Olympic National Park, City Of Port Angeles Working To Prevent Water Quality Problems

Problems with sediment loads have officials from Olympic National Park and the City of Port Angeles collaborating on ways to ensure the city's water supply isn't harmed from work to remove the Glines Canyon Dam from the Elwha River.

The dam removal is part of the larger endeavor to demolish the Elwha and Glines Canyon dams and restore the Elwha River to its free-flowing past.

Last year problems with sediments arose at the Elwha Water Facilities plant when filters failed to keep sediment, gravel, and woody debris out of the facility.

“Although the sediment has and is behaving as predicted, the water facilities have not,” said Olympic Superintendent Sarah Creachbaum. “The root of the issues is the surface water intake. We are very pleased to report that we have made a number of operational improvements at EWF. In addition, construction of an alternate intake will be completed by November.”

The Park Service plans to resume removal of Glines Canyon Dam this fall. Removal of the 210-foot-high dam began in September 2011 and is scheduled for completion in September 2014. Approximately 50 feet of the dam remains in place. Notching a section of the dam this fall is expected to release less sediment overall than continuing to delay dam removal.

The Park Service has completed a number of measures to improve protection of Port Angeles' water supply, including the use of two powerful mining pumps and other operational improvements to the Elwha Water Facilities. This fall, the Park Service will remove a mound of sediment at the entrance of the side-channel that helps supply water to the city’s Ranney Collector and complete construction of an alternate intake system at EWF through a $3.8 million contract awarded to Macnak Construction of Lakewood, Washington.

The city and National Park Service will continue to work together in good faith to discuss issues related to protecting the City’s water quality and quantity from the adverse impacts of dam removal, a park release said.

“We are committed to continuing to work collaboratively with the city and look forward to successful completion of dam removal,” said Superintendent Creachbaum.

Added Port Angeles City Manager Dan McKeen: “We are continuing to work with the National Park Service and are pleased with the positive cooperation between our two organizations to secure the City’s ability to provide water to the citizens of Port Angeles during the largest dam removal project in our nation’s history.”

The overall Elwha River Restoration project budget remains at $325 million.

Comments

Notching a section of the dam this fall is expected to release less sediment overall than continuing to delay dam removal.

How does that work? It could be said that releasing sediment gradually, or in several stages, could be less disruptive than releasing it all in a shorter time ... but that wouldn't reduce the amount released overall.

Maybe they read this off that 1978 map?
=====

Actually, sediment will be coming over the remains of the Glines dam, once heavy rains begin, whether the dam is notch or lowered this fall, or not. High water in the Elwha river, cutting through the 'perched' sediments in the former Lake Mills channel, will mobilize large amounts of material.

Since sediment already fills this channel to the rim of the dam, increased erosion of the sediment-deposits will send material downstream ... "Ready or not".

Much depends on how the weather unfolds. Rapid onset of heavy rain could take events out of management's hands (and control), while a gentler increase of river-current would give the project some maneuvering room.