Crews are removing accumulated sediment from two ponds in the Ashland Watershed to keep material from entering Reeder Reservoir, which stores the city's water.
The project began earlier this week and is expected to wrap up on Friday of the coming week, city officials said.
The two ponds being excavated once stored the city's water supply before Hosler Dam was built to form Reeder Reservoir, said city of Ashland Engineering Technician Rob Morris.
"When the dam was built, they conveniently acted as sediment traps," he said.
The ponds lie just upstream from the reservoir on forks of Ashland Creek.
Ashland Creek flows down off of Mount Ashland, which has soil made of easily eroded decomposed granite.
"We're trying to keep up with natural erosive processes," Morris said.
Keeping sediment out of Reeder Reservoir improves the water quality there, city officials said.
Additionally, more sediment in the reservoir would reduce space for holding water, Morris said.
Water flowing into the ponds was diverted so that heavy equipment operators could move down into the ponds to excavate sediment.
Morris said crews hope to excavate sediment from the ponds until they reach the natural ground. However, no one knows for sure how much sediment is in the ponds and how deeply the ground is buried.
The city of Ashland had to get permits from the U.S. Army Corps of Engineers and the U.S. Forest Service, as well as meet Oregon Department of Environmental Quality conditions, in order to carry out the work, Morris said.
Excavated sediment will be trucked to the city's upper granite pit and stored for later use as backfill, city officials said.
In decades past, Ashland sluiced accumulated sediment from Reeder Reservoir downstream via Ashland Creek, but that had negative impacts on water quality, fish and irrigation, according to past reports on sluicing operations.
During the current sediment removal project, roads are closed to protect the public from vehicles that are hauling about 20 to 25 truck-loads of sediment away per day.
The city of Ashland has closed Granite Street at Glenview Drive, a spot across from a swimming reservoir in upper Lithia Park.
Ashland Loop Road, also known as Forest Service Road 2060, is closed above Horn Gap.
The Water Line Trail remains open, but side trails to a water treatment plant road are closed.
"It's important for people to take heed of the construction signs and not wander up into the area," Morris said.
The road used by the trucks is narrow with many blind turns. The fully loaded trucks cannot stop quickly or easily, he said.
Staff reporter Vickie Aldous can be reached at 541-479-8199 or firstname.lastname@example.org.