Ohio State University Extension

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Logan County Ground-Water Resources

AEX-490.46

Chuck Gamble
A. Wayne Jones
Larry C. Brown
Kristina M. Boone

Water stored under the earth's surface is a plentiful, yet precious, resource in most areas of Ohio. Many human activities may affect the quality and quantity of this resource. However, the availability and quality of this resource are influenced directly by the properties of the geologic formations that hold water. The chemical and physical nature of these formations varies from area to area, creating a wide range of water yields and quality at different depths. This publication contains information about the ground-water resources underlying Logan County. Its purpose is to help the reader better understand the factors that influence the quantity and quality of ground water. An overview of the county's water resources is provided in the publication Logan County Water Resources, AEX-480.46.

Much of the water resource and water quality terminology used in this publication is described in Extension Facts Sheets AEX 460 and 465. Ohio Extension publications are available through the Logan County office of Ohio State University Extension.

Aquifers

Geologic formations (e.g., sand, gravel, limestone, sandstone) have the ability to receive, store and transmit water. In general, if a formation is capable of yielding enough water to support a well or spring, it is called an aquifer. The material from which the formation originally was made influences its ability to store and transmit water. For example, sand and gravel allow water to flow through easily. By comparison, shale, which originated from compacted layers of mud and clay, generally allows very little water to flow through it unless the shale is highly fractured.

The regional carbonate aquifer, which is composed of layers of limestone and dolomite, is the principal source of ground water in west-central Ohio, including Logan County. Limestone consists of fossilized sea shells, shell fragments, calcareous sand and consolidated limy mud. The main mineral in limestone is calcium carbonate, CaCO₃. Dolomite is similar to limestone, but has few recognizable fossils; its main mineral is calcium magnesium carbonate, (Ca,Mg)CO₃. Both limestone and dolomite are commonly referred to as carbonate rocks. The limestone and dolomite formations, which underlie most of the western portion of Ohio, were deposited about 400 to 500 million years ago. These formations are covered by a layer of glacial till, which is an unsorted mixture of clay, silt, sand, gravel and boulders deposited by glacial processes.

Limestone formations usually are adequate sources of ground water because of their naturally formed solution channels, joints and fractures, which provide water storage capacity and pathways for water movement. The number of fractures and other openings in limestone varies greatly from one location to another and affects the amount of water that may be encountered when drilling a well. The position of such openings rarely can be determined from the land surface; therefore, there is always some uncertainty as to the production capability of a proposed well. Ground water also occurs in lenses (or pockets) of sand and gravel deposited by glacial processes. These deposits occur above the carbonate bedrock and may be embedded in the glacial till or deposited in stratified layers.

Well Yield

The actual yield of a well, in gallons per minute (gpm), will vary considerably depending on the age and depth of the well, the diameter of the casing, well construction, pump capacity and age, and most importantly, properties of the geologic formation. The exact yield and depth of each well will depend on the properties of the geologic formation at the specific location of the well.

Ground-Water Availability

To support the development of ground-water availability assessments in Ohio, the Ohio Department of Natural Resources (ODNR), Division of Water, maintains a statewide database of more than 700,000 well logs. The Ground-Water Resources Section of the Division manages this valuable database, which includes some information collected by the U.S. Geological Survey (USGS) and the Ohio Environmental Protection Agency (Ohio EPA). Since 1948, well-log information has been collected to increase the understanding of the ground-water resources in Ohio. Geologists and hydrogeologists continue to study the state's ground-water resources. As a result, Ohio is one of only a few states that has been completely mapped for ground-water availability (mapped by river basin, from 1959 to 1962).

Estimates of the size, shape, geologic make-up and yields of aquifers are being mapped county by county. Most of Ohio's counties have a completed map. The map presented in Figure 1 is a generalized representation of the water-bearing formations underlying Logan County (adapted from map by Schmidt, 1983). This illustration is based on a hydrogeologic interpretation of the well-log data from Logan County and surrounding areas. It should be used only as a guide to understanding the ground-water resources in the county. The section below provides a brief description of the types of aquifers illustrated on the map in Figure 1. Figure 2 is a generalized cross section (referenced in Figure 1 as the line X-X') of the majority of Logan County. This cross section shows the range of depth to bedrock as well as the variation in composition of the glacial till. Notice the buried valley located in the western part of the county. Also, note the highest point in Ohio at Campbell Hill, east of Bellefontaine, with an elevation of 1549 feet above sea level.

Figure 1. Ground-water resources of Logan County, Ohio (adapted from ODNR Division of Water map by J. Humphreys).

Figure 2. Generalized cross section of Logan County, Ohio (adapted from ODNR Division of Water map by R. Roberts).

AREA A: Limestone, High-Yield Potential

Area A in Figure 1 is the primary and most productive aquifer in Logan County. Yields of 500 gpm or more may be obtained at depths ranging from 120 to 285 feet. Farm and domestic supplies of 10 to 15 gpm are usually encountered at depths of less than 125 feet. However, lenses of sand and gravel interbedded with clayey till may serve as a source of water supply at depths ranging from 25 to 75 feet.

AREA B: Flowing Wells

Located in Perry Township, Area B is characterized by the presence of artesian flowing wells. As a result of the differences in the elevation of the water level and ground surface between two parts of the area underlain by this limestone formation, water pressure causes some of the wells to continually flow once drilled.

AREA C: Thick, Permeable Sand and Gravel

Area C is located around the town of West Liberty near the Mad River. When large-diameter wells have been properly constructed and screened, these permeable sand and gravel deposits have proven yields in excess of 500 gpm at depths of less than 100 feet.

AREA D: Fine Sand, Silt and Clay

A buried valley filled with thick deposits of fine sand, silt and clay is represented as Area D. These deposits are interbedded with lenses of permeable sand and gravel. Yields sufficient for domestic supplies of 5 to 15 gpm are common, but greater yields can be expected. Properly screened wells yield as much as 500 gpm at depths of about 100 feet, although these glacial deposits are more than 300 feet thick.

AREA E: Limestone/Dolomite

The limestone/dolomite aquifer in Area E yields as much as 100 gpm at depths of less than 250 feet. Water from this aquifer contains sulfur. However, wells of less than 100 feet are often drilled to secure sulfur-free water from the sand, gravel and limestone that lie above this limestone/dolomite formation.

AREA F: Shallow Permeable Sand and Gravel

The sand and gravel deposits beneath the headwaters of the Mad River are illustrated as Area F. Properly screened and developed wells may yield up to 50 gpm at depths as shallow as 80 feet.

AREA G: Limestone, Low-Yield Potential

Area G contains wells that are developed in limestone bedrock at depths usually greater than 125 feet. Domestic supplies of 10 to 20 gpm are commonly developed in the surface layers of glacial deposits at depths of less than 90 feet.

AREA H: Shallow Sand, Gravel Interbedded with Thick, Clayey Till

The poorest yielding formation in Logan County is located in Area H. Water is obtained from thin layers of sand and gravel interbedded in thick layers of clayey till. These interbedded layers are underlain by non-water-bearing shale bedrock. Yields from the interbedded layers are satisfactory for domestic use, but caution should be used if wells are drilled into the shale bedrock. Wells developed at depths greater than 200 feet encounter limestone bedrock, but the presence of sulfur may be objectionable.

Ground water, whether obtained from bedrock or glacial deposits, may require some treatment. In some areas, water containing calcium carbonate (CaCO₃, i.e., hard water), and iron concentrations greater than 0.3 ppm may require treatment for some uses (see notes in Table 1). Wells drilled into shale or limestone may produce water that contains objectionable quantities of hydrogen sulfide (rotten egg odor). In general, the probability of obtaining sulfur in objectionable amounts increases with the depth drilled.

Ground-Water Levels

The water level in any well usually does not remain constant, but may change depending upon several factors. Rainfall distribution and amount, and fluctuating water level in a stream that is hydraulically connected to an aquifer, may affect ground-water recharge and discharge, and subsequently may affect the water level in area wells. Also, in some cases, depending upon the hydraulic properties of the geologic formation, the intense pumping of a well, or number of wells, may cause the water level in some nearby wells to be lowered. The ODNR Division of Water does not monitor any wells in Logan County. However, an observation well is located in neighboring Shelby County near Sidney. This well is one of a number of wells throughout west-central Ohio used to monitor the natural seasonal fluctuation on water levels in the carbonate aquifer.

The Shelby County observation well is 280 feet deep and the depth to limestone is approximately 136 feet. It is representative of many limestone wells in the region. Continuous water level measurements have been recorded at SH-4 since September 1979. The lowest level recorded on SH-4 (Sidney) was 94 feet below land surface in October 1982; the highest level recorded was 56 feet below land surface in April and June 1990.

Ground-Water Quality

Various state and federal agencies have participated in programs to determine the ground-water quality in Ohio. For six wells in Logan County, water-quality data were available from the ODNR Division of Water. In Figure 1, these wells are noted as Chemical Analysis Sites 1 through 6. These sites are either municipal or private wells.

The results from some of the chemical tests performed on these Logan County wells are given in Table 1. The chemical constituents listed are total dissolved solids, hardness (as CaCO₃), iron and sulfate. For comparison purposes, secondary drinking water-quality standards for these chemical constituents also are shown. These standards are established by the U.S. Environmental Protection Agency (USEPA) for public water systems for aesthetic reasons (taste, odor, appearance, etc.), and are not enforceable. These chemical constituents do not pose a risk to human health (see notes in Table 1). For private wells, there are no legally enforceable drinking water-quality standards other than total coliform, which is an indicator of bacteriological quality.

The information in Table 1 can be used as a guide to what one might expect from an existing or new well developed in similar geologic material in the county. This information provides a general representation of the quality of the water at the time of sampling, which was not the same for all wells. In most cases, the data provided in Table 1 was taken from a water sample obtained just after the well was put into operation. Even though four of these wells were developed in the limestone underlying Logan County, and these wells are in the range of 200 to 350 feet deep, some variation exists in the concentrations of each of these chemical constituents. Just as well yields differ, water quality will vary depending on aquifer properties at the specific location of each well. One should not forget that many human activities also affect the quality of ground water (see AEX 465).

Table 1. Chemical constituents of selected Logan County wells1.
Well No.	1	2	3	4	5	6	WQ Std2
Well Depth (feet)	350	260	95	200	33	202
Capacity (gpm)	220	10	210	400	20	115
Depth to Bedrock (feet)	17	203	NE3	119	NE	120
Water-Bearing Formation4	LS	LS	SG	LS	SG	LS
Chemical Constituents5
Total Dissolved Solids	502	487	1049	435	329	-6	500
Hardness (as CaCO3)	460	469	770	444	310	349	none7
Iron	0.83	0.11	0.6	0.49	0	1.09	0.3
Sulfate	100	111	440	80	46	25	250
1 Data on these wells from map by J.J. Schmidt, 1983; General location of each well is shown on Figure 1.
2 USEPA Secondary Water Quality Standard.
3 Well constructed in this formation did not encounter bedrock.
4 SG - Sand and Gravel; LS - Limestone.
5 Units are parts-per-million, ppm; Comments as per "Interpreting Your Water Test Report" (1988); Total Dissolved Solids: Concentrations above 500 ppm may cause adverse taste and deteriorate domestic plumbing and appliances. Use of water containing 500 ppm is common. Hardness: Primary concerns are that more soap is required for effective cleaning, a film may form on fixtures, fabrics may yellow and scales may form in boilers, water heaters and cooking utensils. Iron: Concentrations greater than 0.3 ppm may cause rust-colored stains on laundry, plumbing fixtures and sinks. Metallic taste may be present, which may affect the taste of beverages made from the water. Sulfate: Concentrations in excess of 250 ppm may have laxative effect on people unaccustomed to the water. Also affects the taste of water and will form a hard scale in boilers and heat exchangers.
6 Data not available.
7 No USEPA Secondary Standard.

Summary

Logan County's ground-water resources are valuable assets to the county's citizens and industry. The availability and quality of these resources are directly influenced by the properties of the geologic formations underlying the county. The productive limestone, and sand and gravel formations that underlay much of Logan County have the potential to provide excellent water adequate for domestic and agricultural uses, and many municipal uses. By understanding the physical and chemical nature of these resources, better decisions can be made about ground-water protection, management and use. This publication provided an overview of the county's ground-water resources. It should be used as a guide, and not as a substitute for detailed information and professional advice when drilling a well.

Where to Get More Information

The Logan County office of Ohio State University Extension can provide other publications on the county's water resources. Your Extension agent, the Logan County Health Department, and Ohio EPA Southwest District Office - SWDO (40 South Main St., Dayton, OH 45402) can provide information on well-water testing and drinking- water quality. The ODNR Division of Water - Ground-Water Resources Section (Fountain Square, Columbus, OH 43224) is an excellent source of information on ground water. Some of the information in this publication was summarized from a map titled Ground-Water Resources of Logan County, and other information available through the Division of Water. This map is much more detailed than that given in Figure 1 of this publication. In addition, personnel in the Ground-Water Resources Section can provide you with more detailed information about ground-water availability and wells. The USGS, Ohio District (975 W. Third Ave. Columbus, OH 43212), also provides information concerning ground water in Ohio.

Bibliography

Ground-Water Resources of Logan County. 1983. J.J. Schmidt. ODNR Division of Water. (map).

Interpreting Your Water Test Report. 1988. D. Lundstrom and S. Fundingsland. AE-937, No. 13-AENG-10. North Dakota State University Extension Service.

Logan County Water Resources. 1993. C.H. Gamble, K.M. Boone and L.C. Brown. AEX-480.46. Ohio State University Extension.

Nonpoint Source Pollution: Water Primer. 1993. R. Leeds and L.C. Brown. AEX 465. Ohio State University Extension.

Ohio Ground-Water Quality. USGS National Water Summary - Ohio. 1986. U.S. Geological Survey Water-Supply Paper 2325.

Ohio Ground-Water Resources. USGS National Water Summary - Ohio. 1984. U.S. Geological Survey Water-Supply Paper 2275.

Shelby County Ground-Water Resources. 1992. R.F. Bender, A.W. Jones, K.M. Boone and L.C. Brown. AEX-490.75. Ohio State University Extension.

Southwest Ohio Water Plan. 1976. ODNR Division of Water.

Surface and Ground Water Terminology. 1990. L.C. Brown and L.P. Black. AEX 460. Ohio State University Extension.

Underground Water Resources (maps of various river basins). 1958-1962. ODNR Division of Water.

Water Testing. 1988. K. Mancl. AEX 314. Ohio State University Extension.

Acknowledgments

This publication was produced through the Ohio Water Resources Education Project, in cooperation with: ODNR Division of Water; Ohio EPA; USGS, Ohio District; and Ohio Department of Health (ODH). Project leaders are Larry C. Brown and Kristina M. Boone. Support for this publication was provided, in part, by: cooperating agencies; Ohio State University Extension, Logan County; Logan County Commissioners; Greater Logan County Area Chamber of Commerce; Logan County Farm Bureau; Logan County Health Department; Logan Soil and Water Conservation District; Logan County Schools (Benjamin Logan, Indian Lake and Riverside); Overholt Drainage Education and Research Program; and USDA Extension Service grant Nos. 90-EWQI-1-9018 and 90-EHUA-1-0020. The project leaders acknowledge the following reviewers: William A. Verbsky (Logan County Health Commissioner); Rita Edwards and Rebecca Newland (Logan County District Library); Scott Golden (Environmental Health, ODH); Steve Hindall (USGS, Ohio District); and Rich Bendula (Ohio EPA, SWDO).

A special thanks to Michelle Roby, Ross Roberts, and John Humphreys (Agricultural Engineering Undergraduate Assistants) for help in graphic and manuscript preparation, and Judy Kauffeld, Publications Editor (Section of Communications and Technology, Ohio State University), for editorial and graphic production.