KARST PHASE I INVESTIGATION - IDENTIFY SINKHOLES BEFORE THEY DEVELOP

After a sinkhole develops is not the most opportune or the most cost effective time to investigate. Typically in karst areas, a cursory investigation is conducted during the planning stages of land development, mostly to satisfy municipal ordinances. To better understand the subsurface conditions of a site underlain by carbonate geology, a more comprehensive investigation must be completed. Surface geophysics is the most practical, efficient, and cost effective non-intrusive method of evaluating the subsurface because it can be used to screen a large area that would be too costly or inefficient to use other more intrusive methods such as borings or excavation. Geophysics can reveal voids, pinnacles, or wet zones that can be more thoroughly investigated prior to construction. These areas of concern can be investigated with the use of borings or excavation to observe the nature and extent of the possible hazard. At this time, if the situation warrants, the area may be addressed and any potential sinkholes repaired. The important aspect of sinkhole repair is not the repair method but rather identifying the potential sinkhole before it develops. A more comprehensive investigation that identifies subsurface problems will assist in answering some questions; Is it better to repair the potential sinkhole in an open field prior to construction activities or be surprised when a sinkhole opens up under a newly paved street with several utility lines undermined giving no support? When is it more cost effective to budget for sinkhole repairs, during the planning stage before loan process or after construction when there is no budget for such repairs? These questions need to be addressed when planning any construction in karst areas to determine risk tolerance. The answers may be more than the budget permits.