Maine Medical Center, The Story of an 80 ft Tall Permanent SOE Constructed through a Maze of Buried Utilities and Deep Foundations-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes the support-of-excavation design and risk management for Maine Medical Center’s New Congress Street Tower in Portland, Maine. The project involved a deep urban excavation, approximately 43–84 feet deep, beside an operating hospital and complex existing campus infrastructure.<br /><br />A key design challenge was reusing the south wall of a 1970s parking garage. The team assessed its condition through drawing reviews, visual inspections, nondestructive and destructive testing, laboratory analysis, and 3D laser scanning. The wall was used only as temporary facing during demolition, with tieback loads initially limited to 50% of design load. A new permanent facing and extended tiebacks were installed before excavation, allowing the system to carry full design loads.<br /><br />Construction proceeded in phases: tiebacks were installed while the garage remained in use; garage slabs were selectively demolished to allow further tieback installation; and a secant pile wall, cap beam, and 2-foot-thick cast-in-place concrete facing were constructed.<br /><br />Risk management focused on maintaining hospital operations and structural integrity, avoiding conflicts with pile foundations and buried utilities, controlling excavation-induced movement, and meeting a 100-year service-life objective. Three-dimensional modeling compared as-designed and as-built locations of tiebacks, piles, and other structures. The team also developed obstruction tables and reviewed installation angles. For high-risk tiebacks near foundations, drilling was paused near the obstruction, the drilled orientation was checked with a gyroscope, and the tieback was either approved, relocated, or abandoned.<br /><br />A movement-monitoring program tracked nearby infrastructure, including a steam line, throughout demolition and construction.

Keywords

support of excavation

deep excavation

hospital infrastructure

tieback anchors

secant pile wall

temporary facing

risk management

3D laser scanning

movement monitoring

Maine Medical Center