The design of California’s Rory M. Shaw Wetlands Park provides a holistic, systems-based solution with multiple benefits to the environment, economy, and society. Michael Pollard of Psomas and Christine Wartman of the Los Angeles County Department of Public Works explain.
By Michael Pollard, PE, Psomas and Christine Wartman, Los Angeles County Department of Public Works
In Los Angeles County’s San Fernando Valley, plans are underway to transform the site of what was once a 46-acre, inert material landfill into a multipurpose stormwater management facility. Known as the Rory M. Shaw Wetlands Park, it is one of several projects identified within the Sun Valley Watershed Management Plan that recently received the Institute for Sustainable Infrastructure’s EnvisionTM Platinum Award.
The park is a joint project between the county and city of Los Angeles, as well as the environmental non-profit Tree People, the Council for Watershed Health, and community stakeholders. The project design was a systems-based approach that balanced the intrinsic interactions that exist among the three pillars of sustainability: the environment, the economy, and society. The county selected Psomas as the prime consultant responsible for the overall project design and direction of the consultant team.
The Sun Valley Watershed Management Plan is a multi-benefit project that is a first-of-its-kind venture, geared at managing stormwater for the watershed in order to provide myriad improvements. Solving the local flooding problem was central to the plan, which identified projects – including the wetlands park – that collectively achieve the established watershed goals.
Solving the local flooding problem was central to the Sun Valley watershed management plan, which identified projects that collectively achieve the established watershed goals.
The Sun Valley Watershed is located in the San Fernando Valley, approximately 14 miles northwest of downtown Los Angeles. Measuring approximately 2,800 acres, the watershed is in an urban area consisting of industrial, commercial, and residential uses.
The underlying purpose of the watershed project is cleaning up urban runoff, improving the quality of local receiving waters, and increasing flood protection. The project went further by selecting a former landfill site and repurposing it to feature a green, native-habitat-rich treatment approach for the new wetlands park. Environmental benefits of the project include stormwater capture and pretreatment; stormwater detention; constructed treatment wetlands; and groundwater replenishment.
To provide relief to a community that regularly floods when it rains, runoff will be captured from a 929-acre tributary area in the Sun Valley Watershed and collected in a 21-acre detention basin. Prior to entering the basin, untreated runoff will pass through a hydrodynamic separator, providing removal of oil, grease, and trash.
The detention basin will provide improved flood protection with a storage capability of approximately 400 acre-feet. It will be divided into three separate chambers, which can be isolated for maintenance and cleaning while keeping the pond in operation during periods of low runoff volumes. Further pretreatment is provided by allowing solids to settle out and floatables to be captured within the limits of the basin.
Pretreated stormwater will be pumped through a series of two wetlands, to provide physical removal of pollutants via filtration and settling and biological removal through natural processes. The wetlands will be operated in series under normal conditions and are designed to minimize velocities and provide a plug flow scenario, which improves treatment capacity. Valving and piping will be installed to allow either wetland to be taken out of service while maintaining treatment capabilities. The wetlands will also provide valuable habitat for migrating waterfowl and other wildlife.
The wetlands are designed to remain wet year round, therefore during dry summer months when evapotranspiration and lack of rain reduces or eliminates the runoff to the detention basin, the pumps will recycle the treated water back to the head of the wetlands as a continuous loop. If evaporation drops the levels too low, an emergency pipeline connection from the potable water system provides supplemental water.
Continuous monitoring of water quality at the wetlands will be provided. During wet weather flows, if treated water quality from the wetlands is unacceptable, then valving and piping will allow the water to be pumped to the existing Sun Valley park water treatment system, which will provide further filtration and treatment prior to discharge to a groundwater infiltration system.
From the wetlands, treated stormwater will be pumped to an existing groundwater infiltration system, which will contribute to aquifer recharge thereby providing a future drinking water source.
The suite of projects, located in the densely populated community of Sun Valley, introduces a variety of social and municipal benefits.
Social and Economic Benefits
It is believed the wetlands park project will add important economic and social benefits to the neighboring community as well – including much more than the conversion of a former landfill into a beautiful amenity.
The multi-use park will provide a wide range of recreational features, including new basket-ball courts, tennis courts, a soccer field, fitness stations, and trails, as well as restrooms, picnic tables, an amphitheater, a “tot lot,” and other amenities. The improvements will also serve an educational purpose: a sustainability demonstration site will feature interpretive signage to help visitors understand the benefits to the complex and the ecosystems.
Additionally, a host of short-term and long-term economic benefits will stem from the project – including job creation for the local workforce during construction and ongoing operations; increased local and regional property values; reuse of urban runoff and aquifer recharge, reducing future reliance on imported potable water; and the leveraging of multiple resources through a multi-agency collaborative approach.
The Rory M. Shaw Wetlands Park exemplifies the balanced and systematic consideration of environmental, social, and economic objectives in a sustainable project that will benefit the Sun Valley community for generations to come.
Michael Pollard is the project manager for Psomas on the Rory M. Shaw Wetlands Park project. Christine Wartman is an associate civil engineer with Los Angeles County Department of Public Works and the project manager for the Sun Valley Watershed Multi-Benefit Project.