Carson City leverages private development to remove wastewater plant from 100-year floodplain

Carson City leverages private development to remove wastewater plant from 100-year floodplainA developer-funded flood mitigation project will excavate 56,000 cubic yards of soil on city-owned land, protecting critical utility infrastructure and creating wetland habitat at no cost to ratepayers.

CC Nevada, LLC will construct flood storage on municipal property to offset floodplain fill for its Lompa Ranch East housing development.

The downstream excavation will lower water surface elevations, removing the city's wastewater treatment plant from the 100-year and 500-year floodplains.

The developer assumes all construction costs and will provide a $71,177 endowment to fund 40 years of ongoing site maintenance.

The Carson City Board of Supervisors approved a Flood Volume Mitigation Improvement Agreement on July 16 that will utilize private development funds to protect critical municipal water infrastructure from flooding. Under the agreement, developer CC Nevada, LLC will excavate 56,000 cubic yards of material from the city's Wastewater Treatment Plant property and the adjacent Moffat Open Space. The excavation will create flood storage to offset floodplain fill required for the developer's Lompa Ranch East multi-family housing project. According to Public Works Director Darren Schulz, the city had long considered either building a flood wall or excavating storage to protect the wastewater facility from inundation, but high costs and competing priorities deferred the work. "This is an opportunity to take it off of our list," Schulz said, noting that the partnership allows the city to achieve its flood protection goals without spending taxpayer dollars. Amy Majznikowski, a hydrologist with Terra Phase Engineering representing the developer, stated that hydraulic modeling shows the downstream excavation will significantly reduce water surface elevations. The project utilizes natural spillways to direct high-flow storm events into the restoration areas before returning water to Eagle Valley Creek. Majznikowski noted the project will formally remove the wastewater treatment plant and the city's Emergency Operations Center from both the 100-year and 500-year floodplains once a Letter of Map Revision (LOMR) is approved by FEMA. Beyond flood protection, Open Space Manager Lyndsey Boyer highlighted that the project will restore the creek's ecological function by reconnecting it to the floodplain and establishing native riparian vegetation to replace noxious weeds. In addition to covering all design, permitting, and construction costs, the developer will provide the city with a $71,177 financial endowment. Ken Krater of Krater Consulting Group noted the endowment was calculated based on a 40-year life-cycle cost analysis to fund future municipal maintenance, including post-storm silt removal and weed abatement. The board approved the agreement in a 4-1 vote, with Supervisor Maurice White dissenting over concerns regarding the use of open space property for developer mitigation.