Ohio State University Extension

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Hardin County Ground-Water Resources

AEX-490.33

Gene McCluer
Cynthia A. Brookes
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 Hardin 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 Hardin County Water Resources, AEX-480.33.

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 Hardin 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 carbonate aquifer, which is composed of layers of limestone and dolomite, is the principal source of ground water in west central Ohio, including Hardin 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 between about 400 and 500 million years ago. In most areas of this region, 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 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 Hardin County (adapted from map by J.J. Schmidt, 1983). This illustration is based on a hydrogeologic interpretation of the well-log data from Hardin County and surrounding areas. It should be used only as a guide to understanding the ground-water resources in the county. The remainder of this section provides a brief description of the types of aquifers illustrated on the map in Figure 1.

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

Area A: Limestone and Dolomite

Area A in Figure 1 represents aquifers where wells may yield 100 to 500 gpm, or more, from the limestone and dolomite bedrock at depths of less that 300 feet. Many contractors drill wells less than 65 feet deep in attempts to develop wells free of hydrogen sulfide. Farm and domestic supplies usually are developed at depths of less than 135 feet.

Area B: Glacial Moraines with Unconsolidated Sand, Gravel and Clay

Portions of the county illustrated as Area B are represented by unconsolidated deposits associated with glacial moraines. Most wells are more than 55 feet deep. Adequate domestic supplies are developed from the thin lenses of sand and gravel interbedded in thick glacial till. When sand and gravel are not present, wells are deepened to the principal aquifer, the limestone bedrock.

Area C: Thin Lenses of Sand and Gravel

Area C designates the locations of thin lenses of sand and gravel interbedded in thick layers of clay that partially fill buried valleys in the county. Yields of 5 to 20 gpm may be developed. However, wells as deep as 340 feet into the underlying limestone are noted.

Area D: Limestone and Dolomite, Low-Yield Potential

Wells in Area D can produce from 25 to 100 gpm at depths of less than 200 feet. Shallow wells less than 65 feet deep are often drilled to attempt the development of sulfur-free water. Yields of less than 5 gpm are possible in the massive carbonate (non-fractured) formation.

Figure 2 is a generalized cross section (referenced in Figure 1 as the line X-X') located in Liberty and Washington Townships of the county. This cross section illustrates the limestone overlain by the glacial till. The glacial till in this area covers the bedrock with an average thickness of 30 feet. Within this layer of till, there are lenses of sand and gravel, which range from between 5 to 80 feet in thickness. Figure 2 also illustrates how the sand and gravel lenses occur in Areas A and B designated in Figure 1.

Figure 2. Generalized cross section of Hardin County, Ohio (adapted from Underground Water Resources map, A-4, ODNR Division of Water, by R. Roberts).

Ground water, whether obtained from bedrock or glacial deposits, may require some treatment. In some areas, water containing concentrations of calcium carbonate (CaCO₃, i.e., hard water), iron (greater than 0.3 ppm) and manganese (greater than 0.5 ppm) may require treatment for some uses (see notes in Table 1). Wells drilled into the limestone or dolomite may produce water that contains objectionable quantities of hydrogen sulfide (rotten egg odor). The occurrence of hydrogen sulfide is common in deposits containing gypsum interbedded in the glacial till. 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 levels 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 monitors ground-water levels in two wells in Hardin County. One well, located near Dola, is designated as observation well Hn-2a on Figure 1. The other well, near Alger, is designated as Hn-1. These wells are two of a number of wells throughout west-central Ohio used to monitor the natural seasonal fluctuation on water levels in the limestone aquifer.

Observation well Hn-2a (Dola) has a depth of 51 feet, and the depth to bedrock is 16 feet. It is representative of many limestone wells in the region. Continuous water-level measurements have been recorded at Hn-2a since December 1954. The lowest level recorded on Hn-2a was 15.9 feet below land surface in January 1965; the highest level recorded was 5.5 feet below land surface in March 1984. Observation well Hn-1 is 40 feet deep and encountered bedrock at approximately 30 feet. Continuous water-level measurements have been recorded at Hn-1 since April 1946. A low of 23.9 feet was recorded in August 1991; a high level of 5.8 feet was recorded in July 1946.

Ground-Water Quality

Various state and federal agencies have participated in programs to determine the ground-water quality in Ohio. For nine wells in Hardin 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 9. These sites are designated as either test wells or domestic wells.

The results from some of the chemical tests performed on these Hardin County wells are given in Table 1. The chemical constituents listed are total dissolved solids, hardness (as CaCO₃), iron, sulfate, hydrogen sulfide and fluoride. 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. Except for fluoride concentrations greater than 4.0 ppm, 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. Seven of these wells were developed in the limestone underlying Hardin County, at depths of 200 to 410 feet. The remaining wells were developed in either sand and gravel, or gravel, at depths of 66 to 108 feet. Some variation exists in the concentrations of all 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 Hardin County wells1.
Well No.	1	2	3	4	5	6	7	8	9	WQ Std2
Well Depth (feet)	220	250	210	325	330	410	66	108	200
Capacity (gpm)	600	200	400	670	60	550	10	12	1200
Depth to Bedrock (feet)	28	18	63	37	41	93	NE3	NE	27
Water-Bearing Formation4	LS	LS	LS	LS	LS	LS	SG	G	LS
Chemical Constituents5
Total Dissolved Solids	1020	725	1080	564	1080	598	999	614	741	500
Hardness (as CaCO3)	754	592	837	420	768	430	755	481	580	none6
Iron	0.36	3.4	0.96	0.76	1.4	0.26	8.5	0.24	2.6	0.3
Sulfate	552	239	516	160	580	210	489	226	290	250
Hydrogen Sulfide	0	0.7	0.5	0	0.7	0	0	0	0.5	none
Fluoride	2	1.4	1.6	1.8	1.7	1.7	1.4	1.4	2	2
1 Data on these wells from map by 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 G - Gravel; LS - Limestone; SG - Sand and Gravel.
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. Hydrogen Sulfide: Presence of this unpleasant smelling gas is difficult to measure but not difficult to detect, even in small concentrations. Highly corrosive to pump parts and plumbing fixtures, but has no known harmful effects in humans. Fluoride: At concentrations greater than 1.5 ppm, fluorosis (mottling) of teeth may occur. USEPA Primary Standard is 4 ppm.
6 No USEPA Secondary Standard.

Summary Hardin 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 limestone formations, and sand and gravel deposits within the glacial till underlying Hardin County have the potential to supply water adequate for most domestic and agricultural uses, and some municipal supplies. 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 Hardin County office of Ohio State University Extension can provide other publications on the county's water resources. Your Extension agent, the Hardin County Health Department, and Ohio EPA Northwest District Office - NWDO (347 North Dunbridge Rd., Bowling Green, OH 43402) 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 Hardin 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 about ground water in Ohio.

Bibliography

Central Ohio Water Plan. 1977. ODNR Division of Water.

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

Hardin County Water Resources. 1993. G. McCluer, C.A. Brookes, K.M. Boone and L.C. Brown. AEX-480.33. Ohio State University Extension.

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

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.

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, Hardin County; Hardin County Economic Development Council; Hardin County Trustee and Clerk's Association; Ohio Northern University; Hardin County Farm Bureau, Inc.; Hardin County Chamber of Commerce; Hardin County Regional Planning Commission; 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: Doug Deardorff (USDA-Soil Conservation Service); Mark Doll (Hardin County Regional Planning Commission); Bradley Campbell (Hardin County Commissioners); Scott Golden (Environmental Health, ODH); Steve Hindall (USGS, Ohio District); and Tim Fishbaugh (Ohio EPA, NWDO).

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.