This paper discusses the principles and arrangement of pumping wells esigned as part of a dewatering system to ensure the stability of deep soil excavations and the safety of adjacent structures. The paper presents a case study of a large-scale dewatering system in a deep excavation for an underground Power Transformer Station in Shanghai, People's Republic of China. Various construction methods are discussed to prevent excessive total and differential settlements that may result from dewatering. Theoretical predictions of settlement, based on the calculation of pore water pressure, are also presented, including the calculation of ground water table in the aquifers. The ground water table, pore water pressure and surface settlements were measured during the excavation process. This allows for comparisons between the measured values and the theoretical predictions. The paper concludes that the prediction of settlements, by the methods presented, is in good agreement with field measurements. These theoretical models can become powerful tools for the geotechnical engineer during the design stage of a dewatering system for an excavation project. Optimized designs will likely result from the use of theoretical models and allow the geotechnical engineer to present a variety of “what if” scenarios that will result in a well engineered dewatering system.