions to determine whether
Action recommendations for chemical plants
emitting benzene near a US petroleum refinery
• Initiate on-going dialogue with neighboring refineries
regarding what their fence-line monitoring data show
about any possible impacts of your plant’s benzene
emissions on their concentration levels.
• Conduct an independent ambient benzene
monitoring study to proactively identify potential
problems with your operations that could be revealed
through nearby refinery fence-line monitoring
programs.
