Beginning December 21, 2015, South Coast AQMD has been conducting mobile survey measurements in and around Porter Ranch to better characterize methane concentration levels and concentration gradients within the community and to support the fixed site methane monitoring efforts. For this purpose, a state-of-the-art methane analyzer (LI-COR 7700) and a Global Positioning System (GPS) were mounted on top of a hybrid vehicle and driven around Porter Ranch and other surrounding areas of the San Fernando Valley.

The LI-COR 7700 is an open-path instrument capable of measuring methane concentrations as low as single parts per billion (ppb) at rates as fast as 40 times per second with high accuracy and precision. This technology has previously been used and validated by the Environmental Defense Fund (EDF), Google Earth Outreach, and Colorado State University (CSU) for mapping methane plumes rising from leaking natural gas pipes below streets: https://www.edf.org/climate/methanemaps

Several routes in and around Porter Ranch and neighboring communities were selected for these surveys. Monitoring was conducted during different times of the day (e.g., morning, afternoon and evening) and under different meteorological conditions. As depicted in the map below, the highest methane concentrations measured thus far (up to 70 part per million [ppm]) were recorded at night in Sesnon Blvd, south of the Aliso Canyon Facility. These results support the placement of the South Coast AQMD fixed monitoring sites and the idea that the fixed South Coast AQMD sites will provide appropriate coverage for long term monitoring in Porter Ranch.

Additional methane maps created using this mobile system can be found here.