The rainwater is routed through one of two roof rain washers before entering a 10,000-gallon (38 cubic meters) underground cistern. Water from the cistern is filtered and chlorinated before servicing the janitor's mop sink and lavatories in the restrooms and classroom. An off-the-shelf composting toilet system eliminates the need for potable water for sewage conveyance.
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Water for spraying the composting bins and for the exterior wall hydrants is filtered but not chlorinated. The architects have estimated conservatively that 44 percent of the building's water needs will be met with collected rainwater.
Sweetwater's approach to waste treatment for this project includes the dual goals of eliminating the use of municipally provided potable water for sewage conveyance and treating 100 percent of the waste on-site in an ecologically healthy manner, without the use of chemicals.
Except for a single 3-ounce (85-gram) per flush foam-flush toilet that uses harvested rainwater, all toilets and urinals are waterless. The foam-flush toilet and the waterless fixtures connect to four composting bins below.
The resulting compost is then used to enrich the soil in nearby gardens. The architects worked with engineers in designing a drip irrigation system that combines nitrogen-rich liquid from the composting bins with the building's "gray water" to irrigate and fertilize the surrounding landscape.
Gray water from lavatories, water fountains, mop sink, and shower is mixed with any excess effluent liquid ("compost tea") that may occur in the composting bins. Diluting this "tea" with much larger amounts of gray water allows more frequent irrigation than would be possible with undiluted "tea."
Particles that may be suspended in the gray water are filtered out when the mixture passes through a 1,000-gallon (3.8-cubic-meter) septic tank, and then through a 1,000-gallon (3.8-cubic-meter) dosing tank, before entering the irrigation system. The system uses no chemicals or biocides.
Traditional septic systems, after separating solid waste from effluent, distribute nutrient-rich effluent into the soil at a level that is typically below the roots of any plants growing above the drain lines. Such a system allows the high-nutrient concentrations from the drain lines to potentially leach downward and contaminate the groundwater aquifer below.
In contrast, Sweetwater's drip irrigation system distributes the mixture of gray water and "tea" into a demonstration garden at a depth between 6 to 10 inches (15 to 25 centimeters) below the surface, allowing the plant roots to absorb the nutrients. A demonstration garden is the final component of an integrated system that redefines the concept of "waste." This system eliminates any contribution to a centralized waste treatment plant.
The architects' integrated design approach began with the site placement and design of the building. This siting allows the sun to warm the interior in winter while effectively blocking the sun's direct rays in the summer. A 10.5-kilowatt photovoltaic array consisting of new and recycled solar panels produces electricity equivalent to an estimated 20 percent of the building's needs.
Vegetated roofs, in addition to reducing stormwater runoff, further lower the building's energy needs by keeping the interior at a more constant temperature. Overall, energy consumption is estimated at 51 percent less than a comparable building, avoiding 27 tons (24 metric tons) of carbon emissions annually.
With the Sweetwater Creek project, Gerding Collaborative has demonstrated that high-efficiency buildings can also be reasonably low in cost. The project was completed for a competitive $175 per square foot. A U.S. Department of Energy Report on sustainable design concluded that through integrated design and use of sustainable materials and technologies, the first cost of a sustainable building can be the same as, or lower than, that of a traditional building.
"The Sweetwater Project is a great example of how a new way of looking at design is good for the building's owner, good for the people who use the building on a daily basis, and good for the environment," says Dan Gerding, AIA, managing principal of Gerding Collaborative. "It is our hope that this building will be a catalyst for the advancement of high-performance green building concepts and environmental stewardship."
Much to their credit, Gerding Collaborative is introducing this kind of integrated environmental design process into other projects, even when the clients choose not to pursue LEED certification. By incorporating aspects of such systematic thinking into public- and private-sector projects, Gerding has helped their clients save money on daily building operations while increasing the productivity and well-being of their employees.
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Architect: Gerding Collaborative
LEED Consultant: Donna McIntire
Civil Engineer: Long Engineering
Structural Engineer: Palmer Engineering
Electrical Engineer: Barnett Consulting Engineers
Mechanical/ Plumbing Engineer: Johnson, Spellman & Associates
Landscape Architect: jb+a
Contractor: Mooney Construction
Commissioning Agent: Commissioning and Green Building Services