2021 Southern California Gas Company Emission Factor Update, Distribution Main & Service Buried Leak Emission Factors and Decision Tree Output Factors for Large Leak Prioritization Screening Process

This report is part of an overall project to develop Company-Specific leak-based emissions factors for buried Distribution system leaks, and a Decision Tree methodology for identifying and differentiating leaks that have high flow leak rates characterized by a leak rate of 10 CFH or greater, for the purpose of prioritizing repairs and reducing natural gas emissions from the distribution system. By reducing the number and duration of higher emitting non-hazardous leaks, actual emissions can be reduced and the approach for identifying and differentiating leaks is expected to result in a more accurate demonstration of emissions reductions. A preliminary analysis of the Decision Tree methodology was published in the August 21, 2020 GTI Report titled “2019 Emission Factor Pilot Study”. The objective of this study is to further refine the Decision Tree methodology for flagging large leaks through additional measurements collected in 2019 and 2020.