The Berkman Apartments, located directly across from Mayo Clinic’s Saint Mary’s Hospital, is constructed over one of the most geotechnically challenging sites in Minnesota. Bolander worked hand-in-hand with Alatus, Weis Builders and Braun Intertec to develop and implement adaptable deep foundation methods to support the 15-story concrete structure.
Braun, relying on their extensive experience in this region, recommended alternating between cased micropiles and drilled piers. Micropiles were used in areas of weak soils and/or voids and drilled piers could be utilized on competent bedrock. To bring order to highly unpredictable karst subsurface conditions, Bolander developed a flow chart that accelerated the team decision making process when soft soils or voids were encountered. Further, Bolander provided schedule and cost saving solutions by fabricating a custom drill rig to quickly discover and evaluate voids before foundations were drilled.
Micropile drilling was challenging and unpredictable with depths as shallow as 50-ft and as deep as 120-ft. Drill pier foundations were drilled through 35-ft of competent bedrock.
Foundations By the Numbers:
- DTH Micropile: 256-Each (13,879-LF)
- Drilled Piers: 130-Each (3-ft to 8-ft Diameter)