Soil Compaction & Testing

Fill material must be approved type — no organics, no debris, no expansive clay. Engineered fill typically requires testing and approval.

1. Check fill material — should be clean, granular soil or approved engineered fill

2. Verify no organic material (roots, topsoil, vegetation) is mixed with fill

3. Check for construction debris — no wood, plastic, or trash in fill

4. Verify fill material was tested and approved (for structural fills)

5. Check that different fill types are separated (don't mix clay with granular)

6. Verify fill source is documented and consistent

- Organic material mixed with fill (decomposes, creates voids)

- Construction debris used as fill (unpredictable settling)

- Expansive clay used as fill (swells and shrinks)

- Untested fill for structural purposes

- Mixed fill types creating differential settlement

Fill must be placed and compacted in lifts (maximum 8" loose). Compaction to 95% Standard Proctor for structural fills. Moisture content must be near optimum.

1. Verify fill placed in lifts — maximum 8" loose (6" compacted)

2. Check compaction test results — minimum 95% for structural fills, 90% for non-structural

3. Verify moisture content is near optimum (within 2% of optimum moisture)

4. Check that each lift was tested before the next was placed

5. Walk on compacted fill — should feel firm with no give

6. Verify equipment used was appropriate for fill type and area

7. Check that fill was not placed on frozen ground or in standing water

- Fill placed in lifts too thick — bottom of lift not compacted

- Fill too dry or too wet — will not compact properly

- No compaction testing for structural fills

- Fill placed on frozen ground

- Fill placed in standing water

- Light equipment used for deep fills