What is QL-A?
QL-A (Quality Level A) means physically exposing or otherwise directly accessing the utility at specific points to obtain precise horizontal position and vertical elevation, plus type/size/material/condition. It's most commonly achieved by nondestructive test holes ("daylighting") and then surveyed to project control.
Method: Physical Exposure • Purpose: Precise 3D Position + Attributes • Standard: ASCE 38-22 • Also Known As: "Daylighting"
Primary QL-A Methods (Widely Accepted)
Vacuum Excavation — Hydrovac ("Water Vac")
Core/cut a small hole, use water jet + vacuum to expose the asset; measure X/Y/Z and attributes; backfill/restore.
Process
- • High-pressure water jet loosens soil
- • Vacuum system removes debris
- • Precise utility exposure
- • Measure position and attributes
- • Proper backfill and restoration
Vacuum Excavation — Air Lance ("Air-Vac")
Same as hydrovac using compressed air instead of water; useful where water is undesirable.
When to Use
- • Frozen ground conditions
- • Around sensitive electronics
- • Where water contamination is a concern
- • Clay soils where water may cause swelling
"Soft-Dig" Hand Excavation
Hand excavation in the tolerance zone to expose the asset for direct measurement (often combined with vac trucks).
Applications
- • Shallow utilities near surface
- • Areas with restricted access
- • Combined with vacuum trucks
- • Final exposure in tolerance zones
Core-Through-Pavement + Vac
Drill an ~8–12 in (≈200–300 mm) core, then vac-excavate to the utility (common in paved corridors).
Typical Process
- • Core drill through pavement
- • 8-12 inch diameter opening
- • Vacuum excavate to utility
- • Measure and document
- • Restore pavement section
Direct Measurements from Accessible Structures
Direct measurements from accessible structures (e.g., manholes/inlets) when you can physically measure to the utility/invert; these can count as QL-A points when method and references are documented.
Examples
- • Manhole invert measurements
- • Inlet pipe connections
- • Accessible valve boxes
- • Junction box measurements
ASCE 38-22 Training Principle
"Any physical measurement on a subsurface utility can be a QL-A data point." Vac-excavation is most common, but not the only path.
What Does Not Qualify as QL-A (On Its Own)
Surface Geophysics Without Physical Exposure
Surface geophysics (EM, GPR, sondes) without physical exposure → QL-B, not QL-A.
One-Call/811 Marks or Locator Sketches
One-Call/811 marks or locator sketches (even if surveyed) without exposure → not QL-A.
Minimum Workflow to Claim QL-A (Practical Checklist)
Select Locations
Target crossings, close parallels, and critical clearances flagged by QL-B/design.
Permit & Safety
Valid locate ticket; ground-disturbance permit; owner conditions; follow OH&S and damage-prevention best practices. For HV cables/pipelines, follow owner rules (e.g., utility rep present, max water pressure).
Safety Requirements
- • Valid locate tickets
- • Ground disturbance permits
- • OHS compliance
- • Utility owner requirements
Daylight/Expose
Daylight/expose by hydrovac/air-vac/soft-dig (or access via structures where applicable). Protect coatings/cables; manage spoils.
Measure & Survey to Control
Capture X/Y to project grid and Z to a defined surface (top/OD/centerline/invert as appropriate), plus size, material, condition, bedding/cover.
Document with Test-Hole Data Sheet
Document with a test-hole data sheet (unique ID, northing/easting, ground elev., measured depth/elev., method, date, crew, photos) and upload to the utility base. (Many DOTs require this.)
Documentation Requirements
- • Unique test hole ID
- • Surveyed coordinates
- • Ground and utility elevations
- • Method, date, crew
- • Photos and measurements
Tag as QL-A
Tag as QL-A in your mapping/GIS and note any limitations (e.g., partial exposure).
Notes for Rail/LRT Corridors
Special Considerations
EM Interference & Metal Clutter
Expect EM interference/metal clutter; rely on vac-exposure for final clearance points and treat QL-A as point-specific (do not assume entire runs are QL-A between holes).
Where "Inches Matter"
Use QL-A where "inches matter" - critical clearances, crossings, and areas where precise positioning is essential for design and construction.
Why Invest in QL-A?
Precise Positioning
Accurate 3D coordinates for critical design decisions and conflict resolution.
Complete Attributes
Size, material, condition, and other critical attributes for design and maintenance.
Risk Reduction
Minimize construction conflicts, change orders, and project delays.
When QL-A Is Essential
Critical Clearances
When vertical clearance is tight and precise measurements are required
Conflict Resolution
When QL-B indicates potential conflicts requiring precise verification
Ready to Implement Professional QL-A Standards?
Contact us to learn how our Visual Ground Disturbance System can help you document and manage QL-A test holes with proper data sheets and workflow management.