Excavation and trenching

0:00 Intro

Excavation and trenching, for the ASP exam. Every rule and number here is cited to its primary source, on screen.

0:10 Learning objectives

In this lesson, you'll learn to: state the depth thresholds that trigger each rule, explain the competent person's inspection duties, classify soil and match it to a maximum slope, and apply slope math to size a cut.

0:29 Two depths to memorize

Two depth thresholds drive most exam questions here. Protective systems are required, except when made entirely in stable rock, or under 5 feet with no sign of cave-in, per a competent person. At 4 feet or more, a trench needs egress within 25 feet of lateral travel. Test before entry if deeper than 4 feet and oxygen deficiency or a hazardous atmosphere could reasonably be expected.

1:02 Underground installations

Underground utilities come in three stages. Before opening, estimate locations and contact owners. No response in 24 hours (unless law requires longer), or no exact location? Proceed with caution and detection equipment. Approaching them, determine the exact location by safe and acceptable means.

1:32 Competent person duties

While open, protect, support or remove them as necessary. The competent person carries the inspection duty. Inspect daily: before work starts and as needed throughout the shift. Inspect after every rainstorm or other hazard-increasing occurrence. All inspections are only required when employee exposure can be reasonably anticipated.

2:03 Appendix A soil classification

If hazards are found, remove exposed employees until precautions are taken. The competent person also monitors water removal equipment. A competent person classifies each deposit using at least one visual and one manual analysis. 5 tsf or greater, but never if fissured, vibrated, or previously disturbed. 5 tsf, or granular soil like angular gravel and silt. 5 tsf or less, sand or gravel, or submerged or freely seeping soil.

2:51 Table B-1

A layered system takes its weakest layer, unless a more stable layer lies under a less stable one. The default slope is no steeper than one and a half to one. Alternatively, with soil classified per Appendix A, Table B-1 gives the steepest slope under 20 feet deep. Other options: tabulated data or an engineer's design. Stable rock may be vertical. Type A is three-quarters to one, Type B one to one, Type C one and a half to one.

3:30 Worked example: slope

Short-term, open 24 hours or less, Type A at 12 feet or less may be one-half to one. Over 20 feet needs an engineer. Example: an 8-foot-deep simple slope in Type B soil. How far back is each side cut?

3:54 Actual slope

Type B is 1 to 1, so run equals depth times 1. 8 feet times 1 is 8 feet per side. 5 is 12 feet. Weaker soil means a flatter slope. The actual slope can never be steeper than the maximum allowable slope. With signs of distress, cut back at least one-half horizontal to one vertical less steep.

4:16 Edges, water, equipment

With surcharge loads from stored material, equipment or traffic, a competent person decides how much flatter. Four rules set concrete distances and limits. Keep spoil and equipment at least 2 feet from the edge, or use retaining devices.

4:43 Common exam traps

No work in accumulated or accumulating water without adequate precautions. Walkways need guardrails at 6 feet or more above lower levels. No employee may be underneath loads handled by lifting or digging equipment. Now, six traps that catch people on exam day. One: under 5 feet is exempt only with no sign of cave-in. Two: trench egress starts at 4 feet, within 25 feet of lateral travel. Three: inspect before work, as needed, and after every rainstorm.

5:27 Recap quiz

Four: a competent person classifies soil, with at least one visual and one manual analysis. Five: short-term Type A, 12 feet or less deep, may be one-half to one. Six: with signs of distress, cut back at least one-half to one flatter. Question 1. Maximum simple slope, Type C under 20 feet deep? A: three-quarters to one. B: one to one. C: one and a half to one. D: one-half to one. C. Type C is one and a half to one, 34 degrees. Question 2. A 6-foot trench in sound soil, not stable rock. A: protection required. B: exempt if no cave-in sign. C: exempt, under 8 feet. D: egress not required. A. The exception covers only excavations under 5 feet, or stable rock. Question 3. Owners cannot locate lines in 24 hours; law requires no longer. A: wait indefinitely. B: proceed with caution, detection equipment. C: dig without precautions. D: skip the request. B. Proceed with caution, using detection equipment or other acceptable means. Want to see where you stand on every ASP domain? com.

25 questions, free, no card. You get a readiness score for each ASP domain.