by Evan Canfield, Pima County Regional Flood Control District, and Irene Ogata, City of Tucson
When Tucson’s water harvesting guru, Brad Lancaster, illegally cut the curb in front of his house to collect stormwater runoff, he did so on a Sunday to avoid notice from local authorities. Today government agencies encourage, reward, and in some cases, require water harvesting. So what’s changed? The multiple benefits of using decentralized structures to capture and utilize rainwater are being recognized as the solution to many of our water resources problems. These benefits include reduction in demand for potable water, improved water quality, flood mitigation, habitat creation, urban heat island mitigation, and creating a more pedestrian-friendly community. For these reasons water harvesting and decentralized stormwater management practices have gone from being outlawed to becoming mainstream.
Implementation and construction of Green Infrastructure (GI) features along major collector and arterial roads now includes greater institutional requirements of design detailing, grading and modeling done by professional engineers and landscape architects. Pima County and the City of Tucson are preparing guidance for the beneficial use of stormwater at the neighborhood scale in response to shared recognition that stormwater has become a major element in the equation of balancing water needs in urban areas. Creation of this Low Impact Development and Green Infrastructure Guidance Manual coincides with the direction of stormwater management promoted by the Environmental Protection Agency (EPA) in developing new Clean Water Act stormwater rules.
The goal of Low Impact Development (LID) is for post-development runoff to mimic pre-development conditions. In most cases, this means creating small-scale GI features that use vegetation, soils and natural processes to mitigate stormwater volumes as close as possible to where rain falls. Much of the runoff from impervious surfaces flows into these features rather than increasing roadway flooding, and thus can reduce the need for investment in traditional stormwater management structures. The City of Tucson has partnered with the non-profit organizations Watershed Management Group and Tucson Audubon, which enlist citizen volunteers to provide hands-on installation of water harvesting features and GI on residential collector streets.
Locally, elected officials, grassroots organizations and the general public have supported the implementation of GI/LID. The Pima Association of Governments Regional Council has recognized the potential benefits of Low Impact Development and Green Infrastructure by adopting a resolution supporting GI/LID. The City of Tucson passed a Commercial Water Harvesting Ordinance requiring commercial projects to integrate water harvesting in their development plans. An internal Department of Transportation Green Streets Policy requires all public streets to integrate GI from the initial design concepts.
For residential properties, Tucson Water has a rebate program offered to customers who plan to install a rainwater harvesting system. Participating customers must take a workshop where they learn the principles of water harvesting to ensure their residential systems are designed and installed effectively. These workshops have been an overwhelming success, necessitating additional workshops taught by educators and professionals from the University of Arizona/Pima County Cooperative Extension, Watershed Management Group, and Southern Arizona Rain Gutters --a local business.
The Pima County Regional Flood Control District is in the process of preparing new design standards for stormwater detention and retention. These new standards will allow the flood control benefit of LID/GI to be calculated so that the use of these features can be justified in terms of their flood prevention and mitigation benefits. Integrating GI/LID practices is becoming more the norm than the exception as we begin to integrate the concept of the triple bottom line of environment, economics and social equity into development in the urban areas.
At the national level, the EPA recently released the National Stormwater Calculator, which provides a standardized way to calculate the stormwater captured by common GI practices using local climatic conditions. Many professional organizations have their specific rating system and GI/LID practices are recognized in all. These include: Leadership in Energy & Environmental Design (LEED) certification by the US Green Building Council (USGBC); Sustainable SITES from the American Society of Landscape Architects and the Lady Bird Johnson Wildflower Center; and Envision, developed by the Institute for Sustainable Infrastructure and Harvard’s Zofnass Program for Sustainable Infrastructure, and supported by the American Society of Civil Engineers and the American Public Works Association.
Here in Pima County, what began as a quiet grassroots effort recognizing the importance of valuable water resources in an arid climate has come full circle with local and national jurisdictional acknowledgement, and professional recognition to include GI/LID as an essential integration for development to occur in a sustainable fashion in the southwest desert.