State: Massachusetts
City: Boston
Owner: Trinity Church
General Contractor: Shawmut Design & Construction

Project Description:
The Trinity Church is well known Historic Landmark in downtown Boston.  Lowering of the water table from numerous construction projects and deep basements has resulted in the deterioration of the wood pile foundations that support many of Boston’s Historic Structures.  At Trinity Church, Schnabel both repaired the existing wood piles and installed new micropiles.

Schnabel began the repair work by carefully hand excavating around the pile tops.  Temporary supports were then placed beneath the huge granite block foundations supported by the piles.  The rotted pile tops were then cut away and replaced with steel struts and the entire excavation filled with lightweight concrete.

Micropiles were installed in the basement of the church and around the perimeter of the building (20 ft below street level) using a small drill for use in limited access applications.  The drill rig can be lifted in place by a crane and driven through doorways and hallways.  The small but powerful drill rotated 10-inch casing through caving soils and timber pile obstructions to reach a suitable bearing stratum.