OLYMPIC NATIONAL PARK — The remnants of the last dam on the Elwha River are expected to be blasted out this week.

On Friday, crews with Barnard Construction Inc. of Bozeman, Mont., were continuing to drill holes for explosives in the last few feet of Glines Canyon Dam visible above the river.

That’s the tip of a 30-foot segment, the stub of the once-210-foot dam built in 1927 to form Lake Mills 13 miles from the mouth of the Elwha River west of Port Angeles.

The contractor hopes to blast sometime this week, said Barb Maynes, Olympic National Park spokeswoman. She did not know which days.

Aaron Jenkins, Elwha River dam-removal project superintendent for Barnard, has said that drilling would take seven to 10 days, while two or three days would be needed for blasting.

The explosion will “disintegrate whatever is left of the dam,” Maynes said.

After that, crews will scoop out concrete debris from the river channel, a task that will take between six weeks to two months to complete.

“Most of the concrete debris that used to be the dam is still in the river,” Maynes said.

“A good amount has been removed, but there’s still quite a bit.”

Workers will lift debris out with a crane and let it dry out atop the canyon before it is trucked to the county road facility on Place Road.

There, the concrete will be pulverized and turned into road base.

“The contractor is hoping to be completely done by the end of October,” Maynes said.

Once the dam is gone, the Elwha River will be returned to its wild state, one that historically supported huge salmon populations — the goal of the $325 million Elwha River Restoration begun in September 2011.

Elwha Dam, built more than a century ago 5 miles from the river’s mouth, was taken down by March 2011.

Work on Glines was delayed by repair of the Elwha Water Treatment Plant in October after sediment released from behind the two dams clogged the plant’s intakes, fish windows and, most recently, a raging river.

To work on the dam, crews needed the river to be running no higher than 800 cubic feet per second, Maynes said.

In March, the river was running as high as 10,500 cfs, and flows topped 1,000 cfs for most of July, according to the U.S. Geological Survey.

By the end of July, it began to slow, and by Friday, it was running at 425 cfs, according to USGS data.

Delays have led to an extension of Barnard Construction’s contract, which had an original end date of Sept. 5.

“There will be an extension. It hasn’t been finalized yet,” Maynes said.

Maynes has said a contract extension probably would not push the entire project over the expected cost because other restoration work was less than expected.

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Managing Editor/News Leah Leach can be reached at 360-417-3531 or at leah.leach@peninsuladailynews.com.