Underneath Boston: A City Built on Wood Piles Preserved by Groundwater

Boston Groundwater Trust (BGwT) has been working underneath the scenes to preserve the structural integrity of Boston since 1986, monitoring groundwater levels to be sure the wood pilings holding up businesses and homes in several neighborhoods remain strong.

To understand the importance of BGwT, one must look all the way back to 1630, when Boston was first founded as the Shawmut Peninsula. At that time, the city was a much narrower land mass. As the city grew, areas that were once mud flats, including the Back Bay, Fenway and parts of the North End, were filled in with sand and gravel.

Buildings then built in these areas were constructed on top of wood piles. These pilings continue to support our buildings today, and it’s important they remained submerged in water to prevent rotting.

This is where BGwT comes in. This Trust monitors groundwater level in areas of the city that are threatened by low levels. Groundwater levels can drop due to underground infrastructure like tunnels, pipes and basements. When there is a leak such as in a pipe, water is pumped or drained, causing groundwater to also drop.

When the wood piles are no longer submerged they start to deteriorate, causing buildings to settle unevenly and bricks or walls to crack. Using an observation well network of over 800 wells, the BGwT monitors water levels every 5-6 weeks to identify areas of concern and recommend repairs on comprised wood piles. Pilings can be repaired, though it is a pricey, labor-intensive task.

Earlier this year BGwT released a video series to better explain Boston’s structural history, how it is changing, and the importance of groundwater levels. This three-part series was awarded the Golden Telly Award, which honors excellence in local, regional and cable television commercials and digital videos. Watch parts 1 & 2 above and the final video on the process of repairing pilings below.

Learn more at bostongroundwater.org.