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It's All About The Water: Managing Stormwater with Rain Gardens, Permeable Surfaces, and Tree Boxes
On September 27 the Organic Land Care Program hosted its third Advanced Workshop in 2012 about stormwater management at the Beardsley Zoo in Bridgeport, Connecticut. Attendees gathered in the Hanson Education building at the Beardsley Zoo. The workshop opened with a brief welcome from Jeanne Yuckienuz, Senior Keeper and Associate Curator of the Beardsley Zoo (and also an Accredited Organic Land Care Professional) and some background about the City of Bridgeport's green infrastructure projects from Steve Hladun of the City of Bridgeport Department of Parks and Recreation.
Donald Watson, an architect with Earth Rise Design LLC, and one of the developers of the Beardsley Zoo's next rainwater infiltration project, presented on a biofiltration project in Trumbull that modeled different biofiltration features and then outlined the Beardsley zoo project. There are six phases, but the 319 Grant provides funding for the first phase, shown below.
Heather Crawford, an Accreditation Course Instructor and former Extension Educator with the Connecticut Sea Grant provided an overview of water pollution, the Pequonnock River, low impact development and bioretention features. Heather explained that polluted runoff is the number one water quality problem in the United States, especially in dense residential and urban areas where the run off rates are 3 to 10 times greater. The Pequonnock Watershed (where the Beardsley Zoo is located) has been classified as a priority watershed as having an impact on Long Island Sound's water quality. Heather discussed Low Impact Development which combines pollution prevention with water filtration features to reduce the impact of development on a river's flow and water quality. Low Impact Development includes: rain gardens, bio-infiltration systems, grassed swales, green roofs and permeable pavement.
Rain gardens are the most effective way to deal with run off from roofs onsite for most residential properties. Heather outlined the basic design principles:
To determine the ideal size for the rain garden, one must first calculate the roof area and then the volume of water running off the roof during severe rain events. One must also consider the challenge of compacted soil (compacted soils should be loosened to a depth of at least 18-24 inches).
Plant choice is dependent on the site location, but generally rain gardens require a mixture of groundcovers, perennials shrubs and small trees in larger gardens. Plants must be tolerant of both standing water and dry soil. Because the garden is meant to filter out water pollution, it can never be fertilized or treated with pesticides. Heather also warned that invasives are likely to move into your rain garden, the conditions are perfect for many invasive plants.
Michael Dietz, Program Director with CT NEMO taught about calculating stormwater runoff and water pollution from lawns. Michael discussed mapping tools to calculate the drainage area for a rain garden (you can use Google Maps and ArcGIS Online; there is even an iPhone app). Then the class went outside with Michael and Jeanne to look at the area of the parking lot which will become a rain garden and drainage area for the zoo's parking.
After lunch Lisa and Kyle Turoczi, owners of Earth Tones Native Plants nursery and provided detailed lists of trees, shrubs, flowers and ground cover for a rain garden. Lisa encouraged everyone to think about the kinds of plants that can survive in a flood plain, because of their tolerance for very wet and very dry conditions.
Lisa, Heather and Jeanne showed the class the types of plants in the three rain gardens directly outside the Hanson Education Center. Lisa shows the group ironweed, one of the plants recommended for rain gardens (keeping in mind how tall it might grow).
After the plant choice section, Tom Barry from Read Custom Soils presented on the appropriate soils to use in a rain garden that will drain quickly and filter toxins while supporting plant growth.
The next presentation was from Brendan Tyson who works with Unilock New York, which producing permeable paving stones. He discussed when to use permeable pavements, how to maintain them, and assured the class that they can be used even in areas with snowfall.
Permeable pavement works by allowing water through openings in the pavement, and the water filtering through a bedding layer of fine stones/course soil for filtration and then a base layer with higher porosity to store a greater amount of water, but also allow for quick drainage to reduce surface runoff and decrease or eliminate the need for other drainage systems. The presentation included a number of large scale projects in cities and suburbs, where the motivation to use permeable paving was simpler or more economical than installing a traditional drainage system using storm drains and pipes. View the full permeable paver presentation.
The final presenter was Paul Iorio from Storm Tree and Stormwaterworks.com. Paul presented on Tree Filter Systems, which are most applicable for suburban and urban larger scale projects - like parking lots. Tree filters use the same soil mediums to capture, store and filter water, but also include a tree to aid with water storage and filtration using plant uptake and microbial decomposition. Below is a slide from Paul's presentation that shows a tree box uses in a parking lot:
- Save the Sound (Connecticut Fund for the Environment)'s Green Infrastructure Page
- NEMO's Site on Planning for Stormwater
- The Connecticut LID Inventory
- Connecticut Environmental Conditions Online (CT ECO)
- UConn Extension Service's Rain Garden Brochure