According to BTB Contributor Jim Branson, a fire burned up part of a hill on the east side of SR-509 Friday afternoon around 3-3:30pm:

North Highline fire crew put out a brush fire beside SR-509, a block or two north of 128th.

Two trucks responded, and the fire seemed to be out when I drove by and took the pictures at 3:55.

Winds were from the northwest at the time, about 9 mph.

The picture is looking east.

The burn pattern seems to fit the scenario of someone pitching a cigarette beside the road, and the flames spread uphill and toward the southeast, pushed by the wind, spreading out up the hill.

A small outbuilding may also have been burned partially.