Huge Oil Spill in Alaska

As much as 798,000 gallons (second only to the Exxon Valdez spill) were spilled recently from a leak in the Alaskan pipeline. The breach was found by someone who heard a 'gurgling noise'.
Operators knew there was a leak 36 hours before they located it. (link)

With all the technology on the Alaskan pipeline, someone walking around sniffing and listening a day and a half after a leak is detected is the best way to find hundreds of thousands of gallons of crude oil?