The right combination of seed was the solution to one landfill’s erosion problems.
Written by James Enyart
Sunshine Canyon Landfill handles the waste disposal needs of Los Angeles city and county businesses and residences. The facility is located in a highly visible site at the intersection of Interstate 5 and Highway 14 in Sylmar, CA. It has been under scrutiny by the public as well as city, county, and state regulatory agencies with concerns about water runoff, dust, odor, and escaping trash.
In September 2011, Republic Services, the national waste management company that owns and operates Sunshine Canyon Landfill, asked S&S Seeds to visit the 54-year-old site to make erosion control recommendations. The mission was to establish vegetative growth on a non-irrigated site that would stop slope erosion and stabilize the slopes to comply with the runoff requirements set forth by government regulatory agencies.
The challenge was that of the soils and the length and pitch of the slope runs. The slopes are 3 to 1 or steeper; the runs are over 400 feet. The fill soil, which comes from offsite, has extremely varied composition.
After considering the slope factor, distance, and soils, S&S Seeds felt that hydroseeding with the seed of California native species coupled with the use of bonded fiber matrices would be the best management practice. In order to accomplish this, it was necessary for the company to design a non-irrigated California native seed palette that would provide erosion control and be acceptable to the botanists of three separate agencies. S&S also had to find the right products to stabilize soil until the native seeds germinated and grew.
A seed mix was designed with nurse crop annual species that would germinate and grow quickly as well as perennial species that have a longer life cycle. All species were selected to germinate and survive under the difficult soil conditions and without any supplemental water or irrigation. Additional hydroseeding slurry components were added, such as slow-release organic fertilizer, soluble humate, and mycorrhizae to enhance germination and growth in the unproductive soils.
S&S Seeds worked closely with Profile Product engineers to determine which erosion control products would be most effective at the Sunshine Canyon Landfill. The bonded fiber matrices (BFMs) recommended were a combination of Hydro-Blanket Bonded Fiber Matrix and Terra-Matix Stabilized Mulch Matrix. These BFMs were chosen because they are an economical solution and they are engineered with cross-linked fibrous material incorporated into their structure, which holds the soils in place and gives the seeds time to germinate and grow.
Hydro-Blanket Bonded Fiber Matrix sprays on as mulch, but dries to form a breathable blanket that bonds more completely with the soil, more effectively prevents erosion, and saves time and money compared with erosion control blankets as well as other BFMs. Terra-Matrix Stabilized Mulch Matrix is preblended with a combination of wood fibers, cross-linked tackifiers, and activators to anchor the fiber matrix firmly to the soil surface.
In November 2012, a native California plant seed mixture combined with the erosion solutions was hydroseeded in one pass onto all areas of the site. Because of a lack of rain, there has been minimal vegetative growth to date, but the slopes are being held and the dust, odor, and trash pickups have been greatly reduced.
The Sunshine Canyon Landfill project was a runner-up in the Profile Products 2011 Projects of the Year awards this February, at the 2012 International Erosion Control Association conference in Las Vegas.
Contributing writer James Enyart is a biologist with S&S Seeds in Carpinteria, CA.