The Cumberland River Compact worked with KCI Technologies to conduct a feasibility study, as well as design, permit and construction to remove the Richland Creek dam. The impoundment behind the structure provided the adjacent McCabe Golf Course with irrigation water since its original construction. Removal of the outdated structure was required as part of a Tennessee Department of Environment and Conservation (Metro) permit to continue drawing water from the creek.
The practice of dam removal is becoming more common to promote aquatic organism passage, alleviate the risks inherent to dated or compromised structures, and address the ongoing maintenance expenses incurred by dam owners and operators. The Richland Creek project is unique because it is one of only a small number of dam removal projects completed within the state and the only removal within the city of Nashville. It demonstrated that lowhead dam removal projects, with their many constraints, can be completed within a short life cycle, using and adapting techniques that are already established, and with a relatively streamlined permitting process.
The purpose of KCI’s initial feasibility study was to determine if there were any contaminants within the impounded sediments, define the amount and spatial distribution of the impounded sediment, develop a conceptual plan for the removal of the dam, and calculate the probable cost of implementing the removal. After confirming that the removal was feasible, recommendations from the study were used to acquire project funding from The Nature Conservancy and the Metropolitan Government of Nashville & Davidson County. Thereafter, the Compact contracted KCI to complete full design, permitting, construction implementation, and construction oversight for the dam removal.
The primary design constraint revolved around the need for a permanent pool of water adequate for withdrawal in the absence of the dam, while mimicking natural bed form diversity upstream of and through the project area. The regulatory agencies and a local watershed group had voiced their concern over using a traditional boulder vane structure because they perceived the small steps over the boulders as potential barriers to aquatic organism passage. KCI designed a constructed riffle/constrictor that was built using boulders and the native stream sediment that was impounded upstream of the dam. This structure provides a much more natural appearance and mimics a natural riffle, with interspersed refuge that is better suited for organism passage.
One of the other regulatory concerns was working within the flowing channel during construction. Environmental restoration projects on streams of this size would routinely work in the flowing channel, but due to the more sensitive nature of this project and it being in an urban environment, KCI’s solution called for installing an in-channel diversion of 160 feet of 24-inch pipe from a notch in the dam and through the work area. This pipe conveyed approximately 70 percent of the flow through the work area, so that while building the structure, we were working in a reduced volume of water. Once the structure was built, the flume was removed and most of the work in the channel was completed from the new exposed higher parts of the channel bed, out of the active flow of water. The design also incorporated the impounded sediment into the designed structures so that none of the sediment had to be removed from the site.
Open lines of communication are key to expediting any dam removal project to address all concerns and questions, provide information needed to properly inform the public, and build grass roots support.
Adam Spiller, CPESCRegional Practice Leader, Senior Environmental Scientist
Construction was made more complex by the fact that the site was on an active golf course. All materials and equipment had to travel over multiple fairways and golf cart paths on an open golf course. Based on the solid relationship that was built with Metro during this project, KCI arranged for any rock materials brought in and all of the concrete from the dam that was removed to be hauled using Metro trucks and staff. The timing of construction was also a constraint that had to be worked around. There was a strong desire by the Compact and Metro to complete construction as soon as possible following the issuance of the permits. Since this was completed under a design-build delivery, we were able to commence construction one day after receiving the permits, with completion less than a week later.