In cooperation with the City of Delphos, Ohio
Background Hydrogeologic Data, Water Quality, and Aquifer Characteristics, Western Allen County, Ohio
By Rodney A. Sheets
ABSTRACT
The carbonate aquifer of northwestern Ohio is used extensively for domestic, industrial, and public water supplies. The City of Delphos, Ohio, would like to expand its current ground-water supplies with wells completed in the carbonate aquifer in Amanda Township, Allen County. Surface- and borehole-geophysical surveys were used to determine thickness of the glacial till overlying the carbonate bedrock and the extent and orientation of fractures in the carbonate bedrock. Water- quality and water-level data were collected before and during a constant-rate aquifer test to determine general hydrogeologic characteristics of the area. Previous drilling and borehole geophysical data indicated water-bearing fractures in the aquifer at depths greater than 190 feet. Aerial photographs and surface geophysical data indicate northwest-southeast-trending features that might be related to near-surface fracturing of the overburden. Water quality and tritium data show that recharge rates through the glacial till covering the carbonate bedrock are slow and that sand lenses within the till contain water of different quality than that within the carbonate aquifer. The potentiometric surface of the carbonate aquifer is virtually flat (nearly zero gradient), but water levels in paired wells indicate that recharge takes place near a proposed well field and that regional discharge is to the Auglaize River, east of the proposed well field.
A constant-rate aquifer test on a well in the proposed well field yielded an average transmissivity of the carbonate aquifer of approximately 28,000 to 36,000 gallons per day per foot and an average storage coefficient of 3x10-5. The aquifer test was prematurely terminated because of a decrease in flow from a nearby spring that flows into and forms a wetland. Water quality of the spring more closely matches that of water from the carbonate aquifer than the water from the glacial aquifer. Historical accounts, response of spring flow to pumping of nearby wells, and proximity of several abandoned wells all suggest that the spring is actually an abandoned flowing artesian well.
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