Groundwater Lowering in Construction - a practical guide

By P.M. Cashman & M. Preene: Published by Spon Press, 11 New Fetter Lane, London, EC4B 4FH, UK: 2000: ISBN 0-419-21110-1: 246 ´ 189mm: xviii + 476pp: Hardback: £80.00.

You may remember from digging holes on the beach either as a child or with your own children, that once you get down to the water you cannot dig any deeper without causing the sides to collapse. The reason is that the pore water pressures in saturated sand holds the grains apart and reduces the frictional grip between the grains. As a result the sand grains move easily past each other and produce a quicksand effect keeping the hole full while causing it to collapse along the sides. The same sort of thing happens when large excavations are dug in civil engineering construction. To prevent collapse and allow the building work to continue the sand is dewatered so that it is no longer fully saturated. Dewatering is also important when digging in materials other than sand where groundwater pressure may cause the excavation to collapse, the base to heave up or cause damage to the engineering structures.

This book is concerned with all aspects of groundwater control in construction with the by-line in the title claiming it to be a practical guide, a claim that is well met throughout the text. In a sense the book is an unusual co-operation, in that Pat Cashman started writing soon after his retirement, basing the book on a lifetime career in dewatering and groundwater control. Sadly, he died midway through the project and the editors asked Martin Preene to complete the work. As it turns out this was a wise choice as he has achieved Pat Cashman's objective of a practical guide with the new text blending seamlessly with the original.

The contents of the book are "topped and tailed" by an introductory personal view of groundwater lowering by Pat Cashman and a look to the future provided as a final chapter by Toby Roberts. The fourteen chapters in between provide a structured guide through what Martin Preene calls the challenging business of groundwater control. Chapter 2 introduces the history of groundwater theory and practice from the ancient Greeks and Romans through to the present day. Chapter 3 covers groundwater and permeability introducing and describing these basic concepts as well as aquifers, aquitards and aquicludes; groundwater flow; and groundwater chemistry. Chapter 4 then describes the ways in which groundwater affects the stability of excavations with the next chapter introducing methods for controlling surface water and groundwater.

Succeeding chapters cover site investigation methods and the design of groundwater lowering systems, with the common methods of pumping from a sump, well points and deep well systems each being given a separate chapter. Less commonly used methods are also covered including the use of horizontal wellpoints, pressure relief wells and electro-osmosis. Practical guidance is provided on the choice of pumps for dewatering schemes. The potential unwanted impacts of dewatering include settlement, reductions in groundwater supplies and deterioration in groundwater quality as well as surface water impacts from discharging the pumped water. These are fully covered together with monitoring and maintenance, and safety, contractual and environmental regulatory considerations. Throughout the authors provide a blend of theory and differential equations with practical tips on how to achieve your objectives without causing disaster. The book has a large number of excellent diagrams and black and white photographs which are all used to great effect in assisting the understanding of the text. The index extends to six pages and is sufficiently comprehensive to help the reader. Each chapter has a list of references although there is no index of authors to help find details of texts and papers without having to look through each list. The book includes the helpful additions of a key to the notation used, a glossary of terms, conversion factors and a list of abbreviations for units of measurement. Overall the choice of paper, the clarity of print and the layout have produced a book that is pleasing to handle and a pleasure to use.

The book has been written from what the authors describe as an unashamed engineering viewpoint. Nevertheless, I am sure that it will be well received by hydrogeologists working in allied fields and will make a useful contribution to the growing number of practical textbooks in the groundwater field.

I am pleased to recommend this book to all those who have any interest in groundwater control whether as a practitioner of groundwater control, a design or site engineer involved in construction, or as an environmental manager. Unusually for a textbook it also provides an interesting read for the informed layman. In addition it may go some way to improve an understanding between the often-competing objectives of removing a construction problem by the engineer and protecting water resources and the environment by the environmental manager.

This review appeared in the Journal of the Chartered Institution of Water and Environmental Management 2002, Volume 16, No 4, page 300.

Copyright © CIWEM 2002