OLYMPIC NATIONAL PARK — An explosion took down about an additional 6 feet of Glines Canyon Dam last week, and at least one more explosion is expected next month.

Barnard Construction Company Inc. crews blew up a portion of the upper dam on the Elwha River on Thursday.

“We took out some of the concrete from the dam that we couldn’t get to with the barge on the far right-hand side [looking downstream],” said Brian Krohmer, project manager.

“The shoreline is too shallow for the barge, so we had to drill and blast it,” he said.

Glines Canyon Dam is now about 42 feet shorter than its original 210-foot height.

Barnard, a Bozeman, Mont.-based company contracted by Olympic National Park to remove both Glines Canyon Dam and the lower Elwha Dam, drilled holes for the explosives during snowstorms the week of Jan. 15.

Crews used a “man basket” to lower themselves to that section of the dam, Krohmer said.

At least one more explosion will be needed later on that side of the Glines Canyon Dam, Krohmer said.

Before that happens, crews will chisel another 3 feet or so off the top of the dam by midweek and then wait through a 14-day hold period designed to give the river time to erode the sediment in the Lake Mills delta.

Underwater pillars

During the hold period, Barnard crews will install two underwater pillars called “spud piles” on the front corners of the barge.

The piles will brace the barge against the face of the dam.

After the two-week hold period, “we’ll have at least one more blast on that side” of Glines Canyon Dam, Krohmer said, which will remove another 6- to 8-foot section.

“There’s so much rebar in the concrete next to the embankment that it’s difficult to drill,” he added.

“There are still a lot of unknowns there,” Krohmer said.

“There’s a lot of work left to do.”

The dam is expected to be completely demolished in early 2014.

“Glines is obviously going to take longer to complete than the Elwha Dam,” Krohmer said.

The Elwha Dam is expected to be completely removed by early 2013.

Work is much farther along there.

Some 44 feet remains to be removed from the lower dam, which was originally 108 feet tall, so it won’t be long before the visible part of the dam is taken down to the riverbed.

“What you can’t see is the work on the powerhouse,” Krohmer said.

“We’re still removing the substructure of that,” and that work should be finished by midweek, Krohmer said.

The river was diverted to the left channel late last week and will remain there for three to five weeks while crews finish removing the gravity dam.

Then, crews will begin moving some 67,000 cubic yards of dirt and rock that were fill material just upstream of the dam.

The material will be placed on the slope where the powerhouse and penstocks, the large metal pipes that led from the dam to the powerhouse, once stood.

Barnard Construction crews began in September chipping away at the two dams, built without fish ladders nearly a century ago, as part of a $325 million federal project to restore the river’s once-famous salmon runs.

The Elwha Dam was built in 1913 five miles from the mouth of the river, forming the now-disappeared Lake Aldwell, and the Glines Canyon Dam, which formed Lake Mills 14 miles upriver, followed in 1927.