Flagstaff details Spruce Wash flood fixes, warns wetter-than-normal monsoon; urges resident readiness

Flagstaff city staff told the City Council on May 27 that the city is in the final year of construction on a multi-project effort to reduce post‑fire flood risk in the Spruce Wash watershed and urged residents to prepare ahead of a monsoon season the National Weather Service expects to be warmer and wetter than normal.

The update matters because the Spruce Wash suite of projects — funded by a voter-approved bond and federal grants and paired with upstream county work — is intended to reduce runoff from burned slopes that caused damaging floods in 2021. City engineers said many elements will be in place before the heart of monsoon season, but some work will remain and residents should plan accordingly.

Scott Overton, Public Works director, told the council the city is in “our third and final year of delivery” for Spruce Wash and that staff are coordinating remaining construction, outreach and operational readiness with partner agencies. He said the project is complex and that members of the council would be invited to field tours so they could see what is finished and what remains.

Brian Klamowski, meteorologist in charge at the National Weather Service Flagstaff, gave the seasonal outlook. “We’re leaning toward a monsoon that is gonna be wetter than normal and warmer than normal,” Klamowski said. He said long‑term factors and recent winter dryness point to an increased chance of near‑or‑above normal summer precipitation and noted increased year‑to‑year variability in monsoon rainfall.

Julie Lead, a consulting engineer for Peak Engineering and the city’s Spruce Wash project lead, summarized the engineering approach and design standards. She said the projects are being sized to manage a 2‑inch rainfall spread across 45 minutes — roughly a 25‑year, high‑intensity design storm for these planning analyses — and described key elements now in place: completed roadway modifications on Grandview Drive that route more water in the street instead of homeowners’ yards; an offline detention structure known as the Wedge designed to hold about 15 acre‑feet of runoff temporarily; a new rectangular shotcrete channel and pipe conveyance downstream; and upgrades that route flows through the Killip regional basins and to a West Street wash outlet.

Hydrology modeler Joe Levrich of JE Fuller showed simulations comparing pre‑project flood depths to modeled depths with constructed elements. He said modeled flood depths fall in residential areas while increasing in engineered channels and detention facilities — the expected outcome when conveyance and storage are improved. “It’s a whole lot better than it was,” he said, while cautioning that additional construction yet to be completed will further reduce neighborhood risk.

Lead and city staff outlined funding and partnerships: the voter‑approved local measure set aside $26,000,000 for the city’s portion of Spruce Wash work; combined project costs and leveraged upstream work total roughly $56,000,000; grant partners include FEMA (with state DEMA), the U.S. Army Corps of Engineers and the Forest Service; the Coconino County Flood Control District and USDA‑NRCS contributed roughly $16,000,000 of upstream work; and staff reported more than $8,000,000 in awarded grants that offset local spending.

Operational items and near‑term actions discussed included an accelerated schedule for the Cedar Avenue crossing at Spruce Wash timed with the Fourth/Cedar/West roundabout work, a plan to partially open the Wedge basin by cutting an access plate so some flow will be diverted into temporary detention before the basin’s final gate is installed, and ongoing work to coordinate detours and business outreach during road closures. City staff said they will use targeted door‑hanger outreach, news releases and Nextdoor messages for neighborhoods affected by closures.

Ed Shanks, a city section director working the operational side, reviewed readiness measures: a self‑fill sandbag station at the end of Aztec Street in Thorpe Park, a dedicated phone line for households with access or functional needs and for sandbag delivery and assessments — (928) 213‑2102 — and an increase in channel maintenance and vegetation clearing ahead of monsoon. He said contracted crews and conservation corps workers cleared roughly four miles of open channel and removed large quantities of debris this calendar year.

Daniel Kelly, the city emergency program manager, said the county and city will test sirens in the Grandview and Sunnyside neighborhoods on June 5 (test timing subject to weather or smoke). Brady Henderson, the city’s health and resilience coordinator, described a city flood‑proofing grant that offers up to $7,500 per household for flood gates, sealants and temporary barriers and said staff had distributed roughly 1,500 door hangers in impacted neighborhoods while conducting in‑person outreach.

Council members raised traffic and business concerns tied to the Cedar closure and the Fourth/Cedar/West roundabout work; staff said law enforcement and traffic engineers are monitoring cut‑through behavior, that a clear detour route using collector streets will be signed, and that further mitigation steps are ready to deploy if neighborhood cut‑throughs materialize.

Staff and consultants urged residents to register for alerts, prepare flood plans, consider flood insurance and use the city’s phone number for property assessments. City leaders said they will continue public tours and “meet in the streets” outreach events ahead of July’s likely monsoon activity.