U.S. Department of the Interior

U.S. Geological Survey

GEOHYDROLOGY AND GROUND-WATER QUALITY,

BIG ELK CREEK BASIN,

CHESTER COUNTY, PENNSYLVANIA,

AND CECIL COUNTY, MARYLAND

by Ronald A. Sloto

Water-Resources Investigations Report 02-4057

In cooperation with

CHESTER COUNTY WATER RESOURCES AUTHORITY

and

CHESTER COUNTY HEALTH DEPARTMENT

New Cumberland, Pennsylvania

2002
ii

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information Copies of this report may be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

215 Limekiln Road Box 25286

New Cumberland, Pennsylvania 17070-2424 Denver Federal Center

Email: dc_pa@usgs.gov Denver, Colorado 80225-0286

Internet Address: http://pa.water.usgs.gov Telephone: 1-888-ASK-USGS
iii

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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Location and physiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Well-numbering system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Previous investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Ground water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Well and aquifer characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Water-bearing zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Well yield . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Specific capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Water levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Depth to water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Fluctuations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Surface water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Ground-water/surface-water relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Base flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Low-flow statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Ground-water availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Water budget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Recharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Ground-water quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Physical properties and field-determined constituents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Major ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Nutrients. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Metals and trace constituents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Radon-222 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Volatile organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

CONTENTS

Page
iv

Figures 1-2. Maps showing:

1. Location of the Big Elk Creek Basin, Pennsylvania and Maryland. . . . . . . . . . . . . 3

2. The Big Elk Creek Basin study area, Pennsylvania and Maryland . . . . . . . . . . . . 4

3. Generalized geologic map of the Big Elk Creek Basin, Pennsylvania and Maryland . . . 6

4. Diagram showing wells in fractured rock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5. Map showing location of streamflow-measurement stations, observation wells, and

precipitation gages in the Big Elk Creek Basin, Pennsylvania and Maryland . . . . 14

6. Hydrographs showing depth to water in wells CH-5423, CH-5428, CE Ae 8, and

CE Ae 9, 1998-99, Big Elk Creek Basin, Pennsylvania and Maryland . . . . . . . . . . 15

7. Hydrograph showing depth to water in well CH-254, 1990-99, Big Elk Creek Basin,

Chester County, Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

8-10. Graphs showing:

8. Duration of mean daily flow of Big Elk Creek at Elk Mills, Maryland,

water years 1933-99, and Little Elk Creek at Childs, Maryland,

water years 1949-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

9. Relation among precipitation, ground-water levels, and streamflow, 1998-99,

Big Elk Creek Basin, Pennsylvania and Maryland . . . . . . . . . . . . . . . . . . . . 19

10. Cumulative annual base-flow frequency of Big Elk Creek at Elk Mills,

Maryland, 1933-99, and Little Elk Creek at Childs, Maryland, 1949-57 . . . . 21

11. Map showing location of wells sampled for water-quality analyses, Big Elk Creek

Basin, Pennsylvania and Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

12. Graph showing relation between concentrations of sodium and chloride in

ground water in the Big Elk Creek Basin, Pennsylvania and Maryland. . . . . . . . . . 32

13. Piper diagram showing relative concentrations of major ions in ground water

in the Big Elk Creek Basin, Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

ILLUSTRATIONS

Page
v

Table 1. Geologic units in the Big Elk Creek Basin, Pennsylvania and Maryland . . . . . . . . . . . . . 7

2. Number of water-bearing zones reported per 100 feet of uncased borehole drilled

in the Big Elk Creek Basin, Chester County, Pennsylvania . . . . . . . . . . . . . . . . . . 10

3. Minimum, maximum, and median reported well yields for wells in the Big Elk Creek

Basin, Chester County, Pennsylvania, and Cecil County, Maryland . . . . . . . . . . . . 11

4. Minimum, maximum, and median reported specific capacity for wells in the

Big Elk Creek Basin, Chester County, Pennsylvania, and Cecil County,

Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5. Minimum, maximum, and median reported depth to water in wells in the Big Elk

Creek Basin, Chester County, Pennsylvania, and Cecil County, Maryland. . . . . . . 13

6. Annual streamflow and estimated annual base flow for Big Elk Creek and

Little Elk Creek, Pennsylvania and Maryland, 1933-99 . . . . . . . . . . . . . . . . . . . . . 20

7. Low-flow statistics for streamflow-measurement station Big Elk Creek at Elk Mills,

Maryland (station 01495000), based on log Pearson Type III frequency

distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8. Ground-water availability in the Big Elk Creek Basin, Pennsylvania and Maryland. . . . 22

9. Annual water budgets for the Big Elk Creek Basin, Pennsylvania and Maryland,

1998-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

10. Estimated annual recharge for the Big Elk Creek Basin, Pennsylvania and

Maryland, 1998-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

11. Summary of physical properties and field-determined constituents for

water samples from wells in the Big Elk Creek Basin, Pennsylvania and

Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

12. Summary of concentrations of major ions and radon-222 in ground water in the

Big Elk Creek Basin, Pennsylvania and Maryland . . . . . . . . . . . . . . . . . . . . . . . . . 30

13. U.S. Environmental Protection Agency maximum contaminant levels and secondary

maximum contaminant levels for selected constituents in drinking water . . . . . . . 31

14. Summary of concentrations of nutrients in ground water in the Big Elk Creek Basin,

Pennsylvania and Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

15. Summary of concentrations of dissolved metals and trace constituents in ground

water in the Big Elk Creek Basin, Pennsylvania and Maryland. . . . . . . . . . . . . . . . 35

16. Volatile organic compounds detected in ground water in the Big Elk Creek Basin,

Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

17. Pesticides detected in ground water in the Big Elk Creek Basin, Pennsylvania and

Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

18. Records of selected wells, Big Elk Creek Basin, Pennsylvania and Maryland . . . . . . . 47

19. Water-level measurements, Big Elk Creek Basin, Pennsylvania and Maryland. . . . . . . 52

20. Results of field determinations and laboratory analyses for selected inorganic

constituents in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin,

Pennsylvania and Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

TABLES

Page
vi

Multiply By To obtain

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929—a geodetic

datum derived from a general adjustment of the first-order level nets of the United States and Canada,

formerly called Sea Level Datum of 1929.

Abbreviated water-quality units used in report:

mg/L, milligrams per liter

μg/L, micrograms per liter

μS/cm, microsiemens per centimeter at 25 degrees Celsius

Length

inch (in.) 2.54 centimeter

foot (ft) .3048 meter

mile (mi) 1.609 kilometer

Area

acre 4,047 square meter

square mile (mi2) 2.590 square kilometer

Volume

gallon (gal) 3.785 liter

million gallons (Mgal) 3,785 cubic meter

cubic foot (ft3) .02832 cubic meter

Flow rate

cubic foot per second (ft3/s) .02832 cubic meter per second

cubic foot per second per square mile

[(ft3/s)/mi2]

.01093 cubic meter per second per square

kilometer

gallon per minute (gal/min) .06309 liter per second

gallon per day (gal/d) .003785 cubic meter per day

gallon per day per acre [(gal/d)/acre] .11 cubic meters per day per hectare

million gallons per day (Mgal/d) .04381 cubic meter per second

million gallons per day per square mile

[(Mgal/d)/mi2]

1,461 cubic meter per day per square

kilometer

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

Radioactivity

picocurie per liter (pCi/L) .037 becquerel per liter

Specific capacity

gallon per minute per foot [(gal/min)/ft)] .2070 liter per second per meter

Mass

pound, avoirdupois (lb) .4536 kilogram

Temperature

degree Fahrenheit (°F) °C=5/9(°F-32) degree Celsius

CONVERSION FACTORS AND ABBREVIATIONS
1

ABSTRACT

A study of ground-water quantity and quality

was conducted in the Big Elk Creek Basin, a rural

area undergoing rapid growth. The 79.4-square

mile study area is in the Piedmont Physiographic

Province and is underlain almost entirely by crystalline rocks. Most of the basin in Pennsylvania is

underlain by Wissahickon Schist, a fractured crystalline-rock aquifer. Yields of wells in the Wissahickon Schist range from 5 to 200 gal/min (gallons

per minute); the median yield is 15 gal/min. Specific capacity ranges from 0.03 to 15 (gal/min)/ft

(gallons per minute per foot) of drawdown; the

median specific capacity is 0.4 (gal/min)/ft.

Recharge to the basin occurs by infiltration of

precipitation, and ground water discharges locally

to streams. The median annual ground-water discharge to streams (base flow) for 1933-99 was

10.79 in. (inches) or 0.518 (Mgal/d)/mi2 (million

gallons per day per square mile), which was

63 percent of the median annual streamflow. The

median annual ground-water discharge to streams

ranged from 5.32 in. or 0.255 (Mgal/d)/mi2 in 1966

to 17.98 in. or 0.863 (Mgal/d)/mi2 in 1972.

Estimated ground-water availability ranges from

0.127 to 0.535 (Mgal/d)/mi2, depending on the estimation method used.

Annual water budgets were calculated for the

Big Elk Creek Basin for 1998-99. The 1998-99

average annual streamflow was 15.38 in., change

in ground-water storage was an increase of

1.32 in., ground-water exports were 0.03 in., and

estimated evapotranspiration (ET) was 30.5 in.

Despite a 12.27-in. difference in precipitation

between 1998 and 1999, the percentage of precipitation as ET (65.6 and 64 percent, respectively)

is similar. Estimated average annual recharge for

1998-99 was 12.12 in. [0.580 (Mgal/d)/mi2].

For this study, water samples from 20 wells in

the Big Elk Creek Basin were collected for analysis

for inorganic constituents and pesticides. In addition, data were available from 44 additional wells.

Major ions, in order of decreasing concentration,

based on median concentrations for the Wissahickon Schist, are silica, calcium, chloride, sodium,

sulfate, magnesium, and potassium. The Wissahickon Schist and Peters Creek Schist have similar

water types; ground water from serpentinite, the

basal unit of the Baltimore Mafic Complex that

straddles the Pennsylvania-Maryland border, is distinctly different. For the Wissahickon Schist and

Peters Creek Schist, no cation is predominant; calcium, magnesium, and sodium are in nearly equal

concentrations expressed in milliequivalents per

liter. Bicarbonate is the dominant anion. Water

from serpentinite is of the magnesium bicarbonate

type; magnesium is the dominant cation, and bicarbonate is the dominant anion.

Water from 2 percent of sampled wells

exceeded the U.S. Environmental Protection

Agency (USEPA) secondary maximum contaminant level (SMCL) for total dissolved solids. None

of the chloride or sulfate concentrations exceeded

the USEPA SMCL. Water from 10 percent of sampled wells exceeded the USEPA maximum contaminant level (MCL) of 10 mg/L (milligrams per

liter) nitrate as nitrogen. All of those wells are in the

Wissahickon Schist. The median concentration of

nitrate in water samples from the Wissahickon

Schist was 3.6 mg/L, and the maximum concentration was 36 mg/L. Except for iron and manganese,

metals and other trace inorganic constituents do

not appear to pose a water-quality problem. Fourteen percent of water samples analyzed for iron

and 29 percent of water samples analyzed for

manganese exceeded the USEPA SMCL’s. The

median activity of radon-222 for all formations was

2,400 pCi/L (picoCuries per liter). The median

activity for water from 35 wells sampled in the Wissahickon Schist in the Big Elk Creek Basin was

2,500 pCi/L. Water from 94 percent of sampled

wells exceeded the proposed USEPA MCL of

300 pCi/L, and water from 25 percent of sampled

wells exceeded proposed USEPA alternate MCL of

4,000 pCi/L.

GEOHYDROLOGY AND GROUND-WATER QUALITY,

BIG ELK CREEK BASIN,

CHESTER COUNTY, PENNSYLVANIA

AND CECIL COUNTY, MARYLAND

by Ronald A. Sloto
2

In addition to the 20 wells sampled for pesticides for this study, data were available for 20 other

wells sampled for pesticides. The most commonly

detected pesticides in the Big Elk Creek Basin are

deethyl atrazine (71 percent of sampled wells),

atrazine (35 percent of sampled wells), metolachlor

(32 percent of sampled wells), carbaryl (19 percent

of sampled wells), picloram (14 percent of sampled

wells), simazine (13 percent of sampled wells), and

carbofuran (11 percent of sampled wells). Most

concentrations are extremely low and are in the

parts per trillion range. Concentrations of pesticides detected did not exceed USEPA MCL’s. Out

of 43 volatile organic compounds analyzed, only

4 were detected—chloroform, total phenols, tertbutyl methyl ether (MTBE), and toluene. None of

the concentrations exceeded USEPA MCL’s.

INTRODUCTION

Many rural areas of southeastern Pennsylvania

are undergoing a rapid population increase. New

development and an expanding population

increase consumptive water use, increase surface

runoff, and have the potential to reduce groundwater recharge. The Big Elk Creek Basin in southeastern Pennsylvania and eastern Maryland is a

rural basin that is begining to grow. Population in

the Big Elk Creek Basin is projected to increase

20 percent between 1998 and 2020 with a corresponding projected increase in water demand of

162 Mgal per year (Chester County Water

Resources Authority, 2001). In addition to

increased demands for a reliable potable water

supply, this projected growth also will require

accommodating disposal of an increased volume

of treated wastewater. An assessment of the

ground-water resources, both quantity and quality,

is necessary to guide this growth.

The Big Elk Creek Basin is between the Delaware and Susquehanna River Basins and drains

directly to the Chesapeake Bay (fig. 1). The Delaware and Susquehanna River Basins have basin

commissions that regulate and oversee surfacewater and ground-water withdrawals. The Big Elk

Creek Basin, located between these much larger

basins, does not have a regulatory agency to oversee withdrawal of ground water.

In 1996, the Chester County Board of Commissioners adopted Landscapes, a comprehensive

planning policy document, to guide growth management across the county (Chester County,

1996). By providing information about water quality

and quantity in the Big Elk Creek Basin, the study

described in this report supports the following

goals of Landscapes: achieve and sustain a highquality natural resource system to protect public

health and safety and support and protect a diversity of ecosystems (goal 2.1), protect a safe, longterm supply of water that is adequate for all uses

(goal 2.1.1); protect and enhance the quality of

ground water (goal 2.1.7); encourage a sustainable

water-cycle balance within watersheds as development occurs (goal 2.1.9); and provide a safe,

clean, long-term supply of water that meets the

needs of all users (goal 6.1.6).

This study was done by the U.S. Geological

Survey (USGS) in cooperation with the Chester

County Water Resources Authority and the Chester County Health Department. The study provides

county and township officials, planners, managers,

and residents with the basic information necessary

for management of the ground-water resource in

the Big Elk Creek Basin.

This report presents and interprets groundwater quantity and quality data for the Big Elk

Creek Basin in Chester County, Pa., and Cecil

County, Md. The report focuses primarily on the

Pennsylvania part of the basin. The report

describes the geohydrology of aquifers in the basin

and presents a summary of ground-water quality.

Basin water budgets for the calendar years 1998

and 1999 are presented using streamflow data

from the USGS streamflow-measurement station

on Big Elk Creek and ground-water-level and precipitation data collected for this study.
3

Figure 1. Location of the Big Elk Creek Basin, Pennsylvania and Maryland.

39°30′

40°00′

76°00′ 75°00′

CHESTER COUNTY

LANCASTER COUNTY

BERKS COUNTY

PHILADELPHIA

PENNSYLVANIA

NEW JERSEY

DELAWARE

BALTIMORE CHESAPEAKE BAY

DELAWARE BAY

DELAWARE

MONTGOMERY

DELAWARE RIVER

SUSQUEHANNA RIVER

BIG ELK

MARYLAND

COUNTY

COUNTY

CREEK

BASIN

NEWARK

NEW

CASTLE

COUNTY

CECIL

COUNTY

0 5 10 15 MILES

0 5 10 15 KILOMETERS
4

Location and Physiography

The 79.4-mi2 study area extends from the

headwaters in Chester County, Pa., downstream to

the USGS streamflow-measurement station on Big

Elk Creek at Elk Mills, Md., and an inactive USGS

streamflow-measurement station on Little Elk

Creek at Childs, Md. (fig. 2). The study area

includes 52.6 mi2 of the Big Elk Creek Basin and

26.8 mi2 of the Little Elk Creek Basin. A small part

of the Big Elk Creek Basin downstream of the

study area lies in New Castle County, Del.

Figure 2. The Big Elk Creek Basin study area, Pennsylvania and Maryland.

BIG ELK CREEK

ELKTON

OXFORD

PENNSYLVANIA

MARYLAND

DELAWARE

1 2 3 4 5

0 1 2 3 4 5 MILES

0

BOROUGH

ELK

TOWNSHIP

TOWNSHIP

TOWNSHIP

TOWNSHIP

TOWNSHIP

TOWNSHIP

PENN

OXFORD

LONDONDERRY

LOWER OXFORD

NEW LONDON

WEST FALLOWFIELD

TOWNSHIP

TOWNSHIP

TOWNSHIP

NOTTINGHAM

FRANKLIN

CHESTER COUNTY

CECIL COUNTY

STUDY AREA

STREAMFLOW-MEASUREMENT

STATION AND IDENTIFICATION

NUMBER

01495000

01495000

01495500

39°50′

39°40′

39°45′

39°35′

76° 75°55′ 75°50′ 75°45′

I-95

US 1

EAST

 KILOMETERS

UPPER

LITTLE ELK CREEK
5

Little Elk Creek is a tributary to Big Elk Creek.

Both streams flow south-southeast towards their

confluence at Elkton, Md. A short distance south of

Elkton, the Big Elk Creek becomes the Elk River

and discharges to the Chesapeake Bay.

The Big Elk Creek Basin in the study area is in

the Piedmont Physiographic Province and is

underlain by crystalline rocks. The topography generally is rolling uplands, common to the Piedmont.

The basin exhibits well-developed dendritic drainage patterns, and streams are moderately incised.

Climate

The climate in the Big Elk Creek Basin is a

humid, modified continental climate characterized

by warm summers and moderately cold winters.

The nearby Atlantic Ocean exerts a considerable

influence on the climate. The normal (1971-2000)

mean annual temperature at the National Oceanic

and Atmospheric Administration (NOAA) station at

Newark, Del., approximately 3 mi east of the Big

Elk Creek Basin, is 54.8°F (12.7°C) (National

Oceanic and Atmospheric Administration, 2002).

The normal (1971-2000) temperature for January,

the coldest month, is 32.5°F (-0.3°C), and the normal temperature for July, the warmest month, is

76.4°F (24.7°C).

The normal annual (1971-2000) precipitation

at the NOAA Newark, Del., station is 45.35 in.

Precipitation is distributed fairly evenly throughout

the year, although slightly more falls in May through

August than in the other months. Much of the summer rainfall is supplied by thundershowers. Snowfalls seldom exceed a total of 5 to 10 in. Usually the

snow cover disappears rapidly under the relatively

mild winter temperatures.

Well-Numbering System

The well-numbering system in Pennsylvania is

different from that in Maryland. In Pennsylvania,

the well-identification number consists of a countyabbreviation prefix followed by a sequentially

assigned local well number. The prefix CH denotes

a well in Chester County. In Maryland, the wellnumbering system follows that of the Maryland

Geological Survey and consists of two sets of two

letters followed by a number. The first two letters of

the well-identification number are the countyabbreviation prefix. The prefix CE denotes a well in

Cecil County. The second two letters designate the

5-minute quadrangle into which the county has

been divided. The first letter denotes the 5-minute

segment of latitude, and the second letter denotes

the 5-minute segment of longitude. Wells are

numbered sequentially within each 5-minute quadrangle.

Previous Investigations

In Pennsylvania, the geology was described by

Bascom and Miller (1920) and Bascom and

Stose (1932) and summarized by Sloto (1994).

The geohydrology and ground-water quality of

Chester County was described by Sloto (1994).

Basic data for Chester County is given by Sloto

(1989). Potentiometric-surface maps for the Big Elk

Creek Basin are presented by Mohammad (2000;

2001).

In Maryland, the geology was described by

Bascom and Miller (1920) and Higgins and Conant

(1986; 1990). The ground-water resources are

described by Overbeck and others (1958), Nutter

and Otton (1969), and Otton and others (1988).

Hydrologic data for Cecil County is presented by

Willey and others (1987).

Acknowledgments

The cooperation of well owners who allowed

access to their wells for sampling and water-level

measurements is appreciated greatly. The author

especially thanks the following observers who

maintained and read precipitation gages for this

study: Larry Fazio, Mary Gruber, William Laird,

Robert Lester, Fred Muller, Rikki Saunders, Martha

Straus, William Swoyer, and S.L. Walls.

Assistance and data also were provided by

Cynthia Rossetti, the Elk Creeks Watershed Association, Fair Hill Natural Resources Management

Area, Oxford Borough Water Department, Oxford

Sewer Authority, and the Exelon Corporation. Kevin

Grazul, formerly with the USGS, and Abdul

Mohammad of the USGS collected data for this

study.
6

GEOLOGY

The Big Elk Creek Basin in the study area is

underlain almost entirely by crystalline rocks of the

Piedmont Physiographic Province (fig. 3). Most of

these rocks have undergone more than one episode of deformation, and almost all exhibit compositional alteration. The lowermost part of the study

area and almost all of the Big Elk Creek Basin

south of the study area is underlain by unconsolidated Coastal Plain sediments of the Potomac

Group (fig. 3). The geologic units range in age from

Lower Paleozoic to Cretaceous (table 1).

Figure 3. Generalized geologic map of the Big Elk Creek Basin, Pennsylvania and Maryland.

LITTLE ELK CREEK

BIG ELK CREEK

PENNSYLVANIA

pc

wb

wb

wb

Csp

Csp

Cgb

pg

mg

Pz

gel

grm

ggh

mg

Pz

Pz

Pz

Pz

Kp

Kp

Kp

ggh

MARYLAND

DELAWARE

1 2 3 4 5 KILOMETERS

0 1 2 3 4 5 MILES

0

Csp

Cgb

pc

wb

Kp

pg

mg

Pz

gel

grm

ggh

PENNSYLVANIA

MARYLAND

serpentinized ultramafite

metagabbro and gabbro

Peters Creek Schist

Wissahickon Schist

Potomac Group

pelitic gneiss

metagraywacke

James Run Formation, undivided

gneiss near Elkton

gneiss at Rolling Mill

gabbro and serpentinite at Grays Hill

39°50′

39°40′

39°45′

39°35′

76° 75°55′ 75°50′ 75°45′
7

Most of the Big Elk Creek Basin in Pennsylvania is underlain by Wissahickon Schist. The Wissahickon Schist consists of metasediments metamorphosed to amphibolite grade. The Wissahickon is a

light to medium gray, fine- to medium-grained,

quartzo-aluminous schist and gneiss. Composition

ranges from quartz-orthoclase-biotite and orthoclase-quartz-muscovite schist to quartz-biotite-plagioclase and quartz-plagioclase-biotite schistose

gneiss. Garnet and/or sillimanite are abundant

locally. Foliation generally is very well developed.

In places, the Wissahickon is cut by diabase and

pegmatite dikes. Bascom and Stose (1932) estimated the Wissahickon Schist and Octoraro Phyllite (formerly considered part of the Wissahickon

Schist) to be 5,000 to 8,000 ft thick.

In Maryland, the name Wissahickon Schist is

no longer used. The rocks formerly assigned to the

Wissahickon Schist have been subdivided into an

informally named pelitic, diamictite, and metagraywacke metasedimentary lithofacies by Higgins

and Conant (1990). Pelitic gneiss and metagraywacke are present in the Big Elk Creek Basin.

The metagraywacke is an interbedded, tan to

grayish green, chlorite-biotite-plagioclase-muscovite-quartz gneiss or silvery-gray to grayish-green,

plagioclase-quartz-biotite-muscovite schist (Higgins and Conant, 1986). It consists of pelitic

schists, metasiltstones, and metagraywacke collectively referred to as metagraywacke by Higgins and

Conant (1990, p. 19-20). The metagraywacke

sequences commonly consist of graded metagraywacke and metasiltsone beds that range in

thickness from 1 to 8 ft and are interbedded with

sections of approximately the same thickness of

finely laminated pelitic schist. The layers are less

than 1/16 in. thick and occur in sections up to 40 ft

thick.

The pelitic gneiss is a lustrous, brown,

medium- to coarse-grained, layered, strongly

schistose rock riddled with quartzofeldspathic and

aplitic segregations and cut by numerous pegmatite veins and veinlets. It generally is a muscovitebiotite-quartz-plagioclase gneiss with abundant

garnets. It weathers to a red-brown clayey saprolite

containing abundant vein quartz fragments and

fairly abundant quartz grains. The contacts of the

pelitic gneiss appear to be gradational with other

units of the metasedimentary rock sequence (Higgins and Conant, 1990, p. 9).

The allochthonous Baltimore Mafic Complex

straddles the Pennsylvania-Maryland border in the

western part of the Big Elk Creek Basin. The Baltimore Mafic Complex consists of a basal unit of

interlayered metamorphosed peridotite-gabbro

overlain by gabbro containing upper level peridotite

(Hanan and Sinha, 1989). The complex may have

formed in a marginal basin originating inland from

a continental margin volcanic arc or as a sub-arc

plutonic complex. The basal unit is mapped as serpentinized ultramafite in Pennsylvania and serpentinite in Maryland. It is called serpentinite in this

report. The serpentinite is a lustrous, highly

sheared and fractured, bluish-green, talcose serpentinite or “soapstone,” with no visible evidence of

original texture or other features (Higgins and

Conant, 1990, p. 39-41). It contains minor amounts

of unserpentized ultramafic rocks and some mafic

rocks. The most distinguishing feature is that it

Table 1. Geologic units in the Big Elk Creek Basin, Pennsylvania and Maryland

[Compiled from Sloto (1994) and Higgins and Conant (1986)]

Geologic unit and map symbol

Age

Pennsylvania Maryland

Potomac Group (Kp) Upper and Lower Cretaceous

Peters Creek Schist (pc) Late Precambrian to Middle Ordovician

James Run Formation (Pz) Lower Paleozoic

gneiss near Elkton (gel) and gneiss at Rolling

Mill (grm)

Lower Paleozoic to Upper Precambrian

gabbro and metagabbro (Cgb) gabbro (Cgb) Lower Paleozoic to Upper Precambrian

serpentinized ultramafite (Csp) serpentinite (Csp) Lower Paleozoic to Upper Precambrian

gabbro and serpentinite at Grays Hill (ggh) Lower Paleozoic to Upper Precambrian

Wissahickon Schist (wb)

pelitic gneiss (pg) Lower Paleozoic

metagraywacke (mg) Lower Paleozoic
8

commonly contains significant amounts of

chromite, as disseminated elongated grains and as

massive pediform ore bodies.

The metagabbro and gabbro unit in Pennsylvania is called gabbro in Maryland. It is called gabbro

in this report. The gabbro generally is massive

hypersthene gabbro in various stages of alteration

to uralite gabbro but includes minor amounts of a

wide variety of mafic and, locally, ultramafic rocks

(Higgins and Conant, 1990, p. 41-42). The gabbro

is in thrust fault contact with the Wissahickon

Schist. Hanan and Sinha (1989) estimate that the

Baltimore Mafic Complex is less than 6,500 ft thick.

Gabbroic rocks and lesser amounts of serpentinite are present in the valley of Big Elk Creek and

its tributaries north of Elkton. These rocks are

mapped as “gabbro and serpentinite at Grays Hill”

and consist of black to very dark green, coarse- to

very coarse-grained, uralized hypersthene gabbro

and serpentinite. The rocks are poorly exposed

and deeply weathered (Higgins and Conant, 1990,

p. 42-43).

A medium-grained, plutonic-appearing rock

mapped as “gneiss near Elkton” extends about

1 mi west of Big Elk Creek. It is a well foliated,

gray-tan, medium- to coarse-grained biotite-quartzplagioclase, homogeneous, well-foliated, biotite

granodiorite gneiss with granoblastic texture

(Higgins and Conant, 1990, p. 49). A medium gray,

fine- to medium-grained biotite-plagioclase gneiss,

commonly containing tiny garnets and magnetite

crystals, underlies a large area between Little Elk

Creek and the Delaware State line. This gneiss is

mapped as “gneiss at Rolling Mill.” The “gneiss at

Rolling Mill” is similar petrographically to the

“gneiss near Elkton” and may be correlative

because the two are separated by only a thin belt

of metavolcanic rocks (Higgins and Conant, 1990,

p. 49).

The James Run Formation, which is undivided

on figure 3, is an interlayered quartz amphibolite

and biotite-quartz-plagioclase gneiss of probable

volcanic and volcaniclastic origin. The James Run

Formation is divided into seven formally named

members described by Higgins and Conant (1990,

p. 21-37).

A small area in the northwestern corner of the

Big Elk Creek Basin is underlain by the Peters

Creek Schist. The Peters Creek Schist consists of

a flyschoid sequence of metagraywacke and pelite

rich in quartz and magnetite (Lyttle and Epstein,

1987). The Peters Creek Schist generally is a

green, fine-grained, finely laminated, mica schist

with numerous thin to thick interbeds of chloritebearing granular quartzite. The pelitic part usually

is a quartz-muscovite-chlorite-orthoclase schist.

Bascom and Stose (1932) estimate that the Peters

Creek Schist is about 2,000 ft thick.

The Cretaceous-age deposits of the Potomac

Group underlie the southern part of the Big Elk

Creek Basin. The Potomac Group is made up of an

irregular succession of lenses and layers of a thick

sequence of non-marine quartzose sands, silts,

clays, and gravelly sands, as well as various intermediate mixtures of these that accumulated in a

fluviatile environment (Higgins and Conant, 1990,

p. 124-132). The maximum thickness is about

1,300 ft.

HYDROLOGY

All of the crystalline-rock units in the Big Elk

Creek Basin are considered to be aquifers. The

terms geologic unit and aquifer are used interchangeably in this report. These rocks sometimes

are referred to as “bedrock aquifers.” Nearly all

wells have casing set into the upper few feet of

unweathered rock and are completed as open-hole

wells. The hydrology of the unconsolidated Potomac Group is not discussed in this report but can

be found in Overbeck and others (1958).

Ground Water

In crystalline rocks, ground water moves

through intergranular openings in the weathered

zone (saprolite) and through a network of interconnecting secondary openings—fractures and

joints—in the underlying unweathered bedrock

(fig. 4).The permeability of fractured crystalline

rock depends on the number of fractures, the size

of the fracture openings, and the degree of interconnection of the fractures. A considerable quantity of water may be stored in the weathered zone

(saprolite) where it is thick.
9

The ground-water-flow systems in crystalline

rock are of local extent with streams acting as

drains. Flow paths are short, and ground water

flows from areas of higher elevation to adjacent

streams. Ground-water and surface-water divides

usually coincide. The hydrologic system generally

is unconfined (water-table conditions), and the

water table is a subdued replica of the land surface. In areas where fractures are far apart and

poorly interconnected, a true water table may be

absent, and each system of fractures may have its

own water level. Locally, ground water may be

semiconfined. A few wells flow; these wells penetrate water-bearing zones with hydraulic heads

greater than the land-surface altitude.

Well and Aquifer Characteristics

Some of the aquifer characteristics used to

describe ground-water flow and assess the productivity of an aquifer are the number of water-bearing

zones, well yield, and specific capacity. These

aquifer characteristics are discussed briefly in the

following sections.

Water-Bearing Zones

Primary (intergranular) porosity below the

weathered zone is nonexistent in the crystalline

rocks of the Big Elk Creek Basin. Ground water

flows through a network of interconnected secondary openings that comprise the water-bearing

zones that provide water to wells. The number and

size of the water-bearing openings determines the

secondary porosity of the rock; the number, size,

and degree of interconnection of the openings

Figure 4. Diagram showing wells in fractured rock.

WATER TABLE

WEATHERED

ZONE

NOT TO SCALE

FRACTURES

(SAPROLITE)

WELL OPEN TO

ONE FRACTURE MULTIPLE FRACTURES

WELL OPEN TO

BEDROCK
10

determines the secondary permeability. The larger,

more numerous, and more interconnected the

openings, the greater the yield of a well drilled into

that rock. Where a formation is extensively fractured, permeability may be high; elsewhere, where

few fractures are present, the same unit may be

nearly impermeable.

The distribution of reported water-bearing

zones was analyzed for wells completed in the

Wissahickon Schist in the Big Elk Creek Basin,

and, for comparison, in Chester County. Available

data for wells completed in the Peters Creek Schist

and serpentinite in the Big Elk Creek Basin were

insufficient for statistical analysis. Therefore, data

were analyzed for all wells in Chester County for

those geologic units. Available data for wells completed in gabbro were insufficient for statistical

analysis.

The frequency of water-bearing zones in the

Wissahickon Schist was analyzed for 87 wells with

173 water-bearing zones in 4,865 ft of uncased

borehole and well depths to 400 ft for the Big Elk

Creek Basin and for 407 wells with 800 water-bearing zones in 46,369 ft of uncased borehole and

well depths to 1,000 ft for wells in Chester County

(table 2). The frequency of water-bearing zones is

expressed in units of water-bearing zones per

100 ft of uncased borehole. Wells in the Wissahickon Schist in the Big Elk Creek Basin had a

higher mean (3.56) of water-bearing zones per

100 ft of uncased borehole than did wells in the

Wissahickon Schist in Chester County (mean of

1.73). The mean number of water-bearing zones

per 100 ft of uncased borehole was similar (1.53-

1.93) for wells in the Wissahickon Schist, Peters

Creek Schist, and serpentinite in Chester County.

For all geologic units, the frequency of occurrence

of water-bearing zones generally decreases with

depth (table 2).

Table 2. Number of water-bearing zones reported per 100 feet of uncased borehole drilled in the Big Elk Creek Basin,

Chester County, Pennsylvania

[--, no data]

Interval

(feet below land

surface)

Number of water-bearing zones Footage drilled

(feet)

Number of water-bearing

zones Footage drilled

(feet)

Total Per 100 feet

of borehole Total Per 100 feet ofborehole

Wissahickon Schist, Big Elk Creek Basin (87 wells) Wissahickon Schist, Chester County (407 wells)

0 - 50 11 3.34 330 85 3.09 2,752

51-100 85 4.16 2,041 318 2.35 13,533

101-150 59 3.36 1,756 183 1.57 11,688

151-200 14 2.91 481 96 1.40 6,833

201-250 2 1.87 107 49 1.13 4,321

251-300 0 0 50 35 1.19 2,938

301-350 1 2 50 13 .86 1,518

351-400 1 2 50 12 1.18 1,017

401-450 -- -- -- 4 .73 546

451-500 -- -- -- 5 1.11 452

501-1,000 -- -- -- 0 0 771

Total (mean) 173 (3.56) 4,865 800 (1.73) 46,369

Peters Creek Schist, Chester County (77 wells) Serpentinite, Chester County (27 wells)

0 - 50 21 2.64 796 11 3.16 348

51-100 78 2.68 2,728 17 1.77 961

101-150 32 1.71 1,869 7 1.31 533

151-200 8 .78 1,027 2 .62 325

201-250 10 1.58 633 1 .53 190

251-300 1 .26 387 0 0 140

301-350 0 0 205 1 1.92 52

351-400 1 1 100 -- -- --

401-500 0 0 77 -- -- --

Total (mean) 151 (1.93) 7,822 39 (1.53) 2,549
11

Well Yield

Reported well yield is the discharge of a well

measured during pumping, usually near the time of

well completion, and does not represent a longterm yield for the well. Well construction, well-bore

storage, pumping rate, and pumping duration can

affect the well yield. Reported yields for wells in the

Big Elk Creek Basin are summarized in table 3.

Because few data are available for geologic units

other than the Wissahickon Schist in the Big Elk

Creek Basin, data for all wells in Chester and Cecil

Counties for the geologic units present in the basin

are given in table 3. Yields of wells in the Wissahickon Schist in the Big Elk Creek Basin range

from 5 to 200 gal/min with a median yield of

15 gal/min. The median yield was similar (10-

15 gal/min) for wells in all geologic units in Chester

and Cecil Counties.

Specific Capacity

Specific capacity is a more meaningful measure of aquifer productivity than well yield because

it can be related directly to aquifer transmissivity.

Specific capacity is calculated by dividing the

pumping rate of a well by the drawdown and

reflects combined efficiency of the well and aquifer

transmissivity. Specific capacity for a well pumped

at a constant yield decreases with time.

Because few specific-capacity data are available for geologic units other than the Wissahickon

Schist in the Big Elk Creek Basin, data for all wells

in Chester and Cecil Counties for the geologic units

present in the basin are given in table 4. Specificcapacity data are determined from aquifer tests

performed by drillers, water purveyors, and consultants. The median specific capacities (0.2-

0.4 (gal/min)/ft of drawdown) of all the geologic

units are similar (table 4).

Table 3. Minimum, maximum, and median reported well yields

for wells in the Big Elk Creek Basin, Chester County, Pennsylvania,

and Cecil County, Maryland

[gal/min, gallons per minute; --, insufficient data to compute median]

Geologic unit Number

of wells

Well yield

(gal/min)

Minimum Median Maximum

Big Elk Creek Basin

Peters Creek Schist 4 10 -- 45

Gabbro 3 15 -- 75

Serpentinite 6 4 -- 45

Wissahickon Schist 125 5 15 200

Chester County

Peters Creek Schist 207 .2 10 312

Gabbro 5 15 -- 75

Serpentinite 46 2 12 80

Wissahickon Schist 808 0 15 412

Cecil County1

Gabbro 35 3 10 100

Serpentinite 23 2 10 200

Pelitic gneiss 12 3 10 200

Metagraywacke 20 1 10 100

1 From Otton and others (1988, p. 19).
12

Water Levels

Water levels measured in wells in an unconfined aquifer indicate the level of the water table.

Water levels commonly are measured and

reported as the depth to water below land surface.

Static water levels in an aquifer that is not being

pumped or stressed by other anthropogenic activities reflect natural conditions.

Approximately 800 wells were measured on a

one-time only basis to construct two potentiometric-surface (water-table) maps of the Big Elk Creek

Basin in Pennsylvania. The upper part of the basin

was mapped by Mohammad (2000) in 1999, and

the lower part was mapped by Mohammad (2001)

in 2000. On the maps, the potentiometric surface is

the water table represented by measured water

levels in wells. The water table is a subdued replica

of the land surface. The maps show that groundwater flow paths are short, and ground-water flow

is from areas of higher elevation to adjacent

streams. The streams act as drains for the groundwater system.

Depth to water

Under natural conditions in an unconfined

aquifer, water levels generally are closest to land

surface in valleys near streams (discharge areas)

and deepest below land surface on hilltops

(recharge areas). Water-level data categorized by

topographic position for wells in the Wissahickon

Schist in the Big Elk Creek Basin show that the

median depth to water is 19 ft for wells in valleys,

25 ft for wells on hillsides, and 30 ft for wells on hilltops (table 5). In the Big Elk Creek Basin, the

median depth to water ranged from 13 ft for wells in

serpentinite to 28 ft for wells in Peters Creek

Schist.

Fluctuations

Water levels fluctuate in response to recharge

to the ground-water system from precipitation and

discharge from the ground-water system to pumping wells, to the atmosphere by ground-water

evapotranspiration, and to streams. Water levels in

the Big Elk Creek Basin generally rise during the

late fall, winter, and early spring when groundwater and soil-moisture evapotranspiration are at a

minimum and recharge is at a maximum. Water

Table 4. Minimum, maximum, and median reported specific capacity for wells

in the Big Elk Creek Basin, Chester County, Pennsylvania, and Cecil County,

Maryland

[(gal/min)/ft, gallons per minute per foot of drawdown; --, insufficient data to

compute median; <, less than]

Geologic unit Number of

wells

Specific capacity

[(gal/min)/ft]

Minimum Median Maximum

Big Elk Creek Basin

Peters Creek Schist 5 0.16 -- 0.8

Gabbro 3 .11 -- 3.4

Serpentinite 6 .04 -- 15

Wissahickon Schist 84 .03 0.4 15

Chester County

Peters Creek Schist 42 <.01 .4 11.3

Gabbro 4 .1 -- 4.17

Serpentinite 21 <.01 .2 15

Wissahickon Schist 325 <.01 .3 100

Cecil County1

Gabbro 27 <.1 .4 17

Serpentinite 19 <.1 .3 20

Pelitic gneiss 9 <.1 .2 2

Metagraywacke 16 <.1 .4 5

1 From Otton and others (1988, p. 19).
13

levels generally decline during the late spring,

summer, and early fall when ground-water evapotranspiration and soil-moisture evapotranspiration

are at a maximum and recharge is at a minimum.

Water levels were measured monthly in eight

wells from January 1998 through December

1999 (fig. 5). Additionally, three wells were instrumented with digital water-level recording loggers

(fig. 5). Water levels in observation wells in different geologic units in the Big Elk Creek Basin show

similar patterns of response to seasonal changes

in recharge and evapotranspiration (fig. 6). Water

levels generally decline in the summer and fall

despite precipitation because recharge is offset by

evapotranspiration. The range in fluctuation in

these wells for 1998-99 was up to 12.55 ft.

Although the seasonal fluctuations in water levels are similar from year to year, changes in climatic conditions affect the seasonal pattern (fig. 7).

For example, 1991 and 1992 were drier than normal years, and little recharge occurred during the

cold months. 1996 was a wetter than normal year,

and recharge occurred during the entire year.

Table 5. Minimum, maximum, and median reported depth to water in wells in the Big Elk

Creek Basin, Chester County, Pennsylvania, and Cecil County, Maryland

[A negative number indicates water level above land surface; --, insufficient data to compute

median]

Geologic unit Number of

wells

Depth to water

(feet below land surface)

Minimum Median Maximum

Big Elk Creek Basin

Peters Creek Schist 12 15 28 44

Gabbro 3 14 -- 24

Serpentinite 6 5 13 20

Wissahickon Schist, all wells 209 0 25 73

Wissahickon Schist, hilltop wells 44 15 30 59

Wissahickon Schist, hillside wells 155 0 25 73

Wissahickon Schist, valley wells 5 7 19 20

Chester County

Peters Creek Schist 198 2 32 144

Gabbro 4 8 -- 24

Serpentinite 37 5 20 70

Wissahickon Schist 907 -3 26 115

Cecil County1

Gabbro 48 3 20 50

Serpentinite 27 3 17 50

Pelitic gneiss 19 4 15 43

Metagraywacke 31 6 20 64

1 From Otton and others (1988, p. 17).
14

Figure 5. Location of streamflow-measurement stations, observation wells, and precipitation gages

in the Big Elk Creek Basin, Pennsylvania and Maryland.

0 1

0 1

2

2

MILES

KILOMETERS

LITTLE ELK

BIG ELK CREEK DELAWARE

PENNSYLVANIA

CH-5423

CH-5425

CH-5428

CH5421 CH-5433

CE Ae 9

CE Ae 8

MARYLAND

CREEK BASIN

BASIN

CH-254

CH-5422

CH-5427

CH-5429

01495500

39°50′

39°40′

39°45′

39°35′

76° 75°55′ 75°50′ 75°45′

CH-5427 01495000

WELL MEASURED MONTHLY

AND IDENTIFICATION

WELL INSTRUMENTED WITH

WATER-LEVEL RECORDER

AND IDENTIFICATION NUMBER

CE Ae 9

STREAMFLOW-MEASUREMENT

STATION AND IDENTIFICATION

NUMBER

01495000

PRECIPITATION GAGE

NUMBER

I-95

US 1
15

Figure 6. Depth to water in wells CH-5423, CH-5428, CE Ae 8, and CE Ae 9, 1998-99,

Big Elk Creek Basin, Pennsylvania and Maryland. Wells CH-5423 and CH-5428 were

measured monthly. Wells CE Ae 8 and CE Ae 9 were equipped with continuous water-level

recorders.

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

1998 1999

13

26

14

15

16

17

18

19

20

21

22

23

24

25

DEPTH TO WATER, IN FEET BELOW LAND SURFACE

WELL CE Ae 9

WELL CE Ae 8

WELL CH-5428

WELL CH-5423
16

Figure 7. Depth to water in well CH-254, 1990-99, Big Elk Creek Basin, Chester County, Pennsylvania. (Precipitation data are from theNational Oceanic and Atmospheric Administration Newark, Delaware, station.)

1990 1991 1992 1993 1994 1995 1996 1997 1998 199

1430

151617181920212223242526272829

DEPTH TO WATER, IN FEET BELOW LAND SURFACE

51.16 37.53 44.86 49.70 45.37 40.63 60.52 37.16 34.77 51.

ANNUAL PRECIPITATION, IN INCHES
17

Surface Water

Streamflow from 52.6 mi2 of the Big Elk Creek

Basin has been measured since April 1, 1932, at

the USGS streamflow-measurement station

01495000, Big Elk Creek at Elk Mills, Md. Streamflow from 26.8 mi2 of the Little Elk Creek Basin was

measured from October 1, 1948, to September 30,

1958, at the USGS streamflow-measurement station 01495500, Little Elk Creek at Childs, Md. The

mean daily flow of Big Elk Creek from 1932

through 1999 was 69.1 ft3/s. The mean daily flow of

Little Elk Creek for the period of record was

38.2 ft3/s or 1.43 (ft3/s)/mi2. The mean daily flow of

Big Elk Creek for the same period (1948-58) was

70.4 ft3/s or 1.34 (ft3/s)/mi2.

The capacity of a basin to store ground water

can be illustrated by flow-duration curves. A flowduration curve is a cumulative frequency curve that

shows the percentage of time specified discharges

were equaled or exceeded during a given period.

The curve describes the flow characteristics of a

stream without regard to the sequence of occurrence. The flow-duration curves for Big Elk Creek

for water years (October 1 to September 30) 1932-

99 and Little Elk Creek for water years 1949-57 are

shown on figure 8. Flow-duration curves on

figure 8 are mean daily flow in cubic feet per

second. The flow-duration curve for Big Elk Creek

is representative of the long-term probability distribution. The curves have approximately the same

slope, indicating little variability of streamflow

between the basins. The curve for the Big Elk

Creek is positioned higher on the graph because

the drainage basin is larger. The slopes start to

flatten at 10-percent exceedence, indicating a large

contribution of ground-water discharge to streamflow.

Ground-Water/Surface-Water Relations

The ground-water and surface-water systems

are well connected in the Big Elk Creek Basin. In

most areas, streams act as drains for the shallow

ground-water system and gain water. Potentiometric-surface maps for the Elk Creek Basin in

Chester County (Mohammad 2000; 2001) show

water levels in wells near streams are higher than

stream elevations, indicating ground water discharges to streams, and most stream reaches are

gaining reaches.

Streamflow is composed of base flow and surface runoff. Base flow is ground water discharged

to streams. After rainfall or snowmelt, precipitation

that does not infiltrate or evaporate enters streams

as surface runoff. The proportions of streamflow

that are base flow and surface runoff, as well as the

relation between rainfall and surface runoff in a

basin, depend on the hydrologic characteristics of

the basin. Commonly, more surface runoff is

observed in small basins with steep slopes and

low-permeability soils and rocks than in large

basins with shallow slopes and high-permeability

soils and rocks. In urbanized areas, pavement or

other land cover with low permeability reduces natural infiltration and can increase the intensity and

volume of surface runoff relative to that in undeveloped areas.

The quantity of ground water discharged to

streams is related to the altitude of the water table

near the stream. Olmsted and Hely (1962) found a

linear relation between the monthly average

ground-water level in index wells and the base flow

of Brandywine Creek during winter months. The

relation among precipitation, the water level measured in well CE Ae 9, and streamflow and base

flow at the streamflow-measurement station Big

Elk Creek at Elk Mills during 1998-99 is shown on

figure 9. The shapes of the base-flow hydrograph

and water-level hydrograph are very similar. Base

flow generally declines as ground-water levels

decline and increases as ground-water levels

increase. The time of lowest base flow generally

coincides with the lowest ground-water levels. Precipitation during the summer (June through September) generally produces little increase in

ground-water levels; most infiltrated precipitation

replenishes soil moisture and does not recharge

the ground-water system.
18

Figure 8. Duration of mean daily flow of Big Elk Creek Creek at Elk Mills, Maryland (station 01495000),

water years 1933-99, and Little Elk Creek at Childs, Maryland (station 01495500), water years 1949-57.
19

Figure 9. Relation among precipitation, ground-water levels, and streamflow, 1998-99, Big Elk Creek

Basin, Pennsylvania and Maryland.

1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW

BASE FLOW

12

20

14

16

18

DEPTH TO WATER, IN FEET

BELOW LAND SURFACE

STREAMFLOW OF BIG ELK CREEK AT ELK MILLS, MARYLAND

WATER LEVEL IN WELL CE Ae 9

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

1998 1999

0

5

1

2

3

4

PREIPITATION,

AVERAGE DAILY PRECIPITATION IN THE BIG ELK CREEK BASIN

IN INCHES

10.04

INCHES
20

Base Flow

Streamflow can be separated into base-flow

and surface-runoff components by use of

hydrograph-separation techniques (see fig. 9 for an

example). Hydrographs for Big Elk Creek and Little

Elk Creek for their period of record were separated

into base-flow and surface-runoff components

(table 6) by use of the local-minimum technique of

the computer program of Sloto and Crouse (1996).

A detailed discussion of hydrograph separation for

Pennsylvania streams is given by White and Sloto

(1991). The median base flow for Big Elk Creek in

table 6 is representative of the long-term average.

Streamflow, base flow, and surface runoff in table 6

are expressed in inches so that basins with different drainage areas can be easily compared. Inches

can be converted to million gallons per day per

square mile by multiplying by 0.048. A comparison

between the period of record (1949-57 calendar

years) for Little Elk Creek at Childs, Md., and the

same period for Big Elk Creek at Elk Mills, Md., is

provided in table 6. The median annual base flow

for both streams is similar (10.59 in. for Big Elk

Creek and 10.64 in. for Little Elk Creek). The percentage of streamflow as base flow is higher for

Big Elk Creek (65.2 percent) than for Little Elk

Creek (59.4 percent) because the median total flow

for Big Elk Creek (16.25 in.) is less than the median

total flow for Little Elk Creek (17.50 in.).

In the Big Elk Creek Basin, the median annual

base flow (ground-water discharge to the stream)

for calendar years 1933-99 was 10.79 in. or

0.518 (Mgal/d)/mi2, which was 63 percent of the

median annual streamflow (table 6). The annual

ground-water discharge to streams ranged from

5.32 in. or 0.255 (Mgal/d)/mi2 in 1966 to 17.98 in.

or 0.863 (Mgal/d)/mi2 in 1972. Median annual surface runoff for 1933-99 was 6.22 in., which was

37 percent of the median annual streamflow

(table 6). The quantity of precipitation that

becomes surface runoff depends on the season;

the form (rain or snow), intensity, and duration of

precipitation; and soil-moisture conditions. Frozen

ground and snowmelt also may be contributing factors.

For part of the Delaware River Basin in southeastern Pennsylvania, the Delaware River Basin

Commission has set a maximum ground-water

withdrawal limit equal to the 25-year annual base

flow recurrence (Delaware River Basin Commission, 1999, p. 30). Annual base flows for Big Elk

Creek at Elk Mills for calendar years 1933-99 are

shown on figure 10, which is a base-flow-frequency

curve. A base-flow-frequency curve relates magnitude of base flow to frequency of occurrence. From

this base-flow-frequency curve, the 25-year annual

base-flow recurrence is 8.52 in., which is equal to

0.409 (Mgal/d)/mi2.

Table 6. Annual streamflow and estimated annual base flow for Big Elk Creek and Little Elk Creek,

Pennsylvania and Maryland,1933-99

Total streamflow

(inches)

and year

Estimated base

flow (inches)

and year

Percentage of

streamflow as

base flow and year

Estimated surface

runoff (inches)

and year

Percentage of

streamflow as

surface runoff

Big Elk Creek, 1933-99

Minimum 8.65 (1966) 5.32 (1966) 49.2 (1942) 2.47 (1954) 23.6 (1997)

Maximum 33.01 (1996) 17.98 (1972) 76.4 (1997) 15.94 (1966) 50.8 (1949)

Median 17.04 10.79 63.0 6.22 37.0

Big Elk Creek, 1949-57

Minimum 9.91 (1954) 7.45 (1954) 54.4 (1955) 2.47 (1954) 24.9 (1954)

Maximum 26.13 (1952) 16.57 (1952) 73.6 (1949) 9.56 (1952) 45.6 (1955)

Median 16.25 10.59 65.2 5.66 34.9

Little Elk Creek, 1949-57

Minimum 10.04 (1954) 7.32 (1954) 48.6 (1955) 2.73 (1954) 27.1 (1954)

Maximum 26.61 (1952) 14.80 (1952) 72.9 (1954) 11.71 (1952) 51.4 (1955)

Median 17.50 10.64 59.4 7.25 40.6
21

Low-Flow Statistics

Low-flow statistics for the Big Elk Creek Basin

were published in Schreffler (1998). Statistical

information based on streamflow data can be used

to predict future variability of streamflow, not in

terms of specific events but in terms of probability

of occurrence over a span of years. Low-flow statistics are derived from long-term streamflow data.

The long-term data are used to calculate historical

low flows and their frequency of occurrence. A statistic typically determined to characterize low flow

is the 7-consecutive day, 10-year (7Q10 or Q7-10)

low-flow value. The 7Q10 is defined as the lowest

mean streamflow over 7 consecutive days, which,

on average, has and probably will occur once every

10-year period. The 7Q10 is of particular importance to wastewater dischargers. The 7Q10 commonly is adopted by regulators as the minimum

flow to define discharge and instream pass-by permit conditions to protect stream-water quality.

Low-flow statistics determined by Schreffler

(1998) include the 1-day 10-year (1Q10), 7Q10,

and 30-consecutive-day 10 year (30Q10) low-flow

values (table 7). These statistics are based on the

minimum average 1-day, 7-day, and 30-day flow

from each year of record with a recurrence interval

of 10 years (cumulative probability of 0.10).

A 7Q10 of 1.0 ft3/s means the probability is 1 in 10

that the annual minimum average 7-consecutiveday streamflow for any year will be less than

Figure 10. Cumulative annual base-flow frequency of Big Elk Creek Creek at Elk Mills, Maryland (station

01495000), 1933-99, and Little Elk Creek at Childs, Maryland (station 01495500), 1949-57.

Table 7. Low-flow statistics for streamflow-measurement station

Big Elk Creek at Elk Mills, Md. (station 01495000), based on log

Pearson Type III frequency distribution (from Schreffler (1998, p.15))

[1Q10, 1-day, 10-year low-flow value; 7Q10, 7-day, 10-year low-flow value;

30Q10, 30-day, 10-year low-flow value; ft3/s, cubic foot per second]

Period of

record

Low-flow statistics

1Q10

(ft3/s)

7Q10

(ft3/s)

30Q10

(ft3/s)

Harmonic mean

(ft3/s)

April 1932-94 9.1 10.3 12.8 37.6
22

1.0 ft3/s, or that the annual minimum average

7-consecutive-day streamflow of less than 1.0 ft3/s

should be expected at the site, on average, once

every 10 years. Low-flow data were analyzed by

Schreffler (1998) on the basis of a climatic year

(April 1 to March 31). This period was used so that

streamflow through the entire low-flow season,

generally July through October, is included within

the year. Schreffler also determined an additional

low-flow statistic, the harmonic mean (table 7).

The harmonic mean is determined by summing the

inverses of daily mean streamflow data for the

entire period of record and dividing the resulting

sum into the number of data values. In Pennsylvania, the harmonic mean may be used to evaluate

effects on surface water from diffuse flow of contaminated ground water under regulations of the

Pennsylvania Department of Environmental Protection Land Recycling Program.

Ground-Water Availability

Ground-water availability is defined and estimated in a number of ways. It commonly is based

on the concept of “safe yield,” “optimal basin yield,”

or “perennial yield.” Todd (1980, p. 363) defines

“perennial yield” as the rate at which water can be

withdrawn perennially from a ground-water basin

under specified operating conditions without producing an undesired result. Undesired results may

differ from basin to basin depending on socioeconomic and legal viewpoints and can include

reduced streamflow, reduced base flow, reduced

ground-water levels, well interference, and degradation of water quality.

Methods to determine ground-water availability

in a basin include determinations of average

annual recharge (commonly assumed to be equal

to average annual base flow), dry-year base flow

(McGreevy and Sloto, 1977), 1-year in 25 average

annual base flow (Delaware River Basin Commission, 1999, p. 30), and the 7Q10 or a percentage of

it [proposed by the Green Valleys Association

(2000, p. 5-10 and 5-11) as a limit for ground-water

sustainability]. A comparison of withdrawal rates

using these methods is presented in table 8.

The optimal method is the one that best meets a

set of socioeconomic and/or social and environmental objectives associated with the use of the

water. However, all the methods indicate there will

be sufficient ground water on a basin-wide scale to

meet the 162 Mgal-per-year increase in demand

projected to 2020 (Chester County Water

Resources Authority, 2001).

Table 8. Ground-water availability in the Big Elk Creek Basin, Pennsylvania and

Maryland

[7Q10, 7-day, 10-year low-flow value]

Method of availability determination

Withdrawal rate

Million gallons per day

per square mile

Gallons per day

per acre

Average annual base flow 0.535 836

Median annual base flow .518 809

1-year in 25 average annual base flow .409 639

Dry-year base flow (1966) .255 389

7Q10 .127 198
23

Water Budget

A water budget is an estimate of water entering

and leaving a basin plus or minus storage changes

for a given time period. A water budget quantifies

the hydrologic cycle and defines the water balance

for a basin. Water enters as precipitation and

leaves as streamflow, evapotranspiration (ET), and

diversions, such as exported water. Water also is

taken into or released from ground-water and soilmoisture storage. Sewer systems can import or

export water into or out of a basin.

Because the water budgets in this report begin

and end in winter when soil moisture usually is at

field capacity, the change in soil moisture is

assumed to be equal to zero, and a soil-moisture

term is not included in the water-budget equation.

Therefore, for basins where ground-water and surface-water divides coincide, such as the Big Elk

Creek Basin, a simple annual water budget can be

expressed as

P = SF + ∆GWS + ET+ GWEXP, (1)

where P is precipitation,

SF is streamflow,

∆GWS is change in ground-water storage,

ET is evapotranspiration and other losses,

and

GWEXP is ground water exported from the basin.

All terms in the water-budget equation can be

measured or estimated except ET; and, therefore,

equation 1 is solved for ET.

Equation 1 was used to calculate water budgets for the Big Elk Creek Basin for 1998-99

(table 9). The water budget is expressed in inches

so that water budget components can be related to

precipitation and compared to other basins with different drainage areas. Inches can be converted to

million gallons per day per square mile by multiplying by 0.048. Data-collection sites necessary to

calculate a water budget include one or more precipitation gages (P), a streamflow-measurement

station (SF), and observation wells to estimate the

change in ground-water storage (∆GWS). The

location of data-collection stations in the Big Elk

Creek Basin is shown on figure 6.

Precipitation data for the Big Elk Creek Basin

were collected at nine sites by volunteer observers.

Annual precipitation in table 9 is the sum of average monthly precipitation measured at those

gages. Precipitation for 1998 (41.04 in.) is below

the normal (45.35 in.) for Newark, Del. The total

precipitation for 1999 (53.31 in.) was above the

normal for Newark, Del. Precipitation from the

storm of August 26-27, 1999, was 4.38 in., and

precipitation from Hurricane Floyd (September 16,

1999) was 10.04 in. If the 14.42 in. of precipitation

from these two storms were subtracted from the

annual total, precipitation for 1999 would be

38.89 in., which is below the normal for Newark,

Del.

Streamflow was measured at the streamflowmeasurement station Big Elk Creek at Elk Mills,

Md. On the basis of the streamflow record, the surface runoff from Hurricane Floyd was 3.48 in. However, precipitation was 10.04 in., and it is unlikely

that all the remaining 6.56 in. of water infiltrated or

evaporated. This discrepancy is reflected in the ET

term and may cause ET to be overestimated in the

water budget for 1999.

Ground-water storage is the water in and moving through the ground-water system. A positive

change (gain) in ground-water storage indicates an

increase in the volume of water in the ground-water

system. A negative change (loss) in ground-water

storage indicates a decrease in the volume of

water in the ground-water system. Water-level data

from January of each year from 10 observation

wells (table 19) were used to calculate the annual

change in ground-water storage. The median

Table 9. Annual water budgets for the Big Elk Creek Basin, Pennsylvania and Maryland, 1998-99

[A negative number indicates a decrease in ground-water storage.]

Year Precipitation

(inches)

Streamflow

(inches)

Percentage of

precipitation as

streamflow

Change in

groundwater

storage

(inches)

Groundwater

exports

(inches)

Evapotranspiration

and other losses

(inches)

Percentage of

precipitation as

evapotranspiration

1998 41.04 14.22 34.7 -0.12 0.03 26.91 65.6

1999 53.31 16.54 31.0 2.76 .02 34.11 64

Average 47.18 15.38 37.5 1.32 .03 30.50 64.8
24

annual change in water level was multiplied by

0.08, the specific yield of the zone of water-level

fluctuation in crystalline rocks (McGreevy and

Sloto, 1980, p. 18), to calculate the annual change

in ground-water storage. Annual changes in water

level ranged from 3.07 to -3.15 ft for 1998 with an

average change of -0.12 ft. Annual changes in

water level ranged from 6.92 to -1.48 ft for 1999

with an average change of 2.76 ft. The rise in water

level caused by recharge from the August 26-27,

1999, storm and Hurricane Floyd calculated by

comparing the August 18 and September 22, 1999,

measurements ranged from -0.45 to 5.72 ft with an

average rise of 2.71 ft.

Ground water is exported from wells pumped

in the basin by the Oxford Borough Water Department. The Oxford Borough Water Department

pumped 93.2 Mgal in 1998 and 82.2 Mgal in 1999

from the Big Elk Creek Basin. The Oxford Sewer

Authority uses a spray irrigation system for disposal in the Big Elk Creek Basin. The quantity of

effluent sprayed was 62 Mgal in 1998 and

63.5 Mgal in 1999. The percentage of the effluent

that recharged the ground-water system is

unknown. Assuming that 50 percent of the effluent

is returned to the ground-water system as

recharge, the net ground-water export from the

basin was 31.2 and 18.7 Mgal for 1998 and 1999,

respectively. This is equal to 0.03 in/yr for 1998 and

0.02 in/yr for 1999.

The ET term in the water budget includes ET,

other losses, and errors in the measurement of the

other water-budget components. Estimated ET calculated using equation 1 was 26.91 and 34.10 in.

for 1998 and 1999, respectively. Despite a

12.27-in. difference in precipitation between 1998

and 1999, the percentage of precipitation as ET

(65.6 and 64 percent, respectively) is similar

(table 9).

Recharge

All natural recharge to the ground-water system in the Big Elk Creek Basin is derived from local

precipitation. Some additional recharge is derived

from the Oxford Sewer Authority spray irrigation

system. Infiltrated precipitation first replenishes soil

moisture. After the soil-moisture deficit has been

satisfied, infiltrated precipitation recharges the

ground-water system. Recharge to the groundwater system depends on many factors, including

the duration and intensity of precipitation, antecedent soil-moisture conditions, slope, quantity of

impervious surface areas associated with urbanization, and soil and bedrock characteristics.

Recharge varies from season to season and from

year to year. Generally, recharge occurs on hilltops

and hillsides; topographically low areas commonly

are discharge areas.

Annual recharge was estimated for the Big Elk

Creek Basin for 1998-99 (table 10) by the following

equation:

R = BF + ∆GWS + GWET+ GWEXP, (2)

where R is estimated recharge,

BF is base flow,

∆GWS is change in ground-water storage,

GWET is estimated ground-water

evapotranspiration, and

GWEXP is ground water exported from the basin.

Base flow was estimated by the local minimum

computer hydrograph-separation technique of

Sloto and Crouse (1996). Ground-water ET is ET

directly from the saturated zone; it takes place

where the water table is close to the land surface.

Ground-water ET is estimated to be about 2 in/yr

on the basis of simulations of hydrologic budgets

using a ground-water-flow model by Sloto (1991).

Olmsted and Hely (1962, p. 13) estimated an

annual ground-water ET of 5.5 in/yr for the Piedmont. Most observation wells used to calculate

change in ground-water storage do not have water

levels close to land surface; therefore, loss to

Table 10. Estimated annual recharge for the Big Elk Creek Basin, Pennsylvania and Maryland, 1998-99

[A negative number indicates a decrease in ground-water storage.]

Year Recharge

(inches)

Percentage of

precipitation as

recharge

Base flow

(inches)

Change in

ground-water

storage

(inches)

Estimated

ground-water

evapotranspiration

(inches)

Ground-water

exports

(inches)

1998 11.28 27.4 9.37 -0.12 2.00 0.03

1999 12.95 24.3 8.28 2.76 2.00 .02

Average 12.12 25.9 8.83 1.32 2.00 .03
25

ground-water ET is not reflected in water levels

from these wells. Estimated recharge in table 10 is

given in inches so that recharge can be related to

precipitation and compared to other basins with different drainage areas. Inches can be converted to

million gallons per day per square mile by multiplying by 0.048.

Estimated recharge calculated using equation

2 was 11.28 in. [0.540 (Mgal/d)/mi2] in 1998, and

12.95 in. [0.621 (Mgal/d)/mi2] in 1999. Average

estimated annual recharge for 1998-99 was

12.12 in. [0.580 (Mgal/d)/mi2]; this is equal to a

recharge rate of 909 gal/d per acre. Recharge as a

percentage of precipitation was 27.4 percent for

1998 and 24.3 percent for 1999, respectively. Average annual recharge for 1998-99 as a percentage

of average annual precipitation was 25.9 percent.

GROUND-WATER QUALITY

The quality of water is determined primarily by

the type and quantity of substances dissolved in it.

As water moves through the hydrologic cycle,

gases and minerals from the atmosphere, soil, and

rock are dissolved. Additional substances may be

added by anthropogenic activities. Nutrients from

septic systems and fertilizers, salts from road salting and septic systems, pesticides, and industrial

solvents and chemicals can be introduced into

ground water. Biological activity also can change

the chemical composition of ground water.

Major ions dissolved from soil and rock make

up most dissolved solutes in ground water; the

remainder mostly comes from constituents dissolved in precipitation. Major cations (positively

charged ions) are calcium (Ca+2), sodium (Na+),

magnesium (Mg+2), and potassium (K+). Major

anions (negatively charged ions) are bicarbonate

(HCO3

-

), sulfate (SO4

-2), chloride (Cl-

), nitrate

(NO3

-

), and fluoride (F-). Silica (SiO2) is a major

constituent commonly present as undissociated

silicic acid (H4SiO4), an uncharged ion, below a pH

of 10.

Precipitation is the primary source of water for

the ground-water system in the Big Elk Creek

Basin. Precipitation contains trace and major elements scavenged from the atmosphere. The

source of constituents in precipitation can be natural, such as sodium and chloride from the ocean, or

anthropogenic, such as sodium and chloride from

road salt. Atmospheric precipitation commonly is a

major source of chloride and nitrogen. The average

concentration of selected major ions in precipitation in Chester County is given by Sloto (1994,

p. 57) and summarized by Senior and others

(1997, p. 47). Precipitation quality in the Big Elk

Creek Basin should be similar. For typical precipitation in Pennsylvania, the dominant anions are

sulfate and nitrate, and the dominant cations are

hydrogen and ammonium. Rain from summer

storms is relatively enriched in sodium and chloride

from the ocean, and precipitation from winter

storms is relatively enriched in sulfur and nitrogen

from the burning of fossil fuels.

pH is a measurement of the activity of hydrogen ions in water and is expressed in logarithmic

units with a pH of 7 considered neutral. Water with

a pH less than 7 is acidic; water with a pH greater

than 7 is basic. The pH of distilled water in contact

with the atmosphere is about 5.6 because of dissolution of carbon dioxide. However, in southeastern

Pennsylvania where emissions from combustion of

fossil fuels contribute to acidity of atmospheric precipitation, the pH commonly is less than 5. The

median pH measured by Lynch and others (1992)

for 1982-91 was 4.24. Acidic precipitation can react

aggressively with some minerals to accelerate mineral weathering.

Ground-water composition evolves through a

series of chemical interactions with minerals in the

aquifer. Some chemical reactions are mediated

biologically, such as denitrification, during which

nitrate is reduced to nitrogen gas. The main chemical reactions are mineral dissolution and precipitation, mineral weathering, ion adsorption and

exchange, and natural radioactive decay. Sources

of many elements in natural waters and general

and important chemical reactions governing water

chemistry are summarized by Hem (1985).

In crystalline rocks, silicate minerals are the

most abundant minerals. These minerals can

include feldspars, micas, and quartz. Other minerals that may be present are pyrite (a sulfide), secondary iron and manganese hydroxides, and traceelement oxides. The weathering of feldspars and

micas causes an increase in alkalinity, pH, and

concentrations of dissolved silica, sodium, calcium,

magnesium, and/or potassium. The weathering of

pyrite can cause an increase in the concentration

of dissolved sulfate and a decrease in pH.

For this study, water samples were collected

from 20 wells for analysis for inorganic constituents

and pesticides. The USGS has collected and analyzed ground-water samples in the Big Elk Creek
26

Basin since 1925, and data were available from an

additional 44 wells. A few wells are at or just over

the drainage divide. These data were collected for

previous studies and for a ground-water-quality

sampling program conducted by the USGS in

cooperation with the Chester County Water

Resources Authority and the Chester County

Health Department. Ground-water samples were

analyzed by the USGS. Complete analyses are

given in tables 20 and 21. Locations of sampled

wells are shown on figure 11.

Figure 11. Location of wells sampled for water-quality analyses, Big Elk Creek Basin, Pennsylvania

and Maryland.

0 1

0 1

2

2

MILES

KILOMETERS DELAWARE

PENNSYLVANIA .

MARYLAND

CH-3316

39°50′

39°40′

39°45′

39°35′

76° 75°55′ 75°50′ 75°45′

CH-5430

WELL SAMPLED 1998

AND IDENTIFICATION NUMBER

CH-3317 CH-5420

CH-5423

CH-5425

CH-1724

CH-5231

CH-1835

CH-5428

CH-5470

CH-1720

CH-5443 CH-5479

CH-2461

CH-1996 CH-525

CH-1737

CH-5434

CH-5442

CH-5430

CH-2459

CH-528 CH-4933

CH-5476

CH-4275

CH-5439

CH-4118

CH-5477

CH-1770

CH-5440

CH-1765

CH-5421

CH-5426

CH-5437

CH-75

CH-2186

CH-4297

CH-526

CH-2460

CH-1735

CH-2678

CH-1702

CH-2440

CH-2439

CH-2673

CH-1777

CH-1703

CH-5432

CH-1761

CH-1776

CH-1778

CH-1829

CH-5433

CH-1783

CH-4931

CH-5424 CH-5431

CH-5450

CE Ae 9

CE Ae 8

CE Ae 13

CE Bf 77

I-95

US 1

CH-1720

WELL SAMPLED PRIOR TO OR AFTER 1998

AND IDENTIFICATION NUMBER

CH-4126

CH-4806
27

Physical Properties

and Field-Determined Constituents

Water quality may be characterized by physical

properties and the concentration of dissolved and

suspended constituents. Physical properties and

chemical constituents determined in the field

include pH, specific conductance, hardness,

alkalinity, temperature, and the concentration of

dissolved oxygen; these properties are unstable

and are measured in the field at the time a water

sample is collected.

The range and median pH, specific conductance, alkalinity, hardness, temperature, and concentration of dissolved oxygen in ground water in

the Big Elk Creek Basin are presented in table 11.

Complete chemical analyses are given in table 20.

The pH, alkalinity, and dissolved-oxygen concentration were measured in the field according to

established procedures (Wood, 1981). Where

more than one analysis of water was available for a

well, the most recent one was used for statistical

analysis. Extreme values may represent anthropogenic contamination.

The median pH of water (5.9) from wells in the

Wissahickon Schist is acidic. Only three water

samples were collected from serpentinite; the pH

ranged from 7.8 to 8.5. McGreevy and Sloto (1977,

p. 47) reported the median pH of ground water in

serpentinite was 8.1.

Table 11. Summary of physical properties and field-determined constituents for water samples from

wells in the Big Elk Creek Basin, Pennsylvania and Maryland

[°C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams

per liter; --, insufficient data to compute median]

Property or constituent and

geologic unit

Number of

samples Minimum Median Maximum

pH

Peters Creek Schist 4 4.8 -- 7.1

Serpentinite 3 7.8 -- 8.5

Wissahickon Schist 48 5.2 5.9 7.7

Pelitic gneiss 2 6 -- 6.6

Specific conductance (μS/cm)

Peters Creek Schist 4 54 -- 500

Serpentinite 3 396 -- 457

Wissahickon Schist 46 50 160 849

Pelitic gneiss 3 128 -- 699

Alkalinity (mg/L as CaCO3)

Peters Creek Schist 2 2 -- 18

Serpentinite 1 243 -- --

Wissahickon Schist 34 6 20 90

Pelitic gneiss 0 -- -- --

Hardness1 (mg/L as CaCO3)

Peters Creek Schist 3 13 -- 80

Serpentinite 3 220 -- 250

Wissahickon Schist 41 9 38 99

Pelitic gneiss 3 42 -- 320

Temperature (°C)

Peters Creek Schist 2 13.5 -- 15

Serpentinite 3 13.7 -- 18.1

Wissahickon Schist 40 11.5 13.6 18

Pelitic gneiss 3 12.9 -- 13.2

Dissolved oxygen (mg/L)

Peters Creek Schist 1 9.3 -- --

Serpentinite 1 1.8 -- --

Wissahickon Schist 23 3.4 7.5 10

Pelitic gneiss 0 -- -- --

1 Includes both laboratory determinations and computed values.
28

Specific conductance is a measurement of the

ability of water to conduct an electric current and is

expressed in units of microsiemens per centimeter

at 25°C. Specific conductance is related directly to

the concentration of dissolved solids; the higher

the specific conductance, the greater the concentration of dissolved solids. The concentration of

total dissolved solids (TDS) can be estimated by

multiplying specific conductance by 0.65 (Sloto,

1994, p. 58). The median specific conductance of

water from wells in the Wissahickon Schist is a relatively low 160 μS/cm.

The alkalinity of water is the capacity for solutes (bases) it contains to react with and neutralize

acid and is expressed in terms of an equivalent

amount of calcium carbonate. Alkalinity is produced by dissolution of minerals or reactions that

generate bicarbonate, carbonate, or other basic

anions. Bicarbonate alkalinity predominates in

most natural ground water. The median alkalinity of

water from wells in the Wissahickon Schist is

20 mg/L.

Hardness is a poorly defined property of water

and is caused by the dissolved alkaline earth elements, chiefly calcium and magnesium. Hard water

restricts the lathering and cleaning action of soap

and causes the formation of encrustations when

water is heated. Hardness usually is expressed in

equivalent concentrations of calcium carbonate.

Hardness is classified by Dufor and Becker (1964,

p. 27) as: soft, 0-60 mg/L; moderately hard, 61-

120 mg/L; hard, 121-180 mg/L; and very hard,

more than 180 mg/L. Water from wells in the Wissahickon Schist is soft; the median hardness is

38 mg/L. Only three water samples were collected

from serpentinite; the hardness ranged from 220 to

250 mg/L, which would classify the water as very

hard.

The median temperature of water samples

from wells in the Wissahickon Schist is 13.6°C

(56.5°F). Ground-water temperature commonly is

similar to the mean annual air temperature. The

1971-2000 normal annual air temperature at the

NOAA station in Newark, Del., is 54.8°F (12.7°C).

Ground-water temperatures measured monthly

from December 1983 to December 1984 in six

wells in different parts of Chester County by Sloto

(1987) had an average annual fluctuation range of

about 3.3°C (6°F).

Dissolved oxygen in ground water indicates

infiltration of recharge is rapid and/or few biological

and chemical reactions that consume oxygen have

taken place. Oxygen can be consumed in the oxidation of organic and inorganic (including minerals)

compounds. Ground water in fractured-rock aquifers in the Piedmont commonly contains some dissolved oxygen. For the range of ground-water

temperature observed in the basin (11.5 to

18.1°C), the saturated concentration of dissolved

oxygen ranges from 6.5 to 11 mg/L (American Public Health Association and others, 1995, p. 4-99).

The concentration of dissolved oxygen in ground

water from the Wissahickon Schist ranges from 3.4

to 10 mg/L; the median concentration is 7.5 mg/L.
29

Major Ions

Major ions dissolved from soil and rock constitute most of the dissolved solutes in ground water;

some solutes are dissolved in precipitation. Major

ions, in order of decreasing concentration, in the

ground water of the Big Elk Creek Basin, based on

median concentrations for the Wissahickon Schist

(table 12), are silica, calcium, chloride, sodium, sulfate, magnesium, and potassium. Complete chemical analyses for major ions are given in table 20.

Because the number of water-quality analyses

for wells in geologic units other than the Wissahickon Schist is small, these analyses may not be

representative of the water quality of those units.

Differences in ground-water quality among geologic units were not tested statistically.

The U.S. Environmental Protection Agency

(USEPA) has set maximum contaminant levels

(MCL’s) and secondary maximum contaminant levels (SMCL’s) for some constituents in drinking

water (table 13). MCL’s usually are set because

elevated concentrations of these constituents may

cause adverse health effects. SMCL’s usually are

set for aesthetic reasons; elevated concentrations

of these constituents may impart an undesirable

taste or odor to water.

Total dissolved solids (TDS) is a measurement

of the total solutes in water. Water from crystalline

rocks, which are resistant to weathering, generally

contain low concentrations of TDS. The USEPA

SMCL for TDS concentration in drinking water is

500 mg/L. Water from only 1 of 49 wells sampled

(2 percent) in the Big Elk Creek Basin exceeded

the SMCL for TDS; a water sample from well CE

Ae 9 in the pelitic schist had a TDS concentration

of 599 mg/L. The median concentration of TDS in

water samples from the Wissahickon Schist is

100 mg/L.

Mineral sources of calcium include calcite

(CaCO3), dolomite [CaMg(CO3)2], and anorthite

(CaAl2Si2O8) or other calcium-bearing feldspars.

Sources of magnesium include dolomite and chlorite [Mg5Al2Si3O10(OH)8]. Median concentrations

of calcium and magnesium in water samples from

the Wissahickon Schist are 9.3 and 3.9 mg/L,

respectively (table 12). Serpentinite is a calciumdeficient and magnesium-rich rock. The calcium

concentration of three water samples from serpentinite ranged from 1.8 to 4.6 mg/L, and the magnesium concentration ranged from 53 to 59 mg/L.

Mineral sources of potassium include mica

[muscovite, KAl3Si3O10(OH)2 and biotite,

K(Mg,Fe)3AlSi3O10(OH)2] and orthoclase, a potassium-bearing feldspar (KAl3Si3O8), which are

abundant in crystalline rocks. Potassium also is a

component in fertilizers. The median concentration

of potassium in water samples from the Wissahickon Schist is 1.7 mg/L (table 12).

Mineral sources of sodium include albite

(NaAl3Si3O8) or other sodium-bearing feldspars

and clay minerals. Road salt is a source of sodium

and may produce elevated sodium concentrations

in ground water. The median concentration of

sodium in water samples from the Wissahickon

Schist is 6.7 mg/L (table 12). The predominant natural source of chloride in the Big Elk Creek Basin

probably is precipitation. Chloride concentrations in

precipitation (median 0.5 mg/L, Sloto, 1994, p. 57)

can be increased by evaporation before infiltration.

The minimum reported concentrations of chloride in ground water (about 2-6 mg/L) probably represent natural background concentrations (table

20). Chloride concentrations range up to 218 mg/L

(table 12). Elevated concentrations of chloride in

the Big Elk Creek Basin probably are caused by

anthropogenic activities, such as input from road

salt, fertilizers, and septic systems. Increases in

chloride concentration commonly are accompanied

by increases in sodium. A linear relation between

concentrations of sodium and chloride is evident

for ground-water samples (fig. 12). If the sole

source of sodium and chloride were salt as NaCl,

the mass ratio of chloride to sodium should be the

same in ground water as in salt (about 1.54),

although cation exchange can affect ion ratios.

Because the mass ratio is greater than 1.54 for

chloride to sodium, the data suggest sources of

chloride other than salt. In southeastern Pennsylvania, both calcium chloride and sodium chloride

salts are applied to roads in the winter months.

None of the chloride concentrations in the groundwater samples exceeded the USEPA SMCL of

250 mg/L for chloride. The median concentration of

chloride in water samples from the Wissahickon

Schist is 8.3 mg/L.
30

Table 12. Summary of concentrations of major ions and radon-222 in ground water

in the Big Elk Creek Basin, Pennsylvania and Maryland

[mg/L, milligrams per liter; pCi/L, picocuries per liter <, less than; --, insufficient data

to compute median]

Constituent

Number

of wells

sampled

Concentrations (mg/L)

Minimum Median Maximum

Total dissolved solids (mg/L)

Peters Creek Schist 3 79 -- 263

Serpentinite 3 230 -- 249

Wissahickon Schist 38 33 100 231

Pelitic gneiss 3 102 -- 599

Calcium (mg/L)

Peters Creek Schist 3 2.9 -- 27.1

Serpentinite 3 1.8 -- 4.6

Wissahickon Schist 38 1.9 9.3 66.1

Pelitic gneiss 3 13.3 -- 66.1

Chloride (mg/L)

Peters Creek Schist 4 4.1 -- 150

Serpentinite 3 4.9 -- 5.4

Wissahickon Schist 47 1.8 8.3 130

Pelitic gneiss 3 3.3 -- 218

Fluoride (mg/L)

Peters Creek Schist 3 <.1 -- .1

Serpentinite 3 <.1 -- <.1

Wissahickon Schist 40 <.1 <.1 .5

Pelitic gneiss 3 <.1 -- <.1

Magnesium (mg/L)

Peters Creek Schist 3 1.5 -- 3.2

Serpentinite 3 53 -- 59

Wissahickon Schist 38 .8 3.9 36.7

Pelitic gneiss 3 2.2 -- 37.4

Potassium (mg/L)

Peters Creek Schist 3 .7 -- 1.8

Serpentinite 3 .1 -- .2

Wissahickon Schist 37 .4 1.7 3.3

Pelitic gneiss 3 1 -- 2.1

Radon-222 (pCi/L)

Peters Creek Schist 2 4,300 -- 5,300

Serpentinite 3 42 -- 392

Wissahickon Schist 35 285 2,500 11,000

Pelitic gneiss 3 528 -- 2,400

Silica (mg/L)

Peters Creek Schist 3 12 -- 23.9

Serpentinite 3 5.3 -- 46.8

Wissahickon Schist 37 7.5 18 34

Pelitic gneiss 3 28 -- 34

Sodium (mg/L)

Peters Creek Schist 3 4.5 -- 5.8

Serpentinite 3 1.5 -- 3.4

Wissahickon Schist 38 2.5 6.7 33.3

Pelitic gneiss 3 7.6 -- 38.8

Sulfate (mg/L)

Peters Creek Schist 3 12 -- 23.9

Serpentinite 3 3.5 -- 8.8

Wissahickon Schist 45 .1 4 21

Pelitic gneiss 3 10.1 20.3
31

Table 13. U.S. Environmental Protection Agency maximum contaminant levels

and secondary maximum contaminant levels for selected constituents in drinking water

[From U.S. Environmental Protection Agency, 1991; 1992a; and 1999;

concentrations in micrograms per liter except as indicated; mg/L, milligrams per

liter; pCi/L, picocuries per liter; --, no set limit]

Constituent

Maximum

contaminant

level

Secondary

maximum

contaminant level

Inorganic

Arsenic 50 --

Barium (mg/L) 1 --

Cadmium 5 --

Chloride (mg/L) -- 250

Chromium 100 --

Copper -- 1,000

Fluoride 4 2

Iron -- 300

Lead 115 --

Manganese -- 50

Mercury 2 --

Nitrate as nitrogen (mg/L) 10 --

Nitrite as nitrogen (mg/L) 1 --

Selenium 50 --

Silver -- 100

Sulfate (mg/L) -- 250

Total dissolved solids (mg/L) -- 500

Zinc (mg/L) -- 5

Organic

Benzene 5 --

Carbon tetrachloride 5 --

1,2-dichloroethane 5 --

1,1-dichloroethylene 7 --

1,2-dichloropropane 5 --

Ethylbenzene 700 --

PCB .5 --

Styrene .1 --

Tetrachloroethylenen (PCE) 5 --

Toluene 1,000 --

1,1,1-trichloroethane (TCA) 200 --

Trichloroethylene (TCE) 5 --

Vinyl chloride 2 --

Xylenes 10,000 --

Pesticide

Alachlor 2 --

Atrazine 3 --

Chlordane 2 --

Endrin .2 --

Heptachlor .4 --

Heptachlor epoxide .2 --

Lindane 4 --

Methoxychlor 100 --

Toxaphene 5 --

2,4-D 100 --

2,4,5-TP (silvex) 10 --

Radionuclide

Radon-222, no indoor air program (pCi/L) 2300 --

Radon-222, with indoor air program (pCi/L) 24,000 --

1 Action level.

2 Proposed.
32

Sulfate (SO4

-2) is a common constituent of

ground water derived from atmospheric precipitation and minerals. Sulfuric acid generated during

coal combustion contributes to the acidity of rain in

eastern Pennsylvania—the median concentration

of sulfate in precipitation in Chester County is

about 10 mg/L (Sloto, 1994, p. 57). Mineral

sources of sulfur include metallic sulfides, such as

pyrite (FeS2). Sewage is another source of sulfate.

Most sulfate in the ground water in the Big Elk

Creek Basin probably is from natural mineral

sources. The median concentration of sulfate in

water samples from the Wissahickon Schist is

4 mg/L. None of the sulfate concentrations in the

ground-water samples exceeded the USEPA

SMCL of 250 mg/L for sulfate.

Figure 12. Relation between concentrations of sodium and chloride in ground water in the Big Elk

Creek Basin, Pennsylvania and Maryland.

0 5 10 15 20 25 30 35 40

SODIUM CONCENTRATION, IN MILLIGRAMS PER LITER

0

240

20

40

60

80

100

120

140

160

180

200

220

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

MASS RATIO 1.54
33

Waters commonly are characterized by the relative percentage of major ions in solution. A trilinear diagram for cations and anions (expressed in

milliequivalents per liter), known as a Piper diagram (fig. 13), shows ground-water compositions

(water types) that reflect aquifer mineralogy and

chemical loads to ground water. According to Hem

(1985, p. 166), a water in which no one cation or

anion constitutes as much as 50 percent of the

totals should be recognized as a mixed water type

and identified by the names of all the important cations and anions. Ground water from the Wissahickon Schist and Peters Creek Schist is of a

similar water type; ground water from the serpentinite is distinctly different. For the Wissahickon

Schist and Peters Creek Schist, no cation is predominant; calcium, magnesium, and sodium are in

nearly equal concentrations expressed in milliequivalents per liter. Bicarbonate is the dominant

anion. Ground water from serpentinite is of the

magnesium bicarbonate type; magnesium is the

dominant cation, and bicarbonate is the dominant

anion.

Figure 13. Relative concentrations of major ions in ground water in the Big Elk Creek Basin,

Pennsylvania.

EXPLANATION

PETERS CREEK SCHIST

SERPENTINITE

WISSAHICKON SCHIST

PERCENTAGE OF TOTAL MILLIEQUIVALENTS PER LITER
34

Nutrients

Nutrients in ground water include nitrogen and

phosphorus species, which are essential for plant

and animal growth. Nitrogen is found in water principally as nitrate (NO3), nitrite (NO2), and ammonia

(NH4). Phosphorus is found in water principally as

a form of the orthophosphate ion species. Nutrient

concentrations above natural background levels

indicate pollution resulting from human activities.

Sources of nutrients in ground water include fertilizers, storm runoff, animal wastes, and effluent

from septic systems. Concentrations of nutrients

are summarized in table 14. Complete chemical

analyses for nutrients are given in table 20.

Some nitrate concentrations in table 14 were

computed by subtracting the concentration of nitrite

from the concentration of nitrate plus nitrite. When

nitrite was below the detection limit, zero was used

in the computation. The median concentration of

nitrate in water samples from the Wissahickon

Schist is 3.6 mg/L (table 14). Of 60 water samples

from wells in the Big Elk Creek Basin, concentrations of nitrate exceed the USEPA MCL of 10 mg/L

nitrate as nitrogen in water from 6 wells (10 percent

of wells sampled). All of these wells are in the Wissahickon Schist. The maximum concentration was

36 mg/L.

Nitrite, ammonia, and phosphorus species

generally are present in concentrations less than

0.10 mg/L; median concentrations of these constituents for the Wissahickon Schist are equal to or

less than 0.02 mg/L (table 14). Concentrations of

ammonia or phosphate above background concentrations in ground water can indicate contamination, as can elevated concentrations of nitrate.

Ammonium (NH4

+) is the dominant form of ammonia (NH3) in most natural waters. Ammonium commonly is oxidized to form nitrate and rarely is

detected in uncontaminated ground water in concentrations greater than about 0.5 mg/L.

Table 14. Summary of concentrations of nutrients in ground water in the Big Elk

Creek Basin, Pennsylvania and Maryland

[All concentrations are given in milligrams per liter; <, less than; --, insufficient

data to compute median]

Constituent

Number

of wells

sampled

Concentration

Minimum Median Maximum

Nitrate as nitrogen

Peters Creek Schist 3 <0.050 -- 4.1

Serpentinite 3 .050 -- .392

Wissahickon Schist 48 <.050 3.6 36

Pelitic gneiss 3 <.050 -- 2.31

Nitrite as nitrogen

Peters Creek Schist 4 <.010 -- <.010

Serpentinite 3 <.010 -- .013

Wissahickon Schist 43 <.010 <.010 .012

Pelitic gneiss 3 <.010 -- <.010

Ammonia as nitrogen

Peters Creek Schist 3 <.010 -- .022

Serpentinite 3 .020 -- .052

Wissahickon Schist 43 <.010 .010 .080

Pelitic gneiss 3 <.020 -- .024

Phosphorus

Peters Creek Schist 2 <.010 -- .040

Serpentinite 2 <.010 -- --

Wissahickon Schist 21 <.010 <.050 .105

Pelitic gneiss 3 <.050 -- <.050

Orthophosphate as phosphorus

Peters Creek Schist 3 <.010 -- .040

Serpentinite 3 .010 -- .028

Wissahickon Schist 40 <.010 .020 .090

Pelitic gneiss 3 .015 -- .028
35

Metals and Trace Constituents

Metals, such as iron, lead, and manganese,

and trace constituents, such as arsenic, typically

are present in low concentrations (less than

1 mg/L) in water samples from wells in the Big Elk

Creek Basin. Other constituents, such as antimony

and silver, may be present but commonly are not

analyzed. If present, concentrations generally are

below the detection limit of analytical instruments

or procedures. The USEPA has established MCL’s

and SMCL’s for some of these constituents in drinking water (table 13).

Most metals and trace constituents in natural

ground water are leached from the soil or dissolved

from the underlying bedrock in minute quantities by

circulating ground water. Some are present in precipitation. Many metals are soluble in acidic water.

Copper, lead, and zinc in tap water may be leached

from household plumbing systems by acidic

ground water. Copper leached from pipes commonly is deposited as blue or green precipitates on

plumbing fixtures.

Data on the concentration of metals and other

trace constituents in ground water are summarized

in table 15. Except for iron and manganese, these

constituents do not pose a water-quality problem in

the Big Elk Creek Basin. The median concentrations of constituents in table 15 represent natural

background concentrations. Data for trace constituents are difficult to evaluate statistically because

concentrations commonly are below detection limits. In addition, a constituent may have several

detection limits. The action level for lead (table 13),

as defined by the USEPA, means a public water

purveyor must take corrective action if the concentration of lead is above 15 μg/L in more than

10 percent of tap-water samples collected during

any monitoring period. The USEPA SMCL’s were

exceeded only for iron and manganese.

Table 15. Summary of concentrations of dissolved metals and trace constituents

in ground water in the Big Elk Creek Basin, Pennsylvania and Maryland

[All concentrations are given in micrograms per liter; <, less than; --, insufficient

data to compute median]

Constituent Number of

samples

Number of

samples above

detection level

Concentration

Minimum Median Maximum

Aluminum 12 6 <1 -- 50

Antimony 3 3 <1 -- --

Arsenic 41 7 <1 <1 2

Barium 36 29 4 -- 208

Boron 12 2 <20 <20 80

Cadmium 46 3 <.1 -- 8

Chromium 46 4 <1 -- 14.3

Cobalt 35 0 <1 -- --

Copper 42 18 <1 -- 380

Iron 60 42 <1 20 3,400

Lead 46 13 <1 -- 10

Lithium 33 18 <1 -- 12.7

Manganese 49 41 2 20 330

Mercury 20 0 <.1 -- --

Nickel 41 12 <1 -- 39

Selenium 11 4 <1 <1 3

Silver 35 0 <1 -- --

Zinc 43 22 1 <20 1,300
36

Elevated concentrations of iron and manganese in water may impart a bitter taste and stain

laundry and plumbing fixtures. The USEPA SMCL’s

are set for aesthetic rather than health reasons.

Sources of iron in ground water include minerals in

the bedrock, such as pyroxenes, amphiboles,

hematite, magnetite, and pyrite, and corrosion of

iron well casings. Bacterial activity may elevate iron

concentrations. Sources of manganese in ground

water include minerals in the bedrock, such as

biotite and hornblende. Of the water samples analyzed, 9 of 59 samples (15 percent) analyzed for

iron and 16 of 56 samples (29 percent) analyzed

for manganese exceeded the USEPA SMCL.

Water samples exceeding the 300 μg/L USEPA

SMCL for iron were from six wells in Wissahickon

Schist, one well in Peters Creek Schist, one well in

pegmatite, and one well in pelitic gneiss. Water

samples exceeding the 50 μg/L USEPA SMCL for

manganese were from 13 wells in Wissahickon

Schist, 1 well in Peters Creek Schist, 1 well in pegmatite, and 1 well in pelitic gneiss. Water from

three wells in Wissahickon Schist (CH-1778,

CH-3316, and CH-5430), one well in Peters Creek

Schist (CH-5425), one well in pegmatite

(CH-5450), and one well in pelitic gneiss (CE Ae 8)

had concentrations of both iron and manganese

that exceeded the USEPA SMCL’s (table 20).

Radon-222

Radon-222 is a naturally occurring, colorless,

odorless, radioactive gas that is soluble in water. It

is produced through the radioactive decay of uranium and radium, which is present naturally in soil

and in minerals in bedrock. The rate of radon’s

radioactive decay is defined by its half-life, which is

the time required for one half of the amount of

radon present to break down to form other elements. Radon has a short half-life of 3.8 days. The

Surgeon General of the United States has recognized exposure to radon gas as being second only

to cigarette smoking as a cause of lung cancer

(U.S. Environmental Protection Agency, 1992b).

Radon gas can cause lung cancer if inhaled

because its decay products can accumulate in the

lungs and damage lung tissue. Radon moves from

its source in rocks and soils through voids and fractures. It can enter buildings as a gas through foundation cracks, or it can dissolve in ground water

and be carried to buildings through the use of

water-supply wells. The USEPA has proposed an

MCL of 300 pCi/L for radon-222 in drinking water

for water systems without an individual indoor air

radon program and 4,000 pCi/L for water systems

with an individual indoor air radon program (U.S.

Environmental Protection Agency, 1999). Radon222 in the ground water of Chester County is discussed in detail by Senior (1998) and summarized

by Sloto and Senior (1998).

Water samples from 44 wells were analyzed

for radon-222 activity (table 12). The samples were

collected from 35 wells in the Wissahickon Schist,

3 wells in serpentinite, 2 wells in the Peters Creek

Schist, 3 wells in pelitic gneiss, and 1 well in pegmatite. Radon-222 activity in ground water generally differs among rock types and can vary

considerably within the same geologic formation.

The median activity for all formations sampled

in the Big Elk Creek Basin was 2,400 pCi/L. Water

from 41 of 44 wells sampled (94 percent) in the

basin exceeded 300 pCi/L, and water from 5 of

44 wells sampled (25 percent) exceeded

4,000 pCi/L. The median activity for water from

35 wells sampled in the Wissahickon Schist was

2,500 pCi/L (table 12). Activities of radon-222 in

water samples from the Wissahickon Schist ranged

over three orders of magnitude—from 285 to

11,000 pCi/L. Radon-222 activities in water from

one of three wells sampled in serpentinite

(33 percent) exceeded 300 pCi/L; the maximum

activity was 392 pCi/L. Serpentinite contains few

radioactive minerals. Radon-222 activities in water

from both wells sampled in the Peters Creek Schist

exceeded 4,000 pCi/L. Of all the geologic units

sampled in Chester County, ground water in the

Peters Creek Schist has the highest median radon222 activity (4,400 pCi/L), and ground water in serpentinite has the lowest median radon-222 activity

(150 pCi/L) (Sloto and Senior, 1998).

Organic Compounds

One of the most serious consequences of

urbanization is the introduction of human-made

organic compounds into the subsurface environment. Some of these compounds have been entering the ground-water system for decades, but

awareness of their presence in drinking-water supplies did not begin until the mid-1970’s, when analytical techniques became available to detect their

presence. The USEPA has set MCL’s for some

organic compounds in drinking water (table 13).
37

Volatile Organic Compounds

Volatile organic compounds (VOC’s) are used

extensively in industrial, commercial, and household applications. Their presence in ground water

presents a serious problem for public water suppliers, industries, and domestic well owners that rely

on ground water. Many VOC’s are confirmed or

suspected human or animal carcinogens. VOC’s

generally enter the ground-water system by spills,

leakage from storage tanks, discharge from septic

systems, and from lagoons and disposal sites.

Once in the ground-water system, VOC’s are difficult to remove, and treatment generally is expensive.

Water samples analyzed for VOC’s are summarized in table 16, which also includes total phenols, total polychlorinated biphenyls (PCB), and

total polychlorinated napthalenes (PCN). The

choice of wells for sampling generally was biased

toward wells where the potential existed for the

presence of VOC’s in ground water, such as near

landfills and industrial sites. Out of 43 compounds

analyzed, only 4 were detected—chloroform, total

phenols, tert-butyl methyl ether (MTBE), and toluene. None of the samples exceeded USEPA MCL’s.

This is different from Chester County as a whole,

where VOC’s were detected in 32 percent of wells

sampled, and the most commonly detected compounds in decreasing order were trichloroethylene

(TCE), 1,1,1-trichloroethane (TCA), and 1,2-transdichlorethylene (Sloto, 1994, p. 70-71).

Pesticides

Pesticides are used widely in the Big Elk Creek

Basin. Pesticides are divided into insecticides and

herbicides on the basis of their use. Insecticides

are used in agricultural areas to control crop-damaging insects and in residential areas to control

household and garden insects. Herbicides are

used to control weeds that compete with crops in

agricultural areas and home gardens. They also

are used to control broad-leaf weeds on lawns and

turf and to defoliate utility, railroad, and highway

rights-of-way. For this study, water samples were

collected from 20 wells and analyzed for pesticides. An additional 20 wells in the Big Elk Creek

Basin were sampled for pesticides prior to this

study. Not all wells were sampled for the same pesticides. A summary of pesticide data is presented

in table 17. Complete analyses are presented in

table 21.

The most commonly detected pesticides in the

Big Elk Creek Basin are deethyl atrazine (71 percent of sampled wells), atrazine (35 percent of

sampled wells), metolachlor (32 percent of sampled wells), carbaryl (19 percent of sampled wells),

picloram (14 percent of sampled wells), simazine

(13 percent of sampled wells), and carbofuran

(11 percent of sampled wells). Most concentrations

are extremely low and are in the parts per trillion

range (table 17). A concentration of 0.003 μg/L is

equivalent to 3 parts pesticide per trillion

(1,000,000,000,000) parts water. Pesticide concentrations detected did not exceed USEPA MCL’s

(table 13). Only pesticides detected in water samples are discussed below.

Atmospheric deposition may be the source of

some pesticides in ground water. The atmosphere

is now recognized as a major pathway by which

pesticides can be transported and deposited in

areas sometimes removed from their source. Pesticides have been found in both rain and air in all

parts of the United States sampled by the USGS.

The most commonly detected pesticides in rain in

decreasing order are atrazine, alachlor, lindane,

alpha-HCH, methoxychlor, DDT, deethyl atrazine,

dieldrin, and simazine. The most commonly

detected pesticides in the air in decreasing order

are DDT, methidathion, lindane, alpha-HCH, diazinon, heptachlor, malathion, and dieldrin (U.S. Geological Survey, 1995).

Atrazine, cyanazine, and simazine belong to a

class of compounds known as triazine herbicides.

Deethyl atrazine is a major degradation product of

atrazine. The triazine herbicides are used mainly

for preemergence applications on corn, soybeans,

hay, and other crops for control of grassy and

broadleaf weeds. Atrazine was detected in water

from 12 of 34 wells sampled (35 percent), and

deethyl atrazine was detected in water from 22 of

31 wells sampled (71 percent). In Chester County,

atrazine commonly is used to control weeds in

corn, soybeans, and hay crops. In 1997, atrazine

was the most heavily used herbicide; an estimated

75-82 million pounds were applied in the United

States (Aspelin and Grube, 1999). Effective in

1993, its use for non-crop vegetation in fallow and

noncrop land was eliminated by the USEPA. Microbial activity possibly accounts for significant degradation of atrazine in soil (U.S. Environmental

Protection Agency, 2001).
38

Table 16. Volatile organic compounds detected in ground water in the Big Elk Creek Basin,

Pennsylvania

[Concentrations given in micrograms per liter; --, concentration below detection limit]

Compound

Number of

wells

sampled

Number of wells with

concentration above

detection limit

Maximum

concentration

Benzene 14 0 --

Bromodichloromethane 14 0 --

Bromoform 14 0 --

Carbon tetrachloride 14 0 --

Chlorobenzene 14 0 --

Chloroethane 11 0 --

2-Chloroethyl vinyl ether 11 0 --

Chloroform 14 1 0.2

Dibromochloromethane 14 0 --

1,2-Dibromoethylene 2 0 --

1,2-Dibromomethane 4 0 --

1,2-Dichlorobenzene 9 0 --

1,3-Dichlorobenzene 9 0 --

1,4-Dichlorobenzene 9 0 --

Dichlorodifluoromethane 14 0 --

1,1-Dichloroethane 14 0 --

1,2-Dichloroethane 14 0 --

1,1-Dichloroethylene 14 0 --

cis-1,2,-Dichloroethylene 3 0 --

trans-1,2,-Dichloroethylene 14 0 --

1,2-Dichloropropane 14 0 --

Dichloropropene 11 0 --

cis-1,3-Dichloropropene 5 0 --

trans-1,3-Dichloropropene 5 0 --

Ethylbenzene 14 0 --

Methyl bromide 11 0 --

Methylchloride 5 0 --

Methylene chloride 14 0 --

Phenols, total 10 4 2

Polychlorinated napthalenes, total 10 0 --

Polychlorinated biphenyls, total 10 0 --

Styrene 8 0 --

1,1,2,2-Tetrachloroethane 11 0 --

tert-Butyl methyl ether (MTBE) 3 1 .1

Tetrachloroethylene (PCE) 14 0 --

Toluene 14 1 .11

1,1,1-Trichloroethane (TCA) 14 0 --

1,1,2-Trichloroethane 11 0 --

Trichloroethylene (TCE) 14 0 --

Trichlorofluoromethane 14 0 --

1,1,2-Trichlorofluoromethane (Freon 113) 3 0 --

Vinyl chloride 14 0 --

Xylene 7 0 --
39

Table 17. Pesticides detected in ground water in the Big Elk Creek Basin, Pennsylvania and Maryland

[All concentrations are given in micrograms per liter; <, less than; --, no data; E, concentration is below the

reporting limit and is estimated]

Compound Number of

wells sampled

Number of wells

with concentration

above reporting limit

Minimum

concentration

Maximum

concentration

Acetochlor 26 0 <0.002 --

Alachlor 34 1 <.002 2.49

Aldrin 16 0 <.01 --

Alpha BHC 27 0 <.002 --

Ametryne 8 0 <.05 --

Atrazine 34 12 <.001 .209

Benfluralin 27 0 <.002 --

Butylate 27 0 <.002 --

Carbaryl 27 5 <.003 .015 E

Carbofuran 27 3 <.003 .073 E

Carbophenothion 9 0 <.01 --

Chlordane 16 0 <.1 --

Chlorpyrifos 33 0 <.01 --

Cyanazine 31 1 <.004 .007

DCPA 27 0 <.002 --

DDD 16 0 <.01 --

DDE 37 0 <.006 --

DDT 16 0 <.01 --

Deethyl atrazine 31 22 <.002 .33

DEF 6 0 <.1 --

Diazinon 35 2 <.002 57

Dicamba 7 0 <.04 --

Dieldrin 40 2 <.001 .056

Disulfoton 33 0 <.017 --

Endosulfan 16 0 <.01 --

Endrin 16 0 <.01 --

EPTC 27 0 <.002 --

Ethalfluralin 27 0 <.004 --

Ethion 9 1 <.01 .02

Ethoprop 27 0 <.003 --

Fonofos 32 0 <.01 --

Heptachlor 16 0 <.01 --

Heptachlor epoxide 16 0 <.01 --

Lindane 40 2 <.004 .03

Linuron 27 0 <.002 --

Malathion 35 2 .002 E 25

Methoxychlor 16 1 <.01 .09

Methyl azinphos 27 0 <.001 --

Methyl parathion 35 0 <.01 --

Metolachlor 34 11 <.002 .1

Metribuzin 32 0 <.004 --

Mirex 16 0 <.01 --

Molinate 27 0 <.004 --
40

Simazine was detected in water from 5 of

40 wells sampled (13 percent). Simazine is a

preemergence herbicide used on a number of

crops, as well as in noncrop areas. Simazine is

used to control broad-leaved weeds and annual

grasses in field corn; alfalfa, vegetable, and ornamental crops; turf grass; orchards; and vineyards.

At higher application rates, it is used for nonselective weed control in industrial areas.

Cyanazine was detected in water from 1 of

31 wells sampled. Cyanazine is a widely used preand postemergent herbicide to control grasses and

broadleaf weeds primarily on corn fields. Cyanazine is atrazine with cyanide attached to it. In 1997,

cyanazine was the eighth most heavily applied herbicide; an estimated 18-22 million pounds were

applied in the United States (Aspelin and Grube,

1999). Cyanazine is classified by the USEPA as a

restricted-use pesticide. In 1995, the USEPA

announced it had reached an agreement with the

manufacturer to phase out cyanazine for use in the

United States. All sales and distribution were prohibited after December 31, 1999 (U.S. Environmental Protection Agency, 1995).

The amide class of pesticides includes alachlor

and metolachlor. Metolachlor was detected in

water from 11 of 34 wells sampled (32 percent),

and alachlor was detected in water from 1 of

34 wells sampled. Metolachlor is a preemergence

herbicide used to control some broadleaf and

Napropamide 27 0 <0.003 --

Parathion 35 0 <.01 --

Pebulate 27 0 <.004 --

Pendimethalin 27 0 <.004 --

Permethrin 27 0 <.005 --

Perthane 16 0 <.1 --

Phorate 33 0 <.002 --

Picloram 7 1 <.05 0.32

Prometone 32 0 <.018 --

Prometryn 8 0 <.1 --

Pronamide 27 0 <.003 --

Propachlor 27 0 <.007 --

Propanil 27 0 <.004 --

Propargite 27 0 <.013 --

Propazine 8 0 <.05 --

Silvex 7 0 <.02 --

Simazine 40 5 .003 E .041

Tebuthiuron 27 0 <.01 --

Terbacil 27 1 <.007 .034

Terbufos 27 0 <.013 --

Thiobencarb 27 1 <.002 .003 E

Toxaphene 16 0 <.1 --

Triallate 27 0 <.001 --

Trifluralin 30 1 <.002 .001

2,6-Diethylaniline 26 0 <.003 --

2,4,5-T 7 0 <.04 --

2,4-D 7 0 <.04 --

2,4-DP 5 0 <.01 --

Table 17. Pesticides detected in ground water in the Big Elk Creek Basin, Pennsylvania and Maryland—Continued

[All concentrations are given in micrograms per liter; <, less than; --, no data; E, concentration is below the

reporting limit and is estimated]

Compound Number of

wells sampled

Number of wells

with concentration

above reporting limit

Minimum

concentration

Maximum

concentration
41

annual grassy weeds in field corn, soybeans, grain

sorghum, highway right-of-ways, and woody ornamentals. In 1997, metolachlor was the second

most heavily applied herbicide; an estimated 63-

69 million pounds were applied in the United

States (Aspelin and Grube, 1999).

Alachlor is a pre- and postemergent herbicide

used to control annual grasses and many broadleaved weeds mainly on corn and soybean fields,

but it also is used in commercial nurseries. In 1997,

cyanazine was the twelfth most heavily applied

herbicide; an estimated 13-16 million pounds were

applied in the United States (Aspelin and Grube,

1999). It is used widely in Chester County.

The carbamate class of insecticides includes

carbaryl, carbofuran, and thiobencarb. Carbaryl

was detected in water from 5 of 27 wells sampled

(19 percent), carbofuran was detected in water

from 3 of 27 wells sampled (11 percent), and

thiobencarb was detected in water from 1 of

27 wells sampled. Carbaryl is a wide-spectrum

insecticide that controls a range of chewing and

sucking insects on more than 120 agricultural

crops, as well as on poultry, livestock, and pets.

Carbaryl also has been used to control earthworms in turf and grass. Carbofuran is a widespectrum pesticide that controls insects, mites, and

nematodes on field, fruit, vegetable, and forest

crops. Thiobencarb most commonly is used on rice

crops, but it also is used to control grasses and

broadleaf weeds in such crops as lettuce, celery,

and endive.

Picloram was detected in water from one of

seven wells sampled (14 percent). Picloram

belongs to the pyridine family of compounds. It is a

systemic herbicide used to control broad-leaved

weeds, brush, and broadleaf trees on pasture,

rights-of-way along roads and power lines, forestland, and some grains. It also is used to control

plants on industrial facility sites.

The organochlorine class of compounds

includes DDT, dieldrin, lindane, and methoxychlor.

Organochlorine compounds were the first organic

pesticides developed and have been in use since

the 1940’s. Organochlorine insecticides have low

solubility in water, are persistent in the environment, and are strongly bioaccumulated by many

organisms. The use of many organochlorine insecticides has been prohibited or restricted to limited

uses by the USEPA. In Chester County, endrin, lindane, and methoxychlor are or have been used by

mushroom growers.

Dieldrin was detected in water from 2 of

40 wells sampled (5 percent). Dieldrin is a highly

persistent organochlorine compound that has low

mobility in soil. It has been used as a contact

insecticide to control soil pests, termites, and many

other pests. Dieldrin also is a degradation product

of the pesticide aldrin. Aldrin is converted rapidly to

dieldrin under most environmental conditions.

Dieldrin is more persistent in soils with a high

organic matter content. Most uses for aldrin and

dieldrin were banned in 1975; at present, these

compounds are no longer produced in or imported

into the United States. The use of dieldrin has been

restricted by the USEPA to certified personnel for

application below the ground surface or within

structures to control termites.

Lindane was detected in water from 2 of

40 wells sampled (5 percent). Sloto (1994, p. 73)

found lindane to be the most commonly detected

organochlorine pesticide in Chester County. It generally is associated with the mushroom industry.

Lindane is an insecticide fumigant used on a wide

range of soil-dwelling and plant-eating insects.

Most uses of lindane in agriculture and in the dairy

industry have been cancelled by the USEPA. Lindane is no longer manufactured in the United

States. Lindane presently is used primarily for lumber and seed treatment and in lotions, creams, and

shampoos for the control of fleas, lice, and mites.

Methoxychlor was detected in water from 1 of

16 wells sampled. Methoxychlor is an analog of

DDT. Methoxychlor is used as an insecticide

against flies, mosquitoes, cockroaches, chiggers,

and a wide variety of other insects. It is used on

agricultural crops, livestock, animal feed, grain

storage, home gardens, and on pets. Methoxychlor

is registered for use on fruits, vegetables, forage

crops, and shade trees. It also is registered for veterinary use to kill parasites on dairy and beef cattle.

Organophosphorus insecticides have been

used as substitutes for the banned organochlorine

insecticides because they are less persistent in the

environment and more selective in their targets.

The organophosphorus class of compounds

includes diazinon, ethion, and malathion. Diazinon

was detected in water from 2 of 35 wells sampled

(6 percent). Diazinon, first marketed in 1948, is a

non-systemic insecticide used on home gardens

and farms to control a wide variety of sucking and

leaf-eating insects. It is used on fruit trees, corn,

tobacco, potatoes, and horticultural plants. It com-
42

monly is used in Chester County for control of the

European corn borer, lawn-damaging insects, and

on trees and shrubs. Diazinon is an ingredient in

pest strips, household ant and roach sprays, and

pet flea and tick collars. Over 13 million pounds of

diazinon are applied annually in the United States

(U.S. Environmental Protection Agency, 2000a).

On March 31, 2001, the USEPA began a phase out

of diazinon because of its potential health risks to

children (U.S. Environmental Protection Agency,

2000b). The highest concentration of diazinon

measured in a water sample from the Big Elk

Creek Basin (57 μg/L) was from a well at a former

mushroom-growing operation. Sloto (1994, p. 74)

found diazinon to be the most commonly detected

organophosphorus pesticide in Chester County;

it was found in water samples from 13 percent of

wells sampled.

Ethion was detected in water from one of nine

wells sampled. Ethion is an insecticide used to kill

aphids, mites, scales, leafhoppers, maggots, and

foliar feeding larvae. It is used on a wide variety of

food, fiber, and ornamental crops, including greenhouse crops, lawns, and turf.

Malathion was detected in water from 2 of

35 wells sampled (6 percent). Malathion is a nonsystemic, wide-spectrum insecticide introduced in

1950. Malathion is used for the control of sucking

and chewing insects on fruits and vegetables and

to control mosquitoes, flies, household insects, and

animal and human parasites. The highest concentration of malathion measured in a water sample

from the Big Elk Creek Basin (25 μg/L) was from a

well at a former mushroom-growing operation.

Trifluralin was detected in water from 1 of

30 wells sampled. In 1997, trifluralin was the tenth

most heavily applied herbicide; an estimated

21-25 million pounds were applied in the United

States (Aspelin and Grube, 1999). Trifluralin

belongs to the dinitroaniline class of compounds.

It is a selective, preemergence herbicide used to

control many annual grasses and broadleaf weeds

on a wide variety of crops including alfalfa, barley,

corn, soybeans, and wheat. It also is used on vegetable crops and in orchards.

Terbacil was detected in water from 1 of

27 wells sampled. Terbacil belongs to the uracil

class of compounds. It is a selective herbicide used

for control of annual grasses, broad-leaved weeds,

and some perennial weeds in alfalfa and fruit trees.

It is sprayed on soil surfaces preferably just before,

or during, the period of active weed growth.

SUMMARY

The 79.4-mi2 Big Elk Creek study area extends

from the headwaters in Chester County, Pa., downstream to the USGS streamflow-measurement station on Big Elk Creek at Elk Mills, Md., (52.6 mi2),

and an inactive USGS streamflow-measurement

station on Little Elk Creek at Childs, Md. (26.8 mi2).

Little Elk Creek is a tributary to Big Elk Creek.

The Big Elk Creek Basin in the study area is in

the Piedmont Physiographic Province and is

underlain almost entirely by crystalline rocks. Most

of the basin in Pennsylvania is underlain by Wissahickon Schist. In Maryland, the rocks formerly

assigned to the Wissahickon Schist in the Big Elk

Creek Basin have been subdivided into an informally named pelitic and metagraywacke metasedimentary lithofacies. All the crystalline-rock geologic

units in the Big Elk Creek Basin are bedrock aquifers. The ground-water-flow system in crystalline

rock is local with streams acting as drains. Flow

paths are short, and ground water flows from areas

of higher elevation to adjacent streams. The hydrologic system generally is under unconfined (watertable) conditions. Ground water flows through a

network of interconnected secondary openings

that comprise the water-bearing zones that provide

water to wells. The larger, more numerous, and

more interconnected the openings, the greater the

yield of a well.

Wells in the Wissahickon Schist in the Big Elk

Creek Basin had a mean of 3.56 water-bearing

zones per 100 ft of uncased borehole. The frequency of occurrence of water-bearing zones generally decreases with depth. Yields of wells in the

Wissahickon Schist range from 5 to 200 gal/min;

the median yield is 15 gal/min. The specific capacity of wells in the Wissahickon Schist ranges from

0.03 to 15 (gal/min)/ft; the median specific capacity

is 0.4 (gal/min)/ft.
43

Ground-water levels generally rise during the

late fall, winter, and early spring when groundwater and soil-moisture evapotranspiration are at a

minimum and recharge is at a maximum. Water

levels generally decline during the late spring,

summer, and early fall when ground-water evapotranspiration and soil-moisture evapotranspiration

are at a maximum, and recharge is at a minimum.

The range in water-level fluctuation for 1998-99

was up to 12.55 ft. Water levels generally are closest to land surface in valleys near streams (discharge areas) and deepest below land surface on

hilltops (recharge areas).

Ground water discharged to streams provides

more than half of streamflow. Streamflow is composed of base flow and surface runoff. Base flow is

ground water discharged to streams. Streamflow

hydrographs for Big Elk Creek and Little Elk Creek

for their period of record were separated into baseflow and surface-runoff components. The median

base flow for Big Elk Creek is representative of a

long-term average. In the Big Elk Creek Basin, the

median annual ground-water discharge to the

stream (base flow) for 1933-99 was 10.79 in. or

0.518 (Mgal/d)/mi2, which was 63 percent of the

median annual streamflow. The median annual

ground-water discharge to streams ranged from

5.32 in. or 0.255 (Mgal/d)/mi2 in 1966 to 17.98 in.

or 0.863 (Mgal/d)/mi2 in 1972. Median annual surface runoff for 1933-99 was 6.22 in., which was

37 percent of the median annual streamflow.

Ground-water availability is defined and estimated in a number of ways. Estimated groundwater availability for the Big Elk Creek Basin

ranges from 0.127 to 0.535 (Mgal/d)/mi2, depending on the method used. The optimal method is the

one that best meets a set of socioeconomic and/or

social and environmental objectives associated

with the use of the water.

Water budgets were calculated for the Big Elk

Creek Basin for 1998-99. The 1998-99 average

streamflow was 15.38 in. The average change in

ground-water storage was an increase of 1.32 in.

The net ground-water exports from the basin averaged 0.03 in/yr. Estimated average annual ET was

30.50 in. Recharge was estimated for the Big Elk

Creek Basin for 1998-99. Estimated recharge was

11.22 in. [0.540 (Mgal/d)/mi2] in 1998, and

12.95 in. [0.621 (Mgal/d)/mi2] in 1999. Estimated

average annual recharge for 1998-99 was 12.12 in.

[0.580 (Mgal/d)/mi2]; this is equal to a rate of

909 gal/d per acre.

For this study, water samples from 20 wells

were collected for analysis for inorganic constituents and pesticides, and data were available from

an additional 44 wells. Physical properties and

chemical constituents determined in the field

include pH, specific conductance, hardness, alkalinity, temperature, and the concentration of dissolved oxygen. The median pH of water from wells

in the Wissahickon Schist, the principal aquifer in

the study area, is moderately acidic (pH of 5.9).

The median specific conductance of water from

wells in the Wissahickon Schist is a relatively low

160 μS/cm. The median alkalinity of water from

wells in the Wissahickon Schist is 20 mg/L. Water

from wells in the Wissahickon Schist is soft; the

median hardness is 38 mg/L. The median temperature of ground-water samples from wells in the

Wissahickon Schist is 13.6°C (56.5°F), which is

near the mean annual air temperature. The median

concentration of dissolved oxygen in ground water

from the Wissahickon Schist was 7.5 mg/L.

Major ions, in order of decreasing concentration, in the ground water of the Elk Creek Basin,

based on median concentrations for the Wissahickon Schist, are silica, calcium, chloride, sodium,

sulfate, magnesium, and potassium. Water from

only 1 of 49 wells sampled (2 percent) in the Big

Elk Creek Basin exceeded the USEPA SMCL of

500 mg/L for TDS. The median concentration of

TDS in water samples from the Wissahickon Schist

is 100 mg/L. The median concentration of chloride

in water samples from the Wissahickon Schist is

8.3 mg/L. None of the chloride concentrations in

the ground-water samples exceeded the USEPA

SMCL of 250 mg/L for chloride. The median concentration of sulfate in water samples from the Wissahickon Schist is 4 mg/L. None of the sulfate

concentrations in the ground-water samples

exceeded the USEPA SMCL of 250 mg/L for sulfate.

The median concentration of nitrate in water

samples from the Wissahickon Schist is 3.6 mg/L.

Of 60 water samples from wells in the Big Elk

Creek Basin, concentrations of nitrate exceed the

USEPA MCL of 10 mg/L nitrate as nitrogen in water

from 6 wells (10 percent of wells sampled), all of

which are in the Wissahickon Schist. The maximum concentration was 36 mg/L. Nitrite, ammonia,

and phosphorus species generally are present in

concentrations less than 0.10 mg/L.
44

Eight of 59 water samples (14 percent) analyzed for iron and 16 of 56 samples (29 percent)

analyzed for manganese exceeded the USEPA

SMCL’s. Water samples exceeding the 300 μg/L

USEPA SMCL for iron were from six wells in Wissahickon Schist, one well in Peters Creek Schist,

one well in pegmatite, and one well in pelitic

gneiss. Water samples exceeding the 50 μg/L

USEPA SMCL for manganese were from 13 wells

in the Wissahickon Schist, 1 well in the Peters

Creek Schist, 1 well in pegmatite, and 1 well in

pelitic gneiss.

Water from 41 of 44 wells in the Big Elk Creek

Basin sampled (94 percent) for radon-222

exceeded 300 pCi/L, the proposed USEPA MCL,

and water from 5 of 44 wells sampled (25 percent)

exceeded 4,000 pCi/L, the proposed USEPA alternate MCL. The median activity for all formations

was 2,400 pCi/L. The median activity for water

from 35 wells sampled in the Wissahickon Schist

was 2,500 pCi/L. Activities of radon-222 in water

samples from the Wissahickon Schist ranged over

three orders of magnitude—from 285 to

11,000 pCi/L. Radon-222 activities in water from

one of three wells sampled in serpentinite

(33 percent) exceeded 300 pCi/L; the maximum

activity was 392 pCi/L. Serpentinite contains few

radioactive minerals. Radon-222 activities in water

from both wells sampled in the Peters Creek Schist

exceeded 4,000 pCi/L.

Out of 43 VOC compounds analyzed, only 4

were detected: chloroform, total phenols, tert-butyl

methyl ether (MTBE), and toluene. None of the

concentrations exceeded USEPA MCL’s.

For this study, 20 wells were sampled for pesticides, and data were available for 20 additional

wells sampled for pesticides. Not all wells were

sampled for the same pesticides. The most commonly detected pesticides in the Big Elk Creek

Basin are deethyl atrazine (71 percent of sampled

wells), atrazine (35 percent of sampled wells),

metolachlor (32 percent of sampled wells), carbaryl

(19 percent of sampled wells), picloram (14 percent of sampled wells), simazine (13 percent of

sampled wells), and carbofuran (11 percent of

sampled wells). Most concentrations are extremely

low and are in the parts per trillion range. Concentrations of pesticides detected did not exceed

USEPA MCL’s.

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U.S. Geological Survey Open-File Report

01-329, 1 pl., scale 1:24,000.

National Oceanic and Atmospheric Administration,

2002, Monthly station normals of temperature,

precipitation, and heating and cooling degree

days 1971-2000: National Oceanic and

Atmospheric Administration Climatography of

the United States No. 81, 9 p.

Nutter, L.J., and Otton, E.G., 1969, Ground-water

occurrence in the Maryland Piedmont:

Maryland Geological Survey Report of

Investigations 10, 56 p.

Olmsted, F.H., and Hely, A.G., 1962, Relation

between ground water and surface water in

Brandywine Creek Basin, Pennsylvania:

U.S. Geological Survey Professional Paper

417-A, 21 p.

Otton, E.G., Wiley, R.E., McGregor, R.A., Achmad,

G.J., Hiortdahl, S.N., and Gerhart, J.M., 1988,

Water resources and estimated effects of

ground-water development, Cecil County,

Maryland: Maryland Geological Survey

Bulletin 34, 133 p.

Overbeck, R.M., Slaughter, T.H., and Hulme, A.E.,

1958, Water resources of Cecil, Kent, and

Queen Annes Counties: Maryland

Department of Geology, Mines, and Water

Resources Bulletin 21, 478 p.

Schreffler, C.L., 1998, Low-flow statistics of

selected streams in Chester County,

Pennsylvania: U.S. Geological Survey WaterResources Investigations Report 98-4117,

43 p.

Senior, L.A., 1998, Radon-222 in the ground water

of Chester County, Pennsylvania: U.S.

Geological Survey Water-Resources

Investigations Report 98-4169, 77 p.

Senior, L.A., Sloto, R.A., and Reif, A.G., 1997,

Geohydrology and water quality, West Valley

Creek Basin, Chester County, Pennsylvania:

U.S. Geological Survey Water-Resources

Investigations Report 94-4137, 160 p.

Sloto, R.A., 1987, Effect of urbanization on the

water resources of eastern Chester County,

Pennsylvania: U.S. Geological Survey WaterResources Investigations Report 87-4098,

131 p.

_____1989, Selected ground-water data, Chester

County, Pennsylvania: U.S. Geological

Survey Open-File Report 87-217, 198 p.

_____1991, Geohydrology and simulation of

ground-water flow in the carbonate rocks of the

Valley Creek Basin, eastern Chester County,

Pennsylvania: U.S. Geological Survey WaterResources Investigations Report 89-4169,

60 p.

_____1994, Geology, hydrology, and ground-water

quality of Chester County, Pennsylvania:

Chester County Water Resources Authority

Water-Resource Report 2, 127 p.

REFERENCES CITED—Continued
46

Sloto, R.A., and Crouse, M.Y., 1996, HYSEP—

A computer program for hydrograph separation

and analysis: U.S. Geological Survey WaterResources Investigations Report 96-4040,

46 p.

Sloto, R.A., and Senior, L.A., 1998, Radon in the

ground water of Chester County, Pennsylvania:

U.S. Geological Survey Fact Sheet 120-98,

4 p.

Todd, D.K., 1980, Ground water hydrology (2d ed.):

New York, John Wiley and Sons, 535 p.

U.S. Environmental Protection Agency, 1991,

Maximum contaminant level goals and national

primary drinking water regulations for lead and

copper; final rule: Federal Register, June 7,

1991, p. 26,460-26,563.

_____1992a, Drinking water regulations, U.S.

Code of Federal Regulations, Title 40, Part

141.61, Part 141.62, and Part 143.30; revised

December, 1992: Washington, U.S.

Environmental Protection Agency Office of

Water, 12 p.

_____1992b, Consumers guide to radon

reduction—How to reduce radon levels in your

home: EPA Report 402-K92-003, 17 p.

_____1995, International pesticide notice

cyanazine pesticide voluntarily canceled and

uses phased out: accessed September 7,

2001, at URL

www.epa.gov/oppfead1/17b/cyanazin.htm

_____1999, National primary drinking water

regulation, Radon-222, proposed rule:

Federal Register, v. 64, no. 211, November 2,

1999, p. 59,245-59,294.

_____2000a, Diazinon summary: accessed

September 7, 2001, at URL

www.epa.gov/pesticides/op/diazinon/summary.

htm

_____2000b, EPA announces elimination of all

indoor uses of widely-used pesticide diazinon:

press release accessed September 7, 2001,

at URL http://yosemite.epa.gov/opa/

admpress.nsf/b1ab9f485b098972852562e700

4dc686/c8cdc9ea7d5ff585852569ac0077bd31

_____2001, Technical fact sheet on atrazine:

accessed September 7, 2001, at URL

http://www.epa.gov/OGWDW/dwh/tsoc/atrazine.html

U.S. Geological Survey, 1995, Pesticides in the

atmosphere: U.S. Geological Survey Fact

Sheet 152-95, 4 p.

White, K.E., and Sloto, R.A., 1991, Base-flowfrequency characteristics of selected

Pennsylvania streams: U.S. Geological

Survey Water-Resources Investigations Report

90-4161, 66 p.

Willey, R.E., McGregor, R.A., deGrouchy, Joanne,

and Tompkins, M.D., 1987, Hydrologic data for

Cecil County, Maryland: Maryland Geological

Survey Basic Data Report 16, 150 p.

Wood, W.W., 1981, Guidelines for collection and

field analysis of ground-water samples for

selected unstable constituents: U.S.

Geological Survey Techniques of WaterResources Investigations, book 1, chap. D2,

24 p.

REFERENCES CITED—Continued
47

Table 18. Records of selected wells, Big Elk Creek Basin, Pennsylvania and Maryland

Township or borough: Name refers to township unless noted as borough.

Driller license number: 0110, Brown Brothers Drilling; 0154, Leroy Myers; 0176, R. Walter Slaugh and

Son; 1083, Kenneth L. Madron; 0248, Thomas G. Keyes; 0319, Myers Brothers Drilling; 0384,

E.J. Myers and Sons; 1583, J. Ernest Brewer; 1715, Arthur A. Astle; 1878, Cooks Environmental

Services; 1889, David Powell

Use of site: U, unused; W, withdrawal; O, observation well.

Use of water: C, commercial; H, domestic; I, industrial; P, public supply; S, stock watering; T, institutional;

U, unused.

Topographic setting: F, flat; H, hilltop; S, slope; V, valley.

Hydrogeologic unit codes: 300WSCK, Wissahickon Formation; 300PRCK, Peters Creek Schist;

000SPRN, serpentinite; 000PGMT, pegmatite; 300UFGB, gabbro and serpentinite at Gray’s Hill;

300MGCK, metagraywacke

Altitude of land surface is estimated from topographic maps. Datum is sea level.

Water level is in feet below land surface. F indicates flowing well.

Date water level measued is year, month, and date.

[--, no data; gal/min, gallons per minute; (gal/min)/ft, gallons per minute per foot of drawdown]
48

Table 18. Records of selected wells, Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Location

Township or

borough

Driller

license

number

Year

drilled

Primary Elevation

of land

surface

Topographic

setting

Latitude

(degrees)

Longitude

(degrees)

Use of

site

Use of

water

CH-75 394735 755809 Oxford Borough -- 1938 W P 509 S

CH-254 394457 755816 East Nottingham 0384 1982 O U 517 F

CH-525 394829 755537 Lower Oxford -- 1907 U T 540 H

CH-526 394745 755830 Lower Oxford 0390 1911 W P 590 H

CH-528 394755 755820 Lower Oxford -- -- W P 560 S

CH-1702 394545 755912 East Nottingham 0110 1972 W H 563 H

CH-1703 394445 755800 East Nottingham 0176 1972 W H 522 S

CH-1720 394803 755638 Lower Oxford 0176 1969 W H 444 S

CH-1722 395115 755502 Upper Oxford 0110 1970 W H 552 S

CH-1724 395056 755640 Upper Oxford 0176 1971 W C 606 S

CH-1735 394628 755926 East Nottingham 0176 1967 W H 540 S

CH-1737 394752 755459 Lower Oxford 0176 1966 W H 517 S

CH-1761 394407 755625 Elk 0176 1968 W H 365 S

CH-1765 394620 755412 New London 0176 1966 W H 466 S

CH-1770 394657 755236 New London 0176 1966 W H 484 S

CH-1776 394545 755005 Franklin 0110 1971 W H 315 S

CH-1777 394536 755016 Franklin 0110 1971 U P 340 S

CH-1778 394519 754938 Franklin 0248 1971 W P 290 S

CH-1783 394433 755322 Elk 0110 1972 W H 370 S

CH-1829 394455 754940 Franklin 0154 1966 W H 410 S

CH-1835 395110 755321 Londonderry 0110 1971 W H 555 S

CH-1996 394848 755615 Lower Oxford 0176 1965 W T 440 V

CH-2186 394755 755839 Lower Oxford -- 1941 W P 538 S

CH-2439 394625 755850 East Nottingham -- -- W H 525 F

CH-2440 394605 755855 East Nottingham -- -- W H 520 F

CH-2459 394800 755640 Lower Oxford -- -- W H 420 S

CH-2460 394635 755901 East Nottingham -- -- W H 555 F

CH-2461 394940 755240 Penn -- -- W I 500 S

CH-2673 394630 755851 East Nottingham -- -- W H 540 S

CH-2678 394609 755901 East Nottingham -- -- U C 530 S

CH-3039 394810 755515 Lower Oxford 0176 1967 W H 520 S

CH-3316 395154 755509 West Fallowfield -- -- W S 590 F

CH-3317 395142 755544 Upper Oxford -- -- W H 635 F

CH-4118 394638 755636 East Nottingham 1583 1984 W H 500 S

CH-4126 394752 755828 Lower Oxford 0176 1937 W H 575 F

CH-4275 394656 755518 East Nottingham 1083 1990 W H 411 S

CH-4297 394752 755822 Lower Oxford 1083 1984 W H 553 S

CH-4806 394750 755829 Lower Oxford -- 1937 W H 574 F

CH-4931 394425 755333 Elk 1878 1992 W H 410 F

CH-4933 394759 755601 Lower Oxford 0176 1976 W H 480 H

CH-5231 395010 755544 Upper Oxford 0384 -- W H 610 H

CH-5420 395143 755256 Londonderry -- -- W H 625 F

CH-5421 394616 755434 New London -- -- W H 469 F

CH-5422 395141 755254 Londonderry -- -- W I 619 S

CH-5423 395149 755359 Londonderry -- -- U H 579 F
49

Table 18. Records of selected wells, Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Hydrogeologic

unit

Depth

of well

(feet)

Casing

Water level

(feet)

Date water level

measured

Reported

yield

(gal/min)

Specific

capacity

[(gal/min)/ft]

Wellidentification

number

Diameter

(inches)

Depth

(feet)

300WSCK 400 8 70 0.00 19381222 116 0.8 CH-75

300WSCK 250 -- 102 26.33 19990920 7 -- CH-254

300WSCK 184 8 38 20.00 19250101 38 .2 CH-525

300WSCK 1,000 8 -- -- -- 45 -- CH-526

300WSCK 478 8 -- -- -- 85 -- CH-528

300WSCK 103 6 95 32.53 19811221 20 1.67 CH-1702

300WSCK 146 6 106 21.00 19740620 15 .1 CH-1703

300WSCK 111 6 78 31.00 19740624 10 .13 CH-1720

300WSCK 120 6 82 28.00 19700616 120 15 CH-1722

300PRCK 247 6 42 35.00 19740624 18 .16 CH-1724

300WSCK 106 6 40 44.00 19670125 10 .02 CH-1735

300WSCK 68 6 36 33.00 19660906 25 1.25 CH-1737

000SRPN 73 6 21 5.00 19680722 30 1.5 CH-1761

300WSCK 72 6 52 38.00 19660824 25 2.08 CH-1765

300WSCK 72 6 60 22.00 19660610 25 1.9 CH-1770

300WSCK 33 6 20 21.00 19710907 75 75 CH-1776

300WSCK 167 6 31 3.00 19711104 100 14.3 CH-1777

300WSCK 300 8 250 -3.00 19710118 130 .6 CH-1778

300WSCK 83 6 42 25.00 19720602 12 1.7 CH-1783

300WSCK 165 6 54 31.00 19661101 15 .31 CH-1829

300WSCK 63 6 57 13.00 19740727 400 400 CH-1835

300WSCK 300 8 40 7.00 19650601 160 3.02 CH-1996

300WSCK 400 8 56 3.00 19410501 90 .58 CH-2186

300WSCK -- -- -- -- -- -- -- CH-2439

300WSCK -- -- -- -- -- -- -- CH-2440

300WSCK -- -- -- -- -- -- -- CH-2459

300WSCK -- -- -- -- -- -- -- CH-2460

300WSCK -- -- -- -- -- -- -- CH-2461

300WSCK -- -- -- -- -- -- -- CH-2673

300WSCK -- -- -- -- -- -- -- CH-2678

300WSCK 87 6 72 8.00 19670325 20 .62 CH-3039

300WSCK -- -- -- -- -- -- -- CH-3316

300PRCK -- -- -- -- -- -- -- CH-3317

300WSCK 160 6 63 44.09 19910708 20 .57 CH-4118

300WSCK 118 -- -- -- -- -- -- CH-4126

300WSCK -- 6 -- 13.81 19920909 -- -- CH-4275

300WSCK 165 6 101 19.76 19921001 30 -- CH-4297

300WSCK -- 6 -- -- -- -- -- CH-4806

300WSCK 132 6 59 25.29 19940721 41 3.2 CH-4931

300WSCK 157 5 87 34.3 19931124 6 .14 CH-4933

300WSCK 100 6 70 30.52 19950814 -- -- CH-5231

300WSCK 185 6 -- 14.69 19980609 -- -- CH-5420

300WSCK 204 -- -- 54.31 19980202 -- -- CH-5421

300WSCK 49.4 6 -- 21.42 20000920 -- -- CH-5422

300WSCK 70 -- -- 21.78 19980107 -- -- CH-5423
50

CH-5424 394357 755452 Elk -- -- W H 391 F

CH-5425 395128 755530 Upper Oxford -- -- W H 605 H

CH-5426 394703 755651 East Nottingham -- -- W H 506 H

CH-5427 394539 755345 New London -- -- W H 489 F

CH-5428 395020 755321 Penn -- -- W H 490 S

CH-5429 394936 755638 Upper Oxford -- -- W H 550 F

CH-5430 394904 755502 Upper Oxford -- -- W C 531 F

CH-5431 394333 755210 Elk -- -- W H 396 F

CH-5432 394434 755700 Elk -- -- W H 400 F

CH-5433 394530 755030 Franklin -- -- W H 411 H

CH-5434 394836 755252 Penn -- -- W H 550 S

CH-5436 394328 755203 Elk 1290 1994 W H 375 H

CH-5437 394445 755556 Elk 0319 -- W H 405 H

CH-5438 394445 755557 Elk 0319 -- W H 407 H

CH-5439 394348 755552 Elk -- -- W H 342 F

CH-5440 394645 755346 New London -- -- W H 393 S

CH-5442 394857 755648 Lower Oxford -- -- W H 561 S

CH-5443 394921 755255 Penn -- -- W C 522 F

CH-5450 394527 755156 New London 1083 1999 W H 265 S

CH-5470 394847 755824 Lower Oxford 1715 1992 W C 552 S

CH-5476 394732 755610 East Nottingham 0319 1996 W H 412 S

CH-5477 394620 755612 East Nottingham 1889 1995 W H 482 H

CH-5479 394913 755229 Penn 0176 1939 W H 557 S

CE Ae 8 394256 755023 -- -- -- U H 230 S

CE Ae 9 394225 755125 -- -- -- W H 360 H

CE Ae 13 394201 755327 -- -- -- W H 303 S

CE Bf 77 393621 754903 -- -- 1964 W H 40 S

Table 18. Records of selected wells, Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Location

Township or

borough

Driller

license

number

Year

drilled

Primary Elevation

of land

surface

Topographic

setting

Latitude

(degrees)

Longitude

(degrees)

Use of

site

Use of

water
51

300WSCK 140 -- -- 2.33 19980624 -- -- CH-5424

300PRCK 97 5 -- 17.20 19980701 -- -- CH-5425

300WSCK 260 5 125 42.23 -- 6 -- CH-5426

300WSCK -- -- -- -- -- -- -- CH-5427

300WSCK -- -- -- 16.65 19980202 -- -- CH-5428

300WSCK 70 -- -- -- -- -- -- CH-5429

300WSCK -- -- -- -- -- -- -- CH-5430

300WSCK 131 6 80 30.85 19980130 -- -- CH-5431

000SRPN 118 -- -- 23.29 19980714 -- -- CH-5432

300WSCK -- -- -- 28.70 19980202 -- -- CH-5433

300WSCK 100 -- -- 16.50 19980715 -- -- CH-5434

300WSCK 280 6 80 -- -- 6 -- CH-5436

300WSCK 150 6 -- 37.00 19981118 -- -- CH-5437

300WSCK 175 6 105 -- -- -- -- CH-5438

000SRPN 43 -- -- 7.22 19980130 6 -- CH-5439

300WSCK 323 6 -- 18.12 19981104 -- -- CH-5440

300WSCK 75 -- -- -- -- -- -- CH-5442

300WSCK 111 6 -- 37.36 19981112 -- -- CH-5443

000PGMT 302 6 81 20.36 20000911 30 -- CH-5450

300PRCK 120 6 97 24.95 19960822 45 0.08 CH-5470

300WSCK 390 6 70 31.76 19960904 8 -- CH-5476

300WSCK 345 6 92 43.39 19960904 4 -- CH-5477

300WSCK 105 5 -- 8.00 19960905 -- -- CH-5479

300MGCK 78 -- -- 58.70 19980202 -- -- CE Ae 8

300MGCK 235 -- -- 15.75 19980203 -- -- CE Ae 9

300MGCK 201 -- -- 46.15 -- -- -- CE Ae 13

300UFGB 201 6 135 F 19640428 25 -- CE Bf 77

Table 18. Records of selected wells, Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Hydrogeologic

unit

Depth

of well

(feet)

Casing

Water level

(feet)

Date water level

measured

Reported

yield

(gal/min)

Specific

capacity

[(gal/min)/ft]

Wellidentification

number

Diameter

(inches)

Depth

(feet)
52

Table 19. Water-level measurements, Big Elk Creek Basin, Pennsylvania and Maryland

[--, no data]

Date CH-5421 CH-5423 CH-5425 CH-5427 CH-5428 CH-5429 CH-5433 CE Ae 8 CE Ae 9 Date CH-254

01/15/1998 54.31 21.78 21.18 65.30 16.65 4.25 28.70 24.57 15.75 1/20/1998 23.75

02/27/1998 53.46 19.27 17.91 58.56 14.96 3.85 26.50 23.23 15.09 2/24/1998 22.55

03/27/1998 51.25 17.62 15.79 65.45 14.65 3.10 19.42 21.14 13.62 3/23/1998 20.60

04/29/1998 51.01 17.30 17.13 54.90 14.48 3.60 18.36 18.56 13.95 4/21/1998 19.12

05/28/1998 50.75 16.89 17.87 56.25 14.43 3.77 18.92 21.85 14.01 5/21/1998 18.40

06/18/1998 51.40 17.00 17.72 55.80 16.08 5.18 19.79 20.00 14.89 6/22/1998 18.22

07/24/1998 52.00 18.01 19.36 -- 17.23 4.87 26.10 -- -- 7/20/1998 18.73

08/15/1998 53.04 18.93 20.52 57.08 18.49 5.17 22.41 21.87 16.85 8/21/1998 19.74

10/29/1998 55.60 20.20 20.28 58.52 18.46 5.79 25.02 -- 17.98 10/20/1998 21.90

12/08/1998 55.07 21.20 21.27 57.91 19.29 5.70 25.35 23.75 18.62 11/24/1998 23.13

01/07/1999 55.69 21.45 20.43 62.87 18.91 5.40 25.63 24.14 18.90 12/22/1998 23.99

01/22/1999 55.34 20.55 18.95 67.45 17.31 4.22 26.15 24.03 18.46 1/20/1999 24.61

02/24/1999 54.71 19.45 18.17 61.48 15.67 4.23 29.25 24.25 17.29 2/22/1999 24.61

03/23/1999 54.19 18.49 16.75 64.42 15.05 3.47 24.49 23.87 16.45 3/19/1999 24.50

04/19/1999 53.61 18.40 17.84 58.66 15.19 3.54 21.96 22.27 15.79 4/21/1999 23.66

05/20/1999 53.38 18.92 18.82 57.72 16.37 4.18 20.98 21.85 16.11 5/20/1999 23.60

06/22/1999 54.55 19.60 19.82 63.08 17.75 5.38 21.88 21.82 17.04 6/29/1999 24.45

07/23/1999 55.97 21.10 21.17 63.83 18.98 6.97 23.26 22.34 18.16 7/19/1999 24.95

08/18/1999 56.03 22.72 23.21 64.64 20.53 9.45 24.05 23.08 19.21 8/19/1999 25.88

09/22/1999 54.44 21.17 18.62 58.92 18.14 4.75 24.35 22.67 18.75 9/20/1999 26.33

10/18/1999 52.97 20.12 17.63 -- 15.68 4.28 22.36 21.81 18.10 10/19/1999 25.63

11/18/1999 53.00 20.10 19.04 60.88 16.28 4.46 21.48 21.22 17.76 11/22/1999 25.50

12/21/1999 53.17 19.26 17.57 55.95 15.46 3.25 21.67 20.99 17.05 12/20/1999 25.47

01/24/2000 52.53 19.09 18.57 53.92 15.78 3.99 21.85 20.97 16.71 1/21/2000 25.00
53

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents in ground water,

Big Elk Creek Basin, Pennsylvania and Maryland

μS/cm, microsiemens per centimeter at 25 degrees Celsius;

°C, degrees Celsius;

mg/L, milligram per liter;

μg/L, micrograms per liter;

ND, not detected with detection limit not reported;

<, less than;

--, no data;

E, estimated concentration;

U, below detection limit, detection limit unknown;

Geologic Unit Codes:

300WSCK, Wissahickon Schist;

300PRCK, Peters Creek Schist;

000SPRN, serpentinite;

000PGMT, pegmatite;

300UFGB, gabbro and serpentinite at Gray’s Hill;

300MGCK, metagraywacke
54

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Geologic

unit

Sample

date

Dissolved

oxygen

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Alkalinity

(mg/L as

CaCO3)

Water

temperature

(°C)

CH-75 300WSCK 7/14/86 -- 5.6 165 -- 14

CH-75 300WSCK 8/23/90 8.5 5.2 192 90 13

CH-75 300WSCK 8/8/00 5.7 5.6 227 -- 14.1

CH-525 300WSCK 9/21/25 -- -- -- 18 --

CH-526 300WSCK 9/21/25 -- -- -- 26 --

CH-528 300WSCK 9/21/25 -- -- -- 13 --

CH-1702 300WSCK 10/14/74 -- 5.9 50 9

CH-1703 300WSCK 8/5/91 7.5 6.4 76 52 14.5

CH-1720 300WSCK 10/1/92 5.9 6 239 -- 13.5

CH-1720 300WSCK 4/6/93 6.3 5.9 240 52 13

CH-1720 300WSCK 6/10/93 6 5.9 253 -- 13.5

CH-1720 300WSCK 9/16/93 6.9 5.9 302 -- 13.5

CH-1724 300PRCK 10/14/74 -- 6.2 115 -- --

CH-1735 300WSCK 9/6/00 9.4 5.4 283 16 14.7

CH-1737 300WSCK 7/11/91 7.6 6.4 235 28 14

CH-1761 000SRPN 8/22/91 1.8 8.5 457 -- 14

CH-1765 300WSCK 8/22/91 9.9 5.7 164 10 13.5

CH-1770 300WSCK 10/15/74 -- 5.8 190 8 --

CH-1776 300WSCK 10/15/74 -- 6.4 70 10 --

CH-1777 300WSCK 8/1/74 -- 7.2 -- 35 --

CH-1778 300WSCK 1/14/71 -- 7.7 -- 41 --

CH-1783 300WSCK 10/15/74 -- 6.2 80 15 --

CH-1829 300WSCK 8/31/95 7 5.3 849 12 13.5

CH-1835 300WSCK 10/14/74 -- 5.7 70 7 --

CH-1996 300WSCK 2/27/74 -- 6.0 -- 27 --

CH-2186 300WSCK 8/18/93 7.2 6.1 141 20 13.5

CH-2439 300WSCK 8/17/81 -- 5.9 105 -- 17

CH-2440 300WSCK 8/17/81 -- 5.7 180 -- 18

CH-2459 300WSCK 8/4/82 -- 5.4 105 -- 11.5

CH-2460 300WSCK 8/4/82 -- 5.6 235 -- 14

CH-2461 300WSCK 8/4/82 -- 5.7 130 -- 13.5

CH-2461 300WSCK 7/7/83 -- 5.8 165 -- 13

CH-2461 300WSCK 8/8/95 6.4 5.8 229 22 13.5

CH-2673 300WSCK 8/6/85 -- 5.7 208 40 16

CH-2678 300WSCK 8/28/84 -- 5.8 225 -- 14.5

CH-2678 300WSCK 6/25/85 -- 5.7 265 20 15

CH-3316 300WSCK 8/8/88 -- 6.7 180 -- 13

CH-3316 300WSCK 9/6/90 0 6.8 193 57 12.5

CH-3317 300PRCK 8/8/88 -- 4.8 500 -- 15

CH-4118 300WSCK 7/8/91 9 5.7 94 8 14

CH-4126 300WSCK 8/7/91 9.2 5.9 202 14 13.5

CH-4275 300WSCK 9/9/92 7.1 6 154 21 14
55

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Total

hardness

(mg/L as

CaCO3)

Calcium,

dissolved

(mg/L

as Ca)

Magnesium,

dissolved

(mg/L

as Mg)

Potassium,

dissolved

(mg/L

as K)

Sodium,

dissolved

(mg/L

as Na)

Chloride,

dissolved

(mg/L

as Cl)

Fluoride,

dissolved

(mg/L

as F)

CH-75 7/14/86 -- -- -- -- -- 21 --

CH-75 8/23/90 -- -- -- -- -- 26 --

CH-75 8/8/00 65 13.6 7.62 2.5 12.1 33 <0.1

CH-525 9/21/25 32 5.4 4.6 1.6 3.7 4 --

CH-526 9/21/25 28 6 3.2 1.8 4.5 1.8 --

CH-528 9/21/25 18 3.9 1.9 1.3 2.8 1.9 --

CH-1702 10/14/74 9 1.9 1 .4 2.5 2 .1

CH-1703 8/5/91 15 3.2 1.8 1.5 5.2 3 .1

CH-1720 10/1/92 -- -- -- -- -- 21 <.1

CH-1720 4/6/93 73 17 7.5 3 15 22 <.1

CH-1720 6/10/93 80 19 8 3 16 27 <.1

CH-1720 9/16/93 81 19 8.1 2.9 24 40 <.1

CH-1724 10/14/74 27 5.6 3.2 .7 5.5 5 .1

CH-1735 9/6/00 37 9.26 3.35 2.9 33.3 38.8 <.1

CH-1737 7/11/91 52 11 5.9 1 9.8 16 <.1

CH-1761 8/22/91 250 4.2 59 .2 2.3 5.4 <.1

CH-1765 8/22/91 51 9.4 6.6 2.1 5.2 20 <.1

CH-1770 10/15/74 47 6.5 7.5 2 8.1 20 .1

CH-1776 10/15/74 10 2.5 .8 1.2 4.4 3.3 .1

CH-1777 8/1/74 36 -- -- -- -- 4.5 .2

CH-1778 1/14/71 34 -- -- -- -- 13 0

CH-1783 10/15/74 17 3.5 1.9 1.3 4.9 5 .1

CH-1829 8/31/95 -- -- -- -- -- 130 --

CH-1835 10/14/74 11 2 1.5 .6 3.1 4.8 .1

CH-1996 2/27/74 48 5.5 .1

CH-2186 8/18/93 47 11 4.8 1.7 6.5 8.3 <0.1

CH-2439 8/17/81 -- -- -- -- -- -- --

CH-2440 8/17/81 -- -- -- -- -- -- --

CH-2459 8/4/82 -- -- -- -- -- -- --

CH-2460 8/4/82 -- -- -- -- -- -- --

CH-2461 8/4/82 -- -- -- -- -- -- --

CH-2461 7/7/83 -- -- -- -- -- -- --

CH-2461 8/8/95 71 16 7.5 3 7.9 10 <.1

CH-2673 8/6/85 -- -- -- -- -- -- --

CH-2678 8/28/84 -- -- -- -- -- -- --

CH-2678 6/25/85 81 19 8.2 -- 12 51 --

CH-3316 8/8/88 -- -- -- -- -- 5.7 --

CH-3316 9/6/90 -- -- -- -- -- 6.7 --

CH-3317 8/8/88 -- -- -- -- -- 150 --

CH-4118 7/8/91 27 2.6 5 1.3 2.9 6.1 <.1

CH-4126 8/7/91 -- -- -- -- -- 31 <.1

CH-4275 9/9/92 -- -- -- -- -- 17 <.1
56

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Silica,

dissolved

(mg/L

as SiO2)

Sulfate,

dissolved

(mg/L as SO4)

Solids,

residue at 180 °C,

dissolved

(mg/L)

Radon-222,

dissolved

(pCi/L)

NO2 + NO3

dissolved

(mg/L as N)

Nitrogen

nitrate,

dissolved

(mg/L as N)

Nitrogen

nitrite,

dissolved

(mg/L as N)

CH-75 7/14/86 -- 5 110 4,200 7.6 7.58 0.02

CH-75 8/23/90 -- 16 125 2,900 7.4 -- <.010

CH-75 8/8/00 16.6 12.1 -- -- 4.75 -- <.010

CH-525 9/21/25 23 5 74 -- -- 3.6 --

CH-526 9/21/25 24 8.9 68 -- -- .12 --

CH-528 9/21/25 18 4.9 48 -- -- 1.3 --

CH-1702 10/14/74 14 5.1 33 -- 1.1 1.1 <.010

CH-1703 8/5/91 19 3 57 2,900 2.2 -- <.010

CH-1720 10/1/92 -- 2.4 164 3,900 11 -- <.010

CH-1720 4/6/93 28 3 185 4,500 11 -- <.010

CH-1720 6/10/93 28 3.4 200 3,800 11 -- <.010

CH-1720 9/16/93 30 4 198 4,100 13 -- <.010

CH-1724 10/14/74 14 <1.0 79 -- 4.1 4.1 <.010

CH-1735 9/6/00 17.1 10.4 -- 4,400 8.47 -- <.010

CH-1737 7/11/91 14 4.6 113 2;500 14 -- <.010

CH-1761 8/22/91 28 3.5 239 120 .05 -- <.010

CH-1765 8/22/91 13 3 115 1,400 8 -- <.010

CH-1770 10/15/74 11 .5 112 -- 9.7 9.7 <.010

CH-1776 10/15/74 15 2.9 50 -- .18 .18 <.010

CH-1777 8/1/74 -- 12 89 -- -- .42 --

CH-1778 1/14/71 -- 7 112 -- -- .71 --

CH-1783 10/15/74 16 1.4 57 -- 2.1 2.1 <.010

CH-1829 8/31/95 -- -- -- 1,500 36 -- <.010

CH-1835 10/14/74 10 <1.0 40 -- 2 2 <.010

CH-1996 2/27/74 -- 3 86 -- -- 3.5 --

CH-2186 8/18/93 17 5.3 -- 5,200 7.1 -- <.010

CH-2439 8/17/81 -- -- -- -- 3.1 3.09 .01

CH-2440 8/17/81 -- -- -- -- 2.9 2.89 .01

CH-2459 8/4/82 -- -- -- -- -- -- --

CH-2460 8/4/82 -- -- -- -- -- -- --

CH-2461 8/4/82 -- -- -- -- -- -- --

CH-2461 7/7/83 -- -- -- -- 7 -- <.010

CH-2461 8/8/95 20 2.6 -- 3,000 15 -- <.010

CH-2673 8/6/85 -- -- -- -- 9.8 9.78 .02

CH-2678 8/28/84 -- -- -- -- 7.3 -- <.010

CH-2678 6/25/85 -- 1.1 226 -- 2.2 -- <.010

CH-3316 8/8/88 -- 21 122 -- <0.100 -- <.010

CH-3316 9/6/90 -- 21 119 11,000 < .100 -- <.010

CH-3317 8/8/88 -- .7 263 -- 2.9 -- <.010

CH-4118 7/8/91 7.5 .2 56 1,400 6.8 -- <.010

CH-4126 8/7/91 -- .2 135 5,100 6.5 -- <.010

CH-4275 9/9/92 -- 7 107 4,200 5.9 -- <.010
57

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Nitrogen

ammonia,

dissolved

(mg/L as N)

Phosphate,

ortho,

dissolved

(mg/L as PO4)

Phosphorus,

dissolved

(mg/L as P)

Phosphate,

ortho,

dissolved

(mg/L as P)

Aluminum,

dissolved

(μg/L as Al)

Antimony,

dissolved

(μg/L as Sb)

Arsenic,

dissolved

(μg/L as As)

CH-75 7/14/86 0.02 0.061 0.02 0.02 -- -- --

CH-75 8/23/90 <.010 -- -- -- -- -- <1.0

CH-75 8/8/00 <.020 .04 .019 .013 -- -- --

CH-525 9/21/25 -- -- -- -- -- -- --

CH-526 9/21/25 -- -- -- -- -- -- --

CH-528 9/21/25 -- -- -- -- -- -- --

CH-1702 10/14/74 .02 0 -- <.010 10 -- <1.0

CH-1703 8/5/91 <.010 .092 -- .03 -- -- --

CH-1720 10/1/92 <.010 .123 -- .04 -- -- <1.0

CH-1720 4/6/93 .01 .153 -- .05 -- -- --

CH-1720 6/10/93 .01 .184 -- .06 -- -- --

CH-1720 9/16/93 .01 .123 -- .04 -- -- --

CH-1724 10/14/74 .01 .123 -- .04 10 -- 2

CH-1735 9/6/00 <.020 .126 .047 .041 -- -- <2.0

CH-1737 7/11/91 .02 .092 -- .03 -- -- --

CH-1761 8/22/91 .02 .061 -- .02 -- -- --

CH-1765 8/22/91 .01 .031 -- .01 -- -- --

CH-1770 10/15/74 .03 .031 -- .01 50 -- <1.0

CH-1776 10/15/74 .01 .153 -- .05 <100 -- <1.0

CH-1777 8/1/74 -- .061 -- .02 -- -- --

CH-1778 1/14/71 -- -- -- -- -- -- --

CH-1783 10/15/74 .03 .092 -- .03 <100 -- <1.0

CH-1829 8/31/95 <.015 .031 -- .01 -- -- --

CH-1835 10/14/74 .01 .061 -- .02 20 -- <1.0

CH-1996 2/27/74 -- .031 -- .01 -- -- --

CH-2186 8/18/93 <.010 .061 -- .02 -- -- --

CH-2439 8/17/81 .01 -- -- -- -- -- 1

CH-2440 8/17/81 .02 -- -- -- -- -- 1

CH-2459 8/4/82 -- -- -- -- -- -- 1

CH-2460 8/4/82 -- -- -- -- -- -- 1

CH-2461 8/4/82 -- -- -- -- -- -- 1

CH-2461 7/7/83 .01 -- -- -- -- -- --

CH-2461 8/8/95 <.015 -- <.010 <.010 -- -- <1.0

CH-2673 8/6/85 .08 -- -- -- -- -- <1.0

CH-2678 8/28/84 <.010 -- -- -- 10 -- <1.0

CH-2678 6/25/85 -- -- -- -- <10 -- 1

CH-3316 8/8/88 .02 -- -- -- -- --

CH-3316 9/6/90 .01 -- -- -- -- -- <1.0

CH-3317 8/8/88 <.010 -- -- -- -- -- --

CH-4118 7/8/91 <.010 -- -- <.010 -- -- --

CH-4126 8/7/91 .02 -- -- <.010 -- -- --

CH-4275 9/9/92 .08 -- -- <.010 -- -- <1.0
58

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Barium,

dissolved

(μg/L as Ba)

Boron,

dissolved

(μg/L as

B)

Cadmium,

dissolved

(μg/L as Cd)

Chromium,

dissolved

(μg/L as Cr)

Cobalt,

dissolved

(μg/L as Co)

Copper,

dissolved

(μg/L as Cu)

Iron,

dissolved

(μg/L as Fe)

CH-75 7/14/86 -- -- -- -- -- -- --

CH-75 8/23/90 -- -- 8 <1.0 -- 26 10

CH-75 8/8/00 -- <16 -- -- -- -- 60

CH-525 9/21/25 -- -- -- -- -- -- 110

CH-526 9/21/25 -- -- -- -- -- -- 410

CH-528 9/21/25 -- -- -- -- -- -- 60

CH-1702 10/14/74 <100 <20 ND ND ND <20 120

CH-1703 8/5/91 -- -- -- -- -- -- 20

CH-1720 10/1/92 -- -- <1.0 <1.0 -- 18 40

CH-1720 4/6/93 -- -- -- -- -- -- 80

CH-1720 6/10/93 -- -- -- -- -- -- 50

CH-1720 9/16/93 -- -- -- -- -- -- <10

CH-1724 10/14/74 <100 <20 ND ND ND 110 20

CH-1735 9/6/00 -- 16 -- -- -- -- <10

CH-1737 7/11/91 -- -- -- -- -- -- 30

CH-1761 8/22/91 -- -- -- -- -- -- <1

CH-1765 8/22/91 -- -- -- -- -- -- <1

CH-1770 10/15/74 <100 <20 <2.0 ND ND 40 80

CH-1776 10/15/74 <100 <20 ND ND ND ND 50

CH-1777 8/1/74 -- -- -- -- -- -- 1,970

CH-1778 1/14/71 -- -- -- -- -- -- 400

CH-1783 10/15/74 <100 <20 ND ND ND ND 20

CH-1829 8/31/95 -- -- -- -- -- -- --

CH-1835 10/14/74 <100 <20 ND ND ND 90 20

CH-1996 2/27/74 -- -- -- -- -- -- 390

CH-2186 8/18/93 13 -- <1.0 <5.0 <3 <10 10

CH-2439 8/17/81 -- -- <1.0 <1.0 -- -- <10

CH-2440 8/17/81 -- -- <1.0 <1.0 -- -- 30

CH-2459 8/4/82 -- -- 1 <1.0 -- 20 --

CH-2460 8/4/82 -- -- <1.0 <1.0 -- 33 <1

CH-2461 8/4/82 -- -- <1.0 <1.0 -- 6 <1

CH-2461 7/7/83 -- -- -- -- -- -- --

CH-2461 8/8/95 52 -- <1.0 <5.0 <3 <10 10

CH-2673 8/6/85 -- <1.0 3 -- 58 90

CH-2678 8/28/84 <100 <20 1 <10.0 -- 2 20

CH-2678 6/25/85 72 <20 <1.0 10 -- 4 10

CH-3316 8/8/88 -- -- -- -- -- -- --

CH-3316 9/6/90 -- -- 1 <1.0 -- 1 3,400

CH-3317 8/8/88 -- -- -- -- -- -- --

CH-4118 7/8/91 -- -- -- -- -- -- 20

CH-4126 8/7/91 -- -- -- -- -- -- 10

CH-4275 9/9/92 -- -- <1.0 <1.0 -- 17 80
59

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Lead,

dissolved

(μg/L as

Pb)

Lithium,

dissolved

(μg/L as Li)

Manganese,

dissolved

(μg/L as Mn)

Mercury,

dissolved

(μg/L as

Hg)

Nickel,

dissolved

(μg/L as Ni)

Selenium,

dissolved

(μg/L as Se)

Silver,

dissolved

(μg/L as Ag)

Zinc,

dissolved

(μg/L as

Zn)

CH-75 7/14/86 -- -- -- -- -- -- -- --

CH-75 8/23/90 5 -- 55 <0.1 -- -- -- <3

CH-75 8/8/00 -- -- 103 -- -- -- --

CH-525 9/21/25 -- -- -- -- -- -- -- --

CH-526 9/21/25 -- -- -- -- -- -- -- --

CH-528 9/21/25 -- -- -- -- -- -- -- --

CH-1702 10/14/74 <2 <10.0 80 < .5 4 <2.0 ND 120

CH-1703 8/5/91 -- -- 6 -- -- -- -- --

CH-1720 10/1/92 <1 -- 2 <.1 -- -- -- 4

CH-1720 4/6/93 -- -- 7 -- -- -- -- --

CH-1720 6/10/93 -- -- <10 -- -- -- -- --

CH-1720 9/16/93 -- -- 20 -- -- -- -- --

CH-1724 10/14/74 <2 <10.0 <10 < .5 3 <1.0 ND <20

CH-1735 9/6/00 -- -- 22 -- -- -- -- --

CH-1737 7/11/91 -- -- 41 -- -- -- -- --

CH-1761 8/22/91 -- -- 1 -- -- -- -- --

CH-1765 8/22/91 -- -- 26 -- -- -- -- --

CH-1770 10/15/74 4 <10.0 160 < .5 4 <1.0 ND 1,300

CH-1776 10/15/74 2 <10.0 <10 < .5 3 3 ND 220

CH-1777 8/1/74 -- -- 40 -- -- -- -- --

CH-1778 1/14/71 -- -- 180 -- -- -- -- --

CH-1783 10/15/74 2 <10.0 <10 < .5 <2 2 ND 30

CH-1829 8/31/95 -- -- -- -- -- -- -- --

CH-1835 10/14/74 3 <10.0 <10 < .5 8 2 ND 20

CH-1996 2/27/74 -- -- 40 -- -- -- -- --

CH-2186 8/18/93 <10 9 27 -- <10 -- <1 33

CH-2439 8/17/81 <1 -- 3 <.1 3 -- -- --

CH-2440 8/17/81 1 -- 3 <.1 3 -- -- --

CH-2459 8/4/82 1 -- 3 <.1 <1 <1.0 -- 68

CH-2460 8/4/82 2 -- 20 <.1 2 <1.0 -- 13

CH-2461 8/4/82 1 -- 5 <.1 1 <1.0 -- <4

CH-2461 7/7/83 -- -- -- -- -- -- -- --

CH-2461 8/8/95 10 8 3 <.1 <10 -- <1 <3

CH-2673 8/6/85 1 -- 110 <.1 5 <1.0 -- 80

CH-2678 8/28/84 1 10 10 <.1 -- -- 20

CH-2678 6/25/85 4 10 23 <.1 <1 -- -- 27

CH-3316 8/8/88 -- -- -- -- -- -- -- --

CH-3316 9/6/90 <1 330 <.1 -- -- -- <3

CH-3317 8/8/88 -- -- -- -- -- -- -- --

CH-4118 7/8/91 -- -- 11 -- -- -- -- --

CH-4126 8/7/91 -- -- <10 -- -- -- -- --

CH-4275 9/9/92 <1 36 <.1 -- -- -- <3
60

CH-4297 300WSCK 10/1/92 7.2 6.2 228 22 13.5

CH-4806 300WSCK 6/28/94 9.4 5.7 248 26 12

CH-4931 300WSCK 7/21/94 10 5.3 74 6 12.9

CH-4933 300WSCK 7/14/94 8.9 7.4 106 16 14.7

CH-5231 300WSCK 8/14/95 9 5.8 161 20 13

CH-5420 300WSCK 6/9/98 -- 6.1 179 -- 14.3

CH-5421 300WSCK 6/10/98 -- 6.3 173 -- --

CH-5423 300WSCK 6/16/98 -- 5.2 162 -- 14.3

CH-5424 300WSCK 6/24/98 -- 5.7 85 -- 13.6

CH-5425 300PRCK 7/1/98 -- 7.1 191 -- 15.5

CH-5426 300WSCK 11/5/98 -- 6.8 81 -- 13.2

CH-5428 300WSCK 11/3/98 -- 7.4 131 -- 14.6

CH-5430 300WSCK 7/7/98 6.5 5.3 374 -- 18.1

CH-5431 300WSCK 7/7/98 -- 7.1 126 -- 14.1

CH-5432 000SRPN 7/14/98 -- 7.8 410 -- 13.7

CH-5433 300WSCK 7/14/98 -- 5.9 169 -- 16.5

CH-5434 300WSCK 7/15/98 -- 6.0 89 -- 14.6

CH-5437 300WSCK 11/18/98 -- 6.0 154 -- 14.0

CH-5439 000SRPN 11/16/98 -- 8.3 396 -- 18.1

CH-5440 300WSCK 11/4/98 -- -- 134 -- 12.2

CH-5442 300WSCK 11/24/98 6.9 5.8 88 -- 12.5

CH-5443 300WSCK 11/12/98 7.5 6.4 284 -- 13.2

CH-5450 000PGMT 9/11/00 .2 6.9 101 -- 13.3

CH-5470 300PRCK 8/22/96 9.3 5.4 54 -- 13.5

CH-5476 300WSCK 9/4/96 3.4 6.8 158 44 13

CH-5477 300WSCK 9/4/96 7.1 5.9 126 23 12.5

CH-5479 300WSCK 9/5/96 6.7 6 82 -- 13.5

CE Ae 8 300MGCK 10/28/98 -- -- 128 -- 12.9

CE Ae 9 300MGCK 10/26/98 -- 6 784 -- 12.9

CE Ae 13 300MGCK 12/3/98 -- 6.6 699 -- 13.2

CE Bf 77 300UFGB 3/31/83 -- 8.1 242 -- 13

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Geologic

unit

Sample

date

Dissolved

oxygen

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Alkalinity

(mg/L as

CaCO3)

Water

temperature

(°C)
61

CH-4297 10/1/92 -- -- -- -- -- 20 <0.1

CH-4806 6/28/94 65 14 7.1 3.3 11 29 <.1

CH-4931 7/21/94 20 2.8 3.1 1.7 3.3 6.5 <.1

CH-4933 7/14/94 28 5.6 3.4 1.4 6.6 6.7 <.1

CH-5231 8/14/95 -- -- -- -- -- 14 --

CH-5420 6/9/98 56 7.7 8.84 1 8.6 12.5 <.1

CH-5421 6/10/98 59 15.6 4.88 2.8 6.8 10.6 <.1

CH-5423 6/16/98 53 8.34 7.8 2.1 4.6 13.6 <.1

CH-5424 6/24/98 22 4.89 2.36 2.1 5.1 4.7 <.1

CH-5425 7/1/98 80 27.1 3.08 1.8 5.8 4.1 .1

CH-5426 11/5/98 18 3.26 2.36 .9 7.7 3.9 <.1

CH-5428 11/3/98 47 13.5 3.3 1.6 6 6.2 <.1

CH-5430 7/7/98 94 15.5 13.2 2.2 28.8 69.7 <.1

CH-5431 7/7/98 38 10.1 3.07 1.9 8.2 3.4 .2

CH-5432 7/14/98 230 4.55 54.1 .1 1.5 4.9 <.1

CH-5433 7/14/98 47 12.4 3.87 2.5 9.2 13 <.1

CH-5434 7/15/98 23 5.8 2.1 1.7 6.6 3.2 <.1

CH-5437 11/18/98 48 10.2 5.49 2.6 5.6 16.4 <.1

CH-5439 11/16/98 220 1.8 53 .2 3.4 5.3 <.1

CH-5440 11/4/98 41 11.7 2.79 1.6 11.6 2.8 .2

CH-5442 11/24/98 22 5.23 2.06 1.3 6.8 5.7 <.1

CH-5443 11/12/98 99 23.4 9.73 1.9 10.1 38.9 <.1

CH-5450 9/11/00 24 5.53 2.54 1.8 8.1 2.6 .2

CH-5470 8/22/96 13 2.9 1.5 .8 4.5 3.7 <.1

CH-5476 9/4/96 49 14 3.4 1.7 10 4.7 .5

CH-5477 9/4/96 37 8.4 3.9 1.7 5.9 7.5 <.1

CH-5479 9/5/96 21 5.5 1.7 1.7 6.6 4 <.1

CE Ae 8 10/28/98 42 13.3 2.17 2.1 7.6 3.3 <.1

CE Ae 9 10/26/98 270 47.9 37.4 1.3 38.8 218 <.1

CE Ae 13 12/3/98 320 66.1 36.7 1 19.4 113 <.1

CE Bf 77 3/31/83 -- 18 5.8 3.6 23 15 <.1

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Total

hardness

(mg/L as

CaCO3)

Calcium,

dissolved

(mg/L

as Ca)

Magnesium,

dissolved

(mg/L

as Mg)

Potassium,

dissolved

(mg/L

as K)

Sodium,

dissolved

(mg/L

as Na)

Chloride,

dissolved

(mg/L

as Cl)

Fluoride,

dissolved

(mg/L

as F)
62

CH-4297 10/1/92 -- 4.3 145 3,300 11 11 0.01

CH-4806 6/28/94 19 .1 -- 5,800 12 -- <.010

CH-4931 7/21/94 9.5 1.5 57 2,000 4.6 -- <.010

CH-4933 7/14/94 22 1 81 3,500 -- -- <.010

CH-5231 8/14/95 -- -- -- 2,200 7.1 -- <.010

CH-5420 6/9/98 18 8.6 117 2,800 6.33 6.32 .011

CH-5421 6/10/98 18.8 9.4 117 2,100 3.41 3.4 .01

CH-5423 6/16/98 11.9 2.2 112 3,700 -- -- --

CH-5424 6/24/98 17.3 2 69 2,000 3.55 -- <.010

CH-5425 7/1/98 23.9 18.2 127 5,300 <.050 -- <.010

CH-5426 11/5/98 21.8 .5 78 936 4.23 -- <.010

CH-5428 11/3/98 16.6 8.5 90 1,600 .38 -- <.010

CH-5430 7/7/98 13.8 19.1 212 1,700 6.96 -- <.010

CH-5431 7/7/98 29.6 11.9 80 586 .08 -- <.010

CH-5432 7/14/98 46.8 8.8 249 392 .403 .392 .011

CH-5433 7/14/98 25.3 20.6 114 9,800 2.31 2.3 .011

CH-5434 7/15/98 30.4 1.3 82 2,500 3.4 3.38 .012

CH-5437 11/18/98 13.4 .4 133 5,100 7.91 -- <.010

CH-5439 11/16/98 5.3 6.8 230 42 .147 .134 .013

CH-5440 11/4/98 22.7 5.9 98 285 <.050 -- <.010

CH-5442 11/24/98 21.4 .1 82 2,400 2.79 -- <.010

CH-5443 11/12/98 26.1 13.2 231 980 6.36 6.35 .011

CH-5450 9/11/00 29.6 7.9 -- 311 <.050 <.010

CH-5470 8/22/96 12 <.1 -- 4,300 3.8 -- <.010

CH-5476 9/4/96 16 8.6 -- 1,400 2.4 -- <.010

CH-5477 9/4/96 10 .5 -- 2,100 9.3 9.29 .01

CH-5479 9/5/96 25 .9 -- 3,700 2.6 -- <.010

CE Ae 8 10/28/98 28 13.6 102 1,200 <.050 -- <.010

CE Ae 9 10/26/98 28.9 10.1 599 2,390 2.31 -- <.010

CE Ae 13 12/3/98 34 20.3 457 528 2.9 -- <.010

CE Bf 77 3/31/83 18 6.2 145 -- <.1 -- --

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Silica,

dissolved

(mg/L

as SiO2)

Sulfate,

dissolved

(mg/L as SO4)

Solids,

residue at 180 °C,

dissolved

(mg/L)

Radon-222,

dissolved

(pCi/L)

NO2 + NO3

dissolved

(mg/L as N)

Nitrogen

nitrate,

dissolved

(mg/L as N)

Nitrogen

nitrite,

dissolved

(mg/L as N)
63

CH-4297 10/1/92 0.02 0.061 -- 0.02 -- -- --

CH-4806 6/28/94 .01 .061 -- .02 -- -- --

CH-4931 7/21/94 .03 -- <0.010 <.010 -- -- --

CH-4933 7/14/94 <.010 .184 .08 .06 -- -- --

CH-5231 8/14/95 .05 -- -- <.010 -- -- --

CH-5420 6/9/98 .034 .172 .016 .056 -- -- <1.0

CH-5421 6/10/98 .035 -- <.010 <.010 -- -- <1.0

CH-5423 6/16/98 -- -- -- -- -- -- <1.0

CH-5424 6/24/98 .022 .037 .018 .012 -- -- <1.0

CH-5425 7/1/98 .022 -- <.010 <.010 -- -- <1.0

CH-5426 11/5/98 <.020 .251 .073 .082 -- -- <1.0

CH-5428 11/3/98 <.020 .031 <.050 .01 -- -- <1.0

CH-5430 7/7/98 <.020 .061 <.010 .02 -- -- <1.0

CH-5431 7/7/98 <.020 .181 .074 .059 -- -- <1.0

CH-5432 7/14/98 .052 .086 <.010 .028 -- -- <1.0

CH-5433 7/14/98 .057 .178 .105 .058 -- -- <1.0

CH-5434 7/15/98 .064 .181 .058 .059 -- -- <1.0

CH-5437 11/18/98 .025 .058 <.050 .019 -- -- <1.0

CH-5439 11/16/98 .022 .031 <.050 .01 -- -- <1.0

CH-5440 11/4/98 .027 .08 <.050 .026 -- -- <1.0

CH-5442 11/24/98 .021 .034 <.050 .011 -- -- <1.0

CH-5443 11/12/98 .042 .058 <.050 .019 -- -- <1.0

CH-5450 9/11/00 <.020 .092 -- .03 <1 <1 --

CH-5470 8/22/96 <.015 .092 .04 .03 -- -- <1.0

CH-5476 9/4/96 <.015 -- .03 <.010 -- -- --

CH-5477 9/4/96 .07 -- -- <.010 5 <1 --

CH-5479 9/5/96 <.015 .276 .07 .09 3 <1 --

CE Ae 8 10/28/98 <.020 .046 <.050 .015 -- -- <1.0

CE Ae 9 10/26/98 .024 .061 <.050 .02 -- -- <1.0

CE Ae 13 12/3/98 <.020 .086 <.050 .028 -- -- <1.0

CE Bf 77 3/31/83 -- -- -- <.010 <100 -- 1

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Nitrogen

ammonia,

dissolved

(mg/L as N)

Phosphate,

ortho,

dissolved

(mg/L as PO4)

Phosphorus,

dissolved

(mg/L as P)

Phosphate,

ortho,

dissolved

(mg/L as P)

Aluminum,

dissolved

(μg/L as Al)

Antimony,

dissolved

(μg/L as Sb)

Arsenic,

dissolved

(μg/L as As)
64

CH-4297 10/1/92 -- -- -- 30

CH-4806 6/28/94 120 -- <1.0 <5.0 <3 20 40

CH-4931 7/21/94 -- -- -- -- -- -- --

CH-4933 7/14/94 -- -- -- -- -- -- 10

CH-5231 8/14/95 -- -- -- -- -- -- --

CH-5420 6/9/98 2 -- <8.0 <14.0 <12 <10 <10

CH-5421 6/10/98 13 -- <8.0 <14.0 <12 <10 <10

CH-5423 6/16/98 75 -- <8.0 <14.0 <12 36 <10

CH-5424 6/24/98 5 -- <8.0 <14.0 <12 <10 <10

CH-5425 7/1/98 4 -- <8.0 <14.0 <12 <10 450

CH-5426 11/5/98 2 -- <8.0 <14.0 <7 9 E 10 E

CH-5428 11/3/98 15 -- <8.0 <14.0 <7 <10 10 E

CH-5430 7/7/98 123 -- <8.0 <14.0 <12 <10 710

CH-5431 7/7/98 6 -- <8.0 <14.0 <12 <10 200

CH-5432 7/14/98 1 -- <8.0 <14.0 <12 <10 <10

CH-5433 7/14/98 10 -- <8.0 <14.0 <12 <10 <10

CH-5434 7/15/98 21 -- <8.0 <14.0 <12 29 <10

CH-5437 11/18/98 125 -- <8.0 <14.0 <7 7 E <10

CH-5439 11/16/98 4 -- <8.0 <14.0 <7 <10 <10

CH-5440 11/4/98 14 -- <8.0 <14.0 <7 <10 60

CH-5442 11/24/98 18 -- <8.0 <14.0 <7 9 E 120

CH-5443 11/12/98 110 -- <8.0 <14.0 <7 <10 40

CH-5450 9/11/00 32 -- <1.0 < .8 <1 <1 1,560

CH-5470 8/22/96 17 -- <1.0 <5.0 <3 10 <1

CH-5476 9/4/96 16 -- <1.0 <5.0 <3 <10 <1

CH-5477 9/4/96 54 -- <1.0 <1.0 <1 6 10

CH-5479 9/5/96 25 4 <1.0 <1.0 <1 28 10

CE Ae 8 10/28/98 14 -- <8.0 <14.0 <7 <10 250

CE Ae 9 10/26/98 208 -- <8.0 14.2 <7 <10 110

CE Ae 13 12/3/98 15 -- <8.0 <14.0 <7 41 <10

CE Bf 77 3/31/83 -- 80 <1.0 10 -- -- 160

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Barium,

dissolved

(μg/L as Ba)

Boron,

dissolved

(μg/L as

B)

Cadmium,

dissolved

(μg/L as Cd)

Chromium,

dissolved

(μg/L as Cr)

Cobalt,

dissolved

(μg/L as Co)

Copper,

dissolved

(μg/L as Cu)

Iron,

dissolved

(μg/L as Fe)
65

CH-4297 10/1/92 -- -- 20 -- -- -- -- --

CH-4806 6/28/94 10 7 52 -- <10 -- <1 17

CH-4931 7/21/94 -- -- 38 -- -- -- -- --

CH-4933 7/14/94 -- -- 5 -- -- -- -- --

CH-5231 8/14/95 -- -- -- -- -- -- --

CH-5420 6/9/98 <100 6.7 55 -- <40 -- <4 <20

CH-5421 6/10/98 <100 7.5 <4 -- <40 -- <4 <20

CH-5423 6/16/98 <100 <4.0 32 -- <40 -- <4 <20

CH-5424 6/24/98 <100 <4.0 5 -- <40 -- <4 40

CH-5425 7/1/98 <100 6.2 416 -- <40 -- <4 24

CH-5426 11/5/98 <100 5.0 E 11 -- <40 -- <4 <20

CH-5428 11/3/98 <100 <6.0 8 -- <40 -- <4 <20

CH-5430 7/7/98 <100 <4.0 147 -- <40 -- <4 <20

CH-5431 7/7/98 <100 12.7 107 -- <40 -- <4 <20

CH-5432 7/14/98 <100 <4.0 <4 -- <40 -- <4 <20

CH-5433 7/14/98 <100 8.3 <4 -- <40 -- <4 <20

CH-5434 7/15/98 <100 5 <4 -- <40 -- <4 <20

CH-5437 11/18/98 <100 3.9 E 22 -- <40 -- <4 <20

CH-5439 11/16/98 <100 <6.0 <3 -- <40 -- <4 <20

CH-5440 11/4/98 <100 6.4 99 -- <40 -- <4 <20

CH-5442 11/24/98 <100 <6.0 61 -- <40 -- <4 7 E

CH-5443 11/12/98 <100 6 6 -- <40 -- <4 <20

CH-5450 9/11/00 <1 -- 161 -- <1 -- <1 1

CH-5470 8/22/96 <10 <4.0 16 <.1 <10 -- <1 9

CH-5476 9/4/96 <10 5 33 -- <10 -- <1 <3

CH-5477 9/4/96 <1 -- 64 -- 4 -- <1 10

CH-5479 9/5/96 <1 -- 2 -- <1 -- <1 38

CE Ae 8 10/28/98 <100 9.1 100 -- <40 -- <4 <20

CE Ae 9 10/26/98 <100 3.3 E 10 -- 39 E -- <4 18 E

CE Ae 13 12/3/98 <100 6.4 <3 -- <40 -- <4 18 E

CE Bf 77 3/31/83 <10 -- 10 <.1 -- -- -- --

Table 20. Results of field determinations and laboratory analyses for selected inorganic constituents,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Sample

date

Lead,

dissolved

(μg/L as

Pb)

Lithium,

dissolved

(μg/L as Li)

Manganese,

dissolved

(μg/L as Mn)

Mercury,

dissolved

(μg/L as

Hg)

Nickel,

dissolved

(μg/L as Ni)

Selenium,

dissolved

(μg/L as Se)

Silver,

dissolved

(μg/L as Ag)

Zinc,

dissolved

(μg/L as

Zn)
66

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland

All concentrations are given in micrograms per liter;

Date is year, month, day;

--, no data;

<, less than;

E, estimated concentration
67

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Acetochlor,

dissolved

Alachlor,

dissolved

Alachlor,

total

Aldrin,

total

Alpha BHC,

dissolved

Ametryn,

dissolved

CH-75 19900823 -- -- <0.1 <0.010 -- --

CH-1720 19921001 -- <0.050 -- -- -- <0.05

CH-1720 19930610 -- -- -- <.010 -- --

CH-1735 20000906 <0.002 <.002 -- -- <0.002 --

CH-2186 19930818 -- <.002 -- <.010 <.002 --

CH-2439 19810817 -- -- -- <.010 -- --

CH-2440 19810817 -- -- -- <.010 -- --

CH-2459 19820804 -- -- -- <.010 -- --

CH-2460 19820804 -- -- -- <.010 -- --

CH-2461 19820804 -- -- -- <.010 -- --

CH-2461 19830707 -- -- -- -- --

CH-2461 19950808 <.002 2.49 -- <.010 <.002 --

CH-3316 19880808 -- -- <.1 <.010 -- --

CH-3316 19900906 -- -- -- -- -- --

CH-3317 19880808 -- -- <.1 <.010 -- --

CH-4126 19910807 -- <.050 -- <.010 -- <.05

CH-4297 19921001 -- <.050 -- <.010 -- <.05

CH-4806 19940628 -- <.050 -- <.010 -- <.05

CH-4931 19940721 <.002 <.002 -- -- <.002 --

CH-4933 19940714 <.002 <.002 -- -- <.002 --

CH-5420 19980615 <.002 <.002 -- -- <.002 --

CH-5421 19980615 <.002 <.002 -- -- <.002 --

CH-5423 19980616 <.002 <.002 -- -- <.002 --

CH-5424 19980624 <.002 <.002 -- -- <.002 --

CH-5425 19980701 <.002 <.002 -- -- <.002 --

CH-5426 19981105 <.002 <.002 -- -- <.002 --

CH-5428 19981103 <.002 <.002 -- -- <.002 --

CH-5430 19980707 <.002 <.002 -- -- <.002 --

CH-5431 19980707 <.002 <.002 -- -- <.002 --

CH-5432 19980714 <.002 <.002 -- -- <.002 --

CH-5433 19980714 <.002 <.002 -- -- <.002 --

CH-5434 19980715 <.002 <.002 -- -- <.002 --

CH-5437 19981118 <.002 <.002 -- -- <.002 --

CH-5439 19981116 <.002 <.002 -- -- <.002 --

CH-5440 19981104 <.002 <.002 -- -- <.002 --

CH-5442 19981124 <.002 <.002 -- -- <.002 --

CH-5443 19981112 <.002 <.002 -- -- <.002 --

CH-5450 20000911 <.002 <.002 -- -- <.002 --

CH-5470 19960822 <.002 <.002 -- <.010 <.002 --

CH-5476 19960904 -- -- -- <.010 -- --

CH-5477 19960904 -- -- -- <.010 -- --

CE Ae 8 19981028 <.002 <.002 -- -- <.002 --

CE Ae 9 19981026 <.002 <.002 -- -- <.002 --

CE Ae 13 19981203 <.002 <.002 -- -- <.002 --
68

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania

and Maryland—Continued

Wellidentification

number

Date of

sample

Ametryne,

total

 Atrazine,

dissolved

Atrazine,

total

Benfluralin,

total

Butylate,

dissolved

Carbaryl,

dissolved

CH-75 19900823 <0.1 -- 0.1 -- -- --

CH-1720 19921001 -- <0.050 -- -- -- --

CH-1720 19930610 -- -- -- -- -- --

CH-1735 20000906 -- <.004 -- <0.002 <0.002 <0.003

CH-2186 19930818 -- <.001 -- <.002 <.002 <.003

CH-2439 19810817 -- -- -- -- -- --

CH-2440 19810817 -- -- -- -- -- --

CH-2459 19820804 -- -- -- -- -- --

CH-2460 19820804 -- -- -- -- -- --

CH-2461 19820804 -- -- -- -- -- --

CH-2461 19830707 < .1 -- .2 -- -- --

CH-2461 19950808 -- .172 <.002 <.002 .015 E

CH-3316 19880808 < .1 -- < .1 -- -- --

CH-3316 19900906 -- -- -- -- -- --

CH-3317 19880808 < .1 -- < .1 -- -- --

CH-4126 19910807 -- <.050 -- -- -- --

CH-4297 19921001 -- <.050 -- -- -- --

CH-4806 19940628 -- <.050 -- -- -- --

CH-4931 19940721 -- .006 -- <.002 <.002 <.003

CH-4933 19940714 -- <.001 -- <.002 <.002 <.003

CH-5420 19980615 -- .005 -- <.002 <.002 .012 E

CH-5421 19980615 -- .014 -- <.002 <.002 <.003

CH-5423 19980616 -- .011 -- <.002 <.002 .007 E

CH-5424 19980624 -- <.001 -- <.002 <.002 <.003

CH-5425 19980701 -- .01 -- <.002 <.002 <.003

CH-5426 19981105 -- <.001 -- <.002 <.002 <.003

CH-5428 19981103 -- <.001 -- <.002 <.002 <.003

CH-5430 19980707 -- .209 -- <.002 <.002 .012 E

CH-5431 19980707 -- <.001 -- <.002 <.002 <.003

CH-5432 19980714 -- <.001 -- <.002 <.002 <.003

CH-5433 19980714 -- <.001 -- <.002 <.002 <.003

CH-5434 19980715 -- <.001 -- <.002 <.002 <.003

CH-5437 19981118 -- .003 E -- <.002 <.002 <.003

CH-5439 19981116 -- <.001 -- <.002 <.002 <.003

CH-5440 19981104 -- <.001 -- <.002 <.002 <.003

CH-5442 19981124 -- <.001 -- <.002 <.002 <.003

CH-5443 19981112 -- .005 -- <.002 <.002 <.003

CH-5450 20000911 -- <.001 -- <.002 <.002 <.003

CH-5470 19960822 -- .007 -- <.002 <.002 <.003

CH-5476 19960904 -- -- -- -- -- --

CH-5477 19960904 -- -- -- -- -- --

CE Ae 8 19981028 -- <.004 -- <.002 <.002 .007 E

CE Ae 9 19981026 -- <.001 -- <.002 <.002 <.003

CE Ae 13 19981203 -- .02 -- <.002 <.002 <.003
69

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Carbofuran,

dissolved

Carbophenothion,

dissolved

Chlordane,

total

Chlorpyrifos,

dissolved

Chlorpyrifos,

total

Cyanazine,

dissolved

CH-75 19900823 -- <0.01 <0.1 -- <0.01 --

CH-1720 19921001 -- -- -- -- -- <0.200

CH-1720 19930610 -- <.01 < .1 -- <.01 --

CH-1735 20000906 0.030 E -- -- <0.004 -- <.004

CH-2186 19930818 <.003 -- < .1 <.004 -- <.004

CH-2439 19810817 -- -- < .1 -- -- --

CH-2440 19810817 -- -- < .1 -- -- --

CH-2459 19820804 -- -- < .1 -- -- --

CH-2460 19820804 -- -- < .1 -- -- --

CH-2461 19820804 -- -- < .1 -- -- --

CH-2461 19830707 -- <.01 -- -- -- --

CH-2461 19950808 .010 E -- < .1 <.004 -- <.004

CH-3316 19880808 -- <.01 < .1 -- -- --

CH-3316 19900906 -- -- -- -- -- --

CH-3317 19880808 -- <.01 < .1 -- -- --

CH-4126 19910807 -- <.01 < .1 -- <.01 <.200

CH-4297 19921001 -- <.01 < .1 -- <.01 <.200

CH-4806 19940628 -- <.01 < .1 -- <.01 <.200

CH-4931 19940721 <.003 -- -- <.004 -- <.004

CH-4933 19940714 <.003 -- -- <.004 -- <.004

CH-5420 19980615 <.003 -- -- <.004 -- <.004

CH-5421 19980615 <.003 -- -- <.004 -- <.004

CH-5423 19980616 <.003 -- -- <.004 -- <.004

CH-5424 19980624 <.003 -- -- <.004 -- <.004

CH-5425 19980701 <.003 -- -- <.004 -- <.004

CH-5426 19981105 <.003 -- -- <.004 -- <.004

CH-5428 19981103 <.003 -- -- <.004 -- <.004

CH-5430 19980707 <.003 -- -- <.004 -- <.004

CH-5431 19980707 <.003 -- -- <.004 -- <.004

CH-5432 19980714 <.003 -- -- <.004 -- <.004

CH-5433 19980714 <.003 -- -- <.004 -- <.004

CH-5434 19980715 <.003 -- -- <.004 -- <.004

CH-5437 19981118 <.003 -- -- <.004 -- <.004

CH-5439 19981116 <.003 -- -- <.004 -- <.004

CH-5440 19981104 <.003 -- -- <.004 -- <.004

CH-5442 19981124 <.003 -- -- <.004 -- <.004

CH-5443 19981112 <.003 -- -- <.004 -- <.004

CH-5450 20000911 <.003 -- -- <.004 -- <.004

CH-5470 19960822 .073 E -- < .1 <.004 -- <.004

CH-5476 19960904 -- <.01 < .1 -- <.01 --

CH-5477 19960904 -- -- < .1 -- -- --

CE Ae 8 19981028 <.003 -- -- <.004 -- .007

CE Ae 9 19981026 <.003 -- -- <.004 -- <.004

CE Ae 13 19981203 <.003 -- -- <.004 -- <.004
70

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Cyanazine,

total

DCPA,

dissolved

P,P’-DDD,

total

P,P’ DDE,

dissolved

P,P’-DDE,

total

P,P’-DDT,

total

Deethyl

atrazine,

dissolved

CH -75 19900823 <0.1 -- <0.010 -- <0.010 <0.010 --

CH-1720 19921001 -- -- -- -- -- -- <0.050

CH-1720 19930610 -- -- <.010 -- <.010 <.010 --

CH-1735 20000906 -- <0.002 -- <0.006 -- -- .032 E

CH-2186 19930818 -- <.002 <.010 <.006 <.010 <.010 .047 E

CH-2439 19810817 -- -- <.010 -- <.010 <.010 --

CH-2440 19810817 -- -- <.010 -- <.010 <.010 --

CH-2459 19820804 -- -- <.010 -- <.010 <.010 --

CH-2460 19820804 -- -- <.010 -- <.010 <.010 --

CH-2461 19820804 -- -- <.010 -- <.010 <.010 --

CH-2461 19830707 < .1 -- -- -- -- -- --

CH-2461 19950808 -- <.002 <.010 <.006 <.010 <.010 .19 E

CH-3316 19880808 < .1 -- <.010 -- <.010 <.010 --

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 < .1 -- <.010 -- <.010 <.010 --

CH-4126 19910807 -- -- <.010 -- <.010 <.010 .2

CH-4297 19921001 -- -- <.010 -- <.010 <.010 .06

CH-4806 19940628 -- -- <.010 -- <.010 <.010 .2

CH-4931 19940721 -- <.002 -- <.006 -- -- .014 E

CH-4933 19940714 -- <.002 -- <.006 -- -- .076 E

CH-5420 19980615 -- <.002 -- <.006 -- -- .28 E

CH-5421 19980615 -- <.002 -- <.006 -- -- .20 E

CH-5423 19980616 -- <.002 -- <.006 -- -- .10 E

CH-5424 19980624 -- <.002 -- <.006 -- -- .03 E

CH-5425 19980701 -- <.002 -- <.006 -- -- .003 E

CH-5426 19981105 -- <.002 -- <.006 -- -- <.002

CH-5428 19981103 -- <.002 -- <.006 -- -- .011 E

CH-5430 19980707 -- <.002 -- <.006 -- -- .33 E

CH-5431 19980707 -- <.002 -- <.006 -- -- <.002

CH-5432 19980714 -- <.002 -- <.006 -- -- <.002

CH-5433 19980714 -- <.002 -- <.006 -- -- <.002

CH-5434 19980715 -- <.002 -- <.006 -- -- <.002

CH-5437 19981118 -- <.002 -- <.006 -- -- .32 E

CH-5439 19981116 -- <.002 -- <.006 -- -- <.002

CH-5440 19981104 -- <.002 -- <.006 -- -- <.002

CH-5442 19981124 -- <.002 -- <.006 -- -- .038 E

CH-5443 19981112 -- <.002 -- <.006 -- -- .018 E

CH-5450 20000911 -- <.002 -- <.006 -- -- <.002

CH-5470 19960822 -- <.002 <.010 <.006 <.010 <.010 .13 E

CH-5476 19960904 -- -- <.010 -- <.010 <.010 --

CH-5477 19960904 -- -- <.010 -- <.010 <.010 --

CE Ae 8 19981028 -- <.004 -- <.012 -- -- .003 E

CE Ae 9 19981026 -- <.002 -- <.006 -- -- .090 E

CE Ae 13 19981203 -- <.002 -- <.006 -- -- .038 E
71

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

DEF,

total

Diazinon,

dissolved

Diazinon,

total

Dicamba,

dissolved

Dicamba,

total

Dieldrin,

dissolved

Dieldrin,

total

CH-75 19900823 <0.01 -- <0.01 -- -- -- <0.010

CH-1720 19921001 -- -- -- -- -- -- --

CH-1720 19930610 <.01 -- <.01 -- -- -- <.010

CH-1735 20000906 -- <0.002 -- -- -- <0.001 --

CH-2186 19930818 -- <.002 -- -- -- <.001 <.010

CH-2439 19810817 -- -- -- -- -- -- <.010

CH-2440 19810817 -- -- -- -- -- -- <.010

CH-2459 19820804 -- -- -- -- -- -- <.010

CH-2460 19820804 -- -- -- -- -- -- <.010

CH-2461 19820804 -- -- -- -- -- -- <.010

CH-2461 19830707 -- -- <.01 -- <0.01 -- --

CH-2461 19950808 -- <.002 -- -- -- .039 .04

CH-3316 19880808 -- -- <.01 -- -- -- <.010

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 -- -- <.01 -- <.01 -- <.010

CH-4126 19910807 <.01 -- 57 -- <.01 -- <.010

CH-4297 19921001 <.01 -- <.01 -- <.01 -- <.010

CH-4806 19940628 <.01 -- <.01 -- <.01 -- <.010

CH-4931 19940721 -- <.002 -- <0.04 -- <.001 --

CH-4933 19940714 -- <.002 -- <.04 -- <.001 --

CH-5420 19980615 -- <.002 -- -- -- <.001 --

CH-5421 19980615 -- <.002 -- -- -- <.001 --

CH-5423 19980616 -- <.002 -- -- -- <.001 --

CH-5424 19980624 -- <.002 -- -- -- <.001 --

CH-5425 19980701 -- <.002 -- -- -- <.001 --

CH-5426 19981105 -- <.002 -- -- -- <.001 --

CH-5428 19981103 -- <.002 -- -- -- <.001 --

CH-5430 19980707 -- .022 -- -- -- <.001 --

CH-5431 19980707 -- <.002 -- -- -- <.001 --

CH-5432 19980714 -- <.002 -- -- -- <.001 --

CH-5433 19980714 -- <.002 -- -- -- <.001 --

CH-5434 19980715 -- <.002 -- -- -- <.001 --

CH-5437 19981118 -- <.002 -- -- -- <.001 --

CH-5439 19981116 -- <.002 -- -- -- <.001 --

CH-5440 19981104 -- <.002 -- -- -- <.001 --

CH-5442 19981124 -- <.002 -- -- -- <.001 --

CH-5443 19981112 -- <.002 -- -- -- <.001 --

CH-5450 20000911 -- <.002 -- -- -- <.001 --

CH-5470 19960822 -- <.002 -- -- -- <.001 <.010

CH-5476 19960904 <.01 -- <.01 -- -- -- <.010

CH-5477 19960904 -- -- -- -- -- -- <.010

CE Ae 8 19981028 -- <.002 -- -- -- <.001 --

CE Ae 9 19981026 -- <.002 -- -- -- <.001 --

CE Ae 13 19981203 -- <.002 -- -- -- .056 --
72

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Disulfoton,

dissolved

Disulfoton,

total

Endosulfan,

total

Endrin,

total

EPTC,

dissolved

Ethalfluralin,

dissolved

Ethion,

total

CH-75 19900823 -- <0.01 <0.010 <0.010 -- -- <0.01

CH-1720 19921001 -- -- -- -- -- -- --

CH-1720 19930610 -- <.01 <.010 <.010 -- -- <.01

CH-1735 20000906 <0.017 -- -- -- <0.002 <0.004 --

CH-2186 19930818 <.017 -- <.010 <.010 <.002 <.004 --

CH-2439 19810817 -- -- <.010 <.010 -- -- --

CH-2440 19810817 -- -- <.010 <.010 -- -- --

CH-2459 19820804 -- -- <.010 <.010 -- -- --

CH-2460 19820804 -- -- <.010 <.010 -- -- --

CH-2461 19820804 -- -- <.010 <.010 -- -- --

CH-2461 19830707 -- -- -- -- -- -- <.01

CH-2461 19950808 <.017 -- <.010 <.010 .01 <.004 --

CH-3316 19880808 -- -- <.010 <.010 -- -- <.01

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 -- -- <.010 <.010 -- -- <.01

CH-4126 19910807 -- <.01 <.010 <.010 -- -- .02

CH-4297 19921001 -- <.01 <.010 <.010 -- -- <.01

CH-4806 19940628 -- <.01 <.010 <.010 -- -- <.01

CH-4931 19940721 <.017 -- -- -- <.002 <.004 --

CH-4933 19940714 <.017 -- -- -- <.002 <.004 --

CH-5420 19980615 <.017 -- -- -- <.002 <.004 --

CH-5421 19980615 <.017 -- -- -- <.002 <.004 --

CH-5423 19980616 <.017 -- -- -- <.002 <.004 --

CH-5424 19980624 <.017 -- -- -- <.002 <.004 --

CH-5425 19980701 <.017 -- -- -- <.002 <.004 --

CH-5426 19981105 <.017 -- -- -- <.002 <.004 --

CH-5428 19981103 <.017 -- -- -- <.002 <.004 --

CH-5430 19980707 <.017 -- -- -- <.002 <.004 --

CH-5431 19980707 <.017 -- -- -- <.002 <.004 --

CH-5432 19980714 <.017 -- -- -- <.002 <.004 --

CH-5433 19980714 <.017 -- -- -- <.002 <.004 --

CH-5434 19980715 <.017 -- -- -- <.002 <.004 --

CH-5437 19981118 <.017 -- -- -- <.002 <.004 --

CH-5439 19981116 <.017 -- -- -- <.002 <.004 --

CH-5440 19981104 <.017 -- -- -- <.002 <.004 --

CH-5442 19981124 <.017 -- -- -- <.002 <.004 --

CH-5443 19981112 <.017 -- -- -- <.002 <.004 --

CH-5450 20000911 <.017 -- -- -- <.002 <.004 --

CH-5470 19960822 <.017 -- <.010 <.010 <.002 <.004 --

CH-5476 19960904 -- <.01 <.010 <.010 -- -- <.01

CH-5477 19960904 -- -- <.010 <.010 -- -- --

CE Ae 8 19981028 <.017 -- -- -- <.002 <.004 --

CE Ae 9 19981026 <.017 -- -- -- <.002 <.004 --

CE Ae 13 19981203 <.017 -- -- -- <.002 <.004 --
73

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Ethoprop,

dissolved

Fonofos,

dissolved

Fonofos,

total

Heptachlor,

total

Heptachlor

epoxide,

total

Lindane,

dissolved

Lindane,

total

CH-75 19900823 -- -- <0.01 <0.010 <0.010 -- <0.010

CH-1720 19921001 -- -- -- -- -- -- --

CH-1720 19930610 -- -- <.01 <.010 <.010 -- .02

CH-1735 20000906 <0.003 <0.003 -- -- -- <0.004

CH-2186 19930818 <.003 <.003 -- <.010 <.010 <.004 <.010

CH-2439 19810817 -- -- -- <.010 <.010 -- <.010

CH-2440 19810817 -- -- -- <.010 <.010 -- <.010

CH-2459 19820804 -- -- -- <.010 <.010 -- <.010

CH-2460 19820804 -- -- -- <.010 <.010 -- <.010

CH-2461 19820804 -- -- -- <.010 <.010 -- <.010

CH-2461 19830707 -- -- -- -- -- -- --

CH-2461 19950808 <.003 <.003 -- <.010 <.010 <.004 <.010

CH-3316 19880808 -- -- -- <.010 <.010 -- <.010

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 -- -- -- <.010 <.010 -- <.010

CH-4126 19910807 -- -- <.02 <.010 <.010 -- .03

CH-4297 19921001 -- -- <.01 <.010 <.010 -- <.010

CH-4806 19940628 -- -- <.01 <.010 <.010 -- <.010

CH-4931 19940721 <.003 <.003 -- -- -- <.004 --

CH-4933 19940714 <.003 <.003 -- -- -- <.004 --

CH-5420 19980615 <.003 <.003 -- -- -- <.004 --

CH-5421 19980615 <.003 <.003 -- -- -- <.004 --

CH-5423 19980616 <.003 <.003 -- -- -- <.004 --

CH-5424 19980624 <.003 <.003 -- -- -- <.004 --

CH-5425 19980701 <.003 <.003 -- -- -- <.004 --

CH-5426 19981105 <.003 <.003 -- -- -- <.004 --

CH-5428 19981103 <.003 <.003 -- -- -- <.004 --

CH-5430 19980707 <.003 <.003 -- -- -- <.004 --

CH-5431 19980707 <.003 <.003 -- -- -- <.004 --

CH-5432 19980714 <.003 <.003 -- -- -- <.004 --

CH-5433 19980714 <.003 <.003 -- -- -- <.004 --

CH-5434 19980715 <.003 <.003 -- -- -- <.004 --

CH-5437 19981118 <.003 <.003 -- -- -- <.004 --

CH-5439 19981116 <.003 <.003 -- -- -- <.004 --

CH-5440 19981104 <.003 <.003 -- -- -- <.004 --

CH-5442 19981124 <.003 <.003 -- -- -- <.004 --

CH-5443 19981112 <.003 -- -- -- -- <.004 --

CH-5450 20000911 <.003 <.003 -- -- -- <.004 --

CH-5470 19960822 <.003 <.003 -- <.010 <.010 <.004 <.010

CH-5476 19960904 -- -- <.01 <.010 <.010 -- <.010

CH-5477 19960904 -- -- -- <.010 <.010 -- <.010

CE Ae 8 19981028 <.003 <.003 -- -- -- <.004 --

CE Ae 9 19981026 <.003 <.003 -- -- -- <.004 --

CE Ae 13 19981203 <.003 <.003 -- -- -- <.004 --
74

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Linuron,

dissolved

Malathion,

dissolved

Malathion,

total

Methyl

azinphos,

dissolved

Methyl

parathion,

total

Methyl

parathion,

dissolved

Methoxychlor,

total

CH-75 19900823 -- -- <0.01 -- <0.01 -- <0.01

CH-1720 19921001 -- -- -- -- -- -- --

CH-1720 19930610 -- -- <.01 -- <.01 -- <.01

CH-1735 20000906 <0.002 <0.005 -- <0.001 -- <0.006 --

CH-2186 19930818 <.002 <.005 -- <.001 -- <.006 <.01

CH-2439 19810817 -- -- -- -- -- -- <.01

CH-2440 19810817 -- -- -- -- -- -- <.01

CH-2459 19820804 -- -- -- -- -- -- <.01

CH-2460 19820804 -- -- -- -- -- -- <.01

CH-2461 19820804 -- -- -- -- -- -- <.01

CH-2461 19830707 -- -- <.01 -- <.01 -- --

CH-2461 19950808 <.002 .002 E -- <.001 -- <.006 <.01

CH-3316 19880808 -- -- <.01 -- <.01 -- <.01

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 -- -- <.01 -- <.01 -- <.01

CH-4126 19910807 -- -- 25 -- <.01 -- .09

CH-4297 19921001 -- -- <.01 -- <.01 -- <.01

CH-4806 19940628 -- -- <.01 -- <.01 -- <.01

CH-4931 19940721 <.002 <.005 -- <.001 -- <.006 --

CH-4933 19940714 <.002 <.005 -- <.001 -- <.006 --

CH-5420 19980615 <.002 <.005 -- <.001 -- <.006 --

CH-5421 19980615 <.002 <.005 -- <.001 -- <.006 --

CH-5423 19980616 <.002 <.005 -- <.001 -- <.006 --

CH-5424 19980624 <.002 <.005 -- <.001 -- <.006 --

CH-5425 19980701 <.002 <.005 -- <.001 -- <.006 --

CH-5426 19981105 <.002 <.005 -- <.001 -- <.006 --

CH-5428 19981103 <.002 <.005 -- <.001 -- <.006 --

CH-5430 19980707 <.002 <.005 -- <.001 -- <.006 --

CH-5431 19980707 <.002 <.005 -- <.001 -- <.006 --

CH-5432 19980714 <.002 <.005 -- <.001 -- <.006 --

CH-5433 19980714 <.002 <.005 -- <.001 -- <.006 --

CH-5434 19980715 <.002 <.005 -- <.001 -- <.006 --

CH-5437 19981118 <.002 <.005 -- <.001 -- <.006 --

CH-5439 19981116 <.002 <.005 -- <.001 -- <.006 --

CH-5440 19981104 <.002 <.005 -- <.001 -- <.006 --

CH-5442 19981124 <.002 <.005 -- <.001 -- <.006 --

CH-5443 19981112 <.002 <.005 -- <.001 -- <.006 --

CH-5450 20000911 <.002 <.005 -- <.001 -- <.006 --

CH-5470 19960822 <.002 <.005 -- <.001 -- <.006 <.01

CH-5476 19960904 -- -- <.01 -- <.01 -- <.01

CH-5477 19960904 -- -- -- -- -- -- <.01

CE Ae 8 19981028 <.002 <.010 -- <.001 -- <.006 --

CE Ae 9 19981026 <.002 <.005 -- <.001 -- <.006 --

CE Ae 13 19981203 <.002 <.005 -- <.001 -- <.006 --
75

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Metolachlor,

total

Metolachlor,

dissolved

Metribuzin,

dissolved

Metribuzin,

total

Mirex,

total

Molinate,

dissolved

Napropamide,

dissolved

CH-75 19900823 0.1 -- -- <0.1 <0.01 -- --

CH-1720 19921001 -- <0.050 <0.050 -- -- -- --

CH-1720 19930610 -- -- -- -- <.01 -- --

CH-1735 20000906 -- .064 <.004 -- -- <0.004 <0.003

CH-2186 19930818 -- .004 <.004 -- <.01 <.004 <.003

CH-2439 19810817 -- -- -- -- <.01 -- --

CH-2440 19810817 -- -- -- -- <.01 -- --

CH-2459 19820804 -- -- -- -- <.01 -- --

CH-2460 19820804 -- -- -- -- <.01 -- --

CH-2461 19820804 -- -- -- -- <.01 -- --

CH-2461 19830707 -- -- -- -- -- -- --

CH-2461 19950808 -- .005 <.004 -- <.01 <.004 <.003

CH-3316 19880808 < .1 -- -- < .1 <.01 -- --

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 < .1 -- -- < .1 <.01 -- --

CH-4126 19910807 -- <.050 <.050 -- <.01 -- --

CH-4297 19921001 -- <.050 <.050 -- <.01 -- --

CH-4806 19940628 -- <.050 <.050 -- <.01 -- --

CH-4931 19940721 -- <.002 <.004 -- -- <.004 <.003

CH-4933 19940714 -- <.002 <.004 -- -- <.004 <.003

CH-5420 19980615 -- .022 <.004 -- -- <.004 <.003

CH-5421 19980615 -- .006 <.004 -- -- <.004 <.003

CH-5423 19980616 -- .007 <.004 -- -- <.004 <.003

CH-5424 19980624 -- .003 E <.004 -- -- <.004 <.003

CH-5425 19980701 -- <.002 <.004 -- -- <.004 <.003

CH-5426 19981105 -- <.002 <.004 -- -- <.004 <.003

CH-5428 19981103 -- <.002 <.004 -- -- <.004 <.003

CH-5430 19980707 -- .024 <.004 -- -- <.004 <.003

CH-5431 19980707 -- <.002 <.004 -- -- <.004 <.003

CH-5432 19980714 -- <.002 <.004 -- -- <.004 <.003

CH-5433 19980714 -- <.002 <.004 -- -- <.004 <.003

CH-5434 19980715 -- <.002 <.004 -- -- <.004 <.003

CH-5437 19981118 -- <.002 <.004 -- -- <.004 <.003

CH-5439 19981116 -- <.002 <.004 -- -- <.004 <.003

CH-5440 19981104 -- <.002 <.004 -- -- <.004 <.003

CH-5442 19981124 -- <.002 <.004 -- -- <.004 <.003

CH-5443 19981112 -- .005 <.004 -- -- <.004 <.003

CH-5450 20000911 -- <.002 <.004 -- -- <.004 <.003

CH-5470 19960822 -- .024 <.004 -- <.01 <.004 <.003

CH-5476 19960904 -- -- -- -- <.01 -- --

CH-5477 19960904 -- -- -- -- <.01 -- --

CE Ae 8 19981028 -- <.004 <.004 -- -- <.004 <.003

CE Ae 9 19981026 -- <.002 <.004 -- -- <.004 <.003

CE Ae 13 19981203 -- <.002 <.004 -- -- <.004 <.003
76

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Parathion,

dissolved

Parathion,

total

Pebulate,

dissolved

Pendimethalin,

dissolved

Permethrin,

dissolved

Perthane,

total

Phorate,

dissolved

CH-75 19900823 -- <0.01 -- -- -- <0.1 --

CH-1720 19921001 -- -- -- -- -- -- --

CH-1720 19930610 -- <.01 -- -- -- < .1 --

CH-1735 20000906 <0.004 -- <0.004 <0.004 <0.005 <0.002

CH-2186 19930818 <.004 -- <.004 <.004 <.005 < .1 <.002

CH-2439 19810817 -- -- -- -- -- < .1 --

CH-2440 19810817 -- -- -- -- -- < .1 --

CH-2459 19820804 -- -- -- -- -- < .1 --

CH-2460 19820804 -- -- -- -- -- < .1 --

CH-2461 19820804 -- -- -- -- -- < .1 --

CH-2461 19830707 -- <.01 -- -- -- -- --

CH-2461 19950808 <.004 <.004 <.004 <.005 < .1 <.002

CH-3316 19880808 -- <.01 -- -- -- < .1 --

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 -- <.01 -- -- -- < .1 --

CH-4126 19910807 -- <.01 -- -- -- < .1 --

CH-4297 19921001 -- <.01 -- -- -- < .1 --

CH-4806 19940628 -- <.01 -- -- -- < .1 --

CH-4931 19940721 <.004 -- <.004 <.004 <.005 -- <.002

CH-4933 19940714 <.004 -- <.004 <.004 <.005 -- <.002

CH-5420 19980615 <.004 -- <.004 <.004 <.005 -- <.002

CH-5421 19980615 <.004 -- <.004 <.004 <.005 -- <.002

CH-5423 19980616 <.004 -- <.004 <.004 <.005 -- <.002

CH-5424 19980624 <.004 -- <.004 <.004 <.005 -- <.002

CH-5425 19980701 <.004 -- <.004 <.004 <.005 -- <.002

CH-5426 19981105 <.004 -- <.004 <.004 <.005 -- <.002

CH-5428 19981103 <.004 -- <.004 <.004 <.005 -- <.002

CH-5430 19980707 <.004 -- <.004 <.004 <.005 -- <.002

CH-5431 19980707 <.004 -- <.004 <.004 <.005 -- <.002

CH-5432 19980714 <.004 -- <.004 <.004 <.005 -- <.002

CH-5433 19980714 <.004 -- <.004 <.004 <.005 -- <.002

CH-5434 19980715 <.004 -- <.004 <.004 <.005 -- <.002

CH-5437 19981118 <.004 -- <.004 <.004 <.005 -- <.002

CH-5439 19981116 <.004 -- <.004 <.004 <.005 -- <.002

CH-5440 19981104 <.004 -- <.004 <.004 <.005 -- <.002

CH-5442 19981124 <.004 -- <.004 <.004 <.005 -- <.002

CH-5443 19981112 <.004 -- <.004 <.004 <.005 -- <.002

CH-5450 20000911 <.004 -- <.004 <.004 <.005 -- <.002

CH-5470 19960822 <.004 -- <.004 <.004 <.005 < .1 <.002

CH-5476 19960904 -- <.01 -- -- -- < .1 --

CH-5477 19960904 -- -- -- -- -- < .1 --

CE Ae 8 19981028 <.004 -- <.004 <.004 <.005 -- <.002

CE Ae 9 19981026 <.004 -- <.004 <.004 <.005 -- <.002

CE Ae 13 19981203 <.004 -- <.004 <.004 <.005 -- <.002
77

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Phorate,

total

Picloram,

dissolved

Picloram,

total

Prometon,

dissolved

Prometone,

total

Prometryn,

dissolved

Prometryne,

total

CH-75 19900823 <0.01 -- -- -- <0.1 -- <0.1

CH-1720 19921001 -- -- -- <0.050 -- <0.05 --

CH-1720 19930610 <.01 -- -- -- -- --

CH-1735 20000906 -- -- -- <.018 -- -- --

CH-2186 19930818 -- -- -- <.018 -- -- --

CH-2439 19810817 -- -- -- -- -- -- --

CH-2440 19810817 -- -- -- -- -- -- --

CH-2459 19820804 -- -- -- -- -- -- --

CH-2460 19820804 -- -- -- -- -- -- --

CH-2461 19820804 -- -- -- -- -- -- --

CH-2461 19830707 -- -- <0.01 -- < .1 -- < .1

CH-2461 19950808 -- -- -- <.018 -- --

CH-3316 19880808 -- -- -- -- < .1 -- < .1

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 -- -- <.01 -- < .1 -- < .1

CH-4126 19910807 <.02 -- .32 <.050 -- <.05 --

CH-4297 19921001 <.01 -- <.01 <.050 -- <.05 --

CH-4806 19940628 <.01 -- <.01 <.050 -- <.05 --

CH-4931 19940721 -- <0.05 -- <.018 -- -- --

CH-4933 19940714 -- <.05 -- <.018 -- -- --

CH-5420 19980615 -- -- -- <.018 -- -- --

CH-5421 19980615 -- -- -- <.018 -- -- --

CH-5423 19980616 -- -- -- <.018 -- -- --

CH-5424 19980624 -- -- -- <.018 -- -- --

CH-5425 19980701 -- -- -- <.018 -- -- --

CH-5426 19981105 -- -- -- <.018 -- -- --

CH-5428 19981103 -- -- -- <.018 -- -- --

CH-5430 19980707 -- -- -- <.018 -- -- --

CH-5431 19980707 -- -- -- <.018 -- -- --

CH-5432 19980714 -- -- -- <.018 -- -- --

CH-5433 19980714 -- -- -- <.018 -- -- --

CH-5434 19980715 -- -- -- <.018 -- -- --

CH-5437 19981118 -- -- -- <.018 -- -- --

CH-5439 19981116 -- -- -- <.018 -- -- --

CH-5440 19981104 -- -- -- <.018 -- -- --

CH-5442 19981124 -- -- -- <.018 -- -- --

CH-5443 19981112 -- -- -- <.018 -- -- --

CH-5450 20000911 -- -- -- <.018 -- -- --

CH-5470 19960822 -- -- -- <.018 -- -- --

CH-5476 19960904 <.01 -- -- -- -- -- --

CH-5477 19960904 -- -- -- -- -- -- --

CE Ae 8 19981028 -- -- -- <.018 -- -- --

CE Ae 9 19981026 -- -- -- <.018 -- -- --

CE Ae 13 19981203 -- -- -- <.018
78

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Pronamide,

total

Propachlor,

dissolved

Propanil,

dissolved

Propargite,

dissolved

Propazine,

dissolved

Propazine,

total

Silvex,

dissolved

CH-75 19900823 -- -- -- -- -- <0.1 --

CH-1720 19921001 -- -- -- -- <0.05 -- --

CH-1720 19930610 -- -- -- -- -- -- --

CH-1735 20000906 <0.003 <0.0007 <0.004 <0.013 -- -- --

CH-2186 19930818 <.003 <.007 <.004 <.013 -- -- --

CH-2439 19810817 -- -- -- -- -- -- --

CH-2440 19810817 -- -- -- -- -- -- --

CH-2459 19820804 -- -- -- -- -- -- --

CH-2460 19820804 -- -- -- -- -- -- --

CH-2461 19820804 -- -- -- -- -- -- --

CH-2461 19830707 -- -- -- -- -- < .1 --

CH-2461 19950808 <.003 <.007 <.004 <.013 -- -- --

CH-3316 19880808 -- -- -- -- -- < .1 --

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 -- -- -- -- -- < .1 --

CH-4126 19910807 -- -- -- -- <.05 -- --

CH-4297 19921001 -- -- -- -- <.05 -- --

CH-4806 19940628 -- -- -- -- <.05 -- --

CH-4931 19940721 <.003 <.007 <.004 <.013 -- -- <0.02

CH-4933 19940714 <.003 <.007 <.004 <.013 -- -- <.02

CH-5420 19980615 <.003 <.007 <.004 <.013 -- -- --

CH-5421 19980615 <.003 <.007 <.004 <.013 -- -- --

CH-5423 19980616 <.003 <.007 <.004 <.013 -- -- --

CH-5424 19980624 <.003 <.007 <.004 <.013 -- -- --

CH-5425 19980701 <.003 <.007 <.004 <.013 -- -- --

CH-5426 19981105 <.003 <.007 <.004 <.013 -- -- --

CH-5428 19981103 <.003 <.007 <.004 <.013 -- -- --

CH-5430 19980707 <.003 <.007 <.004 <.013 -- -- --

CH-5431 19980707 <.003 <.007 <.004 <.013 -- -- --

CH-5432 19980714 <.003 <.007 <.004 <.013 -- -- --

CH-5433 19980714 <.003 <.007 <.004 <.013 -- -- --

CH-5434 19980715 <.003 <.007 <.004 <.013 -- -- --

CH-5437 19981118 <.003 <.007 <.004 <.013 -- -- --

CH-5439 19981116 <.003 <.007 <.004 <.013 -- -- --

CH-5440 19981104 <.003 <.007 <.004 <.013 -- -- --

CH-5442 19981124 <.003 <.007 <.004 <.013 -- -- --

CH-5443 19981112 <.003 <.007 <.004 <.013 -- -- --

CH-5450 20000911 <.003 <.007 <.004 <.013 -- -- --

CH-5470 19960822 <.003 <.007 <.004 <.013 -- -- --

CH-5476 19960904 -- -- -- -- -- -- --

CH-5477 19960904 -- -- -- -- -- -- --

CE Ae 8 19981028 <.003 <.007 <.004 <.013 -- -- --

CE Ae 9 19981026 <.003 <.007 <.004 <.013 -- -- --

CE Ae 13 19981203 <.003 <.007 <.004 <.013 -- -- --
79

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Silvex,

total

Simazine,

dissolved

Simazine,

total

Tebuthiuron,

dissolved

Terbacil,

dissolved

Terbufos,

dissolved

Thiobencarb,

dissolved

CH-75 19900823 -- -- <0.1 -- -- -- --

CH-1720 19921001 -- <0.050 -- -- -- -- --

CH-1720 19930610 -- -- -- -- -- -- --

CH-1735 20000906 -- <.005 -- <0.010 <0.007 <0.013 <0.002

CH-2186 19930818 -- <.005 -- .034 <.007 <.013 <.002

CH-2439 19810817 -- -- -- -- -- -- --

CH-2440 19810817 -- -- -- -- -- -- --

CH-2459 19820804 -- -- -- -- -- -- --

CH-2460 19820804 -- -- -- -- -- -- --

CH-2461 19820804 -- -- -- -- -- -- --

CH-2461 19830707 <0.01 -- < .1 -- -- -- --

CH-2461 19950808 -- .041 -- <.010 <.007 <.013 <.002

CH-3316 19880808 -- -- < .1 -- -- -- --

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 <.01 -- < .1 -- -- -- --

CH-4126 19910807 <.01 <.050 -- -- -- --

CH-4297 19921001 <.01 <.050 -- -- -- -- --

CH-4806 19940628 <.01 <.050 -- -- -- -- --

CH-4931 19940721 -- <.005 -- <.010 <.007 <.013 <.002

CH-4933 19940714 -- <.005 -- <.010 <.007 <.013 <.002

CH-5420 19980615 -- .003 E -- <.010 <.007 <.013 <.002

CH-5421 19980615 -- <.005 -- <.010 <.007 <.013 <.002

CH-5423 19980616 -- .003 E -- <.010 <.007 <.013 <.002

CH-5424 19980624 -- <.005 -- <.010 <.007 <.013 <.002

CH-5425 19980701 -- <.005 -- <.010 <.007 <.013 <.002

CH-5426 19981105 -- <.005 -- <.010 <.007 <.013 <.002

CH-5428 19981103 -- <.005 -- <.010 <.007 <.013 <.002

CH-5430 19980707 -- .026 -- <.010 <.007 <.013 <.002

CH-5431 19980707 -- <.005 -- <.010 <.007 <.013 <.002

CH-5432 19980714 -- <.005 -- <.010 <.007 <.013 <.002

CH-5433 19980714 -- <.005 -- <.010 <.007 <.013 <.002

CH-5434 19980715 -- <.005 -- <.010 <.007 <.013 <.002

CH-5437 19981118 -- <.005 -- <.010 <.007 <.013 <.002

CH-5439 19981116 -- <.005 -- <.010 <.007 <.013 <.002

CH-5440 19981104 -- <.005 -- <.010 <.007 <.013 <.002

CH-5442 19981124 -- <.005 -- <.010 <.007 <.013 <.002

CH-5443 19981112 -- <.005 -- <.010 <.007 <.013 <.002

CH-5450 20000911 -- <.005 -- <.010 <.007 <.013 <.002

CH-5470 19960822 -- <.005 -- <.010 <.007 <.013 <.002

CH-5476 19960904 -- -- -- -- -- -- --

CH-5477 19960904 -- -- -- -- -- -- --

CE Ae 8 19981028 -- <.036 -- <.010 <.007 <.013 .003 E

CE Ae 9 19981026 -- <.005 -- <.010 <.007 <.013 <.002

CE Ae 13 19981203 -- .011 -- <.010 <.007 <.013 <.002
80

Table 21. Results of laboratory analyses for pesticides in ground water, Big Elk Creek Basin, Pennsylvania and

Maryland—Continued

Wellidentification

number

Date of

sample

Toxaphene,

total

Triallate,

dissolved

Trifluralin,

dissolved

Trifluralin,

total

2,6-Diethylaniline,

dissolved

2,4,5-T,

dissolved

2,4,5-T,

total

CH-75 19900823 <1 -- -- <0.1 -- -- --

CH-1720 19921001 -- -- -- -- -- -- --

CH-1720 19930610 <1 -- -- -- -- -- --

CH-1735 20000906 -- <0.001 <0.002 -- <0.003 -- --

CH-2186 19930818 < 1 <.001 <.002 -- <.003 -- --

CH-2439 19810817 < 1 -- -- -- -- -- --

CH-2440 19810817 < 1 -- -- -- -- -- --

CH-2459 19820804 < 1 -- -- -- -- -- --

CH-2460 19820804 < 1 -- -- -- -- -- --

CH-2461 19820804 < 1 -- -- -- -- -- --

CH-2461 19830707 -- -- -- -- -- -- <0.01

CH-2461 19950808 < 1 <.001 .001 E -- <.003 -- --

CH-3316 19880808 < 1 -- -- < .1 -- -- --

CH-3316 19900906 -- -- -- -- -- -- --

CH-3317 19880808 < 1 -- -- < .1 -- -- <.01

CH-4126 19910807 < 1 -- -- -- -- -- <.01

CH-4297 19921001 < 1 -- -- -- -- -- <.01

CH-4806 19940628 < 1 -- -- -- -- -- <.01

CH-4931 19940721 -- <.001 <.002 -- <.003 <0.04 --

CH-4933 19940714 -- <.001 <.002 -- <.003 <.04 --

CH-5420 19980615 -- <.001 <.002 -- <.003 -- --

CH-5421 19980615 -- <.001 <.002 -- <.003 -- --

CH-5423 19980616 -- <.001 <.002 -- <.003 -- --

CH-5424 19980624 -- <.001 <.002 -- <.003 -- --

CH-5425 19980701 -- <.001 <.002 -- <.003 -- --

CH-5426 19981105 -- <.001 <.002 -- <.003 -- --

CH-5428 19981103 -- <.001 <.002 -- <.003 -- --

CH-5430 19980707 -- <.001 <.002 -- <.003 -- --

CH-5431 19980707 -- <.001 <.002 -- <.003 -- --

CH-5432 19980714 -- <.001 <.002 -- <.003 -- --

CH-5433 19980714 -- <.001 <.002 -- <.003 -- --

CH-5434 19980715 -- <.001 <.002 -- <.003 -- --

CH-5437 19981118 -- <.001 <.002 -- <.003 -- --

CH-5439 19981116 -- <.001 <.002 -- <.003 -- --

CH-5440 19981104 -- <.001 <.002 -- <.003 -- --

CH-5442 19981124 -- <.001 <.002 -- <.003 -- --

CH-5443 19981112 -- <.001 <.002 -- -- -- --

CH-5450 20000911 -- <.001 <.002 -- <.003 -- --

CH-5470 19960822 < 1 <.001 <.002 -- <.003 -- --

CH-5476 19960904 < 1 -- -- -- -- -- --

CH-5477 19960904 < 1 -- -- -- -- -- --

CE Ae 8 19981028 -- <.001 <.002 -- <.003 -- --

CE Ae 9 19981026 -- <.001 <.002 -- <.003 -- --

CE Ae 13 19981203 -- <.001 <.002 -- <.003 -- --
81

Table 21. Results of laboratory analyses for pesticides in ground water,

Big Elk Creek Basin, Pennsylvania and Maryland—Continued

Wellidentification

number

Date of

sample

2,4-D,

total

2,4-D,

dissolved

2,4-DP,

total

CH-75 19900823 -- -- --

CH-1720 19921001 -- -- --

CH-1720 19930610 -- -- --

CH-1735 20000906 -- -- --

CH-2186 19930818 -- -- --

CH-2439 19810817 -- -- --

CH-2440 19810817 -- -- --

CH-2459 19820804 -- -- --

CH-2460 19820804 -- -- --

CH-2461 19820804 -- -- --

CH-2461 19830707 <0.01 -- <0.01

CH-2461 19950808 -- -- --

CH-3316 19880808 -- -- --

CH-3316 19900906 -- -- --

CH-3317 19880808 <.01 -- <.01

CH-4126 19910807 <.01 -- <.01

CH-4297 19921001 <.01 -- <.01

CH-4806 19940628 <.01 -- <.01

CH-4931 19940721 -- <0.04 --

CH-4933 19940714 -- <.04 --

CH-5420 19980615 -- --

CH-5421 19980615 -- -- --

CH-5423 19980616 -- -- --

CH-5424 19980624 -- -- --

CH-5425 19980701 -- -- --

CH-5426 19981105 -- -- --

CH-5428 19981103 -- -- --

CH-5430 19980707 -- -- --

CH-5431 19980707 -- -- --

CH-5432 19980714 -- -- --

CH-5433 19980714 -- -- --

CH-5434 19980715 -- -- --

CH-5437 19981118 -- -- --

CH-5439 19981116 -- -- --

CH-5440 19981104 -- -- --

CH-5442 19981124 -- -- --

CH-5443 19981112 -- -- --

CH-5450 20000911 -- -- --

CH-5470 19960822 -- -- --

CH-5476 19960904 -- -- --

CH-5477 19960904 -- -- --

CE Ae 8 19981028 -- -- --

CE Ae 9 19981026 -- -- --

CE Ae 13 19981203 -- -- --