PORT ANGELES, Wash. — The largest dam deconstruction effort attempted in North America is on pause for the next few months.
That’s because the first scheduled “fish window” just opened on the Elwha River dam removal project in Olympic National Park.
According to the Elwha Fish Restoration Plan, these fish-window periods have been built into the three-year dam deconstruction project to accommodate migrating and spawning salmon.
This time-lapse video shows the final hour of deconstruction Friday on the Elwha Dam, which is located 5 miles from the mouth of the river west of Port Angeles.
The historic dam removal project began in September and during the past seven weeks construction crews have removed 48 feet of the 108-foot Elwha Dam and 32 feet of the 210-foot Glines Canyon Dam, representatives from Barnard Construction reported.
An estimated 16 million cubic yards of sediment is impounded by Glines Canyon Dam in Lake Mills and an estimated 4 million cubic yards is impounded by Elwha Dam in Lake Aldwell. Combined, there’s about 23 Empire State Buildings’ worth of smaller-grained material built up above the dams.
Breaching these dams has caused that sediment to begin to move downstream, clouding the green waters of the Elwha River.
Pausing the deconstruction process will allow the sediment settle in the river. With the movement of sediment curtailed, migrating salmon will be able to spawn in clearer waters.
Demolition of the Elwha Dam, which was built in 1913, is expected to be finished in early 2013, while the Glines Canyon Dam, which was built in 1927, is scheduled to be demolished by 2014.
Deconstruction will resume in January and continue through April until the next fish window which starts May 1.
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