Harvesting Rainwater at Eden Hall Campus
In January, Governor Jerry Brown called a drought State of Emergency in California. Five months later, the National Oceanic and Atmospheric Administration released data showing that May was the wettest month on record in the contiguous U.S. with an average precipitation total 1.45 inches above average. While these are two very different problems, they both point to “two sides of the same coin:” how we must manage water more effectively in our changing climate.
Pittsburgh is rainy: We get an average of 146 days of precipitation compared to a national average of 100 days. On those days, excess water – water that is neither collected nor absorbed by the ground – flows into storm drains. Underground, the stormwater system joins with our sewage system, and sewage and water travel together to be treated at the Allegheny County Sanitary Authority (ALCOSAN) wastewater treatment plant, which processes up to 250 million gallons of wastewater daily.
This system worked fine when it was built at the turn of the century, and it still works in dry weather. But the population has grown, and now whenever it rains more than ¼ inch, the system becomes flooded, and ALCOSAN must close its gates. Sewage flows into our rivers, streams, and creeks, carrying debris, chemicals, bacteria, and animal waste.
At Chatham University’s net zero Eden Hall Campus, we are modeling both innovative and age-old techniques around water management, including rainwater harvesting for collecting and using rainwater. For his thesis project, Master of Sustainability alumnus Tony Miga ’14 designed and implemented a rather large-scale rainwater harvesting system for Eden Hall. On a Friday in May 2015, it was used for the first time.
Barn and underground cistern tanks
Here’s how it works: Rain falls onto the roof of the storage barn, runs into the gutters, and is piped into three 1500-gallon underground cisterns, where it’s stored for use for irrigation. Overflow from the cisterns waters a nearby rain garden.
“Debris from the rooftops gets mixed in there,” Miga notes, and water is filtered six times, starting with fine mesh screens that fit over the gutters and ending with a UV filter that eliminates pathogens and other contaminants. “It’s probably overkill for our purposes,” he acknowledges. “We’re only using it for irrigation. There’s very little risk. We’re not spraying it, or bringing it into buildings. “
The state of the gutters before being cleaned
When the system is turned on, water runs from the cisterns, underneath a road, and into the moveable high tunnel and hoop house on the other side, where it’s used to water crops. It’s not the only source of water there – a line for municipal water was added for flexibility, back up, and research. Miga says that it allows them to experiment with using different types of water for growing. Harvested rainwater will also be used to irrigate the agriculture field.
The moveable high tunnel and the hoop house
Miga anticipates that the rainwater harvest system will provide 35,000-40,000 gallons of water annually. He’s also proud that the project makes use of an existing structure, rather than calls for new construction. “We inherited this property, and we’re making an effort to use what is here,” he says.
At Chatham's Eden Hall Campus, rainwater harvesting is combined to manage stormwater runoff with permeable surfaces, natural drainage, 22,027 sf of infiltration galleries (small pipes in gravel that collect water when it rains), and almost 30,000 sf of rain gardens. Rain gardens feature deep-rooted native shrubs, perennials, and grasses that receive runoff from roofs, sidewalks, streets and parking lots, and hold the water in a shallow depression as it slowly infiltrates into the ground.
Eden Hall will also treat wastewater on-site, using a six-step system that can handle up to 6,000 gallons per day. Once disinfected, wastewater will be used for toilet flushing and irrigating land. Water quality will meet or exceed all State of Pennsylvania standards.
Learn more at chatham.edu/edenhall.