Some of Boston’s Priciest Real Estate Is Sinking Into the Earth

Boston — from its history to its culture — is a fascinating place to visit, but if you’re going to visit some of its most expensive real estate, you’d better hurry. That’s because depleted groundwater levels are causing the rot of wooden piles that support historic buildings across the city. Approximately 6,000 buildings in the city are supported by wooden pilings, constituting 50% of the city’s residential tax base. When European settlers first arrived in the area, much of modern-day Boston was underwater. As the city expanded, it filled parts of Massachusetts Bay with soil, sand, and gravel. To build on such an unstable surface, builders drove tree trunks into the fill until they hit firmer ground and then placed foundation stones on top of the wooden pilings. Wooden pilings can remain intact for hundreds of years if covered by groundwater, but as the city has grown, construction of tunnels, sewers, basements, and subways has caused the groundwater level to drop in many areas and that exposes the tops of the pilings. Air then causes them to rot and the foundation stones then sink, along with the structures they support. Repairing the wood pilings can be enormously expensive, sometimes costing upwards of $250,000. Unfortunately for unsuspecting out-of-state buyers, Massachusetts is a “buyer beware” state — meaning home sellers don’t have many disclosure requirements — and many owners are opting to keep their mouths shut about the wooden pilings.