U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5041

Borehole Geophysical, Water-Level, and Water-Quality 

Investigation of a Monitoring Well Completed in the St. 

Francois Aquifer in Oregon County, Missouri, 2005–08
Front cover photograph. Night drilling of monitoring well USGS-D1 during September 2005 near Winona, Missouri (photograph 

courtesy of Michael J. Kleeschulte, U.S. Geological Survey). 

Back cover photograph. Big Spring near Van Buren, Missouri (photograph courtesy of Jeffrey L. Imes, U.S. Geological Survey).
Borehole Geophysical, Water-Level, and 

Water-Quality Investigation of a Monitoring 

Well Completed in the St. Francois Aquifer 

in Oregon County, Missouri, 2005–08

By John G. Schumacher and Michael J. Kleeschulte

Scientific Investigations Report 2010–5041

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Schumacher, J.G., and Kleeschulte, M.J., 2010, Borehole geophysical, water-level, and water-quality investigation of 

a monitoring well completed in the St. Francois aquifer in Oregon County, Missouri, 2005–08: U.S. Geological Survey 

Scientific Investigations Report 2010–5041, 22 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Description of the Study Area ............................................................................................................1

Previous Investigations........................................................................................................................4

Purpose and Scope ..............................................................................................................................4

Methods and Approach................................................................................................................................4

Monitoring Well Construction.............................................................................................................5

Borehole Geophysical Methods.........................................................................................................5

Water-Level Measurements and Water-Quality Sampling............................................................8

Quality Assurance for Water-Level and Water-Quality Data ......................................................10

Borehole Geophysical Logs .......................................................................................................................10

Water-Level Measurements ......................................................................................................................13

Water Quality................................................................................................................................................16

Summary and Conclusions.........................................................................................................................20

References Cited..........................................................................................................................................21

Figures

1. Map showing location of monitoring well USGS-D1, dye traces to Big 

Spring and Greer Spring, geohydrologic units, and physical features of 

south-central Missouri ................................................................................................................2

2. Generalized geohydrologic units in south-central Missouri.................................................3

3. Summary of well construction and data from borehole geophysical 

logs of monitoring well USGS-D1 near Winona, Missouri.....................................................6

4. Graph showing water levels in the Ozark aquifer and St. Francois 

aquifer in monitoring well USGS-D1 near Winona, Missouri, and weekly 

precipitation recorded at West Plains, Missouri, September 1, 2005, 

through December 31, 2008.......................................................................................................14

5. Trilinear diagram of major constituents in water samples from monitoring 

well USGS-D1, City of Marquand well W3, and mine seeps from the 

Sweetwater Mine in the Viburnum Trend...............................................................................19
iv

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

square inch (in2) 6.452 square centimeter (cm2)

Volume

gallon (gal) 3.785 liter (L) 

Flow rate

Foot per minute (ft/min) 0.3048 meter per minute (m/min)

foot per day (ft/d) 0.3048 meter per day (m/d)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

Specific capacity

gallon per minute per foot 

[(gal/min)/ft)] 0.2070 liter per second per meter 

[(L/s)/m]

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Conversion Factors

Tables

1. Quality-assurance data for continuous recording pressure transducers

 and manual water-level measurements at monitoring USGS-D1, 2005–08 .....................11

2. Values of selected physical properties and concentrations of chemical

constituents in the regular and replicate sample from monitoring well 

USGS-D1, August 30, 2005.........................................................................................................12

3. Summary of borehole flowmeter measurements in monitoring well 

USGS-D1, September 3, 2005....................................................................................................13

4. Manual water-level measurements in monitoring well USGS-D1, 

September 14, 2005, through October 1, 2008 ........................................................................15

5. Selected water-quality data from monitoring well USGS-D1, City of 

Marquand well W3, and mine seeps from the Sweetwater Mine in the 

Viburnum Trend...........................................................................................................................17
v

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

 °C=(°F-32)/1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29)

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).”

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).
vi
Abstract

A deep (more than 2,000 feet) monitoring well was 

installed in an area being explored for lead and zinc deposits 

within the Mark Twain National Forest in southern Missouri. 

The area is a mature karst terrain where rocks of the Ozark 

aquifer, a primary source of water for private and public supplies and major springs in the nearby Eleven Point National 

Wild and Scenic River and the Ozark National Scenic Riverways, are exposed at the surface. The potential lead deposits 

lie about 2,000 feet below the surface within a deeper aquifer, 

called the St. Francois aquifer. The two aquifers are separated 

by the St. Francois confining unit. The monitoring well was 

installed as part of a series of investigations to examine potentiometric head relations and water-quality differences between 

the two aquifers.

Results of borehole flowmeter measurements in the open 

borehole and water-level measurements from the completed 

monitoring well USGS-D1 indicate that a seasonal upward 

gradient exists between the St. Francois aquifer and the overlying Ozark aquifer from about September through February. The upward potentiometric heads across the St. Francois 

confining unit that separates the two aquifers averaged 13.40 

feet. Large reversals in this upward gradient occurred during the late winter through summer (about February through 

August) when water levels in the Ozark aquifer were as much 

as 138.47 feet higher (average of 53.84 feet) than water levels 

in the St. Francois aquifer. Most of the fluctuation of potentiometric gradient is caused by precipitation and rapid recharge 

that cause large and rapid increases in water levels in the 

Ozark aquifer. 

Analysis of water-quality samples collected from the 

St. Francois aquifer interval of the monitoring well indicated 

a sodium-chloride type water containing dissolved-solids 

concentrations as large as 1,300 milligrams per liter and large 

concentrations of sodium, chloride, sulfate, boron, and lithium. 

In contrast, water in the overlying Ozark aquifer interval of the 

monitoring well was a calcium-magnesium-bicarbonate type 

water containing less than 250 milligrams per liter dissolved 

solids and substantially smaller concentrations of major and 

trace elements.

Introduction

Good stewardship of our Nation’s natural resources 

requires that the extraction and refining of minable ore deposits be conducted in harmony with the protection of the environment. This dilemma is faced by many land- and water-management agencies in mining areas of the Nation. As lead and 

zinc ore is mined, milled, and sent to the smelter, it leaves its 

footprint behind. These “footprints” can become remnants that 

may be environmentally detrimental to other natural resources. 

As ore reserves are depleted in one area, other deposits need to 

be found in previously unmined areas. The Viburnum Trend in 

southeastern Missouri (fig. 1) has been a world-class lead-zinc 

mining subdistrict since the 1960’s. As ore reserves are being 

depleted in the Viburnum Trend, the search for additional lead 

and zinc reserves has focused on an area about 40 miles (mi) 

southwest where the potential reserves lie about 2,000 feet (ft) 

below the surface (fig. 1). This “exploration area” is within the 

Mark Twain National Forest and the watershed of the Eleven 

Point National Wild and Scenic River.

Description of the Study Area

The exploration area is in southeastern Missouri near 

the town of Winona, and lies between the Ozark National 

Scenic Riverways (ONSR) to the northeast and the Eleven 

Point National Wild and Scenic River to the south (fig. 1). The 

area is a region of mature karst terrain that has an extensive 

network of solution-enlarged fractures and bedding planes 

ranging from small channels to large conduits. The region is 

underlain by Ordovician and Upper Cambrian Series sedimentary rocks (Jefferson City Dolomite to the base of the Lamotte 

Sandstone) of the Ozark Plateaus aquifer system that overlie 

Precambrian granites and rhyolites that are exposed in the St. 

Francois Mountains to the northeast (fig. 1). The Ozark aquifer, which is more than 1,000 ft thick (fig. 2), comprises rocks 

from the Jefferson City Dolomite to the Potosi Dolomite and 

is exposed at the surface throughout most of southern Missouri 

(Imes and Emmett, 1994). In addition to having an extensive 

karst system, the Ozark aquifer is the primary source of water 

Borehole Geophysical, Water-Level, and Water-Quality 

Investigation of a Monitoring Well Completed in the St. 

Francois Aquifer in Oregon County, Missouri, 2005–08

By John G. Schumacher and Michael J. Kleeschulte
2 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08 PULASKI

STE. GENEVIEVE

BOLLINGER

OREGON

HOWELL

TEXAS

RIPLEY

CARTER

IRON

MADISON

BUTLER

SHANNON

DENT

PHELPS

CRAWFORD

REYNOLDS

WASHINGTON

ST. FRANCOIS

DOUGLAS OZARK

WAYNE

Winona

Poplar 

West Bluff

Plains

Willow Springs

Eminence

Salem

Dye trace information modified from the Missouri Department of 

Natural Resources Division of Geology and Land Survey, 2007; and 

Imes and others, 2007

10 20 30 40 KILOMETERS

0 10 20 30 MILES

0

63

63

63

60

60

60

60

160

160

160

19

19

67

67

67

67

USGS-D1

Ozark National 

Scenic 

Riverways

Exploration 

area

Eleven Point 

National Wild 

and Scenic River

City of 

Marquand 

well W3

St. Francois

Mountains

Viburnum

Trend

Sweetwater Mine

Greer Spring

Big 

Spring

Eleven

Jacks

Fork

Big

Big 

River

Black

River

River

Current

River

Piney

Meramec

St. Francois River

Point

River

River

92° 91°

38°

37°

Base from U.S. Geological Survey digital data, 1994 1:100,000 

Universal Transverse Mercator projection

Zone 15

MISSOURI

ARKANSAS

Geohydrologic unit

 Mississippi River Valley alluvial aquifer

 Western Interior Plains confining unit

 Ozark aquifer

 St. Francois aquifer and St. Francois confining unit

 Basement confining unit (Precambrian igneous rocks)

Mark Twain National Forest

Dye trace

EXPLANATION

 St. Louis

MISSOURI

Exploration 

area

Map

area

Figure 1. Location of monitoring well USGS-D1, dye traces to Big Spring and Greer Spring, geohydrologic units, 

and physical features of south-central Missouri.
Introduction 3

for private- and public-water supplies and major springs in 

southern Missouri (Miller and Vandike, 1997). Yields of water 

to wells generally is higher in the lower part of the Ozark aquifer with the Potosi Dolomite being the most productive and 

reliable water producing unit in the aquifer (fig. 2).

The two largest springs in Missouri are near the exploration area and developed within the Ozark aquifer: Big Spring 

(fig. 1), which has an annual mean discharge of 446 cubic 

feet per second (ft3/s), and Greer Spring, which has an annual 

mean discharge of 343 ft3/s (U.S. Geological Survey, 2009). 

Discharge from these springs helps sustain flow in the Current River (Big Spring) and the Eleven Point River (Greer 

Spring). During low-flow conditions, Big Spring contributes 

more than 30 percent of the water to the Current River where 

its flow enters the river (Mugel and others, 2009). Dye-trace 

studies indicate that the exploration area probably lies within 

the recharge area for Big Spring and immediately north of the 

recharge area for Greer Spring (Imes and others, 2007).

Average 

approximate 

thickness, 

in feet

Formation General lithology Geohydrologic 

unit

General hydrologic 

properties

OZARK AQUIFER

Crystalline cherty dolostone with 

abundant thin shale partings and 

occasional thin sandstone beds 

Adequate for small domestic 

supply. Yields of 5 to 10 

gallons per minute locally

Jefferson City Dolomite

Roubidoux Formation

upper Gasconade 

Dolomite

lower Gasconade 

Dolomite

Gunter Sandstone 

Member of Gasconade 

Dolomite

Eminence Dolomite

Potosi Dolomite

Derby-Doerun 

Dolomite

Davis Formation

Bonneterre Formation

Lamotte Sandstone

Cherty, sandy dolostone. 

Middle 20 to 30 feet can be a 

clean sandstone

Normal yields of 15 to 50 

gallons per minute 

Massively bedded, crystalline 

dolostone

Lower permeability than 

surrounding units

Cherty dolostone with massive 

chert beds

Combined yields of upper 

and lower units range from 

50 to 75 gallons per minute

Sandstone or sandy 

dolostone

Normal yield of 40 to 50 

gallons per minute, may 

exceed 200 gallons per 

minute in some locations

Crystalline dolostone with less 

than 5 percent chert and sand

Yields of 75 to 250 gallons 

per minute

Crystalline dolostone with 

abundant small solution 

cavities and quartz druse

Generally fine-grained 

dolostone with shale and 

glauconite near base

Shale, siltstone, and fine-grained 

sandstone with interbedded 

limestone and dolostone

Fine- to medium-grained 

dolostone with shale (False 

Davis unit) near top

Sandstone and sandy dolostone 

with arkose near base. Locally 

absent

Target zone of most high 

capacity wells. Yields of 200 

to 1,000 gallons per minute

Usually not a significant 

water source

Not water bearing

Low yields of 5 to 15 gallons 

per minute

Normal yields of 70 to 125 

gallons per minute

0 to 200

200

150

180

350

100 to 300

220

25 to 30

250

40

0 to 200

 (170 average)

ST. FRANCOIS 

CONFINING UNIT

ST. FRANCOIS 

AQUIFER

BASEMENT CONFINING 

UNIT

SystemORDOVICIAN CAMBRIAN

PRECAMBRIAN IGNEOUS ROCKS

Thickness, stratigraphic information, 

and general hydrologic properties

from Miller and Vandike,1997 and 

Imes and Emmett, 1994

NOTE: Nomenclature follows that of the

Missouri Department of the Natural Resources 

Division of Geology and Land Survey 

Figure 2. Generalized geohydrologic units in south-central Missouri.
4 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

Beneath the Ozark aquifer is a less permeable sequence 

composed primarily of dolostone, limestone, and shale known 

as the St. Francois confining unit (fig. 2). This confining unit 

separates the overlying Ozark aquifer from the deeper St. 

Francois aquifer (Imes and Emmett, 1994). The St. Francois 

confining unit consists of the Derby-Doerun Dolomite and the 

Davis Formation (fig. 2). Along the Viburnum Trend, the St. 

Francois confining unit is 230 to 280 ft thick, with a net shale 

thickness ranging from less than 25 to greater than 100 ft, 

and the thickness increases toward the west (Kleeschulte and 

Seeger, 2003).

The St. Francois aquifer lies beneath the St. Francois 

confining unit and consists of the Bonneterre Formation and 

underlying Lamotte Sandstone (fig. 2). The Bonneterre Formation primarily is a dolostone with variable quantities of shale 

in the upper part. The formation is the primary host rock for 

the lead and zinc mineralization in the Viburnum Trend and is 

the target unit in the exploration area (Kleeschulte and Seeger, 

2003). The Lamotte Sandstone, which unconformably overlies 

the Precambrian igneous rocks, primarily is a clean quartzose 

sandstone that contains a basal arkosic conglomerate composed of weathered Precambrian igneous rocks. The thickness 

of the St. Francois aquifer can vary considerably because of 

the irregular surface of the underlying Precambrian rocks. In 

areas of southeastern Missouri near the St. Francois Mountains 

where the St. Francois aquifer is close to the land surface or 

crops out, the aquifer is the only source of groundwater available and yields adequate supplies of water for domestic and 

moderate capacity [100 to 200 gallons per minute (gal/min)] 

public-supply wells—with most of the yield originating from 

the Lamotte Sandstone (Miller and Vandike, 1997). Little is 

known about the quantity or quality of water in the aquifer 

outside of the St. Francois Mountains area because the overlying Ozark aquifer has sufficient quantity and quality of water 

for human use and few wells are drilled to the St. Francois 

aquifer. 

Previous Investigations

Little information exists regarding the quantity and quality of water within the St. Francois aquifer and the degree of 

interconnectivity between the Ozark and St. Francois aquifers 

in the exploration area. The potential for lead-zinc mining in 

this environmentally sensitive karst area has concerned the 

U.S. Forest Service, the National Park Service, U.S. Department of the Interior Bureau of Land Management, and other 

land managers in regard to possible effects that mining may 

have on the water resources of the area. The concerns include 

the potential for mine dewatering in the St. Francois aquifer 

to cause water-level declines in the overlying Ozark aquifer 

and decreased spring flows in the area, and the effect that 

mine water pumped from the St. Francois aquifer will have on 

spring and stream water quality in the area.

To determine if mining in the exploration area potentially could affect groundwater levels and spring discharges 

in the overlying Ozark aquifer, the U.S. Geological Survey 

(USGS) conducted a series of geohydrologic investigations. 

The objectives of these investigations were to: (1) assess the 

permeability of the St. Francois confining unit (Kleeschulte 

and Seeger, 2003); (2) investigate the hydraulic characteristics, 

recharge area, and age of water discharged from Big Spring in 

the ONSR (Imes and others, 2007); and (3) install a monitoring well more than 2,000 ft deep (all depths in this report are 

feet below land surface) in the St. Francois aquifer within the 

exploration area to obtain potentiometric head and water-quality data from the Ozark and St. Francois aquifers.

Purpose and Scope

The purpose of this report is to describe methods used 

in the installation, borehole geophysical logging, and waterlevel measurement and water-quality sampling of a multi-port 

monitoring well (USGS-D1) installed in the exploration area 

and to present and interpret data collected during the installation, borehole geophysical logging, and sampling of the 

well. A focus of the study and this report is to examine the 

potentiometric head relations and water-quality differences 

between the St. Francois aquifer, where a potential lead-zinc 

ore body exists, and the overlying Ozark aquifer. Monitoring 

well USGS-D1 was installed during 2005, and data presented 

in this report were collected during 2005 through 2008. Borehole geophysical logs included caliper, natural gamma, and 

borehole flowmeter logs. A water-quality sample was collected 

from the Ozark aquifer during drilling of the well, and waterquality samples from the St. Francois aquifer were collected 

from the completed well during 2005 and 2006. Manual waterlevel measurements were collected beginning in 2005, and 

continuous water-level recorders were installed during 2006 

and 2007 to further examine the potentiometric head relations 

between the St. Francois aquifer and overlying Ozark aquifer. 

To provide a framework for the interpretation of water-quality 

data from monitoring well USGS-D1, water-quality data for 

the Bonneterre Formation (St. Francois aquifer) were collected from several seeps in an active Viburnum Trend mine 

(Sweetwater Mine) about 40 mi northeast of monitoring well 

USGS-D1, and from a public-supply well about 80 mi to the 

northeast in Marquand that is completed in both the Ozark and 

St. Francois aquifers (fig. 1). 

Methods and Approach

The following section discusses methods used for the 

installation and subsequent data collection from monitoring 

well USGS-D1. A summary of well installation and construction is presented, followed by a general discussion of borehole 

geophysical methods, water-level measurements, water-quality 

sampling, and analytical methods used. Except for waterquality data from mine seeps, all water-level and water-quality 

data are available online through the U.S. Geological Survey 
Methods and Approach 5

National Water Information System at URL http://waterdata.

usgs.gov/nwis. Unpublished water-quality data for mine seeps 

(L.R. Lee, U.S. Geological Survey, written commun., 2007) 

were collected as part of a U.S. Geological Survey Central Region Mineral Resources Center investigation on the 

economic and environmental characteristics of Ozark-region 

mineral deposits (URL http://minerals.cr.usgs.gov/projects/

ozarks/index.html).

Monitoring Well Construction

Monitoring well USGS-D1 was installed using a combination of mud rotary and air-rotary methods. Mud-rotary 

drilling was attempted, but abandoned after substantial circulation loss between 200 and 300 ft deep, and the borehole was 

finished using air-rotary drilling. The target borehole depth 

was 2,250 ft; however, because large openings and caves were 

penetrated during drilling and considerable quantities of water 

were produced between 500 and 1,440 ft deep (estimated at 

more than 500 gal/min), two strings of steel casing set from 

0 to 520 ft deep [12-inch (in.) inside diameter] and from 0 to 

1,440 ft deep (7-in. inside diameter) were required to stabilize 

the borehole, the borehole diameter and depth were decreased 

(fig. 3). The borehole was air-rotary drilled to a final depth of 

2,098 ft within the Bonneterre Formation. Immediately after 

drilling, caliper and natural gamma geophysical logs were 

run in the borehole, and a heat-pulse flowmeter was used to 

measure vertical groundwater flow in the borehole across the 

St. Francois confining unit. 

Monitoring well USGS-D1 was constructed with three 

open ports to allow the collection of water-level and waterquality data from both the Ozark and St. Francois aquifers 

(fig. 3). A 2-1/2-in. inside diameter 80-ft long schedule 80 

polyvinylchloride (PVC) screen was installed within the Bonneterre Formation from 2,018 to 2,098 ft deep (total depth of 

the borehole) and placed in a 118-ft thick silica-sand (WB10-

20) filter pack in a 6-1/2-in. diameter borehole. The PVC riser 

was suspended from the 7-in. inside diameter secondary steel 

casing to minimize bowing of the long string of riser pipe 

and to facilitate installation of the 1-1/2 in. inside diameter galvanized tremie pipe used to place the filter pack and 

bentonite grout. Centralizers were placed at the bottom and 

top of the screen, and at 400-ft intervals along the PVC riser 

between the top of the screen and 560 ft. The screened and 

filter pack interval (1,980 to 2,098 ft deep) is designated port 

3 (P3, USGS station ID 365117091215502) and is used for 

the collection of water samples and water-level measurements 

from the Bonneterre Formation of the St. Francois aquifer. 

To facilitate placement of a submersible sampling pump, the 

diameter of the PVC riser for P3 increases to a 3-1/2-in. inside 

diameter schedule 80 PVC riser above 560 ft (fig. 3). The 

annular space above the P3 filter pack partially was grouted, 

leaving an open interval designated as port 2 (P2, USGS ID 

365117091215501) that extends from the top of the bentonite-grout annular seal at 1,698 ft to the base of a secondary 

string of 7-in. diameter steel casing at 1,440 ft. P2 is open to 

the lower part of the Ozark aquifer (lower part of the Potosi 

Dolomite) and the upper part of the St. Francois confining unit 

(upper part of the Derby-Doerun Dolomite). P2 is accessed 

from the surface through the annulus between the 3-1/2-in. 

PVC riser of P3 and the 7-in. steel secondary casing (fig. 3). 

For the discussion in this report, data from P2 is attributed to 

the lower part of the Ozark aquifer (and not the St. Francois 

confining unit because of the low permeability of the confining 

unit) and data from P3 is attributed to the St. Francois aquifer. A second open annulus designated as port 1 (P1, USGS 

ID 365117091215503) extends from the top of the Portland 

cement annular seal for the 7-in. diameter steel secondary casing at 1,370 ft and the bottom of the 12-in. steel surface casing 

at 520 ft. P1 is open to the middle part of the Ozark aquifer 

(lower part of the Gasconade Dolomite, Eminence Dolomite, 

and the upper part of the Potosi Dolomite). P1 and P2 are 

adequate for water-level measurements, but their diameter is 

not sufficient for the collection of water samples.

Borehole Geophysical Methods

Geophysical logs were run in the monitoring well USGSD1 borehole immediately after drilling was completed. The 

logs were run to determine the location and size of fractures, 

voids, or caves in the borehole and to assist in the determination of lithology and the potentiometric head across the St. 

Francois confining unit. Geophysical logs run at monitoring 

well USGS-D1 included caliper, natural gamma, and heatpulse flowmeter logs.

The caliper log measures the diameter of the borehole 

using three spring-loaded mechanical “arms”. The log provides a continuous record of the average borehole diameter. 

The arms ride along the side of the borehole as the caliper 

tool is pulled up the borehole. A sharp increase in the borehole diameter indicates the presence of a solution-enlarged 

fracture, bedding plane, or “void”. Softer rocks, such as shale 

and mudstone, generally are eroded by the drilling process 

and can be recognized by an increase in borehole diameter 

and corresponding increase in natural gamma radiation. The 

caliper log was calibrated to within 0.1-in. immediately before 

use by using a 3-in. inside diameter PVC pipe and a 10.21-in. 

diameter calibration ring. 

The natural gamma log records the amount of gamma 

radiation (photons) emitted by the radioactive decay of naturally occurring radioisotopes in the bedrock. Most gamma 

radiation in natural materials is the result of the radioactive 

decay of uranium-238, thorium-232, their daughter products, 

and potassium-40 isotopes (Dresser Atlas Industries Inc., 

1974). Clay minerals contain substantial quantities of potassium in their crystal lattice. Trace elements such as uranium 

also adsorb preferentially to clay minerals. As a result, an 

increase in natural gamma radiation generally indicates an 

increase in clay minerals, such as a shale or mudstone bed 

or clay-filled solution opening. Uranium and thorium also 
6 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08 Void or cave

-0.1 0 0.1 0.2

Borehole Flowmeter,

September 2, 2005

Flow, in gallon per minute

DEPTH BELOW LAND SURFACE, IN FEET

0

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

1,800

1,900

2,000

2,100

2,200

6.0 7.0 8.0 9.0 10.0

Caliper Log

September 2, 2005

Borehole Diameter, 

in inches

0 100 200 300 400

Sullivan 

Siltstone

member 

Bentonite drilling 

mud lost into 

cave

Natural Gamma Log

September 2, 2005

Natural gamma, 

in American Petroleum 

Institute (API) units

Roubidoux 

Formation

Gasconade 

Dolomite

Eminence

Dolomite

Potosi

Dolomite

Derby-Doerun

Dolomite

Davis

Formation

Bonneterre

Formation

Down

flow

Up

flow

1,440 feet 

Base of 7-inchdiameter steel 

secondary casing

Check measurement

inside well casing

Figure 3. Summary of well construction and data from borehole geophysical logs of monitoring 

well USGS-D1 near Winona, Missouri.
Methods and Approach 7

Schematic of Monitoring Well 

USGS-D1

(Section 11, Township 25 North, Range 04 West)

Steel casing

965 feet

Land-surface altitude

0 to 83 feet 

Portland cement plug

83 to 395 feet 

bentonite grout

395 to 520 feet 

Portland cement annular seal 

520 feet 

Bottom of 12-inch steel casing 

in 17-inch-diameter borehole

Open annualus

(P1 interval)

21⁄2-inch riser pipe

1,370 feet 

Top of Portland cement annular seal 

1,440 feet 

Bottom of 7-inch steel secondary 

casing in 117⁄8-inch-diameter borehole

1,440 to 1,698 feet 

Open annulus (P2 interval) in 

61⁄2-inch-diameter borehole

1,698 feet

Top of bentonite grout annular seal

1,980 feet 

Top sand filter pack

2,018 feet

Top of 80 feet long 

2,098 feet 

Bottom of hole

31⁄2-in. diameter riser pipe

DEPTH BELOW LAND SURFACE, IN FEET

0

100

200

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

1,800

1,900

2,000

2,100

2,200

ORDOVICIAN CAMBRIAN

Gasconade Dolomite Roubidoux Formation

Ozark aquifer St. Francois aquifer

Potosi Dolomite Eminence Dolomite Derby- Doerun Dolomite Davis Formation Bonneterre Formation FORMATION

GEOHYDROLOGIC 

UNIT

SYSTEM

PRIMARY ORE ZONE 

IN VIBURNUM TREND

St. Francois 

confining unit

PORT 1 (P1)

520 to 1,370 FEET,

(Site identifier 

365117091215503;

Middle Ozark Aquifer)

PORT 2 (P2)

 1,440 to 1,698 FEET

(Site identifier 

365117091215501; 

Lower Ozark Aquifer-Upper 

St. Francois confining unit)

PORT 3 (P3)

 1,980 to 2,098 FEET

(Site identifier

 365117091215502; 

St. Francois Aquifer)

21⁄2-inch-diameter well screen

Figure 3. Summary of well construction and data from borehole geophysical logs of monitoring 

well USGS-D1 near Winona, Missouri.—Continued
8 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

may adsorb to iron oxides, and an increase in natural gamma 

could indicate the presence of iron oxides containing these 

trace elements. The natural gamma log can be used in dry or 

fluid-filled boreholes, and in cased or uncased wells. Well 

casing, however, decreases the gamma signal. Natural gamma 

logs commonly are used to help determine lithology and 

correlate geologic units between boreholes or wells (Keys, 

1990). At monitoring well USGS-D1, the caliper and natural 

gamma logs were run simultaneously. These two logs were run 

upward from the bottom of the borehole at a logging rate of 15 

feet per minute (ft/min) on September 2, 2005. One measure 

of the accuracy of logs is a comparison of depth readings from 

the logging unit at the beginning and end of the log run. The 

top of tools were zeroed to the land surface before lowering 

the tools down the borehole. The bottom of the borehole was 

reached at 2,098 ft, compared to an estimated 2,100 ft measured from the drill string. Upon return to the land surface 

after logging, the unit recorded a depth of 1.48 ft at the land 

surface, indicating a depth error of 1.48 ft in 2,098 ft or about 

0.07 percent.

Vertical movement of water in a borehole is caused 

by the borehole intersecting geohydrologic units, zones, or 

fractures within units that have different potentiometric heads 

and permeabilities. The downward movement of water in 

a borehole indicates that shallower formations have higher 

potentiometric heads than deeper formations, whereas upward 

movement of water indicates higher potentiometric heads in 

deeper formations. The rate of water flow is related to the 

permeabilities of the various zones contributing and accepting water in the borehole. The direction and rate of vertical 

movement of water within the monitoring well borehole was 

measured using a heat-pulse flowmeter. A thorough discussion of the use of borehole-flowmeter measurements to detect 

higher permeability zones in a borehole is in Paillet (1998). 

The instrument functions by rapidly heating a small parcel 

of water using a metal mesh. High resolution thermisters are 

located above and below the metallic mesh and record the 

water temperature. The instrument has a flexible packer to seal 

the borehole between the instrument and the borehole wall to 

divert fluid flow in the borehole through the metallic mesh and 

past the thermisters. After the instrument is lowered to a specified depth, the direction and rate of fluid flow in the borehole 

is calculated when a temperature spike (heat pulse) is recorded 

by one of the thermisters. By convention, upward flow is 

recorded as a positive value and downward flow is recorded as 

a negative value. The heat-pulse flowmeter used at monitoring 

well USGS-D1 has a minimum operating range of about 0.01 

gal/min in most boreholes (Conger, 1996) to a maximum of 

about 1.5 gal/min. Heat-pulse flowmeter measurements may 

be affected by a poor seal between the borehole wall and the 

instrument, especially if the borehole wall is rough or uneven 

If the seal between the instrument and the borehole wall is 

not complete, some water can bypass the instrument, resulting in measurements of flow that are less than the actual rate. 

Although the heat-pulse flowmeter is a calibrated probe, the 

data commonly are used as a relative indicator to identify 

the direction of flow and water-producing or receiving zones 

within the borehole because the instrument is not easily calibrated in the field. At monitoring well USGS-D1, the factory 

calibration was used; however, a field check for “zero” flow 

was done by making several flow measurements inside the 

steel casing at 1,431 ft where no vertical flow should exist. 

These measurements indicated less than 0.03 gal/min of flow 

inside the casing.

Water-Level Measurements and Water-Quality 

Sampling

A primary objective for the installation of monitoring 

well USGS-D1 was to obtain water-level measurements from 

the Ozark and St. Francois aquifers to determine potentiometric head relations between these two aquifers. The potentiometric head is the altitude to which water would stand in 

a tightly cased well open to the aquifer. Potentiometric head 

relations between the St. Francois aquifer and overlying Ozark 

aquifer were determined by measuring depths to water in 

the Ozark aquifer (P1 and P2) and St. Francois aquifer (P3). 

Manual water-level measurements (depth to water) were 

made periodically in monitoring well USGS-D1. The depth to 

water was measured to the nearest 0.01 ft using a 400-ft long 

calibrated electric tape. Water-level measurements in each 

port were made from a common reference point at the top of 

the protective steel casing. The depth to water (water level) 

recorded was the average of three consecutive measurements. 

Submersible pressure transducers were installed in P2 and P3 

during early 2007 and late 2006, respectively, and to provide 

continuous hourly water-level measurements. Because the 

pressure transducers used were non-vented and recorded the 

depth of water above the transducer relative to an absolute 

pressure, an additional pressure transducer suspended inside 

the top of the well casing was used as a barometer to correct for barometric changes by subtracting the output of the 

barometer from the submerged transducers as described in 

Freeman and others (2004). Data from the transducers were 

downloaded using a laptop computer at the time the periodic 

manual water-level measurements were made. The daily mean 

water level was computed from continuous hourly water-level 

measurements obtained from the pressure transducers. 

Water-quality samples were collected from monitoring 

well USGS-D1 during 2005 and 2006 from the lower part of 

the Potosi Dolomite (Ozark aquifer) and from the Bonneterre 

Formation (St. Francois aquifer). All samples were collected 

according to established USGS protocols from the USGS 

National Field Manual (U.S. Geological Survey, 1997–2006). 

Samples were collected using a 3-in. diameter stainless 

steel submersible pump. The pump was suspended by 1-in. 

inside diameter threaded PVC riser pipe and powered using 

a portable generator. Because the unstable borehole required 

installation of a secondary steel casing and subsequent reduction of the borehole diameter, plans for a well screen in the 

lower part of the Potosi Dolomite (P2) were abandoned, and as 
Methods and Approach 9

an alternative, water samples were collected from this interval during drilling. After the 7-in. diameter secondary steel 

casing was installed to 1,440 ft and cemented into place, the 

borehole was advanced to 1,520 ft, the drill tools removed, 

and a 3-in. submersible pumped installed to 540 ft deep. The 

borehole was pumped at 10 gal/min for 10 hours (hrs) before 

water-quality samples were collected from 1,500 ft deep using 

a discrete (point) sampler. Water samples from this interval 

were associated with the P2 interval in the completed monitoring well. After the well was completed, water samples from 

the Bonneterre Formation (P3) were collected by installing 

a dedicated 3-in. submersible pump in the P3 riser to 560 ft 

(point where the riser diameter reduced to 2-1/2 in.). The P3 

interval yielded considerably less water than the P2 interval 

and required a PVC gate valve to reduce the pump discharge 

to less than 0.5 gal/min after the water level had been lowered 

to less than 40 ft above the pump. The small annulus between 

the pump and the P3 well casing (less than 1 in.) hampered 

the collection of water-level measurements, and only sporadic 

water-level measurements were made in P3 until the pump 

was removed in December 2006.

Sample intervals were purged before the collection of 

water samples. During purging, field measurements of specific 

conductance, temperature, pH, and dissolved oxygen were 

made in a flow-through chamber at 20- to 40-minute intervals 

until stable readings were obtained. Stable readings for field 

measurements were defined as readings that did not vary by 

more than the following amounts over three consecutive measurements: specific conductance (within 2 percent), temperature [within 0.5 degrees Celsius (o

C)], pH (within 0.2 standard 

pH units), and dissolved oxygen [within 0.5 milligrams per 

liter (mg/L)]. Specific conductance values were measured 

using a portable conductivity meter with temperature compensation designed to express readings in microsiemens per centimeter at 25 degrees Celsius (μS/cm). The pH was measured 

to the nearest 0.05 standard unit with a portable pH meter 

with temperature compensation. The meter was calibrated 

immediately before use using Natural Bureau of Standards 

(NBS) traceable buffers of pH 4.0, 7.0, and 10.0 at 25 oC. 

Water temperature was measured to the nearest 0.1 oC using 

the thermistor on the specific conductance meter. Dissolved 

oxygen was determined by a Rhodazine-D spectrophotometric 

method using vacuum ampules manufactured by CHEMetrics, 

Incorporated (White and others, 1990).

Once stable readings of field measurements were 

obtained, water samples were collected and processed in a 

mobile laboratory immediately after collection using methods described by Wilde and others (1999) designed to minimize changes to the water-sample chemistry before analysis. 

Samples for analyses of dissolved major cations and anions, 

nutrients, trace elements, and carbon isotopes were filtered by 

placing a 0.45-μm (micrometer) nominal pore-sized disposable capsule filter directly at the pump discharge outlet (after 

reducing the pump discharge to 0.1 gal/min). These samples 

were placed in precleaned polyethylene bottles after the bottles 

had been field rinsed with filtered groundwater. Samples for 

analyses of major cations and trace elements were placed in 

acid-washed polyethylene bottles and preserved to pH value 

less than 2.0 using concentrated ultrapure nitric acid. Samples 

for analyses of dissolved major anions were not preserved. 

Samples for analysis of nutrients were placed in amber polyethylene bottles and placed on ice for overnight shipment to 

the laboratory. Glass sample bottles for the analyses of carbon 

isotopes were filled from the bottom using a 0.25-in. diameter 

Teflon tube attached to the discharge end of the capsule filter 

and allowed to overflow for several minutes to avoid contact 

with the atmosphere before they were sealed with septum 

caps. Samples for analyses of oxygen isotopes were placed in 

glass bottles (bottom filled using the Teflon tubing) and sealed 

with a polyethylene “polyseal” cap after overfilling for several 

minutes. Additionally, an unfiltered, unpreserved sample was 

collected in a polyethylene bottle for determination of alkalinity (acid neutralizing capacity or ANC) onsite immediately 

after the collection of all samples. Sample bottles for alkalinity and isotopes were filled first followed by nutrients, major 

anions, and finally major cations and trace elements.

Analysis of water-quality samples for inorganic constituents, nutrients, and total organic carbon were performed by the 

USGS National Water Quality Laboratory (NWQL) in Lakewood, Colorado, according to methods described in Fishman 

(1993) or Garbarino and others (2006). Alkalinity and concentrations of bicarbonate (HCO3

) and carbonate (CO3) were 

determined onsite in the water-quality vehicle by incremental 

titration past the CO3-HCO3 and HCO3-carbonic acid (H2CO3) 

inflection points using 0.1600 normal (N) sulfuric acid.

Analysis of oxygen isotopes were done at the USGS 

Stable Isotope Laboratory in Reston, Virginia (Epstein and 

Mayeda, 1953; Coplen, 1994), and analysis of carbon isotopes 

were done at the University of Waterloo in Ontario, Canada 

(Gleason and others, 1969). Analytical results for stable oxygen isotopes are presented as a ratio of the oxygen-18 (18O) 

and oxygen-16 (16O) relative to the isotopic ratio of a known 

standard and expressed in delta (δ) notation in per thousand 

parts or per mil (‰) of 18O or δ18O. Analytical results for the 

stable isotopes of carbon are presented as a ratio of the carbon-13 (13C) and carbon-12 (12C) relative to the isotopic ratio 

of a known standard and also expressed in per mil or δ13C. The 

reference standard for stable oxygen isotope (18O/16O) ratios 

is Vienna Standard Mean Ocean Water (VSMOW), and the 

Vienna Pee Dee Belemnite (VPDB) is the reference standard 

for stable carbon isotope (13C/12C) ratios. Concentrations of the 

radioactive carbon-14 (14C) isotope are reported as a percent of 

modern carbon (pmC) referenced to an international standard 

known as “modern carbon” (mC) that is defined as 95 percent 

of the 14C activity in 1950 of the National Bureau of Standards 

(NBS) oxalic acid standard.
10 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

Quality Assurance for Water-Level and WaterQuality Data

The manual water-level measurements periodically made 

in monitoring well USGS-D1 were used to verify the accuracy 

of the submersible pressure transducer measurements. The 

average absolute difference between the manual and submersible pressure transducer measurements was less than or 

equal to 0.09 ft and ranged from -0.16 to 0.18 ft (table 1). The 

differences were small as a percentage of the total depth of 

the measurements (within 0.05 percent) and generally within 

the accuracy of the transducers reported by the manufacturer 

of 0.066 ft (transducer used in P3) to 0.12 ft (transducer used 

in P2). The manual water-level measurements are considered 

the standard or “true” readings and the recorded pressure 

transducer data were adjusted to match the manual measurements made each time that the transducers were downloaded 

to correct for instrument drift. Because the transducers were 

initially set to match the manual measurements at the beginning of each recorded period, differences between the recorded 

and manual measurement made when each transducer was 

downloaded were prorated over the period of the record. For 

example, the pressure transducer was installed in P2 on February 12, 2007, and the transducer was set to match the manual 

water-level measurement of 319.66 ft below the land surface 

(table 1). On March 6, 2007, the transducer was downloaded 

and the difference of -0.11 ft between the ending recorded 

value of 292.90 ft and the manual measurement of 292.79 ft 

was prorated over the 22 days of record from -0.0050 ft on day 

1 to -0.11 ft on day 22.

Adherence to established and published USGS protocols 

for the collection, processing, and analysis of water-quality 

samples was done to ensure that water-quality samples represented, as accurately as possible, the water quality of the 

sampled intervals of the aquifers. In addition, a quality assurance (replicate) sample was collected from the P2 interval of 

monitoring well USGS-D1 on August 30, 2005 while the well 

was being drilled (table 2). Immediately after the collection 

of the regular P2 sample at 0130, the replicate sample was 

collected using the same equipment and filter as the regular 

sample. The replicate sample was not analyzed for carbon 

isotopes. Because of concerns regarding stability of samples 

pumped from such a deep depth (such as sample warming and 

degassing) and time required to fill and process the large number of individual sample containers for each complete sample, 

a replicate sample rather than a duplicate water sample was 

collected.

Comparison of the regular and replicate sample results 

for constituents whose concentrations were not censored 

(less than) or estimated by the laboratory below the method 

reporting limit (Oblinger Childress, 1999), generally indicate 

that the relative percent difference (RPD) between concentrations of most major ions, nutrients, and trace elements in the 

regular and replicate samples generally were within 10 and 

often less than 5 percent (table 2). The RPD was calculated 

as the difference between the constituent concentration in 

the regular sample minus the concentration in the replicate 

sample divided by the average concentration in the regular and 

replicate sample. Although samples were not collected until 

purge parameters had stabilized, because the samples were 

replicate and collected 10 minutes apart, in addition to sample 

collection and analytical error, differences in concentrations 

also could be the result of subtle changes in water chemistry 

or small collodial particulates that could pass through the 

0.45-μm pore-size filter used to filter the samples for dissolved 

major and trace constituents. 

The RPD of potassium (K), nitrite as nitrogen (NO2), 

and several trace elements such as boron (B), chromium 

(Cr), lead (Pb) selenium (Se), and thallium (Tl) in the regular 

and replicate samples were larger than 20 percent (table 2); 

however, concentrations of these constituents in one or both 

of the samples were near the reporting levels where analytical 

precision decreases. Several trace constituents had much larger 

RPDs that probably were not the result of lower analytical 

precision near the reporting levels including arsenic (As, 118 

percent), iron (Fe, greater than -198 percent), manganese (Mn, 

-117 percent), and zinc (Zn, -147 percent). Concentrations of 

Fe [1,330 micrograms per liter (μg/L)], Mn (38 μg/L), and 

Zn (115 μg/L) in the replicate sample were larger than those 

in the regular sample (all less than 20 μg/L) and may indicate 

that small colloidal Fe-rich particles may have passed through 

the 0.45-μm pore-size filter used to filter the water samples for 

dissolved major and trace constituents. Trace elements such 

as Mn and Zn commonly are associated with Fe-rich particles 

(Hem, 1985).

Borehole Geophysical Logs

The caliper log indicated a generally smooth borehole 

wall between the bottom of the 7-in. secondary steel casing at 

1,440 ft and the bottom of the borehole at 2,098 ft deep (fig. 

3). Except for a 20-ft thick section immediately below the bottom of the casing from 1,440 to about 1,460 ft deep, and several short sections within the upper 60 ft of the Derby-Doerun 

Dolomite from 1,485 to 1,540 ft deep, the borehole diameter 

varied less than 0.25-in. from the 6.5-in. diameter bit used to 

drill the lower 660 ft of the borehole. 

The generally small [less than about 100 American 

Petroleum Institute (API) units] natural gamma counts in the 

natural gamma log (fig. 3) reflected the predominant carbonate 

lithology of the bedrock. Natural gamma counts in dolostone 

generally are less than 100 API units (Dresser Atlas Industries 

Inc., 1974). The large spike in the natural gamma log between 

200 and 300 ft deep is the result of more than 200 bags of 

bentonite drilling mud being lost into a large void or cave 

during drilling (fig. 3). The increase in gamma counts in the 

1,640 to 1,845 ft deep interval corresponds to the shale-rich 

Davis Formation. A geologic log of drill cuttings confirmed 

the presence of substantial quantities of shale (up to 80 percent) with dolostone beginning at about 1,640 ft deep. The 
Borehole Geophysical Logs 11

Table 1. Quality-assurance data for continuous recording pressure transducers and manual waterlevel measurements at monitoring USGS-D1, 2005–08.

[ID, identifier; --, no data; all depths in feet below land surface unless noted otherwise]

Water level depth, in feet 

below land surface

Difference between manual 

measurement and submersible

pressure transducer

Date Time 

(hours)

Manual

measurement

Submersible 

pressure 

transducer

Difference, in feet 

below land surface

Percent 

difference

P2 (lower part of the Ozark aquifer1; station ID 365117091215501)

02/12/07 1115 319.66 -- -- --

03/06/07 1045 292.79 292.90 -.11 0.04

04/25/07 1215 326.93 326.83 .10 -.03

06/20/07 1025 351.60 351.50 .10 -.03

08/01/07 1015 373.54 373.53 .01 0

09/10/07 1105 383.71 383.59 .12 -.03

10/09/07 1015 391.17 391.20 -.03 .01

11/19/07 1045 398.00 -- --

01/07/08 1020 389.63 389.63 0 0

03/11/08 1030 305.96 306.12 -.16 .05

05/28/08 1030 275.15 275.26 -.11 .04

07/25/08 1050 319.88 319.78 .10 -.03

10/01/08 1035 367.56 367.43 .13 -.04

Average absolute difference .09 .03

P3 (St. Francois aquifer2 ; station ID 365117091215502)

12/18/06 1105 364.30 -- -- --

12/27/06 0956 366.24 366.24 0 0

01/31/07 1020 363.63 363.63 0 0

03/06/07 1030 363.26 363.29 -.03 .01

04/25/07 1145 367.26 367.35 -.09 .02

06/20/07 1000 367.33 367.38 -.05 .01

08/01/07 0945 370.31 370.13 .18 -.05

09/10/07 1055 373.05 373.14 -.09 .02

10/09/07 1030 374.31 374.34 -.03 .01

11/19/07 1015 376.38 376.38 0 0

01/07/08 1000 376.58 376.58 0 0

03/11/08 1005 372.56 372.38 .18 -.05

05/28/08 1005 362.20 362.33 -.13 .04

07/25/08 1040 365.05 365.06 -.01 0

10/01/08 1010 367.80 367.78 .02 -.01

Average absolute difference .06 .02

1

Sample interval open to the lower part of the Potosi Dolomite (lower Ozark aquifer) and the upper part of the DebryDoerun Dolomite (St. Francois confining unit).

2

Sample interval within the Bonneterre Formation.
12 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

Table 2. Values of selected physical properties and concentrations of chemical constituents in the regular and replicate 

sample from monitoring well USGS-D1, August 30, 2005.

[mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; CaCO3, calcium carbonate; N, 

nitrogen; P, phosphorus; μg/L, microgram per liter; <, less than; >, greater than; --, no data; E, estimated value; all concentrations dissolved 

unless noted otherwise]

Property or chemical constituent Unit Reporting 

level

P21, regular 

sample collected 

at 0130

P21, replicate 

sample collected 

at 0140

Relative percent 

difference (RPD)2

Dissolved oxygen mg/L 0.1 0.6 0.6 0

pH, units standard units -- 7.5 7.5 0

Specific conductance μS/cm 5 420 420 0

Water temperature °C -- 15.2 15.2 0

Hardness mg/L 1 240 240 0

Calcium mg/L .044 49 47.8 2.5

Magnesium mg/L .02 29.7 29.8 -.3

Potassium mg/L .008 .9 1.5 -50

Sodium mg/L .1 1.5 1.5 0

Alkalinity as CaCO3 mg/L 1 208 208 0

Bicarbonate mg/L 1 257 257 0

Carbonate mg/L 1 <1 <1 --

Chloride mg/L .12 1.38 1.44 -4.3

Sulfate mg/L .18 15.3 15.2 .7

Fluoride mg/L .08 <.1 <.1 --

Silica mg/L .058 10.2 9.7 4.7

Dissolved solids (TDS), total mg/L 10 234 235 -.4

Ammonia as N mg/L .02 <.04 <.04 --

Nitrate plus nitrite as N mg/L .04 <.06 <.06 --

Nitrite as N mg/L .002 <.008 E.004 >66.7

Orthophosphate as P mg/L .02 <.02 <.02 --

Phosphorus as P mg/L .04 <.04 <.04 --

Organic carbon, total mg/L .6 -- .9 --

Organic carbon, dissolved mg/L .4 -- .5 --

Antimony μg/L .054 2.4 2.5 -4.1

Arsenic μg/L .044 3.5 .9 118

Barium μg/L .6 14 15 -6.9

Beryllium μg/L .2 <.2 <.2 --

Boron μg/L 2 8 E6.4 22.2

Cadmium μg/L .02 0.1 .1 0

Chromium μg/L .12 E.03 <.04 >- 28.6

Cobalt μg/L .01 1.3 1.3 0

Copper μg/L 1 E.4 .4 0

Iron μg/L 6 <6 1,330 > -198

Lead μg/L .03 .12 <.08 > 40

Lithium μg/L .06 <2 <2 --

Manganese μg/L .26 10 38 -117

Molybdenum μg/L .028 5.4 7 -25.8

Nickel μg/L .12 7 6.9 1.4

Selenium μg/L .04 6.1 <.08 195

Strontium μg/L .4 33 39 -16.7

Thallium μg/L .02 .06 0.11 -58.8

Vanadium μg/L .8 <2 <2 --

Zinc μg/L 2.8 17.4 115 -147

1

Sample interval open to the lower part of the Potosi Dolomite (lower Ozark aquifer) and the upper part of the Derbry-Doerun Dolomite (St. 

Francois confining unit).

2

Calculated as the difference between the regular minus the replicate sample result divided by the average of the regular and replicate result 

expressed as percent.
Water-Level Measurements 13

natural gamma counts abruptly decrease below 1,845 ft deep 

at the top of the Bonneterre Formation. The Sullivan Siltstone 

member of the Bonneterre Formation (about 1,880 to 1,930 ft 

deep) has a substantially larger gamma signature than the rest 

of the Bonneterre Formation. The geologic log identified the 

Sullivan Siltstone member as a dark gray, medium-to finegrained siltstone. 

Borehole-flow measurements made in the lower part of 

monitoring well USGS-D1 indicate an upward flow of water 

from the Bonneterre Formation that exits the borehole in the 

Derby-Doerun Dolomite and lower part of the Potosi Dolomite (fig. 3). Borehole-flow measurements were made under 

ambient (non-pumping) conditions on September 3, 2005, 

about 20 hours after the drill rods had been removed. Measurements were made in the open borehole within the lower 

Potosi Dolomite, Derby-Doerun Dolomite, Davis Formation, 

and Bonneterre Formation at 14 depths ranging from 1,474 to 

2,065 ft deep (fig. 3). At the time the flow measurements were 

made, the borehole was open from 1,440 to 2,098 ft, and the 

static water level in the borehole was 406.4 ft below the top of 

the protective steel casing. The borehole-flow measurements 

were all positive values, indicating upward flow at rates ranging from an estimated 0.02 to 0.15 gal/min with an average 

upward flow of 0.06 gal/min (table 3). The upward flow in 

the borehole indicates that at the time of the borehole-flow 

measurements, the potentiometric head in the St. Francois 

aquifer was higher than the potentiometric head in the overlying St. Francois confining unit and the lower part of the Ozark 

aquifer.

Water-Level Measurements

Water-level measurements from the completed monitoring well indicate a complex relation between the potentiometric head in the Ozark aquifer and potentiometric head in 

the upper part of the St. Francois aquifer at monitoring well 

USGS-D1. Considerable variability in the potentiometric 

head within the Ozark aquifer (P1 and P2) may be in response 

to precipitation (fig. 4). The water level in the lower part of 

the Ozark aquifer (P2) fluctuated more than 170 ft with the 

pressure transducer recording large increases during February through about May followed by a period of generally 

decreasing water level from about June through January. The 

largest water level increases generally occurred during or after 

periods of higher weekly rainfall recorded at a weather station 

in West Plains, Missouri (National Oceanic and Atmospheric 

Table 3. Summary of borehole flowmeter measurements in monitoring well USGS-D1, September 3, 2005. 

[E, estimated value; <, less than; n/a, not applicable; all measurments made using a heat-pulse flowmeter]

Depth below land surface,

in feet

Borehole flow, 

in gallons per 

minute

Flow direction Geologic unit Geohydrologic unit

1,431 E<.01 none Inside steel casing n/a

1,474 .05 up Potosi Dolomite Ozark aquifer

1,511 E.02 up Debry-Doerun Dolomite St. Francois confining unit

1,570 E.02 up Debry-Doerun Dolomite St. Francois confining unit

1,662 .04 up Davis Formation St. Francois confining unit

1,737 .06 up Davis Formation St. Francois confining unit

1,741 .06 up Davis Formation St. Francois confining unit

1,780 .04 up Davis Formation St. Francois confining unit

1,865 .15 up Bonneterre Formation St. Francois aquifer

1,877 .07 up Bonneterre Formation St. Francois aquifer

1,932 .10 up Bonneterre Formation St. Francois aquifer

1,970 .06 up Bonneterre Formation St. Francois aquifer

2,040 .07 up Bonneterre Formation St. Francois aquifer

2,045 .04 up Bonneterre Formation St. Francois aquifer

2,065 .04 up Bonneterre Formation St. Francois aquifer

Average upward flow .06
14 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

Administration, 2009). For example, between February and 

April 2008, the water level in P2 increased more than 170 

ft after several weeks of higher precipitation. After peaking 

during April 2008, the water level in P2 gradually decreased 

through December 2008, when data collection ended. The correlation between the water level increase in P2 and precipitation is not exact, possibly because the water level in monitoring well USGS-D1 may be responding to local precipitation 

events that may not necessarily be reflected in the precipitation 

record at the West Plains weather station about 40 mi southwest of monitoring well USGS-D1. Although manual waterlevel measurements made during 2005 and 2006 before the 

pressure transducers were installed also indicate considerable 

variability in water level, the measurements were not of sufficient density to discern the complexity of the seasonal pattern 

observed in the pressure transducer data (fig. 4). The large and 

rapid response of water level in P2 to weekly precipitation 

is consistent with observations made by Miller and Vandike 

(1997) in an unused municipal well in West Plains, Missouri. 

The unused municipal well at West Plains has been used as 

an observation well by the Missouri Department of Natural 

Resources (MDNR) since the 1950s. Although the well has 

800 ft of pressure-grouted casing, water levels in the well can 

increase as much as 200 ft within a few hours after a major 

precipitation event. The large and rapid increases in water 

levels in the West Plains observation well were attributed by 

Miller and Vandike (1997) to be caused by hydraulic pressure 

head increases in the shallow zones of the aquifer being rapidly transmitted to deeper zones as a result of the intense karst 

development in the aquifer. This mechanism probably is the 

cause of the rapid and large increases in water levels observed 

in P2 (fig. 4). 

A comparison of manual water-level measurements 

indicates that, with one exception, water levels in the middle 

Ozark aquifer (P1) were about 0.3 ft higher than those in the 

lower Ozark aquifer (P2) indicating a generally downward 

gradient within the Ozark aquifer (table 4). On December 6, 

2006, the water level in P2 (273.90 ft) was slightly higher 

S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

2005 2006 2007 2008

EXPLANATION

Pressure transucer

 Port P2

 Port P3

Manual measurement

 Port P1

 Port P2

 Port P3

Port P1—Station identifier 365117091215503; middle Ozark aquifer 

 (lower part of the Gasconade Dolomite, Eminence Dolomite, and 

 upper part of the Potosi Dolomite)

Port P2—Station identifier 365117091215501; lower part of the Ozark 

 aquifer (lower part of the Potosi Dolomite) and upper part of the 

 St. Francois confining unit (upper part of the Derby-Doerun Dolomite)

Port P3—Station identifier 365117091215502; St. Francois aquifer 

 (Bonneterre Formation)

8

4

0

WEEKLY

RAINFALL, 

IN INCHES

220

240

260

280

300

320

340

360

380

400

420

WATER LEVEL, IN FEET BELOW LAND SURFACE

No data

Figure 4. Water levels in the Ozark aquifer and St. Francois aquifer in monitoring well USGS-D1 near Winona, Missouri, 

and weekly precipitation recorded at West Plains, Missouri, September 1, 2005, through December 31, 2008.
Water-Level Measurements 15

Overall, water-level fluctuations in P3 were a subdued 

response to those in P2 or P1. Sharp increases in the P2 water 

level were mimicked by much smaller water level increases 

in P3. For example, the large 170 ft water level increase in 

P2 during February through April 2008 was followed by a 

similar, but smaller (less than 20 ft) water level increase in P3 

that peaked in April 2008 (fig. 4). The similar, but subdued 

response in P3 water level to water-level changes in P2, was 

unexpected and may indicate a small degree of connection 

between the Ozark and St. Francois aquifers. This connection 

may be the result of faulty well construction, such as a poor 

well seal or leaking well casing that will be discussed in more 

detail in the water-quality section.

An important finding from the water-level data from 

monitoring well USGS-D1 is that, at times, the potentiometric head in the St. Francois aquifer is higher than that in the 

overlying Ozark aquifer, indicating periods of an upward 

gradient across the St. Francois confining unit. This condition existed at the time the borehole flowmeter log was run 

in September 2005. The continuous water-level data from the 

pressure transducers indicate that the upward gradient between 

P3 and P2 occurred on 288 of the 688 days (about 42 percent) 

for which continuous data are available. The magnitude of the 

upward potentiometric head across the St. Francois confining 

unit (maximum of 22.84 ft; average of 13.40 ft) was much 

smaller than the magnitude of the downward potentiometric 

heads (maximum of 138.47 ft; average of 53.84 ft). Based 

on nearly 2 years of continuous water-level data, an upward 

gradient existed across the Ozark confining unit from late 

summer through late winter (about September to February) 

with an abrupt transition to a downward gradient from late 

winter through late summer (about February through August). 

The abrupt change from upward to downward gradients in 

about February is mostly the result of large increases in water 

levels in the Ozark aquifer in response to precipitation (fig. 4) 

and rapid recharge.

Although P3 is open to more than 100 ft of the Bonneterre Formation of the St. Francois aquifer, this interval 

yielded only small quantities of water. The quantity of water 

that could be pumped from the P3 interval during purging 

before the collection of water-quality samples was small and 

averaged only about 0.4 gal/min with drawdowns of 94 to 111 

ft—resulting in an estimated specific capacity of about 0.004 

gallons per minute per foot of drawdown (gal/min/ft). The P3 

interval could be only minimally stressed to avoid drawing 

the water level down to the pump because the diameter of the 

riser pipe decreased from 3-1/2 to 2-1/2-in. at 560 ft, limiting 

the depth to which the 3-in. diameter sampling pump could 

be installed. The estimated small specific capacity of the P3 

interval is consistent with small vertical hydraulic conductivity measurements of the Bonneterre Formation in the Viburnum Trend of less than 10-10 foot per day (ft/day) reported by 

Kleeschulte and Seeger (2003) and published data indicating 

limited yield of water to wells open to the Bonneterre Formation in southern Missouri (Miller and Vandike, 1997).

Table 4. Manual water-level measurements in monitoring 

well USGS-D1, September 14, 2005, through October 1, 2008. 

[--, no data; ID, identifier; all values in feet below land surface]

Date P11 P22 P33

09/14/2005 -- -- 382.36

10/14/2005 -- -- 383.67

11/02/2005 412.80 413.14 384.16

11/03/2005 -- 413.09 --

11/04/2005 -- 413.05 --

12/01/2005 -- 302.03 359.32

01/11/2006 -- 393.25 382.52

01/19/2006 -- 383.71 380.28

03/29/2006 -- -- 360.22

04/12/2006 -- -- 367.62

12/06/2006 274.01 273.90 362.75

12/18/2006 299.70 300.30 364.30

12/27/2006 315.05 315.45 366.24

01/31/2007 291.74 292.28 363.63

02/12/2007 -- 319.66 --

03/06/2007 292.34 292.79 363.26

04/25/2007 326.52 326.93 367.26

06/20/2007 351.34 351.60 367.33

08/01/2007 373.37 373.54 370.31

09/10/2007 383.55 383.71 373.05

10/09/2007 391.04 391.17 374.31

11/19/2007 397.78 398.00 376.38

01/07/2008 389.45 389.63 376.58

03/11/2008 305.65 305.96 372.56

05/28/2008 274.50 275.15 362.20

07/25/2008 319.20 319.88 365.05

10/01/2008 367.19 367.56 367.80

1

Station ID 365117091215503, sample interval open to the middle part 

of the Ozark aquifer (lower part of the Gasconade Dolomite, Eminence 

Dolomite, and upper part of the Potosi Dolomite).

2

Station ID 365117091215501, sample interval open to the lower part 

of the Ozark aquifer (lower part of the Potosi Dolomite) and the upper 

part of St. Francois confining unit (upper part of the Derby-Doerun 

Dolomite).

3

Station ID 365117091215502, sample interval within the Bonneterre 

Formation.

(0.11 ft) than the water level in P1 (table 4). This slight difference is within 0.1 percent (about 0.27 ft) of the depth measured and could be the result of measurement error or indicate 

short-term responses to recent rainfall (fig. 4).

Water levels in the St. Francois aquifer (P3) were less 

variable than water levels in the overlying Ozark aquifer, 

and fluctuated less than 30 ft during the study period (fig. 4). 
16 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

Water Quality

Analyses of water samples collected from monitoring 

well USGS-D1 indicated substantial differences between 

the water quality in the upper part of the St. Francois aquifer 

and the overlying Ozark aquifer. Water samples from the St. 

Francois aquifer [Bonneterre Formation (P3)] contained larger 

specific conductance values and concentrations of the major 

ions sodium (Na), K, chloride (Cl), and sulfate (SO4) and 

trace elements such as B and lithium (Li), as compared to the 

water sample collected during August 2005 from the Ozark 

aquifer [lower part of the Potosi Dolomite (P2)] during drilling 

(table 5). The initial P3 sample (November 4, 2005) contained 

1,300 mg/L of dissolved solids and was a Na-Cl type water 

that plots near the Na plus K- SO4 plus Cl vertex on the trilinear diagram (fig. 5). In contrast, background Ozark aquifer 

water samples and the P2 sample generally contained less than 

250 mg/L dissolved solids, are calcium (Ca) plus magnesium 

(Mg)- HCO3 type water and generally contained less than 

5 milligrams per liter Na and Cl and less than 10 μg/L of B 

(Imes and Emmett, 1994; Imes and others, 1996; Miller and 

Vandike, 1997). The concentrations of Na (450 mg/L), Cl (469 

mg/L), sulfate (214 mg/L) B (1,980 μg/L), and Li (261 μg 

/L) in the initial P3 sample were about 10 to 300 times larger 

than those in the P2 sample (table 5). However, concentrations of Ca (9.5 mg/L) and Mg (8.6 mg/L) in the initial P3 

sample were unusually low and may reflect the exchange of 

these cations for Na from the Na-bentonite used as the annular 

seal. Data for subsequent P3 samples plot along a line trending between the P2 sample and the initial P3 sample (fig. 5), 

indicating that P3 samples collected during 2006 probably 

were a mixture of water from the two aquifers possibly caused 

by a faulty well seal or casing leak. The geochemical code 

PHREEQC (Parkhurst and Appelo, 1999) was used to evaluate the mixing of water from the P2 and P3 intervals assuming 

that the November 2005 P3 sample represents a St. Francois 

aquifer (Bonneterre Formation) end member mixing with 

an Ozark aquifer water represented by the August 2005 P2 

sample. Results of simple mixing and allowing for exchange 

of Ca and Mg for Na on the bentonite used as the annular seal 

indicated that the water quality of the P3 samples collected 

during 2006 can be approximated by mixing from 1 percent 

(April 2006 sample) to 43 percent (October 2006 sample) of 

St. Francois aquifer water (November 2005 P3 sample) with 

water from the lower part of the Ozark aquifer (P2 sample). 

The mixing scenarios support the hypothesis of a faulty well 

construction, allowing mixing of water from the Ozark and St. 

Francois aquifers. Based on the continuous water-level data 

collected during 2007 and 2008 (fig. 4), downward flow of 

water from the Potosi Dolomite probably was occurring when 

the April and May 2006 samples were collected, causing a 

leftward shift in plotting position on figure 5. Upward flow of 

water from the Bonneterre Formation probably was occurring 

during the fall of 2006, resulting in a shift to the right of the 

October 2006 sample (fig. 5). As previously discussed, a leak 

caused by faulty well construction also may be the cause of 

the subdued response of water levels in P3 to changes in water 

levels in P2 (fig. 4).

The magnitude of the apparent leakage of water between 

the P2 and P3 zones suggested by the shift in plotting position 

of the P3 water samples on figure 5 and similar, but subdued 

response, of continuous water-level measurements in P3 to 

water level changes in P2 (fig. 4) probably is small and nearly 

undetectable. According to the mixing model, the leftward 

shift in plotting position from the November 2005 P3 sample 

to the April 2006 (1 percent P3 water) sample represents a 

downward flux of nearly 750 gallons (gal) of P2 water (volume of water in the well pipe, filter pack, and volume of water 

removed during purging). Assuming that this water moved 

steadily downward during the 160 days between the collection 

of the two samples and mixed completely within the well pipe 

and filter pack (degree of mixing would depend upon where 

the leak occurred), an estimated 5 gal of leakage occurred 

each day or about 0.003 gal/min. This rate is nearly an order 

of magnitude smaller than what could be measured with the 

heat-pulse flowmeter. This estimated leakage rate likely is a 

maximum value because it is unlikely that complete mixing 

occurs, especially within the filter pack. The rate of leakage is 

dependant upon the differential head between the P2 and P3 

intervals and is expected to vary with time.

Despite an apparent well-construction problem or casing leak that is allowing mixing of water from the Ozark and 

St. Francois aquifers and possible Ca-Mg:Na exchange on 

bentonite grout, sample results indicated that water within the 

Bonneterre Formation at this location is a Na-Cl type water 

with large specific conductance values and large concentrations of dissolved solids, Na, Cl, SO4

, B, and Li (table 5). 

The large concentrations of Na, Cl, SO4 and other ions in 

P3 samples (excluding the April 2006 sample) are unusual 

because water in the St. Francois aquifer in most of southern 

Missouri typically has low dissolved solids concentration and 

is a Ca-Mg-HCO3 type water (Miller and Vandike, 1997). 

However, except where the St. Francois aquifer is exposed 

near the St. Francois Mountains in southeastern Missouri 

(fig. 1), few wells penetrate the St. Francois aquifer because of 

the adequate yields of potable water from the overlying Ozark 

aquifer. Consequently, relatively little is known about the variability of water quality within the St. Francois aquifer in much 

of southern Missouri. 

Two other occurrences of unusual water quality within 

the St. Francois aquifer are the City of Marquand well W3 on 

the southeast flank of the St. Francois Mountains and several 

mine seeps from the Sweetwater Mine in the southern part of 

the Viburnum Trend (fig. 3). Marquand well W3 is a flowing 

well more than 1,000 ft deep and open to both the Ozark and 

St. Francois aquifers. A May 2003 water sample collected at 

the surface by the MDNR (presumably a mixture of water 

from the Ozark and St. Francois aquifers) had large (about 

250 mg/L) concentrations of Na, Cl, and SO4. Because of the 

large Cl and SO4 concentrations, the city never put the well 

into production (Ken Duzan, Missouri Department of Natural 
Water Quality 17

Table 5. Selected water-quality data from monitoring well USGS-D1, City of Marquand well W3, and mine seeps from the Sweetwater Mine in the Viburnum Trend.[μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; ID, identifier; rep, replicate sample; N, nitrogen; P, phosphorus; μg/L, microgram per liter; <, less than; --, no data; E, estimated value, all concentrations dissolved unless noted otherwise]

Date Time

Specific

conductance

(μS/cm)

Water temperature (°C) pH (units) Dissolved oxygen (mg/L) Hardness (mg/L) Calcium (mg/L) Magnesium (mg/L) Potassium (mg/L) Sodium (mg/L) Alkalinity as CaCO3 (mg/L) Bicarbonate (mg/L) Carbonate (mg/L)

P21, USGS-D1 (lower part of the Ozark aquifer2 ; station ID 365117091215501)

8/30/2005 0130 420 15.2 7.5 0.6 240 49 29.7 .9 1.5 208 257 0

8/30/2005 (rep) 0140 420 15.2 7.5 .6 240 47.8 29.8 1.5 1.5 208 257 <18/30/2005 0440 -- -- -- -- -- -- -- -- -- -- -- --

P3, USGS-D1 (St. Francois aquifer3 ; station ID 365117091215502)

11/4/2005 1200 2,410 22.8 8.4 1.0 59 9.5 8.6 4.8 450 221 255 44/13/2006 0800 457 20 7.4 <1.0 220 41.9 27.4 1.0 12 220 268 <15/11/2006 1440 768 20 7.9 -- 150 28.2 19.4 1.9 108 204 251 <110/12/2006 1515 1,320 22.2 8.0 .4 92 17.8 11.5 3 220 212 257 <1

City of Marquand well W3 (Ozark aquifer and St. Francois aquifer; station ID 372555090101101)

12/12/20064 1730 5,950 14.4 7.9 -- 460 119 37.5 9.9 1,030 216 260 --12/12/20065 1757 2,690 14.4 7.7 -- 230 53.8 22.5 5.7 460 277 336 --

Viburnum Trend Sweetwater Mine seeps (St. Francois aquifer)6

12/11/2002 (S1) -- 6,040 18.3 7.7 -- -- 416 7.6 5.4 960 -- 72 --12/11/2002 (S2) -- 1,653 18.8 8.1 -- -- 48.0 13.0 3.3 220 -- 211 --12/11/2002 (S3) -- 463 18.0 7.5 -- -- 38.0 20.0 1.3 18 -- 274 --

Date Time Chloride (mg/L) Sulfate (mg/L) Fluoride (mg/L) Silica (mg/L)

Dissolved 

solids,

 total sum 

(mg/L)

Ammonia 

as N

(mg/L)

Nitrate plus 

nitrite as N 

(mg/L)

Nitrite as N 

(mg/L)

Ortho- phosphate as P

(mg/L)

Phosphorus 

as P

(mg/L)

Organic 

carbon, total

(mg/L)

Organic 

carbon, 

dissolved 

(mg/L)

P21, USGS-D1 (lower part of the Ozark aquifer2 ; station ID 365117091215501)

8/30/2005 0130 1.38 15.3 <0.1 10.2 234 <0.04 <0.06 <0.008 <0.02 <0.04 -- --8/30/2005 (rep) 0140 1.44 15.2 <.1 9.7 235 <.04 <.06 E.004 <.02 <.04 0.9 0.58/30/2005 0440 -- -- -- -- -- -- -- -- -- -- -- --

P3, USGS-D1 (St. Francois aquifer3 ; station ID 365117091215502)

11/4/2005 1200 469 214 7.7 6.5 1,300 <.04 <.06 <.008 <.09 <.04 1.7 --4/13/2006 0800 7.32 23.5 .3 7.4 258 <.04 <.06 .013 <.02 <.04 1 --5/11/2006 1440 82.8 53.2 2.1 7.4 430 -- -- -- -- -- -- --10/12/2006 1515 202 103 4.6 7.6 701 .03 <.06 <.002 E.004 <.04 1.2 --

City of Marquand well W3 (Ozark aquifer and St. Francois aquifer; station ID 372555090101101)

12/12/20064 1730 1,480 727 3.5 8.0 3,540 .17 <.06 <.002 E.005 <.04 -- --12/12/20065 1757 585 294 2.4 7.9 1,600 .13 <.06 E.001 E.006 <.04 -- --

Viburnum Trend Sweetwater Mine seeps (St. Francois aquifer)6

12/11/2002 (S1) -- 1,400 1,100 3.5 4.9 -- -- 1.8 -- -- -- -- --12/11/2002 (S2) -- 270 200 2.8 4.5 -- -- .3 -- -- -- -- --12/11/2002 (S3) -- 11 44 1.9 3.8 -- -- .08 -- -- -- -- --
18 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08 Table 5. Selected water-quality data from monitoring well USGS-D1, City of Marquand well W3, and mine seeps from the Sweetwater Mine in the Viburnum Trend.—Continued [μS/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius; mg/L, milligrams per liter; CaCO3, calcium carbonate; ID, identifier; rep, replicate sample; N, nitrogen; P, phosphorus; μg/L, microgram per liter; <, less than;--, no data; E, estimated value, all concentrations dissolved unless noted otherwise] Date Time Antimony (μg/L) Arsenic (μg/L) Barium (μg/L) Beryllium (μg/L) Boron (μg/L) Cadmium (μg/L) Chromium (μg/L) Cobalt (μg/L) Copper (μg/L) Iron (μg/L) Lead (μg/L) Lithium (μg/L) P21, USGS-D1 (lower part of the Ozark aquifer2 ; station ID 365117091215501) 8/30/2005 0130 2.4 3.5 14 <0.2 8 0.1 E0.03 1.3 E0.4 <6 0.12 <2 8/30/2005 (rep) 0140 2.5 .9 15 <.2 E6.4 .1 <.04 1.3 .4 1,330 <.08 <2 8/30/2005 0440 -- -- -- -- -- -- -- -- -- -- -- -- P3, USGS-D1 (St. Francois aquifer3 ; station ID 365117091215502) 11/4/2005 1200 .5 .4 11 <.2 1,980 E.02 1.2 .2 <.40 E3 E.04 261 4/13/2006 0800 <.20 .1 28 <.2 45 E.02 .4 .2 E.3 5,020 1.51 6 5/11/2006 1440 <.20 .2 30 <.2 462 <.04 .3 .2 E.3 2,450 <.08 66 10/12/2006 1515 <.06 .4 26 <.2 1,100 <.04 2 .1 <.40 782 .74 151 City of Marquand well W3 (Ozark aquifer and St. Francois aquifer; station ID 372555090101101) 12/12/20064 1730 E.2 1.3 12 <.6 1,140 .2 E.2 .4 <1.2 29 <.36 614 12/12/20065 1757 <.12 .5 13 <.6 674 .1 E.2 E.04 <.80 1,100 <.24 249 Viburnum Trend Sweetwater Mine seeps (St. Francois aquifer)6 12/11/2002 (S1) -- -- 7.2 43 -- -- .05 -- 1.43 1 150 .5 1,090 12/11/2002 (S2) -- -- 4.5 25 -- -- .02 -- .6 .5 50 2.6 191 12/11/2002 (S3) -- -- 1 9 -- -- .33 -- 4.82 11 50 27.5 11 Date Time Manganese (μg/L) Molybdenum (μg/L) Nickel (μg/L) Selenium (μg/L) Strontium (μg/L) Thallium (μg/L) Vanadium (μg/L) Zinc (μg/L) Carbon-14, percent modern Carbon-14, percent modern error Carbon 13/12 ratio (per mil) Oxygen 18/16 ratio (per mil) P21, USGS-D1 (lower part of the Ozark aquifer2 ; station ID 365117091215501) 8/30/2005 0130 10 5.4 7 6.1 33 .06 <2 17.4 -- -- -- -- 8/30/2005 (rep) 0140 38 7 6.9 <.08 39 .11 <2 115 36.78 0.25 -12.5 -6.36 8/30/2005 0440 -- -- -- -- -- -- -- -- 37.02 .24 -12.4 -- P3, USGS-D1 (St. Francois aquifer3 ; station ID 365117091215502) 11/4/2005 1200 65 6.8 .9 0.14 201 E.02 2 97.5 -- -- -- -- 4/13/2006 0800 125 5.4 3.8 <.08 56 <.04 <2 17.2 -- -- -12.26 -6.36 5/11/2006 1440 50 3.4 1.2 -- 135 <.04 <2 68 -- -- -- -6.38

10/12/2006 1515 20 1.9 .2 -- 191 <.04 <.6 48.1 19.2 .13 -8.96 -6.6

City of Marquand well W3 (Ozark aquifer and St. Francois aquifer; station ID 372555090101101)

12/12/20064 1730 90 30.4 2 -- 3,560 <.12 <2 25.4 -- -- -- --12/12/20065 1757 47 9.5 .2 -- 1,230 <.08 <2 1,330 -- -- -- --

Viburnum Trend Sweetwater Mine seeps (St. Francois aquifer) 6

12/11/2002 (S1) -- 179 72 8.2 -- 6,320 .3 -- 2 -- -- -- --

12/11/2002 (S2) -- 4.8 19 1.9 -- 988 .1 -- 2 -- -- -- --12/11/2002 (S3) -- 4.2 2.9 12.9 -- 109 .1 -- 31 -- -- -- --

1 Point sample collected from 1,500 feet deep during drilling. Borehole open from 1,440 to 1,520 feet and purged 10 hours at 10 gallons per minute before sampling. 2 Sample interval open to the lower part of the Potosi Dolomite (Ozark aquifer) and the upper part of the Debry-Doerun Dolomite (St. Francois confining unit).3 Sample interval within the Bonneterre Formation.4 Point sample collected at 950 feet deep from the St. Francois aquifer part of the well. Water flowing from well about 2 gallons per minute. 5 Sample collected from water flowing from wellhead at the land surface.6 Data from, U.S. Geological Survey Central Region Mineral Resources Center (L.R. Lee, U.S. Geological Survey, written commun., 2007).
Water Quality 19

Resources, Public-Drinking Water Program, written commun., 

2007). A December 2006 point sample collected by the USGS 

from 950 ft deep (within the St. Francois aquifer) had even 

larger concentrations of Na, Cl, and SO4 (table 5) than the 

May 2003 MDNR sample, indicating a large dissolved solids 

concentration and Na-Cl type water in the St. Francois aquifer 

beneath Marquand. Similar to samples from P3 of monitoring 

well USGS-D1, water samples from Marquand well W3 were 

a Na-Cl type water and also contained large concentrations of 

B (674 and 1,140 μg/L) and Li (249 and 614 μg/L; table 5).

Several water samples collected from seeps emerging 

from the Bonneterre Formation in the Sweetwater Mine on 

the southern end of the Viburnum Trend (fig. 1) also contained 

large concentrations of Na, Cl, SO4, and Li (B was not analyzed in these samples). Mine seeps S1 and S2 contained the 

largest concentrations of Na (960 and 220 mg/L), Cl (1,400 

20

40

60

80

80

80

80

60

60

40

40

20

20

20

20

20

40

40

60

60

80

80

80

20

20

40

60

80

MAGNESIUM

CARBONATE PLUS BICARBONATE

CALCIUM CHLORIDE PLUS NITRATE

SODIUM PLUS POTASSIUM

PERCENT OF TOTAL MILLIEQUIVALENTS PER LITER

Possible mixing trendPossible mixing trend

Background range for 

Ozark aquifer groundwater 

samples (Imes and Emmett, 

1994; Miller and Vandike, 

1997) 

04-13-06

08-30-05

05-11-06 10-12-06

11-04-05

SULFATE PLUS CHLORIDE PLUS NITRATE

PERCENT OF TOTAL MILLIEQUIVALENTS PER LITER

SULFATE

CALCIUM PLUS MAGNESIUM

PERCENT OF TOTAL MILLIEQUIVALENTS PER LITER

EXPLANATION

P2, USGS-D1 and collection date—Station identifier 

 365117091215501; lower part of Ozark aquifer (lower part 

 of the Potosi Dolomite) and upper part of the St. Francois 

 confining unit (upper part of the Derby-Doerun Dolomite)

P3, USGS-D1 and collection date—Station identifier 

 365117091215502; St. Francois aquifer, Bonneterre Formation

City of Marquand well W3—Station identifier 372555090101101;

 Ozark aquifer and St. Francois aquifer

Sweetwater Mine Seep and identifier

 (St. Francois aquifer, Bonneterre Formation)

 S1

 

 S2

 

 S3 

8-30-05

04-13-06

Figure 5. Trilinear diagram of major constituents in water samples from monitoring well USGS-D1, City of Marquand 

well W3, and mine seeps from the Sweetwater Mine in the Viburnum Trend.
20 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

and 270 mg/L), Li (1,090 and 191 μg/L) and other constituents (table 5) and are near a fault within the mine known as 

the Sweetwater Fault (Walker, 1993). The water chemistry 

of these seeps may be indicative of relict formation water 

or mineralizing brines within the St. Francois aquifer that 

migrated along this fault (L.R. Lee, written commun., 2007). 

The unusual water quality in the Marquand W3 samples and 

P3 sample also may be of similar origin.

Isotopes of carbon in groundwater can provide insight in 

understanding the evolution of groundwater chemistry, flow 

paths, and interpretation of groundwater age (Clark and Fritz, 

1997). Carbon generally enters the groundwater system as 

carbon dioxide (CO2) dissolved in precipitation or as dissolved CO2 gas produced from the decomposition of organic 

matter in the soil zone (Fritz and Fontes,1980). This carbon 

subsequently is transported through the unsaturated zone to 

the water table where, in the case of the Ozark aquifer, it is 

diluted (enriched) by exchange and dissolution of the carbonate minerals in the unsaturated zone and the aquifer matrix. In 

temperate climate regions, such as Missouri, the δ 13C value of 

the soil zone/unsaturated zone CO2 gas is about -25 ‰ (Fritz 

and Fontes, 1980). Carbonate rocks (dolostone and limestone) 

in the Ozark aquifer have δ 13C values of about 0 ‰ (Clark 

and Fritz, 1997).

Water samples from springs and wells in the Ozark aquifer of southern Missouri generally plot along a line of carbonic 

acid weathering (dissolution) of dolomite (Imes and others, 

1996; 2007) according to the equation:

Ca, Mg(CO3)2 + 2H2O + 2CO2 = Ca2+ + Mg2+ + 4HCO3

- (1)

In the above equation, carbon is equally derived from 

CO2 gas and dissolution of carbonate minerals, which yields 

an estimated δ 13C of the bicarbonate in water of about -12.5 

‰. The δ 13C values of the two P2 samples (-12.5 and -12.4; 

table 5) are consistent with the dissolution of carbonate minerals by carbonic acid. The October 2006 P3 sample had a δ 13C 

value of -8.96 ‰, which is heavier than the value predicted 

by equation 1. The heavier δ 13C value in the P3 sample may 

indicate that water in the Bonneterre Formation is much older, 

allowing for enrichment in 13C by isotopic exchange between 

aqueous dissolved inorganic carbon (DIC) and carbonate minerals in the aquifer matrix. The δ 13C value in the April 2006 

P3 sample (-12.26 ‰) was nearly identical to the P2 δ 13C values and is consistent with the mixing model derived from the 

major ion data indicating that the April 2006 P3 sample actually is mostly P2 water. Overall the δ 13C values in samples 

from P2 (-12.5 and -12.4 ‰) were depleted as compared to δ 

13C values (-6.78 to -9.41) reported for samples from Ozark 

aquifer wells in southwestern Missouri and southeastern Missouri (Pope and others, 2009).

The DIC 14C activity in the October 2006 P3 sample 

(19.2 pmC) was smaller than the DIC 14C in the P2 sample 

(about 37 pmC; table 5), indicating that the DIC in the St. 

Francois aquifer (P3 sample) probably is older than the DIC 

in the overlying Ozark aquifer (P2 sample). Using the simple 

“leaky casing” mixing model derived from the major constituent data, the estimated DIC 14C activity for the St. Francois 

aquifer at P3 is about 2 pmC, indicating that the water potentially is thousands to tens of thousands of years old. However, 

because 14C is likely lost by isotopic exchange or dissolution 

of “dead” carbon (millions of years old) in aquifer carbonate 

minerals (Maloszewski and Zuber, 1991), this estimated value 

and the laboratory reported DIC 14C values in table 5 may be 

too small and not provide reliable estimates of actual ages 

of water in the samples. Perhaps coincidently, the estimated 

DIC 14C activity value in P3 of about 2 pmC, is similar to 

values reported by for the confined Ozark aquifer in southwestern Missouri and southeastern Kansas (Pope and others, 

2009). The pmC values in Ozark aquifer water samples from 

southwestern Missouri and southeastern Kansas samples were 

determined by Pope and others (2009) to be unreliable because 

of exchange with dead carbon in the aquifer matrix.

Summary and Conclusions

A deep (more than 2,000 feet deep) monitoring well 

(USGS-D1) was installed within an area being explored for 

lead and zinc deposits within the Mark Twain National Forest 

in southern Missouri. The area is a mature karst terrain where 

rocks of the Ozark aquifer, a primary source of water for 

private and public-supplies and major springs in the nearby 

Eleven Point National Wild and Scenic River and the Ozark 

National Scenic Riverways, are exposed at the surface. The 

potential lead deposits lie about 2,000 feet below the surface 

within a deeper aquifer, called the St. Francois aquifer. The 

two aquifers are separated by the St. Francois confining unit. 

The deep monitoring well was installed as part of a series of 

investigations to determine the degree of connection between 

the two aquifers, specifically to examine potentiometric head 

relations and water-quality differences between the St. Francois aquifer, where a potential lead-zinc ore body exists, and 

the overlying Ozark aquifer.

Results of borehole flowmeter measurements in the open 

borehole and water-level measurements from the completed 

monitoring well USGS-D1 indicate that a seasonal upward 

gradient exists between the St. Francois aquifer and the overlying Ozark aquifer from about September through February. The upward potentiometric heads across the St. Francois 

confining unit that separates the two aquifers averaged 13.40 

feet with a maximum value of 22.84 feet. Large reversals in 

this upward gradient occurred during late winter through summer (about February through August) when water levels in the 

Ozark aquifer were as much as 138.47 feet higher (average of 

53.84 feet) than water levels in the St. Francois aquifer. Most 

the fluctuation of potentiometric gradient is driven by precipitation and rapid recharge causing large and rapid increases in 

water levels in the Ozark aquifer.

Analysis of water-quality samples collected from 

monitoring well USGS-D1 indicated that the water within the 
References Cited 21

upper part of the St. Francois aquifer in the exploration area 

is a sodium-chloride type water containing dissolved solids 

concentrations as large as 1,300 milligrams per liter and large 

concentrations of sodium and chloride (equal to or greater than 

450 milligrams per liter), sulfate (more than 200 milligrams 

per liter), and the trace elements boron and lithium (more than 

1,900 and 200 micrograms per liter). In contrast, water in the 

overlying Ozark aquifer is a calcium-magnesium-bicarbonate 

type water that contains dissolved solids concentrations less 

than 250 milligrams per liter), less than 5 milligrams per liter 

sodium and chloride, and less than 10 micrograms per liter of 

boron and lithium. Outside of the St. Francois Mountains area, 

few wells in southern Missouri penetrate the St. Francois aquifer and relatively little known about the quality of water in the 

aquifer. The small quantity of previously available data indicate that water in the St. Francois aquifer has low dissolved 

solids concentration and is calcium-magnesium-bicarbonate 

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well W3, and several seeps within the Sweetwater Mine in the 

Viburnum Trend indicated the presence of local areas of the 

St. Francois aquifer that have a sodium-chloride type water 

with concentrations of sodium, chloride, and sulfate exceeding 

several hundred milligrams per liter and concentrations of the 

trace elements boron and lithium exceeding several hundred 

micrograms per liter.

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24 Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08

Publishing support provided by: 

Rolla Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Missouri Water Science Center

1400 Independence Road

Rolla, MO 65401

(573) 308–3667

Or visit the Missouri Water Science Center Web site at: 

http://mo.water.usgs.gov
References Cited 25
Schumacher and Kleeschulte—Borehole Geophysical, Water-Level, and Water-Quality Investigation, Missouri, 2005–08 — Scientific Investigations Report 2010–5041