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Las Cruces Dam described as high‑hazard but repairable; town outlines mitigation steps
Summary
GIS analyst Tim Korner told council the Las Cruces earthen dam is rated high-hazard and in poor condition mainly due to incomplete documentation. Modeling shows a low‑likelihood but high‑consequence breach scenario; the town has removed vegetation, exercised the slide gate, engaged Rocky Mountain Youth Corps and plans rodent abatement, conduit inspection and an emergency action plan.
Tim Korner, the town’s GIS analyst, presented a technical briefing on the Las Cruces flood-control dam, describing its history, current condition, modeled flood risk and near-term mitigation steps.
Korner said the half‑mile earthen dam, built in 1966 in partnership with federal NRCS and local entities, was designed with a principal outlet (30‑inch concrete conduit) and a siltation tower. He reported a current reservoir capacity he estimates at roughly 337–378 acre‑feet and noted the dam’s formal rating as “high hazard” and condition as “poor,” largely because key design documents were missing from town files. He credited recent archival searches and NRCS support for locating historic design documentation.
Using Dam Safety Bureau modeling, Korner presented a breach simulation under an extreme historical-storm input (a 1966-level precipitation scenario). The model showed rapid inundation—up to about 18 feet in the area between the dam and Kit Carson Road—and an inundation footprint of roughly 1,700 acres, with about 1,180 structures and an estimated nighttime population of roughly 1,932 in the modeled area. He emphasized the scenario’s low probability but high consequences and said results inform evacuation planning and emergency action plans.
Korner outlined mitigation steps already taken and planned: clearing woody vegetation (to remove burrowing‑rodent habitat), lubricating and exercising the slide gate, burning brush piles with Pueblo Natural Resources collaboration, and working with Rocky Mountain Youth Corps crews. Planned next steps include rodent abatement, fence repair, conduit inspection, installation of a monitoring system to track flow rates, producing an operations & maintenance manual and preparing a formal emergency action plan; town staff expect to pursue funding in the next fiscal year.
Councilors asked about arroyo obstructions through town and the possibility of forming a watershed district; Soil & Water and other partners said cooperation and potential statutory mechanisms exist to formalize long‑term stewardship. Korner recommended continued documentation and follow-up with the Dam Safety Bureau to reassess the condition rating as mitigation work and paperwork are completed.
