Ohio State University Extension

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Crawford County Ground-Water Resources

AEX-490.17

Steven C. Prochaska
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 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 Crawford 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 Crawford County Water Resources, AEX-480.17.

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 Crawford 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 primary aquifer formations underlying Crawford County include: consolidated layers of limestone composed of fossilized sea shells and calcareous sand; shale bedrock composed of compacted layers of mud and clay; and sandstone composed of compacted layers of sand and shale bedrock layers. The Silurian-aged limestone and dolomite formations, which underlie most of the western portion of Crawford County, were deposited between about 400 and 500 million years ago. In most areas of the county, the above formations are covered by a layer of glacial till, which is an unsorted mixture of clay, silt, sand, gravel and boulders deposited by glacial activity. The Devonian-aged shale, located in the center of the county, and the Mississippian-aged sandstone, located in the eastern section of the county, are both covered with variable thicknesses of glacial till.

The different bedrock formations will have different capacities to store water. The Silurian limestone found in western Crawford County usually is an adequate source of water because of its many fractures, fissures and solution channels that provide water storage and pathways for water distribution. The shale and sandstone formations found in the eastern three-fourths of the county do not have the abundance of fractures and channels found in limestone, and thus, they are less productive water sources. Ground water also occurs in lenses (or pockets) of sand and gravel deposited by glacial processes. These deposits occur above the limestone, shale and sandstone 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 estimates 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 Crawford County (adapted from map by Schmidt, 1981). This illustration is based on a hydrogeologic interpretation of the well-log data from Crawford 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 Crawford County, Ohio (adapted from ODNR Division of Water map by J. Humphreys).

AREA A: Clayey Till above Limestone

Area A in Figure 1 illustrates the western one-fourth of the county where well yields of more than 100 gpm can be developed from the limestone bedrock formations. This aquifer is the most productive in the county in terms of ground-water availability, quantity and quality. Farm and domestic water supplies are often developed at depths of 95 feet or less.

AREA B: Clayey Till above Sandstone and Shale

In the southeastern corner of the county, illustrated as Area B, wells may be developed in the Mississippian-aged sandstone and shale formations, which often produce yields of up to 20 gpm. Hydrogen sulfide is often present in this area of the county. The glacial till is composed predominantly of clay, but also contains sand and gravel deposits. Depth to bedrock ranges from 15 to 135 feet.

AREA C: Clayey Till above Sandstone and Shale, Low-Yield Potential

Area C illustrates aquifers in the eastern one-fourth of the county, where wells may yield up to 10 gpm. The average depth of wells developed in the Mississippian sandstone is from 35 to 90 feet. Hydrogen sulfide is often present in this formation.

AREA D: Glacial Moraines of Sand and Gravel, and Clay

Well yields of up to 10 gpm may be obtained in Area D, which consists of water-bearing lenses of sand and gravel interbedded in thick layers of clay. These materials were deposited as glacial moraines. If permeable sand and gravel are not encountered above the limestone or sandstone bedrock, wells may be deepened to develop adequate yields from the underlying bedrock.

AREA E: Clayey Till Above Non-productive Shale

The central one-half of Crawford County, illustrated as Area E, yields less that 3 gpm from the Devonian shale bedrock. Dry wells and poor quality water (hydrogen sulfide) are common. Occasionally, more productive wells may be developed from the sand and gravel lenses deposited by glacial processes.

AREA F: Fine-grained Sand and Silt above Shale

Area F consists of fine-grained sand and silt deposits underlain by non-water-bearing shale bedrock. These deposits generally contain water, but it is difficult to withdraw. Yields of less than 1 gpm are common.

Figure 2 is a generalized cross section of a portion of Crawford County (referenced in Figure 1 as the line X-X'). This cross section illustrates the range in depth to bedrock, as well as the variation in composition of the glacial till.

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) and iron (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.

Figure 2. Generalized cross section of Crawford County, Ohio (adapted from Underground Water Resources map, C-3, ODNR Division of Water, by R. Roberts).

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 monitors ground-water levels in one well in Crawford County. This well is located near Bucyrus and is designated as Observation Well CR-1 on Figure 1. It is one of a number of wells throughout north-central Ohio used to monitor the natural seasonal fluctuation of water levels in the sand and gravel aquifer.

Observation well CR-1 is 54 feet deep, and the depth to the sand and gravel is approximately 54 feet. Continuous water-level measurements have been recorded at CR-1 since April 1962. The lowest level recorded on CR-1 was 37.6 feet below land surface in December 1962; the highest level recorded was 16.2 feet below land surface in January 1991.

Ground-Water Quality

Various state and federal agencies have participated in programs to determine the ground-water quality in Ohio. For seven wells in Crawford 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 7. These sites are representative of domestic private wells.

The results from some of the chemical tests performed on these Crawford County wells are given in Table 1. The chemical constituents listed are total dissolved solids, hardness (as CaCO₃), iron, sulfate, and hydrogen sulfide. 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 Crawford County, and are in the range of 285 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 Crawford County wells1.
Well No.	1	2	3	4	5	6	7	WQ Std2
Well Depth (feet)	330	350	67	285	60	32	313
Capacity (gpm)	1000	50	6	1000	100	6	1500
Depth to Bedrock (feet)	19	63	NE3	24	NE	15	50
Water-Bearing Formation4	LS	LS	SG	LS	SG	SS	LS
Chemical Constituents5
Total Dissolved Solids	357	2900	415	1190	882	445	570	500
Hardness (as CaCO3)	325	2180	336	924	730	391	490	none6
Iron	0.64	3.4	2.1	0.12	3.8	0.47	1.7	.03
Sulfate	53	1800	40	642	310	31	180	250
Hydrogen Sulfide	-7	40	-	7.5	-	-	-	none
1. Data on these wells from map by Schmidt, 1981; 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; SS - Sandstone.
5. Units are parts-per-million, ppm; Comments as per "Interpreting Your Water Test Report" 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.
6. No USEPA Secondary Standard.
7. Data not available.

Summary

Crawford 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 portions of Crawford County have the potential to supply water adequate for most domestic and agricultural 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 Crawford County office of Ohio State University Extension can provide other publications on the county's water resources. Your Extension agent, the Crawford 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 Crawford 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

Crawford County Water Resources. 1993. S.C. Prochaska, K.M. Boone and L.C. Brown. AEX-480.17. Ohio State University Extension.

Ground-Water Resources of Crawford County. 1981. 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.

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

Northwest Ohio Water Plan. 1986. ODNR Division of Water.

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, Crawford County; Crawford County Commissioners; Overholt Drainage Education and Research Program; and USDA Extension Service Grant No. 90-EWQI-1-9018. The project leaders acknowledge the following reviewers: Steve Brinkman (Crawford County Health Department); Brad Van Voorhis (USDA-Soil Conservation Service); 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.