The Huntington Library in San Marino California is a private, nonprofit institution that encourages research and promotes education in the arts, humanities and botanical sciences. The library is replacing the current 9,000 square-foot entrance with a new Education and Visitor Center. The $60 million project features 6.5 acres of new gardens and about 43,000 square feet of educational facilities and visitor amenities. The new facility will provide much improved services for more than 550,000 visitors who come to The Huntington each year.
The new buildings are designed to be compatible with the formality, scale and materials of the original 20th-century Beaux- Arts architecture on the property. The landscaping will include gardens highlighting the natural, agricultural and cultural landscape origins of the estate in a Mediterranean plant palette.
Given the dense site and the need to comply with Los Angeles County Standard Urban Storm Water Mitigation Plan (SUSMP), Breen Engineering selected a below ground infiltration system with pretreatment from Contech Engineered Solutions to manage runoff from the site.
Water from the roof and other impervious surfaces is conveyed to two Contech CDS hydrodynamic separators. The CDS is a swirl concentrator hybrid technology that provides continuous deflective separation – a combination of swirl concentration and patented indirect screening – into a unique product. The indirect, self cleaning screening capability of the system allows for 100% removal of floatables and neutrally buoyant material, without binding. Pretreament with a CDS removes trash and solids debris to protect infiltration beds from solids occlusion, protects outlet control structures, and isolates sediment into a single structure to provide easy maintenance.
After treatment, the runoff is directed to a below ground infiltration system made from 310 LF of pipe-arched 71” x 47” 10 GA Aluminized Type II perforated pipe designed to provided 8,731 CF of storage; 5,606 CF from the pipe and 3,125 CF from the stone. The system stores runoff in the pipe and surrounding stone during a storm until it can be slowly released into the surrounding native soil.
Pipe-arch was used instead of large diameter pipe because the site was very flat with limited depth. Using pipe-arch allowed for a larger volume of storage per foot of pipe; maximizing storage and minimizing the depth of the trench.
“Breen Engineering decided to use this particular system at Huntington because it provided a concentrated treatment area for a large project acreage," said Evan Fernandez, Civil Designer at Breen Engineering. “Infiltration being the recommended and preferred method for storm water treatment by MS4 Permittees, it gave us the option to use the CMP system. The CMP, along with the CDS units, allowed the site to maintain the original layout the architects intended, as well as utilizing the existing storm drain system in many areas to create a complex storm drain system that can provide flood protection and treatment control.”
Installation of the stormwater management system was completed in the Fall of 2013. The new Education and Visitor Center is scheduled to open in early 2015.