When backfilling trenches in areas subjected to heavy vehicle traffic (e.g., roads or parking lots), what is the typical minimum compaction requirement for the backfill material, expressed as a percentage of its Proctor maximum dry density?

Question: When backfilling trenches in areas subjected to heavy vehicle traffic (e.g., roads or parking lots), what is the typical minimum compaction requirement for the backfill material, expressed as a percentage of its Proctor maximum dry density?

Answer options:

• 85% Standard Proctor
• 90% Modified Proctor
• 95% Standard Proctor ✅ 98% Modified Proctor

Correct answer: 98% Modified Proctor

Explanation: For areas with heavy vehicle traffic, specifications commonly require a minimum of 98% Modified Proctor compaction. This high density provides the necessary structural support to prevent settlement and deformation of the roadway, ensuring long-term stability and reducing maintenance. Standard Proctor typically applies to less critical applications.