8 min read • Foundation Training

Excavation and Backfill

Proper excavation and backfill techniques are essential for creating a stable, long-lasting drainage system foundation.

Why This Matters

Accurate excavation and proper backfill procedures ensure system longevity, prevent settling issues, and maintain proper water flow throughout the drainage network.

Section 1: Excavation

1

Set Slope with Precision

Accurate slope is critical for proper water flow and system performance.

  • Use a laser level and grade rod or a 4' stick level
  • Ensure a minimum 1% slope throughout the trench for proper water flow (½" drop every 4 feet)
2

Check Depth Requirements

Verify project specifications before beginning excavation work.

  • Match the project's depth requirements: 12", 14", or 18" minimum, depending on system specs
3

Dig the Rough Trench

Create the basic trench path while maintaining communication and accuracy.

  • The excavator operator digs the basic trench path
  • Stay within depth and slope targets, communicating with the trench operator
4

Smooth and Prep the Trench Floor

A trench operator inside the trench should prepare a level, stable base.

  • Remove humps with a shovel
  • Fill in low spots with dirt, compacting as needed
  • Ensure slope is kept
  • Communicate with the excavator operator about grade adjustments
5

Keep the Sides Clean

Maintain clean work areas and protect landscaping during excavation.

  • Maintain clean trench walls
  • Place excavated dirt on one side only, preferably on plywood sheets to prevent turf damage
6

Hand Dig Near Utilities

Safety requires hand digging around all sensitive infrastructure.

  • Always switch to hand tools around gas lines
  • Use hand tools around irrigation systems
  • Hand dig around other sensitive areas

Section 2: Backfill

1

Inspect Trench Before Backfill

Ensure the trench is completely clean before beginning backfill operations.

  • Remove all tools from the trench
  • Remove all trash and debris
  • Clear loose materials that could affect compaction
2

Backfill with Excavator

Use controlled backfill techniques to avoid damage to installed systems.

  • Use the bucket to push dirt from plywood or surrounding piles into the trench in controlled amounts
3

Hand Backfill Sensitive Areas

Protect critical connections and components with careful hand backfilling.

  • Use shovels around downspouts
  • Hand backfill around catch basins
  • Carefully backfill around pipe connections
  • Use hand tools around utility lines
4

Use a Hard Rake if Needed

Smooth the surrounding area for a professional finish.

  • Use the excavator's bucket teeth to pull dirt into the trench and smooth the surrounding yard
5

Compact Thoroughly

Proper compaction prevents future settling and maintains yard stability.

  • Run the excavator or skid steer tracks over the trench at least 6–10 passes
  • Use more passes for clay or compact-resistant soil
6

Leave a Mound

Account for natural settling to ensure a level final grade.

  • Leave a 2–3" mound above the trench
  • This allows for natural soil settling over the next 6-12 months, resulting in a flat, even yard for the client