State of California • Natural Resources Agency Gavin Newsom, Governor DEPARTMENT OF PARKS AND RECREATION Armando Quintero, Director Acquisition and Real Property Services
2241 Harvard Street, Ste. 200
Sacramento, California 95815
April 27, 2023
Steve Penn
Asset Management Division Chief
Los Angeles County Department of Beaches & Harbors
13837 Fiji Way
Marina Del Rey, CA 90292
RE: Manhattan Beach 28
th Street Stormwater Infiltration Project – Property Coordination
Dear Mr. Penn,
California Department of Parks and Recreation (“State Parks”) has received the attached information about the City of Manhattan Beach’s 28 th Street Storm Drain
Infiltration Project (“Project”) that impacts parcels granted to the County of Los Angeles (“County”) by the State of California, by and through State Parks, in 1995. You have requested an exemption to the conditions subsequent in the attached Grant Deed recorded as document 95-1527005 in the Los Angeles County Recorder’s Office (“Grant Deed”).
State Parks has determined that due to the public benefit of the Project, to the extent the Project would conflict with the conditions subsequent, it will waive the conditions for this Project. State Parks does not consider this to be an “intentional material breach of any condition” as described in the Grant Deed, and therefore is not required to terminate the County’s interest pursuant to Civil Code section 885.010 et seq.
By granting this limited waiver, State Parks does not waive or alter the conditions subsequent for any other project in the future, or otherwise alter or amend State Parks’ rights as stated in the Grant Deed.
If you have any questions or comments, please do not hesitate to contact Bahadur Mann at (916) 804-1207 or [email protected].
Sincerely,
Brian Dewey
Assistant Deputy Director
Facilities and Development
Enclosures
cc: Email to Steve Penn at [email protected]
DocuSign Envelope ID: 72B127B9-CFE9-4690-A054-36FF7DC91521
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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1. Introduction
The City of Manhattan Beach (City) proposes to implement the 28th Street Storm Drain Infiltration Project (Project) to improve water quality at the beach and for the Santa Monica Bay. The primary goal of the Project is to improve water quality locally, on the beach, and in the Santa Monica Bay by:
➢ Reducing bacterial discharges from the storm drain system and ➢ Reducing trash/debris discharge from the storm drain system.
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.
Implementation of a beach infiltration system was identified as the highest priority capital project for the City in the Beach Cities Enhanced Watershed Management Program (EWMP). The EWMP 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 EWMP identified capital improvement projects in the participating jurisdictions to help improve water quality and address applicable pollutants in the Santa Monica Bay, specifically related to bacteria. Figure 1-1 illustrates the Project area, surrounding drainage areas, and the Beach Cities EWMP Group.
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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Figure 1-1 Surrounding Watersheds and Watershed Group
The Project’s drainage area 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 (28th Street Storm Drain). Almost the whole area is within the City of Manhattan Beach, as illustrated in Figure 1-2. The Project captures 60% of the City’s area. The pollutants generated in the drainage area are mitigated by the Project, preventing them from reaching the beach and Santa Monica Bay.
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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Figure 1-2 Project Drainage Area
1.1 Project Conceptual Approach
The City seeks to implement the Project to achieve the water quality goals identified in the Beach Cities EWMP. The Project addresses discharges that drain into the 28th Street Storm Drain and ultimately the Santa Monica Bay. Figure 1-3 illustrates the general concept of the Project. The Project will reduce pollutants sent to downstream water bodies by capturing runoff, such as rainwater and irrigation overspray. Captured runoff will be discharged into an underground system that facilitates infiltration.
Figure 1-3 General Project Concept
Divert urban
runoff from storm
drain
Pretreat runoff
Pump runoff to
an underground
infiltration system
Infiltrate runoff
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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1.2 Benefits
The Project provides multiple benefits, which are summarized below:
➢ Improve water quality locally, on the beach, and in the Santa Monica Bay ▪ Reduce bacteria discharges from drainage system
▪ Reduce discharge of trash/debris from drainage system ➢ Enhance beach conditions
▪ Reduced debris from the upstream drainage system
▪ Reduce the potential for odors related to drainage system ➢ Reduce the potential for beach closures
➢ Create opportunities for education and outreach in local communities ▪ Inform the community of water quality challenges and strategies to improve it ▪ Install permanent educational signage
▪ Engage in dialogue with stakeholders and the public through community meetings ➢ Provide an enhanced environment for marine life
➢ Improve the 26th Street Parking Facility
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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2. Proposed Improvements
The City proposes to use a phased approach to accomplish the goals of the Project. Phase 1 includes improvements at the 26th Street Parking Facility, while Phase 2 includes improvements on the beach.
Figure 2-1 illustrates the Project areas for each phase.
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 Phase 2 implementation. In total, the two phases will ultimately capture runoff from the drainage area illustrated in Figure 1-2.
Figure 2-1 Concept Layout
2.1 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 on Ocean Drive. Opportunities to include a gravity diversion upstream will be evaluated during the design process. The diverted runoff will be pretreated to remove trash and sediment and pumped to a matrix of drywells located in and around the parking facility.
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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The storm drain is a reinforced concrete tunnel that is approximately 40 feet deep near Manhattan Avenue. The diversion along Ocean Drive will reduce the amount of excavation required for the pretreatment unit and pump station.
The intent of Phase I is to maximize capture at this location due to the high infiltration rates and the proximity to the beach outfall. A total of 48 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 2-2 illustrates the preliminary drywell layout at the 26th Street Parking Facility.
Figure 2-2 Phase 1: 26th Street Parking Facility Drywell Concept
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 55 acre-feet of runoff is expected to be captured during a single storm event following implementation of Phase 1. The parking facility will look the same as what is there now with some upgrades (new pavement, new landscape, signage, etc.). Manholes will be in the parking facility above each drywell, like what exists in the street for various utilities, and the rest of the improvements will be underground.
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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2.2 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. Like Phase 1, a diversion, pretreatment system, and pump will be required to capture runoff from the existing storm drain on 28 th Street. It is expected that at least part of the system used for Phase 1 will also be used for Phase 2, which will reduce construction impacts and costs. Runoff will be pumped into a buried infiltration trench on the beach, as is illustrated in Figure 2-3. The 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.
Figure 2-3 Phase 2: Beach Infiltration Concept
Up to 10 acre-feet of runoff is expected to be captured during a single storm event under Phase 2. In total, the two phases of the Project aim to capture up to 63 acre-feet of runoff during a single storm event, or 1-inch of rainfall generated within the 1,500-acre drainage area.
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.
City of Manhattan Beach 28th Street Storm Drain Infiltration Project Project Description
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Figure 2-4 illustrates the improvements of both phases, which is the eventual goal. Specific sizes and locations may move slightly during the design process, while the overall concept will remain the same.
Figure 2-4 Full Project Implementation Concept
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