United States Forest Service press release
The Owens River Fire has been determined to have been caused by a re-ignition of the Clark Fire. Specifically, fire investigators determined that the Owens River Fire ignited in a box canyon meadow near the Clark Fire from a layer of dense organic material that was smoldering beneath the ground surface. This organic material, in combination with wind patterns in the canyon on September 17, 2016, re-ignited surface vegetation, causing the Owens River Fire.
The Clark Fire was ignited by lightning on August 4, 2016. Fire managers determined that it was fully contained on August 12, 2016, at 2,819 acres and controlled on September 7, 2016. Crews continued to patrol the Clark Fire perimeter until September 17, 2016, when the Owens River Fire ignited. Other Forest Service employees have monitored the fire area from the Bald Mountain Lookout and from other areas to observe post-fire effects of the Clark Fire. All observed a continued decrease in visible smoke associated with the Clark Fire.
The Owens River Fire started on the afternoon of September 17, 2016, and grew quickly under strong winds and dry conditions. The fire remains at 5,443 acres and is 98% contained.
The Forest Service also has determined that the fire suppression efforts for the Clark Fire employed the normal standard of care, including post-containment monitoring and mop-up work when determined to be necessary. Residual sub-surface heat caused by the smoldering organic layer in the area where the Owens River Fire began was not apparent and, therefore, was not detected by any firefighting personnel or other Forest Service employees.
The presence of a subterranean, dense organic layer that could potentially support a fire for long duration is difficult to detect and not a normal occurrence. This is the first such documented occurrence on the Inyo National Forest.