On a gorgeous fall day, people jog and walk dogs along Tacoma’s waterfront in the new Dune Peninsula at Point Defiance Park. Locals appreciate the almost miraculous transformation of this land. The human-made peninsula, named for the science-fiction book by Tacoma author Frank Herbert, was built over an accumulation of slag a manufacturer dumped into Puget Sound for 70 years.

As Tacoma Park Board Commissioner Erik Hanberg said in a news release, “The theme in ‘Dune’ of a world destroyed by environmental catastrophe drew in part from Frank Herbert’s life experiences in Tacoma, which in the 1950s was one of the nation’s most polluted cities. The characters in the novel have a goal to ‘terraform’ their planet back to its inhabitable origins. That’s what we’ve done here. We have terraformed a polluted wasteland into a beautiful environment for all to enjoy.”

Related: Recycled botanical garden in Seattle brings visitors decades of joy

The 11-acre addition to Point Defiance Park opened in July. The new Wilson Way bridge also opened, connecting Point Defiance Park to Ruston Way. Bicyclists, runners and walkers have long bemoaned the lack of connection between trails at this point, now solved by the new bridge.

The most fun part of the design is a series of six slides connecting the park with the marina below. Stairs nearby offer another way to get down the slope, or a way to get back up, for those who want to repeat the slide experience — sometimes over and over. Concerts and other outdoor events have a new venue in the park’s Cambia Legacy Lawn. The paved Frank Herbert Trail provides a pedestrian path.

Developers had a complex job of building this project around so many active uses, competing interests and different jurisdictions, according to Clayton Beaudoin, the principal of landscape architecture firm Site Workshop. This Seattle-based landscape architecture firm worked with Metro Parks Tacoma on designing the cleanup and layout of Dune Peninsula at Point Defiance.

Metro Parks commissioned Adam Kuby and Nichole Rathburn to create site-specific artworks. Kuby’s work, Alluvion, uses steel pipes to suggest the smelter smokestack of the former ASARCO plant, long infamous for wafting “the Tacoma aroma” over the city. Rathburn’s Little Makers, a series of bronze forms, are based on the novel Dune, drawing parallels between the book’s plot and the transformation of a slag pile into a park.

Beaudoin talked to Inhabitat about the transformation from slag heap to beloved new park.

tall grasses in foreground with water and forests in background

Inhabitat: What was this site like before you started building the park?

Beaudoin: A portion of the site was occupied by the Tacoma Yacht Club, including their clubhouse, access road and parking. The other portion of the site was generally flat and covered with yard soils from the North Tacoma remediation project. There was no vegetation or infrastructure.

Inhabitat: Tell us about the toxic slag — what were its risks to people?

Beaudoin: The contaminants of concern (COCs) were lead and arsenic. When a new fracture face opened up, which happened as the slag weathered, small amounts of lead and arsenic would make their way into Commencement Bay, which caused heavy metal loading. The shoreline armoring and capping of the peninsula, which is located beneath the park, eliminates the metal loading to Commencement Bay. In addition, the slag could be ingested either by inhalation or eating it. The cap allows people to be on the peninsula and keeps them from having contact with the slag. Lead ingestion can cause severe mental impairment, and arsenic is a carcinogen.

bronze and weathered steel sculptures in a park

Inhabitat: How did you move it and where did the toxic slag go?

Beaudoin: As part of the shoreline armoring, the slag was excavated to a 2:1 slope, so the shoreline armoring would be stable over time. The slag was moved using conventional construction equipment (excavator, articulated dump trucks and dozers). The excavated slag was placed on the peninsula (in the Yacht Club parking lot and under the park). The elevation of the peninsula was raised 10 to 20 feet to accommodate the slag and contaminated soil. This lowered the carbon footprint of the project by keeping the contamination onsite and not hauling it offsite. The capping system was then placed on top of the contaminated slag and soil.

Inhabitat: Describe the woven geotextile cap. What is it? How big is it? What does it do?

Beaudoin: There are three kinds of caps on the peninsula: low perm asphalt, low perm concrete and a multilayer cap composed of a geocomposite clay layer, 40 mil HDPE and a geonet. Each cap type prevents water from infiltrating the contaminants and then getting into Commencement Bay, and it also prevents people from coming in contact with the contaminants. The cap system is required to have a permeability less than 1 x 10-7 cm/sec. The cap covers all of the peninsula, which is about 13 acres. It also ties into the adjacent Point Ruston site, which is also a Superfund site and has a cap underneath it. This is the largest Superfund Redevelopment Project in Region 10 of the EPA.

person going down tall blue slide

Inhabitat: What inspired you to build the slides?

Beaudoin: Together with Metro Parks, Site Workshop has designed a lot of parks and public spaces, and we’ve learned to anticipate how people use space. At the very top of the slope is an overflow parking lo,t which we imagined would be used by boaters. After launching their boats, they would have to drive their trucks to the top and race back down some 90 feet of elevation to their boats. Slides seemed like the fastest — and most fun — way to do it. We’ve been working hillside slides into many of sloped projects, and since the Dune Peninsula was never intended to host a traditional playground, this seemed like a nice way to work something playful into the trail portion of project.

aerial view of stairs and slides on a hillside

Inhabitat: What do you like best about the resulting park?

Beaudoin: The most gratifying and inspiring result is how the citizens of Tacoma have embraced the park in all of its rustic, rough and less-manicured edges. We think Dune Peninsula resonates with people because of how it celebrates Tacoma’s cultural and natural history without beating you over the head with it. There’s plenty of mystery to discover and beauty to inhale, and people (and the wildlife!) are responding in ways that should make everyone involved feel proud.

Also, for such a large site, we were able to utilize several creative features, which were constructed in especially cost-effective but impactful ways. For example, the Moment Bridge, which has become a bit of an icon for the city, is constructed from off-the-shelf concrete girders akin to what you might see over a highway. However, the design team was able to craft those basic materials in a way that make it feel special, including the “moment” at the center, the railings and the unusually shaped piers. The planting scheme was developed to utilize site soils and be delivered in a way that minimizes maintenance compared to traditional landscapes (which import topsoil and bark mulch and require persistent maintenance). Early in the project, we created test plots to evaluate how the site soils responded to various amendments, which helped minimize cost and improve the success of the plantings.

+ Site Workshop

Images via Teresa Bergen / Inhabitat