Prepared in cooperation with Maine Department of Transportation

Relations Among Water Levels, Specific Conductance, 

and Depths of Bedrock Fractures in Four Road-SaltContaminated Wells in Maine, 2007–9

Scientific Investigations Report 2012–5205

U.S. Department of the Interior

U.S. Geological Survey
Cover. Photograph shows South Sullivan project well.
Relations Among Water Levels, Specific 

Conductance, and Depths of Bedrock 

Fractures in Four Road-Salt-Contaminated 

Wells in Maine, 2007–9

By Charles W. Schalk and Nicholas W. Stasulis

Prepared in cooperation with Maine Department of Transportation

Scientific Investigations Report 2012–5205

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Schalk, C.W., and Stasulis, N.W., 2012, Relations among water levels, specific conductance, and depths of bedrock 

fractures in four road-salt-contaminated wells in Maine, 2007–9: U.S. Geological Survey Scientific Investigations 

Report 2012–5205, 47 p., at http://pubs.usgs.gov/sir/2012/5205.
iii

Acknowledgments

The authors thank the private land owners who gave us access to their wells and welcomed the 

installation of instrument shelters in their front yards. Thanks to the Well Claims Unit at Maine 

Department of Transportation for field and data support during this project. Thanks to Carole 

Johnson of the USGS for her assistance in collecting and analyzing geophysical data.
THIS PAGE INTENTIONALLY LEFT BLANK
v

Contents

Acknowledgments........................................................................................................................................iii

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

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

Purpose and Scope ..............................................................................................................................2

Background............................................................................................................................................2

Previous Investigations........................................................................................................................3

Description of Study Areas and Study Wells ...................................................................................4

Climate....................................................................................................................................................6

Methods of Data Collection .........................................................................................................................8

Continuous Water Levels and Water-Quality Data .........................................................................8

Gray..... .........................................................................................................................................11

West Gardiner ............................................................................................................................11

North Sullivan.............................................................................................................................11

South Sullivan.............................................................................................................................11

Water-Quality Samples and Profiling ..............................................................................................11

Geophysical Data................................................................................................................................12

Quality Assurance...............................................................................................................................12

Water Levels and Specific Conductance in Wells.................................................................................13

Relation Between Specific Conductance and Chloride Concentrations ..................................13

Site-by-Site Characteristics..............................................................................................................13

Gray........ ......................................................................................................................................13

West Gardiner ............................................................................................................................15

North Sullivan.............................................................................................................................17

South Sullivan.............................................................................................................................18

Effects of Stresses on Chloride Concentrations............................................................................19

Precipitation................................................................................................................................19

Thawing.......................................................................................................................................19

Pumping.......................................................................................................................................19

Effects of Fractures on Water Quality .............................................................................................20

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

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

Appendix 1. Geophysical Data ...............................................................................................................25

Appendix 2. Daily Water Levels, Specific Conductance, and Precipitation, All Wells.................43

Figures

1. Graph showing salt use for deicing roads in the United States since 1970. .....................2

2. Graph showing salt and sand use for deicing roads by Maine Department of

Transportation, 1990–2008. .........................................................................................................3

3. Map showing locations of towns and wells used in the road-salt study, Maine, 2007–9

......................................................................................................................................................... 5
4. Map showing location of U.S. Geological Survey well 435103070191701 in Gray, Maine

......................................................................................................................................................... 6

5. Map showing location of U.S. Geological Survey well 441226069502201 in West

Gardiner, Maine ............................................................................................................................7

6. Map showing locations of U.S. Geological Survey wells 443145068131801 and

443113068115101 in Sullivan, Maine ..........................................................................................8

7. Graph showing December-April snowfall totals in Gardiner, Maine, 1997–2009...............9

8. Graph showing December-April departures from average temperatures in

Gardiner, Maine, 1997–2009 ........................................................................................................9

9. Photographs showing A, instrumentation shelter and B, arrangement of

data-collection instruments at U.S. Geological Survey well 441226069502201 in

West Gardiner, Maine................................................................................................................10

10. Graph showing relation between concentrations of chloride and specific

conductance in three road-salt study wells, Maine.............................................................13

11. Graph showing 10-day unit-value water levels for May 12–22, 2008, in four road-salt

study wells, Maine......................................................................................................................14

12. Graph showing vertical water-quality profile in U.S. Geological Survey well

435103070191701 in Gray, Maine, October 22, 2008...............................................................14

13. Graphs showing A, a hydrograph and B, correlation of daily water levels and

specific conductance in U.S. Geological Survey well 435103070191701 in Gray,

Maine, July 10–October 19, 2008..............................................................................................15

14. Graph showing vertical water-quality profile in U.S. Geological Survey well

441226069502201 in West Gardiner, Maine, January 16, 2008 .............................................17

15. Graph showing water levels and specific conductance in U.S. Geological Survey

well 443145068131801 in North Sullivan, Maine, November 2007–July 2008 ....................18

Table

1. Characteristics of wells used during the road-salt study in Maine, 2007–9.......................4

vi
vii

Conversion Factors and Datums

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

gallon (gal) 3,785 milliliter (mL) 

gallon (gal) 0.003785 cubic meter (m3

) 

gallon (gal) 3.785 cubic decimeter (dm3

) 

Flow rate

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

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

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 North American Vertical Datum of 1988 

(NAVD88).

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).
viii

THIS PAGE INTENTIONALLY LEFT BLANK
Relations Among Water Levels, Specific Conductance, 

and Depths of Bedrock Fractures in Four Road-SaltContaminated Wells in Maine, 2007–9

By Charles W. Schalk and Nicholas W. Stasulis

Abstract

Data on groundwater-level, specific conductance (a surrogate for chloride), and temperature were collected continuously from 2007 through 2009 at four bedrock wells known to 

be affected by road salts in an effort to determine the effects of 

road salting and fractures in bedrock that intersect the well at a 

depth below the casing on the presence of chloride in groundwater. Dissolved-oxygen data collected periodically also were 

used to make inferences about the interaction of fractures 

and groundwater flow. Borehole geophysical tools were used 

to determine the depths of fractures in each well that were 

actively contributing flow to the well, under both static and 

pumped conditions; sample- and measurement-depths were 

selected to correspond to the depths of these active fractures. 

Samples of water from the wells, collected at depths corresponding to active bedrock fractures, were analyzed for 

chloride concentration and specific conductance; from these 

analyses, a linear relation between chloride concentration and 

specific conductance was established, and continuous and periodic measurements of specific conductance were assumed to 

represent chloride concentration of the well water at the depth 

of measurement.

To varying degrees, specific conductance increased in 

at least two of the wells during winter and spring thaws; the 

shallowest well, which also was closest to the road receiving 

salt treatment during the winter, exhibited the largest changes 

in specific conductance during thaws. Recharge events during 

summer months, long after application of road salt had ceased 

for the year, also produced increases in specific conductance in 

some of the wells, indicating that chloride which had accumulated or sequestered in the overburden was transported to 

the wells throughout the year. Geophysical data and periodic 

profiles of water quality along the length of each well’s borehole indicated that the greatest changes in water quality were 

associated with active fractures; in one case, high concentration of dissolved oxygen at the bottom of the well indicated 

the presence of a highly transmissive fracture that was in good 

connection with a surficial feature (stream or atmosphere). 

Data indicated that fractures have a substantial influence on 

the transport of chlorides to the subsurface; that elevated 

specific conductance occurred throughout the year, not just 

when road salts were applied; and that chloride contamination, 

as indicated by elevated specific conductance, may persist 

for years.

Introduction

In 1969 and also in 1987, the State of Maine legislature 

signed into law a process by which any landowner believing 

his or her water supply to be adversely affected by public construction, reconstruction, or maintenance of roads can apply to 

the political subdivision for redress (23 M.R.S.A. §652 (Maine 

Legislature, 2012, p. 60–61) and §3659 (Maine Legislature, 

2012, p. 227–229)). Adverse effects can include those from 

road salting (University of Maine, School of Law, 2003; 

Maine Department of Transportation, 2004; State of Maine 

Judicial Branch, 2008), and redress can include replacing 

plumbing and (or) heating systems, replacing the water supply, 

repairing damage to the water supply, paying a designated sum 

of money, and (or) purchasing the real estate served by the 

water supply.

Such remedial efforts have been expensive. In complying with the law, the Well Claims Unit at Maine Department 

of Transportation (MaineDOT) has handled almost 450 well 

claims since 1990, of which 130 have been related to roadsalt contamination.1

 Claims for road-salt contamination have 

1

The secondary maximum contamination level for chloride is 250 milligrams per liter (U.S. Environmental Protection agency, 2012). Background 

concentrations of chloride in groundwater in the crystalline bedrock areas of 

New Hampshire and Maine are in the range of 20 to 30 mg/L (New Hampshire Department of Environmental Services, 2010; Maine Interagency 

Report, 2001).
2 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

grown from about 1 in 1990 to as many as 23 in 2006 (though 

not all of these claims were valid). Costs to the State to remediate a valid claim usually range from $10,000 to $35,000, and 

this amount can be much greater if construction (such as laying municipal water-supply lines) or the purchase of real estate 

is needed (Joshua Katz, Maine Department of Transportation, 

written commun., 2009).

The process of evaluating well claims includes an assessment of groundwater quality, particularly the concentrations of 

sodium and chloride. MaineDOT has kept long-term waterquality records from several wells, including some that were 

part of the well-claim process and others that are on publicly 

owned land and were suitable for monitoring. As of 2007, 

data collected by MaineDOT indicated that concentrations of 

chloride in groundwater spiked annually in the autumn, before 

road salts were applied for the winter and as groundwater levels were recovering from summer declines. This observation 

led MaineDOT to question whether chloride concentrations 

were increasing with time in groundwater in fractured bedrock 

in Maine as an outcome of general road salting practice, and 

the extent to which fractures were contributing to the apparent 

increases in chloride concentrations in the autumn.

The data collected by MaineDOT over the years had two 

shortcomings: first, the samples were discrete in time, being 

collected quarterly or less frequently; and second, each sample 

was mixed over the length of the borehole from which it was 

collected. To address these shortcomings, MaineDOT and 

the U.S. Geological Survey (USGS) began an investigation 

in 2007 into the nature and timing of the processes whereby 

road-salt constituents, particularly chloride, move into groundwater in fractured bedrock. By use of continuous monitoring 

and focusing on measurements as a function of depth, this 

investigation sought to determine whether the changes in chloride concentrations are related to the presence of fractures and 

hydrologic stresses, such as recharge and pumping.

Purpose and Scope

The purpose of this report is to enable concerned parties 

to understand the nature of the road-salt problem in parts of 

Maine. The report describes the occurrence of road-salt constituents in groundwater in selected bedrock wells in Maine 

and presents an evaluation of those occurrences with respect 

to fractures in the bedrock and timing of recharge events. This 

report does not address the theoretical aspects of flow in fractures but rather uses the body of literature and data observed 

from 2007 through 2009 to make general inferences about the 

roles of fractures in the transport of road-salt constituents.

Although this report presents parts of the data collected 

during the project, primarily those that are most important 

to the analyses described herein, complete data sets (discrete 

and continuous water levels, water temperatures, and specific 

conductance) are available online through the USGS Web site 

(http://waterdata.usgs.gov/me/nwis/gw or http://wdr.water.

usgs.gov/) for water years 2008 (October 1, 2007 through 

September 30, 2008) and 2009 (October 1, 2008 through 

September 30, 2009) or by request from the Maine Water 

Science Center.

During the 18 months to 2 years in which data were collected, the hydrologic events that occurred may not have been 

typical. Because of the highly variable nature of hydrologic 

events, local and regional fracturing in bedrock, and differences in bedrock composition throughout Maine, the results 

described in this report may not be transferable to locations 

other than those studied.

Background

Salt, most commonly in the form of sodium chloride 

(NaCl), began to be used in the United States as a deicing 

agent about 1940. The use of salt for deicing increased through 

2008, when it reached a peak of about 25 million tons (fig. 1), 

or about two-thirds of all salt used for all purposes in the 

0

5

10

15

20

25

30

1970 1980 1990 2000 2010

Salt for deicing use, in million tons

Year

Figure 1. Salt use for deicing roads in the 

United States since 1970. Data are from 

Kostick (1994, 1996–2012) and U.S. Geological 

Survey (2010).
Introduction 3

United States. Although annual use for deicing is variable, the 

amounts used in 2005 and 2008 are more than twice that used 

in 1990. The data in figure 1 are not adjusted for increases in 

miles of road or severity of winters.

The State of Maine’s use of salt for deicing (fig. 2) also 

has doubled since 1990, increasing from about 70,000 metric 

tons per year (t/yr) to about 140,000 t/yr. The data in figure 2 

also do not take into account the severity of winters. Corresponding to the increase in salt use, however, has been a 

98 percent reduction in the volume of sand applied to State 

highways since 1990. These trends reflect MaineDOT’s policy 

toward anti-icing (proactive maintenance which does not use 

sand) rather than deicing, which has resulted in not only better service for the public (clear roads in short times) but also 

significant cost savings (Joshua Katz, Maine Department of 

Transportation, written commun., 2009). MaineDOT maintains about 18 percent of Maine’s roads, so total salt use in 

the State is larger than the amounts shown in figure 2, perhaps 

about 490,000 t/yr (Rubin and others, 2010).

0

100,000

200,000

300,000

400,000

500,000

600,000

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

1990 1995 2000 2005 2010

Sand used, in cubic yards

Road salt used, in tons

Ending Year

Figure 2. Salt and sand use for deicing roads by Maine 

Department of Transportation, 1990–2008. Data are from B. Burne, 

Maine Department of Transportation, written commun., 2009.

In the 1980s, MaineDOT covered or otherwise engineered their salt and sand piles to minimize the extent to which 

improper storage contributes to local groundwater quality. 

Olson and others (1985) indicated that improper storage had 

contributed to chloride concentrations as much as 2,900 milligrams per liter (mg/L) in one bedrock well. After engineered 

solutions were put in place, concentrations were lowered to 5 

to 20 mg/L, much nearer to typical background levels.

Previous Investigations

Concerns about road salt as a potential contaminant in 

drinking water date to the 1950s, when it was discovered 

that salt was contaminating drinking-water supplies because 

of improper storage and, in some cases, highway runoff 

(Transportation Research Board, 1991). Research has shown 

that road-salt constituents, including anticaking agents such as 

iron cyanide (Paschka and others, 1999), continue to be present in streams and wetlands long after the winter season has 

passed (Demers and Sage, 1990), to the detriment of natural 

ecosystems and safe consumption of water (Andrews, 1996; 

Williams and others, 1999; Forman and Deblinger, 2000; 

Richburg and others, 2001; Blasius and Merritt, 2002; Godwin 

and others, 2003; Corsi and others, 2010). In some locations 

including the northeastern United States, those constituents 

are increasing in concentration in surface waters (Rosenberry 

and others, 1999; Nimiroski and Waldron, 2002; Jackson 

and Jobbagy, 2005; Kaushal and others, 2005). In their 

review of the effects of chemical deicers on the environment, 

Ramakrishna and Viraraghavan (2005) summarized the effects 

of sodium chloride on surface water: increasing density-driven 

gradients, increasing chloride concentrations, increasing saltinduced stratification, and stimulating algal growth.

The connection between application of deicing chemicals and the quality of groundwater is not difficult to deduce. 

Although streams can carry high loads of road salts away from 

an area, especially during runoff events (Ostendorf and others, 

2009; Corsi and others, 2010; Harte and Trowbridge, 2010), 

some of the applied salts find their way into underlying aquifers during the recharge process (Blomkvist and Johanssen, 

1999). Studies have shown that although the presence of road 

salts in groundwater may be masked by time, dilution, and 

spatial distribution, concentrations in groundwater tend to be 

relatively stable, enduring perhaps for decades after salting 

ceases (Williams and others, 1999; Foos, 2003; Bester and 

others, 2006; Ostendorf and others, 2006; Harte and Trowbridge, 2010). Some research has shown that splashing, plowing, and air currents transport 20 to 63 percent of road salts by 

weight to land surfaces as much as 120 feet (ft) from the road 

(Blomkvist and Johanssen, 1999), from which the salts may 

be carried into surface-water drainage or infiltrate the subsurface. The presence of road salts in groundwater has been 

studied most frequently in unconsolidated deposits near roads 

(Granato and others, 1995; Aichele, 2004; Kunze and Sroka, 

2004; Andrews and others, 2005). Gradient-driven recharge 

from the surface and horizontal groundwater flow tends to 

dilute the salts, thereby seemingly alleviating any acute problems (Methuel, 2007). However, the effects also are noticeable 

in bedrock environments, where fractures and bedding planes 

greatly influence flow volumes and directions (Foos, 2003). 

Although chloride may be present naturally in bedrock minerals and aquifers (Aichele, 2004), its presence has been linked 

to road salting in urban and rural areas; chloride tends to be 

mobile in the environment, whereas sodium tends to adhere to 

soil particles. Groundwater contamination by road salt appears 
4 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

to be present primarily near road surfaces and in direct proportion to the application rate (Foos, 2003), even if the flow paths 

are unknown.

Because groundwater flow rates are much lower than 

those of streams, the problem of salt-contaminated groundwater often is chronic rather than acute. Salts can be present 

in the aquifers for years or decades, often at concentrations 

greater than are found in samples from monitoring wells. If the 

practice of deicing by use of road salts continues, concentrations in the aquifers can increase (Bester and others, 2006; 

Kelly, 2008). Generally, chloride-contaminated groundwater 

becomes diluted with distance from its source as it mixes with 

fresh recharge over time; however, dilution may not be an 

effective process in bedrock wells, depending on the groundwater flow path and the open interval of the well. In bedrock 

aquifers, where hydraulic conductivities usually are lower 

than those in unconsolidated materials, the residence time of 

contaminants may be decades or longer. Although, because 

of low hydraulic conductivities, it may take a long time for 

salt concentrations in groundwater to reach a level unfit for 

consumption, it also takes a long time for the contamination 

to be remediated (Rubin and others, 2010). Recognizing this 

problem, Bester and others (2006) recommend that “every 

effort should be made to reduce or eliminate [road] salting 

where possible,” whereas Rubin and others (2010) state that 

“new policies are needed to encourage the use of chemicals 

and technologies that have fewer environmental effects than 

those of sand and salt.”

Description of Study Areas and Study Wells

Most of Maine is underlain by crystalline bedrock of 

variable composition capped with shallow glacial materials 

(till, moraines, outwash) (Osberg and others, 1985; Thompson and Borns, 1985). Granite is the primary rock in about 

one-fourth of the State, and metamorphosed rock in the other 

three-fourths of the State. In general, the bedrock in Maine 

would be incapable of yielding sufficient water for domestic 

supply except for the presence of transmissive fractures in 

the upper 500 ft. The presence of fractures in the bedrock is 

ubiquitous throughout the State, and any bedrock well yielding 2 or more gallons per minute (gal/min) almost certainly is 

intersected by one or more fractures (Caswell, 1979). Zones of 

highest-yielding bedrock wells in the State coincide with locations of faults and other geologic structures.

Four wells, each of which had to meet the following 

criteria, were chosen for the study (table 1). These criteria 

included:

• open-hole completion in bedrock;

• known to be affected by road salt;

• accessible by permission of the owner;

• along a State-maintained road.

Preliminary investigations by MaineDOT in response to 

landowner claims were used to determine the first two criteria. 

At the time a well claim is filed, MaineDOT samples the 

well for basic chemistry and salt-related constituents, including sodium, chloride, and bromide (Snow and others, 1990). 

Waters having a bromide signature are considered indicative 

of trapped seawater (natural brine contribution), whereas those 

lacking bromide, but still containing a salt signature, are considered indicative of anthropogenic sources that can include 

road salting, septic systems, or water softeners. Depth to 

bedrock, hydraulic gradient, and concentrations of nitrates also 

are considered when MaineDOT assesses the potential sources 

of contamination to wells.

The four wells chosen for this study were in the towns 

of Gray, West Gardiner, and Sullivan, Maine (fig. 3). Three 

of the four wells had been or were being used for domestic 

supply; the fourth was drilled for use as a domestic supply but 

had not been activated by the time the project ended. Drillers’ logs were not available for any of the study wells, but 

geophysical logs were obtained for each well (appendix 1). 

Although construction data were available only for the south 

Sullivan well, geophysical data indicated that the casings of all 

wells extended below the bottom of the overburden. All wells 

were 6-inches in diameter, cased in steel, and open holed. 

Table 1. Characteristics of wells used during the road-salt study in Maine, 2007–9.

[All coordinates are given in decimal degrees, North American Datum of 1983; --, not applicable]

Well identifier Latitude, 

North

Longitude, 

West Town

Depth, 

in feet 

below land 

surface

Casing 

height, 

in feet above 

land surface

Casing 

depth, 

in feet 

below land 

surface

Distance 

to nearest 

State road, 

in feet

Distance 

to Maine 

Turnpike, 

in feet

435103070191701 43.8508 -70.3214 Gray 327 1.0 75 40 380

441226069502201 44.2072 -69.8395 West Gardiner 347 1.5 25 160 1,200

443145068131801 44.5292 -68.2217 Sullivan 97.2 .5 15 25 --

443113068115101 44.5200 -68.1981 Sullivan 245 2.0 40 150 --
Introduction 5

KENNEBEC

HANCOCK

443145068131801

443113068115101

441226069502201

435103070191701

CUMBERLAND

EXPLANATION

435103070191701

Well and identifier

Town

HANCOCK County

Gray

MAINE

Study

area

WestGardiner

Gray

Sullivan

GULF OF MAINE

Base from Maine Office of GIS,

Universal Transverse Mercator projection,

Zone 19N, 1:24,000 scale.

0 105 20 MILES

0 105 20 KILOMETERS

43°30'

44°

44°30'

70° 69°

Figure 3. Locations of towns and wells used in the road-salt study, Maine, 2007–9.

Except for the south Sullivan well, which was grouted during 

construction, grouting (providing a surface seal to prevent 

surface-water runoff into the borehole) of the study wells 

was unknown.

The study area in Gray is underlain with carboniferous 

muscovite-biotite granite capped with glacial till, which generally is massive but can contain beds and lenses of stratified 

sediments (Osberg and others, 1985; Thompson and Borns, 

1985). Geophysical logs show that the overburden is less 

than 75 ft thick (appendix 1). Groundwater-flow direction 

is assumed to be west to east, following the contours of the 

land surface (fig. 4). USGS well 435103070191701 is 380 ft 

downgradient from Interstate 95 and 40 ft from State Routes 

26/100 to the west. The 327-ft-deep well formerly was used 

for domestic supply, but because this and some other domestic wells along State Routes 26/100 south of Whitney Road 

were contaminated with road salts, MaineDOT and the Maine 

Turnpike Authority (MTA) developed infrastructure to bring 

municipally supplied water to landowners.

The study area in West Gardiner is underlain by the 

Silurian-age Waterville Formation, which consists of thinly 

bedded, gray to greenish-gray slate or pelitic schist with some 

wacke and calc-silicate rocks (Osberg, 1968; Osberg and others, 1985; U.S. Geological Survey, 2009b). Surficial sediments 

are fine-grained facies of glaciomarine origin, commonly 

clayey silts (Thompson and Borns, 1985). Groundwater-flow 

direction is assumed to be southeast to northwest, following contours of the land surface toward Cold Stream (fig. 5). 
6 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

400

380

360

320

300

420

440

460

480

500

280 300

380

300

Base from Maine Office of GIS,

Universal Transverse Mercator projection,

Zone 19 N, 1:24,000 scale. 0 10050

0 200 400 800 FEET

200 METERS

CONTOUR INTERVAL 10 FEET

NORTH AMERICAN VERTICAL DATUM OF 1988

Hunt Hill

Wetland area

340

MAINE TURNPIKE

300

WHITNEY ROAD

Probable direction

of groundwater flow

INSET AREA

EXPLANATION

Study well and identifier

435103070191701

Land-surface contours

43°51'

43°51'10"

70°19'40" 70°19'20"

95

26

100

435103070191701

Figure 4. Location of U.S. Geological Survey well 435103070191701 in Gray, Maine.

USGS well 441226069502201 is within 1,200 ft of a tollbooth 

station on Interstate 95 to the southeast and 160 ft of State 

Routes 9/126 to the north. The MTA has a maintenance yard 

at the intersection of Interstate 95 and State Routes 9/126 less 

than 0.5 mile (mi) east of the well. MaineDOT has a maintenance yard about 700 ft southwest of the well; the maintenance yard included an open salt pile from 1968 through 

1988, when it was covered (E. Kluck and P. Coughlan, Maine 

Department of Transportation, written commun., 2009). The 

347-ft-deep well formerly was used for domestic supply, 

but because this and some other wells nearby were contaminated with chloride, MaineDOT drilled a new supply well for 

the homeowners.

The study area in Sullivan is underlain with the quartzgranofels member of the Ellsworth Formation of Cambrian 

age (Osberg and others, 1985; Stewart, 1998). Surficial 

sediments are fine-grained facies of glaciomarine origin, 

commonly clayey silts (Thompson and Borns, 1985). Geophysical logs showed the overburden is less than 40 ft thick 

(appendix 1). Groundwater-flow directions near the wells 

are uncertain, but probably follow contours of the land 

surface toward the bay (fig. 6). The 97-ft-deep North Sullivan well (USGS 443145068131801), which was still in use 

by the homeowner during the project, is within 25 ft of and 

at about the same elevation as U.S. Route 1 (maintained by 

MaineDOT) and within 530 ft of Taunton Bay. The South 

Sullivan well (USGS 443113068115101) is within 150 ft of 

and slightly uphill from U.S. Route 1 and within 370 ft of 

Taunton Bay. The 245-ft-deep South Sullivan well was drilled 

by MaineDOT to serve as a replacement water supply for a 

homeowner but was not activated for water supply until after 

the end of the project.

Climate

Average annual snowfall in Maine ranged from about 

70 inches (in.) along the southern coast to 111 in. in the 

north during 1940–2002 (National Oceanic and Atmospheric 
Introduction 7

INSET

AREA

EXPLANATION

Maintenance lot

Other well

Study well and identifier

Land-surface contours

69°50'30" 69°50'

44°12'15"

44°12'30"

44°12'45"

0

0 255 510 1,020 FEET

50 100 200 METERS

Base map from Maine Office of GIS.

Universal Transverse Mercator projection,

Zone 19 N, 1:24,000 scale.

170

180

190

150

200

210

220

170

220

200

210

170

220

180

190

170

220

MAINE TURNPIKE

CONTOUR INTERVAL 10 FEET

NORTH AMERICAN VERTICAL DATUM OF 1988

LIBERTY LANE

Cold Stream

Maine

Department Of

Transportation

lot

Maine

Turnpike

Authority

lot

160

441226069502201

441226069502201

Probable direction

of groundwater flow

95

9 126

Figure 5. Location of U.S. Geological Survey well 441226069502201 in West Gardiner, Maine.
8 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Schalk_fig 06

Base map from Maine Office of GIS.

Universal Transverse Mercator projection,

Zone 19 N, 1:24,000 scale.

EXPLANATION

Study well and identifier

443145068131801

Land-surface contours

20

40

60

80

100

140

160

120

160

120

140

60

68°13' 68°12'

44°31'45"

44°31'30"

44°31'15"

SULLIVAN

TAUNTON BAY

Clapham Brook

Mill Brook

443113068115101

443145068131801

TAUNTON BAY

0 350 700 1,400 FEET

0 150 300 METERS 75

CONTOUR INTERVAL 10 FEET

NORTH AMERICAN VERTICAL DATUM OF 1988

1

200

120

160

100

INSET

AREA

Figure 6. Locations of U.S. Geological Survey wells 443145068131801 and 443113068115101 in Sullivan, Maine.

Administration, 2002) and 1895–1935 (Fobes, 1942). The 

snowiest years since 1997 at the National Oceanic and 

Atmospheric Administration (NOAA) observation station in 

Gardiner, Maine, were 2007 and 2009 (fig. 7). Average annual 

precipitation is about 45.8 in. in midcoastal Maine. Summer 

2009 (June through August) was the wettest (22.31 in.) 

on record in Portland, Maine. Precipitation totals for 2005 

(66.45 in.), 2006 (60.86 in.), 2008 (61.24 in.), and 2009 

(58.61 in.) were among the eight highest ever recorded in Portland (National Weather Service, 2011).

Departures from normal monthly winter (December–

April) temperatures during 1997–2009 at the NOAA observation station in Gardiner, Maine, are shown in figure 8. In 

general, the winter temperatures during 1997–2002, 2006, and 

2008 were higher than normal, whereas the winter temperatures during 2003–5, 2007, and 2009 were lower than normal. 

The normal daily range in January temperatures in Gardiner 

is 4 to 28 degrees Fahrenheit (°F), whereas the normal daily 

range in April temperatures is 30 to 52 °F.

Methods of Data Collection

Standard methods were used to collect the water-level 

data (Cunningham and Schalk, 2011). All wells were instrumented with continuous water-level, temperature, and specific conductance monitors for periods of at least 15 months, 

including two spring snowmelt seasons. Data collected 

periodically included water-quality samples, water-quality 

profiles, and geophysical logs.

Continuous Water Levels and Water-Quality 

Data

The four wells were equipped with instruments to record 

and transmit continuous water levels, specific conductance, 

and water temperature. For the duration of the project, instruments for each well were housed in ventilated, waterproof, 

and locked aluminum shelters (fig. 9A). Instruments included 

a Design Analysis (DA) H522 data-collection platform (DCP) 
Methods of Data Collection 9

Schalk_fig 07

0

20

40

60

80

100

120

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Snowfall, in inches

Year

December−April snowfall totals, 1997−2009, Gardiner, Maine

April

March

February

January

December

EXPLANATION

Figure 7. December–April snowfall totals in Gardiner, Maine, 1997–2009.

-8

-6

-4

-2

0

2

4

6

8

10

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Departure from normal monthly temperature,

in degrees Fahrenheit

Year

December−April departures from normal temperatures, 1997−2009, Gardiner, Maine

April

March

February

January

December

EXPLANATION

Figure 8. December–April departures from average temperatures in Gardiner, Maine, 1997–2009.
10 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

A

B

Figure 9. A, Instrumentation shelter and B, arrangement of data-collection instruments at U.S. Geological Survey well 441226069502201 

in West Gardiner, Maine.
Methods of Data Collection 11

attached to a DA H310 submersible pressure transducer and a 

Campbell Scientific (CS) CR10 DCP attached to a CS H547A 

temperature and conductance probe (fig. 9B). The DCP transmitted 15-minute water-level, water-temperature (from both 

the pressure transducer and the conductance probe), and specific-conductance data every hour over the geostationary satellite (GOES) system. The CS H547A temperature and conductance probe measures water temperature by use of a resistor 

that responds rapidly to changes in temperature but measures 

conductance only as water moves through the probe. If little 

to no vertical flow is present in the well, this instrument can 

indicate slow to no response to changes in conductance.

Specific conductance and temperature probes were 

checked for calibration against a range of calibration standards 

before deployment in the field, at least once during deployment, and when the probes were removed from the wells. All 

probes met manufacturer specifications during each calibration check.

Water levels were collected to 0.01 ft in all wells and 

were reported as depth below land surface datum (LSD). 

Temperature originally was collected to 0.1 degree Celsius 

(°C) in all wells, but after about December 7, 2007, it was collected to 0.01 °C. Specific conductance was recorded to three 

significant figures.

Gray

Installation of the monitoring instruments in the Gray 

well began on December 12, 2007, and concluded December 

14, 2007. The pressure transducer was set at a depth of 42 ft 

below LSD and the conductance probe was set at a depth of 

90 ft below LSD. Both instruments were replaced soon after 

installation was completed on December 14, 2007, because 

of issues with instrumentation catching on the pump in the 

well. The pump was removed the same day. Specific conductance data from December 2007 through January 2008 were 

considered unreliable and are not used in this report. All of the 

instruments were removed from the well and data collection 

ended on May 14, 2009.

West Gardiner

On August 30–31, 2007, a CS CR10 DCP was installed 

in a plastic shelter mounted over the well casing. The DCP 

was connected to a CS temperature and conductance probe at 

a depth of 44 ft below LSD. A DA DH21 pressure transducer 

also was installed in the well at a depth of 30 ft below LSD. 

This installation was to collect data temporarily until the realtime equipment was installed.

On October 15, 2007, the West Gardiner well was converted to a permanent installation. The pressure transducer 

was set at a depth of 42 ft below LSD and the conductance 

probe at a depth of 41 ft below LSD. On November 2, 2007, 

the pressure transducer was raised to a depth of 34 ft below 

LSD to prevent possible issues with the probes catching on 

one another. The instruments were removed from this well and 

data collection ended on November 6, 2009.

North Sullivan

Instruments to measure water level and temperature 

were installed in the North Sullivan well at depths of 18 ft 

and to measure specific conductance and temperature at 80 ft 

on September 24, 2007. Because the data from winter 2008 

showed high variability, possibly related to the effect of the 

daily use of water from the well, a second probe for specific 

conductance and temperature was installed in the well at a 

depth of 40 ft on June 4, 2008. The instruments were removed 

from this well and data collection ended on June 3, 2009.

South Sullivan

On January 10, 2008, the pressure transducer in the 

South Sullivan well was set at a depth of 45 ft below LSD 

and the conductance probe set at a depth of 42 ft below LSD. 

On June 4, 2008, the conductance probe was replaced with a 

new H547A probe set at a depth of 220 ft below LSD. These 

instruments were removed and data collection ended on 

June 3, 2009.

Water-Quality Samples and Profiling

Water-quality samples were collected to determine a relation between specific conductance, which was monitored continuously, and concentrations of chloride. Water samples were 

collected by use of diffusion samplers. The diffusion medium, 

from Spectrum Laboratories, Inc., was molecular porous cellulose membrane tubing with a 20.4-millimeter (mm) diameter 

and a molecular weight cutoff of 12,000 to 14,000 daltons.

In the USGS laboratory, samplers were filled with deionized water, sealed at both ends, and immersed in a deionized 

water bath for transport to the field. In the field, samplers were 

lowered to the appropriate depth and allowed to equilibrate 

under environmental conditions for at least a week. When a 

sampler was removed, the sample was poured immediately 

into a labeled 125 milliliter (mL) poly bottle and taken to the 

USGS laboratory. Specific conductance was measured in the 

laboratory by use of an Orion model 160 conductivity meter 

before the sample was sent to the USGS National WaterQuality Laboratory for analysis of chloride. The reporting 

limit for chloride concentration was 0.12 milligrams per liter 

(mg/L).

Vertical profiling of specific conductance, water temperature, dissolved-oxygen concentration, and pH was done 

at least once in each well. For this process, a rope of length 

greater than the depth of the well was attached to a calibrated, 

internally logging water-quality probe from Hydrolab or YSI. 

The rope was marked every 10 ft. While one hydrographer 

kept notes of the clock time and length of rope deployed, the 

other hydrographer lowered the probe through the well bore, 
12 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

stopping for a minute at each 10- or 20-ft increment to allow 

the probe to equilibrate and record. Probe calibrations were 

checked at the end of each day of profiling; in all cases, the 

probes remained within the calibration settings. Data from the 

probe were paired with corresponding depth data recorded in 

the field on the basis of clock time.

Geophysical Data

The USGS used conventional and advanced geophysical 

methods to characterize the wells and to provide information 

about the types of rock at each well location, orientation of 

bedding planes, degree of fracturing, and vertical flow directions of water in each well. Conventional logs collected in 

each well included caliper, natural-gamma, specific conductance (fluid-resistivity), and fluid-temperature logs. Advanced 

methods included optical and acoustic televiewer logging and 

heat-pulse flowmeter logging. Descriptions of these methods 

are from Johnson and others (2002).

Caliper logging generates a continuous profile of borehole diameter with depth. The caliper tool is pulled up the 

borehole, allowing three spring-loaded arms to open as they 

pass borehole enlargements. The enlargements generally are 

related to fractures but can also be caused by changes in lithology or borehole construction.

Natural-gamma logging measures the natural gamma 

activity of the formation around the borehole. Gamma emissions generally can be correlated with rock type or fracture 

infilling. Deviations in the gamma log indicate changes in 

lithology or the presence of altered zones or mineralized fractures. Because the gamma log does not have a unique lithologic response, interpretation must be guided by the information provided by other logs.

Changes in the total dissolved solids (TDS) content of the 

water in the well are measured by use of specific-conductance 

logging. As the tool is lowered down the well, fluid resistivity is measured directly and its inverse, specific conductance, 

is calculated. To ensure that an undisturbed distribution of 

TDS was measured, fluid-resistivity logging was done first at 

each well. Because fluid resistivity generally is low in water 

containing salts, calibration of the fluid-resistivity tool can be 

difficult. Consequently, changes in specific conductance with 

depth are expected to provide more information than absolute 

values of specific conductance.

Temperature logging is used to sense locations where 

water enters or exits a well. In the absence of fluid flow in the 

borehole, water temperature generally decreases about 1 °F 

per 100 ft of depth (Keys, 1990). Deviations in this expected 

gradient indicate transmissive zones in the borehole.

Optical-televiewer (OTV) logging records a high-resolution, continuous, magnetically oriented, digitized 360-degree 

(°) color image of the borehole wall. The image permits direct 

examination of the borehole for locations and details of fractures, changes in lithology, water level, bottom of casing, and 

borehole enlargements. Because the images are magnetically 

oriented, they can be used to infer strike and dip of the rocks. 

Because the OTV is an optical system, however, it makes 

low-contrast features, such as small fractures in dark rocks, 

difficult to discern. Constituents in the water, such as sediment 

or oxidation products, can obscure the image.

Acoustic-televiewer (ATV) logging records a high-resolution, continuous, magnetically oriented image that is used 

to map the location and orientation of fractures that intersect a 

borehole. An acoustic beam is transmitted by the logging tool 

and the reflected wave is recorded. Fractures and other features in a borehole tend to scatter the acoustic wave, thereby 

producing high contrast on the borehole image.

A heat-pulse flowmeter (HPFM), sensitive to flows as 

low as 0.01 ± 0.005 gal/min, was used to measure the direction and rate of vertical flow in the boreholes under ambient 

and stressed conditions. Under ambient conditions, differences 

in hydraulic head between two transmissive fractures produce 

vertical flow in the borehole. If the hydraulic heads are nearly 

the same, however, no flow may be detected. Therefore, the 

HPFM also is used under pumping conditions to identify 

transmissive zones with similar ambient heads that would 

not be identified without stressing the aquifer. The HPFM 

uses a heat-pulse tracer that moves upward or downward 

with the flow in the borehole. After the tools described above 

were deployed to identify the depths of the fractured zones, 

the HPFM was used above and below the fractured zones to 

determine the transmissivity of the fractures and the direction 

of flow.

Most geophysical logging was done at rates of 11 to 15 

feet per minute (ft/min). Because of the large amounts of data 

that the televiewers collected, their rates were about 8 ft/min. 

The HPFM was stationary when it was used to collect flowrate information at specified depths.

Quality Assurance

The USGS maintained high-quality data by use of 

calibration checks before, during, and after deployment. All 

water-quality instruments (specific conductance, temperature, 

and water-quality probes) were shown to be functioning within 

manufacturers’ specifications. Performance of water-level 

transducers was checked during site visits by use of standard 

tape-down techniques. During the data-collection period, 

little drift (no more than 0.04 ft) was found in any transducer. 

Water-level, specific conductance, and temperature data were 

subject to standard record review at the end of each water 

year; erroneous data (usually associated with normal maintenance at the wells) were removed from the published record.
Water Levels and Specific Conductance in Wells 13

Water Levels and Specific 

Conductance in Wells

Evidence for the role of fractures on the presence and 

movement of road-salt constituents, particularly chloride, 

in bedrock aquifers is presented in the following sections. 

Discussion of findings on a site-by-site basis also is included. 

Final daily-value data collected at the four study wells during 

water years 2008–9 are presented through the USGS Web 

portal (U.S. Geological Survey, 2009a) and in appendix 2.

Relation Between Specific Conductance and 

Chloride Concentrations

To reduce analytical costs and facilitate real-time reporting of data, USGS used specific conductance as a surrogate for 

chloride concentration on the basis of samples collected and 

analyzed for both constituents. Although this relation was not 

analyzed in a rigorous manner (as, for example, in Granato 

and Smith, 1999), the data showed a linear correlation over a 

range of about 3,000 μS/cm in six samples from three of the 

wells (fig. 10).

For the remainder of this report, changes in concentrations of specific conductance are considered indicative of 

changes in concentration of chloride. The following relation 

was established, with R2

 = 0.9965:

Chloride concentration (in mg/L) = 

Specific conductance (in μS/cm) × 0.324 – 66, (1)

which does not differ greatly from that used by Harte 

and Trowbridge (2010) for a small watershed in southern 

New Hampshire.

Site-by-Site Characteristics

Features of the geophysical, water-level, and specificconductance data collected at each of the four wells are presented in this section. In some cases, the data are interpreted in 

the context of the landscape and (or) geologic environment at 

the site. Typical 10-day unit-value hydrographs of water levels 

in the four wells are presented in figure 11.

Gray

Active fractures, which are those that were actively 

contributing flow to the well under both static and pumped 

conditions, were found at depths of 84, 114, 186, and 294 ft 

below LSD (appendix 1). Under ambient conditions, water 

entered the borehole at the 294 ft depth and exited the borehole at the 114- and 186-ft depths. Vertical profiling (fig. 

12) indicated slight water-chemistry changes near the bottom of casing (75 ft), probably in relation to the fracture at 

84 ft, and larger changes below the 294 ft deep fracture. The 

specific conductance and temperature probe was set below the 

84-ft fracture.

Water levels in the Gray well, collected between 

December 2007 and May 2009, exhibited consistent semidiurnal Earth-tide effects, fluctuating 0.1 ft to 0.2 ft daily (fig. 

11). Daily water levels ranged from 10.26 to 13.96 ft below 

LSD during the period of record (fig. 2–1). Highest and lowest water levels were observed in April 2009 and July 2008, 

respectively. Water levels increased during spring snowmelt 

(from February through early April, both years) and declined 

through the summer months.

The minimum specific conductance, about 450 μS/cm, 

corresponds to a chloride concentration of about 80 mg/L, 

which is about four times higher than the background 

y = 0.3237x - 66.176

R2

= 0.9965

0

100

200

300

400

500

600

700

800

900

1,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500

Chloride concentration, in milligrams per liter

Specific conductance, in microsiemens per centimeter at 25 degrees Celsius

Relation between specific conductance and chloride concentration

Secondary maximum contaminant level (SMCL) for chloride

(U.S. Environmental Protection Agency, 2012)

Figure 10. Relation between 

concentrations of chloride and 

specific conductance in three roadsalt study wells, Maine.
14 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Schalk_fig 11

4

6

8

10

12

14

16

30

32

34

36

38

40

42

5/12/20085/13/20085/14/20085/15/20085/16/20085/17/20085/18/20085/19/20085/20/20085/21/20085/22/2008

Water level in West Gardiner, Gray, and North Sullivan wells,

in feet below land surface

Water level in South Sullivan well, in feet below land surface

Date

South Sullivan

West Gardiner

Gray

North Sullivan

EXPLANATION

Figure 11. 10-day unit-value water levels for May 12–22, 2008, in four road-salt study wells, Maine.

0

1

2

3

4

5

6

7

8

9

10

0

200

400

600

800

1,000

1,200

30 80 130 180 230 280 330

Water temperature, in degrees Celsius; dissolved oxygen

concentration, in milligrams per liter; or pH, in standard units 

Specific conductance,

in microsiemens per centimeter at 25 degrees Celsius 

Depth, in feet below top of casing 

Specific conductance

Water temperature

Dissolved oxygen

pH

EXPLANATION

Figure 12. Vertical water-quality profile in U.S. Geological Survey well 435103070191701 in Gray, Maine, October 22, 2008.
Water Levels and Specific Conductance in Wells 15

concentration reported by Olson and others (1985). Changes in 

specific conductance were neither large nor abrupt. Throughout the monitoring period, the range of recorded specific 

conductance was 450 to 485 μS/cm. Specific conductance 

increased from about 450 to 481 μS/cm from May 30 to June 

28, 2008; the timing of this increase seems to indicate that 

the arrival of chloride to the well lags about 3 months behind 

spring snowmelt, which could be indicative of a long flow 

path for chloride. The peak conductance value may have been 

affected somewhat by the removal of the instruments from the 

well June 23–24 for geophysical logging.

From July 10 to October 19, 2008, daily water levels and 

specific conductance showed strong negative correlation (R2

= 0.675) (fig. 13); that is, as water level rose during three consecutive events, specific conductance increased. This relation 

indicates that during storm-related recharge events, a net transport of salts occurs into the part of the aquifer penetrated by 

the Gray well. Salt is apparently stored along the flow path and 

is subsequently mobilized during recharge events. In general, 

peaks in specific conductance lagged about 2 days after peaks 

in water levels during these summer and autumn months.

Two mechanisms may have been involved in the longand short-term responses of water levels and specific conductance in the Gray well. Long-term recharge, driven primarily 

by spring thaw and other wet periods over relatively long flow 

paths from land surface to the deep fractures in the well, provide a delayed response of specific conductance to changes in 

water level, whereas short-term changes in water level, driven 

primarily by summer or autumn rains when water levels are 

low, provide smaller pulses of high conductance water to the 

well. This could indicate that chloride is “pushed” into the 

well from surrounding fractures during rainfall events.

West Gardiner

Active fractures were found at depths of 36, 92, 120, 136, 

170, 248, and 340 ft below LSD. Under ambient conditions, 

groundwater enters the well primarily at the 248 ft depth and 

exits at the 92 ft depth.

In general, water levels in the West Gardiner well were 

relatively higher than those in the other wells (fig. 2–2). 

Effects of pumping in the well were evident during the first 

few days of monitoring (after which MaineDOT moved the 

source of domestic supply to another well) and also during the 

middle of November, 2007, when geophysical logging was 

done at the well. The normal range of water levels was from 

4 to 10.5 ft below LSD. Water levels increased during spring 

snowmelt (from February through early April, both years) and 

declined through the summer and autumn months. Water levels rose after about June 15, 2009, in response to the wetness 

of the summer. Sharp declines in water levels were probably in 

response to pumping in nearby wells. Water levels responded 

quickly to recharge events (fig. 2–2) and showed strong semidiurnal Earth-tide effects (fig. 11).

Two extreme water levels were affected by actions being 

performed on a well 30 ft away (15-minute data not shown). 

The lowest water level recorded, 19.93 ft below LSD on 

September 2, 2007, was in response to the nearby well being 

pumped; and the highest water level recorded, 3.90 ft below 

LSD on December 4, 2007, was in response to the same well 

being filled with bentonite as it was abandoned. The rapid and 

abrupt response of water levels to displacement of groundwater in the nearby well is indicative of the nature of groundwater flow in fractured-rock environments. It is likely that the 

same transmissive fracture intersected both the West Gardiner 

well and the nearby abandoned well.

Specific conductance generally was higher in the West 

Gardiner well than in other study wells, ranging from 681 to 

3,890 μS/cm (corresponding to chloride concentrations of 

about 150 to 1,200 mg/L). The high chloride concentrations 

may have been associated historically with the presence of 

salt piles (which were covered in 1988) at the MaineDOT and 

MTA maintenance lots, as well as with ongoing winter maintenance practices at the MTA tollbooth area east of the well. 

The high chloride concentrations necessitated the abandonment of several wells nearby (Joshua Katz, Maine Department 

of Transportation, oral commun., 2007). Overall, specific 

conductance in the well shows a 2-year increase punctuated by 

(possibly) event-based peaks (fig. 2–2).

Figure 2–2 indicates that, after about May 1, 2008, specific conductance and water level shared an inverse relation; 

as water levels declined, specific conductance increased. Two 

explanations are possible. The first possible explanation for 

this inverse relation is that near-well recharge diluted the high 

concentration of chloride in the well. The probable ambient 

groundwater flow gradient in this area is from southeast to 

northwest, which tends to transport road salts applied to State 

Routes 9/126 away from the West Gardiner well rather than 

toward it. Thus, recharging groundwater probably is not transporting new chloride near the well to the subsurface. However, 

if dilution were occurring, specific conductance in the well 

should be decreasing consistently, but it is not (fig. 2–2).

The second possible explanation for the observed 

behavior of water levels and specific conductance is that a 

3- to 6-month lag exists between precipitation events and the 

arrival of chloride to the well from a different source—the 

Maine Turnpike (Interstate 95), which lies upgradient toward 

the southeast. Some ancillary evidence for this hypothesis is 

on file with MaineDOT (Joshua Katz, Maine Department of 

Transportation, oral commun., 2008).

Vertical profiles from January 16, 2008, in the West 

Gardiner well (fig. 14) present evidence of the roles of fractures on all water-quality constituents. Dissolved oxygen concentration, pH, and specific conductance were approximately 

constant throughout the profile to a depth of 220 ft; at 220 ft, 

specific conductance increased to more than 5,000 μS/cm, 

pH decreased, and dissolved oxygen increased. At a depth of 

about 320 ft, specific conductance increased to 15,000 μS/cm 

(corresponding to a chloride concentration of 4,800 mg/L, 

about one-fourth that of seawater), pH decreased again, and 

dissolved oxygen content increased to concentrations observed 

far more regularly in surface water than in groundwater (Hem, 
16 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

464

466

468

470

472

474

476

0 478

2

4

6

8

10

12

14

16

Specific conductance, in microsiemens per centimeter at 25 degrees Celsius

Daily precipitation, in inches, or water level, in feet below land surface

Date

Water level

Precipitation

Specific conductance

EXPLANATION

7/10/2008

10/02/2008

7/24/20088/07/20088/21/20089/04/20089/18/2008

10/16/2008

A

468

469

470

471

472

473

474

475

476

477

478

10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0

Specific conductance, in microsiemens per centimeter

at 25 degrees Celsius

Water level, in feet below land surface

R2

 = 0.675

B

Figure 13. A, A hydrograph and B, correlation of daily water levels and specific conductance in U.S. Geological Survey well 

435103070191701 in Gray, Maine, July 10–October 19, 2008.
Water Levels and Specific Conductance in Wells 17

Figure 14. Vertical waterquality profile in U.S. 

Geological Survey well 

441226069502201 in West 

Gardiner, Maine, January 16, 

2008.

Schalk_fig 14

0

1

2

3

4

5

6

7

8

9

10

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

0 50 100 150 200 250 300

Water temperature, in degrees Celsius; dissolved oxygen

concentration, in milligrams per liter; or pH, in standard units 

Specific conductance,

in microsiemens per centimeter at 25 degrees Celsius

Depth, in feet below top of casing

Specific conductance

Water temperature

Dissolved oxygen

pH

EXPLANATION

1985). These trends with depth also were observed in two subsequent profiles on different dates. One possible explanation is 

the existence of a near-vertical fracture that quickly transports 

oxygen-rich recharge water to the bottom of the well; if this 

were the case, however, it is likely that dilution effects on 

specific conductance would be more apparent.

North Sullivan

Geophysical data indicate that active fractures exist 15 ft 

below LSD at the base of the casing (table 1; appendix 1), and 

at depths of 25, 72, and 85 ft. Under ambient conditions, water 

entered the borehole at the 25-ft depth and exited the borehole 

at the 85-ft depth. Under pumping conditions, water entered 

the borehole at the 72-ft depth also.

Water levels in the North Sullivan well were affected by 

pumping from the well throughout the duration of the project. 

No Earth-tide effects were observed during any time period 

(fig. 11), even when the well was unused for a month. This 

well was relatively shallow (97 ft) and probably unconfined; 

that is, the water table is exposed to atmospheric pressure and 

is not subject to Earth tides.

The maximum and minimum water levels observed were 

9.96 ft below LSD (April 7, 2009, during spring melt) and 

17.89 ft below LSD (October 8, 2007, in response to pumping), respectively (15-minute values not shown). Water-level 

declines in response to pumping usually were in the range of 

2 ft in 15-minute increments (fig. 11). Notwithstanding the 

effects of pumping, water levels generally increased during 

spring snowmelt (from February through early April) and 

autumn rains and declined through the summer and (or) winter 

months (fig. 2–3).

Specific conductance data used from the North Sullivan 

well in this report are on the basis of observations at the 

80-ft depth. Although a second specific conductance probe 

was deployed at the 40-ft depth in June 2008, the two sets of 

specific-conductance data did not vary greatly (R2

 = 0.95) after 

about July 1, 2008.

Initially, in autumn 2007 and winter 2007–8, specific 

conductance decreased in response to increases in water level 

from recharge (fig. 15), probably because the first recharge 

water entered the well through large fractures that did not 

contain appreciable concentrations of salt; chloride in the well 

was diluted initially from about 1,000 to 900 μS/cm (about 

250–225 mg/L chloride). Thereafter, however, recharge water 

brought additional chloride with it, probably through small 

fractures or through the bulk matrix, and specific conductance 

increased with water level. Several examples of the initial 

decrease, then rapid increase in specific conductance with 

recharge are shown in figure 15 for December 24–25, 2007, 

and February 13 and April 30, 2008.

The degree to which specific conductance responded 

to recharge varied on the basis of antecedent conditions. 

About 26 in. of snow fell between December 24, 2007, and 

January 5, 2008, resulting in a snowpack depth of about 2 ft 

deep; temperatures were between 38 and -10 °F (National 

Oceanic and Atmospheric Administration, 2008). On 

January 9, 2008, water levels began to rise at noon in response 

to a major thaw January 6–13 (maximum high temperature of 52 °F on January 8 and minimum low temperatures 

above freezing January 7–9), during which no precipitation 

fell; temperature and specific conductance responded about 

16 hours later. In total, the January 6–13 thaw caused the 

snowpack to diminish to 8 in., water levels to rise about 1.5 
18 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Schalk_fig 15

0

2

4

6

8

10

12

14

16

18

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

10/30/200712/19/2007

2/7/2008

3/28/20085/17/2008

7/6/2008

Precipitation, in inches, or water level, in feet below land surface

Specific conductance,

in microsiemens per centimeter at 25 degrees Celsius

Date

Specific conductance

Water level

Precipitation

December 24-25

February 13 April 30

EXPLANATION

Figure 15. Water levels and specific conductance in U.S. Geological Survey well 443145068131801 in North Sullivan, Maine, November 

2007–July 2008.

ft, water temperature to rise about 2 °F, and specific conductance to rise about 3,000 μS/cm. Increases in water levels 

and specific conductance also occurred around January 30 

in response to warm temperatures January 29–30 (maximum 

high temperature 45 °F on January 30 and minimum low temperatures slightly below freezing; decrease in snowpack); and 

on February 14 in response to warm temperatures February 

13–15 (maximum high temperature 43 °F on February 13 and 

minimum low temperatures 15–18 °F). The February 13–15 

thaw was accompanied by more than 5 in. of new snow but 

produced an overall decrease in the snowpack. A warm period 

February 18–19 (maximum temperature 48 °F on February 18, 

and minimum low temperatures around freezing) produced a 

decrease in snowpack, an increase in water levels, and little 

change in temperature or specific conductance. Between 

February 15 and 18, less than 0.5 in. of snow had fallen, so 

additional road salt probably had not been applied. In all 

likelihood, the January 9–10 thaw allowed an accumulation of 

road salts that had been applied during the antecedent snowy 

weather to enter the well with melted snow, as evidenced by 

the large spike in specific conductance that lasted about 3 

weeks; the later events produced smaller spikes in specific 

conductance because antecedent weather had required the use 

of less road salt.

The effects of the annual spring snowmelt were observed 

in March and April 2008. Snowpack depth decreased or held 

steady throughout March and disappeared around April 7. The 

highest water level since the thaw of February 18 occurred 

on April 5. Specific conductance rose steadily from March 

21 through April 7, 2008, probably in response to the annual 

spring snowmelt; at the same time, temperature decreased 

1 °F because the snowmelt water was colder than the 

ambient water.

From June 6 through 9, 2008, when water levels spiked 

downward (3-ft declines) due to pumping, specific conductance spiked upward as much as 700 μS/cm. Later in summer 

2008, on many occasions when water levels spiked downward 

due to pumping, specific conductance did not respond. These 

data, in concert with those described above, indicate that 

hydrologic events, and in particular their timing in relation to 

the presence of road salt, played a larger role in the transport 

of chlorides than did pumping alone.

South Sullivan

Geophysical data indicate that active fractures exist 

at depths of about 40, 53, 186, 198, and 208 ft below LSD. 
Water Levels and Specific Conductance in Wells 19

Under ambient conditions, water enters the borehole at the 

186- and 198-ft depths and exits the borehole at the 40- and 

53-ft depths. The 208-ft fracture became active under pumping 

conditions.

Water levels in the South Sullivan well exhibited strong 

semi-diurnal fluctuations of 1 foot or more (fig. 11), possibly 

in response to both Earth tides and ocean tides. Occasional, 

periodic declines of water levels as much as 2 ft (fig. 11) 

may have been in response to pumping from a nearby well 

that was not identified. The minimum and maximum water 

levels recorded were 28.06 ft below LSD and 37.22 ft below 

LSD, respectively (15-minute data not shown). Water levels 

generally increased during spring snowmelt (from February 

through early April) and declined through the summer months 

(fig. 2–4).

At the 220 ft depth, specific conductance remained 

above about 750 μS/cm (corresponding to 180 mg/L chloride) 

throughout the year (fig. 2–4). Water-level fluctuations had no 

major effect on specific conductance at 220 ft, which is below 

the active fractures. Small changes in specific conductance at 

42 ft, however, lagged about 5 days behind changes in water 

level. The South Sullivan well was slightly uphill from U.S. 

Route 1; runoff and infiltration probably were directed away 

from the well head, and it is likely that the topography of the 

area masked any possible cause-and-effect relation that might 

otherwise have been observed.

Effects of Stresses on Chloride Concentrations

The data presented in the “Site-by-Site Characteristics” 

section indicate that natural and anthropogenic hydrologic 

stresses play meaningful roles in the presence of chloride in 

groundwater. Natural stresses, including recharge by precipitation and thawing, generally affect chloride concentrations 

by transporting chloride to the well from overlying soil and 

rock. Anthropogenic stress (pumping) affects chloride concentrations by creating artificially steep, temporary gradients 

between the water table and the water level in the well. Effects 

of stresses are seen throughout the year.

Precipitation

Specific conductance in the Gray and North Sullivan 

wells responded positively to recharge events throughout the 

year. In general, when water levels rose in these wells, specific 

conductance increased, although to varying degrees. Dailyvalue water levels and specific conductance from the Gray 

well were correlated (fig. 13B), and the data indicated that 

changes in specific conductance lagged about 3 days behind 

changes in water levels. This lag may have been because the 

initial water-level changes were because of increased pressure from the water column, and not from an actual influx of 

recharging water; or it may have been because the specific 

conductance probe was set at 190 ft and the chloride entering the well with recharge water required 3 days to diffuse to 

that depth. Recharge-related effects were most marked in the 

North Sullivan well, probably because of its shallowness, the 

shortness of the well casing (15 ft below LSD), and pumping 

in the well.

The positive response of specific conductance to changes 

in water level indicates that the recharge water typically was 

higher in chlorides than the water in the well—not just during 

winter thaws or spring recharge, but throughout the year. In 

general, after early recharge of relatively clean water, specific conductance began to rise, indicating that the recharge 

water percolating through smaller fractures or the bulk matrix 

contained higher concentrations of chlorides than did the 

early recharge water. These hydrologic responses imply that 

chlorides are retained in the unsaturated zone, small fractures, 

and (or) the bulk matrix throughout the year, not just during 

the winter.

The responses to recharge observed in the Gray and 

North Sullivan wells were not observed in the West Gardiner 

well, where the conceptual flow model indicates that shortterm recharge near the well tends to dilute chloride present in 

the well, whereas long-term recharge along flow paths from 

the southeast tend to concentrate chlorides, even when groundwater level declines.

Thawing

Specific conductance in the Gray and North Sullivan 

wells showed a notable response to snowmelt. Although 

recharge can occur throughout the winter (as evidenced by 

increases in water levels in all wells during winter 2007–8 

(appendix 2), the largest values of specific conductance—or 

increases in concentration of chloride—were associated with 

thaws. Labadia and Buttle (1996) found that as much as 50 

percent of the applied road salt remains in the snowbank until 

a thaw; if a connecting fracture exists from the surface to the 

subsurface, concentrations or road-salt constituents will spike 

during a thaw. Once again, the most remarkable example was 

the North Sullivan well.

Pumping

The combination of effects observed at the North 

Sullivan well during summer 2008 supports the hypothesis 

that chloride is sequestered in the matrix or disconnected 

fractures until mobilized by recharge. During the late spring, 

when ambient water levels and soil moisture were presumably high from the spring thaw, specific conductance increased 

in response to pumping; chloride-bearing groundwater was 

drawn into the well. During the late summer, when ambient 

water levels and soil moisture were presumably low from the 

effects of evapotranspiration, specific conductance did not 

respond to pumping; groundwater drawn to the well did not 

contain new concentrations of chloride.

These data support the idea that chloride is “suspended” 

in the bulk matrix or in small, partially disconnected fractures 
20 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

until activated by recharge. When hydrologic events were few 

and far between, specific conductance was unlikely to respond 

to pumping alone; but when precipitation was sufficient to 

produce recharge or when air temperature was sufficient to 

produce significant thawing, chloride was transported into the 

well, causing an increase in specific conductance.

Effects of Fractures on Water Quality

Water-quality profiles of the wells supported data 

acquired by geophysical methods and confirmed that the active 

fractures in each well played prominent roles in the quality of water in the well. Distinct changes in water chemistry 

were observed at depths correlating to the presence of active 

fractures, as, for example, in the West Gardiner well (fig. 14). 

Profiles in the South Sullivan well (not shown) were similar, 

though not as dramatic.

The behavior of dissolved oxygen concentrations with 

depth in the West Gardiner well (fig. 14) are probably the most 

noteworthy example of the role of fractures on water quality. From land surface to a depth of 220 ft, dissolved oxygen 

concentration decreased from about 0.1 to 0.03 mg/L, which is 

typical for groundwater. From 220 to 300 ft, dissolved oxygen 

concentration increased to about 0.7 mg/L, and below 300 ft, 

dissolved oxygen concentration increased to 10 mg/L. This 

behavior was repeated during three separate visits, and the 

meter was found to be within calibration specifications each 

visit after the profiling effort. One possible explanation is the 

existence of a near-vertical fracture that quickly transports 

oxygen-rich recharge water to the bottom of the well; if this 

is true, then the same fracture can readily be cited as playing a major role in the transport of chloride to the subsurface 

as well.

Summary and Conclusions

In 2007, in cooperation with Maine Department of 

Transportation (MaineDOT), the U.S. Geological Survey 

began an investigation of the processes that enable chlorides 

from road salt to be present in bedrock aquifers. Data collected 

by MaineDOT’s Well Claims Unit had shown that chloride 

concentrations in wells affected by road salt increased in the 

autumn, after water levels declined in the summer, and before 

road salts were applied in the winter. This investigation sought 

to determine a relation between specific conductance and 

chloride concentration, and, on the basis of that relation, to 

explore the role of fractures on the quality of groundwater; 

a link between road salting and chloride contamination; and 

the hydrologic conditions and timing of events that affected 

chloride concentrations in groundwater.

Continuous data on water levels, specific conductance, 

and temperature were collected from 2007 through 2009 at 

four bedrock wells in Maine that were known to be affected by 

road salts. Geophysical data were collected to locate fractures 

and determine whether the fractures were contributing groundwater to the well under static and pumped conditions. Vertical 

profiles of water-quality indicators (dissolved oxygen, specific 

conductance, pH, and temperature) were collected at least 

once at the three wells not being used for domestic supply. 

Water-quality samples were collected to establish a linear relation between specific conductance and chloride concentration.

Geophysical methods identified the active fractures in 

each well, and vertical profiling verified the contributions of 

these fractures to the distributions of water quality with depth 

in each well. All abrupt changes in water-quality constituents 

during profiling were at depths corresponding to those of the 

active fractures identified by geophysical methods.

Data collected during the project indicated that chloride 

concentration was relatively stable in the wells, except when 

concentrations increased during the main spring recharge or 

during major winter thaws. Minimum specific conductance, 

about 450 μS/cm in the Gray well (corresponding to about 

80 mg/L chloride), indicated that chlorides at concentrations 

greater than background levels continued to be present after 

large recharge events such as snowmelt and rainfall, especially 

in the spring. In contrast, in highly permeable, unconsolidated 

environments, the literature documents a breakthrough-curve 

behavior for chloride.

Contamination of the wells was linked to road salting 

in at least one well on the basis of large increases in specific 

conductance associated with winter thaws and spring recharge, 

when road salts are most prevalent in the environment. A winter thaw in January 2008 produced the largest spike in specific 

conductance observed at the North Sullivan well, and specific 

conductance did not recover to the pre-thaw concentration for 

3 weeks. Annual high specific conductances were observed in 

at least two wells during the spring snowmelt.

Data showed that chloride can be transported to the wells 

throughout the year, not only during the winter. Although 

the largest changes in specific conductance were associated 

with thaws, other hydrologic events also triggered changes in 

specific conductance. Recharge events throughout the summer, for example, produced increases in specific conductance. 

These data indicate that road salts are sequestered in the bulk 

matrix of the unsaturated zone or in isolated fractures, and 

that, when recharge events occur, they can be flushed into the 

system.

Hydrologic events were the driving factor behind changes 

in specific conductance. Winter and spring thaws and rainfall transported chloride to the groundwater during recharge 

events. Some effects of pumping on chloride concentrations 

also were observed, but substantially greater changes in chloride concentration were observed when recharge was a factor 

than when pumping was the only factor.

The magnitude of chloride concentrations with depth in 

the wells also was related to the presence of fractures. Vertical profiles consistently showed relatively abrupt changes in 

water-quality constituents at depths of active fractures.
References Cited 21

References Cited

Aichele, S., 2004, Arsenic, nitrate, and chloride in groundwater, Oakland County, Michigan: U.S. Geological Survey 

Fact Sheet 2004–3120, 6 p.

Andrews, W.J., 1996, Water-quality assessment of part of the 

Upper Mississippi River Basin, Minnesota and Wisconsin—

Ground-water quality in an urban part of the Twin Cities 

metropolitan area, Minnesota: U.S. Geological Survey 

Water-Resources Investigations Report 97–4248, 54 p.

Andrews, W.J., Stark, J.R., Fong, A.L., and Fallon, J.D., 2005, 

Water-quality assessment of part of the upper Mississippi 

River basin, Minnesota and Wisconsin—Ground-water 

quality along a flow system in the Twin Cities metropolitan 

area, Minnesota, 1997–98: U.S. Geological Survey Scientific Investigations Report 2005–5120, 44 p.

Bester, M.L., Frind, E.O., Molson, J.W., and Rudolph, D.L., 

2006, Numerical investigation of road salt impact on an 

urban watershed: Ground Water, v. 44, no. 2, p. 165–175.

Blasius, B.J., and Merritt, R.W., 2002, Field and laboratory 

investigations on the effects of road salt (NaCl) on stream 

macroinvertebrate communities: Environmental Pollution, 

v. 120, no. 2, p. 219–231.

Blomkvist, G., and Johanssen, E.-L., 1999, Airborne spreading 

and deposition of de-icing salt—A case study: The Science 

of the Total Environment, v. 235, p. 161–168.

Caswell, W.B., 1979, Maine’s ground-water situation: Ground 

Water, v. 17, no. 3, p. 235–243.

Corsi, S.R., Graczyk, D.J., Geis, S.W., Booth, N.L., and 

Richards, K.D., 2010, A fresh look at road salt—Aquatic 

toxicity and water-quality impacts on local, regional, and 

national scales: Environmental Science and Technology, v. 

44, no. 19, p. 7376–7382.

Cunningham, W.L., and Schalk, C.W., comps., 2011, Groundwater technical procedures of the U.S. Geological Survey: 

U.S. Geological Survey Techniques and Methods, book 1, 

chap. A1, 151 p., at http://pubs.usgs.gov/tm/1a1/.

Demers, C.L., and Sage, R.W., 1990, Effects of road deicing 

salt on chloride levels in four Adirondack streams: Water, 

Air, and Soil Pollution, v. 49, no. 3–4, p. 369–373.

Fobes, C.B., 1942, Snowfall in Maine: Geographical Review, 

v. 32, no. 2, p. 245–251.

Foos, A., 2003, Spatial distribution of road salt contamination 

of natural springs and seeps, Cuyahoga Falls, Ohio, USA: 

Environmental Geology, v. 44, p. 14–19.

Forman, R.T., and Deblinger, R.D., 2000, The ecological roadeffect zone of a Massachusetts (U.S.A.) suburban highway: 

Conservation Biology, v. 14, no. 1, p. 36–46.

Godwin, K.S., Hafner, S.D., and Buff, M.F., 2003, Long-term 

trends in sodium and chloride in the Mohawk River, New 

York—The effect of fifty years of road-salt application: 

Environmental Pollution, v. 124, p. 273–281.

Granato, G.E., Church, P.E., and Stone, V.J., 1995, Mobilization of major and trace constituents of highway runoff in 

groundwater potentially caused by deicing chemical migration: Washington, D.C., Transportation Research Record 

1483, p. 92–104.

Granato, G.E., and Smith, K.P., 1999, Estimating concentrations of road-salt constituents in highway-runoff from measurements of specific conductance: U.S. Geological Survey 

Water-Resources Investigations Report 99–4077, 22 p.

Harte, P.T., and Trowbridge, P.R., 2010, Mapping of roadsalt-contaminated groundwater discharge and estimation 

of chloride load to a small stream in southern New Hampshire, USA: Journal of Hydrological Processes, v. 24, no. 

17, p. 2349–2368, accessed April 16, 2012, at http://dx.doi.

org/10.1002/hyp.7645.

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water: U.S. Geological Survey 

Water-Supply Paper 2254, 264 p.

Jackson, R.B., and Jobbagy, E.B., 2005, From icy roads to 

salty streams: Proceedings of the National Academy of Sciences, v. 102, no. 41, p. 14487–14488.

Johnson, C.D., Haeni, F.P., Lane, J.W., Jr., and White, E.A., 

2002, Borehole-geophysical investigation of the University 

of Connecticut landfill, Storrs, Connecticut: U.S. Geological Survey Water-Resources Investigations Report 01–4033, 

187 p.

Kaushal, S.S., Groffman, P.M., Likens, G.E., Belt, K.T., 

Stack, W.P., Kelly, V.R., Band, L.E., and Fisher, G.T., 2005, 

Increased salinization of fresh water in the northeastern 

United States: Proceedings of the National Academy of Sciences, v. 102, no. 38, p. 13517–13520.

Kelly, W.R., 2008, Long-term trends in chloride concentrations in shallow aquifers near Chicago: Ground Water, v. 46, 

no. 5, p. 772–781.

Keys, W.S., 1990, Borehole geophysics applied to groundwater investigations: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 2, chap. E–2, 149 p.
22 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Kostick, D.S., 1994, Salt, in Metals and minerals: U.S. Bureau 

of Mines Minerals Yearbook 1992, v. 1, p. 1103–1132, 

accessed April 11, 2012, at http://digicoll.library.wisc.edu/

cgi-bin/EcoNatRes/EcoNatRes-idx?type=article&did

=EcoNatRes.MinYB1992v1.WBolen&id=EcoNatRes.

MinYB1992v1&isize=M

Kostick, D.S., 1996–2012, Salt, in Metals and minerals: U.S. 

Geological Survey Minerals Yearbook 1994–2010, accessed 

April 11, 2012, at http://minerals.usgs.gov/minerals/pubs/

commodity/salt/index.html.

Kunze, A.E., and Sroka, B.N., 2004, Effects of highway deicing chemicals on shallow unconsolidated aquifers in Ohio–

Final report: U.S. Geological Survey Scientific Investigations Report 2004–5150, 187 p.

Labadia, C.F., and Buttle, J.M., 1996, Road salt accumulation 

in highway snow banks and transport through the unsaturated zone of the Oak Ridges moraine, southern Ontario: 

Hydrological Processes, v. 10, p. 1575–1589.

Maine Department of Transportation, 2004, Road salt contamination claims—Technical and legal issues: Maine 

Department of Transportation, accessed February 4, 2009, 

at http://www.maine.gov/mdot/community-programs/roadsaltclaims_000.php.

Maine Interagency Report, 2001, Sand and salt storage in 

Maine—Report to the 120th Maine Legislature: Augusta, 

Maine, Maine Department of Environmental Protection and 

Maine Department of Transportation, January 6, 47 p.

Maine Legislature, 2012, Maine revised statute title 

23—Highways: Maine Legislature, 331 p., available at 

http://www.mainelegislature.org/legis/statutes/23/title23.

pdf.

Methuel, R.W., 2007, Effects of deicing salts on the chloride 

levels in water and soil adjacent to roadways: Michigan 

Department of Transportation Construction and Technology 

Division, Research Report R–1495, 16 p.

National Oceanic and Atmospheric Administration, 2002, 

Snowfall—Average total in inches: National Oceanic and 

Atmospheric Administration database, accessed September 

29, 2010, at http://lwf.ncdc.noaa.gov/oa/climate/online/ccd/

snowfall.html.

National Oceanic and Atmospheric Administration, 2008, 

Daily climatological data for Ellsworth, Maine, January 

2008: National Climatic Data Center data on file with U.S. 

Geological Survey, Augusta, Maine.

National Weather Service, 2011, Wet year in Portland, Maine: 

CNYCentral.com, accessed August 31, 2011, at http://

www.cnycentral.com/weather/blog_post.aspx?id=398150#.

Tl5Ep2HMo8k.

New Hampshire Department of Environmental Services, 2010, 

Sodium and chloride in drinking water: New Hampshire 

Department of Environmental Services Factsheet WD–

DWGB–3–17, 3 p., accessed September 10, 2012, at http://

des.nh.gov/organization/commissioner/pip/factsheets/dwgb/

documents/dwgb-3-317.pdf.

Nimiroski, M.T., and Waldron, M.C., 2002, Sources of sodium 

and chloride in the Scituate Reservoir drainage basin, 

Rhode Island: U.S. Geological Survey Water-Resources 

Investigations Report 02–4149, 16 p.

Olson, A.C., Allenwood, M., and Williams, J.S., 1985, 

Replacement of salt contaminated water supplies in bedrock 

aquifers in Maine: Proceedings of the Second Annual Eastern Regional Ground Water Conference, National Ground 

Water Association, Ground Water Technology Division, 

July 16–18, 1985, Portland, Maine, p. 201–212.

Osberg, P.H., 1968, Stratigraphy, structural geology, and metamorphism of the Waterville-Vassalboro area, Maine: Maine 

Geological Survey Bulletin, no. 20, 64 p.

Osberg, P.H., Hussey, A.M., II, and Boone, G.M., 1985, Bedrock geologic map of Maine: Maine Geological Survey, 1 

sheet, scale 1:500,000.

Ostendorf, D.W., Hinlein, E.S., Rotaru, C., and DeGroot, D.J., 

2006, Contamination of groundwater by outdoor highway 

deicing agent storage: Journal of Hydrology, v. 326, no. 

1–4, p. 109–121.

Ostendorf, D.W., Palmer, R.N., and Hinlein, E.S., 2009, 

Seasonally varying highway deicing agent contamination in 

a groundwater plume from an infiltration basin: Hydrology 

Research, v. 40, no. 6, p. 520–532.

Paschka, M.G., Ghosh, R.S., and Dzombak, D.A., 1999, 

Potential water-quality effects from iron cyanide anticaking 

agents in road salt: Water Environment Research, v. 71, p. 

1235–1239.

Ramakrishna, D.M., and Viraraghavan, T., 2005, Environmental impact of chemical deicers—A review: Water, Air, and 

Soil Pollution, v. 166, no. 1–4, p. 49–63.

Richburg, J.A., Patterson, W.A., and Lowenstein, F., 2001, 

Effects of road salt and Phragmites australis invasion on 

the vegetation of a western Massachusetts calcareous lakebasin fen: Wetlands, v. 21, no. 2, p. 247–255.

Rosenberry, D.O., Bukaveckas, P.A., Buso, D.C., Likens, 

G.E., Shapiro, A.M., and Winter, T.C., 1999, Movement of 

road salt to a small New Hampshire lake: Water, Air, and 

Soil Pollution, v. 109, p. 179–206.
References Cited 23

Rubin, Jonathan, Gärder, P.E., Morris, C.E., Nichols, K.L., 

Peckenham, J.M., McKee, Peggy, Stern, Adam, and Johnson, T.O., 2010, Maine winter roads—Salt, safety, environment and cost: University of Maine, Margaret Chase Smith 

Policy Center, February, 142 p. (Also available at http://

mcspolicycenter.umaine.edu/2010/02/19/winterroadmaintfinal/.)

Snow, M.S., Kahl, J.S., Norton, S.A., and Olsen, Christine, 

1990, Geochemical determination of salinity sources in 

ground water wells in Maine, in Focus Conference on Eastern Regional Ground Water, Springfield, Mass., Proceedings: Columbus, Ohio, National Ground Water Association, 

October 17–19, 1990, p. 313–327.

State of Maine Judicial Branch, 2008, Jeanannette Waning versus Department of Transportation, Maine Supreme Judicial 

Court docket Cum–07–651: State of Maine Judicial Branch, 

8 p., accessed February 4, 2009, at http://www.courts.state.

me.us/court_info/opinions/2008%20documents/08me95wa.

pdf.

Stewart, D.B., 1998, Geology of northern Penobscot Bay, 

Maine, with contributions to geochronology by Robert D. 

Tucker: U.S. Geological Survey Miscellaneous Investigations Series Map I–2551, 2 sheets, map scale 1:62,500.

Thompson, W.B., and Borns, H.W., Jr., 1985, Surficial 

geologic map of Maine: Maine Geological Survey, scale 

1:500,000.

Transportation Research Board, 1991, Highway deicing—

Comparing salt and calcium magnesium acetate: Washington, D.C., National Research Council, Transportation 

Research Board Special Report 235, accessed December 17, 

2008, at http://onlinepubs.trb.org/Onlinepubs/sr/sr235.html.

U.S. Environmental Protection Agency, 2012, Secondary 

drinking water regulations—guidance for nuisance chemicals: U.S. Environmental Protection Agency, accessed October 30, 2012, at http://water.epa.gov/drink/contaminants/

secondarystandards.cfm.

U.S. Geological Survey, 2009a, National Water Information 

System (NWISWeb): U.S. Geological Survey database, 

accessed November 7, 2009, at http://waterdata.usgs.gov/

me/nwis/.

U.S. Geological Survey, 2009b, Silurian Waterville Formation: U.S. Geological Survey database, accessed July 6, 

2009, at http://tin.er.usgs.gov/geology/state/sgmc-unit.

php?unit=MESw%3B0.

U.S. Geological Survey, 2010, Salt statistical compendium: 

U.S. Geological Survey, accessed April 11, 2012, at http://

minerals.usgs.gov/minerals/pubs/commodity/salt/stat/index.

html.

University of Maine, School of Law, 2003, Bouchard versus 

City of Lewiston civil action, Androscoggin Superior Court 

docket CV–03–124: University of Maine, School of Law, 9 

p., accessed February 4, 2009, at http://mainelaw.maine.edu/

library/SuperiorCourt/decisions/ANDcv-03-124.pdf.

Williams, D.D., Williams, N.E., and Cao, Y., 1999, Road salt 

contamination of groundwater in a major metropolitan 

area and development of a biological index to monitor its 

impact: Water Research, v. 34, no. 1, p. 127–138.
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Appendix 1. Geophysical Data

The following abbreviations and acronyms are used in appendix 1:

ABI acoustic televiewer

amb ambient

Azi azimuth

cond conductance

cps counts per second

deg degrees

deg C degrees Celsius

deg F degrees Fahrenheit

DOT Department of Transportation

EMI electromagnetic induction

Ft, ft, or FT feet

gal/min gallons per minute

HPFM heat-pulse flowmeter

ID identifier

in or in. inches

LMP log-measuring point

ME Maine

MP measuring point

MSI Mount Sopris Instruments

OBI optical televiewer

OGW–BG Office of Groundwater Borehole Geophysics Unit

SC specific conductance

SN serial number

Temp temperature

uS/cm microsiemens per centimeter

USGS U.S. Geological Survey

WL water level

Appendix 1 25
26 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Office/logging unit OGW-BG Storrs

Logs in composite, date and time, manufacturer, serial number (SN), condition 

EMI and Gamma, 06/23/08, MSI-2PIA+2PGA, SN: 2307, gamma factory calibrated; count per second used

 EMI tool - calibrated after log; data adjusted

Fluid and Caliper, 06/23/08, MSI-2PCA+2FSB, SN: 3009, calibration checked after log; data adjusted to calibration

values

OBI-40-Mk4, 06/24/08, MSI-ALT, MSI SN: 073612, Alt SN:061101, tilt and direction check at time of log

ABI-40, 06/23/08, MSI-ALT, MSI SN: 3078, Alt SN: 020906, tilt and direction check at time of log

HPFM, 06/24/08, MSI 2293, SN: 2060, calibration values updated in MsHeat for tool 2060

 ambient and pumping logs collected

Altitude of LMP 342 feet Magnetic declination ~-14

Remarks Stickup=1 foot, Pumping at 0.25-.3 gal/min was conducted as part of stressed flowmeter tests on

6/24/08. 

ME DOT reports elevation of MP at 327.55, USGS reports 342 feet. Well reports indicate 20 feet

of casing, but there appears to be casing to 75.25 feet

Company USGS

County/State Cumberland/Maine

Logging operator MJN, CWS Observer CDJ

Casing depth/diameter/type 75.25 feet / 6 in. / steel

Height of LMP above/below land-surface datum (in feet) 1.0

Date of log 06/23/2008

Site ID 435103070191701

Other ID Gray well

Borehole fluid type Water

Borehole depth/diameter/type 327 feet / 6 in. / open

Borehole fluid depth and date 14.10 feet at 10:05 on 6/23/08

Hydrologic conditions Ambient- Pre-injection conditions

Station name CW-2028

Description of log-measuring point (LMP) Top of casing
Appendix 1 27

Depth

(feet) 

1:150

Travel Time Amplitude Gamma

0 count per second 600

Conductivity (full)

-1000 uS/cm 1000

Fluid Conductivity CW-2028

300 uS/cm 400

Temperature

0 3 Deg C

Image New Caliper

3 to 9 inches

Conductivity (mini)

250 uS/cm 350

New Caliper

0 80 HPFM-Ambient

-0.1 gal/min 0.1

Ambient Interpretation

HPFM-Pumping

-0.4 gal/min 0.4

Pump Interpretation

10

20

30

40

50

60

70

80

90

100

13.70

ambient

WL (ft)

18.10

ending

WL (ft)

71.96

Bottom

of

casing

 (feet) 
28 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

110

120

130

140

150

160

170

180

190

200

210

220

230
Appendix 1 29

240

250

260

270

280

290

300

310

320
30 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

0°

30°

60°

90°

120°

150°

180°

210°

240°

300°

330°

1:64 [ft]

True North

-15 -10 -5 o5 10 15

-5

-10

-15

5

10

15

20.0ft
Appendix 1 31

Depth

 (feet)

OBI-raw ABI-raw Tilt 

0 8

OBI ABI Azi

OBI-Tadpole

0 90

ABI-Tadpole

0 90

OBI-Stereo

Schmidt Plot - Structure

ABI-Stereo

Schmidt Plot - LH - Structure

 OBI

80

100

120

140

160

180

200

220

240

260

280

300

320

Depth: -100.00 [ft] to 330.00 [ft]

Mean

Counts

68

Dip [deg]

31.37

Azi [deg]

134.48

2 39.27 284.54

19 25.34 154.09

3 64.24 272.08

40 30.93 124.14

4 38.15 44.61

0°

180°

Schmidt Plot - Structure

Depth: 50.13 [ft] to 430.00 [ft]

Mean

Counts

3

Dip [deg]

36.90

Azi [deg]

234.48

3 36.90 234.48

0°

180°
32 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Office/logging unit OGW-BG Storrs

Logs in composite, date and time, manufacturer, serial number (SN), condition 

EMI and Gamma, 10/31/07, MSI-2PIA+2PGA, SN: 2307, gamma factory calibrated; count per second used

 NE-EMI tool - calibrated after log; data adjusted

Fluid and Caliper, 10/31/07, MSI-2PCA+2FSB, SN: 3009, calibration checked after log; data adjusted to calibration

values

OBI-40-Mk4, 10/31/07, MSI-ALT, MSI SN: 073612, Alt SN:061101, tilt and direction check at time of log

ABI-40, 10/31/07, MSI-ALT, MSI SN: 3078, Alt SN: 020906, tilt and direction check at time of log

HPFM, 10/31/07, MSI 2293, SN: 2060, calibration values updated in MsHeat for tool 2060

 ambient and pumping logs collected

Altitude of LMP 169 feet

Remarks Stickup=1.5 foot, Pumping at 0.25-.3 gal/min was conducted as part of stressed flowmeter tests on

10/31/07. 

Company USGS

County/State Kennebec/Maine

Logging operator MJN, CWS Observer CDJ

Casing depth/diameter/type 25 feet / 6 in. / steel

Height of LMP above/below land-surface datum (in feet) 1.5

Date of log 10/31/2007

Site ID 441226069502201

Other ID West Gardiner Liberty Lane well

Borehole fluid type Water

Borehole depth/diameter/type 347 feet / 6 in. / open

Hydrologic conditions Ambient- Pre-injection conditions

Station name KW-891

Description of log-measuring point (LMP) Top of casing
Appendix 1 33

Depth Travel time Amplitude

 (feet)

Image

ABI

Gamma

0 count per second 400

Median Amplitude 

0 200

Caliper

Caliper 

0 20 in

Cond.-ambient

0 8000

Temp.-ambient

45 60Deg F

SC-ambient

0 3200

Cond.-post pump

0 8000

Temp.-post pump

45 60Deg F

SC-post pump

0 3200

HPFM-ambient

-0.1 gal/min 0.1

HPFM-pumping

-0.5 gal/min 0.5

20

40

60

80

100

120

140

160

180

200

220

240

260

280

300

320

340
34 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

0°

15°

30°

45°

60°

75°

90°

105°

120°

135°

150°

165°

180°

195°

210°

225°

240°

255°

285°

300°

315°

330°

345°

1:115 [ft]

True North

-30 -20 -10 10 20 30

-10

-20

-30

10

20

30

20.0ft
Appendix 1 35

Office/logging unit OGW-BG Storrs

Logs in composite, date and time, manufacturer, serial number, condition 

EMI and Gamma, 06/25/08, MSI-2PIA+2PGA, SN: 2307, factory calibrated

 NE-EMI tool - calibrated at time of log

Fluid and Caliper, 06/25/08, MSI-2PCA+2FSB, SN: 3009, calibration checked at time of log

OBI-40-Mk4, 06/25/08, MSI-ALT, MSI-SN 073612 Alt SN:061101, tilt and direction check at time of log

ABI-40, 06/26/08, MSI-ALT, MSI SN:3078, ALT SN: 020906, tilt and direction check at time of log

HPFM, 06/26/08, MSI 2293, SN:2060, calibration values updated in MsHeat for tool 2060

 ambient and pumping logs collected

Altitude of LMP 46.13 feet Magnetic declination ~-14 deg

Remarks 120 gallons removed =~80 feet of water column, pulling water from

205 feet to 125 feet

Fractures at 43 feet, 186 feet, 198 feet, and 207 feet are hydraulically

active

Company USGS

County/State Hancock /Maine

Logging operator MJN, CWS Observer CDJ

Casing depth/diameter/type 40 feet / 6 in. / steel

Height of LMP above/below land-surface datum 2.0 feet

Date of log 6/25/08

Site ID 435103070191701

Other ID South Sullivan well

Borehole fluid type Water

Borehole depth/diameter/type 245 feet / 6 in. / open

Borehole fluid depth and date 37.02 feet at 9:54 on 6/25/2008

Hydrologic conditions Ambient with possible tidal influence

Station name HW-181

Description of log-measuring point (LMP) Top of 6-inch steel casing
36 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Depth

 (feet)

Temperature

9 2 Deg C 0

Fluid Cond. - ambient

0 uS/cm 800

Tool Amplitude HW-181

0° 180°90° 270°0°

Caliper

4 7 inch

Tool Image

0° 180°90° 270° 0°

Ambient flow

-0.04 gal/min 0.04

Ambient interpretation

Caliper 

7 4 inch

pumping

-0.8 gal/min 0.8

Interpretation - pumping

Fluid Cond.-pumping

0 uS/cm 800

Gamma

0 cps 500

EMI Cond

10000 cps 20000

20

40

60

80

100

120

140

0.000

-0.007

-0.025

-0.030

-0.032

-0.028

0 027

0.000

0.000

0

0.5

0.5

0 

 Pump set at about 55 ft 
Appendix 1 37

160

180

200

220

240

-0.022

0.000

0.000

0.000

0.000

0.000

0.4

0.100

0.000
38 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

0°

30°

60°

90°

120°

150°

180°

210°

240°

300°

330°

1:13 [ft]

True North

-3.0 -2.0 -1.0 1.0 2.0 3.0

-1.0

-2.0

-3.0

1.0

2.0

3.0

20.0ft
Appendix 1 39

Office/logging unit OGW-BG Storrs

Logs in composite, date and time, manufacturer, , condition 

EMI and Gamma, 06/27/08, MSI-2PIA+2PGA, SN: 2307, factory calibrated

 EMI tool - calibrated at time of log

Fluid and Caliper, 06/27/08, MSI-2PCA+2FSB, SN: 3009, calibration checked at time of log - ambient

 post-pumping log collected after removing 65 gallons of water

OBI-40-Mk4, 06/27/08, MSI-ALT, MSI-SN 073612 Alt SN:061101, tilt and direction check at time of log

ABI-40, 06/27/08, MSI-ALT, MSI SN:3078, ALT SN: 020906, tilt and direction check at time of log

HPFM, 06/27/08, MSI 2293, SN:2060, calibration values updated in MsHeat for tool 2060

 ambient and pumping logs collected

Mag declination ~14

Remarks Domestic submersible pump pulled before logging and re-installed 

at end of day

Altitude of LMP 30.5 feet

Company USGS

Logging operator C. Schalk Observer C. Johnson

County/State Hancock /Maine

Casing depth/diameter/type 15.2 feet / 6 in. / steel

Height of LMP above/below 0.5 feet

Date of log 06/27/2008

Borehole depth/diameter/type 97.16 feet / 6 in. / open

Borehole fluid type Water

Other ID North Sullivan well

Site ID 443145068131801

Hydrologic conditions Ambient and Pumping 

Borehole fluid depth and date 15.50 feet at 8:17 on 06-27-2008

Description of log-measuring point (LMP) Top of casing

Station name HW-180
40 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

Depth

(feet)

Image Caliper

Image-no spin

Fluid Cond - amb

0 1600

Temp - amb

8 12 Deg C

 Travel Time Amplitude Gamma

0 200cps

EMI-Conductivity

250 uS/cm 350

Ambient HPFM

-1.25 gal/min 1.25

Ambient Interpretation

Caliper

2 8 inch

Amplitude median

0 100

Fluid Cond - pump

0 1600

 Temp - pump

8 12 Deg C

 Cond ambient

0 2000

Cond pump

0 2000

EMI-Conductivity

-600 600

OBI-Structure Pumping HPFM

-1.25 gal/min 1.25

 Pump Interpretation

10

20

30

40

50

60

70

80

90
Appendix 1 41

0° 10°

20°

30°

40°

50°

60°

70°

80°

90°

100°

110°

120°

130°

140°

150°

160°

170° 180° 190°

200°

210°

220°

230°

240°

250°

260°

280°

290°

300°

310°

320°

330°

340°

350°

1:3 [ft]

True North

-0.8 -0.6 -0.4 -0.2 0.2 0.4 0.6 0.8

-0.2

-0.4

-0.6

-0.8

0.2

0.4

0.6

0.8

10.0ft
Depth Image

(feet) 

AmplitudeABI ABI Tadpole

0 90

ABI-Stereo

Schmidt Plot - Structure

OBI Tadpole

0 90

 OBI OBI-Stereo 

Image

30

40

50

60

70

80

90

0°

180°

0°

180°

42 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9
Appendix 2. Daily Water Levels, Specific Conductance, 

and Precipitation, All Wells

Figure 2–1. Graph showing water levels, liquid-equivalent precipitation, and specific conductance 

in U.S. Geological Survey well 435103070191701 in Gray, Maine, December 2007–May 2009.

Figure 2–2. Graph showing water levels, liquid-equivalent precipitation, and specific conductance 

in U.S. Geological Survey well 441226069502201 in West Gardiner, Maine, August 2007–November 

2009.

Figure 2–3. Graph showing water levels, liquid-equivalent precipitation, and specific conductance 

in U.S. Geological Survey well 443145068131801 in North Sullivan, Maine, September 2007–June 2009.

Figure 2–4. Graph showing water levels, liquid-equivalent precipitation, and specific conductance 

in U.S. Geological Survey well 443113068115101 in South Sullivan, Maine, January 2008–June 2009.

Appendix 2 43
44 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

450

455

460

465

470

475

480

0 485

2

4

6

8

10

12

14

16

12/15/2007 2/15/2008 4/15/2008 6/15/2008 8/15/2008 10/15/2008 12/15/2008 2/15/2009 4/15/2009

Specific conductance, in microsiemens per centimeter at 25 degrees Celsius

-

Date

Water level

Precipitation

Specific conductance

EXPLANATION

Water level, in feet below land surface, or liquid-equivalent precipitation, in inches

Figure 2–1. Graph showing water levels, liquid-equivalent precipitation, and specific conductance in U.S. Geological Survey well 

435103070191701 in Gray, Maine, December 2007–May 2009.
Appendix 2 45

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 4,500

2

4

6

8

10

12

9/1/2007 12/1/2007 3/1/2008 6/1/2008 9/1/2008 12/1/2008 3/1/2009 6/1/2009 9/1/2009

Specific conductance, in microsiemens per centimeter at 25 degrees Celsius

Date

Water level

Precipitation

Specific conductance

EXPLANATION

Water level, in feet below land surface, or liquid-equivalent precipitation, in inches

Figure 2–2. Graph showing water levels, liquid-equivalent precipitation, and specific conductance in U.S. Geological Survey well 

441226069502201 in West Gardiner, Maine, August 2007–November 2009.
46 Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 5,000

2

4

6

8

10

12

14

16

18

20

9/17/2007 12/17/2007 3/17/2008 6/17/2008 9/17/2008 12/17/2008 3/17/2009

Specific conductance, in microsiemens per centimeter at 25 degrees Celsius

Date

Water level

Precipitation

Specific conductance—80 feet

EXPLANATION

Specific conductance—40 feet

Water level, in feet below land surface, or liquid-equivalent precipitation, in inches

Figure 2–3. Graph showing water levels, liquid-equivalent precipitation, and specific conductance in U.S. Geological Survey well 

443145068131801 in North Sullivan, Maine, September 2007–June 2009.
Appendix 2 47

100

200

300

400

500

600

700

800

900

0 1,000

5

10

15

20

25

30

35

40

1/10/2008 3/10/2008 5/10/2008 7/10/2008 9/10/2008 11/10/2008 1/10/2009 3/10/2009 5/10/2009

Specific conductance, in microsiemens per centimeter at 25 degrees Celsius

Date

Water level

Precipitation

Specific conductance—42 feet

EXPLANATION

Specific conductance—220 feet

Water level, in feet below land surface, or liquid-equivalent precipitation, in inches

45 0

Figure 2–4. Graph showing water levels, liquid-equivalent precipitation, and specific conductance in U.S. Geological Survey well 

443113068115101 in South Sullivan, Maine, January 2008–June 2009.
THIS PAGE INTENTIONALLY LEFT BLANK
Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

Office Chief

U.S. Geological Survey

New England Water Science Center 

Maine Water Science Office

196 Whitten Road

Augusta, ME 04330

dc_me@usgs.gov

or visit our Web site at:

http://me.water.usgs.gov
Schalk and Stasulis—Relations Among Three Variables in Four Road-Salt-Contaminated Wells in Maine, 2007–9—Scientific Investigations Report 2012–5205