The Hills’ four constructed rises—the 70-ft Outlook Hill, 39-ft Discovery Hill, 36-ft Slide Hill and 26-ft Grassy Hill—represent the last stage in the redevelopment of the southern tip of the 172-acre former military base, according to the nonprofit Trust for Governors Island. Landscape architect West 8 designed the 10-acre Hills section, which opened to the public on July 19. The rises were built by Bedford-Carp Construction Inc. from recycled demolition debris, general fill and lightweight pumice. They are stabilized with geotechnical reinforcement. Lead civil engineer Magnusson Klemencic Associates and geotechnical engineer Hart Crowser Inc. had to ensure the landscaped hills’ weight would not overload the seawall or cause the island’s underlying fill to fail.