Groundwater Quality and Simulation of Sources of Water 

to Wells in the Marsh Creek Valley at the U.S. Geological 

Survey Northern Appalachian Research Laboratory, 

Tioga County, Pennsylvania

Scientific Investigations Report 2012–5042

U.S. Department of the Interior

U.S. Geological Survey
Cover. Photograph of Marsh Creek valley looking west from the Northern Appalachian Research Laboratory, November 2, 2010. 

(Photograph courtesy of Linda Jo Kraemer)
Groundwater Quality and Simulation of 

Sources of Water to Wells in the Marsh 

Creek Valley at the U.S. Geological 

Survey Northern Appalachian Research 

Laboratory, Tioga County, Pennsylvania

By Dennis W. Risser and Kevin J. Breen

Scientific Investigations Report 2012–5042

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:

Risser, D.W., and Breen, K.J., 2012, Groundwater quality and simulation of sources of water to wells in the Marsh 

Creek valley at the U.S. Geological Survey Northern Appalachian Research Laboratory, Tioga County, Pennsylvania: 

U.S. Geological Survey Scientific Investigations Report 2012-5042, 41 p., at http://pubs.usgs.gov/sir/2012/5042/.
iii

Figures

1. Map showing the location of the study area in the Marsh Creek valley, near 

Wellsboro, Tioga County, Pennsylvania....................................................................................3

2. Photograph showing Northern Appalachian Research Laboratory NARL well 3 

(TI 271) showing the A, wellhead and concrete cover of the access pit, and 

B, sampling port on supply pipe in the pit.................................................................................7

3. Photograph showing equipment for sampling groundwater for radium...........................14

4. Map showing finite-difference grid and boundary conditions for the 

groundwater-flow model of Marsh Creek valley, Tioga County, Pennsylvania................22

5. Map showing steady-state groundwater budgets for average and dry hydrologic

conditions without groundwater withdrawals simulated by the groundwater-flow

model of Marsh Creek valley, Tioga County, Pennsylvania .................................................24

Contents

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

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

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

Previous Investigations........................................................................................................................2

Study Methods ..............................................................................................................................................4

Groundwater-Quality Sampling ..........................................................................................................4

Collection and Analysis of Samples .........................................................................................4

Quality Assurance......................................................................................................................16

Simulation of Groundwater Sources to Wells................................................................................16

Updates to the Model................................................................................................................16

Steady-State Simulation Inputs and Parameters.................................................................21

Groundwater Quality in Marsh Creek Valley...........................................................................................23

Sources of Water from Steady-State Simulations .................................................................................25

Average Conditions with 1,000 Gallons per Minute Withdrawals .............................................25

Average Conditions with 2,000 Gallons per Minute Withdrawals ..............................................25

Average Conditions with 2,000 Gallons per Minute Withdrawals Plus 1,000 Gallons 

per Minute Withdrawal from the New Production Well.................................................25

Average Conditions with 3,000 Gallons per Minute Withdrawals Plus 1,000 Gallons 

per Minute Withdrawal from the New Production Well.................................................29

Dry Conditions with 1,000 Gallons per Minute Withdrawals .......................................................29

Dry Conditions with 1,000 Gallons per Minute Withdrawals Plus 1,000 Gallons 

per Minute Withdrawal from the New Production Well.................................................29

Dry Conditions with 2,000 Gallons per Minute Withdrawals .......................................................34

Dry Conditions with 2,000 Gallons per Minute Withdrawals Plus 1,000 Gallons 

per Minute Withdrawal from the New Production Well.................................................34

Time of Travel.......................................................................................................................................34

Assumptions and Limitations of the Model Simulations ..............................................................34

Summary and Conclusions.........................................................................................................................39

References Cited..........................................................................................................................................40
iv

6. Map showing simulated A, areas contributing recharge to wells and water-table

contours, B, sources of water to wells, and C, hydraulic response of the aquifer

during average hydrologic conditions with withdrawals of 1,000 gallons per minute

from the Northern Appalachian Research Laboratory (NARL) wells, Tioga County,

Pennsylvania ...............................................................................................................................26

7. Map showing simulated A, areas contributing recharge to wells and water-table

contours, B, sources of water to wells, and C, hydraulic response of the aquifer

during average hydrologic conditions with withdrawals of 2,000 gallons per minute

from the Northern Appalachian Research Laboratory (NARL) wells, Tioga County,

Pennsylvania ...............................................................................................................................27

8. Map showing simulated A, areas contributing recharge to wells and water-table

contours, B, sources of water to wells, and C, hydraulic response of the aquifer

during average hydrologic conditions with withdrawals of 2,000 gallons per minute

from the Northern Appalachian Research Laboratory (NARL) wells and 

1,000 gallons per minute from the new well, Tioga County, Pennsylvania........................28

9. Map showing simulated additional drawdown caused by a proposed groundwater

withdrawal of 1,000 gallons per minute southwest of the Northern Appalachian

Research Laboratory (NARL) during average hydrologic conditions, Tioga County,

Pennsylvania ...............................................................................................................................30

10. Map showing simulated A, areas contributing recharge to wells and water-table

contours, B, sources of water to wells, and C, hydraulic response of the aquifer

during average hydrologic conditions with withdrawals of 3,000 gallons per minute

from the Northern Appalachian Research Laboratory (NARL) wells and 

1,000 gallons per minute from a new production well, Tioga County, Pennsylvania.......31

11. Map showing simulated A, areas contributing recharge to wells and water-table

contours, B, sources of water to wells, and C, hydraulic response of the aquifer

during dry hydrologic conditions with withdrawals of 1,000 gallons per minute 

from the Northern Appalachian Research Laboratory (NARL) wells, Tioga County,

Pennsylvania ...............................................................................................................................32

12. Map showing steady-state simulation of groundwater flow showing A, areas

contributing recharge to wells and water-level contours, B, sources of water to

wells, and C, hydraulic response of the aquifer during dry hydrologic conditions

with withdrawals of 1,000 gallons per minute from the Northern Appalachian

Research Laboratory (NARL) wells and 1,000 gallons per minute from a new

production well, Tioga County, Pennsylvania ........................................................................33

13. Map showing simulated A, areas contributing recharge to wells and water-table

contours, B, sources of water to wells, and C, hydraulic response of the aquifer

during dry hydrologic conditions with withdrawals of 2,000 gallons per minute from

the Northern Appalachian Research Laboratory (NARL) wells, Tioga County,

Pennsylvania ...............................................................................................................................35

14. Map showing simulated A, areas contributing recharge to wells and water-table

contours, B, sources of water to wells, and C, hydraulic response of the aquifer

during dry hydrologic conditions with withdrawals of 2,000 gallons per minute 

from the Northern Appalachian Research Laboratory (NARL) wells and 

1,000 gallons per minute from a new production well, Tioga County, Pennsylvania.......36

15. Map showing simulated additional drawdown caused by a proposed groundwater

withdrawal of 1,000 gallons per minute southwest of the Northern Appalachian

Research Laboratory (NARL) during dry hydrologic conditions, Tioga County,

Pennsylvania ...............................................................................................................................37

16. Map showing simulated areas contributing recharge to wells and extent of the

areas captured during 100 or 200 days of steady pumping during dry hydrologic

conditions in the model area, Tioga County, Pennsylvania .................................................38
v

Tables

1. Water-quality characteristics and constituents from a periodic sampling program

for selected ions and other measures in groundwater from wells sampled in the 

Marsh Creek valley, Tioga County, Pennsylvania, 2010..........................................................5

2. Characteristics and identifiers of wells from which samples were collected in the

Marsh Creek valley, Tioga County, Pennsylvania, November 2–4, 2010..............................6

3. Water-quality characteristics, major ions, and nutrients in groundwater from 

wells sampled in the Marsh Creek valley, Tioga County, Pennsylvania, 

November 2–4, 2010 .....................................................................................................................8

4. Trace metals and radiochemicals in groundwater from wells sampled in the 

Marsh Creek valley, Tioga County, Pennsylvania, November 2–4, 2010............................10

5. Detailed radiochemical analytical results for water samples collected from wells 

in the Marsh Creek valley, Tioga County, Pennsylvania, November 2–4, 2010.................11

6. Dissolved gases in groundwater from wells sampled in the Marsh Creek valley,

Tioga County, Pennsylvania, November 2–4, 2010. ..............................................................13

7. Stable isotopic composition of hydrogen, oxygen, and carbon in groundwater 

from wells sampled in the Marsh Creek valley, Tioga County, Pennsylvania, 

November 2–4, 2010 ...................................................................................................................14

8. Summary of laboratories, laboratory codes, and methods used to analyze water

samples collected in the Marsh Creek valley, Tioga County, Pennsylvania,

November 2–4, 2010 ...................................................................................................................15

9. Analytical results for the environmental sample and the sequential replicate

of groundwater from well 2 (TI 270) in the Marsh Creek valley, Tioga County,

Pennsylvania, November 3, 2010..............................................................................................17

10. Performance of the U.S. Geological Survey National Water Quality Laboratory 

in analyzing standard-reference samples in the fall 2010 inter-laboratory 

comparison study .......................................................................................................................20

11. Hydrologic conditions and pumping rates simulated by the steady- state

groundwater-flow model of Marsh Creek valley, near Wellsboro, Tioga County,

Pennsylvania. .............................................................................................................................23
vi

Conversion Factors, Datum and Abbreviations

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

liter (L) 0.2642 gallon (gal)

Flow Rate

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

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

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

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

Pressure

inch of mercury at 60°F (in Hg) 3.377 kilopascal (kPa) 

Radioactivity

picocurie per liter (pCi/L) 0.037 becquerel per liter (Bq/L) 

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

°F=(1.8×°C)+32

Vertical coordinate information is referenced to theNational Geodetic Vertical Datum of 1929 

(NGVD 29).”

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

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

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C).

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

or micrograms per liter (μg/L) or picocuries per liter (pCi/L).
vii

List of Acronyms

ARGUS Argus Numerical Environments 

MCL maximum contaminant level

NARL Northern Appalachian Research Laboratory

NWQL National Water Quality Laboratory 

PADEP Pennsylvania Department of Environmental Protection 

SRBC Susquehanna River Basin Commission 

USEPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey
This page has been left blank intentionally.
Groundwater Quality and Simulation of Sources of Water 

to Wells in the Marsh Creek Valley at the U.S. Geological 

Survey Northern Appalachian Research Laboratory, 

Tioga County, Pennsylvania

By Dennis W. Risser and Kevin J. Breen 

infiltration from Straight Run, a tributary to Marsh Creek, 

provides nearly all the water to the NARL wells. During dry 

conditions, the areas contributing recharge expand such that 

Asaph Run contributes about half of the water to the NARL 

wells when withdrawals are 1,000 or 2,000 gallons per minute. 

The addition of a simulated withdrawal of 1,000 gallons per 

minute from the nearby new well does not substantially affect 

the sources of water captured by the NARL wells.

These results are subject to some limitations. The waterquality samples represent a snapshot of groundwater chemistry 

for only one hydrologic condition; the concentrations of some 

constituents may change temporally. In addition, samples were 

collected and analyzed for hydrocarbon gases, but not organic 

constituents associated with hydraulic fracturing; additional 

sampling for these constituents would provide a more 

complete water-quality baseline. The sources contributing 

water to the NARL wells and the new well were simulated 

by use of a simplified one-layer model of the glacial sand and 

gravel aquifer for steady-state conditions that in reality are 

never achieved. Steady-state simulations of dry hydrologic 

conditions show that it is possible for the NARL wells to 

capture water from Asaph Run; however, maps of simulated 

groundwater time-of-travel indicate that a dry period of 

unusually long duration would be required. A better analysis 

could be done by recalibrating the groundwater-flow model 

with a finite-difference grid having multiple layers, cells 

smaller than the 200-foot by 200-foot cells used in this study, 

and transient stress periods.

Introduction

Development of natural-gas resources from the 

Marcellus Shale is underway in the vicinity of the U.S. 

Geological Survey (USGS) Northern Appalachian Research 

Laboratory (NARL) near Wellsboro, Pennsylvania (fig. 1). 

Gas wells are being permitted and drilled in the Marsh 

Creek valley and adjacent uplands to the north and south 

of the valley. From November 2009 to June 2010, 50 wells 

Abstract

This report provides a November 2010 snapshot of 

groundwater quality and an analysis of the sources of water 

to wells at the U.S. Geological Survey (USGS) Northern 

Appalachian Research Laboratory (NARL) near Wellsboro, 

Pennsylvania. The laboratory, which conducts fisheries 

research, currently (2011) withdraws 1,000 gallons per minute 

of high-quality groundwater from three wells completed in 

the glacial sand and gravel aquifer beneath the Marsh Creek 

valley; a fourth well that taps the same aquifer provides the 

potable supply for the facility. The study was conducted to 

document the source areas and quality of the water supply for 

this Department of Interior facility, which is surrounded by the 

ongoing development of natural gas from the Marcellus Shale. 

Groundwater samples were collected from the four wells 

used by the NARL and from two nearby domestic-supply 

wells. The domestic-supply wells withdraw groundwater from 

bedrock of the Catskill Formation. Samples were analyzed for 

major ions, nutrients, trace metals, radiochemicals, dissolved 

gases, and stable isotopes of oxygen and hydrogen in water 

and carbon in dissolved carbonate to document groundwater 

quality. Organic constituents (other than hydrocarbon gases) 

associated with hydraulic fracturing and other human activities 

were not analyzed as part of this assessment. Results show low 

concentrations of all constituents. Only radon, which ranged 

from 980 to 1,310 picocuries per liter, was somewhat elevated. 

These findings are consistent with the pristine nature of the 

aquifer in the Marsh Creek valley, which is the reason the 

laboratory was sited at this location.

The sources of water and areas contributing recharge to 

wells were identified by the use of a previously documented 

MODFLOW groundwater-flow model for the following 

conditions: (1) withdrawals of 1,000 to 3,000 gallons per 

minute from the NARL wells, (2) average or dry hydrologic 

conditions, and (3) withdrawals of 1,000 gallons per minute 

from a new well 3,500 feet to the southwest that was drilled 

to provide water for Marcellus gas-well operations. Results of 

simulations indicate that during average hydrologic conditions, 
2 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

were permitted within a 200-square-mile area (mi2) around 

the NARL. Land disturbance from access roads, gas wells, 

and pipeline construction is anticipated, and hydrologic 

effects from hydraulic fracturing with associated water use 

and waste handling are possible. A monitoring program is 

needed to document potential effects of the gas exploration 

and production activities on the quantity and quality of water 

produced by wells completed in and adjacent to the valley.

The NARL is an aquatic biology research station of the 

USGS with facilities that include an outdoor raceway system 

and wet and dry laboratories. The NARL was established in 

the late 1970s after a lengthy search for a pristine water supply 

of sufficient quantity and quality. Water for operations of the 

55-acre, four-building complex is obtained from four wells 

that tap the glacial sand and gravel aquifer beneath the Marsh 

Creek valley.

Wells 1, 3, and 5 withdraw a combined total of 

1,000 gallons per minute (gal/min) for fisheries research, 

and well 2 provides the potable supply for the facility. 

Hereafter, the four wells are collectively termed the NARL 

wells. The NARL groundwater withdrawals are nearly 

100 percent non-consumptive. The small withdrawals for 

domestic-supply use from well 2 are returned through an 

on-site wastewater leach field, and the withdrawals for the fish 

hatchery from wells 1, 3, and 5 are discharged about 400 feet 

(ft) downstream from the confluence of Straight Run and 

Marsh Creek. The metered discharge is equal to or greater 

than the metered total withdrawals from the wells (William 

Lellis, Director, U.S. Geological Survey Northern Appalachian 

Research Laboratory, oral commun., 2011). Total groundwater 

withdrawals of as much as 3,000 gal/min are permitted by 

the Susquehanna River Basin Commission under certain 

hydrologic conditions provided that the streamflow in Straight 

Run and groundwater levels beneath wetlands are monitored 

(Susquehanna River Basin Commission, 2003).

The NARL is a public resource that is used to perform 

large-scale laboratory and field research on aquatic organisms. 

To help protect Department of Interior interests and 

infrastructure from the possible effects of gas exploration and 

production activities, a study was initiated on October 1, 2010, 

to collect initial samples to document groundwater quality in 

the glacial sand and gravel and the bedrock aquifers, and to 

identify the sources of water for the NARL wells.

The glacial sand and gravel aquifer in the Marsh Creek 

valley near the NARL is a potential source of water for 

hydraulic fracturing operations associated with gas-well 

development. A permit to withdraw 1,000 gal/min of water 

from a new well in the glacial sand and gravel aquifer 3,500 ft 

southwest of the NARL is now (March 2011) pending with 

the Susquehanna River Basin Commission (SRBC). Use of 

water for hydraulic fracturing is assumed to be 100 percent 

consumptive by the SRBC, so in this study, simulated 

withdrawals of water from this well are assumed to be lost 

to the glacial sand and gravel aquifer. A determination of the 

areas contributing recharge and sources of water to NARL 

wells is needed to protect the water supply from potential 

sources of contamination and possible declines in yield as a 

result of additional withdrawals. Understanding the sources 

of water and potential flow paths to the NARL wells is 

important if the need arises to modify operations to address 

the transport of contaminants that may enter the glacial sand 

and gravel aquifer from a source related to resource extraction 

or other activities.

The glacial sand and gravel aquifer is composed of 

interbedded silty sand and gravel lenses, laid down as icecontact and stream deposits, overlain by alluvium and finegrained swamp deposits (Williams, 1991). In the vicinity of 

the NARL, the glacial sand and gravel aquifer ranges from a 

few feet thick at the bounding valley walls to a maximum of 

about 120 ft. The glaciated valley and surrounding uplands 

are underlain mostly by sandstone and shale of Devonian 

through Pennsylvanian age, mantled by less than 10 ft of 

till. The bedrock is a much less productive aquifer than the 

glacial-drift deposits beneath the valley floor. Williams (1991) 

determined that recharge to the glacial sand and gravel aquifer 

is derived mostly from infiltration of water from Straight Run 

and Asaph Run (71 percent of the total). The remainder of 

the recharge is provided by unchanneled runoff, groundwater 

inflow from upvalley, and precipitation on the valley. 

Purpose and Scope

This report provides (1) a snapshot during November 

2–4, 2010, of the groundwater quality in the four NARL wells 

completed in the glacial sand and gravel aquifer and in two 

nearby private domestic-supply wells completed in fractured 

bedrock and (2) an estimation of the areas contributing 

recharge and sources of water to wells at the NARL by the 

use of a previously documented groundwater-flow model of 

the glacial sand and gravel aquifer. Groundwater-quality data 

include concentrations of major ions, nutrients, trace elements, 

radiochemicals, dissolved gases, and stable isotopes of oxygen 

and hydrogen in water and carbon in dissolved carbonate; 

these data provide some documentation of the groundwater 

geochemistry of the glacial sand and gravel and bedrock 

aquifers at and near the NARL. This study does not establish 

a baseline for organic constituents (other than hydrocarbon 

gases) associated with hydraulic fracturing activities, though 

establishing a baseline for selected anthropogenic organic 

compounds would provide a more complete water-quality 

baseline and would be a useful objective for future sampling. 

The areas contributing recharge and sources of groundwater 

to wells were determined from simulations of steady-state 

groundwater flow conducted by the use of a two-dimensional 

MODFLOW model previously documented by Williams and 

Morrissey (1996).

Previous Investigations

Williams (1991) describes the hydrology of the Marsh 

Creek valley and the hydraulics of groundwater/surface-water 
Introduction 3

Figure 1. Location of the study area in the Marsh Creek valley, near Wellsboro, Tioga County, Pennsylvania.

Marsh Creek

Straight Run

Asaph Run

Wellsboro

Tl 729

3

2 5

1

Tl 536

New well

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-quality sampling well and identifier

3

TI-729

Northern Appalachian Research Laboratory

production

Private domestic-supply

New well

Well–Site of proposed withdrawal
4 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

interactions at the NARL (formerly the National Fisheries 

Research and Development Laboratory). Williams established 

that infiltration from streams draining the bedrock uplands 

provided 71 percent of the recharge to the glacial sand and 

gravel aquifer and described the concentrations of selected 

major ionsin groundwater. Risser and Madden (1994) used 

a two-dimensional groundwater model to compare different 

approaches for delineating areas contributing recharge to 

the NARL wells, but this (1992) model was not calibrated to 

observations of groundwater levels or streamflow; thus, those 

results should be considered rough estimates. Williams and 

Morrissey (1996) constructed a calibrated two-dimensional 

groundwater model to simulate stream seepage and generate 

water budgets for the glacial sand and gravel aquifer but did 

not delineate areas contributing recharge to the NARL wells.

Water-quality samples from the NARL wells were 

collected and analyzed during the spring (February and 

March) and fall (October and November) of 2010 by a 

private laboratory. The samples were analyzed for major ions, 

trace metals, bacteria, and methane to provide background 

information on constituents that are often associated with 

contamination from the extraction of natural gas. Results 

from the private laboratory are listed in table 1 to allow for 

comparison to the suite of constituents analyzed at lower 

detection limits for this study.

Study Methods 

The study was conducted by sampling groundwater 

from wells and simulating groundwater flow by use of a 

numerical model. Groundwater samples were analyzed and 

quality-assurance measures were reported. Simulations of 

groundwater flow were accomplished by updating an available 

numerical model and simulating the sources of water and areas 

contributing recharge to wells.

Groundwater-Quality Sampling

Groundwater samples were collected from the four 

NARL wells and two nearby privately owned domesticsupply wells during November 2–4, 2010. The locations 

of the wells are shown in figure 1, and the local names and 

USGS identifiers are cross referenced in table 2. Samples 

were analyzed for broad sets of chemical constituents at 

detection levels that allow concentrations at low levels to be 

quantified. Organic constituents associated with hydraulicfracturing activities were not analyzed, primarily because of 

budget limitations.

Collection and Analysis of Samples

Water samples were collected from the wells and were 

processed using standard field methods of the USGS (U.S. 

Geological Survey, variously dated). The NARL wells had 

been pumping for at least 24 hours prior to sampling, and 

the private domestic-supply wells were purged using the 

homeowner’s pump, then sampled after stabilization of field 

water-quality characteristics. Water was collected from the 

wells through a 15-ft length of polytetrafluoroethylene- 

(PTFE) lined plastic tubing, hereafter termed “sampling 

tubing,” with a 0.45-micron capsule filter attached to the 

discharge end of the tubing, which minimized exposure of 

the sample to the atmosphere. Water samples were obtained 

directly from wells 1, 3, and 5 (TI 269, TI 271, and TI 730, 

respectively) by attaching the sampling tubing to the sampling 

port on the distribution pipe that was accessible in a pit 

adjacent to the well (fig. 2). Water from well 2 (TI 270) was 

obtained through the sampling tubing attached to a spigot on a 

large (about 1,200 gal) holding tank in the laboratory isolation 

room. The spigot on the tank was opened for 24 hours prior 

to sampling to flush out the water stored in the tank. Water 

from the private domestic-supply wells was collected through 

the sampling tubing attached to a spigot on the pressure tank 

inside the house at well TI 729 and attached to the frost-free 

hydrant at the wellhead for well TI 536.

Water from each well was analyzed for field properties, 

major ions, nutrients, trace metals, radiochemicals, dissolved 

gases, and stable isotopes (tables 3–7). The pH, water 

temperature, specific conductance, dissolved oxygen, and 

oxidation-reduction potential were measured in the field with 

a multi-parameter meter and flow-through chamber that was 

connected to the sampling tubing. Alkalinity (acid neutralizing 

capacity) was titrated in the field at the time of sample 

collection. Samples were processed according to protocols 

outlined in Wilde and others (2004) and, except for the 

samples for radium and uranium, were preserved and chilled 

(if necessary), then shipped to the appropriate laboratory by 

overnight express under chain-of-custody protocols. Radium 

and uranium isotopes were processed in the field by flushing 

at least 100 gallons of water directly from the well though 

filters impregnated with potassium permanganate (fig. 3). 

Those filters were driven directly to the USGS radiochemistry 

laboratory in Reston, Virginia, for analysis after all wells 

were sampled.

The following laboratories were used to analyze the water 

samples. Details about the laboratory codes and methods for 

each constituent are listed in table 8.

• USGS National Water Quality Laboratory (NWQL)—

Major ions, nutrients, trace metals, and radon.

• Eberline Services, Inc.—Gross alpha and gross 

beta radioactivity.

• USGS radiochemical laboratory in Reston, Virginia—

Isotopes of radium and uranium.

• Isotech Laboratories, Inc.—Dissolved gases and 

stable isotopes.

The NWQL is certified by the National Environmental 

Laboratory Accreditation Program for analysis of nonpotable 

waters using USGS methods. Details about the NWQL 
Study Methods 

5

Table 1. Water-quality characteristics and constituents from a periodic sampling program for selected ions and other measures in groundwater from wells sampled in the Marsh Creek valley, Tioga County, Pennsylvania, 2010.[USGS, U.S. Geological Survey; PADEP, Pennsylvania Department of Environmental Protection; MCL, maximum contaminant level; USEPA, U.S. Environmental Protection Agency; Grab sampling and analysis of unfiltered groundwater by Seewald Laboratories, Inc.; --, not determined; NA, not applicable; °C, degrees Celsius; NTU, nephelometric turbidity unit; <, less than; MBAS, methylene-blue active substances; X, presence or absence of total coliforms based on number or percentage of total coliform positive samples per month or fecal coliform or E. coli positive routine or check samples.]

USGS well name TI 269 TI 270 TI 271 TI 730

PADEP 

MCL1

Local well name Well 1 Well 2 Well 3 Well 5

Date sampled 2/25/2010 11/2/2010 2/25/2010 10/19/2010 3/2/2010 10/19/2010 3/9/2010 11/2/2010

Time sampled (local) 11:20 09:25 11:05 09:40 09:30 09:50 10:15 09:15

Value, in units as noted

Characteristics

Water temperature (°C, field) 8.8 8.30 8.0 12.3 8.3 9.7 13.1 8.30 NA

pH (field) 7.3 7.22 7.55 6.84 7.87 8.09 7.33 7.40 6.5–8.5*pH (laboratory) 6.97 6.83 6.83 6.93 8.13 8.09 7.25 6.99 6.5–8.5*

Turbidity, in NTU (field) 0.09 <0.05 0.22 <0.05 0.28 <0.05 0.18 <0.05 NA

Concentration, in milligrams per liter

Major constituents

Alkalinity, as calcium carbonate -- 30.0 -- 28.0 -- 46.0 -- 34.0 NA

Chloride (USEPA Method 300.0) 1.99 2.33 1.57 1.72 1.89 2.39 1.66 1.60 250*Dissolved solids dried at 180°C 98 34 70 57 36 78 53 59 500*Hardness, as calcium carbonate -- 10.0 -- 8.00 -- 64.0 -- 14.0 NASodium (USEPA Method 200.7) 1.52 1.66 1.24 1.61 1.8 1.65 1.4 1.30 NA

Concentration, in micrograms per liter

Trace metals and other measures

Arsenic (USEPA Method 200.7) <1 <1 <1 <1 <1 1 <1 <1 10

Barium (USEPA Method 200.7) 30 30 10 10 30 40 20 20 200Iron (USEPA Method 200.7) <10 <10 50 20 10 <10 10 10 300*Methane <20 <20 <20 <20 <20 <20 <20 <20 NAStrontium (USEPA Method 200.7) 40 40 40 40 40 50 40 40 NASulfate (USEPA Method 300.0) -- 8.75 -- 8.20 -- 8.63 -- 8.23 NASulfide <50 <50 <50 <50 <50 <50 <50 <50 NASurfactants, MBAS <50 <50 <50 <50 <80 <50 <50 <50 NA

Most probable number per 100 milliliters of water

Bacteria

Total coliform <2 <2 <2 <2 <2 <2 <2 <2 X

Fecal coliform <2 <2 <2 <2 <2 <2 <2 <2 X

1Primary and secondary maximum contaminant levels for public supplies of drinking water (April 2006) are listed where applicable. The values are for primary contaminants except where followed by an 

“*”, denoting a secondary contaminant.
6 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania Table 2. Characteristics and identifiers of wells from which samples were collected in the Marsh Creek valley, Tioga County, Pennsylvania, November 2–4, 2010. [USGS, U.S. Geological Survey; --, not determined; NARL, Northern Appalachian Research Laboratory; Private, household-supply well owned by private individual] Characteristic Well USGS well name TI 269 TI 270 TI 271 TI 536 TI 729 TI 730 Local well name Well 1 Well 2 Well 3 -- -- Well 5 USGS site identifier 414634077235201 414637077235601 414640077235101 414639077234001 414655077240501 414637077235203 Owner NARL NARL NARL Private Private NARL Date sampled 11/2/2010 11/3/2010 11/4/2010 11/4/2010 11/3/2010 11/2/2010 Time sampled 13:00 12:00 09:00 11:45 09:00 15:00 Year drilled 1977 1977 1977 1985 1997 2000 Well depth (feet) 93 96 97 114 90 105 Open interval (feet below land surface) 73–93 77–96 70–81 and 94–97 34–114 53–90 76–85 and 94–105 Geologic unit Glacial outwash Glacial outwash Glacial outwash Catskill Formation Catskill Formation Glacial outwash Use of water Aquaculture Domestic Aquaculture Domestic Domestic Aquaculture Lithology Sand/gravel Sand/gravel Sand/gravel Shale Shale Sand/gravel Depth to water (feet below land surface during sampling)1 33 18 27 -- -- 52

1Determined from airline in well.
Study Methods 7

B

Sampling port

A

Well head

Pit with concrete cover

Figure 2. Northern Appalachian Research Laboratory NARL well 3 (TI 271) showing the A,

wellhead and concrete cover of the access pit, and B, sampling port on supply pipe in the pit.
8 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania Table 3. Water-quality characteristics, major ions, and nutrients in groundwater from wells sampled in the Marsh Creek valley, Tioga County, Pennsylvania, November 2–4, 2010. [USGS, U.S. Geological Survey; PADEP, Pennsylvania Department of Environmental Protection; MCL, maximum contaminant level; --, not determined; °C, degrees Celsius; mm Hg, millimeters of mercury; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per liter; CaCO3, calcium carbonate; SHE, standard hydrogen electrode; <, less than; N, nitrogen; P, phosphorus; SiO2, silicon dioxide] Characteristics USGS well name: TI 269 TI 270 TI 271 TI 536 TI 729 TI 730 PADEP MCL1 Local well name: Well 1 Well 2 Well 3 private private Well 5 Date sampled: 11/2/2010 11/3/2010 11/4/2010 11/4/2010 11/3/2010 11/2/2010 Time sampled, local: 13:00 12:00 09:00 11:45 09:00 15:00 Value, in units as noted Depth to water in well (feet below land surface) 33 18 53 -- -- 52 Water temperature (°C) 9.2 11.3 9.1 10.0 10.9 9.1 Barometric pressure (mm Hg) 743 737 724 724 737 743 Specific conductance (μS/cm) 92 81 118 110 99 93 Dissolved oxygen (mg/L) 7.8 8.9 7.5 7.9 8.6 8.2 Dissolved oxygen (percent saturation) 70 84 68 74 80 73 pH 6.3 6.4 8.0 6.9 6.5 6.5 6.5–8.5* Carbon dioxide (mg/L) 35 22 1.1 9.6 21 22 Acid neutralizing capacity2 (mg/L as CaCO3

) 34.6 28.6 52.1 39.1 35.1 34.6

Oxidation reduction potential [SHE] (millivolts) 440 340 290 350 300 210

Concentration, in milligrams per liter

Major ions3

Calcium 12.1 10.9 19.0 16.5 7.58 12.7Magnesium 1.93 1.81 2.00 2.08 1.39 1.92Sodium 1.71 1.44 1.68 1.75 10.5 1.51Potassium 0.76 0.78 0.78 0.74 0.81 0.80Bicarbonate 42.2 34.9 63.5 47.7 42.8 42.2Chloride 2.48 1.57 2.14 2.07 3.53 1.69 250*Sulfate 8.74 8.33 8.74 10.9 9.86 8.4 250*Fluoride 0.06 0.04 0.05 0.06 0.09 0.05 2Silica (as SiO2

) 5.24 4.96 5.70 7.07 5.55 4.91

Hardness (as CaCO3

) 38.3 34.9 55.7 49.8 24.7 39.7

Dissolved solids, sum of constituents 55 48 72 66 61 54 500*Dissolved solids dried at 180°C 60 43 76 66 56 51 500*
Study Methods 

9

Table 3. Water-quality characteristics, major ions, and nutrients in groundwater from wells sampled in the Marsh Creek valley, Tioga County, Pennsylvania, November 2–4, 2010.[USGS, U.S. Geological Survey; PADEP, Pennsylvania Department of Environmental Protection; MCL, maximum contaminant level; --, not determined; °C, degrees Celsius; mm Hg, millimeters of mercury; μS/cm, microsiemens per centimeter at 25°C; mg/L, milligrams per liter; CaCO3, calcium carbonate; SHE, standard hydrogen electrode; <, less than; N, nitrogen; P, phosphorus; SiO2, silicon dioxide]

Characteristics

USGS well name: TI 269 TI 270 TI 271 TI 536 TI 729 TI 730

PADEP 

MCL1

Local well name: Well 1 Well 2 Well 3 private private Well 5

Date sampled: 11/2/2010 11/3/2010 11/4/2010 11/4/2010 11/3/2010 11/2/2010

Time sampled, local: 13:00 12:00 09:00 11:45 09:00 15:00

Concentration, in milligrams per liter

Nutrients3

Ammonia (as N) <0.010 <0.010 <0.010 <0.010 0.012 < 0.010 

Nitrite (as N) <0.001 <0.001 <0.001 <0.001 0.001 < 0.001 1Nitrate, water (as N)4 0.28 0.18 0.18 0.18 0.19 0.22 10Nitrate plus nitrite (as N)5 0.28 0.18 0.18 0.18 0.19 0.22 10

Total nitrogen (nitrate + nitrite + ammonia + 

organic-N, as N)

0.27 0.18 0.20 0.19 0.25 0.21

Orthophosphate (as P) 0.007 0.009 0.01 0.011 0.015 0.008

1Primary and secondary maximum contaminant levels for public supplies of drinking water (April 2006) are listed where applicable. The values are for primary contaminants except where 

followed by an “*”, denoting a secondary contaminant.

2Acid neutralizing capacity was determined for an unfiltered sample. This is essentially equivalent to the bicarbonate concentration expressed as CaCO3.

3Major constituents and nutrients analyzed by U.S. Geological Survey National Water Quality Laboratory in samples filtered using a capsule filter with 0.45-micron pore size.4Nitrate is computed from other analytically determined constituents.5Some values for nitrate plus nitrite exceed values for the corresponding total nitrogen. These results are within the limits of analytical precision of methods.
10 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Table 4. Trace metals and radiochemicals in groundwater from wells sampled in the Marsh Creek valley, Tioga County, 

Pennsylvania, November 2–4, 2010.

[USGS; U.S. Geological Survey; PADEP; Pennsylvania Department of Environmental Protection; MCL, maximum contaminant level. Samples were filtered 

through a membrane with 0.45-micron pore size for all analyses except radon; <, less than; ND, not detected indicates results for radiochemicals detected at 

concentrations less than the site-specific critical level (ssLc) when the ssLc was negative; 72-h, sample analyzed for concentration at approximately 72 hours 

after sample collection as referenced to a detector calibrated using 230Th for gross alpha and 137Cs for gross beta; 30-d, sample used for the 72-hour analysis 

is counted a second time approximately 30 days after the initial count as referenced to a detector calibrated using 230Th for gross alpha and 137Cs for gross beta]

USGS well name: TI 269 TI 270 TI 271 TI 536 TI 729 TI 730

PADEP 

MCL1

Local well name: Well 1 Well 2 Well 3 private private Well 5

Date sampled: 11/2/2010 11/3/2010 11/4/2010 11/4/2010 11/3/2010 11/2/2010

Time sampled, local: 13:00 12:00 09:00 11:45 09:00 15:00

Concentration, in micrograms per liter

Trace metals2

Aluminum <1.7 <1.7 3 4.5 23.3 <1.7 200 s

Antimony <0.03 <0.03 <0.03 <0.03 <0.03 <0.03 6

Arsenic 0.18 0.06 0.64 0.25 0.27 0.17 10

Barium 24 12 37 54 18 20 2,000

Beryllium <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 4

Boron 5 6 5 5 20 6

Bromide 20 20 20 20 20 10

Cadmium 0.04 <0.02 <0.02 <0.02 <0.02 <0.02 5

Chromium <0.06 <0.06 0.18 0.17 <0.06 <0.06 100

Cobalt <0.02 <0.02 0.02 0.03 <0.02 <0.02 

Copper <0.50 41.9 <0.50 2.4 4.5 1.1 1,000

Iron 6 5 <3 11 23 <3 300*

Lead 0.07 0.12 <0.01 0.16 0.12 0.14 5

Lithium 1.6 0.9 2.1 2.7 7.3 1.3

Manganese <0.1 0.4 0.6 0.3 1.4 0.3 50*

Molybdenum <.03 <.03 <.03 0.1 0.1 <.03

Nickel <0.09 <0.09 <0.09 0.09 0.11 <0.09 

Selenium 0.04 0.05 0.04 0.04 0.03 0.04 50

Silver <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 100*

Strontium 38.5 36.5 44 42.8 29.1 38.5

Uranium (natural) 0.03 0.01 0.07 0.12 0.08 0.03 30

Zinc <1.4 <1.4 <1.4 5.5 31.2 <1.4 5,000

Radioactivity, in picocuries per liter

Radiochemicals3

Gross alpha (72-h) 0.5 0.3 <0.2 0.6 <0.2 0.6 15

Gross alpha (30-d) <0.4 <0.1 ND <0.3 ND ND 15

Gross beta (72-h) 0.8 1.1 0.7 1.2 <0.4 <0.5 

Gross beta (30-d) <0.2 <0.7 <0.7 1.3 <0.2 <0.2 

Radon-222 1310 1260 1150 1020 980 1310

Radium-223 0.0002 0.0006 0.0006 0.0008 ND 0.0003

Radium-224 0.006 0.007 0.025 0.015 ND 0.010

Radium-226 0.010 0.007 0.015 0.021 0.012 0.012 5**

Radium-228 0.011 0.008 0.014 0.019 0.012 0.010 5**

1

Primary and secondary maximum contaminant levels for public supplies of drinking water (April 2006) are listed where applicable. The values are for 

primary contaminants except where followed by an “*”, denoting a secondary contaminant. The lead and copper primary MCLs are applicable only to bottled, 

vended, retail, and bulk water hauling systems. “**” denotes that the MCL for radium is for radium-226 plus radium 228.

2

Trace metals analyzed by U.S. Geological Survey National Water Quality Laboratory.

3

Radon-222 analyzed by U.S. Geological Survey National Water Quality Laboratory. Radium-223, 224, 226, and 228 analyzed by USGS Reston 

Radiochemical Laboratory. Gross alpha and beta analyzed by Eberline Services, Inc.
Study Methods 11

Table 5. Detailed radiochemical analytical results for water samples collected from wells in the Marsh Creek valley, Tioga 

County, Pennsylvania, November 2–4, 2010.

[Result, radiological concentration; CSU, combined standard uncertainty (1-sigma); ssLc, sample-specific critical level; 72-h, sample analyzed for 

concentration at approximately 72 hours after sample collection as referenced to a detector calibrated using 230Th for gross alpha and 137Cs for gross beta; 

30-d, sample used for the 72-hour analysis is counted a second time approximately 30 days after the initial count as referenced to a detector calibrated 

using 230Th for gross alpha and 137Cs for gross beta; pCi/L; picocuries per liter; D, analyte detected; ND, analyte not detected, concentration is less than the 

sample-specific critical level; a, blank is greater than the ssLc; b, value extrapolated at low end; z, sample-specific critial level not reported by laboratory; 

EBER, Eberline Services, Inc.; NWQL, U.S. Geological Survey National Water Quality Laboratory; REST, U.S. Geological Survey radiochemical 

laboratory in Reston, Virginia]

Well 

identifier

Sample 

collection 

date and time

Radiological 

constituent

Result 

(pCi/L)

CSU 

(pCi/L) Remarks ssLC(pCi/L) Laboratory

TI 269 (Well 1) 11/2/10 13:00 Gross alpha (72-h) 0.53 0.21 D 0.24 EBER

Gross alpha (30-d) 0.42 0.49 ND, a 0.69 EBER

Gross beta (72-h) 0.78 0.27 D 0.41 EBER

Gross beta (30-d) 0.2 0.49 ND 0.78 EBER

Radon-222 1,310 74 D 11.8 NWQL

Radium-223 0.0002 0.00004 D z REST

Radium-224 0.006 0.0003 D z REST

Radium-226 0.010 0.0005 D z REST

Radium-228 0.011 0.0004 D z REST

TI 270 (Well 2) 11/3/10 12:00 Gross alpha (72-h) 0.35 0.23 D 0.26 EBER

Gross alpha (30-d) 0.12 0.28 ND, a 0.4 EBER

Gross beta (72-h) 1.11 0.39 D 0.58 EBER

Gross beta (30-d) 0.7 0.75 ND 1.3 EBER

Radon-222 1,260 71 D 12.7 NWQL

Radium-223 0.0006 0.00014 D z REST

Radium-224 0.007 0.0003 D z REST

Radium-226 0.007 0.0004 D z REST

Radium-228 0.008 0.0005 D z REST

TI 270 (Well 2) 

replicate

11/3/10 12:01 Gross alpha (72-h) 0.3 0.26 ND 0.34 EBER

Gross alpha (30-d) -0.09 0.33 ND, a, b 0.56 EBER

Gross beta (72-h) -0.17 0.44 ND, b 0.72 EBER

Gross beta (30-d) 0.3 0.5 ND 0.83 EBER

Radon-222 1,244 71 D 12.9 NWQL

Radium-223 0.0006 0.00014 D z REST

Radium-224 0.007 0.0003 D z REST

Radium-226 0.007 0.0004 D z REST

Radium-228 0.008 0.0005 D z REST

TI 271 (Well 3) 11/4/10 9:00 Gross alpha (72-h) 0.18 0.27 ND 0.37 EBER

Gross alpha (30-d) -0.38 0.31 ND, b 0.6 EBER

Gross beta (72-h) 0.73 0.38 D 0.57 EBER

Gross beta (30-d) 0.7 0.5 ND 0.81 EBER

Radon-222 1,150 65 D 13.2 NWQL

Radium-223 0.0006 0.00006 D z REST

Radium-224 0.025 0.0005 D z REST

Radium-226 0.015 0.0004 D z REST

Radium-228 0.014 0.0006 D z REST
12 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Table 5. Detailed radiochemical analytical results for water samples collected from wells in the Marsh Creek valley, Tioga 

County, Pennsylvania, November 2–4, 2010.

[Result, radiological concentration; CSU, combined standard uncertainty (1-sigma); ssLc, sample-specific critical level; 72-h, sample analyzed for 

concentration at approximately 72 hours after sample collection as referenced to a detector calibrated using 230Th for gross alpha and 137Cs for gross beta; 

30-d, sample used for the 72-hour analysis is counted a second time approximately 30 days after the initial count as referenced to a detector calibrated 

using 230Th for gross alpha and 137Cs for gross beta; pCi/L; picocuries per liter; D, analyte detected; ND, analyte not detected, concentration is less than the 

sample-specific critical level; a, blank is greater than the ssLc; b, value extrapolated at low end; z, sample-specific critial level not reported by laboratory; 

EBER, Eberline Services, Inc.; NWQL, U.S. Geological Survey National Water Quality Laboratory; REST, U.S. Geological Survey radiochemical 

laboratory in Reston, Virginia]

Well 

identifier

Sample 

collection 

date and time

Radiological 

constituent

Result 

(pCi/L)

CSU 

(pCi/L) Remarks ssLC(pCi/L) Laboratory

TI 536 11/4/10 11:45 Gross alpha (72-h) 0.6 0.3 D 0.3 EBER

Gross alpha (30-d) 0.3 0.4 ND 0.52 EBER

Gross beta (72-h) 1.2 0.4 D 0.59 EBER

Gross beta (30-d) 1.26 0.65 D 1 EBER

Radon-222 1,020 59 D 13.1 NWQL

Radium-223 0.0008 0.00005 D z REST

Radium-224 0.015 0.0003 D z REST

Radium-226 0.021 0.0006 D z REST

Radium-228 0.019 0.0011 D z REST

TI 729 11/3/10 9:00 Gross alpha (72-h) 0.2 0.3 ND 0.44 EBER

Gross alpha (30-d) -0.41 0.33 ND 0.65 EBER

Gross beta (72-h) 0.43 0.37 ND 0.58 EBER

Gross beta (30-d) 0.2 0.8 ND 1.3 EBER

Radon-222 980 57 D 12.8 NWQL

Radium-223 0.0000 0.00000 ND z REST

Radium-224 -0.000 -0.0000 ND z REST

Radium-226 0.012 0.0004 D z REST

Radium-228 0.012 0.0005 D z REST

TI 730 (Well 5) 11/2/10 15:00 Gross alpha (72-h) 0.55 0.22 D 0.25 EBER

Gross alpha (30-d) -0.23 0.21 ND 0.39 EBER

Gross beta (72-h) 0.46 0.32 ND 0.51 EBER

Gross beta (30-d) 0.16 0.39 ND 0.63 EBER

Radon-222 1,310 74 D 11.7 NWQL

Radium-223 0.0003 0.00003 D z REST

Radium-224 0.010 0.0003 D z REST

Radium-226 0.012 0.0005 D z REST

Radium-228 0.010 0.0006 D z REST
Study Methods 13

Table 6. Dissolved gases in groundwater from wells sampled in the Marsh Creek valley, Tioga County, Pennsylvania, 

November 2–4, 2010. 

[USGS, U.S. Geological Survey; Gas analyses were performed at Isotech Laboratories, Inc. ND, not detected; NA, not analyzed; mg/L, milligrams per liter; <, 

less than]

Constituent

USGS well name: TI 269 TI 270 TI 271 TI 536 TI 729 TI 730 

Local well name: Well 1 Well 2 Well 3 private private Well 5

Date sampled: 11/2/2010 11/3/2010 11/4/2010 11/4/2010 11/3/2010 11/2/2010

Time sampled: 13:00 12:00 9:00 11:45 9:00 15:00

Concentration in headspace, in volume percent1

(methane is also expressed as mg/L dissolved in water, where noted)

Argon 1.49 1.37 1.58 1.42 1.62 1.5

Oxygen 19.67 21.91 21.49 21.62 18.52 21.78

Carbon dioxide 1.47 1.32 0.19 1.56 1.83 1.15

Nitrogen 77.35 75.37 76.7 75.38 77.65 75.55

Carbon monoxide 0.018 0.033 0.027 0.022 0.039 0.022

Methane ND ND 0.015 0.002 0.341 ND

Methane, dissolved (mg/L) <0.0003 <0.0003 0.002 0.001 0.07 <0.0003

Ethane ND ND ND ND ND ND

Ethylene ND ND ND ND ND ND

Propane ND ND ND ND ND ND

Propene NA ND ND NA NA NA

Iso-butane ND ND ND ND ND ND

Normal butane ND ND ND ND ND ND

Iso-pentane ND ND ND ND ND ND

Normal pentane ND ND ND ND ND ND

Hexanes plus ND ND ND ND ND ND

1

Results for gas composition were normalized by Isotech Laboratories, Inc., to 100 percent and reported in mole percent. Mole percent is approximately 

equal to volume percent and is reported here as volume percent.
14 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Table 7. Stable isotopic composition of hydrogen, oxygen, and carbon in groundwater from wells sampled in the Marsh Creek valley, 

Tioga County, Pennsylvania, November 2–4, 2010.

[USGS, U.S. Geological Survey; Isotopic analyses were performed at Isotech Laboratories, Inc. Stable isotope data reported relative to Vienna Standard Mean 

Ocean Water (VSMOW) and carbon stable isotope data reported relative to Vienna PeeDee Belemnite (VPDB). dD H2O, hydrogen isotopes of water; d18O H2O, 

oxygen isotopes of water; d13C DIC, carbon isotopes of dissolved inorganic carbon]

Constituent

USGS well name: TI 269 TI 270 TI 271 TI 536 TI 729 TI 730 

Local well name: Well 1 Well 2 Well 3 private private Well 5

Date sampled: 11/2/2010 11/3/2010 11/4/2010 11/4/2010 11/3/2010 11/2/2010

Time sampled: 13:00 12:00 9:00 11:45 9:00 15:00

Isotopic composition, in per mil

dD H2O -67.58 -67.84 -66.99 -67.22 -70.01 -69.05

d18O H2O -9.97 -9.95 -9.91 -10.01 -10.29 -10.23

d13C DIC -16.53 -14.79 -13.92 -16.77 -15.01 -13.89

Filters for extracting radium

Sampling tubing from well

Figure 3. Equipment for sampling groundwater for radium. About 100 gallons of water is flushed through permanganateimpregnated filters that concentrate the radium prior to analysis. 
Study Methods 15

Table 8. Summary of laboratories, laboratory codes, and methods used to analyze water samples collected in the Marsh Creek 

valley, Tioga County, Pennsylvania, November 2–4, 2010.

[NWQL, U.S. Geological Survey National Water Quality Laboratory; TDS, total dissolved solids; GC, Gas chromatography; MS, mass spectrometry; 

°C, degrees Celsius; REST, U.S. Geological Survey Radiochemistry Laboratory in Reston, Virginia; IST, Isotech Laboratories, Inc.; ESL, Eberline 

Services Laboratory]

Characteristic/

constituent Method Characteristic/constituent Method

Field characteristics and unstable constituents

pH Field meter with combination electrode Temperature, water Thermistor

Alkalinity, carbonate Titration, incremental Water level Authority

Barometric pressure Thommen barometer Pumping rate Authority

Specific conductance Field meter with Wheatstone bridge

Dissolved oxygen Field meter with membrane electrode

Major ions 

(dissolved, 0.45 micron filtration) NWQL Schedule 2750 + Strontium (Fishman and Friedman, 1989; Fishman,1993)

Calcium I-2057-85 Bicarbonate Titration, incremental

Magnesium I-1472-87 Bromide I-2057-85

Strontium I-1472-87 Chloride I-2057-85

Potassium I-1630-85 Fluoride I-2327-85

Sodium I-1472-87 Sulfate I-2057-85

Silica I-1472-87 TDS, residue 180°C I-1750-89

Iron I-1472-87 pH, laboratory I-2587-89

Manganese I-1472-87 Specific conductance, laboratory I-2781-85

Trace metals 

(dissolved, 0.45 micron filtration) NWQL Schedule 2703 plus Boron and Lithium (Garbarino and others, 2006; Fishman and Friedman, 1989)

Aluminum I-2020-05 Copper I-2020-05

Antimony I-2020-05 Lead I-2020-05

Arsenic I-2020-05 Lithium I-2477-92 

Barium I-2020-05 Molybdenum I-2020-05

Beryllium I-2020-05 Nickel I-2020-05

Boron I-2477-92 Selenium I-2020-05

Cadmium I-2020-05 Silver I-2020-05

Chromium I-2020-05 Uranium, natural I-2020-05

Cobalt I-2020-05 Zinc I-2020-05

Nutrients (dissolved, 0.45 micron filtration) NWQL Schedule 2755 (Fishman,1993; Patton and Kryskalla, 2003)

Nitrogen, ammonia I-2525-89, I-2522-90 Nitrogen, nitrite + nitrate I-2545-90

Nitrogen, nitrite I-2540-90, I-2542-89 Phosphorus, orthophosphate I-2601-90, I-2606-89

Nitrogen, total I-2650-03

Dissolved gases in groundwater

Argon GC- IST Methane GC- IST

Carbon dioxide GC- IST Ethane GC- IST

Helium GC- IST Propane GC- IST

Hydrogen GC- IST Isobutane GC- IST

Hydrogen sulfide GC- IST Normal butane GC- IST

Nitrogen GC- IST Isopentane GC- IST

Oxygen GC- IST Normal pentane GC- IST

Hexanes plus GC- IST
16 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

accreditations, laboratory audits, and proficiency testing 

are available online at http://nwql.usgs.gov/quality.shtml. 

Eberline Services, Inc., laboratory is certified by the U.S. 

Environmental Protection Agency (USEPA). The USGS 

radiochemical laboratory in Reston, Virginia, is a research 

facility used in this study to analyze radium and uranium 

isotopes because very small concentrations of these 

constituents were anticipated—concentrations well below 

those commercial laboratories typically report. Isotech 

Laboratories, Inc., is widely used for analysis of hydrocarbon 

gases and isotopes and has been chosen by USEPA to analyze 

samples for their study to evaluate the effect of hydraulic 

fracturing on drinking-water resources.

Quality Assurance

Chain-of-custody procedures were used with each 

laboratory to track samples and ensure sample integrity 

during shipment, except for the radium and uranium isotopic 

samples analyzed by the USGS laboratory in Reston, 

Virginia. The radiochemistry laboratory is a research facility 

that does not have a chain-of-custody protocol; however, 

the radiochemical samples were collected, transported, and 

analyzed by the laboratory director.

One replicate sample was collected from well 2 (TI 270) 

to show the reproducibility of results (table 9). Results were 

reproduced within acceptable limits. Results differing by 

greater than 10 percent were partly the result of comparing 

the rounded values of very small concentrations. To check 

the laboratory results for major cations and anions, charge 

balances were computed and found to range from 0.42 to 

5.6 percent, which is acceptable for low ionic-strength waters 

(Hem, 1985, p. 164).

NWQL performance on the fall 2010 inter-laboratory 

comparison study is shown in table 10. This study indicates 

how well the laboratory detected known concentrations 

of various constituents in double-blind standard-reference 

samples. NWQL performance was acceptable, except for 

analyses for vanadium, copper, and nickel; thus, reported 

concentrations for these constituents should be viewed as less 

reliable than those for the other analytes.

Simulation of Groundwater Sources to Wells

The areas contributing recharge and sources of water 

were estimated for the three high-capacity wells at NARL by 

use of a two-dimensional, steady-state groundwater model 

originally developed by Williams and Morrissey (1996) 

with the use of MODFLOW-88 (McDonald and Harbaugh, 

1988). They calibrated the model by comparing simulated 

streamflow losses in Asaph Run and Straight Run to the 

average losses determined from streamflow measurements 

made during various flow conditions during 1985, and by 

comparing simulated groundwater levels to average levels for 

18 wells measured weekly from November 1984 to January 

1985, during a period that was considered by Williams and 

Morrisey (1996) to approximate long-term average conditions. 

The hydrologic characteristics were not changed for this study, 

except for the location and withdrawal rates of the NARL 

wells. The model was updated to newer software packages as 

described below.

Updates to the Model

The model datasets of Williams and Morrissey (1996) 

were imported into a GIS-based graphical user interface 

Table 8. Summary of laboratories, laboratory codes, and methods used to analyze water samples collected in the Marsh Creek 

valley, Tioga County, Pennsylvania, November 2–4, 2010.

[NWQL, U.S. Geological Survey National Water Quality Laboratory; TDS, total dissolved solids; GC, Gas chromatography; MS, mass spectrometry; 

°C, degrees Celsius; REST, U.S. Geological Survey Radiochemistry Laboratory in Reston, Virginia; IST, Isotech Laboratories, Inc.; ESL, Eberline 

Services Laboratory]

Characteristic/

constituent Method Characteristic/constituent Method

Isotope ratios (if gases are present)

2H/1H Methane MS- IST 13C/12C Methane MS- IST

13C/12C Carbon dioxide MS- IST

Radiochemicals

Gross Alpha Count Th-230 curve, ESL Radon-222 Liquid Scintillation, NWQL-LC1369

Gross Beta Count Cs-137 curve, ESL Uranium-234 Alpha Spectrometry, REST

Radium-223 Alpha Spectrometry, REST Uranium-238 Alpha Spectrometry, REST

Radium-224 Alpha Spectrometry, REST

Radium- 226 Alpha Spectrometry, REST

Radium-228 Beta Counting, REST
Study Methods 17

Table 9. Analytical results for the environmental sample and the sequential replicate of 

groundwater from well 2 (TI 270) in the Marsh Creek valley, Tioga County, Pennsylvania, 

November 3, 2010.

[°C, degrees Celsius; <, less than; as N, as nitrogen; as P, as phosphorus; ND, reported as not detected by 

laboratory; N/A, could not compute percent difference; mg/L, milligrams per liter; 72-h, sample analyzed for 

concentration at approximately 72 hours after sample collection as referenced to a detector calibrated using 230Th 

for gross alpha and 137Cs for gross beta; 30-d, sample used for the 72-hour analysis is counted a second time 

approximately 30 days after the initial count as referenced to a detector calibrated using 230Th for gross alpha 

and 137Cs for gross beta; Isotopic analyses were performed at Isotech Laboratories, Inc. Stable isotope data 

for hydrogen and oxygen are reported relative to Vienna Standard Mean Ocean Water (VSMOW), and stable 

isotope data for carbon is reported relative to Vienna PeeDee Belemnite (VPDB). dD H2O, 2H/1H ratio in water; 

d18O H2O, 18O/16O ratio in water; d13C DIC, 13C/12C ratio in dissolved inorganic carbon]

Constituent

 TI 270 

(environmental 

sample 

collected at 

12:00 p.m.)

TI 270 

(replicate 

sample 

collected at 

12:01 p.m.)

Percent 

difference

Major Ions (milligrams per liter)

Calcium 10.9 10.9 0.00

Magnesium 1.81 1.81 0.00

Sodium 1.44 1.44 0.00

Potassium 0.78 0.80 -2.56

Chloride 1.57 1.58 -0.64

Sulfate 8.33 8.32 0.12

Fluoride 0.04 < 0.04 N/A

Silica (as SiO2) 4.96 5.01 -1.01

Hardness (as CaCO3) 34.9 34.8 0.29

Dissolved solids, sum of constituents 48 48 0.00

Dissolved solids dried at 180°C 43 49 -13.95

Nutrients (milligrams per liter)

Ammonia (as N) < 0.010 < 0.010 0.00

Nitrite (as N) < 0.001 < 0.001 0.00

Nitrate, water (as N) 0.18 0.17 5.56

Nitrate plus nitrite (as N) 0.18 0.17 5.56

Total nitrogen (nitrate + nitrite + ammonia + 

organic-N), as N

0.18 0.17 5.56

Orthophosphate (as P) 0.009 0.009 0.00

Trace metals (micrograms per liter)

Arsenic 0.06 0.05 16.67

Barium 12 12 0.00

Beryllium < 0.01 < 0.01 0.00

Boron 6 6 0.00

Bromide 20 10 50.00

Cadmium < 0.02 < 0.02 0.00

Chromium < 0.06 < 0.06 0.00

Cobalt < 0.02 < 0.02 0.00

Copper 41.9 44.1 -5.25

Iron 5 5 0.00

Lead 0.12 0.12 0.00
18 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Table 9. Analytical results for the environmental sample and the sequential replicate of 

groundwater from well 2 (TI 270) in the Marsh Creek valley, Tioga County, Pennsylvania, 

November 3, 2010.

[°C, degrees Celsius; <, less than; as N, as nitrogen; as P, as phosphorus; ND, reported as not detected by 

laboratory; N/A, could not compute percent difference; mg/L, milligrams per liter; 72-h, sample analyzed for 

concentration at approximately 72 hours after sample collection as referenced to a detector calibrated using 230Th 

for gross alpha and 137Cs for gross beta; 30-d, sample used for the 72-hour analysis is counted a second time 

approximately 30 days after the initial count as referenced to a detector calibrated using 230Th for gross alpha 

and 137Cs for gross beta; Isotopic analyses were performed at Isotech Laboratories, Inc. Stable isotope data 

for hydrogen and oxygen are reported relative to Vienna Standard Mean Ocean Water (VSMOW), and stable 

isotope data for carbon is reported relative to Vienna PeeDee Belemnite (VPDB). dD H2O, 2H/1H ratio in water; 

d18O H2O, 18O/16O ratio in water; d13C DIC, 13C/12C ratio in dissolved inorganic carbon]

Constituent

 TI 270 

(environmental 

sample 

collected at 

12:00 p.m.)

TI 270 

(replicate 

sample 

collected at 

12:01 p.m.)

Percent 

difference

Trace metals (micrograms per liter)

Manganese 0.4 0.4 0.00

Molybdenum <.03 <.03 0.00

Nickel < 0.09 < 0.09 0.00

Silver < 0.005 < 0.005 0.00

Strontium 36.5 36.9 -1.10

Zinc < 1.4 < 1.4 0.00

Antimony < 0.03 < 0.03 0.00

Aluminum < 1.7 < 1.7 0.00

Lithium 0.9 0.9 0.00

Selenium 0.05 0.04 20.00

Uranium (natural) 0.01 0.01 0.00

Radiochemicals (picoCuries per liter)

Gross alpha (72-h) 0.3 < 0.3 N/A

Gross alpha (30-d) < 0.1 ND N/A

Gross beta (72-h) 1.1 ND N/A

Gross beta (30-d) < 0.7 < 0.3 N/A

Radon-222 1260 1240 1.59

Radium-223 0.0006 0.0006 0.87

Radium-224 0.007 0.007 -5.82

Radium-226 0.007 0.007 2.78

Radium-228 0.008 0.008 2.85

Dissolved gases (volume percent in headspace)

Argon 1.37 1.37 0.00

Oxygen 21.91 21.92 -0.05

Carbon Dioxide 1.32 1.36 -3.03

Nitrogen 75.37 75.32 0.07

Carbon Monoxide 0.033 0.026 21.21

Methane ND ND N/A

Methane, dissolved (mg/L) <0.0003 <0.0003 N/A

Ethane ND ND N/A

Ethylene ND ND N/A

Propane ND ND N/A
Study Methods 19

Table 9. Analytical results for the environmental sample and the sequential replicate of 

groundwater from well 2 (TI 270) in the Marsh Creek valley, Tioga County, Pennsylvania, 

November 3, 2010.

[°C, degrees Celsius; <, less than; as N, as nitrogen; as P, as phosphorus; ND, reported as not detected by 

laboratory; N/A, could not compute percent difference; mg/L, milligrams per liter; 72-h, sample analyzed for 

concentration at approximately 72 hours after sample collection as referenced to a detector calibrated using 230Th 

for gross alpha and 137Cs for gross beta; 30-d, sample used for the 72-hour analysis is counted a second time 

approximately 30 days after the initial count as referenced to a detector calibrated using 230Th for gross alpha 

and 137Cs for gross beta; Isotopic analyses were performed at Isotech Laboratories, Inc. Stable isotope data 

for hydrogen and oxygen are reported relative to Vienna Standard Mean Ocean Water (VSMOW), and stable 

isotope data for carbon is reported relative to Vienna PeeDee Belemnite (VPDB). dD H2O, 2H/1H ratio in water; 

d18O H2O, 18O/16O ratio in water; d13C DIC, 13C/12C ratio in dissolved inorganic carbon]

Constituent

 TI 270 

(environmental 

sample 

collected at 

12:00 p.m.)

TI 270 

(replicate 

sample 

collected at 

12:01 p.m.)

Percent 

difference

Dissolved gases (volume percent in headspace)

Propene ND ND N/A

Iso-butane ND ND N/A

Normal butane ND ND N/A

Iso-pentane ND ND N/A

Normal pentane ND ND N/A

Hexanes plus ND ND N/A

Isotopic composition (per mil)

dD H2O -67.84 -67.74 0.14

d18O H2O -9.95 -10.02 -0.70

d13C DIC -14.79 -14.66 0.84
20 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Table 10. Performance of the U.S. Geological Survey National Water Quality Laboratory in analyzing standard-reference samples in 

the fall 2010 inter-laboratory comparison study.

[NWQL, National Water Quality Laboratory; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; as N, as nitrogen; as P, as phosphorus; 

μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, could not compute percent difference; bold font indicates NWQL result is outside of acceptable 

deviation from most probable value]

Constituent NWQL reported value Most probable value Percent difference

Nutrients

Ammonia + Organic Nitrogen as N 0.556 mg/L 0.53 4.91

Ammonia as N 0.448 mg/L 0.46 -2.61

Nitrite + Nitrate as N 0.931 mg/L 0.935 -0.43

Orthophosphate as P 0.510 mg/L 0.522 -2.3

Total Nitrogen 1.46 mg/L 1.46 0

Total Phosphorus as P 0.548 mg/L 0.535 2.43

Major constituents

Alkalinity as CaCO3 81.4 mg/L 78.9 3.17

Boron 11.9 μg/L 13 -8.46

Bromide 0.146 mg/L 0.165 -11.52

Calcium 27.7 mg/L 27.1 2.21

Chloride 32.3 mg/L 32.7 -1.22

Fluoride 0.881 mg/L 0.84 4.88

Magnesium 8.81 mg/L 9.17 -3.93

pH 7.7 8.03 -4.11

Potassium 1.87 mg/L 1.78 5.06

Residue on Evaporation 184 mg/L 190 -3.16

Silica 5.46 mg/L 6.1 -10.49

Sodium 25.7 mg/L 25 2.8

Specific Conductance 347 μS/cm 339 2.36

Strontium 218 μg/L 224 -2.68

Sulfate 31.8 mg/L 33.2 -4.22

Vanadium 0.206 μg/L 0.47 -56.17

Trace metals

Aluminum 109 μg/L 109 0

Antimony 0.375 μg/L 0.458 -18.12

Arsenic 1.55 μg/L 1.61 -3.73

Barium 10.1 μg/L 10.1 0

Beryllium 0.467 μg/L 0.52 -10.19

Boron <2.80 μg/L 4.58 --

Cadmium 0.867 μg/L 0.864 0.35

Calcium 11.7 mg/L 11.1 5.41

Chromium 0.826 μg/L 0.88 -6.14

Cobalt 0.498 μg/L 0.559 -10.91

Copper 1.19 μg/L 1.61 -26.09

Iron 52.6 μg/L 52.1 0.96

Lead 11.2 μg/L 11 1.82

Lithium 5.59 μg/L 6.3 -11.27

Magnesium 1.26 mg/L 1.25 0.8
Study Methods 21

Table 10. Performance of the U.S. Geological Survey National Water Quality Laboratory in analyzing standard-reference samples in 

the fall 2010 inter-laboratory comparison study.

[NWQL, National Water Quality Laboratory; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; as N, as nitrogen; as P, as phosphorus; 

μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, could not compute percent difference; bold font indicates NWQL result is outside of acceptable 

deviation from most probable value]

Constituent NWQL reported value Most probable value Percent difference

Trace metals

Manganese 122 μg/L 127 -3.94

Molybdenum 4.32 μg/L 4.11 5.11

Nickel 0.238 μg/L 0.402 -40.8

Potassium 1.30 mg/L 1.22 6.56

Selenium 0.345 μg/L 0.397 -13.1

Silica 4.90 mg/L 4.71 4.03

Silver 2.56 μg/L 2.76 -7.25

Sodium 10.2 mg/L 10.8 -5.56

Strontium 43.9 μg/L 45.5 -3.52

Thallium 1.91 μg/L 1.95 -2.05

Uranium 0.681 μg/L 0.75 -9.2

Vanadium 1.07 μg/L 1.1 -2.73

Zinc 35.0 μg/L 36 -2.78

linked to Argus Numerical Environments (ARGUS) 

software (Winston, 2000) and reformatted for use with 

MODFLOW-2000 (Harbaugh and others, 2000) and 

MODPATH (Pollock, 1994), a particle-tracking program 

commonly used to delineate contributing recharge areas. 

The two-dimensional finite-difference grid was georeferenced 

on the basis of figure 6 in Williams and Morrissey (1996).

The modeled area, two-dimensional finite-difference 

grid, and hydrologic boundary conditions are shown in 

figure 4. The model is oriented N. 67°E., and grid cells are 

200 ft by 200 ft squares that define the active model area, 

which is bounded by bedrock valley walls, except where 

crossing Straight Run, Asaph Run, and Marsh Creek. The 

model has one layer, specified as unconfined. The bottom 

of the layer represents the altitude of the base of the glacial 

sand and gravel aquifer ranging from 1,035 to 1,180 ft above 

the National Geodetic Vertical Datum of 1929 (NGVD 29). 

Hydraulic conductivity ranges from 52 to 311 feet squared 

per day (ft2/d). General-head boundaries were assigned across 

the Marsh Creek valley to simulate groundwater inflow and 

outflow. Recharge from precipitation on the valley floor was 

simulated as a constant flux by use of the recharge package in 

MODFLOW-2000. Streams were simulated with the stream 

package of Prudic (1989) with streambed-conductance values 

calibrated against measured seepage rates from Straight Run 

and Asaph Run (Williams and Morrissey, 1996). Unchanneled 

upland runoff and withdrawals from the NARL wells and a 

new well were simulated with constant-flux cells by use of the 

well package.

All the MODFLOW-2000 data sets were regenerated 

using ARGUS, except the data for the stream package. 

The stream-package data set produced by ARGUS could not 

exactly reproduce the original data set without considerable 

manipulation of the stream-segment data, so the streampackage dataset from Williams and Morrissey (1996) was 

used directly. This resulted in a MODFLOW-2000 model of 

the study area that exactly produced the output of Williams 

and Morrissey (1996) with results that could be plotted by 

use of a geographic information system. A summary of the 

model documentation and available calibration is provided in 

Williams and Morrisey (1996).

Steady-State Simulation Inputs and Parameters

Using the previously calibrated model inputs and 

parameters, eight simulations were conducted to delineate 

the areas contributing recharge and sources of water to wells 

for steady-state conditions (table 11). Simulated recharge, 

streamflow, and pumping rates were varied to illustrate the 

range in extent of the areas contributing recharge to wells. 

The “average” and “dry” hydrologic conditions were defined 

by Williams and Morrissey (1996, p. 101). The conditions 

from November 1984 through January 1985 were chosen by 

them as an approximation of long-term average conditions, 

and the conditions during October 1984 were chosen to 

represent low-flow (or dry) conditions. Recharge rates 

applied to the model were 18.9 inches per year (in/yr) for 

average conditions and 2.7 in/yr for dry conditions. Because 

streamflow in Asaph Run and Straight Run was measured for 
22 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Finite-difference grid

Marsh Creek

Straight Run

Asaph Run

Wellsboro

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Cell type in finite-difference grid

General head

Constant-flux

Stream

Boundary of active model area

Streams

Figure 4. Finite-difference grid and boundary conditions for the groundwater-flow model of Marsh Creek valley, Tioga County, 

Pennsylvania.
Groundwater Quality in Marsh Creek Valley 23

only 18 months during 1984–85, the long-term average and 

dry conditions cannot be computed for the study area, but 

insights can be gained by analysis of the streamflow record 

from Corey Creek near Mainesburg (a small stream in Tioga 

County about 20 miles east of NARL, not shown on maps) 

during 1954–2009. Average streamflow in Corey Creek during 

November 1984 through January 1985 corresponded to the 

60th percentile of all monthly mean streamflow values for 

that creek from 1954 to 2009; the streamflow during October 

1984 corresponded to the 22d percentile of all monthly mean 

streamflow values. Thus, the average conditions simulated in 

the model probably represent wetter than median conditions 

(60th percentile), and the dry period represents conditions that 

could be expected 2 to 3 months per year (22d percentile), 

not a severe drought. The groundwater budgets for average 

and dry conditions (without withdrawals from wells) are 

shown in figure 5. For average conditions, the total simulated 

groundwater flow through the study area is 4,820 gal/min; for 

dry conditions, the total simulated groundwater flow through 

the study area is 2,340 gal/min.

Groundwater withdrawals from the NARL wells 1, 3, and 

5 (TI 269, TI 271, and TI 730, respectively) were simulated 

in the model as steady, equal withdrawal rates from each 

well. Currently (2011) withdrawals from the three wells 

total about 1,000 gal/min; thus, simulations were conducted 

for that rate and for 2,000 gal/min, which is the maximum 

withdrawal permitted unless the flow of Straight Run is 

gaged and effects on the wetland along Marsh Creek are 

monitored (Susquehanna River Basin Commission, 2003). 

If those actions are taken, NARL is permitted to withdraw an 

amount equal to the flow of Straight Run but not to exceed 

3,000 gal/min. Therefore, pumping 3,000 gal/min was 

simulated for the average hydrologic condition but not for 

the dry condition because the simulated flow of Straight Run 

is only 500 gal/min entering the modeled area during dry 

conditions. Therefore, withdrawals greater than 2,000 gal/min 

would not be allowed. Simulations also were made to 

evaluate the effects of proposed withdrawals of 1,000 gal/min 

from a new well, located about 3,500 ft southwest of the 

NARL facility.

The sources of water and hydraulic response of the 

system were estimated from particle tracking by the use of 

MODPATH. The results are approximate because some of 

the sinks are characterized as “weak” sinks, which imparts 

ambiguity as to exactly which particles should be stopped and 

which should be allowed to pass through the sink. For this 

study, all particles entering a cell were stopped at that cell 

if more than half of the flow entering it discharged to a well 

or stream.

Groundwater Quality in Marsh 

Creek Valley

Results of water-quality analyses indicate that samples 

from the wells in the glacial sand and gravel and bedrock 

aquifers contained high quality, low-ionic strength water, 

with less than 80 milligrams per liter (mg/L) of dissolved 

solids (table 3). The major-ion chemistry indicates that the 

samples were all calcium-bicarbonate type waters, except 

for the sample from TI 729, which contained more sodium 

than calcium. The groundwater is described as “soft” 

on the basis of measured hardness (Hem, 1985, p. 159). 

Nutrient concentrations were far below the maximum 

contaminant levels (MCLs) established for drinking water in 

Pennsylvania (Pennsylvania Department of Environmental 

Protection, 2006).

Concentrations of trace metals and most radiochemicals 

also were low; some trace metals are listed as non-detects at 

low levels (table 4). All trace metals and radiochemicals were 

less than the MCLs. Trace-metal concentrations of aluminum, 

Table 11. Hydrologic conditions and pumping rates simulated by the steady-state groundwater-flow model of Marsh Creek valley, 

near Wellsboro, Tioga County, Pennsylvania. 

[NARL, Northern Appalachian Research Laboratory]

Simulation 

number

Hydrologic 

conditions

Total pumping rate 

from three 

NARL wells 

(gallons per minute)

Proposed 

withdrawals 

from the new well

(gallons per minute)

Simulated flow 

in headwater of 

Asaph Run 

(gallons per minute)

Simulated flow 

in headwater of 

Straight Run 

(gallons per minute)

1 Average 1,000 0 9,694 4,663

2 Average 2,000 0 9,694 4,663

3 Average 2,000 1,000 9,694 4,663

4 Average 3,000 1,000 9,694 4,663

5 Dry 1,000 0 1,616 494

6 Dry 1,000 1,000 1,616 494

7 Dry 2,000 0 1,616 494

8 Dry 2,000 1,000 1,616 494
24 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Wellsboro

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Groundwater budget term

Average conditons / Dry conditions–Flow 

rate, in gallons per minute

Blue represents inflow to groundwater 

system. Yellow represents ouflow from groundwater system

Recharge from 

precipitation on 

valley floor

390 / 60

Marsh Creek

Straight Run

Asaph Run

Unchanneled upland runoff 

(from all bedrock upland areas 

adjacent to the valley) 

700 / 100

Infiltration from 

ASAPH Run

1,860 / 1,620

Recharge from

 precipitation on 

valley floor

390 / 60

Infiltration from 

Straight Run

1,840 / 500

Groundwater

inflow

30 \ 60

Groundwater

outflow

250 \ 140

Discharge to Marsh

Creek

4,570 / 2,200

Figure 5. Steady-state groundwater budgets for average and dry hydrologic conditions without groundwater withdrawals simulated by 

the groundwater-flow model of Marsh Creek valley, Tioga County, Pennsylvania.
Sources of Water from Steady-State Simulations 25

iron, lithium, nickel, and zinc were greater in water from 

the domestic-supply wells completed in the bedrock aquifer 

than from the NARL wells completed in the glacial sand and 

gravel aquifer. The concentration of copper was greatest in 

the sample from well 2 (TI 270), possibly because the sample 

was collected from a tank in the NARL building far from the 

wellhead and had more contact with copper pipes than did the 

other samples.

Radon gas was present in the wells at concentrations 

ranging from 980 to 1,310 picocuries per liter (table 4). 

Although there currently is not an MCL for radon in drinking 

water in Pennsylvania, the U.S. Environmental Protection 

Agency (USEPA) proposed MCL is 300 pCi/L, with an 

alternate MCL of 4,000 pCi/L if an indoor-air mitigation 

program has been enacted by the State or water purveyor (U.S. 

Environmental Protection Agency, 1999). Although the radon 

concentrations found in the wells are elevated compared to 

the proposed USEPA MCL of 300 pCi/L, they are similar to 

natural levels found in the glacial sand and gravel deposits and 

fractured bedrock of the Catskill Formation in other areas of 

northern Pennsylvania (Senior, 2009, p. 52).

Concentrations of dissolved gases are listed in table 6. 

Dissolved gases are reported as volume percent in headspace, 

which is the reporting convention used by the laboratory. 

Methane is also reported in table 6 as the concentration 

dissolved in water, in milligrams per liter.

 Concentrations of headspace gases were similar to 

concentrations found in the atmosphere or soil. Methane 

was the only hydrocarbon gas detected. It was found in 

water from NARL well 3 (TI 271) and domestic-supply 

wells TI 536 and TI 729 at concentrations ranging from 

0.0006 to 0.07 mg/L as dissolved methane in water. These 

concentrations are low. A methane concentration of 10 mg/L in 

groundwater is considered a warning level as to the possibility 

of accumulation in air that could lead to a subsequent 

explosion (Eltschlager and others, 2001, p. 40). Osborn and 

others (2011) reported an average methane concentration of 

1.9 mg/L in five groundwater samples collected from wells in 

the Catskill Formation. The concentrations of methane from 

the NARL samples were too low to allow a determination of 

the isotopic composition of carbon and hydrogen atoms in the 

methane molecule, which can be useful for determining the 

origin of the gas.

Sources of Water from SteadyState Simulations

Eight simulations were made to identify the sources 

of water contributing to the NARL wells and a new well. 

The results are presented in the order shown in table 11. 

Figures in the following sections illustrate the simulation 

results. Travel time from source area to well discharge point 

is described. Finally, the assumptions and limitations of the 

model simulations are discussed.

Average Conditions with 1,000 Gallons per 

Minute Withdrawals 

Simulations were made for average hydrologic conditions 

with groundwater withdrawals totaling 1,000 gal/min from the 

NARL wells. The areas contributing recharge to each well and 

the configuration of the water table are illustrated in figure 6A. 

The wells capture water from a small area that directs stream 

infiltration from Straight Run to the wells. Infiltration from 

Straight Run accounts for about 99 percent of the groundwater 

withdrawn by the wells during average conditions (fig. 6B). 

The capture of water by the wells affects the water budget 

of the study area by decreasing the groundwater discharge 

to Marsh Creek by about 360 gal/min (36 percent of 

1,000 gal/min) and increasing seepage from Straight Run by 

about 640 gal/min (fig. 6C). The ultimate effect on Marsh 

Creek downstream from the NARL, however, is negligible 

because the water use is nearly 100 percent non-consumptive 

and the water is discharged about 400 ft downstream from the 

confluence of Straight Run and Marsh Creek.

Average Conditions with 2,000 Gallons per 

Minute Withdrawals

Simulations were made for average hydrologic conditions 

with groundwater withdrawals totaling 2,000 gal/min from the 

NARL wells. The areas contributing recharge to each well and 

the configuration of the water table are illustrated in figure 7A. 

Even at 2,000 gal/min, the wells capture water from only a 

small area; stream infiltration from Straight Run is directed 

to the wells. Infiltration from Straight Run accounts for 

about 98 percent of the groundwater withdrawn by the wells 

during average hydrologic conditions (fig. 7B). This capture 

affects the water budget of the study area by decreasing 

the groundwater discharge to Marsh Creek by about 

680 gal/min (34 percent of 2,000 gal/min) and increasing 

seepage from Straight Run by about 1,320 gal/min (fig. 7C). 

The ultimate effect on Marsh Creek, however, is negligible 

because the groundwater withdrawals are discharged about 

400 ft downstream from the confluence of Straight Run and 

Marsh Creek.

Average Conditions with 2,000 Gallons per 

Minute Withdrawals Plus 1,000 Gallons 

per Minute Withdrawal from the New 

Production Well

Simulations were made for average hydrologic conditions 

with groundwater withdrawals totaling 2,000 gal/min from 

the NARL wells and a new withdrawal of 1,000 gal/min 

from the production well 3,500 ft to the southwest. The areas 

contributing recharge to each well and the configuration of the 

water table are illustrated in figure 8A. The area throughout 

which recharge is captured for the NARL wells is essentially 
26 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

1,146

1,150

1,154

1,162

1,158

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,1 94

1,146

1,170

1,166

1,174

1,182

1,178

Precipitation 

on valley 

1% 

Straight Run 

seepage 

99% 

Decreased 

groundwater 

discharge to 

stream

36% 

Increased 

stream 

leakage 

64% 

B. Sources of water C. Hydraulic response

A.

1,146

1,150

1,154

1,162

1,158

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,1 94

1,146

1,170

1,166

1,174

1,182

1,178

3

5

1

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NGVD 29. Interval 4 feet

Well 3

Well 5

Well 1

Simulated contributing areas and 

location of well and identifier

1,150

Marsh Creek

Straight Run

Asaph Run

Figure 6. Simulated A, areas contributing recharge to wells and water-table contours, B, sources of water to wells, and C, hydraulic 

response of the aquifer during average hydrologic conditions with withdrawals of 1,000 gallons per minute from the Northern 

Appalachian Research Laboratory (NARL) wells, Tioga County, Pennsylvania.
Sources of Water from Steady-State Simulations 27

1,146

1,150

1,154

1,162

1,158

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,1 94

1,146

1,170

1,166

1,174

1,182

1,178

Upland 

runoff 

1% 

Decreased 

groundwater 

discharge to 

stream 

34% 

B. Sources of water C. Hydraulic response

A.

1,146

1,150

1,154

1,162

1,158

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,1 94

1,146

1,170

1,166

1,174

1,182

1,178

Precipitation

on valley 

1% 

Straight Run 

seepage 

98% 

Increased 

stream 

leakage 

66% 

3

5

1

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NGVD 29. Interval 4 feet

Well 3

Well 5

Well 1

Simulated contributing areas and 

location of well and identifier

1,150

Marsh Creek

Straight Run

Asaph Run

Figure 7. Simulated A, areas contributing recharge to wells and water-table contours, B, sources of water to wells, and C, hydraulic 

response of the aquifer during average hydrologic conditions with withdrawals of 2,000 gallons per minute from the Northern 

Appalachian Research Laboratory (NARL) wells, Tioga County, Pennsylvania.
28 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Upland 

runoff 

1% 

Upland 

runoff 

9% 

B. Sources of water–Northern Appalachian Research Laboratory wellsB. Sources of water–New well

A.

Precipitation 

on valley 

1% 

Decreased 

groundwater 

discharge to 

stream 

37% 

C. Hydraulic response

Precipitation 

on valley 

7% 

Asaph Run 

seepage 

83% 

Straight Run 

seepage 

98% 

Decreased

outflow

8%

Aquifer

inflow

1% 

Increased 

stream 

leakage 

55% 

1,170

1,174

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,194

1,178

1,146

1,166

1,182

1,146

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,194

1,178

1,146

1,166

1,182

1,170

1,174

1,142

1,146

3

5

1

New well

1,150

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NGVD 29. Interval 4 feet

Well 3

Well 5

Simulated contributing areas and 

location of well and identifier

1,150

Well 1

New well

Marsh Creek

Straight Run

Asaph Run

Figure 8. Simulated A, areas contributing recharge to wells and water-table contours, B, sources of water to wells, and C, hydraulic 

response of the aquifer during average hydrologic conditions with withdrawals of 2,000 gallons per minute from the Northern 

Appalachian Research Laboratory (NARL) wells and 1,000 gallons per minute from the new well, Tioga County, Pennsylvania.
Sources of Water from Steady-State Simulations 29

unchanged by the addition of the new well (compare 

figures 7A and 8A). The area contributing recharge to the 

new well extends from Asaph Run to the western boundary 

of the glacial sand and gravel aquifer. Seepage from Asaph 

Run is the major source of water to the new well, providing 

83 percent of water withdrawals (fig. 8B). The sources of 

groundwater withdrawn by the NARL wells are the same as 

if the new well was not operating (see fig. 7B for sources). 

Capture from these sources affects the water budget of the 

study area by decreasing the groundwater discharge to Marsh 

Creek about 1,110 gal/min (37 percent of 3,000 gal/min) and 

increasing seepage from Straight Run and Asaph Run by 

about 1,650 gal/min (55 percent of 3,000 gal/min; fig. 8C). 

The ultimate effect on Marsh Creek downstream from 

the NARL, however, is caused only by the consumptive 

withdrawal from the new well because groundwater 

withdrawals from the NARL wells are discharged about 

400 ft downstream from the confluence of Straight Run and 

Marsh Creek.

Results of model simulations indicate that pumping 

1,000 gal/min of water from the new well will not cause 

any substantial additional drawdown in the NARL well field 

during average hydrologic conditions (fig. 9). The magnitude 

of the drawdown, however, might be greater than the twodimensional model results indicate because the vertical 

hydraulic conductivity of the glacial sand and gravel aquifer 

between the well screen depth and Asaph Run is not simulated 

by the one-layer model.

Average Conditions with 3,000 Gallons per 

Minute Withdrawals Plus 1,000 Gallons 

per Minute Withdrawal from the New 

Production Well

Simulations were made for average hydrologic conditions 

with groundwater withdrawals totaling 3,000 gal/min from 

the NARL wells and a new withdrawal of 1,000 gal/min 

from the production well 3,500 ft to the southwest. The areas 

contributing recharge to each well and the configuration of 

the water table are illustrated in figure 10A. The increased 

area in which recharge is captured for the NARL wells is 

barely discernible when the total withdrawals are increased 

from 2,000 gal/min to 3,000 gal/min (compare figures 8A 

and 10A). Seepage from Asaph Run is the major source of 

water to the new well, providing 83 percent of the water 

withdrawn (fig. 10B). The sources of groundwater withdrawn 

by the NARL wells are the same as those shown in figure 7B. 

Capture from these sources affects the water budget of the 

study area by decreasing the groundwater discharge to Marsh 

Creek by about 1,480 gal/min (37 percent of 4,000 gal/min) 

and increasing seepage from Straight Run and Asaph Run by 

about 2,280 gal/min (57 percent of 4,000 gal/min; fig. 10C). 

The ultimate effect on streamflow in Marsh Creek downstream 

from the NARL is caused only by the consumptive withdrawal 

of 1,000 gal/min from the new well; withdrawals from the 

NARL wells are returned as wastewater discharge to Marsh 

Creek about 400 ft downstream from the confluence of Marsh 

Creek and Straight Run.

Dry Conditions with 1,000 Gallons per 

Minute Withdrawals

Simulations were made for dry conditions with 

groundwater withdrawals totaling 1,000 gal/min from the 

NARL wells. The areas contributing recharge to each well 

and the configuration of the water table are illustrated in 

figure 11A. The area throughout which recharge is captured 

is more extensive than that for withdrawals of the same 

magnitude during the wetter “average” conditions of 

recharge and streamflow shown in figure 6. The contributing 

area encompasses more than half the study area, capturing 

infiltration from multiple sources and directing stream 

infiltration from both Straight Run and Asaph Run to the 

wells. Infiltration from Straight Run and Asaph Run accounts 

for about 49 and 33 percent, respectively, of the groundwater 

withdrawn by the wells during dry conditions (fig. 11B). 

Capture from these sources affects the water budget of the 

study area by decreasing the groundwater discharge to Marsh 

Creek by about 770 gal/min (77 percent of 1,000 gal/min) and 

increasing the total seepage from Straight Run and Asaph Run 

by about 220 gal/min (fig. 11C). The ultimate effect on Marsh 

Creek downstream from the NARL, however, is negligible 

because the groundwater withdrawals are discharged about 

400 ft downstream from the confluence of Straight Run and 

Marsh Creek.

Dry Conditions with 1,000 Gallons per Minute 

Withdrawals Plus 1,000 Gallons per Minute 

Withdrawal from the New Production Well

Simulations were made for dry conditions with 

groundwater withdrawals totaling 1,000 gal/min from the 

NARL wells and a withdrawal of 1,000 gal/min from a 

new well 3,500 ft to the southwest. The areas contributing 

recharge to each well and the configuration of the water table 

are illustrated in figure 12A. The contributing area extends 

throughout nearly all of the study area, capturing infiltration 

from multiple sources and directing stream infiltration from 

Straight Run, Asaph Run, and Marsh Creek to the wells. 

The new well competes only slightly with the NARL wells 

for infiltration from the headwaters of Asaph Run; thus, 

the contributing areas for the NARL wells are essentially 

unchanged (compare figs. 11A and 12A). Infiltration from 

Straight Run and Asaph Run accounts for about 49 and 

33 percent, respectively, of the groundwater withdrawn by 

the NARL wells during dry conditions (fig. 12B). Induced 

infiltration from Marsh Creek is not a substantial percentage 

of the water captured by the wells. The capture by the wells 

affects the water budget of the study area by decreasing the 
30 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

3

5

1

New well

2

Wellsboro

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Additional drawdown from proposed 

withdrawal at new well, in feet

0.50 - 2.00

2.01 - 4.00

4.01 - 6.00

6.01 - 8.68

Northern Appalachian Research 

Laboratory production well and

identifer

New well, site of proposed 

groundwater withdrawal

3

Production well

Marsh Creek

Straight Run

Asaph Run

Figure 9. Simulated additional drawdown caused by a proposed groundwater withdrawal of 1,000 gallons per minute southwest of the 

Northern Appalachian Research Laboratory (NARL) during average hydrologic conditions, Tioga County, Pennsylvania.
Sources of Water from Steady-State Simulations 31

Upland 

runoff 

1% 

Upland 

runoff 

9% 

B. Sources of water–Northern Appalachian Research Laboratory wellsB. Sources of water–New well

A.

Precipitation 

on valley 

1% 

Decreased 

groundwater 

discharge to 

stream 

37% 

C. Hydraulic response

Precipitation 

on valley 

7% 

Asaph Run 

seepage 

83% 

Straight Run 

seepage 

98% 

Decreased

outflow

6%

Aquifer

inflow

1% 

Increased 

stream 

leakage 

57% 

1,170

1,174

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,194

1,178

1,146

1,166

1,182

1,146

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178

1,182

1,186

1,190

1,194

1,178

1,146

1,166

1,182

1,170

1,174

1,142

1,146

3

5

1

New well

1,150

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NGVD 29. Interval 4 feet

Well 3

Well 5

Simulated contributing areas and 

location of well and identifier

1,150

Well 1

New well

Marsh Creek

Straight Run

Asaph Run

Figure 10. Simulated A, areas contributing recharge to wells and water-table contours, B, sources of water to wells, and C, hydraulic 

response of the aquifer during average hydrologic conditions with withdrawals of 3,000 gallons per minute from the Northern 

Appalachian Research Laboratory (NARL) wells and 1,000 gallons per minute from a new production well, Tioga County, Pennsylvania.
32 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

1,146

1,150

1,154

1,162

1,158

1,166

1,170

1,174

1,178 1,182

1,186

1,142

1,170

1,166

1,174

1,178

Upland 

runoff 

9% 

Increased 

stream 

leakage 

22% 

B. Sources of water C. Hydraulic response

A.

1,146

1,150

1,154

1,162

1,158

1,166

1,170

1,174

1,178 1,182

1,186

1,142

1,170

1,166

1,174

1,178

Precipitation

on valley 

4% 

1,162

1,158

Decreased

outflow

1%

Asaph Run 

seepage 

33% 

Straight Run 

seepage 

49% 

Aquifer

inflow

5% 

Decreased 

groundwater 

discharge to 

stream 77% 

3

5

1

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NGVD 29. Interval 4 feet

Well 3

Well 5

Well 1

Simulated contributing areas and 

location of well and identifier

1,150

Marsh Creek

Straight Run

Asaph Run

Figure 11. Simulated A, areas contributing recharge to wells and water-table contours, B, sources of water to wells, and C, hydraulic 

response of the aquifer during dry hydrologic conditions with withdrawals of 1,000 gallons per minute from the Northern Appalachian 

Research Laboratory (NARL) wells, Tioga County, Pennsylvania.
Sources of Water from Steady-State Simulations 33

1,170

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178

1,142

1,166

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178

1,142

1,166

1,170

1,126

1,158

1,142

1,142

1,146

Upland 

runoff 

9% 

Upland 

runoff 

2% 

B. Sources of water–Northern Appalachian Research Laboratory wellsB. Sources of water–New well

A.

Precipitation 

on valley 

4% 

Decreased 

groundwater 

discharge to 

stream 71% 

C. Hydraulic response

Precipitation 

on valley 

1% 

Decreased

outflow

6%

Aquifer

inflow

16% 

Asaph Run 

seepage 

81% 

Asaph Run 

seepage 

33% 

Straight Run 

seepage 

49% 

Aquifer

inflow

5% 

Increased 

stream 

leakage 

15% 

Increased 

inflow

8% 

1,142

1,138

1,182

1,186

1,174

1,178

3

5

1

New well

1,138

1,178

1,174

1,182

1,186

1,150

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NDVD 29. Interval 4 feet

Well 3

Well 5

Simulated contributing areas and 

location of well and identifier

1,150

Well 1

New well

Marsh Creek

Straight Run

Asaph Run

Figure 12. Steady-state simulation of groundwater flow showing A, areas contributing recharge to wells and water-level 

contours, B, sources of water to wells, and C, hydraulic response of the aquifer during dry hydrologic conditions with withdrawals 

of 1,000 gallons per minute from the Northern Appalachian Research Laboratory (NARL) wells and 1,000 gallons per minute from a 

new production well, Tioga County, Pennsylvania.
34 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

groundwater discharge to Marsh Creek by about 1,420 gal/min 

(71 percent of 2,000 gal/min) and increasing seepage from 

Straight Run and Asaph Run by about 300 gal/min (fig. 12C). 

The ultimate effect on streamflow in Marsh Creek downstream 

from the NARL is caused only by the consumptive withdrawal 

of 1,000 gal/min from the new well; withdrawals from the 

NARL wells are returned as wastewater discharge to Marsh 

Creek about 400 ft downstream from the confluence of Marsh 

Creek and Straight Run.

Dry Conditions with 2,000 Gallons per 

Minute Withdrawals

Dry conditions were simulated with groundwater 

withdrawals totaling 2,000 gal/min from the NARL wells. 

The areas contributing recharge to each well and the 

configuration of the water table are illustrated in figure 13A. 

The area throughout which recharge is captured is more 

extensive than that for withdrawals of the same magnitude 

during the wetter “average” conditions of recharge and 

streamflow shown in figure 7. The contributing area extends 

throughout about 80 percent of the study area, capturing 

infiltration from multiple sources and directing stream 

infiltration from Straight Run, Asaph Run, and Marsh Creek 

to the wells. Infiltration from Asaph Run and Straight Run 

accounts for about 47 and 25 percent, respectively, of the 

groundwater withdrawn by the wells during dry conditions 

(fig. 13B). Induced seepage from Marsh Creek supplies about 

20 percent of the water captured by wells. The capture of 

these sources by wells affects the water budget of the study 

area by decreasing the groundwater discharge to Marsh Creek 

by about 1,380 gal/min (69 percent of 2,000 gal/min) and 

increasing seepage from Straight Run and Asaph Run by 

about 600 gal/min (fig 13C). The ultimate effect on Marsh 

Creek downstream from the NARL, however, is negligible 

because the groundwater withdrawals are discharged about 

400 ft downstream from the confluence of Straight Run and 

Marsh Creek.

Dry Conditions with 2,000 Gallons per Minute 

Withdrawals Plus 1,000 Gallons per Minute 

Withdrawal from the New Production Well

Simulations were made for dry conditions with 

groundwater withdrawals totaling 2,000 gal/min from the 

NARL wells and a withdrawal of 1,000 gal/min from a new 

well. The areas contributing recharge to each well and the 

configuration of the water table are illustrated in figure 14A. 

The area throughout which recharge is captured is more 

extensive than that for withdrawals of the same magnitude 

during the wetter “average” conditions of recharge and 

streamflow shown in figure 8. The contributing area extends 

throughout nearly all of the study area, capturing infiltration 

from multiple sources and directing stream infiltration from 

Straight Run, Asaph Run, and Marsh Creek to the wells. 

The contributing area for the new well competes for water 

from Asaph Run, thereby causing some changes in the areas 

contributing recharge to the NARL wells (compare figures 

13A and 14A). Infiltration from Straight Run and Asaph 

Run accounts for about 25 and 45 percent, respectively, of 

the groundwater withdrawn by the NARL wells during dry 

conditions (fig. 14B). Induced seepage from Marsh Creek 

supplies about 21 percent of the water captured by the NARL 

wells. Seepage from Asaph Run contributes 73 percent of 

the groundwater withdrawn from the new well. Capture 

from these sources affects the water budget of the study area 

by decreasing the groundwater discharge to Marsh Creek 

by about 1,920 gal/min (64 percent of 3,000 gal/min) and 

increasing total seepage from Straight Run and Asaph Run 

by about 780 gal/min (fig 14C). The ultimate effect on Marsh 

Creek downstream from the NARL, however, is caused only 

by the consumptive withdrawal from the new well because 

groundwater withdrawals from the NARL wells are discharged 

about 400 ft downstream from the confluence of Straight Run 

and Marsh Creek.

Model simulations indicate that pumping 1,000 gal/min 

of water from the new well will cause about 0.5 ft of 

additional drawdown in the NARL well field during dry 

hydrologic conditions (fig. 15). However, the magnitude of the 

drawdown might be greater than the two-dimensional model 

results indicate because the vertical hydraulic conductivity of 

the glacial sand and gravel aquifer between the well screen 

depth and Asaph Run is not simulated by the one-layer model.

Time of Travel

The contributing areas and sources of water to wells 

described in the previous section were determined from 

steady-state model simulations that do not take into account 

the time required to move water through the contributing 

zone. In reality, hydrologic conditions do not remain steady 

forever. Thus, particularly for simulations of dry conditions, a 

more accurate depiction of the contributing areas and sources 

of water would be obtained if time of travel were considered. 

Figure 16 shows the part of the simulated contributing area 

from which water is captured by the wells during 100 or 

200 days of steady withdrawals totaling 2,000 gal/min from 

the NARL wells and 1,000 gal/min from a new well during 

dry hydrologic conditions, assuming an effective porosity of 

20 percent. Note that the NARL wells do not capture water 

from Asaph Run even during 200 days of dry conditions, 

which is a long period for dry conditions to persist.

Assumptions and Limitations of the 

Model Simulations

Because the areas contributing recharge and sources 

of water to wells at the NARL were simulated by the use 

of a previously documented groundwater-flow model, 
Sources of Water from Steady-State Simulations 35

1,150

1,130

1,134

1,142

1,154

1,154

1,158

1,158

1,162

1,166

1,170

1,174

1,178

1,182

1,186

1,142

1,138

1,170

1,166

1,174

1,178

1,162

Precipitation 

on valley 

2%

Decreased 

groundwater 

discharge to 

stream 

69% 

Increased 

stream 

leakage 

30% 

B. Sources of water C. Hydraulic response

A.

1,142

1,154

1,154

1,158

1,158

1,162

1,166

1,170

1,174

1,178

1,182

1,186

1,142

1,170

1,166

1,174

1,178

1,162

3

5

1

Straight Run 

seepage 

25% 

Upland 

runoff 

4% Marsh Creek

seepage 

20%

Asaph Run 

seepage 

47% 

Aquifer

inflow

2% 

Decreased

outflow

1%

1,138

1,134

1,130

1,150

1,146

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NGVD29. Interval 4 feet

Well 3

Well 5

Well 1

Simulated contributing areas and 

location of well and identifier

1,150

Marsh Creek

Straight Run

Asaph Run

Figure 13. Simulated A, areas contributing recharge to wells and water-table contours, B, sources of water to wells, and C, hydraulic 

response of the aquifer during dry hydrologic conditions with withdrawals of 2,000 gallons per minute from the Northern Appalachian 

Research Laboratory (NARL) wells, Tioga County, Pennsylvania.
36 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

Upland 

runoff 

4% 

Upland 

runoff 

1% 

B. Sources of water–Northern Appalachian Research Laboratory wellsB. Sources of water–New well

A.

Precipitation 

on valley 

2% 

Decreased 

groundwater 

discharge 

to stream 

64% 

C. Hydraulic response

Marsh Creek

seepage 

6%

Decreased

outflow

4%

Aquifer

inflow

19% 

Straight 

Run seepage 

25% Asaph Run 

seepage 

73% 

Increased 

stream 

leakage 

26% 

Precipitation on valley

1% Marsh Creek

seepage 

21%

Asaph Run 

seepage 

45% 

Aquifer

inflow

3% 

Increased 

inflow

6%

1,138

1,142

1,170

1,174

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178 1,182

1,186

1,178

1,166

1,142

1,150

1,154

1,158

1,162

1,166

1,170

1,174

1,178

1,182

1,186

1,178

1,166

1,170

1,174

1,138 1,158 1,162

1,154

1,146

1,142

1,138

1,134

1,130

3

5

1

New well

1,150

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Water-table contour, in feet 

above NGVD29. Interval 4 feet

Well 3

Well 5

Simulated contributing areas and 

location of well and identifier

1,150

Well 1

New well

Marsh Creek

Straight Run

Asaph Run

Figure 14. Simulated A, areas contributing recharge to wells and water-table contours, B, sources of water to wells, and C, hydraulic 

response of the aquifer during dry hydrologic conditions with withdrawals of 2,000 gallons per minute from the Northern Appalachian 

Research Laboratory (NARL) wells and 1,000 gallons per minute from a new production well, Tioga County, Pennsylvania.
Sources of Water from Steady-State Simulations 37

3

2 5

1

New well

Wellsboro

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Additional drawdown from proposed 

withdrawal at new well, in feet

0.50 - 2.00

2.01 - 4.00

4.01 - 6.00

6.01 - 9.53

Northern Appalachian Research 

Laboratory production well and

identifer

New well, site of proposed 

groundwater withdrawal

3

Production well

Marsh Creek

Straight Run

Asaph Run

Figure 15. Simulated additional drawdown caused by a proposed groundwater withdrawal of 1,000 gallons per minute southwest of 

the Northern Appalachian Research Laboratory (NARL) during dry hydrologic conditions, Tioga County, Pennsylvania.
38 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

3

5

1

New well

Wellsboro

77°24'30" 77°24' 77°23'30"

41°

46'

40"

41°

46'

20"

Base imagery from PAMAP, 2003, 1:2,400

0 1,000 2,000 FEET

0 200 400 METERS

EXPLANATION

Travel time to well

100 day

200 day

Well 3

Well 5

Well 1

New well

Contributing areas and location 

of well and identifier

Marsh Creek

Straight Run

Asaph Run

Figure 16. Simulated areas contributing recharge to wells and extent of the areas captured during 100 or 200 days of steady pumping 

during dry hydrologic conditions in the model area, Tioga County, Pennsylvania.
Summary and Conclusions 39

the limitations of the model need to be recognized. 

The groundwater-flow model of Williams and 

Morrissey (1996) used in this study is a two-dimensional 

(one-layer) representation of steady-state groundwater flow in 

the glacial sand and gravel aquifer. The model uses a finitedifference grid with cells of 200 ft by 200 ft throughout the 

model domain and recharge rates specified to represent either 

average or dry periods. The two-dimensional model is a 

limitation because vertical differences in boundary conditions 

and hydraulic properties cannot be incorporated into the 

model, and vertical hydraulic gradients in the glacial sand 

and gravel aquifer cannot be simulated. A three-dimensional, 

multiple-layer model would allow for a more accurate 

representation of groundwater withdrawals from the wells that 

are not screened throughout the entire saturated thickness of 

the aquifer and would allow the vertical hydraulic conductivity 

to be assigned values typical for stratified sediments. The 

rather coarse finite-difference grid causes the boundary of 

the glacial sand and gravel aquifer and well locations to be 

represented with less accuracy than would be possible if the 

number of model layers and rows were increased. Smaller 

cells, combined with more model layers would allow a better 

simulation of vertical gradients near streams and wells, which 

could affect the simulated drawdown and the delineation of 

areas contributing recharge to the wells.

The simulations in this report were based on steady-state 

conditions of uniform recharge and groundwater withdrawals, 

although both are known to vary widely. Williams (1991) 

showed that groundwater recharge to the glacial sand and 

gravel aquifer varies seasonally, principally on the availability 

of streamflow from Straight Run and Asaph Run. Thus, 

although steady-state simulations of dry hydrologic conditions 

show that it is possible for the NARL wells to capture water 

from Asaph Run, maps of simulated groundwater time-oftravel indicate that a dry period of unusually long duration 

would be required. Also, simulations were made for two 

conditions of steady-state recharge reported in Williams and 

Morrissey (1996)—termed “average” and “dry” conditions in 

this report. On the basis of data from the long-term streamgage 

at Corey Creek near Mainesburg, Pennsylvania, the average 

recharge probably represents wetter conditions than does the 

long-term mean recharge, and the dry-condition recharge 

represents conditions that would happen 2 to 3 months per 

year. Thus, conditions for a severe drought were not simulated.

In all of the simulations, the sources of water include 

seepage from streams or runoff that originated from the 

bedrock uplands. However, because the bedrock aquifers 

were not explicitly simulated, the areas contributing recharge 

as illustrated in this study extend only to the boundary of the 

glacial sand and gravel aquifer along the bedrock valley wall. 

It should be recognized that capture of stream seepage or 

upland runoff implies that upland areas outside of the model 

domain contribute water to the wells.

The new well 3,500 ft to the southwest of the NARL is 

near the general-head boundary where groundwater exits the 

glacial sand and gravel aquifer downvalley. Drawdown of 4 

to 6 ft, caused by groundwater withdrawals from this well, 

reaches the general-head boundary as does the simulated 

area contributing recharge to the well. Thus, the properties 

of this artificial model boundary location probably affect the 

magnitude of simulated drawdown and might also affect the 

analysis of the area contributing recharge and sources of water 

to the well.

Summary and Conclusions

A study was conducted to document source areas and 

quality of the groundwater supply at the U.S. Geological 

Survey (USGS) Northern Appalachian Research Laboratory 

(NARL) near Wellsboro, Pennsylvania, which is surrounded 

by the ongoing development of natural gas in the Marcellus 

Shale. Development of natural gas in the Marcellus Shale 

poses a potential threat to the quality and quantity of 

groundwater available to the NARL. Natural gas wells are 

being permitted and drilled in the Marsh Creek valley and 

adjacent uplands to the north and south of the valley. A largecapacity water well has been drilled in the glacial sand and 

gravel aquifer about 3,500 feet southwest of the NARL 

wells to provide water for a gas company. Land disturbance 

from access roads, gas wells, and pipeline construction is 

anticipated, and hydrologic effects from hydraulic fracturing 

with associated water use and waste handling are possible.

Groundwater samples collected during November 2–4, 

2010, from the four wells used by the NARL (tapping 

the glacial sand and gravel aquifer) and from two nearby 

domestic supply wells (tapping the Catskill Formation) 

indicate that the baseline quality of the water is good. 

The samples were analyzed for major ions, nutrients, trace 

metals, radiochemicals, dissolved gases, and stable isotopes 

of oxygen and hydrogen in water and carbon in dissolved 

carbonate to document groundwater quality. Samples were not 

analyzed for anthropogenic organic constituents associated 

with hydraulic fracturing activities, but additional sampling 

for these constituents would provide a more complete 

water-quality baseline. Results showed low concentrations 

of all constituents; only radon, which ranged from 980 to 

1,310 picocuries per liter, was somewhat elevated. These 

findings are consistent with the pristine nature of the aquifer in 

the Marsh Creek valley, which is the reason the laboratory was 

sited at this location.

Groundwater modeling simulations showed that the 

principal source of water to the NARL wells is infiltration 

from Straight Run with major contributions possible from 

Asaph Run during dry periods. The sources of water and 

areas contributing recharge to wells were identified by the 

use of a previously documented MODFLOW groundwaterflow model for the following conditions: (1) withdrawals 

of 1,000 to 3,000 gallons per minute from the NARL wells, 

(2) average or dry hydrologic conditions, and (3) withdrawals 

of 1,000 gallons per minute from a new well 3,500 feet to 
40 Groundwater Quality and Simulation of Sources of Water to Wells in the Marsh Creek Valley at NARL, Tioga County, Pennsylvania

the southwest of the NARL that was drilled to provide water 

for Marcellus gas-well operations. Simulations indicated 

that during average hydrologic conditions, infiltration from 

Straight Run, a tributary to Marsh Creek, provides nearly all 

the water to the NARL wells. During dry conditions, the areas 

contributing recharge expand such that Asaph Run contributes 

about half of the water to the NARL wells at rates of 1,000 

or 2,000 gallons per minute. The addition of a simulated 

withdrawal of 1,000 gallons per minute from the nearby new 

well does not substantially affect the sources of water captured 

by the NARL wells. 

The results described in this report have some 

limitations. The water-quality samples represent only a 

snapshot of groundwater chemistry for one hydrologic 

condition; the concentration of some constituents may 

change temporally. In addition, samples were not analyzed 

for organic constituents associated with hydraulic fracturing 

and other human activities. The sources contributing water 

to the NARL wells and a new well were simulated by use 

of a simplified one-layer model of the glacial sand and 

gravel aquifer for steady-state conditions that are never 

achieved in reality. Although steady-state simulations of dry 

hydrologic conditions show that it is possible for the NARL 

wells to capture water from Asaph Run, maps of simulated 

groundwater time-of-travel indicate that a dry period of 

unusually long duration would be required. A better analysis 

could be achieved if the groundwater-flow model were 

recalibrated with a finite-difference grid having multiple 

layers, small cells (as small as 10-foot squares near wells), and 

transient stress periods.

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Appalachian Research Laboratory, Tioga County, Pennsylvania—Scientific Investigations Report 2012–5042