When St. Louis set out to redevelop Washington Avenue between 7th Street and Memorial Drive in 2016-2017, the city faced a familiar urban puzzle: how to create an inviting streetscape on a tight budget while working around the constraints of a busy downtown corridor.

The project team had to match the design quality of two previous streetscape phases that had enjoyed significantly larger budgets. Adding to the complexity, the street’s lineup of historic buildings meant coordinating with individual property owners alongside city officials to ensure everyone’s needs were met.

The Vision Meets Reality

The designers envisioned transforming Washington Avenue with a grove of healthy street trees that would deliver far more than visual appeal. These trees would generate oxygen, capture carbon, improve public health, reduce the urban heat island effect, muffle traffic noise, and naturally calm vehicle speeds.

But the street itself presented its own challenges. Its dense urban infrastructure created a web of underground obstacles that hindered tree growth options. Basement foundations extended all the way to the curb line, leaving minimal for root systems. Meanwhile, the hardscape requirements of a major downtown thoroughfare demanded durable surfaces that could handle heavy pedestrian and vehicle traffic.

Making Every Inch Count

With such constrained planting areas, the project required a strategic approach where every cubic foot of available space had to work overtime. The solution lay in maximizing soil volume within the existing footprint, rather than expanding the planting areas themselves.

This is where RootSpace soil cells proved essential. With the largest usable void space available in the market, these systems allowed the design team to provide the maximum amount of readily available soil into the limited underground area. The result was a streetscape that achieved the original vision for healthy street trees while respecting the practical demands of downtown St. Louis infrastructure.