MOUNT VERNON — A round hole, about 18 inches across and 4 feet deep, appeared Wednesday morning in the parking lot of the Public Library of Mount Vernon and Knox County. The best guess of Library Director John Chidester and Mount Vernon City Engineer Cameron Keaton is there is an old cistern underneath.

Before water systems were available in cities, Keaton said, individual homeowners dug holes and lined them, most often with brick, to store water for washing and other home use. There are also several cisterns around Public Square that were dug by the city for fire protection.

The hole will need to be excavated to determine what is down there. Chidester said an 1871 city map shows a dwelling was on the lot. Library maintenance man Jack Boesher said he can see brick and sandstone in the hole.

Keaton said workers will have to open the hole and clean out the cistern to determine if there are any breaks or openings where water may be draining out. When the cistern is closed, it will be filled with gravel and paved over. The library is responsible for the repair, Keaton said, as there are no city water or sewer lines involved.