by Steve Roy, LEED AP, Marcus Quigley, P.E. and Chuck Raymond, CPSM
Rainwater harvesting is becoming more and more common in both commercial buildings and single-family and multi-family residential buildings as one aspect of green design, also referred to as green infrastructure or sustainable development. Rainwater harvesting is the collection, pretreatment (as needed), storage, and re-use of rainwater, usually on-site. There are several variations of these systems, and rainwater can be collected from building roofs and both paved and landscaped surfaces.
Rainwater is typically directed to any of a number of types of cisterns which can be either aboveground or underground. Once collected, the stored rainwater can be used for a variety of functions. While not suitable for drinking water, it can be used for landscape watering, washing vehicles, cooling water make-up, industrial processes, additional fire protection, and others.
Having a dependable, well-designed rainwater harvesting system for on-site re-use of stored runoff is all well and good, but who has the time or excess personnel to check on the fullness of the cisterns, calculate and verify that they have the capacity to handle the next rainstorm, and, if needed, empty them ahead of time? This time and money constraint is what has led to the next step in their advancement – the step towards “smart” rainwater harvesting
Geosyntec Consultants has developed an advanced rainwater harvesting controller, known as OptiRTC, that receives internet-based weather forecast information to automatically empty rainwater cisterns in advance of storm events to maximize storage. The smart aspect of this, as mentioned above, is that it’s all done automatically with no human intervention. Its actions are based on software programming and on-line NOAA weather forecasts. Computing and data are stored in the cloud and access to the system functions is provided through simple-to-use dashboards. Cloud computing, or the cloud, is a term used to describe a variety of different types of computing concepts that involve a real-time communication network such as the Internet.
For example, if the cisterns are, say, 75% full, and the NOAA forecast indicates that there will be enough rain the next day to overfill the cisterns, OptiRTC will automatically empty the cisterns ahead of the storm. Not only does this ensure that the cisterns will have the capacity to capture and store the expected rain, but it will have emptied the cisterns when the city’s storm sewer system has the capacity to handle it. This helps to reduce impacts to the stormwater system, especially if you happen to be in a community with combined sewers where large rainstorms combined with municipal sewage can easily overflow the system. This sends a combination of raw untreated rainwater and sewage into waterways, wetlands, and other sensitive areas. Utilizing OptiRTC, rainwater harvesting systems provide dual benefits of water conservation and stormwater management through real-time control of rainwater storage.
Geosyntec has designed and installed these smart rainwater harvesting systems in some very urban locations thus far, where the owner or proponent has seen that the ability to automatically capture, store, and manage rainwater that would otherwise be wasted is of great value. In Washington, DC, Geosyntec designed and installed a smart OptiRTC-based rainwater harvesting system at two District fire stations. This will not only allow the District to save money by washing their trucks with captured rainwater versus paying for City water, but having OptiRTC empty the cisterns ahead of storms keeps runoff from the stations from impacting the District’s combined sewer system. The District is also saving money on a stormwater utility fee from which they are now exempt because of the cisterns and porous pavement they installed in their parking areas. Other examples of the use of smart rainwater harvesting include several private and City-owned locations in and around New York City and multi-family residential locations in the St. Louis area.
Benefits of Advanced Rainwater Harvesting
This article has touched on a few of the benefits to the municipalities that have these smart rainwater harvesting systems installed within them, but there are also many tangible and cost-based benefits to the real estate owners, developers, and other groups that have these systems on their own properties or those that they develop, including:
- Green building credits (e.g., LEED Sustainable Sites and Water Efficiency)
- Lower stormwater utility fees/taxes and possibly even fewer penalties in combined sewer system communities
- Water conservation (potable water offsets, reduced overall water demand) and associated cost reductions
- Stormwater runoff volume reduction and combined sewer overflow mitigation
- Improved local surface water quality
- Environmental stewardship
- Additional water capacity in support of climate resiliency planning
OptiRTC is very effective when designed and installed as part of new construction, but it can also be used as a low cost retrofit method during reconstruction, and can provide another reliable method to lessen a building’s footprint on the environment.
Steve Roy, LEED AP, Marcus Quigley, P.E and Chuck Raymond, CPSM are Geosyntec Consultants