Remediation Scenario

The following simplified field-scale remediation scenario is considered in this study phenanthrene (PHE) is emitted from a NAPE source with a constant concentration of 200 dg/L and the contaminant plume is captured by an extraction well 25 meters downstream the source zone (Fig. 7.9). 

It is assumed that the aquifer is confined and hydraulically homogeneous (average hydraulic transmissivity T= 10 m /s, gradient of the natural uniform flow field /= 0.2 %) and composed of Neckar river alluvial (NRA). The lithological composition and grain size distribution of NRA (Tab. 7.1), as determined by Riigner et al. (1997), is 

Grain Size (d in mm) Qnartz Stuben Sandstone Jurassic Limestone Triassic Limestone NRA Sample 

Mean grain diameters of lithological subcomponents (in mm) Mean 1.7 16.6 16.6 

---

Walton-Day, K., Paschke, S.S., Runkel, R.L Kimball, B.A. 2007. Using the OTIS solute-transport model to evaluate remediation scenarios in Cement Creek and the Upper Animas River. U.S. Geological Survey Professional Paper 1651, 979-1028. 

The technology is applicable to many remediation scenarios including large contaminated surface areas. 

Beside the presentation of the SMART concept, the objectives of this paper are (i) to examine how organic contaminant transport is influenced by properties of natural aquifer material and (ii) to show how surfactants may enhance the remediation of sites contaminated with polycyclic aromatic hydrocarbons (PAH). This is done in an exemplary way by applying the transport model to a simplified field-scale remediation scenario where Phenanthrene (PHE) and the non-ionic surfactant Terrasurf G50 (TG50) are considered as solutes. 

Figure 7.9 Simplified remediation scenario extraction well in uniform flow field.

Conservative transport has been modelled using standard software. The flow field for the remediation scenario described above has been calculated by MODFLOW (McDonald and Harbaugh, 1984). The particle-tracking software MODPATH (Pollock, 1988,1994) has been used to calculate total travel time of each particle from the injection plane to the well screen. The simulation of conservative transport leads to the pdf of travel time as shown in Fig. 7.10. 

Many remediation scenarios will involve both containment and treatment. However, in some conntries where economic resonrces are not plentiful, using a remediation technology that requires ex situ treatment may not be a viable option, particularly if treatment of wastewater, for example, is not already practiced routinely. 

Maqsood, L, Jianbing, L., Guohe, H. Uefei, H., 2005. Simulation-based risk assessment of contaminated sites under remediation scenarios, planning periods, and land-use patterns a Canadian case study. Stochastic Environ Research and Risk Asses, 19 146 157. 

Identifying the initial project/operable unit, likely response scenarios, and remedial action... 

Several recovery scenarios were considered for remediation. Initially, construction of a narrow, permeable trench parallel to the canal appeared to be an appropriate interception system. The construction technique considered was use of a specially designed deep trenching unit. This type of trench would have included a tile drain leading to a single two-pump recovery well. However, a review of the subsurface site plans and interviews with long-term employees determined that an unknown number of buried pipes traverse the area intended for the trench construction. Disruption of refining operations and safety considerations resulted in rejection of this option. 

Researchers stated that ion exchange removal of nitrate was cost prohibitive at this site due to the high cost of waste disposal. They concluded that the perchlorate-only alternative was the most cost-effective solution. Under this scenario, nitrate would be removed by another remediation technology. Perchlorate disposal costs under this option were 350/year, and minimal... 

Reductive biotransformation of a contaminant can occur when the contaminant serves as the terminal electron acceptor. Many contaminants that are recalcitrant to bio-oxidation will undergo reductive biotransformations. These biotransformations can lead to detoxification, mineralization, or changes in the mobility of the targeted contaminant. Hexavalent chromium and tetra-chloroethene (PCE) have been investigated as candidates for reductive biotransformation. This technology may be most applicable for in situ remediation for the following scenarios PCE contamination, low-yield aquifers, areas contaminated by both alkylbenzenes and chlorinated ethenes, and deep aquifer contamination. 

I have learned other tricks from my own memory problems and those of my patient informants. First and foremost, I know just how totally helpless one becomes when recent memory fails. Dreams emphasize this point through the frequency of these disconcerting, incomplete arrangement scenarios that we have already considered. Without recent memory I am lost, disoriented, feel confused, get very anxious, and run around in circles. So armed with dream neurodynamics, I can empathize more effectively with amnesics, and I can advocate a gamut of remedies more authoritatively. 

In implementing the risk-based waste classification system developed in this Report, the selection of exposure scenarios appropriate to waste disposal is an important technical issue that must be addressed. NCRP believes that scenarios for inadvertent intrusion into near-surface disposal facilities are appropriate in classifying waste for purposes of disposal and, further, that scenarios involving permanent occupancy of disposal sites after loss of institutional control would be appropriate (see Section 6.1.3) such scenarios are commonly used in regulating near-surface disposal of low-level radioactive waste and in risk assessments at hazardous waste sites subject to remediation under CERCLA. 

A large number of groundwater pollution cases are never published. This is especially true for severe cases. Yet an ever-growing number of case studies are being published. Every hydrochemist should read as many of these papers as possible, as each provides examples of possible scenarios and possible modes of diagnosis and remedy. A selection of pollution case studies is reviewed in the following sections. 

From consultations with the agencies involved, the community, and with the industrial participants, the risks posed by the site should be classifiable and appropriate response and remedial measures agreed upon. We have confidence that this scenario will be followed to reach a satisfactory resolution of the problems associated with this site. 

---