Courtyard Rain Garden

Allegheny County recently converted the planters in the Courthouse Courtyard into rain gardens.

Master Gardener volunteers plant the rain garden.

Master Gardener volunteers plant the rain garden.

In the Courthouse Courtyard, four downspouts that previously drained into the city’s sewer system are now being diverted into four existing raised beds that have been planted with native plants.

In Southwestern Pennsylvania, an average rain storm can produce two inches of rain in a 24-hour period. Even two inches of rain falling on a roof can result in more than 600 gallons of water rushing through downspouts and into sewer systems. As little as 1/10 inch of rain can cause combined sewers to overflow.

As rain travels over hard surfaces, it picks up and carries pollutants, such as oils, silt, chemicals and debris. The large amount of impervious surfaces in urban areas does not allow rainwater to permeate into the soil. Instead, rainwater flows into storm and sanitary sewers, as well as local streams, which are often unable to handle the higher water volumes, causing back up and eventual flooding.

Master Gardeners were asked to collaborate with the county to plant, maintain and provide educational programming for the rain gardens. In the summer of 2009, crews of Master Gardeners installed the native plants in the courthouse gardens. Existing sweetbay magnolias (Magnolia virginiana) and serviceberry (Amelanchier sp.) provide the canopy for a variety of natives including, fothergilla (Fothergilla gardenii), oakleaf hydrangea (Hydrangea quercifolia ‘Pee Wee’), summersweet clethra (Clethra alnifolia) and dwarf sweetspire (Itea virginica ‘Little Henry’).

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