bluuebunny/crossref_metadata_2025 huggingface dataset:
Survey and containment of contaminated underwater sediments
Authors: Degen B. T. A. J. , Deibel I. K. , Maurenbrecher P. M.
Published: April 2008

The underwater sediments of the waterways, lakes and harbours of the Netherlands are sufficiently contaminated in many areas to necessitate their removal or isolation. The degree and nature of contamination and the general extent can be determined by sampling methods. To determine the thicknesses and distribution of the contaminated layers, shallow reflection geophysical surveys can be used in many situations, especially if previous erosion or dredging has created a slightly overconsolidated layer relative to subsequent deposition. The method is also used to aid investigation with respect to quantity control for sand placement to contain contaminated sediments
in situ
and to determine the depositional modes of hydraulically transported contaminated spoil in repository basins. Repository design for the Ketelmeer Lake allows for a certain amount of contaminant loss to the environment. The principal criterium is to significantly lessen contamination by 50%. Complete isolation would only improve the drop in contamination levels by a further small percentage.
Use of geophysical surveys during the planning, construction and remediation of landfills
Authors: Reynolds John M. , Taylor David I.
Published: April 2008

There are growing environmental pressures over the development, use and remediation of closed landfill sites throughout the UK, as well as overseas. There is also a reluctance to use direct investigative methods for fear of compromising the integrity of the landfill cap and liner systems. Consequently, there is an increasing role for geophysical surveys to be undertaken that are technically reliable, cost-effective and environmentally benign.

Geophysical surveys have been proven to be successful in the assessment of site suitability during the planning stage. For example, evidence of former mining, adverse geological structure, soft zones and areas with anomalous permeability may be detected. Geophysics can be used for mapping the thickness of mineral liners during the construction phase. Closed landfill sites can be investigated geophysically without invasion of the structure to determine the location of margins and the depth of fill, map possible leachate ponding and migration, and to assess the integrity of mineral and artificial liners, etc.

It is concluded that with current developments in data acquisition, processing, display and interpretation of geophysical data, the scope of environmental applications where multi-method geophysical surveys can be used is increasing rapidly. The range of geophysical methods currently available provides a powerful suite of investigative tools which complement direct observations.
Settlement of Beddingham Landfill
Authors: Di Stefano A. B.
Published: April 2008

Traditionally, the settlement of landfills has been empirically determined by observation and measurement conducted on landfills after final restoration. Since measurements undertaken in this manner do not normally commence until several years after the commencement of deposition, settlement characteristics immediately after placement cannot be determined. Further, the range of typical settlement values currently adopted, 10–35% of deposited waste thickness, is too great to enable accurate planning and design of restoration profiles.

A long-term research programme has been instigated, utilizing pressure cells buried within the refuse mass as landfilling progresses, to enable the determination of settlement characteristics from immediately after deposition has taken place through to final waste stabilization several decades into the future.

The programme has been running for approximately two years to date, and the data collected in the first year are presented, together with a preliminary analysis.
A groundwater trace study using a fluorescent dye
Authors: Townend M. , Aldridge R.
Published: April 2008

The test procedure for a groundwater trace study in a sandstone aquifer is described. The field test was simple, quickly implemented and carried out within a limited budget. A result was obtained and this formed part of the hydrogeological assessment of the site.
The construction of clay liners for landfills
Authors: Clark R. G. , Davies G.
Published: April 2008

Correct liner installation is fundamental to the construction of a containment landfill. The significance of material properties and the requirements of field placement and compaction are presented. The principle of demonstrating by means of construction quality assurance (CQA) that a mineral liner has been placed in accordance with the design requirements is discussed. Procedures are reviewed and the technical requirements of a landfill project that appertain to the CQA work are outlined.
Geotechnical investigations for a deep radioactive waste repository: drilling
Authors: Ball T. G. , Beswick A. J. , Scarrow J. A.
Published: April 2008

Comprehensive geotechnical investigations of potential repository sites for deep disposal of low- and intermediate-level solid radioactive wastes at Sellafield, Cumbria and Dounreay, Highland Region included drilling and testing cored boreholes up to 2000 m deep. The drilling technology used combines geotechnical site investigation procedures with oil and gas drilling technology and mineral exploration wireline methods to produce high-quality continuous cores. The drilling programmes are closely linked to geophysical and hydrogeological and geochemical test schedules. At Sellafield, deep boreholes are drilled with standard diesel electric and mechanical oilfield land rigs modified with top-drive units for heavy-duty wireline coring and sensitive mud control, well control and automatic drilling systems. Lorry-mounted site investigation rigs are used for shallow boreholes which have been drilled for pump testing and
in situ
stress measurements. At Dounreay a hydraulic top-drive mining exploration rig was used for deep drilling. Triple tube corebarrels have been used throughout which include uPVC liners for core protection. By October 1994, 31 boreholes had been drilled, with over 19 km cored out of a total depth of 26'/2 km. A summary of the equipment and procedures adopted is presented together with some comments on the application of these experiences to future geotechnical investigations.
Geotechnical investigations for a deep radioactive waste repository:
in situ
stress measurements
Authors: Christiansson R. , Scarrow J. A. , Whittlestone A. P. , Wikman A.
Published: April 2008

Comprehensive geotechnical investigations of potential repository sites for deep disposal of low- and intermediate-level solid radioactive wastes at Sellafield, Cumbria and Dounreay, Caithness included drilling and testing cored boreholes up to 2000 m deep. The investigation at Sellafield included the measurement of
in situ
stresses using the overcoring technique at various depths in a 250 m deep, vertical borehole drilled from the surface. The measuring instrument and method used for overcoring had, therefore, to perform reliably under high hydrostatic heads.

The equipment used to carry out these measurements was the Swedish Borre Probe. Previous work with this equipment has been carried out in slim holes and hard crystalline rocks. In contrast, this project required
in situ
stress measurements to be taken in a relatively large-diameter borehole, drilled in weak sedimentary rocks by wireline drilling techniques, and consequently, significant adaptations to the installation equipment.

The paper describes the adaption of the Borre Probe and its successful application in this project up to the end of 1992. Possible future applications of the technique are discussed.
Evaluation of clays as linings to landfill
Authors: Murray E. J. , Rix D. W. , Humphrey R. D.
Published: April 2008

The use of remoulded natural clays as low-permeability barriers or as part of multiple-layered lining systems to landfill cells is widespread. Geotechnical considerations in the evaluation of possible sources of clay and the design and construction of clay liners are addressed.

A study made of individual geological deposits within Lincolnshire is outlined and use of the term ‘material suitability’ to define the potential of a deposit to form a low-permeability barrier is discussed. A scheme for classifying deposits as unsuitable, marginal or suitable based primarily on plasticity data and variability is discussed and examples from the classification study are presented.

The term ‘acceptability in earthworks’ is also introduced and relates to the requirement to place acceptance limits on the proposed lining material to achieve the desired low-permeability barrier and to ensure the practicality of constructing the lining. The use of the moisture condition value (MCV) test in the assessment of acceptability and control of earthworks is discussed. The requirement of a maximum allowable permeability for a clay lining dictates the upper limit to the acceptable MCV range while the shear strength would usually dictate the lower limit.
The engineering of a cementitious barrier
Authors: Claisse P. A. , Unsworth H. P.
Published: April 2008

When cementitious materials are used for the containment of waste they act in two different and sometimes conflicting ways. The first is physical containment in which the waste is physically isolated from the environment. The second is chemical containment in which the water passing through the barrier is buffered to high pH thereby very substantially reducing the solubility of many harmful species and promoting sorption onto the cement matrix. Chemical barriers have been extensively researched for nuclear waste containment and this paper explores the possibility of using them for non-nuclear waste.

Initial results are presented which show that cementitious barriers containing cement replacement materials may be well suited to barrier construction. It is, however, concluded that cementitious barriers would have to be used as part of a composite system in order to comply with current legislation.
An assessment of permeability of clay liners: two case histories
Authors: Langdon N. J. , Al Hussaini M. J. , Walden P. J. , Sangha C. M.
Published: April 2008

Two sites, each utilizing natural clay from the same geological formation but from sources in different depositional basins, are compared together with their method of site control and their test results. From a series of laboratory test results the geotechnical differences in the material are compared and tentative trend lines for various parameters drawn. Conclusions from these two sites and these soils suggest that precise determinations of permeability would not have been easily predicted from relationships in published information. However, there remains a major need for a method of determining permeability appropriate to the site conditions and limitations pertaining to a landfill site. The concept of the falling head test ‘failing safe’ and determining a rough threshold level at 109 m s-1 can be used but an on-site water absorption approach or infiltrometer may be more readily adaptable to determine permeability rapidly in quantities and also cost-effectively.
Research into the mobility of a gas phase within a porous network
Authors: Boltze U. , de Freitas M. H.
Published: April 2008

This paper presents work conducted at Imperial College on the mobility of a gas phase through a partially saturated porous medium. The research is based on the observation of the behaviour of a discrete gas phase in place rather than on gas in solution. The experiments were designed to ensure that chemical reactions and the nucleation of the gas phase were kept to a minimum if not prevented.

Glass micromodels of porous media were used to allow visual analysis of the movement of the gas phase in a partially saturated porous medium under conditions of rapidly changing head. Both conditions of heavy localized rainfall or rapid increase in atmospheric pressure, and rapidly changing water levels are simulated.

Images of gas bubble positions, sizes and frequencies under given potentials are analysed using a Geographical Information System (GIS) to enable the bubble population to be quantified in time and space.

From these studies conclusions concerning the behaviour of the gas phase under these conditions have become apparent. These have significant implications for the monitoring of gas emissions and movement of gas
in situ
.
The protection of groundwaters from the effects of waste disposal
Authors: Hart P. A. , Davey I.
Published: April 2008

Powers available to the NRA are summarized. Definitions of waste and groundwater are given. The scale of the problem is described by reference to the legacies of historical ‘dilute and attenuate’ landfills, mainly occupying disused surface mineral excavations.

An explanation is given of an interpretation of the National Rivers Authority
Policy and Practice for the Protection of Groundwater
in context of waste disposal. Special emphasis is placed on the protection of groundwaters by development control. Reference is made to work regarding best practice for containment and management of leachates generated at landfills.

Scenarios are described which are then used to assess the likely impact of the policy on the future of waste disposal.

It is concluded that the NRA's policy provides a framework which is being used to promote the practical protection of vital natural groundwater resources.
Setting the standard for geophysical surveys in site investigation
Authors: McCann D. M. , Culshaw M. G. , Fenning P. J.
Published: April 2008

This paper reviews the state of geophysics as applied to the engineering and environmental industries in the 1990s. The site investigation process is described emphasizing that inadequate attention is paid to understanding the ground in, or on, which structures are built. The basic principles of geophysical surveying are described, particularly the five major factors that influence the success of a geophysical survey: depth of penetration, vertical and lateral resolution, contrast in physical properties, signal to noise ratio and existing information about the site. The main surface, downhole and crosshole geophysical methods used in engineering and environmental investigations are discussed and illustrated with brief case histories from the literature. The integration of geophysical surveys into the site investigation process is described and a new procedure for the designing, commissioning and carrying out of a successful geophysical survey is presented. The underlying reasons why geophysics is perceived as ‘not working,’ are identified as a lack of understanding of both geological variability and geophysical methods on the part of the engineer and of engineering design and practice on the part of the geophysicist.
Geotechnical applications of the spectral analysis of surface waves
Authors: Cuéllar V.
Published: April 2008

Spectral analysis of surface waves is a simple and efficient method of determining the shear-wave velocity of soils
in situ
and their variation with depth. The non-destructive character of the method, together with the possibility of generating long wavelengths by letting a weight drop from a certain height, makes it a very suitable technique to obtain shear wave velocity profiles without requiring the drilling of boreholes.

In this paper, examples are given of how the method has been used in Spain to identify the deformability of compacted embankments and waste landfills, to assess the liquefaction potential of alluvial sediments, to characterize the geomechanical behavior of foundations and rock-fill dams, to determine the extent of the alteration zone behind the lining of a tunnel excavated in rock and to judge the degree of improvement achieved in some ground treatments.
Some improvements in the processing of borehole acoustic signals for the characterization of geological structures
Authors: Rousseau A. , Jeantet D.
Published: April 2008

We show how a new type of 3D visualization of the raw data of full waveforms can be used as a method of signal processing, allowing the characterization of fractures, dykes, and soft/hard formation contacts. We provide a method of calculating the interface dip in adequate conditions and we propose a new means of calculating the velocities of all types of waves by ‘animation’. Finally we suggest a way to assess the dip azimuths.
Application of the microgravity technique to cavity location in the investigations for major civil engineering works
Authors: Emsley S. J. , Bishop I.
Published: April 2008

The detection of subsurface cavities, including mine workings, mine shafts and solution features, is an essential component of any site investigation for major civil engineering works and often relies on drilling investigations to identify the presence of any cavities. However, there is no standard, cost-effective site investigation technique which can be readily used for the physical investigation of such features.

Whilst a desk study may yield documentary information on the presence of recorded mine workings and shafts, the location of solution features is generally even more problematical. Two complementary approaches have been developed for the location of subsurface cavities. Firstly, closely spaced boreholes are drilled in a specific pattern to locate cavities. This method can prove prohibitively expensive, with no guarantee of intersecting all voids or cavities. Secondly, remote sensing geophysical techniques have been used. Such techniques rely on the existence of contrasts in physical properties between the rock mass and the cavities, which can be detected using suitable geophysical methods.

This paper describes the application of the microgravity technique to the detection of solution cavities and mine workings with reference to three case histories. In the first and second examples the microgravity technique was used as a reconnaissance method for defining targets for subsequent physical investigation; in the third, the technique was used to define the extent of solution features, having been initially and unexpectedly encountered by a drilling programme. These examples demonstrate the applicability of the microgravity method in detecting and delineating both solution cavities and mine workings within differing geological settings.
Cross-hole seismic tomography for engineering site investigation
Authors: Jackson P. D. , McCann D. M.
Published: April 2008

The results of cross-hole seismic tomography at sites where there is good geological control are presented. Comparisons have been made between the tomograms and the geological cross sections in order to assess the technique under
in situ
conditions. It is shown that while the geological sections do not contain velocity information they have provided structural constraints which provided fresh insight when interpreting the seismic tomograms.

Processing artefacts in field-data tomograms, particularly when the angular ray coverage is incomplete, have been identified using ‘synthetic’ tomograms based on the geological section. In addition, velocity anisotropy and critically refracted arrivals were identified as likely causes of differences between ‘synthetic’ and ‘field data’ tomograms, given a knowledge of the geological section.

It is proposed that cross borehole tomographic surveys should not be taken immediately at their face value in the absence of geological control.
Hydraulic tomography in fractured bedrock aquifers using high-resolution borehole flowmeter measurements
Authors: Paillet Frederick L. , Morin Roger H.
Published: April 2008

Geophysical soundings and tomographs can provide two- and sometimes three-dimensional images of the structure of fractured rock masses, but regions of anomalous geophysical properties are only indirectly related to the hydraulic properties of rocks. Hydraulic tomography based on cross-borehole flow tests cannot rigidly constrain all possible fracture flow connections, but such tests provide direct measurements of hydraulic connections between boreholes. The combination of flow tomographs based on high-resolution flowmeter measurements and conventional geophysical tomography can provide information about the hydraulic connections and large-scale flow paths that cannot be obtained by either method alone. The effectiveness of this combination of flowmeter and geophysical measurements is illustrated by results obtained in cross-borehole flow measurements at Mirror Lake, New Hampshire, and a hydraulic fracture experiment near Boulder, Colorado.
Azimuthal resistivity and seismic measurements for the determination of fracture orientations
Authors: Bushy J. P. , Peart R. J.
Published: April 2008

There is an increasing need to map and understand rock fracture networks in order, for instance, to predict the spread of contaminants in the sub-surface, to optimize borehole siting in aquifers whose storage results from fracturing, and for civil engineering applications. The use of azimuthal resistivity and seismic measurements for the determination of concealed sub-vertical fracture orientations has been previously reported but to date the methods have found little general
application.

The results of resistivity and seismic azimuthal measurements on chalk and limestone at several sites in southern and eastern England are reported. A number of distinct preferred azimuths are apparent in the data and the two independent techniques give generally consistent results. The geophysical indications are assessed relative to outcrop measurements of fracture and joint azimuths and conclusions are drawn on the persistence of fracture sets both laterally and vertically.
Geophysical survey planning for the Dounreay and Sellafield geological investigations
Authors: Norton M. G. , Arthur J. C. R. , Dyer K. J.
Published: April 2008

Between 1989 and 1994 two large engineering site investigation projects in the United Kingdom at Dounreay in Caithness and the Sellafield area in West Cumbria were carried out for the study of possible locations for a deep underground facility for low-level and intermediate-level radioactive waste. In the geophysical domain, management of a diverse range of specialist services required initial desk studies, survey design, acquisition and processing supervision, interpretation, reporting and archiving.

Document creation (design intent memoranda, tenders and contracts, Quality Assurance, technical reviews and reports) together with technical control during the data acquisition phase was followed by involvement in the interpretation of the results. A range of geophysical methods were employed including onshore and offshore seismic reflection with associated gravity acquisition, transition zone seismic, airborne geophysics (utilizing spectroscopy, magnetics and VLF) and ground electromagnetic surveys.

At the peak of activity, responsibility for the geophysical operations involved the simultaneous management of five field crews - two land seismic with some gravity, one marine seismic with gravity and two helicopters acquiring airborne data - as well as ongoing VSP in the deep, fully cored, boreholes. Some of the work undertaken for each of these disciplines will be described in relation to both projects.
Thermal conductivities of argillaceous sediments
Authors: Midttømme K. , Roaldset E. , Aagaard P.
Published: April 2008

Thermal conductivities of selected samples of shales, clay- and mudstones from the Norwegian Continental Shelf have been measured with a divided bar apparatus. The samples investigated are from conventional cores and side wall cores. Thermal conductivities for watersaturated samples measured perpendicular to the layering vary from 0.79 to 1.14 W/m K. The conductivities measured parallel to the layering are up to 1.7 times higher than those measured in the perpendicular direction. The investigation also confirms that the temperature has an influence on the conductivity. A model to predict thermal conductivity, based on water content and mineralogy has been proposed and tested.
Assessment and specification of armourstone quality: from CIRIA/CUR (1991) to CEN (2000)
Authors: Latham J.-P.
Published: April 2008

As a typical by-product to normal quarrying, armourstone has many attributes that make its objective specification and testing less straightforward than most producers would wish. Neither, it appears, has the market forces principle and tendering practices in the UK construction industry, leading to minimal forward planning of armourstone testing, helped to enhance quality control of materials. The undoubted advances heralded by the standardizing approach of the CIRIA/CUR
Manual on the Use of Rock in Coastal and Shoreline Engineering
and its model specification have done much to rationalize a previously over-simplistic view of armourstone specification. However, recent practical experience with many coastal contracts which have adopted the CIRIA/CUR specification has exposed a number of problems with the detailed implementation of the rock quality testing part of the model specification. In particular, this experience draws attention to a lack of published correlation studies between the various abrasion tests and between strength tests. Rock suppliers are reporting that designers are continuing to specify using the BS812 suite of aggregate tests. The potential for bias in the taking and preparation of representative test portions has also remained a problem.

The manual specification's rationale, its strengths and weaknesses, are outlined. Correlation analysis of new research data from a suite of rocks is presented. A re-examination of the manual specification's acceptance criteria for resistance to wear and to breakage is presented. A way forward is offered for the continued use of the manual specification until its supersedence by the European CEN specification for armourstone. Improvements in the 16th draft of the CEN standard are briefly discussed, and it is found that certain problems that the manual began to address remain unsolved.
Meeting the demand for rock armour and its grading specification
Authors: Rees-Jones R. G. , Storhaug E.
Published: April 2008

An analysis of tenders for contracts requiring armourstone issued since 1991 has been carried out. The results show the market size, the impact of major projects, the proportion of deliveries by sea and the extent to which the CIRIA/CUR specifications have been adopted. Proposals from the CEN armourstone committee regarding grading and shape are discussed, together with developments in quality control procedures at the loading port.
Lime stabilization of inorganic contaminants in clays
Authors: Glendinning S. , Rogers C. D. F. , Boardman D. I.
Published: April 2008

The legacy of industrial operations over the past 200 years are contaminated natural clays and clay-based sediments. There is an urgent need for economic methods to stabilize these materials since the problem is widespread. Chemical fixation or encapsulation of inorganic contaminants using lime provides one potential solution that has yet to be adequately explored.

This paper aims to review the methods of chemical stabilization of inorganic contaminants using pozzolanas, and in particular discuss the interaction of clays with both metal ions and lime. The parallels between cement, lime-fly ash and lime-clay stabilization reactions are examined to determine the potential for contaminant stabilization using lime and suggest the mechanisms upon which success would rely. The factors affecting the lime stabilization process are discussed. Methods of incorporation of lime in practice are thereafter discussed, covering deep mixing as well as surface mixing
in situ
and mixing
ex situ
. Specific research required to prove the potential of lime is then discussed.

The paper concludes that lime stabilization provides a potentially valuable and economic means of treating both natural clays and (often very wet) clay-rich sediments. This is achieved via both enhanced contaminant adsorption and precipitation of metal ions under conditions of high pH, and binding in of the contaminants with the reaction products of the pozzolanic reaction between lime and clay. However, the fundamental nature of the clay/sediment is altered by the lime-clay reactions, most notably in the context of future potential for ion mobility by an immediate increase followed by a progressive decrease in coefficient of permeability. The degree to which inorganic contaminants become associated with the reaction products and the permanency of this association under conditions of seepage (i.e. resistance to leaching) need to be researched in detail before confidence in the technique can be engendered.
Policy maturity and the development of novel remedial techniques
Authors: Wills J. G. C. , Jones C. J. F. P.
Published: April 2008

The need for a legislative framework to deal with contaminated land and its relationship to the market for novel remedial techniques is described. Problems of bureaucracy, inflexibility and liability are cited as reasons for a move towards more mature policy approaches, including brownfield development, the use of economic incentives, and remedial action based on suitability of land use. The contaminated land policy of the UK is outlined and the question as to whether this policy will prevent the kind of protracted legal battles experienced in the USA under Superfund is posed. Regulatory capture is suggested as a reason for the UK's predominantly deregulatory stance and it is proposed that this has the potential to stifle the development of advanced techniques. Barriers and opportunities to development are outlined: licensing, pilot studies and perception. It is concluded that ‘Suitable for Use’ will protect public health and the environment cost effectively — albeit at the expense of a strong market for advanced remedial techniques in the UK. Poor policy decisions by government are highlighted as a reason for uncertainty in the UK's remedial market. Niche markets and turnkey operations are identified as areas where UK firms have the potential to succeed.
Integration of environmental assessment indicators into site assessment procedures
Authors: Tucker P. , Ferguson C. , Tzilivakis J.
Published: April 2008

The amount of information that can be gathered for contaminated site assessment is often limited by the cost of making measurements. Effective decisions on site management rely heavily on this information. Lower cost measurements or more effective use of the diverse information already available should increase the quality of these decisions, provided that final data quality is not compromised. However, fundamental problems can arise from interpreting the reliability, uncertainty and significance of the raw measurements or other indicators. Such problems are paralleled in Environmental Impact Assessment and Life Cycle Analysis methodologies. Drawing on the work undertaken within these disciplines may help clarify the solution for site assessment. Scoring, ranking and valuation techniques have been used successfully in providing decision support for the design of sampling strategies for contaminated sites through maximizing the use of desk study data and site reconnaissance observations.
Hydrochemistry of pollutant attenuation in groundwater contaminated by coal tar wastes
Authors: Torstensson Daniel , Thornton Steven F. , Broholm Mette M. , Lerner David N.
Published: April 2008

This paper describes a preliminary hydrochemical study of a Triassic Sandstone aquifer in the UK East Midlands which is contaminated by coal tar waste products from a former coal-carbonization plant. Processes controlling the attenuation of inorganic species within the identified plume are examined, supported by equilibrium and reactive transport modelling of contaminant fate. The study forms part of a more detailed research programme examining the long term fate of pollutants from this site in the aquifer. Groundwater beneath the site is polluted with NH
4
(up to 350 mg l
-1
), SO
4
and NVOC from the plant and nearby coal mining operations. Concentrations of organic chemicals within the plume are not significant. The aquifer is calcareous, (Fe) oxide-rich and aerobic, and geochemical modelling suggests that the native groundwater chemistry is primarily controlled by carbonate equilibria. Anaerobic conditions are sustained within the plume by microbial oxidation of the NH
4
and NVOC load which is coupled to the reduction of native Fe oxides. Sulphate is transported conservatively within the plume. The NH
4
load is primarily attenuated by cation exchange reactions with the aquifer sediments. This is supplemented by nitrification at the plume margins under conditions of higher oxygen flux which generates locally elevated NO
3
concentrations and depressed pH in the contaminated groundwater. Elevated alkalinity within the plume is consistent with dissociation of the ammonia waste stream during groundwater transport and is an important control on the increased porewater Ca and Fe load mobilized by cation-exchange and redox reactions. A conceptual model of the key processes affecting contaminant fate within the plume is presented and the implications for aquifer clean-up are discussed.
Distribution of volatile organic compounds in porewater of the seasonally unsaturated Chalk aquifer
Authors: Fretwell B. A. , Burgess W. G. , Jefferies N. L. , Dottridge J.
Published: April 2008

The Chalk aquifer is contaminated at many sites at outcrop by volatile organic compounds (VOCs). Most studies of VOCs concentrate on the saturated zone, ignoring potentially significant accumulations of dissolved contaminants within porewaters of the unsaturated zone. Of particular interest in the Chalk is the large zone of the aquifer over which seasonal fluctuation of the water table occurs. VOCs accumulated in this zone (resulting from vertical migration and diffusion from contaminated ground water at seasonal high water levels) can form a reservoir of contaminants which will be released into the aquifer over a long period. Better understanding of the VOC behaviour in the seasonally unsaturated zone is needed to improve risk assessment and optimize remediation response.

Determination of VOC occurrence and concentration in the seasonally unsaturated zone at a contaminated site on the Chalk outcrop is described. Some 500 samples of chalk have been taken from cores drilled in the unsaturated zone over a depth interval of 20 m. Headspace analysis has been used to determine porewater chemistry for a range of VOCs. Vertical profiles of contaminant con- centration are presented and interpreted in terms of VOC transport mechanisms. Hydrocarbon contamination at the site poses an additional element of complexity. The presence of chloride associated with VOC contamination provides a conservative comparison for the distribution behaviour of the VOCs.
The relevance of a DNAPL-tracer test conducted at Base Borden, Canada, to solvent groundwater contamination in the UK
Authors: Rivett Michael O. , Feenstra Stan , Cherry John A.
Published: April 2008

The relevance of key conclusions obtained from a tracer test performed at the Base Borden research site in Canada to solvent contamination in the UK is indicated. The tracer test represented a world unique opportunity to study groundwater contamination arising from a known DNAPL source zone in a natural aquifer environment. The test involved the controlled emplacement of a source zone of residual solvent DNAPL (dense non-aqueous phase liquid) below the water table from which a dissolved plume of chlorinated solvents developed. Significant data were collected on DNAPL dissolution, plume transport and remediation. Conclusions from the test are shown to be relevant to the development, investigation and remediation of solvent contamination in UK aquifers.
Volcanic hazards and their mitigation
Authors: McGuire W. J.
Published: April 2008

Over the past century, a range of volcanic hazards, particularly pyroclastic flows and debris flows, have claimed over 60000 lives, and between 1980 and 1990 alone, have detrimentally affected the day-to-day lives of over 600 000 people. Although a battery of mitigation measures are now available to reduce the impact of volcanic hazards, rapidly increasing populations near active volcanoes in the developing world will ensure increasing vulnerability to hazardous volcanogenic phenomena into the next millenium, and new initiatives are required to prevent a contemporaneous rise in the numbers of volcanic disasters. Alongside increased monitoring, partly through improved satellite observations, a programme of public education and training is needed to ensure that both civil authorities and local populations are able to respond rapidly and appropriately to a developing volcanic emergency. This in turn requires greater focus on improved communication between scientists and the responsible civil authorities, and the formulation of workable contingency plans based upon reliable and informed scientific opinion.
Integrated use of Landsat TM and SPOT panchromatic imagery for landslide mapping: case histories from southeast Spain
Authors: Eyers Richard , Moore John McM. , Hervás Javier , Liu J. G.
Published: April 2008

This paper demonstrates some of the ways in which digital space imagery can be used for landslide mapping. Landslides ranging in size from a few metres to several hundred metres across have been studied at a test site in semi-arid terrain in Almeria Province, SE Spain. The study illustrates the capabilities and limitations imposed by spatial and spectral resolution in Landsat Thematic Mapper (TM) and SPOT panchromatic space imagery. The results demonstrate the scales at which, landsliding which can be studied, using SPOT P and Landsat TM imagery.

Spectral and textural features of landslides were enhanced digitally. Textural discrimination was improved by linear contrast stretching combined with edge enhancement by adding back the results of Laplacian filtering. Spectral features of landslides, including soil moisture dependent vegetation and rock debris types, are well-displayed in supervised RGB colour composites and band ratio images.

A data integration technique, the Brovey Transformation, was used to produce colour composites combining textural and spectral features from SPOT Pan and Landsat TM imagery. Landslides with a minimum width of 250 metres can be identified in space images. Interpretation of results revealed the presence of several previously unrecorded landslides.

Daedalus 1268, Airborne Thematic Mapper (ATM) digital imagery has been used to demonstrate the value of improved spatial and spectral resolution imagery for landslide mapping on the scale of the Spanish test sites. The results illustrate the future system requirements for more detailed landslide mapping and demonstrate the improvements of scale which will occur when space imagery with pixel sizes of five metres becomes more readily available.
Inspection and risk assessment of slopes associated with the UK canal network
Authors: Holland G. J. , Andrews M. E.
Published: April 2008

Canals in the UK typically comprise artificial channels, with a wide range of embankments and cuttings. These structures often suffer from a range of problems unique to the canal environment including age, wide variation in construction methods and, in the case of embankments, a requirement to retain water. It is the responsibility of British Waterways to regularly inspect and evaluate these slopes with regard to long-term safety and identification of maintenance requirements.

A system of slope inspection procedures has been developed which is tailored to aspects of slope stability related to canal structures. This is used in conjunction with a risk evaluation procedure to identify areas of concern on a proactive basis. The results are used to co-ordinate maintenance effort, and identify requirements for more detailed ground investigation.
Silica gels: a possible explanation for slope failures in certain rocks
Authors: Butenuth Christine , Frey Marie-Luise , de Freitas Michael Henry , Passas Nikolaos , Forero-Duenas Carlos
Published: April 2008

Studies of a weak sandstone which disaggregates in water reveal that particles of colloidal dimensions are released as the sand-sized particles separate. Colloids are the building blocks of gels and their presence suggests that gels (in this case silica gels) could be a component of this material. Samples of the disaggregated sandstone were collected soon after a landslide within it had occurred and, when left to stand in the ground water collected with them, naturally recemented themselves. Such behaviour implies that gels are not only present in this sandstone but also contribute to its strength. The role of gels may therefore be significant to those geohazards arising from a loss of strength.
Graphical methods for hazard mapping and evaluation
Authors: Smith G. J. , Rosenbaum M. S.
Published: April 2008

Graphical techniques are presented as a practical approach to hazard assessment. These were initially developed for the evaluation of potential collapse associated with old chalk mine workings. However, the underlying methodology is free-standing and now capable of being tailored to other ground engineering situations. This places a strong emphasis on the inclusion of abstract factors, otherwise excluded from mechanistic forms of assessment by traditional methods. The ways in which such varied information can be analysed and then synthesized in an assessment are discussed. The graphical approach lends itself to both overview and audit, and is therefore relevant for project evaluation as well as geohazard assessment.
Chalk solution features at three sites in southeast England: their formation and treatment
Authors: Rhodes S. J. , Marychurch I. M.
Published: April 2008

Solution features are common phenomena within Chalk areas and the classical theory states that solution features are formed entirely by dissolution of the Chalk as a result of chemical weathering, probably during the Quaternary period. These solution features pose a risk to development and infrastructure works in these areas due to the presence of soft or loose infill materials. As a result a number of treatment methods have been developed to overcome the problems of construction in these areas.

Observations of solution features encountered at three sites in southeast England, all underlain by Upper Chalk, are reviewed and the treatment methods designed to overcome the hazards posed are discussed.
Geohazards and the urban environment
Authors: McCall G. J. H.
Published: April 2008

Recent escalation of urbanization throughout the world has increased the attention to geoscience in the urban setting. In the urban context, earlier attention to routine engineering geology and hydrogeology investigations was later augmented by the introduction of thematic mapping and the erection of urban databases to support environmental assessments and land use planning. More recently, the role of the urban environment in exporting pollution regionally and globally, and the problems of degradation of the urban environment itself, together with the immediately surrounding area on which the urban community depends for resources, have attracted attention; as has the mushrooming of megacities which threatens disastrous environmental problems. In this paper, the aim is to review the geohazards that threaten the urban setting (using the term ‘geohazard’ in the broadest sense, i.e. both natural and human-made, and both intensive rapid-onset and slow-onset pervasive geohazards).

To illustrate the extent of urban problems, the principal natural geohazards which threaten towns and cities, most of them of the intensive, rapid-onset type, are briefly considered. However, the emphasis is on the various human-made geohazards, most of them pervasive and of slow onset. Examples are cited of these human-made problems, all of which involve the interaction between human activity and natural processes. Details are given of some of the acute problems facing cities and towns, as well as urbanized regions.
Hazards induced by groundwater recharge under rapid urbanization
Authors: Lawrence A. R. , Morris B. L. , Foster S. S. D.
Published: April 2008

Urban population growth across most of Latin America and Asia is relentless. Rapid urbanization has profound impacts on the hydrological cycle, including major changes in groundwater recharge. Existing infiltration mechanisms are radically modified, and new ones introduced, with evidence of an overall increase in recharge rates. There is also widespread diffuse pollution of groundwater by nitrogen compounds (normally nitrate, but sometimes ammonium), salinity (especially sodium chloride) and dissolved organic carbon. Groundwater contamination by petroleum and chlorinated hydrocarbons, related synthetic organic compounds, and, on a more localized basis, pathogenic bacteria and viruses, is also encountered. An analysis of the processes involved is made through citing detailed case histories.
Natural hazards in the urban environment: the need for a more sustainable approach to mitigation
Authors: Degg Martin
Published: April 2008

In a variety of environmental and socio-economic circumstances, the medium to long-term effectiveness and sustainability of traditional approaches to managing natural hazards and their impact on urban areas are increasingly being questioned. This is reflected in two trends of particular relevance to the geosciences and engineering, namely (a) changing attitudes towards the use of ‘hard’ engineering to manage environmental processes; and (b) calls for greater involvement and responsibility on the part of the community and individual in hazard mitigation. The latter, in particular, is increasingly seen as crucial to reducing vulnerability to loss in both developed and developing societies. It requires a conceptual change in how the issue of human vulnerability is viewed and portrayed, and greater public accessibility to information about environmental processes, the potential dangers they pose and the ways in which these can be mitigated. In this respect the geoscientist has a vital role to play in providing the non-specialist with essential earth science information, in formats that are environmentally, economically and culturally appropriate.
Landfill disposal of urban wastes in developing countries: balancing environmental protection and cost
Authors: Griffin A. R. , Mather J. D.
Published: April 2008

Controlled landfilling with minimal engineering is appropriate for urban waste disposal in most developing countries. Case histories from Tanzania, the Gambia and Mauritius show how unsanitary dumpsites can be replaced by controlled landfills using simple technology at a sustainable and realistic cost commensurate with Gross Domestic Product (GDP). In each country care has been taken to tailor schemes to local conditions.
GIS techniques for mapping and evaluating sources and distribution of heavy metal contaminants
Authors: Fragkos C. , Rosenbaum M. S. , Ramsey M. H. , Goodyear K. L.
Published: April 2008

Spatially dependent phenomena related to heavy metal concentration in a drainage system have been evaluated using GIS methodology, so providing an indication of areas which may contain contaminated land. The geochemical distribution is used to identify the heavy metal sources. The GIS facilitates dispersion modelling defined by a digital elevation model. This can be used to delineate drainage catchments and to examine its interaction with stream sediment geochemistry. The resulting drainage basin-segment images can then be used to identify heavy metal sources. Such modelling of geochemical dispersion of metals within drainage basins allows predictions to be made as to which areas of contamination originate from which point source. The accuracy of such maps depends fundamentally on the accuracy of the dispersion model. This model includes both descriptive and deductive components concerning the influential criteria for describing the distribution of heavy metals. Each criterion is defined using an interactive discussion process that leads to the generation of a set of weighting coefficients. The integration of such criteria is achieved using fuzzy set methodology to produce images ranked according to how well they meet the selected site assessment criteria.