Federal, state, and local agencies are all looking at fence line monitoring. Right now, the federal program looks at benzene monitoring. For PSD issues, there can be requirements to get permits. For post construction, monitoring for PSD could apply to any criteria pollutant at the administrator’s discretion. Section 114 of the CAA has some specific requirements for particular chemicals.
California is looking at refineries in particular, but there are District level rules as well. Underground gas storage has ambient monitoring for methane. Colorado has requirements for ozone precursors, particularly VOC monitoring. Chicago has requirements for fugitive dust and toxic metals, especially in EJ communities. Passive sampling includes Method 325A and Method 325B for VOC concentrations. The samplers are placed along the fence line in a hooded installation to protect against the elements. The sampling period is 14 days. Generally, 12 samplers are required, but more may be needed for large facilities. Equal spacing or special placement, depending upon size and shape, can be used. The device is simple and the sample tube is removed and analyzed in the lab. The disadvantage is that the data only comes back after the lab analysis. Short term detection can be a problem. Time integrated samples can be done with Summa canisters. A flow controller draws the sample over a fixed period of time. A sorbent captures the VOCs of interest. The collected samples are still sent to a lab for analysis. Costs are somewhat higher. However, the time frame could be as low as 1 hour. The detection limits are much lower. The data is still lagged due to lab analysis requirements. Continuous monitoring can also be installed. These provide near real time data. The number of continuous monitors has been increasing significantly. There are federal reference methods. There are near reference monitors at lower cost. Data validity might be an issue.
EPA does not particularly like the use of low-cost sensors and does not really use that data. Data resolution is better. For EPA use, strict performance criteria are set by EPA. A climate-controlled shelter is typically required. The results are verifiable. Line power is required. The low-cost sensors do not meet the EPA requirements. Open path monitoring is required in some states. FTIR analysis uses a laser system. Continuous measurements across the fence line can be obtained. As a general rule, if data is available for 75% of the time, it is considered continuous. Thus, 45 minutes out of any hour or 18 hours out of any day would satisfy the requirement for continuous ambient monitoring. These are the most expensive. Annual calibration is typical. EPA supports community based monitoring. Both mobile and stationary systems can be deployed. EPA has developed an Air Sensor Toolbox. To get good data, there is a need for QA/QC, as opposed to just a number. In many cases, an alarm system is required. An agency must be notified of any alarm condition within a specified timeframe. Data is kept for at least 2 years. The EPA is continuing to focus on fugitive emissions. EJ considerations are taking on higher importance. Local regulations are increasing. Being involved is getting more important. Comments on proposed regulations are helpful.
– Scott Adamson, Trinity Consultants, Inc.-MSI