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The city of Danville will shift the hours of operation at its water treatment plant when Duke Energy’s contractor begins removing the coal ash deposit found in the Dan River near Schoolfield Dam.
Duke Energy said Friday that crews are completing site preparation. Dredging could begin late next week.
“We plan to close our water intake valve during the daytime when dredging is taking place,” said Barry Dunkley, Danville Utilities’ division director for water and wastewater treatment. “We will open it up during the evening and overnight when there will be no dredging.”
The deposit of coal ash is located on the north bank of the river, across from Abreu-Grogan Park and the city’s water intake. The deposit spans 350 yards by 20 yards, according to Duke Energy. It measures up to one foot in depth.
Duke Energy’s contractor, Phillips and Jordan of Knoxville, Tenn., will use a more sophisticated dredging technique than simply scooping into the river bottom as is common. The technique it will use will work somewhat like a household vacuum cleaner, with the dredging tool sweeping up the ash, minimally disturbing the river bottom.
Turbidity barriers, also known as silt barriers or silt curtains, will be placed into the river. These special curtains are designed specifically to contain and control the dispersion of silt – or in this case, coal ash – in a water body. They will surround the submerged parts of the dredging tool.
The city has placed two cameras at the park to allow citizens to watch the dredging operation. Go to www.danrivercleanup.org to watch a live stream of the activity.
“We handled the initial spill without any problems, so we are confident that we will be okay during the dredging operation,” Dunkley said. “The decision to change the hours of operation is a matter of exercising an abundance of caution.”
During the dredging operation, the city will collect and test raw water samples at the intake pipe where it draws its water from the river. In addition, the city will collect and test samples of the water after treatment.
Dunkley said the plant’s operating schedule might return to normal hours if the sampling confirms that the dredging is not posing problems.
The coal ash deposit was created after a pipe under the main ash pond at Duke Energy’s shuttered Dan River Steam Station – located 20 miles upstream from Danville – broke on Feb. 2 and spewed 30,000-39,000 tons of coal ash and 24-27 million gallons of water into the river.
Duke Energy estimates 2,500 tons, or 6 to 8 percent of the entire spill, accumulated near the Schoolfield Dam, which is the first dam downstream from the Duke Energy plant. This deposit is the largest that Duke Energy and state and federal agencies have found.
Duke Energy is using Abreu-Grogan Park on Memorial Drive as a base of operation. The city closed the park on April 1 to allow Duke Energy crews and its contractor to begin mobilizing its operations for the ash removal. A security fence has been erected, and a barge and dredging and dewatering equipment have been brought to the site.
During the removal process, the ash will be separated from the water, and the dried muck will be transported in tankers away from Danville for disposal.
Phillips and Jordan used the same separation process for ash that accumulated at the city’s water treatment plant during the filtering process following the spill. The city stored that ash until Duke Energy arranged for its removal.
The removal of ash at the plant began in late March and ended this week, with the removal of a total of 253 tons of dried ash.
Duke Energy expects its work at the park will be finished and the park re-opened to the public in early July. The EPA and other agencies have reviewed the ash removal plan and techniques.
The park features a boat access ramp and a boathouse. The boathouse opens seasonally and allows water sports enthusiasts to rent a canoe, stand-up paddleboard or kayak hourly, daily or for the weekend. The Danville Parks and Recreation Department also uses the park as a river access point when it conducts water recreational classes. The department plans to conduct many of the classes at other points along the river in the city, but the boathouse is now closed and access to the boat ramp is blocked.