Audubon Center & Sanctuary Rainwater Harvesting Project

Acknowledgments: This project was designed and installed in 2010 as part of the 10,000 Rain Gardens Project. Special thanks to the Richardson Bay Audubon Center & Sanctuary, Americorps Watershed Steward Program interns, and the many workshop participants and volunteers who worked to make this project possible.


Interpretive sign at project site
Project Overview

Richardson Bay Audubon Center & Sanctuary offers educational programs designed to foster a love for the outdoors and inspire a sense of stewardship. Throughout the year, many school groups, bird watchers, and other visitors enjoy the site. This rainwater demonstration project was designed to be integrated into the "Audubon at Home" program, which educates and encourages the public to take individual conservation action in yards and neighborhoods that can sustain birds, other wildlife, and healthy habitats , as well as other activities held on site.

Rainwater Catchment System Unique Features

The system is designed to capture water from two sections of the community building roof, directing run-off into a network of rain gardens at the front of the building and a 550-gallon cistern at the side of the building. Stored water is saved for use in the summer to establish native plants and/or for use in the worm bins. Overflow from the cistern is directed to the rain gardens designed with native plants to attract wildlife and provide habitat while helping to infiltrate water from the roof into the soils. At the front of the building, run-off has been redirected to help mitigate problems of pooling at the building's foundation, and pooling and erosion of the adjacent paths, field and watershed. Two rain gardens are integrated to preserve existing shrubs and native grasses; and new native plants have been planted on the rain garden berms. The upper rain garden overflows through a pipe buried safely under the path to the lower rain garden, which provides additional are for the water to infiltrate in the ground and passively water native plantings.
Community building

General System Statistics

          Watershed A (front roof) to rain garden only:
          Gallons per inch of rain (90% efficiency):
          Gallons per year (22 inch average rain):
          Watershed B (side roof) to cistern and rain garden:
          Gallons per inch of rain (90% efficiency):
          Gallons per year (22 inch average rain):
          Rain catchment capacity:
          Rain garden #1 basin area:
          Rain garden #1 basin area:
          Total rain garden design capacity:
          Total materials cost:

315 sq. ft.
176 gallons
3,885 gallons
189 square ft.
105 gallons
2,331 gallons
550 gallons
35 sq. ft. (35 cubic ft.)
65 sq. ft.
100 sq. ft.

550 gallon cistern
Rainwater Catchment System Unique Features

The ground below the 550-gallon cistern was leveled, and a foundation ring filled with pea gravel was installed to provide a stable foundation. The existing downspout was cut off at a height that allowed a manufactured combination downspout/first flush diverter to be inserted with adequate space to run the water to the cistern by gravity.

This system is plumbed so that the fist flush water goes to the rain garden via the same pipe as the overflow. A hose bib at the bottom of the cistern allows buckets to be filled or a hose to be attached for low-pressure use of the water. Due to issues with the old plumbing to this building, the cistern provides the only water available.

Rainwater run-off enters the cistern through the top. A slip union was used to allow the inflow pipe to be disconnected easily for access to the cistern through the porthole for annual inspection. The overflow pipe coming off the side provides ventilation, and is covered with wire mesh secured by a pipe clamp to prevent mosquitoes or other critters from entering the tank. A backflow prevention device was installed at the water meter.

Rain Garden and Watershed Friendly Landscaping

To provide the water a safe way to overflow from the first rain garden, a trench was dug across the path to a second rain garden. 

An atrium grate was installed at the desired height to maximize the holding capacity of the first rain garden while allowing water to spill through the drain pipe before going over a berm and potentially causing erosion to the berm and adjacent path. A water bar was installed above the trench to direct surface water flows from the path, where there had been problems with flooding and erosion, into the second rain garden.
Volunteers dig trench for drain pipe
In the lower rain garden, a spillway was installed at the low point in the berm to allow excess water to overflow into the surrounding meadow. Rocks were clustered at the spillway to dissipate the enrgy of the water, screen out any mulch or sediments, and minimize the potenntial for erosion. 
ns and the berms.

Native plants including Coffeeberry, Coyote Brush, Artemesia, Yarrow, Monkey Flower, Nine Bark were installed on the berms of the rain garden, and rushes in the basin. A thick layer and wood chips provided for free by a local tree company were used to lay a thick later of mulch to both the basi
Volunteers dig basin of rain garden and prepare to plant natives

Atrium grate is installed

          System Costs

          550-gallon polypropylene tank:
          Gravel foundation ring:
          0.5 cubic yard pea gravel, incl. delivery:
          First flush and leaf diverter:
          Pipe and various fittings:
          Backflow prevention installation:
          Backflow inspection (5 years):

                                                             Total approximate costs:  $2,975.00