Reimagining the Urban Rain Garden

“I absolutely would spec this product in my projects,” says landscape architect Michelle Pinkston Ohle, about the new patent pending Freno rain garden system created by HOK colleagues in St. Louis. “It seems like an incredibly innovative system.”

Developed for HOK Product Design, LLC, Freno is a segmental wall and curbing system that makes it easier to build rain gardens in urban settings. Created by architect Paul Wilhelms along with landscape architects Matt Snelling and Jim Fetterman, Freno – the name is Latin for “curb” or “restrain” – provides a smart new alternative to traditional methods of building urban rain gardens.

A rain garden is a shallow depression filled with water-loving plants in a prescribed profile of soil, sand and aggregate. It catches rainwater, stores it for a short time and filters out pollutants. In recent years, rain gardens have become more common in urban areas, where they are set into streetscapes or parking lots and contained by concrete enclosures or planters.

Building these relatively low-tech bioretention areas in non-porous urban landscapes is a sustainable idea that’s quickly gaining traction among developers and municipalities seeking to protect waterways from toxic runoff.

“It’s not a new idea,” says Snelling. “Cities like Portland, Seattle and Kansas City have been using urban rain gardens for a while as an alternative to conventional water treatment approaches, which are energy-intensive and expensive. Freno’s value proposition is to provide a simple, durable solution with a high-quality finish at a lower cost.”

A typical rain garden at the scale needed by a municipality or big-box retailer requires a labor-intensive process to excavate a large enough area to build the formwork and pour the cast-in-place reinforced concrete structures on the site. With the modular Freno system, what would typically take a couple of weeks to build can be compressed into just a couple of days.

The Freno system features a set of simple precast concrete pieces based on three shapes – “S,” “T” and “N” – that act as building blocks. As with the ubiquitous segmental retaining walls we’re all so familiar with, the individual pieces can be arranged in a nearly limitless amount of configurations. The system has also been designed to accommodate future expansion of the product line, with the possible addition of complementary accessories like benches, bike racks or decorative fencing. It is offered in three basic colors and can be ordered in custom colors and aggregates.

“I played a lot with Legos as a kid,” says Snelling, whose desk features an iPod stand made of Legos. “The Lego instruction sheet showing how different pieces can go together definitely influenced our original sketches.”

Making the system easier to construct means it requires less labor and is much more affordable. “We also can use denser concrete that is much more durable than typical ready-mix concrete,” says Snelling. “And because it isn’t weather-sensitive, it can be installed whether it is freezing outside or 100 degrees.”

Freno gives clients much more control over the quality of the installation, adds Wilhelms. “The pieces can be built with a very high level craftsmanship and installed with a great deal of ease and accuracy.”

There also are aesthetic benefits to the system. “We could easily manage stormwater with an underground tank,” says Wilhelms. “But it’s a nice way to make something beautiful out of something that serves a very utilitarian purpose. Why bury that investment underground when we can create an amenity for people to enjoy?”

As municipalities across the country look for a consistent, cost-effective approach to managing stormwater, the potential market for Freno is enormous. “Stormwater detention already is being mandated by some municipalities,” says HOK Product Design Director Susan Grossinger. “There are a handful of cities in Southern California where you can’t build a surface parking lot or public project without diverting stormwater. The time has come.”

St. Louis-based Midwest Products Group is the manufacturer. HOK Product Design has partnered with The Partnership for Downtown St. Louis to install the first Freno rain garden on 11th Street, a few blocks from HOK’s office. Construction will begin in May.

“We’ll measure the amount of water captured as well as the health and performance of the plants,” says Wilhelms. “Our hope is that this will help set the stage for an overall revamping of the downtown streetscape.”

The product design process has opened the eyes of Snelling and Wilhelms to a new world.

“Once you understand the product design process, you see how easy it is to apply this kind of design thinking to other challenges,” says Wilhelms, who already is working on another product. “It feels good to have the potential to get more value out of something we create rather than participating as bystanders and using products developed by others. We have the ability to make such a large impact on the world with just one strong idea.”

Click here to watch a YouTube video about Freno.

Learn more about Freno Rain Garden.