Impervious Layer Research Articles

The Leakage Risk Monetization Model for Geologic CO2 Storage.

We developed the Leakage Risk Monetization Model (LRiMM) which integrates simulation of CO2 leakage from geologic CO2 storage reservoirs with estimation of monetized leakage risk (MLR). Using geospatial data, LRiMM quantifies financial responsibility if leaked CO2 or brine interferes with subsurface resources, and estimates the MLR reduction achievable by remediating leaks. We demonstrate LRiMM with simulations of 30 years of injection into the Mt. Simon sandstone at two locations that differ primarily in their proximity to existing wells that could be leakage pathways. The peak MLR for the site nearest the leakage pathways ($7.5/tCO2) was 190x larger than for the farther injection site, illustrating how careful siting would minimize MLR in heavily used sedimentary basins. Our MLR projections are at least an order of magnitude below overall CO2 storage costs at well-sited locations, but some stakeholders may incur substantial costs. Reliable methods to detect and remediate leaks could further minimize MLR. For both sites, the risk of CO2 migrating to potable aquifers or reaching the atmosphere was negligible due to secondary trapping, whereby multiple impervious sedimentary layers trap CO2 that has leaked through the primary seal of the storage formation.

An Analytical Solution for Predicting Transient Seepage into Partially Penetrating Ditch Drains Receiving Water from a Ponded Field

A transient analytical model is worked out for predicting seepage from a ponded field of infinite extent to a network of equally spaced ditch drains in a homogeneous and anisotropic soil underlain by an impervious barrier at a finite distance from the surface of the soil. The solution can account for finite width and finite level of water in the ditches, finite penetration of the drains in the soil, and also a variable ponding field at the surface of the soil. The study highlights the fact that the transient state duration of a partially penetrating ponded drainage scenario may be considerable should the drains be dug in a lowly conductive soil with a high storage coefficient, particularly if the underlying impervious layer lies at a large distance from the bottom of the ditches and the separation between the adjacent ditches is also large at the same time.

Use of Sepiolite and Zeolite Mixtures as a Landfill Liner

This study presents an investigation into the possibility of using sepiolite and zeolite mixtures to design a landfill liner. Leakage from the impervious layer into the environment is the main difficulty of storing hazardous waste. Therefore, determining the impermeable layer and in-situ application procedure is very important and needs laboratory experimentation. For this purpose, a series of experiments have been conducted on a mixture of zeolite+sepiolite. The geotechnical, physico-chemical and micro-structural properties of 30% sepiolite by weight of zeolite have been determined through laboratory testing. At the end of the research, the results show that zeolitesepiolite mixtures can be effectively used in bottom lining systems for hazardous, industrial and municipal waste.

Rising Groundwater Levels Problem in Urban Areas: A Case Study from the Central Area of Madinah City, Saudi Arabia

In this research, the hydrogeological conditions in the central area of Madinah city, Saudi Arabia, were investigated in an attempt to gain insight into the shallow groundwater table rise problem that has recently been observed in this important location. Four wells were drilled in the study area, and soil samples were collected during the drilling process for lithological characterization. Water level in each well was recorded, and water samples were collected from the wells and analyzed for all important water quality parameters including temperature, pH, turbidity, electrical conductivity, dissolved oxygen, total dissolved solids, biochemical oxygen demand, bacteriological parameters (total coliform, fecal coliform, E. coli), major anions and cations, heavy metals, BTEX compounds and organophosphorus pesticides. In addition, geophysical loggings were conducted on two of the wells and a pumping test was conducted on one of the wells. Results revealed that the hydrogeological features in the study area consist of a top impervious layer, followed by a productive confined aquifer that extends over basement complex bedrock. Water quality analyses showed that the groundwater in the study area is not contaminated by leakage from different sources, indicating that these sources are not major contributors to SWTR. Most likely, the partial blockage of groundwater flow by large infrastructure in the study area is responsible for the SWTR. Results obtained from this research provide useful information regarding the hydrogeology of an important area and can aid authorities in preparing well-founded scientific plans to deal with SWTR problem including the appropriate reuse of excess water.

INFLUENCE OF WELL LOCATION ON DRAWDOWN IN AREA SURROUNDED BY VERTICAL CUTOFF WALLS

Dewatering systems with vertical partially penetrating cutoff walls are usually used in the case of deep excavation for side support system and further increases the efficiency of the groundwater control system. In this study a parametric analysis was carried out using the finite difference software VISUAL MODFLOW4.2® to study the effect of placing a deep well at different locations inside the excavated area surrounded by impervious wall on drawdown results. The dewatering system under consideration consists of a single partially penetrating deep well having a penetration depth (lw) and well yield (Q). The well is located at variable distances from the corner (the origin of X and Y axes) inside the excavated area surrounded by an impervious wall. The vertical impervious wall has a depth (lc), and the excavated area (A) surrounded with impervious wall is square and having a width (W). The aquifer is unconfined with a depth (H) and is underlain by an impervious layer. The aquifer consists of an extended layer of fine to medium sand having permeability (k). The soil is assumed to be homogenous and isotropic.

A qualitative approach for identifying areas prone to urban floods with the support of LiDAR

AbstarctIn urban areas, the land surface is often covered with impervious layers increasing the potential for storm water flooding. Thus, runoff water management during intensive rain events has become an important issue to be tackled in fast-growing cities with increasingly large populations. This paper presents a LiDAR-aided qualitative methodology for defining areas prone to urban floods on a regional scale at the early phases of land use planning. The developed methodology is based on different datasets describing water infiltration capacity of the ground and tested in the city of Vantaa, Finland. The methodology utilizes datasets that are freely and easily available. The selected factors for analysis are soil permeability, soil sealing and surface topography. The presented approach gives tools for the preliminary identification of areas prone to storm water flooding. The developed analysis is user-friendly and quick to perform. It is a qualitative method that can support land use planners and other municipal and regional actors in the environmental and technical sectors in early-phase storm water flood management. The developed method is applicable for different planning scales.

Seepage and stress analysis of anti-seepage structures constructed with different concrete materials in an RCC gravity dam

This study used the finite element method (FEM) to analyze the stress field and seepage field of a roller-compacted concrete (RCC) dam, with an upstream impervious layer constructed with different types of concrete materials, including three-graded RCC, two-graded RCC, conventional vibrated concrete (CVC), and grout-enriched vibrated RCC (GEVR), corresponding to the design schemes S1 through S4. It also evaluated the anti-seepage performance of the imperious layer in the four design schemes under the normal water level and flood-check level. Stress field analysis of a retaining section and discharge section shows that the maximum tensile stress occurs near the dam heel, the maximum compressive stress occurs near the dam toe, and the stress distributions in the four schemes can satisfy the stress control criteria. Seepage field analysis shows that the uplift pressure heads in schemes S3 and S4 descend rapidly in the anti-seepage region, and that the calculated results of daily seepage flow under the steady seepage condition in these two schemes are about 30%–50% lower than those in the other two schemes, demonstrating that CVC and GEVR show better anti-seepage performance. The results provide essential parameters such as the uplift pressure head and seepage flow for physical model tests and anti-seepage structure selection in RCC dams.

Description of particle induced damage on protected silver coatings.

In the visible to infrared spectral range, highly-reflective silver mirrors are applied in the manufacture of optical instruments such as telescopes. However, it is still difficult to combine high reflectivity and long-term stability of the protected silver coating. We show that the deposition of impervious protective layers is necessary but often not sufficient for long-term environmental stability. Hygroscopic air borne particles absorbed by the protections surface attract water molecules and form a solution. This solution first damages the protection, subsequently permeates the protection and finally damages the silver whereby the reflectivity is reduced. We demonstrate this particular damage mechanism with different experiments and describe this mechanism in detail.

The mixture theory for unsaturated bentonite

Bentonite is a material with low permeability and as such is the preferred material for impervious layer in a refuse landfill. Given the multi-scale structure of the bentonite, contaminant transport in it is a very complex process. In fact, it is coupled with consolidation. The coupling effect affects the contaminant transport by changing the inherent transport feature. In addition, the bentonite clay liner is usually unsaturated. In this article, the mixture theory is used as a framework that describes the transport phenomena and the interactions of the unsaturated bentonite under the multi-field coupling effect. It is also a valuable reference for simulating the contaminant transport in bentonite clay liners.

Construction of relief wells under artesian flow conditions at dam toes: engineering experiences from Karkheh earth dam, Iran

We report engineering experiences from the critical task of relief well installation under high artesian flow conditions at the downstream toe of the Karkheh earth dam, Iran. Due to the establishment of excessive uplift pressure at the downstream toe of the Karkheh dam, installation of a series of new relief wells was considered to permanently relieve part of these pressures. The mentioned uplift pressure, as high as around 30 m above the ground level, was produced in a confined conglomerate aquifer bounded above and below by relatively impervious mudstone layers which reduced the safety factor of the dam toe to below 1.0. Investigations on the shortcomings of the old relief wells installed at the dam site showed that the main problems were: insufficient well numbers, insufficient well diameters, irregular well screens causing their blockage by time passing, and insufficient total opening area. Despite engineering difficulties and associated risk of downstream toe instability, installation of new relief wells was successfully completed under high artesian flow conditions” was successfully completed. The employed technique for the construction of the new relief wells under flowing artesian conditions was based on: 1) cement grouting and casing of the well, 2) telescopic drilling, 3) application of appropriate drilling fluid, and 4) controlling the artesian flow by adding a long vertical pipe to the top of the relief wells. Numerical modeling of seepage for the Karkheh dam foundation showed that, as a result of the installation of the new relief wells, the safety factor of the downstream toe increased to the safe value of 1.3 for the normal reservoir water level.

Design of Barrage on Heterogeneous and Anisotropic Soils

The present study reports on the design of barrages on heterogeneous and anisotropic soils, based on the analysis of subsurface flow by finite element method. The study indicates that the location of impervious layer below the sheet piles marginally changes the uplift pressures, but with an advantage of reduction in the exit gradient. On the contrary, the location of a pervious layer below the sheet piles drastically changes the uplift pressures along with a drastic increase in the exit gradient and therefore, will have a major impact on the design of a barrage. The isotropic and anisotropic soils behave differently under subsurface flow considerations and unlike isotropic soils, the depth of upstream sheet pile/cut-off can be an important factor for the design of a barrage on anisotropic soils. The uplift pressures and exit gradients can be reduced by increasing the depth of upstream sheet pile for anisotropic soils.

Porous double-layer polymer tubing for the potential use in heterogeneous continuous flow reactions.

Functional polymer tubing with an OD of 1/16 or 1/8 in. was fabricated by a simple polymer coextrusion process. The tubing was made of an outer impervious polypropylene layer and an inner layer, consisting of a blend of a functional polymer, polyethylene-co-methacrylic acid, and a sacrificial polymer, polystyrene. After a simple solvent leaching step using common organic solvents, the polystyrene was removed, leaving behind a porous inner layer that contains functional carboxylic acid groups, which could then be used for the immobilization of target molecules. Solution-phase reactions using amines or isocyanates have proven successful for the immobilization of a series of small molecules and polymers. This flexible multilayered functional tubing can be easily cut to the desired length and connected via standard microfluidic fittings.

Paleovalley-related uranium: exploration criteria and case-studies from Australia and China

Uranium exploration and mining in Australia and China are significant and increasingly important sectors of each country's respective mineral industry. Here we focus on similarities in the geology of paleovalley-related uranium mineralising systems, which can be used to refine strategies for exploration. Paleovalley-related uranium resources are developed as sandstone-hosted and surficial deposits within paleovalley-fills, deposited either on incised crystalline bedrock, or incised sedimentary cover that is often of similar age to the sediments that host the mineralisation. With respect to Sino-Australian examples, paleovalley-related uranium occurs mostly around the margins of Mesozoic and Cenozoic basins; often the mineralisation is hosted within sands contained within paleovalleys developed upon, or proximal to, Precambrian crystalline rock that contains primary uranium mineralisation. Numerous examples are known in Australia and China where granitic rocks of pre-Mesozoic age contain uranium in the range 10-100 ppm, concentrations significantly above the crustal average of 2.8 ppm uranium. Crystalline rocks with above-background levels of uranium that are incised by paleovalleys are often the inferred source of the sandstone-hosted uranium. In these regions, extensive fluvial systems developed particularly during Mesozoic and early Cenozoic times, eroded weathered basement rocks to physically disperse uranium into the cover sediments, with subsequent chemical remobilisation, dispersion and concentration of uranium occurring throughout the late Cenozoic. Paleovalley-related uranium deposits are typically hosted within unlithified sand, lignitic clays or calcreted channel-fill, deposited in continental or marginal marine environments. Sandstone-hosted uranium deposits in many cases contain impermeable clay layers, intercalated within the sedimentary sequence; impervious layers often form the upper and lower bounding strata of individual deposits. Uranium deposits are associated with reduced lithologies; mineralisation is developed where oxidising fluids (carrying dissolved U) were modified by interaction with reduced sands, the latter commonly containing pyrite and dispersed organic matter and/or seams of lignite. Mineralised bodies, often tabular or roll-shaped, formed along the interface between clay horizons and the sandy facies of paleovalley sediments. Geological, geophysical and geochemical features of the paleovalleys and related uranium deposits have been used to construct models to understand ore genesis and assist exploration for paleovalley-hosted uranium deposits. Australia and China remain highly prospective for the discovery of new paleovalley-related uranium deposits. The precise geometric definitions of the basin margin and paleovalley architecture are important in identifying exploration targets and improving the effectiveness of drilling. This requires the integration of various geoscientific data sets. Refinements in remote sensing, geophysical techniques and data processing, in combination with sedimentological and depositional interpretations, provide an efficient approach for outlining the principal drainage patterns and channel dimensions. To help reduce risk, an exploration strategy should combine these technologies with a detailed understanding of the physicochemical parameters of uranium reduction, mobilisation and preservation.

Performance of gap graded cold asphalt containing cement treated filler

Previous studies have revealed the beneficial effects of adding Ordinary Portland Cement (OPC) to Bitumen Emulsion Mixtures (BEMs). These effects were confirmed for some dense graded mixtures based on recipes currently used for hot asphalt concrete mix in the UK and being considered for usage in BEMs. On the other hand, Hot Rolled Asphalt (HRA) which is a gap graded mixture is extensively used for surfacing major roads in the UK because it provides a dense, impervious layer, resulting in a weather-resistance durable surface able to endure the demands of modern traffic loads and providing good resistance to fatigue cracking.This laboratory study describes the development of novel gap-graded Cold Rolled Asphalt (CRA) by using OPC instead of conventional mineral filler. Stiffness modulus, uniaxial creep, four point load fatigue, and semi-circular bending monotonic tests were used to assess the mechanical properties while stiffness modulus ratio was determined to assess the water sensitivity of the produced mixtures.The study concluded that there is a considerable enhancement in the mechanical properties and water sensitivity of CRA containing OPC. Also, the produced cement treated gap-graded CRA shows a significant lower thermal sensitivity than conventional HRA. More interestingly, the new cement treated CRA is found to be comparable with the mechanical properties of the conventional HRA after less than 1day.

Comparative Non-linear Regression - Case of Infiltration Rate Increase from Upstream in Valley

Abstract In Tropical Savannah flooded valley soils, very low infiltration rates often result in acidic conditions favourable to high concentrations of metallic ions, toxic for rice. Determination of the under-phreatic infiltration rate is important in drainage design to reclaim degraded soils. Several studies have addressed the mapping of the infiltration rate. Yet, its relationship with the toposequence of the valley is not clarified. This paper has investigated such a possibility, examining the case of the irrigated rice valley of Tiefora, Burkina Faso. Nine boreholes – from 1 to 5 m deep – were implemented from upstream to downstream. The Lefranc permeability test of the under-phreatic level in waterlogged soils – used when the impervious layer is close to soil surface or absent – was conducted. First, a comparative regression was applied to the data, including all the parameters of the regression curves. In the case of dissimilarity of the infiltration processes, the comparison focused on the final permeability. The results show a permeability increase from upstream (0.10±0.10cmh-1)todownstream (greater than 20±10 cm h-1 in some places). Taking into account such a permeability increase in the subsurface drainage system design would result in implementation of more efficient and cost effective systems.

STEADY-STATE SUBSURFACE DRAINAGE OF PONDED FIELDS BY RECTANGULAR DITCH DRAINS

A comprehensive analytical solution is presented for the steady‐state two‐dimensional drainage problem of the water flow from a horizontal ponded surface into rectangular cross‐section array ditches. The ditches partially penetrate into a homogeneous and isotropic porous medium of finite depth over an impervious layer. The solution includes the equations for drainage discharge into ditches, the drainage discharge through the seepage face and the water depth portion of a ditch, and seepage velocities along the ponded surface. The equations are obtained using the Schwarz–Christoffel transformation in the conformal mappings of the physical and hodograph planes on to an auxiliary plane. The proposed analytical solution is validated by comparing the results with the known experimental data and the other analytical works. The results of the analyses show that seepage velocity along the ponded surface water decreases with distance from the ditch and accordingly leaching of salts is non‐uniform. Closer spacing between two adjacent ditches, shallower water depth in the ditches, and deeper depth of the ditches are advantageous in removing salts from fields.

Superior cold rolled asphalt mixtures using supplementary cementations materials

Hot Rolled Asphalt (HRA), which is a gap-graded mixture, is extensively used for surfacing major roads in the UK because it provides a dense, impervious layer, resulting in a weather-resistant durable surface able to endure the demands of modern traffic loads and providing good resistance to fatigue cracking.This paper describes a laboratory study on the production of new, superior, cold Bitumen Emulsion Mixtures (BEMs) with the same gradation used with conventional HRA mixtures and collectively incorporating different types of supplementary cementitious materials (SCM) instead of the conventional mineral filler. Accordingly, two ternary blended fillers termed as TBF-1 and TBF-2, have been blended from different SCMs and optimised to replace the conventional mineral filler.To develop the gap-graded Cold Rolled Asphalt (CRA) mixtures evaluation of stiffness modulus, creep performance and fatigue testing was used to assess the mechanical properties while stiffness modulus ratio was used to investigate the water sensitivity.The study concluded that there is a substantial improvement in the mechanical properties and water sensitivity of CRA containing TBF-1 and TBF-2. Also, the superior CRA mixtures produced showed a significant lower thermal sensitivity than conventional HRA. More remarkably, the new CRA were found to be comparable with the conventional HRA after a very short curing time (after 4h).

Shallow hydrostratigraphy in an arsenic affected region of Bengal Basin: Implication for targeting safe aquifers for drinking water supply

To delineate arsenic (As) safe aquifer(s) within shallow depth, the present study has investigated the shallow hydrostratigraphic framework over an area of 100km2 at Chakdaha Block of Nadia District, West Bengal. Drilling of 29 boreholes and subsequent hydrostratigraphic modeling has identified three types of aquifer within 50m below ground level (bgl). Aquifer-1 represents a thick paleochannel sequence, deposited parallel to the River Hooghly and Ichamati. Aquifer-2 is formed locally within the overbank deposits in the central floodplain area and its vertical extension is strictly limited to 25m bgl. Aquifer-3 is distributed underneath the overbank deposits and represents an interfluvial aquifer of the area. Aquifer-3 is of Pleistocene age (~70ka), while aquifer-1 and 2 represent the Holocene deposits (age <9.51ka), indicating that there was a major hiatus in the sediment deposition after depositing the aquifer-3. Over the area, aquifer-3 is markedly separated from the overlying Holocene deposits by successive upward sequences of brown and olive to pale blue impervious clay layers. The groundwater quality is very much similar in aquifer-1 and 2, where the concentration of As and Fe very commonly exceeds 10μg/L and 5mg/L, respectively. Based on similar sediment color, these two aquifers have jointly been designated as the gray sand aquifer (GSA), which constitutes 40% (1.84×109m3) of the total drilled volume (4.65×109m3). In aquifer-3, the concentration of As and Fe is very low, mostly <2μg/L and 1mg/L, respectively. This aquifer has been designated as the brown sand aquifer (BSA) according to color of the aquifer materials and represents 10% (4.8×108m3) of the total drilled volume. This study further documents that though the concentration of As is very low at BSA, the concentration of Mn often exceeds the drinking water guidelines.

Consolidation of archaeological gypsum plaster by bacterial biomineralization of calcium carbonate

Gypsum plasterworks and decorative surfaces are easily degraded, especially when exposed to humidity, and thus they require protection and/or consolidation. However, the conservation of historical gypsum-based structural and decorative materials by conventional organic and inorganic consolidants shows limited efficacy. Here, a new method based on the bioconsolidation capacity of carbonatogenic bacteria inhabiting the material was assayed on historical gypsum plasters and compared with conventional consolidation treatments (ethyl silicate; methylacrylate–ethylmethacrylate copolymer and polyvinyl butyral). Conventional products do not reach in-depth consolidation, typically forming a thin impervious surface layer which blocks pores. In contrast, the bacterial treatment produces vaterite (CaCO3) biocement, which does not block pores and produces a good level of consolidation, both at the surface and in-depth, as shown by drilling resistance measurement system analyses. Transmission electron microscopy analyses show that bacterial vaterite cement formed via oriented aggregation of CaCO3 nanoparticles (∼20nm in size), resulting in mesocrystals which incorporate bacterial biopolymers. Such a biocomposite has superior mechanical properties, thus explaining the fact that drilling resistance of bioconsolidated gypsum plasters is within the range of inorganic calcite materials of equivalent porosity, despite the fact that the bacterial vaterite cement accounts for only a 0.02 solid volume fraction. Bacterial bioconsolidation is proposed for the effective consolidation of this type of material. The potential applications of bacterial calcium carbonate consolidation of gypsum biomaterials used as bone graft substitutes are discussed.

The hydrogeochemistry of subsurface brines in and west of the Jordan–Dead Sea Transform fault

AbstractThis study is based on 113 analyses of brines with Cl &gt; 0.57 mol l−1 (modern seawater), which were collected and analysed mostly during several decades of exploration for gas and oil in Israel. Based on critical evaluation of correlations of elements and ionic ratios and on spider patterns, six different brine events or source brines were identified in the Phanerozoic: the Triassic, Lower Cretaceous and the Mio/Pliocene brine families which were identified in boreholes Sdom‐1, Sdom Deep‐1 and Ha'on, and the Holocene Dead Sea brines. The Triassic brines are nowadays also encountered in under‐ and overlying rock units such as the Paleozoic Negev‐Yam Suf and the Jurassic Arad Groups, respectively. The southern Jordan–Dead Sea Transform (also known as the Rift) hosts the Mio‐Pliocene Sdom Deep and Sdom brine families. Brine bodies not sufficiently isolated by impervious sedimentary layers were flushed out during the Pliocene when the southern Valley drained north‐ and westwards through the Yizre'el Valley to the Mediterranean Sea. In the northern Rift Miocene to Pliocene seawater evaporated and infiltrated into the Rift sediments and into adjacent rocks. Further diluted by freshwater, it emerges as the Ha'on brine. Together with its derivatives, they form the Ha'on family. The derivatives of the Holocene Dead Sea brine family occur along the shoreline of the recent Dead Sea. Apart of all these evaporation brines, brines deriving from dissolution of evaporites locally occur in the area. The time‐bound chemical composition of paleoseawater is considered when discussing the ionic ratios of brines generated during different geological periods. Spider patterns of each brine family are compared and, where necessary, the relationship of brines to distinct families of brines is supported by inverse modelling.