Wells - Introduction
Using the Well Location Map
Welcome to the well section of the Boston Groundwater Trust website. As part of its charge to re-establish and maintain a system for monitoring groundwater levels in parts of the City of Boston, the Boston Groundwater Trust is making available data on groundwater level as shown on the map and accompanying charts.
You can access data on a particular groundwater observation well by clicking directly on the well location on the map or by entering the address in the box located above the map. After reading the information below and agreeing to the terms, you will see our interactive map. Click on the zoom in button and then click on the area of the map in which you are interested, and the map will zero in on the location that you want. If you have a particular address that you are interested in, enter it including the Zip Code (i.e. 234 Clarendon St, 02116) and click enter.
When you can see the well that you want, click on well data. The current reading for that well will appear in a flag on the map, with historical data and additional information to the right of the map, along with a link to a chart of all readings for the well. Returning to the map, you can click on other wells to see readings in the area around the first well. To navigate to areas beyond the edges of the map, you can click on the arrows at the top of the map.
Another way to reach the data for a particular well is to click on "Well locations". Click on a particular well, and you’ll get a map showing the well, current data on the map, and historic data on the side. The map also shows nearby wells.
A general description of the location of each observation well is shown on the map and listed below the well elevation chart. Plan locations are considered accurate within approximately 5 feet. More information about the wells, including the approximate elevation of the rim measured against BCB, is available by clicking on the Identify button before clicking on the well.
Groundwater and Pile Cutoff Elevations
The groundwater elevations are referenced to Boston City Base datum (BCB) and were measured by the Trust’s field researchers in each observation well at the dates and times indicated. For reference, the Charles River is typically maintained between elevation 7.5 and elevation 8.0 (BCB).
While the well data shows the groundwater level at a particular location, the important issue for wood pile preservation is the relationship between the groundwater level and the level of the tops of those wood piles. The level of the wood piles that support a house is sometimes called the "piling cut-off grade". When wood piles were originally driven, the tops usually ended up at different levels, so to set the granite block pile cap stones, the wood pile tops were all cut to the same level, thus the "cut-off grade". Wood pile cut-off elevations can vary substantially between neighboring buildings; sometimes there will be more than one cut-off elevation for wood piles within one building. For a diagram showing the importance of this relationship between groundwater level and cut-off grade, click here.
The Boston Groundwater Trust has been reviewing City of Boston records to find wood pile cutoff elevations listed on building permits or other city records. For more information on what we have found and how to use these records, click here.
We continue to review City records and will be adding cut-off level data on more addresses as we find it. However, for many rowhouses there is no information available on elevation of wood pile tops. We will also be listing those structures, generally newer, that ISD records show are not supported on wood pilings.
The groundwater levels reported are in the surficial, miscellaneous fill, which begins at ground surface and generally extends down 15 to 25 feet throughout the study area. The tops of wood pilings occur in the fill stratum. These wood pile foundations support many rowhouses and historic buildings throughout the area. Although many wood piles were cut off at elevation 5 (BCB); many have been observed to be cut off above elevation 5. The higher the piling cutoff elevation, the more vulnerable the pilings are to lowered groundwater. On occasion, wood pile tops are found to be below elevation 5, and those are at less jeopardy of exposure to air and rotting by localized lowering of groundwater.
Groundwater Level Variability
The groundwater level data presented apply to each individual observation well. Groundwater levels may, and often do, vary within relatively short distances, being affected by: leaking tunnels, pipes and basements; buried impermeable structures/walls; infiltration of precipitation on ground surfaces, or the lack thereof due to buildings or pavements; local dry wells that are periodic recharge sources; and local withdrawals of water by pumping from sumps, dewatering wells, or other drainage systems. The Groundwater Trust, in the presentation of this data, makes no engineering assessment or legal interpretation. Groundwater levels can vary from day-to-day and often rise following heavy rainstorms or prolonged periods of precipitation. No attempt has been made to explain or otherwise interpret the groundwater levels and/or variations herein presented.
Thank you for your interest in groundwater levels of the study area, within which it is essential to maintain groundwater sufficiently high to keep wood pilings submerged, thereby preventing exposure to air and subsequent wood rot.