Behind the Scenes with The Graystone Seattle

Tell us a bit about the project.

Zach Whitman: The Graystone is a 30-story high rise containing 270 condominium units in Seattle’s First Hill neighborhood. The northern portion of the block is home to the residential tower while the southern portion contains a two-story plaza/terrace. The project also features four full levels of below-grade parking for residents.

Kyle Malaspino: This 300-foot high rise exists on a very tight footprint at the corner of 8th and Columbia. From a civil perspective, the 15,000-square-foot site contained a steep grade change, preexisting trees, and an underdeveloped public alley that needed to be addressed. It was a lot of hard work to make it the residential experience that it is today.

What are some unique features and how did we support them?

Kyle: One of the most unique features was created in response to the utility cuts we needed to make on Columbia Street. Going in, we knew that there was cobblestone below the asphalt road because we could see it on the curb and gutter as it got closer to the sidewalk. To avoid repairing the entire street, our team came up with a really cool detail to patch the concrete into the cobblestone at our curb cuts. Ken Wiersema in our office helped me out with this detail. He had done something similar on another project and it had been approved by the city, so we knew it could be done again. After suggesting it to The Graystone team, everyone agreed that it was the best solution, including Seattle Department of Transportation (SDOT). As small of a detail as this may seem, solutions like this add so much value to the project in the long run.

Zach: The entire site sits within the groundwater table, so to keep the building anchored in the ground, we utilized a full site mat foundation that resisted the hydrostatic loads. To reduce the amount of excavation into the water table during construction, the mat foundation was also used as the lowest floor level instead of installing a separate slab-on-grade. The team extensively detailed and coordinated the foundation geometry to allow for the steps and slopes required to accommodate the lowest parking level.

Another unique feature is the exterior cladding at the podium levels, which is a non-structural CMU wall system rather than masonry veneer cladding. Due to how close the neighboring building was to ours, the CMU wall was detailed and coordinated to allow installation to occur from inside the building.

Do you have a favorite feature? Any engineering standouts?

Kyle: The cobblestone detailing is my favorite feature but permitting for utility services under 100 linear feet is a definite standout. For SDOT there’s a line in the sand of 100 linear feet so that for anything less, the permits are pretty straightforward. But if it exceeds that length, the process is much more complicated. At first, we were under 100 linear feet, so we anticipated it would be an easier utility permit. But at the review stage, SDOT decided that because of the street we were in, they would prefer that we review traffic control and look closer at a portion of our duct bank that was 5 feet into an area they were concerned about. Navigating that more complicated process with SDOT was not something that we planned for, but because of our relationship with the city, we were able to take this challenge head on and handle it as efficiently as possible.

Zach: The stepped plaza/landscape areas are my favorite because they allow you to walk from the on-grade level up to a lower rooftop area adjacent to the east alley. It really blends the building into the sloping of the site/block and is a great feature.

What was the biggest challenge the team faced?

Kyle: The biggest challenge on the civil side was the grade change. From the southeast to the northwest corner, there was a tremendous amount of sloping that we needed to mitigate. From a calculation standpoint, getting the rise over run correct was critical. Miscalculating by even a few inches would have thrown off the project’s entire elevation, especially since we coordinated building entrances at different grades. To account for this, we intentionally built some flexibility into the design to give the contractor wiggle room during construction. We also helped identify strategies to preserve the existing east side elevation and incorporate critical elevations for the alley, loading dock, and the plaza.

And I’d be remiss not to mention how much coordination went into developing the public alley that contained our retaining wall. To incorporate a loading dock and general accessibility, this was the one area on site where we were allowed to remove trees. However, it had to be done without disturbing the grade or rockery wall mere inches away. Not an easy feat! Together with the contractor we decided the best course of action would be to grind down the trees below the rock level of the asphalt and put rock on top of it. Removing the trees (and their roots) entirely would have been too risky for the stability of the retaining wall, which SDOT agreed with. And this way, we were able to maintain our existing grades on the east and west sides of the alley.

Zach: A significant challenge was the project delay imposed by COVID. The restart process afterwards was challenging and meant the construction of the project took about 5 years. It really helped to have strong relationships with LMN Architects and other consultants to maintain continuity from construction through completion.

Were there any examples of issues we were able to identify early that helped the design process?

Kyle: SDOT was unwilling to let us remove the 24-inch-diameter preexisting trees on site. And since the site was vacant before this project, everything from the roots to the canopies were overgrown, which also made utility connections difficult. By understanding SDOT requirements and the state of the site early, our team was able to put an immediate “tree plan” into action. Canopies were trimmed back to get our shoring in, portions of the tree roots in the retaining wall were carefully removed to avoid disturbing the wall, and the sidewalk was artificially raised to address sidewalk buckling (caused by tree roots). To address the sidewalk, we knew we couldn’t depress the grade because it would cut into the roots, so we paved over it to artificially raise the elevation (which does not harm the roots). This solution was a win-win for us, SDOT, and Urban Forestry.

Zach: Our team did a great job identifying concerns with the sloping site and seismic system early in the design process. Special detailing was provided between the building slabs and the basement walls, and a seismic joint was provided between the shorter podium park structure and the tower. This approach allowed the team to simplify some aspects of the peer review and deliver permit approval within the required window.

What was one thing you learned during this process?

Kyle: This project reconfirmed for me how important it is to put yourself in other team members’ shoes. What seems like a simple fix for us as the civil engineer may not be as simple for another consultant. Especially when there’s unanticipated changes to the schedule like with COVID and the concrete strike. So taking that extra time to consider the bigger picture is very important.

Zach: A good civil consultant is key. Kyle was critical in smoothing out a lot of issues and concerns with the alley during construction – which made the rest of the teams’ lives a lot easier!

How does this project impact our city or its community?

Kyle: It turned a vacant, overgrown corner lot into a project that has place in the neighborhood. The new building looks great, and the generously landscaped, 9,000-square-foot park is open for anyone to use. Featuring an open plaza, astroturf, artwork, and a sizeable waterfall feature, I may escape there sometimes myself.

Zach: The location couldn’t be better and beyond housing, the public park is a welcome addition to the neighborhood. 

What does it feel like to see this project complete?

Kyle: It’s always rewarding to see the tangible results of your hard work.

Zach: It feels like the culmination of a decade of hard work! We started in the summer of 2015, so closing this out has been very rewarding. I was very excited to see the final photography come through.

Go behind the scenes with some of our other favorite projects: Seattle Storm Center for Basketball Performance, The Astor at The Washington Building, WWU Interdisciplinary Sciences Building, The Lodge at Saint Edward State Park, The Little School Rivers Building, and Mount Si High School.

Project Team: Owner: Daniels Real Estate / Architect: LMN Architects/ Civil & Structural Engineer: Coughlin Porter Lundeen / General Contractor: Andersen Construction Company / Landscape Architect: HEWITT / Geotechnical Engineer: Hart Crowser, a division of Haley & Aldrich / Mechanical & Electrical Engineer: IMEG Corp. / Interior Design: Robin Chell Design

Images © Cory Holland Clarity NW Photography