In recent years, wireline temperature profiling methods have evolved to offer new insight into fractured rock hydrogeology. An important advance in temperature logging makes use of boreholes temporarily sealed with flexible impervious fabric liners so that the water column is static and effects of cross-connection are eliminated. For this project a characterization technique was developed based on combining fibre optic distributed temperatures sensing (DTS) with active heating within boreholes sealed with underground liners. DTS systems provide a temperature profiling method that offers improved temporal resolution when compared with wireline trolling based techniques. The ability to collect temperature profiles rapidly in time can improve understanding of transient processes. In this study the advantage of a sealed borehole environment for temperature investigations is demonstrated. Evidence for identifying active groundwater flow under natural gradient conditions using DTS heat pulse testing is presented through a comparison with high resolution geologic logging and hydraulic datasets.

The use of temperature logging for identifying water flow through fractures in sedimentary rock has declined since the 1960’s and 70’s primarily because of low sensor resolution and cross-connected flow along the borehole. Although sensor resolution has improved to the order of 10-3 C for several decades, temperature logging has not experienced a notable increase in popularity. This thesis studies these and other fundamental limitations to the application of borehole temperature logging for identifying flow through fractured rock, and tests the hypothesis that the limitations can be overcome, presents new methods for accomplishing that goal, and increases the applicability of the technology. Although some conventional open-hole testing (e.g. flow meters) rely on vertical cross-connected flow in the borehole annulus to identify transmissive fractures, the flow is recognized to both distort open-hole temperature logs and facilitate chemical cross contamination. Removable polyurethane coated nylon liners have recently been developed to seal boreholes and minimize cross-contamination. High sensitivity temperature logs collected in the stagnant water column of lined boreholes under different hydrogeologic conditions herein show the degree to which cross connected flow can mask important flow conduits and thereby distort the interpretation of which fractures control flow. Results from the lined holes consistently lead to identification of more hydraulically active fractures than the open-hole profiles and an improved qualitative ranking of their relative importance to flow consistent with contaminant distributions observed in rock core. The identification of flow in fractures with temperature logs depends on the presence of a temperature contrast between the water and the rock matrix to create an aberration in the otherwise gradually varying profile. Atmospherically driven thermal disequilibrium commonly only extends several tens of meters from surface and dissipates with depth, making temperatures logs a variable assessment of flow that is depth limited to the heterothermic zone. The active line source (ALS) method, a series of temperature logs measured before and within a day after the water column of a lined borehole is placed into thermal disequilibrium with the broader rock mass with a heating cable, is shown to provide two advantages. First, the method eliminates the depth limitation allowing flow zones to be identified below the hetro-homothermic boundary and second, the qualitative assessment of ambient water flow in fractures is improved throughout the test interval. The identification of the flow conduits is supported by the combined evidence from visual inspection of core, rock contamination profiles, acoustic televiewer logs and tests for hydraulic conductivity using straddle packers. A new device, the thermal vector probe (TVP) is presented. It measures the temperature of the borehole fluid with four high sensitivity temperature sensors arranged in a tetrahedral pattern which is orientated using three directional magnetometers. Based on these, the total thermal gradient, its horizontal and vertical components as well as the direction and inclination are determined, typically at less than 0.01m intervals. Comparison of TVP data collected in lined boreholes under ambient conditions (thermal and hydraulic) as well during thermal recovery after ALS heating demonstrate the reproducibility of the results and superior characterization of thermal aberrations indicative of flow relative to single sensor temperature data. A detailed comparison of subdivisions in the thermal field to the vertical changes in the hydraulic gradient measured from three nearby high detail (12-14 port) multi-level installations demonstrates the interrelationship between hydraulic and thermal fields and thereby the potential benefit of the TVP in hydrogeologic investigations. Developing confidence in the use of both the TVP and ALS techniques in lined holes relies on demonstrating the reproducibility of results, consistency with observations from other technologies, and numerical simulation. Comparisons of field data with highly detailed numerical simulations using the program SMOKER shows that the influence of water flow in a fracture around a lined borehole on the temperature patterns is complex and factors such as convection likely influence the shape of the thermal aberrations observed. Model results suggest that the temperature aberrations are related to the volumetric water flow, a distinct lower resolution limit exists (approximately 5.6x10-7 m3/sec per metre across the fracture, m2/s), and although flow above 10-4 m2/s is readily detectable, prospects for quantification of higher flows are poor. Some field data indicate the numerically determined lower limit is conservative and the details of the limit require additional study. The aspects of temperature logging historically limiting applicability for detecting and comparing flow through discrete or groups of fractures in rock are hereby better understood and consistently overcome. The high level of detail achieved in the data highlights the complexity of the system and offers opportunities for further refinement. The TVP and ALS technique applied in a lined borehole promise both new insights into, and potential for quantification of ambient groundwater flow through fractures in rock.

Groundwater recharge is an essential metric for understanding and protecting groundwater resources. Quantifying this parameter remains extremely challenging due to the uncertainties associated with the extent to which the vadose zone affects groundwater movement and the highly heterogeneous nature of the aquifer systems being monitored. The difficulty surrounding recharge quantification is compounded when considering a fractured rock aquifer system, where classification and modeling is complicated by highly complex structural geology. However, the ability to distinguish the character and geometry of fractured rock aquifers is indispensable for quantifying recharge to evaluate sustainable yields, as well as for implementing protective measures to manage these systems. The primary intention of this study is to assess the hydrogeologic properties that have led the unique recharge signals within the fractured crystalline-rock aquifer system near Ploemeur, France. Infiltration and groundwater movement are characterized via time-series hydraulic head and precipitation data collected at daily, monthly, yearly, and at decadal intervals. In spite of the nearly one million cubic meters of groundwater extraction, measured drawdowns are marginal, suggesting that local and regional recharge plays a significant role in moderating water-level declines and raising questions as to the origins of the substantial inflow required to sustain this complex system. A roughly two-month lag has been observed between seasonal water level and monthly precipitation at Ploemeur, which has previously been attributed solely to slow vertical migration of water through the low-permeability micaschist layer to the fractured contact zone and interconnected fault. However, results from this study suggest that a significant portion of the observed lag can be attributed to vadose-zone processes, particularly the thickness of the vadose zone. This investigation also reveals a recharge signal that continues throughout the calendar year, departing from the traditional simplified concept that recharge quantity is essentially equivalent to the value of evapotranspiration subtracted from infiltration. / Master of Science / Groundwater recharge is the amount of water added to underground water sources, called aquifers. This occurs as precipitation falls to the ground, moves downward through the unsaturated subsurface, and accumulates at the top of the saturated zone, deemed the water table. The saturated zone is so named because all pore spaces between sediment grains or crevices in rocks are fully filled with water. Understanding groundwater recharge is important to the protection of groundwater resources, but is hard to estimate due to the lack of knowledge about water movement in the unsaturated zone and the uncertainties related to the systems being studied. Aquifers forming within fractured rocks are even more challenging to investigate, because the complex geological structures are difficult to replicate with computer modeling. However, fractured rock aquifers are an important groundwater resource, and understanding them is the first step in estimating recharge within the system. Recharge estimates are used to calculate how much water can be safely removed from the aquifer for years to come, so that the resource can remain protected. The aim of this investigation is to assess the aquifer properties that lead to the unique recharge signal in a fractured crystalline-rock aquifer in Ploemeur, France, where nearly 1 million cubic meters of water have been removed each year since 1991 but water table levels have not fallen significantly. This behavior raises questions about the water returned to the system as recharge that is sustaining such a highly productive resource. This site also shows a roughly two-month lag between seasonal precipitation falling and the reflection of that precipitation recorded in the water level of the aquifer. It was previously thought that the lag occurred because water travelled slowly through the mica-schist layer, which has little pore space for water to move, and into the contact zone and interconnected fault. However, this study shows instead that a majority of the lag is associated with the unsaturated zone properties and processes, particularly thickness. This investigation also shows recharge entering the aquifer system throughout the calendar year, a departure from earlier studies conceptualizations.

<p>The aim of this study was to test whether one could use the same methods as used for sampling heavy metals and apply them to radioactive elements. Furthermore a sampling protocol was developed, the first of its kind, for the sampling of radioactive elements in fractured rock aquifers. This was achieved by initially examining local as well as international manuals and methods. The aforementioned was done in conjunction with a literature review of the movement of radioactive elements in these fractured rock aquifers. Beaufort West was utilised as a study area and the geology, hydrogeology and topography was outlined. Background radioactivity was generally acceptable except for two samples which were anomalously high. Taking cognisance of the methods used, as well as those previously applied in the area and abroad, a sampling protocol for radioactive elements in fractured rock aquifers was developed and attached as an appendix. In conclusion it was suggested that multiple methods be tested on one well in order to check whether similar results would occur. This would thus determine the best applicable methods. Also it was proposed that a new method, called DGT sampling, be applied in order to gain a time weighted average of the heavy metals and radioactive elements in groundwater. It could also be clearly seen, by comparing historical data and the current data, that the methods used for sampling heavy metal can be applied to radioactivity.</p>

Much is known about natural attenuation of contaminants in granular aquifers because many contaminant plumes in these aquifers have been intensively monitored with detailed sampling along cross sections positioned across the plumes (i. e. transects). However, little is known about natural attenuation of contaminant plumes in fractured rock. In this thesis study, strong natural attenuation of a persistent co-mingled plume of trichloroethylene (TCE) and an herbicide (metolachlor) in a 100 <em>m</em> thick dolostone aquifer used for municipal water supply in Cambridge, Ontario is shown based on detailed delineation of groundwater contaminant concentrations along a single transect located 150 <em>m</em> downgradient from the area where the metolachlor entered the dolostone and 300 <em>m</em> downgradient from the TCE source area. This delineation was accomplished using depth-discrete, multilevel groundwater monitoring systems in five cored holes and detailed analyses of contaminant concentration in rock cores. The maximum metolachlor concentration on the transect is a factor of 20 below the maximum concentration in the metolachlor source area and the maximum TCE concentration on the transect is lower by a factor of 100 from the TCE source area. <br /><br /> Matrix diffusion and strong temporal variability of the groundwater flow system caused by pumping of nearby municipal wells have likely caused strong natural attenuation of metolachlor and TCE and degradation has likely contributed to even stronger TCE attenuation. The transect shows rock core concentrations much higher than the groundwater concentrations in the multilevel systems at the same locations and in the conventional monitoring wells, which indicates that plume persistence is likely maintained by back diffusion from the rock matrix, which has very low hydraulic conductivity but substantial porosity, into the active groundwater flow in the fractures. <br /><br /> Metolachlor has been observed at very low concentrations and has persisted at these concentrations in the nearest municipal pumping well located approximately 780 <em>m</em> downgradient of the transect, however this well shows no detectable TCE. The relatively low concentrations along the transect and the replenishment of the plume by back diffusion suggests that a substantial increase of metolachlor or TCE in the municipal well is unlikely.

The current understanding of contaminant migration in fractured sedimentary rock aquifers is inadequate due to the difficulty in describing the geologic and hydrogeologic controls on contaminant fate and transport with appropriate detail. To address contamination at fractured rock sites, multiple methods focusing on different aspects of the hydrologic system are required, and particular emphasis needs to be placed on the rock matrix. This thesis shows the further development and utility of the decade-old rock core VOC method (i.e. CORETM), a rock matrix method, when used in conjunction with multiple high resolution datasets as it applies to a 100 m thick highly productive dolostone aquifer in Guelph, Ontario. The research site and surrounding area, located in the northwestern quadrant of the municipality of Guelph, was a productive zone for water supply until the early 1990s when the two closest municipal supply wells (Sacco, Smallfield) were shut down (1991, 1993 respectively) due to volatile organic compounds (VOCs) in the groundwater. Trichloroethene (TCE), a VOC, was used as a degreaser at the Guelph site and likely entered the groundwater more than 20 years ago. The thin overburden, shallow water table, relatively constant dolostone mineralogy, proximity to the UW analytical laboratory, relatively simple plume composition showing minimal degradation, and local importance make this an excellent study site for TCE fate and migration in fractured sedimentary rocks. This thesis is composed of four chapters. Chapter 1 provides a brief background to the rock core VOC method and gives the conceptual framework for the investigation. Chapter 2 focuses on the further development of the rock core VOC method by providing the field validation of a recently adapted extraction method for VOCs in rock core using microwave assisted extraction (MAE), demonstrating the importance of rapid field preservation of samples, and comparing to the industry standard purge and trap method for VOCs on solid matrices. Results indicate that the microwave assisted extraction (MAE) method typically provides equivalent or higher concentrations when compared with the shake-flask and purge and trap extraction methods, indicating more complete extraction or less loss during transfer and/or storage. The purge and trap method provided false negatives (i.e. non-detects) due to inadequate preservation, incomplete extraction, and the elevated detection limit for TCE. The necessity for field preservation was examined by comparing crushed rock samples preserved in methanol in the field to samples unpreserved in the field with a laboratory addition of methanol less than 12 hours later. Chapter 3 creates high resolution porosity and bulk density logs by using selected geophysical logging tools in combination with core derived physical properties for the purpose of calculating porewater concentrations from total contaminant mass concentrations obtained from the rock core VOC method and sample specific rock properties relevant to the conversion. This is beneficial because total mass estimates obtained from the rock core VOC method are not necessarily indicative of the groundwater concentrations given the presence of solid organic carbon controlled sorption. Chapter 4 is a demonstration of the discrete fracture network approach (Parker 2007) applied to the Guelph field site with emphasis on the insights gained through high resolution contaminant profiles generated from cored holes in or near the source area and along a transect. Together, these four chapters present a framework for investigating VOC contamination in fractured sedimentary rocks and with emphasis on evaluating recent advances in the rock core VOC methodology in a field site context.

A study was carried out in a sedimentary fractured rock site located in south central Wisconsin, US, which was impacted by DNAPL releases estimated to occur in the 1950’s and 1960’s. The majority of the DNAPL has accumulated in the upper portion of the Lone Rock Formation at a depth between 140 and 180 ft bgs referred as Layer 5 in this study. A groundwater VOC plume of more than 3km long has formed in this Layer. The DNAPL is mainly composed of 1,1,1-TCA, PCE, TCE and BTEX, while large amounts of biodegradation products such as cis-DCE and 1,1-DCA are present in the plume. Long term VOC data have been collected at the site and diverse geological and hydrogeological techniques have been applied to have a better understanding of the DNAPL history and behavior of the VOC plume. Evidence of biodegradation was also documented near the DNAPL source in these studies. The thesis objectives of the present study aimed first to have a better understanding of the long term contaminant distribution and degradation history at the site. This objective was accomplished reviewing the VOC historical concentration data collected from 1992 to 2006 in the wells tapping the most contaminated. hydrogeological unit in the bedrock (Layer 5) and in the overburden aquifer (referred as Layer 2). The second objective aimed to evaluate the current degree or extent of biodegradation of chlorinated compounds, which was accomplished evaluating the current groundwater redox conditions and using a combined analysis of VOC concentration and carbon isotope data collected in groundwater in September 2007. The historical data collected between1992 to 2006 showed the degradation of the VOC plume in Layer 5 was controlled by the availability of electron acceptors and redox conditions in the fracture bedrock aquifer. This pattern and the extension of the VOC plume were linked to different DNALP pumping events in the source zone and the operation of a Hydraulic Barrier System. The current geochemical and isotope study showed a different pattern of biodegradation of chlorinated compounds in different parts of the plume. The cis-DCE tend to accumulate in the area from the source to the middle of the plume and around 80 % of biodegradation of 1,1,1-TCA to 1,1-DCA was observed in this area. The fringes of the plume were characterized by a dominant presence of TCE and 1,1,1 TCA. These patterns were linked to different redox conditions and amount of electron acceptors. The cis-DCE dominated area is characterized by anaerobic conditions and the presence of relative high amount of BTEX. The TCE-dominated area is under aerobic condition and no BTEX was found in this area. The operation of the Hydraulic Barrier System seems to have change redox condition which influenced the extent of degradation in the plume, especially in the area between the extraction wells. The formation of large amounts of VC in Layer 2 and the more reducing (at least sulfate reducing and maybe methanogenic conditions) of the groundwater in this Layer compared to Layer 5 confirmed the extent of VOC biodegradation is linked to the availability of electron donors. This study provides information about the current degree of the biodegradation of chlorinated compounds at a fracture rock site. This information is very valuable for the evaluation of natural attenuation as strategy for long term plume management or for future remediation strategies such as biostimulation or bioaugmentation at the site. This study also shows the present and long term behavior of the chlorinated compounds (degradation history) in the most contaminated hydrogeologic unit (Layer 5), has mainly been controlled by plume management strategies including DNAPL pumping in the source and the creation of a Hydraulic Barrier System. The ketones and BTEX, that acted as electron donors and carbon substrate for the microbial community responsible for the dechlorination of chlorinated compounds were shown to have controlled the past and current redox conditions and thus the degree and potential of biodegradation of chlorinated ethenes and chlorinated ethanes at the study site.

Much is known about natural attenuation of contaminants in granular aquifers because many contaminant plumes in these aquifers have been intensively monitored with detailed sampling along cross sections positioned across the plumes (i. e. transects). However, little is known about natural attenuation of contaminant plumes in fractured rock. In this thesis study, strong natural attenuation of a persistent co-mingled plume of trichloroethylene (TCE) and an herbicide (metolachlor) in a 100 <em>m</em> thick dolostone aquifer used for municipal water supply in Cambridge, Ontario is shown based on detailed delineation of groundwater contaminant concentrations along a single transect located 150 <em>m</em> downgradient from the area where the metolachlor entered the dolostone and 300 <em>m</em> downgradient from the TCE source area. This delineation was accomplished using depth-discrete, multilevel groundwater monitoring systems in five cored holes and detailed analyses of contaminant concentration in rock cores. The maximum metolachlor concentration on the transect is a factor of 20 below the maximum concentration in the metolachlor source area and the maximum TCE concentration on the transect is lower by a factor of 100 from the TCE source area. <br /><br /> Matrix diffusion and strong temporal variability of the groundwater flow system caused by pumping of nearby municipal wells have likely caused strong natural attenuation of metolachlor and TCE and degradation has likely contributed to even stronger TCE attenuation. The transect shows rock core concentrations much higher than the groundwater concentrations in the multilevel systems at the same locations and in the conventional monitoring wells, which indicates that plume persistence is likely maintained by back diffusion from the rock matrix, which has very low hydraulic conductivity but substantial porosity, into the active groundwater flow in the fractures. <br /><br /> Metolachlor has been observed at very low concentrations and has persisted at these concentrations in the nearest municipal pumping well located approximately 780 <em>m</em> downgradient of the transect, however this well shows no detectable TCE. The relatively low concentrations along the transect and the replenishment of the plume by back diffusion suggests that a substantial increase of metolachlor or TCE in the municipal well is unlikely.

The current understanding of contaminant migration in fractured sedimentary rock aquifers is inadequate due to the difficulty in describing the geologic and hydrogeologic controls on contaminant fate and transport with appropriate detail. To address contamination at fractured rock sites, multiple methods focusing on different aspects of the hydrologic system are required, and particular emphasis needs to be placed on the rock matrix. This thesis shows the further development and utility of the decade-old rock core VOC method (i.e. CORETM), a rock matrix method, when used in conjunction with multiple high resolution datasets as it applies to a 100 m thick highly productive dolostone aquifer in Guelph, Ontario. The research site and surrounding area, located in the northwestern quadrant of the municipality of Guelph, was a productive zone for water supply until the early 1990s when the two closest municipal supply wells (Sacco, Smallfield) were shut down (1991, 1993 respectively) due to volatile organic compounds (VOCs) in the groundwater. Trichloroethene (TCE), a VOC, was used as a degreaser at the Guelph site and likely entered the groundwater more than 20 years ago. The thin overburden, shallow water table, relatively constant dolostone mineralogy, proximity to the UW analytical laboratory, relatively simple plume composition showing minimal degradation, and local importance make this an excellent study site for TCE fate and migration in fractured sedimentary rocks. This thesis is composed of four chapters. Chapter 1 provides a brief background to the rock core VOC method and gives the conceptual framework for the investigation. Chapter 2 focuses on the further development of the rock core VOC method by providing the field validation of a recently adapted extraction method for VOCs in rock core using microwave assisted extraction (MAE), demonstrating the importance of rapid field preservation of samples, and comparing to the industry standard purge and trap method for VOCs on solid matrices. Results indicate that the microwave assisted extraction (MAE) method typically provides equivalent or higher concentrations when compared with the shake-flask and purge and trap extraction methods, indicating more complete extraction or less loss during transfer and/or storage. The purge and trap method provided false negatives (i.e. non-detects) due to inadequate preservation, incomplete extraction, and the elevated detection limit for TCE. The necessity for field preservation was examined by comparing crushed rock samples preserved in methanol in the field to samples unpreserved in the field with a laboratory addition of methanol less than 12 hours later. Chapter 3 creates high resolution porosity and bulk density logs by using selected geophysical logging tools in combination with core derived physical properties for the purpose of calculating porewater concentrations from total contaminant mass concentrations obtained from the rock core VOC method and sample specific rock properties relevant to the conversion. This is beneficial because total mass estimates obtained from the rock core VOC method are not necessarily indicative of the groundwater concentrations given the presence of solid organic carbon controlled sorption. Chapter 4 is a demonstration of the discrete fracture network approach (Parker 2007) applied to the Guelph field site with emphasis on the insights gained through high resolution contaminant profiles generated from cored holes in or near the source area and along a transect. Together, these four chapters present a framework for investigating VOC contamination in fractured sedimentary rocks and with emphasis on evaluating recent advances in the rock core VOC methodology in a field site context.

A study was carried out in a sedimentary fractured rock site located in south central Wisconsin, US, which was impacted by DNAPL releases estimated to occur in the 1950’s and 1960’s. The majority of the DNAPL has accumulated in the upper portion of the Lone Rock Formation at a depth between 140 and 180 ft bgs referred as Layer 5 in this study. A groundwater VOC plume of more than 3km long has formed in this Layer. The DNAPL is mainly composed of 1,1,1-TCA, PCE, TCE and BTEX, while large amounts of biodegradation products such as cis-DCE and 1,1-DCA are present in the plume. Long term VOC data have been collected at the site and diverse geological and hydrogeological techniques have been applied to have a better understanding of the DNAPL history and behavior of the VOC plume. Evidence of biodegradation was also documented near the DNAPL source in these studies. The thesis objectives of the present study aimed first to have a better understanding of the long term contaminant distribution and degradation history at the site. This objective was accomplished reviewing the VOC historical concentration data collected from 1992 to 2006 in the wells tapping the most contaminated. hydrogeological unit in the bedrock (Layer 5) and in the overburden aquifer (referred as Layer 2). The second objective aimed to evaluate the current degree or extent of biodegradation of chlorinated compounds, which was accomplished evaluating the current groundwater redox conditions and using a combined analysis of VOC concentration and carbon isotope data collected in groundwater in September 2007. The historical data collected between1992 to 2006 showed the degradation of the VOC plume in Layer 5 was controlled by the availability of electron acceptors and redox conditions in the fracture bedrock aquifer. This pattern and the extension of the VOC plume were linked to different DNALP pumping events in the source zone and the operation of a Hydraulic Barrier System. The current geochemical and isotope study showed a different pattern of biodegradation of chlorinated compounds in different parts of the plume. The cis-DCE tend to accumulate in the area from the source to the middle of the plume and around 80 % of biodegradation of 1,1,1-TCA to 1,1-DCA was observed in this area. The fringes of the plume were characterized by a dominant presence of TCE and 1,1,1 TCA. These patterns were linked to different redox conditions and amount of electron acceptors. The cis-DCE dominated area is characterized by anaerobic conditions and the presence of relative high amount of BTEX. The TCE-dominated area is under aerobic condition and no BTEX was found in this area. The operation of the Hydraulic Barrier System seems to have change redox condition which influenced the extent of degradation in the plume, especially in the area between the extraction wells. The formation of large amounts of VC in Layer 2 and the more reducing (at least sulfate reducing and maybe methanogenic conditions) of the groundwater in this Layer compared to Layer 5 confirmed the extent of VOC biodegradation is linked to the availability of electron donors. This study provides information about the current degree of the biodegradation of chlorinated compounds at a fracture rock site. This information is very valuable for the evaluation of natural attenuation as strategy for long term plume management or for future remediation strategies such as biostimulation or bioaugmentation at the site. This study also shows the present and long term behavior of the chlorinated compounds (degradation history) in the most contaminated hydrogeologic unit (Layer 5), has mainly been controlled by plume management strategies including DNAPL pumping in the source and the creation of a Hydraulic Barrier System. The ketones and BTEX, that acted as electron donors and carbon substrate for the microbial community responsible for the dechlorination of chlorinated compounds were shown to have controlled the past and current redox conditions and thus the degree and potential of biodegradation of chlorinated ethenes and chlorinated ethanes at the study site.