A Case Study in Unconventional Urban Renewal

Situated along historic 4th Street in the heart of downtown Sioux City, Iowa, the Promenade is a public space adjacent to the local movie theatre and Sioux City Convention Center, and surrounded by nearby coffee shops, bars, and restaurants. Home of the popular Fridays on the Promenade and Awesome Biker Nights, the Promenade brings many residents downtown and serves as the City’s cultural and community epicenter.

However, in recent years, the Promenade’s shine had begun to fade. Frequent use during the spring, summer, and fall for popular street events had worn on the relatively dated site paving and hardscapes  over the decades, with plans for even more frequent and greater attended events in the future.

In particular, stormwater management had proven inefficient across the site’s impervious surfaces, which covered much of Promenade. Adding to the challenge was the fact that 7 inches of concrete lay beneath the existing pavers, with tightly compacted sub-surface soil below. Coupled with the fact that the area received storm runoff from adjacent building rooftops, this combination of conditions generated excessive amounts of runoff during even the smallest rainfall events.

Pavers heaved. Water ponded. And in 2016, the City set out to find a design and engineering partner to help them address these compounding issues, and to take proactive actions to preserve the still wildly popular Promenade. Alongside Iowa Secretary of Agriculture Bill Northey, the City and ISG proudly opened a revitalized Sioux City Promenade to the public the following fall – a Promenade that offers enhanced educational, environmental sustainability, and pedestrian opportunities using easy-to-implement yet unconventional urban renewal site and system improvement strategies.

Some Sioux City Flare

In addition to replacing the Promenade’s concrete and aging pavers with standard and colored concrete patterns, improvements also added a new native planting plan, modern site furnishings, a concrete seating wall, and 50% increase in total greenspace. Together, this renewed outdoor space allows visitors to take part in more active and healthy lifestyles, with designs that create a sense of place not captured elsewhere in the community.

A key element of these efforts was to preserve the Historic Roth Fountain, which now serves as a centerpiece. To do so, the updated Promenade was restructured to promote pedestrian versus vehicular traffic, allowing it to be a dedicated space to travel through, stop and relax, have conversations, experience community events, or enjoy lunch with a view.

Rain, rain, go away

The City didn’t just want to improve the stormwater management issues across the site; they wanted to implement truly sustainable designs that also promoted local businesses, outdoor opportunities, efficient stormwater management, and responsible environmental stewardship. Taking this holistic approach, ISG worked with the City to incorporate low impact development (LID) designs that not only address stormwater management challenges, but also demonstrate water quality best management practices. Let’s explore a few!

‍Multifunctional Urban Greenspace - Bioretention Cells, Soil Quality Restoration, and Native Planting

‍Approximately 50% of the paved surface area in the existing Promenade was removed to incorporate bioretention cells, green space, and soil quality restoration. Called “multi-functional urban greenspaces,” these designs are literally green in that they introduce more natural landscapes, tree, and plant species to the area, and that they also leverage naturally occurring biological processes to reduce erosion and water pollution during rain events.

For example, the four bioretention cells installed in Sioux City look like standard planting area to the naked eye. However, these areas collect stormwater redirected from adjacent buildings via new curb and gutter infrastructure, with water collected through curb-cuts along the roadway also flowing from the adjacent watershed. The water then ponds in the bioretention areas until it slowly infiltrates into the ground, naturally treating the stormwater through microbiac processes and providing nutrients to the native plant material.

‍Strategic Stormwater Management Infrastructure

‍Remember the new curb-cuts and gutters we mentioned? Those were highly strategic elements of the project as well, with each foot of curb and gutter along the plaza designed to properly redirect and transport water during rain events away from problem flooding areas.

Sustainability Education Opportunities

The Promenade’s high pedestrian traffic created the perfect opportunity to promote the innovative stormwater management solutions implemented across the site. Following project completion, a stormwater demonstration event presented to the community showcased how the new stormwater infrastructure and permeable surface manages rainfall, run-off, and roof drainage.

Today, newly installed permanent signage provides educational components within the site to inform visitors of the purpose and benefits of sustainable urban design practices.

Collaboration + Unconventional Renewal - Something to Celebrate

The product of collaboration across multiple stakeholder groups, including the Iowa Department of Agriculture and Land Stewardship (IDALS) Urban Conservationists, City staff, local businesses, and various project partners, the Sioux City Promenade improvement reflects the interdependence of social, natural, and built environments. And, the positive impacts collaboration and unconventional revitalization solutions can have on local community life.

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