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Standing Watch at the Fenceline – Compliance Monitoring for Benzene Underway

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As of February 1, 2018, passive sorbent tubes are stationed around the perimeter of every petroleum refinery in the U.S., standing watch at the fenceline.  Sentinels for fugitive emissions, these sorbent tubes are continuously monitoring benzene and providing valuable information to the refineries on the effectiveness of their emission controls. With a new set of tubes deployed every 14 days, the refinery is able to track benzene concentrations at each station around the fenceline, and evaluate the site’s incremental benzene EPA 325 Fenceline Monitoringconcentration contribution, expressed as ΔC.  In many cases, ΔC is the difference between the highest and lowest benzene concentration measured at the fenceline over the sampling period. After collecting fenceline data for a year, the benzene concentrations at each monitoring station and the facility’s annual average ΔC values will be posted to the EPA website and available to the public.  The refinery is required to conduct a root cause analysis and corrective action if the annual average ΔC value is greater than the EPA action limit of 9 µg/m3.

In the period since the fenceline monitoring provision in the Petroleum Refinery Sector Rule was promulgated on December 1, 2015, a number of refineries have conducted pilot studies following procedures in EPA Method 325A for sampler deployment and EPA Method 325B for sampler preparation and analysis.  Eurofins Air Toxics has analyzed thousands of these pre-compliance samples and worked closely with industry to develop best practices to minimize anomalous benzene readings.  In an effort to determine the sensitivity of the method to field handling protocols, we evaluated the impact of several probable non-ideal field scenarios on benzene concentrations (Hayes and Reese, 2016) and collaborated with a site to troubleshoot anomalous concentrations.  With the exception of deploying the tube “upside-down” such that the diffusion screen cap was affixed to the incorrect end of the sorbent tube, the method was found to be robust and relatively insensitive to inadvertent field handling missteps.  Additionally, field QC consistently met method requirements with Field Duplicates routinely within the precision acceptance limits of <30% Relative Percent Difference (RPD) with few rare exceptions, and Field Blanks generally below laboratory detection limits.

Conducting pilot programs and planning for regulatory monitoring also helped to identify gaps in EPA Method 325 and prescribed work practices.  In response, ExxonMobil proposed corrections and clarifications via an Alternative Test Method (ATM) request.  The ATM request was approved and updates were provided by the EPA as an official letter to ExxonMobil dated September 11, 2017 which is posted on the EPA website as ATM-122

The three main areas addressed by ATM-122 include:

  • Correction of equations used to calculate benzene concentrations and clarification that reported concentrations are expressed at normal ambient temperature (25°C) and pressure (760 mm Hg);

  • Consistent language on sample collection timing, reinforcing the 14+1 day window with provisions to further modify the window in the event of access and/or safety concerns; and

  • Direction to use the average concentration of the field duplicate pair for purposes of ΔC determination and clarification of field duplicate and field blank collection frequency:
    1. 19 or fewer stations require a minimum of 1 field blank and 1 field duplicate
    2. 20 or more stations require a minimum of 1 field blank and 2 field duplicates

Additional descriptions and justifications for the Alternative Test Method request submitted and approved by the EPA can be found in the paper entitled “Patching the Holes in the Fenceline – Updates to EPA 325 Requirements” presented at the 2017 AFPM Environmental Conference (Hayes and Reese, 2017).

Since the posting of ATM-122, the EPA has proposed revisions to testing regulations for air emission sources that cover updates to EPA 325A and EPA 325B, including the adoption of the revised ATM-122 concentration equation. The proposed EPA rule can be found in the Federal Register, Document Citation 83 FR 3636, with the comment period closing March 27, 2018.  While formal adoption of the proposed EPA Method 325A and 325B revisions is still pending, fenceline monitoring continues forward under the current method and ATM-122 updates.

While new challenges are sure to be encountered as the compliance phase begins, Eurofins Air Toxics is prepared to respond. We have unmatched thermal desorption GC/MS capacity and trained chemists to analyze and report samples routinely in 5 days or less, demonstrated accuracy and quality systems as evidenced by our Proficiency Testing results and our NELAP accreditation, and convenient sampling kits to support the field sampling effort.  But perhaps most importantly, we have a depth of knowledge and experience that only comes with years of testing and evaluating passive sorbent technology, proactively investigating and resolving anomalous results in the field and the lab, and supporting field efforts to identify emission sources. As compliance is now officially underway, we look forward to supporting the industry in meeting the challenges ahead.  

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References: 

Hayes, H. and Reese, J.D., “Sensitivity of EPA 325 to Field Handling Protocols”, AFPM Environmental Conference, New Orleans, LA, October 16-18, 2016.
Hayes, H. and Reese, J.D., “Patching the Holes in the Fenceline – Updates to EPA 325 Requirements”, AFPM Environmental Conference, Denver, CO,  October 15-17, 2017.