I took the picture above a few days ago, walking through Battery Park. That’s Castle Clinton with a construction fence around most of it and two trailers parked in front for contractors’ use. The building was constructed more than 200 years ago as a fort to protect Manhattan from an attack by sea; it has since served as a theater, an immigration station, an aquarium, and now a museum. It was built on a small island – a pile of rocks, really – off the shore of Manhattan; landfill has it now some twenty yards from the water. It’s a designated NYC landmark, of course, but also a National Monument.
In 1997, we were lucky enough to get a project investigating the structural conditions at the old fort, including some worrying outward tilt of the walls. Given that the walls are on the order of 7 feet thick, the tilt didn’t seem to mean instability, but the cause was a mystery. (If you look closely, you can see the tilt in the picture above which was taken more than half of the fort’s lifetime ago.) We came to the conclusion that there did not seem to be any active structural movement, and that the past movement was probably some combination of crushing of the timber grillage that the walls sit on (and which, in turn, sits on the bunch-of-rocks island) and settlement from ground dewatering during the construction of the Brooklyn-Battery Tunnel and the Battery Park Underpass, both of which are not far away. The anti-climactic conclusion of our report was to suggest the National Park Service monitor the situation and see if anything changes.
A few yeast ago, we got to return to the fort, on a team headed by John G. Waite Associates. After another thorough investigation, including some quite fancy non-destructive testing and modeling by STRAAM, it became clear that the structural conditions hadn’t changed in the twenty-plus years since our first go-round. That doesn’t mean there were no problems, but ordinary deterioration of stone is not a structural problem if it’s caught early enough, so JGWA is addressing that rather than us. Our structural recommendations are…monitor the situation and see if anything changes. This time we’ve spelled out exactly how the monitoring should be performed.
So, my thanks to Derek Trelstad for his work in the 90s, Gabriel Pardo for his work in the 2010s, Nancy Rankin and the team at JGWA, Tom Winant and the team at STRAAM, and everyone involved at the National Park Service over the last 24 years. I look forward to the restoration work about to start, and to re-investigating conditions there in 2045.