From Pacific Gas and Electric:

Pacific Gas and Electric Company (PG&E) will conduct routine low-level helicopter patrols [today] to inspect gas transmission lines for potential threats & future maintenance in rural and remote areas in parts of Humboldt County. PG&E will patrol by air from about 7 a.m. to 4 p.m. on Thursday, October 6, weather permitting. The general areas to be patrolled include Eureka, Fortuna, Arcata and surrounding areas.

A helicopter will fly at approximately 500 feet, depending on the area and if livestock are present. PG&E patrols remote gas lines, which are often located in rural areas, by helicopter as part of its continuing effort to ensure safety and reliability of its gas system. If issues are identified, it is possible helicopters may need to fly at a lower altitude for additional inspections. 

The observer uses a GPS-enabled tablet with GIS mapping data to navigate the pipelines and document excavation and construction activity, or other observations that warrant follow-up. Where appropriate, PG&E ground personnel are then sent to the identified areas to verify that safe practices are being followed. This includes confirming that 811 was called prior to excavating, so underground utility lines could be marked properly.

PG&E regularly conducts aerial patrols of all its gas transmission pipelines in the interest of public safety and system integrity, especially in areas where pipelines have a higher rate of dig-ins.  Damage from digging is a common cause of natural gas pipeline accidents. In 2015, there were more than 1,600 third party dig-ins in PG&E’s service territory alone and the national average is 1 dig-in every 6 minutes.

Dig-ins cause damage to underground gas, electric and telecommunications infrastructure, which is one of the most critical threats to public safety. Striking a gas line during excavation can cause injury, repair costs, fines and inconvenient outages to an entire neighborhood.

PG&E contracts with a helicopter company to fly the PG&E inspectors.