The Cornell Tech campus on New York’s Roosevelt Island is centered on the 150,000 SF Bloomberg Center, designed to be one of the largest Net-Zero energy buildings in the US and the standard-setter for energy performance among buildings of its type. The geothermal system includes a heat exchanger of 80 closed-loop, 400’-deep geothermal boreholes. Thermal capacity of the groundwater-filled bores is increased by a novel annulus pumping system that draws water through natural fissures leading to the East River, providing 265 tons of peak cooling capacity.