and processing equipment to upgrade gas to pipeline quality, including dehydrators, heaters, acid gas removal units, and associated ares and tanks. These two facilities oer a unique perspective as they represent opposite ends of the midstream sector complexity. In both cases, the enhanced surveillance measured all known sources, using a ground team performing optical gas imaging (OGI) and per-source measurements of all detected sources using highow samplers. Additionally, compressor engines on facility E had stack testing and crankcase vent measurements conducted on the measurement day. These two facilities provide compact case studies of issues when using TD methods to estimate emissions for midstream facilities.