U.S. Department of the Interior

U.S. Geological Survey

Historical Trends and Concentrations

of Fecal Coliform Bacteria

in the Brandywine Creek Basin,

Chester County, Pennsylvania

by Debra A. Town

Water-Resources Investigations Report 01-4026

Prepared in cooperation with the

CHESTER COUNTY WATER RESOURCES AUTHORITY

CHESTER COUNTY HEALTH DEPARTMENT

New Cumberland, Pennsylvania

2001
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, Colorado 80225-0286
iii

CONTENTS

Page

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

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

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description of study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Fecal-indicator bacteria and water quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Methods of site selection, data collection, and data analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Data collection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Spatial analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Historical trends in fecal coliform bacteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Factors affecting bacteria concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Land use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Field-measured properties of water and streamflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Seasonality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Effect of reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Comparison of bacteria concentrations during base flow and stormflow. . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Extent and potential sources of fecal and Escherichia Coli bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

West Branch Brandywine Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

East Branch Brandywine Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Main Stem Brandywine Creek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Point discharges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Selected references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
iv

ILLUSTRATIONS

Page

Figures 1-2. Maps showing:

1. Location of Brandywine Creek Basin, Chester County, Pennsylvania. . . . . . . . . .2

2. Sampling sites in the Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . . .6

figures 3-4. Graphs showing:

3. Annual median concentrations of fecal coliform bacteria at Brandywine

Creek at Chadds Ford, East Branch Brandywine Creek below

Downingtown, and West Branch Brandywine Creek at Modena,

1973-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

4. Relation between streamflow and concentration of fecal coliform bacteria,

Brandywine Creek at Chadds Ford, East Branch Brandywine Creek

below Downingtown, and West Branch Brandywine Creek at

Modena, 1973-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

figures 5-10. Boxplots showing:

5. Distribution of annual median concentrations of fecal coliform bacteria at

three USGS long-term water-quality monitor and streamflowmeasurement stations during base flow and stormflow, Brandywine

Creek Basin, 1973-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

6. Distribution of concentrations of fecal coliform bacteria during base flow

and stormflow at sites in agricultural, forested, residential, and mixed

subbasins, Brandywine Creek Basin, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . .12

7. Distribution of monthly water temperatures during base flow and

stormflow at West Branch Brandywine Creek at Modena, East Branch

Brandywine Creek below Downingtown and Brandywine Creek at

Chadds Ford, 1990-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

8. Distribution of monthly fecal coliform bacteria concentrations for base

flow and stormflow, West Branch Brandywine Creek at Modena,

East Branch Brandywine Creek below Downingtown, and

Brandywine Creek at Chadds Ford, 1990-99 . . . . . . . . . . . . . . . . . . . . . . . . . .15

9. Distribution of concentrations of fecal coliform bacteria during base flow

and stormflow at sampling sites above and below Chambers Lake

Reservoir, Rock Run Reservoir, and Marsh Creek Reservoir, 1998-99 . . . . .16

10. Distribution of fecal coliform bacteria concentrations during base flow and

stormflow at selected sampling sites in the Brandywine Creek Basin,

1998-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

figures 11-12. Maps showing median concentrations of fecal coliform bacteria:

11. During base flow, Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . . . . .20

12. During stormflow, Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . . . .21

figures 13-15. Boxplots showing distribution of concentrations of fecal coliform bacteria:

13. During base flow and stormflow at sampling sites on West Branch

Brandywine Creek, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

14. During base flow and stormflow at sampling sites on East Branch

Brandywine Creek, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

15. During base flow and stormflow at sampling sites on main stem

Brandywine Creek, 1998-99. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
v

TABLES

Page

Table 1. Sites sampled for bacteria, Brandywine Creek Basin, Chester County, Pennsylvania . . . . . .4

2. Indicator bacteria, filter size, ideal count range, holding times, and incubation time

and temperature for collected bacteria samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

3. Quality-control results for fecal coliform and E. coli bacteria, Brandywine Creek Basin,

1998-99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

4. Spearman rank correlations significant at the 95-percent confidence interval for baseflow and stormflow samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

5. Range and median concentrations of fecal coliform bacteria during base flow and

stormflow for five sites in the Brandywine Creek Basin, 1998-99 . . . . . . . . . . . . . . . . . . . .17

table 6-11. Streamflow, physical and chemical properties, and fecal coliform and

E. coli bacteria concentrations:

6. During base flow, West Branch Brandywine Creek Basin, July 1998

to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

7. During base flow, East Branch Brandywine Creek Basin, July 1998

to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

8. During base flow, main stem Brandywine Creek Basin, July 1998

to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

9. During storms, West Branch Brandywine Creek Basin, July 1998

to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

10. During storms, East Branch Brandywine Creek Basin, July 1998

to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

11. During storms, main stem Brandywine Creek Basin, July 1998

to September 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
vi

CONVERSION FACTORS AND ABBREVIATIONS

Temperature: Temperature is given in degrees Celsius (°C), which can be converted to degrees Fahrenheit

(°F) by use of the following equation:

°F = 1.8 (°C) + 32

Concentrations of bacteria are given in colonies per 100 milliliters (col/100 mL), which is the same as

colony forming units per 100 milliliters (CFU/100 mL).

Other abbreviations used in report:

mg/L milligrams per liter

mS/cm microsiemens per centimeter at 25 degrees Celsius

mL milliliters

E. coli Escherichia coli, a fecal-indicator bacterium

mTEC Membrane filter media for Escherichia coli

CWA Clean Water Act

DMR Discharge Monitoring Report

USGS U.S. Geological Survey

USEPA U.S. Environmental Protection Agency

PaDEP Pennsylvania Department of Environmental Protection

CCWRA Chester County Water Resources Authority

CCHD Chester County Health Department

Multiply By To obtain

inch (in.) 2.54 centimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

square mile (mi2) 2.590 square kilometer

cubic foot per second (ft3/s) 0.02832 cubic meter per second
1

ABSTRACT

The Brandywine Creek in Chester County is used

for recreation and as an important source of drinking

water. For this study, 40 sites were established for

collection of water samples for analysis of fecal coliform

and Escherichia coli bacteria in 1998-99. Samples were

collected during base-flow conditions and during five

storms in which rainfall exceeded 0.5 inch. During baseflow conditions, the median concentrations of fecal

coliform bacteria exceeded 200 col/100 mL at 26 of the

40 sites (65 percent). During stormflow conditions, the

median concentration of fecal coliform bacteria exceeded

the Pennsylvania Department of Environmental

Protection (PaDEP) criterion of 200 col/100 mL at 30 of

33 sites sampled (91 percent). Trends in fecal coliform

bacteria concentrations were downward for the period

1973-99 at three long-term water-quality monitor

stations, the result of upgrades in wastewater treatment

plants, decreases in point-source discharges, and a

decrease in agricultural land. A positive relation exists

between streamflow and concentrations of fecal coliform

bacteria at two of the long-term stations, but

concentrations are elevated in base flow and stormflow

at all three stations.

Factors affecting bacteria concentrations in the

Brandywine Creek Basin include nonpoint-source

contaminants, reservoirs, seasonality, and stormflow.

Nonpoint sources of bacterial contamination in the

basin include, but are not limited to, land-surface

runoff, urbanization, agricultural processes, groundwater contamination, and wildlife. Bacteria concentrations in streams that flow directly from the reservoirs

are much lower than the concentrations in the streams

flowing into the reservoirs. During March, April, May,

October, and November, the Brandywine Creek tends to

have lower water temperatures and bacteria

concentrations than during June, July, August, and

September. The 10-year median concentrations of

bacteria at West Branch Brandywine Creek at Modena

and East Branch Brandywine Creek below

Downingtown exceed the criterion of 200 col/100 mL

established by the PaDEP during the swimming season.

The 10-year median concentrations of bacteria at

Brandywine Creek at Chadds Ford exceed the criterion

of 200 col/100 mL only during June. None of the

stations exceed the criterion of 2,000 col/100 mL as

established by the PaDEP for the remainder of the year.

INTRODUCTION

The aesthetic, recreational, and ecological

health of the Brandywine Creek in Chester County

may be influenced by high concentrations of fecal

coliform bacteria. Chapter 93 of the “Pennsylvania

Water Quality Standards” lists the following as

uses for the Brandywine Creek: water supply

(potable, industrial, and livestock), irrigation,

aesthetics, boating and fishing, wildlife water

supply, trout stocking, and fishes (warmwater,

coldwater, and migratory) (Pennsylvania

Department of Environmental Protection, 1999,

p. 62). Five public water suppliers in Chester

County withdraw water from the Brandywine

Creek for domestic, commercial, and industrial

use. Three reservoirs on the creek play host to

boaters, fishermen, and canoeists (Grieg and

others, 1998).

As part of a cooperative program among the

Chester County Water Resources Authority

(CCWRA), Chester County Health Department

(CCHD), and the U.S. Geological Survey (USGS),

fecal coliform bacteria, temperature, pH, dissolved

oxygen, and specific conductance of the

Brandywine Creek are measured at the West

Branch Brandywine Creek at Modena (USGS

station number 01480617), the East Branch

Brandywine Creek below Downingtown (USGS

HISTORICAL TRENDS AND CONCENTRATIONS

OF FECAL COLIFORM BACTERIA

IN THE BRANDYWINE CREEK BASIN,

CHESTER COUNTY, PENNSYLVANIA

by Debra A. Town
2

station number 01480870), and the main stem of

the Brandywine Creek at Chadds Ford (USGS

station number 01481000) (fig. 1). Temperature,

pH, dissolved oxygen, and specific conductance

are measured hourly, and concentrations of fecal

coliform bacteria are measured bi-weekly. Data

have been collected from March to November

(Wood, 1998) since 1973 at main stem Brandywine

Creek at Chadds Ford, since 1980 at East Branch

Brandywine Creek below Downingtown, and since

1981 at West Branch Brandywine Creek at Modena.

Data from the long-term water-quality monitor

stations show that concentrations of fecal coliform

bacteria during storms typically are greater than

those during base flow. Water samples containing

fecal coliform bacteria typically contain Escherichia

coli (E. coli) bacteria, which indicate the potential

presence of water-borne pathogens that may

present a public health risk for humans that

consume or have bodily contact with contaminated

water (Dufour, 1977).

This study supports the objectives and goals of

Chester County’s Landscapes program (Chester

County, 1996, p. 114). The study will help to

achieve and sustain a high-quality natural resource

system and will help to protect public health and

safety. This report also reinforces the Phase I and II

results of the Christina River Basin Water Quality

Management Strategy (Grieg and others, 1998).

The Christina project aims at improving water

quality and addressing nonpoint-source pollution

reduction; the CCWRA is a local coordinator.

Figure 1. Location of Brandywine Creek Basin, Chester County, Pennsylvania.
3

Purpose and Scope

This report identifies trends in historical

concentrations of fecal coliform bacteria at three

USGS long-term water-quality monitor and

streamflow-measurement stations on the

Brandywine Creek from 1973 to 1999. Relations

between concentrations of fecal coliform bacteria

and streamflow also are compared for the stations.

This report discusses the extent and possible types

of sources for fecal coliform and E. coli bacteria in

the Brandywine Creek Basin. Bacteria data, field

chemistry, and streamflow measurements were

collected by the USGS at 40 sites on the Brandywine Creek during July through October 1998 and

March through September 1999 during base flow

and stormflow. Relations between fecal coliform

bacteria and field chemistry constituents are

determined. Relations between land use and

concentrations of fecal coliform bacteria are

compared. The effect of the three reservoirs in the

basin on bacteria concentrations is evaluated.

Other factors, such as the ratio of E. coli to fecal

coliform bacteria in water samples and seasonality,

are discussed. Water-sample analyses are

evaluated to determine the current extent of

bacterial contamination from the subbasins in the

Brandywine Creek Basin.

The length of the study and the number of sites

determined that the evaluation of potential sources

for bacteria would be limited to the subbasin level

within the basin rather than specific sources for

bacteria. Bacterial contamination is identified on

the basis of the median concentration of fecal

coliform bacteria for each subbasin during base

flow and stormflow.

Acknowledgments

The author gratefully acknowledges the

assistance of Linda Tracey of the CCHD, who was

a tremendous asset with the interlaboratory

quality assessment of the bacteria analyses. In

addition, USGS interns Carrie Gillespie, Tammi

Renninger, and Kiley McDaniel contributed a great

deal of time and effort to the data-collection phase

of the project along with USGS staff members

Kevin Grazul, Cynthia Rowland-Lesitsky, and

Abdul Mohammad. The cartography in this report

was completed by Scott Hoffman of the USGS in

Lemoyne, Pa.

Description of the Study Area

The Brandywine Creek Basin drainage area is

approximately 325 mi2, most of which is in Chester

County, Pa. The estimated population in 1998 was

197,460 (Greig and others, 1998). The Brandywine

Creek is one of four streams that constitute the

larger Christina River Basin, which drains to the

Delaware River. Land use in the West Branch

Brandywine Creek Basin is predominantly

agricultural with an urban area around the city of

Coatesville. The East Branch Brandywine Creek

Basin is predominantly forested with an urban

area around the borough of Downingtown. The

main stem basin is predominantly agricultural.

The Brandywine Creek is lined by forest for most

of its length.

The Brandywine Creek Basin lies in the

Piedmont Physiographic Province. Typically,

diabase, gneiss, and marble are found north of the

Great Valley. The borough of Downingtown and

the City of Coatesville lie in the Great Valley, which

is underlain by limestone and dolomite and cuts a

midline through the basin. Schists and gneisses

make up the bedrock of the southern part of the

basin.

The Brandywine Creek attracts canoeists,

fisherman, waders, and even cyclists and hikers

who use the paved areas beside the creek to bike

and walk. While most of these activities are

pursued during the swimming season, recreational

use around the creek goes on year-round.

Latitude and longitude locations were

established for each of the 40 sampling sites along

the Brandywine Creek (table 1). A USGS stationidentification number, station name, local alphanumeric identification number, drainage area of

each site’s subbasin, and the subbasin’s land-use

percentages also are listed.

FECAL-INDICATOR BACTERIA

AND WATER QUALITY

Fecal coliform bacteria are present in water

when bacterial pathogens from fecal

contamination are present. Indicator organisms,

such as fecal coliform bacteria, are not usually

pathogenic but rather indicate the possible

presence of pathogenic organisms. Because fecal

coliform bacteria are present in higher

concentrations than the actual pathogens and

because they can survive longer, the bacteria are

more likely to be detected. Fecal coliform bacteria
4

Table 1. Sites sampled for bacteria, Brandywine Creek Basin, Chester County, Pennsylvania

[ID, identification number; USGS, U.S. Geological Survey; WB, West Branch; EB, East Branch; MS, main stem]

Local

ID

USGS

site ID Site name Latitude Longitude

Drainage

area

(square

miles)

Percentage land use

Agricultural Forested Residential Urban

WB1 01480269 WB Brandywine Creek at Rockville 40 04 50 75 52 20 5.68 72.0 11.0 9.0 0.5

WBA 01480295 Two Log Run at Birdell 40 04 06 75 52 25 2.75 34.0 54.0 9.9 1.0

WB2 101480300 WB Brandywine Creek near Honey Brook 40 04 22 75 51 40 18.4 68.0 20.0 7.0 1.0

WB3 01480349 WB Brandywine Creek at Brandamore 40 02 39 75 49 51 24.0 58.0 27.0 10.0 1.0

WB4 01480390 Birch Run near Martins Corner 40 01 50 75 52 20 2.48 30.0 54.0 13.0 8.0

WB5 101480400 Birch Run near Wagontown 40 01 38 75 50 43 4.66 31.0 53.0 13.0 2.0

WB6 01480458 Rock Run near Philipsville 40 00 20 75 52 44 2.32 58.0 29.0 10.0 2.0

WBE 01480463 Rock Run at Reservoir near Coatesville 40 00 07 75 51 20 5.11 52.0 26.0 17.0 2.0

WB7 01480466 Rock Run below Coatesville Reservoir 40 00 22 75 51 09 5.56 49.0 26.0 16.0 2.0

WBD 01480470 Rock Run at Rock Run near Coatesville 39 59 34 75 49 53 45.5 47.0 33.0 14.0 2.0

WBB 01480434 WB Brandywine Creek at Rock Run 39 59 36 75 49 41 37.6 48.0 33.0 14.0 1.0

WBC 01480480 WB Brandywine Creek below Rock Run at

Coatesville

39 59 28 75 49 52 45.7 47.0 33.0 15.0 2.0

WB8 1

01480500 WB Brandywine Creek at Coatesville

Reservoir

39 59 08 75 49 40 46.0 47.0 33.0 15.0 2.0

WB9 101480617 WB Brandywine Creek at Modena 39 57 42 75 48 06 55.3 42.0 33.0 16.0 4.0

WB10 01480629 Buck Run at Doe Run 39 55 46 75 49 24 21.5 58.0 26.0 11.0 2.0

WB11 014806318 Doe Run above tributary at Springdell 39 54 25 75 49 42 8.76 76.0 15.0 5.1 1.0

WB12 01480634 WB Brandywine Creek near Embreeville 39 56 04 75 45 00 116.0 53.0 30.0 12.0 3.0

WB13 01480637 Little Broad Run near Marshallton 39 57 38 75 42 44 1.02 38.0 27.0 26.0 5.0

WB14 01480638 Broad Run at Northbrook 39 55 49 75 41 06 6.38 37.0 29.0 29.0 3.0

WB15 01480640 WB Brandywine Creek at Wawaset 39 55 34 75 39 47 134.0 52.0 30.0 12.0 3.0

EB1 01480648 EB Brandywine Creek near Cupola 40 05 41 75 51 14 6.86 60.0 25.0 7.0 1.0

EB2 01480653 EB Brandywine Creek at Glenmoore 40 05 48 75 46 44 16.2 53.0 34.0 7.0 .4

EB3 01480658 Indian Run at Springton 40 04 32 75 46 55 4.26 37.0 46.0 12.0 3.0

EB4 101480675 Marsh Creek near Glenmoore 40 05 52 75 44 31 8.53 39.0 46.0 8.0 3.0

EB5 101480685 Marsh Creek near Downingtown 40 03 19 75 43 00 20.1 34.0 38.0 17.0 2.0

EB6 01480660 EB Brandywine Creek at Lyndell 40 03 34 75 44 39 27.1 45.0 39.0 10.0 1.0

EB7 01480662 Culbertson Run at Lyndell 40 03 29 75 45 07 4.41 44.0 33.0 21.0 1.0

EB8 101480700 EB Brandywine Creek near Downingtown 40 02 05 75 42 32 60.0 39.0 37.0 16.0 2.0

EB9 01480775 Beaver Creek near Downingtown 40 00 12 75 43 28 16.5 33.0 29.0 25.0 4.0

EBA 01480800 EB Brandywine Creek at Downingtown 40 00 19 75 42 18 76.4 36.0 36.0 19.0 3.0

EBC 01480840 EB Brandywine Creek at Altor 39 58 33 75 40 59 89.0 34.0 37.0 20.0 3.0

EB13 01480878 Uwchlan Run at Exton 40 01 35 75 39 52 1.50 67.0 16.0 10.0 2.0

EBB 01480887 Valley Creek at Ravine Road near

Downingtown

39 59 55 75 39 52 14.4 20.0 31.0 26.0 7.0

EB10 101480870 EB Brandywine Creek below

Downingtown

39 58 07 75 40 25 89.7 34.0 37.0 20.0 3.0

EB11 01480905 Valley Creek at Altor 39 58 12 75 39 59 20.6 30.0 33.0 19.0 7.0

EB12 01480930 Taylor Run at Copesville 39 57 19 75 38 55 5.52 23.0 26.0 37.0 4.0

EB14 01480950 EB Brandywine Creek at Wawaset 39 55 35 75 38 54 123.0 31.0 35.0 22.0 4.0

MS1 01480970 Brandywine Creek at Pocopson 39 54 04 75 37 26 264.0 42.0 32.0 17.0 3.0

MS2 01480975 Pocopson Creek at Pocopson 39 54 03 75 38 16 8.57 49.0 21.0 26.0 1.0

MS3 1

01481000 Brandywine Creek at Chadds Ford 39 52 11 75 35 37 288.0 42.0 32.0 18.0 3.0

1 USGS streamflow-measurement station.
5

are easy to culture and typically are harmless to

humans; therefore, they were chosen as the

primary indicator bacteria. Because fecal coliform

bacteria were sampled from 1973 to 1999 in the

Brandywine Creek, the historical data could be

compared with data collected for this study.

The Pennsylvania Department of Environmental

Protection (PaDEP) and the U.S. Environmental

Protection Agency (USEPA) have the same set of

criteria on the basis of water use. For bathing (fullbody contact) in recreational freshwater, on the

basis of a statistically sufficient number of samples

(generally not less than five samples equally

spaced over a 30-day period), the geometric mean

of the indicated bacterial densities of fecal coliform

should not exceed 200 col/100 mL during the

swimming season (May 1 through September 30)

and should not exceed 2,000 col/100 mL for the

remainder of the year. (Pennsylvania Department

of Environmental Protection, 1999, p. 16).

For water supply, bacteria concentrations should

not exceed 5,000 col/100 mL as a monthly average

in more than 20 percent of the samples collected

during a month and should not exceed

20,000 col/100 mL in more than 5 percent of the

samples (Pennsylvania Department of

Environmental Protection, 1999).

E. coli bacteria are found within the fecal

coliform group in smaller concentrations than fecal

coliform bacteria. E. coli were chosen as the

secondary indicator of bacterial contamination

because they are a specific indicator of fecal

pollution. E. coli inhabit the gastrointestinal tract of

warm-blooded animals and are an indicator of the

presence of intestinal pathogens that cause human

diseases (Francy and others, 1993). The USEPA

(1998) has set a criterion on the basis of water use.

For bathing (full-body contact) in recreational

freshwater, on the basis of a statistically sufficient

number of samples (generally not less than five

samples equally spaced over a 30-day period), the

geometric mean of the indicated bacterial densities

of E. coli should not exceed 126 col/100 mL.

Fecal-indicator bacteria assess the sanitary

quality of water and include Enterococci, the

coliform group, and the streptococcal group. For

this study, the coliform group were used as the

indicator organisms of choice. Within the coliform

group, total coliforms (of which fecal coliform and

E. coli are part), fecal coliforms (of which E. coli is

part), and E. coli are the most widely used

indicators. Total coliforms, and to some extent fecal

coliforms, have been used as indicators of the

possible presence of pathogens in surface waters

and have been associated with a risk of disease on

the basis of epidemiological evidence of

gastrointestinal disorders from ingestion of

contaminated surface water. Contact with

pathogens in contaminated surface water can

cause ear or skin infections or respiratory diseases.

The pathogens responsible for these diseases can

be bacteria, viruses, protozoans, fungi, or parasites

that live in the gastrointestinal tract and are shed in

the feces of warm-blooded animals. Because it is

difficult to analyze for this myriad of pathogens,

fecal coliform and E. coli bacteria are used as the

primary indicators of fecal contamination in

recreational waters. E. coli is considered to have a

high degree of association with outbreaks of

certain diseases and are recommended as a fecalindicator for bacterial water-quality standards by

the USEPA (1986).

Bacterial contamination can come from point

and nonpoint sources. Point sources are single,

identifiable points of origin, such as municipal or

industrial discharges. Nonpoint sources are from

diffuse origins. Agricultural nonpoint sources

include animal waste, the application of manure

and biosolids to fields, and crop irrigation from

contaminated storage ponds. Urban/residential

nonpoint sources include active construction areas,

failed waste-disposal systems, residential septic

systems, pet waste, litter, and landfill leakage.

Wildlife waste also is a nonpoint source. The

Brandywine Creek is affected by nonpoint sources

of bacterial contamination during base flow and

especially during stormflow.

METHODS OF SITE SELECTION,

DATA COLLECTION, AND DATA ANALYSIS

Data were collected by the USGS from July to

October 1998 as part of a reconnaissance sampling

of the Brandywine Creek Basin under base-flow

conditions to determine preliminary base-flow

concentrations of fecal coliform bacteria. This

information, along with data from the PaDEP and

the CCHD, were used to determine the location of

base-flow sampling sites. Site locations also were

selected on the basis of land use, known point

discharges, and areas where recreational use was

evident. Thirty-two sites initially were selected for

sample collection. All nine USGS streamflowmeasurement stations in the basin were used as

sampling sites. Eight additional sampling sites

were added midway through the study to pinpoint
6

potential sources of elevated bacteria measured

during monthly sampling (fig. 2).

Data Collection

Water samples were collected for analysis for

fecal coliform and E. coli bacteria at the sites

established as a result of the reconnaissance

sampling. Sampling frequency was approximately

monthly from March to September 1999 to provide

sufficient temporal variation and different flow

regimes for the evaluation of bacterial

contamination. Fecal coliform bacteria were

measured monthly at all 40 sites during base flow,

and E. coli bacteria were measured monthly at a

subset of those 40 sites during base flow. During

the course of the study, each of the initial 32 sites

was sampled for E. coli bacteria at least once

during base flow.

Figure 2. Sampling sites in the Brandywine Creek Basin, Chester County, Pennsylvania,

1998-99. (See table 1 for full names and characteristics of sampling sites.)
7

Storm sampling also was conducted as a part

of this study. Data were collected during five

storms in which rainfall exceeded 0.5 in. Most of

the USGS streamflow-measurement stations were

sampled during every storm. The selection of these

stations as sampling sites eliminated the need for

current-meter measurements of streamflow.

During storms, only specific conductance,

temperature, and gage height were measured at

the time the sample was collected. In addition, for

each storm, five sites not at streamflowmeasurement stations were sampled.

All water samples were analyzed for fecal

coliform and E. coli bacteria by use of the

membrane filtration method described in Myers

and Wilde (1997) (table 2). Water samples were

collected as grab samples, by use of individually

labeled sterile 250-mL plastic bags. The plastic bag

was submerged in the stream at the center of flow

and opened to allow water to enter. It was then

sealed and placed in a cooler for transportation to

the laboratory. Samples were incubated

immediately after filtration. CCHD samples were

collected in 250-mL plastic bottles. The bottles

were submerged in the stream in the same place as

the plastic bags, opened and filled with water, and

sealed and placed in a cooler for transportation to

the CCHD laboratory.

Field chemistry measurements and streamflow

measurements were made for all base-flow

samples collected. Field chemistry included

dissolved oxygen, pH, specific conductance, and

water temperature. Dissolved oxygen was

measured by use of the Winkler Method (Clesceri

and others, 1998). The pH, specific conductance,

and water temperature were measured with

meters.

Quality assurance was conducted by USGS

and CCHD personnel by use of guidelines from

Clesceri and others (1998). Quality-assurance

methods were used in the field and the laboratory

and for the equipment and media. Quality control

was conducted according to guidelines from

Clesceri and others (1998). Quality control for

variability was conducted by use of interlaboratory

comparisons of sequential replicate samples.

Duplicate samples were analyzed by the CCHD

laboratory. Quality-control results are shown in

table 3. Quality control for bias was conducted by

use of membrane filter equipment blanks with

sterile buffered water filtered and plated before

every sample to test for contamination.

Data Analysis

Bacteria concentrations in samples collected

from July to October 1998 and from March to

September 1999 from the Brandywine Creek Basin

were compared to maximum acceptable

concentrations established by the PaDEP (1999).

Median concentrations of fecal coliform

bacteria were calculated for all 40 sites. A limited

number of samples were analyzed for E. coli

bacteria at each site; therefore, median

concentrations of E. coli bacteria were not

determined for either base flow or stormflow.

Graphical analyses (boxplots) were used to

evaluate water-quality measurements and bacteria

concentration during base flow and stormflow. The

water-quality measurements and bacteriaconcentration data collected during base flow and

stormflow are listed in tables 6-11 at the end of this

report. Graphical analyses also were used to

evaluate historical data at three USGS long-term

water-quality monitoring and streamflowmeasurement stations on Brandywine Creek.

Table 2. Indicator bacteria, filter size, ideal count range, holding times, and incubation time and temperature for

collected bacteria samples (from Myers and Wilde, 1997)

[m-FC, fecal coliform media; M-TEC, Escherichia coli media; °C, degrees Celsius]

Indicator bacteria

(and media type)

Filter size

(microns)

Ideal count

range

(colonies per

filter)

Holding

time Incubation time and temperature

Fecal coliform bacteria

(m-FC media)

0.65 20-60 6 hours 22 to 26 hours at 44.5°C

Escherichia coli bacteria

(m-TEC media)

.45 20-80 6 hours 2 hours at 35.0°C and then 22 to 24 hours at 44.5°C

(filter then transferred to urea substrate broth for

15 to 20 minutes before counting).
8

Relations between bacteria, chemical

constituents, and streamflow for data collected in

1998-99 were evaluated statistically by use of

Spearman Rank correlations significant at the

95-percent confidence interval. Relations were

evaluated at base-flow and stormflow conditions.

Relations between bacteria concentrations and

land use were evaluated statistically by use of the

Kruskal-Wallis test.

Spatial Analysis

A geographical information system (GIS)

spatial analysis was used to determine the landuse percentages of the subbasins within the

Brandywine Creek Basin. Land use was divided

into four categories: agricultural, forested,

residential, and urban. The agricultural category

consists of cropland, livestock, and pasture.

Forested areas are defined as those with more than

50 percent cover of deciduous, coniferous, and

mixed woody vegetation. The residential category

consists of areas of single- and multi-family

residences. Urban areas include institutions,

transportation/utilities, commercial businesses,

and industries. All other categories—examples

would be mining, water, vacant/barren, public

and private open space—constituted a very low

percentage of land use and were not used in the

spatial analysis. The Brandywine Creek Basin was

divided into 40 subbasins relative to each sampling

site. An individual subbasin usually extended

from each sampling site to the sampling site

immediately upstream from it. Where sampling

sites were clustered (as in the supplemental sites),

a subbasin included both the initial sites and

supplemental sites. A land-use coverage obtained

from the Water Resources Agency for New Castle

County was used to determine the percentages of

each type of land use within each subbasin.

Subbasins with greater than 50 percent of one type

of land use were designated as predominantly that

type of land use. Subbasins with less than

50 percent of one type of land use were assigned a

“mixed” designation. Although the urban category

was used to differentiate land use during the GIS

spatial analysis and did not appear as a predominant land use, it is an indicator of areas of nonpoint

source land-surface runoff.

Twenty-five sites were identified as being in

subbasins of mixed land use (table 1), 11 sites were

identified as being in predominantly agricultural

subbasins, 3 sites were identified as being in

predominantly forested subbasins, and 1 site was

identified as being in a predominantly residential

Table 3. Quality-control results for fecal coliform and E. coli bacteria,

Brandywine Creek Basin, Chester County, Pennsylvania, 1998-99

[ID, identification number; —, no data collected; FC, fecal coliform; EC, E. coli;

E, estimated; >, greater than; col/100 mL, colonies per 100 milliliters; CCHD,

Chester County Health Department; USGS, U.S. Geological Survey]

Date Local ID Site ID

FC Concentrations

(col/100 mL)

EC Concentrations

(col/100 mL)

CCHD USGS CCHD USGS

05/04/99 EB4 01480675 23.E 12.E 15.E 2.E

05/04/99 EB8 01480700 170 160 150 170

05/04/99 EB13 01480950 180 200 150 150

07/19/99 WB2 01480300 25,000 > 6,000 2,700 > 8,000

07/19/99 WB13 01480637 1,500 2,000.E 1,100 —

07/20/99 EB1 01480648 2,000 > 1,200 890.E —

08/03/99 EB1 01480648 220 260 180 240

08/16/99 WB1 01480269 4,000 5,100 2,700 5,900

08/16/99 WB3 01480349 500 590 460 —

08/16/99 WB10 01480629 270 310 170 260

08/17/99 EB7 01480662 280 300 210 340

08/26/99 WB8 01480500 7,600 9,200 2,600 1,400.E

09/13/99 WB14 01480638 460 470 530 320

09/14/99 EB6 01480660 200 140.E 140 100.E

09/15/99 MS2 01480975 220 140 190 180

09/16/99 WB6 01480458 > 6,000 540,000.E >1,600.E 16,000.E
9

subbasin. Although urban land use ranged from

1-7 percent, no subbasin was identified as predominantly urban. Each subbasin was examined as

an individual entity with regards to impact on the

Brandywine Creek’s bacteria concentration.

HISTORICAL TRENDS IN FECAL

COLIFORM BACTERIA

Data from East Branch Brandywine Creek

below Downingtown (EB10), West Branch

Brandywine Creek at Modena (WB9), and

Brandywine Creek at Chadds Ford (MS3) were

evaluated for historical trends (fig. 3). All three

USGS long-term water-quality monitoring and

streamflow-measurement stations show decreased

bacteria concentrations since the beginning of

record collection. The data were collected at these

sites bi-monthly, usually between March to

November, regardless of flow conditions. Only

MS3 shows median concentrations of bacteria

below 200 col/100 mL for most of the time from

1992 to 1999. All three sites show elevated median

concentrations of bacteria in 1980, 1983, and 1989.

The elevated median concentrations are on both

branches and the main stem of Brandywine Creek.

From 1980 to 1999, the median bacteria

concentrations at EB10 have decreased by a factor

of 1,000, showing the most dramatic and consistent

improvement of the three stations. The median

bacteria concentrations at MS3 have decreased by

at least a factor of 10 from a peak in 1980. Since

data collection began in 1973, the median bacteria

concentrations at MS3 increased until 1980 and

then progressively decreased to below the PaDEP

criterion of 200 col/100 mL. The median bacteria

concentrations at WB9 showed a peak in 1981,

decreased to the PaDEP criterion in 1987, and

increased until 1999 to one-tenth of its highest

recorded median bacteria concentration.

In 1972, the U.S. Congress enacted landmark

legislation, in the form of a statute, to protect the

Nation’s waters. The Federal Water Pollution

Control Act Amendments of 1972 (referred to as

the Clean Water Act of 1972 or CWA), expanded

and built upon existing laws designed to control

and prevent water pollution. The CWA may have

contributed to the decrease in bacteria concentrations between 1972 and 1987. The Clean Water Act

of 1977 and the Water Quality Act of 1987, which

Figure 3. Annual median concentrations of fecal coliform bacteria at Brandywine Creek at

Chadds Ford, East Branch Brandywine Creek below Downingtown, and West Branch

Brandywine Creek at Modena, Pennsylvania, 1973-99.

1970 1975 1980 1985 1990 1995 2000

100

1,000,000

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

CHADDS FORD

DOWNINGTOWN

MODENA

PaDEP CRITERION

MEDIAN ANNUAL FECAL COLIFORM BACTERIA CONCENTRATION,

IN COLONIES PER 100 MILLILITERS
10

are successive amendments to the 1972 CWA,

have continued to strengthen that law.

Concentrations of bacteria decreased

dramatically from 1980 to 1987, rose and fell

between 1987 and 1996, and then stabilized

from 1996 to 1999. Possible factors that would

lower bacteria concentrations are the addition

and upgrade of wastewater treatment plants,

an expansion of collection systems, decreases

in point-source discharges, and decreases in

agricultural land use in the basin.

Comparisons between streamflow and

concentrations of fecal coliform bacteria during

base flow and stormflow for sites MS3, EB10,

and WB9 are shown in figure 4. There is a

general relation between streamflow and

concentrations of fecal coliform bacteria at sites

MS3 and WB9. When streamflow is elevated,

bacteria concentrations tend to be elevated.

A relation between streamflow and concentrations of fecal coliform bacteria is not apparent

at EB10.

Median concentrations of fecal coliform

bacteria were highest at WB9 and lowest at

MS3 (fig. 5). EB10 had the greatest range in

bacteria concentrations.

FACTORS AFFECTING BACTERIA

CONCENTRATIONS

Numerous factors affect bacteria

concentrations in the Brandywine Creek. Land

use, the chemical and physical properties of

stream water, seasonality, and reservoirs are

all factors that can affect the concentration

of bacteria. Land-use differences in the

Brandywine Creek do not appear to affect

bacteria concentrations to a statistically

significant extent. A moderate positive relation

exists between water temperature and fecal

coliform and E. coli bacteria during base flow.

Seasonal changes in water temperature can

either promote or inhibit bacteria growth.

Water flowing from reservoirs is low in

bacteria concentration.

1 100 10,000 1,000,000 10

5,000

20

50

100

200

500

1,000

2,000

STREAMFLOW,

CONCENTRATION OF FECAL COLIFORM BACTERIA,

Figure 4. Relation between streamflow and concentration of

fecal coliform bacteria, Brandywine Creek at Chadds Ford,

East Branch Brandywine Creek below Downingtown, and West

Branch Brandywine Creek at Modena, Pennsylvania, 1973-99.

 IN COLONIES PER 100 MILLILITERS

IN CUBIC FEET PER SECOND

10

5,000

20

50

100

200

500

1,000

2,000

STREAMFLOW,

IN CUBIC FEET PER SECOND

1 100 10,000 1,000,000

10

5,000

20

50

100

200

500

1,000

2,000

STREAMFLOW,

IN CUBIC FEET PER SECOND

1 100 10,000 1,000,000

BRANDYWINE CREEK

AT CHADDS FORD

EAST BRANCH BRANDYWINE CREEK

BELOW DOWNINGTOWN

WEST BRANCH BRANDYWINE CREEK

AT MODENA

(MS3)

(EB10)

(WB9)
11

Land Use

Bacteria concentrations in water samples from

subbasins with agricultural, forested, residential,

and mixed land-use settings were compared. The

Kruskal-Wallis test was used to test for statistically

significant differences in the ranks of concentrations of fecal coliform bacteria between land-use

categories at the 95-percent confidence level for all

base-flow and stormflow samples. The test was

run twice, once for three categories of land use

(agricultural, forested, and residential) and once

for four categories (agricultural, forested,

residential, and mixed). In both cases, the KruskalWallis test showed no statistically significant

difference for concentrations of fecal coliform

bacteria among the three predominant land-use

groups (agricultural, forested, and residential) or

the second group that included the mixed category

for base flow and stormflow.

While there seems to be no direct relation

between land use and bacteria concentrations

within a subbasin, bacteria concentrations in base

flow and stormflow are different. The base-flow

bacteria concentrations for all four categories are

lower than stormflow concentrations by a factor of

approximately 10. During base flow and

stormflow, the agricultural, forested, residential,

and mixed subbasins have approximately the same

median bacteria concentration. However, the

forested subbasins show a much wider range of

bacteria concentrations (fig. 6).

Field-Measured Properties

of Water and Streamflow

Relations among bacteria concentrations, fieldmeasured properties of water, and streamflow

were evaluated statistically by use of Spearmanrank correlations. Statistically significant relations

(for p < 0.05) were found to exist. Spearman-rank

correlations significant at the 95-percent

confidence interval are given in table 4.

A moderate positive correlation exists between

temperature and concentration of fecal coliform

bacteria (rs = 0.346) and E. coli bacteria (rs = 0.351).

Concentrations of bacteria are lower when water

temperatures are less than approximately 15°C

(usually during March and April) than when water

temperatures are greater than approximately 15°C

(usually from June to September). A weak negative

Figure 5. Distribution of annual median concentrations of fecal coliform bacteria at three USGS long-term

water-quality monitor and streamflow-measurement stations during base flow and stormflow, Brandywine Creek

Basin, Chester County, Pennsylvania, 1973-99.

CHADDS FORD DOWNINGTOWN MODENA

50

1,000,000

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

MEDIAN ANNUAL CONCENTRATIONS OF

MS3 EB10 WB9

IN COLONIES PER 100 MILLILITERS

FECAL COLIFORM BACTERIA,

EXPLANATION

1.5 TIMES THE INTERQUARTILE

OR EQUAL TO 3 AND MORE THAN

OUTLIER DATA VALUE LESS THAN

3 TIMES THE INTERQUARTILE

OUTLIER DATA VALUE MORE THAN

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

OR EQUAL TO 1.5 TIMES

DATA VALUE LESS THAN

THE INTERQUARTILE RANGE

RANGE OUTSIDE THE QUARTILE

RANGE OUTSIDE THE QUARTILE

OUTSIDE THE QUARTILE

PaDEP criterion
12

FECAL COLIFORM BACTERIA CONCENTRATION,

Figure 6. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at sites in

agricultural, forested, residential, and mixed subbasins, Brandywine Creek Basin, Chester County, Pennsylvania,

1998-99. IN COLONIES PER 100 MILLILITERS

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

1.5 TIMES THE INTERQUARTILE RANGE

DATA VALUE LESS THAN OR EQUAL TO

1.5 TIMES THE INTERQUARTILE RANGE

OR EQUAL TO 3 AND MORE THAN

OUTLIER DATA VALUE LESS THAN

FECAL COLIFORM BACTERIA CONCENTRATION,

AGRICULTURAL FORESTED RESIDENTIAL

IN COLONIES PER 100 MILLILITERS

BASE FLOW

1

100,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

10

1,000,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

STORMFLOW

MIXED

INDICATES SINGLE SAMPLE

N=66 N=15 N=6 N=165

N=18 N=3 N=50 N=2

N INDICATES NUMBER OF SAMPLES

 OUTSIDE THE QUARTILE

 OUTSIDE THE QUARTILE

PaDEP criterion

PaDEP criterion
13

correlation exists between dissolved oxygen and

concentration of fecal coliform bacteria (rs = -0.309)

and E. coli bacteria (rs = -0.267). When water

temperatures are higher, dissolved oxygen

concentrations are lower (rs = -0.553). The weak

correlation between bacteria concentrations and

dissolved oxygen probably is the result of the

correlation between water temperature and

dissolved oxygen and not low dissolved oxygen

causing an increase in bacteria concentration.

A weak negative correlation exists between

streamflow and concentration of fecal coliform

bacteria (rs = -0.212) and E. coli bacteria

(rs = -0.231). A weak positive correlation exists

between specific conductance and concentration of

fecal coliform bacteria (rs = 0.250) and E. coli

bacteria (rs = 0.257). As expected, a strong positive

correlation exists between fecal coliform and E. coli

bacteria (rs = 0.745). When concentrations of fecal

coliform bacteria are elevated, concentrations of E.

coli bacteria also are elevated.

During stormflow, a strong positive correlation

exists between fecal coliform bacteria and E. coli

bacteria (rs = 0.612). When concentrations of fecal

coliform bacteria are elevated, concentrations of

E. coli bacteria also are elevated (table 4).

Seasonality

Seasonality in this region of temperate climate

affects bacteria concentrations in the Brandywine

Creek through water temperature variations.

USGS water-quality monitor stations do not collect

data between December and February. Base flow

and stormflow water temperatures from 1990 to

1999 at West Branch Brandywine Creek at Modena

(WB9), East Branch Brandywine Creek below

Downingtown (EB10), and Brandywine Creek at

Chadds Ford (MS3) are grouped by month and

shown in figure 7. At all three stations water

temperatures are lower during spring (March,

April, and May) and fall months (September,

October, and November) than during summer

months (June, July, and August).

Fecal coliform bacteria concentrations roughly

follow the same rise and fall as water temperatures

(fig. 8). The PaDEP criterion defines the swimming

season as May 1 through September 30. While

none of the three stations are completely below the

PaDEP criterion during the swimming season,

bacteria concentrations are lowest at MS3.

The 10-year median concentration of bacteria at

WB9 always exceeds the PaDEP criterion of

200 col/100 mL during the swimming season and

commonly exceeds the higher PaDEP criterion of

2,000 col/100 mL, the criterion that pertains to the

remainder of the year. However, during March,

April, October, and November, some individual

bacteria samples do exceed the PaDEP criterion.

The 10-year median concentration of bacteria at

EB10 exceeds the PaDEP swimming season

criterion. The remainder of the year at EB10, the

10-year median concentration of bacteria does not

exceed the PaDEP criterion. The 10-year median

concentration of bacteria at MS3 exceeds the

PaDEP swimming season criterion only in June.

Effect of Reservoirs

Three reservoirs are located in the Brandywine

Creek Basin: Chambers Lake Reservoir (also

known as Birch Run Reservoir), Rock Run

Reservoir (also known as Coatesville Reservoir),

and Marsh Creek Reservoir. Samples were

collected above and below each reservoir.

A comparison of the bacteria concentrations at

sites above and below each reservoir during base

flow and stormflow is shown in figure 9. Bacteria

concentrations in streams that flow out of the

reservoirs are much lower than the bacteria

concentrations in the streams that flow into the

Table 4. Spearman rank correlations significant at the

95-percent confidence interval for base-flow and

stormflow samples

[n, number; rs, Spearman Rho coefficient; p-value,

significance value]

Correlation n rs p-value

Base flow

Temperature - dissolved oxygen 209 -0.553 0.0001

Fecal coliform - dissolved oxygen 208 -.309 .0001

E. coli - dissolved oxygen 69 -.267 .0263

Fecal coliform - water temperature 251 .346 .0001

E. coli - water temperature 76 .351 .0018

Fecal coliform - streamflow 219 -.212 .0016

E. coli - streamflow 72 -.231 .0505

Fecal coliform - specific conductance 243 .250 .0001

E. coli - specific conductance 76 .257 .0251

Fecal coliform - E. coli 76 .745 .0001

Stormflow

Fecal coliform -E. coli 32 .612 .0002
14

0

30

5

10

15

20

25

MAR APR MAY JUN JUL AUG SEPT OCT NOV

MONTH

0

30

5

10

15

20

25

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE INTERQUARTILE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE

0

30

5

10

15

20

25

Figure 7. Distribution of monthly water temperatures during base flow and stormflow at West Branch

Brandywine Creek at Modena, East Branch Brandywine Creek below Downingtown and Brandywine

Creek at Chadds Ford, Pennsylvania, 1990-99. TEMPERATURE, TEMPERATURE, TEMPERATURE,

WEST BRANCH BRANDYWINE CREEK

AT MODENA

EAST BRANCH BRANDYWINE CREEK

BELOW DOWNINGTOWN

BRANDYWINE CREEK

AT CHADDS FORD

EB10

WB9

MS3

IN DEGREES CELSIUS IN DEGREES CELSIUS IN DEGREES CELSIUS
15

Figure 8. Distribution of monthly fecal coliform bacteria concentrations for base flow and stormflow,

West Branch Brandywine Creek at Modena, East Branch Brandywine Creek below Downingtown, and

Brandywine Creek at Chadds Ford, Pennsylvania, 1990-99.

MONTH

EXPLANATION

25th PERCENTILE

MEDIAN

75th PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE INTERQUARTILE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE

1

100,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

1

100,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

MAR APR MAY JUN JUL AUG SEPT OCT NOV

1

100,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

WEST BRANCH

BRANDYWINE CREEK

AT MODENA

EAST BRANCH

BRANDYWINE CREEK

BELOW DOWNINGTOWN

BRANDYWINE CREEK

AT CHADDS FORD

PaDEP criterion

PaDEP criterion

FECAL COLIFORM BA CTERIA CONCENTRATIONS,

IN COLONIES PER 100 MILLILITERS

FECAL COLIFORM BACTERIA CONCENTRATIONS,

IN COLONIES PER 100 MILLILITERS

FECAL COLIFORM BACTERIA CONCENTRATIONS,

IN COLONIES PER 100 MILLILITERS

PaDEP criterion

(swimming season)

(remainder of year)

PaDEP criterion

(remainder of year)

(swimming season)

PaDEP criterion

(swimming season)

PaDEP criterion

(remainder of year)

WB9

EB10

MS3
16

Figure 9. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at

sampling sites above and below Chambers Lake Reservoir, Rock Run Reservoir, and Marsh Creek

Reservoir, Chester County, Pennsylvania, 1998-99.

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INDICATES SINGLE SAMPLE

WB4 WB5 WB6 WB7 EB4 EB5

1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

CHAMBERS LAKE ROCK RUN MARSH CREEK

above below above below below above

FECAL COLIFORM BACTERIA CONCENTRATION,

 IN COLONIES PER 100 MILLILITERS

PaDEP criterion

RESERVOIR

RESERVOIR RESERVOIR

BASE FLOW

WB4 WB5 EB4 EB5

10

1,000,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

EXPLANATION

FECAL COLIFORM BACTERIA CONCENTRATION,

 IN COLONIES PER 100 MILLILITERS

CHAMBERS LAKE MARSH CREEK

RESERVOIR

STORMFLOW

RESERVOIR

PaDEP criterion
17

reservoirs. Because the volume of water flowing

into the reservoir is very small compared to the

volume of water already residing in the reservoir,

the bacteria concentrations in the streams below

the reservoirs reflect bacteria concentrations in the

reservoirs, and not the bacteria concentrations in

the streams that flow into the reservoirs.

On the West Branch, Chambers Lake Reservoir

and Rock Run Reservoir typically release water

from the bottom. The chemistry of the water

released from the bottom of a reservoir is different

than the water entering from a source above the

reservoir. The water at the bottom of a reservoir is

usually colder (between 1 to 5°C), anoxic, and may

have become stratified. In addition, the residence

time of the water in a reservoir is long and allows

for natural die-off of bacteria. On the East Branch,

Marsh Creek Reservoir releases water on a multilevel basis. Typically, Marsh Creek Reservoir

releases water from the middle of the reservoir.

In most cases, during storms at all three

reservoirs, water flows over the top of the

reservoir, reducing residence time. During large

storms, such as Hurricane Floyd on September 16,

1999, water also is released from the bottom.

A sample collected on July 20, 1999, during a storm

at EB5 (below Marsh Creek Reservoir) had a

concentration of fecal coliform bacteria of

40 col/100 mL. No sample was collected from the

site above the reservoir. On September 16, 1999,

a sample collected during Hurricane Floyd

from EB4 (above Marsh Creek Reservoir)

had a fecal coliform bacteria concentration of

66,000 col/100 mL. The sample collected at EB5

(below the reservoir) had a fecal coliform bacteria

concentration of 2,200 col/100 mL. The bacteria

concentration below the reservoir reflects a

mixture of the older-residence time water being

released from the bottom and the youngerresidence time water, which was the result of the

hurricane.

COMPARISON OF BACTERIA

CONCENTRATIONS DURING BASE FLOW

AND STORMFLOW

Comparisons were made between bacteria

concentrations observed during base flow and

stormflow. Bacteria concentrations at five sites

where at least four samples at each site were

collected during both base flow and stormflow are

listed in table 5. A comparison of bacteria

concentrations during base flow and stormflow is

shown in figure 10. For all five sites, bacteria

concentrations were higher during stormflow than

during base flow.

Storm runoff contains elevated concentrations

of bacteria. Rainfall flushes the land surface and

causes bacteria to be transported into Brandywine

Creek, thereby increasing the bacteria concentration. Consequently, storms accelerate the influx

of bacteria from any given source through landsurface runoff. In all analyses, Brandywine Creek

tributaries have higher bacteria concentrations

during stormflow than during base flow. During

stormflow, median concentrations of fecal coliform

bacteria at sites on 14 of 15 tributaries (93 percent)

to Brandywine Creek were greater than

200 col/100 mL.

Table 5. Range and median concentrations of fecal coliform bacteria concentrations during base flow and

stormflow for five sites in the Brandywine Creek Basin, Chester County, Pennsylvania, 1998-99

[FC, fecal coliform; col/100 mL, colonies per 100 milliliters; ID, identification number]

Local

ID

U.S.

Geological

Survey

site ID

Site name

Base flow

range of FC

concentration

(col/100 mL)

Base flow

FC median

concentration

(col/100 mL)

Stormflow

range of FC

concentration

(col/100 mL)

Stormflow

FC median

concentration

(col/100 mL)

WB2 01480300 West Branch Brandywine Creek near

Honey Brook

63.- 10,000 4,500 1,100. - 610,000 12,000

WB8 01480500 West Branch Brandywine Creek at

Coatesville Reservoir

2.- 1,800 410 3,700.- 16,000 7,200

WB9 01480617 West Branch Brandywine Creek at

Modena

6.- 4,400 940 2,700.- 15,000 6,000

EB10 01480870 East Branch Brandywine Creek below

Downingtown

80.- 8,000 590 1,400. - 12,000 4,500

MS3 01481000 Brandywine Creek at Chadds Ford 2.- 2,200 110 160.- 6,700 2,200
18

Figure 10. Distribution of fecal coliform bacteria concentrations during base flow and stormflow at selected

sampling sites in the Brandywine Creek Basin, Chester County, Pennsylvania, 1998-99. FECAL COLIFORM BACTERIA CONCENTRATION,

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

AND MORE THAN 1.5 TIMES THE

OUTLIER DATA VALUE LESS THAN OR EQUAL TO 3

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

OUTLIER DATA VALUE MORE THAN 3 TIMES THE

IN COLONIES PER 100 MILLILITERS

WB2 WB2 WB8 WB8 WB9 WB9 EB10 EB10 MS3 MS3

LOCAL SITE NUMBER

1

1,000,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

40,000

100,000

200,000

500,000

HATCHES DESIGNATE STORMFLOW

PaDEP criterion
19

EXTENT AND POTENTIAL SOURCES OF

FECAL AND ESCHERICHIA COLI

BACTERIA

Bacteria sources were identified by examining

bacterial counts in downstream sequence. An

increase in bacteria concentration at a sampling

site compared to the concentration at the closest

upstream sampling site indicates a bacteria source

between the two sites. Data on concentrations of

E. coli bacteria are noted in this section; however,

the fecal coliform bacteria data provided a more

comprehensive picture of the extent and potential

source of bacteria and were used for primary

analysis. During base flow, 91 percent of the

24 non-estimated water samples contained E. coli/

fecal coliform bacteria ratios greater than 1:2.

During storms, 37 percent of the eight nonestimated water samples contained E. coli/fecal

coliform bacteria ratios greater than 1:2. The data

given in tables 6 to 11 at the back of the report are

field chemistry measurements and bacteria

concentrations during base flow and stormflow

conditions.

Bacteria concentration and land use were

compared at each of the 40 sites on the Brandywine

Creek. Data for the branches and the main stem

were examined individually. Median

concentrations of fecal coliform bacteria were used

for a comparison between the branches and main

stem during base flow and stormflow and are

shown in figures 11 and 12, respectively. Typically,

elevated bacteria concentrations during base flow

and stormflow indicate pollution from point and

nonpoint sources. During base flow, elevated

bacteria concentrations in the Brandywine Creek

appear to come from nonpoint sources such as

contaminated ground water, or from farm animals

and wildlife entering and leaving waste in the

stream. During stormflow, land-surface runoff, a

nonpoint source, is the causal agent for the

elevated bacteria concentrations in all of the

subbasins.

At base flow, the median concentrations of

fecal coliform bacteria at sites on the West Branch

exceed 200 col/100 mL at 15 of the 20 sites

(75 percent). The median concentrations of fecal

coliform bacteria at sites on the East Branch exceed

200 col/100 mL at 10 of the 17 sites (58 percent).

The median concentrations of fecal coliform

bacteria at sites on the main stem exceed

200 col/100 mL at one of the three sites

(33 percent). During stormflow, the median

concentrations of fecal coliform bacteria at sites on

the West Branch exceed 200 col/100 mL at 12 of the

13 sites (92 percent). The median concentrations of

fecal coliform bacteria at sites on the East Branch

exceed 200 col/100 mL at 15 of the 17 sites

(88 percent). The median concentrations of fecal

coliform bacteria at sites on the main stem exceed

200 col/100 mL at all 3 sites.

Samples analyzed for E. coli bacteria were

limited in number at each site; therefore, median

concentrations of E. coli bacteria were not

determined for either base flow or stormflow.

West Branch Brandywine Creek

Distributions of fecal coliform bacteria

concentrations in the West Branch Brandywine

Creek during base flow and stormflow are shown

in figure 13. During base flow, 75 percent of the

sites had bacteria concentrations above the PaDEP

criterion of 200 col/100 mL. During storms,

92 percent of the sites had bacteria concentrations

above the PaDEP criterion. Of the 20 sites sampled,

11 sites were on tributaries. During base flow, Birch

Run, Rock Run, and Buck Run had median

bacteria concentrations below 200 col/100 mL.

During stormflow, only Birch Run below the

Reservoir had a median bacteria concentration that

was below 200 col/100 mL.

In the headwaters of the West Branch

Brandywine Creek, fecal coliform concentrations at

West Branch Brandywine Creek at Rockville (WB1)

at base flow ranged from 200 to 5,500 col/100 mL;

the median was 4,100 col/100 mL. Three samples

were analyzed for E. coli; the concentrations were

greater than 600, 1,000 and 5,900 col/100 mL. No

samples were collected at WB1 during stormflow.

West Branch Brandywine Creek at Rockville (WB1)

and West Branch Brandywine Creek near Honey

Brook (WB2) are very close to one another and

have similar land uses; WB2 is at a USGS

streamflow-measurement station. Because baseflow samples at both sites were similar in bacteria

concentration, stormflow sampling was done at

WB2, and the sample was considered to be

representative for both sites. WB1 is located in a

subbasin that is predominantly agricultural

(72 percent). Cows and horses are pastured in an

area upstream of WB1 that has an unfenced creek,

causing a nonpoint source for bacteria during base

flow and stormflow. Farms that support crops and

livestock are within 0.5 mi upstream of WB1.
20

Figure 11. Median concentrations of fecal coliform bacteria during base flow, Brandywine Creek

Basin, Chester County, Pennsylvania, 1998-99.
21

Figure 12. Median concentrations of fecal coliform bacteria during stormflow, Brandywine

Creek Basin, Chester County, Pennsylvania, 1998-99.
22

Figure 13. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at sampling

sites on West Branch Brandywine Creek, Chester County, Pennsylvania, 1998-99.

WB1 WBA WB2 WB3 WB4 WB5 WB6 WBE WB7 WBD WBB WBC WB8 WB9 WB10 WB11WB12 WB13 WB14 WB15

1

100,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

FECAL COLIFORM BACTERIA CONCENTRATION

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

DATA VALUE LESS THAN OR

INTERQUARTILE

3 AND MORE THAN 1.5

OUTLIER DATA VALUE

INDICATES SINGLE SAMPLE

PaDEP criterion

WB2 WB3 WB4 WB5 WB6 WB8 WB9 WB10 WB11 WB12 WB13 WB14 WB15

LOCAL SITE NUMBER

10

1,000,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

100,000

200,000

500,000

IN COLONIES PER 100 MILLILITERS

PaDEP criterion

IN COLONIES PER 100 MILLILITERS

FECAL COLIFORM BACTERIA CONCENTRATION

BASE FLOW

STORMFLOW

DESIGNATES A TRIBUTARY

INTERQUARTILE RANGE

 OUTSIDE THE QUARTILE

LESS THAN OR EQUAL TO

TIMES THE

 RANGE OUTSIDE THE

 QUARTILE

 EQUAL TO 1.5 TIMES THE

 INTERQUARTILE RANGE

OUTSIDE THE QUARTILE
23

Fecal coliform bacteria concentrations at Two

Log Run at Birdell (WBA) during base flow were

measured three times. Concentrations were 540,

740, and 960 col/100 mL. No stormflow or E. coli

bacteria samples were collected at this site. The

subbasin is predominantly forested (54 percent).

Cropland is within 0.5 mi upstream of WBA. This

site, which is on a tributary below WB1 and above

WB2, was added midway through the study to

collect additional data to evaluate the bacteria

contribution of this tributary to elevated bacteria

concentrations measured at WB2. Although the

median concentration of fecal coliform bacteria at

WBA is lower than at WB2, the median

concentration of bacteria at WBA still exceeds the

PaDEP criterion of 200 col/100 mL. Two Log Run

contributes elevated bacteria concentrations to

West Branch Brandywine Creek.

At West Branch Brandywine Creek near Honey

Brook (WB2), concentrations of fecal coliform

bacteria at base flow ranged from 63 to

10,000 col/100 mL; the median concentration was

4,800 col/100 mL. Three samples were analyzed

for E. coli bacteria; concentrations were less than

1,900, 6,600, and greater than 8,000 col/100 mL.

During stormflow, the concentrations of fecal

coliform bacteria at WB2 ranged from 1,100 to

610,000 col/100 mL; the median concentration was

12,000 col/100 mL. Three samples were analyzed

for E. coli bacteria; concentrations were 8,000,

16,000 and 250,000 col/100 mL. The maximum

bacteria concentrations during stormflow for fecal

coliform and E. coli were measured during

Hurricane Floyd and are not considered to be

normal storm event bacteria concentrations. The

subbasin is predominantly agricultural

(68 percent). Within 0.5 mi upstream of WB2 is

cropland, and horses are in a pasture that contains

an unfenced stream.

Concentrations of fecal coliform bacteria at

West Branch Brandywine Creek at Brandamore

(WB3) during base flow ranged from 200 to

720 col/100 mL; the median concentration was

250 col/100 mL. One sample was collected for

E. coli bacteria; the concentration was

470 col/100 mL. One stormflow sample was

collected and analyzed for E. coli bacteria; the

concentration was 1,000 col/100 mL. No stormflow

samples were measured for fecal coliform bacteria.

The subbasin is predominantly agricultural

(58 percent). The lower base-flow concentrations at

WB3 may be attributable to the site’s distance from

WB2. The long reach of stream between the two

sites allows die-off of bacteria by deposition (into

the streambed), ultra-violet inactivation (sunlight),

grazing (by protozoa and other microorganisms),

or simply natural attenuation of the bacteria

resulting in a decrease in concentration.

Concentrations of fecal coliform bacteria at

Birch Run near Martins Corner (WB4) during base

flow ranged from 33 to 1,400 col/100 mL; the

median concentration was 510 col/100 mL. Two

samples were collected for analysis of E. coli

bacteria; concentrations were 180 and

230 col/100 mL. Two samples were collected

during stormflow for analysis of fecal coliform and

E. coli bacteria. Concentrations of fecal coliform

bacteria were greater than 6,000 and greater than

240,000 col/100 mL, and concentrations of E. coli

bacteria were greater than 8,000 and greater than

320,000 col/100 mL. The maximum bacteria

concentrations during stormflow for fecal coliform

and E. coli were measured during Hurricane Floyd

and are not considered to be normal storm event

bacteria concentrations. The subbasin is predominantly forested (54 percent), and the stream for

0.5 mi above WB4 is forested. This site is above the

Chambers Lake Reservoir. Birch Run contributes

elevated bacteria concentrations to Chambers Lake

Reservoir.

Concentrations of fecal coliform bacteria at

Birch Run near Wagontown (WB5) during base

flow ranged from 3 to 33 col/100 mL; the median

concentration was 7 col/100 mL. Both E. coli

bacteria sample concentrations were less than

3 col/100 mL. One stormflow sample was

collected; the concentration of fecal coliform

bacteria was 24 col/100 mL. No E. coli bacteria

sample was collected at stormflow. The subbasin is

predominantly forested (53 percent). Because this

site is below the Chambers Lake Reservoir, it has

low bacteria concentrations. The outflow from the

reservoir does not contribute elevated bacteria

concentrations to the West Branch Brandywine

Creek.

Concentrations of fecal coliform bacteria at

Rock Run near Philipsville (WB6) during base flow

ranged from 20 to 15,000 col/100 mL; the median

concentration was 1,900 col/100 mL. Three

samples were analyzed for E. coli bacteria;

concentrations were 1,400, 1,500, and

1,600 col/100 mL. Two samples were analyzed

for fecal coliform and E. coli bacteria during stormflow. Concentrations of fecal coliform bacteria

were 6,000 and 540,000 col/100 mL; E. coli bacteria
24

concentrations were 8,000 and 16,000 col/100 ml.

The maximum bacteria concentrations during

stormflow for fecal coliform and E. coli were

measured during Hurricane Floyd and are not

considered to be normal storm event bacteria

concentrations. The subbasin is predominantly

agricultural (58 percent). This site is above the

Rock Run Reservoir. Forest and cropland is within

0.5 mi upstream of WB6. Rock Run contributes

elevated bacteria concentrations to Rock Run

Reservoir.

Concentrations of fecal coliform bacteria at

Rock Run at Coatesville (Rock Run) Reservoir near

Coatesville (WBE) were measured twice during

base flow. The bacteria concentrations were 3,300

and 3,900 col/100 mL. No stormflow or E. coli

bacteria samples were collected. The subbasin is

predominantly agricultural (52 percent). This site

was added midway through the study to collect

additional data between sites WB6 and WB7. The

right side of the creek is forested within 0.5 mi

upstream of WBE. On the left side, the creek runs

past cropland, cattle pasture, and an open field.

Site WBE is downstream from site WB6, and

bacteria concentrations increase from site WB6 to

site WBE. Rock Run is usually about 20 ft in width.

During the drought in 1999 when samples were

collected, Rock Run was only 4 to 5 ft wide.

A possible cause for the increased concentration of

bacteria is the decrease in streamflow in Rock Run

because of the drought.

Concentrations of fecal coliform bacteria at

Rock Run below Coatesville (Rock Run) Reservoir

(WB7) during base flow ranged from 20 to

580 col/100 mL; the median concentration was

100 col/100 mL. Two samples were collected for

E. coli bacteria; concentrations were 93 and

97 col/100 mL. No stormflow samples were

collected. The land use in the subbasin is mixed—

49 percent agriculture, 26 percent forested, and

16 percent residential. Because this site is below

the Rock Run Reservoir, bacteria concentrations

are lower than at sites WB6 and WBE, which are

above the reservoir.

Concentrations of fecal coliform bacteria for

Rock Run at Rock Run near Coatesville (WBD)

were measured three times during base flow.

The concentrations were 240, 453, and

1,900 col/100 mL. No stormflow or E. coli bacteria

samples were collected. The land use in the

subbasin is mixed—47 percent agriculture,

33 percent forested, and 15 percent residential.

This site was added midway through the study to

collect additional data between sites WB7 and

WB8. Bacteria concentrations at site WBD, which is

just upstream from the confluence of Rock Run

and the Brandywine Creek, are much higher than

at upstream site WB7, which is below the Rock

Run Reservoir. The land is forested and residential

within 0.5 mi upstream of WBD. Concrete banks

line Rock Run at the sample site. Disposable

diapers and rodents were present in Rock Run at

times when samples were collected. A nonpoint

source for bacteria during base flow is the

surrounding urbanized area. Rock Run contributes

elevated bacteria concentrations to the West

Branch Brandywine Creek.

Concentrations of fecal coliform bacteria at

West Branch Brandywine Creek at Rock Run

(WBB) were measured three times during base

flow. Concentrations were 200, 210, and

370 col/100 mL. No stormflow or E. coli bacteria

samples were collected. The land use in the

subbasin is mixed—48 percent agricultural,

33 percent forested, and 14 percent residential.

Residences and forest line the creek within 0.5 mi

upstream of WBB. This site was added midway

through the study to collect additional data

between WB7 and WB8. The Brandywine Creek

above WBB has a lower bacteria concentration

than at WBC, which is below WBB, and receives

water with elevated bacteria concentrations from

Rock Run. The bacteria concentrations at WBB

were only slightly above the PaDEP criterion.

Concentrations of fecal coliform bacteria at

West Branch Brandywine Creek below Rock Run at

Coatesville (WBC) during base flow were

measured three times; concentrations were 250,

320, and 600 col/100 mL. No stormflow or E. coli

bacteria samples were collected. The land use in

the subbasin is mixed—47 percent agricultural,

33 percent forested, and 15 percent residential.

This site was added mid-way through the study to

collect additional data between WB7 and WB8.

Residences are on both sides of the creek within

0.5 mi upstream of WBC. WBC is downstream

from site WBB, and bacteria concentrations are

higher at WBC than at site WBB.

Concentrations of fecal coliform bacteria at

West Branch Brandywine Creek at Coatesville

(Rock Run) Reservoir (WB8) during base flow

ranged from 2 to 1,800 col/100 mL; the median

concentration was 410 col/100 mL. Three samples

were analyzed for E. coli bacteria; concentrations
25

were 100, 240 and 500 col/100 mL. Fecal coliform

bacteria concentrations during stormflow ranged

from 3,700 to 16,000 col/100 mL; the median

concentration was 7,200 col/100 mL. Two samples

were analyzed for E. coli bacteria during

stormflow; concentrations were 1,400 and

12,000 col/100 mL. The maximum bacteria

concentrations during stormflow for fecal coliform

and E. coli were measured during Hurricane Floyd

and are not considered to be normal storm event

concentrations. The land use in the subbasin is

mixed—47 percent agricultural, 33 percent

forested, 15 percent residential, and 2 percent

urban (around the city of Coatesville). Residences

and forested areas line both sides of the creek

within 0.5 mi upstream of WBB. Site WB8 is in an

industrial area of Coatesville. Bacteria concentrations increase between WBB and WB8. A nonpoint

source for the elevated bacteria concentrations

during base flow is the urbanized area between

WBB and WB8.

Concentrations of fecal coliform bacteria at

West Branch Brandywine Creek at Modena

(WB9) during base flow ranged from 6 to

4,400 col/100 mL; the median concentration was

940 col/100 mL. Concentrations of E. coli bacteria

ranged from 100 to 800 col/100 mL. Fecal coliform

bacteria concentrations during stormflow ranged

from 4,000 to 15,000 col/100 mL; the median

concentration was 6,000 col/100 mL. Three

samples were analyzed for E. coli bacteria;

concentrations were 600, 2,900, and greater than

8,000 col/100 mL. The land use in the subbasin is

mixed—42 percent agricultural, 33 percent

forested, 16 percent residential, and 4 percent

urban. Approximately 1 mi upstream of WB9 is an

industrial plant with a wastewater treatment plant

and a storm sewer outfall. Immediately upstream

of WB9 are residences and forested areas on the

right side of the creek and an urban/industrial

area on the left side of the creek. Bacteria

concentrations increase substantially between WB8

and WB9. Nonpoint sources for bacteria

contamination are the urban area surrounding the

creek.

Concentrations of fecal coliform bacteria at

Buck Run at Doe Run (WB10) during base flow

ranged from 7 to 370 col/100 mL; the median

concentration was 180 col/100 mL. Two E. coli

bacteria samples were collected; concentrations

were 69 and 260 col/100 mL. One sample was

collected during stormflow; the concentration

of fecal coliform bacteria was greater than

6,000 col/100 mL, and the E. coli bacteria

concentration was greater than 8,000 col/100 mL.

The land use in the subbasin is predominantly

agricultural (58 percent); however, 28 percent of

the subbasin is forested and 11 percent is

residential. At base flow, Buck Run does not

contribute elevated bacteria concentrations to Doe

Run to which it is a tributary.

Concentrations of fecal coliform bacteria

at Doe Run above tributary at Springdell

(WB11) during base flow ranged from 10 to

1,100 col/100 mL; the median concentration was

300 col/100 mL. Two samples were collected and

tested for E. coli bacteria; concentrations were 110

and 690 col/100 mL. One sample was collected

during stormflow; the fecal coliform bacteria

concentration was 580 col/100 mL. No E. coli

bacteria samples were collected during stormflow.

The land use in the subbasin is predominantly

agricultural (76 percent). Within 0.5 mi upstream

of WB11 is cropland on the right side and horses in

a fenced pasture on the left side of Doe Run. Doe

Run contributes elevated bacteria concentrations

to the West Branch Brandywine Creek.

Concentrations of fecal coliform bacteria at

West Branch Brandywine Creek near Embreeville

(WB12) during base flow ranged from 18 to

500 col/100 mL; the median concentration was

110 col/100 mL. Two water samples were collected

and tested for E. coli bacteria; concentrations were

68 and 120 col/100 mL. One sample was collected

during stormflow and analyzed for fecal coliform

and E. coli bacteria; concentrations were 220 and

190 col/100 mL, respectively. The subbasin

surrounding WB12 is predominantly agricultural

(53 percent). Bacteria concentrations decrease

between WB9 and WB12. The long reach between

the two sites and the consequent die-off of bacteria

through deposition, UV inactivation, grazing, or

natural attenuation account for the decrease in

bacteria concentration.

Concentrations of fecal coliform bacteria at

Little Broad Run near Marshallton (WB13) during

base flow ranged from 15 to 2,000 col/100 mL; the

median concentration was 320 col/100 mL. Three

samples were analyzed for E. coli bacteria;

concentrations were 200, 330, and 330 col/100 mL.

Three samples were analyzed for fecal coliform

bacteria during stormflow; concentrations were 24,

720, and 22,000 col/100 mL. One E. coli bacteria

sample was collected during stormflow; the

concentration was 670 col/100 mL. The land use in
26

the subbasin is mixed—38 percent residential,

27 percent forested, and 26 percent agricultural.

Within 0.5 mi upstream of WB13 is riparian forest

75-120 ft wide; the remainder of the area is

residential. Little Broad Run contributes elevated

bacteria concentrations of bacteria to Broad Run.

Concentrations of fecal coliform bacteria

during base flow at Broad Run at Northbrook

(WB14) ranged from 100 to 840 col/100 mL; the

median concentration was 480 col/100 mL. Two

water samples were collected and tested for

E. coli bacteria; concentrations were 46 and

320 col/100 mL. One sample was collected during

stormflow; the fecal coliform bacteria concentration was 1,400 col/100 mL, and the E. coli

bacteria concentration was 1,300 col/100 mL. The

land use in the subbasin is mixed—37 percent

agricultural, 29 percent forested, and 29 percent

residential. Dense riparian forest approximately

90-120 ft wide is on both sides of Broad Run within

0.5 mi upstream of WB14. Open, uncut fields

extend out from the forest on both sides. A few

residences are scattered on either side of the creek

upstream. Broad Run contributes elevated

concentrations of bacteria to the West Branch

Brandywine Creek.

Concentrations of fecal coliform bacteria at

West Branch Brandywine Creek at Wawaset

(WB15) during base flow ranged from 10 to

350 col/100 mL; the median concentration was

150 col/100 mL. Three samples were analyzed for

E. coli bacteria; concentrations were 60, 200, and

260 col/100 mL. One sample was collected during

stormflow; the fecal coliform bacteria concentration was 3,600 col/100 mL, and the E. coli bacteria

concentration was 1,300 col/100 mL. The land use

in the subbasin is predominantly agricultural

(52 percent). Bacteria concentrations increase

between sites WB12 and WB15 as a result of Broad

Run’s elevated bacteria concentrations. However,

WB15’s median bacteria concentration is below the

PaDEP criterion.

East Branch Brandywine Creek

Fecal coliform bacteria concentrations on East

Branch Brandywine Creek during base flow and

stormflow are shown in figure 14. During base

flow, bacteria concentrations at 58 percent of the

sites exceeded the PaDEP criterion of

200 col/100 mL. During storms, bacteria

concentrations at 88 percent of the sites exceeded

the PaDEP criterion. Of the 17 sites on the East

Branch Brandywine Creek, 9 sites are located on

tributaries. Four tributaries, Indian Run, Marsh

Creek, Culbertson Run, and Valley Creek, had

median bacteria concentrations below

200 col/100 mL during base flow. Only the median

bacteria concentrations at Indian Run remained

below 200 col/100 mL during stormflow.

Concentrations of fecal coliform bacteria in the

headwaters of the East Branch Brandywine Creek

at East Branch Brandywine Creek near Cupola

(EB1) during base flow ranged from 31 to

1,200 col/100 mL; the median concentration was

260 col/100 mL. Two samples were analyzed for

E. coli bacteria; the concentrations were 86 and

240 col/100 mL. Two stormflow samples were

collected and analyzed for fecal coliform bacteria;

concentrations were 600 and greater than

1,200 col/100 mL. No stormflow samples were

collected for analysis of E. coli bacteria. Land use in

the subbasin surrounding EB1 is predominantly

agricultural (60 percent). Within 0.5 mi upstream of

EB1 on one side is fenced farmland with cows and

chickens. On the opposite side are residences.

Cropland is further upstream.

Concentrations of fecal coliform bacteria at

East Branch Brandywine Creek at Glenmoore

(EB2) during base flow ranged from 63 to

330 col/100 mL; the median concentration was

220 col/100 mL. Two samples were collected and

analyzed for E. coli bacteria; the concentrations

were 110 and 170 col/100 mL. Three samples were

analyzed for fecal coliform bacteria during

stormflow; concentrations were 450, greater than

1,200, and greater than 12,000 col/100 mL. One

sample was collected during stormflow and

analyzed for E. coli bacteria; the concentration was

greater than 16,000 col/100 mL. EB2 is in a

predominantly agricultural subbasin (53 percent).

Cropland is on the right side and forest on the left

side of the creek within 0.5 mi upstream of EB2.

Bacteria concentrations decrease between EB1 and

EB2. One possible reason for the decrease is the

change in land use. Farm animals are replaced by

forest at EB2. Overall the subbasin becomes less

agricultural and more forested than the subbasin

above EB1.

Concentrations of fecal coliform bacteria at

Indian Run at Springton (EB3) were measured

three times during base flow. The concentrations

were 11, 65, and 71 col/100 mL. One sample was

collected and analyzed for E. coli bacteria; the

concentration was 90 col/100 mL. One sample was

collected at stormflow; the fecal coliform bacteria

concentration was 150 col/100 mL. No E. coli
27

EB1 EB2 EB3 EB4 EB5 EB6 EB7 EB8 EB9 EBA EBC EB13 EBB EB10 EB11 EB12 EB14 10

100,000

20

50

100

200

500

1,000

2,000

5,000

10,000

20,000

50,000

FECAL COLIFORM BACTERIA CONCENTRATION,

PaDEP criterion

 IN COLONIES PER 100 MILLILITERS

EB1 EB2 EB3 EB6 EB7 EB8 EB9 EBA EBC EB13 EBB EB10 EB11 EB12 EB14 1

10,000

2

5

10

20

50

100

200

500

1,000

2,000

5,000

FECAL COLIFORM BACTERIA CONCENTRATION,

 IN COLONIES PER 100 MILLILITERS

EB4 EB5

PaDEP criterion

Figure 14. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at

sampling sites on East Branch Brandywine Creek, Chester County, Pennsylvania, 1998-99.

EXPLANATION

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

INTERQUARTILE RANGE OUTSIDE THE QUARTILE

DATA VALUE LESS THAN OR EQUAL TO 1.5 TIMES THE

INDICATES SINGLE SAMPLE

LOCAL SITE NUMBER

BASE FLOW

STORMFLOW

DESIGNATES A TRIBUTARY
28

bacteria samples were collected at stormflow. The

land use in the subbasin is mixed—46 percent

forested, 37 percent agricultural, and 12 percent

residential. Forested areas become prevalent over

agricultural areas between the subbasin above EB2

and the subbasin above EB3. Median bacteria

concentrations decrease between the two

subbasins. Indian Run does not contribute elevated

concentrations of bacteria to East Branch Brandywine Creek.

Concentrations of fecal coliform bacteria

during base flow at Marsh Creek near Glenmoore

(EB4), which is above the Marsh Creek Reservoir,

ranged from 12 to 200 col/100 mL; the median

concentration was 78 col/100 mL. Two samples

were collected and analyzed for E. coli bacteria; the

concentrations were 2 and 230 col/100 mL. Two

samples were collected during stormflow and

analyzed for fecal coliform bacteria; the

concentrations were 400 and 66,000 col/100 mL.

One sample was collected and analyzed for E. coli

bacteria; the concentration was 2,500 col/100 mL.

The second stormflow sample analyzed for fecal

coliform and E. coli bacteria was collected during

Hurricane Floyd and is not considered to be a

bacteria concentration for a normal storm event.

The land use in the subbasin is mixed—46 percent

forested, 39 percent agricultural, and 8 percent

residential. At base flow, Marsh Creek does not

contribute elevated concentrations of bacteria to

the Marsh Creek Reservoir.

Concentrations of fecal coliform bacteria at

Marsh Creek near Downingtown (EB5) during

base flow were measured three times. The

concentrations were 22, 67, and 81 col/100 mL.

One E. coli bacteria sample was collected at base

flow; the concentration was 75 col/100 mL.

Samples were collected twice during stormflow

and analyzed for fecal coliform bacteria; the

concentrations were 40 and 2,200 col/100 mL.

One sample was collected during stormflow and

analyzed for E. coli bacteria; the concentration was

2,400 col/100 mL. The land use in the subbasin is

mixed—38 percent forested, 34 percent

agricultural, and 17 percent residential. This site is

below Marsh Creek Reservoir. Bacteria

concentrations decrease between EB4 and EB5. The

second stormflow sample analyzed for fecal

coliform and E. coli bacteria was collected during

Hurricane Floyd and is not considered to be a

normal storm event bacteria concentration. During

base flow, Marsh Creek does not contribute

elevated bacteria concentrations to the East Branch

Brandywine Creek.

Concentrations of fecal coliform bacteria at

East Branch Brandywine Creek at Lyndell (EB6)

during base flow ranged from 9 to 970 col/100 mL;

the median concentration was 290 col/100 mL.

Two samples were collected at base flow and

analyzed for E. coli bacteria; concentrations were

100 and 120 col/100 mL. Two samples were

collected during stormflow and analyzed for fecal

coliform bacteria; concentrations were 3,200 and

9,200 col/100 mL. One sample was collected

during stormflow and analyzed for E.coli bacteria;

the concentration was 2,200 col/100 mL. The land

use in the subbasin is mixed—45 percent

agriculture, 39 percent forested, and 10 percent

residential. Forested area is on the left side of the

creek within 0.5 mi of EB6. Approximately 150 ft

upstream of EB6 is a campground. A pond on the

campground property supports fish and geese.

Bacteria concentrations increase between EB2 and

EB6. During base flow, nonpoint sources for

bacteria include wildlife and possibly several small

tributaries between EB2 and EB6 that were not

included in this study.

Concentrations of fecal coliform bacteria at

Culbertson Run at Lyndell (EB7) during base flow

ranged from 9 to 430 col/100 mL; the median

concentration was 180 col/100 mL. Two samples

were collected during base flow and analyzed for

E. coli bacteria; concentrations were 200 and

340 col/100 mL. One sample was collected during

stormflow; the concentration of fecal coliform

bacteria was 19,000 col/100 mL, and the concentration of E. coli bacteria was 960 col/100 mL. The

land use in the subbasin is mixed—44 percent

agricultural, 33 percent residential, and 21 percent

forested. Residences are on both sides of

Culbertson Run within 0.5 mi upstream of EB7.

At base flow, Culbertson Run does not contribute

elevated concentrations of bacteria to East Branch

Brandywine Creek.

Concentrations of fecal coliform bacteria at

East Branch Brandywine Creek near Downingtown (EB8) during base flow ranged from 110

to 170 col/100 mL; the median concentration

was 160 col/100 mL. Two samples were analyzed

for E. coli bacteria; concentrations were 110 and

170 col/100 mL. Two samples were collected

during stormflow and analyzed for fecal

coliform bacteria and E. coli. Concentrations of
29

fecal coliform bacteria were 9,800 and

16,000 col/100 mL, and concentrations of E. coli

bacteria were 4,000 and 4,400 col/100 mL. The

maximum bacteria concentrations during

stormflow for fecal coliform and E. coli were

measured during Hurricane Floyd and are not

considered to be normal storm event bacteria

concentrations. The land use in the subbasin is

mixed—39 percent agricultural, 37 percent

forested, and 16 percent residential. Bacteria

concentrations decrease between EB6 and EB8.

Concentrations of fecal coliform bacteria at

Beaver Creek near Downingtown (EB9) during

base flow ranged from 140 to 1,700 col/100 mL; the

median concentration was 700 col/100 mL.

Two samples were collected at base flow and

analyzed for E. coli bacteria; concentrations were

210 and 1,000 col/100 mL. Two samples were

collected during stormflow and analyzed for fecal

coliform bacteria; concentrations were 1,700 and

6,800 col/100 mL. No sample was collected during

stormflow for analysis of E. coli bacteria. The land

use in the subbasin is mixed—33 percent

agricultural, 29 percent forested, and 25 percent

residential. An open field, a park, and a pumping

station are within 0.5 mi upstream from EB9.

Beaver Creek contributes elevated bacteria

concentrations to East Branch Brandywine Creek.

Concentrations of fecal coliform bacteria at

East Branch Brandywine Creek at Downingtown

(EBA) during base flow were measure three times.

The concentrations were 100, 210, and

470 col/100 mL. Two samples were collected at

base flow and analyzed for E. coli bacteria;

concentrations were 340 and 350 col/100 mL.

One sample was collected during stormflow; the

concentration of fecal coliform bacteria was greater

than 1,200 col/100 mL, and the concentration of

E. coli bacteria was greater than 800 col/100 mL.

The land use in the subbasin is mixed—36 percent

agricultural, 36 percent forested, and 19 percent

residential. A paper board company and the center

of the borough of Downingtown is within 0.5 mi

upstream of EBA. This site was added midway

through the study to collect additional data

between EB8 and EB10. Bacteria concentrations

increase between EB8 and EBA. A tributary

draining a pond in the center of Downingtown

flows into the East Branch Brandywine Creek

above EBA. Resident geese abound on this pond

and may contribute to the slightly elevated

bacteria concentrations at EBA. During storms, the

nonpoint source is land-surface runoff, exacerbated by the urban areas of Downingtown. The paper

board company discharges into the local sewer

system and, therefore, is not considered to be a

point source for bacterial contamination.

Concentrations of fecal coliform bacteria at

East Branch Brandywine Creek at Altor (EBC)

during base flow were analyzed three times. The

concentrations were 200, 270, and 410 col/100 mL.

No samples were collected for analysis of E. coli

bacteria during either base flow or stormflow. One

sample was collected during stormflow; the

concentration of fecal coliform bacteria was greater

than 1,200 col/100 mL. The land use in the

subbasin is mixed—37 percent forested, 34 percent

agricultural, and 20 percent residential. Forest,

cropland, residences, and an unmanned

wastewater treatment plant are within 0.5 mi

upstream of EBC. Another wastewater treatment

plant is approximately 1.4 mi upstream from EBC,

and a paper plant is approximately 1.8 mi

upstream. This site was added midway through

the study to collect additional data between EBA

and EB10. Bacteria concentrations increase

between EBA and EBC.

Fecal coliform bacteria concentrations at

Uwchlan Run at Exton (EB13) during base flow

ranged from 6 to 2,000 col/100 mL; the median

was 310 col/100 mL. Two samples were analyzed

for E. coli bacteria; concentrations were 150 and

220 col/100 mL. Two fecal coliform bacteria

samples were collected during stormflow;

concentrations were 6,000 and 20,000 col/100 mL.

No E. coli bacteria samples were collected during

stormflow. Uwchlan Run was dry during July and

August 1999 and was not sampled. The land use in

the subbasin is predominantly residential

(67 percent). A mixture of townhouses, open fields,

forest, and urban area is within 0.5 mi upstream of

EB13. Uwchlan Run contributes elevated

concentrations of bacteria to Valley Creek.

Samples were collected twice at Valley Creek

at Ravine Road near Downingtown (EBB) during

base flow for analysis of fecal coliform bacteria;

concentrations were 31 and 60 col/100 mL. No

samples were collected for analysis of E. coli

bacteria. One sample was collected during

stormflow; the concentration of fecal coliform

bacteria was 70 col/100 mL. No sample was

collected during stormflow for analysis of E. coli

bacteria. The land use in the subbasin is mixed—

31 percent forested, 26 percent residential, and

20 percent agricultural. This site was added
30

midway through the study to collect additional

data between EB13 and EB11. Bacteria

concentrations were below the PaDEP criterion of

200 col/100 mL. An instream discharge facility is

located between EB13 and EBB. The instream

discharge is made by a quarry and consists of

ground water pumped from the quarry. Ground

water contains little or no bacteria, and the

addition of ground water to the stream probably

dilutes bacteria concentrations in Valley Creek.

Concentrations of fecal coliform bacteria at

East Branch Brandywine Creek below

Downingtown (EB10) during base flow ranged

from 80 to 8,000 col/100 mL; the median

concentration was 590 col/100 mL. One sample

was collected during base flow and analyzed

for E. coli bacteria; the concentration was

110 col/100 mL. Concentrations of fecal coliform

bacteria during stormflow ranged from 1,400 to

12,000 col/100 mL; the median concentration was

4,500 col/100 mL. Two samples were collected

during stormflow and analyzed for E. coli

bacteria; the concentrations were 1,000 and

16,000 col/100 mL. The maximum concentrations

for both fecal coliform and E. coli bacteria were

measured during Hurricane Floyd and are not

considered to be normal storm event bacteria

concentrations. The land use in the subbasin is

mixed—37 percent forested, 34 percent

agricultural, and 20 percent residential. Forest lines

both sides of the creek within 0.5 mi upstream of

EB10.

Concentrations of fecal coliform bacteria at

Valley Creek at Altor (EB11) during base flow

ranged from 40 to 220 col/100 mL. One sample

was collected during base flow and analyzed

for E. coli bacteria; the concentration was

290 col/100 mL. Two samples were collected

during stormflow and analyzed for fecal

coliform bacteria; concentrations were 1,200 and

3,600 col/100 mL. One sample was collected

during stormflow and analyzed for E. coli bacteria;

the concentration was 1,600 col/100 mL. The land

use in the subbasin is mixed—33 percent forested,

30 percent residential, and 19 percent agricultural.

Bacteria concentrations slightly increased between

EBB and EB11; however, Valley Creek does not

contribute elevated concentrations of bacteria to

East Branch Brandywine Creek.

Concentrations of fecal coliform bacteria at

Taylor Run at Copesville (EB12) during base flow

ranged from 20 to 920 col/100 mL; the median

concentration was 390 col/100 mL. Two samples

were collected at base flow and analyzed for

E. coli bacteria; the concentrations were 130 to

390 col/100 mL. One sample was collected during

stormflow and analyzed for fecal coliform bacteria;

the concentration was 4,700 col/100 mL. No

sample was collected for analysis of E. coli bacteria.

The land use in the subbasin is mixed—37 percent

residential, 26 percent forested, and 23 percent

agricultural. The site is surrounded by hayfields.

Taylor Run contributes elevated concentrations of

bacteria to East Branch Brandywine Creek.

Concentrations of fecal coliform bacteria at

East Branch Brandywine Creek at Wawaset

(EB14) during base flow ranged from 120 to

410 col/100 mL; the median concentration was

230 col/100 mL. Three samples were analyzed for

E. coli bacteria; concentrations were 81, 360, and

410 col/100 mL. One sample was collected during

stormflow and analyzed for fecal coliform bacteria;

the concentration was 280 col/100 mL. No sample

was collected during stormflow for analysis of

E. coli bacteria. The land use in the subbasin is

mixed—35 percent forested, 31 percent agricultural, and 22 percent residential. An open field and

a fenced pasture containing livestock is within

0.5 mi upstream of EB14. Bacteria concentrations

decrease between EB10 and EB14 because of the

distance between sites and the natural die-off of

the bacteria during stream transport.

Main Stem Brandywine Creek

Bacteria concentrations on the main stem of

the Brandywine Creek during base flow and

stormflow are shown in figure 15. At base flow, the

median bacteria concentration exceeded

200 col/100 mL only at MS2 on Pocopson Creek,

which is a tributary to the main stem. During

stormflow, the median concentrations of fecal

coliform bacteria exceeded 200 col/100 mL at all

three sites.

Concentrations of fecal coliform bacteria at

Brandywine Creek at Pocopson (MS1) during base

flow ranged from 2 to 85 col/100 mL; the median

concentration was 50 col/100 mL. Two samples

were analyzed for E. coli bacteria; concentrations

were 70 and 93 col/100 mL. Two samples were

collected during stormflow and analyzed for fecal

coliform bacteria; concentrations were 4,400 and

5,500 col/100 mL. One sample was collected

during stormflow for analysis of E. coli bacteria;

the concentration was 180 col/100 mL. The land
31

0

1,200

100

200

300

400

500

600

700

800

900

1,000

1,100

FECAL COLIFORM BACTERIA CONCENTRATION,

Figure 15. Distribution of concentrations of fecal coliform bacteria during base flow and stormflow at sampling

sites on main stem Brandywine Creek, Chester County, Pennsylvania,1998-99.

25TH PERCENTILE

MEDIAN

75TH PERCENTILE

MS1 MS2 MS3

LOCAL SITE NUMBER

100

100,000

200

1,000

2,000

5,000

10,000

20,000

50,000

FECAL COLIFORM BACTERIA CONCENTRATION,

 IN COLONIES PER 100 MILLILITERS IN COLONIES PER 100 MILLILITERS

500

OUTLIER DATA VALUE MORE THAN

STORMFLOW

BASE FLOW

DESIGNATES TRIBUTARY

EXPLANATION

INDICATES SINGLE SAMPLE

PaDEP criterion

PaDEP criterion

RANGE OUTSIDE THE QUARTILE

 3 TIMES THE INTERQUARTILE

MS1 MS2 MS3
32

use in the subbasin is mixed—42 percent

agricultural, 32 percent forested, and 17 percent

residential. Bacteria concentrations decrease

between EB14 on the East Branch and WB15 on the

West Branch and MS1. This decrease in

concentration is due to the distance between sites

and the natural die-off of the bacteria.

Concentrations of fecal coliform bacteria for

Pocopson Creek at Pocopson (MS2) during base

flow ranged from 3 to 1,100 col/100 mL; the

median concentration was 430 col/100 mL. Three

samples were analyzed for E. coli bacteria;

concentrations were 20, 80, and 390 col/100 mL.

Two samples were collected during stormflow and

analyzed for fecal coliform bacteria; concentrations

were 15,000 and 20,000 col/100 mL. No samples

were collected during stormflow for analysis of

E. coli. The land use in the subbasin is mixed—

49 percent agricultural, 26 percent residential, and

21 percent forested. A hayfield is on the upstream

right side and horses are pastured on the left side.

Approximately 300 ft upstream is riparian forest

90-120 ft wide on both sides of the creek. Pocopson

Creek contributes elevated bacteria concentrations

to the main stem Brandywine Creek.

Concentrations of fecal coliform bacteria at

Brandywine Creek at Chadds Ford (MS3) during

base flow ranged from 2 to 2,200 col/100 mL; the

median concentration was 120 col/100 mL. Two

samples were collected at base flow and analyzed

for E. coli bacteria; concentrations were 44 and

180 col/100 mL. Concentrations of fecal coliform

bacteria during stormflow ranged from 160 to

6,700 col/100 mL; the median concentration was

2,200 col/100 mL. Two samples were collected

during stormflow and analyzed for E. coli bacteria;

concentrations were 440 and 620 col/100 mL.

Bacterial concentrations increase between sites

MS1 and MS3; however, the median concentration

does not exceed the PaDEP criterion. A nonpoint

source for the increase in bacteria concentration

during base flow is Pocopson Creek, a tributary

between sites MS1 and MS3 with elevated bacteria

concentrations.

Point Discharges

Eighteen point discharges are known in the

Brandywine Creek Basin. The point discharges are

identified as wastewater treatment plants and

instream discharge facilities. Instream discharge

facilities are commercial and industrial, such as

paper mills and steel plants. The quality of the

water being discharged from the wastewater

treatment plants and the instream discharge

facilities at the time of sampling was not

determined. Each wastewater treatment plant

must submit a Discharge Monitoring Report

(DMR) to the PaDEP and resolve any exceedance

in bacteria concentrations. It was beyond the scope

of this project to research and evaluate each

facility’s record of DMR’s. While any one of the

point discharges in the Brandywine Creek Basin

occasionally could be a point source for bacteria

contamination, they are not viewed as causal

agents because of their regulation by the PaDEP.

SUMMARY AND CONCLUSIONS

Concentrations of fecal coliform bacteria at

three USGS long-term water-quality monitoring

stations in the Brandywine Creek Basin show a

general downward trend for 1973-99. Implementation of regulations stemming from of the Clean

Water Act of 1972 contributed to the decrease of

bacteria concentrations between 1973 and 1987.

With the upgrade in wastewater treatment plants,

a decrease in point-source discharges, and the

general decrease of agricultural land use in the

basin, bacteria concentrations decreased

dramatically and then stabilized. Concentrations

of fecal coliform bacteria were highest at West

Brandywine Creek at Modena and lowest at

Brandywine Creek at Chadds Ford. Streamflow

and concentrations of fecal coliform bacteria were

positively related at both sites, that is, bacteria

concentrations increase as streamflow increases.

Concentrations of fecal coliform bacteria are

elevated—they exceed the regulatory criterion of

200 colonies per 100 milliliters—during both base

flow and stormflow conditions at all three

monitoring stations.

The concentrations of fecal coliform and E. coli

bacteria in the Brandywine Creek Basin were

assessed on the basis of data collected at 40 stream

sites. Thirty-two sampling sites were selected on

the basis of historical data, land use, known point

discharges of bacteria, and areas where

recreational use was evident; nine of these sites

were at established U.S. Geological Survey (USGS)

streamflow-measurement stations. Eight

additional sampling sites were added midway

through the study to collect additional data

between established sites with elevated bacteria

concentrations measured during monthly

sampling. Sampling was conducted at base flow

approximately monthly from March to September
33

1999. Sampling also was conducted during five

storms where rainfall exceeded 0.5 in. Samples

were collected at all of the USGS streamflowmeasurement stations during every storm, and five

selected sites were sampled during each storm.

During 1998-99, the median concentration of

fecal coliform bacteria in the water samples

collected during base flow in the Brandywine

Creek Basin exceeded 200 col/100 mL at 26 sites

(65 percent). The median concentration of fecal

coliform bacteria at sites sampled on the West

Branch exceeded 200 col/100 mL at 15 of the

20 sites (75 percent). The median concentration of

fecal coliform bacteria at sites sampled on the East

Branch exceeded 200 col/100 mL at 10 of the

17 sites (58 percent). The median concentration of

fecal coliform bacteria on the main stem exceeded

200 col/100 mL at one of the three sites

(33 percent). During 1998-99, the median

concentration of fecal coliform bacteria in the

water samples collected during stormflow

exceeded 200 col/100 mL at 30 of 33 sites

(91 percent). The median concentration of fecal

coliform bacteria at sites on the West Branch

exceeded 200 col/100 mL at 12 of 13 sites sampled

(92 percent). The median concentration of fecal

coliform bacteria at sites on the East Branch

exceeded 200 col/100 mL at 15 of the 17 sites

sampled (88 percent). The median concentration of

fecal coliform bacteria on the main stem exceeded

200 col/100 mL at all three sites sampled.

Every water sample analyzed contained E. coli

bacteria. During base flow, in 21 of 24 samples

(91 percent of non-estimated measurements) the

ratio of E. coli to fecal coliforms was greater than

1:2. During stormflow, in 2 of 8 samples (37 percent

of non-estimated measurements) the ratio of E. coli

to fecal coliforms was greater than 1:2.

The Kruskal-Wallis test for statistically

significant differences in bacteria concentrations at

the 95-percent confidence level showed no

significant differences between fecal coliform

concentrations in agricultural, forested, residential

or mixed subbasins during base flow and

stormflow. However, sites in forested subbasins

had a greater range in bacteria concentrations than

did sites in agricultural, residential, or mixed

subbasins.

Factors affecting bacteria concentrations in the

Brandywine Creek Basin include nonpoint sources,

stormflow, reservoirs, and seasonality. Nonpoint

sources may include agriculture, ground-water

contamination (residential septic systems or

leaking landfills), urban/residential activities,

resident wildlife, and land-surface runoff.

Bacteria concentrations are higher in

stormflow than in base flow. Rainfall flushes the

land surface, and overland runoff transports

bacteria into the stream. The bacteria

concentrations at five sites where at least four

samples were collected during both base flow and

stormflow were compared. For all five sites,

bacteria concentrations were substantially higher

during storms than during base flow. During

stormflow, sites on 14 of 15 tributaries

(93 percent) to Brandywine Creek had median

concentrations of fecal coliform bacteria

greater than 200 col/100 mL.

Sites above and below each of the three

reservoirs in the Brandywine Creek Basin

(Chambers Lake, Rock Run, and Marsh Creek

Reservoirs) were sampled. Bacteria concentrations

in the streams that flow from the reservoirs are

lower than bacteria concentrations in the streams

that flow into the reservoirs. The bacteria

concentration in the water flowing out of the

reservoir is reflective of the bacteria concentration

in the reservoir, not the stream flowing into the

reservoir. The volume of water in the incoming

stream is very small compared to the volume of

water in the reservoir.

Seasonality plays a role in the concentration of

bacteria in Brandywine Creek. During March,

April, May, October, and November, water

temperatures and bacteria concentrations are

lower in the Brandywine Creek than during June,

July, August, and September. The 10-year median

concentrations of bacteria at West Branch

Brandywine Creek at Modena and East Branch

Brandywine Creek below Downingtown exceeded

the criterion of 200 col/100 mL established by the

PaDEP for the swimming season. The 10-year

median concentrations of bacteria at Brandywine

Creek at Chadds Ford exceeded criterion of

200 col/100 mL only during June. None of the

three stations exceeded the criterion of

2,000 col/100 mL established by the PaDEP for

the remainder of the year.

Tributaries on the West Branch that contribute

elevated bacteria concentrations to Brandywine

Creek during base flow include Birch Run, Rock

Run, Doe Run, Little Broad Run, Broad Run, and

Two Log Run. During stormflow, Buck Run also

contributes elevated bacteria concentrations.
34

Tributaries on the East Branch that contribute

elevated bacteria concentrations to Brandywine

Creek during base flow include Beaver Creek,

Uwchlan Run, and Taylor Run. During stormflow,

Marsh Creek, Culbertson Run, and Valley Creek

also contribute elevated bacteria concentrations.

Pocopson Creek, the only tributary on the main

stem that was evaluated, contributes bacteria

concentrations to the Brandywine Creek during

base flow and stormflow.

SELECTED REFERENCES

Chester County, 1996, Landscapes-Managing

change in Chester County 1996-2000—

Comprehensive Plan Policy Element:

West Chester, Pa., 128 p.

Clesceri, L.S., Greenberg, A.E., and Eaton, A.D.,

eds., 1998, Standard methods for the

examination of water and wastewater, 20th

edition: Washington, D.C., American Public

Health Association, American Water Works

Association, and Water Environment

Federation [variously paged].

Dufour, A.P., 1977, Escherichia—the fecal coliform,

in Hoadley, A., and Dutka, B.J., eds., Bacterial

indicators/health hazards associated with

water: American Society for Testing and

Materials, STP 635, p. 48-58.

Francy, D.S., Myers, D.M., and Metzker, K.D., 1993,

Escherichia coli and fecal coliform bacteria as

indicators of recreational water quality:

U.S. Geological Survey Water-Resources

Investigations Report 93-4083, 34 p.

Grieg, D., Bowers, J., and Kauffman, G., 1998,

Christina River Basin Water Quality

Management Strategy, Phase I & II: Water

Resources Agency for New Castle County,

Chester County Conservation District, and

Chester County Water Resources Authority,

Chester County, Pa. [variously paginated]

Myers, D.N., and Wilde, F.D., eds., 1997, Biological

indicators: U.S. Geological Survey

Techniques of Water-Resources Investigations,

book 9, chap. A7, 38 p.

Pennsylvania Department of Environmental

Protection, 1999, Pennsylvania Code, Title 25,

Chapter 93, Water Quality Standards:

Commonwealth of Pennsylvania, 212 p.

U.S. Environmental Protection Agency, 1986,

Quality criteria for water 1986: Office of

Water, EPA 440/5-86-001 [variously paged].

_____1998, Bacterial water quality standards for

recreational waters: Office of Water, EPA 823-

R-98-003, [variously paged]

Wilde, F.D., Radtke, D.B., Givs, J., and Iwatsubo,

R.T., 1998, National field manual for the

collection of water-quality data: U.S.

Geological Survey Techniques of WaterResources Investigations, book 9, chap. A4

[variously paginated].

Wilhelm, L.J., and Maluk, T.L., 1998, Fecalindicator bacteria in surface waters of the

Santee River Basin and coastal drainages,

North and South Carolina, 1995-98:

U.S. Geological Survey Fact Sheet 085-98,

6 p.

Wood, C.R., 1998, The U.S. Geological Survey

cooperative water-resources program in

Chester County, Pennsylvania: U.S.

Geological Survey Fact Sheet 067-98, 4 p.
35

Table 6. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, West Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; >, greater than; <, less than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)

WB1 West Branch Brandywine Creek at Rockville (01480269)

08-04-98 — — — 291 20.5 5,500 —

04-09-99 — 12.4 7.3 274 11.5 200 —

05-05-99 3.5 10.9 7.0 271 13.5 1,900 E —

06-04-99 3.1 8.2 7.0 279 20.0 5,000 —

07-19-99 .60 7.1 7.4 293 24.5 3,100 >600

08-16-99 .72 6.5 7.1 286 23.5 5,100 5,900

09-13-99 .93 7.5 7.0 302 17.0 4,100 1,000

WBA Two Log Run at Birdell (01480295)

07-19-99 1.1 8.5 7.8 276 20.0 540 —

08-16-99 — 9.6 7.3 278 17.5 960 —

09-13-99 — 9.2 7.4 294 16.5 740 —

WB2 West Branch Brandywine Creek near Honey Brook (01480300)

07-29-98 3.3 — — 280 23.0 6,600 E —

08-04-98 2.7 — — 308 21.0 4,100 —

04-09-99 5.9 9.8 7.0 288 12.0 63 —

05-05-99 5.3 10.3 7.3 — 14.5 2,300 E —

06-04-99 2.0 7.2 7.1 327 19.0 4,800 —

07-19-99 .70 — 7.7 405 25.0 >6,000 >8,000

08-16-99 .70 6.5 7.6 382 23.0 >6,000 6,600

09-13-99 .87 7.8 7.4 372 19.0 10,000 1,900 E

WB3 West Branch Brandywine Creek at Brandamore (01480349)

07-29-98 9.9 — — 246 23.0 270 —

09-24-98 — — — 254 14.0 230 —

05-04-99 17 10.8 7.6 237 15.0 200 —

06-02-99 11 8.1 7.1 210 20.5 200 —

07-19-99 — 8.5 7.8 255 24.0 720 470

08-16-99 3.0 7.0 7.1 272 21.5 590 —

WB4 Birch Run near Martins Corner (01480390)

07-29-98 .81 8.7 7.6 118 19.0 1,400 —

04-08-99 2.0 9.1 8.2 104 17.0 33 —

05-04-99 1.8 10.9 7.5 100 14.5 300 E —

06-02-99 .86 9.1 6.8 89 17.5 130 180

07-19-99 — 8.3 7.1 98 22.0 650 —

08-16-99 .19 8.4 6.8 128 19.5 510 —

09-13-99 .23 8.8 6.8 151 16.0 820 230 E

WB5 Birch Run near Wagontown (01480400)

07-29-98 2.0 6.8 7.3 135 18.0 28 E —

04-08-99 4.0 9.9 6.9 123 12.5 3 E —

05-05-99 3.4 10.0 7.2 127 14.0 3 E 3 E

06-03-99 1.7 8.4 7.0 135 13.0 7 E 1 E

09-13-99 1.7 7.8 6.9 150 20.0 33 —
36

WB6 Rock Run near Philipsville (01480458)

07-29-98 1.2 — — 180 20.5 2,400 —

04-08-99 1.8 9.5 8.9 165 18.5 20 E —

05-04-99 1.6 10.8 8.1 164 15.5 1,600 E —

06-02-99 .98 8.5 7.0 181 20.5 15,000 E >1,600

07-19-99 — 8.0 7.6 191 22.5 870 E 1,400

08-16-99 .39 8.0 7.2 214 21.0 2,100 1,500 E

WBE Rock Run at Reservoir near Coatesville (01480463)

08-04-99 — — — — 19.5 3,900 —

08-16-99 — — — 232 20.0 3,300 —

WB7 Rock Run below Coatesville Reservoir (01480466)

07-29-98 1.2 — — 202 19.5 33 E —

09-24-98 — — — 300 12.5 580 —

05-05-99 1.4 11.4 8.6 192 16.5 20 E —

05-18-99 .93 8.6 6.8 193 12.0 100 93

09-13-99 1.1 6.8 6.7 215 21.0 120 97

WBD Rock Run at Rock Run near Coatesville (01480470)

07-19-99 — — — — 21.5 1,900 E —

08-17-99 — — — — 19.5 453 —

09-13-99 — — — 276 16.0 240 —

WBB West Branch Brandywine Creek at Rock Run (01480434)

07-19-99 — — — — 22.5 370 —

08-17-99 — — — — 23.0 210 —

09-13-99 — — — 283 16.0 200 —

WBC West Branch Brandywine Creek below Rock Run at Coatesville (01480480)

07-19-99 — — — — 23.0 600 —

08-17-99 — — — — 22.5 320 —

09-13-99 — — — 270 16.5 250 —

WB8 West Branch Brandywine Creek at Coatesville Reservoir (01480500)

07-27-98 20 — — 233 21.5 1,800 E —

08-04-98 20 — — 236 19.5 280 100 E

09-24-98 12 — — 251 13.0 410 —

04-07-99 36 12.1 8.3 213 15.5 2 E —

05-05-99 32 9.6 7.3 228 13.5 130 —

05-18-99 25 9.8 7.4 221 14.0 410 240

06-01-99 3.7 9.2 7.6 232 22.0 >600 —

07-19-99 8.1 8.3 7.3 236 25.0 420 —

08-16-99 9.8 10.0 7.7 254 23.5 330 —

09-13-99 8.4 9.3 7.2 254 17.5 450 500

Table 6. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, West Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999—Continued

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; >, greater than; <, less than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)
37

WB9 West Branch Brandywine Creek at Modena (01480617)

07-07-98 38 10.0 7.7 316 21.5 500 —

07-13-98 30 10.2 7.8 313 21.5 820 —

07-27-98 27 9.6 8.3 330 22.5 940 —

08-04-98 26 — — 337 20.5 1,800 100 E

08-24-98 26 11.8 8.2 338 24.0 1,500 E —

09-09-98 6.5 10.5 7.6 314 18.0 3,000 —

09-22-98 23 8.5 7.7 359 22.0 2,100 —

03-11-99 46 12.9 8.2 285 4.0 150 —

04-08-99 43 12.0 9.2 301 17.5 6 E —

04-16-99 59 10.4 7.6 265 11.5 390 —

04-29-99 42 8.3 7.6 283 12.0 240 —

05-03-99 38 8.3 7.8 296 13.5 280 —

05-18-99 33 9.7 7.8 307 16.0 1,400 E 800

05-25-99 43 10.2 7.8 276 17.5 2,800 —

06-02-99 28 10.3 7.8 298 22.5 480 —

06-23-99 23 10.8 8.2 335 22.5 2,000 E —

06-28-99 19 7.3 7.5 356 23.0 2,100 —

07-15-99 15 11.3 8.2 368 21.0 2,200 E —

07-19-99 13 8.4 7.8 409 24.5 2,300 —

07-26-99 14 10.2 8.4 395 25.5 750 —

08-03-99 13 9.5 8.0 402 24.5 1,300 —

08-16-99 16 9.1 8.2 380 25.5 860 660

09-08-99 30 7.8 7.6 333 22.5 4,400 —

09-13-99 16 8.1 7.9 433 16.0 610 310

WB10 Buck Run at Doe Run (01480629)

07-28-98 13 — — 223 22.0 190 —

04-07-99 23 11.9 7.8 215 12.0 7 E —

05-04-99 21 11.2 7.5 214 14.0 18 E —

06-02-99 16 9.1 7.3 217 23.5 170 —

08-16-99 7.1 9.5 7.7 236 23.5 310 260

09-13-99 8.6 9.1 7.1 246 17.0 370 69 E

WB11 Doe Run above Tributary at Springdell (014806318)

07-29-98 — — — 152 19.5 200 —

04-07-99 12 11.6 7.6 153 12.5 10 E —

05-04-99 11 11.9 7.1 155 13.0 82 —

06-03-99 6.9 8.8 7.0 155 18.5 1,100 690

07-19-99 4.2 8.7 7.3 152 23.0 620 —

08-16-99 2.1 8.9 7.1 148 22.5 360 —

09-13-99 3.8 10.0 7.0 155 16.5 300 110 E

Table 6. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, West Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999—Continued

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; >, greater than; <, less than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)
38

WB12 West Branch Brandywine Creek near Embreeville (01480634)

07-28-98 66 — — 266 22.0 260 —

04-08-99 123 11.3 8.0 240 12.0 18 E —

05-03-99 112 11.3 8.1 236 13.0 93 —

06-01-99 84 9.4 7.6 262 22.0 500 E —

07-19-99 38 9.4 7.5 291 24.5 130 120

08-16-99 39 8.2 7.4 297 23.0 85 E 68 E

WB13 Little Broad Run near Marshallton (01480637)

07-29-98 .37 — — 251 19.0 450 —

08-04-98 .37 — — 254 17.0 260 200

04-08-99 .73 11.6 8.0 235 14.0 15 E —

05-03-99 .63 10.4 6.9 249 12.5 27 E —

06-01-99 .42 8.5 7.1 250 19.5 140 —

07-19-99 .21 8.8 7.0 254 21.0 2,000 E —

08-16-99 .35 9.0 7.1 249 20.5 530 330

 09-13-99 .09 9.8 7.2 243 15.5 380 330

WB14 Broad Run at Northbrook (01480638)

07-28-98 4.2 8.7 7.7 195 19.0 480 —

05-18-99 5.4 9.5 7.3 190 15.0 100 46 E

07-19-99 1.2 9.3 7.1 194 20.5 840 —

08-16-99 .80 8.4 7.0 208 20.5 720 —

09-13-99 1.7 9.7 7.2 203 15.0 470 320

WB15 West Branch Brandywine Creek at Wawaset (01480640)

07-28-98 70 8.9 7.9 254 22.5 350 —

04-08-99 134 10.5 8.7 231 14.5 10 E —

05-03-99 101 8.9 7.0 226 13.0 120 —

06-01-99 77 9.9 7.1 238 22.5 150 —

07-21-99 40 8.4 7.7 284 23.5 220 200

08-18-99 28 7.2 7.3 288 24.0 200 E 260

09-14-99 36 8.9 7.6 294 19.0 100 60 E

Table 6. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, West Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999—Continued

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; >, greater than; <, less than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)
39

Table 7. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, East Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)

EB1 East Branch Brandywine Creek near Cupola (01480648)

03-31-99 4.4 10.6 8.3 203 13.5 31 E —

05-04-99 3.7 13.3 8.5 220 15.5 140 —

06-02-99 2.2 8.2 6.5 217 18.5 1,200 —

08-03-99 .44 8.6 7.3 219 19.0 260 E 240

08-17-99 .57 7.6 7.3 228 20.0 260 86 E

EB2 East Branch Brandywine Creek at Glenmoore (01480653)

03-31-99 14 12.2 7.6 191 8.0 63 E —

05-04-99 14 11.5 7.4 201 12.5 200 —

06-02-99 8.0 8.9 6.7 200 21.5 160 170

08-03-99 — 6.9 7.0 200 20.0 330 —

08-17-99 2.6 7.7 7.2 209 21.0 270 —

09-15-99 1.7 7.9 7.0 228 18.0 220 E 110 E

EB3 Indian Run at Springton (01480658)

03-31-99 5.8 12.3 8.5 158 12.5 11 E —

05-04-99 4.2 11.0 8.5 177 14.5 65 —

06-02-99 3.2 8.9 6.8 183 18.5 71 E 90

EB4 Marsh Creek near Glenmoore (01480675)

07-29-98 2.7 8.3 7.6 201 21.0 78 —

03-31-99 8.2 11.4 7.2 182 9.0 14 E —

05-04-99 6.9 10.4 6.9 191 12.5 12 E 2 E

06-02-99 3.0 8.3 6.7 183 20.5 100 —

08-17-99 .76 7.9 7.1 241 21.5 200 230

EB5 Marsh Creek near Downingtown (01480685)

7-29-98 9.0 7.2 8.0 169 26.5 22 E —

05-04-99 5.2 10.2 7.2 197 13.5 67 75

08-03-99 8.7 7.6 6.4 203 10.0 81 E —

EB6 East Branch Brandywine Creek at Lyndell (01480660)

07-27-98 14 — — 197 20.0 430 —

03-31-99 29 12.2 8.5 187 13.5 9 E —

05-05-99 23 11.2 7.6 223 17.5 67 —

06-02-99 12 8.6 6.6 197 23.0 970 E 120

08-03-99 3.6 9.4 7.4 201 20.5 440 —

09-14-99 5.7 9.4 7.2 217 17.0 140 E 100 E

EB7 Culbertson Run at Lyndell (01480662)

07-27-98 3.5 — — 237 20.0 180 —

03-31-99 5.0 11.9 8.1 228 12.5 9 E —

05-05-99 4.9 10.7 7.3 254 13.5 120 —

08-17-99 .34 8.1 7.2 237 21.5 300 340

09-14-99 .72 8.8 7.2 257 17.0 430 200
40

EB8 East Branch Brandywine Creek near Downingtown (01480700)

07-27-98 41 — — 200 23.0 160 —

08-04-98 38 — — 203 20.0 170 —

03-31-99 66 12.3 6.6 212 6.5 110 —

05-04-99 39 11.1 7.5 218 13.0 160 170

06-02-99 39 9.0 7.8 206 22.0 110 110

EB9 Beaver Creek near Downingtown (01480775)

07-28-98 7.7 8.2 — 350 19.0 490 —

03-31-99 18 12.5 7.2 315 8.0 140 —

05-03-99 15 10.2 7.9 312 12.5 740 —

06-02-99 9.0 8.8 7.6 324 21.0 1,700 E 1,000

08-03-99 2.2 9.2 7.7 405 20.5 1,200 E —

08-17-99 2.3 8.3 7.6 403 20.5 700 —

09-14-99 4.0 9.0 7.6 383 17.5 140 E 210

EBA East Branch Brandywine Creek at Downingtown (01480800)

08-03-99 17 11.4 8.3 282 23.5 100 350

08-17-99 — — 8.4 267 23.0 470 340

09-14-99 — 12.5 8.3 285 19.5 210 —

EBC East Branch Brandywine Creek at Altor (01480840)

08-03-99 19 7.3 7.4 354 21.5 410 —

08-17-99 — — 7.4 363 23.5 200 —

09-14-99 — — 7.5 402 20.0 270 —

EB13 Uwchlan Run at Exton (01480878)

07-29-98 1.5 — — 401 21.0 480 —

08-04-98 .30 — — 412 19.0 230 220

03-31-99 1.2 13.5 8.6 415 10.0 6 E —

05-04-99 .65 11.8 7.8 407 13.5 200 150

06-04-99 .30 8.2 7.2 406 18.5 2000 —

09-14-99 .04 8.1 7.8 417 18.0 390 220

EBB Valley Creek at Ravine Road near Downingtown (01480887)

08-03-99 1.6 8.5 7.6 584 22.0 60 E —

08-17-99 — — — 575 24.0 31 E —

EB10 East Branch Brandywine Creek below Downingtown (01480870)

07-07-98 76 9.0 7.8 286 21.1 480 —

07-13-98 101 9.4 7.4 261 21.5 590 —

07-27-98 65 10.9 8.3 307 23.0 340 —

08-04-98 61 — — 309 20.5 880 —

08-10-98 59 8.7 7.7 308 24.0 300 —

08-18-98 112 8.4 7.4 220 22.0 > 600 —

08-24-98 68 9.8 7.9 304 24.0 520 —

09-09-98 55 9.3 7.7 304 18.5 640 —

09-22-98 65 8.0 7.4 329 21.0 >8,000 —

Table 7. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, East Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999—Continued

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)
41

03-31-99 114 13.8 7.7 265 8.5 80 E —

04-29-99 84 10.4 7.5 286 12.5 190 —

05-03-99 80 11.3 7.7 295 14.0 660 —

05-18-99 69 9.9 7.8 285 16.0 150 110

06-02-99 71 6.7 7.7 303 22.0 530 —

06-23-99 58 9.6 7.9 334 23.5 1,600 E —

06-28-99 52 6.2 7.5 342 24.0 390 —

07-15-99 43 8.5 7.7 386 20.5 390 E —

07-19-99 38 6.4 7.4 405 24.0 470 —

07-26-99 42 8.0 7.7 360 24.5 920 —

08-03-99 35 6.8 7.4 390 24.0 680 —

08-16-99 42 6.8 7.6 349 24.5 550 —

09-08-99 48 6.6 7.3 330 23.0 4,000 —

09-14-99 49 6.8 7.5 379 20.0 410 —

EB11 Valley Creek at Altor (01480905)

07-27-98 9.0 11.8 8.4 400 21.0 83 E —

03-31-99 24 10.6 7.5 398 6.5 40 E —

05-03-99 18 11.2 8.0 375 12.0 77 —

06-04-99 11 11.0 8.0 334 22.0 220 290

08-03-99 2.5 8.0 7.5 332 21.0 88 E —

08-17-99 4.7 9.1 7.6 444 22.0 200 —

EB12 Taylor Run at Copesville (01480930)

07-28-98 4.7 12.3 8.6 518 25.0 580 —

03-31-99 7.0 13.0 7.7 500 14.5 20 E —

05-03-99 6.8 10.9 7.4 426 12.5 200 —

06-02-99 4.9 — 7.8 489 22.0 390 —

08-03-99 2.1 7.4 7.1 706 20.5 920 —

08-17-99 2.3 7.3 7.0 591 22.5 800 390

09-14-99 3.0 10.7 7.7 530 19.0 250 130 E

EB14 East Branch Brandywine Creek at Wawaset (01480950)

07-28-98 56 7.3 7.6 346 22.0 410 —

05-03-99 — 10.8 7.2 330 13.0 120 —

06-02-99 59 — 7.4 335 22.0 220 —

07-21-99 31 7.6 7.2 392 23.0 230 360

08-18-99 24 6.9 7.4 408 24.0 330 410

09-14-99 28 9.0 7.4 415 21.5 130 E 81 E

Table 7. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, East Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999—Continued

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)
42

Table 8. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during base flow, main stem Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter

at 25°C; mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(

oC)

Fecal coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)

MS1 Brandywine Creek at Pocopson (01480970)

07-28-98 139 — — 293 23.0 15 E —

09-24-98 — 8.3 7.8 305 16.0 28 E —

04-08-99 — 13.0 7.6 265 15.0 2 E —

06-01-99 146 9.2 6.8 283 22.5 63 E —

08-18-99 53 8.0 7.4 319 26.0 83 93

09-15-99 43 7.3 7.2 347 20.5 85 E 70

MS2 Pocopson Creek at Pocopson (01480975)

07-28-98 3.3 — — 232 21.0 430 —

09-24-98 — 12.1 8.1 222 13.0 620 —

04-08-99 — 11.5 8.0 215 15.0 3 E —

05-03-99 7.9 10.6 6.9 220 11.0 1,100 —

06-01-99 4.6 9.1 6.8 — 19.5 1,100 —

07-21-99 2.1 8.8 7.5 234 22.0 420 390

08-18-99 .39 8.1 7.3 244 22.5 130 E 80 E

09-15-99 1.7 8.5 7.1 248 19.0 240 20 E

MS3 Brandywine Creek at Chadds Ford (01481000)

07-07-98 195 8.3 7.5 300 22.0 180 —

07-13-98 222 7.5 7.7 283 21.5 60 E —

07-27-98 162 8.0 7.5 313 23.0 120 —

08-10-98 122 7.5 7.4 330 25.0 580 —

08-18-98 382 — 7.2 190 23.0 > 600 —

08-24-98 131 7.5 7.2 316 24.0 120 —

09-09-98 131 8.0 7.5 260 19.0 88 —

09-22-98 116 6.6 7.4 341 22.0 210 —

09-24-98 106 5.2 7.6 365 17.0 60 E —

03-11-99 265 10.0 6.3 267 4.0 27 —

04-07-99 294 12.3 7.9 265 13.5 2 E —

04-16-99 348 10.0 7.5 229 11.5 52 —

04-29-99 241 9.7 7.4 258 13.5 98 —

05-03-99 219 9.3 7.4 262 14.5 78 —

05-18-99 195 10.1 7.7 275 18.0 94 E 44 E

06-02-99 173 8.2 7.6 277 23.0 110 —

06-23-99 163 10.0 7.4 293 22.0 150 E —

06-28-99 135 6.5 7.0 303 25.0 100 —

07-15-99 104 8.4 7.5 321 22.0 2,200 E —

07-19-99 85 6.5 7.4 341 26.5 180 —

07-21-99 104 7.4 7.4 293 25.0 110 —

07-26-99 80 7.1 7.5 338 26.5 120 —

08-03-99 63 6.0 7.4 372 26.0 180 —

08-16-99 92.3 7.8 7.5 316 25.5 105 —

09-08-99 181 7.6 7.4 271 24.5 210 —

09-15-99 99.7 7.8 7.7 335 21.5 140 180
43

Table 9. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during storms, West Branch Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25°C;

mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)

WB2 West Branch Brandywine Creek near Honey Brook (01480300)

10-08-98 20 — — 265 16.0 150,000 E —

03-22-99 92 10.9 7.2 203 6.5 1,100 —

08-14-99 10 — — 294 23.0 >6,000 >8,000

08-26-99 4 — — 219 19.01 >12,000 >16,000

09-16-99 202 — — 116 17.5 610,000 E 250,000

WB3 West Branch Brandywine Creek at Brandamore (01480349)

08-26-99 — — — 238 20.0 — 1,000

WB4 Birch Run near Martins Corner (01480390)

08-14-99 — — — 145 22.0 >6,000 >8,000

09-16-99 — — — 119 17.5 >240,000 >320,000

WB5 Birch Run near Wagontown (01480400)

03-22-99 40 12.9 7.1 123 6.0 24 E —

WB6 Rock Run near Philipsville (01480458)

08-14-99 — — — 218 23.0 > 6,000 > 8,000

09-16-99 — — — 118 18.0 540,000 E 16,000 E

WB8 West Branch Brandywine Creek at Coatesville Reservoir (01480500)

10-08-98 40 — — 209 15.5 3,700 —

03-22-99 734 12.7 7.71 139 5.0 5,100 —

08-26-99 25 — — 172 20.0 9,200 1,400 E

09-16-99 410 — — — 18.0 16,000 12,000

WB9 West Branch Brandywine Creek at Modena (01480617)

10-08-98 51 — — 243 17.5 15,000 —

03-22-99 817 12.7 7.8 146 5.0 5,000 —

08-14-99 21 5.7 7.7 328 26.0 > 6,000 > 8,000

08-26-99 38 6.1 7.7 252 20.5 11,000 E 600 E

09-16-99 596 3.1 7.5 410 19.0 4,000 2,900

09-27-99 30 9.0 8.0 377 17.5 2,700 E —

WB10 Buck Run at Doe Run (01480629)

08-14-99 — — — 220 27.0 > 6,000 > 8,000

WB11 Doe Run above Tributary at Springdell (014806318)

10-08-98 12 11.6 7.6 153 15.5 580 —

WB12 West Branch Brandywine Creek near Embreeville (01480634)

08-14-99 — — — 210 26.5 220 190

WB13 Little Broad Run near Marshallton (01480637)

10-08-98 2.1 — — 165 16.5 22,000 —

03-22-99 2.0 11.1 7.7 209 9.0 24 E —

08-14-99 — — — 249 24.0 720 670

WB14 Broad Run at Northbrook (01480638)

08-14-99 — — — 197 23.5 1,400 E 1,300

WB15 West Branch Brandywine Creek at Wawaset (01480640)

08-26-99 — — — 263 21.0 3,600 E 1,300
44

Table 10. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during storms, East Branch Brandywine Creek Basin, Chester County, Pennsylvania,

July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter

at 25 °C; mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)

EB1 East Branch Brandywine Creek near Cupola (01480648)

07-30-98 2.4 — — 224 21.0 600 —

07-20-99 .67 7.6 7.5 227 21.5 > 1,200 —

EB2 East Branch Brandywine Creek at Glenmoore (01480653)

07-30-98 8.5 — — 211 21.5 450 —

07-20-99 5.4 6.8 7.1 204 22.0 >1,200 —

08-26-99 — — — 173 19.5 >12,000 >16,000

EB3 Indian Run at Springton (01480658)

07-30-98 2.5 — — 191 20.0 150 —

EB4 Marsh Creek near Glenmoore (01480675)

03-22-99 100 12.2 6.7 146 5.5 400 E —

09-16-99 320 — — 188 18.0 66,000 2,500

EB5 Marsh Creek near Downingtown (01480685)

07-20-99 8.5 7.5 7.0 200 9.5 40 E —

09-16-99 10 — — 281 12.0 2,200 2,400

EB6 East Branch Brandywine Creek at Lyndell (01480660)

07-20-99 10 7.6 7.7 185 22.5 3,200 —

08-26-99 — — — 158 19.0 9,200 2,200

EB7 Culbertson Run at Lyndell (01480662)

08-26-99 — — — 240 19.5 19,000 E 960 E

EB8 East Branch Brandywine Creek near Downingtown (01480700)

08-26-99 94 — — 181 18.0 9,800 >4,000

09-16-99 588 — — — 18.0 16,000 4,400

EB9 Beaver Creek near Downingtown (01480775)

07-20-99 4.0 8.8 7.2 356 21.5 6,800 —

08-26-99 — — — 248 19.5 1,700 E —

EBA East Branch Brandywine Creek at Downingtown (01480800)

07-20-99 — 9.7 8.4 262 22.0 > 1,200 > 800

EBC East Branch Brandywine Creek at Altor (01480840)

07/20/99 39 9.4 7.1 388 23.5 > 1,200 —

EB13 Uwchlan Run at Exton (01480878)

10-08-98 6.2 — — 106 18.0 20,000 E —

07-20-99 .34 8.9 7.3 285 23.5 > 6,000 —

EBB Valley Creek at Ravine Road near Downingtown (01480887)

07-20-99 — 6.0 7.4 299 23.0 70 E —

EB10 East Branch Brandywine Creek below Downingtown (01480870)

03-22-99 973 11.4 7.4 152 6.5 2,100 —

05-25-99 132 9.4 7.7 244 18.0 4,500 —

07-20-99 59 5.5 7.2 342 24.5 6,500 E —

08-26-99 142 3.9 7.0 220 20.5 5,000 1,000

09-16-99 1,210 4.2 7.4 166 19.5 12,000 16,000

09-27-99 398 7.0 7.2 232 16.0 1,400 E —
45

EB11 Valley Creek at Altor (01480905)

07-20-99 8.1 9.5 7.0 240 23.5 > 1,200 —

08-26-99 — — — 148 21.0 3,600 E 1,600

EB12 Taylor Run at Copesville (01480930)

07-20-99 3.3 8.2 7.1 516 23.5 4,700 —

EB14 East Branch Brandywine Creek at Wawaset (01480950)

08-26-99 — — — 167 21.0 280 E —

Table 10. Streamflow, physical and chemical properties, and fecal coliform and E. coli bacteria

concentrations during storms, East Branch Brandywine Creek Basin, Chester County, Pennsylvania,

July 1998 to September 1999—Continued

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter

at 25 °C; mg/L, milligrams per liter; E, estimated; >, greater than; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)
46

Table 11. Streamflow, physical and chemical properties, and fecal coliform and E. coli

bacteria concentrations during storms, Main Stem Brandywine Creek Basin, Chester County,

Pennsylvania, July 1998 to September 1999

[°C, degrees Celsius; ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter

at 25°C; mg/L, milligrams per liter; E, estimated; —, no data; mL, milliliter]

Date Discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH

(standard

units)

Specific

conductance

(μS/cm)

Temperature

(°C)

Fecal

coliform

(colonies

per

100 mL)

E. coli

(colonies

per

100 mL)

MS1 Brandywine Creek at Pocopson (01480970)

10-09-98 — — — 200 16.5 4,400

09-16-99 — — — 347 20.5 5,500 180 E

MS2 Pocopson Creek at Pocopson (01480975)

10-09-98 — — — 186 16.0 15,000 —

09-16-99 — — — 108 20.0 20,000 E —

MS3 Brandywine Creek at Chadds Ford (01481000)

03-22-99 3,620 11.4 7.4 150 6.5 2,200 —

05-25-99 409 8.3 7.4 210 16.0 6,700 —

08-26-99 747 7.3 7.4 300 22.0 2,600 620

09-16-99 8,290 7.4 7.1 125 17.0 960 E 440 E

09-27-99 395 8.8 7.6 257 16.5 160 —