DAQ Releases STEPP Study Findings to Legislature
The Utah Division of Air Quality (DAQ) has released to the Legislature the results of their Storage Tank Emissions Pilot Project (STEPP). The STEPP study was designed to measure fugitive organic compound emissions from liquid storage tanks in the Uinta Basin. The study was funded primarily through a legislative appropriation designed to help the State better understand emissions leading to high ozone concentrations in the Basin during some wintertime inversion episodes. It was a fact finding effort to try to better understand emissions in the Basin rather than trying to regulate them. STEPP was a joint effort between the Bingham Research Center, TriCounty Health Department and the Utah Division of Air Quality.
In late 2016, the research team used an infrared imaging camera at approximately 400 natural gas and oil well pads in Uintah and Duchesne Counties to detect emissions of hydrocarbon gases to the atmosphere from liquid storage tanks.
Even though these tanks were equipped with emissions controls, infrared-visible emission plumes were detected at 39% of the well pads.
The emissions control devices are designed to capture hydrocarbon gases before they can be emitted to the atmosphere and either convert them by combustion to carbon dioxide or recover them. Most of the observed plumes were emitted before they reached the control device leading to the conclusion that much of the problem lies in a failure to adequately deliver escaping gases to the control devices, however there could be a number of potential causes or sources of the perceived plumes.
It's not yet clear how the study will impact future actions by DAQ or its interpretation or view of the 2014 basin wide emissions inventory conducted on these same sources. A question raised by the study was whether emission factors for the category of "fugitive emissions" should be modified in light of the reported results. The study concludes it is possible that the fugitive emission rate at the wells surveyed was higher than was reported in the 2014 inventory. However, since the IR camera used in this study was not able to provide quantitative information about emissions, the data collected can't in a direct comparison with the inventory. Additional work to quantify fugitive emissions from controlled tanks is needed to determine definitively whether adjustments to the 2014 inventory are needed.
UPA will stay engaged on this and other Uinta Basin air quality related issues as they evolve.
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