November 2024 Update

City Council Public Hearing

On May 21, 2024, the City Council held a public hearing for the project. During the hearing, City Council considered and approved a Final Mitigated Negative Declaration prepared for the project (see California Environmental Quality Act information below), the conceptual project engineering design, and a Coastal Development Permit prepared for the project. A copy of the public hearing notice for the project can be found at the following link:

Notice of Public Hearing (May 21, 2024) (PDF)

California Environmental Quality Act (CEQA)

Pursuant to the California Environmental Quality Act, the City of Manhattan Beach circulated a Draft Initial Study/Mitigated Negative Declaration (IS/MND) for public review and comment. The review period began on February 16, 2024 and ended March 18, 2024.

Notice of Intent to Adopt a Mitigated Negative Declaration (PDF)
Draft Initial Study/Mitigated Negative Declaration (PDF)

Responses to the comments received during the public review were incorporated into the final CEQA documents, which are available for review at the links provided below.

Initial Study/Final Mitigated Negative Declaration with Response to Comments (PDF)
Mitigation Monitoring and Reporting Program (PDF)

As noted above, the City Council considered the Final IS/MND, as well as a Mitigation Monitoring and Reporting Program (MMRP) prepared for the project at its May 21, 2024 meeting.

The City of Manhattan Beach previously completed a feasibility study for creating an underground infiltration system to capture stormwater diverted from an existing storm drain located beneath 28th Street. The drainage area for the proposed system covers approximately 60% of the City’s area.   

At the February 15, 2022 City Council  Regular Meeting, the Manhattan Beach City Council approved an agreement with CWE to design an infiltration system for stormwater flows diverted from the existing storm drain on 28th Street. Once constructed, this project will improve water quality at the beach and within Santa Monica Bay. The primary goals of the project are:

• Reduce bacterial discharges from the storm drain system; and
• Reduce trash/debris discharge from the storm drain system.

It is anticipated that the project will generate additional benefits, including:

• Enhancing beach conditions;
• Reducing the potential for beach closures;
• Providing an enhanced environment for marine life;
• Creating educational and outreach opportunities for the local community; and
• Improving the 26th Street Parking Facility.

Construction of a stormwater infiltration system to capture flows from the 28th Street storm drain was identified as the highest priority capital project for the City of Manhattan Beach in the Beach Cities Watershed Management Program (WMP). The WMP was developed in a collaborative effort involving the Cities of Manhattan Beach, Hermosa Beach, Redondo Beach, Torrance, and the Los Angeles County Flood Control District (LACFCD). The WMP identifies capital improvement projects in these participating jurisdictions that will help improve water quality and address applicable sources of bacteria entering the Santa Monica Bay.

Figure 1 illustrates the proposed Project area, surrounding drainage areas, and the jurisdictions of the Beach Cities WMP agencies.

Figure 1 Surrounding Watersheds and Watershed Group (PDF)

The drainage area for the 28^th Street Infiltration Project covers over 1,500 acres. A drainage area is defined as the land area where rain falls and is then captured in a single drainage system (e.g., the 28th Street Storm Drain). Almost the entire drainage area feeding into this Project site is within the City of Manhattan Beach, as illustrated in Figure 2, below.  The project will divert and capture runoff generated within the drainage area, up to the design storm, and prevent pollutants, such as bacteria, trash, and debris generated in the drainage area from reaching the beach and Santa Monica Bay.

Figure 2 Project Drainage Area (PDF)

Project Conceptual Approach
The City seeks to achieve water quality goals identified in the Beach Cities WMP, and implementation of this Project will help that effort. As envisioned, the Project will divert dry weather and wet weather discharges that would otherwise drain into the 28th Street Storm Drain and ultimately into Santa Monica Bay. Figure 3 illustrates the general concept of the Project, whereby captured runoff will be redirected into an underground system that facilitates treatment and infiltration.

Figure 3 General Project Concept (PDF)

 Letters of Support

• 7th Generation Advisors Letter of Support (PDF)
• Manhattan Beach Botanical Garden (PDF)

Proposed Improvements
The City proposes to use a phased approach to accomplish the goals of the Project. Phase 1, which is currently in the early design stages, includes improvements at the 26th Street Parking Facility. Phase 1 will maximize, to the greatest extent practicable, the volume of water diverted and infiltrated. The City will assess improvements made to water quality through the implementation of Phase 1 to determine the need for implementation of a second phase. If necessary, Phase 2 will likely include improvements on the beach. Figure 4 illustrates the proposed Project areas for each phase.

Figure 4 Concept Layout (PDF)

Phase 1
Phase 1 improvements focus on the 26th Street Parking Facility, which is bordered by Manhattan Avenue, Ocean Drive, 27th Street, and 26th Street, as shown in the figure above. Runoff will be diverted from the storm drain on 28th Street through a pipe aligned southeast below Manhattan Avenue. The diverted runoff will be pretreated to remove trash and sediment, and then pumped to a matrix of drywells located within the parking facilities and below the western portion of Bruce’s Beach Park.

The existing storm drain is a reinforced concrete tunnel that is approximately 40 feet deep near Manhattan Avenue. Piping from the intercept location at 28th Street and Manhattan Avenue to the pump vault below Manhattan Avenue south of 27th Street will be bored into place to minimize the amount of open trenching along Manhattan Avenue. 

The intent of Phase I is to maximize captured runoff at this location due to the high infiltration rates and the proximity to the beach outfall. A total of 40 drywells are anticipated to be installed. Captured runoff will fill the drywells, which are six-foot diameter shafts, partially filled with gravel. Water will be able to infiltrate through the soil, improving water quality. Figure 5 illustrates the preliminary drywell layout at the 26th Street Parking Facility

Figure 5 Phase 1: 26th Street Parking Facility Drywell Concept (PDF)

The exact location of each drywell will be determined during final design and will be placed to avoid existing utilities, retaining walls, and other onsite features. The parking lot will be repaved as part of the Project using pervious pavement, to maximize the infiltration on site. Improvements to the landscaping and existing walls of the facility may also be incorporated.

Approximately 67 acre-feet of runoff is expected to be captured during a single storm event following implementation of Phase 1. The parking facility will look very similar to what is there now with some upgrades (new pavement, new landscape, signage, etc.). Manholes will be located throughout the parking facility above each drywell, similar what exists in the street for various utilities. The remaining stormwater capture improvements will be below ground.

Phase 2
Following implementation of Phase 1, the improvements to water quality will be monitored and assessed to determine the need and goals for Phase 2 implementation. If construction of Phase 2 is necessary, a diversion, pretreatment system, and pump will be required to capture runoff from the existing storm drain on 28th Street. Runoff will be pumped into a buried infiltration trench on the beach. An infiltration trench is essentially a pit filled with gravel and perforated pipes wrapped in a filter fabric. The pipes and void space from the gravel allow for water to be stored while infiltration occurs into the sand. Other buried structures that meet the Project objective are also under consideration as alternatives. The system will be buried under the surface and potential future impacts associated with sea level rise have been considered

Following Phase 2 implementation, the surface will be restored to match existing conditions and dune restoration may also be included as part of the Project. Manholes will be visible on the street at the diversion, pretreatment, and pump, while the rest of the infrastructure will be underground.

The following Frequently Asked Questions (FAQs) are related to Project components, impacts, and implementation. The City is available to answer additional questions or expand on the responses provided below. The Introduction and Proposed Improvements and Project Phases sections above include an overview of the 28th Street Storm Drain Infiltration Project (Project) and should be reviewed in advance of this FAQ.

How long will it take to construct?

What is the cost and how will it be paid?

Will the Project generate odors?

Will the Project be impacted by sea level rise?

Additionally, groundwater levels, which are associated with sea levels, will not impact the infiltration structure at the beach during its design life. There will be adequate separation between the infrastructure and groundwater during the design life of the project, based on the medium-high risk aversion projections from the California Coastal Commission Sea Level Rise Policy Guidance (2018).

Will adjacent slopes or existing structures on nearby properties be impacted by construction of the infiltration facilities?

What impacts will I experience during construction?

How loud will construction activities be?

Additionally, the Contractor will monitor noise levels and implement sound blankets and other measures to reduce the noise to meet the Municipal Code. Construction will be permitted Monday through Friday only. No work will be permitted on weekends or holidays. All construction activities will comply with exterior noise standards defined in the Manhattan Beach Municipal Code, Section 5.48.160.

Glossary of Terms
The following terms used in the Introduction, Proposed Improvements and Project Phases and Frequently Asked Questions (FAQ) sections above are defined with additional detail.

Drywell
A drywell is an underground structure that can be used to capture, store, and infiltrate stormwater and urban runoff. Drywells typically include a vertical shaft that is impervious near the ground surface (does not allow water through it) and pervious at the bottom (allows water to infiltrate). The pervious bottom portion is filled with gravel and allows the water to infiltrate downward and through all sides of the well.

The depth of a typical drywell varies from a few feet to over 50 feet deep. It is estimated that the drywells installed in conjunction with this project will be on the order of 30 feet deep.

One benefit of drywells over other types of infiltration structures is that they require a small surface footprint, yet they provide a large surface area for infiltration (all sides of the pervious shaft).

Pervious Pavement
Pervious, or permeable, pavement contains a network of interconnected void spaces which allows water to percolate through the pavement and into the ground below. These types of pavement are typically constructed of asphalt, concrete, or pavers, and are commonly used in parking lots, sidewalks, and bike paths to improve water quality and reduce the quantity of runoff reaching the storm drain system. The images below illustrate the direction of water flow associated with typical pavement and pervious pavement.

Pretreatment System
In developed areas like Manhattan Beach, stormwater and urban runoff (rainfall and irrigation overspray) commonly carry pollutants, sediments, yard waste, trash, and debris to the local drainage system.

If runoff is pumped together with the trash and debris, over time, the trash and debris damage the pump system. If runoff is carried into an infiltration system together with sediment, trash, and debris, over time, the system will clog and lose effectiveness. The Project intends to capture the runoff in the storm drain system, and a pretreatment system would remove trash, debris, and other large particles (such as sediment) from captured runoff before it is carried downstream to the pump station and infiltration systems.

Pretreatment systems can vary, depending on the need. A simple steel grate can be used for some pretreatment systems (as shown in the first image below), or vortex technology can be used (as shown in the second image below).

A vortex-type system is anticipated for this Project. Runoff enters the system, which creates a swirling action that results in the trash, debris, and sediment dropping to a pit at the bottom of the unit, while the pretreated water leaves the system. The accumulated trash and debris is typically removed from the pretreatment system twice yearly during routine maintenance

February 15, 2024 Community Meeting

Date: Thursday, February 15, 2024

Time: 6:00 PM to 8:00 PM

Location: Manhattan Heights Community Center

Interested community members were invited to attend this project overview and CEQA discussion.

28th Street Community Notice Postcard (PDF)

Presentation Slides from Feb 15 2024 Community Meeting (PDF)

October 10, 2023 - 28th St Stormwater Infiltration Project Community Outreach Pop-up Event

Date: Tuesday, October 10, 2023

Time: 4:00 PM to 6:30 PM

Location: 26th Street and Manhattan Avenue

Additional Info: This event was held outdoors at the location of the proposed improvements. Interested community members were invited to stop by any time between 4:00 PM and 6:30 PM to receive information and ask questions about the project.

23-09-29 28th Street Infiltration Postcard (PDF)

Jeff Fijalka, P.E.
Phone: (310) 802-5358
Email: jfijalka@manhattanbeach.gov