The creek running down American Fork Canyon
has become clogged with muck after an upstream reservoir was
drained as part of dam rehabilitation project.
The fine-grained sediments turned water black below Tibble
Fork Dam, leaving a trail of dead trout and potentially
degrading habitat for all sorts of aquatic life, according
"It would be a surprise if anything could live through this.
It is suffocating the fish it is so thick," said Brian
Wimmer, president of a Utah County chapter of Trout
Unlimited. "There is 4 inches of this disgusting mud 3 feet
above the high water mark. It will take a major flush to
bring the life back to this river.
Wimmer and colleague Grant Bench spent Monday afternoon in
the canyon and observed dead fish as far downstream as
Swinging Bridge, near the mouth of the canyon. They
encountered places in Tibble Fork with sediments up to 2
feet deep in places where normally water runs clear to a
depth of 3 feet.
The incident could wind up dealing a ecological blow to
American Fork Canyon, a popular recreation destination,
especially among anglers, in the Uinta-Wasatch-Cache
National Forest east of Pleasant Grove.
On Monday, officials were scrambling for answers and the
project contractor agreed to cease releases from the dam.
Biologists from the Utah Division of Wildlife Resources (DWR)
and the U.S. Forest Service examined the creek and muddy
remains of the drained Tibble Fork Reservoir. They will
return Tuesday with electroshocking equipment to determine
whether fish have survived downstream, according to DWR
fisheries biologist Mike Slater. The stream was so murky
Monday that it was not possible to detect any fish activity,
although plenty of living macro-invertebrates could be found
"The majority of the dead fish are coming from the
reservoir. They are getting pushed down the system," Slater
said. "We haven't suffocated everything downstream. Fish end
up being more resilient than we give them credit for. That's
my hope here."
Earlier this summer, the federal Natural Resources
Conservation Service (NRCS) commenced a $7.3 million project
to rehabilitate the 50-year-old dam. The goal is to
strengthen the earthen structure dam, which is at risk of
failure, and raise the reservoir by 9 feet. DWR normally
stocks Tibble Fork with 14,000 rainbow trout each year, but
this year the reservoir will be closed to fishing and other
uses while dam reconstruction is completed.
The reservoir stores irrigation water for the North Utah
County Water Conservancy District. Over the years, sediment
piling up behind the dam has reduced the 10-acre reservoir's
capacity by more than 50 acre-feet, indicating that the
lakebed is buried to an average depth of 5 feet.
This weekend, crews began draining the reservoir and NRCS
posted a notice that elevated levels of sediment would be
apparent downstream to Timpanogos Cave National Monument.
"Best management practices are installed as much as
practical to help minimize sediment transport in the stream
flow below the dam," the notice said. "All discharges are in
accordance with the environmental analysis, permits and
laws." An agency spokesman could not be reach for comment
Slater believes the draining discharged far more sediment
than NRCS anticipated.
Once the reservoir emptied, the stream carved a path through
sediment accumulated in the lakebed and pushed the material
down the canyon through the river channel, he said. The
dam-project contractor closed the gate in an effort to build
water back up in the reservoir with the idea of releasing
the water in pulses.
"They are doing everything they can to minimize the
sediments. The fish can handle it in pulses," Slater said.
Brian Maffly covers public lands for The Salt
Lake Tribune. Maffly can be reached at email@example.com or