DR-4344-CA Public Notice 027

FINAL PUBLIC NOTICE: Arroyo Las Positas Restoration Project (Phase 1b-Geotech), Alameda County, California | HMGP 4344-138-035

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 Livermore in Alameda County, California, to complete geologic mapping and soil sampling to support the restoration and regrading of Arroyo Las Positas Creek (proposed action). 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 overall purpose of the proposed action is to reduce flood hazards by removing silt and sediment and grading the banks of Arroyo Las Positas Creek to increase flood conveyance capacity. The project grant was divided into Phase 1 (design) and Phase 2 (construction). Phase 1 was awarded in June 2021 and included a field survey, hydrology/hydraulics, environmental review, permitting, and design. During Phase 1, it was determined by the City of Livermore that subsurface exploration work was also needed to characterize the creek channel and support project design. As such, Phase 1b of the proposed action consists of shallow hand-excavated soil sampling in sections of the creek channel above the waterline and in areas of selected sediment deposits using a handheld shovel. Sampling would be limited to eight samples measuring a maximum of 14-inches in diameter by 8-inches deep.

The project area is depicted on the FEMA Flood Insurance Rate Map (FIRM), Map Number 06001C0329G, effective August 3, 2009. The FIRM shows the proposed action lies within Zone AE, an area that has a 1-percent probability of flooding every year and where predicted floodwater elevations have been established. The project area is also partially within a regulatory floodway. The U.S. Fish and Wildlife Service National Wetlands Inventory Map shows a freshwater emergent wetland within to the project area. The City of Livermore would have an biologist on-site to identify wetlands in the project area to ensure the avoidance of soil sampling within wetlands.

Maps of the project area and its location within the floodplain and potential adjacent freshwater emergent 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: Install Sheet Pile Wall Alternative. Alternative 1 would result in no action being taken to mitigate flood hazards. This Alternative is not recommended because the risk of flood hazards, including damage to property and people, would continue. Alternative 2 included installing sheet pile wall on the south side of the Las Positas Creek channel, raising the access road on the north side of the channel, and dredging sediment from the channel to allow greater capacity for containing flood waters. This Alternative is not recommended because it would require a complex design process, prolonged coordination with agencies at the local, state, and federal levels, extensive environmental mitigations, and would require longer than 36 months to complete construction. Under Alternative 2, there would be large costs related to the temporary relocation of commercial and community facilities and functions, especially to Las Positas Golf Course. 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 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 flood damage. Therefore, measures to minimize impacts on the floodplain are not necessary. The City of Livermore 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.