Sketch of rainwater’s course through the OSC. Courtesy GBD.
“A Living Building is water independent.”
So says the Living Building Challenge (LBC), and so will be the Oregon Sustainability Center, employing water conservation measures that will complement a comprehensive rainwater collection system and an on-site sanitary wastewater treatment system, the Living Machine.
As with energy, water in the built environment is an ecological issue that demands significant attention from all new design. The LBC explains:
“Scarcity of clean potable water is quickly becoming a serious issue in many countries around the world. Most regions of the United States and Canada have avoided the majority of these limitations and problems to-date due to the presence of abundant fresh water, but highly unsustainable water use patterns and the continued draw-down of major aquifers portent significant problems ahead…
“The Living Building Challenge envisions a future whereby all buildings are designed to harvest sufficient water to meet the needs of occupants, while respecting the natural hydrology of the site, the water needs of neighbors and the ecosystem it inhabits. Indeed, water can be used and purified and then used again.”
Example of a green wall, one potential stop for storm water on its path through a living building. Courtesy inhabitat.com.
With this in mind, the LBC has defined the following prerequisites for a Living Building’s water strategy:
- Prerequisite 10 – Net Zero Water 100% of occupants’ water use must come from captured precipitation or closed loop water systems that account for downstream ecosystem impacts and that are appropriately purified without the use of chemicals.
- Prerequisite 11 – Sustainable Water Discharge 100% of storm water and building water discharge must be managed on-site and integrated into a comprehensive system to feed the project’s demands.
Storm water flowing into a bioswale near Mt. Tabor (click to enlarge). Photo courtesy Kevin Robert Perry.
Given the rainy climate of the Pacific Northwest, water issues are of particular interest around here. According to the City of Portland’s Bureau of Environmental Services, it rains an average of 37 inches in Portland per year. This yields roughly 10 billion gallons of storm water runoff, the volume and speed of which leads to flooding, erosion, natural habitat destruction, and, potentially, combined sewer overflows (CSOs).
Such an abundance of rain feeds the regional misconception that water conservation issues are of a lesser concern, yet as the LBC points out, a lack of regard for water use today, coupled with the mistreatment of the water that does get used, is foreshadowing a significant environmental crisis just around the bend.
This challenge has driven the OSC team to commit to strategies to achieve net zero water that will in fact move the project much further, toward a goal of hydro equity, giving back to its local ecosystem clean water that it does not need.
The Oregon Road Map for Achieving Water Independence in Buildings (click to enlarge). This study was prepared by a team from Gerding Edlen Development, Central City Concern, SERA, and Interface Engineering, with funding by the Bullitt Foundation, Cascadia GBC, Enterprise Community Partners, and Portland Development Commission. You can find the complete report here.
Similar to the building’s strategy for net zero energy, the design team added water conservation measures first, incorporating into the basis of design the lowest flow fixtures available on the market today, most of which will be equipped with optical sensors.
To achieve net zero water, the building will collect rainwater for potable uses from the rooftops. As described in earlier posts, a 6,200 square foot bifacial photovoltaic (PV) array on the 4th floor of the building, and a 3,000 square foot bifacial PV array on the 3rd floor, will create a translucent canopy covering the OSC’s ground floor plaza. Organically shaped PV arrays will also top the building, once on the 10th floor, and a second time on the very top, adding another 18,400 square feet of impermeable surface.
Bird’s eye view of the OSC solar canopies (click to enlarge).
Collectively, the PV panels (along with other impermeable surfaces throughout the site) will double as rainwater collectors, sending the water into a 200,000-gallon epoxy lined waterproof concrete storage tank, which will be fitted with circulation pumps to circulate water within the tank, preventing stagnation. The rainwater will be treated via filters and a chlorine injection system before being pumped and/or circulated into a 500-gallon/day tank. A duplex pump system will draw from this day tank and deliver the treated rainwater for potable uses throughout the building.
Swales as part of the stormwater management plan for Portland’s South Waterfront. Photo courtesy Nevue Ngan Assoc.
On the ground level, porous pavement, vegetated planters, and bioswales will also contribute to the management of the storm water that is not captured by any of the rooftops. Together these features filter and slow the flow of rainwater as it makes it way back into the ground.
To address Prerequisite 11, Sustainable Water Discharge, the OSC design will incorporate an on-site sanitary sewer system that is known as a Living Machine, chosen both for its low energy use and derivation from biophilic design. Living machines mimic the natural cleansing processes of wetlands, employing plants, bacteria, algae and other organisms to do the hard work of filtering black water. The OSC’s system will include an initial screening and collection of solid materials from black water sources (ie. toilets) for use as compost and fertilizer for onsite landscaping. The treated effluent from the living machine will be reused for flushing toilets and urinals and at hose bibs.
Green roof on a Washington Mutual building. Photo Phillips Farevaag Smallenberg.
All excess storm water and treated wastewater that is not used internally will be either infiltrated back into the soil on site, where it will replenish the groundwater supply, or it will be used to irrigate gardens and green roofs throughout the building. Ideally, the excess storm water will also be funneled back to the Montgomery Green Street for irrigation there, as well.
While the OSC itself will do the lion’s share of the work to achieve net zero water, through its extensive catchment and filtration systems, ultimate success still relies on the active participation of the tenants in the building. Metering the tenants’ use of water will be imperative, and the team is looking into metering systems for each office and retail space, to track usage on a daily, or even hourly, basis. Water bills will vary according to each tenants’ level of consumption.
But will that be enough? What if, as was discussed during one recent steering committee meeting, tenants had to swipe a card before using a toilet or urinal, so that every last drop of water consumed was tracked and accounted for?
Sounds crazy to some, but for others such a step would be prescient. Not long from now, will we have any other choice?
(Thank you Kevin Robert Perry of Nevue Ngan Associates for his help with gathering images.)