Prior to the promulgation of the Tennessee Solid Waste Regulations in March 1990 subsurface investigations at all solid waste landfills were limited to a few drill holes which were primarily used to determine the approximate depth to bedrock. Additional investigations for proposed landfill facilities in Karst terranes were generally limited to a search for karst features by performing a site walkover. If a surface depression was discovered at a site the Division had a policy which limited filling of waste directly above sinkhole depressions. Current regulations specifically address Karst terranes. The following paragraphs detail the requirements that must be satisfied when landfill facilities are proposed within karst terranes.