Control excavations

Quotation marks indicate designations for specimens of unknown provenance, i.e., not obtained from controlled excavations. 

In addition to finding cochineal in Nazca material, we have also found it in samples of Moche material (AD 200-500) from controlled excavations. 

Soil Stabilization/Grouting. Sodium sihcates have been used in soil stabih2ation for most of the twentieth century. This usage represents the largest market in Japan in the mid-1990s. Sodium sihcates can be used for water control and soil stabih2ation in tunneling and excavation projects. 

Principal Option for Containment/ Recovery Excavation Vacuum extraction Temporary cap/cover Hydraulic modification No action Groundwater pumping Subsurface drains Hydraulic barriers Low permeability barriers No action Overflow/underflow containment (i.e. oil booms) Run off/run on control Diversion/collection No action Capping/ nsulation Operations modifications Gas collection/removal No action... 

Adequate controls of any operations (e.g. excavation) that may cause damage to or weaken third-party property ... 

In cases where in situ biological treatment cannot be applied, the contaminated soil is excavated and transferred to specially prepared areas where bioremediation can be carried out under well-controlled conditions. Some common ex situ biological methods are the landfarming technique and the biopile or biopit treatment options.32... 

High-permeability passive perimeter gas control systems entail the installation of highly permeable (relative to the surrounding soil) trenches or wells between the hazardous waste site and the area to be protected (Figure 16.6). The permeable material offers conditions more conductive to gas flow than the surrounding soil, and provides paths of flow to the points of release. High-permeability systems usually take the form of trenches or wells excavated outside the site, then backfilled with a highly permeable medium such as coarse crushed stone. 

The applications and limitations of passive gas control systems must also be understood. They can be used at virtually any site where there is the capability to trench or drill and excavate to at least the same depth as the landfill. Limiting factors could include the presence of a perched water table or rock strata. Passive vents should generally be expected to be less effective in areas of high rainfall or prolonged freezing temperatures. 

Figure 16.8 shows an active perimeter gas extraction system. Active systems can be used at virtually any site where there is the capability to drill and excavate through the materials in the action area to the required depth. Limiting factors of active systems include the presence of freestanding leachate (i.e., saturation) or impenetrable materials. Active perimeter gas control systems are not sensitive to freezing or saturation of the surface or cover soils. 

Fugitive dusts are caused by wind erosion on waste sites, by vehicular traffic, and by excavation of waste during remedial action. The most commonly used control methods include the following ... 

Similar to soil remediation, in situ control and excavation-and-treat methods can be applied to sediment remediation. 

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). 

On a site, materials handling and dust control are always the issues which must be faced. Because the site contains MPA which can pose both an environmental and a direct health risk, the entire excavated site will have to be wet down regularly for dust control, and despite the mud problems this creates, water and mnoff from the site must be collected, tested, treated, prior to its release. The same thing must happen for the treated soils. 

The major cost factors of an evaporation pond include pond liners, land preparation, excavation and clearing, site surveying, bank construction, pumps, control systems, disposal of precipitated solids, maintenance and geotechnical investigation of the site (Singh and Christen 2000). Of these, pond liners typically represent the greatest cost (Nicot et al. 2009). 

Trenches excavated across the veins are typically flooded by surface water however, three partially flooded trenches have exposed bedrock. From small (< 5m ) outcrops exposed in three of the trenches, it is apparent that the average grain size of the clastic sedimentary rocks and the abundance of coarse-grained detritus, increases from NE to SW away from the buried Caradocian shale, with arkosic sandstone most abundant in the SW near the Christopher vein. An extensive array of 98 drill holes provides excellent downhole, 3-D control on our understanding of the geology. 

In the past, this technology has been used for groundwater control and to strengthen walls at excavation sites. According to the vendor, the principle aspects of this technology have been demonstrated in various applications for nearly 50 years. The technology is currently commercially available. 

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