Lake Tomahawk drained for repair

Forebay reconstruction project underway

Fred McCormick
The Valley Echo
October 22, 2020

Lake Tomahawk will be empty for approximately two weeks as work begins on reconstruction of the forebay at the northern end of the park. Photo by Fred McCormick

The watery centerpiece of a popular Black Mountain park will be empty for a couple of weeks. 

Lake Tomahawk was drained last week by the town as work to rebuild the forebay at the north end of the park got underway. The project, which will include deepening the stretch of Tomahawk Branch that feeds the lake, the addition of a rock weir and construction of a decorative stone retaining wall, is scheduled to be completed between late November and early December. 

The water was released to allow South Core Environmental to begin the work, according to town manager Josh Harrold, but the lake will not be empty for the duration of construction. 

“We will be able to start refilling the lake in about two weeks,” he said. “Some of the work to address the abutment near the pedestrian bridge will be complete by then and that will allow it to hold water.”

Designed by Wildlands Engineering, the new forebay will replace the previous system that was destroyed by heavy rain in 2018. A forebay is a pool in front of a larger body of water that prevents sediment and other debris from reaching the latter. The failure of the old system allowed sediment to remain suspended in the water and flow directly into the lake. 

“The old forebay set-up was there for a number of years, and it was essentially a large concrete box, a large pipe and an earthen dam,” Harrold said. “The rain pretty much destroyed the earthen dam and rendered the forebay non-functional.”

The $130,000 project is intended to improve water quality in the lake and is one of several steps taken by the town in an effort to remove a local stretch of the Swannanoa River from the N.C. Department of Environmental Quality 303 (d) impaired waters list. 

“When we started looking into this work, I was drawn to a holistic approach to fixing the forebay,” Harrold said. “This is a more natural way of addressing this issue than the previous system.”

Crews will dredge the creek north of the pedestrian bridge and install rock vanes in the bed. The placement of the rocks is intended to separate the water from the sediment and allow silt to drop into a deeper pool, which can be dredged as needed. 

Work on the forebay at Lake Tomahawk will focus primarily on the area north of the pedestrian bridge, where a rock retaining wall will be constructed along a section of Tomahawk Branch, which feeds the lake. Photo by Fred McCormick

Retaining walls will be constructed along the creek, creating access for dredging equipment when the sediment collection basin is full. Trees along the creek were removed to create an access point for sediment management. 

“We need an area where we can access the creek safely and dredge that spot when needed,” Harrold said. “If you don’t reinforce it with walls the heavy dredging equipment can collapse the banks.”

Once completed, the project should accomplish two goals, according to Harrold. 

“It will help stop sediment from easily entering the lake, and that will help us with our ultimate goal of getting this section of the Swannanoa River off the impaired waters list,” he said.