DR-4344-CA Public Notice 026

FINAL PUBLIC NOTICE: Laguna Creek Restoration and Flood Control Project, Contra Costa County, California | HMGP 4344-605-023

The U.S. Department of Homeland Security’s Federal Emergency Management Agency (FEMA) intends to provide federal financial assistance under the Hazard Mitigation Grant Program to the Town of Moraga (Town) to replace the Laguna Creek culvert with a daylighted creek within the Hacienda de las Flores Park in Contra Costa County, California. The proposed action would mitigate impacts caused by flooding in the area. 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 reduce flood hazards by removing the undersized culvert and constructing a channel that would convey FEMA’s 100-year flood flow without flooding the Pavilion. The existing 242-foot long, 8-foot diameter metal pipe culvert would be removed, the creek would be restored to its natural setting (“daylighted”), a bridge with shoring would be constructed over the daylighted creek, and the banks would be stabilized using natural river rock and boulders. A total of 39 trees would be removed from the riparian area. The existing sewer main line would be relocated, and new precast concrete manholes would be installed along its length. An access road would be constructed for the bridge installation.

The project action area would be in a Special Flood Hazard Area as depicted on the FEMA Flood Insurance Rate Map (FIRM) Number 06013C0407F, effective date June 16, 2009. The FIRM shows that the project area 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 U.S. Fish and Wildlife Service National Wetlands Inventory Map shows Freshwater Forested/Shrub Wetland (0.25 acres) and Riverine habitat (0.27 acres) within the project area for a total potential impact of 0.52 acres.

After completing a storm-damage repair project in 2013, the Town initiated an alternatives analysis with the goal of identifying an approach to permanently reduce flood risk at the project site. The alternatives analyzed included: 1) no build; 2) line the inside of the existing culvert with a smooth lining; 3 and 4) two configurations of a parallel 9-foot reinforced concrete pipe (RCP) culvert; 5) replacing the existing culvert with a larger 14-foot by 12-foot reinforced concrete box (RCB) culvert; 6) installing an upstream detention basin to reduce peak flows; 7) raising the Pavilion floor elevation above the 100-year water surface elevation (WSE) of Laguna Creek; 8) relocating the entire Pavilion structure outside of the 100-year floodplain; 9) constructing a flood wall around the Pavilion; and 10) daylighting and restoring Laguna Creek to contain the 100-year flow. The six alternatives with potential to lower WSEs were analyzed through hydraulic modeling. The results indicated that only two alternatives would actually convey the 100-year event without flooding: 5) replacing the existing culvert with a larger 14-foot by 12-foot RCB culvert, and 10) daylighting and restoring Laguna Creek.

FEMA has determined that the proposed project of daylighting and restoring Laguna Creek to contain the 100-year flow 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 flood damage to the Pavilion and improve visitor safety. Additionally, it would recreate aquatic habitat, improve fish passage, and create California Red-Legged Frog habitat. Therefore, measures to minimize impacts on the floodplain are not necessary. The 9-acre Hacienda de las Flores Park is owned and operated by the Town as both a public park and a private event venue. Because the Town already owns, operates, and maintains the project site, the change in annual maintenance costs resulting from project implementation would be negligible. In fact, implementing the project may decrease annual maintenance costs for the entire park by reducing the area requiring landscaping, ameliorating a source of erosion, and a reducing time spent preparing, monitoring, and repairing damage from flood events, such as placing sandbags and cleaning sediment and debris. Additionally, the goal of the project is to create a self-sustaining channel that requires minimal human intervention and maintenance inputs.

Additional information about FEMA’s proposed action, including maps showing the potential impacts on floodplains and wetlands, may be obtained 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 within 15 days after publication of this notice.