City of Denison Improves Water Quality and Infrastructure through Urban Conservation Practices

The City of Denison is in west central Iowa where the rolling hills of the Loess Hills begin. In this region of the state, water sheds from the surface more rapidly than other areas of the state causing numerous issues including degraded water quality. Due to the rapid surface runoff on Denison’s landscape, the city wanted to take a different approach to managing storm water. In 2014, City Manager and Engineer, Terence Crawford, sought out the resources from the IDALS Regional Urban Conservationist to implement more Low Impact Development (LID) into the community and chose to demonstrate water quality in the city’s Washington Park. The success of this project initiated the push for more storm water management practices like it.

The search for additional projects led the city to apply and receive an Urban Demonstration Water Quality Initiative (WQI) grant to assist the city with improvements to the heavily utilized and degrading 14th Street “Safety Zone” parking lot downtown. Many businesses and pedestrians alike use this parking lot to access downtown businesses. Before implementing water quality practices into the parking lot, the parking lot contained two raised deteriorating islands which diverted dirty runoff from the parking lot and surrounding buildings to storm drains. In addition to the runoff concerns from the parking lot Crawford mentioned, “During heavy rainfall events some of the stores were actually getting storm water in their basements”.

The LID improvements to the parking lot incorporated four bioretention cells in place of the raised islands and a strip of permeable pavers at the rear of the downtown businesses. At a minimum, LID practices are designed to capture the first 1.25” of rainfall in 24 hours. The majority of pollutants such as sediment and nutrients are transported during these rainfall events. In this project, both the bioretention cells and permeable pavers are sized to capture the first 2.4” of rainfall in 24 hours increasing the water quality benefits of these practices.

Along with capturing storm water, plants including many native Iowa species were planted throughout the bioretention cells to uptake pollutants commonly found in storm water. Over 600 plants were planted in the cells thanks to the help and expertise of ISU Outreach and Extension Master Gardener, Pam Soseman, and Denison High School FFA students. Soseman worked closely with Denison High School teachers Alise Meyers and Dana Weeda to educate the students about water quality, conservation and plant characteristics. Students were tasked with selecting plants based on their hardiness to Denison’s climate and flower bloom times.

As part of the High School’s Community Betterment Day students, teachers, IDALS staff, and staff from Crawford Soil and Water Conservation District showed up ready to plant. Soseman remarked at the efficiency of the students and teachers in planting over 600 plants in one day. Student, Hunter Underwood, showed his appreciation for the hands-on experience saying, “I learned concepts of how to build a bioretention cell that would help conserve and filter rain water and I was able to help out my community while doing it”.

This project demonstrated to the FFA students the importance of protecting urban water quality in addition to agriculture water quality. Mayor, Dan Leinen, continues to see the benefits of this project playing out. “As a former agriculture instructor it has always been an issue of importance that we educate young people about water quality issues.” Leinen praised the efforts of involving the local FFA chapter in the project, “This project was an important teaching component to show cities should also take a part in maintaining water quality.”

The educational component of this project serves as an important part of this project.
In addition to holding a ribbon cutting ceremony and various presentations to local groups such as the Rotary and Garden Club to demonstrate how each practice works, two signs were installed. One permeable paver and one bioretention cell sign explain how the practices work along with the benefits they provide. The success of the “Safety Zone” project would not have been possible without the cooperation of the various partnerships created. Compliments continue to pour in from the public and business owners who feel the grant was a great way for the city to solve storm water runoff issues while making these improvements more cost effective. As Leinen defines it, the Safety Zone project is a fantastic project for the community.