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Neffs Canyon Emergency Facilities Improvement
Project Purpose
The Neffs Canyon Emergency Facilities & Flood Mitigation Improvement project is a coordinated effort led by Millcreek, the U.S. Forest Service, Utah Division of Emergency Management (DEM), Salt Lake County Flood Control, including support from the Federal Emergency Management Agency (FEMA) and the Mount Olympus community, to reduce flood risk, improve wildfire response, and enhance public safety in the Neffs Creek area. The project responds to growing hazards on the active alluvial fan, including historic flood and fire events, and focuses on infrastructure improvements and long-term mitigation strategies.
Neffs Creek is located on an active alluvial fan, a fan-shaped area formed by streams and debris flow deposits. These areas are subject to sudden and unpredictable flooding, which has increased over time due to development, erosion, severe storms, and wildfire damage.
In 2013, FEMA and DEM flood officials began a flood assessment study in the Neffs Creek area. From previous studies, they recognized that the existing Flood Insurance Rate Map (FIRM), which indicated Zone A without flood depth information, did not accurately represent the flood hazards associated with the alluvial fan in this area. Therefore, an update to the map was necessary.
A qualified consultant specializing in alluvial fans and floodplain mapping completed the study in 2016. They utilized the latest survey techniques, hydrologic and hydraulic modeling, and mapping data and technology to produce the preliminary work maps. From 2016 to 2019, this information was reviewed and discussed in collaboration with the community, FEMA, DEM, Salt Lake County, and Millcreek officials, ultimately resulting in a new preliminary FIRM.
Millcreek officials accepted the updated map (Figure 1) after additional reviews, public open houses, an appeals period, and a final determination letter in 2020. Consequently, an effective Neffs Creek FIRM was issued on November 19, 2021. This map is now used to accurately determine insurance rates and regulate development within more clearly defined flood hazard zones.
The recent updates to the FIRM and FEMA floodplain designations have significant implications for homeowners and vital infrastructure in the Neffs Creek area. Numerous properties are now categorized within newly established flood zones, necessitating residents to obtain flood insurance, frequently resulting in higher premiums due to increased risk levels. Beyond the financial impact, homeowners face stricter development regulations that complicate or restrict their ability to remodel or rebuild their homes unless such improvements adhere to the current floodplain standards.
One of the significant consequences of the current floodplain designation is its effects on the Unified Fire Authority (UFA) Station 112. Due to its location within the floodplain, the station cannot be upgraded or modernized. Once we address FEMA's flood hazards and implement the necessary improvements, UFA can upgrade Station 112 to meet modern demands and grow potential capabilities for wildland fire response and other emergencies.
Flooding Event in 2019
On May 20, 2019, Mother Nature reminded us of the flooding risks in Millcreek's Mount Olympus neighborhood. After a storm that brought six inches of heavy, wet snow combined with spring rainfall, Neffs Creek overflowed its banks. This led to a debris flow that rerouted water back into the creek's original channel, flooding yards and homes in the neighborhoods below the canyon. While the incident was classified as minor, it served as a warning about the potential dangers highlighted in the updated FEMA floodplain maps. The unpredictability of such debris flows is typical for an active alluvial fan, reminding residents to stay vigilant.
Wildfire Event in 2020
On the morning of September 22, 2020, lightning struck near the Neff's Canyon trailhead, igniting a wildfire that spread over approximately 60 acres of U.S. Forest Service land. The Unified Fire Authority faced challenges in containing and extinguishing the fire, primarily due to the lack of nearby water sources and insufficient parking spaces, which hindered their operational capabilities. After the fire was contained, residents remained on edge due to the risk of debris flow in their community. Heavy snowfall and rainfall threatened to erode the bare areas left by the fire, where vegetation that typically stabilizes the steep slopes had been destroyed.
Parking Lot Reconstruction and Emergency Facilities Improvement
After two significant events, Millcreek and the U.S. Forest Service quickly recognized the limitations of our emergency response operations, especially as we encountered more flooding and wildfires across the West. Currently, the conditions of the parking lot do not include designated parking stalls and do not allow sufficient space for emergency vehicles to respond swiftly to incidents in the area.
Thanks to the efforts of our mayor and council members, who collaborated with our congressional delegation, we secured an $800,000 federal earmark from Congress for the project's first phase, alongside approximately $58,000 in funding from the city.
The first phase will focus on completely reconstructing the existing parking lot by removing the deteriorating asphalt and replacing it with new pavement. This phase will also include the addition of designated parking stalls for emergency vehicles and ADA users. Furthermore, we will construct a helicopter pad and a 16,000-gallon water well to support wildfire response in the surrounding mountains on the east side of the valley, not just in Neffs Canyon.
We recognize that the reconstruction of the parking lot will temporarily decrease the number of available spaces for recreational users. However, the benefits to public safety make this trade-off worthwhile. Once the project is completed, we plan to expand the parking lot to include approximately 60 new spaces.
Construction for the first phase of the Neffs Canyon Emergency Facilities Improvement Project is expected to start in the summer of 2025*. Once the city selects a contractor in collaboration with the Utah Department of Transportation (UDOT), we will provide more details about the construction schedule and share this information with the public.
Debris Basin & Parking Lot Expansion
Following a feasibility study in 2021, conducted in collaboration with the U.S. Forest Service and FEMA, we determined, based on the area's boundaries and topographical constraints, that the most cost-effective and least invasive solution of impacting approximately 3 acres of the Neffs Canyon area is a below-natural-grade debris basin featuring a stormwater outlet pipe. This solution explicitly addresses previous community concerns about the visibility and aesthetics of residential regions throughout Salt Lake Valley.
Millcreek was awarded a Legislative Pre-Disaster Mitigation (L-PDM) grant of $3,027,000 in the fall of 2024. The funding will be used to complete the geotechnical investigation, required environmental documents, and the design phase of the debris basin project. Millcreek has submitted multiple grant applications for FEMA funding, which include environmental reviews and support from the U.S. Forest Service. These applications were submitted in 2021, 2022, and 2023, incorporating feedback received from FEMA.
Following a successful appeal regarding the 2022 application results, Millcreek received a notice of intent to award a $21,051,000 FEMA Flood Mitigation Assistance (FMA) grant. This award is pending and awaits further information requests from FEMA. We will utilize the funding to construct the project, which is estimated to cost $24,078,000.
Currently, any sediment or debris carried downstream is deposited randomly, which creates anxiety for nearby neighborhoods, as evidenced by the active alluvial fan. The proposed debris basin will be situated near the mouth of the canyon to collect debris, sediment, and floodwater from the canyon's catchment area. The design will allow the water to flow through the basin and into a new storm drainpipe. The pipe then transports floodwaters beneath local roads to Wasatch Boulevard and back to Neffs Creek.
The debris basin design is currently in the environmental assessment phase, during which we are working closely with our engineering consultants and the U.S. Forest Service to document any potential environmental impacts associated with the project. In addition to environmental documentation, geotechnical and ecological investigations are being carried out to evaluate the site's conditions. The U.S. Forest Service has not mandated the installation of a barrier or fence surrounding the debris basin, and we will continue to coordinate with them. Throughout the environmental phase, Millcreek is committed to transparency, public engagement with the broader community, not just the Mount Olympus community, and coordination with federal, state, and local partners.
After the debris basin is constructed, the city intends to expand the current parking area by adding approximately 60 additional parking spaces. This expansion aims to decrease the number of recreational users parking in the nearby neighborhoods and provide more room for emergency vehicles and operations.
Project Tentative Schedule*
*Project schedule subject to change due to material, weather, and delay
