Contemporaneous study onsite estimate (SOE – stacked bars) and tracer facility estimate (TFE – square markers) (n = 16). Facilities are divided into three groups and rank ordered in each group by total SOE. Three facilities had mean TFE of zero and are shown in the left group, with upper TFE confidence limit at the facility-specific lower limit of detection (LOD) of the method. Facilities with episodic vented liquid unloading are grouped to right of figure, the largest of which exhibits an emission rate more than two orders of magnitude larger than the highest emitting facility without an unloading. Panel (a) Shows facility-total emissions and 95% confidence limits are indicated by red whiskers for SOE and black whiskers for TFE. TFEs which are statistically similar to SOEs are indicated by green marker fill (15 facilities), while statistically different estimates are indicated by red marker fill (1 facility). Panel (b) Illustrates the fraction of SOE emissions contributed by each SOE category. When unloadings were observed, these sources dominate total facility emission rate. DOI: https://doi.org/10.1525/elementa.266.f1