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Lyon County adopts South Silver Springs drainage master plan to reduce flood risk
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Summary
The Lyon County Board of County Commissioners voted 5-0 on March 19 to adopt the South Silver Springs Area Drainage Master Plan, a package of measures including homeowner standards, targeted culvert upgrades and a program to raise at-risk structures; staff will pursue FEMA funding where feasible.
Lyon County on March 19 adopted a drainage master plan aimed at reducing flash-flood risks in South Silver Springs, approving the move by a 5-0 vote.
James Springate of Wood Rogers, the county's contracted engineer, told the Board the plan models historic flash floods in the area — including events in 2017, 2020 and a recent April storm — and maps where water ponds behind raised infrastructure such as US 95 and the Union Pacific Railroad. Springate said the study identified more than 100 parcels that would experience at least six inches of interior flooding in a 100-year storm and proposed a multi-part strategy: adopt the ADMP into county review, publish standard details for homeowner measures (cutoff ditches), upgrade specific culverts to preserve emergency access and pursue targeted structure-raising for homes in the flood zone.
"Raising the structures has a BCR of 2.99," Springate said, using the project's benefit‑cost analysis to explain that lifting houses could qualify for FEMA funding; by contrast he said two proposed culvert upgrades have a BCR of about 0.23 and would not qualify for FEMA grants but are recommended to keep emergency corridors usable.
Why it matters: County staff and the consultant emphasized that large-scale drainage works across the whole basin are not cost-effective now and that a modular approach — helping some homeowners raise structures while preparing standard county details for individual property protection — delivers more immediate benefit. Springate said the plan found the majority of existing at-risk structures are manufactured homes and estimated roughly 28 structures as priorities for elevation work; he noted that raising a home typically involves lifting the structure, rebuilding the foundation and reconnecting utilities.
Commissioners asked detailed questions about downstream impacts, maintenance needs (siltation in catch basins), and permitting. Gavin Harrison, Lyon County community development director, clarified that county code requires structure elevation measures in master-plan review (chapter 800 references), which affects newly permitted construction but not older homes already built before those standards went into effect.
The board approved the plan after public comment and commissioner discussion. Commissioner Casanelli moved adoption and Commissioner Hartley seconded; the motion passed 5-0. County staff will now prepare steps to incorporate the ADMP into applicable review processes and to pursue feasible grant opportunities to fund individual-structure elevation and other mitigation measures.
Next steps: Staff will prepare implementation materials for community services, refine the project list for state and FEMA grant applications, and return to the board with specific funding or permitting items as they are developed.
