The following is Part I of a three part series focusing on the City of Scottsbluff’s 319 grant projects. These projects are designed to reduce impervious cover in parking lots, filtering and infiltrating stormwater runoff.
In 2014, the City of Scottsbluff was awarded $40,000 through the Nebraska Department of Environmental Quality’s 319 grant program. The purpose of the grant was to allow the City to install demonstration projects that would promote better stormwater management throughout the City. Through this project, the City was able to remove over 9,600 square feet of concrete throughout several parking lots and replace it with landscaping. In addition, some of the remaining concrete in the parking lots were sloped so as to allow runoff from the concrete to be captured by the landscaped areas.
Scottsbluff has a Business Improvement District (BID), which owns several parking lots downtown. Historically, these parking lots have been all concrete, with no landscaping at all. In recent years, there has been interest from the BID advisory board in adding landscaping to the parking lots to help soften their appearance. The BID has been able to work with the Scottsbluff Stormwater Department to install landscaping areas in the parking lots that not only look more attractive, but also serve an important environmental function by capturing and filtering stormwater.
The vast amounts of hardscape in these parking lots made them a very inhospitable environment. No vegetation meant that they got extremely hot in the summer. Additionally, because the entire surface of the lots was impervious, any rain that fell quickly ran off into the storm drains. While this periodically washed the lots clean, it meant that any pollutants that had been on the lot, like dirt, oil, antifreeze, and trash, to name a few, were carried directly to the North Platte River. We also get very limited rainfall here in Western Nebraska, averaging 16″ per year. By capturing the runoff from the parking lots in the landscaped areas, we can cut down on the need for irrigation and take advantage of what little rain we do get.
The lots also had raised medians that were a maintenance headache in the winter; every time it snowed, they had to be cleared by hand. So when designing the lots, we had a few goals in mind. We wanted to eliminate the amount of areas that would have to be cleared of snow by hand, we wanted to lose as few parking places as possible, and we wanted to strategically place our landscape areas in a way that would capture as much stormwater as possible. We also wanted to add in trees and other vegetation that would help cool the lot in the summer, making it a more desirable place to park.
The first step in the process was design. With technical assistance from the Nebraska Forest Service (NFS) and the Nebraska Statewide Arboretum (NSA), we were able to come up with a plan that created several large landscape beds designed to capture stormwater runoff as well as provide adequate soil volume for tree planting. Trees commonly struggle to survive in harsh, hot urban environments, and it is our hope that by providing large amounts of space for our trees, they will be able to survive and thrive long-term. NFS and NSA were also able to help us to select native and well-adapted plants that are better suited to the hot, harsh environment of a parking lot.
The next step was concrete removal, which was done by our streets department. One of the biggest challenges of the project was not knowing what kind of soils would be underneath the concrete. In some places, because the paving was so thick, we had to bring in fill material. In other places, we simply added a small amount of compost to increase the organic content of the soil. Once the concrete was removed and the soil was prepped, we installed a drip system. While these are low-water use landscapes, the deep-rooted prairie plants that we chose take time to establish their root systems, and until they have those root systems, they will need some irrigation. The drip system can also be used in dry years to keep the plants from becoming stressed. After that, we planted and mulched. However, just because the projects had been installed didn’t mean that we were finished. There are several challenges that come with a project like this, and over the next couple of articles we are going to describe some of the ongoing challenges and lessons learned from these unique landscapes.