When you spend enough time exploring the underground as subsurface utility mapping professionals, you learn to expect the unexpected: pipes that appear nowhere in public records, century-old vaults, and maze-like utility corridors squeezed into the smallest of places. Across New England and beyond, DGT regularly encounters subsurface anomalies that challenge conventional planning. What sets our team apart is our ability to make sense of these surprises, using a blend of advanced technology, on-site experience, and multi-disciplinary collaboration to quickly identify and help designers adjust with confidence. Every project site has a story beneath the surface, and uncovering that story is essential to designing safely, building efficiently, and protecting communities.

Extreme weather is reshaping seasonal expectations for many communities nationwide. Events once considered “100-year floods” now occur with unsettling regularity, causing widespread damage and putting lives at risk, often because infrastructure is outdated or overwhelmed. Some municipalities have begun investing its underground drainage and storage systems, but designing solutions requires a detailed understanding of what already exists beneath the surface. However, due to the age of the existing systems, reliable utility records are often limited or nonexistent in many communities.

On one project, DGT has been supporting the long-term effort of creating new stormwater systems in Fall River, MA to improve climate resilience. The design team engaged DGT to map a large section of the community using high-accuracy photogrammetric mapping, survey all above-ground streets, and investigate subsurface conditions to ASCE 38-22 Quality Level B Standards. The underground network includes water, sewer, gas, electrical, and telecommunications systems—all of which must be located, protected, relocated, or reconstructed to accommodate new infrastructure. Using total stations, mobile mapping, and ground-penetrating radar (GPR), we uncovered a variety of underground obstacles, including abandoned utilities and historic streetcar tracks. While the project is still in its early stages, the initial mapping has provided a crucial foundation for upcoming design decisions and demonstrated the essential role comprehensive subsurface mapping plays in climate preparedness. This underground information will guide the new design plans, reducing utility relocations and helping protect subsurface networks during construction.

At 470 Atlantic Avenue in downtown Boston, Independence Wharf stands between South Station and the historic Boston Tea Party site. While the building itself is modern, its location sits atop centuries of layered history, resulting in complex subsurface site conditions. As part of the property’s redevelopment, DGT was engaged to create a detailed subsurface map to guide the placement of new utility connections and help determine safe, stable locations for heavy crane outriggers. What the team uncovered beneath the sidewalk and surrounding streets told a story of decades of undocumented change.

During field investigations, DGT uncovered a dense network of utilities tightly clustered around the building’s foundation, along with abandoned chambers, underground areaways, and vaults. Parts of the building sit over the old Fort Point Channel, leaving behind old footings, plazas, and other remnants from earlier industrial uses. The team also uncovered an unidentified structure linked to a forgotten era of piers and docks. Most notably, just steps from the building’s main entrance, DGT pinpointed the primary slurry walls installed during construction of the Central Artery Tunnel. These massive structural elements consumed a significant portion of the underground space along Atlantic Avenue, necessitating the relocation and reconstruction of public utilities in ways that created a highly compressed and unconventional subsurface environment.

As many of the utilities were buried very shallow, DGT pinpointed critical 3-dimensional data to help the construction team avoid inadvertently damaging existing building service lines. By documenting these conditions in detail, DGT provided the design and construction teams with a clear understanding of landscape they were working within, allowing the project to progress with greater certainty and confidence.

While many Massachusetts cities boast deep historical roots, the city of Quincy stands apart. As the birthplace of two U.S. presidents, John Adams and John Quincy Adams, as well as John Hancock, the first signer of the Declaration of Independence, the city carries a legacy that spans centuries. DGT has completed numerous projects across Quincy, many of which involve subsurface utility mapping, offering a unique window into the city’s evolving infrastructure.

A recent project near Quincy Center initially appeared to be a routine utility mapping effort. But, as is common in older urban corridors, decades of redevelopment revealed a much more complex reality. A century ago, the site featured train tracks, cobblestone roads, and a limited number of utility networks. Over time, steady growth and densification transformed these corridors into heavily layered, highly congested infrastructure zones. Today, smooth pavement conceals the accumulated “road scars” of countless improvements and rehabilitation projects.

Fortunately, DGT’s wide-array, multi-frequency GPR system can map and visualize these buried conditions with remarkable clarity, producing high-definition, geo-referenced images of the underground environment. Traditional locating methods on streets and private property remain essential, but GPR adds another invaluable dimension, detecting underground anomalies and historic features that give design and construction teams the insight they need to plan safely and effectively. Soon, the design team will share this information with the geotechnical, environmental, and civil design teams to outline the critical challenges that need to be resolved prior to groundbreaking.

Professional engineers and surveyors have been mapping underground utilities for centuries, but even today, the reliability of a composite utility plan is only as strong as the documents behind it. Many of these records were created decades apart, by different owners, and according to vastly different standards. On one recent project, DGT was brought in to produce a single, accurate map that captured both above- and below-ground conditions for designers and a soil remediation team working across public and private property. The challenge became apparent almost immediately: previous surveys, plans, and geophysical reports all conflicted with one another.

To resolve these discrepancies, DGT deployed a combination of traditional locating techniques, GPS surveys, wide-array ground penetrating radar, and terrestrial scanning—capturing not only the built environment above ground but also the interior of a 150-year-old drainage culvert. By integrating all of these datasets into a unified 3D model, the team delivered the clarity needed to advance the project. While projects of this scale are not common, they highlight DGT’s unique ability to merge above-ground and subsurface mapping into a single, reliable deliverable.

Regardless of a project’s size or location, unexpected subsurface conditions are often inevitable because underground environments are both hidden and unpredictable. What matters is the ability to identify the conditions, interpret them, and integrate them into a safe and effective design strategy. SUM empowers project owners and design teams to make well-informed decisions, involve asset owners early in the design process, and ensure risk management plans reflect both the known and hidden conditions on site.

DGT’s blend of advanced technology and experienced field teams allows us to transform complex underground conditions into clear, reliable insight. These few projects demonstrate that, no matter how many unknowns lie beneath the surface, a thoughtful and comprehensive mapping approach can reveal the whole picture—and help project owners move forward with confidence while mitigating significant financial risks.

To learn more about how DGT Associates can support your next project, check out our SUE/SUM services.