KA Block Project Update
Demolition and early site work at the KA Block redevelopment site in downtown Minneapolis
The KA Block redevelopment was underway in downtown Minneapolis.
The construction team mobilized at the site, bounded by Eighth and Ninth streets and Fifth and Portland avenues, at the beginning of April. Demolition of the existing 1970s-era headquarters building was completed on April 19.
The team then began site preparation for the five-story, 100,000-square-foot Kraus-Anderson headquarters building and the full-block mixed-use development. Project Manager Chad Rempe provided the following update.
General Progress Update
All building and site demolition was complete. Sheet-pile installation was scheduled for completion that week, while temporary waler and tieback installation and mass excavation were in progress.
What Alternative Foundation-Wall System Was Used?
Rempe: The project used a sheet-pile foundation system made of interlocking steel sheeting, a product originating in Germany. It served as an alternative to the standard wall-retention and lagging system commonly used for excavation.
How Was the Sheet-Pile System Installed?
Rempe: Interlocking steel sheets were vibrated into place using a vibrating hammer. After installation, temporary walers and tiebacks were added so mass excavation could proceed to the design depth.
Sheet-pile installation was completed in 26 working days. Temporary waler and tieback installation began next, followed by mass excavation. Both activities were scheduled for completion within 60 days.
What Were the Advantages of the System?
Rempe: A permanent sheet-pile foundation system differs from the traditional approach because one system replaces several separate systems.
A conventional foundation approach may include a temporary earth-retention system, such as soldier beams and lagging; a permanent concrete foundation wall; below-grade waterproofing; backfilling; and removal of the temporary earth-retention system.
Why Was This System Selected for the KA Block?
Rempe: After reviewing alternative solutions, the permanent sheet-pile foundation-wall system offered the best value through significant cost and time savings compared with a traditional approach.
How Common Is This System?
Rempe: Permanent sheet-wall systems are widely used in Europe and maritime environments. A few Minneapolis projects had used this system successfully, but its use and adoption in the United States were still developing.
What Were the Primary Construction Challenges?
Rempe: The primary challenge was managing vibration during sheet-pile installation.
Before construction began, KA completed a detailed pre-existing-condition survey documenting neighboring and adjacent properties, plus right-of-way improvements such as curbs, gutters, roads and sidewalks.
Working with Braun Intertec, the team developed a vibration-monitoring and control plan designed to keep vibration levels within an acceptable range and avoid potential damage to adjacent improvements.
What Was Next?
Rempe: Concrete foundation work was scheduled to begin within two to three weeks. The first of two tower cranes was scheduled for erection in early June.
Learn more about the KA Block redevelopment, the start of headquarters and residential-tower construction, the new downtown Minneapolis headquarters approval and a tower crane operator’s perspective.
CATEGORY: Construction