What is the difference between standing column wells and closed loop geothermal?

Standing column wells circulate groundwater directly from a deep bedrock borehole through the heat pump exchanger and return it to the same well, offering maximum thermal transfer efficiency in New England's granite bedrock. Closed loop systems circulate a food-grade antifreeze solution through sealed high-density polyethylene (HDPE) U-tubes grouted into boreholes, isolating the heat exchange fluid from surrounding groundwater.

What incentives and tax credits exist for geothermal heating and cooling in Massachusetts?

Massachusetts property owners can combine the 30% Federal Section 25D/48 investment tax credit with MassSave rebates of up to $15,000 for whole-home residential heat pumps and up to $25,000+ for income-eligible or commercial conversions, often offsetting 50% to 70% of upfront installation costs.

How deep are geothermal boreholes drilled in New England?

Typical vertical closed-loop boreholes are drilled between 300 and 500 feet deep per loop ton, while standing column wells often reach 800 to 1,500 feet in competent bedrock to provide 5 to 10+ tons of heating and cooling capacity from a single borehole.

How long does a geothermal borehole loop last?

The ground heat exchanger (borehole and certified HDPE piping) has an expected lifespan exceeding 50 to 100 years. The indoor water-to-water or water-to-air heat pump equipment typically lasts 20 to 25+ years, outlasting conventional gas boilers and exterior air-source condensing units.

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🏛️ Municipal Project · Groton, MA

Town of Groton Municipal Facilities (Town Hall & Public Library)

Flagship municipal decarbonization project demonstrating leadership in sustainable energy, taxpayer cost reduction, and historic town center environmental preservation.

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Project Parameters & Verification

Technical Specifications Ledger

Client / Organization

Town of Groton Building Committee

Groton, MA (Middlesex County)

System Architecture

Vertical Closed-Loop Ground-Source System

Multi-Borehole Vertical Array

Borehole Depth & Strata

400 – 500 ft per borehole

Nashoba Terrane (Gneiss and Ayer Granite)

Delivery Phase

Municipal LEED Construction

Municipal Complex Demand

Site & Operational Challenge

Site Constraints & Environmental Factors

The Town of Groton required a reliable, ultra-efficient heating and cooling solution for high-visibility public buildings including Town Hall and the Public Library. The system had to support municipal LEED green building certification while protecting the underlying Nashoba Valley drinking water aquifer.

Engineering Execution

Turnkey Drilling & Subsurface Solution

GDNE drilled a precision vertical closed-loop borefield. To guarantee complete groundwater protection, non-toxic food-grade propylene glycol was selected as the heat transfer fluid, enclosed in continuous fusion-welded HDPE piping and sealed with impervious bentonite grout. The entire loopfield was positioned beneath municipal green space and paved parking, leaving zero exterior mechanical footprint.

Verified Performance

Operational & Environmental Results

✓Contributed essential energy efficiency credits toward Town of Groton LEED certification.

✓Reduced municipal heating and cooling operating expenditures by over 55% compared to baseline fossil fuels.

✓Zero visible rooftop chillers or ground-level compressors, preserving historic Town Center aesthetics.

✓Zero risk to local groundwater through complete closed-loop isolation and continuous grout seals.

Deployed Equipment & Regulatory Codes

Field Hardware & Tooling

• Heavy-wall steel surface casing sealed into solid crystalline bedrock
• Continuous uninterrupted HDPE 4710 ground loops with zero mechanical joints underground
• Environmentally benign NSF-certified heat transfer fluid formulation
• Central interior mechanical room heat pump integration

Regulatory & Code Compliance

• Nashoba Associated Boards of Health (NABH) well permits and setbacks
• MassDEP 310 CMR Drinking Water and Groundwater Protection Standards
• USGBC LEED Energy & Atmosphere (EA) Credit Guidelines

Explore More GDNE Project Case Studies:

Harvard University Campus Geothermal System →Nichols College Academic & Residence Hall Borefield →

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