1. Excavation Below Subgrade (EBS)
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2. EBS QC/QV personnel do not determine/direct EBS operations.
Engineer ultimately determines the need for EBS.
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3. EBS Remove objectionable materials.
Resulting excavation is then back filled with soil.
Figure 3.1
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4. Figure 3.1: Intercepting Embankment
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5. Predicting EBS Areas Groundwater levels = 3 feet or less.
Silty “B” horizon.
Topsoil depths exceed 12 inches.
Moisture levels above plastic limit.
Depositional characteristics (alluvial, lacustrine).
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6. Predicting EBS Areas Roadway constructed prior to 1940.
Extensive filling.
Roadway is distressed.
Highly variable soil conditions exist.
Subgrade is within 2 ft. of original surface.
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7. Figure 3.2: Detail of EBS
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8. EBS Remove uncertain soil. Note the diagonal rutting= unstable silt.
In addition to excavation.
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9. Figure 3.3: EBS
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11. Rutting of Unstable Material
Transition from cut to fill are important.
Inspect before the subbase or base.
Rutting of unstable material shown.
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12. Figure 3.4: Rutting of Unstable Material
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13. EBS Yielding water-bearing silt. Rock truck-hauling material away.
Backhoe-Loading EBS material out.
Dozer-Pushing material to backhoe.
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14. Figure 3.5: EBS
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15. Backfilling EBS EBS has to be measured.
Original section is template in the cross.
Final section
How much was excavated.
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16. Figure 3.6: Backfilling EBS
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17. EBS Do not do EBS when rain is imminent.
Do not leave EBS excavation open over night.
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18. Topic I

19. Figure 3.7: EBS
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20. Figure 3.8: Loading Unstable Material
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21. Backfilling EBS Careful placement and compact backfill.
Use similar materials in area.
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22. Figure 3.9: Backfilling EBS
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23. Organic & Silty Soils
Have foundation support for equipment.
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24. Figure 3.10: Organic & Silty Soils
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25. Seepage in a Cut Must correct area like this. Ditches may work.
Riprapping
Underdrains
Vegetation will not grow.
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26. Figure 3.11: Seepage in a Cut
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27. Dust Abatement Required to minimize dust.
Use water or dust control materials.
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28. Figure 3.12: Dust Abatement
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29. Stone Piles & Fences
Large rocks outside the shoulder point.
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30. Figure 3.13: Stone Piles & Fences
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31. Marsh Excavation Picture 2:
Excavated marsh either cast out or loaded into marsh.
Used for deeper marshes.
Dragline works slower then backhoe.
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32. Figure 3.14: Marsh Excavation 1
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33. Figure 3.15: Marsh Excavation 2
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