ABSTRACT A man-made deposit at Northbridge Park near Charleston, South Carolina, consists of phosphatic nodules, fossils, and mud dredged from the bottom of the Ashley River; nodules and fossils lay strewn across the banks of the river. This artificial deposit is likely representative of deposits mined extensively in the late nineteenth century and widely referred to as the “Ashley Phosphate Beds.” Many of the taxa discovered at Northbridge Park were historically reported from the phosphate beds, and include sharks, rays, bony fish, sea turtles, giant birds, whales, dolphins, sea cows, and land mammals. Some of these bear adhering matrix indicating origin from the Oligocene Ashley Formation. Others lack matrix but have short geochronologic ranges and are derived from the Ashley Formation, Lower Miocene Marks Head Formation, Lower Pliocene Goose Creek Limestone, and Pleistocene Wando Formation.

Abstract The development of the Vale of St Albans groundwater model made use of two techniques not commonly used in UK regional modelling studies: parameter estimation (using PEST) and representation of dual storage. Parameter estimation techniques can significantly improve model calibration and can be used to inform model development. Because parameter estimation typically involves running a groundwater model many hundreds of times, using a steady-state version of the model can help to keep run times short. Care must be taken to ensure that the parameter distributions produced through these techniques are conceptually defensible, and they must be checked against the conceptual model and modified where necessary. Simulation of extreme conditions such as floods and droughts can be problematic for Chalk aquifers. Previous studies have shown that the Chalk can be resistant to drought, with higher flows recorded in rivers than can be accounted for from releases from fissure storage alone. An approach has been developed that simulates a weak hydraulic connection between fissures and a proportion of matrix storage within the Chalk, providing a delayed yield of significant additional volumes of water during droughts. The application of this approach results in a significant improvement in the simulation of extreme events.

Abstract The first numerical model of solute transport to incorporate Fickian diffusive exchange between mobile fracture water and immobile porewater for an actual case of groundwater contamination at catchment scale was applied to the Chalk aquifer at Tilmanstone in SE England by Bibby ( Water Resources Research , 1981, 17 , 1075–1081). The unconfined aquifer at Tilmanstone had been contaminated by coalfield brine leaking from disposal lagoons operating throughout much of the twentieth century. Recent observations show that the Bibby model underestimates dual-porosity diffusive retardation, and hence underestimates the persistence of contamination, probably by several decades. 2D representation of the aquifer in plan ignored the hydrostratigraphy, and model calibration was limited by the lack of time-variant paired profiles of fracture water and porewater. Vertical profiles through the Chalk determined by packer testing, borehole dilution testing and geophysical logging, together with a new depth profile of chloride concentration in Chalk matrix porewater, are described. The hydrostratigraphy is interpreted in relation to the Chalk lithostratigraphy of SE England, and incorporated into a vertical-section model of chloride transport along the axis of the valley, consistent with the new and historical profiles of fracture water and porewater chloride concentrations. New predictions of the longevity of the chloride contamination at Tilmanstone are presented.

Abstract Regional groundwater resource models are often built to improve confidence in predicted groundwater abstraction impacts on river flows and groundwater levels. By explicitly representing the aquifer system geometry, properties and boundaries, together with transient recharge and abstraction pressures, such models provide a robust platform to support abstraction impact assessment, alongside evidence from field data and investigations. Regulatory drivers include the European Union Habitats and Water Framework Directives and other abstraction licensing decisions. This paper presents examples of the spatial and temporal patterns of groundwater abstraction impacts predicted by several models. A variety of presentation formats are used to illustrate the simulated flow impacts of abstractions both individually, and in combination with other surface water abstractions and discharges. Model predictions from a range of abstraction, aquifer, and river settings are often more complex than would be suggested by simpler tools and approaches. In many cases, absolute low-flow impacts are less than long-term groundwater abstraction rates. The ‘real world’ hydrogeological mechanisms behind these impact patterns are discussed. The paper also recommends a protocol for using regional models to assess individual licensed groundwater abstraction impacts across the full range of historic climate conditions (typically, as monitored since 1970) and in the context of other operational artificial influences.

Abstract Earthworks encompasses a range of engineering activities that goes well beyond the conventional digging out of soil and rock and movement of the material to another part of a site. Although these activities may be amongst the most fundamental of civil engineering construction activities, and take place whenever and wherever a development takes place, earthworks also include embankment dams, foundations (especially those for linear infrastructure) such as capping layers for road construction, structural fill for retaining walls, and for reinforced and anchored soil and earth. Conventional cut and fill operations are often somewhat disparagingly known in the UK as ‘muckshift’, the processes of excavation to form temporary and permanent cuttings and trenches, controlled placement of material for structural backfill, creation of embankments including earth and rockfill dams, and preparation of foundations for all forms of structure is a highly skilled geotechnical design practice. To undertake this work safely and economically requires an evaluation of the engineering geology of the site where the works are to take place, accurate descriptions of the nature and properties of the materials involved, detailed material specifications, assessment of earthwork quantities, settlement calculations for structures and foundations, analysis of short and long term slope and foundation stability, and the design of appropriate construction practices. The methods for excavating materials must be determined, the short and long term stability of excavations must be evaluated, and the suitability of any materials to be used in construction needs to be established. During any fill placement monitoring is necessary to ensure the materials meet specification and which may define pre-determined methods.