Geologists probe causes of sliding SW Portland home

‘This is a wake-up call for anyone living in the West Hills,’ says official

By Shasta Kearns Moore

The Southwest Community Connection, Oct 9, 2008, Updated Oct 30, 2009 (18 Reader comments)

Shasta Kearns Moore / Pamplin Media Group

City workers check the stability of Southwest Burlingame Place on Thursday, one day after a house slid down a hillside and smashed into two other houses near Terwilliger Boulevard.

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City engineers and geologists took core samples of the earth beneath Southwest Burlingame Place Thursday as they tried to determine the cause of a massive landslide that put six Southwest Portland homes in jeopardy Wednesday morning.

Experts said that the exact cause of the slide might never be known as the evidence may have tumbled down the hillside with the 2,270-square-foot home that triggered the slide. But, said Scott Burns, professor of geology at Portland State University and a landslide expert, it is unusual for a landslide to occur outside of the rainy season.

“This is a wake-up call for anyone living in the West Hills area to check their slopes,” Burns said.

The geologist added that there are three possible causes for this slide: a break in the water lines, the sewer lines or the sprinkler system. According to tax records, the homeowners did several additions in 2005, including adding a new sprinkler system.

Burns said the city should take a look at the water meter records to see if there was an anomalous use of water or a sharp spike in water use recently. He said it could take a little as a day of leaking from a water main to cause a landslide of this magnitude, though he added that such a large leak would likely be noticeable.

Portland Water Bureau officials said that immediately after the house slide, crews inspected the six-inch water main and service connections on the street. The bureau also brought in a leak detection crew to search for problems. So far, no leaks have been found and the water main on Burlingame Place was not damaged.

However, bureau officials said the water main is on the downhill side of the street, near the exposed slope. With the concrete street, it was difficult to tell where the top of the slide began. Should movement in the slide continue, the water main could be exposed or broken, causing even more damage.

To prevent that, the water bureau will cut valves into the water main on both sides of the slide so the section of water main crossing the slide can be shut off.

On Friday afternoon, the bureau shut off water to 35 homes in the area to make the changes to the water main. The water was shut off for about six hours.

On Thursday, Portland Fire and Rescue turned the scene over to Portland’s Office of Transportation and the Bureau of Development Services.

Click here to see a slideshow of photos.

Heading up the city’s effort to determine the cause of the slide is Doug Morgan, senior engineer at the city of Portland. Morgan said the slide appears to have been localized to the now-destroyed property at 6438 S.W. Burlingame Place.

“Part of what we’re out here today (Thursday, Oct. 9) for is to confirm that,” he said.

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