The EcoCenter at Heron's Head Park
The EcoCenter at Heron's Head Park is an educational community center that uses sustainable on-site power, water and wastewater systems. It is owned and maintained by the Port of San Francisco and operated by San Francisco Rec & Park. Nearly every feature of this facility is designed to educate the public about renewable energy, pollution and greenhouse gas reduction, wastewater treatment, sustainable building materials, rainwater harvesting, and the green economy. In July 2013, the EcoCenter was certified by the United States Green Building Council as a Leadership in Energy and Environmental Design (LEED) Platinum building. It is the first LEED Platinum - Zero Net Energy Building in San Francisco.
“Off-the-Grid” Solar Energy System
The EcoCenter is the first and only environmental education center in San Francisco that is “off-the-grid," producing and storing its own electrical energy via 24 solar photovoltaic (PV) panels (producing 4.6 kilowatts of power) on the roof and a storage battery bank which provides power during periods of low or no sunlight. All electrical wiring conduits inside the facility are exposed to inform visitors of the sources and pathways of electricity from the rooftop through the building to the devices and fixtures it powers.
Entirely covered with soil and vegetation, the EcoCenter living roof absorbs rainwater, reducing stormwater runoff from the building that could cause erosion. The living roof also restores habitat for wildlife, provides insulation to the building’s interior, and reduces the “urban heat island” effect, the phenomenon that urbanized or highly developed areas tend to be hotter than nearby rural and natural areas due to land modification.
Rainwater Harvesting System
Rainwater harvesting is the practice of collecting and using rainwater for various non-consumptive uses, such as watering plants or flushing toilets. The EcoCenter captures rainwater that falls on the rooftop in three 4,800-gallon tanks. These tanks supply water to the living roof and surrounding native landscaping and will one day provide water to the toilets —saving thousands of gallons per year of water from the Hetch Hetchy Reservoir, which provides drinking water to San Francisco.
On-Site Wastewater Treatment System with Constructed Wetland
The EcoCenter is the first and one of only two buildings in City that treats its own wastewater. Going beyond conventional treatment, the processes at the EcoCenter involve irradiation of effluent and incorporation of a constructed wetland for further purification.
Primary Treatment: In the primary treatment stage, wastewater flows through a 1,000-gallon settling tank where solids sink to the bottom and oily substances float to the surface. The remaining liquid, referred to as effluent, flows by gravity into a second large tank. In addition to the settling and removal of most solid matter, naturally occurring microbes begin anaerobic (i.e., in the absence of oxygen) breakdown and consumption of inorganic and organic matter. Inorganic matter includes nutrients such as phosphorus and nitrogen compounds found in urine. Organic matter refers to human and food waste, soaps, and detergents.
Secondary Treatment: Effluent flows by gravity from the settling tank into a 1,500-gallon recirculation tank. During secondary treatment, organic matter is aerobically (i.e., in the presence of oxygen) digested by naturally occurring microbes. Every twenty minutes, effluent is recirculated through the tank past textiles loaded with the microbes. Removal of most of the organic matter takes place during this treatment phase.
Tertiary Treatment: Before leaving the recirculation tank, effluent passes through an ultraviolet (UV) light that kills most remaining viruses and bacteria.
Constructed Wetland: Constructed wetlands are man-made systems that mimic the cleansing functions of naturally occurring wetlands. At the EcoCenter, the constructed wetland consists of multiple pond-like enclosures that serve to further purify the effluent. Additional settling of solids takes place and inorganic and organic matter are consumed and sequestered by the microbes, algae, plants, invertebrates and vertebrates living in the system.
Subsurface Dispersal to Dripfield with Native Vegetation: Effluent ultimately leaves the EcoCenter via a subsurface irrigation system to a 2,000-square foot area surrounded by fencing in front of the building. This dripfield provides an absorption zone for the effluent that sustains the plants in the “Butterfly Meadow” (it contains plants that adult butterflies and their caterpillars like to eat).
Native Only Landscaping
Only Bay Area native plants are used in the landscaping and living roof at the EcoCenter. Because native plants have evolved in a particular region over thousands to millions of years, they have adapted to the climate, geography, and organisms of the region. They require less water and are used to local soils than non-native plants. Native landscaping can also provide needed food and habitat to local endangered species. Native perennial plants have deeper root systems that help reduce erosion and can out-compete invasive plant species. Plants on the living roof and surrounding landscaping are watered predominantly using harvested rainwater, while the butterfly meadow is maintained by treated effluent.
All pathways and paving around the EcoCenter are made of permeable materials that permit the movement of stormwater through their surfaces into the ground below. This is especially important at the EcoCenter since there is no tie-in to the City’s sewer system. All water that falls on the site should be either captured or made to infiltrate into the ground. In addition to reducing runoff that could lead to erosion, porous surfaces can improve water quality by filtering and trapping pollutants in its subsurface.
Sustainable Building Materials and Other Resource Efficient Design Features
The EcoCenter was created using an extensive array of sustainably harvested, sourced, reused, and recycled materials, as well as energy- and resource-efficient design features and fixtures. These include structurally-insulated panels (SIPs) made with Forest Stewardship Council (FSC)-certified wood and recycled polystyrene foam insulation; FSC-certified wood throughout the building’s interior and reclaimed wood exteriors; concrete foundation and flooring made with 100% recycled aggregate and 75% slag; windows made of reclaimed wood/partially recycled plastic composite, reused cabinetry, interior doors, moldings and furniture; recycled glass countertops; a Trombe wall (a passive solar heating design); highly efficient LED light fixtures; daylighting (i.e., predominantly natural lighting during the daytime); solar thermal and radiant floor heating; low-flow faucets and toilets; and no- or low-VOC (volatile organic carbon) paints, sealants, and adhesives.
About Other EcoCenters
The Port commissioned a comparative study of facilities like the EcoCenter to inform its plans for operating the EcoCenter at Heron's Head Park.