The planted area you see pictured below is a bioswale. A bioswale is a long, often linear depression in the ground that allows water to move from one location to another. It has gentle side slopes where plants can be grown to slow water enough to filter pollutants and allow more runoff to filter into the ground. This bioswale collects all the water from the roof of the library and directs it to the storm drain at the bottom of the swale. Roof runoff often carries many pollutants, such as leaf litter, bacteria and algae that grow in gutters, and bird droppings. The plants in the bioswale will help remove these pollutants before the runoff enters the storm sewer system, where it travels directly to theNorth Platte River.
This bioswale was the Eagle Scout project for Spencer Lake. Lake worked with the City of Scottsbluff to complete the project with help from members of Boy Scout Troop 13 and the UNL Master Gardeners. The project was designed by Amy Seiler and was funded in part with grant funds from the Greener Nebraska Towns Initiative and in part by the Lied Scottsbluff Public Library Foundation. The day of the installation, we had 29 volunteers work for a combined 100 hours.
Scroll through our pictures below for more information on this project.
This is the site before any work was done. This part of the library is a recent addition, and the site was very compacted from construction.
The City Wastewater Department hauled compost in and tilled it into the ground. This was important because there was no topsoil left after construction. The compost added organic matter to the soil, which provides nutrients to the plants and improves infiltration of rainwater.
Next we placed rocks and installed edging. The rocks help hold the steep bank in place and also help to slow the flow of stormwater from the roof drains. The edging gives the garden a defined boundary and keeps grass from spreading into the area.
Next we planted all the trees, shrubs, and perennials. Trees and shrubs were used on the steep bank to help hold the slope in place. Native or well-adapted perennials were used in the bottom of the swale to slow and filter stormwater as it flows from the roof drains to the storm drain.
After the planting was completed, we installed a drip system. In many climates this would probably not be necessary, but here in western Nebraska, where we commonly go for two or more months without any significant precipitation, we felt a drip system would be necessary.
Once the drip system was installed, we added mulch to suppress weed growth, add organic matter, and help retain soil moisture. No mulch was added to the bottom of the swale, however, so that during a rain event, the mulch would not be washed away and plug up the storm drain.
The bioswale will not be fully functional until the plants start spreading and filling in, which will take at least until next spring. So until then, we have placed temporary rock checks around the storm drain inlet and along the length of the swale. This will slow and filter stormwater, so that if there is any erosion in the swale, the sediment will have a chance to drop out of the stormwater before it reaches the inlet. This swale has a very gradual slope (less than .5%), so this should be sufficient for erosion control. On a steeper slope, an erosion control blanket or something similar may be necessary.
In the future, we will be monitoring the bioswale and making any changes needed to make it more functional. Check back here for updates on how it functions over the next year.
A special thanks to Spencer Lake and Boy Scout Troop 13, the UNL Master Gardeners, Amy Seiler, Scottsbluff Landscaping, Greg Suhr, and Doug Hoevet for your contributions to this project.