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Working to save the San Fernando Valley's Last Remaining
16 Acres of UnprotectedOpen Space on the L.A. River
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Feasibility and Water Quality


Community Conservation Solutions is pleased to present these two technical feasibility studies for the Los Angeles RiverNatural Park: a Hydrology, Hydraulic & Water Quality Components Technical Memorandum, produced by Psomas, and a Los Angeles River Regional Public Access Feasibility Analysis, produced by Mia Lehrer and Associates. These studies were funded by the Santa Monica Mountains Conservancy and Save L.A. River Open Space.

The Los Angeles River Natural Park is envisioned as a showcase "Green Solution" river-oriented park that demonstrates how to naturally clean urban runoff and improve water quality, store and reuse runoff, preserve riverfront land and create native habitat, generate solar power, provide regional recreation amenities and establish an L.A. River Regional Public Access Hub and Trailhead for public access to the L.A. River in the San Fernando Valley.

The 16-acre project site is the last remaining unprotected open space along 22 miles of the Los Angeles River in the San Fernando Valley. The L.A. River Natural Park presents a unique opportunity to help improve water quality in the L.A. River through creation of a natural wetlands system, while also providing people from throughout the region with easy, parkingfriendly access to the 51-mile L.A. River Trail and creating a central staging area for both pedestrians and bicyclists. The site's capacity to serve visitors is particularly signifi cant because public access to the L.A. River is very limited elsewhere in the Valley.

The project includes a public parking garage 500 yards downstream and L.A. River trail improvements from the parking garage to Coldwater Canyon. The site links to existing and planned trails and greenways along the Tujunga Wash, Pacoima Wash and Arroyo Seco, as well as to public transit and regional bicycle transportation networks.

The technical studies in this report were directed by Community Conservation Solutions (CCS) and funded by the Santa Monica Mountains Conservancy and Save L.A. River Open Space. The studies were based on the L.A. River Natural Park Vision and Concept Design developed by CCS and BlueGreen Consulting in 2008, with community input and technical assistance from Geosyntec. The feasibility studies provide preliminary analyses and estimated costs of the proposed urban and stormwater runoff management, water quality improvement, regional public access and bicycle hub elements of the Vision and Concept Design.

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Click here to download CCS' L.A. River Natural Park Technical Feasibility Studies Report

Executive Summary

Illustrations

Hydrology, Hydraulics and Water Qality Feasibility Study

L.A. River Regional Public Access Feasibility Study

The L.A. River Natural Park would divert urban runoff from over 200 surrounding acres, providing a treatment volume of 11.4 acre feet and natural treatment of polluted runoff that otherwise fl ows directly to the L.A. River with no treatment of any kind. A "treatment train" would include vegetated swales, subsurface detention and retention, constructed wetlands and associated native habitat to capture and naturally clean all dry weather runoff and fi rst fl ush storm events. Runoff would be stored under the driving range and would be re-used for irrigation, and solar power generated on site would offset normal site electricity usage.

This "Green Solution" approach to improving water quality in the L.A. River through creation of natural wetlands habitat would be integrated with a Los Angeles River Gateway providing bicycle-friendly, regional public access to the L.A. River that would serve people from throughout the entire San Fernando Valley and beyond. The L.A. River Natural Park would provide easily accessible linkages to ample public parking, adjacent public transit and regional bicycle networks, and connects to both the Metro Rail and Metro Bus systems.

Other project benefits would include walking trails, extension of the L.A. River Trail to Coldwater Canyon and preservation of green open space in the densely-developed Valley. Links to public transit and creation of a bicycle-friendly hub and staging area would connect to miles of planned regional bicycle networks. Preservation of the regional tennis components, putting green and driving range would help provide economic support necessary to maintain the park. The project would further the goals of the City of Los Angeles L.A. River Revitalization Master Plan and the Los Angeles City 2010 Bicycle Plan, and would help the City meet state-mandated air quality improvement goals.

water 1

Tributary Area.
The L.A. River Natural park site can capture stormwater and dry weather runoff from over 200 acres of surrounding urban area.


HYDROLOGY, HYDRAULIC &
WATER QUALITY COMPONENTS

Using a "Green Solution" system of natural treatment, the L.A. River Natural Park could divert and treat 11.4 acre-feet (or 3.7 million gallons) of runoff from over 200 acres of its surrounding tributary area. There would be cumulative storage of 11.4 acre-feet, including underground storage, which would provide 8 acre-feet for reuse for irrigation. In addition, during the dry season the project would draw up to 5,000 gallons per day of water from the L.A. River to sustain the wetlands, providing filtration and cleaning before discharging the treated water back into the L.A. River.

Because no storm drains currently exist in the surrounding area between the project site and Moorpark Avenue, diversion of stormwater to the L.A. River Natural Park would help provide needed fl ood control improvements.

Water Quality Improvements
The Green Solution water treatment strategy would consist of a series of urban runoff Best Management Practices (BMPs) that use a system of natural habitats to treat urban runoff on the project site prior to infi ltration, detention and/or release into the Los Angeles River. A wetlands habitat complex would be created to provide open water, marsh, riparian and upland habitats, which would remove sediment, trash, metals, bacteria, oil & grease and organics from runoff flowing through the system. Removal of these pollutants would provide a significant water quality improvement to the L.A. River.

The treatment components consist of the following four stages:

  • Pre-Treatment
  • Structural pre-treatment using separators and vegetated pre-treatment basin to remove trash, debris, sediments, oil and grease.

  • Constructed Wetlands and Underground Storage
  • A series of natural wetland habitats over much of the site to allow dry weather and stormwater runoff to spread out, providing infiltration, absorption, evapotranspiration and storage. A subsurface detention tank under the driving range and an overflow detention/retention basin would provide water storage.

  • Conveyance
  • Vegetated swales promote sedimentation, infi ltration and absorption, and mitigate peak runoff during storm events.

  • Polishing
  • A wet pond provides final treatment and additional habitat before water is discharged to the L.A. River.

Solar Power Potential
The site would be grid-neutral by using on-site solar panels to generate electricity to offset the park's electrical needs. Rooftop panels, free-standing panels on the site and along the L.A. River Trail, and shade-structure panels over on-site parking could provide approximately 37,000 square feet of solar panel coverage. Installation of energy-saving lighting and other energy conservation measures could further reduce electrical demand.


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