ASSESSING THE PERFORMANCE OF A SELF-SUSTAINING WATER SYSTEM IN THE BUILT ENVIRONMENT

The Williams College Class of ’66 Environmental Center (Williamstown, MA), is seeking certification as a Living Building, a project evaluation tool developed by the International Living Future Institute to promote regenerative infrastructure in the built environment. Hydrology can be used to assess water management in a building and behavior of water on a project’s grounds. The Environmental Center includes the first rooftop rainwater catchment system approved as a public water supply in Massachusetts and has an on site storm water retention and infiltration system. Our data collection focused on estimating components of the water balance for the buildings and site in order to evaluate the sustainability and success of project’s hydrological performance. We used a color orthophoto and DEM base map to classify the site into hydrologic units. We measured water consumption by building occupants and production of effluent water (blackwater) and used field observations and hydrologic monitoring to measure the performance of storm water retention and infiltration structures in response to precipitation events. Our results provided project managers with data to adequately plan for changes in the management of building water and the landscape of the site in order to better meet long-term sustainability goals. We found that the rooftop collection system has an efficiency of ~15-30% and is on track to supply the needs of the building, which ranges from ~40-200 liters/day. In addition, there is enough water so that during times of high evapotranspiration the excess collected rainwater can be used to irrigate the gardens and grounds to mitigate the site water deficit. We also found that the site’s storm water management system performs sufficiently but during large events, or when the ground has been previously saturated, some water flows off-site as surface runoff. In total we estimate that 10-15% (700m³) of storm water flowed offsite as surface runoff in 2015-16. We expect offsite surface runoff to decrease in future years as infiltration rates increase in areas compacted by construction and as vegetation grows but we also recommend the use of irrigation pump out of the primary retention and infiltration structure to further decrease off-site surface runoff.