Lake Mingo considered high hazard
Published 11:06 am Thursday, March 14, 2019
After a state study deemed Lake Mingo high hazard, the city council approved a proposal for GRW Engineers Inc. to conduct an analysis to weigh options on dam repairs.
The analysis will run the city $22,000. $5,000 has already been spent on a contract with GRW for a preliminary study.
City Commissioner Alex Carter asked Nicholasville Engineer Tim Cross if there was a deadline for the study.
“What they want to see from us is activity,” Cross said. “Making progress.”
Mary Beth Robson with GRW Engineers also said at a recent workshop, “The state says if there is a breach in the dam if it fails, a body of water will come down through the cemetery through Main Street and inundate the neighborhood (around) Peelmore and Meadow Lane. Preliminary calculations show that those homes will have a few feet of water in them.”
Robson told the commission the principal spillway discharges through a pipe under the road which comes through the cemetery before coming underneath Main Street and traveling in a straight line to the main tributary at town branch. The dam was originally built as a farm pond and was upgraded throughout the years. The dam has also been raised once in 1981 following an inspection from core engineers.
“When state division of water did their (inspection), we wanted to make sure they were not making faulty information,” Robson said. “We tested the 28-inch rainfall and we have determined that it is likely it is a high hazard dam based on the information we have.”
Cross said the dam is considered high hazard based on the failure at the emergency spillway. It is a matter of function of depth and velocity, Cross said, and if a foot of water is in the area and moving at 10 feet per second it could be disastrous.
“It has the potential to wash a home off its foundation or wash somebody into a stream,” Cross said. “It is not just depth it is depth and flow.”
Cross said there are three options. One is to ignore it, which Cross said is the worst option because of liability. The second is to make Lake Mingo a dry basin. The third is to conduct a full analysis for dam repairs.
“(It) must be upgraded to meet minimal hydraulics required set forth,” Cross said. “If you’ve seen that rainfall event, 28.2 inches in a 6-hour storm, that is hurricane type rainfall. We went into contract with GRW (and) we felt we could pretty easily prove the state wrong. And we haven’t yet.”
Nicholasville Mayor Peter Sutherland asked Cross what it would take to repair the dam.
“A lot of people really use that lake to fish and walk around,” Sutherland said.
Cross said it would require draining the lake, opening the dam, removing the spillway and replacing the pipe. Much like what was recently done at Lake of the Orchard.
“We can’t make emergency spillway big enough there is not enough storage to hold that water,” Cross said.