Water Supply Risk at a Glance
One of the most significant risks that the MBTA Communities zoning requirement poses to Carlisle concerns our water supply. It's important to note that Carlisle lacks a town water backup, setting it apart from many other communities. Therefore, preserving our water supply and protecting our drinking water should be of paramount importance when determining how Carlisle will respond to the MBTA Communities zoning requirement.
Town board members recognize the existential risk to the Town from contaminating or depleting our groundwater. At a joint meeting between the Board of Health and the Planning Board on April 14, 2025, members discussed frankly that we have no way of knowing the risk to our aquifer and groundwater, and no feasible way to find out, due to the prohibitive cost of digging and monitoring test wells.
Representatives of these boards also stated that it would be up to individual homeowners – without help
from the town – to fix any problems, even catastrophic ones such as loss of a well.
With so many unknowns – the Carlisle Alliance for Preservation advocates that the Town should proceed as cautiously as possible and should explore avenues for MBTA Communities compliance that reduce to the greatest extent possible risks to the Town. Here is a link to additional information on groundwater.
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If your well is within 400 ft of a MBTA Community housing district your well is at much greater risk of drying up.
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The impact may not be noticed right away but it’ll be known to all concerned, including realtors and developers, before your house is on the market.
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If any unit (new or existing) is within the cone of depression they would risk land subsidence in addition to dry wells.
Aquifer Supply
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MassGIS image shows us that Carlisle, unlike all other towns in the area, has only a confined aquifer to draw from.
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An unconfined aquifer, if we had one, might provide a district with the opportunity to develop a large public water supply.
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Carlisle housing units must continue to rely on limited well water extraction to sustain our current supply for 2 to 12 people on our 2 to 4 acre lots.
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Current Drought Status
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All climate models predict many more drought conditions for the foreseeable future. This certainly means our aquifer will get smaller and wells will be drilled deeper.
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Adding ADU’s will add about 50% more demand and lower the groundwater level further.
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High-density housing with it’s “by-right” feature of unlimited pumping will further increase the excessive extraction of the aquifer by 1250% to 2500%
Water Pollution Risks
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Generations of town leaders have recognized the risk to our town of contaminating or depleting our groundwater.
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Carlisle has had a few hazardous waste spills that have already contaminated our aquifer near the center.
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Any increased extraction and use of the aquifer increases the amount of PFAS, nitrites and nitrates into our drinking water.
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Years ago, the Select Board, the Planning Board and the Board of Health adopted Development Standards to serve as a general policy statement for regulating development in Carlisle. Read more here.
