A Practical Design and Innovative Construction Approach to Stabilizing a 140-Year-Old Historic Bulkhead

This paper presents the technical design challenges encountered due to the condition and historic nature of a 140-year-old bulkhead and will present issues encountered during construction due to the subsurface conditions and marine environment. Observations of the bulkhead during inspections performed between 1980 and 2014 revealed that the alignment was distorted significantly and had settled. The geotechnical investigation revealed that a soft, weak organic silty clay stratum lies on top of a downward sloping hard glacial sand layer. A review of the historic bulkhead construction records, previous bulkhead investigation reports, subsurface conditions, and results of wall stability analyses revealed that the wall movements were likely caused by a down-slope creep of an inadequate foundation on a sloping hard bottom and the use of newly developed construction techniques in a challenging marine environment. Sonically drilled tiebacks and vertical steel pipe piles drilled through the bulkhead and into the glacial deposit were installed to provide the supplemental lateral restraining force needed to stabilize the bulkhead. A carefully designed procedure of pile and tieback installation sequence and the use of innovative construction techniques were successfully implemented to stabilize the bulkhead.