An Italian firm, the Impresa Construzioni Opere Specializate, has long been known in Europe as a specialist organization for dealing with foundation and soil problems. Its activities cover the full range of soil studies, including investigation, treatment to improve bearing capacity and permeability or to provide impervious barriers against seepage, and the design and completion of difficult foundation and drainage jobs in reinforced concrete. Difficult excavations are also a specialty. All of this specialist knowledge has recently been combined in the development of a new system which allows the use of site-cast reinforced concrete instead of driven sheet piling in the construction of underpass retaining walls prior to the main excavation. The result is a stronger, permanent, impervious wall with a number of impressive advantages. The ICOS method was chosen for a London job on the basis of its two outstanding advantages over driven sheet steel piling: lack of noise and lack of vibration. The avoidance of noise was a major factor since most of the work is in the vicinity of a large hospital where pile driving is forbidden by city regulations. In this heavily built-up area vibration could play havoc with sewers and services and existing foundations. A further advantage is the impermeability of the retaining wall, which means that the main excavation and construction can proceed rapidly and safely below ground water level. The wall can also follow the profile of impervious underlying strata and can cross below-grade obstacles without difficulty.