Climate Pledge Arena (Formerly Seattle Key Arena) | USA

Project summary

Service provided:  Monitoring historic stadium during redevelopment
Location:  Seattle, Washington - USA
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Period of the service:  2019-2021
Sixense solutions used: 

Images of the project

Climate Pledge Arena


Completed in 2021, this major $1.15B redevelopment project was commissioned to upgrade and expand a Seattle landmark listed on the Washington Heritage Register and the National Register of Historic Places: the newly named Climate Pledge Arena (formerly Seattle Key Arena). Named by Amazon’s Jeff Bezos to draw attention to the importance of fighting climate change, this venue was rebuilt as a new and improved state-of-the-art live sports and entertainment arena.


Seattle Key Arena Redevelopment

After over 50 years of hosting concerts, basketball games, hockey games, events and gatherings, each welcoming over 15,000 people from all over the world, it was decided in 2016 to upgrade and expand the capacity of this iconic venue to over 17,000. The project also doubled the size of the former arena to enlarge the playing surface of the structure. This project was led by the Oak View Group (OVG) and performed by Mortenson.


Preservation Challenges

On top of the usual challenges inherent to complex construction projects, one of the requirements was to keep the existing Key Arena roof while excavating 75ft under and around the 44 million pounds of steel and concrete structure. This was achieved by lifting the roof off its original foundations, and letting it rest on an array of 72 circular steel piles totaling 4,500 tons.

Due to these unique challenges, there was no room for error, and an accurate and reliable monitoring system was crucial to the success of the project and all eyes were on Sixense’s data during each critical phase of the process.


Monitoring Network

With input from all parties involved in this project, Sixense and HartCrowser (SXNA client) teamed up to develop and implement a system to monitor the Key Arena, the support of excavation, and the adjacent structures over 2 years. Sixense’s long-trusted and spearheading Cyclop and Centaur technology was the chosen workhorse for this 3D deformation monitoring system with:

  • 7 AMTS
  • Over 400 monitoring targets
  • 50 reflectorless targets

In addition to the AMTS, an independent array of 6 automatic GPS was installed by Sixense at key locations in the Arena.



To complete the monitoring, Sixense also integrated Geoscope data collected manually by land surveyors and 7 IPI chains installed around the support of excavation by HartCrowser.

For 2 years, Geoscope allowed fast analysis of the deformation and a comparison of the three independent measurement systems (AMTS, GPS, manual survey, IPIs). This allowed the design and construction teams to progress confidently through each critical phase of the project on a 24/7 schedule throughout the entire year.


Climate Pledge Arena

Despite the never-before-encountered challenges of this project, Sixene’s monitoring expertise allowed Climate Pledge Arena, the first net zero carbon professional sports venue in the nation, to safely open on time, host countless entertainment events, and keep iconic architectural elements of the old arena.

Project Key figures

7 AMTS (Cyclops)
400 Monitoring Targets
50 Reflectorless Targets
6 Automatic GPS
7 IPI Chains

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