Scanning + Potholing Workflow: Sequencing GPR/EM and Vacuum Potholing

Build a Safer, Leaner Scanning Plus Potholing Plan

Underground work is always a balance between safety, schedule, and budget. To dig with confidence, you need a clear plan for how underground scanning and vacuum potholing will work together before equipment arrives on site. Without that plan, crews end up guessing, poking random test holes, and reacting to surprises.

A “scanning plus potholing workflow” is straightforward: first scan with tools like GPR and electromagnetic locating to map likely utilities, then confirm the most critical spots with targeted vacuum potholes. When sequenced well, this reduces risk, change orders, and delays.

A defined workflow protects operators, locators, and field managers. Everyone knows when scanning is enough, when potholing is mandatory, and where you can safely reduce the number of test holes without losing confidence in what is underground.

Start with a High-Confidence Underground Scanning Pass

Begin with a methodical underground scanning pass. Before any intrusive work, capture a current, field-verified picture of subsurface conditions, not just what old drawings indicate.

A thorough scanning scope usually includes:

• Walking the site to find visible utility tie-ins, valves, manholes, meters, and pedestals  

• Electromagnetic sweeps on known and suspected lines, using different frequencies where needed  

• Multi-frequency GPR grids over planned alignments, work areas, and access points  

• Comparing field findings against 811 tickets and any record drawings you have  

This upfront effort helps designers and contractors:

• Adjust alignments and grades before conflicts become field problems  

• Choose safer work methods around high-risk facilities  

• Narrow the area where potholes are truly needed  

The goal is not to avoid potholing, but to ensure every test hole has a clear purpose and meaningful risk reduction.

When Potholing Moves From Optional to Mandatory

Vacuum potholing turns indications into verified locations and depths. In some cases, potholing is helpful but optional; in others, it is essential.

Potholing is typically mandatory at:

• Critical crossings, such as gas, high-voltage power, fiber, and transmission mains  

• Congested corridors with many overlapping utilities in a tight space  

• Locations where 811 marks, record drawings, and scanning results do not agree  

Risk-based triggers where potholing should be prioritized include:

• Very shallow cover indicated by scans or past as-builts  

• Unknown pipe or cable material, size, or owner  

• Signs of past relocations or repairs, such as patched pavement or unusual surface structures  

• Differences between survey or design information and what scanning shows  

Owners, engineers, and contractors all contribute here. Bid documents should identify required test holes. Preconstruction meetings should confirm who can authorize additional potholes if new risks appear in the field, so crews are not delayed while these decisions are made.

Smart Sequencing to Minimize Test Holes

A good scanning plus potholing workflow uses information in the right order, so each step refines the next.

A simple step-by-step flow:

• Desktop review of records, 811 responses, and proposed design  

• Underground scanning to build a current field picture  

• Risk ranking by alignment or segment, based on scanning results  

• Targeted vacuum potholing at the highest risk and highest consequence locations  

Instead of spreading potholes evenly, cluster them at key decision points such as:

• Bends and deflections that control where a line can run  

• Junctions, manholes, valves, and major transitions  

• Crossings between critical utilities  

• Entry and exit pits for boring, pipe bursting, or jack and bore work  

Proving line location and depth at these points often increases confidence over a larger reach of that facility.

Scanning results can also support skipping redundant holes when:

• GPR shows a continuous, clear signature at a consistent depth along the route  

• EM responses stay strong and stable along the trace, with no unusual jumps  

• Plan and profile show safe vertical and horizontal separation between facilities, and the scans are consistent with that  

Linking technology and potholes in this way can reduce the total number of test holes while maintaining safety.

Turning Field Data Into a Defensible Utility Model

Scanning and potholing are most valuable when captured in a format designers and superintendents can use directly. This typically means building a single map or 3D model that combines both data sources.

Strong utility models usually:

• Show each facility with its mapped route, depth, and confidence level  

• Flag locations confirmed by potholes versus those inferred from scanning  

• Tie back to survey control so design teams can plug the model into their base files  

For potholes, documentation should include:

• Exact coordinates and surface reference points  

• Depth to top of facility, size, and material  

• Utility owner or type when known  

• Photos of the exposed utility and any markings  

• Sketches or notes tied back to scan line IDs or grid locations  

Clear documentation creates a defensible record for change management, damage investigations, and future work on the same site.

Put a Decision Framework in Place Before You Dig

Effective underground scanning programs use a simple, written decision matrix that defines:

• When underground scanning is required and to what level  

• Which conditions trigger mandatory potholing  

• Who can approve additional test holes in the field and how that is documented  

The matrix can be tuned to the owner’s risk tolerance, the type of work, and project specifications. For example, a new fiber run in a quiet corridor might call for fewer test holes than a deep sewer replacement under a busy street with gas and power nearby.

At Advanced Underground Utility Locating Inc, we provide underground utility locating, mapping, leak detection, and GPR services to support safer excavation. A well-planned scanning plus potholing workflow turns separate tasks into a single, clear process that supports crews from planning through construction.  We also can coordinate vac trucking to be a stop shop for everything utility detection!

Get Started With Your Project Today

If you are planning work near buried utilities, we can help you reduce risk before you dig with precise underground scanning. At Advanced Underground Utility Locating Inc, we use proven methods and equipment to map what you cannot see, so you can move forward with confidence. Tell us about your timeline and project needs, and we will recommend the most effective approach. To schedule service or request a quote, simply contact us today.