KA’s Block redevelopment is underway. The construction crew mobilized on our downtown site, bounded by Eighth and Ninth streets, Fifth and Portland avenues, at the beginning of April and completed demolition of the existing 1970’s-era KA headquarters building on April 19. Since then, the team has been at work with site work in preparation for construction of the five-story, 100,000 s.f. Kraus-Anderson headquarters building and preparation for the full-block, mixed-use development. Project manager Chad Rempe provides this report.
General Progress Update
Q: You’re implementing an innovative alternative to the standard wall retention lagging system that is typically used in excavation like this.
REMPE: Right, this is a Sheet Pile Foundation System made from interlocking steel sheeting. It’s a product from Germany.
Q: How is it being installed? What is the schedule for installing?
REMPE: Interlocking steel sheets are vibrated into place using a vibrating hammer. Once sheets are installed, temporary walers and tiebacks are installed to allow for mass excavation to proceed to design depth. Installation of sheet piling was completed in 26 working days. Temporary waler and tie-back install is just now beginning, followed by mass excavation; both of which are scheduled to be complete in the next 60 days.
Q: What are the advantages of using this system?
REMPE: Permanent sheet pile foundation systems differ from the traditional approach in that this one system replaces the combination of systems traditionally used. A traditional approach to foundation design would utilize a temporary earth retention system, such as soldier beams and lagging, a permanent concrete foundation wall, below grade waterproofing, backfilling, and removal of temporary earth retention system.
Q: Why is KA using this system on our block project?
REMPE: After considerable review of alternative solutions the permanent sheet pile foundation wall system being utilized offered the best value by delivering significant cost and time savings when compared to a traditional approach.
Q: How unusual is this system?
REMPE: Permanent sheet wall systems are used widely in Europe and in maritime environments. There are a few projects in Minneapolis that have successfully used this system but its use and adoption in the United States is still in its infancy.
Q: What are the challenges to doing it this way?
REMPE: The biggest challenge unique to this system is managing vibration during the installation of sheet piling. Prior to beginning any construction activity on-site, KA conducted an extensive pre-existing condition survey that documented the existing condition of all neighboring/adjacent properties and right of way improvements, such as curb and gutter, roads, sidewalks, etc. Additionally, working with Braun Intertec, we developed a vibration monitoring and control plan designed specifically to insure vibration levels are kept within an acceptable range so as not to potentially damage adjacent improvements.
Q: What’s next?
REMPE: Concrete foundation work scheduled to begin within the next two-three weeks. First of two tower cranes scheduled to be erected first part of June. See webcam