Road base elevation documentation is the final gate before paving authorization. A complete, correctly formatted base elevation QC package gets the DOT inspector to sign off on the same day. A poorly organized or incomplete package delays paving authorization — and every day of delay on a paving project is expensive.
How do you document road base elevations for inspector sign-off?
Road base elevation documentation requires: a level or total station survey at 25-50 ft intervals along the road stationing (at centerline, left edge, and right edge), design elevation and variance at each point, cross-slope calculation per section, and a QC package including the data table, deviation plot, and compaction records. Most DOT specs require base within ±0.03 to ±0.05 ft of design before paving authorization.
The following procedure covers the field survey and documentation for road base elevation verification on a state DOT project:
Three instruments are used for road base elevation surveys on DOT projects:
Set up at an instrument height, read rod at each survey point. Accuracy: ±0.003 to ±0.005 ft. Requires two-person crew (instrument person and rod person). Suited for any road geometry. Best choice when budget is tight and accuracy requirement is ±0.03 ft or better.
Same principle as automatic level but reads the rod electronically, logs data to an internal collector, and eliminates manual recording errors. Accuracy: ±0.001 to ±0.003 ft. Significantly faster than automatic level on long road projects. The preferred tool for projects over 1 mile.
RTK GPS rover achieves ±0.03 to ±0.05 ft vertical accuracy — at the margin of DOT base tolerance. Some DOTs accept GPS rover data for base elevation surveys; others require optical leveling. Confirm the DOT's acceptable instrument list before using GPS for base elevation documentation.
DOT inspectors follow a structured review sequence before authorizing paving. Prepare your package to address each element:
| Inspector Check | What They Look For | Common Failure |
|---|---|---|
| Elevation data completeness | Every required station and offset covered | Missing stations or skipped sections |
| Variance calculation | Correct sign (high vs. low) and magnitude | Design elevation from wrong plan sheet |
| Out-of-tolerance resolution | All flagged areas re-surveyed after correction | Open non-conformances with no corrective action |
| Cross-slope compliance | Within ±0.2% of design at all stations | Cross-slope not calculated; only centerline surveyed |
| Compaction records attached | Base course compaction ≥ spec minimum | Base compaction records not linked to this base report |
| Subgrade acceptance confirmed | Prior subgrade sign-off document referenced | Base placed before subgrade was formally accepted |
When base elevation survey finds areas outside tolerance, the correction options depend on whether the base is high or low:
A base that is too high will reduce pavement thickness below the design minimum. The correction is motor grader trimming — removing the excess base material. After trimming, re-survey and re-compact if the grading disturbed the compaction layer. This is the most common corrective action and can typically be accomplished without delaying the paving schedule if caught early.
A base that is too low means insufficient base depth will be achieved even with the correct pavement thickness, or the pavement surface will be low. Correction: add base material, compact, and re-survey. On a large low area, this is the more expensive correction because it requires additional material, compaction passes, and a full re-survey cycle before the DOT inspector can re-review.
Most state DOT specifications require surveys at 25-foot or 50-foot intervals, with readings at centerline, left edge, and right edge of each lane. Some specifications also require gutter flow line and shoulder edge points. Confirm the required grid with the project DOT inspector.
Typical DOT requirement is ±0.03 to ±0.05 ft from design elevation. High spots that reduce pavement thickness below the design minimum require trimming regardless of the tolerance magnitude. Cross-slope must be within ±0.2% of design.
Inspector sign-off typically requires: complete base elevation survey within tolerance, compaction records for the base course, subgrade acceptance documentation, and QC contractor certification. Some states also require the base elevation survey to be submitted through the project management system before the inspector schedules a paving pre-construction meeting.
Sitemark captures base elevation data in the field, calculates variances, flags out-of-tolerance stations, and compiles the DOT QC package. Start free.