“With a roadway project like this, the surface area to do bioretention is hard to find. The underground Silva Cells were the perfect solution.”
Armorlite Drive in San Marcos, California, underwent renovation in 2016-17 to create a more holistic street setting and improve its industrial backdrop from transport roads. The DeepRoot Silva Cell assisted in bringing this ambitious project to fruition, complying with the Regional Water Quality Control Board storm drain requirements and by providing adequate soil volume and managing the street’s stormwater — including capacity for up to a 100-year rain event.
Number of Silva Cells: 440 (2X)
Amount of Shared Soil Volume: 8,800 ft3
Number of Trees and Type: 52 live oak, Brisbane box, and crape myrtle trees
Type of Project: Integrated trees stormwater
Project Contractor: Tri-Group Construction
Installation Date of Silva Cells: March 2016
Project Timeline: 2016-2017
San Marcos, California, is a vibrant city located forty miles north of San Diego. The growing community is home to Palomar College and California State University. San Marcos also has a history of green infrastructure and a working relationship with DeepRoot: indeed, the North City East downtown neighborhood saw success with their 1,200 Silva Cell installation project in 2016.
Armorlite Drive in San Marcos, situated between I-78 and Palomar College’s light rail stop, is home to a community of apartment complexes, restaurants, public parks, and pedestrian-friendly paths — an area marked for an infrastructure upgrade in 2015 by the Armorlite Drive Smart Growth Improvement Project.
Designers at KTU + A Planning + Landscape Architecture and Michael Baker International (previously RBF Consulting, Carlsbad) set a goal of creating a more natural street setting and differentiating the neighborhood from its industrial backdrop and transport roads and rails. The street included 52 trees for its community members along with an 8-foot-wide bike lane and 10-foot-wide sidewalks for outdoor cafes and restaurants.
DeepRoot provided Armorlite Drive with 440 2x Silva Cells — 8,800 cubic feet of soil was installed under the pavement to support more than 50 new trees and manage the street’s stormwater.
The designers specified DeepRoot Silva Cells in order to support the weight of the sidewalk while also providing adequate soil volume and managing stormwater beneath the paving for the live oak, Brisbane box, and crape myrtle trees. The Silva Cells also minimized infrastructure and maintenance costs by eliminating the need for expensive filtration devices.
Likewise, the Silva Cells allowed runoff to filter through the soil, where it can be cleaned and cooled before entering the city’s storm sewer or nearby San Marcos Creek. The design was made to be able to handle a 100-year rain event (121mm per 24 hours) and manage water quality, peak, and volume.
“We used Silva Cells as a stormwater quality BMP (best management practices) in order to comply with the Regional Water Quality Control Board storm drain requirements and provide pollutant-control and flow-control functions,” observed David Wiener of RBF Consulting. “The best way to achieve this is through biofiltration, which is usually done with a bioretention area at the ground surface.
He went on to say: “We considered permeable pavement, bioretention areas, and proprietary filtration devices. Silva Cells made the most sense because they provide all the stormwater benefits that we need, don’t take up surface area, and are great for the proposed trees.”
The once nondescript Armorlite Drive, lined by warehouses and empty lots, has undergone a complete transformation and is now more livable, green, and pedestrian friendly. The trees’ flourishing health will continue in the coming years and decades, while also providing the neighborhood with more biodiversity.
The enlarged tree canopy and street beautification have contributed to the local economy as well provided shade for the community. The locals have certainly noticed a difference, as Amanda, the assistant manager at the 500+ residence Marc Apartments, recalled in the summer of 2020: “The trees are beautiful to look at and provide a lot of shade. It gives it more of a communal feeling. We are right next to the industrial area, so it helps to partition between community and transit industry.”
The project also won an American Public Works Association Outstanding Award in 2017.
DeepRoot also complies with the Regional Water Board permit, as seen on page E-5 here.