Soils, compaction excavation

A 10-yd3 soil sample was excavated from the site, blended, and characterized for initial hydrocarbon content and nutrient content. The reactor was filled with soil compacted to field density (Figure 12.10). The tank at the bottom was filled with water nutrients and surfactants. Water from this tank was sprayed over the top of the soil at a rate that maintained aerobic conditions. A significant amount of LNAPL was initially released from the soil, which required additional air to be pumped into the well points to maintain favorable growth conditions. After 105 days of operation, more than 87% of the total aliphatics and 89% of the total aromatics were removed. 

A combination method is called the progressive slope or ramp method, where the depositing, covering, and compacting are performed on a slope. The covering soil is excavated in front of the daily cell. Where there is no cover material at the site, it is then brought in from outside sources. 

An embankment refers to a volume of longitudinal earthen material that is placed and compacted for the purpose of raising the level of a roadway (or railway) above the level of the existing ground surface. A fill refers to a volume of earthen material that is placed and compacted for the purpose of filling in a hole, cavity, or excavation. Embankments or fills are constructed of materials that usually consist of soil, but may also include aggregate, rock, or crushed paving material. 

At locations where aboveground blending takes place, the resulting soil material can be placed back in the original excavation (or selected location) and compacted to the desired density. If the solidified material is to have a desired structural strength (i.e, subbase, pavement, controlled fill, etc.) it can be compacted by conventional construction equipment (vibrating or sheeps-foot rollers). 

The bathtub effect occurs, in part, because most wastes have much higher hydraulic conductivities than the natural material into which they are placed they may also have very different unsaturated soil—moisture characteristics. The hydraulic conductivity of some wastes can be reduced by compaction. The bathtub effect also occurs because more infiltration enters the disposal excavation than would under normal undisturbed conditions. Trench covers may be constructed to achieve the desired hydraulic conductivity and to limit infiltration for the required period of containment or until compaction of the wastes occurs however, it is difficult to maintain the trench covers. The covers must withstand attack by plants, weather (freeze—thaw, wet—dry), erosion, and strains caused by consolidation within the trench. Most trench covers are not capable of meeting these demanding requirements without costly long-term maintenance programs. The cover should be designed to allow for expected consolidation and to utilize hydro-geological concepts of saturated and unsaturated flow systems present at the site. 

Regardless of its source, oil released into the subsurface soil moves along the path of least resistance and downwards, under the influence of gravity, as shown in Figure 31. Oil often migrates towards excavated areas such as pipeline trenches, filled-in areas around building foundations, utility corridors, and roadbeds. Such areas are often filled with material that is more permeable or less compacted than the material removed during the excavation. 

In general, estimates of final compost volumes have been based upon rough assumptions, and in some cases, these volumes have been greatly overestimated. The purpose of this study was to present a preliminary estimation of the final compacted volume of treated compost to be backfilled at UMDA following full-scale remediation of the washout lagoons soils. The calculations have been based on a combination of field observations, laboratory analyses, and theoretical calculations. Ultimately, the final compost volume was presented in terms of the initial in-place volume of explosives-contaminated soils to be excavated from the washout lagoons site at UMDA. 

Finally, this finished compost material must be backfilled into the original excavation. Provided that the material is carefully replaced and compacted in thin lifts, a substantial reduction in the volume of the compost may be attainable. The extent of the compaction and volume reduction can be estimated by standard laboratory compaction tests conducted on representative samples of compost. Knowing this final compacted compost volume in terms of the original in-place soil volume is necessary to determine whether substantial excess compost will be created by the composting process, and whether backfilling the excavation and mounding this excess compost will be feasible for the site in question. 

At the Idaho National Engineering Laboratory (INEL), waste is placed either in interim storage on as dialt pads or In permanent disposal in soil excavations. Most of the waste contaminated with small amounts of fissile materials consist of paper, polyethylene wrap, glass, rags, etc., which is usually received as compacted bales or in standardized containers such as DOT 7A wood boxes. 

For Landfill Class I (disposal of mineral or mineralised wastes with low contamination) and for conventional landfills for demolition waste, excavated soil etc. only a compacted clay liner is required. The system components for class I and II cappings, being the most common types nowadays installed in Germany, are listed in Table 9.1. Guidelines with strict requirements for materials selection and testing, construction technique and quality control were published for the standard systems (Muller 1996 Muller 2001 N.N. 1993). 

Densify the loose, liquefiable soil layer. Stone column is often satisfactory if the loose layer is mostly sand. Other approaches, such as jet grouting, deep soil mixing with cementing agents and in situ vibratory densification can all be used. If the liquefiable soil layer is close to the ground surface, a complete excavation and replacement with compacted engineering fill is sometimes also feasible. 

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