Predicted and Back-calculated Coefficients of Permeability of Randomly Fractured Rock Mass: A Case Study

This paper presents the discrepancy between the coefficients of permeability measured for randomly fractured limestone using field falling-head tests and that back-calculated for the same rock mass based on the actual discharge yielded from a dewatering system designed for a typical construction site in Doha, Qatar. The study results showed that the back-calculated coefficient of permeability is outside the range of the values measured from the falling-head tests and almost seven times higher in magnitude than the fallinghead tests average. The need of having a reliable correlation that can be used to predict the actual permeability of randomly fractured rock in terms of its rock quality indices and the results of the commonly conducted field falling-head test is highlighted.The funding provided by the Qatar National Research Fund (QNRF), Qatar, under Project No: NPRP12S-0314-190366, for this research work is deeply appreciated

Prevention of groundwater wells from salinization by subsurface dams: A 2d numerical modelling approach

Eine anhaltende Salzwasserintrusion bei Sullurpeta (Andhra Pradesh, Indien) führte zur Versalzung der Haupttrinkwasserfassungen der Region und beeinträchtigte die regionale Wasserversorgung. Die installierten Versorgungsbrunnen sind überwiegend im Flussbett des Kalangi verfiltert. Im Jahr 2005 wurden entsprechende Abwehrmaßnahmen implementiert, welche zu einer nachhaltigen Reduzierung der Salzgehalte in den Fassungsanlagen führte. Mit Hilfe eines numerischen, dichtegekoppelten 2-D Grundwassermodells wurde die Implementierung einer hydraulischen Barriere (unterirdischer Damm) zur Abwehr einströmender salzhaltiger Wassermassen reproduziert und entsprechende Maßnahmen hinsichtlich ihrer Langfristwirkung auf das hydrogeologische System simuliert. Dafür wurde ein für die Zielregion typisches hydrogeologisches Profil in ein Finite-Elemente Modell überführt. Die Simulation der ergriffenen hydraulischen Maßnahmen bestätigt eine erfolgreiche und nachhaltige Funktionsweise des unterirdischen Damms zur Unterbindung der Salzwasserintrusion. Weitere numerische Untersuchungen wurden hinsichtlich der hydraulischen Durchlässigkeit von möglichen und für die Dammkonstruktion geeigneten Sedimenten unternommen. Auch wurden verschiedene Brunnenförderszenarien hinsichtlich ihres Einfluss auf die Qualität von den geförderten Wassermassen simuliert und dienen damit der Optimierung der hydraulischen Maßnahme.Onward saltwater intrusion into the freshwater resources in the area of Sullurpeta (Andhra Pradesh, India) led to a major salinization problem of local ground water wells and impaired the quality of extracted freshwater water volumes regionally. The installed production wells are mainly tapping the riverbed sediments of the Kalangi River. In the year 2005, technical measures for the reduction and long-term prevention of high salinization levels were installed successfully. The implementation of a subsurface dam was simulated regarding its hydraulic effectiveness based on a 2-D density-driven groundwater flow model. Additionally, further supporting technical measures were modelled for optimization reasons. Here, the numerical 2-D model reflects a characteristic riverbed/aquifer sequence of the study area. The numerical reproduction of installed hydraulic measures states a successful and sustainable implementation of the subsurface dam with respect to various production scenarios. In addition, further simulations were carried out to evaluate the influence of variable permeabilities of available natural construction materials (sediments) on the effectiveness of the hydraulic barrier

LEVANTAMENTO GEOFÍSICO (ELETRORRESISTIVIDADE) NOS LIMITES DO ATERRO CONTROLADO DO JOKEY CLUBE, VILA ESTRUTURAL, BRASÍLIA – DF

A capital do Brasil descarta seus resíduos sólidos em uma área que foi inicialmente um lixão e atualmente é administrada como aterro controlado. O aterro controlado do Jokey Clube de Brasília (JCB) não possui nenhum tipo de impermeabilização do terreno, tendo um passivo ambiental de 40 anos. O aterro do JCB já ultrapassou o limite suporte para a deposição de resíduos sólidos, mas continua sendo utilizada. Os métodos geofísicos são bastante empregados em investigações ambientais devidos os materiais poluentes apresentarem uma boa variação de contraste das propriedades físicas entre o meio que são dispostos. Neste trabalho foram utilizados os métodos de eletrorresistividade, no delineamento da pluma de contaminação por chorume. As seções de eletrorresistividade apresentaram valores de baixa resistividade e relacionada a valores de analise físico – química da água coletada em poços de monitoramento, foram associadas à presença da pluma de contaminação

Evidence for Submarine Groundwater Discharge into the Black Sea—Investigation of Two Dissimilar Geographical Settings

The sustainable management of coastal marine environments requires a comprehensive understanding of the processes related to material transport from land to coastal sea. Besides surface water discharge (e.g., rivers and storm drains), submarine groundwater discharge (SGD) plays a key role since it provides a major pathway for solute and particulate transport of contaminants and nutrients, both having considerable potential to cause deterioration of the overall ecological status of coastal environments. The aim of the presented study was the investigation of SGD in two exemplary and dissimilar areas at the Black Sea coast, one in the west (Romania) and one in the east (Georgia). The approach included the assessment of the geological/geographical setting regarding the potential of SGD occurrence, the use of environmental tracer data (222Rn, δ18O, δ2H, salinity), and the evaluation of sea surface temperature patterns near the coastline using satellite data. Besides the individual site specific results, the study revealed that a combined evaluation of tracer data and satellite based information allows SGD localization with satisfying precision. A downscaling approach starting with large scale satellite data is generally recommended, continuing with medium scale tracer patterns and ending with local spot sampling

Improved Approach for the Investigation of Submarine Groundwater Discharge by Means of Radon Mapping and Radon Mass Balancing

The paper presents an improved approach for investigating submarine groundwater discharge (SGD) based on radon mapping and radon mass balancing in the coastal sea. While the use of radon as an environmental tracer in SGD studies is well-established, we identified based on our longstanding experience six methodical shortcomings of the conventional approach and suggest corresponding developments. The shortcomings include: (1 and 2) inadequate consideration of both detection equipment response delay and influence of tidal stage; (3 and 4) incorrect quantification of radon losses, due to offshore mixing and degassing resulting in a potentially incorrect radon mass balance; (5) inaccurate determination of the terrestrial groundwater endmember, due to inhomogeneous radon distribution in the coastal aquifer; and (6) difficulties in distinguishing between discharged fresh groundwater and recirculated seawater. The improved approach is practically demonstrated in a step by step manner in a large-scale field study, which was carried out in False Bay (South Africa) and which consisted of two parts, namely (i) qualitative SGD localization along the entire False Bay coastline based on coastal radon distribution patterns and (ii) quantitative SGD investigation within a defined coastal area of interest (AOI) based on a radon mass balance (RMB). The plausibility of the AOI related results was evaluated by a hydrogeological model, used for qualitative SGD localization, and a hydrological model, applied for estimating groundwater recharge within the AOI catchment

Compound Specific and Enantioselective Stable Isotope Analysis as Tools To Monitor Transformation of Hexachlorocyclohexane (HCH) in a Complex Aquifer System

Technical hexachlorocyclohexane (HCH) mixtures and Lindane (γ-HCH) have been produced in Bitterfeld-Wolfen, Germany, for about 30 years until 1982. In the vicinity of the former dump sites and production facilities, large plumes of HCHs persist within two aquifer systems. We studied the natural attenuation of HCH in these groundwater systems through a combination of enantiomeric and carbon isotope fractionation to characterize the degradation of α-HCH in the areas downstream of a former disposal and production site in Bitterfeld-Wolfen. The concentration and isotope composition of α-HCH from the Quaternary and Tertiary aquifers were analyzed. The carbon isotope compositions were compared to the source signal of waste deposits for the dumpsite and highly contaminated areas. The average value of δ¹³C at dumpsite was −29.7 ± 0.3 ‰ and −29.0 ± 0.1 ‰ for (−) and (+)­α-HCH, respectively, while those for the β-, γ-, δ-HCH isomers were −29.0 ± 0.3 ‰, −29.5 ± 0.4 ‰, and −28.2 ± 0.2 ‰, respectively. In the plume, the enantiomer fraction shifted up to 0.35, from 0.50 at source area to 0.15 (well T1), and was found accompanied by a carbon isotope enrichment of 5 ‰ and 2.9 ‰ for (−) and (+)­α-HCH, respectively. The established model for interpreting isotope and enantiomer fractionation patterns showed potential for analyzing the degradation process at a field site with a complex history with respect to contamination and fluctuating geochemical conditions