U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2010–1047

Prepared in cooperation with the

New Hampshire Department of Environmental Services and the

U.S. Environmental Protection Agency, Region 1

Hydrostratigraphic Mapping of the Milford-Souhegan 

Glacial Drift Aquifer, and Effects of Hydrostratigraphy on 

Transport of PCE, Operable Unit 1, Savage Superfund Site, 

Milford, New Hampshire
Cover. Photograph of sediments excavated from an upper cobble unit layer about 15 feet below land surface. The poorly sorted unit 

can contain fine sands to boulders, and its hydraulic conductivity is controlled by the amount of fine sands interspersed within a matrix 

between the cobbles and boulders.
Hydrostratigraphic Mapping of the MilfordSouhegan Glacial Drift Aquifer, and Effects 

of Hydrostratigraphy on Transport of PCE, 

Operable Unit 1, Savage Superfund Site, 

Milford, New Hampshire

By Philip T. Harte

Prepared in cooperation with the

New Hampshire Department of Environmental Services and the

U.S. Environmental Protection Agency, Region 1

Open-File Report 2010–1047

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: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Harte, P.T., 2010, Hydrostratigraphic mapping of the Milford-Souhegan glacial drift aquifer, and effects of hydrostratigraphy on transport of PCE, Operable Unit 1, Savage Superfund site, Milford, New Hampshire: U.S. Geological Survey 

Open-File Report 2010–1047, 34 p., 3 pls., at http://pubs.usgs.gov/of/2010/1047/.
iii

Acknowledgments

This study was conducted as part of the remedial effort at the Savage Municipal Well Superfund 

site and is a collaborative effort between Federal, State, and local governments, and private 

companies and individuals. The author wishes to thank Robin Mongeon and Thomas Andrews 

of the New Hampshire Department of Environmental Services (NHDES); Richard Goehlert, site 

remedial project manager of the U.S. Environmental Protection Agency (USEPA), Region 1; and 

Richard Willey, lead hydrogeologist, USEPA, Region 1, for their cooperation and support. Thanks 

to personnel at N.A. Water Systems, Inc., and Roy F. Weston, Inc., for much needed logistical 

assistance. Special thanks to Dr. Stephen L. Snyder of the U.S. Geological Survey, Reston, Va., 

who quantified concentrations of selected radioactive elements in sediment samples using 

gamma-ray spectrometry at his Reston laboratory.
THIS PAGE INTENTIONALLY LEFT BLANK
v

Contents

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

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

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

Purpose and Scope ..............................................................................................................................3

Description of Study Area ...................................................................................................................3

Previous Investigations of Operable Unit 1 (OU1) ...........................................................................5

Hydrostratigraphic Mapping........................................................................................................................6

Methods..................................................................................................................................................6

Drilling Characteristics of Sediments.......................................................................................6

Lithologic Sampling and Logs....................................................................................................6

Borehole Logging.........................................................................................................................7

Gamma-Ray Spectrometry.........................................................................................................8

Hydraulic Characteristics...........................................................................................................8

Results of Hydrostratigraphic Mapping............................................................................................9

Hydrostratigraphic Units ............................................................................................................9

Gamma and Radioisotope Characteristics...................................................................12

Hydraulic Characteristics................................................................................................12

Discussion of Hydrostratigraphic Units ........................................................................14

Hydrostratigraphic Surface Maps ..........................................................................................15

Hydrostratigraphic Sections....................................................................................................20

Hydrostratigraphic Effects on Flow, Transport of PCE, and Remediation ..........................................20

Summary and Conclusions.........................................................................................................................28

Selected References...................................................................................................................................28

Appendix 1.....................................................................................................................................................31

Plates

1a. Locations of groundwater wells, test boreholes, air sparge, and vapor extraction wells 

for Operable Unit 1 (OU1) of the Savage Municipal Well Superfund site, Milford, 

New Hampshire, Pre-2003

1b. Locations of groundwater wells, test boreholes, air sparge, and vapor extraction wells 

for Operable Unit 1 (OU1) of the Savage Municipal Well Superfund site, Milford, 

New Hampshire, 2003–08

2. Locations of vertical profile points and selected groundwater wells for Operable Unit 1 

(OU1) of the Savage Municipal Well Superfund site, Milford, New Hampshire, 2008
vi

Figures

1. Location map of the volatile organic compound contaminant plume in 1994, Savage 

Municipal Well Superfund site, Milford, New Hampshire.....................................................2

2. Map of Operable Unit 1 (OU1), remedial system, selected wells, 1995 contaminant 

plume of tetrachloroethylene (PCE), line of section A-A’, Savage Municipal Well 

Superfund site, Milford, New Hampshire .................................................................................4

3. Logs of well PW-20D showing lithology, hydrostratigraphy, borehole natural gamma 

ray and electromagnetic conductivity in 2006, OU1 area, Savage Municipal Well 

Superfund site, Milford, New Hampshire ...............................................................................11

4. Plot of borehole natural gamma-ray counts to corresponding thorium concentration 

per hydrostratigraphic unit, OU1 area, Savage Municipal Well Superfund site, 

Milford, New Hampshire ...........................................................................................................13

5. Contour map of altitude of top of bedrock surface, OU1 area, Savage Municipal 

Well Superfund site, Milford, New Hampshire......................................................................16

6. Contour map of altitude of top of till surface, OU1 area, Savage Municipal Well 

Superfund site, Milford, New Hampshire ...............................................................................17

7. Contour map of basal till thickness, OU1 area, Savage Municipal Well Superfund 

site, Milford, New Hampshire...................................................................................................18

8. Contour map of altitude of bottom surface for hydrostratigraphic unit MS2, 

OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire..................19

9. Transverse cross section through OU1 showing lithology, OU1 area, Savage 

Municipal Well Superfund site, Milford, New Hampshire...................................................21

10. Transverse cross section through OU1 showing borehole gamma-ray counts, 

OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire..................22

11. Transverse cross section through OU1 showing hydrostratigraphic units, OU1 area, 

Savage Municipal Well Superfund site, Milford, New Hampshire ....................................23

12. Transverse cross section through OU1 showing 2007 PCE concentrations from 

wells, along with hydrostratigraphy, OU1 area, Savage Municipal Well Superfund 

site, Milford, New Hampshire...................................................................................................25

13. Transverse cross section through OU1 showing 1996 PCE concentrations from 

vertical profiling of groundwater, along with hydrostratigraphy, OU1 area, Savage 

Municipal Well Superfund site, Milford, New Hampshire...................................................26

14. PCE concentrations from vertical profiling and logs of borehole natural gamma-ray, 

lithologic, and hydrostratigraphic units at well PW-20D, OU1 area, Savage 

Municipal Well Superfund site, Milford, New Hampshire...................................................27
vii

Tables

1. Lithologic codes and description of sediments, OU1 area, Savage Superfund site, 

Milford, New Hampshire .............................................................................................................7

2. Hydrostratigraphic codes, unit names, and description, OU1 area, Savage Superfund 

site, Milford, New Hampshire...................................................................................................10

3. Summary of unconsolidated hydrostratigraphic units and thickness, OU1 area, 

Savage Superfund site, Milford, New Hampshire.................................................................12

4. Coefficients of determination and significance for correlation of radioactive element 

concentration and associated borehole natural gamma-ray count, OU1 area, 

Savage Superfund site, Milford, New Hampshire.................................................................12

5. Mean concentration of analyzed radioactive elements for selected hydrostratigraphic 

units, OU1 area, Savage Superfund site, Milford, New Hampshire...................................14

6. Estimates of hydraulic conductivity from effective grain size (D90) for selected 

hydrostratigraphic units, OU1 area, Savage Superfund site, Milford, New Hampshire.14

7. Relative ranking of radioactive elements based on concentration, hydraulic 

conductivities, and borehole natural gamma-ray counts for selected hydrostratigraphic units, OU1 area, Savage Superfund site, Milford, New Hampshire ....................15

1–1. Comparison of grain-size-analysis methods from lithologic samples in the OU1 area, 

Savage Superfund site, Milford, New Hampshire.................................................................32

1–2. Comparison of hydraulic conductivities between hydraulic tests of single wells and 

grain-size analyses, OU1 area, Savage Superfund site, Milford, New Hampshire.........33
viii

Conversion Factors, Datum, and Abbreviations

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2) 929.0 square centimeter (cm2)

square foot (ft2) 0.09290 square meter (m2)

square inch (in2) 6.452 square centimeter (cm2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2)

Volume

gallon (gal) 3.785 liter (L)

gallon (gal) 0.003785 cubic meter (m3)

gallon (gal) 3.785 cubic decimeter (dm3)

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) 28.32 cubic decimeter (dm3)

cubic foot (ft3) 0.02832 cubic meter (m3)

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

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

foot per year (ft/yr) 0.3048 meter per year (m/yr)

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

cubic foot per day (ft3/d) 0.02832 cubic meter per day (m3/d)

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

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Pressure

pound per square inch (lb/in2) 6.895 kilopascal (kPa)

Mass

pound 0.4536 kilogram (kg)

Specific capacity

gallon per minute per foot 

[(gal/min)/ft)]

 0.2070 liter per second per meter 

[(L/s)/m]

Hydraulic conductivity

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

Hydraulic gradient

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

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Transmissivity*

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d)
ix

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

 °F=(1.8×°C)+32

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

 °C=(°F-32)/1.8

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

(NGVD 29).

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

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

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

25°C).

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

approximately equivalent to parts per million (ppm), or micrograms per liter (μg/L), approximately 

equivalent to parts per billion (ppb).

ABBREVIATIONS AND EXPLANATIONS OF TERMS USED IN THIS REPORT:

cis-1,2-DCE cis-1,2-dichloroethene

DCE dichloroethene

DNAPL’S Dense Non-Aqueous Phase Liquids

INEEL Idaho National Engineering and Environmental Laboratory

MSGD Milford-Souhegan Glacial-Drift aquifer

OU1 Operable Unit #1 of the Savage Municipal Well Superfund site

OU2 Operable Unit #2 of the Savage Municipal Well Superfund site

PCE tetrachloroethylene

TCE trichloroethylene 

TOC total organic carbon

VOC volatile organic compound

UNITS OF MEASUREMENT:

g grams

min minute

yr year

WELL IDENTIFICATION, ABBREVIATIONS, AND EXPLANATION:

Well names used in this report typically are designated based on previous studies. 
x

Prefix for remedial wells

EW exterior barrier wall extraction well

IW interior barrier wall extraction well

RW recharge well

SP air sparge well (used for remedial technology that reduces concentrations of 

 volatile contaminants adsorbed to soils and dissolved in groundwater in the 

 saturated zone; involves the injection of air into the saturated zone)

SVE soil vapor extraction well (used for remedial technology that reduces 

 concentrations of volatile contaminants adsorbed to soils in the unsaturated 

 zone; involves the extraction of air from the unsaturated zone)

Miscellaneous

VP vertical profile

INEEL well located in INEEL well field

Prefix for observation wells

P piezometer

PW, B, MI, and MW observation wells

Suffix for observation wells

D or C deep cluster well; typically set at depths greater than 70.1 feet below 

 land surface

M or B medium cluster well; typically set at depths between 40.1 and 70.1 feet below 

 land surface

R bedrock well

S or A shallow cluster well; typically set at depths less than 40.1 feet below 

 land surface

Selected lithologic abbreviations (Table 1 contains an expanded list)

c coarse

f fine

m medium

Wx weathered

S sand

g gravel

sg sand and gravel

gs gravel and sand
Abstract

The Savage Municipal Well Superfund site in the 

Town of Milford, New Hampshire, was underlain by a 

0.5-square mile plume (as mapped in 1994) of volatile 

organic compounds (VOCs), most of which consisted of 

tetrachloroethylene (PCE). The plume occurs mostly within 

highly transmissive stratified-drift deposits but also extends 

into underlying till and bedrock. The plume has been divided 

into two areas called Operable Unit 1 (OU1), which contains 

the primary source area, and Operable Unit 2 (OU2), which 

is defined as the extended plume area outside of OU1. The 

OU1 remedial system includes a low-permeability barrier 

wall that encircles the highest detected concentrations of PCE 

and a series of injection and extraction wells to contain and 

remove contaminants. The barrier wall likely penetrates the 

full thickness of the sand and gravel; in many places, it also 

penetrates the full thickness of the underlying basal till and 

sits atop bedrock. 

From 1998 to 2004, PCE concentrations decreased by an 

average of 80 percent at most wells outside the barrier wall. 

However, inside the barrier, PCE concentrations greater than 

10,000 micrograms per liter (μg/L) still exist (2008). The 

remediation of these areas of recalcitrant PCE presents challenges to successful remediation. 

The U.S. Geological Survey (USGS), in cooperation 

with the New Hampshire Department of Environmental 

Services (NHDES) and the U.S. Environmental Protection 

Agency (USEPA), Region 1, is studying the solute transport 

of VOCs (primarily PCE) in contaminated groundwater in the 

unconsolidated sediments (overburden) of the Savage site and 

specifically assisting in the evaluation of the effectiveness of 

remedial operations in the OU1 area. As part of this effort, the 

USGS analyzed the subsurface stratigraphy to help understand 

hydrostratigraphic controls on remediation.

A combination of lithologic, borehole natural gamma-ray 

and electromagnetic (EM) induction logging, and test drilling 

has identified 11 primary hydrostratigraphic units in OU1. 

These 11 units consist of several well-sorted sandy layers 

with some gravel that are separated by poorly sorted cobble 

layers with a fine-grained matrix. Collectively these units 

represent glacial sediments deposited by localized ice-margin 

fluctuations. For the most part, the units are semi-planar, 

particularly the cobble units, and truncated by an undulating 

bedrock surface. The lowermost unit is a basal till that ranges 

in thickness from zero to greater than 10 feet and mantles the 

bedrock surface.

The 11 units have different lithologic and hydraulic 

characteristics. The hydraulic conductivity of the well-sorted 

sand and gravel units is typically greater than the conductivity of the poorly sorted cobble units and the basal till. The 

hydraulic conductivity ranges from 5 to greater than 500 feet 

per day. Lateral and vertical variation in lithology and hydraulic conductivity are inferred by variations in borehole natural 

gamma-ray counts and estimates of hydraulic conductivity. 

The comparison of hydrostratigraphic units with the 

spatial distribution of PCE concentrations suggests that solute 

transport away from source areas is primarily lateral within 

the permeable sandy units in the middle to lower parts of the 

aquifer. Along the centerline of the interior barrier area, highest PCE concentrations are in the sandy units to the east of 

suspected source areas. 

Introduction

The Savage Municipal Well Superfund site (Savage site), 

named after a former municipal water-supply well (the Savage 

well) that served the Town of Milford, New Hampshire, is 

underlain by a 0.5-square mile (mi2) contaminant plume (as 

shown in 1994; fig. 1) of volatile organic compounds (VOCs), 

consisting primarily of tetrachloroethylene (PCE). The VOC 

plume is mostly within highly transmissive stratified-drift 

deposits and extends into the underlying till and bedrock. The 

stratified-drift deposits, part of the Milford-Souhegan-GlacialDrift aquifer (MSGD), are an important source of water for a 

Hydrostratigraphic Mapping of the Milford-Souhegan 

Glacial Drift Aquifer, and Effects of Hydrostratigraphy on 

Transport of PCE, Operable Unit 1, Savage Superfund Site, 

Milford, New Hampshire

By Philip T. Harte
2 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

0

0

20 MILES

20 KILOMETERS

0

0

0.5

0.5

1 MILE

1 KILOMETER

Milford 

village

center

VERMONT

CANADA

MAINE

MASSACHUSETTS

NEW

HAMPSHIRE

Nashua

Keyes

well

43o

44o

72o

45o

71o

Concord

Former 

OK Tool

facility

MI-18

Savage

well

Souhegan River

Purgatory Brook

Hartshorn Brook

Tucker Brook

Great Brook

Ditch

Area shown PFH

on subsequent

figures

Operable Unit 1 (OU1)

Approximate area of Operable Unit 2 (OU2)

Milford-Souhegan Glacial Drift aquifer boundary

Contaminant plume line of equal volatile

 organic concentration, in parts per billion, 1994

General groundwater-flow direction (Harte, 2004)

Inactive former production well

Inactive private fish hatchery withdrawal well

Observation well and identifier

State Fish Hatchery withdrawal well

Industrial withdrawal well and identifier—

 inactive since August 2002

EXPLANATION

MI-18

PFH

FH-5

MI-88

10

MI-88

FH-5

FH-4

10

100

1,000

10

100

1,000

71°42'

71°41'

71°40'

42°51'

42°50'

Figure 1. Location map of the volatile organic compound contaminant plume in 1994, Savage Municipal Well Superfund site, 

Milford, New Hampshire.
Introduction 3

New Hampshire State Fish Hatchery, which uses more than 

2 million gallons per day (Mgal/d). Before contamination with 

VOCs, the aquifer also supplied more than 1 Mgal/d to two 

former municipal water-supply wells (the Savage well and a 

well outside of the study area (Keyes well)). 

For remedial purposes, the plume is divided into two 

Operable Units. A discontinued tool manufacturing facility, 

the OK Tool facility, is part of Operable Unit 1 (OU1) and 

has been identified as the primary source area of the contaminant plume containing PCE that led to the contamination of 

the Savage well (HMM Associates, Inc., 1989; 1991). The 

contaminant plume downgradient of OU1 is designated as 

Operable Unit 2 (OU2), also called the extended plume area.

The State of New Hampshire Department of 

Environmental Services (NHDES) and the U.S. Environmental 

Protection Agency (USEPA), Region 1, have constructed 

a remedial system for the OU1 area (fig. 2). The remedial 

system consists of a low-permeability barrier wall, which 

surrounds the highest concentrations of dissolved PCE 

and, most likely, some Dense Non-Aqueous Phase Liquid 

(DNAPL), and various injection (including a recharge gallery; 

fig. 2) and extraction wells (vapor and water) to capture and 

treat the dissolved contaminants. Several previously identified 

source areas are shown in figure 2 where contaminant 

disposal has been identified (Camp, Dresser, and McKee, Inc., 

Federal Programs Corporation, 1995). The barrier wall was 

constructed from July to November 1998. Remedial operations 

of wells were tested from December 1998 to March 1999. Full 

remedial operation started in May 1999. 

In 1995, maximum concentrations of PCE, the primary 

contaminant, ranged up to 100,000 micrograms per liter 

(μg/L) in areas now inside the barrier wall to 10,000 μg/L 

in areas now outside the wall (Camp, Dresser, and McKee, 

Inc., Federal Programs Corporation, 1995). Concentrations of 

secondary VOCs (TCE and cis-1,2-DCE) were typically one 

to two orders of magnitude less than those of PCE (Harte and 

others, 2001). 

Remediation and containment have led to PCE 

concentration declines in parts of OU1. From 1999 to 2007, 

the mass of dissolved VOCs captured, extracted, and treated 

totaled 2,431 pounds (N.A. Water Systems, 2007). From 2003 

to 2004, additional destruction of VOCs from Insitu Chemical 

Oxidation (ISCO) treatment of target areas inside the barrier 

was estimated at 247 pounds (N.A. Water Systems, 2006a). 

Outside of the barrier, PCE concentrations have declined 

to less than 10 μg/L over a large area of OU1 (as of 2008). 

Inside the barrier, PCE concentrations have declined to less 

than 10,000 μg/L over some areas. Despite these successes, 

remediation of areas of recalcitrant PCE still presents 

new challenges. 

The U.S. Geological Survey (USGS), in cooperation with 

the NHDES and the USEPA, Region 1, conducted a study of 

the stratigraphy of the MSGD aquifer at the OU1 area to (1) 

establish a framework for understanding solute transport of 

VOCs (primarily PCE), (2) assess spatial and temporal concentration patterns of PCE, and (3) provide information to help 

remedial managers develop remedial strategies for addressing 

residual pockets of PCE. The establishment of this framework 

is herein termed “hydrostratigraphic mapping.”

Purpose and Scope

This report presents methods and findings from the 

hydrostratigraphic mapping of subsurface sediments for the 

OU1 area from 2004 to 2008. Included is a discussion of 

the various techniques used in this investigation (lithologic 

sampling and characterization, test drilling, and borehole logging). Important results are highlighted and implications for 

remedial strategies are discussed. The spatial distribution of 

PCE concentrations was compared to the hydrostratigraphic 

framework to identify potential source locations for PCE and 

solute-transport processes (advection, dispersion, diffusion, 

retardation, and degradation).

Description of Study Area

The OU1 study area is delineated in figure 1 and covers a “pie”-shaped area in the western part of the Souhegan 

River Valley and MSGD aquifer area. This section includes 

a description of the river valley and MSGD aquifer area 

(generally coincident), and of the OU1 study area. The MSGD 

aquifer is defined as the entire sequence of unconsolidated 

sediments overlying (overburden) the bedrock in the Souhegan 

River Valley of Milford, New Hampshire.

The Souhegan River Valley slopes gently to the east at 

approximately 12 ft per mile (ft/mi) along the Souhegan River. 

Land-surface altitudes range from 230 to 280 ft (above NGVD 

29) in the valley, and water drains to the Souhegan River 

and its tributaries, including Tucker, Purgatory, Great, and 

Hartshorn Brooks and a number of small, unnamed streams 

(fig. 1). A discharge ditch drained processed waters from a 

manufacturing company in the southwestern part of the study 

area until operations terminated in August 2002.

Land use overlying the MSGD aquifer is predominantly 

industrial in the southwestern area, agricultural in the central 

and northwestern areas, and residential and commercial elsewhere. The contaminant plume underlies a large agricultural 

area (not shown on any figures) and abuts a commercialindustrial area to the south (not shown on any figures). 

Groundwater withdrawals from the MSGD aquifer in 

2001 were used primarily for commercial and industrial 

purposes. Two wells for the State Fish Hatchery in the 

northwestern part of the study area (wells FH-4 and FH-5, 

fig. 1) withdraw more than 2 Mgal/d. Consumptive use is 

small because most of the withdrawn water is returned to 

Purgatory Brook (fig. 1). An inactive withdrawal well at a 

private fish hatchery (PFH, fig. 1) in the eastern part of the 

study area withdrew 0.14 Mgal/d until the late 1990s. An 

inactive (as of August 2002) withdrawal well (MI-88, 

fig. 1) at an industrial complex in the southwestern part of the 

study area withdrew about 0.25 Mgal/d, as reported in 1995. 
4 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Route 101A

974,000 975,000 974,500 975,500

125,500125,000124,500

Ground-water  recharge gallery

P-2

B95-15

PW-2S

PW-2MPW-2DPW-2R

MI-32

PW-12SPW-12DPW-12R

PW-12M

PW-13S

PW-13M

PW-13D

PW-14M

MW-2A

SVE-6

SVE-3

SP-2

SP-1

SVE-5

SVE-4

SVE-2

SVE-1

RW-1

IW-2

IW-1

B95-8

B95-9

RW-3

EW -1

PW-1DPW-1S B95-13

EW -2

MW-16C

MW-16R

MW-16B MW-16A

B95-12

P-1

0 500 FEET0

250

50 100 METERS

MI-63

MW-2B

MW-2R

PW-14D

PW-14S

PW-3S

B95-6

PW-5MPW-5DPW-5R

PW-3D

PW-9M

PW-8M

PW-4DPW-4M

PW-7SPW-7M

B95-3

PW-6R

PW-6S

PW-6M

PW-6D MI-21

MI-25

MI-26

MI-19

MI-20

MI-23 MI-22

B95-5

MW-27

RW-2

PW-19D

PW-20D

PW-18D

PW-6MB

PW-16D

PW-17M

PW-15D

MW-0312

Planimetric base by U.S. Environmental Protection Agency,Region 1 from aerial photographs taken 1987, 500-foot gridbased on New Hampshire State Plane coordinate system,Horizontal Datum-North American Datum, 1983

A'

A

CI WI HCW EI HCE

NWP NCP NEP HCNE

HCN

HCNW

HCSW SWP SCP SEP

SP-1(572)

HCSE

HCS 0 10 20 FEET

0 5 METERS

SVE-4

INEEL (Idaho National Engineering and Environmental Laboratory) test area 

SWMLS SCMLS SEMLS

NWMLS NCMLS NEMLS

Abandoned pit

EXPLANATION

Barrier wall Approximate boundary ofOU1 areaInjection well and identifierExtraction well and identifierAir sparge or soil vapor well and identifierObservation well and identifier

10 – 99100 – 999Greater than 1,000

RW-2EW -1SP-1P-2

Cross-section lineINEEL well identifier CIFormer OK Tool facilityKnown contaminant  disposal areaPCE concentration in middle overburden, in parts per billion, 1995

A A'

Figure 2. Map of Operable Unit 1 (OU1), remedial system, selected wells, 1995 contaminant plume of tetrachloroethylene (PCE), line of section A-A’, Savage Municipal Well Superfund site, Milford, New Hampshire.
Introduction 5

The effluent from this well was formerly discharged to the 

aforementioned drainage ditch (Ditch; fig. 1). 

Solvents were discharged into the subsurface at the OK 

Tool facility for approximately 35 years until the early 1980s 

(HMM Associates, Inc., 1989; 1991). Although discharges 

have ceased, the underlying contaminant-soaked sediments 

and immiscible solvents (most likely DNAPLs) continued to 

contaminate groundwater flowing easterly underneath the site 

until a barrier wall was constructed in 1998. 

The barrier wall (referred to as “barrier” in this report) 

is constructed of low-permeability materials (bentonite 

clay) and is designed to contain the highest concentrations 

of VOCs from being transported into the aquifer. The barrier encircles a 166,000-square foot (ft2

) area. In general, 

the barrier fully penetrates the sand and gravel layers and in 

some places the underlying till, to the bedrock surface. The 

barrier was designed to penetrate at least 3 ft into the basal 

till, but in many locations this minimum depth was exceeded. 

An analysis of barrier wall depth is provided in Harte (2006). 

Various injection and extraction wells (fig. 2) were installed 

to insure hydraulic isolation, reduce contaminant mass inside 

the barrier wall, and capture and treat the contaminants outside 

the barrier. Exterior extraction wells were operated from 1999 

until April 2007 when effluent PCE concentrations from these 

wells approached remedial clean-up levels (less than 10 μg/L). 

Interior extraction continued (as of 2008) to insure hydraulic 

containment inside the barrier and to promote inward hydraulic gradients across the barrier.

Groundwater flow and solute transport were west to east 

prior to construction and operation of the remedial system. 

The Souhegan River in this area is a losing river reach (Harte 

and Mack, 1992), and recharge from the river is an important 

component of the groundwater budget. After the remedial 

system was installed and after commencement of remedial 

operation, local flow patterns changed. During operation of 

remedial extraction wells inside the barrier, inward flow across 

the barrier generally occurs for conditions with a minimum 

net extraction of 20 gallons per minute (gal/min), and flow 

directions locally are opposite the regional flow patterns 

(Harte, 2006).

Three primary VOC sources have been identified 

inside the barrier area in OU1 (Camp, Dresser, and McKee, 

Inc., 1996). They include a floor drain inside the former 

“destroyed” building near a degreasing tank (called 

“abandoned pit area”), a leach field north of the former 

building, and an area northwest of the former building near a 

former degreasing tank. The abandoned pit area (southernmost 

location in fig. 2 and identified as the contaminant disposal 

area in the figure inset) is believed to be the primary source 

input location based on concentrations of PCE in the soil 

and concentrations of PCE in groundwater samples from 

observation wells and vertical profile points (Guilbeault and 

others, 1997; 1998). The locations of these data points are 

shown in figure 2 and on plates 1a, 1b, and 2.

Previous Investigations of Operable Unit 1 (OU1)

The abandoned pit area in the INEEL (Idaho National 

Engineering and Environmental Laboratory, named after the 

lead investigative agency studying the pit area) well field has 

been the focus of most investigations of contaminant source 

characterization (fig. 2). Investigations determined that the 

distribution of PCE is complex and characterized by relatively 

thin, 3 to 15 ft-thick zones of high PCE concentrations (greater 

than 10,000 μg/L) at depths of 15 to 60 ft below land surface, 

interspersed within zones of lower PCE concentrations (less 

than 10,000 μg/L). The variable PCE distribution suggests that 

aquifer heterogeneity is also complex. Guilbeault and others 

(1997; 1998) suggest aquifer porosity as a possible controlling 

mechanism affecting DNAPL distribution and dissolved PCE 

concentrations. Harte and others (2002) and Harte (2008) 

determined that high PCE concentrations were associated with 

stratigraphic contacts between different lithologies. 

Most of the information regarding PCE distribution 

in OU1 was initially obtained from vertical profiling of the 

INEEL field area. Vertical profiling of groundwater by use of 

a direct-push profiler was performed on multiple occasions 

by the University of Waterloo in 1994, 1995, 1997, and 

1998 (Guilbeault and others, 1997; 1998) to map subsurface 

contamination (vertical profile points shown on plate 2). In 

1994–95, profiling detected PCE concentrations exceeding 

100,000 μg/L at a 19-ft depth below land surface at profile 

point VP-1008 (plate 2), located approximately 20 ft south 

of the abandoned pit area (Camp, Dresser, and McKee, 

Inc., Federal Programs Corporation, 1995). In 1997, a line 

of profile points was completed about 17 ft downgradient 

(east) of the pit location; this profiling detected maximum 

PCE concentrations of approximately 70,000 μg/L (profile 

point SMI; plate 2) at a depth of 53 ft below land surface 

(Guilbeaut and others, 1997). The depths of maximum PCE 

concentrations increase to the northeast with the primary 

groundwater-flow direction but also are controlled by the 

heterogeneity of the subsurface. In 1998, vertical profile points 

were installed laterally and upgradient to the pit. These profile 

points intercepted maximum PCE concentrations exceeding 

100,000 μg/L (profile point SMN; plate 2) at depths less than 

40 ft below land surface (Guilbeaut and others, 1998). 

On the basis of profiling results, 17 long-screened 

(45-ft) wells were installed near the abandoned pit area 

(fig. 2 insert). The assembly of wells is referred to as the 

INEEL well field (Tetra Tech EM, Inc., 2003). In addition to 

the 17 long-screened wells (fig. 2 insert), 6 multi-level sampler 

wells (designated by “mls” in the last three letters of the 

identifier in fig. 2 inset) also were installed. The multi-level 

samplers have sample intakes at depths of 22, 28, 42, 48, 58.5, 

and 60.5 ft below land surface. 

The study of the INEEL well field included collection 

of two core holes, slug tests of INEEL wells, and a series 

of primarily conservative interwell tracer tests (CITT) in 

three zones of the overburden (shallow, middle, and deep) 

(Tetra Tech EM, Inc., 2003). Results of the CITT tracer tests 
6 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

showed substantial (more than a factor of 10 in hydraulic 

conductivity) horizontal and vertical heterogeneity. Estimates 

of hydraulic conductivity ranged from 28 to 574 ft/d with 

an average porosity of 0.25 (Tetra Tech EM, Inc., 2003). A 

partioning interwell tracer test (PITT) also was performed to 

measure residual DNAPL saturation and showed substantial 

heterogeneity in the distribution of DNAPL saturation (Tetra 

Tech EM, Inc., 2003).

The USGS collected a string of vertical, closely spaced 

(2 ft) passive diffusion bag samples inside several INEEL 

wells to measure vertical distribution of PCE (Harte and 

others, 2002). The highest PCE concentrations (greater than 

10,000 μg/L) were associated with depths corresponding to the 

till surface at approximately 50 to 60 ft below land surface. 

Other studies by the USGS include construction and 

calibration of two groundwater-flow models (Harte and 

others, 1999; Harte and Mack, 1992), evaluation of the 

effects of groundwater withdrawals on advective transport of 

contaminated groundwater (Harte and Willey, 1997), analysis 

of PCE trends for pre- and post-barrier conditions (Harte and 

others, 2001), and description of a monitoring program of 

continuous water levels from water years 1997–2003 (Brayton 

and Harte, 2001; and Harte, 2005). Simulation of solute 

transport of PCE for the OU1 and OU2 areas is described in 

Harte (2004), and testing of remedial hydraulic operational 

schemes is described in Harte (2006). 

Harte (2006) reported that the capture areas for the 

interior barrier extraction wells are smaller than anticipated 

because of groundwater upflow from the underlying bedrock, 

based on numerical groundwater-flow simulations of remedial 

operations. The hydraulic connection between the overburden and underlying bedrock was identified from water-level 

responses during remedial operations (Brayton and Harte, 

2001; and Harte, 2005).

The subsurface investigations over the years at OU1 have 

resulted in a number of test boreholes, wells, and vertical profile points. Semi-chronological groupings of these data points, 

pre- and post-2003, are shown in plates 1a, 1b, and 2.

Hydrostratigraphic Mapping

Hydrostratigraphic units are geologic units grouped 

by similar hydrogeologic properties (Porges and Hammer, 

2007). Hydrostratigraphic mapping is the spatial delineation 

of these units. Several methods were used during this study to 

characterize and map hydrostratigraphic units. Results of the 

mapping were compared to estimates of hydraulic characteristics and contaminant transport of VOCs (PCE) to provide a 

hydrostratigraphic framework that can be used by site managers to evaluate remedial efforts. 

Methods

Hydrostratigraphic mapping included the use of 

lithologic logs from drilling and borehole geophysical logging 

to differentiate subsurface units for characterization of 

hydraulic properties, groundwater flow, and transport of PCE. 

Test drilling was performed to identify compactness of units 

based on drilling resistance, and to install observation wells. 

Borehole geophysical logging included natural gamma-ray and 

electromagnetic induction (EM) logging. Selected sediment 

samples were analyzed with a gamma-ray spectrometer to 

identify units and their potential natural gamma-ray response.

Delineation of hydrostratigraphic units was facilitated 

by the use of several interpolation techniques. Spatial maps 

of surfaces of hydrostratigraphic units were generated using 

a gridded algorithm and interpolated with kriging methods. 

Three-dimensional models of gamma-ray counts and PCE 

concentrations were made using a horizontal-bias method of 

inverse-distance weighting.

Drilling Characteristics of Sediments

Several types of drilling have been performed at the study 

site. The most recent (2004–2008) drilling was done with a 

CME-55 auger rig operated by the USGS. Most of the USGS 

test drilling (26 out of 27) used a hollow-stem auger method. 

One test hole was drilled with a drive and wash casing to 

allow for installation of a 4-in. polyvinyl chloride (PVC) 

observation well. Twenty-three, 2-in. diameter, PVC observation wells were installed as part of this test-drilling effort. 

The advantage in use of the auger method is that resistive 

“hard to drill” layers in the subsurface are easily identifiable. 

Coarse gravels and larger-size sediments (for example, 

cobbles) cause vibration on the end of the auger bit, and 

advancement into the subsurface is slowed. During drilling, 

these intervals were noted and compared to natural gammaray logs of the borehole (well) to facilitate mapping of the 

hydrostratigraphic units. In contrast, well-sorted fine gravel 

and smaller-size sediments were easily penetrated with 

auger drilling. 

Lithologic Sampling and Logs

The lithology of the OU1 area was reported from drilling 

logs of wells and boreholes. The reliability of lithologic 

descriptions from logs is related, in part, to the type of drilling 

and lithologic sampling. Wells and boreholes designated with 

“MI” (fig. 2, plates 1a and 1b) were drilled in the early to mid1980s using unknown methods. However, lithologic samples 

were often collected with spoon samples as reported on logs. 

Wells and boreholes designated with a “B” were drilled by the 

drive and wash method. Lithologic samples were collected 

continuously with split-spoon samples for wells numbered 

1 through 8 and discontinuously, every 5 ft on center, for wells 

numbered 9 through 17. Wells and boreholes designated with a 
Hydrostratigraphic Mapping 7

“PW” (fig. 2, plates 1a and 1b) and numbered from 1 through 

14 were drilled with an air rotary/barber rig. Lithologic 

samples were primarily collected by grab samples. Wells 

and boreholes designated with a “PW” and numbered 15 and 

greater were drilled with hollow-stem auger by the USGS. 

Lithologic samples were collected by split-spoon 

(in situ) and grab-type methods (ex situ) from auger spin 

material as sediments were removed from the hole. The 

reliability of auger spin materials as representative samples 

is dependent on a number of factors, including the overlying 

stratigraphy and the ability of sediments to be removed by 

the auger. Grab samples were collected at intervals that were 

believed to be representative of a given depth penetrated 

by the auger. Furthermore, the grab samples represent a 

composite non-directional sample.

For this study, an abbreviated lithologic coding system 

was used to describe and interpret lithologic logs (table 1). The 

coding is based on the predominant sediment type encountered. For example, several codes were used to describe sand 

and gravel deposits and these codes start with an “s” or “g,” 

whichever is the predominant sediment type.

Borehole Logging

The two primary borehole-logging techniques used were 

natural gamma-ray logging and EM conductivity. A description of each technique and application follows. 

Natural gamma-ray logging has been performed at most 

wells in OU1 in order to map out the subsurface stratigraphy 

of the unconsolidated sediments underlying the site. Natural 

gamma-ray logs measure natural radioactivity in formations 

adjacent to the well, and therefore, can be used to identify 

lithology. The most important naturally occurring gammaemitting radioactive elements include potassium-40 and 

daughter products of the uranium and thorium-decay series 

(Keys, 1990). Uranium (U) and thorium (TH) are concentrated 

in clay by the processes of adsorption and ion exchange. 

Thus, fine-grained sediments that contain clay tend to be 

more radioactive than “clean” (well washed with little fines) 

sands. Other formations besides those containing fine-grained 

sediments can emit high gamma radioactivity if they contain 

large amounts of radioactive elements. 

Table 1. Lithologic codes and description of sediments, OU1 area, Savage Superfund site, Milford, New Hampshire.

[Grain size based on Wentworth (1922)]

Code Description of lithology

TOPSOIL Topsoil; uppermost soil encountered, typically sandy with limited organic detritus.

COBBLES Large cobbles to fine sand matrix. Can have well-sorted sand lenses but generally poorly sorted matrix 

with silt- to gravel-size sediments. Can include small boulders.

GS Gravel and sand layer; gravel fine to coarse, and sand fine to coarse grained. Varying amounts of finegrained sediments (fine sand and silt).

BOULDERS Large boulders.

SG Sand, fine to coarse; with gravel, fine to coarse.

OVERBURDEN Unknown lithologic material.

GRAVEL Primarily a well-sorted fine to coarse gravel layer with some sand.

SAND Sand, fine to coarse but typically medium to coarse sand; well sorted.

SILT Silt lens typically thin (less than 1 foot layers).

FS Sand, very fine to fine; can contain some silt.

VFS Sand, very fine.

UPPER TILL Older drilling logs indicate some poorly sorted units as an upper till sequence. This unit was characterized as grey to brown, poorly sorted, with fine to coarse sand and gravel. 

GRADATION Layer with gradational sand that changes with depth.

TILL Poorly sorted basal till except in western part of OU1 where it is thicker with some sand lenses. Lower 

till is very dense grey silt with some sand and clay.

WB Weathered bedrock.

BEDROCK Bedrock, typically granite.

REFUSAL Hard resistive layer encountered while drilling that prevents advance. Can be till, bedrock surface, or a 

large boulder interpreted near the bedrock.
8 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Low gamma-ray counts recorded for this study 

corresponded to well sorted sands and gravels and are an 

indicator of relatively more permeable units. In contrast, 

high gamma-ray counts can be associated with poorly sorted, 

less permeable units but also can be associated with coarsergrained sediments and more permeable units that contain 

relatively large amounts of radioactive elements. 

Well construction affects gamma-ray emissions. Well 

diameter, casing and screen material, and grout used in the 

annulus of the borehole outside of the casing can affect readings. Large-diameter, (greater than 5 in.) steel-cased wells 

were found to reduce gamma-ray counts by 20 percent and 

more. For this reason, greater emphasis was placed on the use 

of borehole logs from PVC observation wells than on those 

from wells constructed of other material. 

The spatial distribution of gamma-ray counts was 

analyzed in order to infer the hydrostratigraphy of OU1. 

Spatial patterns of gamma-ray counts were mapped with 

Rockware software, using a form of inverse-distance method 

called horizontal bias. The horizontal bias method limits 

vertical distances in which the gamma-ray count will affect the 

adjacent count during the interpolation process. A vertical to 

horizontal distance ratio of 1 to 2 was used to reduce vertical 

interpolation to one-half the horizontal. This geometry favors 

interpolation of values to represent more realistic conditions 

such as that found in layered stratified deposits.

Electromagnetic (EM) induction logging delineates 

changes in rock type or in the electrical properties of fluids 

in the rock formation by measuring the bulk apparent 

conductivity of the formation and pore fluids surrounding 

the borehole. The conductivity of the formation is measured 

using a magnetic field to induce an electric field, which in 

turn produces electric currents in the formation (Mount Sopris 

Instruments, Inc., 2002). EM induction measurements can be 

made in water-, air-, and mud-filled holes and through PVC 

casing. Major factors that affect induction-log response in 

sand-and-gravel aquifers are the concentration of dissolved 

solids (conductivity) in the groundwater and the silt and clay 

content of the aquifer (Williams and Lane, 1998). 

EM logs were run in combination with gamma logs to 

identify the lithology and zones of electrically conductive 

groundwater from salting of nearby roads, permanganate 

from ISCO treatment, and chloride breakdown products from 

ISCO treatment of VOCs. Relatively high EM readings corresponded to clean sandy units with low gamma-ray count 

readings and, therefore, indicated relatively more permeable 

units with conductive groundwater.

Gamma-Ray Spectrometry

Radioactive elements of the potassium-40 (K) and 

daughter products of the uranium (U) and thorium (TH) 

decay series affect gamma-ray counts recorded during 

borehole logging (Keys, 1990). Although there is a strong 

relation between fine-grained sediments and high gamma-ray 

counts, other sediment types, such as boulders, can contain 

an abundance of high radioactive elements if the parent rock 

material contains high concentrations of these elements. 

Therefore, to assist in mapping of hydrostratigraphic units, 

lithologic samples collected as part of the test-drilling program 

for OU1 were analyzed by gamma-ray spectrometry (Stephen 

Synder, U.S. Geological Survey, written commun., 2007) to 

quantify the amount of TH, K, and U in sediments. A total 

of 25 lithologic samples were analyzed, including 1 topsoil, 

4 upper cobble layer, 18 sand and gravel, and 2 basal till 

samples from test drilling inside the barrier. 

Gamma-ray spectrometry measures the gamma rays emitted by radioactive elements that are present in solid and liquid 

samples. For this work, only three radioisotopes, K, TH, and 

U, were analyzed. The spectrometer yields results for K in percent of sediment, and for TH and U in parts per million (ppm). 

These units of measurement are related to gamma-ray counts 

and can be converted to gamma-ray counts directly using a 

linear-least squares fitting program after factoring in known 

background corrected count rates for these elements (Steve 

Synder, U.S. Geological Survey, written commun., 2007).

Concentrations of K, U, and TH determined from 

gamma-ray spectrometry measurements were compared 

semi-quantatively to borehole gamma-ray counts for the same 

sample depths to evaluate the variability of concentrations in 

sediment types. Results were grouped by hydrostratigraphic 

units that were determined from the gamma logs, drilling 

characteristics, and lithology to identify trends in radioactive 

elements and associated gamma-ray counts. 

Hydraulic Characteristics

Hydraulic characteristics (primarily hydraulic conductivity) were not used to directly map hydrostratigraphic units but 

were evaluated in relation to the mapped hydrostratigraphic 

units. For this study, the spatial frequency of measurements of 

hydraulic characteristics was insufficient for use as a mapping 

tool because most measurements were discrete and coarsely 

spaced (tens of feet apart). However, the subsurface geology 

was differentiated and mapped with the objective of identifying units with potentially different hydraulic characteristics. 

Hydraulic characteristics, primarily hydraulic conductivity, were compiled from a variety of sources and techniques. 

Additional information on hydraulic characteristics also was 

collected as part of this study and compared to the mapped 

hydrostratigraphic units.

Hydraulic testing based on single-well, constant-head 

tests of observation wells (13 tests in total) was completed 

by Camp, Dresser, and McKee, Inc. (1996) at observation 

wells designated with the letter “B.” Camp, Dresser, and 

McKee, Inc. (1996) also performed grain-size analysis, the 

results of which were used in this study to estimate hydraulic 

conductivity using methods discussed in the following 

paragraphs. Hydraulic testing, based on constant-head tests of 

four other observation wells, was conducted by Harding ESE, 

Inc. (2002).
Hydrostratigraphic Mapping 9

Slug tests were performed on selected wells to obtain 

hydraulic conductivity estimates. Both air and water slug 

displacement were used, and rates of water-level changes 

were recorded. Slug tests were analyzed according to methods 

described by Halford and Kuniansky (2002).

Continuous profiles of the hydraulic conductivity index 

(unit less, relative value) were done outside the barrier as part 

of a vertical profiling program by Camp, Dresser, and McKee, 

Inc. (2001) using a Waterloo profiler. The profiles provide a 

relative, not absolute, measure of hydraulic conductivity. 

Pump tests (N.A. Water Systems, 2003 and 2005) had 

been performed at several extraction wells (EW-1 and EW-2; 

fig. 2) and selected wells (SVE-5 and HCNE) inside the barrier. Other hydraulic tests included a tracer demonstration 

program in the INEEL field (Tetra Tech EM, Inc., 2003).

Hydraulic conductivity estimates were developed from 

25 lithologic samples, collected from inside the barrier as part 

of this study, and based on dry sieve grain-size analysis and 

methods described by Olney (1983). Estimates of hydraulic 

conductivity from grain-size analysis provide a non-directional 

measurement because the sediment structure is disturbed 

during collection and the sieving process (Chen, 2000). Two 

ranges of effective grain size were used to estimate hydraulic 

conductivity: D90 (90 percent of grain-size coarser) and D75 

(75 percent of grain-size coarser). Both D90 (smaller grain 

size) and D75 (larger grain size) were found to correlate with 

independent (variable-head and constant-head permeameter 

tests) computation of hydraulic conductivity in a study by 

Olney (1983), and therefore, both are provided. The Olney 

(1983) regression analysis equations are

K D D 90 2 100 10 0 655 90 ( ) = ( )− ( ) , .

, (1)

and

K D D 75 1 655 10 0 730 75 ( ) = ( )− ( ) , .

, (2)

where

K = hydraulic conductivity, in ft/d for the 

respective grain size; 

D90 = 90 percent of grain-size coarser; and

D75 = 75 percent of grain-size coarser.

Estimates of hydraulic conductivity also were compared 

to estimates from two other grain-size methods as described 

by Krumbein and Monk (1942) and Alyamani and Sen (1993). 

The equation from Krumbein and Monk (1942) is

K = intrinsic permeability (in Darcies) = 

760 2 1 31 GMd e sd ( ) ∗ − . , (3)

where

GMd = geometric mean grain diameter, in 

millimeters (mm); and

sd = standard deviation, in phi units.

Intrinsic permeability can be converted to hydraulic conductivity by multiplying by the viscosity of water at a reference 

temperature and dividing by water density at same reference 

temperature and gravity constant. Table 2.3 of Freeze and 

Cherry (1979, p. 29) provides conversion factors for converting intrinsic permeability to hydraulic conductivity.

The equation from Alyamani and Sen (1993) is

K = hydraulic conductivity in m/d = 

1 300 0 025 50 90 2, . Io + − ( ) D D  

 , (4)

where

Io = intercept of slope of percent finer grain size, 

in mm; 

D50 = 50 percent coarser grain size, in mm; and

D90 = 90 percent coarser grain size, in mm.

Results of Hydrostratigraphic Mapping

The physical, radioactive, and hydraulic characteristics 

of the subsurface stratigraphy for the study area are discussed 

in the following sections of the report. Selected examples are 

provided to highlight major features.

Hydrostratigraphic Units

The stratigraphy of OU1 was analyzed based on the 

assemblage of hydrostratigraphic units, which were differentiated and mapped with the objective of identifying units 

with potentially different hydraulic characteristics (table 2). 

Primarily 11 hydrostratigraphic units were identified as areally 

extensive within the inside barrier area. Other units also were 

noted, although less frequently, including very fine sand (vfs) 

and weathered bedrock (wx). A “hydrostratigraphic-type log” 

from well PW-20D is provided showing the 11 primary units 

(fig. 3). Well PW-20D is located near the middle of the OU1 

interior barrier (plates 1 and 2). The generalized lithologic 

log, shown on the left of figure 3, was obtained from 12 auger 

spin samples and 5 split-spoon samples (collected at depths of 

approximately 61, 64, 73, 94, and 100 ft below land surface). 

The observed relative resistance of drilled subsurface materials is shown in the middle of figure 3 and delineated in red 

where resistive “hard to drill” layers were encountered. These 

resistive layers generally correspond to the cobble units (C1, 

C2, and C3). The hydrostratigraphic units (table 2), shown 

second from left in figure 3, are based on the natural gammaray log as well as the lithology, resistance of drilled layers, and 

the EM conductance log. 

The natural gamma-ray log shows that counts vary from 

105 to 65 counts per second (cps) (fig. 3). Gamma-ray counts 

exceeding 85 cps generally correspond to cobble units (C1, 

C2, C3), till, and some “dirty” (with fines) detritus gravel 

layers (IS1). The cobble units are poorly sorted, ranging in 

grain size from silt to cobbles. The cobble clasts are supported 
10 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

within a fine-grained matrix. Gamma-ray counts less than 

85 cps correspond to clean, well-sorted sands and gravels. 

The EM log from PW-20D shows several sharp inflections “spikes” (high anomalous readings above 15 millisiemens per meter (mS/m)), which are likely the results of metal 

in the hole from drilling. The metal corresponds to the competent, hard, resistive units that cause the metal flakes from the 

augers to break off. EM spikes from metal occur at depths of 

8 and 54 ft. Other high EM readings at 24- and 28-ft depths 

correspond to relatively low gamma-ray counts and indicate 

electrically conductive groundwater is present in a permeable, 

clean, sandy unit (US1). 

The cobble units (C1, C2, and C3) and IS1 unit correlate 

over much of the OU1 site from the INEEL test area in 

figure 2, and appear as semi-planar features at similar altitudes. They appear to represent glaciodeltaic topset or 

glaciofluvial deposits. Kostic and others (2005) found that 

ice-marginal glaciodeltaic topset deposits in Germany contained significant amounts of fine-grained sediments within 

the matrix of a pebble-cobble clast. This type of lithology is 

indicative of rapid deposition. The altitude of the base of the 

C1 unit (260 ft above NGVD 29) corresponds to the altitude 

of a former glacial melt-water spillway located in downtown 

Milford, New Hampshire (Koteff, 1970), and, thus, likely 

represents a topset deltaic deposit.

The lowermost sandy units, BS1 and LS1, appear to 

represent delta bottomset (BS1) and foreset (LS1) beds that 

coarsen upward, as indicated by a decrease in gamma-ray 

counts, from the base of BS1 to the top of LS1 (below C3; 

fig. 3). Unit BS1 is discontinuous, deposited in deep bedrock 

troughs, and present in 25 out of 39 test holes at OU1 

(table 3).

The upper sand units (US1, MS1, and MS2) likely represent glacial deposition from cyclic glacial progression and 

regression where proximal to distal sediments are deposited. 

All sandy units contain some gravel; however, the lowermost 

basal sand unit (BS1) contains the least gravel. The sandy 

units are typically thicker than the cobble units (table 3). 

The lowermost overburden unit, the till, mantles the 

bedrock surface. The till is discontinuous but is identifiable 

at 22 out of 39 test holes at OU1 (table 3). Thick till deposits, 

associated with an upper till deposit, have been noted in drilling logs from the western part of OU1, along the western edge 

of the barrier.

Table 2. Hydrostratigraphic codes, unit names, and description, OU1 area, Savage Superfund site, Milford, New Hampshire.

Code Unit name Description of hydrostratigraphic units

S Topsoil Topsoil, in some places penetrated bentonite cap.

C1 Uppermost cobble layer Uppermost cobble layer; large cobbles to fine sand matrix, can have sand lenses within; 

generally poorly sorted.

US1 Uppermost gravel and sand layer Gravel and sand layer; well sorted.

C2 Middle cobble layer 2 Can contain cobbles but in some locations primarily sand and gravel, more permeable 

than C3.

MS1 Middle sand layer 1 Coarse sand (0.5) to fine gravel, pebbles; trace medium sand (1.5).

IS1 Interbedded sand, gravel, and 

cobbles

Some cobbles and gravel, variable matrix material.

VFS Very fine sand layer Very fine sand unit, limited spatially.

MS2 Middle sand layer 2 Primarily a well-sorted sand layer (m–c), some fine sand and some fine gravel.

C3 Lower cobble layer 3 Cobbles, gravel, sand, some silt; poorly sorted layer.

LS1 Lower sand and gravel layer Sand and gravel layer.

BS1 Basal sand Sand layer, less permeable than the unit above.

UPPER TILL Upper till Identified in lithologic logs as a poorly sorted fine to coarse sand and gravel with trace 

amounts of silt or clay; gray to brown. Limited spatially.

TILL Basal till Poorly sorted basal till except in western part of OU1 where it is thicker with some sand 

lenses; olive green.

WX Weathered rock Identified in lithologic logs as weathered bedrock. Limited spatially.

BEDROCK Bedrock Indurated competent bedrock.
Hydrostratigraphic Mapping 11 ELECTROMAGNETIC CONDUCTIVITY, IN MILLISIEMENS PER METER, IN 2006 GAMMA, IN COUNTS PER SECOND

GENERALIZED

LITHOLOGIC LOG

0 20 40 60 80 100 120 140

0

20

40

60

80

100

110

10

30

5070

90

0 5 10 15 20 25 30 35

20406080

100110

1030507090

DEPTH BELOW LAND SURFACE, IN FEET

OBSERVED RESISTIVE

DRILLED LAYERS,

IN RED

SC1US1C2MS1IS1MS2C3LS1BS1TILL

Topsoil; cobbles 

Sand andgravel

Sand and gravel

Sand andgravel:sand, coarse to medium

CobblesSandCoarse sand and gravelTill at 100 feet

DEPTH BELOW LAND SURFACE, IN FEET

HYDROSTRATIGRAPHIC LOG 

(Table 2)

NATURAL 

GAMMA RAY LOG ELECTROMAGNETIC LOG

0

Figure 3. Logs of well PW-20D showing lithology, hydrostratigraphy, borehole natural gamma ray and electromagnetic conductivity in 2006, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.
12 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Gamma and Radioisotope Characteristics

Concentrations of K, U, and TH elements in lithologic 

(sediment) samples of test holes, as determined from gammaray spectrometry measurements, were compared to borehole 

gamma-ray counts from borehole logging for coincident 

depths and locations. The spectrometry concentration for TH 

weakly to moderately correlates to the borehole gamma-ray 

count (R2 = .346, p-value 0.003; table 4). A graphical plot of 

TH concentrations and associated borehole gamma-ray count 

is shown in figure 4, as grouped by hydrostratigraphic unit. In 

contrast, K and U concentrations correlated poorly to borehole 

gamma-ray counts (table 4). 

Samples were grouped by hydrostratigraphic units, and 

mean concentrations for K, U, and TH were computed to identify bulk variation in element concentrations between units. 

Using this approach, variations were noted. The percentage 

of K in the sample, of which the radioisotope element K-40 

represents 0.012 percent (Keys, 1990), ranged from 1.71 (units 

MS2) to 2.53 (unit C3) with a mean from all samples of 2.28. 

The concentration of U ranged from 1.81 parts per million 

(ppm) (unit MS2) to 2.83 ppm (unit C1) with a mean from all 

samples of 2.44 ppm. The concentration of Th ranged from 

6.92 ppm (unit MS2) to 18.33 ppm (unit Till) with a mean for 

all samples of 11.22 ppm. Thus, the lowest element values for 

K, U, and TH were identified in unit MS2, whereas the highest 

element values were identified in the cobble layers (C1 and 

C3) and the till. 

Thorium concentrations show greater variability per 

hydrostratigraphic unit than K or U (table 5). The till and unit 

C1 (uppermost cobble layer) have the highest gamma-ray 

counts and highest measured Th concentration. The sand units 

(MS2 and US1) have the lowest gamma-ray counts and lowest 

measured thorium concentration. Thus, the variability in Th 

concentration appears to contribute to some variability in borehole natural gamma-ray counts. 

Hydraulic Characteristics

Hydraulic conductivity estimates based on methods 

described by Olney (1983) of grain-size analysis compared 

favorably to estimates from slug tests at the site, considering 

differences in sample volume that each method uses 

(appendix 1). Hydraulic conductivity estimates based on 

grain-size analysis represent a non-directional measurement 

of a spherical volume several inches in diameter. Hydraulic 

conductivity estimates based on slug tests likely represent 

horizontal measurements of the most permeable layers within 

the screen length (typically 10-ft long) of the well. Given 

the sample volume differences1, hydraulic conductivity 

estimates from grain-size analysis were deemed reasonable 

in characterizing the variations of hydraulic conductivity per 

hydrostratigraphic unit.

1

 The affected volume of a slug test in a 10-ft long well is likely 100 times 

greater than that of a grain-size analysis.

Table 3. Summary of unconsolidated hydrostratigraphic units 

and thickness, OU1 area, Savage Superfund site, Milford, 

New Hampshire.

[--, no estimate; yellow shading indicates sandy layers]

Units

Number 

of holes 

detected

Thickness,

in feet

Average Maximum Minimum

S 36 6.0 10 3

C1 39 10.7 22 4

US1 38 16.1 23 8

C2 35 5.2 15 0

MS1 36 9.8 25 0

IS1 35 6.9 21 0

MS2 34 7.8 18 0

VFS 1 112 -- --

C3 32 4.0 12 0

LS1 30 8.3 26 0

BS1 25 3.4 22 0

UPPER TILL 1 121 -- --

TILL 22 4.6 36.5 0

WX 1 12 -- --

1

 Individual sample.

Table 4. Coefficients of determination and significance for 

correlation of radioactive element concentration and associated 

borehole natural gamma-ray count, OU1 area, Savage Superfund 

site, Milford, New Hampshire.

[R2 = coefficient of determination; p-value = significance at 95-percent confidence level; K = potassium; U = uranium; TH = thorium. R2

 is a statistic that 

gives information about the goodness of fit of a model. In regression, the R2

coefficient of determination is a statistical measure of how well the regression 

line approximates the real data points. An R2 of 1.0 indicates that the regression line perfectly fits the data. The p-value is the probability that the current 

result would occur if the coefficient of determination were in fact zero (null 

hypothesis). If this probability is lower than the conventional 5 percent 

(p < 0.05), the correlation coefficient is called statistically significant]

Element R2 p-value Comment

K 0.048 0.317

U 0.104 0.133

TH 0.346 0.003 Significant at the 0.05 confidence interval; comparison 

shown in figure 4.
Hydrostratigraphic Mapping 13

Results of the grain-size analysis show that the most 

permeable units are the sandy units: US1, MS1, and LS1 

(table 6). A maximum hydraulic conductivity of 1,479 ft/d was 

estimated in grain-size samples derived from the lower sand 

unit. The cobble units (C1, C2, and C3) and unit IS1 generally 

are less permeable given their poorer degree of sorting than 

the sandy units, although small-scale, more permeable, sandy 

lenses can be present within the cobble units and unit IS1. A 

minimum hydraulic conductivity of 8 ft/d was estimated in 

grain-size samples derived from unit C3 and the till. 

Several units (such as IS1) have no hydraulic 

conductivity estimates and several more units (C3, BS1, and 

Till) have an estimate from only one grain-size sample. To 

augment the quantification of hydraulic conductivity per unit, 

single-well, hydraulic-test data (Camp, Dresser, and McKee, 

Inc., 1996) were used as a means of comparing variations in 

hydrostratigraphic units. 

For the 15 observation wells with hydraulic test data, 

screens in four wells are set in one hydrostratigraphic unit, 

whereas screens in the remaining 11 wells cross multiple 

hydrostratigraphic units. Of the four wells, two are screened 

in the IS1 unit with a hydraulic conductivity estimate of 46 

and 88 ft/d, one is screened in the MS2 unit with a hydraulic 

conductivity estimate of 272 ft/d, and one is screened in the 

LS1 unit with a hydraulic conductivity estimate of 300 ft/d. 

For the LS1 unit, the hydraulic conductivity estimates from 

the hydraulic well test and the grain-size methods compare 

favorably and indicate a relatively highly permeable unit. For 

the MS2 unit, the hydraulic well test indicates a more permeable unit than is indicated by the grain-size method.

4 8 12 16 20 24

40

60

80

100

120

BOREHOLE NATURAL GAMMA-RAY COUNT, COUNTS PER SECOND

THORIUM, IN PARTS PER MILLION (PPM)

TILL

C1

S

BS1

C2(SAND)

LS1

C3

US1

MS2

MS1

S

C1

US1

C2

MS1

MS2

C3

LS1

TILL

Observed range

Topsoil

Uppermost cobble layer

Uppermost gravel and sand layer

Middle cobble layer 2

Middle sand layer 1

Middle sand layer 2

Lower cobble layer 3

Lower sand and gravel layer

Basal till

Basal sand

EXPLANATION

BS1

Y = 2.58 * X + 58.28

Coefficient of determination, 

R-squared = 0.346

Y = 28.27 * ln(X) + 20.62 Coefficient of 

determination, R-squared = 0.324

Figure 4. Plot of borehole natural gamma-ray counts to corresponding thorium concentration per hydrostratigraphic unit, 

OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.
14 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Discussion of Hydrostratigraphic Units

The analysis of radioactive-element concentrations, 

hydraulic conductivity, and borehole natural gamma-ray logs 

indicates that the designated hydrostratigraphic units show 

a combination of lithologic, mineralogic (as a function of 

radioactive element concentrations for K, TH, and U), and 

permeability variations. There is a weak-to-moderate relation 

between the radioisotope concentrations (thorium) and 

borehole natural gamma-ray count. Furthermore, on the basis 

of grain-size analysis, there is a general relation between lower 

hydraulic conductivity estimates derived from grain size and 

the corresponding higher radioactive element concentration or 

borehole gamma-ray count. A relative ranking of radioisotope 

element concentrations (ordered low to high), borehole 

gamma-ray counts (ordered low to high), and hydraulic 

conductivity estimates (ordered high to low) is provided in 

table 7. The till unit shows high borehole gamma-ray counts, 

high radioactive element concentrations, and low hydraulic 

conductivity. In contrast, unit US1 shows low borehole 

gamma-ray counts, low radioactive element concentrations, 

and high hydraulic conductivity. Several exceptions to these 

observations exist, and low radioactive element concentrations 

and borehole gamma-ray counts do not always relate to higher 

hydraulic conductivities. LS1 and MS2 are examples of units 

with low borehole gamma-ray counts that do not correspond 

to high hydraulic conductivity. Unit LS1 has a high hydraulic 

conductivity but relatively high TH concentration and gammaray count, and unit2

 MS2 has a low hydraulic conductivity 

for the grain-size method but low radioactive element 

concentration and low borehole gamma-ray count. 

Additional hydraulic conductivity measurements may 

prove useful to understanding the relations discussed here. 

Specifically, semi-continuous hydraulic-conductivity profiles 

within the barrier area would prove useful in mapping 

hydrostratigraphic units. In addition, improvements to 

the interpretation relating borehole gamma-ray counts to 

radioactive element concentration and hydraulic conductivity 

can be achieved if volumetric (bed thickness) adjustments 

are made to adjust the borehole gamma-ray count per the 

thickness of each unit. Bed thickness affects borehole natural 

gamma-ray counts because of the variation in the amount 

of natural gamma-ray source material. By re-computing 

borehole gamma-ray counts to account for bed thicknesses 

of the corresponding units for the comparison, rather than 

2

 For the MS2 unit, the results of the hydraulic well test indicated a more 

permeable unit than was indicated by the grain-size method.

Table 5. Mean concentration of analyzed radioactive elements 

for selected hydrostratigraphic units, OU1 area, Savage 

Superfund site, Milford, New Hampshire.

[K = potassium; U = uranium; TH = thorium; ppm = parts per million]

Unit

Number of 

samples from 

sediments 

collected in 

2006–08

Mean

K

(percent)

U

(ppm)

TH

(ppm)

ALL 25 2.28 2.44 11.22

C1 5 2.43 2.83 11.41

C2 2 2.21 2.48 9.29

C3 3 2.53 2.52 16.66

LS1 4 2.14 2.61 11.49

MS1 5 2.44 2.26 8.80

MS2 2 1.70 1.81 6.92

TILL 2 2.53 2.71 18.33

US1 2 2.34 2.27 8.79

Table 6. Estimates of hydraulic conductivity from effective 

grain size (D90) for selected hydrostratigraphic units, OU1 area, 

Savage Superfund site, Milford, New Hampshire.

[--, no data; D90 is the effective grain size at 90-percent coarser size; data 

were obtained using the D90 method by Olney (1983); measured hydraulic 

conductivity is non-directional]

Unit

Number of 

samples

Hydraulic conductivity, 

feet/day Comment

Mean Minimum Maximum

S 0 -- -- --

C1 2 18.5 5 32

US1 3 51.8 27 141

C2 2 15.5 13 18

MS1 5 54.2 10 168

IS1 0 -- -- --

MS2 2 11.5 8 15

C3 1 18 -- -- One sample.

LS1 6 296 5 1,479

BS1 1 139 -- -- One sample.

TILL 1 18 -- -- One sample.

1 Individual value.
Hydrostratigraphic Mapping 15

using the point measurements of borehole gamma-ray counts 

associated with the unit themselves, a more representative 

borehole gamma-ray count per hydrostratigraphic unit could 

be determined. 

Hydrostratigraphic Surface Maps

Contours of altitudes of the bedrock surface (fig. 5) and 

till surface (fig. 6) are shown with data points used in the 

surface interpolation process. For the bedrock surface, in addition to well and boring information, confirmed bedrock depths 

from trenching of the barrier were used as a control and appear 

in a footprint oval pattern (fig. 5). 

The bedrock surface varies from an altitude of 160 to 

215 ft (NGVD 29) and slopes to the east. The greatest depth 

to bedrock occurs at a boring near the southeast area of 

the barrier. A deep bedrock trough runs from B95-1 to the 

northeast through PW-5R, PW-2R, up toward PW-11D, and 

toward MW-2R (across the river; fig. 5). A bedrock saddle is 

present near EW-2 (fig. 5). The bedrock surface is shallower to 

the west where a north-south trending bedrock knob underlies 

the INEEL field area. Along the western part of the barrier, the 

bedrock surface is about 8 to 10 ft deeper than near the INEEL 

field but slopes upward to the west from that location. 

The altitude of the top of basal till surface (fig. 6), which 

generally overlies the bedrock surface, follows a pattern 

similar to that of the top of bedrock surface, except where 

the till thickness increases near well PW-19D and near IW-1. 

At these two locations the till thickness increases from an 

average thickness of several feet to more than 10 ft (fig. 7). At 

PW-19D, till thickness is inferred, in part, from encountering 

refusal during auger drilling.

A basal till thickness map shows that till overlies most of 

the OU1 area except for several areas near PW-5R, PW-2R, 

PW-12R, and by EW-2 (figs. 2 and 7). Till thicknesses exceed 

10 ft near IW-1, IW-2, MI-22, and by MW-2R where thicknesses exceed 35 ft.

The altitude of the bottom surface of hydrostratigraphic 

unit MS2 (structure contour map; fig. 8) shows that there is 

a slight dip of 0.04 ft/ft to the east. This map can be used to 

help track lateral solute transport of PCE from source areas in 

the western part of interior barrier area, given that high PCE 

concentrations have been observed within the sandy units of 

the site (Harte, 2008) and PCE concentrations exceeding 

500 μg/L have been measured in several wells (PW-15D, 

PW-16D) screened across the MS2 unit. 

Table 7. Relative ranking of radioactive elements based on concentration, hydraulic conductivities, and borehole natural 

gamma-ray counts for selected hydrostratigraphic units, OU1 area, Savage Superfund site, Milford, New Hampshire.

[K = potassium; U = uranium; TH = thorium; --, no data; blue shading indicates high relative concentration ranking]

Hydrostratigraphic 

units

Concentration

Relative ranking 

(low to high)

Relative ranking 

(high to low) Relative ranking

(low to high)

K 

(1 = low)

U 

(1 = low)

TH 

(1 = low)

Gamma-ray count 

(1 = low)

Hydraulic conductivity estimate 

(1 = high)

C1 5 8 5 7 4

C2 3 4 4 4 5

C3 8 5 7 3 7

LS1 2 6 6 6 1

MS1 6 2 3 5 2

MS2 1 1 1 2 6

TILL 7 7 8 8 8

US1 4 3 2 1 3

BS1 -- -- -- -- --
16 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

 160.0 

 160.0 

 170.0 

 170.0 

 180.0 

 180.0 

 200.0 

125,500125,000

NORTHING

974,800 975,000 975,200 975,400 975,600 975,800 976,000 976,200

EASTING

13+30

13+0

12+80

12+60

11+70

11+60

11+50

10+80

10+70 10+60

10+50

10+40

10+30

10+20

10+10

10+0 9+80

9+70 9+60

9+40

8+80

8+30

7+90

7+10 7+0

6+60

6+50 6+10

6+0

5+90 5+60

5+50 5+10

5+0

4+90

4+50

4+40

4+30 4+0

3+70

3+40

3+10

3+0

2+90

2+80 2+70

2+40

2+30

2+0

1+90

1+80

B95-07

INEL-NWP

INEL-NEP

INEL-NCP

PW-24

INEL-WI

INEL-CI

PW-25S

SP-1

B95-04

PW-4D

B95-05

B95-12

B95-11

EW-2

B95-03

MW-16C

MW-16R B95-08

B95-13 PW-1D

PW-6D

PW-3D

PW-6R

B95-15

B95-02

PW-12R

PW-11D

PW-2R

PW-2D

PW-13D

IW-1

PW-5D

PW-5R

B95-01

PW-14D

MW-2R

12+50

MI-27 VP1002

MI-22

MI-24

MI-27

PW-12R

 170.0 

215.0

210.0

205.0

200.0

195.0

190.0

185.0

180.0

175.0

170.0

165.0

160.0

155.0

150.0Altitude of contour interval—In feet above NGVD 29

Data point and identifier

EXPLANATION

Bedrock surface altitudes—

in feet above NGVD 29

0 100 200 300 400 FEET

0 50 100 METERS

Figure 5. Contour map of altitude of top of bedrock surface, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.
Hydrostratigraphic Mapping 17

160 0.

180.0

200 0.

180.0

220.0

215.0

210.0

205.0

200.0

195.0

190.0

185.0

180.0

175.0

170.0

165.0

160.0

155.0

12+50

6+50

B95-01

B95-02

B95-04

B95-05

B95-06

B95-07

B95-11

B95-12

B95-13

B95-15

B95-3

B95-8

EW-2

IW-1

IW-2

MI-22

MI-24

MI-25

MW-10C

MW-16C

MW-2R

PW-10D

PW-11D

PW-12R

PW-13D

PW-14D

PW-15D

PW-18D

PW-19D

PW-1D

PW-20D

PW-2R

PW-3D

PW-4D

PW-5R

PW-6R SP-1

EXPLANATION

Till surface altitudes—

in feet above NGVD 29 Till—approximate thin or absent 

Altitude of contour interval—in feet above NGVD 29Barrier wallData point and identifier

180.0 

PW-1D

974,800 975,000 975,200 975,400 975,600 975,800 976,000 976,200

EASTING

125,500125,000

NORTHING

0 200 400 FEET

0 50 100 METERS

Figure 6. Contour map of altitude of top of till surface, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.
18 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund SiteFigure 7. Contour map of basal till thickness, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.

 5.0 

 5.0 

 5.0 

 5.0 

 10.0 

 10.0 

 15.0 

 5.0 

38.0

36.0

34.0

32.0

30.0

28.0

26.0

24.0

22.0

20.0

18.0

16.0

14.0

12.0

10.0

8.0

6.0

4.0

2.0

0.0

12+50

6+50

B95-01

B95-02

B95-04

B95-05

B95-06

B95-07

B95-11

B95-12

B95-13

B95-15

B95-3

B95-8

EW-2

IW-1

IW-2

MI-22

MI-24

MI-25

MW-10C

MW-16C

MW-2R

PW-10D

PW-11D

PW-12R

PW-13D

PW-14D

PW-15D

PW-18D

PW-19D

PW-1D PW-20D

PW-2R

PW-3D

PW-4D

PW-5R

PW-6R SP-1

Till

—approximate thin or absent 

Contour of till thickness—in feetBarrier wallData point and identifier

 15.0 

EW-2

EXPLANATION

Till thicknesses—in feet 

974,800 975,000 975,200 975,400 975,600 975,800 976,000 976,200

EASTING

125,500

NORTHING

125,000

0 200 400 FEET

0 50 100 METERS
Hydrostratigraphic Mapping 19 Figure 8. Contour map of altitude of bottom surface for hydrostratigraphic unit MS2, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.

 180.0 200.0 

 200.0 

B95-3

B95-8

HCNE HCNW

HCSE

HCSW

INEEL-WI

INEL-EI

IW-1

IW-2

MW-0312

MW-10C

MW-16C

MW-2R

PW-10D

PW-11D

PW-12R PW-13D

PW-14D

PW-15D

PW-16D

PW-18D

PW-19D

PW-1D

PW-20D

PW-24

PW-25D PW-2R

PW-4D

PW-5R

PW-6R

PW-7M

SP-1

125,500

125,000

NORTHING

974,800 975,000 975,200 975,400 975,600 975,800 976,000 976,200

EASTING

240.0

235.0

230.0

225.0

220.0

215.0

210.0

205.0

200.0

195.0

190.0

185.0

180.0

175.0

170.0

EXPLANATION

Bottom surface altitudes of MS2—

in feet above NGVD 29

0 200 400 FEET

0 50 100 METERS

Contour interval—in feetBarrier wallData point and identifier

180.0 

PW-6R
20 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Hydrostratigraphic Sections

A transverse cross-section A-A′ (shown in fig. 2), trending north to south through the interior barrier wall area of 

OU1, from well B95-3 to PW-4D, is shown in figure 9. Spatial 

variations of lithology based on lithologic logs are difficult 

to discern because of differences in drilling and lithologic 

sampling at each borehole/well. For example, the presence of 

cobbles within 20 ft of land surface were noted on driller’s 

logs for the wells located on the transverse cross-section 

A-A′ installed in 1995 (wells labeled with the letter “B”) and 

wells installed during 2006–07 [well labeled PW-6MB and 

wells labeled PW-15 and above (higher numbers)]. However, 

cobbles were absent in the upper 20 ft for wells installed during 1998–99 (wells labeled PW-14 and less). Good examples 

of this are logs from wells PW-6R (no shallow depth cobbles 

noted; plate 1a) and PW-6MB (shallow depth cobbles listed in 

log; plate 1b). Given the proximity of PW-6MB and PW-6R, 

and the presence of cobbles in logs on either side of the log for 

PW-6R, it is likely that cobbles from C1 unit are contiguous 

throughout this section. 

Fine sand layers are noted on B95-3 log at 245-ft altitude 

and at the 200-ft altitude, whereas they are absent elsewhere, 

except at B95-8 at the 190-ft altitude. Well-sorted sandy layers are present above and below the 230-ft altitude. Sand and 

gravel, and gravel and sand layers are present over most of 

the section. A thin basal till layer (about 5 ft thick) is noted on 

most logs, except for that of PW-6R well.

Spatial variations in gamma-ray counts suggest vertical and horizontal spatial trends in lithology (fig. 10). 

Interpolations of gamma-ray counts were made using the 

horizontal-bias method that favors interpolation of layered, 

stratified deposits (fig. 10). Low gamma-ray counts indicate 

the presence of clean well-sorted sands and gravels, whereas 

high gamma-ray counts indicate the presence of poorly sorted 

gravels, fine sands and silts, or large boulders and cobbles, 

which can emit relatively high radioactive gamma counts. The 

low counts (less than 90 counts per second (cps)) occurred in 

PW-19D east to PW-6 cluster in the middle-to-deep depths. 

Another low count zone occurred near PW-4D at an altitude 

below 230 ft. The presence of fine sands reported in driller 

logs for B95-3 and B95-8 (below 210-ft altitude) are supported by relatively high gamma-ray counts (greater than 

120 cps) at these wells. 

An interpreted stratigraphy for section A-A′ was 

generated based on interpretation of lithology, drilling 

resistance, and borehole geophysical natural gamma-ray 

and electromagnetic logs (fig. 11). The section shows that 

contiguous layers, denoted by yellow in figure 11, represent 

the more permeable sandy units. The non-yellow layers 

generally represent more poorly sorted materials, sometimes 

cobbles to fine-sand sediments; however, within those units 

more permeable lens can be present. Several of the less 

permeable units pinch out and are absent at certain locations 

(such as PW-19D and B95-3). 

Hydrostratigraphic Effects on Flow, 

Transport of PCE, and Remediation

Stratigraphic controls have been shown to be a factor 

in distribution of recalcitrant PCE concentrations in OU1 

(Harte, 2008). The distribution of the recalcitrant PCE layers 

was mapped vertically by analyzing borehole natural gammaray logs in conjunction with PCE concentrations. At several 

locations, recalcitrant PCE concentrations correlated with 

large changes in gamma-ray counts and changes in lithology, 

indicating the presence of stratigraphic contacts (Harte, 2008). 

The highest PCE concentrations occurred within well-sorted 

sands and gravels situated above relatively poorly sorted, less 

permeable sediments. 

The occurrence of the highest PCE concentrations within 

the more permeable layers (near stratigraphic contacts) suggests that either a residual PCE source is located above the 

less permeable layers or residual PCE is vertically migrating 

into the permeable layers from the less permeable layers. A 

residual PCE source, such as a DNAPL source, adsorbed PCE 

on sediments, or high concentrations of dissolved PCE in 

pore water may be located near contacts because the original 

DNAPL source probably was located in this area because the 

low porosity or permeability layer initially retarded DNAPL 

movement. Therefore, remnant high dissolved PCE concentrations (above 10,000 μg/L) are present at that location. In 

the absence of a residual high PCE concentration or source 

zones, PCE concentrations in highly permeable layers would 

be lower than PCE concentrations in less permeable layers 

because of preferential transport and the differential flushing 

rates of cleaner, low PCE-concentration groundwater in high 

permeability layers. 

The distribution of PCE concentrations in 2007 in wells 

along the A-A′ transverse cross section (fig. 12) shows that 

highest PCE concentrations occur near the PW-6 well cluster 

(distance 300 ft on fig. 12) and within the middle to lower 

hydrostratigraphic units (MS1, MS2, and LS1). High PCE 

concentrations also occur near the PW-20 cluster in the lower 

hydrostratigraphic unit (LS1 and BS1). The source area of 

PCE is upgradient to the west because groundwater flow 

is from the west to the east, toward the interior extraction 

wells (IW-1 and IW-2) from the INEEL well field and other 

potential source areas (by RW-1 and SP-2; fig. 2). The overall 

distribution of high PCE concentrations (greater than 

1,000 μg/L) relates to gamma-ray counts of less than 80 cps, 

indicating preferential transport in permeable zones (figs. 10 

and 12). Within hydrostratigraphic units, heterogeneity in 

permeability is supported by variability in hydraulic conductivity measurements from grain-size analysis, slug tests, and 

borehole gamma-ray counts. 

In 1996 (fig. 13), PCE concentrations were measured 

from vertical profiling of groundwater at 5-ft intervals at 

several locations (plate 2) along the same section as shown in 

figure 12. The high-resolution sampling at that time allowed 

for a more comprehensive mapping of PCE concentrations, 
Hydrostratigraphic Effects on Flow, Transport of PCE, and Remediation 21

ALTITUDE, IN FEET ABOVE NGVD 29

100 0 200 300 400

DISTANCE, IN FEET

0 500

BedrockBouldersCobblesfsGravelgs

No recoverSandsg

TillTopsoil

screen

MD M

S S

M

D D

MB

R

9

8

MD

fs

fs

Cobbles

Bedrock

Topsoil

Till

Sand; sand and gravel; gravel layers

Till

Bedrock

Sand

3-59 B

r et sul C91- WP

r et sul C02- WP

R, D, M, S6- WP

B M6- WP

9, 8-59 B

r et sul C4- WP

fs

Lithology index (Explanations in table 1)

EXPLANATION

A A’

Well screen; letter or number  designates suffix nameInferred contactApproximate contact

R

300

250200150

Figure 9. Transverse cross section through OU1 showing lithology, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.
22 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site NORTH SOUTH

ALTITUDE, IN FEET ABOVE NGVD 29

0 100 200 300 400

DISTANCE, IN FEET

B95-3 PW-19D PW-20D PW-6R B95-8 PW-4D

A A’

BEDROCK

?

?

? ? ?

? ? ?

B95-3

130.0

125.0

120.0

115.0

110.0

105.0

100.0

95.0

90.0

85.0

80.0

75.0

70.0

65.0

60.0

55.0

Borehole natural gamma-ray log and well identifierInferred bedrock surface

Interpolated gamma range, in counts per second

EXPLANATION

VERTICAL EXAGGERATION X1.3

500

300250200150

Figure 10. Transverse cross section through OU1 showing borehole gamma-ray counts, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.
Hydrostratigraphic Effects on Flow, Transport of PCE, and Remediation 23 Figure 11. Transverse cross section through OU1 showing hydrostratigraphic units, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.

300250200150

ALTITUDE, IN FEET ABOVE NGVD 29

0 100 200 300 400 500

3- 59 B

D91- WP

D02- WP

R6- WP

8- 59 B

D4- WP

DISTANCE, IN FEET

A A’

BedrockIS1

S C1 US1 C2

MS2 C3 LS1

MS1TILL BS1

Hydrostratigraphic units

(Explanations in table 2)

EXPLANATION

?

?

? ? ?

VERTICAL EXAGGERATION X1.1

Well and identifier

NORTH SOUTH

Well screen

b95-3 screen

PW-19M screen

PW-19D screen

PW-20S screen

PW-20M screen

PW-20D screen

PW-6S screen

PW-6M screen

PW-6MB screen

PW-6D screen

PW-6R screen

B95-8 screen

B95-8 screen

PW-4M screen

PW-4D screen
24 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

which indicates the highest concentrations occurred in the 

middle to lower hydrostratigraphic units at an altitude of 

approximately 220 ft above NGVD 29. At vertical profile 

location VP2007 (distance 330 ft in fig. 13), the maximum 

PCE concentration occurred at the contact between IS1 and 

MS2. From hydrostratigraphic unit MS2 to C3 and C3 to LS1, 

a large decrease in concentrations occurred; this indicates that 

unit C3 retards vertical transport. At the abandoned pit area 

in the INEEL well field, a primary source area of contaminants upgradient (to the west) of VP2007 (plate 2; fig. 2), 

high PCE concentrations were mapped at similar altitudes 

in several profile points (Guilbeaut and others, 1997, 1998). 

This indicates PCE solute transport primarily moves laterally 

away from the pit area and likely within the semi-planar 

hydrostratigraphic units. 

The distribution of the PCE plume in 1996 (preremediation) was wider and concentrations higher (greater 

than 6,000 μg/L) than in 2007 (figs. 12 and 13). In 1996, PCE 

concentrations greater than 2,000 μg/L were present along 

almost the entire length of the section, whereas in 2007, the 

2,000 μg/L concentrations were found in two areas near the 

PW-20 and PW-6 well clusters (fig. 12). Vertically, PCE 

concentrations in unit MS1 were relatively low (less than 

1,000 μg/L) in 2007 but were double that in 1996. In 2007, 

the plume appeared to be separating along the contact of unit 

IS1, indicating that vertical transport of PCE is restricted by 

that unit.

A comparison of PCE concentrations from an adjacent 

vertical profiling point (plate 2) with the borehole gamma 

log at PW-20D shows that the highest PCE concentrations 

occurred within the more permeable sandy units (low gammaray counts) and not the less permeable units with high gammaray counts (fig. 14). This supports the concept that solute 

transport moves primarily laterally within the sandy units. 

Furthermore, it suggests that residual high PCE concentrations 

(above 1,000 μg/L) are upgradient from this location, and PCE 

is transported within the more permeable layers. 
Hydrostratigraphic Effects on Flow, Transport of PCE, and Remediation 25 Figure 12. Transverse cross section through OU1 showing 2007 PCE concentrations from wells, along with hydrostratigraphy, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.

M

D

9

8

R

D

MB

S

M

S

M

D

M

D

B95-3

PW-19 Cluster

PW-20 Cluster

PW-6 Cluster

B95-8,9

PW-4 Cluster

S

C1

US1

C2

MS2 C3 LS1 TILL

MS1

BS1

IS1

US1

C1

MS1

MS2

LS1

C2 C2

C3

BEDROCK

S

MS2

BS1

IS1

C3

C1

S

US1

LS1

TILL

M

Barrier WallWell screen—letter ornumber designates depth associated with well cluster

A A’

ALTITUDE, IN FEET ABOVE NGVD 29

0 100 200 300 400 500

DISTANCE, IN FEET

0.0 − 10.010.0 − 100.0100.0 − 500.0500.0 − 1,000.0

1,000.0 − 2,000.02,000.0 − 4,000.0

Tetrachloroetylene (PCE) concentration

—

in micrograms per liter

EXPLANATION

?

?

? ? ?

NORTH SOUTH

VERTICAL EXAGGERATION X1.1

300250200150
26 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site Figure 13. Transverse cross section through OU1 showing 1996 PCE concentrations from vertical profiling of groundwater, along with hydrostratigraphy, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.

ALTITUDE, IN FEET ABOVE NGVD 29

0 100 200 300 400

DISTANCE, IN FEET

0.0 − 10.0

4,000.0 − 6,000.0

10.0 − 100.0100.0 − 500.0500.0 − 1,000.0

1,000.0 − 2,000.02,000.0 − 4,000.0

Tetrachloroethylene (PCE) concentration

—

in micrograms per liter

EXPLANATION

BEDROCK

VP2001 VP2002 VP2003 VP2006 VP2007 VP2005 VP1001

A A’

S

C1

US1

C2

MS2 C3

LS1

TILL

MS1 IS1

US1

C2

LS1

BS1

S

C1

US1

MS1

MS2 MS2

S

C1

C2 MS1

C3

BS1 TILL

IS1

C3 LS1 ?

?

? ? ?

NORTH SOUTH

VERTICAL EXAGGERATION X1.1

300250200150
Hydrostratigraphic Effects on Flow, Transport of PCE, and Remediation 27 Figure 14. PCE concentrations from vertical profiling and logs of borehole natural gamma-ray, lithologic, and hydrostratigraphic units at well PW-20D, OU1 area, Savage Municipal Well Superfund site, Milford, New Hampshire.

280270260250240230220210200190180170

ALTITUDE, IN FEET ABOVE NGVD 29

0 1,000 2,000 3,000 4,000 5,000

VERTICAL PROFILE-6017

PCE, IN MICROGRAMS PER LITER

280270260250240230220210200190180170 0 20 40 60 80 100 120

GAMMA, IN COUNTS PER SECOND

WELL PW-20D

LITHOLOGICLOG

HYDROSTRATIGRAPHIC UNIT

ALTITUDE, IN FEET ABOVE NGVD 29

Topsoil, cobblesSand and gravelCobbles, poorly sortedSand and gravel: sand coarse to mediumCobbles, poorly sortedSandSand and gravel, gradationalTill at 100 feet

SC1US1C2MS1IS1MS2C3LS1BS1

TILL
28 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Summary and Conclusions

The hydrostratigraphy of the Operable Unit 1 (OU1) area 

of the Savage Municipal Well Superfund site and the underlying Milford-Souhegan Glacial Drift aquifer was mapped 

to establish a framework to understand solute transport of 

volatile organic compounds (primarily tetrachloroethylene 

(PCE)), assess spatial and temporal concentration patterns of 

PCE, and to provide a hydrostratigraphic framework that can 

be used by site managers to evaluate remedial efforts. The 

subsurface unconsolidated sediments (overburden) at OU1 are 

heterogeneous. Test drilling over the years by multiple drillers 

and variations in lithologic descriptions of sediments made it 

difficult to develop a framework for the site from these data. 

In the absence of high-resolution lithologic sampling and 

consistent descriptions, borehole geophysical logging (natural 

gamma-ray and electromagnetic logs) was used to characterize 

the subsurface geology. 

A total of 11 primary hydrostratigraphic units in OU1 

were mapped. These 11 units consist of several well-sorted 

sandy layers with some gravel that are separated by poorly 

sorted cobble layers with a fine-grained matrix. The cobble 

layers likely represent topset beds deposited in a glaciodeltaic 

environment within close proximity to the glacial ice front. 

The 11 hydrostratigraphic units are mostly semi-planar and 

truncated by an undulating, underlying bedrock surface. 

The lowermost overburden unit is a basal till that ranges in 

thickness from zero to greater than 10 feet and mantles the 

bedrock surface.

The 11 primary units have different lithologic and 

hydraulic characteristics. The hydraulic conductivity (nondirectional measurements) of the well-sorted sandy units 

typically is greater than that of the poorly sorted cobble 

units and the basal till. Hydraulic conductivity ranges over 

approximately two orders of magnitude from 5 to greater than 

500 feet per day among the till and the sandy units. Lateral 

and vertical variations in lithology and hydraulic conductivity 

are evident from borehole natural gamma-ray counts and 

hydraulic conductivity measurements. 

Comparison of hydrostratigraphic units with PCE concentrations suggests that solute transport away from source 

areas is primarily lateral within the permeable sandy units in 

the middle to lower parts of the aquifer. Comparison of high 

PCE concentrations (greater than 1,000 micrograms per liter 

(μg/L)) with borehole natural gamma-ray logs shows associations of high PCE concentrations with hydrostratigraphic units 

that are characterized by low gamma-ray counts and consist 

of permeable sandy units. These permeable deposits include a 

lower sand unit (LS1) and several overlying middle sand units 

(MS1 and MS2). Horizontal heterogeneity within the sandy 

units was inferred from borehole gamma-ray counts, which 

indicate the area near borehole PW-6R contains the most 

permeable deposits. 

The location of the contaminant source can be traced 

based on the spatial distribution of high PCE concentrations. 

Because high PCE concentrations were found within the permeable units and primarily near stratigraphic contacts, residual 

PCE sources are probably located at stratigraphic contacts 

between high and low permeability layers and (or) within 

the less permeable layers; if it is within the low permeability 

layers, the PCE would eventually vertically migrate into the 

more permeable layers and be transported within them. In 

the absence of residual high PCE concentrations or source 

zones, PCE concentrations in highly permeable layers would 

be lower than PCE concentrations in less permeable layers 

because flushing rates are faster in high permeability layers 

than in low permeability layers.

For successful remediation inside the barrier wall, high 

residual PCE source areas would need to be targeted for clean 

up, which would reduce transport of PCE to downgradient 

areas. Once this was achieved, conventional pump-and-treat 

remediation may initially prove effective in reducing PCE 

concentrations, given that solute transport occurs primarily in 

the permeable, middle to lower sandy (MS1, MS2, and LS1) 

units. Eventually, the rate of vertical transport of PCE through 

the cobble units (C1, C2, and C3) and the interbedded sand 

and gravel unit (IS1) may limit the effectiveness of the remediation after the permeable units are remediated. 

Selected References

Alyamani, M.S., and Sen, Zekai, 1993, Determination of 

hydraulic conductivity from complete grain-size distribution 

curves: Ground Water, v. 31, no. 4, p. 551–555.

Brayton, M.J., and Harte, P.T., 2001, Results of a monitoring 

program of continuous water levels, specific conductance, 

and water temperature at the OK Tool facility of the Savage 

Municipal Well Superfund site, Milford, New Hampshire: 

U.S. Geological Survey Open-File Report 01–338, 50 p. 

Camp, Dresser, and McKee, Inc., 1996, Conceptual remedial 

design report for OK tool source area, Savage Municipal 

Supply Well, Superfund site-OU1, Milford, New 

Hampshire: Cambridge, Mass., March 1996, v. 1, 5 chaps., 

variously paginated. 

Camp, Dresser, and McKee, Inc., 2001, Summary of 

investigations Re: Draining of bulk solvent storage tank, 

OK Tool/Savage Municipal Supply Well, Milford, New 

Hampshire: Cambridge, Mass., November 2001, variously 

paginated.

Camp, Dresser, and McKee, Inc., Federal Programs 

Corporation, 1995, Final report of vertical contaminant 

profiling, Savage Municipal Supply Well, Superfund 

site-OU1, Milford, New Hampshire: Boston, Mass., 

November 1995, 5 chaps., 5 apps. 

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: 

Englewood, N.J., Prentice Hall, Inc., 604 p.
Selected References 29

Guilbeaut, M.A., 1999, Suspended DNAPL source zones in 

three sandy aquifers: Plume anatomy, mass discharge, 

and sampling scale considerations: Waterloo, Ontario, 

University of Waterloo, Department of Earth Sciences, 

Master’s thesis, 154 p. 

Guilbeaut, M.A., Cherry, J.A., and Parker, B.L., 1997, Final 

report, Groundwater and soil sampling at the Savage Well 

Superfund site, Milford, New Hampshire: Waterloo, 

Ontario, University of Waterloo, Department of Earth 

Sciences, variously paginated.

Guilbeaut, M.A., Cherry, J.A., and Parker, B.L., 1998, 

Phase 2, Groundwater and soil sampling at the Savage 

Well Superfund site, Milford, New Hampshire: Waterloo, 

Ontario, University of Waterloo, Department of Earth 

Sciences, variously paginated.

Guilbeault, M.A., Parker, B.L., and Cherry, J.A., 2005, Mass 

and flux distributions from DNAPL zones in sandy aquifers: 

Ground Water, v. 43, no. 1, p. 70–86.

Halford, K.J., and Kuniansky, E.L., 2002, Documentation of 

spreadsheets for the analysis of aquifer-test and slug-test 

data: U.S. Geological Survey Open-File Report 2002–197, 

51 p.

Harding ESE, Inc., 2002, Draft 2001 field investigation report 

Savage Well Superfund site, Milford, New Hampshire: 

Merrimack, N.H., July 9, 2002, variously paginated.

Harte, P.T., 2004, Simulation of solute transport of 

tetrachloroethylene in ground water of the glacial-drift 

aquifer at the Savage Municipal Well Superfund site, 

Milford, New Hampshire, 1960–2000: U.S. Geological 

Survey Scientific Investigations Report 2004–5176, 84 p. 

Harte, P.T., 2005, Results of a monitoring program of 

continuous water levels and physical water properties at 

the OU1 area of the Savage Municipal Well Superfund 

site, water years 2000–03, Milford, New Hampshire: 

U.S. Geological Survey Open-File Report 2005–1303, 44 p. 

Harte, P.T., 2006, Effects of a remedial system and its 

operation on volatile organic compound-contaminated 

ground water, Operable Unit 1, Savage Municipal Well 

Superfund site, Milford, New Hampshire, 1998–2004: 

U.S. Geological Survey Scientific Investigations Report 

2006–5083, 87 p.

Harte, P.T., 2008, Differential rates of PCE declines in a sand 

and gravel aquifer, in Proceedings of National Ground 

Water Association 2008 Ground Water Summit, Memphis, 

Tenn., 1 p.

Harte, P.T., Andrews, T.C., and Spina, Paul, 2002, Use 

of passive-diffusion bag samplers to estimate vertical 

distribution of DNAPL’s, in Proceedings of National 

Ground Water Association, Eastern Region Focus 

Conference, October 2002, Burlington, Vt., 1 p. 

Harte, P.T., Brayton, M.J., Ives, Wayne, Perkins, Sharon, and 

Brown, Carroll, 2001, Testing and application of waterdiffusion samplers to identify temporal trends in volatileorganic compounds: U.S. Geological Survey Open-File 

Report 00–196, 91 p.

Harte, P.T., Flynn, R.J., Kiah, R.G., Severance, Timothy, 

and Coakley, M.F., 1997, Information on hydrologic and 

physical properties of water to assess transient hydrology 

of the Milford-Souhegan Glacial-Drift aquifer, Milford, 

New Hampshire: U.S. Geological Survey Open-File 

Report 97–414, 96 p. 

Harte, P.T., Flynn, R.J., and Mack, T.J., 1999, Construction 

and calibration of numerical ground-water flow models of 

the Milford-Souhegan Glacial Drift aquifer, Milford, 

New Hampshire: U.S. Geological Survey Open-File 

Report 99–462, 76 p.

Harte, P.T., and Mack, T.J., 1992, Geohydrology of, and 

simulation of, ground-water flow in the Milford-Souhegan 

Glacial-Drift aquifer, Milford, New Hampshire: 

U.S. Geological Survey Water-Resources Investigations 

Report 91–4177, 90 p.

Harte, P.T., and Willey, R.E., 1997, Effects of historical 

withdrawals on advective transport of contaminated ground 

waters in a glacial-drift aquifer, Milford, New Hampshire: 

U.S. Geological Survey Fact Sheet 162–97, 6 p. 

HMM Associates, Inc., 1989, Draft remedial investigation, 

Savage well site, Milford, New Hampshire: Concord, 

Mass., no. 2176 HAZ/2880, 218 p. 

HMM Associates, Inc., 1991, Remedial investigation, Savage 

well site, Milford, New Hampshire: Concord, Mass., 

no. 2176 HAZ/4814, 800 p.

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

of Water-Resources Investigations, book 2, chap. E2, p. 150. 

Kostic, B., Becht, A., and Aigner, T., 2005, 3-D sedimentary 

architecture of a Quaternary gravel delta (SW-Germany): 

Implications for hydrostratigraphy: Sedimentary Geology, 

no. 181, p. 147–171.

Koteff, Carl, 1970, Surficial geologic map of the Milford 

quadrangle, Hillsborough County, New Hampshire: 

U.S. Geological Survey Geologic Quadrangle Map 

GQ–881, scale 1:62,500. 
30 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Krumbein, W.C., and Monk, G.D., 1942, Permeability as a 

function of the size parameters of unconsolidated sand: 

Trans American Institute Mining Metallurgical Engineers, 

v. 151, p. 153–163.

Lyons, J.B., Bothner, W.A., Moench, R.H., and Thompson, 

J.B., 1997, Bedrock geologic map of New Hampshire: 

U.S. Geological Survey State Geologic Map, 2 sheets, 

scale 1:250,000 and 1:500,000.

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Induction Probe Manual: Golden, Colo., Mount Sopris 

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remediation progress at the Savage Municipal Water Supply 

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variously paginated.

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the Savage Municipal Water Supply Well Superfund site, 

OU-1, The OK Tool Site: Moon Township, Pa., N.A. Water 

Systems, Inc., variously paginated.

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remediation progress at the Savage Municipal Water Supply 

Well Superfund site, OU-1, the OK Tool site July 2005–

June 2006: Moon Township, Pa., N.A. Water Systems, Inc., 

variously paginated.

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paginated.

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remediation progress at the Savage Municipal Water Supply 

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June 2007: Moon Township, Pa., N.A. Water Systems, Inc., 

variously paginated.

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First five-year review report for Savage Well Municipal 

Supply Superfund site, OU-1 Milford, Hillsborough County, 

New Hampshire: Concord, N.H., variously paginated. 

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the coefficient of permeability and effective grain size of 

unconsolidated sand: Boston, Mass., Boston University, 

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Agency and Idaho National Engineering and Environmental 

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Contract no. 68-C5-0037, variously paginated.

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monitored natural attenuation at Superfund, RCRA 

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quality inventory—1998 Report: Washington D.C., Report 

no. EPA-841-F-00-006, variously paginated.

U.S. Environmental Protection Agency, 2001, Draft, 

Remedial systems evaluation, Savage Municipal Water 

Supply Superfund site, Milford, New Hampshire: Edison, 

N.J., U.S. Environmental Protection Agency Technology 

Innovation Office, 27 p.

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remediation progress at the Savage Municipal Water Supply 

Superfund site, OU-1, The OK Tool site, July 2002 through 

June 2003: State College, Pa., U.S. Filter Engineering and 

Construction, variously paginated.

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clastic sediments: Journal of Geology, no. 30, p. 377–392.

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borehole geophysics for ground-water investigations: 

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contaminant transport modeling: New York, Van Nostrand 

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Appendix 1 31

Appendix 1

Estimates of hydraulic conductivity were made using 

various grain-size methods (table 1–1). The method developed 

by Alaymani and Sen (1993) produced the lowest estimates 

on average, whereas the method of Olney (1983), utilizing 

the 75 percent effective grain size (D75, 75 percent of grains 

coarser), produced the highest estimates on average. The 

D75 method produced values 1.5 to 30 times that of the 

D90 method (90 percent of grains coarser) used by Olney 

(1983). The median values show that estimates made with 

the Krumbein and Monk (1942) method were consistently 

the highest (table 1–1). Four estimates were made with the 

Alaymani and Sen (1993) method to provide additional 

comparisons.

Estimates of hydraulic conductivity (non-directional) 

from three grain-size methods (excluding Olney D75) 

were compared to estimates of hydraulic conductivity from 

hydraulic tests (individual, single well test) reported for the 

B95 series wells by Camp, Dresser, and McKee, Inc. (1996) 

(table 1–2). The grain-size data were obtained from a 2-ft 

interval from one sample collected within the 10-ft screen 

interval of each well. Therefore, the sample represents only 

20 percent of the screen material. Nevertheless, the 

comparison is useful to gage the reliability of the grainsize methods because the hydraulic test is considered to 

incorporate a larger sample volume around the well screen.

Estimates of hydraulic conductivity made using the 

method developed by Krumbein and Monk (1942) were higher 

than estimates of hydraulic conductivity from hydraulic tests 

in four of five values. In contrast, the estimates made using the 

methods developed by Olney (1983) for D90 and Alaymani 

and Sen (1993) were higher than estimates from the hydraulic tests for two of the five wells. The comparisons indicate 

that the Olney D90 method provides reasonable estimates of 

hydraulic conductivity for the site, considering differences 

among the sample volumes from hydraulic tests and the three 

grain-size methods. Mack and Harte (1996) found similar 

differences among estimated values of hydraulic conductivity 

made using multiple methods. 
32 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

Table 1–1. Comparison of grain-size-analysis methods from lithologic samples in the OU1 area, Savage Superfund site, Milford, 

New Hampshire.

[D90 = 90 percent of grain size is coarser; D75 = 75 percent of grain size is coarser; PS = poorly sorted; MWS = medium-well sorted; VPS = very poorly 

sorted; --, no estimate made; hydraulic conductivity is non-directional]

Well name Sample name

Sample depth below 

land surface, 

in feet

Hydraulic conductivity,

in feet per day

Olney 

(1983) Krumbein 

and Monk 

(1942)

Alymani 

and Sen 

D90 D75 (1993) Sorting characteristic 

of sample

PW-21 S-4B 61.9 196 4,644 PS 5,153 --

PW-21 S-3B 61.9 76 1,246 PS 2,620 --

PW-21 S-3 60 1,479 47,733 MWS 15,526 --

PW-20M S-8 71 6 8 PS 22 8

PW-20M S-9 72 5 7 PS 25 3

PW-6MB S-4B 63 17 66 PS 115 5

PW-6MB S-4A 63 11 45 PS 67 6

PW-6MB S-5 64 8 49 PS 79 --

PW-20M S-4 40 10 69 PS 124 --

PW-20M S-5 47 16 45 PS 60 --

PW-18M S-3 40 27 84 PS 87 --

PW-15M S-1 20 5 20 VPS 24 --

Statistics

Mean 154.7 4,501.3 1,991.8 5.5

Median 13.5 57.5 83.0 5.5

Number of samples 12 12 12 4

Standard deviation 420.6 13,679.6 4,541.9 2.4

Maximum 1,479.0 47,733.0 15,526.0 8.3

Minimum 5.0 7.0 22.0 2.7
Appendix 1 33

Table 1–2. Comparison of hydraulic conductivities between hydraulic tests of single wells and grain-size analyses, OU1 area, Savage 

Superfund site, Milford, New Hampshire.

[Yellow shading indicates grain-size estimate of hydraulic conductivity closest value to single well test; --, no data; hydraulic conductivity is non-directional]

Well 

name

Screen 

interval,

in feet below 

land surface

Grain-size 

sample 

interval, 

in feet below 

land surface

Estimates of hydraulic 

conductivity from 

single well test as 

reported by CDM, Inc. 

(1996)

Hydraulic conductivity from methods of 

grain-size analysis, 

in feet per day

Hydrostratigraphic 

unit

Krumbien 

and Monk 

(1942)

Olney (1983)-D90 

(uses 90 percent 

greater than as 

effective grain size)

Alyamani 

and Sen 

(1993)

Grainsize 

interval

Screen 

interval

B95-8 72–82 74–76 105 624 86 101 LS1 LS1/BS1

B95-5 37–47 43–45 168 712 595 91 -- --

B95-7 46–56 49–51 37 309 13 99 -- --

B95-6 41.5–51.5 46–48 222 95 50 16 -- --

B95-3 61.5–71.5 63–65 72 4,155 112 976 C3 C3/LS1
34 Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site

References

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hydraulic conductivity from complete grain-size distribution 

curves: Ground Water, v. 31, no. 4, p. 551–555.

Camp, Dresser, and McKee, Inc., 1996, Conceptual remedial 

design report for OK tool source area, Savage Municipal 

Supply Well, Superfund site-OU1, Milford, New 

Hampshire: Cambridge, Mass., March 1996, v. 1, 5 chaps., 

variously paginated. 

Chen, X.H., 2000, Measurement of streambed hydraulic 

conductivity and its anisotropy: Environmental Geology, 

v. 39, no. 12, p. 1317–1324.

Krumbein, W.C., and Monk, G.D., 1942, Permeability as a 

function of the size parameters of unconsolidated sand: 

Trans American Institute Mining Metallurgical Engineers, 

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Mack, T.J., and Harte, P.T., 1996, Analysis of aquifer tests 

to determine hydrologic and water-quality conditions 

in stratified-drift and riverbed sediments near a former 

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Olney, S.L., 1983, An investigation of the relationship between 

the coefficient of permeability and effective grain size of 

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unpublished Master’s thesis, 61 p.
Prepared by the Pembroke Publishing Service Center.

For more information concerning this report, contact:

Director

U.S. Geological Survey

New Hampshire-Vermont Water Science Center

331 Commerce Way, Suite 2

Pembroke, NH 03275

dc_nh@usgs.gov

or visit our Web site at:

http://nh.water.usgs.gov
Harte—Hydrostratigraphic Mapping of the Milford-Souhegan Glacial Drift Aquifer, and Transport of PCE, Savage Superfund Site—Open-File Report 2010–1047