1. Ground-water levels and flow directions in the glacial sediments and the Lockport dolomite in southeastern Darke and northeastern Preble counties, Ohio, July 1998 Yale Public content 1999. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; Information Services [distributor]. English. Public. Ohio, Darke County, Preble County, and Lockport Group.