Archival material and site investigations

Abstract

The prediction of subsurface conditions at building sites is a prime responsibility of the geotechnical engineer, and the improved accuracy with which he can make such predictions is a continual challenge. Information is derived primarily by studying the local geological and groundwater conditions, and from sampling and testing of soil and rock. In most instances, this procedure provides adequate assessment of the conditions likely to be encountered during construction. Increasingly, however, particularly in towns and cities, building sites are located where the natural terrain may have been altered significantly by earlier human activity, such as the erection and demolition of buildings and other structures, excavation and subsequent filling of pits and quarries, and the reclamation of land at waterfronts. The remains of these activities are now buried and hidden from view but they may present unusual and sometimes unexpected conditions, which can complicate the construction of new foundations and lead to increased costs for unanticipated work. Records of these earlier activities are sometimes available in drawings, maps, and paintings housed in local archives, and it is the thesis of this paper that these often constitute a useful tool in subsurface investigations—one that is too often overlooked. To support this contention, several case histories illustrating valuable information derived from archival material are cited, including examples from Canada, the United States, and Europe. Key words: archival material, site investigation, anthropogenic material.