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Conservation director outlines plan to locate and plug leaking overflow structure at county lake
Summary
Chad Humple described a multi-step plan to locate and stop a leak in an old intake structure at a county lake: divers will inspect, an inflatable plug will be tried in the 8-inch line, and engineers may reduce the 30-inch intake to about 15 inches and seal the column with concrete if the test confirms the leak.
Chickasaw County conservation staff told the Board of Supervisors on June 8 that they plan in-water testing and concrete sealing to address a suspected leak in a lake overflow structure.
"We think either that valve has failed or something is sheared off," County Conservation Director Chad Humple said, describing the county's 30-inch intake connected to a 15-inch outflow and a suspected failed 8-inch valve. Humple said the county will attempt to insert an inflatable sewer-type plug in the 8-inch line and then remove the 15-inch plug to see whether that stops the leak.
If the inflatable plug confirms the leak source, engineers intend to reduce the 30-inch intake to match the smaller outflow (possibly a 14- or 15-inch throat), bagrete and pour concrete to seal the bottom of the column, and then fill the rest of the riser with concrete to restore lake-level sealing. Humple said the plan is intended to avoid digging through the dyke, which engineers consider riskier.
Humple reported the county had located invoice paperwork for the original materials and planned to test the structure on or about June 22. He said divers from a regional dive team will assist with inspection and that the county had consulted biologists and the Iowa DNR's lake restoration engineer during planning.
Board members discussed how to place concrete into the existing column without losing material into the outflow and noted the engineers' concerns about working inside old structures; supervisors requested follow-up once the in-water test is complete.
Next steps: perform dive inspection, attempt inflatable-plug test on June 22, then report results and recommended repair method to the board.
