FLAGSTAFF — The U.S. Department of Homeland Security’s Federal Emergency Management Agency (FEMA) proposes to provide federal financial assistance under the Hazard Mitigation Grant Program (HMGP) to the City of Flagstaff (sub-applicant), located in Coconino County, Arizona, to upgrade an existing concrete box culvert (proposed action). Pursuant to Executive Order 11988 (Floodplain Management), Executive Order 11990 (Protection of Wetlands), and FEMA’s implementing regulations at Title 44 of the Code of Federal Regulations Part 9, FEMA hereby provides interested parties with a notice of its final decision and an explanation of the alternatives that were considered.
The overall purpose of the proposed action is to increase drainage capacity so post-Museum Fire flooding impacts can be mitigated. The new concrete box culvert will be upsized from 400 cubic feet per second (cfs) to 650 cfs. The new culvert dimensions will be 14 feet wide by 4 feet high by 78 feet long. The project will require installation of concrete headwalls, wing walls and transition channels to connect to channel improvements. The concrete headwalls at each end of the box culvert will be 30 feet high by 20 feet wide by 1 foot thick. The wing walls will taper from 30 feet and will be 20 feet wide and 1 foot thick. Ground disturbance will occur immediately upstream to immediately downstream of the existing culvert openings. Disturbance will include demolition of the roadway, existing culvert, connected stormwater infrastructure, and associated utilities (water, sewer, electric, natural gas, communications) and deepening of the channel at the culvert ingress. Total ground disturbance estimate is 0.3 acres. The project area is in a developed, urban environment. An erosion control plan will be generated by the engineer for Best Management Practices to reduce potential environmental impacts. All staging will occur in the road right-of-way on Cedar Avenue between the cross streets of Grand View/N. Main Street and N. Monte Vista Drive. /N. Rose Street.
The project area is depicted on the FEMA Flood Insurance Rate Map (FIRM) Panel, Number 04005C6828G, effective 9/03/2010. The FIRM shows the proposed action lies within Zone Shaded X, Moderate Flood Hazard Area (0.2-percent-annual-chance, 500-year floodplain), and Zone AE, Special Flood Hazard Area (100‐year floodplain, base floodplain). The U.S. Fish and Wildlife Service National Wetlands Inventory Map shows the project is located within riverine wetlands.
Maps of the project area and its location within floodplains and wetlands are available for public inspection. Parties interested in receiving a copy of either map should contact the FEMA Region IX Environmental Officer using contact information provided in this notice.
Two alternatives to the proposed action were considered: Alternative 1: No Action; and Alternative 2: Construct an open channel to accommodate the post-fire 10- and 25-year storm events without flooding. Alternative 1 would result in no action being taken to mitigate flood hazards. This Alternative is not recommended because the Sunnyside neighborhood will continue to be subjected to repeated floods caused by post-fire storm events. Therefore, Alternative 1 is not feasible. Alternative 2 included the construction of an open channel and bridge to accommodate the post-fire 10- and 25-year storm events without flooding. This Alternative is not recommended because it would require condemnation and demolition of dozens of homes and some businesses at a cost of hundreds of millions of dollars, which is cost-prohibitive and undesirable for private property owners. Therefore, Alternative 2 is not feasible. FEMA has determined that the proposed project is the only practicable alternative available; therefore, the proposed action must be taken at this location in order to serve its intended purpose of increasing drainage capacity to mitigate post-Museum Fire flooding impacts to the Sunnyside neighborhood.
The proposed action would have no significant adverse impact on the floodplain, results in an increase to the useful life of a structure or facility and would benefit the area by minimizing the impact of floods on human health, safety, or welfare. The City of Flagstaff has declared that the proposed action conforms to local floodplain standards, and would be responsible for the management, construction, and maintenance of the proposed action.
Additional information about FEMA’s proposed action may be requested by writing the FEMA Region IX Environmental Officer at FEMA, 1111 Broadway, Suite 1200, Oakland, California 94607, or fema-rix-ehp-documents@fema.dhs.gov. All requests should be received no later than 15 days after publication of this notice. No action will be taken before this date.