Prepared in cooperation with the Tri-County Regional Planning Commission

Fecal-Indicator Bacteria Concentrations in the Illinois River 

between Hennepin and Peoria, Illinois: 2007–08

Open File Report 2012–1075

U.S. Department of the Interior

U.S. Geological Survey
Cover photographs:

(Top) Barge on the Illinois River at Hennepin, IL., photograph by 

Jennifer Sharpe.

(Lower left) USGS hydrologist, David Dupre, collecting water 

sample from the Illinois River., photograph by Jennifer Sharpe.

(Lower right) USGS hydrologists, Paul Terrio, Erin Bertke, and 

Elizabeth Murphy, processing samples for fecal coliform., 

photograph by Jennifer Sharpe.
Fecal-Indicator Bacteria Concentrations 

in the Illinois River between Hennepin and 

Peoria, Illinois: 2007–08

By David H. Dupré, Jon E. Hortness, Paul J. Terrio, and Jennifer B. Sharpe

Prepared in cooperation with the Tri-County Regional Planning Commission

Open File Report 2012–1075

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Dupré, D.H., Hortness, J.E., Terrio, P.J., and Sharpe, J.B., 2012, Fecal-indicator bacteria concentrations in the Illinois 

River between Hennepin and Peoria, Illinois: 2007–08: U.S. Geological Survey Open-File Report 2012–1075, 32 p. 
iii

Contents

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

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

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

Description of Study Area ...................................................................................................................2

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

Hydrologic Perspective.................................................................................................................................2

Data Collection...............................................................................................................................................6

Periodic Sampling.................................................................................................................................6

Synoptic Sampling................................................................................................................................6

Data Analysis................................................................................................................................................26

Conclusions...................................................................................................................................................31

Acknowledgments.......................................................................................................................................31

References Cited..........................................................................................................................................32

Figures

1. Map showing general study area, locations of combined-sewer-overflow points, 

and wastewater-treatment plant discharge points between Hennepin and 

Peoria, Illinois................................................................................................................................3

2. Map showing land cover in the general study area between Hennepin and 

Peoria, Illinois................................................................................................................................4

3. Hydrograph showing comparison between water year 2008 and long-term daily 

mean streamflows for the Illinois River at Henry, Illinois (U.S. Geological Survey 

streamflow-gaging station number 05558300).........................................................................5

4. Hydrograph showing comparison between water year 2008 and long-term 

daily mean streamflows for Big Bureau Creek at Princeton, Illinois (U.S. Geological 

Survey streamflow-gaging station number 05556500)............................................................5

5. Map showing locations sampled during October 2007 and June 2008 synoptic 

samplings and frequently during the study period between Princeton and Peoria, 

Illinois..............................................................................................................................................7

6. Graph showing correlation of fecal coliform to Escherichia coli concentrations 

for all stations and all samples.................................................................................................26

7. Graph showing correlation of fecal coliform to Escherichia coli concentrations 

for Illinois River at Hennepin, Illinois.......................................................................................27

8. Graph showing correlation of fecal coliform to Escherichia coli concentrations 

for Illinois River below Peoria Lake at Peoria, Illinois ..........................................................27

9. Graph showing correlation of A, fecal coliform colonies and B, Escherichia coli

colonies to discharge from tributaries to the Illinois River..................................................28

10. Graph showing correlation of A, fecal coliform colonies and B, Escherichia coli

colonies to discharge for the Illinois River at Hennepin, Illinois ........................................29

11. Graph showing correlation of A, fecal coliform colonies and B, Escherichia coli

colonies to discharge for the Illinois River below Peoria Lake at Peoria, Illinois............30
iv

Tables

1. Physical, chemical, and bacterial data for the Illinois River at Hennepin, Illinois 

(U.S. Geological Survey streamflow-gaging station number 05556200), during 

water year 2008 (October 2007–September 2008)...................................................................8

2. Physical, chemical, and bacterial data for the Illinois River below Peoria Lake at 

Peoria, Illinois (U.S. Geological Survey streamflow-gaging station number 

05562200), during water year 2008 (October 2007–September 2008).................................10

3. Physical, chemical, and bacterial data for Big Bureau Creek near Princeton, Illinois 

(U.S. Geological Survey streamflow-gaging station number 05556500), during 

water year 2008 (October 2007–September 2008).................................................................13

4. Physical, chemical, and bacterial data for Farm Creek at Farmdale, Illinois (U.S. 

Geological Survey streamflow-gaging station number 05560500), during water 

year 2008 (October 2007–September 2008) ............................................................................14

5. Physical, chemical, and bacterial data for Senachwine Creek at Chillicothe, 

Illinois (U.S. Geological Survey streamflow-gaging station number 05559700), 

during water year 2008 (October 2007–September 2008) ....................................................15

6. Physical, chemical, and bacterial data for Partridge Creek near Metamora, Illinois 

(U.S. Geological Survey (USGS) streamflow-gaging station number 05559800), 

and Partridge Creek Tributary near Metamora, Illinois (USGS streamflowgaging station number 05559820), from May to August 2008 ..............................................16

7. Results of synoptic sampling on the Illinois River and selected tributaries between 

Hennepin and Peoria, Illinois, October 10, 2007 ....................................................................18

8. Results of synoptic sampling on the Illinois River and selected tributaries between 

Hennepin and Peoria, Illinois, June 12, 2008..........................................................................24
v

Conversion Factors, Vertical Datum, and Abbreviations

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

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

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

°F=(1.8×°C)+32

Vertical coordinate information is referenced to North American Vertical Datum of 1988 (NAVD 88).

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

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

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).

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

(μg/L).

Bacteria concentrations are given in colony-forming units per 100 milliliters (CFU/100 mL).

Water year is the 12-month period October 1 for any given year through September 30 of the following year. The 

water year is designated by the calendar year in which it ends and which includes 9 of the 12 months. 

Abbreviations

CSO combined sewer overflow

E. coli Escherichia coli

FC fecal coliform

FIB fecal-indicator bacteria

IEPA Illinois Environmental Protection Agency 

TMDL Total Maximum Daily Load

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

Fecal-Indicator Bacteria Concentrations in the Illinois 

River between Hennepin and Peoria, Illinois: 2007–08

By David H. Dupré, Jon E. Hortness, Paul J. Terrio, and Jennifer B. Sharpe

Abstract

The Illinois Environmental Protection Agency has 

designated portions of the Illinois River in Peoria, Woodford, and Tazewell Counties, Illinois, as impaired owing to 

the presence of fecal coliform bacteria. The U.S. Geological 

Survey, in cooperation with the Tri-County Regional Planning Commission, examined the water quality in the Illinois 

River and major tributaries within a 47-mile reach between 

Peoria and Hennepin, Ill., during water year 2008 (October 

2007–September 2008). Investigations included synoptic 

(snapshot) sampling at multiple locations in a 1-day period: 

once in October 2007 during lower streamflow conditions, and 

again in June 2008 during higher streamflow conditions. Five 

locations in the study area were monitored for the entire year 

at monthly or more frequent intervals. Two indicator bacteria 

were analyzed in each water sample: fecal coliform and Escherichia coli (E. coli). Streamflow information from previously 

established monitoring locations in the study area was used in 

the analysis. Correlation analyses were used to characterize 

the relation between the two fecal-indicator bacteria and the 

relation of either indicator to streamflow. Concentrations of 

the two measured fecal-indicator bacteria correlated well for 

all samples analyzed (r = 0.94, p <0.001), indicating a strong 

linear correlation. Presence of one fecal-indicator bacteria generally indicates the presence of another at a similar magnitude 

and may support substitution of generalized data gaps for 

other analyses. Hydrologic conditions during the study period 

can be characterized as wetter than normal, with the mean 

annual flow in the Illinois River about 37-percent above the 

long-term average. However, for the Illinois River below Peoria Lake at Peoria, a statistically significant negative correlation coefficient indicates a weak inverse relation between values of streamflow and fecal-indicator bacteria (fecal coliform: 

rho = −0.44, p = 0.0129; E. coli: rho = −0.43, p = 0.0157). 

The correlation between fecal indicators and streamflow in 

tributaries or in the Illinois River at Hennepin was found to be 

statistically significant, yet moderate in strength with coefficient values ranging from r = 0.4 to 0.6. Indirect observations 

from the June 2008 higher flow synoptic event may indicate 

continued effects from combined storm and sanitary sewers in 

the vicinity of the Illinois River near Peoria, Ill., contributing 

to observed single-sample exceedance of the State criterion for 

fecal coliform.

Introduction

Portions of the Illinois River in Peoria, Woodford, and 

Tazewell Counties, Illinois, are designated as impaired by the 

Illinois Environmental Protection Agency (IEPA) owing to 

the presence of fecal coliform (FC) bacteria (Illinois Environmental Protection Agency, 2008). FC bacteria are used as 

an indicator of possible pathogens. Elevated concentrations 

of FC bacteria could cause a violation of the State waterquality standard for general-use waters primarily because of 

potential ingestion or physical exposure. Epidemiological 

research has demonstrated a relation between illness rates and 

the proximity to known FC bacteria point sources (Cabelli 

and others, 1982; Wade and others, 2006). Combined sewer 

overflows (CSOs) from the City of Peoria occur periodically 

as a result of moderate to heavy rainfall in the area (City of 

Peoria, 2010). CSOs result in the release of storm water, along 

with raw sewage, to the Illinois River, which causes elevated 

bacteria concentrations in the vicinity of the outfalls. However, FC bacteria data collected in the Illinois River upstream 

of the City of Peoria CSO discharge points indicate the Illinois 

River often has background concentrations of FC bacteria that 

exceed the water-quality standard for general-use waters. Both 

point sources and diffuse sources of FC bacteria may contribute to the exceedances of the water-quality standard upstream 

of Peoria (Sercu and others, 2009).

The Tri-County Regional Planning Commission proposed 

to conduct a study to better identify the likely source areas of 

the bacterial contamination in the river upstream from Peoria. 

The overall study objectives were to evaluate the impacts that 

point sources and diffuse sources have on the concentrations 

of FC bacteria in the Illinois River between Hennepin, Ill., and 
2 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

the outlet of Peoria Lake at Peoria, Ill. As part of this study, the 

U.S. Geological Survey (USGS) evaluated bacteria concentrations in streams tributary to the Illinois River between Hennepin and Peoria, Ill., and investigated the possibility that some 

of these streams may be sources of elevated bacteria concentrations in the Illinois River.

After this study began, the U.S. Environmental Protection 

Agency (USEPA) and IEPA initiated the development of a total 

maximum daily load (TMDL) for FC bacteria in this reach of 

the Illinois River. The bacteria data collected by the USGS will 

be a significant resource in the development of these TMDLs. 

The development of a TMDL for FC bacteria assumes the bacteria, and any associated pathogens, result from direct humancontrolled activities (either from point sources or diffuse 

sources) and that successful compliance with a water-quality 

standard can be achieved through managing or removing the 

sources of bacteria. Several limitations to this assumption for 

FC bacteria should be noted: 

• they are not specific to human sources,

• they can persist in a more-varied manner than the associated pathogens they are meant to indicate (Anderson 

and others, 2005; Wade and others, 2006), and 

• they can become non-culturable (Leadbetter, 1997; 

Statham and McMeekin, 1994). 

Generally, Escherichia coli (E. coli) are thought to be a more 

accurate indicator of potential human or animal-influenced 

pathogenic organisms than FC bacteria because they are a subset of the FC bacteria and reside in the gut of warm-blooded 

creatures (U.S. Food and Drug Administration, 1998). Other 

FCs are not necessarily unique to warm-blooded animals.

Purpose and Scope

This report describes the results of sampling for FC and 

E. coli bacteria (collectively referred to as fecal-indicator 

bacteria (FIB)) along the main stem and various tributaries 

of the Illinois River within the study area during water year 

2008. Simple linear regressions of the two FIB data types were 

performed against each other and against streamflow. The 

hydrologic conditions of the study period are compared against 

long-term records to describe the observed FIB concentrations 

in relation to historical streamflows.

Description of Study Area

The general area for this study includes the main stem 

of the Illinois River from Hennepin downstream to Peoria, in 

addition to several small basins that are tributary to this reach 

of the Illinois River (fig. 1). The main stem reach within the 

study area extends approximately 47 river miles and receives 

inflows from about 1,500 mi2 of contributing drainage area. 

Major tributaries to the study reach include Big Bureau Creek 

(491 mi2

), Senachwine Creek (87 mi2), and Farm Creek (61 

mi2). The study area also encompasses several in-channel and 

off-channel lakes including Senachwine Lake, Upper Peoria 

Lake, and Peoria Lake.

The drainage areas along the study reach generally are 

rural with the exception of the area in and around Peoria, 

which is mostly urban. Land use varies throughout the region 

with row-crop farming being the most common, followed by 

deciduous forest areas and pasture lands (fig. 2). 

Combined sanitary and storm sewers are present in Peoria 

and CSOs are common during higher intensity rainfall events. 

CSO occurrences average about 28 times per year, generally 

when total rainfall amounts exceed about 0.15 in. for any 

storm event. There are 20 potential overflow points located in 

Peoria (City of Peoria, 2010). Several smaller towns located 

along the Illinois River and within the various contributing 

drainage basins discharge effluent from wastewater-treatment 

plants to the main stem or tributaries (fig. 1).

Previous Investigations

Several investigations regarding the presence of bacteria 

in the Illinois River were previously conducted. Greenfield 

(1924) studied bacteria concentrations in the approximately 

80-mi reach from LaSalle to Kingston Mines. Hoskins and 

others (1927) studied the entire length of the Illinois River 

from its origin near Joliet, Ill., downstream to the confluence 

with the Mississippi River near Grafton, Ill. (approximately 

275 mi).

Lin and Evans (1980) analyzed water samples collected 

from the Illinois River at Peoria on a weekly basis during June 

1971–May 1976. They found that bacteria concentrations 

ranged widely throughout the year, with the highest concentrations generally occurring during the winter and summer 

months. Building upon the work by Lin and Evans (1980), Lin 

and Beuscher (1994) analyzed weekly water samples during 

June 1976–May 1986. They found that throughout the 15-year 

period (1971–86) only about 17 percent of the samples 

were in compliance with the existing water-quality standard 

(geometric mean of 200 colony-forming units per 100 mL 

CFU/100 mL), from a minimum of five samples collected in a 

30-day period; or 400 CFU/100 mL in a single sample).

The IEPA has in the past and continues to collect and analyze water samples at various locations within the study area 

as part of their Ambient Water Quality Monitoring Network. 

The samples are collected approximately every 6 weeks and 

are analyzed for over 55 parameters including FC bacteria.

Hydrologic Perspective

The period of data collection for this study, in general, 

coincided with a period of relatively high precipitation across 

much of central and northern Illinois, including most of the 
Hydrologic Perspective 3

Chillicothe

TAZEWELL

WOODFORD

PEORIA

MARSHALL

PUTNAM

BUREAU

89°50' 89°40' 89°30' 89°20' 89°10'

41°10'

41°20'

41°

40°50'

40°40'

0 5 10 MILES

0 5 10 KILOMETERS

Hennepin

xv

rp

Creek

Creek

Farm

RIVER

Princeton

Peoria

71

150

29

40

6

150

91

89

26

29

17

89

26

17

98

116

8

90

18

29

91

116

24

Bureau Creek

Big

EXPLANATION

Municipality

Interstate

U.S. Highway

State Highway

U.S. Geological Survey (USGS) real-time

streamflow-gaging station

USGS sampling site

Wastewater-treatment plant

Combined-sewer-overflow location

Big Bureau

Creek near

Princeton, Ill.

Illinois River at Hennepin, Ill.

Farm Creek at Farmdale, Ill.

Senachwine Creek

at Chillicothe, Ill.

Upper

Peoria

Lake

Peoria

Lake

Senachwine

Lake

!

Illinois River at Henry, Ill.

74

74

474

Illinois River below Peoria Lake at Peoria, Ill.

155

74

180

Figure 1. General study area, locations of combined-sewer-overflow points, and wastewater-treatment plant discharge points 

between Hennepin and Peoria, Illinois.
4 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

TAZEWELL

WOODFORD

PEORIA

MARSHALL

PUTNAM

BUREAU

89°50' 89°40' 89°30' 89°20' 89°10'

41°10'

41°20'

41°

40°50'

40°40'

0 5 10 MILES

0 5 10 KILOMETERS

EXPLANATION

Open water

Developed, open space

Developed, low intensity

Developed, medium intensity

Developed, high intensity

Barren land (rock/sand/clay)

Deciduous forest

Evergreen forest

Mixed forest

Shrub/scrub

Grassland/herbaceous

Pasture/hay

Cultivated crops

Woody wetlands

Emergent herbaceous wetlands

U.S. Geological Survey (USGS) real-time

streamflow-gaging station

USGS sampling site

National Land Cover Database 2006

Base from Multi-Resolution Land Characteristics Consortium

National Land Cover Database 2006

Big Bureau

Creek near

Princeton, Ill.

Illinois River at Hennepin, Ill.

Farm Creek at Farmdale, Ill.

Senachwine Creek

at Chillicothe, Ill.

Illinois River at Henry, Ill.

Illinois River below Peoria Lake at Peoria, Ill.

Figure 2. Land cover in the general study area between Hennepin and Peoria, Illinois.
Hydrologic Perspective 5

Illinois River Basin. Average precipitation levels across the 

State for October–December 2007 were near normal to just 

slightly below normal (30-year average; 1971–2000). However, January–June 2008 was the wettest first 6 months of the 

year on record (since 1895), with a statewide average of 27.7 

in., which was 8.3 in. above normal. The statewide average 

precipitation for the entire year (2008) was 50.7 in.—11.4 in. 

above normal—resulting in the second wettest year on record 

(Illinois State Water Survey, 2010). Specific locations within 

the Illinois River Basin showed similar precipitation results: 

Chicago O’Hare International Airport: October–December 

2007, 1.7 in. below normal; 2008, 14.6 in. above normal

Ottawa, Ill.: October–December 2007, 2.4 in. below normal; 

2008, 6.6 in. above normal

Peoria Regional Airport: October–December 2007, 0.8 in. 

below normal; 2008, 10.5 in. above normal (National Oceanic 

and Atmospheric Administration, 2007, 2008).

As a result of the above-normal precipitation, streamflows in the Illinois River and in the tributaries within the 

study area were well above the long-term average. The annual 

mean streamflow for the Illinois River at Henry, Ill., (USGS 

streamflow-gaging station number 05558300, which is located 

north-central in the study area), was 20,600 ft3/s for water 

year 2008. This was about 37-percent higher than the longterm (1982–2008) annual mean streamflow of 15,000 ft3

/s. 

Similarly, the annual mean streamflow for Big Bureau Creek 

at Princeton, Ill., (USGS streamflow-gaging station number 

05556500, a tributary to the Illinois River near the upstream 

end of the study area), was 282 ft3/s for water year 2008. This 

was about 97-percent higher than the long-term (1936–2008) 

annual mean streamflow of 143 ft3/s. Hydrographs showing 

comparisons between water year 2008 and long-term daily 

mean streamflows for the Illinois River at Henry and Big 

Bureau Creek at Princeton are presented in figures 3 and 4, 

respectively.

Discharge, in cubic feet per second

1,000

10,000

100,000

1,000,000

2007

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

2008

EXPLANATION

Water year 2008 daily mean discharge

Long-term daily mean discharge

Figure 3. Comparison between water year 

2008 and long-term daily mean streamflows 

for the Illinois River at Henry, Illinois (U.S. 

Geological Survey streamflow-gaging station 

number 05558300).

Discharge, in cubic feet per second

1

10

100

1,000

10,000

2007

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

2008

EXPLANATION

Water year 2008 daily mean discharges

Long-term daily mean discharges

Figure 4. Comparison between water year 

2008 and long-term daily mean streamflows 

for Big Bureau Creek at Princeton, Illinois 

(U.S. Geological Survey streamflow-gaging 

station number 05556500).
6 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

Data Collection

Samples were collected from the main stem of the Illinois River at Hennepin and Peoria, Ill., and near the outlets 

of three major tributaries to the Illinois River (Big Bureau 

Creek, Senachwine Creek, and Farm Creek) during the same 

time period. In addition, four sets of samples were collected 

at two locations in the upper portion of the Partridge Creek 

Watershed.

Two intensive synoptic sampling efforts also were completed under different environmental conditions. During these 

efforts, samples were collected at multiple locations along the 

main stem of the Illinois River and in several tributaries within 

the study area (fig. 5).

Two types of FIB were assessed: FC and Escherichia coli

(E. coli). All samples were collected and processed following USGS standard protocols and methods documented in 

the USGS National Field Manual (U.S. Geological Survey, 

variously dated); specific details on FIB sampling are found in 

chapter A7 (Myers and others, 2007).

Periodic Sampling

Samples were collected approximately weekly at the 

Illinois River at Hennepin, Ill. (USGS streamflow-gaging 

station number 05556200) (table 1), and at the Illinois River 

below Peoria Lake at Peoria, Ill. (USGS streamflow-gaging 

station number 05562200) (table 2), for a total of 31 times 

during water year 2008. All of the samples were analyzed for 

both FC and E. coli. In addition, the following water-quality 

parameters were measured on-site during the sample collection: air temperature, water temperature, barometric pressure, 

dissolved oxygen, pH, and specific conductance. Streamflow 

is estimated at sites without continuous monitoring.

Samples were collected on a monthly basis near the 

outlets of three major tributaries to the Illinois River within 

the study area. A total of 11 samples were collected at Big 

Bureau Creek near Princeton, Ill. (USGS streamflow-gaging 

station number 05556500) (table 3); a total of 10 samples were 

collected at Farm Creek at Farmdale, Ill. (USGS streamflowgaging station number 05560500) (table 4); and a total of 9 

samples were collected at Senachwine Creek at Chillicothe, 

Ill. (USGS streamflow-gaging station number 05559700) 

(table 5).

Finally, four sets of samples (table 6) were collected 

at two locations in the upper portion of the Partridge Creek 

Watershed in an attempt to identify potential sources of 

bacteria within a specified stream reach. Again, all samples 

were analyzed for both FC and E. coli, and observations of air 

temperature, water temperature, barometric pressure, dissolved 

oxygen, pH, and specific conductance were measured on-site 

during sampling.
Data Collection 7

Bartonville

Chillicothe

Hopewell

Bay View Gardens

Spring Bay

Rome

Washburn

Metamora

TAZEWELL

WOODFORD

PEORIA

MARSHALL

PUTNAM

BUREAU

89°50' 89°40' 89°30' 89°20' 89°10'

41°10'

41°20'

41°

40°50'

40°40'

0 5 10 MILES

0 5 10 KILOMETERS

Sparland Lacon

Henry

Hennepin

xv

rp

Sandy Creek

Crow

Crow

Creek

Creek

Creek

Creek

Creek

Creek

Creek

Creek

Creek

Creek

Senachwine

Dry

Richland

Partridge

Farm

Blalock

Tenmile

RIVER

Princeton

De Pue Spring Valley

East

Peoria

Peoria

Marquette Heights

Creve

Coeur

71

150

29

40

6

150

91

89

26

29

17

89

26

17

98

116

8

90

18

29

91

116

24 West

Peoria

EXPLANATION

Municipality

Interstate

U.S. Highway

State Highway

October 2007 synoptic sampling site

June 2008 synoptic sampling site

October 2007 and June 2008 synoptic sampling site

Site sampled frequently during study period

74

74

155

474

74

180

Big Bureau Creek

between Princeton and Peoria, Illinois.

Figure 5. Locations sampled during October 2007 and June 2008 synoptic samplings and frequently during the study period 
Table 1. Physical, chemical, and bacterial data for the Illinois River at Hennepin, Illinois (U.S. Geological Survey streamflow-gaging station number 0year 2008 (October 2007–September 2008).—Continued [hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pe°C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, central standard time] Sample notes Date Time (24-hour clock, hhmm) Baro- metric pressure, (mm Hg) Tem- pera- ture, air, (°C) Dis- charge, (ft3/s) Dissolved oxygen, water, unfiltered, (mg/L) pH, water, unfiltered, field, (standard units) Specific con- ductance, water, unfiltered, (μS/cm at 25 °C) Tem- perature, water, (°C) Gage height, (ft) Number of sampling points, (count) 

(00025) (00020) (00060) (00300) (00400) (00095) (00010) (00065) (00063) 

Median values from synoptic cross-section Oct 10 2007 1442 CDT 748 E12.0 E6350 9.3 8.5 850 21.8 — 4 Cross-section part 1 of 2; mid-channel Oct 18 2007 1410 CST 725 — E8560 9.4 8.2 860 18.5 — 1 Cross-section part 2 of 2; left-channel Oct 18 2007 1445 CST 725 — E8560 9.4 8.3 872 18.5 — 1 Mid-channel grab Oct 25 2007 1100 CST 754 7.2 E9340 9.4 8.2 863 14.9 — 1 Mid-channel grab Nov 1 2007 1145 CST 757 10.0 E8790 10.9 8.3 831 12.9 — 1 Mid-channel grab Nov 7 2007 0930 CST 756 -3.8 E6820 13.2 8.8 816 9.6 — 1 Cross-section composite Nov 15 2007 0855 CST 750 1.7 E6900 12.2 8.2 856 9.4 — 3 Cross-section composite Nov 21 2007 0850 CST 745 — E9460 13.2 8.8 888 9.5 — 3 Cross-section composite Nov 28 2007 1135 CST 746 4.4 E10300 12.7 8.4 833 5.0 — 3 Cross-section composite Dec 5 2007 1045 CST 747 -1.1 E12100 14.3 8.5 792 1.7 — 3 Cross-section composite Dec 12 2007 1025 CST 756 -1.1 E17000 13.5 8.3 984 2.2 — 3 Cross-section composite Dec 19 2007 1010 CST 750 -5.0 E23700 13.9 8.0 976 1.6 — 3 Cross-section composite Jan 3 2008 0955 CST 763 -15.0 E15400 14.7 8.3 1010 0.0 — 3 Cross-section composite Jan 9 2008 1105 CST 751 2.0 E51800 10.5 7.9 882 7.9 — 3 Cross-section composite Jan 16 2008 0945 CST 748 0.2 E46200 12.8 7.9 564 2.4 — 3 Mid-channel grab, iced conditions Jan 24 2008 0945 CST 758 -20.0 E16400 13.2 8.0 790 0.1 — 1 Cross-section composite Feb 6 2008 1000 CST 729 0.0 E24300 13.3 8.0 1090 1.6 — 3 Cross-section composite Mar 12 2008 1235 CST — 3.9 E21900 12.8 8.1 901 3.3 — 3 Cross-section composite Mar 26 2008 1015 CST 752 5.2 E22300 12.0 8.1 819 6.8 — 3 Cross-section composite Apr 2 2008 0940 CST 759 5.7 E27500 12.0 8.1 977 8.2 — 3 Cross-section composite Apr 9 2008 1050 CST 752 5.7 E22700 11.1 8.1 874 11.0 — 3 
Table 1. Physical, chemical, and bacterial data for the Illinois River at Hennepin, Illinois (U.S. Geological Survey streamflow-gaging station number 0year 2008 (October 2007–September 2008).—Continued[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pe°C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, central standard time]

Sample 

notes

Date

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure, 

(mm Hg)

Temperature, 

air, (°C)

Discharge, 

(ft3/s)

Dissolved 

oxygen, 

water, 

unfiltered, 

(mg/L)

pH,

 water, 

unfiltered, 

field, 

(standard 

units)

Specific conductance, 

water, 

unfiltered, 

(μS/cm 

at 25 °C)

Temperature, 

water, 

(°C)

Gage 

height, 

(ft)

Number 

of 

sampling 

points, 

(count)

(00025) (00020) (00060) (00300) (00400) (00095) (00010) (00065) (00063) 

Cross-section composite Apr 16 2008 0955 CST 745 10.9 E28600 11.3 8.1 838 10.0 — 3 Cross-section composite Apr 23 2008 0940 CST 754 17.1 E20400 10.2 8.2 827 17.1 — 3 Cross-section composite May 1 2008 0945 CST 740 14.5 E15000 11.6 8.2 873 13.6 — 3 Cross-section composite May 7 2008 0940 CST 739 15.8 E15100 10.6 8.2 933 17.4 — 3 Cross-section composite May 21 2008 0930 CST 743 11.0 E14000 10.0 8.1 820 16.6 — 3 Cross-section composite May 28 2008 1015 CST 758 13.0 E13200 11.6 8.5 874 18.1 — 3 Cross-section composite June 12 2008 0805 CDT 747 24.0 E28200 — 7.9 — 23.9 — 3 Cross-section composite July 2 2008 0915 CST 745 22.4 E12700 9.6 8.3 765 24.9 — 3 Cross-section composite July 16 2008 1000 CST 753 22.7 E17200 9.0 8.3 786 — — 3 Cross-section composite Aug 20 2008 1110 CST 756 25.8 E6460 9.2 8.4 726 27.6 — 3 Cross-section composite Sept 22 2008 1235 CST 761 27.3 E45100 6.2 8.0 503 20.8 — 3 
Table 2. Physical, chemical, and bacterial data for the Illinois River below Peoria Lake at Peoria, Illinois (U.S. Geological Survey streamflow-gaging during water year 2008 (October 2007–September 2008).—Continued [hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pemm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, centra

Sample notes Date Time (24-hour clock, hhmm) Barometric pressure (mm Hg) Tem- pera- ture, air (°C) Discharge (ft3/s) Dissolved oxygen, water, unfiltered (mg/L) pH, water, unfiltered, field (standard units) Specific conduc- tance, water, unfiltered (μS/cm at 25 °C) Tem perature, water (°C) Gage height (ft) Number of sampling points (count) E

(

(00025) (00020) (00060) (00300) (00400) (00095) (00010) (00065) (00063) 

Synoptic sample, mid-channel Oct 10 2007 1210 CDT — E10.8 E6760 — — — — — 1 

Oct 18 2007 1220 CST 725 — E6000 8.2 8.1 838 18.2 — 1 Oct 25 2007 0915 CST 752 4.4 E10200 9.8 8.3 868 12.3 — 1 Nov 1 2007 0945 CST 757 7.2 E8970 9.9 8.0 865 12.2 — 1 Nov 7 2007 1110 CST 756 2.8 E7370 11.3 8.1 805 7.9 — 1 Nov 15 2007 1030 CST 751 4.4 E7070 12.0 8.4 805 9.4 — 1 Nov 21 2007 1020 CST 744 — E7550 12.5 8.9 833 10.0 — 1 ENov 28 2007 0845 CST 748 4.4 E12000 13.1 8.5 871 3.7 — 1 Dec 5 2007 0800 CST 743 0.0 E15500 13.6 8.4 818 1.1 — 1 Dec 12 2007 0800 CST 754 -1.1 E13600 14.0 8.3 826 0.8 — 1 Dec 19 2007 0755 CST 749 -4.4 E26200 14.1 8.0 855 1.2 — 1 Jan 3 2008 0815 CST 764 -10.0 E22100 13.9 7.5 888 0.0 — 1 Jan 9 

2008

0800 

CST

750 1.3 E28900 12.7 8.1 982 4.7 — 1 
Table 2. Physical, chemical, and bacterial data for the Illinois River below Peoria Lake at Peoria, Illinois (U.S. Geological Survey streamflow-gaging during water year 2008 (October 2007–September 2008).—Continued[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pemm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, centra

Sample 

notes

Date

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure

(mm Hg)

Temperature, 

air

(°C)

Discharge 

(ft3/s)

Dissolved 

oxygen, 

water, 

unfiltered 

(mg/L)

pH, water, 

unfiltered, 

field

(standard 

units)

Specific 

conductance, water, 

unfiltered

(μS/cm at 

25 °C)

Tem

perature,

 water

(°C)

Gage 

height

(ft)

Number of 

sampling 

points

(count)

E

(

(00025) (00020) (00060) (00300) (00400) (00095) (00010) (00065) (00063) 

Jan 16 

2008

0750 

CST

748 -2.0 E59400 10.9 7.9 591 2.9 — 1 

Jan 24 

2008

0820 

CST

757 -20.5 E33800 11.7 7.8 519 0.0 — 1 

Runoff/snowmelt 

event

Feb 6 

2008

0715 

CST

734 0.0 E27900 11.8 8.0 734 0.1 — 1 

Mar 12 

2008

0805 

CST

744 0.0 E35100 12.3 8.4 843 2.7 — 1 

Mar 26 

2008

0740 

CST

751 2.0 E30600 12.9 8.3 813 6.5 — 1 

Apr 2 

2008

0740 

CST

758 2.0 E33400 11.8 8.4 938 7.6 — 1 

Apr 9 

2008

0740 

CST

751 4.7 E32100 11.0 8.3 903 10.3 — 1 

Apr 16 

2008

0740 

CST

747 8.5 E35300 11.3 8.2 867 9.7 — 1 

Apr 23 

2008

0735 

CST

753 14.8 E30600 10.5 8.2 809 16.7 — 1 

May 1 

2008

0735 

CST

740 14.5 E26300 10.8 8.2 828 14.7 — 1 

May 7 

2008

0740 

CST

740 16.0 E21400 11.9 8.6 865 17.5 — 1 

May 21 

2008

0730 

CST

741 10.4 E24400 11.6 8.6 781 16.3 — 1 

May 28 

2008

0725 

CST

757 9.4 E19800 9.3 8.9 812 16.1 — 1 
Table 2. Physical, chemical, and bacterial data for the Illinois River below Peoria Lake at Peoria, Illinois (U.S. Geological Survey streamflow-gaging during water year 2008 (October 2007–September 2008).—Continued [hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pemm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, centra

Sample notes Date Time (24-hour clock, hhmm) Barometric pressure (mm Hg) Tem- pera- ture, air (°C) Discharge (ft3/s) Dissolved oxygen, water, unfiltered (mg/L) pH, water, unfiltered, field (standard units) Specific conduc- tance, water, unfiltered (μS/cm at 25 °C) Tem perature, water (°C) Gage height (ft) Number of sampling points (count) E

(

(00025) (00020) (00060) (00300) (00400) (00095) (00010) (00065) (00063) 

Synoptic sample, mid-channel June 12 2008 1115 CDT 752 E29.2 E20400 7.0 8.0 620 24.1 — 3 

July 2 2008 0750 CST 746 21.0 E15900 7.8 8.2 728 25.1 — 1 July 16 2008 0720 CST 753 23.0 E18600 7.2 8.4 658 26.7 — 1 Aug 20 2008 0830 CST 752 20.8 E7240 7.3 8.4 703 26.2 — 1 Sept 22 2008 0945 CST 758 22.8 E67100 4.4 8.1 380 20.5 — 1 
Table 3. Physical, chemical, and bacterial data for Big Bureau Creek near Princeton, Illinois (U.S. Geological Survey streamflow-gaging station numwater year 2008 (October 2007–September 2008).[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pemm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, centra

Sample

 notes

Date

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure

(mm Hg)

Temperature, 

air

(°C)

Discharge 

instantaneous

(ft3/s)

Dissolved 

oxygen, 

water, 

unfiltered 

(mg/L)

pH, water, 

unfiltered, 

field

(standard 

units)

Specific 

conductance, water, 

unfiltered

(μS/cm at 

25 °C)

Temper

ature, 

water

(°C)

Gage 

height

(ft)

Number 

of sampling 

points

(count)

(00025) (00020) (00061) (00300) (00400) (00095) (00010) (00065) (00063) 

Sampled 

near mouth, no sample at this location

Oct 10 

2007

— — — — — — — — — — 

Nov 1 

2007

1250 

CST

753 12.8 26 13.1 8.4 781 9.5 1.55 1 

Dec 5 

2007

1200 

CST

743 -1.1 46 14.4 8.4 770 0.2 1.75 1 

Jan 9 

2008

1020 

CST

747 1.0 885 11.6 8.0 682 5.1 4.71 1 

Runoff/snowmelt 

event

Feb 6 

2008

0920 

CST

730 0.0 273 12.9 8.1 667 0.2 3.06 1 

Mar 12 

2008

1030 

CST

742 3.4 939 11.8 8.2 350 1.9 4.83 1 

Apr 9 

2008

1000 

CST

748 3.8 258 11.4 8.2 667 7.3 2.98 1 

May 21 

2008

1005 

CST

741 10.9 187 11.3 8.1 683 13.5 2.66 1 

Synoptic sample June 12 

2008

0835 

CDT

744 19.0 282 8.8 8.2 696 18.5 3.07 1 

July 16 

2008

0915 

CST

749 23.1 405 8.4 8.1 663 21.2 3.49 1 

Aug 20 

2008

1035 

CST

751 21.1 25 8.9 8.1 647 23.5 1.56 1 

Sept 22 

2008

1155 

CST

755 25.3 291 9.0 8.1 672 18.6 3.10 1 
Table 4. Physical, chemical, and bacterial data for Farm Creek at Farmdale, Illinois (U.S. Geological Survey streamflow-gaging station number 05560(October 2007–September 2008) [hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pemm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, centra

Sample notes Date Time (24-hour clock, hhmm) Baro- metric pressure (mm Hg) Tempera- ture, air (°C) Discharge, instanta- neous (ft3/s) Discharge, (ft3/s) Dissolved oxygen, water, unfiltered (mg/L) pH, water, unfiltered, field (standard units) Specific conductance, water, unfiltered (μS/cm at 25 °C) Tempera- ture, water (°C) Gage height (ft) Number of sampling points (count) 

(00025) (00020) (00061) (00060) (00300) (00400) (00095) (00010) (00065) (00063) 

Sampled near mouth, no sample at this location Oct 10 2007 — — — — — — — — — — — 

Nov 1 2007 1430 CST 753 12.8 2.7 — 12.9 8.4 1480 10.7 1.90 1 Dec 5 2007 1205 CST 746 0.0 3.7 — 15.8 8.7 1440 2.7 1.93 1 Jan 9 2008 1230 CST 748 4.1 402 — 11.8 7.9 535 6.1 4.00 1 

Runoff/ snowmelt event Feb 6 2008 1145 CST 729 0.0 679 — 13.6 8.0 336 0.5 4.61 1 

Mar 12 2008 1235 CST 744 7.4 22 — 12.0 8.2 913 5.6 2.24 1 Apr 9 2008 1205 CST 750 7.5 38 — 12.7 8.2 722 9.5 2.44 1 May 21 2008 1200 CST 741 13.9 — 8.8 13.3 8.4 890 15.2 2.01 1 

Synoptic sample June 12 2008 0640 CDT 745 18.0 19 — 8.7 8.0 895 18.5 2.19 1 

July 16 2008 1140 CDT 752 24.6 22 — 8.5 8.2 977 23.3 2.17 1 Aug 20 

2008

1320 

CST

750 24.9 2.8 — 11.1 8.3 1940 23.5 1.74 1 

Sept 22 

2008

0820 

CST

754 18.6 33 — 9.3 8.7 815 16.7 2.38 1 
Table 5. Physical, chemical, and bacterial data for Senachwine Creek at Chillicothe, Illinois (U.S. Geological Survey streamflow-gaging station numbwater year 2008 (October 2007–September 2008).[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams pemm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; E, estimated; k, counts outside acceptable range; CDT, central daylight time; CST, centra

Sample 

notes

Date

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure

(mm Hg)

Tempera

ture, 

air

(°C)

Discharge, 

instantaneous

(ft3/s)

Discharge 

(ft3/s) 

Dissolved 

oxygen, 

water, 

unfiltered 

(mg/L)

pH, water, 

unfiltered, 

field

(standard 

units)

Specific 

conductance, 

water, 

unfiltered

(μS/cm at 

25 °C)

Temperature, 

water

(°C)

Gage 

height

(ft)

Number of 

sampling 

points

(count)

(00025) (00020) (00061) (00060) (00300) (00400) (00095) (00010) (00065) (00063) 

No sample, 

dry

Oct 10 

2007

— — — — — — — — — — — 

No sample, 

dry

Nov 1 

2007

— — — — — — — — — — — 

Dec 12 

2007

0925 

CST

754 -1.1 — E1.7 13.1 8.2 680 0.8 5.81 1 

Jan 9 

2008

0920 

CST

750 0.0 182 — 12.4 8.2 603 4.2 7.95 1 

Runoff/

snowmelt event

Feb 6 

2008

0820 

CST

732 0.0 — E190 13.4 8.1 287 0.0 9.42 1 

Mar 12 

2008

0935 

CST

745 3.8 45 — 12.7 8.3 691 2.4 6.74 1 

Apr 9 

2008

0910 

CST

750 3.7 90 — 11.1 8.3 619 7.3 7.32 1 

May 21 

2008

1110 

CST

743 12.2 44 — 11.6 8.2 673 15.4 6.73 1 

Synoptic 

sample

Jun 12 

2008

1010 

CDT

748 22.5 40 — 9.4 8.2 706 21.3 6.68 1 

Jul 16 

2008

0820 

CST

752 22.3 16 — 7.9 8.1 680 23.4 6.42 1 

No sample, 

dry

Aug 20 

2008

— — — — — — — — — — 

Sep 22 

2008

1105 

CST

758 25.0 26 — 9.3 8.0 732 18.8 6.65 1 
Table 6. Physical, chemical, and bacterial data for Partridge Creek near Metamora, Illinois (U.S. Geological Survey (USGS) streamflow-gaging statioand Partridge Creek Tributary near Metamora, Illinois (USGS streamflow-gaging station number 05559820), from May to August 2008. [hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft3/s, cubic foot per second; micron, micrometer; mg/L, milligrams per liter; mCelsius; μS/cm, microsiemens per centimeter; —, no data; <, less than; CDT, central daylight time; CST, central standard time] Sample notes Date Time (24-hour clock, hhmm) Barometric pressure (mm Hg) Tem- pera- ture, air (°C) Discharge, instanta- neous (ft3/s) Dissolved oxygen, water, unfiltered (mg/L) pH, water, unfiltered, field (standard units) Specific conductance, water, unfiltered (μS/cm at 25 °C) Tem perature, water (°C) Number of sampling points (count) Escherichia 

modifie

m-TEC M

method, w

(col/100 m

(00025) (00020) (00061) (00300) (00400) (00095) (00010) (00063) (90902) 

Partridge Creek near Metamora (05559800) May 28 2008 0915 CST 752 9.5 — 11.4 8.3 815 11.2 1 220 

Synoptic sample June 12 2008 0720 CDT 743 18.2 — 8.6 8.1 831 18.7 1 800 

July 16 2008 1105 CST 750 25.1 — 8.8 8.3 766 23.1 1 1900 Aug 20 2008 1240 CST 749 25.6 — 9.5 8.3 783 22.5 1 580 

Partridge Creek Tributary near Metamora (05559820) May 28 2008 0900 CST 752 9.5 — 11.1 8.4 770 9.9 1 210 

Synoptic sample June 12 2008 0730 CDT 743 18.2 — 8.8 8.1 774 16.9 1 220 

July 16 2008 1100 CST 749 25.1 — 8.6 8.2 761 21.3 1 1100 

Near zero flow, no sample possible Aug 20 2008 1230 CDT 749 25.6 <0.1 4.1 7.8 911 16.1 — — 
Data Collection 17

Synoptic Sampling

Intensive synoptic sampling was completed on October 

10, 2007, and June 12, 2008. These dates were chosen based 

on hydrologic conditions in the area at that time. The October 

10, 2007, sampling took place during a relatively dry period 

with streamflows in the Illinois River and tributaries generally at or below the long-term means. In contrast, the June 12, 

2008, sampling took place during a relatively wet period with 

streamflows in the Illinois River and tributaries generally at or 

above the long-term means (figs. 3 and 4).

During October 2007, samples were collected at 16 sites 

on the Illinois River and at 14 sites on various tributaries 

within the study area. The sample sites on the main stem of 

the Illinois River were selected based mainly on the following 

factors: the location of major tributary inflows, the location of 

sewage-treatment plant discharge points, and the location of 

in-channel lakes where changes in hydraulic characteristics 

may affect the transport and (or) lifespan of bacteria. Tributary 

sample sites were selected to best represent possible bacteria 

loading from a wide range of land-use areas, ranging from 

rural to urban. As was the case with the periodic sampling, all 

samples were analyzed for both FC and E. coli, and observations of air temperature, water temperature, barometric pressure, dissolved oxygen, pH, and specific conductance were 

measured at each sampling location. Streamflow is estimated 

at sites without continuous monitoring. Results of the October 

10, 2007, sampling are presented in table 7.

During June 2008, samples were collected at 12 sites 

on the Illinois River and at 5 sites on tributaries within the 

study area. These sites were a subset of the sites that were 

sampled in October 2007; the results of the October 2007 

sampling indicated that a similar amount of information could 

be obtained while sampling fewer sites throughout the study 

area. The results of the June 12, 2008, sampling are presented 

in table 8.
18 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

Table 7. Results of synoptic sampling on the Illinois River and selected tributaries between Hennepin and Peoria, Illinois, 

October 10, 2007.—Continued

[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, 

micrometer; mg/L, milligrams per liter; mm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; <, less than; E, estimated; 

k, counts outside acceptable range; CDT, central daylight time; CST, central standard time; DS, downstream; US, upstream]

Site name

U.S. 

Geological 

Survey 

station 

number

Sample notes

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure

(mm Hg)

Temperature, 

air

(°C)

Discharge, 

instantaneous

(ft3/s)

Dissolved 

oxygen, 

water, 

unfiltered 

(mg/L)

(00025) (00020) (00061) (00300) 

Illinois River 

Upstream of 

Hennepin near Mile 

209.3

Mid-channel grab 1420 CDT 749 E13.0 — 9.8 

Illinois River 

Upstream of 

Hennepin near 

Mile 208.4

Mid-channel grab 1430 CDT 749 E12.5 — 9.6 

Illinois River at 

Hennepin

05556200 Cross-section part 1 

of 4; Collected near 

right-channel

1435 CDT 749 E12.5 — 10.0 

Cross-section part 2 

of 4; Collected near 

mid-channel

1440 CDT 750 E12.0 — 9.1 

Cross-section part 3 

of 4; Collected near 

island, navigationchannel side

1445 CDT 748 E12.0 — 8.9 

Cross-section part 4 

of 4; Collected sample 

near left-channel

1450 CDT 748 E12.0 — 9.4 

Illinois River 

Upstream of Henry 

near Mile 198.2

Mid-channel grab 1310 CDT — E13.0 — — 

Illinois River at Henry 05558300 Mid-channel grab 1255 CDT — E13.0 7510 — 

Illinois River at Lacon 05558995 Mid-channel grab 1230 CDT — E13.0 — — 

Illinois River 

Downstream of 

Lacon near 

Mile 188.7

Collected sample near 

left-bank

1225 CDT — E12.5 — — 

Illinois River at Chillicothe05559600 Mid-channel grab, 

at public boat ramp

1631 CDT 748 E12.1 — 8.4 

Illinois River downstream of Chillicothe near Mile 179Collected sample near 

right-bank

1555 CDT — E12.1 — — 

Mid-channel grab 1600 CDT — E12.1 — — 

Illinois River at South 

Rome

05559850 Mid-channel grab 1545 CDT E748 E53.8 — 
Data Collection 19

pH, water, 

unfiltered, 

field

(standard 

units)

Specific 

conductance, 

water, unfiltered

(μS/cm at 

25 °C)

Temperature, 

water

(°C)

Gage 

height

(ft)

Sampling 

depth

(ft)

Number of

 sampling 

points

(count)

Escherichia 

coli, modified 

m-TEC MF 

method, water

(col/100 mL)

Fecal coliform, 

M-FC MF 

(0.45 micron) method, 

water

(col/100 mL)

(00400) (00095) (00010) (00065) (00003) (00063) (90902) (31616)

8.5 852 21.9 — 3.00 1 E17 k 50

8.5 974 22.4 — 3.00 1 E13 k E30 k

8.6 849 21.8 — 3.00 1 E10 k 52

8.5 850 21.9 — 3.00 1 E16 k E20 k

8.5 850 21.8 — 3.00 1 E13 k E18 k

8.5 894 21.8 — 2.00 1 770 E36 k

— — — — 3.00 1 38 45

— — — 14.73 3.00 1 E13 k 40

— — — — 3.00 1 E8 k E6 k

— — — — 2.00 1 73 98

8.5 836 20.8 — 3.00 1 E2 k E12 k

— — 20.6 — 2.00 1 45 430

— — 20.6 — 3.00 1 E2 k E9 k

8.5 832 20.6 3.00 1 E12 k E24 k
20 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

Table 7. Results of synoptic sampling on the Illinois River and selected tributaries between Hennepin and Peoria, Illinois, 

October 10, 2007.—Continued

[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, 

micrometer; mg/L, milligrams per liter; mm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; <, less than; E, estimated; 

k, counts outside acceptable range; CDT, central daylight time; CST, central standard time; DS, downstream; US, upstream]

Site name

U.S. 

Geological 

Survey 

station 

number

Sample notes

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure

(mm Hg)

Temperature, 

air

(°C)

Discharge, 

instantaneous

(ft3/s)

Dissolved 

oxygen, 

water, 

unfiltered 

(mg/L)

(00025) (00020) (00061) (00300) 

Illinois River at Water 

Company 

at Peoria

05559900 Mid-channel grab 0845 CDT — E8.8 — — 

Collected sample near 

right-bank

0850 CDT — E8.8 — — 

Illinois River 

at Peoria

05560000 Cross-section part 1 

of 3; near Mile 163, 

left-channel

1245 CDT — E11.7 — — 

Cross-section part 2 

of 3; near Mile 163, 

mid-channel

1250 CDT — E11.7 — — 

Cross-section part 3 

of 3; near Mile 163, 

right-channel

1255 CDT — E11.7 — — 

Illinois River at 

William Kumpf 

Blvd at Peoria

05562100 Mid-channel grab 1240 CDT — E11.2 — — 

Illinois River upstream of Highway 

8/29/116 Bridge at 

Peoria

Mid-channel grab 1235 CDT — E11.2 — — 

Illinois River near 

railroad bridge at 

Peoria near 

Mile 160.8

Collected sample near 

right-bank

1225 CDT — E11.2 — — 

Illinois River below 

Peoria Lake at 

Peoria

05562200 Mid-channel grab 1210 CDT — E10.8 — — 

Collected sample near 

right-bank

1215 CDT — E10.9 — — 

Big Bureau Creek 

at Bureau

05558000 Mid-channel grab 0900 CDT 749 13.0 115 8.4 

Sandy Creek at Henry 05558295 Mid-channel grab 0945 CDT 748 E10.0 16 9.1 

Crow Creek (West) at 

Highway 29 near 

Sparland

Mid-channel grab 0950 CDT 749 E10.0 <.10 2.9 

Thenius Creek at 

Sparland

05558990 Mid-channel grab 1115 CDT 749 E10.5 .10 7.6 

Crow Creek near 

Chillicothe

05559590 Mid-channel grab 0840 CDT 747 E9.0 10 7.1 
Data Collection 21

pH, water, 

unfiltered, 

field

(standard 

units)

Specific 

conductance, 

water, unfiltered

(μS/cm at 

25 °C)

Temperature, 

water

(°C)

Gage 

height

(ft)

Sampling 

depth

(ft)

Number of

 sampling 

points

(count)

Escherichia 

coli, modified 

m-TEC MF 

method, water

(col/100 mL)

Fecal coliform, 

M-FC MF 

(0.45 micron) method, 

water

(col/100 mL)

(00400) (00095) (00010) (00065) (00003) (00063) (90902) (31616)

— — 18.3 — 3.00 1 E15 k E5 k

— — 18.3 — 2.00 1 E5 k E4 k

— — 18.3 — 3.00 1 E8 k 43

— — 18.3 — 3.00 1 E24 k 180

— — 18.9 — 3.00 1 30 160

— — 18.9 — 3.00 1 370 94

— — 19.4 — 3.00 1 93 190

— — 20.0 — 3.00 1 570 870

— — — — 3.00 1 130 300

— — 20.0 — 3.00 1 130 240

7.8 719 13.8 — .50 1 200 200

— 726 14.2 — 1.50 1 260 410

7.7 811 14.7 — .50 1 E5 k E6 k

7.8 903 14.3 — — 1 90 220

— 704 11.6 — 1.50 1 160 150
22 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

Table 7. Results of synoptic sampling on the Illinois River and selected tributaries between Hennepin and Peoria, Illinois, 

October 10, 2007.—Continued

[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, 

micrometer; mg/L, milligrams per liter; mm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; <, less than; E, estimated; 

k, counts outside acceptable range; CDT, central daylight time; CST, central standard time; DS, downstream; US, upstream]

Site name

U.S. 

Geological 

Survey 

station 

number

Sample notes

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure

(mm Hg)

Temperature, 

air

(°C)

Discharge, 

instantaneous

(ft3/s)

Dissolved 

oxygen, 

water, 

unfiltered 

(mg/L)

(00025) (00020) (00061) (00300) 

Senachwine Creek 

at Chillicothe

05559700 No sample, dry — — — — 

Richland Creek below 

Dry Creek Mouth 

near 

Chillicothe

05559770 Mid-channel grab 0745 CDT 745 E7.3 .71 6.2 

Partridge Creek near 

Spring Bay

05559830 Mid-channel grab 1420 CDT 749 E12.6 .46 9.8 

Blalock Creek near 

Spring Bay

05559840 Mid-channel grab 1355 CDT 749 E12.8 .02 7.8 

Tenmile Creek at Trailpark Gardens05559890 Mid-channel grab 1320 CDT 749 E12.1 1.3 10.1 

Farm Creek at U.S. 

Highway 150 at East 

Peoria

05561800 Mid-channel grab 1215 CDT 749 12.5 .43 18.4 

Farm Creek at 

East Peoria

05562000 Mid-channel grab 1120 CDT 750 E10.9 <1.0 19.3 

Farm Creek at Camp 

Street Bridge at East 

Peoria

05562010 Mid-channel grab 1045 CDT 749 E10.8 <1.0 16.6 

Kickapoo Creek at 

Bartonville

05563525 Mid-channel grab 

about 150ft US 

of HWY24

0825 CDT 748 E8.3 4.1 7.7 

Mid-channel grab 

about 1500ft DS 

of HWY24

0805 CDT 749 E7.8 4.1 10.0 
Data Collection 23

pH, water, 

unfiltered, 

field

(standard 

units)

Specific 

conductance, 

water, unfiltered

(μS/cm at 

25 °C)

Temperature, 

water

(°C)

Gage 

height

(ft)

Sampling 

depth

(ft)

Number of

 sampling 

points

(count)

Escherichia 

coli, modified 

m-TEC MF 

method, water

(col/100 mL)

Fecal coliform, 

M-FC MF 

(0.45 micron) method, 

water

(col/100 mL)

(00400) (00095) (00010) (00065) (00003) (00063) (90902) (31616)

— — — — — — — —

— 743 14.4 — .20 1 770 970

— 658 17.1 — 1.00 1 E21 k E34 k

— 774 14.5 — .30 1 740 610

— 781 14.6 — .70 1 410 6

— 1410 15.5 — .40 1 270 800

— 1230 14.4 — .20 1 73 83

— 1290 13.3 — E.60 1 110 140

— 962 15.0 — E.60 1 110 290

— 991 14.9 — E.80 1 E740 k 390
24 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

Table 8. Results of synoptic sampling on the Illinois River and selected tributaries between Hennepin and Peoria, Illinois, June 12, 2008.

[hhmm, hour minute; Hg, mercury; MF, membrane filter; col/100 mL, colonies per 100 milliliters; ft, foot; ft3/s, cubic foot per second; micron, micrometer; 

mg/L, milligrams per liter; mm, millimeter; °C, degrees Celsius; μS/cm, microsiemens per centimeter; —, no data; <, less than; E, estimated; 

k, counts outside acceptable range; CDT, central daylight time; CST, central standard time]

Site name

U.S. 

Geological 

Survey 

station 

number

Sample notes

Time

(24-hour 

clock, 

hhmm)

Barometric 

pressure

(mm Hg)

Tem

perature, 

air

(°C)

Discharge, 

instantaneous

(ft3/s)

(00025) (00020) (00061) 

Illinois River 

at Hennepin

05556200 Cross-section composite 0805 CDT 747 24.0 — 

Illinois River 

at Henry

05558300 Mid-channel grab 0910 CDT 747 25.0 28500 

Illinois River 

at Lacon

05558995 Mid-channel grab 1000 CDT 747 25.0 — 

Illinois River 

at Chillicothe

05559600 Mid-channel grab, at 

public boat ramp

1055 CDT 748 26.5 — 

Illinois River 

at South Rome

05559850 Mid-channel grab 1215 CDT 748 24.5 — 

Illinois River at 

Water Company 

at Peoria

05559900 Mid-channel grab 0950 CDT 751 E26.9 — 

Illinois River 

at Peoria

05560000 Cross-section part 3 of 3; 

near Mile 163, right-channel

1025 CDT 750 E28.0 — 

Cross-section part 2 of 3; 

near Mile 163, mid-channel

1030 CDT 752 E28.1 — 

Cross-section part 1 of 3; 

near Mile 163, left-channel

1040 CDT 753 E28.3 — 

Illinois River at William 

Kumpf Blvd 

at Peoria

05562100 Mid-channel grab 1045 CDT 751 E28.5 — 

Illinois River upstream 

of Highway 8/29/116 

Bridge at Peoria

Mid-channel grab 1100 CDT 751 E28.9 — 

Illinois River near railroad 

bridge at Peoria near 

Mile 160.8

Mid-channel grab 1110 CDT 752 E29.1 — 

Illinois River below 

Peoria Lake at Peoria

05562200 Cross-section composite 1115 CDT 752 E29.2 — 

Illinois River above 

Peoria Lock and Dam 

near Creve Coeur

05563590 Cross-section composite, 

near Mile 159

1135 CDT 751 E29.5 — 

Big Bureau Creek at 

Princeton

05556500 Mid-channel grab 0835 CDT 744 19.0 282 

Senachwine Creek at 

Chillicothe

05559700 Mid-channel grab 1010 CDT 748 22.5 40 

Partridge Creek near 

Metamora

05559800 Mid-channel grab 0720 CDT 743 18.2 — 

Partridge Creek Tributary 

near Metamora

05559820 Mid-channel grab 0730 CDT 743 18.2 — 

Farm Creek at Farmdale 05560500 Mid-channel grab 0640 CDT 745 18.0 19 
Data Collection 25

Dissolved 

oxygen, 

water, unfiltered 

(mg/L)

pH, water,

 unfiltered, 

field

(standard units)

Specific 

conductance, 

water, unfiltered

(μS/cm at 25 °C)

Tem

perature, 

water

(°C)

Gage 

height

(ft)

Sampling 

depth

(ft)

Number of 

sampling 

points

(count)

Escherichia 

coli, modified 

m-TEC MF 

method, water 

(col/100 mL)

Fecal coliform, 

M-FC MF 

(0.45 micron) 

method, water 

(col/100 mL)

(00300) (00400) (00095) (00010) (00065) (00003) (00063) (90902) (31616)

— 7.9 — 23.9 — 3.00 3 90 E100 k

— 7.8 — 23.5 20.64 3.00 1 73 110

— 7.8 — 23.7 — 3.00 1 77 E88 k

— 7.8 — 24.1 — 3.00 1 110 110

— 7.9 — 24.4 — 3.00 1 78 70

7.1 7.9 624 23.9 — 3.00 1 E26 k 35

7.0 8.0 619 24.1 — 3.00 1 55 35

7.3 8.1 620 23.9 — 3.00 1 E28 k 45

7.1 8.0 619 24.1 — 3.00 1 E20 k 71

7.0 8.0 618 24.1 — 3.00 1 E26 k E44 k

7.0 8.0 619 24.2 — 3.00 1 E38 k E48 k

7.0 8.0 623 24.1 — 3.00 1 190 510

7.0 8.0 620 24.1 — 3.00 3 120 410

6.9 8.0 623 24.2 — 3.00 3 250 520

8.8 8.2 696 18.5 3.07 — 1 440 450

9.4 8.2 706 21.3 6.68 — 1 260 430

8.6 8.1 831 18.7 — — 1 800 930

8.8 8.1 774 16.9 — — 1 220 1630

8.7 8.0 895 18.5 2.19 — 1 7300 1030
26 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

Figure 6. Correlation of fecal coliform to Escherichia coli concentrations for all stations 

and all samples.

Data Analysis

Correlation analyses were performed to investigate the 

strength of the relation between FC and E. coli counts, as well 

as correlation between each FIB and streamflow. Linear correlation was calculated with Pearson’s r coefficient and non-linear correlation with Spearman’s rho coefficient, using methods as described in Helsel and Hirsch (1992). Both of these 

coefficients have the characteristic of ranging in value from −1 

to 1. When there is no correlation, the coefficient equals zero. 

Values closer to 1 indicate both variables increase simultaneously. Values closer to −1 indicate as one variable decreases, 

the other increases. Statistical significance was chosen for a 

90-percent confidence with these tests. This is demonstrated 

when the p-value is less than 0.1, or 10 percent.

Concentrations of FC and E. coli bacteria correlated well 

with each other for samples from all locations (r = 0.94, p 

<0.001; fig. 6), for the Illinois River at Hennepin, Ill. (r = 0.95, 

p <0.001; fig. 7), and for the Illinois River below Peoria Lake 

at Peoria, Ill. (r = 0.99, p <0.001; fig. 8). Each of these results 

indicates a strong linear correlation between the concentrations of FC and E. coli bacteria. Spearman’s rho coefficient 

was not calculated because of these findings.

Counts of FC bacteria can encompass more types of coliforms than E. coli alone; therefore, the possibility exists for 

an upward counting bias when relying on FC data to indicate 

potential FIB sources. However, the statistically significant 

correlation observations may indicate incorporation or substitution of E. coli concentrations with those of FC (for non-regulatory purposes) and could be supported for other instances 

depending on the type of investigation. 

Correlation between streamflow and bacteria concentrations also was determined. Weaker relations were found for 

either FIB to streamflow than were observed between the 

FIB; however, the correlation coefficients were found to be 

statistically significant. For both the tributaries and the Illinois 

River at Hennepin, Ill., a positive coefficient value was found. 

Interestingly, a negative coefficient was found for both FC and 

E. coli in relation to streamflow for the Illinois River below 

Peoria Lake at Peoria, Ill.

r = 0.94

1

10

100

1,000

10,000

100,000

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

Fecal coliform, colonies per 100 milliliters

Escherichia coli, colonies per 100 milliliters
Data Analysis 27

Figure 8. Correlation of fecal coliform to Escherichia coli concentrations for Illinois 

River below Peoria Lake at Peoria, Illinois.

Figure 7. Correlation of fecal coliform to Escherichia coli concentrations for Illinois 

River at Hennepin, Illinois.

1

10

100

1,000

10,000

1 10 100 1,000 10,000

r = 0.95

Fecal coliform, colonies per 100 milliliters

Escherichia coli, colonies per 100 milliliters

1

10

100

1,000

10,000

1 10 100 1,000 10,000

r = 0.99

Fecal coliform, colonies per 100 milliliters

Escherichia coli, colonies per 100 milliliters
28 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

The tributaries to the Illinois River had a weak correlation for streamflow to either FC (rho = 0.40, p = 0.0071; r = 

0.44, p = 0.0032) or E. coli (rho = 0.48, p = 0.0008; r = 0.40, 

p = 0.0046), see figure 9. The Illinois River at Hennepin, Ill., 

had a moderate correlation for streamflow to either FC (rho 

= 0.49, p = 0.004; r = 0.60, p <0.001) or E. coli (rho = 0.66, 

p <0.001; r = 0.60, p <0.001), see figure 10. The Illinois River 

below Peoria Lake at Peoria, Ill., had a negative correlation coefficient for streamflow to either FC (rho = −0.44, p 

= 0.0129) or E. coli (rho = −0.43, p = 0.0157), see figure 11. 

This last relation did not have a statistically significant Pearson r coefficient.

Figure 9. Correlation of A, fecal coliform colonies and B, Escherichia coli colonies to 

discharge from tributaries to the Illinois River.

r = 0.44

rho = 0.40

r = 0.40

rho = 0.48

1

10

100

1,000

10,000

100,000

Fecal coliform, colonies per 100 milliliters

1

10

100

1,000

10,000

100,000

0.01 0.1 1 10 100 1,000 10,000

Discharge, in cubic feet per second

Escherichia coli, colonies per 100 milliliters

A.

B.
Data Analysis 29

Figure 10. Correlation of A, fecal coliform colonies and B, Escherichia coli colonies 

to discharge for the Illinois River at Hennepin, Illinois.

r = 0.60

rho = 0.49

r = 0.60

rho = 0.66

1

10

100

1,000

10,000

Fecal coliform, colonies per 100 milliliters

1

10

100

1,000

10,000

Discharge, in cubic feet per second

Escherichia coli, colonies per 100 milliliters

A.

B.

5,000 10,000 50,000
30 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

Figure 11. Correlation of A, fecal coliform colonies and B, Escherichia coli colonies 

to discharge for the Illinois River below Peoria Lake at Peoria, Illinois.

rho = –0.44

rho = –0.43

1

10

100

1,000

10,000

Fecal coliform, colonies per 100 milliliters

1

10

100

1,000

10,000

Discharge, in cubic feet per second

Escherichia coli, colonies per 100 milliliters

A.

B.

5,000 10,000 50,000
Acknowledgments 31

The data from June 2008 indicate a possible influence of 

CSOs on FC concentrations following rainfall-runoff events in 

the reach of the Illinois River immediately near Peoria, Ill. The 

June 2008 synoptic survey of FIB in the Illinois River indicated FC concentrations greater than the water-quality standard only below the known CSO outfalls in Peoria, Ill. Each 

tributary sampled during June 2008 also had FC concentrations above the standard; however, concentrations in the main 

stem of the Illinois River below the mouths of these tributaries 

and still upstream of Peoria, Ill., did not exceed the State of 

Illinois single-sample water-quality standard of 400 CFU/100 

mL. These data are presented in table 8.

The influences of high FIB concentrations in the tributary 

streams on concentrations in the Illinois River are not clear 

from the data collected in this investigation. For example, 

during the June 2008 synoptic sampling, FIB concentrations 

in Partridge and Farm Creeks exceeded the water-quality standard. These tributaries enter the Illinois River well upstream 

of the Highway 8/29/116 bridge (figs. 1 and 5); however, FIB 

concentrations in the Illinois River did not exceed the waterquality standard at any location upstream of the bridge. 

Conclusions

Portions of the Illinois River in Peoria, Woodford, and 

Tazewell Counties, Illinois, are designated as impaired for 

primary-contact recreation by the Illinois Environmental 

Protection Agency, and fecal coliform bacteria are listed 

as a potential cause of impairment. Combined sanitary and 

storm sewers around the City of Peoria might contribute to 

elevated bacteria concentrations during overflow events. The 

U.S. Geological Survey, in cooperation with the Tri-County 

Regional Planning Commission, investigated fecal-indicator 

bacteria (FIB) concentrations in this reach of the Illinois River 

and many of the tributary waterways during water year 2008 

(October 2007–September 2008). Information regarding both 

diffuse- and point-source contributions of FIB will aid in any 

possible future resource-management efforts of these water 

resources at the Federal, State, or local level.

Hydrologic conditions during the study period are characterized as wetter than normal, with the mean annual flow in 

the Illinois River about 37-percent above the long-term average. Rainfall was normal to slightly below normal during the 

first three months of the study period; however, the observed 

rainfall across the State of Illinois for 2008 was the second 

wettest since 1895. Precipitation-recording stations within the 

study area had similar results as did the aggregated State-level 

records.

Two synoptic sampling efforts were conducted to determine FIB concentrations during low- and high-flow conditions 

in the waterways of the study area. The low-flow period was 

characterized during October 2007 sampling, and the highflow period was characterized during June 2008 sampling. The 

Illinois River and 12 tributaries were sampled at 30 different locations during October 2007. The Illinois River and 5 

tributaries were sampled at 17 different locations during June 

2008. The Illinois River also was sampled routinely during 

the study period at the upstream and downstream boundaries 

of the study area, at Hennepin and Peoria, Ill., respectively. 

Additionally, fixed-interval samples were collected from three 

tributaries where streamflow was continuously monitored.

Concentrations of the two measured FIB—fecal coliform 

and Escherichia coli—demonstrated a statistically significant 

correlation to each other for all samples (r = 0.94, p <0.001), 

regardless of the specific sampling location. Correlation of 

FIB concentrations to streamflow also was investigated. A 

weaker statistical relation was found for streamflow to concentrations at any location. For the Illinois River water samples 

from the Hennepin, Ill., location or from any of the tributaries, 

positive correlation coefficients indicate that both streamflow and FIB values increase and decrease simultaneously in 

magnitude. At the downstream study boundary for the Illinois 

River below Peoria Lake at Peoria, Ill., however, a statistically 

significant negative correlation coefficient indicates a weaker 

inverse relation between values of streamflow and FIB.

Possible linkage may be evident between combined 

storm- and sanitary-sewer overflows with assumed elevated 

fecal coliform concentrations, based on previous investigative 

research by the City of Peoria, Ill., and measured concentrations in the Illinois River during June 2008. The data presented in this report indicate both diffuse and point sources of 

fecal indicators in the water column throughout the study area. 

The presence of one of the studied FIB typically indicates the 

presence of the other. 

Acknowledgments

The authors wish to thank USGS personnel who assisted 

with the intensive data-collection efforts required for this 

study: Jon Angel; Ryan Beaulin; Erin Bertke; Charles Bohall; 

David Fazio; Teresa Halfar; Marvin Harris; Robert Holmes, 

Jr.; Patrick Miller; Elizabeth Murphy; and Josiah Peoples.
32 Fecal-Indicator Bacteria Concentrations in the Illinois River between Hennepin and Peoria, Illinois: 2007–08

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