SUE Quality Levels A to D Explained for Indian Projects

Updated: 23 October 2026

What are SUE quality levels?

Subsurface utility engineering (SUE) is a method for managing the risk that buried cables and pipes create for design and construction. Its central tool is a set of four SUE quality levels, labelled A to D, which record how a piece of utility information was obtained. The label tells the reader what a line on the drawing is based on, not merely where it has been drawn.

The scheme comes from the American standard ASCE 38, first published in 2002, and from PAS 128, a British specification first published in 2014. Neither is an Indian standard. Even so, consultants and EPC contractors in India sometimes write their terms into survey specifications, particularly for metro, highway, smart city and large pipeline schemes.

The scale runs from D, the least reliable, to A, the most reliable. A single drawing nearly always mixes levels: one stretch may rest on an old owner map, while a crossing a few metres away has been dug open and measured with a tape.

Why do quality levels matter on Indian projects?

Records of underground utilities in Indian towns are often patchy. Roads get widened, different owners add services over decades, and as-built drawings do not always find their way back to the office that keeps the master record. A designer who treats every line on a compiled sheet as equally accurate is carrying a risk without knowing how large it is.

Quality levels make that risk visible and help in three practical ways:

• Design decisions – a bore profile, foundation or trench line can be given a clearance margin suited to the confidence of each nearby service.
• Contract clarity – the tender states which level is needed where, so every bidder prices the same scope.
• Site safety – excavation gangs can tell which marks came from detection and which were only copied from paper, and dig with matching care.

What are the four SUE quality levels?

Quality Level D – records only

Information taken from existing drawings, owner maps, old project files and verbal accounts, plotted without any check on site. It is fast and inexpensive, and at concept stage it shows which owners need to be contacted. Positions can be far off, and whole services may be absent from the sheet.

Quality Level C – records plus visible features

The records are compared with what can be seen above ground: manhole covers, valve chambers, joint pits, marker posts, poles with cable risers and patched trench lines. A surveyor fixes those features and the record is shifted to fit them. The alignment between two visible features is still an assumption, and depth is not measured.

Quality Level B – detected in the field

Geophysical methods find services from the ground surface. Ground penetrating radar (GPR) responds to metallic and non-metallic targets, plastic pipes and ducts included; electromagnetic (EM) cable locators trace metallic utilities such as conductive cables and metal pipes. Horizontal position is marked and recorded, and depth is given as an estimate. PAS 128 divides this level into sub-levels according to the methods and coverage used. For most route design and excavation planning, Level B is the working basis.

Quality Level A – exposed and measured

The service is uncovered at a chosen spot, usually in a trial pit, and its position, depth, size and material are measured directly. Level A holds only where the pit was dug; a metre along, the same service falls back to whatever level it had before. That is why it is used selectively, at crossings and clash points where a mistake would be expensive.

Which terms appear in a SUE specification?

How is a SUE survey carried out, step by step?

1. Fix the purpose. Agree what the information is for – route selection, detailed design or excavation – and which stretches need which level.
2. Gather records (QL-D). Ask every likely owner – power, water, sewerage, telecom, gas – for maps of the area.
3. Survey surface features (QL-C). Pick up covers, chambers, poles, markers and reinstated cuts, then fit the records to them.
4. Scan the ground (QL-B). Run radar lines along and across the corridor, trace conductive lines with an EM locator and mark each find on the surface.
5. Expose critical points (QL-A). Open trial pits wherever an exact depth will decide the design, or where records and detection disagree.
6. Reconcile and report. Combine every source, assign each feature its level and state plainly what could not be found or reached.

Not every job needs all six steps. A short service connection may stop at Level B, whereas a metro station box or a large HDD crossing under a busy road usually justifies Level A at its clash points. Our comparison of GPR with trial pits and boreholes shows where each method earns its place, and the guide on EM cable locators versus GPR covers the two Level B tools.

How do you choose the right level for your project?

Begin from the consequence of being wrong, not from the budget line. A few working rules:

• Feasibility and route options: Level D, with Level C on the shortlisted alignments.
• Detailed design of cable, pipe or duct routes: Level B along the full corridor.
• HDD entry and exit pits, bores under major services, and foundations near HT cables or gas lines: Level A at those specific points.
• Old town centres with weak records: tighter radar line spacing at Level B and more Level A points than usual.

Ground conditions matter as well. Radar reach drops in wet clay and saline soil, where high moisture content and dissolved salts cause strong signal attenuation, and improves in dry sandy ground, so a deep service in poor ground may never reach Level B with real confidence. Our note on how accurate GPR depth readings are explains why. Where that happens, exposure is the honest answer.

What mistakes should you avoid?

• Asking for "Level B across the site" without saying where Level A is needed.
• Treating a Level D line as clear enough to excavate beside.
• Accepting a drawing that shows no level against each feature.
• Leaving trial-pit permissions and reinstatement out of the contract, so Level A work stalls on site.
• Reading a radar depth as exact; it is an estimate whose reliability depends on soil, moisture and target size.
• Skipping the limitations section of the report, which is where the unresolved risk is written down.

How should SUE records be kept after the survey?

A SUE drawing keeps its value only while the level and date stay attached to each feature. Hold the utility mapping as layers by service type, with attributes for level, method and survey date, instead of a flat PDF. When a trial pit later confirms a service, upgrade that feature to Level A and note the pit reference. When new services go in, add them with their own level rather than redrawing the whole sheet. Drawing sets can be prepared in CAD or GIS form, and our CAD/GIS mapping service sets out the layer and attribute options.

Where can you get a SUE survey done in India?

Mezux Touch carries out Level B detection with 58 company-owned GPR systems and EM locators, operated by our own staff travelling out of the Faridabad yard, and opens trial pits or boreholes on request for Level A points. Route detection costs ₹24 a metre, rising to ₹32 when the depth profile of an L-section is wanted; any order is counted as at least 4 km, a job beyond Delhi NCR is never billed under ₹1,00,000, and GST comes on top. We price travel to site, after-dark shifts, road-traffic permits and any CAD/GIS sheets on their own lines. Scope details are on our SUE survey service page, and every slab is listed in the GPR survey price list.