Forest House Urban Farming

South Bronx, NY



Forest House Urban Farming – Rainwater Harvesting Project For For Greenhouse Irrigation

Green in Bronx wanted their state-of-the-art affordable housing complex in the South Bronx, NY to be more than just “green” for the environment. They also wanted to be able to grow fresh vegetables in a 10,000 square feet (930 sq meters) fully integrated rooftop farm.

And they wanted to water the vegetables in the greenhouse with rainwater collected from the greenhouse roof and other hardscapes.

Wahaso was approached by partner Oldcastle Precast to develop an integrated solution for a complete rainwater harvesting system.


The system needed to be sized to maximize water savings, but there was no room to excavate a cistern outside the building. Water quality needed to be high so that there would not be any harm to plants in the greenhouse. And because the building was to be LEED certified, the Rainwater Harvesting System needed to gather, store and report data on the rainwater and make-up water used.


Water Supply Sustainability Index (2050)

Project Details


South Bronx, NY


Green in Bronx, New York


Plumbing Engineer, Civil Engineer, Commercial Contractors, Commercial Architect




Rooftop Rainwater for Greenhouse Irrigation


Spring 2013

Project Gallery


Wahaso worked with Oldcastle to design a concrete vault for the system to be integrated into the basement of the modular concrete structure – both of which were supplied by Oldcastle Precast. Wahaso’s cistern optimization model determined that 16,000 gallons was the most efficient cistern size to maximize savings using minimum building space. Wahaso designed and supplied the processing equipment to treat and pressurize the rainwater for the greenhouse. Twin vortex filters provided the total capacity needed for most rain events. Water in the cistern was transferred to a processing “day tank” where it was filtered and sanitized using ultraviolet light. The day tank also served as the location for municipal make-up water to be added when the cistern is empty. Wahaso’s series 100 custom control system manages all system functions and records tank water levels, rainwater harvested and applied and the amount of municipal water required during droughts.


The rainwater system should save about 60% of the total water demand for the greenhouse each year – representing about 380,000 gallons per year.

The UV system ensures that the harvested non-potable water should be safe for exposure to greenhouse workers. In addition to the rainwater harvesting system, the greenhouse will use left-over heat from the residential portion of the building. The farm will be used to provide fresh, perishable vegetables to a local non-profit food cooperative.

The rooftop farm will be able to supply enough produce to meet the annual fresh vegetable needs of up to 4500 people. Like many inner-city, low income communities, the South Bronx suffers from the ‘food desert’ effect, where residents lack access to fresh vegetables at affordable prices