CSLB C-27 Landscaping ContractorSite Preparation and DrainageMedium
A C-27 contractor is preparing a site for a new gravel pathway that will experience moderate foot traffic. To ensure a stable and durable surface, what is the minimum recommended compaction percentage for the subgrade beneath the gravel base?
- A100% Modified Proctor
- B85% Modified Proctor
- C90% Modified Proctor
- D95% Modified Proctor
Show answer & explanationAnswer & explanation
Correct answer: C. 90% Modified Proctor
For pathways and light-duty hardscapes experiencing moderate foot traffic, a minimum compaction of 90% Modified Proctor is generally recommended for the subgrade. This provides adequate stability to prevent settling and ensure the longevity of the gravel base and pathway surface.
Why the other options are wrong
- A. 100% Modified Proctor is usually specified for very heavy-duty applications or specific engineered fills where maximum density is critical.
- B. 85% Modified Proctor is typically too low for a pathway subgrade and could lead to settlement and instability.
- D. 95% Modified Proctor is often required for heavier loaded areas like driveways or structural foundations.
Subgrade Compaction (Pathway)
For gravel pathways with moderate foot traffic, the subgrade should be compacted to a minimum of 90% Modified Proctor to ensure stability.
- Prevents future settlement and uneven surfaces.
- Modified Proctor test determines maximum dry density.
- Compaction percentage varies by traffic load and hardscape type.
Memory trick: Ninety for pathways, ninety-five for cars, a hundred for the stars.