Presentation of Geological Data

Engineering for dams and canals requires geological data input at all stages of investigation from pre-feasibility assessment through to the completion of construction, and the engineering geologist must be in a position to influence both the formulation and execution of the various investigation programmes. Engineering geological data for site reconnaissance is available through published sources, air-photo interpretation, and site inspection: for detailed site investigation data sources include engineering geological mapping, engineering geophysics, drilling and sampling, borehole testing, and surface and subsurface excavations. Engineering geological data input is essential to provide construction records, and to permit design modifications that may prove necessary after exposure of the site foundations. The presentation of geological data for dam and canal projects requires standardised descriptive terminology for rocks and soils, as well as appropriate techniques for site mapping and excavation and core logging. The selection of data presentation methods is influenced by the stage of investigation and by the type of geological terrain. It is essential that the information presented is relevant, accurate, and that a clear distinction is drawn between 'fact' and 'inference'. Engineering geological reports constitute essential documentation of site conditions, and should be prepared at appropriate stages of project development, whilst greater publication of New Zealand dam and canal case histories is strongly recommended.