David Winter, CE’78, president and CEO of Seattle-based Hart Crowser, was the geotechnical engineer on the Governors Island project in New York Harbor to build hybrid natural and human-made hills on the island. The tallest hill, called Outlook, gives visitors a 360-degree view of the harbor.

“If the hill is built traditionally, with soil fill placed and compacted in layers, the weight of the new soil would cause several feet of settlement and likely result in a slope stability failure into the harbor,” Winter says.

But Hart Crowser made Outlook weigh about 50 percent less by using debris from demolished island buildings, mechanically stabilized earth and an expanded aggregate, or pumice. Other hills on the island were built with general granular fill barged to the site from a Hudson River quarry.

The construction technique used on Governors Island “reduces the settlement dramatically and forces the critical slope stability failure surface farther back away from the shoreline, thus increasing the stability factor of safety,” Winter says.