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Lake City hears update on Glen Lake restoration; engineers outline design, permitting and funding status
Summary
Engineers reported that survey, wetlands delineation and geotechnical work for the Glen Lake restoration are complete; conceptual design due in May, grant applications pending and dredge disposal and permits remain unresolved.
At its March 31 meeting, the Lake City Council heard a progress update on the Glen Lake Project from an engineering team working on design and permitting.
Engineer Michael Plank of 4 Waters Engineering said crews have completed survey work, wetlands delineation, soil sampling and geotechnical borings and presented a conceptual grading plan that would increase the lake's storage from about 1,300,000 cubic feet to about 2,000,000 cubic feet, a net gain of roughly 700,000 cubic feet. "This is a progress update," Plank said.
The presentation described subsurface probes and SPT borings used to size dredging and to design repaired structures where the existing retaining wall has failed. Plank said dredging depths will be informed by the probes and estimated "it will probably take 6 inches to a foot below those probes." The team reported a target average depth near 6.5 feet for a healthier lake and said construction could take about six months, depending on weather.
Plank described a proposed outfall structure with removable flashboards to allow the city to lower the lake ahead of extreme storms and an emergency spillway integrated with the retaining wall. Materials under consideration for the repaired dam include sheet pile with a concrete cap or cast-in-place concrete; the final choice will depend on geotechnical recommendations.
On permitting, Plank said a pre-application meeting with the regional water management district went "real well" and that the district preliminarily agreed Glen Lake could be self-mitigating, which would avoid additional wetland mitigation. He also said the U.S. Army Corps of Engineers is expected to find the site non-jurisdictional because the lake is an isolated basin; the team plans to notify the Corps and submit a courtesy application.
The engineers said they are finalizing a stormwater model to show little or no off-site impact, and plan another pre-application meeting with the water management district before advancing to 90% design and permitting. Plank said sampling of dredge material for metals and nutrients is pending guidance from the water management district; disposal to a landfill will depend on those results.
City Manager Rosenthal answered council questions about financing. Rosenthal said initial city funds were used to start design work, that the city has applied for more than $6,000,000 in grants and that the project will not proceed beyond available funds: "By law, we can't do that," he said. Plank and staff said Gateway is coordinating a hazard mitigation grant application that is ‘‘in process.’’
The engineering team said the conceptual design is expected in May, followed by a pre-application meeting and then 90% design and permitting steps. No formal council action or vote was taken during the informational presentation.
Next steps the presenters outlined include completing sampling guidance from the water management district, finalizing the conceptual design in May and scheduling the next pre-application meeting before moving into final design and permitting.
