J. Gregory Wilson, senior project manager for Consolidated Technologies Inc. (CTI) which designed the original detention pond and channel, said his company will reduce its earlier estimate of $16,700 for the redesign to $11,800 for a cost savings to the city of about $5,000.
Wilson said CTI will absorb the redesign cost, but will still charge the city for the project’s bid phase, construction phase engineering and providing a resident project representative. He said the redesign is mandated by the Tennessee Department of Environment & Conservation (TDEC) whose inspectors have discovered excessive erosion in the channel due to water volume and flow velocity during periods of heavy rainfall.
Questioned by Cleveland Mayor Tom Rowland and Councilman David May as to why the original design did not include erosion-resistant lining, Wilson said conditions were dry 2 1/2 years ago when the pond and channel were developed. Engineers had no way of anticipating the change in water flow amounts now as compared to the much drier period when the channel was designed.
“What we used was appropriate for the conditions that existed at that time,” Wilson said. “We were in a dry period at that time.”
CTI’s proposed fix is to install an armored liner that will hold up to periods of heavy rainfall, continuously flowing water and high velocity. The liner would be a precast concrete block variety.
City Manager Janice Casteel reported she and Public Works Director Tommy Myers are communicating with TDEC officials to determine if a less expensive alternative using “riprap” (a foundation of large stones) could be used as a channel liner. More money could be saved by allowing Public Works crews to install the loose rock material.
Wilson said he is aware of Casteel’s proposal to TDEC, but said he is uncertain if the state agency will authorize this type of resolution.
Asked by Councilman May for a materials cost estimate of the armored liner proposed by CTI, Wilson said bids could range from $13,000 to $15,000, or more. He said it is difficult to forecast materials cost until the redesign is completed on paper.
“It looks expensive to me,” May said.
Wilson concurred project materials could be costly, but he added that all redesign alternatives will be expensive.
Regardless of cost, types of materials or who does the work, the project must be completed, Casteel said.
“We have to close this project,” the city manager stressed. “We have to finish this channel.”
Failure to comply with the TDEC mandate by the next monitoring cycle (probably next spring) could result in a state fine, she warned, as did Jonathan Jobe, city storm water director and project development manager.
Council members voted unanimously to authorize the redesign contract with CTI, but only if TDEC rejects the city’s offer to install the riprap material using its own municipal crews.
Motion was made by Councilman Richard Banks and seconded by Councilwoman Bambi Hines. The Council approved the motion on a 7-0 vote. Others authorizing the contract were Vice Mayor Avery Johnson, Bill Estes, David May, Bill Robertson and George Poe.