Subsurface Exploration

To

Project team

From

Daniel P. Colwell

Date

October 17, 2026

Re

Phase III, Subsurface Exploration: drilling, sampling, groundwater and logging

What is performed

Subsurface Exploration collects the physical evidence: borings, samples, in-situ test results and groundwater readings. The field engineer or geologist logs each boring as it is drilled, and the engineer later divides each boring into strata. This is the only phase that touches the ground directly, so the quality of everything after it depends on the care taken here.

How it is performed

1. Clear the site. Confirm utility locates, flagging and the safety briefing before the rig sets up.
2. Drill and sample. Run Standard Penetration Tests per ASTM D1586, recording blow counts, recovery and the hammer energy ratio (from ASTM D4633 calibration) so N-values can be corrected to N₆₀. Take thin-walled tube samples per ASTM D1587 in soft clays, and core rock per ASTM D2113 with recovery and RQD.
3. Describe in the field. Classify each sample visually per ASTM D2488, note color, moisture, consistency or density, and take pocket penetrometer readings in cohesive soils.
4. Measure groundwater. Record water levels during drilling, at completion and, where possible, after 24 hours or in an observation well.
5. Enter the field log. Record the boring header (location, ground elevation, drilling method, hammer type and energy ratio, groundwater) and every sample in the workflow's Field Log.
6. Close out. Grout or backfill the holes to state requirements, and send samples to the lab under chain of custody.
7. Prepare the boring logs. The engineer divides each boring into strata (depth, USCS group, name and description) on the Boring Log, drawn from the field data.

Why it matters in the workflow

Every design value in the project traces back to a sample or a blow count from this phase. Accurate depths, a recorded hammer energy ratio and careful field descriptions are what make the laboratory program and the design parameters reliable. Groundwater readings taken now control effective stress, slope stability and construction dewatering later.

What comes in and what goes on

Use and disclaimers

This phase guidance describes general practice for training and reference. It is not engineering advice for any project. Any value, calculation or report prepared with NANCY must be checked and accepted by a professional engineer licensed in the project jurisdiction, and governing codes, owner standards and the current editions of referenced standards take precedence. NANCY is provided as is, without warranty, and is independent of any employer or client. Use is subject to the full Use and Disclaimers.