The effective and efficient remediation of contaminated groundwater sites requires site specific information regarding the physical, chemical and biological properties of the aquifer. Building on the dipole flow test (DFT) and the dipole flow and tracer test (DFTT), the dipole flow and reactive tracer test (DFRTT) has been proposed as an alternative to current aquifer parameter estimation methods. A steady-state dipole flow field is created by circulating groundwater between chambers isolated by the dipole tool. A tracer is released into the injection chamber and the breakthrough curve at the extraction chamber is interpreted with the DFRTT specific model. The overall goal of this thesis was to demonstrate the ability of a prototype dipole system to produce tracer BTCs in conventional wells installed in an unconfined sandy aquifer. The Waterloo dipole probe was constructed and field tested at CFB Borden. DFTs conducted along the length of the screen of non-filter packed monitoring wells provided similar estimates of radial hydraulic conductivity (Kr) to slug tests and literature values. The geometric mean Kr estimated in the filter packed wells was approximately an order of magnitude greater than the mean Kr estimate for the non-filter packed wells due to short-circuiting through the filter pack. A total of 46 DFTTs were completed in the monitoring wells at CFB Borden to investigate the properties of the BTCs. The shape of the BTC for a conservative tracer is affected by test set up parameters, well construction, and aquifer formation properties. The BTCs from the DFTTs completed in the non-filter pack monitoring wells were categorized into four “type curves” based on the BTC properties. The differences between the type curves were largely defined by the ratio of K between the skin zone and the aquifer (Ks/Kr). Now that a series of DFTT BTCs have been generated, the DFRTT model will be used to estimate the aquifer parameters. To continue the work outlined in this thesis, DFRTTs are planned for well-documented contaminated sites.

The purpose of this study was to evaluate the effectiveness of traditional hydrogeologic characterization approaches in a highly heterogeneous glaciofluvial aquifer at the North Campus Research Site (NCRS), situated on the University of Waterloo campus. Continuous soil cores to a depth of approximately 18 m were collected during the installation of the CMT monitoring wells and the multi-screen pumping well. K estimates were obtained for the core by obtaining 471 samples and testing them with a falling head permeameter, as well as by utilizing empirical equations developed to estimate K. A geostatistical analysis performed on the K datasets yielded strongly heterogeneous kriged K fields for the site. K and Ss were also estimated via type curve analysis of slug and pumping test data collected at the site. The various K and Ss estimates were then evaluated by simulating the transient drawdown data using a 3D forward numerical model constructed using Hydrogeosphere (Therrien et al., 2005). Results showed that, while drawdown predictions generally improved as more complexity was introduced into the model, the ability to make accurate drawdown predictions at all of the CMT ports was inconsistent. These results suggest that new techniques may be required to accurately capture subsurface heterogeneity for improved predictions of flow in similar systems.

A patterned, partially-treed, fen in the mid-boreal region of central Saskatchewan was the site of renewed hydrological research from 2002 to 2004. Hydraulic conductivity, transmissivity, and storativity were determined through use of a surface loading test, pumping tests, and an enclosed field drainage test. None of these field tests have been previously described in the literature as having been used in peat environments. The combined results of field and laboratory drainage tests were used to obtain a general storativity with water table depth relationship in the upper peat layer. The hydraulic conductivity, measured with slug tests, the loading test, and pumping tests, is high near the surface, declining greatly with depth. These previously untested field methods have the advantage of representing volumes of peat from tenths of a meter to cubic meters. </p>Characterization of the hydrology of the peatland involved year round observations of water table, piezometric head, peat surface elevations, frost depth and peat temperatures. Fluctuations of the water table, and soil moisture changes produce changes in effective stress that lead to volume change in the highly compressible peat. This is particularly important for sites with thick peat deposits. Independent compressibility estimates were as high as 10-5 N/m2 in the upper peat. At three fen sites, changes in peat thickness were estimated from monthly estimates of effective stress change, using year round hydrological observations, and compared to measured annual peat thickness changes. Water table changes causing soil moisture changes, and freeze-thaw processes, explained the majority of peat surface movements.

This thesis describes a numerical modelling methodology to interpret dynamic fluctuations in pore-pressures to isolate the effects of loading associated with changes in total soil moisture (site water balance) alone. The methodology is required to enhance the data-interpretation and performance-assessment for potential applications of a novel piezometer-based, large-scale, geological weighing lysimeter. This interpretative methodology is based on a method of superimposing computer-based numerical analyses of independent causes of pore-pressure transients to separate the different pore-pressure responses. Finite element coupled load-deformation and seepage numerical models were used to simulate field-observed piezometric responses to water table fluctuations and loading induced by surface water balance (using meteorological data).<p> Transient pore-pressures in a deep clay-till-aquitard arising from variations in the water table within a surface-aquifer were modelled and removed from the measured pore-pressure record (corrected for earth tide and barometric effects) to isolate and identify pore-pressure fluctuations arising from loading associated with site water balance. These estimates were compared to simulated pore-pressure responses to an independently measured water balance using meteorological instrumentation. The simulations and observations of the pore-pressure responses to surface water balance were in good agreement over the dry years of a 9-year period. Some periods of significant differences did occur during wet years in which runoff, which is not accounted for in the current analyses, may have occurred.<p> The identification of pore-pressure response to total soil moisture loading using the developed numerical modelling methodology enhances the potential for the deployment of the piezometer-based geological weighing lysimeter for different applications which include real-time monitoring of site water balance and hydrological events such as precipitation and flooding. Interestingly, the disparity occurring during the wet years even suggests the potential to adapt the method to monitor runoff (net lateral flow).<p> The methodology also demonstrated the capability to accurately estimate in situ elastic and hydraulic parameters. Calibration of the model yielded equivalent properties of the aquitard (hydraulic conductivity, Kv, of 2.1E-5 m/day and specific storage, Ss, of 1.36E-5 /m) for a Skemptons B-bar coefficient of 0.91 for an assumed porosity of 0.26. Sensitivity tests also provided insight into the consolidation and pressure propagation (swelling) behaviour of the aquitard under parametric variations. The parameters obtained are consistent with range of values reported for glacial clay till soil. Therefore, this work also provides a unique case history of a method for determining, large scale, in situ material properties for geo-engineers and scientists to explore by simply using piezometric and meteorological data.

The design and development of isolation or backfill materials, which seal the disposal facility, are important for disposing the wastes. The use of compacted bentonite-sand for construction of shaft seals and liners for waste containment structures has been proposed by various studies. Therefore / it is aimed in this study to develop an isolation material to be used in underground waste repositories. For such designs to be effective, their performance need to be assessed and a minimum hydraulic conductivity requirement defined by regulatory agencies should be satisfied (i.e. 1x10-8 m/s in Turkey, 1x10-9 m/s in USA). Therefore / this study assesses the performance of compacted bentonite/sand mixtures in terms of hydrological and mechanical properties. To be able to assess the performance of this material, a variety of laboratory tests were carried out. Engineering geological tests such as compaction, falling head permeability, swelling, unconfined compression and shear strength tests were conducted to select an optimum mixture. Finally, an optimum bentonite-sand mixture possessing 30% bentonite was recommended for the isolation of underground waste disposal facilities.

Up-to-date methods of numerical modelling of random fields were applied to investigate some features of solute transport in saturated porous media with stochastic hydraulic conductivity. The paper describes numerical experiments which were performed and presents the first results.

Slurry wall is a geotechnical engineering application to control the migration of contaminants by retarding groundwater flow. Sand-bentonite slurry walls are commonly used as levees and containment liners. The performance of bentonite slurry in sand-bentonite slurry walls was investigated by studying the rheological properties of bentonite suspensions, the penetration length of bentonite slurry into clean sand, and stability of the trench under in-situ hydraulic gradients. In this study, the rheological parameters of bentonite suspensions were measured at various bentonite fractions by weight from 6 to 12% with 0-3% of sodium pyrophosphate; an ionic additive to control the rheological properties of the bentonite slurries. The penetrability of the bentonite slurries through Ottawa sand was studied by injecting the slurries into sand columns at different bentonite fractions. The injection tests were performed with the permeameters having different diameters to eliminate any bias on test results due to the different size of permeameter. An empirical correlation for predicting the penetration length of bentonite slurry based on apparent viscosity, yield stress, effective particle size, relative density, and injection pressures was updated by taking into account the effects of the permeameter diameter size. Moreover, the stability of sand-bentonite slurry walls was inspected by studying the hydraulic performance of sand permeated with bentonite suspensions under increasing hydraulic gradients. The critical hydraulic gradient at which washing out of bentonite suspensions is initiated was examined. For specimens with bentonite contents less than the threshold value, the flow occurred through the sand voids and minimal washing out occurred. On the other hand, when the bentonite content was high enough to fill up all the void space between the sand particles, the flow was controlled by the clay void ratio. In this case, washing out did occur with increasing gradients accompanied by an increase in hydraulic conductivity. Accordingly, a relation between the yield stress of bentonite suspensions and the critical hydraulic conductivity was developed. / text

Hydraulic conductivity of variably-saturated soils is critical to understanding processes at the land surface. Yet measuring it over an area comparable to the resolution of land-surface models is fraught because of its strong spatial and temporal variations, which render point measurements nearly useless. We derived unsaturated hydraulic conductivity at the horizontal scale of hectometers and the vertical scale of decimeters by analyzing trends in soil moisture measured using the cosmic-ray neutron method. The resulting effective hydraulic conductivity remains close to its value at saturation over approximately half of the saturation range and then plummets. It agrees with the aggregate of 36 point measurements near saturation, but becomes progressively higher at lower water contents; the difference is potentially reconcilable by upscaling of point measurements. This study shows the feasibility of the cosmic-ray method, highlights the importance of measurement scale, and provides a route toward better understanding of land-surface processes.

Air permeability (ka) is a viable alternative to water- and texture-based methods to rapidly map saturated hydraulic conductivity (Ksat). The ability to measure this important hydraulic property without the use of more cumbersome and time-consuming methods may provide a practical approach to generate more complete data to describe hydrologic conditions. This study presents the development of an air permeameter which is suitable for desert soils. The Soil Corer Air Permeameter (SCAP) is compatible with a standard soil corer and employs digital components to measure flowrates under low-pressure gradients to improve accuracy, ease of use, and portability. SCAP allows for the extraction of undisturbed soil samples for laboratory analysis, providing direct comparisons of ka with other soil physical and hydraulic properties. The applicability of a regression equation to estimate Ksat from field-measured ka using SCAP was examined in unburned and burned soils. Ex situ field ka and laboratory Ksat measurements were compared and air to water permeability (ka/kw) ratios were calculated to determine structural changes due to water saturation. The study also characterized changes in permeability due to fire in woodland-chaparral and coniferous soils. For soils that could be extracted with minimal structural changes, results show ka and Ksat measurements for unburned and burned soils were within the 95% confidence intervals of a ka-Ksat regression developed for agricultural soils. However, correlations for in situ ka measurements in some burned soils showed a decrease in accuracy and may be attributed to soil anisotropy. A three-dimensional steady-state finite element air flow model was developed using FEMLAB 3.0A to consider the effects of anisotropy on in situ ka measurements. Results show that anisotropic conditions can introduce an error as high as a factor of 2 especially for air permeameters with high diameter to height (D/H) ratios, however, the error is much smaller than the anisotropy ratio. If anisotropy is important to characterize, it was shown that paired measurements of in situ and ex situ ka can be used to infer the anisotropy ratio.

Iškritus krituliams ant žemės paviršiaus, dalis jų susigeria į gruntą, o kita dalis nuolydžio kryptimi teka link žemiausių reljefo vietų. Susigėrimo intensyvumas priklauso nuo grunto laidumo. Sunkiuose gruntuose vandens susigeria ir patenka į gilesnius grunto sluoksnius gana sunkiai dėl mažo grunto laidumo. Intensyviausiai vanduo nuo žemės paviršiaus teka drenažo tranšėjomis ir šalia jų. Šios vandens tekėjimo sąlygos tranšėjose susidaro pakitus grunto struktūrai, jas užverčiant. Laikui bėgant, drenažo tranšėjoje atsiradę plyšiai užnešami smulkiomis grunto dalelėmis. Tai įtakoja grunto vandens laidumo savybių prastėjimą. Norint pagerinti vandens nutekėjimą iš viršutinio dirvožemio sluoksnio, padėtų natūralios gamtoje sutinkamos medžiagos, įterptos skersai virš vamzdinio drenažo. Drenažo tranšėjų užpylimui naudojant poringas medžiagas, dalis atitekėjusio vandens akumuliuotųsi naujai įrengtose skersinėse drenažo tranšėjose. Tokios technologijos taikymas leistų padidinti sausinimo efektyvumą nekeičiant jau paklotų drenažo vamzdžių. Modeliuojant skersinių drenažo tranšėjų tankio įtaką vandens lygiui tarpdrenyje, nustatyta, kad papildomas jų įrengimas turi įtakos gruntinio vandens lygiams tarpdrenyje tik esant atstumui iki 30 m. Esant didesniam atstumui, jų poveikis gruntinio vandens lygio nuslūgimui tampa nežymus, siekia vos 1-2%. Didžiausią įtaką gruntinio vandens slūgimui tarpdrenyje turėjo skersinės drenažo tranšėjos įrengiamos 20 m tarpais, kai drenažo tranšėjos užpildo... [toliau žr. visą tekstą] / After rainfall, part of it is absorbed by the ground whereas the rest part flows upon the direction of the inclination towards the lowest points on the relief. Intensity of absorption depends on conductivity of the ground. In the hard ground water is absorbed and enters the deeper layers of the ground with difficulty due to low conductivity of the ground. Water flows most intensely through drainage trenches and next to them. These conditions of water flow in trenches form when the ground structure alters and overloads them. The time passing by, cracks, having occurred in the drainage trench, are filled with small ground particles. It influences deterioration of ground water conductivity qualities. In order to improve water runoff from the upper soil layer, natural substances found in nature, if inserted across, above the drain, could help. Using porous substances in order to cover drainage trenches, part of the water would accumulate in newly equipped cross-section drain trenches. Applying such a technology would allow increasing the efficiency of drainage without changing the already laid drainage pipes. Modeling the influence of cross-section drainage trench density on ground water level between drains, it was determined that additional installation could affect ground water level between the cross-section drains trench, the distance being up to 30 meters. When the distance is larger, its impact on the ground water level recession becomes insignificant and reaches only 1-2%... [to full text]