By Brent Gardner-Smith, Aspen Journalism

BASALT – Pitkin County has started building a temporary cofferdam across the Roaring Fork River in Basalt to bypass the waterway, install wave-producing structures in the riverbed, and ultimately secure recreational flow rights.

As of Friday afternoon, vegetation along the riverbank at the emerging whitewater park had been cut and cottonwood trees flagged. And heavy equipment, trailers, and fencing were set up at the end of Emma Road, which is not in Emma but off of the Basalt Avenue roundabout.

This upper Emma Road curves past The Basalt Store, Subway, and Stubbies Sports Bar and Eatery and then ends in a cul-de-sac, a stone’s throw from the river and the project site. From the staging area, heavy equipment will trundle down a construction road and into a soon-to-be exposed riverbed.

“During the six-month-long project this section of river will be temporarily diverted around the construction site through man-made channels and pipes,” states a press release sent Friday afternoon from the Pitkin County Healthy Rivers and Streams Board. “Heavy equipment will be visible in the dry river channel from Two Rivers Road.”

The construction work in the river will take place across from the entrance to the Elk Run subdivision, at a scenic curve on the river that’s hard to ignore from Two Rivers Road.

Work in the river

The county awarded the $770,000 construction contract for the project in June to Diggin’ It River Works of Durango. The Army Corps of Engineers has issued a permit for the project, as have the state and the town of Basalt.

In-channel construction is expected to last until mid-February on a 400-foot section of the river from Fisherman’s Park to just below the entrance to Elk Run.

Work is also to be done in the river to reshape the eddy below the small boat ramp across from Fisherman’s Park, at a spot river-right just below the low Basalt highway bridge.

After the main stem of the Roaring Fork has been dammed and diverted into a bypass pipe, concrete forms will be affixed into the riverbed to create two waves for kayakers and others to play on.

Once the structures are installed, the cofferdam will be removed.

“The temporary diversion is being created by placing a temporary dam in the Roaring Fork,” the county’s press release says. “The dam will divert water out of the main channel [river right facing down the river] down a secondary channel on river left and through a system of large pipes.”

“We will use pumps and a series of settling ponds to keep the main channel dry and to minimize downstream turbidity during construction,” said Jason Carey of River Restoration, the project engineer, according to the county’s release.

Carey, based in Carbondale, also designed the popular surf wave in the Colorado River in West Glenwood Springs.

When the work is done and water flows over the newly installed wave-producing structures, and someone goes out and plays on the waves, Pitkin County’s conditional water right for a “recreational in-channel diversion” will be all but made absolute.

“The whitewater features will be fully functional for the spring runoff of 2017,” the county’s press release stated.

The resulting water right with a decreed date of 2010 may be relatively junior today, but it’s a sizable right designed by the county to protect the upper Roaring Fork from future diversions.

The recreational water right was obtained to draw between 240 and 1,350 cubic feet per second of water down the upper Roaring Fork to a spot slightly above the Fork’s confluence with the Fryingpan River.

The site

The location is a couple of blocks upriver of the 7-Eleven store and Basalt Elementary School. And it’s well above the emerging “river park” off of Midland Avenue in downtown Basalt, which is below the confluence of the Fork and Pan.

The stretch of river to be reworked is hard against a steep bank below Two Rivers Road that has been eroded by the river once before and repaired. Now an access ramp is to take boaters and others down the bank from Two Rivers Road.

The in-channel construction phase of the project does not include “streamside amenities,” as the Pitkin County release says those are still being designed. The county will present updated plans sometime this fall.

And the county’s press release alludes to the challenges of the site.

“For public safety reasons, pedestrians are asked not to approach or view construction from the top of the riverbank along Two Rivers Road,” the release says. “There is very little room along the road for pedestrians, and the river bank is steep with construction activities occurring immediately below.”

As part of the eventual streamside improvements, the town of Basalt is requiring the county to install three crosswalks across upper Two Rivers Road near the whitewater park, each with flashing cautionary signs to warn and stop motorists.

The county also says that during construction “users navigating the river are asked to take out at Fisherman’s Park (or above), or to put on the river below the project site.”

Boating traffic on this section of the Fork in September is usually light. On Friday morning, the Fork above the Pan was flowing at about 250 cfs, too low for most boaters.

“We deliberately chose late September to do this work since it’s low-water season, and we can minimize ecological and recreational impacts,” Carey said, according to the county’s press release.

Editor’s note: Aspen Journalism, the Aspen Daily News, and Coyote Gulch are collaborating on the coverage of water and rivers. The Daily News published this story on Saturday, Sept. 3, 2016.