By Stephen Floyd

(Klamath Falls) Herald and News

A second sinkhole has been reported in the Klamath Falls area this week, this time in a resident’s backyard.

Jason Walls, who lives on the 4400 block of Boardman Avenue, said he noticed what he thought might have been the work of his dog Monday night but on closer inspection Tuesday found his pets had nothing to do with this hole.

“I thought, ‘Well maybe my dog dug that,’” he said. “And then I came out and saw that cavern under there, and I’m like, ‘She didn’t dig that.’”

The sinkhole took a lawn chair with it and sits feet away from Walls’ house and a cottage in the backyard. Walls said he is unsure what caused the sinkhole and that a sewer line may run nearby.

“As this point, I can’t tell whether this is man-made, natural or has to do with my pipes,” he said.

Waiting on the weather

Walls said he plans to call a contractor but understands, after reading reports about a sinkhole that developed at the Oregon Institute of Technology on Tuesday, it may not be possible to fix the problem until the soil dries out.

The OIT sinkhole occurred in the median of a parking lot; no people were hurt, and no property was damaged. No one was injured in Walls’ sinkhole, either, but he said he is worried about the danger it poses to the foundation of his house.

“That’s especially what I’m concerned about,” he said.

Walls also said he has since learned his homeowner’s insurance policy excludes coverage for sinkhole repairs and other erosion-related damage.

“We’re kind of hoping to find out if other people were going through this,” said Walls, who understands other residents have seen sinkholes developing in the area.

Rare occurrence

Stan Strickland, Klamath County public works director, said he is not aware of other sinkholes being reported and that they are generally pretty rare.

“Every once in a while we will have a culvert start to go bad, and we just go and fix those, but I wouldn’t call that a sinkhole,” he said.

Strickland said most erosion problems develop due to a pipe leaking or another form of water infiltration, but he is not aware of any specific geological properties of the Klamath Basin that would lend themselves toward sinkhole creation.

Marshall Gannett, a hydrologist with the U.S. Geological Survey in Portland, agreed most sinkholes in urban areas are the result of infrastructure problems and, though groundwater erosion can also lead to sinkholes, that is not a problem he is aware of locally.

“Occasionally, in areas where you have fairly thin soils over really permeable lava flows, you may see that,” he said.

Gannett also said if groundwater erosion does lead to a sinkhole, the hole usually covers a large area and is not as small as recent sinkhole reports.

Contributing factor

Local engineer Jeremy Morris, of Adkins Consulting Engineering, said recent local weather could contribute to sinkhole formation, as soil that would normally have eroded gradually during previous years is now being eroded all at once by heavy precipitation.

“Groundwater can wash away fines soils on the surface,” he said. “We have a mixture of lake bed soil, which tends to be sandy and silty.”

Morris said he could not comment specifically on how an individual sinkhole developed without examining it, but his firm has been hired to examine the OIT sinkhole later this week.