Figure 1. Ground-water resources of Knox County, Ohio (adapted from ODNR Division of Water map by J. Humphreys).
F. John Barker III
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 Knox County. Its purpose is to help the reader better understand the factors which influence the quantity and quality of ground water. An overview of the county's water resources is provided in the publication Knox County Water Resources, AEX-480.42.
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 Knox County office of Ohio State University Extension.
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.
Knox County is underlain by three major water-bearing formations: unconsolidated coarse-grained sand and gravel, unconsolidated fine-grained sand and gravel, and sandstone-shale bedrock. These formations serve as primary sources of water throughout northeastern Ohio, including Knox County. The most productive formation in the county is the unconsolidated, coarse-grained aquifer. This formation consists of sand and gravel deposits, generally coarse, combined with a mixture of clay and silt. These aquifers are found in many of the present and buried river valleys in the county.
Unconsolidated, fine-grained aquifers are found in several locations of the county. This aquifer type consists of sand, generally fine, with clay, silt and gravel, and they may be under the confining pressure of overlying clay or till. The thickness and the extent of the sand and gravel in these unconsolidated aquifers determine the amount of storage space available for water.
The Mississippian sandstone-shale formation comprises the largest aquifer in the county. This aquifer consists of massive to thin-bedded units of fine-grained to conglomerate sandstone, which is mostly quartz cemented by calcite, silica, iron, and clay. These formations usually are adequate sources of water because they contain naturally formed openings that store water, and permit water to move easily through the bedrock.
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.
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 Knox County (adapted from map by J.J. Schmidt, 1980). This illustration is based on a hydrogeologic interpretation of the well-log data from Knox 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 2 is a generalized cross section (referenced in Figure 1 as the line X-X') of a portion of Knox County. This cross section shows the variable thickness of the unconsolidated material above the sandstone and shale bedrock.
Figure 1. Ground-water resources of Knox County, Ohio
(adapted from ODNR Division of Water map by J. Humphreys).
Figure 2. Generalized cross section of Knox County, Ohio
(adapted from Underground Water Resources map, P-12, ODNR Division of Water, by R. Roberts).
Area A in Figure 1 illustrates areas with thick deposits of permeable sand and gravel filling buried valleys beneath major perennial streams. These regions have the greatest potential for development of municipal and industrial water supplies. Thick permeable deposits of sand and gravel yield 500 to more than 1,000 gpm at depths ranging from 55 to 135 feet. Water quality in this area is generally adequate for most uses. However, some wells may produce hard water (water containing calcium carbonate, CaCO3) and water with high iron concentrations (greater than 0.3 ppm), requiring treatment for some uses.
Area B is comprised of thick, permeable sand and gravel deposits, which fill ancestral drainage channels. Yields ranging from 100 to more than 350 gpm are developed from permeable sand and gravel encountered at depths of about 60 to 155 feet. Test drilling may be necessary to locate the more permeable deposits, which partially fill these ancestral drainage channels.
The formations shown as Area C are characterized as moderately permeable sand and gravel deposits interbedded with clayey till, in buried valleys. Found primarily in the western one-third of the county, these aquifers closely border Areas A and B. These water-bearing deposits of sand and gravel may be encountered at average depths ranging from 66 to 165 feet. Yields adequate for farm and household supplies are readily available to drilled wells. Extensive test drilling is necessary to develop small public supplies. Deep drilling through as much as 345 feet of sandy clay may only encounter small domestic supplies.
Area D is part of the regional sandstone-shale aquifer of northeast Ohio. The thickness of this aquifer is highly variable. This aquifer is located beneath varying thicknesses of glacial till. Water supplies are developed from the sandstone and shale formations of the Cuyahoga Group. Yields of 10 to more than 20 gpm are readily available. Drilling contractors may encounter thick deposits of clayey till interbedded with thin lenses of permeable sand and gravel in the morainal areas in the western portions of the county. Most wells are drilled to depths ranging from 60 to 290 feet. Wells may be drilled deeper than 325 feet to encounter small supplies in the extreme eastern portion of the county. Industrial and municipal supplies with yields of more than 250 gpm have been reported for properly constructed large-diameter wells at depths less than 350 feet.
Thin to thick glacial moraine deposits, illustrated as Area E, consist of thin lenses of sand and gravel interbedded with thick layers of fine, silty sand and sandy clay. This aquifer yields adequate domestic supplies at depths ranging from about 70 to 320 feet. If water-bearing deposits are not encountered within the moraine deposits, wells may be developed in the underlying sandstone-shale bedrock.
Located in the extreme northeastern tip of the county, Area F is responsible for only a very small portion of the total water resources in Knox County. Adequate domestic supplies are usually developed from the sandy shale formations at depths of less than 140 feet. This aquifer usually produces yields less than 10 gpm.
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 Knox County. It is located near Mount Vernon and designated as observation well K-1 on Figure 1. This well is one of a number of wells throughout central Ohio used to monitor the natural seasonal fluctuation on water levels in the sand and gravel aquifer.
Observation well K-1 is 90 feet deep. It is representative of many sand and gravel wells in the region. Continuous water-level measurements have been recorded at K-1 since April 1946. The lowest level recorded on K-1 was 20.7 feet below land surface in July 1988; the highest level recorded was 1.4 feet above land surface in April 1950.
Various state and federal agencies have participated in programs to determine the ground-water quality in Ohio. For five wells in Knox 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 5. Four of these sites are municipal wells; one is a domestic well.
The results from some of the chemical tests performed on these Knox County wells are given in Table 1. The chemical constituents listed are total dissolved solids, hardness (as CaCO3), iron, and chloride. 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 all five of these wells were developed in the sandstone, or a sand and gravel formation, underlying Knox County, and all are in the range of 68 to 235 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 Knox County wells1. | ||||||
|---|---|---|---|---|---|---|
| Well No. | 1 | 2 | 3 | 4 | 5 | WQ Std2 |
| Well Depth (feet) | 133 | 68 | 235 | 83 | 93 | |
| Capacity (gpm) | 900 | -3 | 130 | 800 | - | |
| Depth to Bedrock (feet) | NE4 | 39 | 40 | NE | NE | |
| Water-Bearing Formation5 | SG | SS | SS | SG | SG | |
| Chemical Constituents6 | ||||||
| Total Dissolved Solids | 355 | 173 | 232 | 350 | 383 | 500 |
| Hardness (as CaCO3) | 283 | 156 | 194 | 289 | 280 | none7 |
| Iron | 0.03 | 0.47 | 0.1 | 0.9 | 1.3 | 0.3 |
| Chloride | 4 | 0.5 | 2 | 6 | 0 | 250 |
| 1 Data on these wells from watershed maps P-12 and P-13; General location of each well is shown on Figure 1. | ||||||
| 2 USEPA Secondary Water Quality Standard. | ||||||
| 3 Data not available. | ||||||
| 4 Well constructed in this formation did not encounter bedrock. | ||||||
| 5 SG - Sand and Gravel; SS - Sandstone. | ||||||
| 6 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. Chloride: Concentrations greater than 250 ppm may result in an objectionable, salty taste to water and the corrosion of plumbing in the hot water system. | ||||||
| 7 No USEPA Secondary Standard. | ||||||
Knox 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 sand and gravel deposits underlying portions of Knox County are excellent sources of 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.
The Knox County office of Ohio State University Extension can provide other publications on the county's water resources. Your Extension agent, the Knox County Health Department, and Ohio EPA Central District Office-CDO (2305 Westbrooke Dr., Columbus, OH 43266-2198) 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 Knox 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.
Ground-Water Resources of Knox County. 1980. 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.
Knox County Water Resources. 1993. F.J. Barker III, K.M. Boone and L.C. Brown. AEX-480.42. 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.
Southeast Ohio Water Plan. 1978. 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.
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, Knox County; Knox County Commissioners; Knox Soil and Water Conservation District; Overholt Drainage Education and Research Program; and USDA Extension Service Grant No. 90-EWQI-1-9018. The project leaders acknowledge the following reviewers: Mark Smith (USDA-Soil Conservation Service); Rob Clendening (Knox Soil and Water Conservation District); Jim Friderich (Knox County Health Department); Scott Golden (Environmental Health, ODH); Steve Hindall (USGS, Ohio District); and Linnea Saukko (Ohio EPA, CDO).
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 Extension), for editorial and graphic production.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868