Fsg = predominantly fines with sand and gravel lenses. This setting is commonly found in valleys. Fines include alluvium, minor lacustrine (slackwater) deposits, till and colluvium
NA = not applicable
SGf = predominantly sand and gravel with minor fines. Typically represents thick sequences of outwash/valley train deposits with minor alluvium, lacustrine deposits, etc.
SGt = predominantly sand and gravel with thin covering of till or thin interbedded layers of till. Commonly associated with ice-contact features, i.e. kames, eskers, some moraines, etc. It is also associated where thin beach ridges directly overly till.
T = predominantly till, water well logs typically lack indication of sand and gravel lenses. Wells are typically finished in the underlying bedrock. Wells commonly are developed at or near the drift/bedrock contact. Shallow dug wells may still be used on a limited basis. Shallow monitor wells may be completed in this unit. Many of these mapped areas are shallow to bedrock; mapping may include small areas where bedrock comes to ground surface
Tsg = predominantly till, contains sand and gravel lenses of varying thicknesses. These lenses may or may not be interconnected. Wells are developed in these lenses.
Thick: <25' = Areas with less than 25 feet of drift. May include areas where bedrock comes up to the ground surface. Area delineated by Div. of Geological Survey Bedrock Topography and Drift Thickness Maps, soils maps, and well log data.
25'-100' = Areas with 25 to 100 feet of drift.
100' = Areas containing over 100' of drift. Thicknesses over 400' have been reported in isolated parts of the state. These areas are predominantly buried valleys, thick end moraine sequences, or thick drift complexes.Thickcode: 1 = <25' 2 = 25-100' 3 = >100' 4 = NA
Yield: Yields refer to a typical or reasonable sustainable yield. In many areas a very large diameter, screened well or a well screened at multiple levels could produce higher yields. It is also possible that lower-yielding wells could be completed within the mapped area.
Yields also roughly correspond to lithology as well. For example, in an area mapped Tsg with a yield of 25-100 gpm, the sand and gravel layers are probably more numerous, thicker, or better interconnected than in a Tsg with a yield of 5-25 gpm. Also, wells completed in areas with sand and gravel lenses occurring at several elevations (i.e. "stacked" sand and gravel lenses) may be able to be screened at multiple depths. This would help to increase the overall yield of wells developed in the drift. Maximum sustainable yields in the "lower" aquifers may be questionable in some areas. In such areas, well logs typically indicate thicker coarse deposits, but high-yielding wells are lacking in the vicinity. Test-drilling or geophysical techniques may be necessary to locate the higher-yielding units. The lateral extent of these units may also be unknown. Many of these units are not overlain by modern streams or may have an overlying aquiclude which inhibits recharge. In these situations, the long-term sustainable yield may be less than anticipated.
<5 gpm = Typically corresponds to areas with thin drift, areas lacking sand and gravel lenses as reported by well logs, and areas where bedrock is almost exclusively the aquifer.
5-25 gpm = Aquifer is typically thin sand and gravel lenses interbedded in thicker sequences of till, finer-grained alluvial, or lacustrine deposits.
25-100 gpm = Transitional areas, typically along the margins of buried valley systems, in smaller "tributary" buried valleys, in coarser alluvial valleys, associated with some end moraines and kames, and in some of the thicker, coarser beach ridges.
100-500 gpm = Commonly associated with buried valley systems containing appreciable outwash sand and gravel, some kame complexes.
Yieldcode: 1 = <5gpm 2 = 5-25gpm 3 = 25-100gpm 4 = 100-500gpm 99 = NA
Local: This coverage consists of a set of localized names for aquifers.
Lake Erie Tributary = Refers to a number of small, non-related tributary streams that empty into Lake Erie. Typically, these streams contain 25-100' of drift and yields of 5-25 gpm are obtained from sand and gravel lenses interbedded with the finer alluvial and underlying lacustrine deposits.
Lake Maumee = This local occupies a very large area in northwestern and north central Ohio. This local extends from the Indiana border eastward to the Rocky River in Cuyahoga County. This area corresponds to the Lake Plain of ancestral Lake Erie. It is typically characterized by flat-lying topography and drift thickness varying from 25-100' to less than 25'. Areas of moderate drift thickness are usually adjacent to modern river valleys. Yields of 5-25 gpm are obtained in areas where sand and gravel lenses interbedded in the fine lacustrine deposits or underlying till occur. Yields are minimal in areas where the drift is very thin, or where sand and gravel lenses are absent. This local also includes numerous thin beach ridge settings. These beach ridges are primarily composed of fine sand with layers of coarser sand and gravel at their base. Where these deposits are thin, minimal yields were obtainable by drive point or dug well methods. In thicker deposits, shallow drilled wells may be utilized. Yields of 5-25 gpm and rarely, 25-100 gpm, may be obtained from the thicker, coarser beach ridge deposits. The Oak Openings in parts of Lucas and Fulton Counties are mapped as separate local aquifers. In parts of Defiance, Fulton, and Williams County immediately adjacent to the Williams local aquifers; thick, coarse sand and gravel outwash deposits are found at depth. These deposits underlie the surficial lacustrine deposits and beach ridges. Yields of 100-500 gpm may be obtained from these thick, underlying deposits.
Maumee River = Important tributary of Lake Erie in northwestern Ohio. These alluvial settings commonly contain 25-100' of drift. Yields of 5-25 to 25-100 gpm are obtained from sand and gravel lenses interbedded with the finer alluivum or the underlying till and lacustrine deposits.
NA = not applicable
Oak Openings = Local includes two large separate areas of beach ridge (delta) settings in western Lucas County and in Fulton County. Both areas are encircled by the Lake Maumee local. Thickness of these beach ridge deposits varies from less than 25' to 25-100'. Deposits are primarily fine sand; however, coarser sand and gravel layers are relatively common at the base of the thicker deposits. Where deposits are thin, shallow well points and dug wells were historically utilized and obtained yields less than 5 gpm to 5-25 gpm. Drilled wells are utilized where the deposits are thicker. Wells commonly obtain yields of 5-25 gpm. Yields of 25-100 gpm are obtained in some areas where wells encounter the coarser deposits at the base of the ridge. Yields are also obtained from sand and gravel lenses interbedded with the underlying till or lacustrine units. These lenses tend to be thicker and more productive in areas where the surficial sand and gravel beach deposits tend to be thicker and more productive.
Williams = Large area in extreme northwestern Ohio including most of Williams County and adjoining sections of Defiance and Fulton Counties. This local consists of both thick drift complex and end moraine settings. Drift thickness is greater than 100' in all parts of this local. Yields of 100-500 gpm to greater than 500 gpm are obtained from thick sand and gravel sequences which underlie the till at depth. In most areas multiple levels or zones of sand and gravel occur.
Setcode: 1 = Buried valley 3 = End moraine 4 = Lacustrine 6 = Alluvial 7 = Beach ridge 9 = Complex 99 = NA
Setting: Alluvial = Areas containing modern streams not associated with major buried valley systems. Includes primarily fines, water obtained from interbedded lenses or layers of sand and gravel. Drift is typically <100 ft.
Beach Ridge = Refers to typically thin, linear features found on the Lake Plain in northern Ohio. Includes dunes, deltas, and other coarse-grained shoreline deposits. Comprised primarily of sand and gravel. Locally, can be important shallow aquifers.
Buried Valley = Thick drift filling previously existing valley incised into bedrock. Drift thickness typically >100ft. Predominantly contains fines (silts, alluvium, lacustrine, etc.) and sand and gravel. Modern streams commonly overlie these features. Yields are typically 100 gpm or greater.
Complex = Areas of thick drift (usually >100ft). Drift typically comprised of thick accumulations of glacial till (and lacustrine). Water is obtained from thin, interbedded lenses of sand and gravel. Areas may consist of a combination of settings such as end moraine overlying a buried valley
End Moraine = Moderately thick (25-100ft) to thick (>100ft) drift primarily composed of till. Water is obtained from thin, interbedded lenses of sand and gravel. Commonly correspond with end moraines as mapped on the Glacial Map of Ohio and other Division of Geological Survey publications. These features are typically ridges with hummocky topography. They often function as local drainage divides.
Lacustrine = Includes areas of Lake Plain adjacent to Lake Erie. Commonly fine-grained silts and clays containing thin, interbedded lenses of sand and gravel. Also includes some areas where the underlying till was heavily eroded by wave activity. Inland, refers to settings containing fine-grained lacustrine and slackwater materials deposited in ponded areas. Ponded areas typically occur between end moraines in western Ohio or in alluvial valleys in eastern Ohio.
NA = not applicable
Name: This coverage combines the local name used in conjunction with settings. Example, Lake Maumee beach aquifers, etc. The locals do not necessarily imply that the aquifers are continuous, but that they are similar in type in a given geographic area.