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Manhattan Beach Awarded $4.9 Million For Flood Mitigation

Oct 04, 2021 09:15AM ● By Mb News Staff
The city of Manhattan Beach has been awarded $4,936,566 from the California Natural Resources Agency to help fund the 28th Street Stormwater Infiltration Project.

The city was one of 26 organizations to receive a segment of the $87.5 million Urban Flood Protection grant program funded by Proposition 68 to protect communities, infrastructure and natural places from worsening flood threats.

“I’m thrilled that the state has taken the lead by providing new funding for the city of Manhattan Beach and communities across California to increase protection of our environment and mitigate flood risks,” said Mayor Hildy Stern in a statement. “This grant aligns with the city’s sustainability initiatives and enables the city to begin the first phase of the project that will enhance beach conditions and provide multiple environmental benefits to reduce water runoff and water pollution.”

The 28th Street Stormwater Infiltration Project is the city's cornerstone project under the Enhanced Watershed Management Program to capture stormwater runoff.

Currently, stormwater outflows at the beach at the terminus of 28th Street. The outfall is submerged during high tide, which can cause backflow and localized flooding during storm events.

The project will divert and capture runoff generated within 60% of the city’s boundaries, and prevent pollutants, such as bacteria, trash, and debris generated in the drainage area from reaching the beach and Santa Monica Bay.

Stormwater Infiltration Project

The 28th Street Storm Drain Infiltration Project would occur in 2 phases –

  • Phase 1 - installation of a matrix of drywells beneath the 26th Street parking facility; and
  • Phase 2 - construction of an infiltration trench at the beach between 25th Street and 28th Street with native dune habitat restoration.
Phase 1 construction is anticipated to begin in early Spring 2023 and be completed in Spring 2024.  Phase 2 will begin upon receiving supplemental funding, once the effectiveness of Phase 1 is determined. Phase 1 should effectively address all trash/debris and bacterial discharge removal as planned.

The total project cost is expected to be approximately $19.1 million. The city is seeking to fund the project primarily through grant funding. The city recently applied for $8.5 million in Proposition 1 Stormwater Funds and will be applying for $10.6 million in Safe Clean Water Program (Measure W) Funds.

According to the city, infiltration should not impact the stability of nearby home foundations because of the depth of the proposed infiltration wells and the observed infiltration rates based on recent tests conducted at the site.

Soil testing performed at the site revealed sandy conditions. The sandy soil helps to facilitate the vertical flow of water with minimal spread during infiltration, which should not affect the local home foundations. 

Additionally, according to the city, the project will be designed to prevent odors from developing. The system facilitates the movement of water through the infiltration system’s components, and the pre-treatment unit would capture any trash, sediment, and debris from the diverted runoff. Everything that the unit captures would be removed regularly as part of routine maintenance.

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