Ohio State University Extension

Food, Agricultural and Biological Engineering

590 Woody Hayes Dr., Columbus, Ohio 43210

Franklin County Ground-Water Resources

AEX-490.25

Patricia L. House
A. Wayne Jones
Larry C. Brown
Karen T. Ricker

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 Franklin 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 Water Resources of Franklin County, AEX-480.25.

Much of the water resource and water quality terminology used in this publication is described in Extension Fact Sheets AEX 460 and 465. Ohio Extension publications are available through the Franklin County office of Ohio State University Extension (614-462-6700).

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 unconsolidated aquifer, composed of coarse-grained sand, gravel and mixtures of clay and silt is a principal source of ground water in Franklin County, and especially in the southeast corner. This aquifer system is the result of glacial outwash and comprises one of the state's most productive aquifer systems.

Another major source of ground water in central Ohio and Franklin County is the carbonate aquifers composed of layers of limestone and dolomite. Limestone is consolidated mud or calcareous sand, sometimes with fossil shells and shell fragments. The main mineral in limestone is calcium carbonate, CaCO₃. Dolomite is similar to limestone, but its main mineral is calcium magnesium carbonate, (Ca,Mg)CO₃. The carbonate aquifers located in the western half of the county yield up to 500 gallons per minute (gpm). Fractures, and weathering of the upper bedrock surface, provides pathways for ground-water flow.

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. Sand and gravel deposits may occur above the carbonate bedrock and may be interbedded in the glacial till or deposited in stratified layers. Glacial till generally does not provide enough water to support a well.

Contact the Ohio Department of Natural Resources (ODNR), Division of Geological Survey, for information on Ohio's geologic formations (Fountain Square, Columbus, OH 43224-1362).

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 Franklin County (adapted from map by J. J. Schmidt, 1993). This illustration is based on a hydrogeologic interpretation of the well-log data from Franklin 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 1. Ground-water resources of Franklin County, Ohio (adapted from Ground-Water Resources of Franklin County map, J. J. Schmidt, 1993, ODNR Division of Water; illustration prepared by J. Humphreys).

AREA A: Unconsolidated Coarse-Grained Sand and Gravel

Area A in Figure 1 is the most productive aquifer in Franklin County. The unconsolidated permeable sand and gravel deposits adjacent to the Scioto River have the greatest potential for development of municipal and industrial ground water supplies. Wells drilled at 60 to 115 feet can yield in excess of 1000 gpm. Presently, the City of Columbus, Division of Water, maintains four collector wells in this aquifer. The induced infiltration of water from the Scioto River helps to generate extremely high yields (the City of Columbus collector wells can yield as much as 5000 gpm). These wells range in depth from 68 to 109 feet, and the combined yield is 20 million gallons of water per day.

AREA B: Thick, Permeable Sand and Gravel

These unconsolidated sand and gravel aquifers, noted as Area B, are primarily located in the southeast part of the county. However, this area is beyond the recharge influence of the Scioto River and Big Walnut Creek. Large-diameter, screened wells may yield as much as 500 gpm. Extensive test drilling is recommended to locate coarse sand and gravel deposits at depths of 30 to 200 feet.

Area C: Permeable Sand and Gravel

Area C denotes the permeable sand and gravel aquifers beneath the area adjacent to the Olentangy River and its confluence with the Scioto River. Wells may be developed in the sand and gravel at depths of 50 to 120 feet, or extended into the underlying bedrock at depths of 225 feet, to yield as much as 350 gpm.

AREA D: Limestone and Dolomite

The principal source of ground water in the western third of the county is delineated as Area D. The limestone and dolomite bedrock may yield up to 250 gpm from wells developed at depths of less than 300 feet. Wells developed at greater depths in this area may produce greater yields, but poorer quality water. Domestic and small industrial supplies of 15 to 25 gpm are available at depths of 65 to 175 feet. Overlying glacial deposits of sand and gravel may yield as much as 20 gpm at depths of about 90 feet.

AREA E: Thin Sand and Gravel in Glacial Till

The aquifers denoted as Area E, located near Whitehall, Gahanna and parts of Sharon Township, are made up of lenses of sand and gravel thinly scattered in the thin or thick layers of clayey till. The till is underlain by the non-water-bearing shale. Properly constructed, screened wells may yield 25 to 100 gpm at average depths of 80 to 135 feet, but ranging in depth to 225 feet.

AREA F: Sandstone and Shale

Area F delineates the sandstone and shale formations that lie primarily in Plain and Jefferson townships. Wells developed at depths of 60 to 75 feet in the sandstone and shale may produce yields that exceed 20 gpm. However, large-diameter wells have exceeded 100 gpm at depths of about 170 feet in this area. Area G: Thin Sand and Gravel Lenses Interbedded in Clayey Till

The thick deposits of fine sand and silty clay at depths of 200 to 300 feet, delineated as Area G, often hinder the development of domestic water supplies. However, yields of 5 to 25 gpm may be developed at depths of 25 to more than 150 feet. Wells in Perry Township not encountering adequate water in the glacial deposits may be extended into the underlying limestone at depths of 110 to 260 feet below the surface.

AREA H: Shaly Sandstone

Area 4-H denotes the shaly sandstone located at the fringe zone of the Berea sandstone. The change to a finer-grained shaly sandstone explains the reduced yields compared to those from the sandstone formation in Area F. Yields of 4 to 6 gpm may be obtained from a very limited area at depths of less than 65 feet, below which is the non-water-bearing shale.

Area I: Sand and Gravel Underlain by Shale

Area I, located near Minerva Park and Bexley, delineates the shallow glacial deposits of sand and gravel overlying shale bedrock. These deposits lie in portions of an eroded ancestral drainage channel that are remnants of an ancient drainage system that cut a valley into the shale before the area was glaciated. Later, with the coming of the glaciers, the valleys were filled with glacial deposits, composed mainly of sand and gravel. Potential yields may not exceed 5 gpm at depths of 15 to 35 feet.

Area J: Shale

Wells developed at depths of less than 100 feet in shale, denoted as Area J, yield less than 2 gpm. Occasionally, thin lenses of sand and gravel may be encountered near the surface of the weathered shale at depths of 18 to 45 feet. These deposits may yield as much as 5 gpm. The limestone that lies beneath the shale in Perry and Sharon townships may yield larger supplies. Proper well construction may deter the presence of hydrogen sulfide.

Figure 2 is a generalized cross section (referenced in Figure 1 as the line X-X') of Franklin County. This cross section shows the range of depth to bedrock as well as the variation in composition of the glacial till. Notice that west from the Olentangy River the geological makeup is primarily limestone and clay while east of this point is largely sandstone and shale bedrock, and sand and gravel. A point of interest is the ancestral buried bedrock channels partially filled with as much as 260 feet of clay, sand and gravel deposits overlying the limestone bedrock as shown in the extreme left side of Figure 2.

The ODNR ground-water resources map by J. J. Schmidt (1993) provides information on areas in Franklin County that contain aquifer characteristics not illustrated in Figure 1. For example, the ODNR map delineates areas where relatively thick layers of fine-silty sand lie in buried valley deposits, and areas where hydrogen sulfide is a common constituent of the ground water. Also, the ODNR map illustrates specific locations in the county where gravel pit, quarry, and large-scale disturbed land activities have occurred.

Figure 2. Generalized cross section of Franklin County, Ohio (adapted from Ground-Water Resources of Franklin County map, J. J. Schmidt, 1993, ODNR Division of Water; illustration prepared by R. Roberts).

Ground-Water Levels

The water level in any well does not remain constant, but changes in response to several factors. Rainfall distribution and amount may affect ground-water recharge and discharge, and subsequently may affect the water level in area wells. Also, wells that are hydraulically connected to a stream may show fluctuations in the water level as the stream level changes. 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 three wells in Franklin County. These wells are noted as Observation Wells FR-3, FR-10 and FR-18 in Figure 1. Observation Wells FR-3 and FR-18 are located in Hamilton Township, while FR-10 is in Clinton Township. These wells, along with other wells throughout central Ohio, are used to monitor the natural seasonal fluctuation on water levels in various aquifers. These Observation Wells have the following depths: FR-3, 56 feet; FR-18, 116 feet; and FR-10, 75 feet. Continuous water-level measurements have been recorded at FR-3 since April 1946; FR-10 since March 1944, and FR-18 since November 1985. Data from these wells show the lowest levels recorded below land surface were: FR-3, 20.8 feet in July 1966; FR-10, 48.2 feet in October 1954; and FR-18, 33.2 feet in February 1992. The highest levels recorded below land surface were: FR-3, 0 feet (right at land surface) January 1959; FR-10, 37.8 feet in April 1951; and FR-18, 7.9 feet in January 1991. These data were taken from a 1992 summary.

Ground-Water Quality

Various state and federal agencies have participated in programs to determine the ground-water quality in Ohio. For 22 wells in Franklin County, water-quality data was available from the ODNR Division of Water. Seven of these wells were selected from across the county and are noted as Chemical Analysis Sites 1 through 7 in Figure 1. These sites are 6 municipal wells and 1 private well.

The results from some of the chemical tests performed on these Franklin County wells are given in Table 1. The chemical constituents listed are total dissolved solids, hardness (as CaCO₃), iron, chloride, sulfate, 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. 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.

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) in concentrations greater than 180 ppm, and iron concentrations greater than 0.3 ppm may require treatment for some uses (see notes in Table 1). Generally, water produced from wells in the carbonate aquifer is highly mineralized, and the unconsolidated aquifer usually contains high levels of iron. 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.

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 three of these seven wells were developed in the sand and gravel underlying Franklin County, and these wells are in the range of 35 to 472 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 Franklin County wells.1
Well No.	1	2	3	4	5	6	7	WQ Std2
Well Depth (feet)	175	200	472	86	212	35	67
Capacity (gpm)	100	500	500	300	600	20	30
Depth to Bedrock (feet)	31	131	170	ne3	211	ne	8
Water-Bearing Formation4	LS	LS	LS	SG	SG	SG	SS
Chemical Constituents5
Total Dissolved Solids	500	2462	986	740	434	390	364	500
Hardness (as CaCO3)	443	1730	745	560	390	302	279	none6
Iron	0.55	0.77	-7	4.2	1.9	0.75	2.8	0.3
Chloride	2.0	45	5.0	77	6.0	2.8	4.3	250
Sulfate	102	1451	520	-	28	24	98	250
Fluoride	1.1	1.8	0.6	0.2	0.4	1.4	0.3	2
1 Data on these wells taken from map by J. J. Schmidt, 1993; general location of each well is shown on Figure 1.
2 USEPA Secondary Water Quality Standard.
3 ne = Well constructed in this formation did not encounter bedrock.
4 SS-Sandstone; 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 and Manganese: Iron concentrations greater than 0.3 ppm and manganese concentrations greater than 0.03 may cause brown or black stains on laundry, plumbing fixtures and sinks. Metallic taste may be present which may affect the taste of beverages made from the water. Chloride: High concentrations may result in an objectionable, salty taste to water and the corrosion of plumbing in the hot water system. Sulfate: 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. 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.
7 Data not available.

Summary

Franklin 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 sand and gravel, and limestone formations that underlay much of Franklin County have the potential to provide excellent water adequate for domestic, agricultural, industrial 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 provides 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 Franklin County office of Ohio State University Extension (614-462-6700) can provide other publications on the county's water resources. Your Extension agent, the Franklin County Health Department (614-462-3160), the Columbus City Health Department (614-645-8191), and Ohio EPA (Central District Office, 2305 Westbrooke Dr., Bldg. C, Columbus, OH 43228) can provide information on potential sources of ground-water contamination, 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 Franklin 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.

Bibliography

Ground-Water Resources of Franklin County. 1993. J. J. Schmidt, ODNR Division of Water. (map).

Hydrogeology and effects of landfills on ground-water quality, southern Franklin County, Ohio. WRI Report 85-4222. USGS Ohio District.

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.

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 Resources of Franklin County. 1994. P. L. House, K. T. Ricker and L. C. Brown. AEX-480.25. Ohio State University Extension.

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 Karen T. Ricker. Partial support for this publication was provided by these cooperating agencies and programs: Ohio State University Extension, Franklin County; Franklin Soil and Water Conservation District (SWCD); the Darby Creek Hydrologic Unit Area Project (USDA Extension Service Grant No. 91-EHUA-1-0059); Overholt Drainage Education and Research Program; and the Ohio Management Systems Evaluation Area Project (USDA Extension Service Grant No. 90-EWQI-1-9018).

The project leaders acknowledge the following reviewers: Brady Kohler (Franklin SWCD); Stephen N. Hainen (City of Columbus, Division of Water); Scott Golden (Environmental Health, ODH); Steve Hindall (USGS, Ohio District); and Linnea Saukko and Jeannette Murin (Ohio EPA, CDO). A special thanks to Michelle Roby, Ross Roberts, and John Humphreys (Agricultural Engineering Undergraduate Assistants) for help in illustration and manuscript preparation, and Kim Wintringham, Associate Editor (Section of Communications and Technology, Ohio State University Extension), for editorial and graphic production.