David A. Mangione
James M. Raab
Kristina M. Boone
Larry C. Brown
Water stored under the earth's surface is a plentiful, yet precious, resource in most areas of Ohio. Humans greatly affect ground water. However, the availability and quality of this resource are influenced directly by the properties of the geologic formation that holds 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 Pickaway County. Its purpose is to help the reader better understand the factors that influence the quantity and quality of ground water. Water resources terminology used in this publication is included in Surface and Ground Water Terminology, fact sheet AEX-460, which provides a listing of generally accepted water resource definitions. This publication is available through your county Extension office. Fact sheet AEX-460 and the publication Pickaway County Water Resources, AEX-480.65, are available through your county Extension office.
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 types of geologic material from which the formation originally was made influence its ability to hold and transmit water. For example, sands and gravels 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 unconsolidated aquifer, composed of coarse- and fine-grained sand, gravel and mixtures of clay and silt, is a principal source of ground water in central Ohio, including Pickaway County. The coarse-grained unconsolidated aquifer consists of highly permeable sand and gravel. The fine-grained unconsolidated formations are less permeable as a result of higher percentages of fine sand, silt and clay. Ground-water productivity in this aquifer type is generally lower. The principal water-quality problem in the unconsolidated aquifer is high levels of iron.
Another major source of ground water in central Ohio, including Pickaway County, is the sedimentary bedrock aquifers composed of limestone, dolomite or shale. The carbonate limestone and dolomite aquifers typically have very good yields of water from fractures and pre-glacial weathered rocks. Generally, water produced from wells in carbonate aquifers is highly mineralized. The shale bedrock aquifers are low yielding, especially in upland areas.
Limestone formations are good sources of ground water because of their naturally formed solution channels, joints and fractures. 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.
Lenses (or pockets) of sand and gravel that were deposited by glacial activity are another source of ground water in some areas of central Ohio. These sand and gravel deposits usually are interbedded in glacial till.
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.
The Ohio Department of Natural Resources (ODNR), Division of Water, maintains a statewide data base of more than 700,000 well logs. The Ground-Water Resources Section of the Division manages this valuable data base, 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, and 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 Pickaway County (adapted from map by Schmidt, 1991). This illustration is based on a hydrogeologic interpretation of the well log data from Pickaway County and surrounding areas. It should be used only as a guide to understanding the ground-water resources in the county. Figure 2 is a cross section of a part of Pickaway County (referenced in Figure 1 as line X-X') showing the relationship of different aquifers. The "?" in Figure 2 indicates that sufficient data have not been collected to properly characterize these specific locations. 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 Pickaway County, Ohio (modified
from J.J. Schmidt, ODNR Division of Water, by R.A. Roberts).
Figure 2. Generalized cross section of buried valley in Pickaway
County, Ohio (modified from Underground Water Resources map M-8).
The coarse-grained aquifer illustrated in Figure 1 as Area A is composed of unconsolidated permeable sand and gravel deposits adjacent to the Scioto River. The Scioto River plays a significant role in the recharge of the aquifer. Properly constructed large-diameter wells can yield in excess of 1,000 gpm, at depths of 75 to 135 feet, which is typically necessary for municipal or industrial uses. Although water is readily available in the sand and gravel aquifer, it may be rated as below average for chemical quality because of hardness and high concentrations of dissolved solids.
Area B is also part of the coarse-grained aquifer, but it is beyond the recharge influence of the Scioto River. Yields of 100 to 500 gpm are possible when wells are developed in coarse deposits of sand and gravel. Large-diameter wells in excess of 125 feet deep are necessary to obtain yields of 500 gpm.
This carbonate aquifer, illustrated as Area C, is located in the northwestern corner the county. Well yields of 5 to 25 gpm at depths of 55 to 175 feet are common for farm and domestic supplies. However, large-diameter wells at depths of 250 to 300 feet can yield as much as 500 gpm. The chemical quality of water produced in this area is below average because of hardness and high levels of iron, dissolved solids and sulfate.
Area D shows the highly permeable sand and gravel aquifers beneath the area adjacent to Big Darby and Deer Creeks. Wells of less than 80 feet in depth can yield as much as 500 gpm.
Sand and gravel layers of variable thickness, mixed with thick layers of clay, are characteristic of the fine- grained aquifers shown as Area E. Within the flood plains of the Big Darby and Salt Creeks, yields of 25 to 100 gpm are possible at depths of less than 75 feet.
Area F lies both east and west of the Scioto River. Thick clay layers interbedded with water-bearing deposits of sand and gravel are part of this fine-grained aquifer. Wells developed east of the Scioto River range in depth from 40 to 185 feet. Shale bedrock deters deeper drilling. Wells developed west of the Scioto are usually less than 145 feet. Yields from wells developed in this area range from 10 to 25 gpm.
The underlying bedrock of Area G is considered non-water-bearing shale. Thin lenses of sand, gravel and clay over this bedrock may yield as much as 15 gpm.
Yields of 3 to 10 gpm to depths of less than 75 feet are typical of wells developed in Area H. Supplies for domestic use may be marginal.
Although low yielding, domestic supplies of water ranging from 3 to 10 gpm may be obtained in these thin lenses of sand and gravel. Area I lies in the eastern edges of the county.
Area J, located west of the Scioto River, is characterized by yields of less than 2 gpm from the shale bedrock. It is possible to develop wells in underlying limestone formations. However, poor water quality,which is characteristic for this area due to hydrogen sulfide content, deters well development.
Area K illustrates clayey till 10 to 70 feet thick overlying non-water-bearing shale bedrock. Yields of less than 2 gpm can be expected. Supplemental supplies of water may be necessary to meet domestic needs.
The water level in any well typically does not remain constant, but changes depending upon the proximity of adjacent wells and surface streams, and natural rainfall. Ground-water discharge and recharge greatly effect water levels in wells. The ODNR Division of Water monitors ground-water levels in five wells in Pickaway County, noted on Figure 1 as: PK-9 (Orient); PK-8 (Williamsport); and PK-4, -6 and -7 (Circleville). These are five of a number of wells throughout central Ohio used to monitor natural seasonal fluctuation or the effects of nearby pumping on water levels.
Observation wells PK-4, -6, -7, -8 and -9 are 136, 120, 172, 18, and 45 feet deep, respectively. All are completed in sand and gravel. Continuous water level measurements have been recorded at: PK-4 since January 1960; PK-6 since July 1966; PK-7 since July 1972; PK-8 since April 1980; and PK-9 since October 1986. Data from observation wells PK-4, -6, -7 and -8 indicate the lowest levels recorded below land surface were: 12.4 feet in January 1988; 54.8 feet in September 1977; 37.3 feet in February 1977; and 80.2 feet in November 1972, respectively. The highest water levels recorded below land surface for wells PK-4, -6, -7, and -8 were: -0.2 feet in May (water level was above land surface on this date) 1990; 38.1 feet in July 1989; 14.5 feet in February 1969; and 47.4 feet in February 1960, respectively. The lowest level recorded on PK-9 (Orient) was 26.1 feet below land surface in December 1987; the highest level recorded was 0.9 feet below land surface in March 1991.
Various state and federal agencies have participated in programs to determine ground-water quality in Ohio. In Pickaway County, water-quality data were available from the ODNR Division of Water for eight wells, noted in Figure 1 as Chemical Analysis Sites 1 through 8.
The results of some of the chemical tests performed on these Pickaway County wells are given in Table 1. The chemical constituents listed are total dissolved solids, hardness (as CaCO3), iron and sulfate. All concentrations are given in parts-per-million (ppm). For comparison purposes, drinking water-quality standards for these chemical constituents are also 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). There are no drinking water-quality standards for private wells.
The information in Table 1
can be used as a guide to what one might expect from an existing or
new well. Wells at sites 3, 5, 6, and 8 are developed in the sand and
gravel aquifers; wells 1, 2, 4, and 7 are developed in limestone.
Although the sand and gravel wells vary only from 28 to 136 feet
deep, and the limestone wells vary from 250 to 350 feet deep, some
variation exists in the concentrations of each of these chemical
constituents within similar aquifers. 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.
| Table 1. Chemical constituents of selected Pickaway County wells. | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Well No. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | WQ Std1 |
| Well Depth (feet) | 250 | 350 | 92 | 250 | 136 | 135 | 250 | 28 | |
| Capacity (gpm) | 300 | 1,000 | 900 | 450 | 1,000 | 1,500 | 10 | 100 | |
| Depth to Bedrock (feet) | NE2 | 118 | NE | 65 | 133 | NE | 169 | NE | |
| Water Bearing Formation3 | LS | LS | SG | LS | SG | SG | LS | SG | |
| Chemical Constituents4 | |||||||||
| Total Dissolved Solids | 727 | 2,850 | 376 | 1,060 | 609 | 410 | 777 | 420 | 500 |
| Hardness (as CaCO3) | 511 | 2,200 | 330 | 780 | 500 | 370 | 570 | 366 | None5 |
| Iron | 0.38 | 0.2 | 2.4 | 1.2 | 2.8 | 2.9 | -6 | 0.5 | 00.3 |
| Sulfate | 239 | 1,750 | 29 | 550 | 150 | 41 | 340 | 51 | 250 |
| 1 USEPA Secondary Water Quality Standard. | |||||||||
| 2 Well constructed in this formation did not encounter bedrock. | |||||||||
| 3 LS - Limestone; SG - Sand and Gravel. | |||||||||
| 4 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 in excess of 0.3 ppm may cause brown and black stains on laundry, plumbing fixtures and sinks, taste may also be affected. Sulfates: Concentrations in excess of 250 ppm may have laxative effect on persons unaccustomed to the water. Also affects the taste of water and will form a hard scale in boilers and heat exchangers. | |||||||||
| 5 No USEPA Secondary Standard. | |||||||||
| 6 No data available. | |||||||||
Pickaway 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. By understanding the physical and chemical nature of these resources, better decisions can be made about ground-water protection, management and use. This publication was designed to provide the reader with 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 Pickaway County Extension office can provide other publications about the county's water resources. Your Extension agent, the Pickaway County Health Department and Ohio EPA Division of Drinking and Ground Water (1800 WaterMark Drive, Columbus, Oh 43266) 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 the map, Ground-Water Resources of Pickaway County, and other information available through the Division of Water. This map is much more detailed than that given in Figure 1, and the Ground-Water Resources Section can provide detailed information on ground-water availability and wells. The USGS, Ohio District (975 W. Third Ave., Columbus, OH 43212), also provides information concerning ground water in Ohio.
Ground-Water Resources of Pickaway County. 1991. 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.
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.
Pickaway County Water Resources. 1992. D.A. Mangione, K.M. Boone and L.C. Brown. AEX-480.65. Ohio Cooperative Extension Service, The Ohio State University..
Surface and Ground Water Terminology. 1990. L.C. Brown and L.P. Black. Fact Sheet No. AEX-460. Ohio Cooperative Extension Service, The Ohio State University.
Underground Water Resources (maps of various river basins). 1958-1962. ODNR Division of Water.
Water Testing. 1988. K. Mancl. AEX-314. Ohio Cooperative Extension Service, The Ohio State University.
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: Pickaway County Extension office; Overholt Drainage Education and Research Program; and USDA Extension Service Grant No. 90-EWQI-1-9018. The project leaders acknowledge the following reviewers: Dan Garver (USDA-Soil Conservation Service); Gary Young and William L. Ingalls (Pickaway County General Health District); David Cashell (ODNR Division of Water); Scott Golden (Environmental Health, ODH); Tom Bean (Agricultural Engineering, OSU); Steve Hindall (USGS, Ohio District); and Linnea Saukko (Ohio EPA Division of Drinking and Ground Water).
A special thanks to Michelle Roby and Ross A. Roberts (Agricultural Engineering Undergraduate Assistants) for help in manuscript and graphics preparation, and Judy Kauffeld and Tonya Ewing (Section of Communications & Technology, OSU 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