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Published: Wednesday, August 15, 2012, 12:01 a.m.

Sinkhole near Stanwood fixed just in time

  • Dike District 7 near Stanwood recently replaced culverts that collapsed, threatening the whole dike.

    Photo courtesy of Dike District 7

    Dike District 7 near Stanwood recently replaced culverts that collapsed, threatening the whole dike.

STANWOOD -- One rainy morning in March, farmers Tyler Breum and Gary Lund went out to Skagit Bay west of town to see why runoff from the uplands wasn't draining from their fields.
The men were walking on the saltwater dike when suddenly the ground gave way and Lund slipped and fell into a huge sinkhole.
"The dike is usually about 12- to 14-feet wide, but there wasn't more than a foot of soil between the water and the sinkhole," said Breum, who with Lund is a member of Drainage and Diking District 7. "It was scary and we knew we had a serious problem. I'm just glad we found it when we did."
The sinkhole was caused by the collapse of three plastic tide-gate culverts maintained by the dike district. The 80-foot-long culverts not only were blocking drainage of field ditches, but their collapse threatened to allow a catastrophic, high-tide failure of the dike itself, said local flooding expert Max Albert.
Such a breach less than a mile from the city would have endangered Stanwood's old town neighborhoods.
"The levee was failing, and a really big tide coupled with river flooding can breach a weak levee," Albert said. County engineers decided that a replacement of the culverts was the only reliable solution. To minimize the cost and the environmental impact, the work had to be done during daytime, at one of the lowest tides of the year.
The last day to do it was Aug. 3.
"The odds we would get this done in four months were appalling," Albert said.
The U.S. Army Corps of Engineers, Snohomish County's Surface Water Management division, U.S. Rep. Rick Larsen and state Sen. Mary Margaret Haugen helped, making sure the state and federal permits were expedited and most of the funding hurdles were cleared just the day before the work was scheduled.
"We pushed it," Beum said. "We barely met that window of opportunity. It could have been a very bad winter."
The U.S. Geological Survey says that sinkholes are common in other parts of the country where the rock below the land surface can be dissolved by ground water. In the Northwest, however, sinkholes usually appear where natural water-drainage patterns are changed and new water-diversion systems are developed.
No one involved wanted to play Russian roulette with the sea dike, Albert said. High winter tides might have brought saltwater flooding over the streets of west Stanwood. Also, without repair of the tidegates, fall rains might again have backed up the farm ditches and flooded hundreds of acres of unharvested crops, Albert said.
Construction was completed in just two days earlier this month and cost under $80,000, a mix of available funding and some grants, Albert said. Among the contributions was one from the Stillaguamish Clean Water District.
About 20 volunteers and Schmidt Bros. construction workers made the repairs using excavators to dig up the damaged culverts.
"I told people to call the Vatican and tell them we'd witnessed a miracle," Albert said.
The emergency repair should protect the Stanwood community, hundreds of acres of farmland and sensitive commercial shellfish areas from flooding, limiting damage to personal property and the local economy, county officials said.
"We're still hoping for a contribution from the city of Stanwood to help pay off $10,000 in remaining bills being carried by the dike district," Albert said. "And we are talking with the city and county about an interlocal agreement to help the dike district convey the city's stormwater out to the bay."
Gale Fiege: 425-339-3427; gfiege@heraldnet.com.

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