Olympic Sculpture Park

Challenge

Formerly a UNOCAL fuel storage and transfer station, the original site dropped over 40 vertical feet from the city core to the water and was divided into three unconnected parcels by a busy arterial and rail lines. The native soil and groundwater were contaminated with petrochemical residues that migrated into Puget Sound during storm events. In the context of these formidable challenges, designers were tasked with establishing the park as a stunning setting for iconic works of art, restoring public access to the city’s waterfront, and bringing ecological function back to the site.

Solution

To address the extreme grade changes and create a sense of procession and continuity across the site, the designers reformed the topography into a z-shaped series of descending planes and bridges over existing road and rail infrastructure. The soil was remediated, and the entire site was capped and covered with no less than 3 feet of clean fill to help prevent stormwater migration into deeper soils that were not reached during the remediation process. A specially formulated layer of topsoil was engineered to filter rainwater, reduce runoff and support the growth of native plants. The shoreline restoration zone features a constructed underwater habitat bench integrated with a newly reinforced seawall as well as a terraced beach that invites users to touch the water and explore the tide pools at low tide.

• 8.5 acres of contaminated soil were remediated, and the entire site was capped and covered with 3 or more feet of clean fill.
• The site’s original asphalt parking lot was left in place and covered to aid in capping the contaminated soil and to decrease construction debris sent to landfills.
• The landforms and plantings were designed to direct, collect, and filter stormwater as it moves through the site before draining into the Pugent Sound’s Elliott Bay.
• The six garden “precincts” use over 85,000 transplanted native plants to represent the prototypical landscapes of the Pacific Northwest and create a “mountains to sound” narrative.
• 3.5 acres of the park is planted and maintained as native meadow instead of turf. The meadow is not irrigated, requires no herbicides or pesticides, and is mowed only once a year.
• Aside from the meadow, the rest of the site is irrigated using a sophisticated system that monitors soil moisture content and supplies water in a way that mimics Pacific Northwest weather patterns.
• The “Valley” precinct was planted as an upland forest with appropriate understory species and is maintained to allow for (and illustrate) natural plant competition and succession. Similarly, a native aspen stand in the “Grove” precinct was planted in a formal grid but will randomize over time, dramatizing ecological change.
• For the “Shore” precinct, riprap rock from the shoreline was relocated to create a typical Pacific Northwest pocket beach, which allows visitors to access the water. Native dunegrass and riparian vegetation were planted around the beach.
• A specially-engineered skirted seawall redesign integrates a shallow subtidal habitat bench for juvenile salmon. The habitat bench creates a shallow angle of rocks that gradually slope to the seafloor providing a shallow water environment for the establishment of juvenile salmon and associated species.
• Informative plaques provide native plant names in English and Salish (indigenous language of the Pacific Northwest) and describe the Native uses and ecological significance of each plant.
• A lighted Water Promenade connects to the Elliott Bay Trail, a paved 3-mile bike and walking path that heads north from downtown Seattle along the waterfront.
• Environmentally-friendly management practices at the sculpture park include composting, pesticide-free gardening and the use of green cleaning products. As a result, the park received certification from Salmon-Safe, a peer-reviewed program linking land management practices with the protection of urban watersheds.

• By reusing the construction cut material from the offsite Seattle Art Museum expansion project as fill for the Olympic Sculpture Park site, 300,000 cubic feet (14,250 tons) of excavated soil was diverted from landfills, saving an estimated $1.47 million in disposal and materials costs.
• Using the integrated seawall/habitat bench design to reinforce the existing seawall cost $5.5 million compared to the initial estimate of $50‐80 million to completely replace that portion of seawall.

• The main path experiences minor wash-outs and the crushed gravel tends to clog the drain at the bottom of the slopes, requiring extra maintenance attention.
• Understory plants in the “Valley” precinct require shade to become established; this was challenging since the overstory plants were also immature at installation. Some loss of understory occured, and subsequent replanting was necessary to maintain plant health and species diversity.
• A full-time site gardener/professional steward is absolutely essential for the maintenance of such a complex and evolving landscape. The site gardener coordinates work parties, evaluates the risks of potential plant pathogens and maintains the overall health and vitality of the Meadow, Valley, Grove and shoreline environments exhibited in the park.

Tree grates: Urban Accessories
Below-grade tree stabilization: Tree Staples
Steel edging: Col-Met
Soil stabilization: Stabilizer Solutions
Irrigation: Toro, Buckner
Landscape lighting: B-K Lighting, Bega, and DAC Lighting 

Project Team

Lead Site Design/Architecture: Weiss/Manfredi
Lead Landscape Architect: Charles Anderson | Atelier ps
Civil and Structural Engineering: Magnusson Klemencic Associates
Aquatic Engineering: Anchor Environmental
Geotechnical Engineering: Hart Crowser
Mechanical and Electrical Engineering: Abacus Engineered Systems
Lighting Design: Brandston Partnership, Inc
Security and AV/IT: Arup
General Contractor: Sellen Construction
Project Management: Barrientos, LLC
Project Manager: Chris Rogers, Seattle Art Museum 

Role of the Landscape Architect

The landscape architect collaborated throughout the design and development process with a complex team of artists, client, project managers, donors, contractors, City officials, and natural resource agencies. The landscape architect was key in advocating for the use of native plant species to improve habitat richness and reduce maintenance throughout the site.