The water feature in front of the new 250-bed residence and food services building at the Orillia, Ontario, Canada, campus of Lake Head University certainly looks pleasant enough and was built for the enjoyment of students, staff and visitors. What is not apparent to passersby is a second water harvesting pond below the pond they see. The water feature sits directly atop a 564-cu-meter water harvesting storage system. The harvested storm water is used in the water feature and for nonpotable toilet flushing inside the residence hall.
System Design
Michael Buske, along with Tim Collingwood, project manager for CC Tatham & Associates, designed the unique system to capture storm water from the adjacent road. This water will flow into a catch basin, move through a filtering system, flow to a chamber for storage and be pumped to the above-ground water feature. The system also includes an outlet pipe to the city’s combined storm sewer system and a manhole for maintenance. In addition to water being pumped to the surface pond, part of the captured graywater is used for toilet and urinal flushing to reduce freshwater use in the building.
The underground harvesting system is comprised of Rainstore3 by Invisible Structures, Inc. , Golden, Colo. Rainstore3 is a modular and stackable system engineered for underground storage of water for retention, detention and harvesting. The entire Rainstore3 chamber at Lakehead University is comprised of 6,000 units stacked into 2-meter-high cells and is capable of holding 564 cu meters of water.
“We needed to calculate the compressive load of the water, the concrete and the granular aggregate above the Rainstore3 chamber to see the effect it would have on the system,” said Kate Wright, engineer with Invisible Structures. The filled ponds and components will exert a point load of 505 lb/sq ft on the chamber. Rainstore3 can withstand in excess of H-20 bridge loading standards, and the concrete pond, filled with water, is well within those limits.
The decorative surface ponds were designed for aesthetic purposes. Each pond is comprised of 30-cm-thick reinforced poured concrete with waterproofing. The pond is about 1 meter deep, 4.4 meters wide and the full length of the underground harvesting system. The ponds have a wood decking plaza surrounding and partially traversing the water feature. Below the decking there is reinforced concrete with strategically placed drainage holes. The holes lead to a granular aggregate designed to drain and convey the water toward the harvesting system.
The captured storm water in the subsurface harvesting chamber also is recycled as graywater for toilet and urinal flushing inside the building.
“The water is pumped from the chamber to a sand filter package and then pumped to the graywater system inside the building,” said Greg Gebert, project manager with Crossey Eng., who designed the mechanical systems for the Orillia Campus building project.
Platinum Potential
This reuse of storm water and reduction of freshwater (potable) will contribute to the project’s U.S. Green Building Council Leadership in Energy and Environmental Design (LEED) Platinum rating. The graywater system is completely separate from the freshwater/potable system provided by the city. The wastewater from the toilets will flow to the municipal sewage treatment.
The water feature ponds and toilet flushing systems comprised the first phase of the storm water treatment plan on the new site. The storm water management plan also includes three infiltration bioswale trenches centered in what will be the newly constructed parking lot. The parking lot will sheet flow all of the storm water into the bioswales, which will be comprised of native plantings, granular aggregate and underground detention chambers. The chambers slowly will release the captured storm water back to the groundwater supply.
The entire site is up for LEED Platinum certification, in part from the recycled content of the Rainstore3 units, storm water management design and water use reduction.
