Soil sampling is an important part of the site/ground investigation process. It is typically carried out by drilling boreholes spaced at intervals along (but not directly within) the alignment of a project with extra boreholes located where additional information is needed for project design. The boreholes usally are sealed after the sampling is complete to prevent them from affecting the subsequent construction process. In some instances (e.g. to investigate the presence of cobbles and boulders for microtunneling), larger trial pits may be used to allow the identification and quantification of the potential obstructions.