Ground Assessment
1.5 hours
Learning Objectives
- •Explain why ground conditions are the foundation of MEWP stability
- •Identify ground hazards that can cause a MEWP to tip over or sink
- •Describe how to assess and support unstable or soft ground before setup
- •Explain how slope, drop-offs, and underground voids affect MEWP placement
Topics Covered
- •Stability begins at the ground: the firmest machine tips if the ground under it fails
- •Soft, saturated, or recently backfilled ground and the risk of a wheel or outrigger sinking
- •Underground hazards: utility trenches, vaults, septic systems, basements, and buried voids
- •Slope and grade limits: every MEWP has a maximum rated slope for both driving and elevating
- •Drop-offs, curbs, floor edges, and floor-load limits when working on elevated slabs or decks
- •Using cribbing, pads, or steel plate to spread load and support outriggers or wheels
- •Checking for holes, depressions, and debris along the intended travel path
- •Weather effects: rain softening soil, frost heave, and thawing ground reducing bearing capacity
- •Coordinating with the site supervisor and reviewing the A92.22 site risk assessment before positioning
Resources
Self-Check Questions
Question 1: Why is ground assessment described as the foundation of MEWP stability?
- A. Because soft ground makes the machine drive faster
- B. Because even a perfectly maintained MEWP will tip if the ground beneath it fails(correct)
- C. Because ground conditions affect only the paint, not safety
- D. Because OSHA requires the ground to be paved
Show Explanation
Explanation:
A MEWP stability rating assumes a firm, supporting surface. If a wheel or outrigger sinks or the ground gives way, the machine goes out of level and can tip — regardless of how well it is maintained.
Question 2: You need to set up a boom lift over an area that was recently excavated and backfilled. What is the concern?
- A. The fresh soil looks unprofessional
- B. Backfilled or uncompacted ground may not support the machine and a wheel or outrigger could sink(correct)
- C. Backfilled ground is always safe to drive on
- D. There is no concern as long as it is not raining
Show Explanation
Explanation:
Recently backfilled trenches and excavations are often uncompacted. A wheel or outrigger can punch through, dropping the machine out of level — assess and support the ground or relocate.
Question 3: What is the purpose of placing cribbing or steel pads under a MEWP outriggers or wheels?
- A. To make the machine taller
- B. To spread the load over a larger area and improve support on less-than-ideal ground(correct)
- C. To keep the tires clean
- D. To allow the machine to exceed its rated capacity
Show Explanation
Explanation:
Cribbing and pads distribute the concentrated load from a wheel or outrigger over more ground area, reducing the pressure on the soil so it is less likely to fail.
Question 4: Before positioning a MEWP, what underground hazards should the operator consider?
- A. Only the color of the soil
- B. Utility trenches, underground vaults, septic systems, basements, and other buried voids(correct)
- C. Nothing below grade matters for aerial lifts
- D. Only the depth of the topsoil
Show Explanation
Explanation:
A buried void — a trench, vault, septic tank, or basement — can collapse under the weight of the machine. These hazards are invisible from the surface, so they must be identified before setup.
Question 5: How does operating slope affect a MEWP?
- A. It has no effect as long as the platform is below 20 feet
- B. Every MEWP has a maximum rated slope; exceeding it for driving or elevating risks a tip-over(correct)
- C. A steeper slope increases the rated capacity
- D. Slope only matters for scissor lifts, not boom lifts
Show Explanation
Explanation:
Manufacturers publish maximum slope ratings because grade shifts the center of gravity toward a tipping line. Exceeding the rated slope — especially with the platform elevated — can tip the machine.
Question 6: It rained heavily overnight and the job site soil is saturated. How should this affect MEWP setup today?
- A. No change — soil moisture does not affect bearing capacity
- B. Saturated soil has reduced bearing capacity, so the operator must re-assess support and may need additional cribbing or a firmer location(correct)
- C. Wet soil is always firmer and safer
- D. Just drive faster to avoid sinking
Show Explanation
Explanation:
Saturated soil loses bearing capacity and can let a wheel or outrigger sink. Ground that was firm yesterday may not be today — re-assess, add support, or move to a firmer surface.