DR-4353-CA Final Public Notice

FINAL PUBLIC NOTICE: McKinleyville Community Services District Sewer Highway Crossing Retrofit, Humboldt County, California | HMGP-4353-059-014

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 to the McKinleyville Community Services District (MCSD) to install three new sewer crossings under U.S. Highway 101 (U.S. 101) in Humboldt County, California. The proposed action would mitigate the impacts of seismic activity on the highway and sewer crossings. Pursuant to Executive Order 11988 (Floodplain Management), Executive Order 11990 (Wetlands Management), 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 purpose of the proposed action is to improve the seismic resiliency of U.S. 101 and the U.S. 101 sewer crossings. The proposed action consists of installing three new high-density polyethylene (HDPE) or polyvinyl chloride (PVC), continuously joined pipe, sewer crossings under U.S. 101. The three new HDPE/PVC sewer crossings would be installed parallel to the three existing sewer crossings using horizontal auger boring. The project would include clearing and grubbing of the project sites, temporary access road improvements, and excavation of entry and exit pits at each crossing. The existing lines would be left in place to provide redundancy.

The project area is depicted on the FEMA Flood Insurance Rate Map (FIRM), Map Numbers 06023C0680G, effective date June 21, 2017, and 06023C0690F, effective date November 4, 2016. The proposed action lies within Zone A, an area that has a 1-percent probability of flooding every year and where predicted floodwater elevations have not been established.

The U.S. Fish and Wildlife Service National Wetlands Inventory map shows freshwater forested/shrub wetlands adjacent to the southern project area. A wetland delineation mapped three wetlands in and along the northern project area access road. The construction of the access road would temporarily impact two of the three wetlands, for a total potential impact area of 0.025 acres.

A map of the project area and its location within the floodplain and wetlands is available for public inspection. Parties interested in receiving a copy of the map should contact the FEMA Region 9 Environmental Officer using contact information provided in this notice. 

Two alternatives to the proposed action were considered: Alternative 1: No Action Alternative and Alternative 2: Second Action Alternative. Alternative 1 would leave the three existing sewer highway crossings as is. This Alternative is not recommended as the pipes are over 40 years old, reaching the end of their life expectancy, and are at an increased risk of failure in the event of an earthquake.

Alternative 2 would directly replace the sewer highway crossing with HDPE inside the existing casing. This Alternative is under consideration, but if the existing casings show signs of damage, or if the existing pipe is too damaged to allow easy removal, this alternative would not be considered.

FEMA has determined that the proposed project is the only practicable alternative available; therefore, the proposed action must be located in the floodplain and wetlands. The proposed action would have no significant adverse impact on the floodplain and would benefit the area by reducing the risk of sewer line failure. Therefore, measures to minimize impacts on the floodplain are not necessary. The MCSD 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. 

The 0.025 acres of wetland impacts would be temporary and, if construction best management practices and general conditions and mitigation measures are implemented, permanent impacts on wetlands are not anticipated. Following construction, wetlands would be revegetated and restored to mitigate for the impacts on native vegetation. 

Additional information about FEMA’s proposed action may be requested by writing the FEMA Region 9 Environmental Officer at FEMA, 1111 Broadway, Suite 1200, Oakland, California 94607, or fema-rix-ehp-documents@fema.dhs.gov, or calling (510) 627-7027. All requests should be received no later than 15 days after publication of this notice. No action will be taken before this date.