Developers are banking big on 5,000 acres in Orange County, Calif., that used to belong to the U.S. Marine Corps. The years since the El Toro Air Station closed in 1999 have been dedicated to removing hazardous waste that accumulated since the base’s opening in 1942. Plans to turn the land into thousands of homes surrounding a huge arts and sports hub, called Orange County Great Park, were well under way by the time EPA removed the site from its Superfund list in early 2014.
Portola Center is the last of five residential communities that are part of this massive transformation. Glenn Ranch Road divides the 195-acre development in Lake Forest, Calif., into north and south sections. The 95.5-acre Portola Center South community features single-family homes and affordable housing; 10,000 square feet of ground-floor commercial space; and five acres of public park and trails.
The project’s magnitude made managing stormwater runoff a major challenge for owner LS-OC Portola LLC. The solution is one of Southern California’s largest and deepest stormwater-management systems.
Developed by Oldcastle Precast, Storm Capture is a scalable system for detention, retention, treatment, and/or harvesting. Its basic component is a precast concrete box strong enough to withstand traffic with as little as 6 inches of cover (designed for American Association of State Highway and Transportation Officials HS-20-44 for full truck load plus impact) without concrete footings. Catch basins, inlets, pipes, manholes, and box culverts can be added to solve virtually any control issue, whether it’s slowing runoff to prevent drain overloading, recharging groundwater for low-impact development, or an entire stormwater harvesting system. The pre-engineered components allow for site-specific configurations while providing significant storage capacity in a small footprint.
With Portola Center South, general contractor Landsea Holding Corp. and engineer Hunsaker & Associates had to figure out how to cost-effectively, safely, and reliably manage runoff from almost 100 acres of impervious area. Called in to consult, Oldcastle Precast helped devise a 10-basin underground detention system that stores 820,886 cubic feet (18.85 acre-feet) of water.
The first to be installed, Basin No. 5 stores 198,152 cubic feet (4.55 acre-feet) and has an internal orifice discharging to a downstream bio-filtration system. The boxes have an inside height of 14 feet and are designed to withstand 16 feet of backfill. The system is fully encased with a geotextile and impermeable liner. Along with the basins, Oldcastle plants in Southern California manufactured and delivered large bio-filtration units to address water quality requirements.
“Unlike companies that only design systems and use third-party manufacturing, we maintain control and ensure quality throughout the design, manufacturing, installation, and life of the project,” says Shelby Hull, director of Oldcastle Stormwater Solutions for the southwest. “Our stormwater experts, design engineers, and national manufacturing capabilities develop custom solutions to meet specific regulatory needs.”
