<p>This Master Thesis presents TMVOC simulations of a NAPL-spill (non-aqueous phase liquid) and following pumping remediation. TMVOC is a simulation program for three-phase non-isothermal multicomponent flow in saturated-unsaturated heterogeneous media. The models presented are based on an actual remediation project. The aim of the thesis was to study if the historical development of the NAPL-spill could be simulated and how long time the pumping remediation would take. A 3D-model and a radially symmetric cylindrical model were created.</p><p>A large effort of the work done was in taking the complex TMVOC model in use and modifying it for the problem at hand. Therefore, the numerical results of the simulations should be considered as preliminary and as forming basis for future studies.</p><p>The results from the spill simulation and historical pumping simulation indicated that the spill volume could be less than the estimated 1400 m³, perhaps around 700 m³, assuming a leakage time of 30 years.</p><p>The historical pumping simulation of a 700 m³ diesel spill showed good agreement with measured values for some wells, but overestimated the recovery in other wells. The overestimation could be due to the fact that the 3D-model did not take seasonal changes in the groundwater level into consideration. Also, the model did not account for any heterogeneity or compartmentalization in soil material properties that could explain the differences between the wells. </p><p>Assuming the same spill of 700 m³, future pumping was simulated. The results from these simulations indicated the remediation time to be long due to fast decreasing mobility of the NAPL phase. The NAPL flow rate to the wells was halved in a couple of years. Much of the NAPL was distributed over a large area at near residual saturation with the highest NAPL saturation found at the opposite side of the pumping wells in the model.</p><p> </p><p>Future simulation studies should address the effect of discretization as well as the effect of uncertainties in material properties e.g. conductivity, residual NAPL saturation and soil heterogeneity.</p>

This Master Thesis presents TMVOC simulations of a NAPL-spill (non-aqueous phase liquid) and following pumping remediation. TMVOC is a simulation program for three-phase non-isothermal multicomponent flow in saturated-unsaturated heterogeneous media. The models presented are based on an actual remediation project. The aim of the thesis was to study if the historical development of the NAPL-spill could be simulated and how long time the pumping remediation would take. A 3D-model and a radially symmetric cylindrical model were created. A large effort of the work done was in taking the complex TMVOC model in use and modifying it for the problem at hand. Therefore, the numerical results of the simulations should be considered as preliminary and as forming basis for future studies. The results from the spill simulation and historical pumping simulation indicated that the spill volume could be less than the estimated 1400 m3, perhaps around 700 m3, assuming a leakage time of 30 years. The historical pumping simulation of a 700 m3 diesel spill showed good agreement with measured values for some wells, but overestimated the recovery in other wells. The overestimation could be due to the fact that the 3D-model did not take seasonal changes in the groundwater level into consideration. Also, the model did not account for any heterogeneity or compartmentalization in soil material properties that could explain the differences between the wells.  Assuming the same spill of 700 m3, future pumping was simulated. The results from these simulations indicated the remediation time to be long due to fast decreasing mobility of the NAPL phase. The NAPL flow rate to the wells was halved in a couple of years. Much of the NAPL was distributed over a large area at near residual saturation with the highest NAPL saturation found at the opposite side of the pumping wells in the model.   Future simulation studies should address the effect of discretization as well as the effect of uncertainties in material properties e.g. conductivity, residual NAPL saturation and soil heterogeneity.

Ce manuscrit s'intéresse au devenir de contaminants organiques dans le sol, et plus précisément celui des composés organo-halogénés volatils (COHV).Il propose des outils d'aide à la décision en utilisant la modélisation numérique appliquée à des problématiques environnementales portant sur le traitement de sites et sols pollués par des COHV. Il présente, à ma connaissance, la première modélisation numérique en 3D, grâce au simulateur TMVOC, d'une technique de dépollution physique, à savoir le pompage réussi au sein d'un aquifère d'un liquide en phase non-aqueuse plus dense que l'eau ou Dense Non-Aqueous Phase Liquid (DNAPL). Les très bons résultats de cette simulation permettent d’envisager l’optimisation d’un système de pompage asservi pour dépolluer un site contaminé aux COHV. Cette thèse s'intéresse aussi à une méthode de d'évaluation, à la fois qualitative et quantitative, de l'efficacité du pompage : un test de traçage utilisant des traceurs bisolubles à coefficients de partage variables (partitioning interwell tracer test – PITT). Ce PITT permet de connaître à la fois la répartition spatiale, au sein d’un aquifère, d’une bulle de DNAPL et aussi d’en évaluer sa saturation et donc son volume. Ce manuscrit met à disposition des outils élaborés et adaptés au traitement d'un DNAPL dans un aquifère. La combinaison des deux techniques présentées, à savoir la modélisation d'un pompage de DNAPL et un PITT, sont parfaitement reproductibles dans des environnements similaires et à l'échelle industrielle. Enfin, ces méthodes permettent de réduire considérablement les coûts de caractérisation (PITT) et d'exploitation par l'optimisation de systèmes de pompage / This manuscript deals with the fate of organic contaminants in soil, more precisely of volatile organo-chlorinated compounds (VOHC) and offers some decision making techniques and tools using numerical modelling applied to environmental issues about the treatment of soils contaminated by VOHC. It presents, to the best knowledge of the auhor, the first 3D numerical modelling, with the simulator TMVOC, of a physical treatment technique, namely the successful pumping within an aquifer, of a Dense Non-Aqueous Phase Liquid (DNAPL). The very good results of this simulation give the opportunity to design a controlled and automated pumping system to remediate a polluted site. This thesis also deols with a tracer test assessment method, both qualitative and quantitative, for the efficiency of this pumping : a partitioning interwell tracer test (PITT). The PITT allows us to determine the spatial repartion of the DNAPL and also to assess its saturation, hence its volume. This manuscript offers elaborated tools adapted to the remediation of a DNAPL in an aquifer. The combination of these two techniques, namely the DNAPL pumping and the PITT, are perfectly reproducible in similar environments up to an industrial scale. Finally, exploitation and characterisation costs for DNAPL remediation can be extremely reduced by numerical modelling and optimisation