Location: Eden Prairie, Minnesota | Client: Non-Profit Organization | Design team: Damon Farber Associates | Features: Rainwater Harvesting and Reuse, Greywater Reuse, LEED, Irrigation Design
In 2016, a Midwestern non-profit organization stayed true to their environmentally sound practices through a new building expansion project. The organization's leaders recognized an opportunity to lead by example and reinforce one of their key philanthropic priorities centered on the environment. In spring 2016, they completed a major building expansion; through sustainable design practices and water management strategies, including recycling water, they tripled their building’s size while reducing its environmental impact. Water in Motion had the honor of designing their initial high efficiency irrigation system and also the expansion. The project included Minnesota’s first greywater drip irrigation system and multiple water storage tanks, which store 55,000 gallons of rainwater to sustain the native plantings, vegetable gardens and orchards on the property.
The philanthropic organization elected to expand its office facility in Eden Prairie, MN in an environmentally sustainable way. The result includes an expansion of rainwater collection and reuse equipment and controls. Landscape irrigation was updated to include:
- Drip grids or spray-type emission devices at selected ground-level planting beds
- Micro irrigation in selected ground-level planters
- Multi-stream-multi-trajectory (MSMT) rotating nozzles atop a new green roof
- Integration of a portion of an existing rainwater reuse landscape irrigation system
- Replacement of existing rainwater irrigation pump with a larger unit to accommodate the additional landscape and green roof
The landscape irrigation was designed to qualify for USGBC LEED® credits including Credit 1.1 (Reduce water use by 50%); Credit 1.2 (No potable water use for irrigation) and Designed by a Certified Irrigation Designer and WaterSense Partner (Water in Motion).
The expanded rainwater collection system consists of two additional banks of rainwater tanks in the parking garage expansion, Tanks A and B. Tank B collects rainwater and overflows to Tank A. The Existing tanks receive rainwater and act as the sole source of rainwater for landscape irrigation.
The reuse of rainwater works this way: Rainwater is collected into the tanks and transferred between the tanks based on need. When the Existing irrigation tanks reach a low-level setpoint a signal is sent to Tank A initiating a transfer; when Tank A reaches a low level setpoint, it send a signal to initiate the transfer of rainwater from Tank B to Tank A. The transfer of rainwater into Existing tanks will stop when those tanks reach a maximum level of 50-60% to leave room for rainwater inflow into Existing tanks should a rain event occur. Tank A is designed to have a 95% full maximum level, as it does not directly collect rainwater. If the tanks reach a low level cut-off limit, the system automatically stops irrigation until a rain event replenishes the tanks.
The reuse of graywater for landscape irrigation works this way: Up to 250 gallons of reuse graywater is available per day from a graywater reservoir tank. A controller enables or disables operation of the graywater irrigation pump, based on the graywater tank level. A landscape irrigation controller with SMART weather-based scheduling module connects to the graywater controller. If the graywater tank reaches its low level cut-off limit, landscape irrigation stops until additional graywater is made available for reuse.