Dune Peninsula at Point Defiance Park Tacoma, Washington, USA by Jacobs
Shortlisted for Brownfield Awards Category 9 - Best International Project
On July 6, 2019, Dune Peninsula at Point Defiance Park officially opened to the public with walking paths, a public amphitheater and sweeping views of Washington’s Puget Sound, Mt. Rainier, and Vashon Island.
This new community gem played a key part in Metro Parks Tacoma’s – the municipal corporation that owns and oversees parks and recreation services in and around the City of Tacoma – recognition from the National Recreation and Park Association with a Gold Medal Award for Excellence in Park and Recreation Management. Additionally, the project has been selected as one of the American Public Works Association’s Public Works Projects of the Year for 2020.
While it’s now garnering recognition for its benefits and beauty, the site wasn’t always viewed this way.
The park, located along the shore of Commencement Bay in south Puget Sound, sits on a portion of the former Asarco Tacoma Smelter site which operated from 1890 to 1986, first as a lead smelter, and later as a copper smelter that processed ores containing high levels of arsenic. The peninsula was built over a period of about 70 years, beginning in 1914, and was the disposal location for smelter slag, a by-product of the smelting process. A portion of the peninsula has been leased for many years by the Tacoma Yacht Club, but members were not allowed to walk around the exterior of the clubhouse due to the ground being covered with smelter slag. The rest of the peninsula was closed to the public because it was also covered with slag and contaminated soil.
The project included robust public and stakeholder engagement:
Metro Parks Tacoma – site owner
U.S. Environmental Protection Agency (EPA) – responsible for remediation on the peninsula
City of Tacoma, Washington
Washington State Recreation and Conservation Office
Washington State Department of Transportation
Washington State Department of Ecology
Tacoma Yacht Club – long term leasing tenant of a portion of site
Point Ruston – owner of a portion of the former smelter that is adjacent to peninsula
Site History and Project Scope
The former Asarco Smelter site, also known as the Tacoma Smelter, was one of the first Superfund sites in the nation. It was located on approximately 67 acres along the shore of Commencement Bay in Ruston and Tacoma Washington. In 1985, smelter operations were discontinued, and in 1986, the facility closed permanently. During the time it operated, the Asarco Smelter used high temperature furnaces to melt the metals away from raw materials. The smelting process resulted in two main type of contaminant releases.
Slag: a hot, liquid residual waste product of the smelting process. The slag contains lead, arsenic, copper, and other metals. Asarco poured hot slag into Commencement Bay to cool and harden, creating an artificial shoreline. Approximately two-thirds of the plant area at the smelter facility and the entire yacht club peninsula are slag. Some slag was cooled on land, resulting in black, rock-like material.
Sulfur Dioxide and Contaminated Dust: much of the dust settled into the soil throughout Ruston and north Tacoma, some fell into the waters of Commencement Bay, and some fell further to the west in Seattle and its suburbs. Under contract with the EPA, Jacobs had been providing innovative and cost-effective solutions at the peninsula for nearly 10 years and on the smelter site for nearly 20 years, helping to prepare the Record of Decision (ROD) and performing remedial construction oversight on the adjacent Point Ruston property, the location of smelter operations. Beginning in 2012, the firm provided oversight for the construction of a multilayer cap on a small portion of the peninsula as part of an agreement between the EPA and Point Ruston. In 2014, Jacobs started the preliminary design for shoreline armoring, the capping of the remainder of the peninsula, and the stormwater infrastructure. And, beginning in July 2016, and continuing for nearly three years, Jacobs provided remedial action (RA) construction oversight on behalf of the EPA. During construction, Jacobs also provided design changes to address differing site conditions and construction issues.
With a goal of mitigating the contaminated Superfund site and redeveloping the land, agencies including Metro Parks Tacoma, the City of Tacoma, the U.S. Environmental Protection Agency, the Washington State Recreation and Conservation Office, the Washington State Department of Transportation, and the Washington State Department of Ecology banded together to create what is now a community amenity and popular destination for more than three million people each year.
Doing our part to reimagine the site, Jacobs led the remedial design for the peninsula that would cap 15 million tons of smelter slag, provide stormwater management, and shoreline stabilization (armoring) along the tip of the peninsula and inside the yacht basin area. In addition, Jacobs delivered Senior Technical Consultant support for critical site infrastructure (retaining walls, stormwater conveyance and gangways) that were impacted by the remedial action. During the construction phase, Jacobs provided RA construction oversight to make sure the work met the requirements described in the ROD of protecting people and animals from coming in contact with the smelter slag and creating a low permeable cap (1 x 10-7 cm/sec) over the slag and contaminated soils.
To achieve compliance with regulatory codes, guidance and requirements, Dune Peninsula was remediated in accordance with the EPA’s Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund regulations. The robust, multi-layer capping system utilizes a geocomposite clay liner (equivalent to 12 inches of compacted clay), 40 mil high-density polyethylene, and a geonet that keeps the surface of the capping system well drained and prevents surface water from infiltrating the smelter slag and causing metals loading to Commencement Bay.
The design also included storm modeling to determine the best solution for nearly 3,500 feet of shoreline capping and protection. Asarco had completed armoring the outer shoreline of the peninsula in 2000; however, the tip, where most of the shoreline erosion was occurring and the inner basin were not capped. Massive 3,000- and 4,500-pound rocks were used along the tip of the peninsula where the storm effects were most pronounced. Much smaller rocks (~10 pounds) were used inside the yacht basin because the design storm was mitigated by the presence of the boat houses.
Applied with state-of-the-art components, the capping system is buried and protected from exposure to potential sunlight damage and damage from equipment operating on the surface. A portion of the capping system consists of low-permeable asphalt which was installed in the Tacoma Yacht Club parking lot. This design feature also prevents surface water from infiltrating into the slag and was included to provide additional onsite disposal capacity for the slag.
Since the capping system is buried beneath the park, there is minimal operations and maintenance associated with the remedial solution. However, the EPA does conduct annual inspections of the shoreline armoring and park surfaces. Changes in surfaces conditions over time would warrant further investigation and possible repair of the capping system. The low-permeable parking lot is also inspected annually for cracks or potholes and would be repaired following EPA approved procedures.
Health, Safety and the Environment
Dune Peninsula at Point Defiance Park is the culmination of 7 years of construction remediation at the former Asarco Slag Peninsula. During
that period, and after nearly 400,000 hours of construction, there were no lost time accidents.
The capping system over the peninsula has eliminated metals loading to Commencement Bay that had been on-going for nearly 100 years. A
portion of shoreline along Commencement Bay, which was closed to the public, is now a park that provides scenic views of Washington’s
Puget Sound, Mt. Rainier, and Vashon Island. In addition, with the opening of Dune Peninsula, residents in the City of Tacoma can now
walk along the shoreline from downtown Tacoma to Point Defiance Park for the first time in 100 years.
The decision to safely keep 400,000 cubic yards (22,000 truck loads) of excavated dirt and slag on site as part of armoring the shoreline, and
consolidating the contamination, was done to reduce disposal costs, eliminate truck traffic that would have been required to haul the contaminated material to a nearby landfill, and mitigate carbon emissions that would have resulted from the landfill transport
Dune Peninsula’s name pays tribute to local author Frank Herbert who was inspired to write the award-winning ecologically-inspired science fiction novel, “Dune,” based on the increasing pollution he saw in the city of his birth. Referring directly to the former industrial site, Herbert said the Asarco smelter created “air so thick you could chew it.”
The new 11-acre park with 180-degree Puget Sound views was, for much of the 20th century, a dumping ground for slag from the former Asarco Smelter.
Today, there are grassy green hills for rolling, rocky outcroppings for climbing, expansive lawns for kite flying, benches and tables for picnicking, and artwork honoring the contribution the smelter had on the history of Tacoma. On clear days you can see the Olympic Mountains, Mount Baker, the Cascades, and Mount Rainier. Visitors can access one of the many viewpoints and watch the sailboats, container ships, Vashon Island ferry, and Orca whales and resident seals skimming Commencement Bay’s calm waters.
Thanks to the contributions of many, the former Superfund site has been converted to an award-winning recreational destination that honors Herbert’s environmental message and the extraordinary vision of Metro Parks Tacoma and the City of Tacoma.