By Aaron Reynolds
The Coast Unified School District (CUSD) sought a solution to irrigate a combined 130,000 square feet of all-season, multipurpose grass fields at its Cambria Elementary School, located in the seaside town of Cambria, CA. Nestled between San Francisco and Los Angeles on the famous Pacific Coast Highway, Cambria faced certain challenges that made conventional delivery systems not feasible: limited water resources, erosion control challenges, and an elevation rise that prevented adequate volume and pressure to transport irrigation water on-site.Injection molded, arched chambers can be used individually or in series to provide a highly effective, clog resistant drainage system.
Due to the stringent water quality and erosion prevention demands of the California Coastal Commission, the CUSD contracted RRM Design Group for architecture and civil engineering services and Earth Systems Pacific for soil engineering to coordinate a resolution. The team chose to implement the Environmental Passive Integrated Chamber (EPIC Chamber™) System, a water management solution from Indianapolis-based Firestone Specialty Products. The system can collect and store water from all available stormwater and hardscape run-off and help reduce municipal irrigation water reliance by more than 50 percent.
The solution was fully customized for Cambria Elementary and comprised two main components:
- EPIC Chamber – injection molded, arched chamber that can be used individually or in series to provide a clog resistant drainage system. The system is non-pressurized with no moving parts. It uses the strategic placement of holes to control water flow through and out of the chamber. The transfer of water is a natural function of gravity.
- EPIC Pan – used as a water barrier for the chamber, the pan allows a certain amount of filtered run-off to infiltrate and recharge the groundwater table.
The system can provide the school with a source of free irrigation water by harvesting rainfall during its two-month wet season, an important consideration in Cambria where summers are long and dry. The water management plan for this project included six strategically located EPIC profile sections across the 12-acre facility, with a combined turf area of 130,000 square feet. The initial storage volume of the profile sections provided 325,000 gallons of storage at 2.5 gallons per square foot. Located beneath the main athletic field, a secondary storage of horizontally placed reservoirs offered the additional capacity to collect 1.7 million gallons.
Preserving the Recreational Fields
Heavy rain events, especially in condensed time frames, and standing water can wreak havoc on parks and fields. When the EPIC system is positioned beneath a park or field, such as the Cambria school installation, the system’s drainage and filtration abilities help mitigate turf issues. Also, this coastal application captures stormwater and hardscape run-off by moving water below ground to help relieve elements that may contribute to surface erosion. Additionally, the passive onsite approach uses sand to retain nitrates, phosphates and other pollutants as nutrients within the system for above-surface vegetative growth, ensuring that the fields remain healthy.The system enables the school to collect, filter and store more than two million gallons of run-off water onsite, reducing its dependency on municipal irrigation water.
Moreover, the school’s multiuse field was surrounded by a 6″ berm to provide temporary storage in case of torrential rains. A 5″-deep profile over the field also provides additional capacity of 269,000 gallons. For added durability, the EPIC sand profile was reinforced with Firestone’s Netlon Advanced Turf™ System (ATS), which consists of small, interlocking, three-dimensional polypropylene mesh elements. Netlon, when integrated into the sand base profile, creates a reinforced layer that increases load-bearing capacities while enhancing infiltration properties. The mesh system also helps the field resist compaction and allows the grass to spring back to shape quickly, enhancing student safety and helping reduce the creation of ruts.
Ultimately, the system has the ability to store approximately 2.2 million gallons of irrigation water. With each EPIC pan/chamber cell covering approximately 25 square feet, the project used 5,200 chambers.
Using a subsurface irrigation and storage system not only frees up prime land space, it is not subject to evaporation and does not promote algae growth. While using the EPIC pan/chamber cell combination was a fit for the Cambria Elementary School project, specific strategic needs can be addressed with alternative configurations such as installing a Firestone EPDM Geomembrane beneath the EPIC system. When using the cured, single-ply liner, water does not recharge the groundwater table; it can be stored and reused for subsurface irrigation.Pans function as a water barrier for the chamber, allowing a certain amount of filtered run-off to infiltrate and recharge the groundwater table.
Permeable paver options can also be integrated at the turf level to increase filtration over an EPIC System. NetPave 25 and NetPave 50 are 100 percent recycled polyethylene pavers that can transform a field into a multipurpose green space. NetPave 25 can be assembled and laid over existing turf to support pedestrian paths, light parking and other traffic applications. NetPave 50 provides a more permanent solution and can convert grass areas into access routes used by service, maintenance, tractor trailers and emergency vehicles. It can also be used in aviation applications including light aircraft taxiways, light aircraft parking and airfield perimeter roads.
Subsurface applications like these can truly deliver a comprehensive on-site water management and reuse solution and help shift the paradigm towards innovative urban stormwater design. In the case of Cambria Elementary School, the subsurface irrigation system reduced the facility’s irrigation water dependencies by controlling excess storm and hardscape run-off, enabling the school to collect, filter and store more than two million gallons of run-off water onsite.
About the Author: Aaron Reynolds, P.E., is Water Management Solutions Manager for Firestone Specialty Products (Indianapolis, IN).