Utility Conflict Matrix: Tracking Design Clashes

What is a utility conflict matrix?

A utility conflict matrix (UCM) is a structured register, often a spreadsheet, of conflicts between a project's design and the underground utilities or overhead services in its path. It records where each conflict is, what the service is and how reliably it has been located. It also states why the service clashes and how the clash will be resolved, so nothing is lost between survey, design and site.

The method was formalised in the United States under the second Strategic Highway Research Program, project R15B. It is now used widely on road and rail work and on any large construction project.

What columns does a conflict matrix have?

• Conflict ID and drawing reference.
• Chainage or station, offset and coordinates.
• Utility type, owner, size, material and number of ducts.
• Depth and quality level (QL-D to QL-A, after ASCE 38).
• Proposed feature: drain, foundation, bore, pavement box-cut.
• Type of conflict: horizontal, vertical, or working-space.
• Recommended resolution, cost and time estimate, responsible party.
• Status and date closed.

A sample matrix at a glance

The scan behind each QL-B row is measured in metres; see the GPR survey cost calculator for what that costs.

How is the matrix used day to day?

It is reviewed at every design and utility coordination meeting until each row is closed. Rows with low quality levels are the first targets for potholing; our glossary has the method under Vacuum Excavation (Potholing). Rows marked protect in place carry a hand-dig strip on the drawings; read Utility Tolerance Zone for how wide that strip should be.

In India the owners in a typical corridor include the power distribution company, the water utility, a city gas distributor and several telecom operators. One shared matrix is a cost-effective substitute for a separate round of letters to each of them.

A worked scenario on a drain project

Suppose a 2 km roadside drain is designed, and the survey finds 37 places where a service crosses or runs inside the excavation. Each becomes a row. Twenty-eight come from utility detection by GPR and electromagnetic tracing at quality level B; nine come only from owners' records at quality level C. The design team asks for test holes at the six QL-C rows that sit closest to the drain invert. Four of those services turn out within 0.2 m of the recorded position and two are a metre away. One of the two is deeper than the drain and drops out of the matrix altogether. The other rows close one by one as diversions and protection details are agreed.

Common mistakes in conflict matrices

A matrix fails when it stops being a live record of individual clashes.

• One row per utility instead of per conflict. A water main crossing a drain three times needs three rows.
• No quality level column. Without it, a guessed record looks as solid as a scanned line.
• Closing rows without evidence. A row should close with a reference to a letter, a drawing or a test-hole record.
• Forgetting working space. Shoring, crane outriggers and stockpiles can clash with services that the permanent design misses.
• Freezing the matrix. Each design revision can create or remove conflicts, so the register is re-run.

What Mezux supplies for a matrix

We provide the survey half of every row, keyed to the drawing. Our Excel schedule gives the conflict ID, chainage, offset, coordinates, utility type, size, depth and quality level for each of the located utility lines. A confidence note is added for each, and the IDs match the CAD layers. The designer adds the proposed feature and resolution; we update depth and QL from the data collected when a test hole is dug. The approach follows the TRB report from SHRP2 project R15B, Identification of Utility Conflicts and Solutions, with quality levels taken from ASCE 38-22.

How does a conflict matrix change as quality improves?

Rows move from guesswork to evidence as the survey moves up the quality levels. At the start of design, many rows rest on owners' records alone, QL-D or QL-C, and their resolutions are provisional. A GPR and electromagnetic survey to detect and map each service lifts most of them to QL-B, which is often enough to settle a clash on paper. The remaining tight rows, where clearances are a few centimetres or the consequences of a strike are severe, get test holes and become QL-A. Tracking that progress in the matrix shows the client where money spent on investigation has removed risk, and where it has not.

Where does the data come from?

From a SUE investigation: records research, GPR and electromagnetic location, and test holes where needed. Ground penetrating radar (GPR) is the geophysical survey tool in that kit: it sends radar pulses into the soil and reads the echoes from metallic and non-metallic objects alike. Read our note on SUE survey for the levels of effort involved. To build a matrix for your corridor, send your site details for your project.

Frequently asked questions

Who prepares the utility conflict matrix?

In most projects, the design consultant or SUE provider, with input from each utility owner. The client keeps it as the single record.

Is a conflict matrix needed for small jobs?

A short list is still useful. Even three or four rows prevent a missed crossing.

Do you also survey land boundaries for the right of way?

Yes; see Mezux land survey services for boundary and strip plans.

How many rows does a typical matrix have?

It varies widely: a short urban crossing may have five, a long highway widening several hundred. The count is less important than keeping every row current.

Should overhead lines be included?

Yes, where they clash with the works, for example with crane movements or new poles. A separate column for overhead or underground keeps the list clear.

Who decides that a conflict row is closed?

The project's utility coordinator or design lead, once the agreed resolution is documented and accepted by the utility owner.

Written by Saniya Parveen · Technically reviewed by Rahul Rai · Updated 8 November 2026