Protecting Ohio's Groundwater

An Ohio groundwater source map provides the framework used by the Division of Oil and Gas Resources Management to establish well casing programs that will protect all groundwater resources when reviewing oil and gas well permit applications.

Pursuant to Section 1509.17 of the Ohio Revised Code, all underground sources of drinking water (USDW) must be isolated and protected from potential contamination when drilling oil, gas and brine wells in the state.

A 1970 study done in northwestern Ohio defined the USDW in that part of the state as the Lockport Dolomite. In 1982, a groundwater mapping study was done to delineate the deepest fresh-salt water interface in eastern Ohio. That interface was defined using the U.S. Environmental Protection Agency definition of a USDW of 10,000 mg/l of total dissolved solids. Water samples from wells throughout the region were collected and analyzed and maps showing the interface were subsequently prepared. In 2011, the Ohio Geological Survey updated and prepared a new map that combines the earlier works into one statewide USDW map.