bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inverse Modeling of Coastal Aquifers Using Tidal Response and Hydraulic Tests
Authors: Alcolea Andrés , Castro Eduardo , Barbieri Manuela , Carrera Jesús , Bea Sergio 
Published: August 2007

AbstractRemediation of contaminated aquifers demands a reliable characterization of hydraulic connectivity patterns. Hydraulic diffusivity is possibly the best indicator of connectivity. It can be derived using the tidal response method (TRM), which is based on fitting observations to a closed‐form solution. Unfortunately, the conventional TRM assumes homogeneity. The objective of this study was to overcome this limitation and use tidal response to identify preferential flowpaths. Additionally, the procedure requires joint inversion with hydraulic test data. These provide further information on connectivity and are needed to resolve diffusivity into transmissivity and storage coefficient. Spatial variability is characterized using the regularized pilot points method. Actual application may be complicated by the need to filter tidal effects from the response to pumping and by the need to deal with different types of data, which we have addressed using maximum likelihood methods. Application to a contaminated artificial coastal fill leads to flowpaths that are consistent with the materials used during construction and to solute transport predictions that compare well with observations. We conclude that tidal response can be used to identify connectivity patterns. As such, it should be useful when designing measures to control sea water intrusion.
Flow to a Well in a Five‐Layer System with Application to the Oxnard Basin
Authors: Li Yanhua , Neuman Shlomo P. 
Published: August 2007

AbstractNearly 40 years ago, Neuman (1968) developed an analytical solution for drawdown in a system of three aquifers separated by two aquitards when one of the aquifers is pumped at a constant rate. Whereas the simpler case of two aquifers separated by one aquitard has been presented by Neuman and Witherspoon (1969a), the full five‐layer solution has not been previously evaluated. We do so here using numerical inversion of its Laplace‐transformed version and present selected results graphically in dimensionless form. The solution demonstrates that the effect of pumping propagates across all five layers, adding emphasis to a question previously raised by Neuman and Witherspoon about the validity of leaky aquifer theories that disregard drawdowns in unpumped aquifers. A large‐scale, long‐term pumping test spanning three aquifers separated by two aquitards near Oxnard, California, has been conducted and analyzed by Neuman and Witherspoon (1972). They evaluated the vertical hydraulic diffusivities of the aquitards using the Neuman‐Witherspoon ratio method and their specific storage values on the basis of laboratory consolidation tests. We reinterpret the Oxnard pumping test by coupling the five‐layer analytical solution of Neuman (1968) with the parameter estimation code PEST (Doherty 2002) and validate our results against drawdowns from a subsequent pumping test at the site. Our parameter estimates compare favorably with those of Neuman and Witherspoon (1972).
Estimating Ground Water Recharge using Flow Models of Perched Karstic Aquifers
Authors: Weiss Menachem , Gvirtzman Haim 
Published: August 2007

AbstractThe fraction of rain that is annually recharged to ground water is a function of the transient quantities of precipitation (wet vs. dry years) as well as other meteorological and geologic factors, and thus it is very difficult to estimate. In this study, we have used long records (20 to 30 years) of precipitation and spring discharge to reconstruct the transient character of yearly recharge. These data sets were used to calibrate numerical ground water flow models on the less than 3 km2 scale for four separate perched karstic aquifers in the Judean and Samarian Mountains of Israel. The stratification and karstic character of the local carbonate rock aquifers cause ground water to flow through discrete dissolution channels and to discharge at isolated springs. An innovative, dual‐porosity approach was used where a finite‐difference solution simulates flow in the rock matrix, while the karstic channels are simulated using computationally simple drains. Perched conditions are also simulated innovatively using MODFLOW by treating the bottom unsaturated layer as if it is saturated, but by assuming zero pressure head throughout the “unsaturated” layer. Best fitting between measured and computed spring hydrograph data has allowed us to develop a set of empirical functions relating measured precipitation to recharge to the aquifer. The generic methodology presented gives insight into the suspected changes in aquifer recharge rates between particularly wet or dry years.
Energetic Compound False Positives in Ground Water Profile Samples
Authors: Clausen Jay , Wessling Elizabeth , Chirgwin Brad 
Published: August 2007

AbstractThe analytical procedure U.S. EPA SW‐846 method 8330 is the predominant technique used for analysis of energetic compounds in water and soil. The basis for compound identification is nonspecific and for some complex samples may yield false‐positive results for energetic compounds. Suspended particulates and drilling fluids are potential interferents introduced to ground water profile samples. Profile samples had a higher frequency of false positives relative to monitoring well samples. Additionally, the false‐positive frequency was lower in samples where no lubricants or greases were used during drilling and sampling. Protocol refinements, the inclusion of photodiode array (PDA) spectral analysis, visual inspection of chromatograms and PDA spectra, and careful manual data evaluation have reduced false‐positive detections. A project team investigating ground water with the potential for energetic compounds must have extensive experience with method 8330, knowledge of how to use PDA analysis, and experience in interpreting chromatograms and PDA spectra for the target compounds.
Ground Water Transfer Initiates Complete Reductive Dechlorination in a PCE‐Contaminated Aquifer
Authors: Lookman R. , Paulus D. , Marnette E. , Pijls C. , Ryngaert A. , Diels L. , Volkering F. 
Published: August 2007

AbstractWe conducted a field test to investigate whether ground water transfer from one site (showing complete natural reductive dechlorination of chlorinated ethenes to ethene) could induce full reductive dechlorination at another site polluted with tetrachloroethene and its partial dechlorination products trichloroethene and cis‐dichloroethene (cDCE). Addition of electron donor (lactate) at the test site established low redox conditions but did not stimulate further dechlorination past cDCE. After transferring 2 m3 of ground water from the first site to the test site, full dechlorination commenced and high levels of ethene were measured to distances up to 6 m downstream of the injection location within 7 months. Ground water samples from monitoring wells were analyzed before and after inoculation of the test site for the presence of Dehalococcoides species (16S ribosomal RNA) and vinyl chloride reductase (vCRA) genes using the polymerase chain reaction. These tests showed that Dehalococcoides species were present both before and after ground water transfer, while vCRA genes were detected at the test site only after ground water transfer. The vCRA genes were detected in ground water samples collected 6 m downstream of the injection locations 7 months after ground water transfer, suggesting that the microorganisms carrying the dehalogenase genes were effectively transported in the aquifer.
PREDICTION OF TRANSCRIPTION FACTOR BINDING SITES USING GENETICAL GENOMICS METHODS
Authors: VON ROHR PETER , FRIBERG MARKUS T. , KADARMIDEEN HAJA N. 
Published: August 2007

In this paper, we wanted to test whether it is possible to use genetical genomics information such as expression quantitative trait loci (eQTL) mapping results as input to a transcription factor binding site (TFBS) prediction algorithm. Furthermore, this new approach was compared to the more traditional cluster based TFBS prediction.The results of eQTL mapping are used as input to one of the top ranking TFBS prediction algorithms. Genes with observed expression profiles showing the same eQTL region are collected into eQTL groups. The promoter sequences of all the genes within the same eQTL group are used as input in the transcription factor binding site search. This approach is tested with a real data set of a recombinant inbred line population of Arabidopsis thaliana. The predicted motifs are compared to results obtained from the conventional approach of first clustering the gene expression values and then using the promoter sequences of the genes within the same cluster as input for the transcription factor binding site prediction.Our eQTL based approach produced different motifs compared to the cluster based method. Furthermore the score of the eQTL based motifs was higher than the score of the cluster based motifs. In a comparison to already predicted motifs from the AtcisDB database, the eQTL based and the cluster based method produced about the same number of hits with binding sites from AtcisDB.In conclusion, the results of this study clearly demonstrate the usefulness of eQTL to predict transcription factor binding sites.
Landslides caused by rapid groundwater changes
Authors: Premchitt J. , Brand E.W. , Phillipson H.B. 
Published: August 2007

Abstract
A severe rainfall event occurs once every two years in Hong Kong, causing widespread landslides which result in human casualties and much damage. It has recently been established that these landslides are caused largely by short-period, high-intensity rainfall, with nearly all failures occurring within a few hours of peak intensity. The failures are therefore attributable mainly to rapid transient variations in groundwater conditions. These findings are in contradiction to previously accepted theories on failure mechanisms, and it is therefore necessary for these to be reconsidered.
A new theoretical model is now being examined in Hong Kong to explain the rapid landslide response following high-intensity rainfall. This is based on well-defined hillslope hydrological theories. Of particular significance in this context are thought to be subsurface erosion pipes and tunnels which have been found to exist in some of Hong Kong’s hillslopes, especially those carpeted with colluvium.
The inter-relationship between changes in groundwater conditions and engineering construction
Authors: Brassington F.C. 
Published: August 2007

Abstract
The presence of groundwater and its effects are often major considerations in the design of civil engineering works. The engineering geologist is expected to provide reliable information on this subject by means of appropriate site investigation techniques. In many instances possible changes in groundwater levels beyond the normal seasonal variations are not considered. Large changes can occur, for example, a reduction in groundwater pumping will cause water tables to rise, flooding basements and tunnels and possibly changes in the load bearing properties of soils. Civil engineering construction can have a similarly significant effect on local water supplies especially in the case of road cuttings, tunnels and pipelines. The British Standard Code of Practice for Site Investigations (BS 5930: 1981) does not contain any recommendation that site investigations should include an examination of local groundwater abstraction. Nor does it suggest that surveys should be carried out to locate and identify local private water supplies where there is a danger that the proposed construction will affect them. It is recommended that the Code of Practice is amended to include both these omissions.
Groundwater conditions in the coastal landslides of the Isle of Sheppey
Authors: Dixon N. , Bromhead E.N. 
Published: August 2007

Abstract
The paper describes an investigation into the groundwater pressure distribution in two sections through the 46 m high London Clay cliffs at Warden Point, Isle of Sheppey. Over 50 piezometers were installed, and these show a groundwater pressure regime which indicates a significant degree of response to stress relief. The paper describes the influence of these pressures on the mechanics of failure of the cliffs, and the engineering implications of their presence.
The effects and consequences of groundwater abstraction on foundations at Drax Power Station, North Yorkshire
Authors: Dobie M. , Newman R.L. 
Published: August 2007

Abstract
In order to provide an additional supply of water for Drax Power Station the CEGB proposed to abstract water from the Bunter Sandstone aquifer which underlies the site. A pumping test was carried out to assess the effects of abstraction, and this involved monitoring groundwater pressures and surface deformations.
The first part of the paper details the ground and groundwater conditions, and describes the design of the pumping test and installation of the instrumentation. Theoretical aspects of analysis and response of groundwater pressures to abstraction are also discussed.
The second part of the paper outlines and analyses the results of the pumping test. The results are presented as a series of graphs of drawdown, surface deformation, and duration and rate of pumping. The true aquifer characteristics were determined from the pumping test results using the analysis of Thiem incorporating Huisman's procedures for partially penetrating wells. Using the same analyses the effects of the pumping test are extrapolated to proposed 'licenced' rates. A discussion follows on the results and some interesting observed responses.
The final part of the paper assesses the consequences of surface deformations due to groundwater abstraction on existing and proposed structures. In particular, the effects of large differential settlements between buried services and piled structures, and also induced negative skin friction on vertical and raking piles are considered. Recommendations were subsequently given on the siting of the well which minimised its effects.
Rising groundwater levels in cities
Authors: Hurst C.W. , Wilkinson W.B. 
Published: August 2007

Abstract
It is well documented that groundwater levels in a number of cities in this country and abroad have been rising over the past few years. Parts of central London are experiencing rises of one metre per year, while in Paris, previously dry basements are now affected by severe flooding.
The extraction of good quality water from city wells for a variety of industrial and domestic purposes led to a general lowering of groundwater levels from the early 1800s. During the period of depressed groundwater levels development within restricted city centre sites required higher buildings with deeper basements and foundations. Communication networks also moved underground to ease congestion at the surface. A large percentage of this work was carried out during a period when the groundwater was tens of metres below ground level; a situation accepted as being stable at the time. Consequently the effect of a higher water table was often not considered in the geotechnical design of structures. Within central London the water table is still very deep and may not cause problems for years to come. In Birmingham the situation is more critical and the rise in groundwater level is already causing problems.
Computer model predictions play a leading role in predicting tomorrow’s groundwater levels. Evidence suggests that groundwater levels in the near future will attain those of natural conditions. The effect that these levels will have on current structures requires assessment. Simplified calculations for the London area show that the bearing capacity of deep basement foundations and piles could be reduced by 25’30% if the rise in groundwater level continues. High levels of sulphates have been recorded during recharge experiments and these will produce adverse effects on unprotected foundations. Problems with high artesian pressure during construction are also likely if the aquifer is confined. These is an urgent need to assess the geotechnical risk to engineering structures with respect to the rising groundwater levels. This should be carried out now so that problems can be properly anticipated and solutions developed in good time.
Tidal variations of groundwater level in an estuarine aquifer
Authors: Money M.S. 
Published: August 2007

Abstract
Groundwater levels in coastal aquifers respond to tides with amplitudes that decrease and time lags that increase inland. Analysis of tidal variations is complicated by the fact that long-term cycles are superimposed on the main diurnal cycle so that there are small but significant differences between successive tides and in the piezometric response.
It is shown that type curves can be constructed on the basis of simple theory to predict the piezometric response by using tidal factors as in navigational calculations.
Type curves have been drawn for piezometers on a site in the Tees estuary but these do not conform with the theoretical plots and it is suggested that the discrepancies are due to groundwater flow towards the coast. Recommendations are made for data collection.
Effects of groundwater on soils, rocks and construction materials: an introduction
Authors: de Freitas M.H. 
Published: August 2007

ABSTRACT
Although the effects of groundwater on soils, rocks and construction materials may appear to be slow to occur, there is increasing evidence to demonstrate that such effects progress at rates that are significant to engineering. A growing body of evidence that demonstrates the influence exerted by groundwater chemistry and flow upon the geotechnical character of the ground is also accumulating. With these thoughts in mind the papers submitted to this session of the conference are introduced and the work they describe reviewed.
The effect of groundwater flow on the strength and stability of silicate grouted soils
Authors: Shirlaw J.N. 
Published: August 2007

ABSTRACT
A considerable volume of data on the strength of silicate grouted soils has been published in recent years. In particular there has been considerable discussion of the confined and unconfined strengths of grouted sands and the effect of creep on those strengths. Little has been said on the effect of groundwater seepage on the strength and residual permeability of the sand/silicate system.
Following observations on site into the effectiveness of silicate grouting, a small laboratory programme was set up to examine the effect of seepage on strength and residual permeability. The findings of the programme are summarised.
Hazardous waste containment
Authors: Mitchell J.K. 
Published: August 2007

ABSTRACT
Containment systems that have been developed to isolate wastes from the soil and water that surround them in the ground include compacted clay barriers, slurry trench cutoff walls, geomembrane walls, concrete diaphragm walls, sheetpile walls, grout curtains, hydraulic barriers, compacted clay liners, and geomembrane liners. The choice in any case is dictated by whether waste from an existing facility or spill or from a new disposal site is to be contained and by the geological setting.
Properly compacted clays have properties that are well-suited for waste containment, as do flexible membrane liners. Compatibility between these materials and the waste must be considered in any case. Evidence is accumulating that the hydraulic conductivity of properly compacted clay is not significantly affected by exposure to most organic solvents and inorganic chemical wastes in dilute solution. Double liner designs that incorporate both compacted clay and flexible membrane liners as well as leachate collection systems have been proposed to satisfy the requirements of recent legislation in the USA.
The higher temperatures and long times associated with nuclear waste isolation by deep burial pose special problems of barrier stability. It appears that smectite clay has adequate stability to be used for repository buffer and seal material.
Trace organic compounds in groundwater: a survey of unpolluted groundwater from three major British aquifer systems
Authors: Clark L. , Kenrick M.A.P. 
Published: August 2007

ABSTRACT
In view of the increased concern about the occurrence and persistence of organic chemicals in the environment, the Water Research Centre instigated a baseline survey of trace organics in groundwater from representative cross-sections of three major British aquifer systems.
A total of 32 public and private supply boreholes in selected areas of the Permo-Triassic Sandstone, Chalk, Lincolnshire Limestone and the Great Oolite aquifers have been sampled. The areas have been chosen with the aim of characterising the organic content of ‘clean’ groundwater from the confined and unconfined zones on each cross-section. The survey was designed to encompass groundwaters of varying ages, from recent recharge in outcrop areas through to ancient waters in deep confined sections. In this way, it was expected that any compounds of anthropogenic origin would be detected only in the younger groundwaters.
The total organic carbon content of the groundwaters sampled was generally very low, between 0.2 and 1.4 mg/1; low levels of aromatic halogenated hydrocarbons, which are generally taken to be contaminants, were found in many of the samples at levels above 0.01 µg/1; low levels of aromatic hydrocarbons were often detected. Although the number of compounds detected averaged 20 per sample (range: 7 to 52), few were present at concentrations greater than 0.1 µg/1. Over 100 different compounds were detected altogether but only 75 could be identified positively. Of these, nine occurred in more than half of the samples. There were no obvious differences in either compound types or levels between the confined and unconfined zones of any of the aquifers.
Uncontaminated groundwater examined in this survey may be typified as having a TOC level below 0.8 mg/1, and no more than four compounds (none of which are chlorinated hydrocarbons) present at levels above 0.1 µg/1.
Application of isotope hydrology to groundwater problems in engineering geology
Authors: Leggo P.J. , Warren C.D. , Blakeway D. 
Published: August 2007

ABSTRACT
Research on the natural variation of the isotopic species of hydrogen and oxygen has led to a firm understanding of the physical processes involved in the isotopic fractionation of these elements in water. Although much use has been made of artificially introduced chemical tracers to investigate flow patterns and characterise the groundwater, this method commonly suffers from bulk dilution and additional problems that limit its applicability to many investigations in engineering geology. Such limitations are avoided in the use of stable isotopic measurements as it is the variability in the isotope species of the water molecule itself that are used as the characterisation parameters providing a ‘fingerprint’ for each particular water sample.
In this paper background details of stable isotopic fractionation are summarised and two recent case histories presented to demonstrate its application to groundwater studies, on a small scale, commonly met in many civil engineering situations, namely investigation of possible leakage from a reservoir and identification of the source of water contained within a large landslip. By the seasonal variations in the isotopic values, trends in groundwater isotopic composition can be identified and interpreted within the often limited geological and hydrogeological constraints of the site so as to provide conclusions as to the origin of the groundwaters.