CA AB1270

Requires owners or operators of natural gas plants (50+ megawatts generating capacity) to develop, install, operate, and maintain fence-line monitoring systems to measure and record methane concentrations at or adjacent to the facility.

Mandates that air districts and plant operators collect real-time data from monitoring systems and provide that data to the public as quickly as possible in a publicly accessible format.

Requires plant operators to report methane concentration readings exceeding background levels to the appropriate air district, which must then report those readings to Members of the Legislature representing the district.

Places all costs associated with implementing the fence-line monitoring system requirement on the owner or operator of the natural gas plant.

Specifies that no state reimbursement is required under the California Constitution because local agencies have authority to levy fees or assessments sufficient to pay for the mandated program.