The Sustainable Water Interactive for Tomorrow (SWIFT) project in eastern Virginia is a Managed Aquifer Recharge project designed to alleviate the depletion of the Potomac Aquifer System due to unsustainable groundwater withdrawals. At the SWIFT Research Center (SWIFTRC) in Nansemond, VA, a pilot testing well (TW-1) has been implemented to help determine the feasibility of full-scale implementation. The pumping data from TW-1 and observation head data from surrounding monitoring wells (MW) at the SWIFTRC were used to calculate hydrogeological parameters (transmissivity, hydraulic conductivity, specific storage, and storage coefficient). Two sets of data were analyzed from before and after TW-1 was rehabilitated to account for the change in the flow distribution to each screen in TW-1. Comparing the results to past literature, the calculated (Theis and Cooper-Jacob methods) hydraulic conductivity/transmissivity values are within the same order of magnitude. Using borehole logs as well as apparent conductance and resistivity logs, multiple single and multi-layered models for both the upper and middle Potomac aquifers were produced with MODFLOW. Parameter estimation using MODFLOW and PEST and the two sets of observation data resulted in hydrogeological parameters similar to those calculated using Theis and Cooper-Jacob methods. The change in the hydraulic conductivity and specific storage between the pre and post rehabilitation flow distributions is proportional to that change in the flow distribution. For future modeling of the aquifer system, the hydrogeological parameters from the model using the 4/26/19 data set with the post rehabilitation flow distribution is recommended. Drawdown results from a multi-layered MODFLOW model were compared to results using the Theis method using both the Theis-calculated and MODFLOW-PEST modeled hydrogeological parameters. The results were nearly identical except for the Upper Potomac Aquifer (UPA) layer 1, as the model has a large change in aquifer thickness with distance from TW-1 that the Theis-based calculations do not consider. Travel times from the monitoring wells to TW-1 were calculated with the single and multi-layered models pumping 700 GPM from TW-1. Travel times from the SWIFT MW within the UPA sublayers ranged from 204 to 597 days depending on the sublayer, while travel times from the USGS MW within the UPA sublayers ranged from 2,395 to 7,859 days. For the single layer model of the UPA, the travel time from the SWIFT MW to TW-1 was 372 days while the travel time from the USGS MW was 4,839 days. Travel times from the SWIFT MW within the MPA sublayers were 416 and 1,195 days, while travel times from the USGS MW within the MPA sublayers were 4,339 and 11,245 days. For the single layer model of the MPA, the travel time from the SWIFT MW to TW-1 was 743 days while the travel time from the USGS MW was 7,545 days. / Master of Science / The Sustainable Water Interactive for Tomorrow (SWIFT) project in eastern Virginia is a project designed to help slow the depletion of the Potomac Aquifer System due to unsustainable groundwater withdrawals. At the SWIFT Research Center (SWIFTRC) in Nansemond, VA, a testing well (TW-1) has been implemented to help determine if the full-scale implementation of the SWIFT project is feasible. The pumping data from TW-1 and observation head data from surrounding monitoring wells (MW) at the SWIFTRC were used to calculate hydrogeological parameters (transmissivity, hydraulic conductivity, specific storage, and storage coefficients). These parameters help describe the behavior of the aquifer system. Two sets of data were analyzed from before and after TW-1 was rehabilitated to account for the change in the flow distribution within TW-1. Comparing the results to past literature, the calculated (using analytical methods, Theis and Cooper-Jacob methods) hydraulic conductivity/transmissivity values are within the same order of magnitude. Using data from the boreholes, multiple single and multi-layered models for both the upper and middle Potomac aquifers were produced with MODFLOW, a groundwater modeling software. Estimating parameters using observation data within MODFLOW resulted in hydrogeological parameters similar to those calculated using the Theis and Cooper-Jacob methods. The change in the hydraulic conductivity and specific storage between the pre and post rehabilitation flow distributions within TW-1 is proportional to that change in the flow distribution. For future modeling of the aquifer system, the hydrogeological parameters from the model using the 4/26/19 (most recent) data set with the post rehabilitation (more current) flow distribution is recommended. Drawdown (decrease in the water table) results from a multi-layered MODFLOW model were compared to results using the Theis method using both the Theis-calculated and MODFLOW modeled hydrogeological parameters. The results were nearly identical except for the Upper Potomac Aquifer (UPA) layer 1, as the model has a large change in aquifer thickness with distance from TW-1 that the Theis-based calculations do not consider. The time it took for a particle of water to travel from the monitoring wells to TW-1 were calculated with the single and multi-layered models pumping 700 GPM from TW-1. Travel times from the SWIFT MW within the UPA sublayers ranged from 204 to 597 days depending on the sublayer, while travel times from the USGS MW within the UPA sublayers ranged from 2,395 to 7,859 days. For the single layer model of the UPA, the travel time from the SWIFT MW to TW-1 was 372 days while the travel time from the USGS MW was 4,839 days. Travel times from the SWIFT MW within the MPA sublayers were 416 and 1,195 days, while travel times from the USGS MW within the MPA sublayers were 4,339 and 11,245 days. For the single layer model of the MPA, the travel time from the SWIFT MW to TW-1 was 743 days while the travel time from the USGS MW was 7,545 days.

Realizar a modelagem de um aqüífero não é tarefa fácil. Em se tratando de um sistema aqüífero, a empreitada se torna ainda mais complexa. Neste trabalho, alguns dos parâmetros importantes para esse fim foram estimados a partir de simulações. Na região de estudo, existem poços tubulares que, em sua maioria, não foram perfurados somente na Formação Adamantina, mas também na Formação Serra Geral. Tal configuração conduziu à formulação de dois conjuntos de cenários a partir dos quais foi possível estimar valores de condutividade hidráulica para as duas formações. Com essa estimativa conseguiu-se também simular testes de bombeamento, seus respectivos cones de rebaixamento, bem como a interferência causada entre cones de rebaixamento. Com essa abordagem foi possível estimar o quanto um poço em funcionamento pode influenciar no nível estático de um vizinho. A contribuição da geofísica está no uso da eletroresistividade. Foram executadas 23 Sondagens Elétricas Verticais (SEV), das quais dezenove são SEV´s curtas (AB/2 500m) e quatro, longas (AB/2 1500), que forneceram informações sobre a espessura saturada do arenito e posição do topo do basalto, especialmente na região com poucos poços. Também foram realizados quatro Caminhamentos Elétricos (CE) no estudo de possíveis estruturas. Unindo os resultados da modelagem (simulação) e da geofísica, pôde-se relacionar os parâmetros hidrogeológicos e geoelétricos. Embora o conjunto de dados para a região não tenha sido o ideal, a metodologia se mostrou adequada e os resultados bastante razoáveis. Deste modo, foi possível a determinação de parâmetros hidrogeológicos em subsuperfície através de parâmetros geoelétricos medidos em superfície. / To perform the aquifer modelling is not an easy task. In the case of an aquifer system, the work becomes even more complex. In this work, some of important parameters for this purpose have been estimated from simulations. In the study area, there are wells that in most cases were not only drilled in Adamantina Formation but also in Serra Geral Formation. This configuration led to the formulation of two sets of scenarios from which it was possible to estimate values for hydraulic conductivity of these formations. With this estimate it could also simulate pumping tests, their cones of depression as well as the interference caused between cones of depression. With this approach it was possible to estimate how much a operating well can influence static level of a neighbour one. Geophysics contribution is in the use of electrical resistivity. Twenty-three Vertical Electrical Soundings (VES) were performed, nineteen of them are short (AB/2 500m), that provided information about the saturated thickness of sandstone as well as top of basalt, especially in the region with few wells, and four are long (AB/2 1500) VESs. Four electrical profiling (EP) were also carried out to study possible structures. Joining modelling (simulation) and geophysics results, it could be related hydrogeological and geoelectrical parameters. Although dataset for region was not the ideal, methodology was satisfactory, and results quite reasonable. Thus, it was possible to determine hydrogeological parameters in subsurface through measured geoelectrical parameters in surface.

Realizar a modelagem de um aqüífero não é tarefa fácil. Em se tratando de um sistema aqüífero, a empreitada se torna ainda mais complexa. Neste trabalho, alguns dos parâmetros importantes para esse fim foram estimados a partir de simulações. Na região de estudo, existem poços tubulares que, em sua maioria, não foram perfurados somente na Formação Adamantina, mas também na Formação Serra Geral. Tal configuração conduziu à formulação de dois conjuntos de cenários a partir dos quais foi possível estimar valores de condutividade hidráulica para as duas formações. Com essa estimativa conseguiu-se também simular testes de bombeamento, seus respectivos cones de rebaixamento, bem como a interferência causada entre cones de rebaixamento. Com essa abordagem foi possível estimar o quanto um poço em funcionamento pode influenciar no nível estático de um vizinho. A contribuição da geofísica está no uso da eletroresistividade. Foram executadas 23 Sondagens Elétricas Verticais (SEV), das quais dezenove são SEV´s curtas (AB/2 500m) e quatro, longas (AB/2 1500), que forneceram informações sobre a espessura saturada do arenito e posição do topo do basalto, especialmente na região com poucos poços. Também foram realizados quatro Caminhamentos Elétricos (CE) no estudo de possíveis estruturas. Unindo os resultados da modelagem (simulação) e da geofísica, pôde-se relacionar os parâmetros hidrogeológicos e geoelétricos. Embora o conjunto de dados para a região não tenha sido o ideal, a metodologia se mostrou adequada e os resultados bastante razoáveis. Deste modo, foi possível a determinação de parâmetros hidrogeológicos em subsuperfície através de parâmetros geoelétricos medidos em superfície. / To perform the aquifer modelling is not an easy task. In the case of an aquifer system, the work becomes even more complex. In this work, some of important parameters for this purpose have been estimated from simulations. In the study area, there are wells that in most cases were not only drilled in Adamantina Formation but also in Serra Geral Formation. This configuration led to the formulation of two sets of scenarios from which it was possible to estimate values for hydraulic conductivity of these formations. With this estimate it could also simulate pumping tests, their cones of depression as well as the interference caused between cones of depression. With this approach it was possible to estimate how much a operating well can influence static level of a neighbour one. Geophysics contribution is in the use of electrical resistivity. Twenty-three Vertical Electrical Soundings (VES) were performed, nineteen of them are short (AB/2 500m), that provided information about the saturated thickness of sandstone as well as top of basalt, especially in the region with few wells, and four are long (AB/2 1500) VESs. Four electrical profiling (EP) were also carried out to study possible structures. Joining modelling (simulation) and geophysics results, it could be related hydrogeological and geoelectrical parameters. Although dataset for region was not the ideal, methodology was satisfactory, and results quite reasonable. Thus, it was possible to determine hydrogeological parameters in subsurface through measured geoelectrical parameters in surface.

<p>Risk assessment is made to determine risks with contaminated areas and to determine which treatment the area requires. In Sweden, risk assessment is divided into three levels: risk analysis, facilitated risk assessment and detailed risk assessment. In detailed risk assessment site-specific guideline values are developed to compare with values of contaminants that are measured in the area.</p><p>Site-specific guideline values vary with geological and hydrogeological parameters. The purpose of this report is to examine which of these parameters that affect the guideline values. The examination was done using a calculating program for consideration from the Swedish Environmental Protection Agency from the year of 1997. The study shows that some of the geological and hydrogeological parameters affect the site-specific guideline values for metals in different ways and others do not.  </p><p>Using the program from the Swedish Environmental Protection Agency is a simple way to calculate site-specific guideline values. It’s important to make sure that relevant values are chosen to get correct results. The calculating program is still not definitive so it’s important to be careful when using it.</p><p>Another purpose of the report is to compare how guideline values have developed from the Swedish Environmental Protection Agency’s model for calculating guideline values from the year of 1997 with their new report whit the same purpose from the year of 2007. Guideline values for all metals that have been considered are lower in the new model from the year of 2007 compared to the model from the year of 1997.</p>

Risk assessment is made to determine risks with contaminated areas and to determine which treatment the area requires. In Sweden, risk assessment is divided into three levels: risk analysis, facilitated risk assessment and detailed risk assessment. In detailed risk assessment site-specific guideline values are developed to compare with values of contaminants that are measured in the area. Site-specific guideline values vary with geological and hydrogeological parameters. The purpose of this report is to examine which of these parameters that affect the guideline values. The examination was done using a calculating program for consideration from the Swedish Environmental Protection Agency from the year of 1997. The study shows that some of the geological and hydrogeological parameters affect the site-specific guideline values for metals in different ways and others do not.   Using the program from the Swedish Environmental Protection Agency is a simple way to calculate site-specific guideline values. It’s important to make sure that relevant values are chosen to get correct results. The calculating program is still not definitive so it’s important to be careful when using it. Another purpose of the report is to compare how guideline values have developed from the Swedish Environmental Protection Agency’s model for calculating guideline values from the year of 1997 with their new report whit the same purpose from the year of 2007. Guideline values for all metals that have been considered are lower in the new model from the year of 2007 compared to the model from the year of 1997.