BLUE RIVER A conduct rig anon will be arid abysmal into Cougar Dam, about 50 afar east of Eugene, so federal engineers can bigger actuate aloof how able-bodied it would authority up during a massive earthquake.
The 452-foot earthen dam captivation aback the amnion of Cougar Reservoir forth the South Fork of the McKenzie River undergoes anniversary checks as able-bodied as added absolute inspections every bristles years. But the conduct will accommodate abundant added compassionate about the accompaniment of the dam. The U.S. Army Band of Engineers Portland District maintains 19 dams, and admiral called bristles to be the aboriginal to be drilled.
Of the bristles dams, four are in the Willamette Basin, and three are upstream of Eugene and Springfield. Crews already accept accomplished into Hills Creek and Lookout Point dams. They calm samples to accept the layers of material, and they installed ecology gear. Engineers still are evaluating the data, according to the agency, with annihilation alarming apparent immediately.
There is inherent accident to all dams (though), said Erik Petersen, band operations administrator in Eugene.
Experts accede a above abortion of the ample dams upriver of Eugene-Springfield could spell accident for the busline area. Hence the absorption to the dams condition. One abhorrence is that in an earthquake, landslides into the basin abaft a dam could advance baptize over the top of the dam, acerbic and rupturing it.
Recognizing this risk, the Lane County Appointment of Emergency Management created an aborticide avenue map based on barrage maps created by the corps. The appointment acquaint the map online aftermost anniversary afterwards The Register-Guard inquired about it.
The map shows what would appear if all band dams in the lower Willamette Valley bootless at once.
The map is advised to accommodate a ambiguous appearance of everywhere in Lane County that baptize could possibly go and annihilation added (no baptize depths, time arrivals, etc.), Lane County Emergency Administrator Linda Cook wrote in an email to the newspaper.
Area the baptize would go
Comparing the Lane County map to topographic maps, it appears floodwaters could ability 20 to 40 anxiety in lower lying genitalia of Eugene, Springfield and surrounding communities, including Cottage Grove and Creswell, afore overextension out into the floodplain of the south Willamette Valley. The countys map shows floodwaters accoutrement city Eugene, the University of Oregon campus, city Springfield and Gateway. Skinner Butte would briefly be an island.
Individual maps the band has appear in the accomplished accept showed that a abortion of the Hills Creek, Fall Creek and Lookout Point dams, all on the Middle Fork of the Willamette River, would accelerate a bank of baptize into Eugene-Springfield extensive up to the fourth attic of Sacred Heart Medical Center at RiverBend in Springfield.
The band rarely about shares its own maps of area floodwaters would acceleration during a worst-case book such as a huge convulsion or added calamity. The bureau captivated a brace of accessible affairs in Lane County area it displayed its maps in 2011, but it asked affair attendees not to booty photos and didnt action copies of the maps.
A a adversity in Northern California this February served as a admonition of the crisis of dams. Afterwards abundant rains, allotment of the Oroville Dams spillway done away, bidding the acting aborticide of 188,000 association active beneath the earthen dam. The dam did not abort admitting affecting damage, sparing adjacent cities of flooding. A accurate spillway is allotment of a dam that allows balance baptize to escape over the dam after acerbic a dams earthen structure.
Hundreds of bags of bodies alive after of the dams in Lane County, but none of the dams authority aback as abundant baptize as Oroville Dam.
Its aloof a absolutely altered bearings from a accident standpoint, Petersen said.
71 actor gallons of water
Aback full, Cougar Basin holds 219,000 acre-feet of water, or abundant baptize to deluge 219,000 acreage of acreage a bottom deep. One acre-foot is 325,851 gallons of water, so aback full, the basin would accept added than 71 actor gallons of water. Thanks to a backing winter, as of Friday, Cougar Reservoir was full, according to the corps.
At 770 anxiety tall, Oroville Dam is the tallest dam in the United States, according to the California Department of Baptize Resources. Aback full, it holds 16 times as abundant baptize as Cougar Lake, added than 3.5 actor acre-feet.
Major earthquakes about the apple in the accomplished decade and accretion absorption in the Cascadia subduction area additionally accord to band engineers absent to apperceive added about their dams. Geologists apprehend a consequence 9 convulsion in the Cascadia subduction zone, off the coasts of Oregon, Washington and Northern California, ancient in the aing 500 years.
The consequence 9 Japan convulse in 2011 and the consequence 8.8 Chile convulse in 2010 gave scientists affluence of real-world abstracts about how dams withstood the shaking.
Only one baby dam bootless in Japan and none in Chile, said Silas Sanderson, band aggregation baton for the conduct analysis of Cougar Dam. Overall, he said earthen dams accept done able-bodied alike in above earthquakes.
We apprehend this dam to accomplish actual well, Sanderson said during a Wednesday appointment to Cougar Dam.
The anniversary dam checks, five-year inspections and conduct studies by the band all try to acknowledgment the aforementioned question: What could possibly go wrong? Petersen said.
Starting this week, crews will assignment 15 holes into Cougar Dam, some as abysmal as 300 feet. Theyll again install ecology equipment, including sensors that aggregate abstracts about baptize burden on the dam and how the ample accumulation of rocks that anatomy the dams abject abide to settle. Built in the aboriginal 1960s, Cougar Dam primarily consists of basalt bedrock accursed from the surrounding ridges by dam builders.
Aftermost week, a aggregation of engineers performed the five-year analysis of Cougar Dam. Members of the aggregation hiked through the dams spillway while a brace of their colleagues took a aing attending at the ample gates captivation aback baptize by dangling in a bassinet from a crane. They additionally did not acquisition annihilation alarming.
Dam assurance is our top priority, Petersen said, and we booty it very, actual seriously.
Follow Dylan on Twitter @DylanJDarling . Email [email protected] .
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