Point Defiance Waterfront Phase I Redevelopment

With miles of hiking trails, scenic shorelines and panoramic views of Commencement Bay, Point Defiance Park is one of Tacoma’s finest natural attractions. But a portion of the park near the entrance had been underutilized for years. Metro Parks Tacoma (MPT) envisioned the full potential of this premiere waterfront property, and in 2014 Tacoma voters approved funding for a multi-phase redevelopment of the park that had been in planning stages for more than a decade—Destination Point Defiance.

One of the first priorities was the redevelopment of the park entrance and waterfront. Known as Waterfront Phase I, it’s the largest single project ever undertaken by MPT, with a total budget of approximately $60 million. MPT planned a large number of improvements to the area, including: regrading an unstable slope, a new road alignment and roundabout at the Pearl Street park entrance, a larger and more accessible boat trailer parking area, a new 11-acre waterfront park area, new regional stormwater treatment facility and a new bike and pedestrian trail and bridge connecting the park to Ruston Way and downtown Tacoma. Regrading the site for the new improvements meant moving approximately 400,000 cubic yards of soil and placing and compacting about half of that in different parts of the site.

The project site is adjacent to the former site of the Asarco Smelter, which was known to contain lead- and arsenic-laden byproducts and has been designated a federal Superfund site by the Environmental Protection Agency (EPA). Nearly 100 years of industrial activity by Asarco left contamination behind throughout the site. To complete MPT’s expansive plans, the contamination needed to be evaluated and remediated.

MPT relied on GeoEngineers to overcome the environmental and geotechnical challenges facing the Waterfront Phase I project. GeoEngineers began preliminary planning and support work in 2000 and started geotechnical and environmental field work in 2014. Along the way, our project team worked closely with partner firms such as OAC Services, CH2M HILL and SiteWorkshop, and coordinated extensively with the City of Tacoma and the EPA.

Approach

The geotechnical team, headed by Associate Geological Engineer Morgan McArthur, provided geotechnical recommendations for the Waterfront Phase I redevelopment. Our team’s geotechnical scope included:

• Performing geotechnical investigations and made recommendations for the new roundabout and park entrance alignment, boat launch and trailer parking, and many other pavement subgrades throughout the park.
• Providing recommendations for regrading an unstable shoreline bluff.
• Making geotechnical recommendations for the foundations of the new pedestrian bridge over Pearl Street. After investigating the glacially consolidated soils beneath the bridge site, the team determined that less expensive shallow foundations would provide ample structural support—a design recommendation that considerably lowered construction costs.
• Overseeing soil management and observation of re-use on site.
• Supporting utility and retaining wall construction and backfilling.
• Assisting with erosion repairs during construction.

Our environmental team, led by Senior Environmental Geologist Tricia DeOme, performed a range of services for MPT, including:

• Testing and characterizing soil at multiple locations within the site, along with confirmation samples once excavation reached non-contaminated soil.
• Helping develop a plan to consolidate and cap the majority of the contaminated soil.
• Completing UST site assessor and remedial excavation of petroleum-contaminated soil.
• Supporting appropriate off-site disposal of contaminated and non-contaminated soil.

Reusing On-Site Soil

Our environmental and geotechnical teams also worked together to propose the reuse of on-site moisture-sensitive soil, much of which was contaminated or impacted. We led the team through the challenges of working with and moving this material. Because of the scale of earthwork required for the project, this creative approach to safely reuse soil already on-site led to a significant construction cost reduction.

In total, GeoEngineers oversaw the movement and management of more than 400,000 cubic yards of soil. To put that large number in perspective, it took approximately 28,000 dump trucks to move that volume of soil.

Improving Efficiency Through Soil Aeration

Most of the soil to be re-used on-site was moisture-sensitive, meaning that it would become unstable and very challenging to work with when wet. Some of this soil was already wet when it was excavated, and it needed time and space to dry out before it could be compacted effectively.

However, EPA construction standards for the site required dust from the soil to be kept to a minimum. To do this, contractors began constantly wetting the soil to keep the dust down. The soil eventually became too saturated and caused issues for the heavy equipment, but GeoEngineers came up with a creative solution that kept the dust down while also helping to dry the soil enough for adequate compaction. Our team suggested using a tractor and large disk aerator traditionally used in farming, which significantly reduced the need for water trucks and helped speed the compaction process, which ultimately saved MPT roughly $500,000 in construction costs.

Results

GeoEngineers expects to continue providing construction observation and other services while many phases of the project approach completion by 2019. By thinking about our client’s needs creatively, GeoEngineers was able to improve construction efficiency and save money. Roger Stanton, the phase 1 waterfront project manager for MPT, has expressed his thanks for GeoEngineers’ work. “This project would not have been a success without GeoEngineers,” Stanton said. “I appreciate everything you have done for us.”

In the coming years, MPT expects Point Defiance Park usage to increase as the new features open. With the completion of the pedestrian bridge over Pearl Street, the “missing link” in the waterfront trail from Downtown Tacoma to Point Defiance will be complete. The trail will also provide direct access from the new Point Ruston development to the park. Planners hope that the park will act as an important anchor for the city’s ongoing development plans.