The Challenge
Developers of Arbor House, a 123−unit affordable housing complex in the South Bronx, needed to maximize space for rainwater harvesting to enable reuse in a 10,000 sf rooftop greenhouse, while mitigating stormwater pollution into New YorkCity’s waterways. Goals included earning and maintaining LEEDcredits for water conservation and meeting strict regulations formitigating combined sewer overflows (CSOs).
Funded by federal, state and city grants, this project promised tobe the first in the United States to provide residents and thesurrounding community with fresh produce grown on a buildingrooftop using stormwater for irrigation while keeping it out of thesewer system. Government stakeholders, whose participationwas critical, increased pressure for meeting expectations.
The Solution
Arbor House uses Opti’s technology to reduce stormwaterstorage needs from two to one cistern while capturing, storing, and retaining rainfall during storms. Installed in 2017, Opti’ssoftware controls the timing of water discharges from the single15,000−gallon cistern. Ahead of a storm, the Opti system drawsdown the stored water level to ensure rainfall is captured during the event. After, stored water is retained for reuse.
Operation and Maintenance
Opti’s software controls an outlet valve installed 12” from thebottom of the cistern. Opti software ingests the NationalWeather Service forecast to predictively draw down storedwater, maximizing storage capacity. Arbor House managersuse Opti’s web-based dashboard to monitor performancestatistics, review historical data summaries, and enableautomatic control of the outflow valve. The Opti platformalso helps them prepare quarterly reports with performancedata to achieve environmental compliance and maintainbuilding LEED-Platinum and other certifications.
The Results
Within one year, Opti's active system increasedefficiency by 4.6X compared to traditionalpassive management. By adding Opti adaptivecontrols, the developer was able to:
- Convert a passive system with two cisterns forstoring 134,650 gallons to an Opti activesystem requiring one cistern for storing 15,560gallons, reducing CAPEX
- Reduce the footprint needed by relocatingthe cistern under a parking lot, creating spacefor alternative use and additional revenue
- Prevent sewer overflows while reusingstormwater on-site to achieve LEED credits,reducing water bills and OPEX
