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County pauses landfill scale-house construction pending CDM Smith floodplain revisions
Summary
Planning director Hal Jensen told commissioners the county should hold construction of a relocated landfill scale house until CDM Smith completes floodplain modeling and FEMA map amendments, citing uncertainty about downstream flow, culvert sizing, and finished-floor elevations.
Hal Jensen, Bannock County planning director, told commissioners on June 9 that CDM Smith provided updated floodplain modeling for the landfill site and that the engineering results favorably reduced earlier FEMA-assumed flow estimates but left unresolved questions about downstream impacts. "They came back with some much smaller numbers which work in our favor," Jensen said, but he and staff remain unsure about culvert sizing, finished-floor elevation decisions and the potential effect on downstream properties.
Jensen recommended holding the scale-house construction until CDM Smith completes its work with FEMA and a possible letter of map revision or amendment is filed. He said engineers estimate four to six months for the floodplain work, and that contractors who bid the project have been patient but that the delay may affect contractors’ schedules and contract timelines. Jensen noted the scale-house drawings include a crawl space that has not yet been analyzed for floodplain flow and that foundation revisions such as switching to slab-on-grade may be necessary depending on finished-floor elevation determinations.
Dylan Evans, landfill director, said CDM Smith’s most recent revised flow estimates had been amended to lower numbers after the county’s storm and flow study. Commissioners instructed staff to coordinate with CDM Smith, keep contractors apprised of timelines, and return with proposed revisions once the floodplain analysis is complete. The commission did not approve construction to proceed while the modeling and FEMA steps are outstanding.
