While a site visit may have taken place during the contracting phase of work, these are rapid tours of a site with little time to stop and observe or take detailed notes. The site walkover is when we get our fi rst chance to make good observations and an initial assessment of general site conditions. It provides an opportunity to evaluate and expand our preliminary understanding of site conditions obtained from the desk study and the review of aerial photos. This initial effort should allow adequate time for the site to be covered. The observations made and information gathered from a site walkover should include geologic and hydrologic observations, inventory of karst features, indications of subsidence or sinkhole activity as well as an assessment of cultural features that may impact access, safety or a particular method of measurement used on site.While the site walkover has many objectives, it should progress from a reconnaissance overview to obtain fi rst impressions and then begin to gradually focus upon the sitespecifi c details. On-site observations must not be limited to a single site walkover, but as the fi eld effort proceeds, additional site walkovers and observations should be incorporated throughout the site characterization process.