Towards a multi-faceted Vadose Zone Assessment Protocol : cemetery guidelines and application to a burial site located near a seasonal wetland (Pretoria, South Africa)

Cemeteries are generally considered low-risk landfills and are, therefore, not adequately governed in terms of minimum requirements for engineering geological and hydrogeological investigations. With the decay of human bodies, bulk of the contaminant load typically is present within one year of burial and decreases over time. Further controls include adsorption of pathogens and particulates to soil in the vadose zone and eventual breakdown in changing aerobic and anaerobic subsurface environments. A case study is presented where a cemetery has been active for decades and contains in excess of 18 000 human bodies. With recent expansion, water seepage was identified into newly excavated burial pits and all further development has ceased. Trial pitting and detailed soil profile descriptions are used to infer hydrological interaction at the site and to address possible contamination pathways. Future work is recommended with respect to water quality, although valuable insight is provided to the consequences of improper ground investigation prior to development. Final comments are made regarding provisional guidelines in the forms of a Cost-Effort-Risk Screen and a multi-faceted Vadose Zone Assessment Protocol.South African Water Research Commission (WRC) of South Africa (project K5/2052)http://link.springer.com/journal/10064hb201

Porosity reviewed : quantitative multi-disciplinary understanding, recent advances and applications in vadose zone hydrology

Porosity—one of the most basic mechanical properties of a medium—has implications in a vast range of disciplines and used for a similar vast range of applications. These include, for instance, the storage and flow of water; the compressible component of earth materials, which can be subjected to consolidation under loading; the variable parameter in the swelling and shrinkage of clays; and possibly a governing parameter in the formation of wetlands and perched water tables. This review notes the relevance of a fourfold quantification of porosity for vadose zone studies, viz. (1) type (matrix or structure), (2) scale (submicro to macro scale), (3) connectivity, and (4) water saturation. This is followed by a review of recent advances in the quantification and description of porosity in porous media (visual and remote sensing methods, porosimetry, geometrical approaches, empirical estimations, densest packing simulations, etc.), the applications to quantification of hydrological parameters, and a brief glimpse into the significance of porosity in a temporary hillslope wetland underlain by Archaean Lanseria gneiss in South Africa. Final comments are made regarding areas where quantification of porosity is problematic.South African Water Research Commission (number K5/2052)http://link.springer.com/journal/10706hb201

Towards hydrological and geochemical understanding of anephemeral palustrine perched water table “wetland” (Lanseria Gneiss, Midrand, South Africa)

Wetland delineation is commonly based on terrain unit, soil form, soil wetness and vegetation indicators. These and the shallow groundwater or proximate surface water are often absent in many ephemeral inland South African areas due to, for instance, prolonged dry periods (seasons to years) which mask these indicators, as well as disruption of surface materials due to construction, agricultural activities and field fires. Furthermore, many “wetlands” in South Africa comply with the four indicators, but the notable absent requirement for wetlands are missing, namely the shallow groundwater table, as many of these systems form in hillslope seeps, catenas or from perched water tables. A 200 m long excavation through one such a system is being studied in Midrand (Gauteng, South Africa). The site is underlain by Lanseria Gneiss and is waterlogged after long and intense periods of intense rainfall. Frequent downslope soil profiling, horizonspecific laboratory analyses for grading and Atterberg Limits, X-Ray Diffraction and X-Ray Fluorescensce Spectroscopy data are interpreted together with soil percolation tests to generate a conceptual model of the system. The results are discussed in terms of the need to consider these temporary systems that do not have a shallow groundwater table and that are not in direct contact with surface drainage features as a possible special type of wetlands, notably in arid regions where they play a very important role in biodiversity and should, therefore, be protected.http://link.springer.com/journal/12665hb201

Characterisation of some fractured-rock aquifers in Limpopo province, South Africa : review and case study

This dissertation collates all available data from the Department of Water Affairs and Forestry’s (DWAF’s) National Groundwater Database (NGDB), DWAF’s Groundwater Resource Information Project (GRIP) and tests conducted during the progress of this project in order to evaluate Basement aquifers. The project was commenced at the request of the Water Research Commission (WRC), situated in Pretoria, South Africa. The study area (Limpopo and Luvuvhu-Letaba Water Management Areas, WMA1 and WMA2 respectively) is underlain by fractured, crystalline Basement terrain. The influences of structures (i.e. joints, faults and shear zones) and the neotectonic stress conditions were also studied to address the influence on groundwater flow and occurrence. The aim of the project was to address the determination of the aquifer parameters (essentially transmissivity and sustainable yield) in Basement terrane. Pumping test data was used and analysed via the Flow Characteristic Programme (Institute for Groundwater Studies, University of Free State). The methods of Logan (1964), Theis (1935), Cooper-Jacob (1946) and Birsoy-Summers (1980) were applied for comparative purposes. Statistically, all four methods supplied results within the same order of magnitude, with Theis and Cooper-Jacob correlating extremely well. Results from the Logan and Birsoy-Summers methods correlated very well too, but the T-values calculated via Logan’s method were almost double those obtained from the step-drawdown data analysed via the Birsoy-Summers method. The combined results adhered to a developed model-setting-scenario approach where each borehole can be evaluated based on three parameters. Firstly, the model refers to the potential water-bearing and/or water-barring features. In the study area, it was found that water predominates in the Hout River Shear Zone, and that the neotectonic stress fields have little influence on determining the orientation of favourable water-bearing structures. Geological contacts often resulted in higher yielding boreholes than geological structures. Secondly, the setting refers to the climatic and tectonic setting of the site. This determines the recharge and the orientation of structures. Based on this, supposedly closed structures (due to prevailing neotectonic stress fields) often supplied higher yielding boreholes than the supposedly open structures. Rainfall and climate however had little influence on the results. Finally, the scenario ranks a borehole in terms of high, intermediate or low transmissivity and subsequently potential yield. High T-values typically exceeded 100 m2/d whereas low T-values were generally below 5 m2/d. Significantly low yielding boreholes therefore formed part of the Low T Scenario, and high yielding boreholes of the High T Scenario. CopyrightDissertation (MSc)--University of Pretoria, 2008.Geologyunrestricte

Aquifer vulnerability using recharge, depth to groundwater, soil type and slope to classify the vadose zone (Molototsi and Middle Letaba quaternary catchments, Limpopo Province, South Africa)

The aquifer vulnerability of the Molototsi (B81G) and Middle Letaba (B82D) quaternary catchments was assessed to determine the influence of the vadose zone on the groundwater regime. The aquifer vulnerability was assessed by developing a new method, which evaluates the vadose zone as a pathway for pollutants using the following four parameters: recharge, depth to water table, soil type (saturated vertical hydraulic conductivity) and slope (RDSS). Recharge was estimated using the chloride mass balance method, and the depth to the water table was measured in the field using dipmeter. The seepage behaviour (soil type) was determined as hydraulic conductivity from in situ infiltration and percolation testing (SABS 0252-2:1993 and double ring infiltrometer). The slopes were determined with the digital elevation method using ArcGIS software. The four parameters were overlaid using weighted sum, weighted overlay and raster calculator to produce the vulnerability map. Different weightings were attributed in the methods and the best selected. The results obtained indicated high vulnerability on the lower and upper parts of both catchments. The benefits of the method described are (a) the easy quantification of the parameters through fairly simple methods and (b) the exclusion of arbitrary index values.National Research Fo ndation (NRF).Water Research Commission (WRC) of South Africa (Report No. KV 243/10)http://link.springer.com/journal/12665hb201

On the cubic law and variably saturated flow through discrete open rough-walled discontinuities

Fracture flow is fairly well documented with the widespread application of, for instance, the cubic law and assumed smooth parallel plate model. Geometrical intricacies such as aperture, roughness and infill do however significantly influence the validity of the cubic law with even its application to smooth parallel systems being contestable. Rock mechanical discontinuity surveys provide valuable information regarding the discontinuity geometry that can likely contribute to the evaluation of flow through individual fractures with variable properties. The hydraulic aperture is available for the transmission of flow, while normal and shear stresses alter discontinuity properties over time. In this, numerous advances have been made to better accommodate deviations of natural discontinuity geometry to that of smooth parallel plates and at partial saturation. The paper addresses these advances and details conditions under which the cubic law, even in local form, fails to adequately estimate the hydraulic properties. The role of roughness in open discontinuities is addressed in particular, as contact areas and high amplitude roughness cause most extensive deviation from the cubic law. Aperture of open fractures still governs hydraulic properties, but inertial forces control flow in very rough fractures, in which instances the applicability of the cubic law should be revisited. Open questions are finally posed,assessment of which will contribute significantly to the understanding of flow through individual discontinuities as well as fracture networks.The Water Research Commission of South Africa (www.wrc.org.za) for funding of project K5/2052 [68] on Multidisciplinary Vadose Zone Hydrology, as well as project K5/2326 on Quantification of Unsaturated Flow in the Fractured Intermediate Vadose Zone by means of Geotechnical Centrifuge (to be published by the WRC in 2016).http://www.elsevier.com/locate/ijrmms2017-11-30hb2016Geolog

Review of engineering, hydrogeological and vadose zone hydrological aspects of the Lanseria Gneiss, Goudplaats-Hout River Gneiss and Nelspruit Suite Granite (South Africa)

Please read abstract in the article.Water Research Commission of South Africa (WRC) project K5/2052 on Multi-disciplinary Vadose Zone Hydrologyhttp://www.elsevier.com/locate/jafrearscihb201

A laboratory study of the pollution of formaldehyde in cemeteries (South Africa)

Cemeteries are known to be associated with soil and groundwater pollution from contaminants in coffin materials. However, possible contamination from embalming fluids such as formaldehyde has not been investigated. Formaldehyde is a recognised carcinogen, which is primarily toxic after inhalation, skin contact or ingestion. Although it is maintained that formaldehyde breaks down into innocuous compounds, this has not been established at sites such as cemeteries where there is a continuous addition of formaldehyde-preserved bodies, sometimes on a daily basis. It is also not confirmed whether different soil types and environmental conditions affect the leaching of formaldehyde into groundwater resources. This study comprises a laboratory study of the leaching potential of formaldehyde through different soils and environmental conditions. Twenty-seven containers with taps were filled with either sandy, silty or clayey soils. Samples of burial materials and a cloth saturated with formalin were buried within each column. These were exposed to conditions simulating that of the environment, i.e. (1) different temperatures, (2) heavy or prolonged rainfall and (3) using either acidic or slightly acid water. Leachate samples were collected every 2 weeks for a period of 24 weeks and analysed for formaldehyde using acid titration. The results showed that most formaldehyde percolated through the soil between week 6 and week 14 of interment, with a greater amount being leached from sand. Neither temperature nor pH affected the amount of formaldehyde leached; however, conditions simulating heavy rainfall facilitated leaching. Although a total of only 3% of the initial amount of formaldehyde mobilised, concentrations of up to 15 mg/L formaldehyde were recorded on two occasions, exceeding the tolerable concentration recommended by the World Health Organisation.Water Research Commission of South Africa [K5/2449]http://link.springer.com/journal/12665hj2019Geography, Geoinformatics and MeteorologyGeolog

Mechanical and hydraulic properties of residual dolomite and wad

The properties of residual dolomite, sometimes termed wad, are variable and uncertain. It represents the insoluble residue after dissolution of dolomite and is commonly found in the Neoarchaean Malmani Subgroup of the Chuniespoort Group (South Africa). This study comprised triaxial tests, crumb tests, X-Ray diffraction and fluorescence spectroscopy, foundation indicators, stereo-microscope imagery and permeability testing of the represented formations outcropping in the northeastern portions of South Africa. Results concur that residual dolomite is not typically dispersive, has low density that can be below that of water, mostly grades in the silt fraction, has high plasticity indices with low to high liquid limits, and has hydraulic conductivities in the order of 1x10-6 m/s. This new knowledge database contributes to our understanding of the flow through these systems and to how ingress scenario subsidences and sinkholes can possibly occur.The South African Water Research Commissionhttp://www.gssa.org.zapm2020Geolog

Lugeon tests at partial saturation : experimental and empirical contributions

Implications of improved understanding of variably saturated flow are numerous, especially given the complexity, heterogeneity, and anisotropy of the intermediate fractured vadose zone. One such an implication is the quantification of water movement for engineering purposes, as flow-through unsaturated discontinuities cannot be quantified through commonly applied saturated approaches. This paper presents an experimental study using geotechnical centrifuge modelling to investigate flow behaviour during Lugeon tests, through the fundamental concept of a smooth, clean, open fracture, at partial saturation. The study comprised flow visualisation experiments conducted on transparent replicas of horizontal and inclined fractures, with water injected under a consecutive series of ascending and descending pressures. Findings from the research proved that preferential flow occupied the minority of cross-sectional area despite the hydraulic pressure. Furthermore, the observed behaviour of these preferential pathways indicated non-linear flow. Deviation from linearity occurred at small fluxes and is likely as a result of inertial effects due to fluid bending at the inlet source into the fracture. To assess these non-linear results, the Forchheimer relationship was used to predict the flow rate at the imposed hydraulic heads. As the width of the fracture could not be used as input into the equation, due to the lack of saturation across its width, the width of the flow path was used instead. This resulted in the predicted results comparing well with the measured flow rates, and indicates that the Forchheimer relationship can potentially be used to describe unsaturated flow in discrete, open fractures.The South African Water Resource Commission (http://www.wrc.org.za) for their financial support by projects K5/2326, together with the National Research Foundation (NRF).http://link.springer.com/journal/6032020-02-01hj2018Geolog