Grasscrete: Meeting California’s demanding stormwater retention requirements has never been easier
By Sean O’Keefe
In construction, innovation is essential and, as the needs of the industry have changed, so too have the means, methods, and materials employed to solve challenges.
Florasource Ltd. is a California horticultural supply firm founded in 1985 by owners Tom and Nancy Hawkins, who met while pursuing
degrees in Environmental Horticulture at UC Davis. Today, the company provides a steady supply of young plants to commercial growers, grower-retailers and low water lawn alternatives to the landscape contractor industry.
Expanding on their interest in environmental horticulture, the company also represents a range of innovative landscape products, including green roof, green wall, and living hardscape systems. As such, when design firms were working on the Orange County Great Park in Irvine, Florasource was able to meet some of their project needs with the right combination of products.
“The Orange County Great Park project is the ongoing transformation of Marine Corps Air Station El Tora, in southern California,” Hawkins said.
Spanning some 1,300 acres, Orange County Great Park is a public-private partnership between the City of Irvine and developer Five Point Communities, and takes aim at becoming one of the largest and best metropolitan parks in the world. A nearly limitless list of in-park amenities includes the Great Park balloon, carousel, kids rock play area, walkable historical timeline, historic Hangar 244, Palm Court, Farm + Food Lab, and the recently opened 53-acre sports complex. Future assets in the five-year development include a 179-acre wildlife corridor, 71 acres of agricultural areas, and an 18-hole golf course and clubhouse.
Designing and building-out an appropriately vegetated park of this magnitude while meeting California’s water conservation in landscaping requirements for new development was no small order. Passed in 2006, the state’s requirements include establishing a maximum amount of supplemental site irrigation and encouraging the capture and retention of 100 percent of stormwater on site. In conjunction with landscape contractor Brightview Landscape Development, Florasource has supplied several stages of park buildout with a combination of materials ideally suited for California’s unique low-water climate and stormwater retention expectations.
“We provided UC Verde Buffalograss for lots of areas at the park” Hawkins said. “It’s a great low-water lawn option that was bred specifically to grow well in California and other drought-prone areas, including the desert valleys in Phoenix and Tucson, Arizona.”
Bred by UC Davis and introduced commercially in 2003, UC Verde Buffalograss requires as little as a fourth of the amount of water of traditional turf grasses, and peaks at a growth height of only six inches, meaning much less need to be mowed regularly. On the hardscape side, Florasource also had a ready response to the stormwater retention requirements in permeable paving solution – Grasscrete.
“Grasscrete is an incredibly durable, permeable paving product that allows grasses or other vegetation to be planted within it,” Hawkins said. “We had experience working with Brightview on a large Grasscrete installation for Hyundai’s US Headquarters in Fountain Valley, CA. There it was used for emergency fire lanes and was also planted with UC Verde Buffalograss.”
Grasscrete is a proprietary blend of product, service, and technique manufactured by Sustainable Paving Systems of Fair Oaks, California. As the manufacturer’s representative for the state, Hawkins joins other distributors across the country and specialty concrete contractors under the Bomanite brand in having exclusive rights to this innovative concrete system in development since the mid-1970s.
At the Orange County Great Park Grasscrete has been used primarily to create hard, drivable surfaces for utility access roads, emergency vehicle fire lanes, and in allowing drivable shoulders for several of the roundabouts in the bordering residential neighborhoods. By forming a concrete lattice of solid and void, Grasscrete combines the strength and rigidity of a single, structural framework while still providing enough access to soil, water, and sunlight to support sustained vegetation. The result is a vegetated permeable surface that remains drivable when needed, capable of supporting the parked weight of a fully loaded fire truck.
“The fire department doesn’t take these things lightly,” says Hawkins. “In 2014, we were required to set up a formal test installation for the City of L.A., to get approval for the newly designed, biodegradable Grasscrete former. They drove one of their biggest trucks out on it, put down the stabilizers and raised the ladder up just like they would in a fire. The Grasscrete surface never moved.”
The Grasscrete system differs from other types of pervious paving systems in the incorporation of molded-pulp formers that allow cast-in-place flatwork to be placed monolithically. Made from recycled paper, the pulp-formers are biodegradable and will slowly begin to dissolve as the concrete hardens. By reinforcing the forms continually with #4 rebar, builders can achieve a compressive strength of between 4,500 and 12,000 psi depending on the specific mix of materials.
“The planting depth with Grasscrete is also a differentiator compared to other permeable paving systems,” Hawkins said. The formers produce an internally reinforced concrete pan that is a stout 5 ½ inches thick and provides deep, well-protected voids for plants to root within. Despite a strength that is identical to other solid concrete flatwork or any other permeable pavement systems, Grasscrete delivers an astounding 37.5 percent non-solid surface, allowing whatever is planted within to truly blanket the concrete.
“Grasscrete seems to check all the boxes related to California’s stormwater retention requirements,” Hawkins said. “But it’s also very flexible in terms of how it can be used: as a drivable, planted lawn-like surface, or a hill stabilizer, a solid surface bottom for detention ponds, for high-end driveways, planted or unplanted, straight or curved, unfinished or polished. There are endless possibilities.”
Sean O’Keefe writes Built Environment stories for publications, architects, builders, and product manufacturers based on 20 years of experience in the design and construction industry. He can be reached at email@example.com.