Mott MacDonald

About: Mott MacDonald is a company organization based out in London, United Kingdom. It is known for research contribution in the topics: Electric power system & Wind power. The organization has 586 authors who have published 529 publications receiving 9801 citations. The organization is also known as: Mott MacDonald Group & MMD.

Modelling the hydrogeology and managed aquifer system of the Chalk across southern England

Abstract: Abstract Six regional recharge and groundwater models have been recently developed of the Chalk and Upper Greensand from Dorset to Kent. Updated Chalk stratigraphy and mapping have improved understanding of geological structure and the development of preferential groundwater flow pathways along hardground horizons. Where shallow dipping folds bring these into the zone of active groundwater flow, extensive ‘underdrainage’ may result in marked differences between surface and groundwater catchments. Hardgrounds and marls are also associated with spring discharges, as are some faults and the clay formations that underlie or confine the aquifer system. Higher specific yield within the Upper Greensand helps support summer baseflow, as do local groundwater discharges from augmentation schemes, watercress and fish farm operations. The aquifer system has been successfully modelled using the ‘variable hydraulic conductivity with depth’ version of MODFLOW. Depths of secondary permeability development have been distributed according to ground and groundwater level data. Interfluve–valley contrasts overlie a base hydraulic conductivity set according to the formation saturated at the water table and enhanced by active hardgrounds. Local parameter overrides may also be needed. The Wessex Basin conceptual and numerical model is described before summarizing similarities and contrasts from the other five regional model areas.

Geothermal exploration in the Fell Sandstone Formation (Mississippian) beneath the city centre of Newcastle upon Tyne, UK: the Newcastle Science Central Deep Geothermal Borehole

Abstract: The postulate that geothermal energy might be recoverable from strata laterally equivalent to the Fell Sandstone Formation (Carboniferous: Mississippian) beneath Newcastle upon Tyne has been examined by the drilling and testing of the 1821 m deep Newcastle Science Central Deep Geothermal Borehole. This proved 376.5 m of Fell Sandstone Formation below 1400 m, much of which resembled braided river deposits found at outcrop, although some lower portions were reddened and yielded grains of aeolian affinity. Downhole logging after attainment of thermal equilibrium proved a temperature of 73°C at 1740 m, and allowed estimation of heat flow at about 88 mW m −2 . This relatively high value probably reflects deep convective transfer of heat over a distance of >8 km from the North Pennine Batholith, along the Ninety Fathom Fault. The Fell Sandstone traversed by the borehole proved to be of low hydraulic conductivity ( c . 7 × 10 −5 m d −1 ). The water that entered the well was highly saline, with a Na–(Ca)–Cl signature similar to other warm waters encountered in the region. It remains for future directional drilling to establish whether sufficient natural fracture permeability can be encountered, or wells stimulated, to support commercial heat production.

The influence of tree root water uptake on the long term hydrology of a clay fill railway embankment

Abstract: This paper uses a numerical model to investigate the influence of tree root water uptake and tree removal on pore water pressures and the vertical movement of a clay fill railway embankment. Simulated results of soil wetting and drying are compared with field measurements from an instrumented railway embankment before and after tree removal. A parametric study compares the influence of vegetation on the seasonal movement of the embankment slope. The simulations and field measurements show that while trees cause significant seasonal variations in pore water pressure and water content near the soil surface, they can maintain persistent soil suctions at depth within the tree rooting zone. Demonstration of this result using a numerical model requires a root water uptake function that separates spatially the processes of water infiltration, evaporation and transpiration. When all of the trees are removed, the persistent soil suctions established by the trees are lost as water infiltrates from the soil surface. Leaving the trees in place over the bottom third of the slope can maintain persistent suctions at the slope toe, while potentially also reducing seasonal ground movements at the crest that may adversely affect railway track geometry.