Lake Tomahawk dam to undergo repair to stop seepage

The design process for plans to repair a Black Mountain dam is underway after town officials voted on May 13 to contract with an engineering firm for the project. 

Seepage observed near the base of the earthen dam on the southern end of Lake Tomahawk, which is classified by the N.C. Dam Safety Program as a Class C, High Hazard Dam, prompted the town to take action.

National firm S&ME, Inc., which operates an office in Arden, was selected to perform the engineering services for the necessary repairs. The town agreed to pay $24,850 for the work.

"It was brought to my attention in early March that there was water trickling from the dam," town manager Josh Harrold said. "I looked at it with the public services director (Jamey Matthews) and we contacted N.C. Dam Safety since that is classified as a high hazard dam."

The dam safety division of the Department of Environmental Quality inspected the area. 

"They had no concerns as to the safety of the dam, but they guided us to have someone with experience working with earthen dams to take a look," Harrold said. "We had S&ME come out and confirmed that it needed to be taken care of before it became a bigger deal later."

Engineers determined that the dam, which was constructed around 1935 by the Civilian Conservation Corps, was displaying signs of seepage "along the downstream face over an approximately 50-foot wide area."

The presence of reedy vegetation indicated that the seepage had been occurring "for some time," the report from the firm stated. No specific point of flow could be located. 

S&ME will perform three tasks for the project, with an optional fourth. A site visit and inspection report will be completed, limited subsurface exploration will be performed and a dam repair design report is to be completed. The firm will secure a pre-construction notification through the U.S. Army Corps of Engineers if necessary. 

The dam has a structural height of 22 feet. The crest is 270 feet long and 15 feet wide. Lake Tomahawk has a surface area of roughly 9.6 acre.

The town removed trees from the dam in 2014 after learning that the roots could impact the structural integrity of the structure. 

"This kind of issue isn't uncommon for earthen dams," Harrold said. "Once they get in there and start doing more of the engineering work, we'll have a better understanding of how it happened and, of course, how to fix it."