MUKILTEO — One big spring storm last month did more than dump two inches of rain in the Harbour Heights Parkway neighborhood.
It triggered a shallow landslide of about 100 feet square. A once-buried 36-inch storm-drain pipe was exposed and broke loose from a manhole.
Storm water rushed down the nearby ravine and into lower Chennault Creek.
The city essentially put “a Band-Aid” on the pipe so that the storm water would again flow through and not further scour the hillside, said Robert McGaughey, director of public works.
No homes or property are endangered, he said.
The city has authorized $200,000 to make more substantive repairs and bring more stability to the area to prevent another landslide, he said.
The project was deemed an emergency to let work begin more quickly and bypass normal contract bidding.
The repairs are scheduled to begin April 20 and are expected to take several weeks.
“There’s a lot of force in the water that goes through it,” McGaughey said. “If we don’t anchor it down, it will buck out of the hill, the joints will separate and water will start eroding the slopes again.”
Even that repair is somewhat temporary, he said. In the next one or two years, permanent repairs will be needed to replace pipe first installed in the 1970s. “It’s at the end of its design life,” he said. “We’ll have to replace the whole system.”
It’s not unusual for landslides near Mukilteo’s bluffs to occur, McGaughey said.
There are records dating back to the early part of the 20th century showing numerous slides occurred prior to development on the bluff, he said.
“It’s the geology that we have here, the hydrology and Mother Nature at work,” McGaughey said.
Meanwhile, the city will keep “a watchful eye” on the site until the repairs are made, he said.
Sharon Salyer: 425-339-3486; salyer@heraldnet.com.
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