U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5150

Prepared in cooperation with the Metropolitan St. Louis Sewer District

Occurrence and Sources of Escherichia coli in 

Metropolitan St. Louis Streams, October 2004 

through September 2007

 ̈¦§44

 ̈¦§270

 ̈¦§55

 ̈¦§70

 ̈¦§255

 ̈¦§

 ̈¦§70

270

 ̈¦§64

 ̈¦§170

0 5 10 KILOMETERS

0 5 10 MILES

90°15'

90°22'30"

90°30'

90°37'30"

90°15'

90°22'30"

90°30'

90°37'30"

38°30'

38°37'30"

38°52'30"

38°45'

38°45'

38°52'

38°30'

#

05587455

06935972

#06935965

#

06935715

#

06935890

# #

06937000

# 07005500

#07010000

# 07010022

06936475

07010097

#

#

07010220

07019370

St. Louis

ST. LOUIS

COUNTY

EXPLANATION

Meramec R iver

Coldwater Creek

River des Peres

Creve Coeur Creek

River des Peres

Mississippi River

Missouri River

Missouri River Maline Creek

Grand Glaize Creek

Meramec

River

#

07019185

#

# 

935890 

07005000 #

Missouri

Index map

Illinois

Study area

ILLINOIS

MISSOURI

ILLINOIS

MISSOURI

#

City of St. Louis municipal area

Western extent of metropolitan St. Louis sewer 

 district service area

Sampling site and U.S. Geological Survey identifier

Wastewater-treatment plant

Precipitation station

se from U.S. Geological Survey digital data, 

100,000, 1992

nsverse Mercator projection

ral meridian 93°00’, origin 00°00’

Mississippi River

1

10

100

1,000

r

2

 = 0.90

MAPE = 19

HUMAN

r2

 = 0.6

MAPE = 

GOOSE

REPLICATE

1 2 3 4 1 2 3 

Environmental sample

Replicate sample

Environmental sample

Replicate sample

Environmental sample

Replicate sample

Environmental sample

Replicate sample

r2

 = 0.44

ESCHERICHIA COLI

MAPE = 27

 DENSITY, IN COLONIES PER 100 MILLILITER

1

10

100

1,000

DOG

UNKNOWN

Mississippi River (5 sites)

Missouri River (3 sites)

Creve 

Coeur Grand 

Creek Glaize 

Creek

River des P

University 

Maline

Creek

Coldwater Cr

River des Peres at 

 St. Louis

IMPERVIOUS COVER, IN PERCENT

y = 184.2e0.085x

r2 = 0.83

0 10

20

30

40

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

ESCHERICHIA COLI DENSITY, 

IN COLONIES PER 100 MILLILITER

Mississippi River (5 sites)

Missouri River (3 sites)

Creve 

Coeur 

Creek

Grand 

Glaize 

Creek

River des Peres near 

University City

Maline

Creek

Coldwater Creek

River des Peres at 

 St. Louis

IMPERVIOUS COVER, IN P

y = 184.2e0.085x

r2 = 0.83

0 10

20

30

40

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

ESCHERICHIA COLI DENSITY, 

IN COLONIES PER 100 MILLILITER

State of Missouri 

 Class A criteria

State of Missouri 

 Secondary contact 

 criteria

State of Missouri 

 Class B criteria

MISSISSIPPI RIVER SITES

ESCHERICHIA COLI 

DENSITIES, IN COLONIES PER 100 MILLILITER

05587455

Below 

Grafton

07005500

Above

St. Louis

07010000

At 

St. Louis

07010220

At 

Oakville

07019370

At 

Kimmswick

MISSOURI RIVER SITES

06935972

Below 

St. Charles

06937000

At Columbia

bottom

(20)

(19)

(19)

51

220

100

100

101

102

103

104

105

106

100

101

102

103

104

105

106

(9)

(9)

(9)

480

250

580

BASE FLOW

(19)

(20)

(19)

(19)

(27)

13

46 32

116

100

(9)

(9)

(9)

(9)

(16)

110 160

32

480

280

STORM EVENT

DIRECTION OF STREAMFLOW

06935715

Near 

Chesterfield

(19) Number of samples 

EXPLANATION

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Upper outside

x

Base flow

Storm event

100

06935715

06935972

06937000

MISSOURI RIVER SITES

05587455

07005500

07010000

07010220

07019370

MISSISSIPPI RIVER SITES

BASE FLO

HUMAN

DOG

GOOSE

UNKNOWN

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

(16)

(16)

(16)

[53]

[84]

[98]

(16)

[19]

(17)

[63]

(18)

[86]

(17)

[92]

(17)

[86]

ESCHERICHIA COLI ATTRIBUTABLE TO HOST SOURCE, IN PERCENT

(16)

(16)

(16)

[24]

[36]

[25]

(16)

(17)

(18)

(17) [4] [19]

[32]

[19]

(17)

[9]

(15)

(16)

(15)

(

[24]

[32]

[20]

[26

(16)

(16)

(16)

[44]

[43]

[44]

(16)

(17)

(18)

(17)

[20]

[30]

[35]

[35]

(17)

[39]

(15)

(16)

(15)

(14)

[48]

[68]

[58]

[29]

(15)

[50]

(16)

[48]

(16)

(16)

(16)

[59]

[75]

[69]

(16)

(17)

(18)

(17)

[31]

[59]

[66]

[72]

(17)

[66]

(15)

(16)

(15)

(14)

[76]

[79]

[64]

[85]

(15)

[60]

(16)

[89]

Mean value

Range of values

Number of samples

Number of isolates

Missouri River

 tributary sites
Cover photograph index

Mississippi River at St. Louis, July 2002, 

photograph by M.E. Slifer, U.S. Geological 

Survey.

Preparing for winter-time flood measurements on the Missouri River at St. Charles, 

photograph by R.J. Huizinga, U.S. Geological 

Survey. Preparing to sample suspended 

sediment from boat, Mississippi 

River at St. Louis, July 2002, 

photograph by M.E. Slifer, U.S. 

Geological Survey.
Occurrence and Sources of Escherichia 

coli in Metropolitan St. Louis Streams, 

October 2004 through September 2007

By Donald H. Wilkison and Jerri V. Davis

Prepared in cooperation with the Metropolitan St. Louis Sewer District 

Scientific Investigations Report 2010–5150

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

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Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Wilkison, D.H., Davis, J.V., 2010, Occurrence and sources of Escherichia coli in metropolitan St. Louis streams, 

October 2004 through September 2007: U.S. Geological Survey Scientific Investigations Report 2010–5150, 57 p.
iii

Contents

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

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

Background............................................................................................................................................1

Purpose and Scope ..............................................................................................................................4

Study Area Description........................................................................................................................8

Previous Studies ...................................................................................................................................8

Methods...........................................................................................................................................................9

Sampling and Laboratory Protocols ..................................................................................................9

Quality Assurance...............................................................................................................................11

Data Analysis.......................................................................................................................................14

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams ............................15

Escherichia coli Densities in Base Flow and Storm Events ........................................................15

Instantaneous Escherichia coli Loads ............................................................................................20

Base-Flow Escherchia coli Sources ...............................................................................................21

Storm-Event Escherchia coli Sources ............................................................................................25

Escherichia coli Host-Source Loads ...............................................................................................28

Bacteroides thetaiotaomicron..........................................................................................................32

Annual Load Estimates.......................................................................................................................33

Hydrologic Effects on Escherichia coli Densities in Streams .....................................................38

Summary and Conclusions.........................................................................................................................46

References Cited..........................................................................................................................................47

Figures

1–2. Maps showing:

1. Location of study area and sampling sites......................................................................2

2. Location of combined sewer overflows, sanitary sewer overflows, and 

wastewater treatment plants maintained by the Metropolitan St. Louis Sewer 

District in relation to study area sampling sites .............................................................5

3. Photograph showing view upstream from River des Peres near University City (site 

07010022) ........................................................................................................................................8

4–19. Graphs showing:

4. Quantile-quantile plots of Escherichia coli and fecal coliform replicate samples 

collected at sites in the metropolitan St. Louis area ...................................................12

5. Host-source Escherichia coli densities determined in environmental and replicate 

rep-PCR samples ...............................................................................................................13

6. Relation between fecal coliform density and Escherichia coli density at 

metropolitan St. Louis sites..............................................................................................15

7. Escherichia coli densities in stream samples collected at sites in metropolitan St. 

Louis between October 2004 and September 2007 ......................................................16

8. Escherichia coli densities in discrete samples collected between October 2004 

and September 2007 at large river sites in the metropolitan St. Louis area............17

9. Escherichia coli densities in discrete samples collected between October 2004 

and September 2007 at small basin sites in the metropolitan St. Louis area ..........18
iv

10. Instantaneous Escherichia coli loads from discrete samples collected between 

October 2004 and September 2007 at large river sites in the metropolitan St. Louis 

area ......................................................................................................................................23

11. Instantaneous Escherichia coli loads from discrete samples collected between 

October 2004 and September 2007 at small basin sites in the metropolitan St. 

Louis area............................................................................................................................24

` 12. Mean percent of Escherichia coli bacteria attributable to host sources at sites 

in the metropolitan St. Louis area from base-flow samples collected between 

October 2004 and September 2007 .................................................................................27

13. Mean percent of Escherichia coli bacteria attributable to host sources at sites 

in the metropolitan St. Louis area from storm-event samples collected between 

October 2004 and September 2007 .................................................................................29

14. Mean Escherichia coli load attributable to host sources at sites in the 

metropolitan St. Louis area from base-flow samples collected between October 

2004 and September 2007.................................................................................................31

15. Mean Escherichia coli load attributable to host sources at sites in the 

metropolitan St. Louis area from storm-event samples collected between October 

2004 and September 2007.................................................................................................36

16. Percent of Escherichia coli identified by host-source category in samples 

collected in the metropolitan St. Louis area between October 2004 and September 

2007 ......................................................................................................................................37

17. Estimated annual loads of Escherichia coli for sites in the metropolitan St. 

Louis area from October 1996 through September 2007 and streamflow and 

precipitation comparison to the long-term (90-year) average...................................41

18. Estimated daily mean Escherichia coli densities for streams in metropolitan St. 

Louis from October 2004 through September 2007 ......................................................44

19. Relation between Escherichia coli densities and the percent of upstream 

impervious cover at sites in the metropolitan St. Louis area.....................................46

Tables

1. Sites sampled as part of this study............................................................................................3

2. Number of combined or sanitary sewer overflow points upstream from sample sites 

and estimated travel time between sites or to receiving stream.........................................6

3. Quality assurance replicate data for fecal indicator bacteria analyzed as part of this 

study..............................................................................................................................................11

4. State of Missouri Escherichia coli bacteria criteria applicable to selected metropolitan 

St. Louis area stream reaches in relation to study area sites.............................................19

5. Percent of discrete Escherichia coli bacteria samples collected between October 2004 

and September 2007 at stream sites in the metropolitan St. Louis area that met the 

applicable State of Missouri criterion.....................................................................................20

6. Tributary inputs of Escherichia coli loads to receiving streams for samples collected 

between October 2004 and September 2007..........................................................................22

7. Summary of microbial source-tracking samples analyzed at metropolitan St. Louis 

sites between October 2004 and September 2007 ................................................................26

8. Summary statistics for Escherichia coli host-source determinations by repetitive extragenic pallindromic polymerase chain reaction (rep-PCR)...................................................53

9. Percent of water samples collected between October 2004 and September 2007 at 

metropolitan St. Louis stream sites that met the applicable State of Missouri Escherichia coli criterion when adjusted by host-source density estimates ...........................30
v

10. Mean tributary inputs of Escherichia coli host-source loads to receiving streams for 

samples collected between October 2004 and September 2007........................................34

11. Regression models for estimating annual loads of Escherichia coli in water at metropolitan St. Louis sites .................................................................................................................39

12. Model (adjusted maximum likelihood estimation method) output for flow-adjusted 

trends in Escherichia coli concentration at metropolitan St. Louis sites..........................40

13. Estimated annual loads, in trillions of colonies, of Escherichia coli at metropolitan St. 

Louis sites for water years 1997 through 2007.......................................................................42

14. Mean annual Escherichia coli loads and yields at stream sites in metropolitan St. Louis 

and tributary inputs to receiving streams for water years 2005 through 2007 .................43

15. Percent of estimated daily mean Escherichia coli densities at stream sites in the 

metropolitan St. Louis area that met the applicable State of Missouri criterion from 

October 2004 through September 2007 ...................................................................................45

Conversion Factors, Abbreviations, and Datums

SI to Inch/Pound

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 0.3861 square mile (mi2)

Volume

liter (L) 0.2642 gallon (gal)

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

Area

square foot (ft2) 0.09290 square meter (m2)

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate

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

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

Vertical coordinate information is referenced to North American Vertical Datum of 1988 

(NAVD 88).

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

Abstract 

The occurrence and sources of Escherichia coli (E. 

coli), one of several fecal indicator bacteria, in metropolitan 

St. Louis streams known to receive nonpoint source runoff, 

occasional discharges from combined and sanitary sewers, and treated wastewater effluent were investigated from 

October 2004 through September 2007. Three Missouri River 

sites, five Mississippi River sites, and six small basin tributary stream sites were sampled during base flow and storm 

events for the presence of E. coli and their sources. E. coli

host-source determinations were conducted using local library 

based genotypic methods. Human fecal contamination in 

stream samples was additionally confirmed by the presence of 

Bacteroides thetaiotaomicron, an anaerobic, enteric bacterium 

with a high occurrence in, and specificity to, humans.

Missouri River E. coli densities and loads during base 

flow were approximately 10 times greater than those in the 

Mississippi River above its confluence with the Missouri 

River. Although substantial amounts of E. coli originated 

from within the study area during base flow and storm events, 

considerable amounts of E. coli in the Missouri River, as well 

as in the middle Mississippi River sections downstream from 

its confluence with the Missouri River, originated in Missouri 

River reaches upstream from the study area. In lower Mississippi River reaches, bacteria contributions from the numerous 

combined and sanitary sewer overflows within the study area, 

as well as contributions from nonpoint source runoff, greatly 

increased instream E. coli densities.

Although other urban factors cannot be discounted, 

average E. coli densities in streams were strongly correlated 

with the number of upstream combined and sanitary sewer 

overflow points, and the percentage of upstream impervious 

cover. Small basin sites with the greatest number of combined 

and sanitary sewer overflows (Maline Creek and the River des 

Peres) had larger E. coli densities, larger loads, and a greater 

percentage of E. coli attributable to humans than other small 

basin sites; however, even though small basin E. coli densities typically were much larger than in large river receiving 

streams, small basins contributed, on average, only a small 

part (a maximum of 16 percent) of the total E. coli load to 

larger rivers. 

On average, approximately one-third of E. coli in metropolitan St. Louis streams was identified as originating from 

humans. Another one-third of the E. coli was determined to 

have originated from unidentified sources; dogs and geese 

contributed lesser amounts, 10 and 20 percent, of the total 

instream bacteria. Sources of E. coli were largely independent 

of hydrologic conditions—an indication that sources remained 

relatively consistent with time. 

Introduction 

The Metropolitan St. Louis Sewer District (MSD) is 

developing a baseline of stream discharge and water-quality 

data at stream sites within its jurisdictional area (fig. 1; 

table 1). Streams within the MSD boundaries receive inputs 

from a variety of sources including, and most predominantly, 

nonpoint source runoff, combined sewer overflows (CSOs), 

sanitary sewer overflows (SSOs), and discharges from wastewater treatment plants (WWTPs). One concern is the presence 

of large densities of fecal indicator bacteria, including Escherichia coli (E. coli), in streams within the MSD area. To better 

understand factors that affect stream water quality in the MSD 

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

the MSD, initiated a study designed to characterize the occurrence, distribution, and sources of E. coli in metropolitan St. 

Louis streams.

Background

MSD serves approximately 1.4 million people in St. 

Louis City and St. Louis County. All of St. Louis City and part 

of eastern St. Louis County are served by a combined sewer 

system (CSS). The remainder of St. Louis County is served 

by separate storm and sanitary sewer systems. Approximately 

750 municipalities in the United States have a CSS (U.S. 

Environmental Protection Agency, 2004). Unlike a separate 

Occurrence and Sources of Escherichia coli in 

Metropolitan St. Louis Streams, October 2004 through 

September 2007

By Donald H. Wilkison and Jerri V. Davis
2 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

§ ̈¦44

§ ̈¦270

§ ̈¦55

§ ̈¦70

§ ̈¦255

§ ̈¦70

§ ̈¦270

§ ̈¦64

§ ̈¦170

0 5 10 KILOMETERS

0 5 10 MILES

90°15'

90°22'30"

90°30'

90°37'30"

90°15'

90°22'30"

90°30'

90°37'30"

38°30'

38°37'30"

38°52'30"

38°45'

38°45'

38°52'

38°30'

#

05587455

06935972

#06935965

#

06935715

#

06935890

# #

06937000

# 07005500

#07010000

#

07010022

06936475

07010097

#

#

07010220

07019370

St. Louis

ST. LOUIS

COUNTY

EXPLANATION

Meramec R iver

Coldwater Creek

River des Peres

Creve Coeur Creek

River des Peres

Mississippi River

Missouri River

Missouri River Maline Creek

Grand Glaize Creek

Meramec

River

# 07019185

#

06935890 #

#

07005000

Missouri

Index map

Illinois

Study area

ILLINOIS

MISSOURI

ILLINOIS

MISSOURI

#

City of St. Louis municipal area

Western extent of metropolitan St. Louis sewer 

 district service area

Sampling site and U.S. Geological Survey identifier

Wastewater-treatment plant

Precipitation station

Base from U.S. Geological Survey digital data, 

 1:100,000, 1992

Transverse Mercator projection

Central meridian 93°00’, origin 00°00’

Mississippi River

Figure 1. Location of study area and sampling sites.
Introduction 

3

Table 1. Sites sampled as part of this study.[mm, mile marker; °, degrees;’, minutes;”, seconds]

Site name (Bold part indicates abbreviated name used in text) Station identi- fier (fig. 1) Site type Latitude Longitude Stream reach General description

Missouri River sites

Missouri River near Chesterfield

at mm 48

06935715 Large river 38°39’46” 90°43’40” Upper Missouri Upstream Missouri River site

Missouri River below St. Charles

at mm 24.5

06935972 Large river 38°49’39” 90°26’27” Mid-Missouri Midstream Missouri River site below confluence with 

Creve Coeur Creek

Missouri River at Columbia Bottom Conservation Area at mm 4 06937000 Large river 38°49’18” 90°10’17” Lower-Missouri Downstream Missouri River site downstream from the confluence with Coldwater Creek just upstream 

from the confluence with Mississippi River

Mississippi River sites

Mississippi River below Grafton, 

Illinois

05587455 Large river 38°57’04” 90°22’16” Upper Mississippi Upstream Mississippi River site above MSD bound- ary and confluence with Missouri River

Mississippi River above St. Louis

at mm 184.5

07005500 Large river 38°42’03” 90°12’29” Mid-Mississippi Mid-Mississippi River site downstream from Missouri River and 3 of the 6 small basin sites

Mississippi River at St. Louis 07010000 Large river 38°37’44.4” 90°10’47.2” Mid-Mississippi Mid-Mississippi River site downstream from Missouri River and 3 of the 6 small basin sitesMississippi River at Oakville at 

mm 164.5

07010220 Large river 38°25’33” 90°17’39” Lower Mississippi Lower Mississippi River stie downstream from other sites in the study area

Mississippi River at Kimmswick, 

Missouri

07019370 Large river 38°21’28” 90°21’24” Lower Mississippi Lower Mississippi River stie downstream from other sites in the study area plus Meramec River

Small basin sites

Creve Coeur Creek near Creve 

Coeur, Missouri

06935890 Small basin 38°40’57.9” 90°29’20.0” Creve Coeur 

Creek

Tributary to Missouri River discharging upstream 

from Missouri River site 06935972

Coldwater Creek near Black Jack, 

Missouri

06936475 Small basin 38°49’04.8” 90°15’04.5” Coldwater 

Creek

Tributary to Missouri River discharging upstream 

from Missouri River site 06937000

Maline Creek at Bellefontaine 

Neighbors, Missouri

07005000 Small basin 38°44’12.4” 90°13’34.3” Maline Creek Tributary to Mississippi River discharging upstream 

from Mississippi River site 07005500

River des Peres near University 

City, Missouri

07010022 Small basin 38°33’33.9” 90°16’59.5” Upper River des 

Peres

Tributary to Mississippi River discharging midway between Mid-Mississippi (07005500 and 

07010000) and Lower Mississippi sites (07010220 and 07019370)

River des Peres at St. Louis, 

Missouri

07010097 Small basin 38°33’33.9” 90°16’59.5” Lower River 

des Peres

Tributary to Mississippi River discharging midway between Mid-Mississippi (07005500 and 

07010000) and Lower Mississippi sites (07010220 and 07019370)

Grand Glaize Creek near Valley 

Park, Missouri

07019185 Small basin 38°34’06.9” 90°28’16.2” Grand Glaize 

Creek

Tributary to Meramec River which then discharges 

between Lower Mississippi sites (07010220 and 07019370)
4 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

sanitary system, CSSs are designed to carry wastewater and 

storm runoff, and to function differently during dry and wet 

weather conditions.

In dry weather, a CSS is designed to operate exactly like 

a separate system and convey sewage from homes, businesses, and industry to a WWTP for treatment. After undergoing treatment, the water is discharged to a receiving stream in 

accordance with applicable water-quality standards.

During wet weather, the CSS carries sewage and stormwater to the treatment plant where the combination is treated 

and discharged. If the stormwater and sewage volume exceed 

pipe or treatment-plant capacities, the excess is diverted 

into receiving streams. All of this excess flow, a mixture of 

stormwater and sewage—regardless 

of the relative ratio of the two 

components—is considered to be part of a 

combined sewer 

overflow (CSO).

CSO discharge points 

primarily are 

located along 

the western and 

eastern edges 

of the City of St. 

Louis, primarily in 

areas where the sewer 

system is more than 100 

years old (fig. 2). Approximately two-thirds of the nearly 200 CSOs 

in the study area discharge either directly into the River des 

Peres or one of its tributaries (fig. 2; table 2). Thirty percent of 

the CSOs discharge directly to the Mississippi River (fig. 2); 

however, because smaller streams in the study area ultimately 

drain to the Mississippi River, any CSO discharge eventually 

makes its way to the Mississippi River. No CSOs in the study 

area discharge to the Missouri River. 

Unlike CSSs, separate sanitary sewer systems do not 

have the capacity to carry stormwater; however, during runoff 

events, infiltration and inflow into the pipes can cause the collection system to be overloaded. Then, in order to relieve system pressure, excess flow is sometimes diverted to receiving 

streams—events termed SSOs. In addition to the CSOs, there 

are approximately 200 constructed SSO points that occasionally discharge in the study area (fig. 2; table 2).

SSOs generally are located along the eastern one-third of 

St. Louis County (fig. 2). As with CSOs, most SSOs discharge 

to the River des Peres or its tributaries (fig. 2; table 2). Maline 

and Coldwater Creek, which are small basin tributaries of the 

Missouri River (fig. 2), receive approximately one-quarter of 

the SSO discharges in the study area. Because of the nature of 

the stream drainage network in the study area, any CSO and 

SSO discharge ultimately drains to the Mississippi River 

(fig. 2).

MSD operates seven wastewater treatment plants within 

the study area (fig. 2). Treated effluent from two of these 

plants is discharged to the Missouri River, three plants discharge to the Mississippi River, and the remaining two to the 

Meramec River. Approximately 75 percent of the treated effluent in any given year is discharged to the Mississippi River.

An increase in the level of bacteriological treatment is planned 

for all plants by 2013; however, currently (2010), disinfection 

is not part of the treatment process (Metropolitan St. Louis 

Sewer District, 2009a).

Other potential sources of wastewater in the study area 

include discharges from septic systems, as well as CSOs, 

SSOs, and treated effluent from WWTPs located outside the 

MSD jurisdictional area. There are 9 permitted CSOs that discharge into the Mississippi River from the Illinois side of the 

river. These are located between sites 07005500 and 07010220 

(fig. 2). The volume of effluent discharged from WWTPs 

in the study area not operated by MSD is approximately 15 

percent of that from MSD-operated facilities (U.S. Environmental Protection Agency, 2010). The bulk of this effluent is 

discharged to the Mississippi River.

Long-term control plans, designed to implement strategies that would reduce the volume and frequency of these 

CSOs and SSOs and to ensure compliance with Federal clean 

water statutes and applicable water-quality standards (U.S. 

Environmental Protection Agency, 1994; Missouri Department 

of Natural Resources, 2009) have been developed (Metropolitan St. Louis Sewer District, 2009b). Data on the system 

status and expected benefits from system alterations were part 

of these plans. Such data can be especially important in urban 

areas where additional factors—beyond CSOs and SSOs—

such as nonpoint source runoff may substantially degrade 

water quality. Water quality degraded by fecal contamination 

is of particular concern because such contamination can be 

indicative of the presence of pathogens and lead to increased 

risk of gastrointestinal illnesses in humans (Wade and others, 

2003; Haack and others, 2008; Duris and others, 2009).

Purpose and Scope

This report characterizes the occurrence and sources of 

the fecal indicator bacteria E. coli in metropolitan St. Louis 

stream reaches that receive urban nonpoint runoff, combined 

and sanitary sewer overflows, and treated wastewater effluent. 

Surface water-quality samples were collected from October 

2004 through September 2007 during base flow and storm 

events for indicator bacteria, including E. coli and sources of 

E. coli, at the sites listed in table 1. Three sites on the Missouri River, 5 on the Mississippi River, and 6 on small streams 

affected by CSOs, SSOs, treated effluent, or urban nonpoint 

source runoff were sampled. In addition, dog and goose feces, 

collected from landscapes closely associated with study sites, 

together with untreated human wastewater samples collected 

from WWTPs operated by MSD (fig. 2), were used to develop 

a genetically based E. coli source library for the study area.

 

Downstream view of the 

River des Peres at St. Louis site 

(photograph by Willie Easterling, 

U.S. Geological Survey).
Introduction 5

70

0 5 10 KILOMETERS

0 5 10 MILES

90°15'

90°22'30"

90°30'

90°37'30"

90°15'

90°22'30"

90°30'

90°37'30"

38°30'

38°37'30"

38°52'30"

38°45'

38°45'

38°52'

38°30'

05587455

06935972

06935965

06935715

06935890

06937000

07005500

07010000

07010022

06936475

07010097

#

07010220

07019370

EXPLANATION

Meramec R iver

Coldwater Creek

River des Peres

Creve Coeur Creek

River des Peres

Mississippi River

Missouri River

Missouri River Maline Creek

Grand Glaize Creek

Meramec

River

07019185

07005000

ILLINOIS

MISSOURI MISSOURI ILLINOIS

Base from U.S. Geological Survey digital data, 

 1:100,000, 1992

Transverse Mercator projection

Central meridian 93°00’, origin 00°00’

Mississippi River

ST. LOUIS

COUNTY

06935890 #

Coldwater Creek basin

River des Peres basin

Maline Creek basin

Creve Coeur Creek basin

Grand Glaize Creek basin

City of St. Louis municipal area

Western extent of metropolitan St. Louis 

 sewer district service area

Sampling site and U.S. Geological Survey 

 identifier

Wastewater-treatment plant

Combined sewer overflow

Sanitary sewer overflow

St. Louis

Figure 2. Location of combined sewer overflows, sanitary sewer overflows, and wastewater treatment plants 

maintained by the Metropolitan St. Louis Sewer District in relation to study area sampling sites.
6 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007 Table 2. Number of combined and sanitary sewer overflow points upstream from sample sites and estimated travel time between sites or to receiving stream. [CSOs, Combined Sewer Overflows; SSOs, Sanitary Sewer Overflows; mm, mile marker; f/s, feet per second; --, not applicable] Site name (Bold part indicates abbreviated name used in text) Station identifier (fig. 1) Mile marker Distance from adjacent up- stream station or to receiving stream, in miles Aggregate distance, in miles Mean storm event velocity, in ft/s Mean base-flow velocity, in ft/s Mean velocity, in ft/s Storm event travel time, in hours Base-flow travel time, in hours Mean travel time, in hours Number of up- stream CSOs Number of up- stream SSOs Receiving stream Missouri River sites Missouri River near Chesterfield at mm 48 06935715 48 -- 0 4.0 3.1 -- -- -- -- 0 0 -- Missouri River below St. Charles at mm 24.5 06935972 24.5 23.5 23.5 4.0 3.1 3.4 9 11 10 0 20 -- Missouri River at Columbia Bottom Conservation Area at mm 4 06937000 4 20.5 44 4.0 3.1 3.4 8 10 9 0 50 -- Confluence with Mis- sisippi River -- 0 48 48 -- -- 3.4 18 23 21 0 50 -- Average travel time between sites -- -- -- -- -- -- -- -- -- 9 -- -- -- Mississippi River sites Mississippi River be- low Grafton, Illinois 05587455 218 -- 0 -- -- -- -- -- -- 0 0 -- Mouth of Missouri River -- 195 23.0 23.0 5.0 3.2 4.0 7 11 8 0 0 -- Mississippi River above St. Louis at mm 184.5 07005500 184.5 10.5 33.5 5.0 3.2 4.0 3 5 4 9 87 -- Mississippi River at St. Louis 07010000 180 4.5 38.0 5.0 3.2 4.0 1 2 2 35 87 -- Mississippi River at Oakville at mm 164.5 07010220 164.5 15.5 53.5 5.0 3.2 4.0 5 7 6 198 192 -- Mississippi River at Kimmswick, Mis- souri 07019370 158.6 5.9 59.4 5.0 3.2 4.0 2 3 2 198 203 -- From Mississippi River below Grafton, Il- linois to Mississippi River at Kimmswick, Missouri “05587455 to 07019370” -- 59.4 59.4 5.0 3.2 4.0 18 27 22 -- -- --
Introduction 

7

Table 2. Number of combined and sanitary sewer overflow points upstream from sample sites and estimated travel time between sites or to receiving stream.—Continued [CSOs, Combined Sewer Overflows; SSOs, Sanitary Sewer Overflows; mm, mile marker; f/s, feet per second; --, not applicable]

Site name (Bold part 

indicates abbreviated 

name used in text)

Station 

identifier 

(fig. 1)

Mile 

marker

Distance 

from adjacent 

upstream station 

or to receiving 

stream, in miles

Aggregate 

distance, 

in miles

Mean 

storm event 

velocity,

in ft/s

Mean 

base-flow 

velocity, in 

ft/s

Mean 

velocity, 

in ft/s

Storm 

event travel 

time,

in hours

Base-flow 

travel 

time, 

in hours

Mean 

travel 

time, 

in hours

Number 

of upstream 

CSOs

Number 

of upstream 

SSOs

Receiving 

stream

Mississippi River sites—Continued

From Missouri River 

near Chesterfield to Mississippi River at Kimmswick, Missouri

“06935715 to

07019370”

-- 107 107 4.6 3.2 3.8 35 50 42 -- -- --

Average travel time 

between sites

-- -- -- -- -- -- -- -- -- 5 -- -- --

Small basin sites

Creve Coeur Creek

near Creve Coeur, Missouri

06935890 -- 5.7 -- 3.6 0.53 2.1 2 16 4 0 7 Missouri 

River

Coldwater Creek

near Black Jack, Missouri

06936475 -- 3.8 -- 1.7 .56 1.1 3 10 5 0 30 Missouri 

River

Maline Creek at 

Bellefontaine Neighbors, Missouri

07005000 -- 1.1 -- 2.2 .56 1.4 1 3 1 0 26 Mississippi 

River

River des Peres near 

University City, Missouri

07010022 -- 12.0 -- 5.9 2.5 4.2 3 7 4 17 15 River des 

Peres at St. Louis

River des Peres near 

University City, Missouri

07010022 -- 14.5 -- 5.2 2.3 3.7 4 9 6 17 15 Mississippi 

River

River des Peres at St. 

Louis, Missouri

07010097 -- 2.5 -- 2.0 .54 1.3 2 7 3 133 103 Mississippi 

River

Grand Glaize Creek

near Valley Park, Missouri

07019185 -- 3.3 -- 1.4 .61 1.0 3 8 5 0 7 Meramec 

River

Grand Glaize Creek

near Valley Park, Missouri

07019185 -- 23.8 -- 1.4 .61 1.0 24 58 34 0 7 Mississippi 

River

Average travel time 

between sites

-- -- -- -- -- -- -- -- -- 8 -- -- Missouri or 

Mississippi River
8 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

Estimates of annual E. coli loads, determined from trend and 

load estimation models developed from discrete data collected 

over a wide range of hydrologic conditions from October 1998 

through September 2007 also are presented. These data may 

be used to better understand the relative contribution of point 

and nonpoint sources to stream contaminants, to understand 

the role that hydrology has in determining concentration and 

load patterns and how those patterns change with time, and to 

provide a baseline for evaluating the effectiveness of longterm CSO control and watershed management plans to meet 

water-quality standards and protect designated stream uses.

Study Area Description

The study area comprises 14 surface-water sites located 

in the MSD, a customer-owned utility providing sanitary sewage and stormwater service within the 535 square miles of St. 

Louis City and most of St. Louis County (fig.1; table 1). Sample sites included 3 sites on the Missouri River, 5 on the Mississippi River, and 6 sites on smaller tributary streams affected 

by CSOs, SSOs, treated effluent, and/or urban nonpoint runoff 

(figs. 1 and 2). Continuous (hourly) streamflow data also 

were collected for the Missouri River at St. Charles (site 

06935965; figs.1 and 2). During an average precipitation 

year, such as 2000, as many as 65 overflow events occur in 

the study area discharging 13.3 billion gallons of overflow 

to receiving streams (Metropolitan St. Louis Sewer District, 

2009b). More than 95 percent of the CSO volume is discharged to the River des Peres or the Mississippi River (Metropolitan St. Louis Sewer District, 2009b).

Land use in the study area is more than 60 percent urban 

(Lanclos and others, 2005). Many stream reaches have been 

substantially modified with resultant changes, such as rapid 

stormwater and contaminant transport from impervious areas 

to streams through drainage pipe networks, to hydrology and 

channel morphology (fig. 3). This typically results in peak 

lag time reductions and increased water-quality degradation 

(Walsh and others, 2005). Additionally, extensive engineered 

modifications designed to facilitate river navigation and 

flood mitigation have occurred in reaches of the Missouri 

and Mississippi River throughout the study area (Pinter and 

others, 2009). One major effect of these modifications has 

been to alter the sediment transport dynamics of these rivers 

from being limited by sediment supply rather than transport 

processes (Meade and Moody, 2010). Nevertheless, suspended 

sediment concentrations, especially on the Missouri and Mississippi Rivers typically are high; concentrations averaged 494 

mg/L for the Missouri River at St. Charles (site 06935965; 

fig. 1) and 532 mg/L for the Mississippi River at St. Louis 

(site 07010000) during the course of this study (U.S. Geological Survey, 2006a; 2007; 2008).

Travel times in the study area, estimated from peak 

arrival times between adjacent stations or stream velocity 

measurements made during discharge measurements, indicate 

that during storm events, CSO and SSO discharges quickly 

move (travel times ranged from 1 to 4 hours) from small 

basin sites into the larger receiving streams (table 2). Average 

travel times from one large river site to the next downstream 

site ranged from 9 hours at Missouri River sites to 5 hours 

for Mississippi River sites (table 2). Instream velocities at 

study sites typically were greater than was needed to maintain 

sediments in suspension; this was especially true at large river 

sites where average stream velocities were more than 10 times 

greater than was needed to keep sediment, even coarse sand 

particles, in suspension (Weiming and Wang, 2006).

Average annual precipitation in the study area, based 

upon precipitation stations (fig. 1) that have at least 90 years of 

record, is 38.2 inches (National Climatic Data Center, 2010). 

Annual precipitation for the 2005 to 2007 water years (from 

October 1 to September 30 of each year) was 96 percent of the 

long-term average. The wettest year was 2005 (117 percent of 

normal), followed by the driest (72 percent of normal) year, 

and then a return to near normal conditions (97 percent) in 

2007 (National Climatic Data Center, 2010).

Previous Studies

Water-quality and streamflow data have been collected in 

the study area since 1996 as part of a cooperative agreement 

between the MSD and the USGS. Data at some sites have been 

collected at long-term stations as part of the USGS National 

Stream Quality Accounting Network (Hooper and others, 

2001). These data, including results from more than 1,800 

water-quality samples, have been published in USGS annual 

reports and made available online (http://waterdata.usgs.gov/

mo/nwis/sw; http://nwis/waterdata.usgs.gov/mo/nwis/qw).

Previous work (Wilkison and others, 2002; 2006; 2009) 

demonstrated that the combination of many factors, including inputs from nonpoint source runoff, CSOs, and WWTP 

Figure 3. View upstream from River des Peres near University discharges, frequently provides a diversity of E. coli sources 

City (site 07010022).
Methods 9

to urban streams. Other work, albeit in more rural settings, has 

demonstrated that elevated fecal indicator bacteria densities in 

receiving streams frequently originate from multiple sources 

(Schumacher, 2003; Davis and Barr, 2006; Ahmed and others, 2008). These factors, coupled with the rapid evolution of 

microbial source-tracking methods, have lead other researchers (Cimenti and others, 2007; Santo Domingo and others, 

2007; Haack and others, 2008) to insist that comprehensive 

source assessments of fecal pollution should include multiple 

approaches.

Once released to the environment, enteric indicator bacteria such as E. coli are subjected to a variety of biotic and abiotic pressures that affect survivability. Biotic pressures include 

grazing and competition for resources by other biota as well 

as bacteria regrowth. Abiotic pressures include bacterial 

inactivation by sunlight, temperature, pH, salinity, or chemicals (Hipsey and others, 2008). Of these, solar inactivation is 

deemed the most important process affecting the environmental mortality of E. coli (Whitman and others, 2004; Deller and 

others, 2006). In general, E. coli survival in the environment 

follows an exponential decay rate (Schultz-Fademrecht and 

others, 2008); however, a number of studies have demonstrated that little, if any, change in E. coli densities occurs 

within the first 24 hours of release into the environment, and in 

the case where sunlight is limited—such as turbid, sedimentladen waters—steady-state conditions can persist for several 

days, if not weeks (Anderson and others, 2005; Chandran and 

Hatha, 2005; Pote and others, 2009; Sevais and others, 2009). 

Methods

Approximately 500 water-quality samples were collected from 14 surface-water sites from October 2004 through 

September 2007 in metropolitan St. Louis. Samples were collected for a variety of hydrologic conditions and analyzed for 

indicator bacteria (E. coli and fecal coliform). The sources of 

E. coli were determined in 328 samples using genotypic methods that included repetitive extragenic palindromic polymerase 

chain reaction (rep-PCR) and determination of Bacteroides 

thetaiotaomicron (B. thetaiotaomicron). Annual load estimates 

were summed from daily estimates developed from load 

regression models. A geographic information system (ArcGIS, 

v. 9.3, ESRI Inc.) was used to determine relations between 

water-quality data and selected land-use factors to evaluate the 

relative role of nonpoint source runoff compared to selected 

point sources (overflows from combined and sanitary sewers) 

at study sites.

Sampling and Laboratory Protocols

Surface-water samples were collected during base flow 

and storm events from 14 sites in metropolitan St. Louis 

between September 2004 and October 2007. Sample collection was distributed over the entire year, but most samples 

were collected between April 1 through October 31 of any 

given year to coincide with the State-defined, recreational 

season (Missouri Department of Natural Resources, 2009). 

For the purposes of this study, base flow is defined as streamflow unaffected by runoff at small basin sites (table 1). Given 

the size of the Missouri and Mississippi River Basins, flows 

in these rivers are, to some extent, always affected by runoff; 

however, during this study, base-flow conditions indicated 

that large river sites had not been affected by localized runoff 

in the previous 72 hours. Likewise, since the intent was to 

measure local, rather than regional, effects, storm-event 

sample collection was determined by precipitation events 

that occurred within the study area; therefore, the hydrologic 

response at small basin sites was greater when compared to 

that of the large river sites during storm events. 

Streamflow was determined by discharge measurements 

made at the time of sample collection or from established 

stage-discharge relations (ratings) using USGS procedures 

outlined by 

Rantz and 

others (1982a, 

1982b) and 

Simpson 

(2001). Ratings 

were periodically updated 

throughout 

the course of 

the study as 

additional measurements and 

analysis of the 

stage-discharge 

relations warranted. Daily 

mean streamflow and waterquality values 

were published 

annually (U.S. 

Geological 

Survey, 2006a, 

2007, 2008) 

and are available in the USGS National Water Information 

System (NWIS) (U.S. Geological Survey, 2009).

All water-quality samples were collected and processed 

using protocols designed to prevent sample contamination.

Collection and processing equipment were comprised of 

inert materials—glass, fluorocarbon polymer, or stainless 

steel capable of sterilization (Lane and others, 2003; Wilde, 

2004; Wilde and others, 2004; Wilde, 2005). Samples were 

depth- and width-integrated across streams unless depth or 

width limitations necessitated the collection of grab samples 

from the centroid of flow (U.S. Geological Survey, 2006b).

On small streams, bacteria samples were collected from 

the centroid of flow; on large rivers, bacteria samples were 

Downstream view of the Missouri River 

at St. Charles site (photograph by Hugh 

Edwards, U.S. Geological Survey).
10 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

composited from three equally distributed cross-section 

points. Storm-event samples were collected during, or immediately following, precipitation events that were expected to 

be of sufficient duration and intensity to trigger CSO and SSO 

events from April 1 through October 31 of each year. Small 

basin sites were sampled only after a minimum 1 foot rise 

in water levels occurred at the gage. Large river sites were 

sampled following local precipitation events of 0.75 inch or 

greater within a 24-hour period. Because the drainage area at 

large river sites was approximately one thousand times greater 

than that of the study area, flows at large river sites during 

sampling events were only partly determined by local runoff.

Characterization of the magnitude and duration of overflow 

events was not part of this study, but at least some overflow 

events were assumed to have occurred during every storm 

event. Field personnel collected samples before storm peaks 

passed, or the event was not sampled. Because the collection 

of storm-event samples was dependent upon local precipitation events, the hydrographic response at small basin sites was 

more pronounced relative to the response observed at large 

river sites for these events.

Stream samples were analyzed for physical properties, fecal-indicator bacteria (E. coli and fecal coliform) and 

sources, nutrients, major ions, and trace metals. This report 

describes the E. coli results; physical properties, fecal coliform, nutrients, major ions, and trace metal data are reported 

elsewhere (U.S. Geological Survey, 2006a, 2007, 2008, 

2009).

E. coli samples were analyzed using culture-based membrane filtration techniques (Dufour and others, 1981; U.S. 

Environmental Protection Agency, 2002; U.S. Environmental 

Protection Agency, 2006; Myers and others, 2007) and enumerated using multiple dilutions (a 

minimum of three) to better 

ensure an optimal range 

in density; any densities outside of 

tolerance limits 

were estimated using 

standardized 

criteria for 

nonideal 

counts 

(Myers 

and others, 

2007). Before 

March 2007 E. 

coli samples were 

cultured using membranethermotolerant E. coli (mTEC) 

agar (U.S. Environmental Protection Agency, 2006), whereas 

samples collected after that date were cultured using modified membrane-thermotolerant E. coli (modified-mTEC) agar 

(U.S. Environmental Protection Agency, 2002). Both methods 

utilize the same nutrient growth media, the difference being 

modified mTEC agar allows for faster and easier enumeration 

of the target organisms because it does not require the transfer of the membrane to another substrate to stain the colonies 

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

Selected base-flow and storm-event samples were analyzed at the University of Missouri, Columbia (UMC), College 

of Veterinary Medicine, Microbial Source Tracking (MST) 

laboratory for presumptive host sources using microbial 

source-tracking methods (Carson and others, 2003; Carson 

and others, 2005; Davis and Barr, 2006; Wilkison and others, 

2005; Yampara-Iquise and others, 2008). The presumptive host 

sources (dogs, geese, and humans) were chosen because they 

were known to exist in the study area in sufficient numbers to 

potentially supply bacteria to streams and because previous 

studies (Wilkison and others, 2009) had demonstrated these 

sources were detected frequently in urban streams. Microbial 

source-tracking methods included rep-PCR for E. coli hostsource determination and analysis of the human symbiotic 

bacterium, B. thetaiotaomicron. Microbial source-tracking 

samples were collected in sterile, DNA-free containers, chilled 

at 4 oC until delivery to the UMC-MST laboratory, and processed within 24 hours of collection. 

The rep-PCR method used multivariate statistical methods to compare the pattern similarity of unknown environmental E. coli isolates to the isolate patterns of known sources. For 

this study, the known host-source library was developed from 

E. coli isolate patterns obtained from sewage (673 isolates), 

dog (404 isolates), and geese (456 isolates) feces collected 

within the study area. Library samples were collected at sites 

that reasonably could have been expected to have contributed fecal contamination to study sites. Library development 

extended over the study period, October 2004 through September 2007, to minimize geographic and temporal variations 

that can occur with isolates. 

Slightly more than 60 percent (199 of 317 total samples) 

of rep-PCR samples additionally were analyzed for genetic 

markers associated with the enteric bacterium, B. thetaiotaomicron, a predominant species in human feces (Holdeman and 

others, 1976). The presence of B. thetaiotaomicron was confirmed by PCR amplification using incremental (1 to 10 nanograms) quantities of 16S ribosomal DNA (Teng and others, 

2004; Carson and others, 2005; Yampara-Iquise and others, 

2008). The presence of B. thetaiotaomicron provides important confirmatory information about the presence of human 

fecal pollution. Because it is considered a human symbiont, B. 

thetaiotaomicron requires different conditions than E. coli for 

survival in the human gut, and is not expected to persist for 

extended periods once released in the environment (Walters 

and Field, 2006); thus, the presence of B. thetaiotaomicron is 

considered a reliable marker for recent environmental human 

fecal contamination. 

Multiple lines of evidence were used to evaluate study 

results, especially as they related to host-source determinations (Stoeckel, 2005). Sampling was designed to evaluate 

bacteria densities and sources in tributary streams as well as 

to compare tributary densities and sources to those measured 

September 2008 flood at Grand Glaize 

Creek near Valley Park site (photograph 

by Paul Rydlund, U.S. Geological Survey).
Methods 11

in the larger river receiving stems during distinct hydrologic 

conditions. Additionally, data were evaluated in the context 

of transport pathways; for example, the amount of impervious 

cover in the basin; potential bacteria contributions, especially 

those such as CSO, SSO, and WWTP inputs that might be 

indicative of human sources; and comparison of annual loadings between sites.

The genetic similarity of E. coli isolated from water 

samples was compared to E. coli isolated from three hosts—

dogs, humans, and geese—all of which were known to be 

present in the basin based on previous data, field observations, 

and knowledge of potential contaminant sources. Genetic fingerprint patterns (rep-PCR), isolated from pure E. coli cultured 

from water samples and amplified using BOX A1R primers, 

were matched against a local host-source library to determine 

sources (Carson and others, 2003). Genetic fingerprint patterns, consisting of between 18 and 30 bands, from environmental samples were compared to those isolated from known 

host sources using pattern recognition computer software 

(Bionumerics software; Applied Maths, Kortrijk, Belgium). 

Host-source classification was assigned only when matches 

were 80 percent or greater based on pairwise maximum similarity coefficients calculated by the curve-based Pearson correlation method for discriminant analysis (Carson and others, 

2003). Environmental isolates with similarities of less than 

80 percent to host sources were classified as unidentified. 

E. coli classified as unidentified may have originated from 

animals not targeted as part of this study or from one of the 

three targeted hosts but whose genetic signature was not represented in the host-source library. Classification accuracy was 

measured by jackknife analysis which qualifies the relative 

uncertainty of correct classification by measuring the distance 

in similarity between unknowns and library samples (Ritter 

and others, 2003). Interpretations related to host-source determinations were made on the central tendency of grouped data 

to minimize the effect that analytical uncertainties in bacteriological measurements may have had on the results.

Quality Assurance

Approximately 10 percent of all field samples collected 

consisted of quality-control samples designed to ensure the 

integrity of the water-quality data analyzed in this report. Field 

replicate samples were collected to determine the effect that 

variability in sample collection and processing procedures 

may have on the precision of environmental concentrations.

Field equipment blank samples were used to detect sample 

contamination during field collection, sample processing 

and cleaning, or from lack of sterility (in the case of bacteria 

samples) of sampling and processing equipment.

Precision estimates of fecal indicator bacteria values, 

determined from the differences between paired environmental samples and field replicates, are presented in figure 

4 and table 3. The mean absolute error between 52 replicate 

sample pair analyses was 17.1 percent. Median absolute error 

values were lower—14.3 percent for E. coli and 10.0 percent 

for fecal coliform—an indication that the central tendency of 

sample replicates was slightly less than the mean. Absolute 

error values below 20 percent generally are regarded as well 

within the range of the sensitivity of these tests (Griffith and 

others, 2006; Francy and Darner, 2000; Noble and others, 

2003; Wilkison and others, 2009). These data indicate that the 

combination of sampling and analytical variability contribute 

relatively small amounts of uncertainty to analytical results. 

More than 100 bacteria blanks of various varieties were 

processed to ensure that sample collection and processing 

procedures were sterile. At least once during each sampling 

trip, a container blank was processed to determine if sample 

collection equipment was properly sterilized. For this blank, 

buffer water was poured into a sterilized sample collection 

bottle, and then a 100-mL aliquot was analyzed for bacteria in 

the same fashion as the environmental samples. Bacteria were 

not detected in any of these samples. Additionally, filter blanks 

were prepared at the beginning of each bacteria processing 

session. For the filter blank, 100 mLs of buffer solution were 

filtered and cultured to ensure that the filter and buffer were 

sterile; none of these samples had bacteria detections. After 

bacteria processing, a procedure blank was prepared to evaluate analyst rinsing techniques and cross-contamination potential between dilutions at any given site. For this blank, the 

filter holder was rinsed by the analyst (as was done between 

sample dilutions), and then, 50 mLs of buffer solution were filtered and cultured. Less than 2 percent of samples had bacteria 

detections and when these did occur, the bacteria densities 

were many times less than those enumerated in samples. Filter 

holders were always changed, or sterilized, between sites to 

ensure that samples were processed using equipment that was 

free from contaminants at other sites. Together these data 

indicate that collection and processing techniques maintained 

Table 3. Quality-assurance replicate data for fecal indicator bacteria analyzed as part of this study.

 [standard error in colonies per 100 milliliters]

Constituent Mean absolute 

error, in percent

Median absolute 

error, in percent

Standard deviation absolute 

error, percent

Coefficent of 

detemination

Standard 

error

Number

 of pairs

Escherichia coli 19.4 14.3 22.8 0.99 4 27

Fecal coliform 14.8 10.0 12.8 .99 3 25

Average 17.1 12.1 17.8 .99 3 52
12 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

equipment sterility and that laboratory sample cross-contamination was not an issue in this study.

The precision and accuracy of the microbial sourcetracking methods employed in this study have been described 

previously (Carson and others, 2003; 2005; Griffith and others, 

2003; Stoeckel and others, 2004; Yampara-Iquise and others, 

2008). To summarize, a five-step, selective growth process 

(Carson and others, 2001) was utilized to ensure that rep-PCR 

analyses were performed only on pure E. coli isolates. Further, 

to assess the ability of rep-PCR to determine unknown E. coli

sources, samples were held from the source library and then 

presented as unknowns using two distinct approaches—resubstitution and holdout (Carson and others, 2003). Samples had 

to demonstrate fidelity with the library (greater than 80 percent 

similarity) before assignment to a host source. Although this 

approach helps to minimize the potential for false-positives 

(assignment to a host class when none exists), it also increases 

the potential for false-negatives (failure to assign to a host 

source when present). In other words, establishment of this 

threshold tends to guard more against over-estimation, rather 

than under-estimation of sources. For the resubstitution 

method, individual isolates were removed from the library 

database and then presented later as test subjects; comparisons 

were determined from Pearson correlation maximum similarity coefficients. This procedure determined the ability of the 

study library to determine host sources as well as the repeatability of the library predictions with time (Ritter and others, 

2003). Resubstituion yielded correct rates of classification of 

97 percent for human, 98 percent for dog, and 83 percent for 

goose (Carson and others, 2003). In the holdout method—considered a more rigorous method test—the validation dataset 

isolates were not part of the reference library, but were instead 

presented as unknowns, a technique designed to assess the representativeness of the library for making predictions (Harwood 

and others, 2000). The rate of correct classification for repPCR method as determined by the holdout method, based on 

the random removal of 25 percent of samples, was determined 

to be human, 100 percent; dog, 100 percent; and goose, 90 

percent (Carson and others, 2003). Additionally, in a separate, 

controlled blind test using a much smaller library, the rep-PCR 

method was able to accurately identify human and sewage 

sources in 83 percent of test samples (Myoda, 2003). 

As an additional test of the rep-PCR method, qualityassurance data were collected specific to this study. For 

example, the library was validated at intervals of about a year, 

through the use of challenge isolates to test the proficiency of 

the library to correctly identify sources (Stoeckel and others, 

2007). For this technique, essentially a variant of the holdout 

method, challenge isolates were collected from host sources 

within the study area and then presented fresh to the library 

as unknowns. The rate of correct classification of challenge 

isolates was determined to be 82 percent for human, 75 percent for dog, and 52 percent for geese. The migratory nature 

of geese may account for variations in genetic signatures and 

the lower rates of classification. These data indicate that the 

rep-PCR method and host-source library were sufficiently representative to accurately characterize human and dog E. coli, 

and to a lesser extent, E. coli from geese.

Some studies have demonstrated that genetic fingerprint patterns can vary geographically and change with time 

(Gordon, 2001; Gordon and others, 2002; Hartel and others, 

2002, 2003). To minimize the effect such changes might have 

had on the development of the host-source library, library 

sample collection varied spatially and temporally in this study 

and eventually included more than 1,500 isolates—distributed 

across the three host-source classes—for comparison with 

environmental samples.

Figure 4. Quantile-quantile plots of Escherichia coli and fecal coliform replicate samples collected at sites in the metropolitan 

St. Louis area.

0 2,000 4,000 6,000 8,000 10,000

Escherichia coli

0

2,000

4,000

6,000

8,000

10,000

0 1,000 2,000 3,000

COLONIES PER 100 MILILITERS IN ENVIRONMENTAL SAMPLE

0

1,000

2,000

3,000

COLONIES PER 100 MILILITERS IN

REPLICATE SAMPLE

12,000

12,000 4,000

4,000

Fecal Coliform
Methods 13

Replicate rep-PCR samples were collected sequentially in 

the field and then each sample (environmental and replicate) 

was processed independently for E. coli density as well as the 

source of E. coli by rep-PCR analysis; therefore, replicate repPCR samples provide data on how variations in E. coli sample 

collection and enumeration techniques (illustrated in fig. 4 

and table 3) coupled with variation in the microbial sourcetracking identification procedures may have affected study 

results. In general, there was good agreement between values 

determined in environmental samples and those determined in 

replicates (fig. 5). Samples typed as humans had the smallest 

mean absolute percent error (19 percent), and those sourced as 

goose had the greatest (34 percent). The average percent error 

for all rep-PCR replicates was 27 percent, greater than that of 

the fecal bacteria measurement errors (table 3) that would be 

expected because the rep-PCR analysis includes these errors as 

well. Individual rep-PCR sample results need to be interpreted 

with caution given the potential range of errors associated with 

such determinations; therefore, the analysis of host-source 

determinations in this study focused on the central tendency, 

or average value, of these data to provide the most meaningful 

results.

Human fecal contamination was additionally identified 

using a genetic marker of B. thetaiotaomicron, enteric bacterium known to have a frequent occurrence in, and specificity 

to, humans (Carson and others, 2005). A sensitivity analysis 

on 1 nanogram of genetic material was used to evaluate the 

ability of the B. thetaiotaomicron marker to verify human fecal 

contamination. The marker was strongly recovered in 96 percent of human samples, showed faint recovery in 16 percent 

of dog samples, and was not recovered in any goose samples.

Positive detections in dog samples indicated there may be the 

1

10

100

1,000

r

2

 = 0.90

MAPE = 19

HUMAN

r

2

 = 0.66

MAPE = 34

GOOSE

REPLICATE

1 2 3 4 1 2 3 4

Environmental sample

Replicate sample

Environmental sample

Replicate sample

Environmental sample

Replicate sample

Environmental sample

Replicate sample

r2 = 0.44

MAPE = 27

ESCHERICHIA COLI DENSITY, IN COLONIES PER 100 MILLILITER

1

10

100

1,000

DOG

r

2

 = 0.73

MAPE = 27

UNKNOWN

Figure 5. Host-source Escherichia coli densities determined in environmental and replicate rep-PCR samples [rep-PCR, repetitive 

extragenic pallindromic polymerase chain reaction; MAPE, mean absolute percent error; r2, coefficient of determination].
14 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

potential for some sharing of enteric bacteria between humans 

and their canine pets but not with geese (Carson and others, 

2005). 

Data Analysis

Water-quality data were analyzed for various factors 

that may have been expected to affect E. coli densities: loads, 

patterns, and trends observed in stream samples and at sites 

during the study. These factors included constituent concentrations and sources, how these factors may have varied spatially 

and temporally in the basin, and how they may have been 

related to land cover in the study area. Where applicable, 

E. coli densities have been compared to current (2010) State 

of Missouri water-quality standards (Missouri Department of 

Natural Resources, 2009) to demonstrate relevance to established thresholds; however, compliance or noncompliance 

with numeric criteria was beyond the scope of this study.

Instantaneous E. coli loads at stream sites were determined by multiplying the bacteria density in discrete samples 

(measured in colonies per 100 milliliters) times the streamflow 

(measured in cubic feet per second) at the time of sample collection and then by an appropriate conversion factor (283.2) to 

provide data in terms of colonies per second. Host-source E. 

coli allocations were determined by multiplying the instantaneous loads by the percentage of bacteria assigned to any 

given host. Data were binned by individual site, by river system (large river sites and small basin sites), and by hydrologic 

event (base flow or storm event) for analysis.

Estimates of E. coli annual loads were determined using 

minimum variance unbiased estimation techniques, a form of 

multiple linear regression analysis, and the S-LOADEST computer program (Runkel and others, 2004) in Spotfire S-Plus 

(version 8.1, TIBCO Software, Inc., Palo Alto, California) 

to develop load estimation models. For model development, 

the dependent variable was constituent concentration, and the 

independent variables were streamflow, decimal time, and season. If appropriate, ladders of power transformation of streamflow (Helsel and Hirsch, 1992) and breakpoints in streamflow 

were used. These procedures were designed to account for 

nonnormal distributions, seasonal or annual cycles, censored 

data, biases associated with logarithmic transformation, and 

serial correlation of the residuals (Cohn, 1988; Cohn and others, 1989).

Model selection was done according to the following 

criteria. From evaluation of the Akaike information criteria 

(Akaike, 1981), the best-fit model was selected using combinations of streamflow, natural logarithm of streamflow, square 

of streamflow, square of the natural logarithm of streamflow, 

decimal time, square of decimal time, sine and cosine of time, 

and square of the sine and cosine of time. Residual plots 

were evaluated for homoscedasticity (constant variance) and 

normality. Models that failed these critical assumptions were 

rejected, and additional combinations of the above variables 

were examined for linearity based upon the rank of the Akaike 

information criteria. Failing that test, an additional step 

involved examination of models that incorporated breakpoints 

in streamflow in combination with the aforementioned time 

terms.

Each observation in the data set was used to develop a 

best-fit model, which was then used to estimate daily loads.

Daily loads were then summed to provide annual estimates. 

Yield estimates were determined by dividing the constituent 

load determined at the site by the site’s drainage area. Flowweighted concentrations were calculated from the estimated 

loads by dividing the daily mean load by the daily mean 

streamflow. Flow-adjusted trend, expressed as the average percent change with the time modeled, was determined from the 

coefficient of the LOADEST model decimal time term using 

a significance level of 0.05 (Sprague and others, 2006). At the 

most downstream Mississippi River site (07019370), fecal 

coliform data were used as a surrogate for the estimation of 

E. coli loads because of the lack of an E. coli fitted model and 

the larger number of samples with fecal coliform data relative 

to E. coli data. Fecal coliform and E. coli densities typically 

are strongly correlated (coefficient of correlations greater 

than 0.94; Rasmussen and Ziegler, 2003; Wilkison and others, 

2006; Garcia-Armisen and others, 2007). On average, 

69 percent of the fecal coliform bacteria enumerated at study 

sites were attributed to E. coli. The relation between fecal 

coliform and E. coli densities at metropolitan St. Louis sites is 

shown in figure 6 (coefficient of correlation, 0.87). 

For the purposes of this study, comparisons of E. coli

densities, loads, and sources between sites assumed that 

bacteria mortality, inactivation, or regrowth were negligible or 

remained constant during the time frame needed for downstream transport through the study area. Assessing these 

conditions was beyond the scope of this study. Although these 

rates can vary with time (Anderson and others, 2005), given 

the increased levels of turbidity and suspended sediment at 

sites, mortality and inactivation of instream E. coli would 

have been minimized as water moved from one site to the next 

(Whitman and others, 2004; Schultz-Fademrecht and others, 

2008; Garcia-Armisen and Servais, 2009; Servais and others, 

2009). 

The survival profile and clonal composition of E. coli

species measured in the external environment were assumed 

to reflect that in the host environments. Some studies have 

indicated that this might not always be the case (McLellan 

and others, 2003; Field and Samadpour, 2007); however, 

these studies typically focused on the behavior of bacteria 

entering lakes, beaches, or septic systems (Gordon, and others, 2002; McLellan, 2004)—thus, the dynamics affecting 

survivability would be expected to differ from rivers with 

increased suspended sediment concentrations and limited 

light penetration. Variations in the environmental signatures 

of E. coli species were minimized when targeted geographic 

sampling, such as occurred in this study, were utilized (Kuntz 

and others, 2003). Additionally, the stability of E. coli isolates 

in natural waters for a wide range of ambient temperatures has 

been demonstrated for up to 150 days (Seurinck and others, 
Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 15

2003). Analysis of the variation and stability of E. coli host 

species signatures was not part of this study, so it is impossible to determine what effect such changes, if any, may have 

had on the results. It is likely that some changes did occur 

during the course of the study; however, the use of multiple 

approaches to assess fecal sources, such as the combination of 

PCR techniques and analysis of a human-specific Bacteroides

marker, has been shown to increase the power of source tracking (Noble and others, 2006). Additionally, given how quickly 

stream E. coli densities can change in response to runoff 

events, some uncertainty is inherent in any attempt to classify 

host sources; therefore, percentages assigned to individual host 

classes were based on the central tendency of the data rather 

than individual samples.

Occurrence and Sources of 

Escherichia coli in Metropolitan St. 

Louis Streams

The occurrence and sources of E. coli, one of several 

fecal indicator bacteria, were determined at sites based on 

several characteristics including hydrologic conditions within 

the study area (base flow or storm event), site type (large river 

or small basin), and selected land-cover characteristics such as 

the percent of upstream impervious cover or potential number 

of wastewater discharges. In general, E. coli densities and 

loads measured in discrete samples collected from October 

2004 through September 2007 were many times greater during storm events than at base flow. This was because E. coli

densities and flow—a major component of loads—increased 

as a result of runoff. Median E. coli storm-event densities were 

substantially greater than base-flow densities for all sites. The 

most substantial increases occurred at small basin sites where 

median E. coli densities increased from 460 colonies per 100 

mL (col/100 mL) during base flow to 5,400 col/100 mL during storm events. Median E. coli densities at small basin sites 

during base flow were even greater than the median densities 

measured in storm-event samples collected at Mississippi 

River sites (131 col/100 mL) and Missouri River sites (380 

col/100 mL) (fig. 7). Even so, E. coli loads at small basin sites 

were small when compared to loads at large river sites. E. 

coli contributions from the Missouri River to the Mississippi 

River were much greater than contributions from upstream 

Mississippi River reaches to lower Mississippi River reaches. 

Increased E. coli densities at stream sites were related to 

increased amounts of impervious cover and the number of 

upstream CSOs and SSOs.

Escherichia coli Densities in Base Flow and 

Storm Events

Median E. coli densities at Missouri River sites increased 

slightly through the study area during base flow from a low of 

51 col/100 mL at the most upstream site (06935715, Missouri 

River near Chesterfield) to a peak of 220 col/100 mL at the 

most downstream site (06937000, Missouri River at Columbia 

Bottom; fig. 8). During storm events, median E. coli densities 

at the most upstream site (06935715) and middle Missouri 

River site (06935972, Missouri River below St. Charles) were 

similar (480 and 580 col/100 mL) and then decreased to about 

40 percent of that level (250 col/100 mL) at the most downstream site (06937000, fig. 8). 

Median E. coli densities at sites on the Mississippi River 

generally increased in a downstream order through the study 

area (fig. 8). The lowest median densities were observed at 

site 05587455, the Mississippi River below Grafton, Illinois, 

for base flow (13 col/100 mL) and storm events (32 col/100 

mL). At the next most downstream Mississippi River site 

(07005500, Mississippi River above St. Louis)—below the 

confluence with the Missouri River—median E. coli densities were approximately three times greater than densities at 

the upstream Mississippi River site (05587455; fig. 8). Below 

the Missouri River confluence, Mississippi River suspended 

sediment concentrations more than triple and an increasing 

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams

y = 0.7796x0.9699

r2 = 0.87

1

10

100

1,000

10,000

100,000

1,000,000

1 10 100 1,000 10,000 100,000 1,000,000

FECAL COLIFORM DENSITY, IN COLONIES PER 100 MILLILTER

ESCHERICHIA COLI DENSITY, 

IN COLONIES PER 100 MILLILTER

Figure 6. Relation between fecal coliform density and Escherichia coli density at metropolitan 

St. Louis sites.
16 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

number of CSOs discharge directly, or indirectly (from tributaries), to the Mississippi River (fig. 2). Additionally, more 

than three-fourths of SSOs and WWTPs discharge in areas 

below the Missouri-Mississippi River confluence. Median 

E. coli densities peaked at site 07010220 (Mississippi River at 

Oakville) and then declined slightly at the most downstream 

site (07019370, Mississippi River at Kimmswick; fig. 8) 

during both base flow and storm events. Inputs from CSOs, 

SSOs, and the River des Peres that contained increased levels 

of E. coli likely played a role in the increases observed at site 

07010220. Inflow from the Meramec River that acted to dilute 

instream E. coli densities on the Mississippi River may have 

accounted for downstream declines at site 07019370. 

For small basin sites the largest median E. coli densities 

were observed during storm events at the two River des Peres 

sites (16,500 col/100 mL at site 07010022, River des Peres 

near University City and 29,000 col/100 mL at site 07010097, 

River des Peres at St. Louis; fig. 9). These values were approximately 3 to 6 times greater than median values measured at 

the other small basin sites: Creve Coeur Creek near Creve 

Coeur, Missouri (06935890), Coldwater Creek near Black 

Jack, Missouri (06936475), Maline Creek at Bellefontaine 

Neighbors, Missouri (07005000), and Grand Glaize Creek 

near Valley Park, Missouri (07019185), during storm events 

(fig. 9). This is likely due, in part, because almost one-half of 

the CSO discharge volume in the study area was expected to 

have discharged to the River des Peres; additionally, more than 

one-half of SSOs in the study area discharge into this basin 

(Metropolitan St. Louis Sewer District, 2009, written comm.). 

The upper River des Peres site (07010022) had the largest 

median E. coli densities during base flow (1,780 col/100 mL) 

followed by samples from Maline Creek (site 07005000; 590 

col/100 mL) and the lower River des Peres (site 07010097; 

480 col/100 mL). Median E. coli densities were approximately 

300 col/100 mL at the Creve Coeur, Coldwater, and Grand 

Glaize Creek sites (fig. 9).

Missouri stream water-quality criteria for E. coli are 

determined by the stream classification and designated use 

(Missouri Department of Natural Resources, 2009). Streams 

are classified into two broad categories, whole body contact 

recreation and secondary contact recreation. Whole body 

contact recreation refers to activities that result in direct 

contact with and complete submergence below the water—for 

example, swimming, water skiing, or diving. Whole body 

contact recreation is further divided into Class A and Class 

B categories. Class A stream reaches are public, open-access 

swimming areas, whereas Class B waters are any other waters 

of the State designated for whole body contact not contained 

within Class A. Secondary contact recreation refers to activities that may result in incidental contact with the water in 

question—for example, boating, fishing, or wading (Missouri 

Department of Natural Resources, 2009). For sites in the study 

area, the E. coli criterion ranges from 126 col/100 mL for 

Class A recreational use, to 206 col/100 mL for Class B recreational use, to 1,134 col/100 col mL for secondary contact 

recreation (table 4).

Numeric water-quality criteria apply to the geometric 

mean of samples collected during the recreational period 

which is defined as April 1 through October 31 of each year. 

Ninety percent of the discrete samples collected during this 

study were collected within this time frame; however, the 

study intent was not to determine compliance with waterquality standards.

Regardless, comparison of instream bacteria densities at 

stream sites to established thresholds can provide useful information. When discrete sample E. coli densities at sites were 

compared to the appropriate criterion for a given stream site 

(table 5), there was little, if any, difference between samples 

Figure 7. Escherichia coli densities in stream samples collected at sites in metropolitan St. Louis between October 

2004 and September 2007.

10

100

1,000

10,000

100,000

1,000,000

ESCHERICHIA COLI DENSITY, IN COLONIES 

 PER 100 MILLILITERS

(28) Number of samples 

EXPLANATION

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

x Upper outside

x

40

102

(58)

460

(104) (113)

131

5,400

380

(28) (52) (44)

Small basin sites

06935890, 06936475

07005000, 07010022

 07010097, 07019185 

Missouri Rivers sites

06935715

06935972

06937000

Mississippi River sites 

05587455, 07005500

07010000, 07010220

07019370

Base flow

Storm event

<1

380
Occurrence and Sources of Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Escherichia coli in Metropolitan St. Louis Streams 17 State of Missouri Secondary contact criteria State of Missouri Class B criteria State of Missouri Class A criteria MISSISSIPPI RIVER SITES

DENSITIES, IN COLONIES PER 100 MILLILITER ESCHERICHIA COLI 

05587455

Below 

Grafton

07005500

Above

St. Louis

07010000

At 

St. Louis

07010220

At 

Oakville

07019370

At 

Kimmswick

MISSOURI RIVER SITES

06935972

Below 

St. Charles

06937000

At Columbia

bottom

(20) (19) (19)

51

220

100

100

101

102

103

104

105106

100

101

102

103

104

105106

(9) (9) (9)

480

250 580

BASE FLOW

(19) (20) (19) (19) (27)

13

46

32

116 100

(9) (9) (9) (9) (16)

110 160

32

480

280

STORM EVENT

DIRECTION OF STREAMFLOW

06935715

Near 

Chesterfield

(19) Number of samples 

EXPLANATION

Upper outside

Upper adjacent75th percentile

Median25th percentileLower adjacent

Lower outside x

Storm event

Base flow

100

Figure 8. Escherichia coli densities in discrete samples collected between October 2004 and September 2007 at large river sites in the metropolitan St. Louis area.
18 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

collected throughout the year compared to those collected 

during the recreational season; therefore, discussion with 

respect to the percentage of discrete samples that were below 

the applicable standard refer to all samples collected over the 

course of the study.

Sixty percent of Missouri River base-flow samples were 

below the E. coli Class B recreational criterion of 206 col/100 

mL (table 5). Because Missouri River storm-event samples 

had substantially greater amounts of E. coli (figs. 7 and 8), 

only 36 percent of storm-event samples had E. coli densities 

below the criterion (table 5).

ESCHERICHIA COLI DENSITIES, IN COLONIES PER 100 MILLILITERS

BASE FLOW

STORM EVENT

(7) (7) (7) (7) (9) (7)

06935890

Creve 

Coeur

Creek

06936475

Coldwater

 Creek

07005000

Maline

Creek

07010022

River des 

Peres near 

University City

07010097

River des 

Peres at 

St. Louis

07019185

Grand 

Glaize 

Creek

(19) (20) (18) (18) (19) (19)

SMALL BASIN SITES

318

590

1,780

280 480 304

3,800 5,000

16,500 29,000

5,200 4,710

4,710

State of Missouri 

 Secondary contact 

 criteria

State of Missouri 

 Class B criteria

(7) Number of samples 

EXPLANATION

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Upper outside

x

Base flow

Storm event

100

101

102

103

104

105

106

100

101

102

103

104

105

106

Figure 9. Escherichia coli densities in discrete samples collected between October 2004 and September 2007 at 

small basin sites in the metropolitan St. Louis area.
Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 19

E. coli criteria for stream reaches of the Mississippi River 

vary through the study area (table 4). The stream reach above 

the confluence with the Missouri River, which includes site 

05587455, is subject to Class A recreational criterion, whereas 

a 6.3-mile reach below the confluence is subject to Class B 

recreational criterion. From this point, downstream to the 

Meramec River, a secondary contact criterion applies (sites 

07005500, 07010000, and 07010220). Below the Meramec 

River—applicable to site 07019370—the criterion reverts to 

the Class B recreational standard (table 4).

E. coli densities at Mississippi River sites were below the 

applicable criterion in approximately 90 percent of base-flow 

samples (table 5). E. coli densities in samples from four sites 

(05587455, 07005500, 07010000, and 07010220) were below 

the applicable criterion in 100 percent of the samples, and 

those in samples from site 07019370 were below the standard 

63 percent of the time. On average, 75 percent of storm-event 

samples collected from Mississippi River sites were below 

the applicable standard; values ranged from 44 percent to 100 

percent (table 5).

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams

Table 4. State of Missouri Escherichia coli bacteria criteria applicable to selected metropolitan St. Louis area stream reaches in 

relation to study area sites. 

[col/100 ml, colonies per 100 milliliters of water; --, not applicable]

Stream reach Applies to site 

number(s); (fig.1) Description Designated use Criterion

Missouri River 06935715, 

06935972, 

 and 

06937000

Geometric mean during the recreational season from April 1 to 

October 31 in waters designated 

for recreation or at any time in 

losing streams

Whole body contact -- Class B 

(Missouri Department of Natural Resources, 2009)

206 col/100 mLa

Mississippi River, 

upstream from the 

confluence with Missouri River

05587455 Geometric mean during the recreational season from April 1 to 

October 31 in waters designated 

for recreation or at any time in 

losing streams

Whole body contact -- Class A 

(Missouri Department of 

Natural Resources, 2009)

126 col/100 mL

Mississippi River, from 

the Missouri River to 

6.3 miles downstream

-- Geometric mean during the recreational season from April 1 to 

October 31 in waters designated 

for recreation or at any time in 

losing streams

Whole body contact -- Class B 

(Missouri Department of Natural Resources, 2009)

206 col/100 mLa

Mississippi River, 

6.3 miles downstream 

from the Missouri 

River to the Meramec 

River

07005500, 

07010000, 

 and 

07010220

Geometric mean during the recreational season from April 1 to 

October 31 in waters designated 

for recreation or at any time in 

losing streams

Secondary contact recreation 

(Missouri Department of Natural Resources, 2009)

1,134 col/100 mL

Mississippi River, 

downstream from the 

Meramec River

07019370 Geometric mean during the recreational season from April 1 to 

October 31 in waters designated 

for recreation or at any time in 

losing streams

Whole body contact -- Class B 

(Missouri Department of Natural Resources, 2009)

206 col/100 mLa

Small basin sites: Creve 

Coeur Creek, Coldwater Creek, Maline 

Creekb,c, and Grand 

Glaize Creek

06935890, 

06936475, 

07005000, 

 and 

07019185

Geometric mean during the recreational season from April 1 to 

October 31 in waters designated 

for recreation or at any time in 

losing streams

Whole body contact -- Class B 

(Missouri Department of Natural Resources, 2009)

206 col/100 mLa

Small basin site: River 

des Peres at St. Louis

07010097 Geometric mean during the recreational season from April 1 to 

October 31 in waters designated 

for recreation or at any time in 

losing streams

Secondary contact recreation 

(Missouri Department of Natural Resources, 2009)

1,134 col/100 mL

Small basin site: River 

des Peres

07010022 -- -- --

a

First adopted by emergency rule on December 15, 2008. Previous standard was 528 colonies per 100 milliters.

b

Reach from streamgage to 0.5 mile below streamgage designated for whole body contact-Class B.

c

A 0.6-mile stream reach upstream from the Mississippi River designated for secondary contact recreation.
20 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

Most small basin sites in the study area are subject to the 

whole body contact-Class B criterion (table 5). Exceptions are 

the upper River des Peres site (07010022) where no standard 

currently (2010) applies, and the lower River des Peres site 

(07010097), which is subject to the least stringent secondary 

contact criterion of 1,134 col/100 mL.

On average, during base flow, only 28 percent of samples 

from sites on Creve Coeur, Coldwater, Maline, and Grand 

Glaize Creeks were below the Class B criterion (table 5). Conversely, only 4 percent of storm-event samples—which have 

substantially higher E. coli densities (fig. 9) than do base-flow 

samples—were below this criterion (table 5). Grand Glaize 

Creek samples never were below the criterion for any hydrologic condition.

Ninety percent of base-flow samples from the lower 

River des Peres site (07010097) were below the secondary 

contact criterion (table 5); however, storm-event samples from 

this site were below the applicable criterion only 11 percent of 

the time.

Instantaneous Escherichia coli Loads

Instantaneous load, the concentration (or density in the 

case of bacteria) of a constituent times the streamflow, is the 

amount of a given constituent in the stream at the time of 

sample collection. Instantaneous loads provide data on the 

relative amounts of constituents in a particular stream reach or 

from tributaries. 

Table 5. Percent of discrete Escherichia coli bacteria samples collected between October 2004 and September 2007 at stream 

sites in the metropolitan St. Louis area that met the applicable State of Missouri criterion.

[col/100 ml, colonies per 100 milliliters of water; --, not applicable]

Site

Station 

identifier 

(fig. 1)

Base flow all 

samples (recreational 

season samples)

Storm event all 

samples (recreational 

season samples)

Applicable criterion. Geometric 

mean of recreational season 

samples, April 1 to October 31 of 

each year

Large river sites

Missouri River Sites

Missouri River near Chesterfield 06935715 65 (65) 44 (44) 206 col/100 mL

Missouri River below St. Charles 06935972 68 (68) 22 (22) 206 col/100 mL

Missouri River at Columbia Bottoms 06937000 47 (47) 40 (40) 206 col/100 mL

Average (Missouri River sites) -- 60 (60) 36 (36) 206 col/100 mL

Mississippi River sites

Mississippi River below Grafton 05587455 100 (100) 88 (90) 126 col/100 mL

Mississippi River above St. Louis 07005500 100 (100) 100 (100) 1,134 col/100 mL

Mississippi River at St. Louis 07010000 100 (100) 100 (100) 1,134 col/100 mL

Mississippi River at Oakville 07010220 100 (100) 67 (67) 1,134 col/100 mL

Average -- 100 (100) 89 (89) 1,134 col/100 mL

Mississippi River at Kimmswick 07019370 63 (63) 44 (44) 206 col/100 mL

Average (Mississippi River) -- 91(91) 75 (76) 126-1,134 col/100 mL

Small basin sites

Creve Coeur Creek 06935890 46 (46) 0 (0) 206 col/100 mL

Coldwater Creek 06936475 40 (40) 14 (14) 206 col/100 mL

Maline Creek 07005000 28 (28) 0 (0) 206 col/100 mLa

Grand Glaize Creek 07019185 0 (0) 0 (0) 206 col/100 mL

Average -- 28 (28) 4 (4) 206 col/100 mL

River des Peres at St. Louis 07010097 90 (88) 11 (0) 1,134 col/100 mL

Average Small basin sites -- 41 (40) 5 (5) 206 col/100 mL

River des Peres near University City 07010022 39 (44) 0 (0) --b

a

Criterion from streamgage to 0.5 mile below streamgage.

b

No standard currrently (2010) applies. Results shown in comparison to secondary contact limit of 1,134 col/100 mL.
Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 21

In general, the largest instantaneous E. coli loads were 

observed at large river sites in the study area (figs. 10 and 11) 

because flows, a primary component of load, were greatest at 

these sites. Storm loads were substantially greater than those 

during base flow, a difference most pronounced at small basin 

sites (fig. 11). This was because only a small part of the Missouri and Mississippi River Basins lies within the study area, 

whereas the small basins lie within the study area; therefore, 

precipitation that fell within the study area affected small basin 

sites in disproportionally larger amounts than the large river 

sites. Additionally, this study targeted precipitation events 

that occurred within the study area as opposed to rarer, more 

widespread geographic events that covered larger parts of the 

Missouri or Mississippi River Basins.

For Missouri River sites, instantaneous E. coli baseflow loads increased downstream through the study area in 

response to increased E. coli densities, increased streamflow, 

or both. This phenomenon also was observed at Mississippi 

River sites (fig. 10). Median base-flow loads from the upper 

Mississippi River site (05587455) were only 10 percent of 

the loads measured at the most downstream Missouri River 

site (06937000; table 6). Median E. coli base-flow loads at 

the lower Mississippi River sites (07010220 and 07019370) 

were 250 to 400 percent greater than loads measured at middle 

Mississippi River sites (07005500 and 07010000; fig. 10). 

Base-flow loads at small basin sites were less than 1 percent of 

the loads measured in the downstream receiving reach of the 

Missouri or Mississippi Rivers (table 6). These data indicate 

that during base flow substantial amounts of E. coli originated 

from within the study area; however, considerable amounts of 

E. coli in the Missouri River, as well as that in sections of the 

Mississippi River downstream from its confluence with the 

Missouri River, originated in reaches of the Missouri River 

upstream from the study area. Lesser amounts of base-flow E. 

coli in the Mississippi River originated in the upstream Mississippi River reaches of the study area, and only minor amounts 

originated in the small basins.

Although there are differences between sites, in general, 

the upper Mississippi River and small basin site E. coli storm 

loads were considerably less than those at Missouri River 

sites (fig. 10 and 11). Median E. coli storm loads at the upper 

Mississippi River site (05587455) were 14 percent of those 

measured in the most downstream reach of the Missouri River 

(site 06937000; table 6). Loads at two Missouri River tributary streams, Creve Coeur Creek and Coldwater Creek (sites 

06935890 and 06936475), had median E. coli storm loads that 

were no more than 4 percent of those measured in receiving 

sections of the Missouri River (table 6).

Median E. coli storm loads at small basin sites, when 

compared to those at downstream receiving reaches of the 

Mississippi River, ranged from a low of 1 percent (Grand 

Glaize Creek, site 07019185) to a peak of 16 percent (Maline 

Creek, site 07005000). For River des Peres sites (07010022 

and 07010097), median E. coli storm loads were 4 and 10 

percent of those measured at lower Mississippi River sites 

(table 6). These comparisons assumed that E. coli moved 

downstream into the next stream reach without degradation or 

loss. 

Although streams in the study area have been modified 

substantially to efficiently convey water downstream, once 

released to the environment, some instream loss of bacteria 

would have been inevitable; however, the sum of the median 

small basin E. coli bacteria loads (at Creve Coeur, Coldwater, 

Maline, and Grand Glaize Creeks; and the lower River des 

Peres) during storm events was only 18 percent of the loads 

measured at the most downstream lower Mississippi River 

reach (average of loads at sites 07010220 and 07019370) and, 

during base flow, it is less than 1 percent (table 6). These data 

indicate that although small basin sites contributed increasing 

amounts of E. coli to large river stream reaches during highflow conditions, substantial amounts of E. coli originated from 

sections of the Missouri River upstream from the study area, 

point source discharges (including CSOs, SSOs, and WWTPs 

in the study area) to the large rivers, or from nonpoint sources 

within the study area. 

The largest E. coli loads were observed at the most downstream Mississippi River sites primarily because flows at these 

sites were greater than at other sites. Large river sites had 

much lower E. coli densities than small basin sites during base 

flow and storm events. Bacteria densities typically were much 

greater during runoff periods, and E. coli densities frequently 

increased by several orders of magnitude over base-flow 

periods.

Base-flow Escherichia coli Sources

Samples from three sites on the Missouri River, five 

sites on the Mississippi River, and six sites on small tributary 

streams, collected between October 2004 and September 2007, 

were analyzed for the source of E. coli bacteria using rep-PCR 

(table 7). Samples were collected during base flow and storm 

events, and the results compared to a locally collected hostsource library of human, dog, and goose samples to identify 

their respective percentages of E. coli in any given sample. 

On average, two-thirds (67 percent) of the more than 4,000 E. 

coli isolates analyzed in this study were presumptively identified with a specific host source; the level of identification was 

slightly greater in base-flow samples (68 percent) compared 

to that in storm-event samples (64 percent; table 7). Such differences, although minor in this study, likely were an indication of increased genetic diversity and more varied sources in 

runoff compared to base flow (Brownell and others, 2007). Of 

the E. coli isolates identified, 1,566 were assigned to human, 

466 to dogs, 893 to geese, and 1,490 to unknown sources.

Unknown sources would include E. coli from urban wildlife, 

feral cats, and birds—excepting geese—but also may have 

included some percentage of human, dog, or geese samples 

that did not meet the 80 percent similarity criteria deemed 

necessary to be considered a match.

During base flow, the mean percentage of E. coli sourced 

as human generally increased through the study area. For 

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams
22 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007 Table 6. Tributary inputs of Escherichia coli loads to receiving streams for samples collected between October 2004 and September 2007. [--, not applicable; <, less than] Receiving stream reach Sites included (fig. 1) Receiving stream median intantaneous load, in millions of colonies per second Tributary or upstream reach Sites included (fig. 1) Receiving stream median intantaneous load, in mil- lions of colonies per second Tributary load, as percent of receiving stream load Hydrologic condition Hydrologic condition Hydrologic condition Base flow Storm event Base flow Storm event Base flow Storm event Missouri River tributary Upper Missouri 06935715 1,180 14,700 -- -- -- -- -- -- Mid-Missouri 06935972 1,370 8,560 Creve Coeur Creek 06935890 0.24 118 <1 1 Lower Missouri 06937000 3,050 7,490 Coldwater Creek 06936475 .47 326 <1 4 Upper Mississippia 05587455 293 1,040 10 14 Mississippi River tributary Mid-Mississippi 07005500, 07010000 1,790 5,850 Maline Creek 07005000 .43 960 <1 16 Lower Mississippi 07010220, 07019370 5,770 18,700 Upper River des Peres 07010022 .51 654 <1 4 Lower River des Peres 07010097 .22 1,900 <1 10 Grand Glaize Creek 07019185 .20 157 <1 1 Average of small basinb sites 06935890, 06936475, 07005000, 07010097, 07019185 .26 692 <1 7 Average of small basinb sites 06935890, 06936475, 07005000, 07010097, 07019185 1.6 3,460 <1 18

aComparison is to lower Missouri site (06937000).bUpper River des Peres site (07010022) not included.
Occurrence and Sources of Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Escherichia coli in Metropolitan St. Louis Streams 23

(9) (9) (9)

14,700 8,560 7,490

(9) (9) (9) (9) (27)

8,970

1,040

2,730

24,700

12,700

(19) (20) (19) (19) (16)

2,240

293

1,340

5,540 5,990

(20) (19) (19)

1,180 1,370

3,050

MISSISSIPPI RIVER SITES

05587455

Below 

Grafton

07005500

Above

St. Louis

07010000

At 

St. Louis

07010220

At 

Oakville

07019370

At 

Kimmswick

MISSOURI RIVER SITES

06935972

Below 

St. Charles

06937000

At Columbia

bottom

100

101

102

103

104

105106

100

101

102

103

104

105106

BASE FLOW

STORM EVENT

DIRECTION OF STREAMFLOW

06935715

Near 

Chesterfield

(9) Number of samples 

EXPLANATION

Upper outside

Upper adjacent75th percentile

Median25th percentileLower adjacent

Lower outside x

Storm event

Base flow

8,970

LOAD, IN MILLIONS OF COLONIES PER SECOND ESCHERICHIA COLI 

Figure 10. Instantaneous Escherichia coli loads from discrete samples collected between October 2004 and September 2007 at large river sites in the metropolitan St. Louis area.
24 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

Missouri River sites, the percent of human E. coli increased 

from a mean of 28 percent at the upstream site (06935715) to 

41 percent at the downstream site (06937000; table 8, at the 

back of this report; fig. 12). A similar increase was observed 

at Mississippi River sites, although the upstream Mississippi 

River site (05587455) had a much lower mean percent of 

human bacteria (14 percent) than did other large river sites.

Mississippi River sites below the Missouri River confluence 

had a mean percent of human E. coli from 40 to 44 percent 

(fig. 12), a value almost three times the percentage above the 

ESCHERICHIA COLI LOAD, IN MILLIONS OF COLONIES PER SECOND

BASE FLOW

STORM EVENT

06935890

Creve 

Coeur

Creek

06936475

Coldwater

 Creek

07005000

Maline

Creek

07010022

River des 

Peres near 

University City

07010097

River des 

Peres at 

St. Louis

07019185

Grand 

Glaize 

Creek

SMALL BASIN SITES

157

(7) Number of samples 

EXPLANATION

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Upper outside

x

Base flow

Storm event

100

101

102

103

104

105

106

100

101

102

103

104

105

106

(7) (7) (7) (8) (8) (7)

326

960

654

1,900

118 157

(19) (20) (18) (18) (19) (19)

.24 .47 .42 .51 .22 .20

Figure 11. Instantaneous Escherichia coli loads from discrete samples collected between October 2004 and 

September 2007 at small basin sites in the metropolitan St. Louis area.
Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 25

confluence. Small basin sites that drained to the Missouri 

River had smaller mean percent of human E. coli (25 percent 

at site 06935890 and 28 percent at site 06936475) than did 

small basin sites that drained to the Mississippi River (values 

ranged from 30 to 37 percent; fig. 12). The largest human E. 

coli mean (37 percent) at small basin sites during base flow 

was observed at Maline Creek (site 07005000) and the upper 

River des Peres site (07010022; fig. 12). 

In general, dog E. coli averaged 10 percent or less of 

the total E. coli in base-flow samples (fig. 12). The middle 

Missouri River site (06935972) had the largest mean percent of dog E. coli (16 percent) of Missouri River sites. The 

upstream Mississippi River site (05587455) had the lowest 

mean percent of dog E. coli (2 percent) of any site. Dog E. coli

at Mississippi River sites increased below the Missouri River 

confluence to a peak of 14 percent (site 07010000) and then 

declined in downstream reaches (fig. 12). Most small basin 

sites averaged close to 10 percent of E. coli identified as dog, 

the exception being the Coldwater Creek site (06936475), 

which averaged 17 percent. 

Approximately 20 percent of the E. coli was attributable to geese in Missouri River base-flow samples (fig. 12) 

with the most upstream site (06935715) having the largest 

mean percentage (23). The upstream Mississippi River site 

(05587455) and the next downstream site (07005500) had the 

greatest percent of E. coli from geese (20 and 23 percent), 

and the mean percent then generally declined in downstream 

Mississippi River reaches (fig. 12). The mean percent of geese 

E. coli in small basin samples ranged from 13 percent (upper 

River des Peres, site 07010022) to 27 percent at Coldwater 

Creek (site 06936475).

For Missouri River base-flow samples, the mean percent 

of unidentified E. coli was approximately 30 percent, with the 

upstream site (06935715) having the largest percent of unidentified E. coli (fig. 12). For Mississippi River sites, the most 

upstream site had the largest percent of unidentified E. coli (57 

percent). Below the confluence with the Missouri River, this 

percent declined dramatically to 27 percent and then increased 

downstream through the study area, but in general, the mean 

percent of unidentified E. coli at Mississippi River sites below 

the Missouri River confluence was near 31 percent (fig. 12).

For small basin sites, the mean percent of unidentified E. coli

ranged from 28 percent to 39 percent (fig. 12).

Storm-Event Escherichia coli Sources

During storm events, the mean percent of E. coli attributable to humans at Missouri River sites was greatest (35 

percent) at the middle site (06935972) and was approximately 

30 percent at other Missouri River sites (fig. 13; table 8). For 

sites on the Mississippi River, the percent of bacteria attributable to humans indicated substantial increases below the 

confluence with the Missouri River increasing from a mean of 

27 percent at the most upstream site (05587455) to 48 percent 

at site 07010220 (fig. 13). Small basin sites that drained to the 

Missouri River averaged substantially less human E. coli (20 

to 25 percent) than did sites that drained to the Mississippi 

River (34 to 63 percent; fig. 13).

The mean percent of E. coli attributable to dogs at Missouri River sites was the greatest (10 percent) at the middle 

site (06935972) and lowest (6 percent) at the upstream site 

(06935715; fig. 13). For Mississippi River sites, the lowest mean percent (2 percent) of E. coli attributable to dogs 

occurred at the upstream site (05587455). This percentage 

increased at Mississippi River sites in the middle reaches 

(maximum of 13 percent at site 07010000) and then declined 

in downstream reaches (fig. 13). At small basin sites, the mean 

percentage of E. coli attributable to dogs was approximately 

10 percent (values ranged from 5 to 15 percent) with the highest mean percent at the upper River des Peres site (07010022; 

fig. 13).

The mean percentage of E. coli attributable to geese 

increased in reaches of the Missouri River from 17 percent 

(site 06935715) to 28 percent (site 06937000; fig. 13). For 

sites on the Mississippi River, the mean percentage of E. 

coli from geese was greatest at the most upstream and most 

downstream sites and declined in the middle reaches (fig. 13).

Compared to other sites in the study area, small basin stormevent samples generally had a lower mean percentage of E. 

coli from geese with values ranging from 8 to 20 percent (fig. 

13).

For Missouri and Mississippi River sites, the largest 

percentage of E. coli from unidentified sources occurred at 

the upstream sites (06935715 and 05587455; fig. 13) and 

then declined in downstream reaches. At small basin sites, 

the mean percentage of unidentified E. coli ranged from 22 

percent (site 07010097) to 59 percent (site 06936475). Larger 

percentages of unidentified bacteria are likely an indication of 

increased nonpoint source contributions in upstream reaches 

that contained bacteria from a myriad of sources, in addition to 

those contributions from human, dog, and goose sources.

Current (2010) water-quality standards have been written 

to address how stream E. coli density compares to applicable 

numeric criteria (table 4), regardless of the source, or sources, 

of these bacteria; however, an understanding of how individual 

sources contributed densities in excess of State criteria could 

be beneficial to design appropriate reduction and management strategies. Additionally, the presence of human E. coli

in streams may indicate an increased potential for the presence of other pathogenic bacteria (Wilkes and others, 2009). 

The percentage of water samples at stream sites that met the 

applicable State E. coli criterion during the recreational season 

when the total instream bacteria was adjusted for host source 

is listed in table 9.

Host-source E. coli densities were determined from the 

percentage of the total E. coli density in the stream attributable to any given host. Because individual hosts were just part 

of the total instream bacteria, individual host-source E. coli

densities were always less than the total density measured 

in samples. Because one primary concern was to evaluate 

the contributions of E. coli from wastewater sources relative 

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams
26 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007 Table 7. Summary of microbial source-tracking samples analyzed at metropolitan St. Louis sites between October 2004 and September 2007. [mm, mile marker; rep-PCR, repetitive extragenic pallindromic polymerase chain reaction; B. Tim, Bacterioides thetatiotaomicron] Station name Station identifier (fig. 1) Baseflow Number of rep-PCR samples Number of rep-PCR isolates identified Mean number of rep-PCR isolates per sample Mean percent identified to host source Median percent identied to host source Number of B. tim samples Missouri River sites Missouri River near Chesterfield at mm 48 06935715 16 180 11 70 72 10 Missouri River below St. Charles at mm 24.5 06935972 16 238 15 71 79 11 Missouri River at Columbia Bottom Conservation Area at mm 4 06937000 16 236 15 73 78 12 All Missouri River sites 48 654 14 71 75 33 Mississippi River sites Mississippi River below Grafton, Illinois 05587455 16 74 5 44 38 7 Mississippi River above St. Louis at mm 184.5 07005500 17 171 10 73 76 9 Mississippi River at St. Louis 07010000 18 219 12 70 74 10 Mississippi River at Oakville at mm 164.5 07010220 17 212 12 68 78 13 Mississippi River at Kimmswick, Missouri 07019370 17 206 12 66 78 11 All Mississippi River sites 85 882 10 67 75 50 Small basin sites Creve Coeur Creek near Creve Coeur, Missouri 06935890 15 199 13 65 73 9 Coldwater Creek near Black Jack, Missouri 06936475 16 240 15 72 80 6 Maline Creek at Bellefontaine Neighbors, Missouri 07005000 15 216 14 68 80 7 River des Peres near University City, Missouri 07010022 14 225 16 62 64 12 River des Peres at St. Louis, Missouri 07010097 15 212 14 72 75 10 Grand Glaize Creek near Valley Park, Missouri 07019185 16 238 15 61 53 10 All small basin sites 91 1,330 15 67 71 54 Totals 224 2,866 13 68 75 137
Occurrence and Sources of Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Escherichia coli in Metropolitan St. Louis Streams 27

Figure 12. Mean percent of Escherichia coli bacteria attributable to host sources at sites in the metropolitan St. Louis area from 

base-flow samples collected between October 2004 and September 2007.

06935715 06935972 06937000

MISSOURI RIVER SITES

05587455 07005500 07010000 07010220 07019370

MISSISSIPPI RIVER SITES

06935890 06936475 07005000 07010022 07010097 07019185

SMALL BASIN SITES

BASE FLOW

HUMAN

DOG

GOOSE

UNKNOWN

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

(16) (16) (16)

[53] [84] [98]

(15) (16) (15) (14)

[51] [61] [74] [85]

(15)

[73]

(16)

[79]

(16)

[19]

(17)

[63]

(18)

[86]

(17)

[92]

(17)

[86]

ESCHERICHIA COLI ATTRIBUTABLE TO HOST SOURCE, IN PERCENT

(16) (16) (16)

[24] [36] [25]

(16) (17) (18) (17)

[4] [19] [32] [19]

(17)

[9]

(15) (16) (15) (14)

[24] [32] [20] [26]

(15)

[29]

(16)

[22]

(16) (16) (16)

[44] [43] [44]

(16) (17) (18) (17)

[20] [30] [35] [35]

(17)

[39]

(15) (16) (15) (14)

[48] [68] [58] [29]

(15)

[50]

(16)

[48]

(16) (16) (16)

[59] [75] [69]

(16) (17) (18) (17)

[31] [59] [66] [72]

(17)

[66]

(15) (16) (15) (14)

[76] [79] [64] [85]

(15)

[60]

(16)

[89]

Mean value

Range of values

Number of samples

Number of isolates

Missouri River

 tributary sites

Mississippi River

 tributary sites
28 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

to those from nonpoint sources, host-source densities were 

divided into two broad categories—E. coli originating from 

human and E. coli originating from nonhuman and unidentified sources. Although there may be some overlap between 

categories, human E. coli was considered to primarily have 

originated from point sources, whereas the remaining E. coli

was considered to have originated from nonpoint sources. 

When only human E. coli bacteria were considered, most 

(greater than 90 percent) of Mississippi River base-flow and 

storm-event samples were below the applicable criterion (table 

9). Sites on the Missouri River met the applicable criteria, 

on average, 79 percent of the time during base flow and 60 

percent of the time during storm events (table 9). Conversely, 

human E. coli contributions to the Missouri River were sufficient to raise instream bacteria levels above the applicable 

standard in 21 percent of base-flow samples and 40 percent 

of storm-event samples. Small basin sites typically had large 

E. coli densities and greater amounts of human E. coli in 

base-flow and storm-event samples when compared to larger 

river samples. At the small basin site (07010097) where the 

applicable criterion is 1,134/col mL, when only human E. 

coli are considered, all of the base-flow samples, but none of 

the storm-event samples were below the standard (table 9).

At the four small basin sites where the criterion is lower, 206 

col/100 mL, an average of 77 percent of base-flow samples 

were below the criterion, but only 21 percent of storm-event 

samples.

When only nonhuman and unidentified E. coli are considered, again, most Mississippi River base-flow (an average of 

96 percent) and storm-event (86 percent) samples were below 

the applicable criterion (table 9). Because of greater densities 

in general, Missouri River sites met the applicable criteria, 

on average, 65 percent of the time during base flow, and 33 

percent of the time during storm events when considering only 

nonhuman and unidentified E. coli (table 9). Nonhuman and 

unidentified E. coli contributions, again, most of which were 

considered to have originated from nonpoint sources,

 to small basins were sufficient to raise instream densities 

above the appropriate criteria, on average, in about onehalf (51 percent) of base-flow samples and all storm-event 

samples. These data indicate that reduction or elimination of 

nonpoint E. coli source contributions to study area streams 

would likely have an equivalent, if not greater, effect on reducing stream E. coli levels below applicable State criteria than 

would the elimination of human sources of E. coli.

Escherichia coli Host-Source Loads

Host-source E. coli loads were determined at stream sites 

by multiplying the total E. coli load by the relative percent 

of bacteria identified by individual host source. Such load 

calculations provide data on the relative contribution of host 

sources from tributaries to receiving streams. In general, hostsource load patterns were similar to the overall E. coli load 

patterns previously described. Host-source loads measured 

in small river basins typically were small in contrast to the 

resident, large river, receiving stream E. coli populations during base-flow conditions. During storm events, E. coli loads 

in small river basins increased substantially when compared 

to base-flow loads. When compared to large river loads, small 

basin host-source E. coli storm loads were substantially larger 

than base flow, but generally small when compared to receiving stream reach loads (table 10).

During base flow, mean host-source E. coli loads at the 

most downstream Missouri River site (06937000) declined 

slightly or remained relatively stable when compared to 

upstream Missouri River sites (fig. 14). By contrast, on the 

Mississippi River, mean Mississippi River host-source E. coli

loads generally increased through the study area with a notable 

increase at sites downstream from the Missouri River confluence (fig. 14). Mean host-source E. coli loads at small basin 

sites typically were lower at Missouri River tributary sites than 

at Mississippi River tributary sites (fig. 14).

The mean human and dog E. coli loads in base-flow samples from the most upstream Mississippi River site (05587455) 

were 5 percent, or less, of those measured at the most downstream Missouri River site (06937000; table 10). Mean 

human and dog E. coli loads from the upstream Mississippi 

River site also were less than 10 percent of the mean loads at 

middle Mississippi River sites (table 10; fig. 14). Although the 

relative percentages were slightly greater (8 to 13 percent), 

the mean goose E. coli loads from the upstream Mississippi 

River site indicated a similar pattern (fig. 14). For samples 

of unidentified origins, mean base-flow loads measured at 

the most upstream Mississippi River site were approximately 

20 percent of the mean loads at the most downstream Missouri River site and 40 percent of those measured at middle 

Mississippi sites (fig. 14; table 10). Mean host-source E. coli

base-flow loads at all small basin sites were less than 1 percent 

of the loads measured at large river sites. Although small 

basin sites contributed E. coli to receiving waters, these data 

indicate that during base flow little of the bacteria in the Missouri and Mississippi Rivers originated from small basin sites 

in the study area. Additionally, these data indicate that during 

base-flow conditions, substantial E. coli contributions to the 

middle and lower Mississippi River originated from within the 

study area, either from point sources (notably CSOs, SSOs, 

and WWTPs), nonpoint sources, or a combination of these 

sources. Substantial contributions to the middle and lower 

Mississippi River also originated from Missouri River reaches; 

furthermore, a large percentage of the Missouri River E. coli

likely originated in areas upstream from the study area. 

The pattern of E. coli bacteria host-source contribution 

during storm events (fig. 15) was similar to that during base 

flow (fig. 14). One exception was that small basin E. coli loads 

increased more substantially, when compared to large river 

loads, during storm events and as a result, the relative size 

of small basin E. coli storm loads to receiving streams was 

greater than during base flow.

Mean host-source E. coli loads at Missouri River sites 

during storm events, remained relatively stable (fig. 15) 
Occurrence and Sources of Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Escherichia coli in Metropolitan St. Louis Streams 29

06935715 06935972 06937000

MISSOURI RIVER SITES

05587455 07005500 07010000 07010220 07019370

MISSISSIPPI RIVER SITES

06935890 06936475 07005000 07010022 07010097 07019185

SMALL BASIN SITES

STORM EVENT

HUMAN

DOG

GOOSE

UNKNOWN

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

0

50

40

30

20

10

100

90

80

70

60

ESCHERICHIA COLI ATTRIBUTABLE TO HOST SOURCE, IN PERCENT

Mean value

Range of values

Number of samples

Number of isolates

Missouri River

 tributary sites

Mississippi River

 tributary sites

(8) (8) (9)

[39] [50] [36]

(5)

[8]

(8)

[52]

(8)

[47]

(8)

[43]

(8)

[58]

(8) (8) (9)

[9] [11] [14]

(8)

[1] [13] [10]

(5) (8) (8)

[15]

(8)

[8]

(6) (66) (6) (5)

[13] [11] [6] [9]

(6)

[13]

(6)

[12]

(8) (8) (9)

[20] [33] [32]

(5)

[9]

(8)

[35]

(8)

[31]

(8)

[17]

(8)

[33]

(6) (6) (6) (5) [17] [12] [24] [13] (6)

[13] (6)[13]

(16) (17) (18) (17)

[9] [32] [29] [36]

(17)

[28]

(6)

[57]

(6) (6) (6) (5)

[29] [23] [40] [36]

(6)

[60]

(6)

[41]

(6) (5)

[49] [28]

(6)

[23]

(6)

[51]

(6)

[66]

(8) (8) (9)

[51] [36] [45]

Figure 13. Mean percent of Escherichia coli bacteria attributable to host sources at sites in the metropolitan St. Louis area from 

storm-event samples collected between October 2004 and September 2007.
30 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

because there was little change in either the E. coli density, 

streamflow, or the percentage of the various host sources 

between Missouri River sites. When compared to either the 

most downstream Missouri River site (06937000) or the midMississippi River sites (07005500 and 07010000), Mississippi 

River E. coli storm loads at the most upstream site (05587455) 

for all sources were substantially greater than during base 

flow (figs. 14 and 15; table 10). Even so, upstream Mississippi 

River human E. coli loads were never more than 19 percent of 

those measured at the most downstream Missouri River reach. 

These data indicate that even during storm events, E. coli

bacteria contributions from the Missouri River to the Mississippi River were considerably larger than those from upstream 

Mississippi River reaches. This would be expected, in part, 

because the Missouri River had suspended sediment concentrations that typically were more than three times greater than 

those on the upper Mississippi (411 mg/L compared to 

115 mg/L).

Because discharge and bacteria densities at small basin 

sites increased greatly in response to storm events, mean 

E. coli loads for all sources were many times greater than 

those measured during base flow. Mean E. coli host-source 

loads measured at site 06935890, Creve Coeur Creek, were 4 

percent or less of those measured at the downstream receiving 

section of the Missouri River (site 06935972; table 10). Mean 

host-source E. coli loads at site 06936475, Coldwater Creek, 

ranged from 9 to 48 percent of those measured at the downstream receiving section of the Missouri River (site 06937000; 

Table 9. Percent of water samples collected between October 2004 and September 2007 at metropolitan St. Louis area stream sites 

that met the applicable State of Missouri criterion when adjusted by host-source density estimates.

 [all values in percent identifed; col/100 ml, colonies per 100 milliliters of water; --, not applicable]

Site name

Station

 identifier 

(fig. 1)

Human Nonhuman and 

unidentified Applicable

criteriona

Base flow Storm event Base flow Storm event

Large river sites

Missouri River sites

Missouri River near Chesterfield 06935715 88 63 63 50 206 col/100 mL

Missouri River below St. Charles 06935972 81 50 69 50 206 col/100 mL

Missouri River at Columbia Bottoms 06937000 69 67 63 0 206 col/100 mL

Average -- 79 60 65 33 206 col/100 mL

Mississippi River sites

Mississippi River below Grafton 05587455 100 100 100 80 126 col/100 mL

Mississippi River above St. Louis 07005500 100 100 100 100 1,134 col/100 mL

Mississippi River at St. Louis 07010000 100 100 100 100 1,134 col/100 mL

Mississippi River at Oakville 07010220 100 100 100 100 1,134 col/100 mL

Mississippi River at Kimmswick 07019370 94 62 82 50 206 col/100 mL

Average -- 99 92 96 86 126–1,134 col/100 mL

Small basin sites

Coldwater Creek 06935890 87 17 47 0 206 col/100 mL

Creve Coeur Creek 06936475 88 50 50 0 206 col/100 mL

Maline Creek 07005000 60b 0b 0b 0b 206 col/100 mLb

Grand Glaize Creek 07019185 75 17 56 0 206 col/100 mL

Average -- 77 21 38 0 206 col/100 mL

River des Peres at St. Louis 07010097 100 0 93 0 1,134 col/100 mL

Average, all small basins -- 82 17 49 0 206–1,134 col/100 mL

River des Peres near University City 07010022 64c 0c 64c 0c --c

a

Geometric mean of recreational season samples, April 1 to October 31 of each year.

b

Criterion from streamgage to 0.5 mile below streamgage.

c

No standard currrently (2010) applies. Results shown in comparison to secondary contact limit of 1,134 col/100 mL.
Occurrence and Sources of Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Escherichia coli in Metropolitan St. Louis Streams 31

(16) (16) (16) (16) (17) (18) (17) (17)

(16) (16) (16) (16) (17) (18) (17) (17) (15) (16) (15) (14) (15) (16)

(16) (17) (18) (17) (17)

(16) (17) (18) (17) (17)

(16) (16) (16)

(16) (16) (16)

(15) (16) (15) (14) (15) (16)

(15) (16) (15) (14) (15) (16)

(15) (16) (15) (14) (15) (16)

06935715 06935972 06937000

MISSOURI RIVER SITES

05587455 07005500 07010000 07010220 07019370

MISSISSIPPI RIVER SITES

06935890 06936475 07005000 07010022 07010097 07019185

SMALL BASIN SITES

BASE FLOW

DOG

1

.1

.01

100,000

10,000

1,000

100

10

1

.1

.01

100,000

10,000

1,000

100

10

1

.1

.01

100,000

10,000

1,000

100

10

1

.1

.01

100,000

10,000

1,000

100

10

Number of samples

Missouri River

 tributary sites

Mississippi River

 tributary sites

HUMAN

GOOSE

UNKNOWN

Mean value

Range of values

ESCHERICHIA COLI LOAD, IN MILLIONS OF COLONIES PER SECOND

Figure 14. Mean Escherichia coli load attributable to host sources at sites in the metropolitan St. Louis area from base-flow samples 

collected between October 2004 and September 2007.
32 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

table 10). Small basin sites on Maline Creek (07005000) and 

the lower River des Peres (site 07010097), which drain to the 

Mississippi River, had on average, E. coli host-source loads 

that were approximately 20 percent of lower Mississippi River 

loads (table 10). Mean E. coli loads at the Grand Glaize Creek 

site (07019185) were 2 percent, or less, of the mean loads in 

the lower Mississippi River (table 10).

These data indicate that during storm events, as during 

base flow, large contributions of E. coli to the mid-Mississippi River originated from the Missouri River—much of it 

upstream from the study area. Additionally, inputs from point 

sources (CSOs, SSOs, and WWTPs) as well as nonpoint 

sources in the study area contributed substantial amounts of 

E. coli to the mid- and lower Mississippi River. Although 

E. coli contributions from the Mississippi River upstream 

from the Missouri River confluence increased during storm 

events, upstream Mississippi River contributions were small 

when compared to Missouri River contributions. Small basins 

sites in the study area contributed varying amounts of bacteria to the larger rivers, but these amounts were less than the 

resident E. coli population of the Missouri and Mississippi 

Rivers. Creve Coeur Creek and Grand Glaize Creek appear to 

contribute less than 5 percent of the storm-event E. coli load 

for any host source to receiving waters. The largest human 

E. coli source contributions from small basin sites originated 

from Coldwater Creek, Maline Creek, and the River des Peres; 

however, these contributions were less than 20 percent of 

those in receiving streams.

Source typing of E. coli bacteria was conducted at 14 

sites in the metropolitan St. Louis area between October 2004 

and September 2007 using rep-PCR. These data indicated that 

stream E. coli bacteria originated from a diverse population of 

organisms in, and outside of, the study area. Sources of E. coli

bacteria varied geographically and by hydrologic condition. 

The upstream reach of the Mississippi River had smaller total 

E. coli densities and smaller mean percentage contributions 

of human and dog E. coli than did other sites in the basin. E. 

coli densities in downstream reaches of the Mississippi River 

generally increased below the confluence with the Missouri 

River, as did the percent of human and dog bacteria, primarily 

in response to contributions from the Missouri River. During base flow, a substantial amount of the E. coli bacteria in 

middle and lower reaches of the Mississippi River originated 

from the Missouri River. Although lesser amounts were contributed during storm events, Missouri River E. coli contributions also constituted a substantial amount of the bacteria 

in middle reaches of the Mississippi River; however, point 

sources—such as CSOs, SSOs, and WWTPs, and nonpoint 

sources that originated within the study area—also contributed 

large amounts of E. coli to the middle and lower reaches of the 

Mississippi River.

Small basin sites typically had the greatest E. coli densities of streams in the study area. This was especially true 

during storm events; however, small river basin loads were a 

small percentage (less than 1 percent) of the E. coli load in the 

larger rivers during base flow, an indication that small basin 

contributions were small. During storm events, small basin 

sites contributed much larger amounts of bacteria to large rivers. Coldwater Creek, Maline Creek, and the lower River des 

Peres contributed the largest amount of human E. coli to large 

rivers during storm events, although in all cases these amounts 

were less than 20 percent of the total receiving stream load. 

On average, slightly more than one-third (35 percent) 

of all E. coli at stream sites was typed as being of human 

origin using rep-PCR (fig. 16). Smaller percentages of E. coli

originated from dogs (10 percent) and geese (20 percent). The 

remaining one-third of E. coli, was attributable to unidentified sources (fig. 16). Small basin sites on Coldwater Creek, 

Maline Creek, and the River des Peres, which collectively 

are downstream of the majority of CSOs and SSOs in the 

study area (table 2) had, on average, 36 percent of the E. 

coli sourced as human (table 8), a value consistent with, but 

generally less than, the percentage of human E. coli detected 

in other urban areas of the State where streams receive CSO 

discharges (Wilkison and others, 2009).

When host-source samples were grouped together, there 

was no statistical difference (Wilcoxon rank sum; p-values, 

0.23 to 0.61) in the percent of E. coli identified in base flow 

compared to that in storm-event samples for any of the hostsource groups (fig. 16). These data are an indication that the 

general origins of E. coli sources in the study area were largely 

independent of hydrologic conditions and remained relatively 

consistent with time (fig. 16).

Because E. coli densities generally were below the applicable water-quality criterion at Mississippi River sites, humansourced E. coli densities, approximately one-third of the total, 

almost always were below the criteria—the only exception 

being the most downstream Mississippi River site. However, 

because E. coli densities at some Missouri River and small 

basin sites frequently were well above the applicable water 

criterion, the percentage attributable to human sources was, at 

times, above the standard—much more so during storms than 

base flow. When stream E. coli loads are taken into account, 

small basin contributions to large rivers generally were small 

because flows in the large, receiving streams were greater. 

This especially was true during base flow when small basin 

E. coli loads were less than 1 percent of those measured at the 

large river sites. During storm events, E. coli loads at small 

basin sites were, on average, 7 percent of large river, receiving stream loads. These data indicate that although small basin 

E. coli densities were large, small basin E. coli contributions 

(loads) to the larger rivers in the study area were small in 

comparison to the resident large river E. coli populations. This 

was because, in part, streamflow in the Missouri and Mississippi Rivers was much greater than small basin flows, and also 

because the contributing drainage area contained within the 

study area of large rivers was only a small part of the overall 

drainage area. Thus, precipitation events in the study area, 

which resulted in large increases in streamflow at small basin 

sites, had a much smaller effect on the flows in the larger 

rivers.
Looking downstream at Coldwater Creek 

near Black Jack site (photograph by 

Willie Easterling, U.S. Geological Survey).

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 33

Bacteroides thetaiotaomicron

Approximately two-thirds (65 percent) of the samples 

analyzed for E. coli host sources using rep-PCR also were analyzed for the presence of an additional genetic marker, Bacteroides thetaiotaomicron, to confirm the presence of human 

fecal contamination. B. thetaiotaomicron has been shown to 

be a good indicator of human fecal contamination because it 

predominates in human feces and occurs infrequently in nonhuman feces (Carson and others, 2005). B. thetaiotaomicron 

was detected in 92 percent of metropolitan St. Louis stream 

samples where rep-PCR identified the presence of human E. 

coli. Only one percent of samples had no detectable B. thetaiotaomicron in the presence of human E. coli. Seven percent of 

samples (14 of 202) had detectable levels of B. thetaiotaomicron but not human E. coli; however, such samples typically 

had small E. coli densities (less than 70 col/100mL) and larger 

(greater than 70) percents of unknown isolates. It also is possible that for these few samples, human E. coli had degenerated 

to the point that it could no longer be identified as originating 

from a human source or could not be sufficiently cultured for 

the rep-PCR analysis. B. thetaiotaomicron has been shown 

to occur in dogs, although in much smaller amounts than in 

humans, so it is possible that the B. thetaiotaomicron in some 

of these 14 samples came from dogs; however, less than onehalf of these samples had detectable E. coli sourced to dogs, 

which would tend to indicate that sharing, if it did occur, was 

minimal. It is important to note that these two tests analyzed 

for different types of bacteria. E. coli are aerobic bacteria, 

whereas B. thetaiotaomicron are anaerobic; thus, survival rates 

in the environment would be expected to differ between these 

organisms. The presence of B. thetaiotaomicron in more than 

90 percent of the samples that also had detectable human E. 

coli underscores the commonality of human fecal contamination of surface waters in the study area.

Annual load estimates

Annual load estimates integrated base-flow and stormevent samples for a broader, and in this case, yearly time 

interval. Estimated annual E. coli loads at selected sites were 

used to provide additional confirmation of the discrete and 

source-tracking E. coli data and provided another measure 

of relative source contributions in the study area. Regression 

models and model output at sites where models met the previously defined minimum fit criteria are reported in tables 11, 

12, and 13. Estimated annual E. coli loads for two Missouri 

River sites (06935972 and 06937000), two Mississippi River 

sites (05587455 and 07019370), and all six small basin sites 

from October 1996 through September 2007 are shown in 

figure 17. Also shown in figure 17 are how streamflow and 

precipitation within the study area compared to the long-term 

(at least 90 years of record) average. Annual load estimates 

and the 95 percent confidence intervals for those estimates are 

provided in table 13. Annual load estimates are provided for 

the period of record available for any given station; however, 

site comparisons were done only in relation to data from 

October 2004 through September 2007 (water years 2005 

through 2007).

The largest annual E. coli loads were observed on the 

Missouri River (sites 06935972 and 06937000) and downstream Mississippi River site (07019370; fig. 17 and table 

13). Estimated annual E. coli loads from these sites generally 

were at least an order of magnitude greater than those from 

the most upstream Mississippi River site (05587455), and 

were two to three orders of magnitude greater than the estimated loads at most small basin sites (fig. 17; table 13). One 

small basin site, the lower River des Peres (07010097), had 

estimated annual loads of the approximate same size as those 

from the upper Mississippi River site (05587455). 

Comparison of the estimated annual E. coli loads at sites 

with those in downstream receiving streams during water 

years 2005 through 2007 provides an additional measure, one 

that integrates 

base-flow and 

storm-event 

contributions 

of tributary 

contributions 

to receiving 

streams (table 

14). The mean 

annual E. coli

load at the 

upper Mississippi River site 

(05587455) was 

small when compared to mean 

loads at sites 

on the Missouri 

River (06935972 

and 06937000) 

or the lower 

Mississippi River (07019370; table 14). The mean annual load 

for the upper Mississippi River site (05587455) was only 12 

percent of that at the lower Mississippi River site (07019370), 

whereas the lower Missouri River site (06937000) was nearly 

equivalent to that of the lower Mississippi River. These data 

indicate that annual E. coli contributions from the Mississippi 

River reach above the Missouri River confluence contributed, 

on average, a much smaller percent of the E. coli to lower 

Mississippi River reaches than did the Missouri River. The 

base-flow and storm-event average contributions to receiving 

streams are shown in table 14 along with the previous instantaneous load determination (table 6) to allow comparisons 

between the two approaches. In the case of the upper Mississippi River, the values were identical.

With the exception of the lower River des Peres (site 

07010097), the mean annual E. coli load at small basin sites 

was less than 1 percent of the mean annual load of large river 

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams
34 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007 Table 10. Mean tributary inputs of Escherichia coli host-source loads to receiving streams for samples collected between October 2004 and September 2007. [--, not applicable; <, less than] Receiving stream reach Site(s) in- cluded (fig. 1) Mean instantaneous Esch- erichia coli load, in millions of colonies per second Tributary or upstream reach Site(s) included (fig. 1) Mean instantaneous Escherichia coli load, in millions of colonies per second Tributary load, as per- cent of receiving stream load Base flow Storm event Base flow Storm event Base flow Storm event Human Missouri River tributary Upper Missouri 06935715 2,770 5,380 -- -- -- -- -- -- Mid-Missouri 06935972 1,900 4,460 Creve Coeur Creek 06935890 0.17 54 <1 1 Lower Missouri 06937000 2,200 3,730 Coldwater Creek 06936475 .16 519 <1 14 Upper Mississippia 05587455 114 720 5 19 Mississippi River tributary Mid-Mississippi 07005500, 07010000 1,750 2,560 Maline Creek 07005000 .61 460 <1 18 Lower Mississippi 07010220, 07019370 3,590 14,900 Upper River des Peres 07010022 4.0 425 <1 3 Lower River des Peres 07010097 3.0 2,230 <1 15 Grand Glaize Creek 07019185 .18 74 <1 <1 Dog Missouri River tributary Upper Missouri 06935715 1,130 1,730 -- -- -- -- -- -- Mid-Missouri 06935972 1,300 897 Creve Coeur Creek 06935890 .17 19 <1 2 Lower Missouri 06937000 606 1,190 Coldwater Creek 06936475 .08 515 <1 43 Upper Mississippia 05587455 13 103 2 9 Mississippi River tributary Mid-Mississippi 07005500, 07010000 311 1,160 Maline Creek 07005000 .06 64 <1 6 Lower Mississippi 07010220, 07019370 408 3,490 Upper River des Peres 07010022 .05 484 <1 14 Lower River des Peres 07010097 1.3 400 <1 12 Grand Glaize Creek 07019185 .06 43 <1 1
Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 35

Table 10. Mean tributary inputs of Escherichia coli host-source loads to receiving streams for samples collected between October 2004 and September 2007.—Continued[--, not applicable; <, less than]

Receiving stream 

reach

Site(s) included 

(fig. 1)

Mean instantaneous Escherichia coli load, in millions 

of colonies per second Tributary or upstream reach Site(s) included (fig. 1)

 Mean instantaneous 

Escherichia coli load, in 

millions of colonies per 

second

Tributary load, as percent of receiving stream 

load

Base flow Storm event Base flow Storm event Base flow Storm event

Goose

Missouri River tributary

Upper Missouri 06935715 2,050 3,100 -- -- -- -- -- --Mid-Missouri 06935972 1,620 3,320 Creve Coeur Creek 06935890 0.16 27 <1 3Lower Missouri 06937000 1,220 3,970 Coldwater Creek 06936475 .17 312 <1 9

Upper Mississippia 05587455 127 663 10 17

Mississippi River tributary

Mid-Mississippi 07005500, 

07010000

823 1,850 Maline Creek 07005000 .26 311 <1 17

Lower Mississippi 07010220, 

07019370

1,920 7,590 Upper River des Peres 07010022 1.7 349 <1 5

Lower River des Peres 07010097 2.5 314 <1 4Grand Glaize Creek 07019185 .44 45 <1 1

Unidentified sources

Missouri River tributary

Upper Missouri 06935715 1,130 1,730 -- -- -- -- -- --Mid-Missouri 06935972 1,300 897 Creve Coeur Creek 06935890 .29 78 <1 4Lower Missouri 06937000 606 1,190 Coldwater Creek 06936475 .26 1,030 <1 48

Upper Mississippia 05587455 300 658 18 31

Mississippi River tributary

Mid-Mississippi 07005500, 

07010000

311 1,160 Maline Creek 07005000 .73 627 <1 32

Lower Mississippi 07010220, 

07019370

408 3,490 Upper River des Peres 07010022 2.0 256 <1 3

Lower River des Peres 07010097 3.1 1,440 <1 19Grand Glaize Creek 07019185 .71 159 <1 2

aComparison is to lower Missouri River site (06937000).
36 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

(8) (8) (9) (5) (8) (8) (8) (8) (6) (6) (6) (5) (6) (6)

(6) (6) (6) (5) (6) (6)

(6) (6) (6) (5) (6) (6)

(6) (6) (6) (5) (6) (6)

(5) (8) (8) (8) (8)

(5) (8) (8) (8) (8)

(5) (8) (8) (8) (8)

(8) (8) (9)

(8) (8) (9)

(8) (8) (9)

06935715 06935972 06937000

MISSOURI RIVER SITES

05587455 07005500 07010000 07010220 07019370

MISSISSIPPI RIVER SITES

06935890 06936475 07005000 07010022 07010097 07019185

SMALL BASIN SITES

STORM EVENT

DOG Number of samples

Missouri River

 tributary sites

Mississippi River

 tributary sites

HUMAN

GOOSE

UNKNOWN

Mean value

Range of values

1

.1

.01

100,000

10,000

1,000

100

10

1

.1

.01

100,000

10,000

1,000

100

10

1

.1

.01

100,000

10,000

1,000

100

10

1

.1

.01

100,000

10,000

1,000

100

10

ESCHERICHIA COLI LOAD, IN MILLIONS OF COLONIES PER SECOND

Figure 15. Mean Escherichia coli load attributable to host sources at sites in the metropolitan St. Louis area from storm-event 

samples collected between October 2004 and September 2007.
Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 37

sites (table 14). Mean E. coli load at the lower River des Peres 

site was 9 percent of the mean load in the lower Mississippi 

River. These data indicate that, when viewed annually, E. 

coli loads at small basin sites in the study area typically were 

small when compared to loads in receiving sections of large 

rivers. The largest annual contributions from small basin sites 

to the larger river receiving streams originated from lower 

River des Peres. These data do not preclude the fact that some 

storm events may provide large amounts of E. coli to receiving 

streams, but rather that small basin streams, over the course of 

any given year, typically contribute no more than 10 percent 

of the E. coli to larger river systems. The bulk of the E. coli

load to the middle Mississippi River, immediately downstream from the confluence with the Missouri River, appears 

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams

B.

A.

20

(7) Number of samples 

EXPLANATION

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper outside

Upper detached

x

x

x

x

x

x

x

o

x

x

x

x

0

40

60

80

100

20

10

50

70

90

30

0

40

60

80

100

20

10

50

70

90

30

o

o

o

(321) (321) (321) (321)

HUMAN DOG GOOSE UNKNOWN

x

x

x

o

x

x

x

x

x x o

xx

x

HUMAN DOG GOOSE UNKNOWN

ESCHERICHIA COLI ATTRIBUTABLE TO HOST SOURCE, IN PERCENT

BASE

FLOW

STORM

EVENT

BASE

FLOW

STORM

EVENT

BASE

FLOW

STORM

EVENT

BASE

FLOW

STORM

EVENT

d

d

a a

b b

c

c

 35 

10 

20

 34

a

b

c

d

 35 34 

 9 

 11 

 21 20 

 36 

 34 

Different letters indicate a 

 significant difference 

 exists between plots

[466] Number of isolates

 identifed

[1,573] [466] [900] [1,495]

(224) (97) (224) (97) (224) (97) (224) (97)

[1,004] [569] [321] [145] [591] [309] [950] [545]

a, b,

c, d

Figure 16. Percent of identified by host-source category in samples collected in the metropolitan St. Louis area 

between October 2004 and September 2007.
38 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

to originate from the Missouri River with smaller amounts 

(approximately 10 percent annually) originating from the 

upper Mississippi River and the lower River des Peres.

Annual loads at small basin sites closely followed the 

precipitation pattern within the study area (fig. 17). This would 

be expected because discharge was a large component of 

loads. Precipitation in the study area from 1997 to 2007 was 

4 percent greater than the long term (90 year) average, and 

streamflow for the Mississippi River at St. Louis was 

1 percent greater than average. For the most part, Mississippi 

River streamflow mirrored the precipitation pattern, but there 

were exceptions. For example, 2001 annual precipitation 

was 16 percent below average, and loads at small basin sites 

declined accordingly (fig. 17). This was followed by 4 years 

of slightly above (14 percent) average precipitation and a corresponding increase in loads. Loads then declined in 2006 in 

response to below average precipitation before increasing in 

2007 when precipitation returned to normal levels. For a few 

years, notably 1999 and 2001, flows in the Mississippi River 

at St. Louis were greater than the long-term average, although 

local precipitation decreased. This happens because given 

the basin’s size, areas may experience wetter than normal 

conditions, whereas others remain dry. These data are another 

indication that flows, and consequently constituent loads in 

large rivers within the study area, are only partly controlled by 

local events.

Yields, which normalize annual loads by contributing 

drainage area, indicated that E. coli contributions per square 

kilometer in small basins were 2 to 3 orders of magnitude 

greater than at large river sites (table 14). This was because, 

in part, the contributing drainage area at large river sites was 

so much larger than for the small basins, but also because 

E. coli densities in small basins in the study area were much 

greater than in the large rivers. Additionally, at the basin-scale 

level, bacteria die-off would be expected to be more of a factor 

in the Missouri and Mississippi Rivers than for the smaller 

basins. The largest mean annual yields were at the two River 

des Peres sites (table 14).

Because estimated annual E. coli loads at basin sites 

were the summation of daily loads, dividing the daily E. coli

load by the daily mean discharge provided an estimated daily 

mean E. coli density. Estimated daily mean E. coli density 

values covered the range of hydrologic conditions at sites and 

provided additional measures for comparing the relative difference between streams and sites (fig. 18). 

Estimated daily mean E. coli densities were significantly 

lower at the upstream Mississippi River site (05587455; 

fig. 18) than at other stream reaches in the study area (Wilcoxon rank sum; p-values less than 0.001). Daily mean E. coli

densities were slightly, but significantly, higher for Missouri 

River sites when compared to the downstream Mississippi 

River site (07019370; fig. 18). Small basin sites had estimated 

daily mean E. coli densities that were significantly higher than 

other stream reaches (fig. 18). Small basin sites located in 

areas with the greatest number of CSOs and SSOs in the study 

area—Maline Creek and the River des Peres—had the largest 

estimated daily mean E. coli densities (fig. 18).

As previously noted, the geometric mean of samples 

collected during the recreational season is used to determine 

compliance to water-quality criteria; however, estimated 

daily mean E. coli densities, which incorporate all interannual hydrologic fluctuations and cover a larger time span than 

do discrete samples, provide another measure to compare 

instream E. coli densities against these criteria (table 14). As a 

means of comparing the two approaches, the weighted average 

values for discrete base-flow and storm-event samples (table 

5) also are provided in table 15.

In general the two approaches were similar (table 15), 

but more so at sites where bacteria densities fluctuated little in 

response to hydrologic events such as occurs on the Missouri 

River and the upper Mississippi River. Based on estimated 

daily mean E. coli values, sites on the Missouri River were 

below the applicable E. coli standard, on average, slightly 

more than one-half (52 percent) of the time—a value identical 

to the Missouri River weighted average (52 percent) of the discrete base-flow and storm-event values (table 15). Estimated 

daily mean E. coli values at the upper Mississippi River site 

(05587455) were below the applicable standard, on average, 

94 percent of the time, a value nearly identical to the average 

(95 percent) of the discrete base-flow and storm-event samples 

(table 15). For the lower Mississippi River site (07019370), 

there was less agreement between the two approaches, 

38 percent compared to 57 percent. Some of these differences may be an artifact of the model estimation approach at 

this site. At small basin sites: Creve Coeur, Coldwater Creek, 

Maline, and Grand Glaize Creeks, where whole body contactClass B E. coli criterion currently (2010) applies, estimated 

daily mean E. coli densities were below the criterion, on 

average, only 4 percent of the time, which is lower than the 

average (29 percent) of the discrete base-flow and storm-event 

values (table 15).

Where secondary contact E. coli criterion currently 

(2010) are in place—the lower River des Peres—estimated 

daily mean E. coli densities were below the criterion, on average, 48 percent of the time, which is lower than the average 

(65 percent) of the discrete base-flow and storm-event values.

Although not intended to illustrate compliance with waterquality standards, these data indicate that, in some instances, 

broadening the scope of the measurement period to include 

daily values—compared to the assessments that use less 

frequent, discrete values—may change assumptions about how 

frequently criteria are met or exceeded. 

Hydrologic Effects on Escherichia coli densities 

in streams

Precipitation affects instream bacteria densities in a 

number of ways, primarily by mobilizing sediments to which 

bacteria particles frequently are associated. Because bacteria particles are associated with suspended stream sediment, 
Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams 39

increased runoff typically results in increased levels of 

instream bacteria. Runoff events also can trigger CSO, SSO, 

and WWTP by-pass events, each of which can result in large 

increases in bacteria loads in streams. Basins with large 

amounts of impervious surface area potentially have increased 

runoff, increased stream velocities, and increased channel erosion and therefore, increased levels of streamflow, suspended 

sediment, and E. coli (Paul and Meyer, 2001). There was a 

strong association (coefficient of correlation, 0.83; p<0.001) 

between the percent of impervious cover and E. coli densities in the study area (fig. 19). Water-quality degradation and 

increased concentrations of constituents, including fecal indicator bacteria, in streams with large amounts of impervious 

cover, have been demonstrated in numerous studies (Mallin 

and others, 2000; Wilkison and others, 2006; Poulton and others, 2007; Schueler and others, 2009); however, it is important 

to note that impervious area alone does not fully represent the 

complexity of urban land cover and that other factors, such as 

the pattern, intensity, and connectivity of these areas may be as 

important as the total area (Alberti and others, 2007).

For sites on the Missouri and Mississippi Rivers, where 

most of the basin lies outside the metropolitan St. Louis, 

instream bacteria concentrations were only partly determined 

by localized runoff events. When grouped by hydrologic 

event, median E. coli densities in Missouri and Mississippi 

River storm-event samples were approximately 4 times greater 

than in base-flow samples (fig. 7); however, small basin stormevent samples had much larger increases in E. coli densities 

over those measured in base-flow samples. At small basin 

sites, the median E. coli densities in storm-event samples 

(5,400 col/100 mL) was more than 10 times greater than the 

density measured in base-flow samples (460 col/100 mL; fig. 

7). This is likely because the small basin sites were draining largely urban land use in the metropolitan St. Louis area, 

whereas most of the area upstream from Missouri and Mississippi River sites lies outside of the St. Louis area, of which 

only a small part is urban.

In addition to mobilizing nonpoint source runoff, precipitation events, especially where intense or prolonged, trigger 

CSOS and SSOs. Such overflows contain large bacteria densities and thus increase instream bacteria densities of receiving 

streams. The combined number of CSOs and SSOs upstream 

from sample sites in the study area ranged from zero at the 

upstream Missouri and Mississippi River sites (06935715 and 

05587455) to more than 400 at the most downstream Mississippi River site (07019370) (table 2; fig. 2). Although these 

eventually drain to the lower Mississippi River, most of the 

CSOs and SSOs in the study area were located in the River des 

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams

Table 11. Regression models for estimating annual loads of Escherchia coli in water at metropolitan St. Louis sites.

[RMSE, root mean square error; r2, coefficient of determination; Ln, natural logarithm; Ecoli, Escherichia coli; FLOW, centered value of flow; Time, centered 

value of time; Sin, Sine; Cos; cosine; FECcoli, fecal coliform; π, pi]”

Station 

identifier 

(fig.1)

Regression model RMSE r2

Missouri River sites

06935972 Ln(Ecoli) = 2.02Ln(FLOW) - 0.434Time + 0.884Sin(Time2π ) + 0.275Cos(2πTime ) + 19.7 1.3 53.7

06937000 Ln(Ecoli) = 3.05Ln(FLOW) - 2.163Ln(FLOW)2 - 0.336Time - 0.892Time2 - 

0.135Sin(2πTime ) + 1.77Cos(2πTime ) + 22.0

1.3 62.5

Mississippi River sites

05587455 Ln(Ecoli) = 2.50Ln(FLOW) + 0.946Ln(FLOW)2 - 0.114Time - 0.327Sin(Time2π ) + 

0.392Cos(Time2π ) + 17.8

.94 54.9

07019370 Ln(FECcoli) = 1.57Ln(FLOW) + 0.899Ln(FLOW)2 - 0.157Time - 0.015Time2 - 

1.22Sin(Time2π ) - 0.915Cos(Time2π ) + 25.6

1.6 83.7

Small basin sites

06935890 Ln(Ecoli) = 2.05Ln(FLOW) - 0.065Ln(FLOW)2 - 0.077Time + 0.055Time2 - 1.114in(Time) 

- 0.672Cos(2πTime ) + 13.5

1.37 87.0

06936475 Ln(Ecoli) = 1.74Ln(FLOW) - 0.017Ln(FLOW)2 - 0.091Time + 0.046Time2 - 

0.628Sin(2πTime) - 0.984Cos(2πTime ) + 14.0

1.36 90.3

07005000 Ln(Ecoli) = 1.59Ln(FLOW) + 0.115Ln(FLOW)2 - 0.112Time - 0.024Time2 - 0.388in(Time) - 

0.754Cos(2πTime) + 13.6

1.34 89.2

07010022 Ln(Ecoli) = 1.53Ln(FLOW) - 0.026Ln(FLOW)2 - 0.192Time - 0.056Time2 - 

0.410Sin(2πTime) - 0.709Cos(2πTime) + 13.0

1.50 91.3

07010097 Ln(Ecoli) = 1.95Ln(FLOW) - 0.070Time - 0.004Sin(2πTime) + 0.073Cos(2πTime) + 13.6 1.75 88.8

07019185 Ln(Ecoli) = 1.77Ln(FLOW) + 0.029Ln(FLOW)2 - 0.098Time - 0.062Time2 - 

0.601Sin(2πTime) - 1.40Cos(2πTime) + 11.8

1.37 89.8
40 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007 Table 12. Model (adjusted maximum likelihood estimation method) output for flow-adjusted trends in Escherichia coli concentration at metropolitan St. Louis sites. [CI, confidence interval; n, number of observations; nC, number of censored observations; RMSE, root mean square error; r2, coefficient of determination; bold numbers indicate significant flow-adjusted trend existed at site] Site name Station ID (fig.1) Reference concentra- tion, in colonies per 100 milliliters Flow-adjusted trend, in average percent per year Properties of the calibration data set Properties of the time term Properties of the fitted model Water yearsa Modeled estimate Up- per 95 percent CI Lower 95 percent CI Start date End date n nC Central value of flow Coeffi- cient Standard deviation p- value Central value of time RMSE r2 Missouri River sites Missouri River be- low St. Charles 06935972 230 2005–2007 -28.9 30.3 -163.9 10/18/2004 8/13/2007 27 0 73,930 -0.668 0.486 0.19 2006.34 1.27 53.7 Missouri River at Columbia Bot- tom 06937000 280 2005–2007 -13.9 21.5 -76.6 10/18/2004 8/13/2007 28 0 74,600 -.336 .272 .16 2006.34 1.27 62.5 Mississippi River sites Mississippi River below Grafton, Ill. 05587455 52 1998–2007 - 4.6 4.2 -14.7 10/16/1997 11/1/2007 155 1 109,200 -.053 .047 .25 2005.27 .49 54.9 Mississippi River at Kimmswick 07019370 1,400b 1998–2007 -3.1 -13.5 -18.0 8/13/1975 11/1/2007 47 0 146,000 - .157 .011 .06 1991.49 .96 83.7 Small Basin sites Creve Coeur Creek 06935890 610 1998–2007 -6.3 3.3 -19.2 8/27/1997 9/12/2007 67 1 30 -.077 .057 .15 2002.94 1.37 87.0 Coldwater Creek near Black Jack 06936475 600 1997–2007 -6.0 0.9 -19.2 8/1/1996 9/12/2007 73 2 66 -.091 .050 .05 2002.34 1.36 90.3 Maline Creek 07005000 1,420 1996–2007 -6.1 -1.5 -20.8 8/1/1996 9/12/2007 71 0 26 -.112 .048 .71 2002.49 1.34 89.2 River des Peres near University City 07010022 4,150 1998–2007 -8.8 -5.8 -32.6 8/19/1997 9/12/2007 67 0 4.3 -.192 .067 .11 2002.92 1.50 91.3 River des Peres at St. Louis 07010097 740 2004–2007 21.6 54.6 -25.3 10/29/2002 9/12/2007 38 1 30 .146 .200 .47 2005.37 1.75 88.8 Grand Glaize Creek 07019185 570 1998–2007 -7.1 1.2 -21.2 8/27/1997 9/12/2007 67 1 16 -.098 .057 .07 2002.97 1.37 89.8

aWater year runs from October 1 to September 30 of each year.bFecal coliform.
Occurrence and Sources of Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Escherichia coli in Metropolitan St. Louis Streams 41

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

EXPLANATION

LARGE RIVER SITES SMALL BASIN SITES

ESTIMATED ESCHERICHIA COLI ANNUAL LOAD, IN TRILLIONS OF COLONIES

106

105

104

103

102

107

108

DEVIATION FROM LONG-TERM AVERAGE,

 IN PERCENT 

0

25

50

-25

-50

St. Louis, Missouri precipitation

Streamflow, Mississippi 

River at St. Louis

Mississippi River below Grafton, Ill. (05587455)

Mississippi River near Kimmswick (07019370)

Missouri River below St. Charles (06935972)

Missouri River near Columbia Bottoms (06937000)

Coldwater Creek (06936475)

Creve Coeur Creek (06935890)

Grand Glaize Creek (07019185)

Maline Creek (07005000)

Upper River des Peres (07010022)

Lower River des Peres (07010097)

B.

A.

Figure 17. Estimated annual loads of Escherichia coli for sites in the metropolitan St. Louis area from October 1996 

through September 2007 and streamflow and precipitation comparison to the long-term (90-year) average.
42 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

Water 

year

Creve Coeur Creek (06935890) Coldwater Creek (06936475)

Load Lower 

95%

Upper 

95% Load Lower 95%

Upper 

95%

Small basin sites

Missouri River tributary

1997 -- -- -- 7,270 1,180 24,500

1998 17,600 2,110 67,400 15,700 1,190 70,300

1999 6,910 794 26,800 6,810 868 25,400

2000 12,200 547 62,700 7,220 539 32,300

2001 900 171 2,740 1,530 298 4,780

2002 5,170 675 19,100 4,540 716 15,500

2003 9,920 956 41,000 4,840 356 21,900

2004 9,030 965 35,900 2,810 526 8,860

2005 5,490 737 20,100 2,390 465 7,440

2006 1,140 113 4,680 715 112 2,450

2007 3,320 651 10,300 1,670 308 5,330

Meana 3,320 500 11,700 1,590 295 5,080

Table 13. Estimated annual loads, in trillions of colonies, of Escherichia coli at metropolitan St. Louis sites for water years 1997 

through 2007.

 [--; not determined; Lower 95%, lower 95 percent confidence interval; Upper 95%, upper 95 percent confidence interval]

Water 

year

Missouri River below 

St. Charles (06935972)

Missouri River at Columbia Bottom (06937000)Mississippi River below Grafton, 

Illinois (05587455)

Mississippi River at Kimmswick, Mo 

(07019370)

Load Lower 

95%

Upper 

95% Load Lower 95%

Upper 

95% Load Lower 95%

Upper 

95% Load Lower 95% Upper 95%

Large river sites

Missouri River sites Mississippi River sites

1997 -- -- -- -- -- -- -- -- -- 20,700,000 26,100 138,000,000

1998 -- -- -- -- -- -- 399,000 174,000 788,000 23,800,000 24,200 156,000,000

1999 -- -- -- -- -- -- 263,000 137,000 459,000 21,600,000 33,700 145,000,000

2000 -- -- -- -- -- -- 89,700 41,200 171,000 3,780,000 84,000 43,000,000

2001 -- -- -- -- -- -- 376,000 169,000 727,000 10,100,000 48,700 68,700,000

2002 -- -- -- -- -- -- 212,000 93,400 416,000 5,590,000 31,500 37,800,000

2003 -- -- -- -- -- -- 49,300 26,900 83,200 1,990,000 294,000 70,020,000

2004 -- -- -- -- -- -- 116,000 56,000 214,000 2,440,000 339,000 8,790,000

2005 472,000 16,600 2,570,000 985,000 241,000 2,740,000 64,000 35,000 109,000 852,000 312,000 1,880,000

2006 111,000 30,300 291,000 170,000 79,800 319,000 28,300 14,800 49,000 302,000 172,000 492,000

2007 361,000 65,600 1,160,000 346,000 144,000 704,000 79,900 39,700 144,000 404,000 173,000 810,000

Meana 315,000 37,500 1,340,000 500,000 155,000 1,250,000 57,500 29,900 101,000 519,000 219,000 1,060,000

Water 

year

Maline Creek (07005000) River des Peres near University 

City (07010022)

River des Peres at St. Louis 

(07010097) Grand Glaize Creek (07019185)

Load Lower 

95%

Upper 

95% Load Lower 95%

Upper 

95% Load Lower 95% Upper 95% Load Lower 95% Upper 95%

Small basin sites—Continued

Mississippi River tributary

1997 -- -- -- -- -- -- -- -- --

1998 6,840 1,090 23,300 43,200 5,720 159,000 -- -- -- 23,700 1,780 106,000

1999 5,170 684 19,000 15,900 1,770 62,500 -- -- -- 2,710 270 11,100

2000 2,480 267 9,830 14,300 951 66,000 -- -- -- 8,140 375 41,700

2001 311 75 872 2,700 464 9,200 -- -- -- 905 108 3,470

2002 2,190 382 7,180 7,080 1,340 22,300 -- -- -- 2,710 219 11,900

2003 4,730 293 22,400 6,400 946 22,500 171,000 3,320 1,030,000 7,420 341 38,000

2004 4,350 419 17,900 5,060 803 17,200 132,000 2,830 746,000 8,350 850 33,900

2005 1,840 193 7,390 3,410 704 10,300 89,000 4,390 450,000 2,420 414 8,000

2006 443 58 1,640 1,180 199 3,920 19,700 775 104,000 2,070 113 10,100

2007 712 142 2,190 3,900 610 13,410 30,300 1,740 147,000 1,250 225 4,030

Meana 999 131 3,740 2,830 505 9,230 46,400 2,300 234,000 1,910 251 7,390

a

Water years 2005 through 2007 (October 1 to September 30). 
Occurrence and Sources of Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams Escherichia coli in Metropolitan St. Louis Streams 43

Table 14. Mean annual Escherichia coli estimated loads and yields at stream sites in metropolitan St. Louis and tributary inputs to receiving streams for water years 2005 through 2007.[<, less than]

Receiving stream 

reach

Site 

included 

(fig. 1)

Mean annual 

Escherichia 

coli load, in 

trillions of 

colonies (table 

12)

Mean annual 

Escherichia coli

yield, in billions 

of colonies per 

square kilometer

Tributary or upstream 

reach

Site 

included

Mean annual 

Escherichia 

coli load, 

in trillions 

of colonies 

(table 12)

Mean annual 

Escherichia coli

yield, in billions 

of colonies per 

square kilometer

Tributary 

load, as 

percent of 

receiving 

stream 

load

Mean of base-flow 

and storm-event 

tributary loads, as 

percent of receiving 

stream load (table 6)

Missouri River tributary

Mid-Missouri 06935972 315,000 229 Creve Coeur Creek 06935890 3,320 58,200 1 <1Lower Missouri 06937000 500,000 364 Coldwater Creek 06936475 1,590 15,200 <1 2

Upper Mississippi 05587455 57,500 129 12 12

Mississippi River tributary

Lower Mississippi 07019370 519,000a 285 Maline Creek 07005000 999 15,800 <1 8

Upper River des Peres 07010022 2,830 122,000 <1 2Lower River des Peres 07010097 46,400 217,000 9 5Grand Glaize Creek 07019185 1,910 33,900 <1 <1

aEstimated annual fecal coliform load in trillions of colonies.
44 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

B.

A.

520

1,095 Number of samples 

EXPLANATION

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper outside

Upper detached

x

Different letters indicate a 

 significant difference 

 exists between plots

a, b,

c, d

x

x

xx

xx

x

x

x

x

x

x

x

x

x

x

x

x

x

x

xx

x

x

x

x

x

x

x

xxx

x

x

x

x

x

x

x

x

x

x

xx

x

790

c

Lower River

Des Peres

(07010097)

Grand

Glaize Creek

(07019185)

x

x

xx

x

x

x

x

x

x

520

b

x

x

xx

x

x

x

x

x

x

x

x

xx

x

x

x

x

x

x

xx

x

ooo

o

o

o

4,500

d

Upper River

Des Peres

(07010022)

1,095 1,095 1,095 1,095 1,095 1,095

xx

x

x

x

x

x

xx

x

x

x

x

150

a

ESTIMATED ESCHERICHIA COLI DENSITY, IN COLONIES PER 100 MILLILITER

x

x

x

x

x

x

xxx

xx

x

x

x

xx

x

x

x

x

x

x

x

x

x

x

x

x

xx

x

x

x

x

xx

x

x

xx

x

x

x

xxx

x

x

x

x

x

x

xx

1,095 1,095 1,095 1,095

Upstream

Mississippi River

(05587455)

Missouri River sites

(06935972)

(06937000)

Small basin

sites

(06936475), (06935890) 

(07019185), (07005000) 

(07010022), (07010097) 

Downstream

Mississippi River 

(07019370)

31

300

1,300

260

a

c

d

b

Coldwater

Creek

(06936475)

xx

xx

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

x

xx

x

x

xx

x

x

x

x

x

x

x

x

xx

x

x

x

530

b

Creve

 Coeur Creek

(06935890)

x

x

xx

x

x

x

x

x

x

x

x

xxx

x

o

880

c

Maline Creek

(07005000)

10,000

100,000

1,000,000

1,000

100

10

1

10,000

100,000

1,000,000

1,000

100

10

Figure 18. Estimated daily mean Escherichia coli densities for streams in metropolitan St. Louis from October 2004 

through September 2007.
 45

Peres Basin (fig. 2). To evaluate the effect that overflow events 

may have had on instream bacteria densities, the combination 

of upstream CSOs and SSOs were compared to the average 

(base flow and storm events) E. coli densities measured at 

downstream sites. For the Missouri River, average E. coli

densities at sites decreased with increasing numbers of CSOs 

and SSOs (coefficient of correlation, 0.71; p=0.45). At Mississippi River sites there was a weak correlation (coefficient of 

correlation, 0.47; p=0.16) between an increase in the number 

of upstream CSOs and SSOs and instream E. coli densities; 

however, at small basin sites there was a strong correlation 

between the number of upstream CSOs and SSOs (coefficient 

of correlation, 0.94, p<0.01) and the average instream E. coli

density. Together these data indicate that any discharges from 

CSOs and SSOs had a negligible effect on E. coli densities in 

the Missouri River, in part because there were relatively few 

of these that discharge to the Missouri River. Although E. coli

associated with CSO and SSO discharges increased instream 

Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams

Table 15. Percent of estimated daily mean Escherichia coli densities at stream sites in the metropolitan St. Louis area that met the 

applicable State of Missouri criterion from October 2004 through September 2007. 

 [--; no data; col/100 ml, colonies per 100 milliliters of water]

Site Station 

identifier

Percent of days or samples

Applicable criterion Estimated daily mean values a

during recreational season 

(April 1st to October 31st)

Discrete base-flow and 

storm-event sample, 

weighted average (table 5)

Large river sites

Missouri River sites

Missouri River near Chesterfield 06935715 -- 59 206 col/100 mL

Missouri River below St. Charles 06935972 52 54 206 col/100 mL

Missouri River at Columbia Bottom 06937000 51 45 206 col/100 mL

Average -- 52 52 206 col/100 mL

Mississippi River sites

Mississippi River below Grafton 05587455 94 95 126 col/100 mL

Mississippi River above St. Louis 07005500 -- 100 1,134 col/100 mL

Mississippi River at St. Louis 07010000 -- 100 1,134 col/100 mL

Mississippi River at Oakville 07010220 -- 89 1,134 col/100 mL

Average -- -- 96 1,134 col/100 mL

Mississippi River at Kimmswick 07019370 38b 57 206 col/100 mL

Average -- 66 88 126–1,1134 col/100 mL

Small basin sites

Creve Coeur Creek 06935890 11 36 206 col/100 mL

Coldwater Creek 06936475 2 33 206 col/100 mL

Maline Creek 07005000 0 20 206 col/100 mLc

Grand Glaize Creek 07019185 3 27 206 col/100 mL

Average -- 4 29 206 col/100 mL

River des Peres at St. Louis 07010097 48 65 1,134 col/100 mL

Average, all small basin -- 13 36 206 col/100 mL

River des Peres near University City 07010022 6 28 --d

a

Geometric mean of recreational season samples, April 1 to October 31 of each year.

b

Estimated from fecal coliform densities.

c

Reach from streamgage to 0.5 mile below streamgage.

d

No standard currrently (2010) applies. Results shown in comparison to secondary contact limit of 1,134 col/100 mL.
46 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

Mississippi River E. coli densities, these contributions were 

not statistically significant, primarily because other, larger, 

basin scale factors—such as inputs from the Missouri River 

and nonpoint source runoff—played a large role. Unlike the 

large rivers, CSO and SSO discharges likely played a large 

role in E. coli densities observed in the small basins, especially 

the River des Peres. Therefore, CSO and SSO elimination 

could reduce small basin E. coli densities to a greater extent 

than that expected in the larger rivers.

Summary and Conclusions

Fecal bacteria contamination, especially E. coli believed 

to have originated from humans, of metropolitan St. Louis 

streams is a concern. The U.S. Geological Survey in cooperation with the Metropolitan St. Louis Sewer District, which 

supplies wastewater treatment to a large part of the St. Louis 

metropolitan area, conducted a study to determine the occurrence, distribution, and sources of E. coli in streams. As part 

of this effort, 14 surface-water sites in metropolitan St. Louis 

were sampled between October 2004 and September 2007 for 

E. coli and E. coli sources. Source sampling was conducted 

using genotypic, local library-based methods that included E. 

coli host-source identification using rep-PCR and the presence 

of the anaerobic, enteric human bacteria, B. thetaiotaomicron. 

Samples were collected during base flow and storm events 

(determined solely by conditions within the study area) from 

three sites on the Missouri River, five sites on the Mississippi 

River, and six sites in smaller basins: Creve Coeur, Coldwater, 

Maline, and Grand Glaize Creeks and the River des Peres, all 

of which are tributaries to the larger rivers. The relative contribution of human, dog, goose, and unidentified E. coli at these 

sites was determined. Linear regression models, developed 

from data collected during a range of hydrologic conditions, 

were used to estimate annual E. coli loads at 10 sites. Waterquality data were compared to selected land-cover factors to 

evaluate the relative role of nonpoint source runoff relative to 

selected point sources (overflows from combined and sanitary 

sewers) at study sites.

E. coli densities and loads typically were many times 

greater in storm events than at base flow, primarily because E. 

coli densities and flow—a major load component—increased 

as a result of runoff. Instantaneous E. coli densities and loads 

at Missouri River sites were about 10 times greater than those 

measured at the most upstream Mississippi River site. A 

substantial part of the E. coli in the middle Mississippi River 

sections downstream from its confluence with the Missouri 

River originated from the Missouri River upstream from 

the study area. In lower Mississippi River reaches, bacteria 

contributions from the numerous combined and sanitary sewer 

overflows within the study area, as well as contributions from 

nonpoint source runoff, greatly increased instream E. coli

densities.

Small basin E. coli densities, especially during storm 

events, were substantially larger than those in the Missouri and 

Mississippi Rivers, but E. coli loads from small basins were 

only a small fraction of the larger, receiving stream loads.

Median small basin E. coli base-flow loads were less than 

1 percent of those measured in the large rivers. Small basin 

E. coli contributions increased substantially during storms, 

but were never more than 16 percent of loads measured in 

receiving sections of the larger rivers. Small basin streams 

with the greatest number of CSOs and SSOs (Maline Creek 

and the River des Peres) had larger E. coli densities and larger 

amounts of bacteria attributed to human sources than other 

small basin sites. 

Instream E. coli densities were compared to current 

(2010) State of Missouri criteria to demonstrate relevance 

to established thresholds rather than numeric compliance 

Mississippi River (5 sites)

Missouri River (3 sites)

Creve 

Coeur 

Creek

Grand 

Glaize 

Creek

River des Peres near 

University City Maline

Creek

Coldwater Creek

River des Peres at 

 St. Louis

IMPERVIOUS COVER, IN PERCENT

y = 184.2e0.085x

r2 = 0.83

0 10 20 30 40 50 60

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

ESCHERICHIA COLI DENSITY, 

IN COLONIES PER 100 MILLILITER

Figure 19. Relation between Escherichia coli densities and the percent of upstream impervious cover 

at sites in the metropolitan St. Louis area.
References Cited 47

which is determined from the geometric mean of recreational 

season (April 1 to October 31) samples. Missouri River E. coli

densities were below the applicable State water-quality E. coli

criterion, on average, in 60 percent of base-flow and 

36 percent of storm-event samples. In contrast, Mississippi 

River E. coli densities were below the applicable State criteria 

in approximately 90 percent of base-flow samples. Primarily 

as a result of increased inputs from runoff, a smaller percent 

(75) of Mississippi River storm-event samples were below 

the applicable criteria, primarily in the most downstream 

reach where a whole body contact-Class B criterion (206 

col/100mL) applied. For small basin sites where whole body 

contact-Class B criterion applied, approximately 30 percent of 

base-flow samples but only 4 percent of storm-event samples 

were below the standard. At the small basin site where a 

less stringent secondary contact recreation criterion (1,134 

col/100mL) applied, 90 percent of base-flow samples, but only 

11 percent of storm-event samples were below the standard.

Although there were differences among sites, on average, the relative contribution of E. coli from various sources 

in the study area did not significantly change between base 

flow and storm events, an indication that the sources remained 

relatively consistent and independent of hydrologic conditions. 

Approximately one-third of the E. coli in the streams was 

identified as human origin. Another one-third was determined 

to be from unidentified sources, and lesser amounts were identified as originating from geese (20 percent) and dogs 

(10 percent), indicating that much of the E. coli in the study 

area likely originated from nonpoint source runoff. Additionally, average instream E. coli densities were correlated 

strongly with the percent of upstream impervious cover and at 

small basin sites, the combined number of upstream CSOs and 

SSOs. CSOs and SSOs had a negligible effect on E. coli densities in the Missouri River, in part because there are relatively 

few that discharge to the Missouri River, and did not have a 

statistically significant effect on Mississippi River E. coli densities because other, larger, basin-scale factors—such as inputs 

from the Missouri River and nonpoint source runoff—played 

a large role.

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Table 8
54 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

Table 8. Summary statistics for Escherchia coli host-source determinations by repetitive extragenic pallindromic polymerase chain 

reaction (rep-PCR). 

[Values in percent of Escherichia coli determined in samples; N, number]

Human Dog Goose Unknown

Base flow Storm event Base flow Storm event Base flow Storm event Base flow Storm event

Missouri River sites

Missouri River near Chesterfield (06935715)

Minimum value 0 0 0 0 0 0 0 20

1st quartile 14 24 0 0 0 4 24 21

Mean 28 30 11 6 23 17 39 47

Median 28 28 10 0 19 15 32 41

3rd quartile 39 41 17 9 34 28 44 65

Maximum value 67 53 33 20 67 40 100 100

N, samples 16 8 16 8 16 8 16 8

N, isolates identified 53 39 24 9 44 20 59 51

Missouri River below St. Charles (06935972)

Minimum value 6 0 0 0 0 0 0 0

1st quartile 24 20 6 4 10 0 14 10

Mean 37 35 16 10 18 22 29 33

Median 36 47 16 8 17 28 21 11

3rd quartile 46 50 24 18 25 37 43 62

Maximum value 89 50 43 22 45 45 75 88

N, samples 16 8 16 8 16 8 16 8

N, isolates identified 84 50 36 11 43 33 75 36

Missouri River at Columbia Bottoms (06937000)

Minimum value 0 0 0 0 0 0 0 11

1st quartile 31 17 4 0 11 20 17 20

Mean 41 27 11 8 21 28 27 37

Median 41 32 11 7 19 33 22 28

3rd quartile 50 37 17 11 25 37 39 47

Maximum value 83 53 26 25 60 50 50 100

N, samples 16 9 16 9 16 9 16 9

N, isolates identified 98 36 25 14 44 32 69 45

All Missouri River sites

Minimum value 0 0 0 0 0 0 0 0

1st quartile 21 22 4 0 10 5 17 15

Mean 35 30 13 8 20 23 32 39

Median 34 32 11 5 17 25 25 28

3rd quartile 46 45 20 17 32 35 41 56

Maximum value 89 53 43 25 67 50 100 100

N, samples 48 25 48 25 48 25 48 25

N, isolates identified 235 125 85 34 131 85 203 132
Table 8 55

Table 8. Summary statistics for Escherchia coli host-source determinations by repetitive extragenic pallindromic polymerase chain 

reaction (rep-PCR). —Continued

[Values in percent of Escherichia coli determined in samples; N, number]

Human Dog Goose Unknown

Base flow Storm event Base flow Storm event Base flow Storm event Base flow Storm event

Mississippi River sites

Mississippi River below Grafton (05587455)

Minimum value 0 0 0 0 0 0 0 0

1st quartile 0 20 0 0 0 18 4 13

Mean 14 27 2 2 20 32 57 40

Median 0 27 0 0 0 40 65 40

3rd quartile 34 38 0 0 27 50 100 45

Maximum value 60 50 20 9 100 50 100 100

N, samples 16 5 16 5 16 5 16 5

N, isolates identified 19 8 4 1 20 9 31 9

Mississippi River above St. Louis (07005500)

Minimum value 0 16 0 0 0 18 0 0

1st quartile 33 28 0 0 6 21 13 17

Mean 40 40 11 10 23 27 27 24

Median 40 42 7 8 19 26 24 24

3rd quartile 50 50 18 19 27 27 38 31

Maximum value 100 64 33 21 100 47 81 43

N, samples 17 8 17 8 17 8 17 8

N, isolates identified 63 52 19 13 30 35 59 32

Mississippi River at St. Louis (07010000)

Minimum value 10 0 0 0 0 12 0 16

1st quartile 29 31 0 5 6 15 8 20

Mean 40 36 14 13 16 25 30 26

Median 41 39 12 15 15 21 26 21

3rd quartile 53 47 26 19 25 36 42 24

Maximum value 71 57 39 25 44 42 80 63

N, samples 18 8 18 8 18 8 18 8

N, isolates identified 86 47 32 15 35 31 66 29

Mississippi River at Oakville (07010220)

Minimum value 0 18 0 0 0 0 0 7

1st quartile 25 38 0 4 5 7 15 16

Mean 43 48 11 8 14 14 32 30

Median 44 48 6 6 13 14 22 32

3rd quartile 64 58 18 11 18 19 50 39

Maximum value 100 80 50 21 45 33 77 55

N, samples 17 8 17 8 17 8 17 8

N, isolates identified 86 58 19 10 35 17 72 36

Mississippi River at Kimmswick (07019370)

Minimum value 0 28 0 0 0 15 0 0

1st quartile 36 32 0 0 10 24 16 11

Mean 44 39 5 6 18 33 34 22

Median 45 40 5 3 17 33 22 28

3rd quartile 59 45 6 10 27 43 43 31

Maximum value 78 56 25 22 38 45 100 35

N, samples 17 8 17 8 17 8 17 8

N, isolates identified 92 43 9 8 39 33 66 28

All Mississippi River sites

Minimum value 0 0 0 0 0 0 0 0

1st quartile 13 29 0 0 0 16 8 16

Mean 37 39 9 8 18 25 36 27

Median 38 40 5 5 14 22 25 26

3rd quartile 53 47 13 17 25 36 63 35

Maximum value 100 80 50 25 100 50 100 100

N, samples 85 37 85 37 85 37 85 37

N, isolates identified 346 208 83 47 159 125 294 134
56 Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007

Table 8. Summary statistics for Escherchia coli host-source determinations by repetitive extragenic pallindromic polymerase chain 

reaction (rep-PCR). —Continued

[Values in percent of Escherichia coli determined in samples; N, number]

Human Dog Goose Unknown

Base flow Storm event Base flow Storm event Base flow Storm event Base flow Storm event

Small basin sites

Creve Coeur Creek(06935890)

Minimum value 0 0 0 5 0 0 0 25

1st quartile 14 21 3 7 13 8 22 36

Mean 25 25 12 11 25 15 39 49

Median 22 24 10 10 20 15 30 43

3rd quartile 38 29 11 14 34 23 53 51

Maximum value 45 50 56 21 67 28 100 95

N, samples 15 6 15 6 15 6 15 6

N, isolates identified 51 29 24 13 48 17 76 57

Coldwater Creek (06936475)

Minimum value 5 0 5 0 10 0 0 29

1st quartile 19 4 9 6 19 3 10 36

Mean 28 20 17 10 27 11 28 59

Median 26 21 15 8 24 10 21 59

3rd quartile 40 28 20 11 36 14 50 79

Maximum value 60 50 50 25 47 29 70 94

N, samples 16 6 16 6 16 6 16 6

N, isolates identified 61 23 32 11 68 12 79 66

Maline Creek (07005000)

Minimum value 0 5 0 0 0 10 0 5

1st quartile 26 23 0 1 10 15 12 20

Mean 37 34 9 5 22 20 32 41

Median 30 35 6 5 14 20 20 38

3rd quartile 42 49 15 9 32 25 50 59

Maximum value 100 55 30 11 67 32 100 85

N, samples 15 6 15 6 15 6 15 6

N, isolates identified 74 40 20 6 58 24 64 49

River des Peres near Unversity City (07010022)

Minimum value 0 8 0 0 0 6 0 6

1st quartile 22 27 0 3 6 10 19 12

Mean 37 37 11 15 13 17 38 32

Median 37 40 9 13 11 18 36 25

3rd quartile 52 50 14 21 22 23 57 40

Maximum value 70 59 41 37 29 26 83 83

N, samples 14 6 14 6 14 6 14 6

N, isolates identified 85 36 26 9 29 13 85 28

River des Peres at St. Louis (07010097)

Minimum value 6 26 0 0 0 0 0 0

1st quartile 24 53 3 0 20 5 14 12

Mean 35 63 13 6 25 8 28 22

Median 31 65 13 10 25 5 25 20

3rd quartile 50 71 20 11 29 6 39 21

Maximum value 62 100 29 12 63 26 61 58

N, samples 15 5 15 5 15 5 15 5

N, isolates identified 73 60 29 13 50 13 60 23
Table 8 57

Table 8. Summary statistics for Escherchia coli host-source determinations by repetitive extragenic pallindromic polymerase chain 

reaction (rep-PCR). —Continued

[Values in percent of Escherichia coli determined in samples; N, number]

Human Dog Goose Unknown

Base flow Storm event Base flow Storm event Base flow Storm event Base flow Storm event

Small basin sites—Continued

Grand Glaize Creek (07019185)

Minimum value 0 5 0 5 0 5 5 25

1st quartile 14 22 5 5 15 6 25 28

Mean 30 35 10 10 21 11 39 43

Median 32 32 11 8 19 13 47 34

3rd quartile 43 54 13 10 25 16 53 50

Maximum value 68 63 33 26 50 16 63 85

N, samples 16 6 16 6 16 6 16 6

N, isolates identified 79 41 22 12 48 13 89 51

All small basin sites

Minimum value 0 0 0 0 0 0 0 0

1st quartile 17 20 5 5 11 6 15 24

Mean 32 34 12 10 22 14 34 43

Median 30 29 11 10 20 15 29 36

3rd quartile 44 51 16 12 29 21 50 60

Maximum value 100 100 56 37 67 32 100 95

N, samples 91 35 91 35 91 35 91 35

N, isolates identified 423 229 153 64 301 92 453 274
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Wilkison and Davis—Occurrence and Sources of Escherichia coli in Metropolitan St. Louis Streams, October 2004 through September 2007—Scientific Investigations Report 2010–5150

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