In situ capping

In situ Capping In situ capping (cover) involves placing a multilayered cover over a contaminated area to shield the contaminated material physically and chemically from water and wind erosion and to prevent direct contact of the contaminated material with animals and humans (Yland and Wachem,... 

Sediment remediation methods can be subdivided according to the mode of handling (e.g., in-place or excavation), or to the technologies used (containment or treatment). Important containment techniques include capping in situ and confined disposal. Biological processes may be applied with in-place treatment. Excavated sediments - apart from physical separation -can be treated to immobilize pollutants, most of which are metals (Table 8.2). 

Delineation/Verification of Gross Contamination Sampling and Analysis Interceptor Trench/Sump/Subsurface Drain Pump and Treat In-situ Treatment Temporary Cap/Cover... 

Remarkably, the addition of only 5-10 mol% of Me3SnOAc to the reactions of the sOyl precursor (1) with aldehydes also cleanly produce the cycloadducts in excellent yields [31]. It then appears that the capping of the alkoxide (61) to form the stannyl ether in situ is efficient enough that only a catalytic amount of Me3SnOAc is sufficient to facilitate reaction. This tin-ejfecC greatly enhances the... 

Various initiation strategies and surfactant/cosurfactant systems have been used. Early work involved in situ alkoxyamine formation with either oil soluble (BPO) or water soluble initiators (persulfate) and traditional surfactant and hydrophobic cosurfactants. Later work established that preformed polymer could perform the role of the cosurfactant and surfactant-free systems with persulfate initiation were also developed, l90 222,2i3 Oil soluble (PS capped with TEMPO,221 111,224 PBA capped with 89) and water soluble alkoxyamines (110, sodium salt""4) have also been used as initiators. Addition of ascorbic acid, which reduces the nitroxide which exits the particles to the corresponding hydroxylamine, gave enhanced rates and improved conversions in miniemulsion polymerization with TEMPO.225 Ascorbic acid is localized in the aqueous phase by solubility. 

Alternative 4 In Situ SVE/Soil Fixation, Cap, and Groundwater Pump-and-Treat... 

For the site remediation case shown in Figure 16.21, this alternative consists of in situ SVE of TCE-contaminated soil (Area 2), in situ soil fixation of lead-contaminated soil (Area 1), cap (Area 1), and the groundwater pump-and-treat components of Alternative 3. 

It is assumed that the moisture content of the soil has been determined to be approximately 50% under worst-case conditions. Using this information and the results from vendor tests, it has been determined that a minimum dose of one part solidification reagent to two parts soil is required for the migration control of lead. Testing has shown that the optimum solidification reagent mixture would comprise ca. 50% fly ash and ca. 50% kiln dust. Thus, ca. 7000 t (6364 T) each of fly ash and cement kiln dust would be required. The reagents would be added in situ with a backhoe. As one area of the soil is fixed, the equipment could be moved onto the fixed soil to blend the next section. It may be anticipated that the soil volume would expand by ca. 20% as a result of the fixation process. This additional volume would be used to achieve the required slope for the cap. An RCRA soil/clay cap placed over the solidified material is necessary to prevent infiltration and additional hydraulic stress on the fixed soil. It is estimated that the fixation would reduce lead migration by 40% and that the fixed soil may pass the U.S. EPA levels for lead. 

Melchior, S., In situ studies on the performance of landfill caps, Proceedings of the International Containment Technology Conference, St. Petersburg, FL, 1997, pp. 365-373. 

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