Micropiles Below Groundwater at the South Auditorium Block Site, Buffalo, New York-Article

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The CANALSIDE redevelopment in Buffalo, New York, placed a four-story children’s museum above the surviving subbasement of the former Buffalo Memorial Auditorium. The building’s loads exceeded the capacity of the subbasement’s original steel H-piles. Because groundwater stood about 10 feet above the subbasement floor, strengthening the foundation while preserving the existing waterproofing was a major challenge.<br /><br />Engineers selected micropiles drilled through the floor into limestone bedrock. To manage water, contractors installed a standpipe at each pile location, bolted and gasketed to the floor slab. Drilling from the subbasement roof through the standpipe allowed the water level inside it to counterbalance groundwater pressure. The piles and annular spaces were then grouted to seal the penetrations.<br /><br />A test installation revealed that groundwater pressure could dislodge a bentonite gasket and that grout could escape into voids in the old slab. The team improved the system by using a neoprene gasket, stronger and more numerous flange bolts, and cement-bentonite grout in the standpipe annulus. Polyurethane grout was injected where leaks persisted.<br /><br />Construction also exposed unexpected slab conditions, including utility trenches, soil-filled areas and existing water pathways. These were addressed with repairs, pile relocations, pumping and additional grouting. Existing infrastructure and the limited subbasement space also led to complex, asymmetrical pile caps carrying eccentric loads; some required substantial thickness and congested reinforcement.<br /><br />The project demonstrated that micropiles can enable reuse of an existing structure and provide flexibility in building design, even below groundwater. Key lessons were that rubber gaskets performed better than unconfined bentonite at the flange, cement-bentonite grout sealed more effectively than cement grout alone, and polyurethane grout was useful for rapidly stopping leaks.

Keywords

CANALSIDE redevelopment

Buffalo New York

children's museum

micropiles

foundation strengthening

groundwater pressure

subbasement waterproofing

limestone bedrock

grout sealing

structural retrofit