A key component of the massive urban redevelopment of downtown St. Louis was renovating Kiener Plaza, a 1.9-acre park adjacent to the Old Courthouse that is located just west of the Gateway Arch. The goal of the $380 million project was to better connect the downtown area to the Arch.

The City of St. Louis tasked Michael Van Valkenburgh Associates (MVVA) with redesigning Kiener Plaza. MVVA’s plans included multiple garden spaces filled with native Missouri plants, including 140 new trees, decorative plantings, and lawn space that could seat up to 2,000 people for public events.

But to have a fully realized green space, Kiener Plaza first needed a solid, well-thought-out soil foundation. MVVA tabbed us to develop soil profile designs that reflected regional, native characteristics and supported sustainable vegetation, including maintaining the soil balance necessary for healthy plants, good drainage after rainfall, and the ability to retain water during dry spells. In addition, the great lawn needed to withstand a lot of foot traffic—2,000 pairs of feet at every event can do a lot of damage to vegetation that hasn’t been properly supported. Olsson’s team had the added challenge of working with an unusual foundation underneath the soil — demolition debris that forms much of the base of downtown St. Louis.

The City of St. Louis requested soil that would need less overall maintenance—less water, less fertilizer, less pesticide. After testing and soil analysis, our team of soil scientists found that the key to Kiener Plaza’s soil design was re-establishing vital soil microbial systems to support deep root growth and soil resilience.

Once the soil mix was identified and the project moved into the implementation phase, we were on-site to provide construction oversight of soil and soil placement. Massive construction equipment can compact and degrade soil when it drives over the top of it, so our on-site presence was essential to the job’s proper completion.

With the soil foundation in place and the green space thriving, Kiener Plaza reopened to the public in 2017—welcoming all to a more beautiful and sustainable downtown St. Louis.