HMGP-4344-CA Final Public Notice

FINAL PUBLIC NOTICE: Water Reliability Transmission and Distribution Improvement Conn Creek Aerial Crossing (Phase 2), Napa County, California | HMGP 4344-402-101

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 City of Calistoga (sub-applicant), in Napa County, California, to upgrade an underground segment of the existing North Bay Aqueduct (NBA) pipeline that crosses underneath Conn Creek floodway, to an aerial crossing (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 purpose of the proposed action is to improve resiliency of the NBA pipeline from flooding, wildfire, earthquake, scour, and other hazards to ensure reliable water supply for the sub-applicant. The proposed action includes replacement of up to 3,000 linear feet of 12-inch-diameter underground pipeline with new 16-inch-diameter underground pipeline parallel to and along the south side of Silverado Trail. At Conn Creek, the proposed action includes relocation of approximately 100 feet of the existing in‐stream pipeline crossing with a new 16-inch pipeline elevated on the Conn Creek Bridge. The bridge was designed to support the new pipeline and includes engineered pipeline suspension inserts, which would be used to hang the new pipeline. The new pipeline would be located at an elevation above the flood level within the creek.

The project area is depicted on FEMA Flood Insurance Rate Map (FIRM) panel 06055C0385E, effective September 26, 2008. The FIRM shows most of the proposed action lies within an AE/Floodway zone, area of Special Flood Hazard Area (100-year floodplain, base floodplain). A "Regulatory Floodway" means the channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. The U.S. Fish and Wildlife Service National Wetlands Inventory Map shows the project is located within Riverine wetlands.

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 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 Independent Utility Bridge. Alternative 1 would result in no action being taken to mitigate hazards to the pipeline, which would leave the existing pipeline crossing at Conn Creek buried in-place. This Alternative is not recommended because it would result in continued risk for failure from flooding, wildfire, earthquake, scour, and other hazards. Alternative 2 would involve construction of a new independent utility bridge downstream of the Conn Creek Bridge where the pipeline would be installed on engineered pipeline suspension inserts which would be used to hang the new pipeline. This Alternative is not recommended because it would be more costly and would cause additional environmental impacts from new construction. Therefore, the proposed action is the preferred alternative.

FEMA has determined that the proposed project is the only practicable alternative available; therefore, the proposed action must be located in the floodplain. The proposed action would have no significant adverse impact on the floodplain and would benefit the area by reducing the risk of flooding and damage to critical water infrastructure. Minimization of flood risk would be achieved through elevating the new pipeline above the flood level within Conn Creek. The City of Calistoga 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.