Published: Monday, November 2, 2009
County dams sound, federal inspectors say
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Associated Press
Workers use a drill and liquid grout to strengthen the Howard Hanson Dam on Sept. 23 near Ravenswood. Problems with the dam were discovered following record rainfall in January, and workers are racing to strengthen the dam for the winter.
There are dozens of dams in Snohomish County, including one bigger than King County’s Howard Hanson Dam.
The dams here are safe, experts say, and aren’t designed to prevent flooding like the weakened Howard Hanson, the dam that’s threatening the Green River Valley.
Dams upriver here range from 9-footers on tributary creeks to the massive Culmback Dam on the Sultan River.
The 270-feet-tall Culmback, bigger than the Howard Hanson, holds more than 160,000 acre feet of water behind it in Spada Lake. The dam provides electricity and drinking water for Snohomish County PUD and the city of Everett.
“Prior to construction, the project underwent an elaborate design process to ensure it was structurally sound,” said Neil Neroutsos, a PUD spokesman.
Federal regulators inspect the dam each year and have found no problems, he said.
Another large dam — on the Tolt River in King County — flows into the Snohomish River watershed via the Snoqualmie River. Seattle Public Utilities operates the 200-foot-tall structure to manage drinking water and to produce a small amount of electricity.
Dave Remlinger, a French Slough Flood Control District commissioner, blamed Seattle’s management of the Tolt Dam for contributing to last year’s flooding here.
“They knew this event was coming,” Remlinger said. “The Tolt Reservoir dumped it. You put this big surge into the system. That whole bubble follows all the way down river.”
Tom Fox, water resources manager with Seattle Public Utilities, says heavy rainfall caused an automatic discharge.
There are three smaller dams in Snohomish County in need of repair, said Doug Johnson, a spokesman for the state Department of Ecology.
If any of the small dams fail, the likely damage would be flooded basements or some other type of property damage.
A county study of worst-case scenarios found that it would take a shallow 7.5-magnitude earthquake to cause widespread dam failure here.
Noah Haglund: 425-339-3465, nhaglund@heraldnet.com.
The dams here are safe, experts say, and aren’t designed to prevent flooding like the weakened Howard Hanson, the dam that’s threatening the Green River Valley.
Dams upriver here range from 9-footers on tributary creeks to the massive Culmback Dam on the Sultan River.
The 270-feet-tall Culmback, bigger than the Howard Hanson, holds more than 160,000 acre feet of water behind it in Spada Lake. The dam provides electricity and drinking water for Snohomish County PUD and the city of Everett.
“Prior to construction, the project underwent an elaborate design process to ensure it was structurally sound,” said Neil Neroutsos, a PUD spokesman.
Federal regulators inspect the dam each year and have found no problems, he said.
Another large dam — on the Tolt River in King County — flows into the Snohomish River watershed via the Snoqualmie River. Seattle Public Utilities operates the 200-foot-tall structure to manage drinking water and to produce a small amount of electricity.
Dave Remlinger, a French Slough Flood Control District commissioner, blamed Seattle’s management of the Tolt Dam for contributing to last year’s flooding here.
“They knew this event was coming,” Remlinger said. “The Tolt Reservoir dumped it. You put this big surge into the system. That whole bubble follows all the way down river.”
Tom Fox, water resources manager with Seattle Public Utilities, says heavy rainfall caused an automatic discharge.
There are three smaller dams in Snohomish County in need of repair, said Doug Johnson, a spokesman for the state Department of Ecology.
If any of the small dams fail, the likely damage would be flooded basements or some other type of property damage.
A county study of worst-case scenarios found that it would take a shallow 7.5-magnitude earthquake to cause widespread dam failure here.
Noah Haglund: 425-339-3465, nhaglund@heraldnet.com.
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