Range Of Hydraulic Conductivities Research Articles

Scrutinate proclivity of regional aquifer hydraulic parameters: apriorisms for borehole failures within parts of the middle Benue Trough, Nigeria

Abstract Water borehole failures in Nigeria's middle Benue Trough are caused by imprecise aquifer features. This study employed empirical data to understand hydraulic parameters, anticipate regional groundwater potential, and explain borehole failures in difficult geological locations. 89 VES stations and quantitative data interpretation were required to determine the geoelectric properties beneath each station. Aquifer layers were delineated and their resistivity and thickness combined using geo-environment specific relations to yield transmissivity, hydraulic conductivity for both basement complex and sedimentary environments variously. Results show that aquifer resistivity ranges from 4.5 – 984.4 ohm-m; aquifer layer thickness varies from 4.4 m – 96.7 m with average thicknesses in sedimentary environment considerably greater; hydraulic conductivities range from 0.056 – 30.15 m/day, Transmissivity values range from 0.31 – 1281.36 m2/day. Log transformed transmissivity values range from 3.51 – 7.1 m2/day. Approximately 60.34% of the entire study area falls within transmissivity magnitude III and IV and can only support withdrawals for local water supply adequate for small communities and private consumption only and this may be the inferred cause for the low yield and high borehole failure rates. Understanding hydraulic characteristics is critical for 6controlling groundwater; research advances knowledge of transmissivity and conductivity in complex terrain.

Experimental Study on the Environmental Effects and Mechanical Characteristics of Solidified Cr(VI)-Contaminated Soil Based on Slag and Desulfurization Gypsum

This study proposed a new curing agent consisting of slag and desulfurization gypsum industrial waste to solidify Cr(VI)-contaminated soils and prevent its migration and bioaccumulation in the ecosphere. The curing agent dosage of 10–30% resulted in a Cr(VI) toxic leaching concentration, compressive strength, and hydraulic conductivity range of 0.118–5.824 mg/L, 2.70–10.22 MPa, and 1.70 × 10−9–1.37 × 10−6 cm/s, respectively. Following four dry and wet cycles, the dosage of the curing agent was found to be 20–30% to achieve minimum environmental safety requirements. Cr(VI) in the cured specimens mainly existed as CrO42−, or acid salt, in which a portion was changed to Cr(III) during precipitation or directly was encased in the silica-alumina mesh structure. The adsorption capacity of hexavalent chrome on the outer of the hydration product groups was insignificant owing to the electronegativity. Hence, the Cr(VI) was solidified by hydrides such as C-S(A)-H and calcium alumina inclusions. Calcite, quartz, and several zeolite-like substances were also found to be colloidal in the pores to block Cr(VI).

Hydraulic Conductivity Tests in the Triaxial Stress State: Is Peat an Aquitard or an Aquifer?

The characteristics of peat’s are crucial for understanding natural processes and their suitable shaping through the management of water relations. This study focused on the results of one of the first hydraulic conductivity (k) laboratory tests of exemplary peat samples from the Biebrza Valley (a peatland of very high environmental importance) in relation to the stress state and hydraulic gradient. Further, the research was devoted to a specific test procedure of peat permeability as a key feature for landform development in wetlands. Detailed tests of dark brown/black samples were selected as the reference for the research investigations. Four long-term test series of water permeability were performed in a modified triaxial compression apparatus. In all selected hydraulic gradient variants (i = 5,10,25,40,55,85), the k values decreased from 6 × 10−8 m/s to 1.6 × 10−10 m/s with a stepwise increase in the effective confining pressures tested (10, 15, 30, 45, and 90 kPa). These results were related to the inherent soil features—a relatively high peat decomposition and external driver—confining pressure (radial stress) magnitude. Compared to the other Polish peat tests, the determined k values were at the lower end of their hydraulic conductivity range. The analysed organic soil is not a typical aquifer. Despite very high porosities (~88%) and a high organic matter content (81.1–89.4%) which is favourable for water accumulation, the characterized peat showed relatively low hydraulic conductivity values. Thus, this specific soil may differentiate the groundwater flow as it complicates strong contact with surface water.

The Ibadan Hydrogeophysics Research Site (IHRS)—An Observatory for Studying Hydrological Heterogeneities in A Crystalline Basement Aquifer in Southwestern Nigeria

Crystalline basement aquifers are important drinking water sources in Nigeria and several sub-Saharan African countries. However, an understanding of their local flow and transport processes and pathways is missing due to limited research. The implication has been their suboptimal management, with frequently reported dry wells and groundwater contaminations. To address this challenge, the Ibadan Hydrogeophysics Research Site was established in 2019 as the first field-scale hydrogeological research laboratory in Nigeria to advance understanding of the geologic, hydraulic, and hydrogeochemical variabilities within crystalline basement aquifers. The over 22,500 m2 research site with a 50 m × 50 m area used for active hydraulic testing is located within the University of Ibadan campus and is instrumented with four initial test wells extending through the weathered and fractured zones to a depth of 30 m each. Preliminary hydrogeological and geophysical studies focused on obtaining a conceptual model and knowledge of hydraulic heterogeneities to aid in detailed experimental and numerical studies. A combination of lithological logs and electrical resistivity revealed areas with subvertical fractures as low-resistivity zones (<200 Ωm), and a pumping test revealed a hydraulic conductivity range of 1.9 × 10−10 to 7.2 × 10−6 m/s. The drawdown–time curve shows flow from single-plane vertical fractures. The results of this study will serve as a basis for further targeted field and numerical studies for the investigation of variability in groundwater flow in complex crystalline basement aquifers. The presented field site is posed to support the adaptation and development of field methods for studying local heterogeneities within these aquifers in Nigeria.

Geomechanical Behaviour of Recycled Construction and Demolition Waste Submitted to Accelerated Wear

The construction industry is one of the most important sectors for economic and social development. However, it is responsible for more than 50% of the depletion of natural resources, for 40% of the energy consumption and construction and demolition waste (CDW) accounting for 30–60% of the total municipal solid waste generated worldwide. In this sense, the recycling of CDW is considered a safe alternative to the current trend, which can produce environmental and economic benefits, namely the reduction of the depletion of natural resources and the volume of waste sent to landfills. Some studies have shown promising results in the use of recycled CDW as geotechnical materials. However, the degradation performance induced by the construction procedures and weather conditions on the geotechnical behaviour of recycled CDW is still a research gap, creating an obstacle for its regular use in general engineering practice. This work evaluated the mechanical performance of recycled CDW over time when subjected to wetting–drying degradation cycles under different temperature and pH conditions. The effects of such degradation were then evaluated qualitatively (changes in particle size distribution and Proctor parameters) and quantitatively (stress–strain response and permeability). The results showed that 10 wetting–drying cycles and different compaction energies have no change in the particle size distribution of CDW compared to the original CDW. The shear strength parameters were very similar for the different degradation conditions except when different pH values were used, which may have weakened the grains and decrease the friction angle of the material. Regarding the permeability, all tested samples were classified in the same hydraulic conductivity range (very low) without significant changes induced by the degradation mechanisms.

Evolution of Hydraulic Conductivity of Unsaturated Compacted Na-Bentonite under Confined Condition-Including the Microstructure Effects.

Compacted bentonite is envisaged as engineering buffer/backfill material in geological disposal for high-level radioactive waste. In particular, Na-bentonite is characterised by lower hydraulic conductivity and higher swelling competence and cation exchange capacity, compared with other clays. A solid understanding of the hydraulic behaviour of compacted bentonite remains challenging because of the microstructure expansion of the pore system over the confined wetting path. This work proposed a novel theoretical method of pore system evolution of compacted bentonite based on its stacked microstructure, including the dynamic transfer from micro to macro porosity. Furthermore, the Kozeny–Carman equation was revised to evaluate the saturated hydraulic conductivity of compacted bentonite, taking into account microstructure effects on key hydraulic parameters such as porosity, specific surface area and tortuosity. The results show that the prediction of the revised Kozeny–Carman model falls within the acceptable range of experimental saturated hydraulic conductivity. A new constitutive relationship of relative hydraulic conductivity was also developed by considering both the pore network evolution and suction. The proposed constitutive relationship well reveals that unsaturated hydraulic conductivity undergoes a decrease controlled by microstructure evolution before an increase dominated by dropping gradient of suction during the wetting path, leading to a U-shaped relationship. The predictive outcomes of the new constitutive relationship show an excellent match with laboratory observation of unsaturated hydraulic conductivity for GMZ and MX80 bentonite over the entire wetting path, while the traditional approach overestimates the hydraulic conductivity without consideration of the microstructure effect.

Dar Zarrouk Parameters for delineation of groundwater potentials in Ganye and Environs, Adamawa State, Northeastern Nigeria

Groundwater is the main source of water supply in areas in Nigeria including the research area. The research is aimed at delineating groundwater potentials in Ganye and environs using Dar Zarrouk parameters. Fourteen (14) vertical electrical soundings were conducted across the study area in order to determine Dar Zarrouk parameters to determine groundwater potentials in Ganye and environs. The area is underlain by migmatite-gneiss and Pan African granites. Weathered/fractured basement constitute the aquifer type in the area. The aquifer conductivity in the study area range between 0.00871 to 0.032032 ?-1 with mean value of 0.019493 ?-1. The aquifer longitudinal conductance ranges between 0.22246 to 0.759252 with mean value of 0.432846. The transverse resistance range between 627.8721 to 1,857.282 ?m2 with average value of 1,235.854 ?m2. The aquifer hydraulic conductivity range between 6.9314 to 15.562 m/day with mean value of 9.738 m/day while the transmissivity across the study area range between 114.2152 to 378.774 m2/day with mean value of 216.0487 m2/day.

Identification of suitable sites for managed aquifer recharge under semi-arid conditions employing a combination of numerical and analytical techniques

Overpumping or overexploitation of groundwater is one of the major threats for aquifer systems in arid and semi-arid areas. Managed aquifer recharge (MAR) has been suggested by many researchers as a sustainable and effective method to alleviate negative impacts of overpumping. Optimizing artificial recharge considers the selection of suitable MAR sites in terms of surface and subsurface characteristics. While surface characteristics at potential MAR sites could be modified (e.g. slope, soil texture, etc.), subsurface characteristics cannot be changed through engineering work. Characteristics of the aquifer, such as depth to groundwater, play an important role in determining the capability of an aquifer to store a specific volume of infiltrated water. Currently, only a limited number of quoted researches are available that consider factors related to aquifer characteristics and the range of these factors to identify optimal MAR sites. In this study, a new approach is presented, that employs numerical groundwater modeling to generate MAR suitability maps considering sub-surface characteristics, such as depth-to-groundwater, aquifer transmissivity and specific yield. Multiple model-runs are conducted to simulate groundwater table response with respect to the volume of infiltrated water. Simulation results are used to calibrate a groundwater mound empirical equation that calculates the groundwater level increase as a function of the transmissivity and infiltrated water volume for a given value of aquifer’ specific yield, range of vertical hydraulic conductivities and a specific design and operation conditions of the MAR system. The empirical equation is employed in GIS to spatially calculate the height of groundwater mound beneath a hypothetical MAR site and to generate, based on that, suitability maps for MAR implementation. Assuming that MAR structures capture the median of monthly surface runoff rates at the respective wadi (catchment area), suitability maps are generated for different configurations/scenarios of aquifer hydraulic conductivity in a parameter study. The results highlight the importance of integrating aquifer characteristics (geometry and hydraulic parameters) and expected magnitudes and fluxes of infiltration water in delineating suitable sites for MAR.

Numerical Model about the Influence of Cyclic Load on the Hydraulic Conductivity of Soft Clay

The hydraulic conductivity k is one of the most important engineering properties of soft clay, and it plays an important role during the whole life cycle of underwater tunnel. Therefore, it is necessary to systematically study the response of k to dynamic load. In this study, a series of seepage tests were conducted on remolded Hangzhou soft clay using dynamic triaxial seepage apparatus after cyclic loading. The results show that the hydraulic conductivitys of all samples decrease after cyclic loading, and the maximum drop of the hydraulic conductivity can reach 29.1%. Also, the hydraulic conductivity of soil samples is significantly affected by cyclic stress ratio (CSR). With the increase of CSR, the decrease range of hydraulic conductivity under cyclic loading is between 22.3% and 24.3%. The dynamic load reconstructed the microstructure of clay and made the number of large pores getting decreased and the small pores increased. This resulted in a decrease in the smaller hydraulic conductivity (k) of the specimens. Futhermore, based on the NMR scanning on the microstructure of soil samples under cyclic loading and the microscopic pore channel theory, a prediction model for the k of soft clay is proposed. The validity of the model is verified based on test data. It is believed that the proposed model could provide some theoretical support for the design and long-term performance prediction in practical engineering issues.

Random finite element analysis of backward erosion piping

Backward erosion piping (BEP) is a type of internal erosion that threatens the integrity of dams and levees. BEP has been shown to be highly sensitive to spatial variations in soil properties; however, there are presently no assessment methods that permit incorporating spatial variation in soil properties into BEP analysis. The Random Finite Element Method (RFEM) is a numerical approach for incorporating spatially variable properties into finite element analysis. In this study, an RFEM approach to simulating BEP was developed to assess pipe progression through variable soils. The soil hydraulic conductivity and critical hydraulic gradient for pipe progression were treated as log-normal random variables. Analyses were conducted for a range of hydraulic conductivity and critical gradient random fields with varied spatial correlation lengths, distribution parameters, and field correlations. Results indicate that the probability of failure increases with increasing spatial correlation length. Additionally, increased variance in soil permeability was shown to increase the probability of failure for large correlation lengths and decrease the probability of failure for short correlation lengths. Regardless of correlation length, increasing values of the mean critical hydraulic gradient led to decreased failure probabilities, and increasing values of critical hydraulic gradient variance led to increased failure probabilities.

Aquifer hydraulic parameters estimation based on hydrogeophysical methods in West Nile Delta, Egypt

Water scarcity is becoming a major constraint not only to the reclamation and cultivation of new areas, but also to the irrigation of already reclaimed areas, which could lead to global desertification. Groundwater exploration is one of the solutions to overcome the water resource shortage crisis in Egypt, especially after the building of the Ethiopian Renaissance Dam and its effects with unfavorable consequences for the water supply. The West Nile Delta region (WND) has been chosen by the Egyptian government in the past 30 years to develop several agricultural programs that rely mainly on groundwater for different aquifers. Vertical Electrical Sounding (VES) is the main method for determining the depths to groundwater, aquifer thicknesses, salinity and possibly hydrophysical parameters (transverse resistance and average transverse resistivity). The hydraulic parameters of aquifer and their important role in estimating the safe yields from production wells are essential for agriculture water management. To estimate of main aquifer parameters using geoelectric measurements, which are of great importance in selecting the suitable wells locations and in maintaining the sustainable management of groundwater, hydrogeological data are collected for 32 drilled wells and the Schlumberger array was used to implement 22 VES at specific sites in the study area. Some VES are performed alongside the already drilled wells that have lithology and pumping test data and others are carried out in well-free places especially in the northern and southern parts. Using the partial-curve matching technique, 22 VES data are interpreted to obtain the different geoelectric parameters (e.g., transverse resistance and average transverse resistivity). The constructed relationships between transmissivity—transverse resistance, hydraulic conductivity—average transverse resistivity, and salinity—average transverse resistivity showed well correlation between these parameters, where R2 equal 0.86, 0.7 and 0.8, respectively. Based on these relationships and the data of 22 VES, the predicted values of transmissivity range between 396.4 and 8830.7 m2/day, hydraulic conductivity range from 107.6 to 7.6 m/day and the TDS vary from 413.2 to 1991.6 mg/l. These results showed that VES is a useful method for exploring the groundwater aquifer and predicting its hydraulic parameters (for example, transmissivity and hydraulic conductivity) and salinity, which can be used as a primary data for drilling groundwater wells and further agricultural irrigation in the West Nile Delta, Egypt.

A New Method to Simultaneously Measure the Soil–Water Characteristic Curve and Hydraulic Conductivity Function Using Filter Paper

Abstract The soil–water characteristic curve (SWCC) and hydraulic conductivity function (HCF) are widely used to study the hydraulic conductivity behavior of unsaturated soil. This article proposes a filter paper–based instantaneous profile method to simultaneously measure the SWCC and HCF of unsaturated soil. The method uses a small soil column that comprises several vertically stacked soil specimens sandwiched with filter papers. The water content and matric suction of the soil column are measured by weighing the soil specimens and filter papers, respectively, at regular time intervals. Therefore, the matric suction profiles and water content profiles can be obtained, and the SWCC and HCF can be calculated with the profile data. The method was applied to intact loess soil. The measured suction range is 0 to 2×105 kPa, and the measured hydraulic conductivity range is 10−5 to 10−13 m/s. Both SWCC and HCF curves display a bimodal characteristic and are consistent with previous mathematical models. This method is an inexpensive method to measure the SWCC and HCF in a large suction range.

Analysis on water-inrush the process of deep excavation in karst area caused by soil internal erosion

Non-negligible internal erosion threatens deep foundation pit excavation safety and stability. A water-inrush incident in Guilin city, a typical karst area, is thoroughly analysed theoretically after revealing groundwater seepage effects on hydraulic conductivity, internal erosion degree and water-flooding probability. The distribution characteristics of the main granular soils at the site are examined. Internal erosion by suffusion of readily erodible gap-graded soil, widely distributed in situ, is specifically studied. The hydraulic conductivity of soil can be determined by the internal erosion extent, S (%), directly calculated by the effective particle size. Comparing the influences of different parameters on permeability, it is found that the formula with uniform coefficient Cu is more practical, because it is more applicable in gap-graded soil with a wide range of hydraulic conductivity, such as the permeability coefficient range of 10−6 to 101 cm/s. The permeability coefficient-based relationship between seepage velocity and hydraulic gradient is determined. By establishing and implementing a numerical model, the pore-pressure history in each excavation phase reveals that the pore pressure notably increases during excavation, especially in areas adjacent to ancient collapse bodies. Seepage flow driven by excess pore pressure potentially generates a penetrating flow upward through the overlaying soil, possibly triggering a water-inrush incident at a maximum seepage velocity of 8.0×10−1 cm/s. Several suggestions are proposed to prevent water-inrush incidents during deep foundation pit excavation in similar geological setting areas.

GEOELECTRIC STUDY OF GROUNDWATER REPOSITORY IN PARTS OF AKWA IBOM STATE, SOUTHERN NIGERIA

Geoelectric survey employing Vertical Electrical Sounding (VES) was carried out in order to assess the groundwater repositories. A total of seven soundings were obtained with their layer resistivity, thickness and depth within the maximum electrode separation. The geoelectric parameters obtained were used to estimate the Dar-Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The result shows the aquifer resistivity ranging from 77.14 to 784.76 Ωm, with thickness ranging from 28.78 to 80.04 m. The longitudinal conductance have values ranging from 0.071 to 0.825 Ω-1 while the values of hydraulic conductivity and transmissivity range from 1.087 to 5.881 m/day and 60.180 to 374.031 𝑚2/day respectively. The contour maps generated show the variation of these parameters across the subsurface, and areas with poor protective capacity were delineated. The results also delineate the groundwater potential of the study area as moderate, while the corrosivity rating indicates non-corrosive and slightly corrosive.

GEOELECTRIC STUDY OF GROUNDWATER REPOSITORY IN PARTS OF AKWA IBOM STATE, SOUTHERN NIGERIA

Geoelectric survey employing Vertical Electrical Sounding (VES) was carried out in order to assess the groundwater repositories. A total of seven soundings were obtained with their layer resistivity, thickness and depth within the maximum electrode separation. The geoelectric parameters obtained were used to estimate the Dar-Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The result shows the aquifer resistivity ranging from 77.14 to 784.76 Ωm, with thickness ranging from 28.78 to 80.04 m. The longitudinal conductance have values ranging from 0.071 to 0.825 Ω-1 while the values of hydraulic conductivity and transmissivity range from 1.087 to 5.881 m/day and 60.180 to 374.031 𝑚2/day respectively. The contour maps generated show the variation of these parameters across the subsurface, and areas with poor protective capacity were delineated. The results also delineate the groundwater potential of the study area as moderate, while the corrosivity rating indicates non-corrosive and slightly corrosive.

Assessing the perturbations of the hydrogeological regime in sloping fens due to roads

Abstract. Roads in sloping fens constitute a hydraulic barrier for surface and subsurface flow. This can lead to the drying out of downslope areas of the sloping fen as well as gully erosion. Different types of road construction have been proposed to limit the negative implications of roads on flow dynamics. However, so far, no systematic analysis of their effectiveness has been carried out. This study presents an assessment of the hydrogeological impact of three types of road structures in semi-alpine, sloping fens in Switzerland. Our analysis is based on a combination of field measurements and fully integrated, physically based modeling. In the field approach, the influence of roads was examined using tracer tests in which the area upslope of the road was sprinkled with a saline solution. The spatial distribution of electrical conductivity downslope provided a qualitative assessment of the flow paths and, thus, the implications of the road structures on subsurface flow. A quantitative albeit not site-specific assessment was carried out using fully coupled numerical models jointly simulating surface and subsurface flow processes. The different road types were implemented and their influence on flow dynamics was assessed for a wide range of slopes and different hydraulic conductivities of the soil. The models are based on homogenous soil conditions, allowing for a relative ranking of the impact of the road types. For all cases analyzed in the field and simulated using the numerical models, roads designed with an L drain (i.e., collecting water upslope and releasing it in a concentrated manner downslope) constitute the largest perturbations in terms of flow dynamics. The other road structures investigated were found to have less impact. The developed methodologies and results can be used for the planning of future road projects in sloping fens.

Development and Assessment of a Seepage-Induced Consolidation Test Apparatus

The design, construction, and evaluation of a seepage-induced consolidation test (SICT) apparatus is described. Three materials were used in this study to encompass a range of compressibility: pure kaolin clay (kaolin), kaolin clay mixed with silica flour (silty clay), and silica flour mixed with fine sand (sandy silt). Consolidation experiments were conducted on each material in the SICT apparatus and conventional oedometer test to evaluate the ability of the experiments to measure consolidation. Consolidation behavior was characterized by void ratio versus effective stress, e-σ′, and hydraulic conductivity versus void ratio, k-e, constitutive relationships. Repeatability tests conducted on kaolin in the SICT yielded nearly identical e-σ′ and k-e relationships; oedometer results were also comparable. Constitutive relationships (e-σ′ and k-e) determined on 12 unique sets of seepage and loading pairs for kaolin were comparable to the composite e-σ′ and k-e models, which supports recommendations that a single seepage rate and single applied load can be used to determine e-σ′ and k-e relationships via the SICT. Compressibility was lower for the silty clay compared to pure kaolin because of the addition of 60 % silt; however, the range of hydraulic conductivity was nearly identical between the two materials and controlled by the kaolin. Hydraulic conductivity measured on the sandy silt in the SICT and computed from oedometer data via small-strain theory were nearly identical, which was attributed to lower compressibility that rendered small-strain theory more reasonable for oedometer data.

Sensitivity of advective contaminant travel time to the soil hydraulic parameters in unsaturated heterogeneous soils

This study deals with the sensitivity of advective contaminant travel time to soil hydraulic parameters through a heterogeneous soil profile, which is often required in many applications such as designing a monitoring network, developing a remediation strategy for contaminated sites, and determining the associated risks of subsurface contamination. The main objective is to determine relative contributions to the output uncertainty of advective travel time from individual input stochastic hydraulic parameters. A new approach is developed to examine the sensitivity of advective contaminant travel time to saturated hydraulic conductivity and macroscopic capillary drive as a result of infiltration from a wet and contaminated surface source. The approach can be applied to both non-stationary layered formation and stationary soil profile. The results demonstrate that the advective contaminant travel time is sensitive to the layers with small saturated hydraulic conductivity and small macroscopic capillary drive values. Larger uncertainty of saturated hydraulic conductivity and macroscopic capillary drive shifts the sensitive layers to the advective travel time to deeper layers. Correlation range of saturated hydraulic conductivity and macroscopic capillary drive has less significant impact on the sensitivity of advective contaminant travel time than the standard deviation. In the stationary saturated hydraulic conductivity and macroscopic capillary drive profile, although the advective contaminant travel time increase significantly for fine textured soil compared to coarse textured soil, the fractional contribution of spatial locations to the overall uncertainty of total advective travel time is virtually identical for both fine textured and coarse textured soils.

Evaluation of groundwater supply potential from hydraulic parameters estimated from vertical electrical sounding (VES) in Ikeduru, south east Nigeria

A Vertical Electrical resistivity Sounding (VES) survey was carried out, to study the groundwater supply potential, protective capacity and soil corrosivity of aquifers in Ikeduru Local Government Area of Imo state, Nigeria. A total of ten (10) geoelectric soundings were acquired. Schlumberger electrode configuration was used in acquiring the data. Six to seven geoelectric layers were delineated from the interpreted results, the Aquifers were delineated between the fifth and sixth geoelectric layers, having an apparent resistivity above 1000Ωm, with the highest thick of 69.0m at a depth of 144.0m. Longitudinal Conductance, Hydraulic Conductivity, Transmissivity and Product Conductance range are as followings for the aquifers; 1.720 – 127.000 x 10-3Ω-1, 15.90 – 188.79m/day, 1093.3 – 1097.1m2/day and 2.590 – 252.50 x 10-3 respectively. Inferring from our hydraulic parameters, all the aquiferous zones have very high designation, wwithdrawal of great regional importance of groundwater supply potential and practically noncorrosive, soil corrosivity. 40% percentage of the aquiferous units have very good protective capacity, while for excellent and good protective capacity of the study are is 30%. All the VES points are said to be a very viable potential for safe source for groundwater exploration.

Characterising Recycled Organic and Mineral Materials for Use as Filter Media in Biofiltration Systems

Filter media (FM) sourced from recycled organic and mineral materials offer an effective and low cost means of treating urban stormwater. Using recycled materials rather than the increasingly scarce source of virgin materials (typically sandy loam soil) can ensure a sustainable and long-term economy and environment. This paper presents the results from the laboratory analysis and mathematical modelling to highlight the performance of recycled organic and mineral materials in removing nutrients and metals from stormwater. The analysis included the physical and chemical characterisation of particle size distribution, saturated hydraulic conductivity (Ksat), bulk density, effective cation exchange capacity, and pollutant removal performance. The design mixes (DM), comprising a combination of organic and mineral materials, were characterised and used to develop/derive the modelling design within the Model for Urban Stormwater Improvement Conceptualisation (MUSIC v6). Comparison is made to the Adoption Guidelines for Stormwater Biofiltration Systems—Summary Report which were based on the Facility for Advancing Water Biofiltration (FAWB) guidelines to assist in the development of biofiltration systems, including the planning, design, construction, and operation of those systems. An observed outcome from over two decades of biofiltration guideline development has been the exclusion of alternative biofilter materials due to claims of excessive leaching. Results from this study indicate that high nutrient and metal removal rates can be achieved over a range of hydraulic conductivities using design mixes of recycled organic and mineral materials that have a demonstrated equivalence to existing guideline specifications.