The challenge for CSL was to have Net-Zero Water Usage and Sustainable Water Discharge. To do this, an overall water-balanced design approach was required. This approach looked at potable water, greywater and blackwater in an integrated manner. Several design choices influenced this system, such as water friendly landscape.
The rainwater captured from the roofs of the conservatory and the CSL building is directed to a 1700 gallon underground tank that supplies the initial water for irrigation and flushing purposes. If there is any overflow, it is captured by the Lagoon indicated in the diagram above (C). This lagoon overflows into rain tanks which are beneath the site access roads, covered with permeable ground covers. These are stackable units covered with a geotextile fabric to ensure that they can bear the weight of vehicular traffic along with having adequate porosity to allow water to percolate. The underground rain tanks have a total capacity of 80,000 gallons.
Water used for flushing in the CSL building remains in a closed loop, originating and ending on the site. To do this, harvested rainwater used for flushing purposes is passed into a tank on the exterior grounds where the solid waste is allowed to settle. The liquid effluents then pass through two wetland treatment cells and a series of filters, into the reuse holding tank. In the holding tank, the water is continuously cycled through a UV filter till the pump draws the water back into the flushing water loop.
RAIN GARDEN
Several rainwater collection mechanisms are adopted by the CSL, such as the one illustrated in the image to the left. In the Phipps-CSL campus, this collected rainwater is used for the irrigation of plantation in Phipps, helping the campus achieve its net zero goal while requiring minimal treatment.
In the parking lot, we observed bio-swales constructed to manage the rainwater incident on the paved lot, which are illustrated in the image below.