Historic Fourth Street District and Riverside Park Promote Water Quality with Recent Upgrades: Sioux City, Iowa

Sioux City’s Promenade is located in the Historic Fourth Street district of downtown. This area is utilized by pedestrians due to its proximity to the Mainstreet theatre, downtown businesses, and convention center. In addition to surrounding rooftops, the Promenade contains impervious surfaces with compacted soil and concrete underlay that generate excessive amounts of runoff during even the smallest rainfall events.

The excess amount and poor quality of runoff from this property led the city to install low impact development (LID) to demonstrate water quality and stormwater management improvements. With the help of IDALS Urban Conservationists and project partners, this area was transformed to capture and treat stormwater from the Promenade property.

Through a Water Quality Initiative (WQI) Urban Demonstration Project grant, four bioretention cells were installed throughout the Promenade. Downspouts collecting rainwater from awnings of the building are tied into two bioretention cells which feature a bubbler to outlet roof water onto the cells. Plants uptake nutrients and contaminants commonly found in stormwater and filter them out before water exits the cells through tiles that connect to storm drains. Incorporating LID in the Promenade slows down, filters, and cools stormwater before it reaches the various stream and river networks located throughout the City.

Sioux City is among the many cities in Iowa that is required to obtain storm water permits for their Municipal Separate Storm Sewer System (MS4). To achieve the goals of the MS4 program Melissa Campbell, Environmental Services Analyst for the City of Sioux City, incorporates stormwater management into infrastructure projects whenever possible. Campbell was excited for the opportunity to demonstrate water quality in the historic downtown district stating, “The Promenade was an ideal location to install stormwater management practices because there is a high amount of impervious surface here and this area is utilized by pedestrians visiting downtown businesses”. Campbell hopes this newly renovated space will draw more people to the area and educate the public about water quality.  

ISG Consulting Group was the lead design firm on the Promenade project. Landscape architect, Nathan Gruver, worked on preparing the masterplan and construction documents. “At the forefront of all my projects, I stress the importance of incorporating storm water management into all of my designs.” Traditionally, stormwater management is an afterthought when planning for development. Gruver hopes to change this perception by demonstrating how sound development plans and stormwater management can work together to accomplish multiple goals. “When designing for this project, I strategically placed the practices in locations with the greatest environmental benefit and visibility to the public.”

To kick off the completion of the project, a Ribbon Cutting ceremony was held on November 3rd for the public and media. Iowa Secretary of Agriculture, Bill Northey, was in attendance to show support for the water quality project. Northey remarked how inviting the Promenade space is and hopes this area can attract out-of-towners as well as Sioux City citizens to see this project in action.

Due to lower than anticipated costs on the Promenade project, the city was able to expand its water quality efforts to Riverside Park. This site was chosen due to its proximity to the Big Sioux River and the amount of use the park receives annually. Riverside Park is a popular recreational area encompassing over a dozen baseball and soccer fields. Due to the limited parking stalls available at the park, the city proposed an additional parking lot.

According to Campbell, the parking lot at Riverside Park was not going to happen unless storm water management was addressed. The city enlisted the expertise of Danny Sturm, Project Manager with JEO Engineering, to incorporate best management practices (BMP) into the design for an additional parking lot. In Sturm’s design, the first two bioretention cells in the system are sized to treat the Water Quality Volume, or the first 1.25 inches of rain in 24 hrs. The two cells then stair step down into a third cell which was designed to meet the 100-year storm event water detention requirements for the City. Sturm designed both systems to work together in treating and detaining runoff from the newly constructed parking lot. Plants were recently planted in the bioretention cells to finish up the project before winter.

In addition to providing a water quality benefit to these areas of Sioux City, these Urban WQI demonstration projects educate the public about water quality. Along with 33 other Urban WQI projects throughout the state of Iowa, these projects demonstrate Iowa’s initiative to accomplish water quality and nutrient reduction goals. The implementation of these projects and others throughout Sioux City are attracting more Green Infrastructure for incoming projects. The success of these projects continue to lead Western Iowa in water quality efforts and set the stage for surrounding communities.