Prepared in cooperation with the Metropolitan Water Reclamation District of Greater Chicago

Hydrogeology and Groundwater Quality at Monitoring Wells 

Installed for the Tunnel and Reservoir Plan System and 

Nearby Water-Supply Wells, Cook County, Illinois, 1995–2013

MW-1

MW-2

MW-3

MW-4 MW-5

MW-6

MW-7

MW-8

MW-9

QD-31

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QC-1 QC-2

QC-2.1

QC-2.2

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QC-8/8.1

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QC-27

QC-28

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QC-30QC-31

QC-32

QC-33 QC-34

QC-35

QC-36 QC-37

QC-9

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal

leg

Markham

leg

140th Street leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

QD-60

Tunnel—Colors indicate legs

 of tunnel systems

Monitoring well location

 and name

Pumping station

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 3. Location of sampled monitoring wells, Tunnel and Reservoir Plan (TARP) System, Cook County, Illinois.

Scientific Investigations Report 2015–5186

Version 1.1, May 2016

U.S. Department of the Interior

U.S. Geological Survey
Cover: Map showing Tunnel and Reservoir Plan System, as shown in figure 3. 
Hydrogeology and Groundwater Quality at 

Monitoring Wells Installed for the Tunnel 

and Reservoir Plan System and Nearby 

Water-Supply Wells, Cook County, Illinois, 

1995–2013 

By Robert T. Kay

Prepared in cooperation with the Metropolitan Water Reclamation District 

of Greater Chicago

Scientific Investigations Report 2015–5186

Version 1.1, May 2016

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia

First release: 2016

Revised: May 2016 (ver. 1.1) 

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.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod/.

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

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Kay, R.T., 2016, Hydrogeology and groundwater quality at monitoring wells installed for the Tunnel and Reservoir Plan 

System and nearby water-supply wells, Cook County, Illinois, 1995–2013: (ver. 1.1, May 2016): U.S. Geological Survey 

Scientific Investigations Report 2015–5186, 347 p., http://dx.doi.org/10.3133/sir20155186

ISSN 2328-0328 (online)
iii

Contents

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

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

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

Description of the Tunnel and Reservoir Plan System and Monitoring Wells............................5

Methods of Study.........................................................................................................................................12

Sample Collection, Laboratory Analysis, and Data Reporting ....................................................12

Data Analysis.......................................................................................................................................13

Hydrogeology in the Vicinity of the Tunnel and Reservoir Plan System.............................................14

Water Quality in Tunnel and Reservoir Plan System Monitoring Wells..............................................21

Temperature.........................................................................................................................................21

Fecal Coliform......................................................................................................................................22

Hardness ..............................................................................................................................................25

Sulfate...................................................................................................................................................41

Chloride.................................................................................................................................................44

Electrical Conductivity .......................................................................................................................48

Total Dissolved Solids ........................................................................................................................50

Ammonia...............................................................................................................................................52

Dissolved Organic Carbon ................................................................................................................54

pH...........................................................................................................................................................54

Analyte Correlations...........................................................................................................................58

Coliform Bacteria and Escherichia coli Data from Water-Supply Wells in the Vicinity of the 

Tunnel and Reservoir Plan System..............................................................................................59

Implications for Future Monitoring ...........................................................................................................59

Summary and Conclusions.........................................................................................................................62

Acknowledgments.......................................................................................................................................63

References Cited..........................................................................................................................................63

Appendixes

1. Summary statistics for analytes and physical properties, by well, Tunnel and Reservoir 

Plan System, 1995–2013.................................................................................................................65

2. Results of temporal trend analysis of analytes and physical properties, by well, Tunnel 

and Reservoir Plan System,1995–2013 .....................................................................................173

3. Seasonality of analytes and physical properties, by well, Tunnel and Reservoir Plan 

System, 1995–2013........................................................................................................................210

4. Analyte and physical property correlations, by well, Tunnel and Reservoir Plan System, 

1995–2013.......................................................................................................................................241
iv

Figures

1. Schematic diagram of Tunnel and Reservoir Plan System operation, Cook County, 

Illinois..............................................................................................................................................2

2. Map showing location and selected features of the Tunnel and Reservoir Plan 

System, Cook County, Illinois ......................................................................................................3

3. Map showing location of sampled monitoring wells, Tunnel and Reservoir Plan 

System, Cook County, Illinois ......................................................................................................4

4. Map showing location of surface-water bodies and selected geologic features in 

the vicinity of the Tunnel and Reservoir Plan System, Cook County, Illinois ......................6

5. Graph showing discharge from the Tunnel and Reservoir Plan System to the 

Stickney and Calumet Water Reclamation Plants, and precipitation at Midway 

Airport, Cook County, Illinois, 1995–2013...................................................................................7

6. Map showing recharge rates for wells, Tunnel and Reservoir Plan System, Cook 

County, Illinois .............................................................................................................................15

7. Map showing geometric mean value of water levels and trends in Tunnel and 

Reservoir Plan System wells, Cook County, Illinois, 1995–2013..........................................16

8. Graph showing water levels in Tunnel and Reservoir Plan System well QC-26, 

Cook County, Illinois, 1999–2013 ...............................................................................................17

9. Graph showing water levels in monitoring wells BH7D, BH16D, and BH18D, 

Cook County, Illinois, 1992–2014 ...............................................................................................18

10. Graph showing water pressure in the Calumet and Des Plaines Tunnel Systems, 

Cook County, Illinois, January 1–December 31, 2010............................................................18

11. Graph showing temperature of groundwater in samples from Calumet System well 

QC-2, Cook County, Illinois, 1995–2004 ....................................................................................22

12. Map showing percentage of samples in which fecal coliform was detected, and 

trends in population in Tunnel and Reservoir Plan System monitoring wells, Cook 

County, Illinois, 1995–2013 .........................................................................................................23

13. Map showing maximum population of fecal coliform detected in samples from 

Tunnel and Reservoir Plan System monitoring wells, Cook County, Illinois, 

1995–2013 .....................................................................................................................................24

14. Graphs showing Tunnel and Reservoir Plan System discharge to the Calumet Water 

Reclamation Plant, and fecal coliform populations in well QC–2, Cook County, 

Illinois, 1995..................................................................................................................................26

15. Map showing hardness of water in samples from shallow drift and Silurian 

aquifers in Cook County, Illinois ...............................................................................................28

16. Map showing geometric mean concentrations of hardness and trends in 

concentration in samples from Tunnel and Reservoir Plan System wells, 

Cook County, Illinois, 1995–2013 ...............................................................................................29

17. Map showing concentration of sulfate in water from the Silurian aquifer in Cook 

County, Illinois .............................................................................................................................42

18. Map showing geometric mean concentrations of sulfate and trends in concentration 

in samples from Tunnel and Reservoir Plan System wells, Cook County, Illinois, 

1995–2013 .....................................................................................................................................43

19. Map showing concentrations of chloride in water from the Silurian aquifer in 

Cook County, Illinois ...................................................................................................................45

20. Graph showing concentrations of chloride in samples from Tunnel and Reservoir 

Plan System discharge to the Stickney Water Reclamation Plant, Cook County,

Illinois, 1989–1991 .......................................................................................................................46
v

21. Map showing geometric mean concentrations of chloride and trends in 

concentration in samples from Tunnel and Reservoir Plan System wells, Cook 

County, Illinois 1995–2013 ..........................................................................................................47

22. Graph showing concentrations of chloride in samples from Tunnel and Reservoir 

Plan System well MW-5, Cook County, Illinois, 1994–2010 ..................................................48

23. Map showing geometric mean values of electrical conductivity and trends in 

samples from Tunnel and Reservoir Plan System wells, Cook County, Illinois, 

1995–2013 .....................................................................................................................................49

24. Map showing geometric mean concentrations of total dissolved solids and trends 

in samples from Tunnel and Reservoir Plan System wells, Cook County, Illinois, 

1995–2013 .....................................................................................................................................51

25. Map showing geometric mean concentrations of ammonia and trends in samples 

from Tunnel and Reservoir Plan System wells, Cook County, Illinois, 1995–2013 ............53

26. Map showing geometric mean concentrations of dissolved organic carbon and 

trends in samples from Tunnel and Reservoir Plan System wells, Cook County, 

Illinois, 1995–2013 .......................................................................................................................55

27. Graph showing concentrations of dissolved organic carbon in samples from Tunnel 

and Reservoir Plan System well QD–28, Cook County, Illinois, 1995–2013........................56

28. Map showing geometric mean values of pH and trends in samples from Tunnel and 

Reservoir Plan System wells, Cook County, Illinois, 1995–2013..........................................57

29. Map showing location of water-supply wells open to the Silurian aquifer within 

5 miles of the Tunnel and Reservoir Plan System, northeast Illinois, with results of 

total coliform and Escherichia coli (E coli) analyses in raw water prior to treatment 

and before entering the water-distribution system, 1999–2015..........................................60

Tables

1. Geometric mean discharge, by month, from the Tunnel and Reservoir Plan System 

to the Stickney and Calumet Water Reclamation Plants, 1995-2013, and average 

monthly precipitation at Midway Airport, 1981–2010, Cook County, Illinois........................7

2. Description of monitoring wells and tunnels, Tunnel and Reservoir Plan System, 

Cook County, Illinois .....................................................................................................................8

3. Groundwater levels and fecal coliform populations at wells QC–1, QC–2, and 

QC–2.2 and discharge to the Calumet Water Reclamation Plant, Tunnel and 

Reservoir Plan System, Cook County, Illinois, 1995–1996.....................................................19

4. Correlation coefficients of fecal coliform populations in monitoring wells with a 

frequency of fecal coliform detection of 10 percent or greater, Tunnel and Reservoir 

Plan System, Cook County, Illinois, 1995–2013.......................................................................27

5. Dates of detection of anomalous analyte values in samples from monitoring wells, 

Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013................................31

6. Summary of correlation coefficients for all analytes in all monitoring wells, 

Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013................................58

7. Summary of water-quality data indicating the presence of combined sewer flow 

effects in monitoring wells in which fecal coliform was detected in 10 percent or 

more of the samples, Tunnel and Reservoir Plan System, Cook County, Illinois, 

1995–2013 .....................................................................................................................................61
vi

Conversion Factors, Datums, and Abbreviations

Inch/Pound to International System of Units

Multiply By To obtain

Length

inch (jn.) 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

) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L)

Flow rate

million gallons per day (Mgal/d) 0.06309 Million liters per day (Ml/d)

million gallons per month (Mgal/m) 0.06309 Million liters per month (Ml/m)

Hydraulic conductivity

foot per day (ft/d) 0.00035 centimeter per second (cm/s)

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as 

°F= (1.8°C) + 32.

Vertical coordinate information is referenced to the Chicago City Datum (CCD). The CCD is 

579.48 feet above the National Geodetic Vertical Datum of 1929 (NGVD 29). 

Elevation, as used in this report, refers to distance above or below the CCD vertical datum.

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

Abbreviated water-quality units used in this report: Concentrations of chemical constituents in 

water are given in milligrams per liter (mg/L). Milligrams per liter are considered equivalents to 

parts per million and the reported concentrations.

Electrical conductance of water is given in micromhos per centimeter (μmho/cm).

pH of water is given in standard units.

Populations of fecal coliform are given in colony-forming units per 100 milliliter (CFU/100 mL).
Hydrogeology and Groundwater Quality at Monitoring 

Wells Installed for the Tunnel and Reservoir Plan System 

and Nearby Water-Supply Wells, Cook County, Illinois, 

1995–2013 

By Robert T. Kay

Abstract 

Groundwater-quality data collected from 1995 through 

2013 from 106 monitoring wells open to the base of the 

Silurian aquifer surrounding the Tunnel and Reservoir Plan 

(TARP) System in Cook County, Illinois, were analyzed by the 

U.S. Geological Survey, in cooperation with the Metropolitan 

Water Reclamation District of Greater Chicago, to assess the 

efficacy of the monitoring network and the effects of water 

movement from the tunnel system to the surrounding aquifer. 

Groundwater from the Silurian aquifer typically drains to the 

tunnel system so that analyte concentrations in most of the 

samples from most of the monitoring wells primarily reflect 

the concentration of the analyte in the nearby Silurian aquifer. Water quality in the Silurian aquifer is spatially variable 

because of a variety of natural and non-TARP anthropogenic 

processes. Therefore, the trends in analyte values at a given 

well from 1995 through 2013 are primarily a reflection of the 

spatial variation in the value of the analyte in groundwater 

within that part of the Silurian aquifer draining to the tunnels. 

Intermittent drainage of combined sewer flow from the tunnel 

system to the Silurian aquifer when flow in the tunnel system 

is greater than 80 million gallons per day may affect water 

quality in some nearby monitoring wells. Intermittent drainage 

of combined sewer flow from the tunnel system to the Silurian 

aquifer appears to affect the values of electrical conductivity, 

hardness, sulfate, chloride, dissolved organic carbon, ammonia, and fecal coliform in samples from many wells but typically during less than 5 percent of the sampling events. Drainage of combined sewer flow into the aquifer is most prevalent 

in the downstream parts of the tunnel systems because of the 

hydraulic pressures elevated above background values and 

long residence time of combined sewer flow in those areas. 

Elevated values of the analytes emplaced during intermittent 

migration of combined sewer flow into the Silurian aquifer 

decrease through time as water from the aquifer drains back 

into the tunnels in response to typical hydraulic conditions. 

Of the analytes sampled, fecal coliform provides the clearest 

indication of the location and timing of combined sewer flow 

into the Silurian aquifer surrounding the tunnel system. 

Introduction

The Metropolitan Water Reclamation District of Greater 

Chicago (MWRDGC) operates the Tunnel and Reservoir 

Plan (TARP) System, which is designed to transmit combined 

sewer flow (stormwater and wastewater) through tunnels in 

the lower part of the Silurian-aged bedrock to storage reservoirs during storms. After a precipitation event, water in the 

reservoirs is pumped to a water reclamation plant where it is 

treated before it is discharged to a nearby surface-water body 

(figs. 1 and 2). 

The MWRDGC, at the request of the Illinois Environmental Protection Agency (IEPA), has performed ongoing 

periodic sampling of groundwater in more than 100 monitoring wells, all located approximately 200 feet (ft) from the 

center line of the TARP tunnels (fig. 3). This sampling is done 

to assess the effect that leakage of combined sewer flow (CSF) 

from the TARP tunnels to the surrounding Silurian aquifer has 

on water quality in the aquifer. For the purposes of this report, 

a CSF event occurs when water from the combined sewers 

is present in the TARP tunnels. These events may or may not 

result in the movement of water from the tunnels into the 

aquifer. 

As part of the sampling effort, depth to water is measured, and water samples collected from the wells are analyzed for pH, temperature, electrical conductivity (EC), 

total dissolved solids (TDS), hardness, ammonia as nitrogen 

(ammonia), dissolved organic carbon (DOC), chloride, sulfate, 

and fecal coliform. These constituents, along with water level, 

are collectively referred to as “analytes” in this report. Many 

of the analytes do not have units of concentration, so the word 

“values” is used to discuss the amount of an analyte whose 

units are not expressed as a concentration. 

No analysis of the sampling data has been performed in 

more than 20 years of data collection. The MWRDGC sought 

technical assistance from the U.S. Geological Survey (USGS) 

to perform this analysis. Subsequently, the USGS conducted 

a study, in cooperation with the MWRDGC, to analyze the 

sampling data. The insights gained from this evaluation 

will be used by MWRDGC and IEPA to design a sampling 
2 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Figure 1. Schematic of Tunnel and Reservoir Plan System operation, Cook County, Illinois (modified from Metropolitan Water 

Reclamation District of Greater Chicago, 2013).

Figure 1. Schematic diagram of Tunnel and Reservoir Plan System operation, Cook County, Illinois (modified from Metropolitan 

Water Reclamation District of Greater Chicago, 2013).

regimen that more effectively monitors the effects of CSF on 

groundwater quality in the Silurian aquifer to ensure continued 

protection of human health and the environment. 

Data from a small number of wells analyzed for this 

investigation were collected beginning in 1994, sampling in 

some monitoring wells did not begin until after 1995, and 

sampling in some wells ended prior to 2013 because of an 

approved monitoring reduction by the IEPA. The precise sampling dates for each well are provided in the tables, figures, 

and appendixes where feasible, but for ease of expression, the 

period of investigation is described as occurring from 1995 

through 2013 regardless of the actual date of the beginning 

and end of data collection in a particular well. This time period 

was chosen because it encompassed the period of sampling in 

most of the wells.

Purpose and Scope

This report summarizes the results of an analysis of 

water-level and water-quality data collected from more 

than 100 monitoring wells from 1995 through 2013. This 

report provides a general overview of the TARP System and 

describes the hydraulics and water quality of CSF in the TARP 

System, the hydrogeology and water quality of the Silurian 

aquifer in Cook County, Illinois, and in the area surrounding 

the TARP System, and the hydraulic and chemical processes 

that affect water quality in the aquifer surrounding the TARP 

System. Summary statistics, correlation coefficients, and 

temporal trends during 1995–2013 calculated for each analyte 

in each well are presented. Dates associated with anomalous 

analyte values, if present, are identified for each well. The 

presence of seasonality (regular and predictable changes 

in data which recur at approximately the same time every 

calendar year) in the values of uncensored analytes (analytes 

whose values were greater than the specified detection limit in 

every sample) is discussed. Correlation coefficients for fecal 

coliform populations within selected groups of wells also have 

been calculated. Results of sampling for total coliform and 

Escherichia coli (E. coli) in water-supply wells near the TARP 

System also are discussed, as are ways to improve the efficacy 

of the monitoring program.
Introduction 3

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LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

Majewski Reservoir

McCook

Reservoir

Thornton

Reservoir

Kirie Water

Reclamation

Plant

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

(Online 1985)

UPPER

DES PLAINES

SYSTEM

(Online 1981)

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

(Online 1999)

North

Branch leg

(Online 1998)

South leg

(Online 1993)

Middle leg

(Online 1993)

West leg

(Online 1993)

Torrence Avenue leg

(Online 2002)

Cal-Sag leg

(Online 1986)

Little Cal leg

(Online 2006)

140th Street leg

(Online 1996)

Markham leg

(Online 1996)

Roosevelt

Road leg

(Online 1993)

Indiana Avenue

leg (Online 1996) (Online 1996)

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel—Colors indicate legs

 of tunnel systems

Well location with elevation

 of bottom of nearby tunnel

 relative to City of Chicago

 Datum, and tunnel diameter,

 in feet

Pumping station

-146/22

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 2. Location and selected features of the Tunnel and Reservoir Plan (TARP) System, Cook County, Illinois.

Figure 2. Location and selected features of the Tunnel and Reservoir Plan (TARP) System, Cook County, Illinois.
4 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

MW-1

MW-2

MW-3

MW-4 MW-5

MW-6

MW-7

MW-8

MW-9

QD-31

QD-32

QD-33

QD-38

QD-39

QD-40

QD-41

QD-42

QD-43

QD-44

QD-45

QD-46

QD-50

QD-51

QD-52

QD-53

QD-54

QD-55

QD-56

QD-57

QD-58

QD-59

QD-60

QM-51

QM-52

QM-53

QM-54

QM-56

QM-57

QM-58

QM-59

QM-61

QM-62

QM-63

QM-64

QM-65

QM-69

QM-70

QM-71

QM-72

QM-73

QM-74

QM-75

QM-76

QM-77 QM-78

QM-79

QM-80 QM-81

QM-82

QD-21 QD-22

QD-23

QD-24

QD-25

QD-26

QD-27

QD-29

QD-28

QD-30

QD-34

QD-35

QD-36 QD-37

QD-47

QD-48

QD-49

QM-66

QM-67

QM-68

QC-1 QC-2

QC-2.1

QC-2.2

QC-3

QC-4

QC-5

QC-6

QC-7

QC-8/8.1

QC-10

QC-11

QC-13 QC-12

QC-14

QC-15

QC-16

QC-17

QC-18

QC-19

QC-20

QC-21

QC-22

QC-23

QC-24

QC-25

QC-26

QC-27

QC-28

QC-29

QC-30

QC-31

QC-32

QC-33 QC-34

QC-35

QC-36

QC-37

QC-9

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal

leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

QD-60

Tunnel—Colors indicate legs

 of tunnel systems

Monitoring well location

 and name

Pumping station

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 3. Location of sampled monitoring wells, Tunnel and Reservoir Plan (TARP) System, Cook County, Illinois.

Figure 3. Location of sampled monitoring wells, Tunnel and Reservoir Plan (TARP) System, Cook County, Illinois.
Introduction 5

Description of the Tunnel and Reservoir Plan 

System and Monitoring Wells

The City of Chicago and 51 other municipalities in Cook 

County have combined sewer systems. These sewer systems 

collect a combination of stormwater runoff, domestic sewage, and industrial wastewater. The water reclamation plants 

in these municipalities were designed to treat about 2 billion 

gallons of wastewater per day in the 1950s (U.S. Environmental Protection Agency, 1988). However, as urbanization 

of the Chicago area increased, the volume of wastewater 

and stormwater runoff entering the sewer system increased 

to the point where the system would become inundated with 

more than 5 billion gallons of runoff following a 1-inch (in.) 

rainstorm (U.S. Environmental Protection Agency, 1988). 

These conditions would result in sewer outfalls discharging 

combined sewer overflow (CSO) to local waterways during a 

substantial portion of the year (U.S. Environmental Protection 

Agency, 1988). During particularly large precipitation events 

area waterways would reverse their direction of flow, releasing 

CSO into Lake Michigan. CSO releases resulted in frequent 

closings of the Lake Michigan beaches and the accumulation 

of contaminants in area waterways, leaving the ecosystem 

dominated by contamination-tolerant organisms (Hill and 

Butts, 1986). 

To eliminate CSO effects, the MWRDGC constructed the 

TARP System. The TARP System is designed to prevent CSO 

discharge to surface water by diverting stormwater and wastewater from the near-surface sewers to the deeper Mainstream, 

Des Plaines, Calumet, and Upper Des Plaines tunnel systems 

constructed in the lower part of the Silurian dolomite beneath 

the Chicago metropolitan area (figs. 1, 2). In this report CSO is 

considered to be water that escaped from the combined sewers 

prior to construction of the TARP. CSF is the water diverted 

into the TARP System from the combined sewers.

The Des Plaines System is beneath the Des Plaines River 

(fig. 4). The Mainstream System is beneath the North Branch 

of the Chicago River, the North Shore Channel of the Chicago 

River, the Chicago River, and the Chicago Sanitary and Ship 

Canal. The Calumet System is beneath the Calumet River, 

Little Calumet River, Grand Calumet River, and the Calumet 

Sag Channel. 

The tunnel system shown west of well QC–1 (fig. 3) is 

an interceptor sewer that drains to the TARP System. This 

sewer is not part of the TARP System and is omitted from 

the following summary of TARP characteristics. The TARP 

System consists of approximately 109 miles (mi) of tunnels. 

The tunnels (fig. 2) are 9–33 ft in diameter with bottom elevations from about -50 to -325 ft relative to the City of Chicago 

Datum (CCD). The tunnels are at about 150 to 300 ft below 

land surface and are excavated through dolomite bedrock (fig. 

1). Fractures in the bedrock intercepting the tunnels have been 

filled with low-permeability grout, and the tunnels are lined 

with concrete to reduce the movement of water between the 

tunnels and the surrounding bedrock. Tunnel construction 

began in 1975, and all the tunnels were operational by 2006 

(fig. 2). 

Flow in the individual tunnel systems is in the direction 

of decreasing elevation of the bottom of the tunnels (fig. 2). 

Flow in the tunnels is from north to south in the Upper Des 

Plaines, Des Plaines, and Mainstream Systems. Flow in the 

tunnels of the Calumet System is toward the Indiana Avenue 

leg.

The tunnels convey CSF to the Majewski, Thornton, 

and (future) McCook reservoirs for storage (figs. 1, 2, and 4) 

(Metropolitan Water Reclamation District of Greater Chicago, 

2013). The Majewski Reservoir is a lined, above ground 

retention basin that began to receive CSF from the Upper Des 

Plaines System in 1998. The Thornton Reservoir occupies part 

of a quarry in the Silurian dolomite. The Thornton Reservoir 

was constructed in two stages. The first stage is a temporary 

reservoir in the western part of the quarry that began accepting stormwater runoff (which is distinct from CSF) from a 

nearby creek in March 2003. The second stage is a permanent reservoir in the northern part of the quarry that began to 

receive CSF from the Calumet System in August 2015. The 

McCook Reservoir also will occupy a quarry in the Silurian 

dolomite and is being constructed in two stages. Construction 

of the first stage of the future McCook Reservoir will occur in 

the southern part of the property, which is projected to begin 

receiving CSF from the Des Plaines and Mainstream Systems 

in 2017. Construction of the expanded reservoir is expected to 

be completed in 2029 after quarry operations have ceased. 

The tunnels are capable of storing 2.3 billion gallons of 

water. Because the McCook and Thornton Reservoirs were not 

connected to the Des Plaines, Mainstream, or Calumet System 

tunnels during 1995–2013, these tunnels were used for CSF 

storage during that period. As a consequence, water derived 

from CSF remained in these tunnels (particularly the downstream part of each tunnel system where the tunnel elevation 

is lowest) for a longer period of time than will occur once the 

tunnels are connected to the reservoirs. Tunnels in the Upper 

Des Plaines System also were used for storage prior to 1998.

Pumping stations dewater the tunnels and reservoirs as 

capacity at the Stickney, Calumet, and Kirie Water Reclamation Plants (WRPs) becomes available (fig. 2). Discharge from 

the TARP System to the Calumet and Stickney WRPs was 

recorded daily during 1995–2013 and closely tracks the timing 

and amount of precipitation near the Stickney WRP at Midway 

Airport (fig. 5), indicating that discharge to the WRPs can be 

used to indicate the timing and amount of CSF in the system. 

Discharge from the TARP System to the WRPs commonly 

exceeds 3 billion gallons (about 100 million gallons per day 

[Mgal/d]) in months with more than about 4 in. of precipitation. TARP discharge of about 200 million gallons per month 

(less than 7 Mgal/d) occurs during periods of minimal or 

absent precipitation because of drainage of groundwater from 

the Silurian dolomite into the tunnels. Geometric mean values 

of monthly discharge from the TARP System at the Calumet 

and Stickney WRPs during 1995–2013 varied during the 

year, with low discharge in January and February, increasing 

discharge from March through May, generally high discharge 

during May–August, and decreasing discharge from September through December (table 1). 
6 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

U

U

U

U

U

U

U U

D

D

D

D

D

D

D D

D

D

U

U

ILLINOIS

INDIANA

DES PLAINES DISTURBANCE

LAKE

MICHIGAN

 COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle

leg

West

leg

Torrence Avenue leg

Cal-Sag leg

Little Cal

leg

Calumet Water

Reclamation

Plant

DES PLAINES DISTURBANCE

Creek

Creek

Creek

Creek

Salt

Flag

Chicago

Sanitary

and

Ship

Canal

Creek

Willow

River

Chicago 

Des Plaines

River

Des Plaines

River

Calumet Sag Channel

North Shore

Channel

Addison

Silver

Tinley Creek

Midlothian

Creek

Creek

Creek

Grand

Calumet River

Calumet

Little

Prairie

Thorn

Majewski

Reservoir

Kirie Water

Reclamation

Plant

River

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Area where dolomite is at or

 near land surface

Tunnel

Fault—Approximate location;

 U, upthrown side;

 D, downthrown side

Monitoring well location

Non-Tunnel and Reservoir

 Plan system monitoring

 well and name

U

D

BH16D

BH18D

BH16D

BH7D

Markham leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Figure 4. Location of surface-water bodies and selected geologic features in the vicinity of the Tunnel and Reservoir Plan (TARP) System,

Cook County, Illinois.

Figure 4. Location of surface-water bodies and selected geologic features in the vicinity of the Tunnel and Reservoir Plan (TARP) 

System, Cook County, Illinois.
Introduction 7

Figure 5. Discharge from the Tunnel and Reservoir Plan (TARP) System to the Stickney and Calumet Water Reclamation Plants, 

and precipitation at Midway Airport, Cook County, Illinois, 1995−2013.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

Precipitation, in inches

Discharge, in million gallons per month

Year

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

Stickney plant

Calumet plant

Precipitation

EXPLANATION

Figure 5. Discharge from the Tunnel and Reservoir Plan System to the Stickney and Calumet Water Reclamation Plants, and 

precipitation at Midway Airport, Cook County, Illinois, 1995–2013.

Table 1. Geometric mean discharge, by month, from the Tunnel and Reservoir Plan System to the Stickney and Calumet Water 

Reclamation Plants, 1995-2013, and average monthly precipitation at Midway Airport, 1981–2010, Cook County, Illinois.

Month

Geometric mean discharge to 

Stickney Water Reclamation Plant1

(million gallons per month)

Geometric mean discharge to Calumet 

Water Reclamation Plant1

(million gallons per month)

Average 

precipitation2

(inches)

January 1,898 928 2.06

February 1,774 914 1.94

March 2,463 1,388 2.72

April 2,870 1,544 3.64

May 3,377 1,650 4.13

June 3,194 1,411 4.06

July 2,751 990 4.01

August 3,199 1,186 3.99

September 2,351 886 3.31

October 2,355 953 3.24

November 2,146 877 3.42

December 1,949 879 2.57

1

Discharge data provided by Kevin Fitzpatrick, Metropolitan Water Reclamation District of Greater Chicago, written commun., 2013. 

2

Precipitation data from National Weather Service http://w2.weather.gov/climate/index.php?wfo=lot; accessed July 26, 2014.
8 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

The amount of discharge from the TARP System to the 

WRPs is affected by a variety of factors, including the availability of treatment capacity at the WRPs and the amount of 

water in the TARP System. Water draining into the tunnels 

from the Silurian aquifer during periods of dry weather flows 

by gravity to the downstream end of the tunnel systems near 

the reservoirs. This water accumulates in the tunnels until it 

is periodically discharged to the WRPs when the tunnels are 

near capacity or to provide storage capacity in anticipation 

of a CSF event. As a result, some dates of elevated discharge 

from the TARP System are associated with this “maintenance” removal of water derived from aquifer infiltration 

rather than removal of CSF from the System. Therefore, 

discharge from the TARP System to the WRPs is a useful, 

but not perfect, indicator of the volume and timing of CSF 

in the TARP System on any given day during 1995‒2013. 

Once the tunnel systems were (for the Upper Des Plaines 

and Calumet Systems) or are to be (for the Des Plaines and 

Mainstream Systems) connected to the reservoirs, the capacity of the TARP System to hold CSF will be increased, the 

amount of CSF that will be stored in the tunnels will decrease, 

the amount of time that CSF will be stored in the tunnels will 

decrease, and the hydraulic pressure the CSF will generate in 

the tunnels will be lower. As a consequence the future relation 

between the volume and timing of CSF in the TARP System 

and discharge from the system to the WRPs is likely to differ 

from the historical relation. In addition, the volume of CSF 

that will migrate from a given tunnel system to the aquifer is 

expected to decrease after the tunnel system is connected to its 

reservoir.

Measurement of water levels in the tunnels also was 

used to assess the timing and magnitude of CSF effects. The 

utility of the water-level data from the tunnels is limited for 

this assessment because the data collection did not begin until 

2004.

CSF pumped to the WRPs is treated prior to being discharged. Discharge is to the nearest receiving water at Willow 

Creek, the Chicago Sanitary and Ship Canal, or the Calumet 

Sag Channel (fig. 4). 

The TARP monitoring wells are open to the Silurian 

aquifer from an elevation typically about 30 ft above the top 

of the nearby tunnel to an elevation about 20 ft below the 

bottom of the tunnel (table 2). Above the open interval is a 

6-in.-diameter steel casing that has been grouted into place. 

The casing extends 2 ft above ground level and is surrounded 

by a protective casing. Because the monitoring wells are open 

only to that part of the Silurian aquifer near the tunnel and 

are sealed off from the rest of the aquifer (as well as overlying units and surface runoff), the construction of the TARP 

wells allows the hydraulic and chemical conditions associated 

with the tunnel system (as opposed to the entire aquifer) to be 

analyzed. The TARP tunnels are excavated near the base of 

the Silurian aquifer, so the monitoring wells are open near the 

base of the aquifer.

Table 2. Description of monitoring wells and tunnels, Tunnel and Reservoir Plan System, Cook County, Illinois.—Continued

[—, no data, ?, unknown]

Well 

name

System 

monitored

Sampling 

dates

Latitude

(degrees, 

minutes, 

seconds)

Longitude 

(degrees, 

minutes, 

seconds)

Land-surface 

elevation 

(feet above 

City of Chicago

 datum)

Elevation 

top/bottom 

of open interval 

of well (feet below 

City of Chicago 

datum)

Elevation 

top/bottom of 

tunnel (feet below 

City of Chicago 

datum)

MW–1 Upper 

Des Plaines

1994–2013 42°1′27.9′′ 87°56′25.0′′ 79.8 -49/-89 -51/-71

MW–2 Upper 

Des Plaines

1994–2010 42°2′8.0′′ 87°56′25.6′′ 76.8 -45/-85 -47/-67

MW–3 Upper 

Des Plaines

1994–2013 42°2′45.4′′ 87°56′25.9′′ 83.6 -41/-81 -43/-63

MW–4 Upper 

Des Plaines

1994–2013 42°3′17.4′′ 87°56′26.3′′ 81.9 -36/-76 -38/-58

MW–5 Upper 

Des Plaines

1994–2010 42°3′31.9′′ 87°57′22.9′′ 88.4 -28/-68 -30/-50

MW–6 Upper 

Des Plaines

1994–2013 42°3′59.6′′ 87°57′26.0′′ 93.6 -22/-68 -30/-50

MW–7 Upper 

Des Plaines

1998–2013 42°3’6.7′′ 87°55′47.3′′ 73.7 -33/-78 -44/-60

MW–8 Upper 

Des Plaines

1997–2013 42°3’43.7” 87°55′42.8” 77.8 -31/-76 -42/-58
Introduction 9

Table 2. Description of monitoring wells and tunnels, Tunnel and Reservoir Plan System, Cook County, Illinois.—Continued

[—, no data, ?, unknown]

Well 

name

System 

monitored

Sampling 

dates

Latitude

(degrees, 

minutes, 

seconds)

Longitude 

(degrees, 

minutes, 

seconds)

Land-surface 

elevation 

(feet above 

City of Chicago

 datum)

Elevation 

top/bottom 

of open interval 

of well (feet below 

City of Chicago 

datum)

Elevation 

top/bottom of 

tunnel (feet below 

City of Chicago 

datum)

MW–9 Upper 

Des Plaines

1997–2013 42°4′16.6′′ 87°55′53.2” 75.8 -28/-68 -34/-50

QD–21 Des Plaines 1995–2013 41°48′56.3′′ 87°51′52.8′′ 46.5 -109/-167 -139/-149

QD–22 Des Plaines 1995–2013 41°49′3.6′′ 87°52′13.0′′ 64.8 -106/-165 -137/-147

QD–23 Des Plaines 1995–2013 41°49′9.2′′ 87°52′51.2′′ 62.4 -104/-162 -134/-144

QD–24 Des Plaines 1995–2013 41°49′16.0′′ 87°53′43.9′′ 64.2 -100/-158 -130/-140

QD–25 Des Plaines 1995–2013 41°49′12.6′′ 87°54′24.6′′ 65.4 -97/-155 -127/-137

QD–26 Des Plaines 1995–2013 41°49′42.4′′ 87°52′49.3′′ 63.0 -99/-157 -128/-138

QD–27 Des Plaines 1995–2013 41°47′50.0′′ 87°49′55.4′′ 32.0 -200/-271 -220/-253

QD–28 Des Plaines 1995–2013 41°48′26.6′′ 87°50′1.8′′ 39.0 -199/-272 -119/-252

QD–29 Des Plaines 1995–2013 41°48′59.2′′ 87°49′59.8′′ 39.0 -195/-266 -215/-248

QD–30 Des Plaines 1995–2013 41°49′27.4′′ 87°49′44.3′′ 33.4 -193/-264 -213/-246

QD–31 Des Plaines 1995–2013 41°49′49.9′′ 87°49′42.7′′ 35.0 -189/-259 -209/-242

QD–32 Des Plaines 1995–2013 41°50′27.3′′ 87°49′41.8′′ 37.0 -182/-253 -202/-235

QD–33 Des Plaines 1995–2013 41°51′0.5′′ 87°49′42.9′′ 44.0 -177/-248 -197/-230

QD–34 Des Plaines 1995–2013 41°49′15.6′′ 87°50′20.5′′ 40.0 -215/-263 -235/-245

QD–35 Des Plaines 1995–2013 41°49′24.4′′ 87°50′27.8′′ 35.0 -213/-261 -233/-243

QD–36 Des Plaines 1995–2013 41°49′47.0′′ 87°50′29.2′′ 40.0 -211/-259 -231/-241

QD–37 Des Plaines 1995–2013 41°49′34.2′′ 87°49′21.0′′ 26.0 -210/-258 -230/-240

QD–38 Des Plaines 1995–2013 41°49′18.0′′ 87°48′35.0′′ 26.0 -207/-255 -227/-237

QD–39 Des Plaines 1995–2013 41°51′41.8′′ 87°49′34.0′′ 42.0 -172/-240 -192/-222

QD–40 Des Plaines 1995–2013 41°52′8.1′′ 87°49′40.3′′ 41.0 -167/-235 -187/-217

QD–41 Des Plaines 1995–2013 41°52′28.9′′ 87°49′38.8′′ 45.0 -163/-231 -183/-213

QD–42 Des Plaines 1995–2013 41°52′58.4′′ 87°49′52.0′′ 46.0 -158/-226 -178/-208

QD–43 Des Plaines 1995–2013 41°53′30.5′′ 87°49′57.9′′ 42.0 -153/-221 -173/-203

QD–44 Des Plaines 1995–2013 41°53′49.3′′ 87°49′47.6′′ 41.0 -149/-217 -169/-199

QD–45 Des Plaines 1995–2013 41°54′34.2′′ 87°49′57.2′′ 44.0 -143/-211 -163/-193

QD–46 Des Plaines 1995–2013 41°51′52.1′′ 87°49′42.3′′ 44.0 -150/-218 -188/-200

QD–47 Des Plaines 1995–2013 41°51′50.2′′ 87°50′34.7′′ 47.0 -147/-215 -185/-197

QD–48 Des Plaines 1995–2013 41°51′49.0′′ 87°51′6.1′′ 48.0 -144/-212 -182/-194

QD–49 Des Plaines 1995–2013 41°51′48.9′′ 87°51′50.6′′ 49.0 -141/-209 -179/-191

QD–50 Des Plaines 1996–2013 41°55′6.3′′ 87°50′24.3′′ 50.5 -141/-202 -171/-183

QD–51 Des Plaines 1996–2013 41°55′43.0′′ 87°50′36.8′′ 49.3 -137/-198 -157/-179

QD–52 Des Plaines 1996–2013 41°56′7.3′′ 87°50′58.7′′ 50.3 -134/-194 -154/-176

QD–53 Des Plaines 1995–2013 41°56′34.4′′ 87°51′13.5′′ 51.0 -131/-191 -151/-173

QD–54 Des Plaines 1996–2013 41°57′15.4′′ 87°51′23.6′′ 46.8 -126/-187 -146/-168
10 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Table 2. Description of monitoring wells and tunnels, Tunnel and Reservoir Plan System, Cook County, Illinois.—Continued

[—, no data, ?, unknown]

Well 

name

System 

monitored

Sampling 

dates

Latitude

(degrees, 

minutes, 

seconds)

Longitude 

(degrees, 

minutes, 

seconds)

Land-surface 

elevation 

(feet above 

City of Chicago

 datum)

Elevation 

top/bottom 

of open interval 

of well (feet below 

City of Chicago 

datum)

Elevation 

top/bottom of 

tunnel (feet below 

City of Chicago 

datum)

QD–55 Des Plaines 1996–2013 41°57′52.0′′ 87°51′16.1′′ 49.9 -123/-183 -142/-164

QD–56 Des Plaines 1996–2013 41°58′23.4′′ 87°51′14.7′′ 55.7 -119/-179 -139/-161

QD–57 Des Plaines 1996–2013 41°58′49.9′′ 87°51′14.6′′ 55.3 -116-176 -136/-158

QD–58 Des Plaines 1996–2013 41°59′25.4′′ 87°51′19.6′′ 54.3 -113/-173 -132/-154

QD–59 Des Plaines 1996–2013 42°0′0.3′′ 87°51′21.3′′ 58.6 -109/-169 -128/-150

QD–60 Des Plaines 1996–2013 42°0′41.8′′ 87°51′35.4′′ 59.9 -104/-164 -124/-146

QM–51 Mainstream No Samples 41°56′35.8′′ 87°41′38.8′′ 10.5 -192/-260 -212/-242

QM–52 Mainstream No Samples 41°53′57.0′′ 87°39′4.4′′ 7.3 -199/-267 -219/-249

QM–53 Mainstream 1995–2013 41°53′46.5′′ 87°38′43.3′′ 17.3 -199/-267 -219/-249

QM–54 Mainstream No Samples 41°53′34.3′′ 87°38′35.3′′ 7.4 -199/-267 -219/-249

QM–55 Mainstream No Samples — — 5.4 -199/-267 -219/-249

QM–56 Mainstream 1995–2009 41°52′30.8′′ 87°38′12.7′′ 6.4 -201/-269 -221/-251

QM–57 Mainstream No Samples 41°51′55.1′′ 87°38′2.8′′ 8.3 -199/-268 -221/-251

QM–58 Mainstream 1995–2008 41°50′52.0′′ 87°39′5.4′′ 10.4 -203/-271 -223/-253

QM–59 Mainstream 1995 41°50′14.1′′ 87°39′46.4′′ 11.6 -203/-271 -223/-253

QM–60 Mainstream No Samples — — 16.2 -197/-275 -227/-257

QM–61 Mainstream 1995–2013 41°49′5.3′′ 87°44′56.5′′ 17.2 -206/-277 -226/-259

QM–62 Mainstream 1995–2013 41°48′44.3′′ 87°46′6.3′′ 19.5 -206/-278 -227/-260

QM–63 Mainstream 1995–2013 41°48′31.2′′ 87°46′46.6′′ 10.1 -208/-279 -228/-261

QM–64 Mainstream 1995–2013 41°48′10.3′′ 87°47′50.8′′ 13.8 -209/-280 -229/-262

QM–65 Mainstream 1995–2010 41°47′25.1′′ 87°49′13.9′′ 12.6 -210/-281 -230/-263

QM–66 Mainstream 2006−2013 41°46′57.7′′ 87°50′11.3′′ 25.2 -284/-338 -287/-320

QM–67 Mainstream 1995–2013 41°47′0.5′′ 87°50′18.6′′ 24.1 -158/-208 -160/-190

QM–68 Mainstream 1995–2013 41°50′40.1′′ 87°39′58.0′′ — — -224/-254

QM–69 Mainstream 1995–2013 42° 2′49.3′′ 87°46′43.0′′ 44.0 -85/-131 -105/-113

QM–70 Mainstream 1995–2013 42° 2′31.3′′ 87°47′8.9′′ 44.0 -121/-179 -131/-161

QM–71 Mainstream 1995–2013 42° 2′9.6′′ 87°47′31.4′′ 45.0 -126/-184 -136/-166

QM–72 Mainstream 1995–2013 42° 1′42.0′′ 87°47′40.2′′ 45.0 -132/-190 -142/-172

QM–73 Mainstream 1995–2013 42° 0′56.9′′ 87°47′54.9′′ 44.0 -141/-199 -151/-181

QM–74 Mainstream 1995–2013 42° 0′30.6′′ 87°47′26.6′′ 41.0 -149/-207 -159/-189

QM–75 Mainstream 1995–2013 41°59′54.2′′ 87°47′14.3′′ 41.0 -145/-213 -165/-195

QM–76 Mainstream 1995–2013 41°59′36.2′′ 87°46′35.8′′ 40.0 -151/-219 -171/-201

QM–77 Mainstream 1995–2013 41°59′18.8′′ 87°45′52.3′′ 31.0 -157/-225 -177/-207

QM–78 Mainstream 1995–2013 41°59′1.5′′ 87°45′6.1′′ 24.0 -164/-232 -184/-214

QM–79 Mainstream 1995–2013 41°58′50.2′′ 87°44′39.2′′ 30.0 -167/-235 -187/-217
Introduction 11

Table 2. Description of monitoring wells and tunnels, Tunnel and Reservoir Plan System, Cook County, Illinois.—Continued

[—, no data, ?, unknown]

Well 

name

System 

monitored

Sampling 

dates

Latitude

(degrees, 

minutes, 

seconds)

Longitude 

(degrees, 

minutes, 

seconds)

Land-surface 

elevation 

(feet above 

City of Chicago

 datum)

Elevation 

top/bottom 

of open interval 

of well (feet below 

City of Chicago 

datum)

Elevation 

top/bottom of 

tunnel (feet below 

City of Chicago 

datum)

QM–80 Mainstream 1995–2013 41°58′30.4′′ 87°43′58.9′′ 25.0 -173/-241 -193/-223

QM–81 Mainstream 1995–2013 41°58′30.6′′ 87°43′12.9′′ 20.0 -177/-245 -197/-227

QM–82 Mainstream 1995–2013 41°58′20.0′′ 87°42′16.3′′ 16.0 -185/-253 --205/235

QC–1 Calumet 1995–2009 41°39′4.8′′ 87°41′33.8′′ 12.4 -206/-265 -226/-247

QC–2 Calumet 1995–2013 41°38′50.0′′ 87°37′14.0′′ 15.6 -271/-330 -291/-312

QC–2.1 Calumet 1995–2013 41°38′52.8′′ 87°37′12.3′′ 19.8 ?/-327 -288/-309

QC–2.2 Calumet 1995–2013 41°38′44.6′′ 87°36′55.9′′ 17.7 ?/-328 -289/-310

QC–3 Calumet 1995–2009 41°35′24.0′′ 87°36′56.7′′ 25.0 — -272/-302

QC–4 Calumet 1995–2013 41°35′48.6′′ 87°37′2.7′′ 24.1 ?/-322 -273/-303

QC–5 Calumet 1995–2013 41°36′32.8′′ 87°37′3.3′′ 16.6 ?/-324 -276/-306

QC–6 Calumet 1995–2013 41°36′54.6′′ 87°37′4.2′′ 18.5 ?/-326 -278/-308

QC–7 Calumet 1995–2013 41°37′22.5′′ 87°37′3.1′′ 19.2 ?/-329 -281/-311

QC–8 Calumet No samples 41°37′46.5′′ 87°37′3.7′′ 21.2 — -281/-311

QC–9 Calumet 1995–2013 41°38′12.9′′ 87°37′2.8′′ 18.7 ?/-335 -287/-317

QC–10 Calumet 1995–2013 41°38′7.3′′ 87°32′27.9′′ 3.5 ?/-298 -265/-280

QC–11 Calumet 1995–2013 41°38′38.7′′ 87°32′58.4′′ 4.3 ?/-303 -269/-284

QC–12 Calumet 1995–2013 41°38′36.6′′ 87°33′31.5′′ 4.2 ?/-321 -272/-302

QC–13 Calumet 1995–2013 41°38′29.9′′ 87°34′37.9′′ 7.0 ?/-327 -279/-309

QC–14 Calumet 1995–2013 41°38′31.7′′ 87°35′53.8′′ 9.9 ?/-330 -282/-312

QC–15 Calumet 1995–2013 41°38′31.0′′ 87°36′36.3′′ 16.5 ?/-333 -285/-315

QC–16 Calumet 1995–2013 41°35′53.1′′ 87°39′30.4′′ 28.5 ?/-286 -257/-267

QC–17 Calumet 1995–2013 41°35′51.1′′ 87°38′42.9′′ 27.1 ?/-281 -253/-263

QC–18 Calumet 1995–2013 41°35′47.9′′ 87°37′49.3′′ 24.2 ?/-297 -269/-279

QC–19 Calumet 1996–2013 41°35′53.3′′ 87°38′42.9′′ — ?/-342 -313/-323

QC–20 Calumet 1999–2013 41°39′0.4′′ 87°33′59.9′′ 10.5 -252/-315 -272/-297

QC–21 Calumet 1999–2013 41°39′46.0′′ 87°33′30.7′′ 6.0 -246/-309 -266/-291

QC–22 Calumet 1999–2013 41°40′26.0′′ 87°33′37.9′′ 10.8 -242/-305 -262/-287

QC–23 Calumet 1999–2013 41°41′17.5′′ 87°33′28.6′′ 11.1 -237/-300 -257/-282

QC–24 Calumet 1999–2013 41°42′16.5′′ 87°33′28.1′′ 9.6 -232/-295 -252/-277

QC–25 Calumet 1999–2013 41°42′55.9′′ 87°32′59.8′′ 11.7 -227/-290 -247/-272

QC–26 Calumet 1999–2013 41°43′41.7′′ 87°32′38.4′′ 15.3 -221/-284 -241/-266

QC–27 Calumet 1999–2013 41°42′7.7′′ 87°32′36.9′′ 9.3 -228/-281 -248/-263

QC–28 Calumet 1999–2013 41°40′21.4′′ 87°32′59.1′′ 9.2 -240/-293 -260/-275

QC–29 Calumet 2003−2013 41°38′11.2′′ 87°39′27.3′′ 17.5 -107/-160 -126/-142

QC–30 Calumet 2003−2013 41°37′53.8′′ 87°38′38.1′′ 18.1 -118/-172 -138/-154
12 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Table 2. Description of monitoring wells and tunnels, Tunnel and Reservoir Plan System, Cook County, Illinois.—Continued

[—, no data, ?, unknown]

Well 

name

System 

monitored

Sampling 

dates

Latitude

(degrees, 

minutes, 

seconds)

Longitude 

(degrees, 

minutes, 

seconds)

Land-surface 

elevation 

(feet above 

City of Chicago

 datum)

Elevation 

top/bottom 

of open interval 

of well (feet below 

City of Chicago 

datum)

Elevation 

top/bottom of 

tunnel (feet below 

City of Chicago 

datum)

QC–31 Calumet 2003−2013 41°37′33.5′′ 87°37′53.9′′ 18.2 -128/-181 -147/-163

QC–32 Calumet 2003−2009 41°36′49.3′′ 87°37′19.2′′ 19.0 -140/-193 -159/-175

QC–33 Calumet 2008 41°36′33.6′′ 87°37′2.3′′ 11.7 -150/-203 -169/-185

QC–34 Calumet 2004−2010 41°36′27.6′′ 87°35′34.4′′ 13.3 -142/-195 -161/-177

QC–35 Calumet 2003−2012 41°36′16.0′′ 87°34′26.5′′ 18.7 -129/-182 -148/-164

QC–36 Calumet 2003−2012 41°35′41.4′′ 87°33′25.0′′ 20.6 -114/-167 -133/-149

QC–37 Calumet 2003−2010 41°35′31.5′′ 87°32′40.6′′ 18.7 -105/-158 -124/-140

Methods of Study

Sample Collection, Laboratory Analysis, and 

Data Reporting

The MWRDGC began collecting and analyzing water 

samples from 120 TARP monitoring wells (table 2) on a 

periodic basis in the mid-1970s. Seven wells became nonfunctional by 1995. As a result, 113 wells were sampled during the 

1995–2013 period of investigation. The sampling frequency 

varied with the well, ranging from approximately every 2 

weeks in wells QC–1, QC–2, QC–2.1, and QC–2.2 from 1995 

through 2004 to more than a year between sampling events 

in some of the wells that were temporarily nonfunctional. 

The typical sampling frequency was approximately every 

2 months. The intensive sampling in wells QC–1, QC–2, 

QC–2.1, and QC–2.2 during 1995–2004 was done to monitor 

the effect of CSF events. Sample collection in the remaining wells (and after 2004 in wells QC–1, QC–2, QC–2.1, and 

QC–2.2) occurred on a fixed schedule not related to the timing 

of CSF events.

Sampling procedures followed established protocols 

(Washington and others, 1981). Sample collection began with 

measurement of the water level in the well, and the volume 

of water in the well was calculated. The well was then purged 

of one well volume. If the yield was insufficient to allow 

sampling immediately after purging, the well was allowed to 

recharge for up to 48 hours, at which time the samples were 

collected. Temperature, electrical conductivity, and pH were 

measured at the well head immediately prior to sample collection. Field samples were poured into appropriate containers and transported on ice to the laboratory where, with the 

exception of fecal coliform, the samples were filtered through 

a membrane with a 0.45-micron pore size. Aliquots were 

then poured into individual bottles containing the appropriate 

preservative. 

Samples were submitted to the Analytical Laboratories 

Division (ALD) of the MWRDGC for analysis. Ammonia 

(NH3

) and sulfate were analyzed using standard methods 

described by the U.S. Environmental Protection Agency 

(1993a, b). Chloride, total dissolved solids, fecal coliform, 

hardness, and dissolved organic carbon were analyzed using 

standard methods described by the American Public Health 

Association (2012). The ALD laboratories are certified by the 

National Environmental Laboratory Accreditation Conference 

(Pauline Lindo, MWRDGC, written commun., 2014). 

Sample results have been compiled and published annually by the MWRDGC beginning in 1994 (for the Upper 

Des Plaines System wells) or 1995 (for the Mainstream, Des 

Plaines, and Calumet System wells). MWRDGC reported 

organic carbon results as total organic carbon. Because the 

samples were filtered prior to analysis, this report describes 

these analyses as dissolved organic carbon (DOC). Paper copies of the results of the analyses performed prior to 1994 or 

1995 have been stored by the MWRDGC but have not been 

compiled or published. Published reports containing the sample results from 1995 to 2004 are available in hard copy from 

the MWRDGC. Reports containing the monitoring results during 2005–13 are available electronically from the MWRDGC 

website (http://www.mwrd.org/irj/portal/anonymous?Navigati

onTarget=navurl://3eecfe6e95b61ff28d87eedb0c778236). The 

1995‒2013 sampling results were compiled into one report 

and published by the MWRDGC (Brose and others, 2016) so 

that persons wishing to view the raw data that were analyzed 

for this investigation can more easily access the data. 
Methods of Study 13

Samples of raw water (water from a point in the distribution system prior to treatment and dispersal to the users) are 

collected by the IEPA from selected water-supply wells in Illinois and analyzed for a variety of constituents, including total 

coliform and Escherichia coli (E. coli), on a periodic basis in 

accordance with standard procedures (Illinois Environmental 

Protection Agency, 2012). The IEPA sampling is unrelated to 

the TARP System or to the TARP monitoring effort. Results 

of IEPA analysis of total coliform and E. coli in samples collected from selected water-supply wells open to the Silurian 

aquifer within 5 mi of the TARP tunnels were obtained from 

the IEPA website at http://163.191.83.31/dww/, accessed 

March 30, 2015. These data were plotted to identify the 

presence of total coliform and E. coli in the Silurian aquifer 

near the TARP System but were not subjected to the analyses 

described in the following section. 

Data Analysis

All data analyses presented in this report were performed 

by the USGS. Water-quality data were compiled from the 113 

TARP System monitoring wells sampled by the MWRDGC 

during 1995–2013. Data from seven wells were compiled but 

not analyzed because fewer than 10 samples were collected 

from those wells. Wells with fewer than 10 samples were not 

analyzed because the data are not considered to be capable 

of providing statistically significant results. Data from the 

remaining 106 wells, each of which typically had 50 to 260 

samples, were subjected to comprehensive statistical analysis 

(table 2). 

The value of every analyte in wells with 10 or more 

samples was plotted through time. Potentially anomalous 

(outlier) values were checked against the original laboratory 

sheets, and erroneously reported values were corrected. 

Anomalous values were determined by the author on the basis 

of visual assessment of the data plots. Data anomalies were 

considered to be present if the value of an analyte was at least 

a factor of two greater than its typical value in the well in 

the years preceding and succeeding the date of the potential 

anomaly or if the value did not appear to be part of a longterm temporal trend. 

Selected analytes were plotted using boxplots and normal 

and lognormal plots using graphic packages in the R statistical 

software package to assess the underlying data distribution. 

Plots for many of the analytes did not indicate a normal 

or lognormal distribution or have heterogeneous variance; 

therefore, nonparametric tests were used for the statistical 

analyses.

Summary statistics (number of samples, number of 

detections, percent detections, maximum value, minimum 

value, arithmetic mean value, geometric mean value, standard 

deviation, and coefficient of variation) were calculated for 

each analyte in each well. When calculating geometric mean, 

analytes whose values were less than the detection limit for 

a particular sample (censored values) were assigned a value 

by assuming a triangular distribution for values less than the 

detection limit (Quinn and Keogh, 2003). This technique was 

deemed preferable to assuming a distribution for the entire 

dataset as other methods would (Helsel, 2012). Analytes with 

censored values were analyzed for the arithmetic mean and 

standard deviation using the flipped Kaplan-Meier estimator 

(Helsel, 2012). Analytes with a detection frequency of less 

than 10 percent in any given well were not subjected to 

statistical analysis for that well. Analytes with a substantial 

number of samples showing values less than the detection 

limit (censored values) frequently had geometric mean, 

arithmetic mean, standard deviation, or coefficient of variation 

values reported as being within a range of values.

Multiple detection limits were utilized for chloride, 

ammonia, sulfate, and DOC samples during the 1995–2013 

period, which prevented the application of the triangular 

substitution method for these analytes for wells having results 

less than multiple detection limits. The samples for which 

analytes were not detected at the highest detection limits 

were retained for the statistical analyses using triangular 

substitution. The samples for which analytes were not detected 

at the lower detection limits were omitted. For example, 

if chloride was not detected in a sample from a well at a 

detection limit of 10 milligrams per liter (mg/L) and was not 

detected in another sample from that well at a detection limit 

of 5 mg/L, the less than (<) 10-mg/L sample was used in 

the analysis, and the <5-mg/L sample was not. The resulting 

calculated values are the maximum possible values; therefore, 

the value is reported as less than the calculated value.

Trend analysis for the 1995–2013 period was performed 

by use of Kendall’s tau correlation with Sen’s slope tests 

(Helsel and Hirsch, 2002). The magnitude of the trend is 

reported for all analytes and grouped by p-values of less 

than or equal to (≤) 0.05 or greater than (>) 0.05. Trends 

with a p-value of ≤0.05 are considered a rejection of the 

null hypothesis of the analysis that the data are statistically 

independent (the occurrence of an analyte value does not 

affect the probability of another value) to a significance level 

of at least 95 percent and, therefore, are considered to show a 

statistically significant trend.

Seasonality in the values of uncensored analytes was 

assessed by grouping the values by month and applying 

periodic functions, sine and cosine, to determine if there was 

a statistically significant variation in the values of the monthly 

data (Helsel and Hirsch, 2002). All analyses with a calculated 

p-value of ≤0.05 (those analyses rejecting the null hypothesis 

that the data are independent to a significance level of at 

least 95 percent) were plotted to determine the timing of low 

and high values. Analytes with a p-value of ≤0.05, showing 

consistent timing in high and low values that could not be 

attributed to random anomalous values and that were detected 

in the analyses of samples from at least five of the TARP 

wells, are discussed in this report.

Analyte values in samples from each well were correlated 

by use of Kendall’s tau correlation with the Akritas-Theil-Sen 

slope estimator (Helsel, 2012). Populations of fecal coliform 
14 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

in wells with a frequency of detection of 10 percent or greater 

also were correlated between wells located within each of the 

tunnel systems. Analytes with a tau-b value of 0.25 or greater 

or -0.25 or less were considered to indicate high correlation. 

Tau-b is a statistic used to measure the association between 

two measured quantities that makes adjustments for ties in the 

data, which makes this statistic useful for analyzing datasets 

with censored values (Helsel, 2012).

Hydrogeology in the Vicinity of the 

Tunnel and Reservoir Plan System

The surficial geologic deposits in most of the TARP area 

are composed primarily of unconsolidated silt- and clay-rich 

tills. These deposits typically are 25–100 ft thick and function 

as a semiconfining unit, restricting groundwater flow to the 

underlying Silurian dolomite (Kay and others, 1996; 2002). 

Northwest of the City of Chicago, the Des Plaines Disturbance (fig. 4) is present beneath the unconsolidated deposits 

(Willman, 1971; McHone and others, 1986). This feature is a 

meteorite effect crater about 5.5 mi in diameter, characterized 

by intensive faulting, surrounded by a 25-square mile (mi2) 

area of less intensive faulting. Within the most disturbed area, 

there is as much as 900 ft of vertical displacement of the bedrock. This feature intercepts small parts of the tunnel system, 

but fractures associated with the disturbance may promote 

groundwater flow and CSF migration.

The Silurian-aged dolomite bedrock surrounding the 

TARP tunnels composes the Silurian aquifer. The dolomite 

is the uppermost bedrock deposit in Cook County outside 

the Des Plaines Disturbance and is about 50–450 ft thick 

(Suter and others, 1959; Csallany and Walton, 1963). Silurian 

dolomite underlies the unconsolidated deposits in most of 

the TARP area but is at or near land surface in the vicinity of 

the Thornton and McCook Reservoirs and northwest of well 

QC–26. The Silurian dolomite also is present at or near land 

surface in the vicinity of well QC–1, near well QM–68, and 

west of well QM–51 (Willman, 1971) (figs. 3 and 4). Areas 

where the aquifer is at the land surface are more susceptible to 

anthropogenic contamination from, for example, road salts or 

septic systems than areas where the aquifer is overlain by the 

semiconfining unit (McKenna and Keefer, 1991). 

The Silurian aquifer is underlain by the Maquoketa 

Group (Willman and others, 1975) (fig. 1). The deposits of the 

Maquoketa Group are composed primarily of shale and function as a semiconfining unit that restricts downward movement 

of groundwater from the Silurian aquifer to deeper watersupply aquifers.

Groundwater flow in the Silurian aquifer is primarily 

through secondary-permeability features (joints, fractures, 

faults, solution openings) that make up less than 1 percent of 

the aquifer by volume. Lower rates of flow occur through the 

porous matrix of the aquifer, which constitutes most of the 

aquifer volume. Secondary-permeability features tend to be 

concentrated in the upper, more weathered, part of the aquifer 

but may also be present along shale beds in the deeper parts 

of the aquifer (Suter and others, 1959; Zeizel and others, 

1962; Nicholas and Healy, 1988) and near the Des Plaines 

Disturbance. Vertical faults in the Calumet area (fig. 4) and an 

irregularly distributed network of vertical fractures also are 

conduits for groundwater flow (Zeizel and others, 1962; Kiefer 

and Associates, 1976; Morse and others, 2000). The Silurian 

aquifer has an average horizontal hydraulic conductivity (Kh) 

of about 1.5 X 10-1 feet per day (ft/d) in the TARP area (Harza 

Engineering Company, 1972; Kiefer and Associates, 1976; 

Kay and others, 1996). 

Because the extent of CSF migration into the Silurian 

aquifer is likely to be greatest in areas where Kh is elevated 

above background values, the conductivity of the aquifer at 

the TARP wells was assessed by evaluating the time required 

for the water level in the well to recover to approximately 

hydrostatic levels after being purged for sampling. Recovery 

time is reported on the MWRDGC sampling sheets as being 

immediate, less than 4 hours, or less than 48 hours. For the 

purposes of this report, immediate recovery indicates the aquifer has high Kh within the open interval of the well. Recovery 

in less than 4 hours (but not immediately) indicates moderate 

Kh. Recovery in greater than 4 to less than 48 hours indicates 

low Kh. 

Using these criteria, 75 percent of the TARP monitoring 

wells (and potentially the nearby tunnel system) are open to 

parts of the aquifer with low Kh (fig. 6). High Kh is present 

in parts of the Upper Des Plaines System. Moderate Kh is 

present along much of the southern parts of the Des Plaines 

and Mainstream Systems, and along much of the 140th Street 

leg of the Calumet System. Maintaining the integrity of the 

tunnel lining in these high-to-moderate Kh areas, therefore, is 

particularly important. The high Kh in parts of the Upper Des 

Plaines System may be related to fracturing associated with 

the nearby Des Plaines Disturbance. Faulting in the Calumet 

area (figs. 4 and 6) has no apparent effect on the Kh of the 

Silurian aquifer at the Calumet System wells. 

Transport of CSF constituents through the Silurian 

aquifer is affected by the differences in water-level elevation 

between the TARP tunnels and the aquifer. Therefore, water 

levels in the TARP monitoring wells and the tunnel system 

were analyzed. These data provide substantial insight into the 

aquifer-tunnel flow dynamic.

The geometric mean value of the water levels in the 

TARP wells during 1995–2013 is spatially variable, but some 

overall patterns can be determined (fig. 7). Water levels typically were highest in the Upper Des Plaines System (above 

-50 ft CCD, or less than 50 ft below the CCD) and especially 

in the wells with high Kh. Water levels were lowest in the 

Calumet System (commonly more than -200 ft CCD). Water 

levels in the wells monitoring the Mainstream and Des Plaines 

tunnels typically were lowest (more than 150 ft below CCD) 

in the southern part of the system near the future McCook 

Reservoir. The lowest water levels are generally associated 

with the deepest parts of the Des Plaines, Mainstream, and 
Hydrogeology in the Vicinity of the Tunnel and Reservoir Plan System 15

MW-1

MW-2

MW-3

MW-4 MW-5

MW-6

MW-7

MW-8

MW-9

QD-31

QD-32

QD-33

QD-38

QD-39

QD-40

QD-41

QD-42

QD-43

QD-44

QD-45

QD-46

QD-50

QD-51

QD-52

QD-53

QD-54

QD-55

QD-56

QD-57

QD-58

QD-59

QD-60

QM-53

QM-56

QM-58

QM-59

QM-61

QM-62

QM-63

QM-64

QM-65

QM-69

QM-70

QM-71

QM-72

QM-73

QM-74

QM-75

QM-76

QM-77 QM-78

QM-79

QM-80 QM-81

QM-82

QD-21 QD-22

QD-23

QD-24

QD-25

QD-26

QD-27

QD-29

QD-28

QD-30

QD-34

QD-35

QD-36 QD-37

QD-47

QD-48

QD-49

QM-66

QM-67

QM-68

QC-1 QC-2

QC-2.1

QC-2.2

QC-3

QC-4

QC-5

QC-6

QC-7

QC-10

QC-11

QC-13 QC-12

QC-14

QC-15

QC-16

QC-17

QC-18

QC-19

QC-20

QC-21

QC-22

QC-23

QC-24

QC-25

QC-26

QC-27

QC-28

QC-29

QC-30

QC-31

QC-32

QC-33 QC-34

QC-35

QC-36

QC-37

QC-9

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

Majewski Reservoir

McCook

Reservoir

Thornton

Reservoir

Kirie Water

Reclamation

Plant

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal

leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

QD-60

Tunnel

Well location and name 

 with recharge rate

 <4 hours 

 >4 to <48 hours

 Immediate recovery

 Less than

 Greater than

 

Pumping station

<

>

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 6. Recharge rates for wells, Tunnel and Reservoir Plan (TARP) System, Cook County, Illinois.

Figure 6. Recharge rates for wells, Tunnel and Reservoir Plan (TARP) System, Cook County, Illinois.
16 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

18

40

37

-6 -47

54

15

-44

-5

-110

-32

-38

25 14

-18

-192

-131

-184

-134

-181

-156

-155

-109

-108

-117 -196

-167

-94

-68

-130

-127

-142

-15

-13

-174

-2

-69

-133

-100

-89

-58

-116

-21

-131

-52

-85

-89

-38

-110

-40

-76

-109

-168

-186

-179

-165

-191

-161

-131

-43

-72

-64

-81

-137 -25

-62 -151

-155

-116 -115

-127 -120

-171

-125 -259

-278

-227

-228

-237

-225

-218

-155

-191

-219

-205 -246 -221

-217

-191

-170

-210

-128

-271

-256

-242

-216

-206

-215

-197

-204

-227

-44

-115 -65

-119

-242

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Ave leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th St.

leg

Roosevelt

Road leg

Indiana Ave

leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel

Well location and geometric mean 

 water-level elevation, 1995−2013,

 City of Chicago datum, with

 trend indicated

 Upward

 Downward

 No trend

 Unclear

 

Pumping station

-43

-62

37

15

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 7. Geometric mean value of water levels and trends in Tunnel and Reservoir Plan (TARP) System wells, Cook County, 

Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 7. Geometric mean value of water levels and trends in Tunnel and Reservoir Plan (TARP) System wells, Cook County, Illinois, 1995-

2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
Hydrogeology in the Vicinity of the Tunnel and Reservoir Plan System 17

to a lesser degree Calumet, tunnel systems which are also 

where the Thornton and McCook Quarries are being dewatered. Dewatering occurs at about 75 gallons per minute 

(gal/min) for Thornton Quarry and 360 gal/min for McCook 

Quarry (Lakhwinder Hundal, Metropolitan Water Reclamation 

District of Greater Chicago, written commun., 2015), lowering water levels in the nearby Silurian aquifer (figs. 2 and 7). 

Dewatering of the Thornton Reservoir, and more prominently 

the future McCook Reservoir, may be lowering water levels in 

the Silurian aquifer near the downstream end of the Calumet, 

Des Plaines, and Mainstream Systems, which also could have 

enhanced movement of water from the TARP System to the 

aquifer during CSF events.

The elevation of the tunnel system affects the water level 

in the Silurian aquifer because groundwater from the aquifer 

drains into the TARP tunnels under typical (no CSF) hydraulic 

conditions. This drainage lowers water levels in the aquifer 

by an amount that is proportionate to the amount of drainage, 

the distance between the well and the location of the drainage, 

and the hydraulic properties of the aquifer in the vicinity of 

the drainage area. The normal aquifer-to-tunnel flow direction 

is indicated by the fact that geometric mean water levels are 

about 5 ft to more than 150 ft higher than the elevation of the 

top of the nearby tunnel (compare figs. 2 and 7), which typically is at least partly dewatered. 

The presence and effect of drainage from the aquifer to 

the tunnel system is demonstrated by an analysis of groundwater levels in well QC–26 (fig. 8). Water-level trends in this 

well are consistent with many of the TARP monitoring wells 

constructed during 1995‒2013 (appendix 1). Water levels in 

these recently constructed wells tend to show a large decrease 

(approximately 200 ft) in response to the initiation of drainage to recently constructed tunnels (dates of tunnel construction shown in figure 2) near the well followed by relatively 

stable water levels once approximately steady-state flow to 

the tunnel has occurred. During the period of relatively stable 

water levels, occasional high water levels were observed 

during CSF events. It is likely that a large decrease in water 

levels occurred in most or all of the TARP wells in response 

to the initiation of drainage from the aquifer to the tunnels 

during and soon after tunnel construction. Excepting the North 

Branch leg of the Mainstream System and most of the Calumet System, tunnel construction was completed prior to 1995 

(fig. 2). Therefore, the large decrease in water levels postulated for most of the TARP wells likely had already occurred 

before the beginning of the data analysis for this investigation 

(1995‒2013) and was not observed.

The spatial extent of the effect of drainage to the tunnels on water levels in the Silurian aquifer is indicated by 

analysis of water levels in monitoring wells BH7D, BH18D, 

and BH16D. These wells are not part of the TARP monitoring network and have a sporadic measurement history. The 

wells are open to the upper part of the Silurian aquifer near the 

Torrence Avenue leg of the Calumet System (fig. 4). Construction of the southern part of the Torrence Avenue leg began in 

1998, proceeded to the northern part of the leg in 1999, and 

was completed in 2002 (Kevin Fitzpatrick, Metropolitan Water 

Reclamation District of Greater Chicago, written commun., 

2015). 

Figure 8. Water levels in Tunnel and Reservoir Plan System well QC- 26, Cook County, Illinois,1999–2013.

-300

-250

-200

-150

20001999 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

-100

-50

0

Water level, in feet below City of Chicago Datum

Year

Combined sewer 

flow event

Figure 8. Water levels in Tunnel and Reservoir Plan System well QC-26, Cook County, Illinois, 1999–2013.
18 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Water levels in well BH16D differed by less than 2 ft 

from 1992 through 2014. The stable water levels at well 

BH16D, which is about 3 mi from the tunnel system (fig. 4), 

indicate this area is representative of “background” water 

levels in the Silurian aquifer and is not affected by the TARP 

System. Groundwater levels in well BH7D (the bottom of 

this well is about 240 ft directly above the top of the Torrence 

Avenue tunnel) declined from about -20 ft CCD in 1992 to -43 

ft CCD in 1993 following construction of a TARP drop shaft 

west of the well, declined from about -43 ft CCD in 1997 to 

about -55 ft CCD in 2010, and have varied by less than 2 ft 

from 2010 through 2014 (fig. 9). Water levels in well BH18D 

(about 4,700 ft east of the Torrence Avenue tunnel) were stable 

from 1992 through 1997, declined by nearly 20 ft between 

1997 and 2009, and have varied by less than 3 ft since 2009. 

The timing of the changes in the water levels at wells BH7D 

and BH18D is attributed to water drainage from the aquifer 

associated with construction and operation of the Torrence 

Avenue tunnel and indicates that water levels (and by implication flow directions) in the shallow part of the Silurian aquifer 

are substantially affected by drainage more than 4,700 ft 

from the tunnel system. The water levels in wells BH7D and 

BH18D during 2013 (fig. 9) were approximately 160 and 

215 ft, respectively, higher than the geometric mean of the 

water-level measurements from the nearest TARP monitoring wells—QC–26 and QC–20 (BH7D and BH18D shown in 

fig. 4; QC–26 and QC–20 shown in fig. 3 with their water levels in fig. 7)—further indicating the potential for flow from the 

upper part of the Silurian aquifer to the tunnels in the lower 

part of the aquifer during most or all of the 1995–2013 period.

Although groundwater typically flows from the Silurian 

aquifer to the TARP tunnels, for periods of hours to days after 

precipitation events, water pressure in the tunnels increases 

by the equivalent of tens to hundreds of feet (fig. 10) as CSF 

fills the tunnels. This transient high water pressure creates a 

substantial force that, depending on its magnitude, has the 

potential to overcome the typical aquifer-to-tunnel hydraulic 

gradient and move CSF-affected water from the tunnels into 

the surrounding Silurian aquifer.

The relation between the amount of discharge from the 

TARP System and the hydraulic potential for outflow from, 

and inflow to, the tunnels is indicated by comparison of 

-60

-50

-40

-30

-20

-10

0

Water level, in feet below 

City of Chicago Datum

Year

1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

Well BH18D

Well BH16D

Well BH7D

EXPLANATION

Figure 9. Water levels in monitoring wells BH7D, BH16D, and BH18D, Cook County, Illinois, 1992−2014.

Drop shaft construction near well BH7D in 1993. Tunnel construction beneath

well BH7D in 1998 and near well BH18D in 1999. Tunnel on line in 2002.

Figure 9. Water levels in monitoring wells BH7D, BH16D, and BH18D, Cook County, Illinois, 1992–2014.

-400

-300

-200

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

-100

0

100

200

300

2010

Des Plaines Tunnel

Calumet Tunnel System

EXPLANATION

Water pressure, in equivalent to feet relative to 

City of Chicago Datum

Figure 10. Water pressure in the 

Calumet and Des Plaines Tunnel 

Systems, Cook County, Illinois, 

January 1–December 31, 2010.
Hydrogeology in the Vicinity of the Tunnel and Reservoir Plan System 19

groundwater levels at wells QC–1, QC–2, and QC–2.2 with 

daily discharge from the TARP System to the Calumet WRP 

during 1995–96 (table 3). Water levels were measured approximately every 2 weeks in wells QC–1, QC–2, and QC–2.2 

during 1995–96. Increases in groundwater levels of about 

15 to 150 ft were observed in wells QC–1 and (or) QC–2 on 

January 25, April 19, and November 16, 1995, and May 16, 

May 30, June 13, June 27, July 25, and October 3, 1996, in 

comparison to preceding or succeeding dates. Groundwater 

levels in well QC–2.2 were higher on November 16, 1995, 

and June 13, 1996, in comparison to preceding and succeeding dates. These increases typically occurred during or shortly 

after periods of discharge from the TARP System to the 

Calumet WRP of greater than about 80 million gallons per day 

(Mgal/d), indicating that a large, short-term, pressure gradient 

affected the flow regime in the aquifer on or near these dates. 

This pressure gradient may have driven CSF water from the 

tunnels into the Silurian aquifer. The high groundwater level 

in the wells typically dissipated over a period of 2–4 weeks, 

with most of the dissipation occurring within 2 weeks. Periods 

of elevated TARP discharge to the WRPs were associated with 

most, but not all, increases in groundwater levels, indicating 

that some of these discharge events were not CSF related but 

may have been discharge of water derived from drainage from 

the aquifer to the tunnels.

From 1995 through 2013, water levels in the TARP System monitoring wells varied by more than 60 ft in 83 wells, 

by 20 to 60 ft in 21 wells, and by less than 20 ft in 2 wells 

(appendix 1). Data from non-TARP monitoring well BH16D 

indicates that background groundwater levels in the Silurian 

aquifer varied by about 2 ft during the study period. These 

variations indicate that nearly every well in the TARP System 

responded to CSF-induced pressure gradients that may have 

at least occasionally been sufficient to overcome the typical 

aquifer-to-tunnel hydraulic gradient and induce flow from the 

TARP System into the Silurian aquifer.

Some indication of the change in the aquifer-to-tunnel 

flow pattern was obtained from analysis of temporal trends 

in groundwater levels during 1995–2013. Trend analysis 

indicates that 91 wells (about 86 percent of the 106 wells 

analyzed) showed a statistically significant trend. Of those 91 

wells, groundwater levels decreased in 51 and increased in 39; 

no trend was indicated in 1 (fig. 7). A statistically significant 

trend was not observed in 15 wells. These wells are considered 

to show an unclear trend. 

Table 3. Groundwater levels and fecal coliform populations at wells QC–1, QC–2, and QC–2.2 and discharge to the Calumet Water 

Reclamation Plant, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–1996.—Continued

[<, less than; ns, no sample collected; underline denotes period of elevated water level or discharge, as well as initial elevation of fecal coliform population]

QC–1 QC–1 QC–2 QC–2 QC–2.2 QC–2.2

Sampling date 

(month/day/

year)

Groundwater 

level 

(feet from 

City of Chicago 

datum)

Fecal coliform 

(colony 

forming 

units per 

100 milliliter)

Groundwater 

level 

(feet from 

City of Chicago 

datum)

Fecal coliform 

(colony 

forming 

units per 

100 milliliter)

Groundwater 

level 

(feet from 

City of Chicago 

datum)

Fecal coliform 

(colony 

forming 

units per 

100 milliliter)

Discharge from Tunnel 

and Reservoir Plan 

system to Calumet 

Water Reclamation 

Plant (million 

gallons per day)

1/11/1995 -121 <1 -260 15 ns ns 1

1/25/1995 -94 <1 -137 500 ns ns 99

2/9/1995 -117 <1 -252 60 -180 <1 10

2/23/1995 -122 <1 -264 <1 -261 14 8

3/9/1995 -121 <1 -260 <1 -218 <1 41

3/23/1995 -122 <1 -261 <1 -210 <1 11

4/6/1995 -122 <1 -265 <1 -219 <1 12

4/19/1995 -107 <1 -206 3,600 -212 <1 87

5/4/1995 -119 <1 -252 1,200 -205 <1 42

5/18/1995 -120 <1 -260 150 -212 <1 20

6/1/1995 -121 <1 -260 <1 -215 <1 106

6/15/1995 -120 <1 -262 3 -214 <1 8

6/29/1995 -120 <1 -264 <1 -214 <1 95

7/13/1995 -121 <1 -264 <1 -217 <1 2

7/27/1995 -122 <1 -259 <1 -224 <1 20

8/10/1995 -122 <1 -263 <1 -220 <1 18
20 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Table 3. Groundwater levels and fecal coliform populations at wells QC–1, QC–2, and QC–2.2 and discharge to the Calumet Water 

Reclamation Plant, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–1996.—Continued

[<, less than; ns, no sample collected; underline denotes period of elevated water level or discharge, as well as initial elevation of fecal coliform population]

QC–1 QC–1 QC–2 QC–2 QC–2.2 QC–2.2

Sampling date 

(month/day/

year)

Groundwater 

level 

(feet from 

City of Chicago 

datum)

Fecal coliform 

(colony 

forming 

units per 

100 milliliter)

Groundwater 

level 

(feet from 

City of Chicago 

datum)

Fecal coliform 

(colony 

forming 

units per 

100 milliliter)

Groundwater 

level 

(feet from 

City of Chicago 

datum)

Fecal coliform 

(colony 

forming 

units per 

100 milliliter)

Discharge from Tunnel 

and Reservoir Plan 

system to Calumet 

Water Reclamation 

Plant (million 

gallons per day)

8/24/1995 -121 <1 -264 <1 -221 <1 12

9/7/1995 -122 <1 -266 <1 -224 <1 1

9/21/1995 -118 <1 -266 <1 -225 <1 4

10/5/1995 -122 <1 -265 <1 -228 <1 4

10/19/1995 -124 <1 -266 <1 -281 <1 9

11/2/1995 -122 <1 -266 <1 -231 <1 22

11/16/1995 -98 <1 -159 <1 -201 <1 81

11/30/1995 -119 <1 -252 750 -218 <1 11

12/14/1995 -122 <1 -262 38 -231 <1 1

12/28/1995 -122 <1 -266 3 -228 <1 4

1/11/1996 -123 <1 -267 <1 -227 <1 8

1/25/1996 -122 <1 -270 <1 -232 <1 9

2/7/1996 -122 <1 -271 <1 ns ns 26

2/22/1996 -122 <1 -269 <1 -240 <1 2

3/7/1996 -122 <1 -272 <1 -244 <1 18

3/21/1996 -122 <1 -271 <1 -247 <1 11

4/4/1996 -122 <1 -275 <1 -240 <1 6

4/18/1996 -122 <1 -273 <1 -248 <1 15

5/2/1996 -122 <1 -273 <1 -248 <1 64

5/16/1996 -248 <1 -108 4,000 -248 <1 94

5/30/1996 -120 <1 -254 8,500 -240 <1 3

6/13/1996 -108 <1 -234 <1 -225 1,100 111

6/27/1996 -111 <1 -229 2,000 -247 <1 20*

7/11/1996 -119 <1 -255 260 -238 <1 18

7/25/1996 -90 <1 -102 3,600 ns ns 80

8/8/1996 -111 <1 -230 3,100 -204 <1 65

8/22/1996 -119 <1 -258 210 -249 <1 12

9/5/1996 -121 <1 -260 19 -246 <1 43

9/19/1996 -121 <1 -266 2 -235 <1 9

10/3/1996 -188 <1 -235 2,600 ns ns 21**

10/17/1996 -122 <1 -262 300 ns ns 31

10/31/1996 -123 <1 -266 68 ns ns 13

11/14/1996 -122 <1 -268 4 ns ns 20

11/27/1996 -123 <1 -272 <1 ns ns 7

12/12/1996 -123 <1 -272 <1 ns ns 43

12/26/1996 -123 <1 -277 <1 ns ns 41

*

Discharge greater than 95 million gallons per day on June 22, 23, and 24, 1996.

**Discharge 77 million gallons per day on September 29, 1996.
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 21

Water Quality in Tunnel and Reservoir 

Plan System Monitoring Wells

Water levels in the monitoring wells near the TARP 

System indicate that CSF in the tunnel systems migrates into 

the Silurian aquifer on an intermittent basis lasting less than 

2–4 weeks during periods of at least 80 Mgal/d discharge into 

the TARP System. However, water typically drains from the 

aquifer to the tunnels throughout the TARP System so that any 

CSF-affected water typically would be flushed from the aquifer back into the tunnels. Therefore, water quality at any TARP 

well is likely to reflect the water quality of the Silurian aquifer 

within the drainage area to that well with potential intermittent influxes of CSF-derived water. The amount of CSF water 

entering the aquifer, and the changes in water quality it produces, will likely depend on a number of factors, including 

• The location of exfiltration points in the tunnel. The 

greater the distance between the well and the point 

of leakage from the tunnel, the less likely analytes 

derived from CSF would be present, the lower the concentrations of those analytes would be, and the shorter 

the period the analyte would be present.

• The hydraulic gradient between the tunnel and the 

aquifer near the monitoring well. The smaller the difference between the water level in the monitoring well 

and the hydraulic pressure in the tunnel, the more readily the typical aquifer-to-tunnel flow direction can be 

reversed and the larger the amount of CSF migration 

into the aquifer.

• The hydraulic properties of the Silurian aquifer 

between the tunnel and the monitoring wells. The 

lower the Kh of the aquifer material, the shorter the 

distance CSF could migrate into the aquifer and the 

smaller the volume of water moving from the aquifer 

to the tunnels to flush out CSF-affected water. 

• Water quality of the CSF water and in the Silurian 

aquifer within the drainage area to the tunnels. Spatial 

variation of water quality within the part of the aquifer 

draining to the tunnel monitored by a well or a large 

difference between the values of an analyte in groundwater and CSF could result in substantial temporal 

variation in the water quality of the samples collected 

from the TARP wells. This variation could have shortterm (1–4 weeks), long-term (1995–2013), or seasonal 

aspects. 

• The magnitude and duration of the CSF event within 

the TARP Systems. CSF discharge to the Silurian aquifer likely was maximized by long or frequent periods 

of high hydraulic pressure in the tunnels. A minimum 

TARP discharge and associated high hydraulic pressure 

in the tunnel system appears to be required to reverse 

the typical aquifer-to-tunnel flow direction. CSF was 

likely to be present longer, and under higher hydraulic pressure, in the downstream parts of the tunnel 

systems, especially the Des Plaines and Mainstream 

Systems, potentially resulting in increased CSF flow 

into the aquifer in these areas.

These factors were considered when the water-quality 

data were analyzed and provided a context for assessing the 

processes affecting water quality and the timing of the effects. 

The basis for these assessments is provided in the appendixes. 

Summary statistics for the individual analytes in each well 

are presented in appendix 1. Analysis of temporal trends in 

the values of each analyte in each well is presented in appendix 2. Results of analyses of seasonality in analyte values are 

presented in appendix 3. Kendall’s tau correlation coefficients 

are listed in appendix 4. 

Temperature

The water temperature in the Silurian aquifer should 

be similar to the mean atmospheric temperature of about 

10.5 degrees Celsius (°C) and is likely to vary by less than 

0.5 °C on an annual basis (Suter and others, 1959; Bundschuh, 

1993). The temperature of the CSF water discharged from the 

TARP System was not measured but is likely to have approximated the range of temperature in rain or snowmelt, from near 

0 °C to more than 30 °C (Harmeson and Schnepper, 1965). 

Abnormally high, low, or variable temperatures in groundwater from the TARP monitoring wells could indicate the presence of CSF-affected water in the aquifer. 

The temperature of the samples from the TARP monitoring wells from 1995 through 2013 ranged from 4.1 to 

25 °C, with the range in a given well typically exceeding 

8 °C (appendix 1). Temperature measurements of 8.0 °C or 

less typically were measured during the fall, winter, and early 

spring. Temperature measurements of 20.0 °C or greater typically were measured during the summer. 

Temperature values measured during sampling of well 

QC–2 were analyzed to assess the sources of temperature 

variation in the TARP samples. Temperature values varied by 

more than 5 °C in a year and showed a cyclic pattern of highs 

during the summer and lows during the winter (fig. 11). These 

variations were too large to be natural and were too consistent 

in their timing to be caused by CSF migration from the TARP 

System into the Silurian aquifer, indicating the readings were 

affected by interaction with atmospheric temperature during 

sampling.

Analysis of seasonality in temperature readings indicates that groundwater samples from every TARP monitoring 

well had high temperatures in summer and low in winter to 

a significance level of at least 95 percent (appendix 3). This 

analysis indicates that reported groundwater temperatures for 

every sample were affected by the atmospheric temperature at 

the time of sampling and were not an accurate measurement 

of groundwater temperatures in the Silurian aquifer. Further 

analysis of these data provides no meaningful insights into 
22 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Figure 11. Temperature of groundwater samples from Calumet System well QC-2, Cook County, Illinois, 1995–2004.

0.0

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

Temperature, in degrees Celsius

Year

Figure 11. Temperature of groundwater in samples from Calumet System well QC-2, Cook County, Illinois, 1995–2004.

conditions in the CSF or the aquifer and was not attempted. 

Accurate measurement of groundwater temperature within 

the open interval of the wells on a continuous basis could be 

a useful indicator of the timing and presence of CSF-affected 

water in the aquifer. 

Fecal Coliform

Fecal coliform (FC) is a bacterium that typically 

originates in the intestines of warm-blooded animals and is 

excreted in feces. Although generally not harmful in itself, 

these bacteria can indicate the presence of disease causing 

bacteria, viruses, and protozoans in the sample. FC is not naturally occurring in the Silurian aquifer, making it the only analyte among those sampled whose presence in samples from the 

TARP wells can be attributed solely to anthropogenic sources. 

FC detection is an unambiguous indication of the presence of 

CSF-affected water in a well on a particular sampling date. 

However, the absence of FC does not necessarily prove the 

absence of CSF-affected water.

FC was not detected in samples from 31 of the 106 

TARP monitoring wells analyzed (appendix 1), was detected 

in 1–2 percent of the samples in 19 wells, was detected in 

10 percent or more of the samples collected from 23 monitoring wells, and was detected in more than 50 percent of the 

samples collected from 3 wells (fig. 12). FC was detected in 

fewer than 10 percent of the samples from nearly 80 percent 

of the wells. Because of the lack of detections, a meaningful 

discussion of the spatial patterns in the geometric mean FC 

populations was not possible. This discussion focuses on spatial patterns in the frequency of detection and the maximum 

FC populations during 1995–2013. 

Wells in which FC was detected in 2 percent or less of 

the samples are scattered throughout the TARP System but 

tend to be located in the Mainstream System north of well 

QM–58 (fig. 3), in much of the northern and central parts 

of the Des Plaines System, and along the Torrence Avenue 

and 140th Street legs of the Calumet System. Wells in which 

FC was detected in 10 percent or more of the samples tend 

to be located in the middle of the North Branch leg of the 

Mainstream System, in most of the Mainstream System 

near the Sanitary and Ship Canal from well QM–68 to the 

future McCook Reservoir, in the northern part of the Upper 

Des Plaines System, in much of the southern part of the Des 

Plaines System, and at wells QC–2, QC–4, and QC–17 in the 

Calumet System (fig. 12). Wells in which FC was detected in 

10 percent or more of the samples tended to have high or moderate Kh, particularly outside the Calumet System (figs. 6 and 

12). The percentage of FC detections also tended to be highest 

in the downstream parts of the Des Plaines, Mainstream, 

and Calumet Systems, most likely because of the increased 

hydraulic pressure and residence time of CSF in these parts of 

the tunnel systems.

Samples with maximum FC populations greater than 

1,000 colony forming units per 100 milliliters (CFU/100 mL) 

were present in wells along the Sanitary and Ship Canal from 

well QM–68 to the future McCook Reservoir, in wells QM–75 

and QM–77 in the North Leg of the Mainstream System, in 

much of the southern part of the Des Plaines System, in the 

middle part of the Upper Des Plaines System, and near the 

confluence of the Indiana Avenue and Cal-Sag legs of the 

Calumet System at wells QC–2, QC–2.2, and QC–9 (fig. 13; 

appendix 1). Populations of FC greater than 100 CFU/100 mL 

were present in samples from wells QM–69 and QM–81 

on the North leg of the Mainstream System; wells QD–52, 

QD–53, and QD–54 in the Des Plaines System; and well 

QC–3 near the Thornton Reservoir.

FC populations in samples from the TARP monitoring wells typically were less than the detection limit of 

1 CFU/100 mL. When FC was detected in a well, it tended to 
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 23

Figure 12. Percentage of samples in which fecal coliform was detected, and trends in population in Tunnel and Reservoir Plan (TARP) 

System monitoring wells, Cook County, Illinois, 1995-2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.

5

4

4

6

22

19

17

31

7

0

0 4

0 4

3

15

17

10

30

8

7

1

11

11

1

0

0

0

4

0

5

2

4 0

4

7

1

1

2

4

2

1

0

3

0

0

0

0

3

0

33

54

36

48

26

81

32

3

7

2

1

2

2

24

8 29

4

1 3 2

0

1

9

6

63

9

22

0

5

0

4 0

0

4

0 0 0

1 1 2

15

4

2

0

0

0

0

0

0

0

0

7

5

0

1

14

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel —Colors indicate legs

 of tunnel systems

Well location and percentage

 of samples with fecal coliform

 detections, with trend indicated

 Upward

 Downward

 Unclear

 Insufficient detections for

 trend analysis

19

17

22

3

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 12. Percentage of samples in which fecal coliform was detected, and trends in population in Tunnel and Reservoir Plan (TARP) 

System monitoring wells, Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or

equal to 0.05.
24 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

11

39

24

1,700 4

480

6,000

3,700

6

87

<1 <1

<1 48

25

260

1

2,200 1,000

360

3,300

7,600

1

290

7

37

<1

<1

<1

1

<1

230

2

170 13 <1

1

6

840

920

3,700

6

<1

7

<1

<1

<1

<1

1

<1

>20,000

>20,000

720,000

>20,000

8,700

6,600

2,300

460

5

1

1

1

2

2,600 19 8,700

15

6 760

<1

<1

7

1,100

28,000

84

220

96

<1

8

<1

5,800 <1

<1

15

<1 <1 <1

1 1 5

51

1

1

<1

<1

<1

<1

<1

<1

<1

<1

49

9

<1

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

460

Tunnel

Well location and maximum

 population of fecal coliform,

 in colony forming units per 

 100 milliliters. <1, below limit 

 of detection

 Less than (<) 1

 1 to 20

 21 to 100

 101 to 1,000

 Greater than 1,000

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 13. Maximum population of fecal coliform detected in samples from in Tunnel and Reservoir Plan (TARP) System monitoring wells, 

Cook County, Illinois, 1995−2013.

Figure 13. Maximum population of fecal coliform detected in samples from Tunnel and Reservoir Plan (TARP) System monitoring wells, 

Cook County, Illinois, 1995–2013.
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 25

be at a relatively large population that would decrease with 

time, eventually returning to non-detect. These trends are 

consistent with the effects of the intermittent movement of 

FC-containing CSF from the TARP tunnels into the Silurian 

aquifer followed by the typical flow of FC-free aquifer water 

into the tunnels flushing CSF-affected water from the aquifer.

The relation between FC populations and outflow from, 

and inflow to, the TARP tunnels is supported by comparison 

of FC populations and groundwater levels during the period 

of intensive data collection in 1995 and 1996 at wells QC–1, 

QC–2, and QC–2.2 (table 3). FC was not detected in well 

QC–1 during this time period, but large (15–25 ft) increases 

in the groundwater level were periodically observed during 

periods of elevated discharge from the TARP. FC was detected 

23 times in well QC–2 during 1995 and 1996. The initial 

detections of FC in well QC–2 occurred during or shortly after 

periods of increased groundwater levels (often in excess of 

100 ft) associated with increased TARP discharge. FC populations in well QC–2 would then decrease through time, often 

increasing when another high-discharge event occurred. FC 

was detected twice in well QC–2.2 during 1995 and 1996, 

both times within 1 month of the occurrence of large (about 15 

to 80 ft) increases in water level and TARP discharge exceeding 95 Mgal/d. 

Trends in FC populations at well QC–2 indicate that FC 

had migrated more than 200 ft (the distance from the tunnel to the monitoring well) into the Silurian aquifer within 

1–2 weeks of discharge from the TARP tunnels in excess of 

about 80 Mgal/d (table 3; fig. 14A, B, F). FC populations then 

decreased to less than the detection limit (typically) within 

4–6 weeks (fig. 14A, B, C, F). Fecal coliform populations 

were below the detection limit during prolonged periods when 

TARP discharge was less than 60 Mgal/d (fig. 14C, D, E), as 

well as during sustained periods of discharge from the TARP 

tunnels in excess of 100 Mgal/d during parts of May, June, 

and November (fig. 14C, F). Periods of high discharge from 

the TARP to the WRPs in late May, June, and early November 

that were not associated with elevated FC populations may 

have resulted from the removal of water that drained from 

the aquifer to the tunnels rather than CSF events. The relation between trends in FC populations, groundwater levels 

(low and high), and flow directions to and from the aquifer 

observed at well QC–2 are consistent with that of other wells, 

accounting for differences in the frequency of sample collection. The processes that affect FC populations also are likely 

to affect the values of other analytes. However, not all analytes 

can be expected to behave identically. For example, elevated 

groundwater levels associated with CSF events dissipate 

quickly in comparison to elevated FC populations associated 

with the same event.

Analysis of trends in FC populations from 1995 through 

2013 was restricted to the 23 wells in which FC was detected 

in at least 10 percent of the samples. Of these wells 8 showed 

an upward trend, 3 showed a downward trend, and 12 did 

not indicate a statistically significant trend (trend unclear) 

(fig. 12). Because CSF is the only source of FC to these wells, 

all of these trends (upward, downward, no trend) are a reflection of the number of times CSF-affected water was sampled 

in the TARP wells each year from 1995 through 2013. 

FC populations were correlated between each well in 

a given tunnel system in which FC was detected in at least 

10 percent of the samples (table 4). From a total of 68 correlations, 57 were highly positively correlated (tau-b greater than 

0.24; appendix 4). These correlations indicate that, at least 

within that part of the TARP System, trends in FC populations 

through time were similar between wells. Correlations indicate 

that a representative assessment of FC populations in the monitoring wells associated with the various tunnel systems can be 

obtained by sampling an appropriate subset of the wells.

Hardness

Hardness (measured as calcium carbonate [CaCO3]) is the 

measure of the concentration of dissolved calcium and magnesium in a sample, along with smaller amounts of divalent 

cation complexes associated with iron, manganese, aluminum, 

and some other compounds. Hardness measured in samples 

collected from water-supply wells open to the chemically 

associated glacial drift and Silurian aquifer throughout Cook 

County between about 1900 and 1958 ranged from less than 

100 to more than 1,000 mg/L as CaCO3 and decreased overall 

from west to east (fig. 15) (Hanson and others, 1943; Suter and 

others, 1959). The highest hardness values were detected in 

groundwater samples collected near what is now the southern 

part of the Des Plaines System in the general area where the 

Silurian aquifer is at or near land surface (fig. 4). These samples were collected prior to construction of the TARP System 

from wells that are not part of the TARP monitoring network. 

These data indicate that hardness values in the Silurian aquifer 

in Cook County, which includes the area of the TARP System, 

are spatially variable.

Hardness values through time were analyzed in groundwater samples collected from wells open to the Silurian 

aquifer that are not part of the TARP monitoring network at 

LaGrange in Cook County, Libertyville in Lake County, and 

Naperville in DuPage County (locations shown in fig. 15) 

(Gibb and O’Hearn, 1980). Hardness values were determined to have remained stable through time at LaGrange but 

increased through time at Libertyville and Naperville. Hardness values at Naperville and Libertyville began to increase 

from about 1968 to 1970, prior to construction of the TARP 

System. These data indicate that the hardness values in the 

Silurian aquifer within the greater Chicago area may be 

affected by non-TARP natural and anthropogenic processes.

The geometric mean values of hardness in the samples 

from the TARP monitoring wells during 1995–2013 ranged 

from 5 to 854 mg/L as CaCO3

 (fig. 16). Wells with a geometric mean hardness of less than 50 mg/L as CaCO3

 are located 

in much of the central part of the Des Plaines System, in the 
26 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Figure 14. Tunnel and Reservoir Plan (TARP) System discharge to the Calumet Water Reclamation Plant, and fecal coliform populations 

in well QC-2, Cook County, Illinois, 1995: A, January–February, B, March–April, C, May–June, D, July–August, E, September–October,

and F, November–December. Note variation in scale of fecal coliform population between plots.

Discharge

Fecal 

0 0

0

100

200

300

400

500

600

0

20

40

60

80

100

120

140

Discharge, in million gallons per day

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

20

40

60

80

100

120

140

200

400

600

800

1,000

1,200

1,400

Fecal coliform, in colony forming units per 100 millimeters 

0.00

0.20

0.40

0.60

0.80

1.00

0.00

0.20

0.40

0.60

0.80

1.00

1995

0

100

200

300

400

500

600

700

800

1995

September October November December

January

May

March

July

February

June

April

August

A B

C D

E F

0 0

20

40

60

80

100

120

140

20

40

60

80

100

120

140

0 0

20

40

60

80

100

120

140

20

40

60

80

100

120

140

Figure 14. Tunnel and Reservoir Plan System discharge to the Calumet Water Reclamation Plant, and fecal coliform populations in 

well QC–2, Cook County, Illinois, 1995. A, January–February, B, March–April, C, May–June, D, July–August, E, September–October, 

and F, November–December. Note variation in scale of fecal coliform population between plots.
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 27

Table 4. Correlation coefficients of fecal coliform populations in monitoring wells with a frequency of fecal coliform detection of 10 

percent or greater, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold indicates tau-b greater than 0.24; —, not applicable]

Correlation coefficients—Fecal coliform populations in Upper Des Plaines system wells using Kendall’s tau with slope estimator

Well MW–5 MW–6 MW–7

MW–6 0.21 — — — — — — —

MW–7 0.34 0.36 — — — — — —

MW–8 0.41 0.27 0.30 — — — — —

Correlation coefficients—Fecal coliform populations in Calumet system wells using Kendall’s tau with slope estimator

Well QC–2 QC–4

QC–4 0.53 — — — — — — —

QC–17 0.30 -0.11 — — — — — —

Correlation coefficients—Fecal coliform populations in Mainstream system wells using Kendall’s tau with slope estimator

Well QM–61 QM–62 QM–63 QM–64 QM–65 QM–67 QM–68 QM–75

QM–62 0.70 — — — — — — —

QM–63 0.76 0.79 — — — — — —

QM–64 0.65 0.60 0.56 — — — — —

QM–65 0.27 0.49 0.58 0.17 — — — —

QM–67 0.29 0.34 0.29 0.17 0.12 — —

QM–68 0.83 0.56 0.69 0.44 0.72 0.31 — —

QM–75 0.35 0.65 0.54 0.49 0.08 0.14 0.68 —

QM–77 0.27 0.25 0.43 0.43 0.31 0.17 0.55 0.70

Correlation coefficients—Fecal coliform populations in Des Plaines system wells using Kendall’s tau with slope estimator

Well QD–27 QD–29 QD–30 QD–31 QD–34 QD–36

QD–29 0.49 — — — — — — —

QD–30 0.19 0.25 — — — — — —

QD–31 0.55 0.48 0.49 — — — — —

QD–34 0.75 0.59 0.72 0.57 — — — —

QD–36 0.65 0.41 0.24 0.56 0.35 — —

QD–46 0.24 0.37 0.38 0.66 0.72 0.37 — —
28 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

0 5 10 MILES

0 5 10 KILOMETERS

TARP tunnel locations from Metropolitan Water

Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

ILLINOIS

INDIANA

COOK COUNTY

DU PAGE COUNTY

DU PAGE COUNTY

WILL COUNTY

COOK COUNTY

WILL COUNTY

LAKE COUNTY

COOK COUNTY

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

Middle leg

West

leg

Torrence

Avenue leg

Cal-Sag leg

Little Cal

leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

South

leg

McCook

Reservoir

Stickney Water

Reclamation

Plant

Thornton

Reservoir

Calumet Water

Reclamation

Plant

Majewski Reservoir

Kirie Water Reclamation Plant

Naperville

La Grange

Libertyville

(approximately

8 miles north)

LAKE

MICHIGAN

EXPLANATION

Hardness of water, in

 milligrams per liter

 calcium carbonate

 Less than 100

 100 to 300

 300 to 600

 600 to 1,000

 Greater than 1,000

Tunnel

Pumping station

88° 87°

42°

41°40'

Figure 15. Hardness of water in samples from shallow drift and Silurian aquifers in Cook County, Illinois. (Modified from

figure 47 in Suter and others, 1959)

Figure 15. Hardness of water in samples from shallow drift and Silurian aquifers in Cook County, Illinois (Modified from 

figure 47 in Suter and others, 1959).
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 29

439

462

433

558 319

391

526

345

392

790

779

790

565

655

443

508

659

715

747

317

33

27

780

746

854

403

244

23

22

398

417

464

268

95

93 237

309 292

7.8

5

18

8

40

168

48

38

121

283

260

138

120

283

146

170

760 228

576

425

174

170 156

204

221

146

96

63

47 43 11 11 21 27

13

543 94

61

44

64

11

9

23

13

61

12

21

155 39

73

14

76

160

119 9

22

16

27

6

12

17

7.3

26

16

222

59

230

17

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel—Colors indicate legs

 of tunnel systems

Geometric mean concentration

 of hardness, in milligrams per

 liter as calcium carbonate, 

 with trend indicated

 Upward

 Downward

 No trend

 Unclear

170

146

27

11

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 16. Geometric mean concentrations of hardness and trends in concentration in samples from Tunnel and Reservoir Plan (TARP) 

System wells, Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 16. Geometric mean concentrations of hardness and trends in concentration in samples from Tunnel and Reservoir Plan (TARP) 

System wells, Cook County, Illinois, 1995–2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
30 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

southern part of the North Branch of the Mainstream System, 

and in much of the eastern part of the Calumet System. Wells 

with a geometric mean hardness of greater than 300 mg/L as 

CaCO3 are located in most of the southern (downstream) part 

of the Des Plaines and Mainstream Systems, at well QC–1 in 

the western edge of the Calumet System, and throughout the 

Upper Des Plaines System. Spatial patterns in hardness values 

in samples from the TARP monitoring wells are generally consistent with the patterns of hardness measured in the glacial 

drift and Silurian deposits in Cook County prior to construction of the TARP System (fig. 15), indicating that the hardness 

values in the TARP wells are affected primarily by the hardness values within the nearby Silurian aquifer. This result was 

expected because, for fixed-schedule sampling events, most 

of the samples are collected during typical (aquifer to tunnel) 

flow conditions that reflect the chemistry of the aquifer water 

rather than the intermittent CSF discharge.

Hardness values for the TARP discharge were not 

measured, so the effect of CSF on hardness values in samples 

from the TARP monitoring wells is unknown. However, 

anomalously low hardness values were measured in samples 

from six wells in the Des Plaines (QD–26, QD–27, QD–38) 

and Calumet Systems (QC–1, QC–2, QC–2.1) on June 25, 

1998 (table 5). TARP discharge measured at the Stickney 

WRP exceeded 100 Mgal/d five times (and exceeded 300 

Mgal/d three times) from June 11 to June 25, 1998, indicating 

that CSF discharge to the Silurian aquifer may have occurred 

during this period and caused the lower hardness. Anomalous 

hardness values were detected in approximately 118 samples 

(42 with low values) from the 106 monitoring wells analyzed 

for this investigation. Of these samples, 54 were associated 

with the detection of anomalous values of other analytes, 

particularly chloride and TDS, including six dates when 

elevated FC populations were present (table 5). The presence 

of anomalous values of multiple analytes in a sample, 

especially FC, tends to indicate the anomalous values are 

the result of CSF migration to the well. Anomalous hardness 

values were not detected in more than five samples from any 

well. This result was expected because, for fixed-schedule 

sampling events, only a minority of the samples are collected 

during atypical (tunnel to aquifer) flow conditions that reflect 

the transient effect of CSF in the aquifer.

Of the 72 wells whose samples exhibited a statistically 

significant trend in hardness from 1995 through 2013, 47 

showed a downward trend, 24 showed an upward trend, and 

1 had stable values (fig. 16). Trends in the remaining 34 wells 

had a significance level of less than 95 percent, indicating no 

clear trend. Wells in the Upper Des Plaines and Des Plaines 

Systems, as well as the northern part of the North Branch leg 

of the Mainstream System and the central part of the Calumet 

System, tended to have downward trends in hardness. Upward 

trends were prevalent in the central part of the Mainstream 

System and in the Calumet System at the Torrence Avenue, 

140th Street, and Little Cal legs. Many of the wells with 

upward trends had geometric mean hardness values of less 

than 30 mg/L as CaCO3

. These data do not clearly indicate a 

cause for the hardness trends, but tend to indicate that trends 

are primarily due to the drainage of water from the aquifer 

through time with spatially variable (higher, lower, and 

consistent) hardness values. For example, the hardness value 

in water from the Silurian aquifer at a well in 1995 may have 

had a value of 50 mg/L as CaCO3, but the hardness value in 

that part of the aquifer 500 ft from the well that drains to the 

well may have had a value of 100 mg/L as CaCO3. Because 

aquifer water drains to the TARP System, the 50 mg/L water 

present in 1995 would eventually be replaced by the 100 mg/L 

water, resulting in an upward trend in hardness. These patterns 

differ from the short-term water-quality effects associated 

with individual CSF events because the hardness in the 

aquifer water draining to the monitoring well would not vary 

appreciably during the short period associated with the CSF 

event.
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 31

Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued[Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in 

at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date]

Well

(number of 

samples)

Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon 

MW–1 (98) 01/26/2012

07/10/201305/23/2013

— 10/17/2012 12/01/2011

—

—

— 08/28/2003 06/11/2009 08/16/2012

MW–2 (73) 02/10/2009

— 06/12/2002 02/14/2001

09/17/2008

— 08/27/1997

— 06/19/2000

—

—

MW–3 (119) 01/26/2012 06/12/1997

— 06/13/2002

08/15/200209/22/2011

— 08/15/2002

— 02/18/1999

02/09/2006

06/11/2009 08/16/2012

MW–4 (113) 08/18/1999

05/23/2013

04/07/94

—

—

— 08/18/2005

— 10/08/1998 11/19/2008 08/16/2012

MW–5 (96) 02/27/1997

03/15/2007

—

— 06/13/2002 

08/09/2007

—

—

— 06/26/1996 03/15/2007

06/11/2009

—

MW–6 (117) 08/28/2002

—

— 10/04/2001 

08/28/200210/04/2006 09/13/2007 05/25/200908/19/2011 06/19/2013

—

— 06/13/2007 02/14/1995

12/12/2001

10/20/201101/19/2012

08/13/1997

MW–7 (86) 02/09/2010 10/02/2002

04/23/2003

— 04/27/2000

10/02/200106/12/200212/10/200309/11/200709/17/200807/27/201106/27/201204/29/2013

—

—

— 10/12/2006 06/28/2006 04/27/2000

06/19/2000

MW–8 (85) 02/22/2001

02/25/2009

—

— 10/04/2000

10/02/200110/03/200210/30/200309/14/200609/11/200808/12/201008/28/2013

12/05/200103/29/2007

—

— 08/19/2004

12/15/2005

06/11/2009 08/19/2004
32 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued [Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date] Well (number of samples) Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon MW–9 (90) 11/17/2005 03/29/2007 02/25/2009 06/11/2009 06/20/2013

—

— 06/06/2002 

08/15/200207/20/2006

—

—

— 12/15/2005 06/11/2009

—

QD–21 (87) 11/28/2006 12/13/2000

—

—

—

—

—

—

— 02/05/1997

08/20/1997

QD–22 (91)

— 12/13/2000

— 02/15/2012

06/20/201212/18/2012

— 04/14/1999 08/24/2005 06/03/1998

08/16/2006

—

—

QD–23 (91) 02/24/2000

03/28/2012

—

—

— 06/24/2010

—

— 04/05/1995

08/16/2006

—

—

QD–24 (91) 07/08/2010

06/26/2013

04/17/2000 04/08/2013 06/11/2002 07/08/2010 06/11/1997

08/05/1998

02/06/2002 08/16/2006 06/11/1997

08/05/1998

04/17/2000

QD–25 (89) 02/24/2000

10/14/200403/28/201204/08/2013

07/08/201007/07/201102/16/201203/28/2012

—

— 10/14/2004 08/20/2003

02/13/2008

— 08/16/2006 08/30/1995

02/26/2004

08/20/1997

QD–26 (87) 08/09/2001

10/04/200102/13/200302/05/200411/08/2007

—

— 08/14/2008

07/05/2012

06/25/199806/07/2001

10/04/200111/08/2007

— 04/01/2004 10/04/2001 10/04/2001

11/08/2007

QD–27 (114)

— 12/16/1999

06/03/200405/26/2011

— 02/27/1997

08/21/199706/05/2003 02/17/200510/02/2008 06/06/2013

02/27/199706/25/1998

08/03/2000

02/27/199708/03/2000

12/06/1995 08/03/2000 02/27/1997

10/04/2001

02/27/199708/03/2000

QD–28 (89) 03/28/2012 10/25/1995

10/14/1998

—

— 10/09/1996

—

— 04/03/2001 06/07/2000 07/18/2012

QD–29 (88)

— 04/17/2002

— 06/05/1996 

08/14/199604/26/200010/10/2001

—

—

—

—

— 07/18/2012
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 33

Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued[Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in 

at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date]

Well

(number of 

samples)

Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon 

QD–30 (80) 06/17/1999

— 12/12/2013 06/13/1996

08/08/1996 08/28/199710/10/200108/05/2004

06/17/1999 08/11/2005

10/06/200505/25/200605/25/2011

— 10/21/2010

—

—

QD–31 (87) 12/09/1999 08/10/2000

10/10/200107/05/2012

— 08/08/1996 

08/28/199704/27/200010/10/2001

06/17/1999 03/01/2007

— 06/17/1999 06/17/1999

10/19/2000

—

QD–32 (85) 06/17/1999

03/01/2012

— 10/21/2004

06/07/2007

08/28/1997 06/17/1999 10/17/2002

— 02/04/1999

10/30/200304/22/2004

04/17/200310/21/2004

08/28/1997

QD–33 (113) 02/13/2004

—

— 10/25/2001 06/10/2010 03/23/2006

10/18/200603/29/200705/17/2007

— 12/03/1998

— 08/28/1997

04/27/2000

QD–34 (70)

—

—

— 04/23/1997

10/17/200110/05/2006

— 10/07/1999

— 1/23/2007

— 08/21/1996

07/18/2012

QD–35 (78)

—

—

—

—

—

—

— 12/05/1996

— 07/18/2012

QD–36 (91) 02/10/2009

—

— 10/17/2001

08/30/201005/20/2013

— 10/31/2005

—

—

— 07/18/2012

QD–37 (112)

— 02/27/1997

08/21/199712/16/1999

— 09/01/2005 12/28/2000

04/04/2002

02/27/199708/03/2000

— 10/17/1996

12/19/199602/27/199708/03/2000

12/19/199610/04/200110/21/2004

02/27/199708/03/2000

QD–38 (90) 03/07/2013 12/16/1999

—

— 08/29/1996

06/25/1998

12/19/199602/27/1997

— 04/10/1996 12/19/1996

02/27/199706/03/2004

08/03/2000

QD–39 (52) 05/25/2006

—

— 04/07/2005 12/13/1995

08/13/2009

08/13/2009

— 08/13/2009

— 04/20/2000

QD–40 (39) 06/08/2006

—

—

—

— 08/29/2013

— 08/29/2013

—

—

QD–41 (50) 06/08/2006

— 04/08/2004

— 12/07/1995

08/13/2009

— 04/09/1997 08/13/2009

—

—
34 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued [Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date] Well (number of samples) Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon QD–42 (53) 04/08/2004

—

—

— 04/19/1995

— 04/25/1996

— 06/10/2010

08/05/2011

—

QD–43 (50) 04/08/2004 08/31/1995

10/17/2002

—

— 06/24/2010 10/08/1999

— 06/22/1995

—

—

QD–44 (55) 03/07/2013

— 02/14/1996 08/14/1996 02/09/1995

—

—

—

—

—

QD–45 (48) 04/08/2004

—

—

— 06/24/2010

03/07/2013

—

—

—

—

—

QD–46 (87) 07/08/2010

11/08/2012

06/23/200411/08/2012

02/21/200108/29/2001

06/05/1996 04/16/199702/10/199904/26/200010/10/2001

 06/07/199510/09/199608/14/199607/08/201007/15/2010

07/08/2010 08/29/2005 11/08/2012 07/08/2010

11/08/2012

07/18/2012

QD–47 (52) 04/08/2004

— 06/19/2008

— 04/11/2001

— 04/9/1997

—

—

—

QD–48 (45)

—

—

— 08/17/1995

09/25/2008

03/07/2013

—

—

—

—

—

QD–49 (44)

—

—

— 10/13/2011

02/28/2013

02/15/1996 02/15/1996

—

—

—

—

QD–50 (84) 02/10/2000

04/15/200412/09/2004

—

—

— 02/15/1996 02/15/1996

— 12/05/2001

04/14/2005

06/05/199702/08/2001

—

QD–51 (84) 08/12/1999

04/15/2004

—

— 07/15/2010 08/23/2001

—

— 12/03/1998

12/05/200104/14/2005

—

—

QD–52 (82) 02/10/2000

—

— 06/28/2012

—

—

— 08/02/2006 10/31/2001

—

QD–53 (83)

—

—

— 10/07/2004

06/28/2012

—

—

—

—

—

—

QD–54 (83) 06/28/2001

04/15/200412/15/200405/11/2006

08/09/200112/15/2004

07/15/2010 09/25/2008

—

—

— 08/02/2006

—

—

QD–55 (83)

—

—

— 06/28/2012

— 04/23/2009 05/15/2010

07/15/2010

08/02/2006

—

—
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 35

Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued[Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in 

at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date]

Well

(number of 

samples)

Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon 

QD–56 (83) 04/12/2001

08/09/2001

— 02/18/1999 — 12/19/2001 05/26/2005 12/04/1996 06/26/1997

10/08/199808/02/2006

— —

QD–57 (74) 10/12/2000 12/02/1999 — 09/25/2008

05/30/2013

— — 12/04/1996 08/02/2006 — 06/17/2004

QD–58 (75) 06/27/2002

10/17/2002 08/20/2003 04/15/200406/30/2005

— — — — 06/30/2005 10/22/1998 10/02/1997

08/03/2006

02/26/200408/02/2007

—

QD–59 (77) 02/26/2004

04/15/200406/28/2012

— — — 05/30/2013 — 05/30/2013 08/03/2006

06/28/2012

— —

QD–60 (82) 04/15/2004

05/02/2007 06/28/2012

— — — — 10/24/1996 — 08/03/2006

06/28/2012

12/07/200002/26/2004

08/26/2004

QM–53 (54) 03/23/2011 — — — — 01/02/2002

01/08/2003

— — 11/01/1995

01/03/199607/14/2004

08/09/2012

QM–56 (40) — 07/14/2004 — — 05/10/1995 — — 05/10/1995 07/14/2004 —QM–58 (53) 07/26/2001

01/17/2002

01/28/1999 11/08/2008

01/04/199601/15/200406/22/2006

— 03/06/1996

11/08/2007

03/06/199601/17/2002

— 03/06/1996 03/06/1996

01/17/2002

—

QM–61 (83) 05/15/2002

02/05/200804/02/200903/29/2010

05/15/200209/04/200808/05/201007/07/2011

09/04/2008 05/07/2003 

02/05/2008

05/15/200202/05/2008

05/15/200212/02/200404/02/200903/29/201008/05/2010

— 05/15/2002

02/05/2008

03/26/200205/15/200204/02/200903/29/2010

—

QM–62 (59) 03/11/1997

03/02/1999

03/06/199605/15/201209/18/2013

03/02/1999 01/18/1995

11/04/199809/06/2001 11/07/2013

11/04/199801/21/1999

07/12/2000 03/26/2002 01/21/1999 01/21/1999

09/07/2000

—
36 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued [Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date] Well (number of samples) Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon QM–63 (113) 04/02/2009 07/29/2011 09/16/2011

— Too 

numerous 

to list

11/06/199611/04/199801/21/199907/12/2000

10/23/200811/17/2010

03/26/2002 01/19/2006

01/23/2007

11/06/199601/21/199907/12/200009/07/2000

08/09/2012

QM–64 (112) 02/21/2008

10/26/2010

05/15/200210/05/200608/05/2010

— 09/12/2001

11/01/2001 09/04/200210/24/200608/23/200702/21/200811/04/2009 08/05/2010

11/06/199607/12/2000

—

— 11/06/1996

07/12/200011/05/2003

11/06/199607/12/2000

08/09/2012

QM–65 (100) 04/02/2009 03/20/1997

10/18/2006

01/29/1998 05/30/1996

 04/02/2009

04/02/2009 09/23/2004

04/02/2009

— 08/03/2006

04/02/2009

05/02/200204/02/2009

04/02/2009

QM–67 (118) 03/18/1999

01/04/2001

11/15/2001

— Too 

numerous 

to list

03/18/199905/26/1999

07/17/199703/18/199905/26/1999

01/04/1996 03/18/1999

05/26/1999

07/17/199705/02/2002

08/09/2012

QM–68 (70) 05/12/2005

—

— 11/16/1995

05/30/199607/25/199605/14/199810/09/2013

—

—

— 03/23/2011 01/17/2002 11/20/1996

08/09/2012

QM–69 (89) 09/12/2002 09/28/1995

— 07/26/1995

—

—

—

—

— 08/15/2012

QM–70 (44)

—

—

— 08/20/2009

—

—

—

—

— 05/25/2000

08/15/2012

QM–71 (51) 03/24/2011

—

—

—

—

— 10/30/1995 03/03/2010

— 08/15/2012

QM–72 (91)

—

—

—

—

— 11/28/2001 10/30/1995 11/28/2001

— 08/15/2012

QM–73 (50) 12/14/2000

—

—

— 12/14/2000

— 05/16/2002 12/14/2000

— 06/22/2006

08/16/2012

QM–74 (48) 05/24/2001 

04/11/2013

—

—

— 01/12/1995

03/16/1995

— 05/16/2002 07/12/1995 05/25/1995 08/16/2012

QM–75 (74) 05/24/2001 05/16/2002

09/18/2008

— 05/16/2002

09/18/200807/29/201010/09/2013

01/31/2013 2/07/2008 05/16/2002 07/23/2009 07/29/2010 09/13/2012
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 37

Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued[Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in 

at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date]

Well

(number of 

samples)

Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon 

QM–76 (49) 12/14/2000

 04/14/2005

—

— 07/28/2011 12/14/2000

— 07/12/1995

05/16/2002

— 07/29/2010 08/16/2012

QM–77 (51)

— 09/18/2008

— 09/18/2008

07/29/201007/28/2011

—

—

—

— 07/27/1995 08/16/2012

QM–78 (75) 03/01/2007

03/29/200712/15/2011

— 09/27/1995

11/28/200105/20/2010

09/26/1996

07/28/2011

01/31/2013 09/14/2006 11/28/2001

— 07/29/2010 09/13/2012

QM–79 (72) 03/25/2010

—

— 07/28/2011 05/27/2010

01/31/2013

09/14/2006

—

— 07/27/1995

05/02/2002

07/28/201109/13/2012

QM–80 (77) 04/17/2008

—

— 07/28/2011 11/18/2010

—

— 05/18/1995

07/24/200606/19/2008

08/09/2007 09/13/2012

QM–81 (87)

— 03/29/2001

11/08/200109/12/2002

09/20/199501/30/199601/30/1997

09/19/2013 01/25/1996

03/26/2009

—

—

— 09/13/2001

—

QM–82 (6)

—

—

—

— 03/26/2009

—

— 04/11/2013 08/09/2007 09/13/2012

QC–1 (263) 10/10/2002

12/19/200203/15/2007

—

— 10/11/2001

03/30/2006

04/18/1996 11/27/199606/25/199810/14/1998

— 11/16/2000 04/18/1996

11/27/199607/23/199810/14/199811/06/200307/15/2004

—

—

QC–2 (294) 02/23/1995

12/14/199504/18/199605/06/199910/12/200006/07/200103/14/200212/19/200203/17/2010

Too 

numerous to list

— Too 

numerous to list

11/27/199605/28/199806/25/199801/23/200306/03/2004

03/20/2003 08/07/2003 11/27/1996

10/14/199807/11/200201/23/200307/24/200311/06/200306/03/2004

07/27/199511/27/199605/28/199810/14/1998

02/22/1996
38 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued [Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date] Well (number of samples) Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon QC–2.1 (226) 07/01/1999 12/19/2002 04/08/2004 03/02/2006 02/08/2007 08/21/2008

—

— 08/28/1997

07/29/199906/17/200411/10/200411/24/2004

 08/28/1997 04/16/1998

06/25/1998

12/17/1998

07/29/2004 12/28/1995 07/11/2002

07/24/200303/02/200608/21/2008

07/27/1995 05/08/1997

QC–2.2 (87) 02/09/1995

02/23/199512/14/199504/18/199605/06/199903/02/200601/10/200808/18/2011

11/04/1999 02/09/1995 02/23/1995

06/13/1996 05/06/199906/12/200808/18/2011

02/23/199512/14/199504/18/1996 

02/09/1995

— 04/06/1995

05/19/2005

04/18/199609/09/2010

02/09/199505/11/200011/16/2000

QC–3 (75)

— 05/15/1996

03/05/199703/26/1998

— 05/15/1996 

03/05/1997 03/26/199805/15/2003

— 03/19/2003

—

—

— 05/17/2000

QC–4 (87) 08/31/2006 03/05/1997

03/26/1998

— 05/15/1996

05/30/1996

01/12/1995 03/19/2003

— 05/03/2012

— 05/17/2000

QC–5 (86) 02/04/2010

04/05/2012

11/07/200208/31/2006

11/06/2003

—

— 04/05/2012

—

—

—

—

QC–6 (87) 04/05/2012 03/05/1997

03/26/1998

— 03/05/1997 

03/26/1998

— 07/02/1998

— 05/21/1997 03/28/1996

—

QC–7 (80) 05/17/2006 01/19/1995

11/16/199507/24/199603/06/1997

—

— 07/24/1996 11/21/1996

05/17/2006

—

— 09/20/2001

—

QC–9 (74) 01/18/1996

11/08/2001

03/06/1997 03/23/2000 09/20/2001 11/02/2000

— 05/25/1995 01/19/1995 05/21/1998 07/19/2012

QC–10 (88)

— 03/06/1997

03/19/1998

11/12/1996

—

— 07/02/1998

11/26/2013

— 01/05/2011

—

—

QC–11 (52)

—

—

—

— 11/03/2004

03/28/2007

—

—

—

— 07/12/2012
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 39

Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued[Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in 

at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date]

Well

(number of 

samples)

Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon 

QC–12 (52)

—

—

— 11/21/1995 04/29/2008

06/04/2008

—

— 01/17/2007

— 01/03/1996

07/12/2012

QC–13 (50)

—

—

—

— 06/04/2008 07/06/1995 07/06/1995

—

—

—

QC–14 (53) 09/26/2013 11/08/2001

—

—

—

—

—

— 01/18/1996

—

QC–15 (50) 03/14/2013

—

—

— 11/06/2003 01/19/1995

—

—

— 07/19/2012

QC–16 (85) 03/23/2000 11/29/2001

—

— 03/14/1996 11/14/1996

— 07/18/1996

09/17/199809/12/2012

07/22/2009 07/12/2012

QC–17 (47)

—

— 09/18/1996 09/07/1995 

12/07/2006 06/03/2010 06/02/2011 07/26/2012

03/21/2013

— 07/13/1995 05/13/1999 07/22/2009 07/26/2012

QC–18 (50) 03/13/2008

— 09/18/1996 05/04/1995 03/14/1996

06/03/201008/31/2011

—

—

— 07/22/2009 07/26/2012

QC–19 (78) 09/20/2001

— 11/20/2003

— 03/21/2013 09/20/2001

— 09/12/2012 07/22/2009 07/26/2012

QC–20 (46)

— 03/08/2001 06/16/2011

— 12/04/2008

06/16/201108/31/201105/09/2013

—

— 12/04/2008

06/16/201105/09/2013

06/16/2011 07/26/2012

QC–21 (58)

— 03/08/2001

—

— 11/29/2001 01/13/2005

— 12/04/2008

04/01/200906/16/201108/31/2011

— 07/26/2012

QC–22 (59)

— 11/09/2006

04/05/2007

11/14/2002

— 11/29/2001

—

— 07/21/2004 06/16/2011 07/26/2012

QC–23 (63)

— 03/08/2001

—

— 06/16/2011

—

—

— 07/25/2002 07/26/2012

QC–24 (63) 09/23/2004 03/22/2001 05/25/2006

— 06/16/2011

03/21/2013

09/23/2004

—

— 06/16/2011 07/26/2012

QC–25 (58)

— 03/22/2001

—

— 09/15/2011

—

— 12/04/2008

09/15/201103/29/2012

— 08/02/2012
40 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 5. Dates of detection of anomalous analyte values in samples from monitoring wells, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.—Continued [Dates are expressed as month/day/year; regular font indicates anomalously high value, underline indicates anomalously low value; —, no anomalous value; italics denote anomalous value of an analyte in at least four wells within a 1-month period; bold denotes anomalous value for two or more analytes in a well on a given date] Well (number of samples) Chloride Groundwater level Electrical conductivity Fecal coliform Hardness Ammonia NH3 as nitrogen pH Sulfate Total dissolved solids Dissolved organic carbon QC–26 (61) 11/16/2006 09/15/2011 03/22/2001 07/23/2009 09/23/2010

—

— 06/23/2011

03/21/2013

07/31/2003

— 03/21/2013 01/17/2002 05/18/2000

08/02/2012

QC–27 (60) 01/11/2001

07/05/200103/14/200509/23/2010

03/09/2001

—

— 01/11/2001

07/05/200103/21/2013

—

—

—

— 08/02/2012

QC–28 (58) 01/11/2001

03/14/200203/17/2005

— 08/21/2008

03/10/201009/23/2010

— 01/11/2001

—

— 05/26/2004

07/22/2004

— 08/02/2012

QC–29 (63) 11/15/2012

07/18/2013

—

—

— 07/18/2013 07/18/2013

— 07/18/2013 07/18/2013 08/02/2012

QC–30 (60) 07/18/2013 03/12/2009

— 04/19/2006

09/21/200601/17/2008

04/28/201108/26/201107/18/2013

—

— 08/07/2008

04/28/201107/18/2013

07/18/2013 03/11/2004

08/02/2012

QC–31 (65)

—

—

— 01/11/2007

05/24/200701/17/2008

—

— 10/01/2008 07/01/2009

— 08/02/2012

QC–37 (12)

—

—

—

—

— 12/30/2009 01/09/2003

—

— 03/11/2004
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 41

Sulfate

Sulfate (SO4

-2) is a naturally occurring ion that typically 

is present in groundwater because of the dissolution of sulfate 

minerals or the oxidation of sulfide minerals in geologic 

deposits. Sulfate concentrations in samples collected from 

non-TARP monitoring wells (Duwelius and others, 1996) 

and from water-supply wells open to the Silurian aquifer in 

Cook County (Voelker, 1986; Voelker and others, 1988) during the mid-1980s through early 1990s tended to be less than 

150 mg/L near Lake Michigan and in the northwestern part 

of Cook County and more than 300 mg/L near the Majewski and future McCook Reservoirs (fig. 17). Wells in figure 

17 are designated Voelker and Duwelius, which refer to the 

data from those authors (Voelker, 1986; Voelker and others, 

1988; Duwelius and others, 1996). The conversion of sulfate 

to sulfide (S-2) has been observed within the upper part of the 

Silurian aquifer in the Calumet area (Duwelius and others, 

1996), which may explain the absence of detectable sulfate in 

some of the samples from wells near the Calumet WRP. These 

samples typically were collected prior to construction of the 

TARP System in the area sampled and were collected from 

wells that are not part of the TARP monitoring network. These 

data indicate that background sulfate concentrations in the 

Silurian aquifer in Cook County are spatially variable. Concentrations of sulfate in samples from TARP wells are listed in 

appendix 1.

Sulfate concentrations in CSF water discharged from 

the Calumet WRP during 1989–93 ranged from about 80 to 

210 mg/L, with a geometric mean concentration of 150 mg/L 

(Dominic Brose, Metropolitan Water Reclamation District 

of Greater Chicago, written commun., 2014). The conversion of sulfate to sulfide has been observed in CSF within the 

TARP tunnels (Washington and others, 1981), although sulfide 

concentrations typically were less than 1.0 mg/L in TARP 

discharge, so the effect of sulfate reduction on sulfate concentrations in CSF is negligible. 

Because sulfate concentrations in the water from the 

Silurian aquifer are not well defined in the immediate vicinity of the TARP System, vary substantially with location, 

and encompass the range of sulfate concentrations in CSF, 

sulfate concentrations may be of limited use in identifying 

CSF effects on groundwater at the TARP wells. Conversion 

of sulfate to sulfide in the Silurian aquifer also may confound 

assessment of the presence of CSF in the TARP monitoring 

wells. 

The geometric mean concentration of sulfate in samples 

from the TARP monitoring wells during 1995–2013 ranged 

from 1 to 746 mg/L (fig. 18). Geometric mean concentrations 

of sulfate less than 25 mg/L were detected in isolated wells in 

the northern part of the Des Plaines System, in much of the 

North Branch of the Mainstream System, and in much of the 

Calumet System outside of the Little Calumet leg and wells 

QC–16 through QC–19. Geometric mean concentrations of 

sulfate greater than 250 mg/L were detected in most of the 

central and southern parts of the Des Plaines System and 

throughout the Upper Des Plaines System. Spatial patterns 

in geometric mean sulfate concentrations in the TARP 

monitoring wells are consistent with patterns in background 

sulfate concentrations in the Silurian aquifer within Cook 

County (fig. 17). Sulfate concentrations in the TARP wells 

appear to primarily reflect the sulfate concentration within 

the Silurian aquifer near the well. This result was expected 

because fixed-schedule sampling events obtain most of their 

samples during typical (aquifer to tunnel) flow conditions that 

reflect the chemistry of the aquifer water.

Anomalously high concentrations of sulfate were 

measured in the north leg of the Des Plaines System at wells 

QD–52, QD–54 through QD–60, and Mainstream well QM–65 

on August 2 and 3, 2006 (table 5). Elevated concentrations of 

sulfate also were measured in the West leg of the Des Plaines 

System at wells QD–22 through QD–25 on August 16, 2006. 

Elevated concentrations of sulfate were measured at wells 

QC–1, QC–2, QM–64, and QD–32 from October 30 through 

November 6, 2003. TARP discharge to the WRPs exceeded 

80 Mgal/d at least five times in the 2 weeks preceding each of 

these dates, indicating that CSF flow into the Silurian aquifer 

may have occurred prior to these sampling events.

Anomalous sulfate concentrations were detected in 129 

samples from the 106 TARP wells. Of these 129 samples, 36 

had low concentrations that probably are not related to CSF 

events (table 5). A total of 40 samples with anomalous sulfate 

concentrations, including low values, also had anomalous values of other analytes, particularly hardness and chloride. Only 

two samples had an anomalous concentration of sulfate and 

an elevated FC population. In no well were anomalous sulfate 

concentrations detected in more than seven samples. 

Of the 81 wells exhibiting a statistically significant trend 

in sulfate concentration from 1995 through 2013, 67 (63 

percent of the106 wells analyzed) showed a downward trend, 

and 14 showed an upward trend (fig. 18). Sulfate concentrations in the samples from the remaining wells did not indicate 

a statistically significant trend, so the trend in these wells is 

unclear. Although downward trends are present throughout the 

TARP System, upward trends were observed in the southern 

part of the Upper Des Plaines System, in the middle of the Des 

Plaines System, near the Stickney WRP on the Mainstream 

System, and the western part of the Little Calumet leg of the 

Calumet System. The downward trend in sulfate concentrations in most of the TARP wells is consistent with the presence of higher sulfate water in the deeper part of the Silurian 

aquifer monitored by the TARP wells during the early part 

of the 1995–2013 period being replaced through time with 

lower sulfate water (perhaps affected by sulfate reduction in 

the upper part of the aquifer) from more distant parts of the 

aquifer within the drainage area to the tunnels. 
42 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

0 5 10 MILES

0 5 10 KILOMETERS

ILLINOIS

INDIANA

COOK COUNTY

DU PAGE COUNTY

DU PAGE COUNTY

WILL COUNTY

WILL COUNTY

COOK COUNTY

LAKE COUNTY

COOK COUNTY

MAINSTREAM

SYSTEM

UPPER DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North

leg

Middle

leg

West leg

Torrence Ave leg

Cal-Sag leg

Little Cal

leg

Markham

leg

140th St. leg

Roosevelt

Road leg

Indiana

Ave leg

South

leg

O’Hare

Reservoir

O’Hare Water

Reclamation Plant

McCook

Reservoir

Stickney Water

Reclamation

Plant

Thornton

Reservoir

Calumet Water

Reclamation

Plant

LAKE

MICHIGAN

65

170

170

190

190

200

220

230

250

270 280

290 290

300

310

330

350

370

390

410

420

550

680

31

40

54

<5

<5

<5

<5

65

81

100

110

120

140

160

170

196

210

230

269

294

300

361

370

370

370

380

380

420

429

450

460

470

EXPLANATION

Tunnel

Sulfate concentration,

 in milligrams per liter, in:

 Voelker well

 Duwelius well

 

Well location

Pumping station

81

54

88° 87°

42°

41°40'

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection

Standard parallels 45° and 33°, central meridan -89°

Figure 17. Concentration of sulfate in water from Silurian aquifer, Cook County, Illinois (compiled from Voelker, 1986; Voelker 

and others, 1988; Duwleius and others, 1996).

Figure 17. Concentration of sulfate in water from the Silurian aquifer in Cook County, Illinois (compiled from Voelker, 1986; 

Voelker and others, 1988; Duwelius and others, 1996).
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 43

351

407

423

382 285

322

393

286

342

307

292

323

194

237

112

54

236

287

336

210

220

197

349

335

390 331

115

103

369

352

285

228

197

214

141 151

271 233

252

122

137

118

140

160

12

89

3

44

101

37

12

173

21

35

746

46

194

51

34

54 56

70

3

4

3

11 49

4

55 21

4

16 13

248

29

5

37

27

16

11

21

4

25 282

35 1.4

54

178

164 38

<7 1.1-2.9

<5

.97-2.6

<5

<3

<3

<3

<4

<3

1

<3

122

65

178

57

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel—Colors indicate legs

 of tunnel systems

Geometric mean concentration

 of sulfate, in milligrams per

 liter, with trend indicated

 Upward

 Downward

 Unclear

 Less than

44

101

160

<

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 18. Geometric mean concentrations of sulfate and trends in concentration in samples from Tunnel and Reservoir Plan (TARP)

System wells, Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 18. Geometric mean concentrations of sulfate and trends in concentration in samples from Tunnel and Reservoir Plan (TARP) 

System wells, Cook County, Illinois, 1995–2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
44 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Chloride

Chloride is a naturally occurring ion in groundwater. 

However, its presence in some groundwater in the Chicago 

area also can be attributed to the dissolution of road salt. 

Concentrations of chloride in samples collected from monitoring wells and water-supply wells that were open to the Silurian 

aquifer throughout Cook County during the mid-1980s and 

early 1990s (Voelker, 1986; Voelker and others, 1988; Duwelius and others, 1996) are shown in figure 19. These wells are 

not part of the TARP monitoring network, and these samples 

typically were collected prior to construction of the TARP tunnels in the area being sampled. Background chloride concentrations in the Silurian aquifer determined from this non-TARP 

sampling were usually less than 20 mg/L in the southwestern 

and northwestern parts of Cook County, exceeded 100 mg/L 

near the future McCook Reservoir, and were 20–50 mg/L in 

the remainder of the county (fig. 19). 

Chloride concentrations were determined to have 

increased through time in non-TARP wells open to the Silurian 

aquifer at LaGrange, Libertyville, and Naperville (locations 

shown in fig. 15) with concentrations beginning to increase 

in about 1960–70, depending on location (Gibb and O’Hearn, 

1980). The increases have been attributed to recharge of snowmelt and precipitation that contains dissolved road salts and 

indicate that chloride concentrations in the Silurian aquifer 

within the greater Chicago area may be affected by non-TARP 

anthropogenic processes, especially in the vicinity of the 

McCook reservoir where the aquifer is near the land surface 

(fig. 4).

Road salt dissolution also results in the presence of high 

chloride concentrations in CSF water. Chloride concentrations 

in CSF discharged from the TARP System during 1989–91 

ranged from about 25 to 600 mg/L with a geometric mean concentration of about 170 mg/L. Chloride concentrations in CSF 

were highest during the winter and spring and lowest in the 

summer and fall (fig. 20), coincident with the timing of road 

salt application. 

The geometric mean concentration of chloride in samples 

from the TARP monitoring wells from 1995 through 2013 

ranged from 5 to 480 mg/L (fig. 21). Concentrations of chloride with geometric means of less than 30 mg/L were detected 

in most of the wells in the central and northern parts of the 

Des Plaines System, in most of the Mainstream System from 

well QM–68 upstream to well QM–75, and in much of the 

Torrence Avenue and Indiana Avenue legs of the Calumet System. Concentrations of chloride with geometric means greater 

than 100 mg/L were detected at wells QM–71 and QM–72 

in the North Branch of the Mainstream System, as well as in 

most of the southern parts of the Des Plaines and Mainstream 

Systems. Spatial patterns in concentrations of chloride in the 

samples from the TARP monitoring wells are generally consistent with patterns in the background concentrations in the Silurian aquifer in the greater Chicago area (fig. 19), indicating 

that concentrations of chloride in the TARP wells are affected 

primarily by the concentration in the surrounding aquifer. This 

result was expected because most of the samples collected 

during fixed-schedule sampling events reflect the chemistry of 

typical (aquifer to tunnel) flow conditions.

Anomalous (mostly elevated) chloride concentrations 

were detected in 10 wells in the Middle and North legs of the 

Des Plaines System and at well QC–2.1 on April 8 and 15, 

2004 (table 5). Elevated chloride concentrations also were 

observed on March 15 or 29, 2007 (QC–1, MW–5, MW–9, 

QM–78), on February 10 or 25, 2009 (QD–36, MW–2, 

MW–8, MW–9), and on March 28 or April 5, 2012 (QD–23, 

QD–25, QC–5, QC–6). Each of these sample dates was in the 

winter or early spring, indicating a seasonal component to 

the high concentrations. These dates were preceded by TARP 

discharge to the Stickney WRP in excess of 90 Mgal/d during 

at least 2 of the 14 days before sample collection, indicating 

that CSF discharge to the Silurian aquifer may have occurred 

prior to each of the dates and resulted in the elevated chloride 

concentrations in the aquifer. 

Anomalous chloride concentrations were detected in 154 

samples from the 106 TARP wells (table 5). Of these anomalies, 43 were low concentrations potentially not related to 

TARP events. A total of 44 samples with anomalous chloride 

concentrations also contained anomalous values of other 

analytes, particularly TDS, ammonia, and hardness. Seven 

samples with high chloride concentrations also had elevated 

FC populations. In no well were anomalous chloride concentrations detected in more than nine samples. 

Statistical analysis indicates that wells MW–5, MW–8, 

and MW–9 in the Upper Des Plaines System; wells QM–62, 

QM–68, and QM–80 in the Mainstream System; well QD–25 

in the Des Plaines System; and well QC–2.2 in the Calumet 

System (appendix 3) had a seasonal variation in chloride concentration to a significance level of at least 95 percent. This 

seasonality reflects a tendency for elevated chloride concentrations in most of these wells (well MW–5 is the clearest example and is shown in figure 22) during the winter and spring to 

decrease to a lower background concentration in the summer 

and fall. The timing of the variation in chloride concentration in the wells was consistent with the seasonal variation in 

concentration in the TARP discharge to the WRPs (fig.20). 

TARP discharge to the Stickney WRP exceeded 140 Mgal/d 

for at least 1 of the 14 days preceding detection of seasonally 

high chloride concentrations on the dates highlighted in figure 

22. This relation indicates that chloride in road salts entered 

the TARP System dissolved in CSF and migrated into parts 

of the Silurian aquifer when hydraulic pressures in the TARP 

System were elevated following substantial precipitation or 

snowmelt events during the winter and spring. Migration of 

chloride from the tunnels to the monitoring wells appears to 

have occurred within 2 weeks and appears to have required 

4–6 months to fully dissipate.
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 45

0 5 10 MILES

0 5 10 KILOMETERS

TARP tunnel locations from Metropolitan Water

Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

ILLINOIS

INDIANA

COOK COUNTY

DU PAGE COUNTY

DU PAGE COUNTY

WILL COUNTY

WILL COUNTY

COOK COUNTY

LAKE COUNTY

COOK COUNTY

MAINSTREAM

SYSTEM

UPPER DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North

leg

Middle

leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal

leg

Markham

leg

140th Street leg

Roosevelt

Road leg

Indiana

Avenue leg

South

leg

McCook

Reservoir

Stickney Water

Reclamation

Plant

Thornton

Reservoir

Calumet Water

Reclamation

Plant

Majewski

Reservoir

Kirie Water

Reclamation Plant

LAKE

MICHIGAN

6

39

11

5

18

23

7

22

2

5

44

61

<1

36

10

1

48

6.9

15

24

13

2 42

7 82

28

4

62

79

74

6

11

2

5

8

120

3

11

220

260

2

22

12

39

3

43

18

140

26

30

27

24

37

38

39

EXPLANATION

Tunnel

Chloride concentration,

 in milligrams per liter, in:

 Voelker well

 Duwelius well

 Less than

 

Pumping station

<

11

27

88° 87°

42°

41°40'

Figure 19. Concentrations of chloride in water from Silurian aquifer in Cook County, Illinois (compiled from Voelker, 1986; Voelker 

and others, 1988; Duwleius and others, 1996).

Figure 19. Concentrations of chloride in water from the Silurian aquifer in Cook County, Illinois. 
46 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

0

100

200

300

400

500

600

700

1989 1990 1991

Chloride, in milligrams per liter

Year

J FMAMJ J AS O NDJ FMAMJ J AS O ND J FMAMJ J AS O ND

Figure 20. Concentrations of chloride in samples from Tunnel and Reservoir Plan System discharge to the Stickney Water

Reclamation Plant, Cook County, Illinois, 1989–91 (data from Metropolitan Water Reclamation District of Greater Chicago, written

commun., 2013). 

Figure 20. Concentrations of chloride in samples from Tunnel and Reservoir Plan System discharge to the Stickney 

Water Reclamation Plant, Cook County, Illinois, 1989–1991 (data from Metropolitan Water Reclamation District of Greater 

Chicago, written commun., 2013).
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 47

33

25

13

52 108

38

35

51

34

253

127

140

95

344

22

314

228 118

131

120

480

362

116

111

127 279

202

31

16

18

18

34

15

17

15

13 17

15

14

12

15

19

17

16

12

12

12

90

47

15

36

16

70

50

51

55

386

179

23

37

49

124

130

39

48 13

12

11

13

19

14 21 29

49 41

34

16

12

11

26

18

11

10

31

23

37

66 42

15

19

9

5 8

18

17

14

20

27

14

12

30

15

97

11

16

28

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection, 

Standard parallels 45 ̊ and 33 ̊, central meridian -89 ̊. 

EXPLANATION

Tunnel—Colors indicate legs of 

 tunnel systems

Geometric mean concentration

 of chloride, in milligrams per

 liter, with trend indicated—

 Bold label indicates seasonal trend

 Upward

 Downward

 Unclear

14

37

21

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 21. Geometric mean concentrations of chloride and trends in samples from Tunnel and Reservoir Plan (TARP) System wells, 

Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 21. Geometric mean concentrations of chloride and trends in concentration in samples from Tunnel and Reservoir Plan (TARP) 

System wells, Cook County, Illinois, 1995-2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
48 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

4/2/09

2/27/97

2/7/96 2/15/01

2/5/98

2/25/04

2/3/05

2/9/06

3/15/07

0

200

400

600

800

1,000

1,200

Chloride concentration, milligrams per liter

Year

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Figure 22. Concentrations of chloride in samples from Tunnel and Reservoir Plan System well MW-5, Cook 

County, Illinois, 1994–2010.

Figure 22. Concentrations of chloride in samples from Tunnel and Reservoir Plan System well MW-5, Cook County, 

Of the 65 wells with a statistically significant trend 

in chloride concentration from 1995 through 2013, 40 

(38 percent of the 106 wells sampled) showed an upward 

trend, and 25 showed a downward trend (fig. 21). The trends 

in the remaining 41 wells had a significance level of less 

than 95 percent and did not indicate a clear trend. Wells with 

upward trends tended to be located in the Des Plaines and 

Upper Des Plaines Systems and in the central part of the 

Mainstream System. Wells with downward trends tended to 

be located in the northern and southern parts of the Mainstream System, along the Roosevelt Road and eastern parts 

of the South leg of the Des Plaines System, and along the 

Indiana Avenue leg of the Calumet System. Increased chloride 

concentrations during 1995–2013 may be partly attributable to 

the periodic migration of high-chloride CSF into the Silurian 

aquifer. Increases in chloride concentration in the Silurian 

aquifer because of road salt application in the greater Chicago 

area, especially near the McCook Reservoir, also may be 

affecting long-term trends in chloride concentrations (Gibbs 

and O’Hearn, 1980). 

Electrical Conductivity

EC is a field measurement of the capacity of a water 

sample to transmit electrical current. EC typically increases as 

the concentration of dissolved ions, especially calcium, magnesium, sodium, potassium, sulfate, chloride, and bicarbonate, in the sample increases, making it an indicator of general 

water quality. EC is commonly referred to as specific conductivity, reported as microsiemens per centimeter (μS/cm), 

and the conversion factor is 1 or 1 micromho/cm (μmho/cm) 

Illinois, 1994–2010.

= 1 microsiemen/cm. EC is described in this report because it 

was the constituent measured and reported by MWRDGC. EC 

values in groundwater from non-TARP monitoring wells open 

to the upper part of the Silurian aquifer in the Calumet area 

ranged from 290 to 3,630 μmho/cm, with a median value of 

484 μmho/cm (Duwelius and others, 1996). Annual geometric mean values of EC in discharge from the TARP System 

to the Calumet WRP during 1989–93 ranged from 1,010 to 

1,224 μmho/cm, indicating that typical EC values in CSF 

water are substantially higher than the typical EC values in the 

Silurian aquifer. Elevated EC values may indicate the presence 

of CSF in the samples from the TARP monitoring wells. 

Geometric mean values of EC in the samples from the 

TARP monitoring wells during 1995–2013 ranged from 234 

to 2,149 μmho/cm (fig. 23). Geometric mean EC values were 

less than 500 μmho/cm in samples from monitoring wells in 

the Torrence Avenue leg of the Calumet System and less than 

750 μmho/cm in samples from monitoring wells in the rest 

of the Calumet System, except wells QC–1 and QC–12. EC 

values in samples from monitoring wells in the Des Plaines 

System increased from typically less than 625 μmho/cm in 

the northern (upstream) part of the system to typically more 

than 1,000 μmho/cm in the southern (downstream) part of the 

system. EC values in samples from monitoring wells in the 

Mainstream System also increased overall from north to south; 

EC values were less than 500 μmho/cm north of well QM–58, 

typically between 500 and 600 μmho/cm in the center of the 

system at wells QM–58 through QM–62, and typically greater 

than 1,000 μmho/cm in the southern (downstream) part of the 

system west of the Stickney WRP. Geometric mean EC values 

exceeded 750 μmho/cm in samples from monitoring wells in 

the Upper Des Plaines System. 
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 49

825

828

789

938 1,005

763

814

769

771

1,226

1,214

1,546

1,582

719

978

1,477

1,333

1,123

2,149

1,767

1,146

1,080

1,241

1,142

1,183

1,182

1,135

941

1,027

1,048

827

723

611

678

797

646

711 640

841

683

647

766

598

602

474

572

386

622

559

267

359

585

579

1,253 616

554

1,642

1,118

334

434

439

557

538

420

350

294

418

234 438 421

273

336

381

925

496

462

561

503

523

766

661

579

411 991 498

403

559

644

418

629 485 562

574

357

400

413

323

316

274

326

327

326

708 434

559

860

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89°

EXPLANATION

Tunnel—Colors indicate legs of 

 tunnel systems

Geometric mean electrical

 conductivity value, in micromhos 

 per centimeter, with trend indicated 

 Upward

 Downward

 Unclear

559

334

644

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 23. Geometric mean values of electrical conductivity and trends in samples from Tunnel and Reservoir Plan (TARP) System wells, 

Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 23. Geometric mean values of electrical conductivity and trends in samples from Tunnel and Reservoir Plan (TARP) System 

wells, Cook County, Illinois, 1995-2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
50 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Spatial patterns in EC values in the TARP monitoring 

wells are generally consistent with patterns in the background 

values of several of the major chemical components in 

groundwater from the Silurian aquifer in Cook County (hardness, sulfate, and chloride; figs. 15, 17, and 19). Because EC 

values are an indication of the general water quality, patterns 

in overall water quality within the Silurian aquifer are likely to 

be similar to EC patterns in the aquifer. For this reason, the EC 

values in the TARP wells appear to be affected primarily by 

the natural variation of EC within the Silurian aquifer rather 

than CSF. 

Anomalous EC values were observed in 38 samples 

from the 106 TARP monitoring wells (table 5). One-half of 

the anomalies were low, indicating they were not affected by 

CSF. Only seven samples with anomalous EC values also had 

anomalous values of other analytes, most commonly chloride, 

TDS, or hardness. No sample with anomalous EC values also 

had an elevated FC population. 

Of the 91 wells with a statistically significant trend in 

EC values during 1995–2013, 89 (84 percent of the 106 wells 

analyzed) showed a downward trend, and 2 showed an upward 

trend (fig. 23). The EC trends in the remaining 15 wells had a 

significance level of less than 95 percent and did not indicate 

a clearly defined trend (no trend). Downward trends in EC 

were present throughout the TARP System, with the exception of the entire Torrence Avenue leg of the Calumet System 

and much of the Little Cal leg of the Calumet System, where 

statistically significant trends were not present.

The downward trend in EC values in more than 

80 percent of the wells sampled is consistent with the higher 

EC water present in the deeper part of the Silurian aquifer 

being replaced through time with lower EC water that flows 

into the monitoring wells from more distant (including shallow) parts of the aquifer in response to the drainage of aquifer 

water into the tunnels. The decrease in EC may be related to 

the decrease in sulfate concentrations observed in many of the 

TARP wells during 1995–2013. In the wells along the Torrence Avenue and Little Calumet legs of the Calumet System, 

where statistically significant trends in EC were not observed 

(fig. 23), EC values within the Silurian aquifer might not have 

differed enough to induce a trend. Alternatively, Torrence 

Avenue and Little Calumet are the two newest tunnel systems (fig. 2), so the lack of EC trends in the samples from the 

wells near these tunnels may indicate that substantial volumes 

of lower EC water may not have had time to migrate to the 

deeper part of the Silurian aquifer in these areas by 2013. 

Total Dissolved Solids

TDS is a measurement of the amount of inorganic salts, 

organic matter, and particulate material in solution. TDS, 

like EC, is an indicator of general water quality and typically 

increases as the concentrations of the major ions (calcium, 

magnesium, sodium, potassium, sulfate, chloride, and bicarbonate) in the sample increase. TDS analyses of background 

water samples from the Silurian aquifer in Cook County are 

not readily available, and TDS was not measured in CSF 

discharged from the TARP. However, TDS concentrations in 

CSF are likely to be elevated in comparison with water in the 

Silurian aquifer on the basis of their relative EC values.

TDS concentrations were determined to have increased 

through time in groundwater samples from wells open to 

the Silurian aquifer at LaGrange and Naperville (Gibb and 

O’Hearn, 1980). TDS concentrations began to increase before 

construction of the TARP system, indicating that TDS concentrations in parts of the Silurian aquifer in the Chicago area are 

affected by non-TARP anthropogenic processes.

The geometric mean concentration of TDS in samples 

collected from the TARP monitoring wells from 1995 through 

2013 ranged from 188 to 1,894 mg/L (fig. 24). TDS concentrations were less than 350 mg/L in the Torrence Avenue leg 

of the Calumet System and less than 600 mg/L in the rest of 

the Calumet System, except for wells QC–1, QC–12, and 

QC–29 where concentrations exceeded 700 mg/L. Geometric 

mean TDS concentrations less than 500 mg/L were detected 

in the Mainstream System upstream (north and east) from the 

Stickney WRP and were more than 900 mg/L in most of the 

wells downstream from the plant. The geometric mean concentrations of TDS in the Des Plaines System show an overall 

increase from north to south, in the direction of flow in the 

tunnel system. The TDS concentration was less than 500 mg/L 

north of well QD–53, typically between 500 and 1,000 mg/L 

from well QD–53 south through well QD–39, and typically 

exceeded 1,000 mg/L south of well QD–39. Geometric mean 

TDS concentrations greater than 750 mg/L were detected in 

samples from the wells in the Upper Des Plaines System. 

Spatial patterns in TDS concentrations are generally consistent 

with patterns in concentration of other analytes in the Silurian 

aquifer (figs. 15, 17, and 19), indicating that TDS concentrations in the TARP wells are primarily affected by the TDS 

concentrations in the aquifer.

Although TDS concentrations appear to primarily be 

affected by the aquifer chemistry, TDS concentrations also had 

a statistically significant seasonal variation in samples from 

26 of the TARP monitoring wells (fig. 24), with concentrations showing a tendency to have been highest in the summer 

and lowest in the winter in most of these wells. Wells showing 

seasonality were present mostly in the upper part of the Upper 

Des Plaines System, the downstream part of the Des Plaines 

System, and North Branch leg of the Mainstream System, and 

the Torrence Avenue leg of the Calumet System (appendix 3). 

Seasonal variation in TDS concentrations may be related 

to seasonal patterns in discharge from the TARP tunnels to the 

WRPs, which may be associated with increased movement of 

CSF from the TARP System to the Silurian aquifer, particularly in the downstream part of the Des Plaines System. This 

discharge tended to be highest in the summer months (table 3). 

Many of the wells with seasonality in TDS concentrations are 

near areas where the Silurian aquifer is at or near land surface 

(fig. 4) and in the LaGrange area where TDS concentrations 

have been showing non-TARP related increases (Gibbs and 

O’Hearn, 1980).
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 51

812

867

836

897 965

777

928

756

800

1,464

1,224

1,301

934

1,421

613

1,236

1,259 1,149

1,263

956

1,894

1,692

1,269

1,226

1,389

1,446

888

866

764

852

803

746

602

588

650 618 537

626

681

570

500

603

460

480

354

432

294

491

445

210

270

466

391

402

1,478

483

1,381

915

274

347 337

489

434

317 276

237

347

188

335

358

230 356

314

830 399

545

389

420

442

599

522

441

328

405

306

891

444 598

337

531

538

416 481

300

330

269

348

270

236

297

276

284

711

418

557

912

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel—Colors indicate legs of

 tunnel systems

Geometric mean concentration of

 total dissolved solids, in milligrams 

 per liter, with trend indicated—

Bold label indicates seasonal trend

 Upward

 Downward

 Unclear

491

434

480

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 24. Geometric mean concentrations of total dissolved solids and trends in samples from Tunnel and Reservoir Plan (TARP) System

wells, Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 24. Geometric mean concentrations of total dissolved solids and trends in samples from Tunnel and Reservoir Plan (TARP) 

System wells, Cook County, Illinois, 1995–2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
52 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

The seasonality indicated by the TDS concentrations was 

not observed for the other analytes. Other analytes that are 

related to TDS (such as EC) or are substantial components of 

TDS (chloride, hardness, and sulfate) did not indicate seasonal 

variation (except chloride), did not exhibit seasonal variation 

in most of the wells with seasonal variation in TDS, and did 

not indicate high values in summer and low values in winter 

(including chloride).

Anomalously high concentrations of TDS were identified on June 11, 2009, at wells MW–1, MW–3, MW–5, 

MW–8, and MW–9 in the Upper Des Plaines System (table 5). 

Anomalous TDS concentrations also were detected in samples 

from four wells collected on July 27, 1995, (QM–77, QM–79, 

QC–2, QC–2.1) and July 22, 2009 (QC–16 through QC–19). 

Discharge from the TARP System to the WRPs exceeded 

100 Mgal/d at least five times in the 2 weeks preceding each 

of these events. These dates are all during the summer months 

and may have contributed to the calculated seasonality in the 

TDS concentrations. CSF discharge to the Silurian aquifer 

may have occurred prior to each of the dates, resulting in the 

elevated TDS concentrations in the aquifer. 

Anomalous TDS concentrations were detected in 94 

samples from the 106 TARP wells (table 5). Of these anomalies, 26 were low concentrations potentially not related to 

CSF events. A total of 33 samples with anomalous TDS 

concentrations also had anomalous values of other analytes. 

Analytes with anomalous values in a sample on the same date 

that anomalous TDS concentrations were observed typically 

were general indicators of water quality, such as EC; probable 

major components of TDS, such as chloride and hardness; and 

CSF indicators, such as ammonia. Samples from well QD–27 

collected on February 27, 1997, and QM-65 collected on 

April 2, 2009, were the only samples with an anomalous (low 

for QD-27) TDS concentration and an elevated FC population. 

In no well were anomalous TDS concentrations detected in 

more than four samples. 

A statistically significant trend in TDS concentrations 

was observed in samples collected from 65 wells during 

1995–2013. Of these wells, 49 indicated a downward trend, 

and 16 indicated an upward trend (fig. 24). TDS trends in the 

41 remaining wells had a significance level of less than 95 percent and did not indicate a clear trend. Downward trends are 

indicated in wells in the upper part of the Upper Des Plaines 

System, in most of the Mainstream and Des Plaines Systems, 

and in most of the Indiana Avenue and Markham legs of the 

Calumet System. Upward trends are indicated in wells in the 

downstream part of the Upper Des Plaines System, appear 

to be present in the downstream parts of the Mainstream and 

Des Plaines Systems, and are indicated in the Little Cal and 

140th Street legs of the Calumet System. The trends were too 

variable and inconsistent to clearly indicate a cause for TDS 

variations. However, if CSF discharge to the Silurian aquifer 

affected the TDS concentrations, it is expected that TDS concentrations typically would increase. The result indicates the 

trends were primarily due to natural variations in TDS within 

the Silurian aquifer.

Ammonia

Ammonia (NH3) is a naturally occurring compound, 

but large quantities are produced anthropogenically by the 

breakdown of human waste and as a component of fertilizer. 

Ammonia concentrations in samples collected from monitoring wells open to the upper part of the Silurian aquifer in the 

Calumet area ranged from 0.1 to 0.9 mg/L during 1993 with 

a median concentration of 0.3 mg/L (Duwelius and others, 

1996). Ammonia concentrations in samples collected from 

water-supply wells open to the Silurian aquifer in suburban 

Cook County during the mid-1980s ranged from less than the 

detection limit of 0.1 mg/L to 0.72 mg/L, with an arithmetic 

mean concentration of about 0.40 mg/L (Voelker and others, 

1988). Annual geometric mean concentrations of ammonia in 

TARP discharge during 1995–2013 ranged from 9 to 30 mg/L. 

Ammonia concentrations are likely to be elevated in CSFaffected samples from the TARP wells.

The geometric mean concentration of ammonia in 

samples collected from the TARP monitoring wells during 

1995–2013 ranged from below the detection limit to 22 mg/L 

(fig. 25) with approximately 95 percent of the concentrations 

being less than 1.0 mg/L. Most of these ammonia concentrations are consistent with background concentrations in the 

Silurian aquifer. Geometric mean ammonia concentrations 

greater than 1.5 mg/L were detected near the future McCook 

Reservoir at monitoring wells QM–63, QM–64, QM–65, and 

QM–67, including a concentration of 22 mg/L at well QD–27. 

Because water was stored in the tunnels of the Des 

Plaines and Mainstream Systems prior to discharge for treatment during 1995–2013, the downstream part of these systems 

is where CSF-affected water is likely to have been present 

for the longest period of time and under the highest hydraulic 

pressure. These conditions would have promoted CSF flow 

from the TARP System to the Silurian aquifer and may have 

caused the elevated (greater than 1 mg/L) ammonia concentrations detected in this area. When the McCook Reservoir 

is placed on line, CSF will flow to the reservoir rather than 

remain in the tunnels, so the conditions that result in CSF 

migration to the aquifer will abate, and ammonia concentrations in the aquifer may decrease. 

Anomalous concentrations of ammonia were detected 

in fewer than four TARP monitoring wells on any given date 

during 1995–2013, indicating that spatially extensive CSF 

migration of ammonia into the Silurian aquifer did not occur 

(table 5). Anomalous ammonia concentrations were detected 

in 79 samples from the 106 TARP wells. Of these anomalies 

16 were low concentrations potentially not related to TARP 

events. A total of 34 samples with anomalous ammonia concentrations also contained anomalous values of other analytes, 

particularly DOC, TDS, sulfate, and hardness. Only one 

sample with high ammonia concentrations also had high FC 

populations. In no well were anomalous ammonia concentrations detected in more than five samples. 
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 53

0.31

0.52

0.3

0.092

0.081

0.48

0.49

0.064

0.35

0.23

0.39

0.46

0.35

0.62

0.35

22

0.67

0.35

0.3

0.2

0.15

0.21

0.34

0.28

0.26

0.28 0.31

<0.096

0.1

0.26

0.29

0.24

0.31

0.27

<0.10

0.25

0.26

0.31

0.078

<0.059

0.078

<0.050

0.19

0.34

0.19

0.27

0.28

0.3

0.33

0.076

0.45

1

0.34

0.54

1.6 2

8.2

1.8

0.61

0.93

0.39

0.44

0.34

0.27

0.22

0.25

0.23

0.12

0.069

<0.052

<0.034

0.062 <0.053

0.35 0.46

0.52

0.42

0.35

0.12

0.1

0.33

0.26

0.41

0.078

0.1

0.24 0.15

0.17

0.18

<0.073

0.25

0.26 0.073

0.13

0.088

0.19

0.09

0.14

0.14

<0.086

0.15

<0.064

0.58

0.22

0.96

0.13

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel—Colors indicate legs of 

 tunnel systems

Geometric mean concentration

 of ammonia as nitrogen, in 

 milligrams per liter, with trend 

 indicated

 Upward

 Downward

 No trend

 Unclear

 Less than

0.12

0.93

0.34

0.49

<

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 25. Geometric mean concentrations of ammonia and trends in samples from Tunnel and Reservoir Plan (TARP) System wells,

Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 25. Geometric mean concentrations of ammonia and trends in samples from Tunnel and Reservoir Plan (TARP) System wells, 

Cook County, Illinois, 1995–2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
54 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Of the 64 wells with a statistically significant trend 

in ammonia concentration from 1995 through 2013, 34 

(32 percent of the 106 wells analyzed) showed an upward 

trend, 14 showed a downward trend, and 16 showed stable 

concentrations (fig. 25). The 42 remaining wells (the single 

biggest category) did not exhibit a statistically significant 

trend in ammonia concentration and are considered to show 

an unclear trend. Upward trends were present in most of the 

wells in the Des Plaines System, the downstream part of the 

Mainstream System, and in much of the Calumet System. The 

variability in the trends, including the high number of wells 

with either statistically stable concentrations or an unclear 

trend, is consistent with drainage of water with spatially variable ammonia concentrations migrating to the lower part of 

the aquifer in response to drainage from the Silurian aquifer 

into the tunnel system. Increasing ammonia concentrations in 

the vicinity of the McCook Reservoir may reflect the increased 

presence of CSF-affected water in this area from 1995 through 

2013, although the possibility of non-TARP anthropogenic 

processes having an effect where the Silurian aquifer is at and 

near the land surface cannot be discounted. 

Dissolved Organic Carbon 

Dissolved organic carbon is a measure of the amount of 

organic material dissolved in water. DOC derived from residential and industrial wastewater results in high concentrations 

of DOC in CSF water; annual geometric mean concentrations 

in TARP discharge to the Calumet WRP during 2003–13 

ranged from about 21 to 51 mg/L. DOC concentrations in 

samples from non-TARP monitoring wells are not available. 

However concentrations of total organic carbon (TOC) in 

samples collected from the upper part of the Silurian aquifer in 

the Calumet area ranged from <2 to 87 mg/L during 1993 with 

a median concentration of 7.1 mg/L (Duwelius and others, 

1996). Concentrations of DOC should be less than or equal to 

those of TOC, indicating that DOC concentrations are likely to 

be elevated in CSF-affected samples from the TARP monitoring wells.

The geometric mean concentration of DOC in samples 

from the TARP monitoring wells from 1995 through 2013 

ranged from 0.70 to 22 mg/L (fig. 26) with more than 80 percent of the concentrations being less than 3.0 mg/L. Geometric mean concentrations of DOC greater than 4.5 mg/L were 

detected near the future McCook Reservoir at wells QD–27, 

QM–65, and QM–67, and at the eastern edge of the Little Cal 

leg of the Calumet System at well QC–37.

Anomalously high DOC concentrations were detected in 

samples from 47 wells located throughout the TARP System from mid-July through mid-September 2012 (table 5; 

fig. 27). During the 62-day period from July 1, 2012, through 

August 31, 2012, discharge from the TARP System to the 

Stickney WRP exceeded 100 Mgal/d a total of 26 days, including 15 days with more than 200 Mgal/d discharge. The high 

discharge from the Stickney WRP during much of the summer 

of 2012 indicates there may have been CSF events capable of 

reversing the flow directions and producing high DOC concentrations in the samples from the aquifer at these 47 wells. 

However, discharge from the TARP System to the Calumet 

WRP during July and August 2012 exceeded 80 Mgal/d for 

only 8 days, and water levels measured in the Calumet and 

Des Plaines tunnels during this period indicate CSF events 

occurred only on July 19 and August 27, 2012. It is likely that 

most of the high-discharge events measured at the Stickney 

WRP were discharge of drainage from the aquifer to the tunnel 

system rather than discharge of CSF. 

Anomalous DOC concentrations were detected in 85 

samples from the 106 TARP wells, including the 47 samples 

collected during the summer of 2012 (table 5). Of these 

anomalies, three were low concentrations potentially not 

related to TARP events. Fourteen samples with anomalous 

concentrations of DOC also had anomalous values of other 

analytes, particularly ammonia and hardness. Five samples 

with high DOC concentrations also had elevated FC populations. However, anomalous values of other analytes were 

detected in samples from only one well during the high DOC 

event in summer 2012. Anomalous DOC concentrations were 

not detected in more than three samples from any well. 

Statistically significant trends in DOC concentrations 

were observed in 103 of the 106 wells. Downward trends were 

indicated in 101 wells, an upward trend in 1 well, and no trend 

in 1 well (fig. 26). The downward trends may be related to a 

2005 upgrade of the instrument used to measure DOC concentrations, which marks a shift in the DOC concentrations from 

comparatively high and variable to low and stable (fig. 27). 

Because of the uncertainty in the cause of the downward 

trends, the DOC data are of limited utility for the assessment 

of CSF effects.

pH

pH is a field measurement of the negative log of the 

concentration of hydrogen ions in water. The pH of samples 

from non-TARP monitoring wells open to the upper part of the 

Silurian aquifer in the Calumet area ranged from about 6.7 to 

9.1, with a median value of about 8.0 (Duwelius and others, 

1996). Samples from water-supply wells open to the Silurian 

aquifer in suburban Cook County during the mid-1980s had 

a pH range of 6.7–8.3, with an arithmetic mean value of 7.2 

(Voelker, 1986; Voelker and others, 1988). The pH of CSF 

water discharged from the TARP System ranged from 7.2–7.7. 

Because the background range of pH values for groundwater 

in the Silurian aquifer encompassed the range of pH in the 

CSF, pH is likely to be of limited use identifying groundwater 

from wells with substantial CSF effects. However, samples 

with pH values greater than 7.7 are likely to contain little or no 

CSF. 
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 55

1.6

1.7

1.2

1.3 1.7

1.8

1.2

1.4

1.5

2.8

2.7

3.5

4.2 3.7

2.5

22

2.6

3.0

2.7

2.1

2.0

2.8

2.1

3.2

3.3 1.4 1.5

1.6

1.6

2.4

2.0

1.9

1.7

1.7

1.9

1.7

1.8

2.3

2.0

2.1

2.0

2.5

1.5

2.1

1.6

1.8

1.2

1.2

<1.1

1.1

1.4

2.3

2.0

2.8

2.9 2.4

10

4.9

1.3

1.3

1.5

1.2

1.5

2.3

2

1.1 1.5

1.4

0.70

1.1

0.77

1.3

1.7

4.0 3.2

3.5

3.1

2.1

1.9

2.6

2.8

2.8

1.9

1.5

1.0

1.4 1.4

3.1

1.6

1.7

1.2

1.1 2.1

1.4

2.6

2.1

<1.2

<1.0

<1.0

<1.0

1.1

1.9

1.3

1.4

1.3

6.5

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

Tunnel—Colors indicate legs

 of tunnel systems

Geometric mean concentration

 of dissolved organic carbon,

 in milligrams per liter, with 

 trend indicated

 Upward

 Downward

 No trend

 Unclear

 Less than

 

1.5

3.1

2.6

1.4

<

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 26. Geometric mean concentrations of dissolved organic carbon and trends from samples from Tunnel and Reservoir Plan (TARP)

System wells, Cook County, Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 26. Geometric mean concentrations of dissolved organic carbon and trends in samples from Tunnel and Reservoir Plan (TARP) 

System wells, Cook County, Illinois, 1995–2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
56 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

gure 27. Concentrations of dissolved organic carbon in samples from Tunnel and Reservoir Plan System well QD-28, Cook 

ounty, Illinois, 1995−2013. 

7/18/2012

0.0

1995 1997 1999 2001 2003 2005 2007 2009 2011 2013

2.0

4.0

6.0

8.0

10.0

12.0

Dissolved organic carbon,

in milligrams per liter

Year

Figure 27. Concentrations of dissolved organic carbon in samples from Tunnel and Reservoir 

Plan System well QD–28, Cook County, Illinois, 1995–2013.

Geometric mean pH values for samples collected from 

the TARP monitoring wells during 1995–2013 ranged from 

7.2 to 8.7 (fig. 28). Geometric mean pH values typically were 

less than 7.5 along the South and West legs of the Des Plaines 

System and were 8.0 or higher in most of the North and 

Middle legs of the Des Plaines System, in much of the North 

leg of the Mainstream System, and along much of the Torrence 

Avenue and Indiana Avenue legs of the Calumet System. 

Anomalously low pH values were measured on 

May 16, 2002, in wells QM–73, QM–74, QM–75, and QM–76 

(table 5). Discharge from the TARP System to the Calumet 

WRP exceeded 100 Mgal/d eight times in the 9 days preceding 

May 16, 2002, indicating that a CSF event may have affected 

the sample chemistry on that date. 

Anomalous pH values were detected in 33 samples from 

the 106 TARP wells (table 5). Anomalous pH values were not 

observed in more than two samples from any well. Dates of 

measured pH anomalies in samples from a well typically were 

associated with anomalies in the values of other analytes in 

only four samples. These data indicate that periodic CSF discharge to the Silurian aquifer did not have a substantial effect 

on pH values in the TARP monitoring wells. 

Of the 44 wells with a statistically significant trend in pH 

values from 1995 through 2013, 40 (about 38 percent of the 

106 wells analyzed) showed a downward trend through time, 

1 showed no trend, and 3 showed an upward trend (fig. 28). 

Most of these wells had a total change in pH of about 0.1 to 

0.5 standard units during 1995–2013. The pH trends in the 

remaining wells had a significance level of less than 95 percent, and the trends were not clearly identified (unclear trend). 

Wells exhibiting statistically significant trends almost always 

had geometric mean pH values in the 7.5–7.9 range, which is 

in the middle of the range for the dataset. Because of the lack 

of clear differences in pH of CSF and the ambient Silurian 

aquifer, the cause of these trends is not clearly indicated. 

However, the trends are consistent with aquifer water with 

consistent or low pH values (depending on location) draining to the monitoring wells in the deeper part of the aquifer 

through time.
Water Quality in Tunnel and Reservoir Plan System Monitoring Wells 57

7.6

7.8

7.7

7.7

7.5

7.4

7.2

7.3

7.4

7.3

7.5

7.6

7.5

7.7

7.8

7.7

7.6

7.9

7.8

7.9

7.8

7.8

7.5

7.8

7.8

7.9 7.8

7.7

8.0

7.4

7.9

8.1

8.0

7.8

7.8

8.1

8.0

7.9

7.4

7.6

7.7

8.2

7.9

7.6

7.8 7.6 7.9

7.7

7.3

7.2

7.4

7.3 7.2

7.3

8.4

8.1

8.7

8.2

7.2

7.2

7.6

7.6

7.6

8.2

7.9 7.7 7.8

8.6

8.5

8.3

8.4

8.3

7.9

8.0

8.0

7.6

7.6

7.3

7.4

7.8

7.9

7.9

8.1

8.3

8.3

8.1

8.0

8.2

8.1

8.1

8.1

8.2

7.7

8.1 7.9

8.1

8.3 7.9

8.4

8.2

8.1

8.3

8.0

8.0

8.1

LAKE

MICHIGAN ILLINOIS INDIANA

COOK COUNTY

DU PAGE COUNTY

COOK COUNTY

WILL COUNTY

McCook

Reservoir

Thornton

Reservoir

Stickney Water

Reclamation

Plant

Calumet Water

Reclamation

Plant

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

North leg

North

Branch

leg

South

leg

Middle leg

West leg

Torrence Avenue leg

Cal-Sag leg

Little Cal leg

Markham

leg

140th Street

leg

Roosevelt

Road leg

Indiana

Avenue leg

Majewski Reservoir Kirie Water

Reclamation

Plant

0 5 MILES

0 5 KILOMETERS

TARP tunnel and well locations from Metropolitan

Water Reclamation District of Greater Chicago

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89° 

EXPLANATION

7.4

Tunnel—Colors indicate legs 

 of tunnel systems

Geometric mean pH value,

 in Standard units, with

 trend indicated

 Upward

 Downward

 No trend

 Unclear

7.5

7.8

7.4

7.8

88°00' 87°50' 87°40' 87°30'

42°00'

41°50'

41°40'

Figure 28. Geometric mean values of pH and trends in samples from Tunnel and Reservoir Plan (TARP) System wells, Cook County,

Illinois, 1995−2013. Upward, downward, and no trends are significant with p-values less than or equal to 0.05.

Figure 28. Geometric mean values of pH and trends in samples from Tunnel and Reservoir Plan (TARP) System wells, Cook County, 

Illinois, 1995–2013. Upward, downward, and no trends are significant with p-values ≤ 0.05.
58 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Analyte Correlations

The value of every analyte in every sample obtained from 

a TARP monitoring well during 1995–2013 was correlated 

with the value of every other analyte in the sample. Correlation coefficients from the individual analyses are presented in 

appendix 4 and are summarized in table 6.

Ammonia concentrations, pH values, and FC populations 

showed either high degrees of positive or negative correlations 

in a small number of wells or did not indicate a preponderance 

of either positive of negative correlations. To a lesser degree, 

chloride concentrations and groundwater levels also did not 

indicate a preponderance of either positive or negative correlations. The lack of substantial correlation between FC populations and the values of other analytes indicates that none of the 

other analytes, by themselves, can be used as a surrogate for 

FC to identify the presence of CSF-affected water in the TARP 

wells if the sampling procedures are not changed. 

Values of hardness, sulfate, EC, TDS, and DOC tended to 

show a high degree of positive correlation with each other in 

at least 24 of the 106 wells sampled. These analytes (with the 

exception of DOC) are major chemical constituents in groundwater or are general indicators of water quality whose values 

are affected by the amount of the major constituents. However, 

no analyte pair (except EC and DOC) was highly correlated in 

samples from more than 50 wells (only one analyte pair was 

highly correlated in at least half of the wells). EC and DOC 

were the only analytes that indicated downward trends in concentration in most of the wells.

The results of this analysis indicate that water quality in 

samples from most of the wells was affected by processes that 

likely reduced the degree of correlation between the major 

analytes. These processes include the periodic migration of 

CSF into the Silurian aquifer, as well as spatial and temporal 

variations in the water chemistry in that part of the Silurian 

aquifer draining to a well because of natural phenomena (such 

as sulfate reduction) and non-TARP anthropogenic activities 

(such as road salt application).

Table 6. Summary of correlation coefficients for all analytes in all monitoring wells, Tunnel and Reservoir Plan System, Cook 

County, Illinois, 1995–2013. 

[Numbers are wells that display Kendall tau-b correlation coefficient for the analyte pair of greater than 0.25 or less than -0.25, +number of wells/−number 

of wells; —, not applicable]

Chloride Electrical 

conductivity

Fecal 

coliform Hardness Ammonia pH Sulfate

Total 

dissolved 

solids

Dissolved 

organic 

carbon

Electrical 

conductivity

+9/-9 — — — — — — — —

Fecal coliform +0/-0 +0/-1 — — — — — — —

Hardness +19/-14 +34/-4 +1/-2 — — — — — —

Ammonia +18/-3 +9/-8 +2/-0 +17/-6 — — — — —

pH +0/-12 +6/-1 +0/-0 +4/-6 +1/-6 — — — —

Sulfate +15/-11 +39/-3 +1/-2 +50/-5 +11/-11 +10/-2 — — —

Total dissolved 

solids

+24/-2 +24/-0 +0/-1 +41/-1 +13/-4 +2/-5 +45/-1 — —

Dissolved 

organic 

carbon

+14/-22 +63/-1 +1/-1 +39/-10 +12/-4 +10/-2 +50/-7 +35/-2 —

Groundwater 

level

+21/-13 +22/-17 +5/-1 +12/-19 +20/-4 +2/-3 +20/-23 +16/-10 +42/-19
Implications for Future Monitoring 59

Coliform Bacteria and Escherichia coli

Data from Water-Supply Wells in the 

Vicinity of the Tunnel and Reservoir 

Plan System

The Silurian aquifer has historically been used for municipal, commercial, and industrial water supply in northeastern 

Illinois. The City of Chicago, which is where most of the 

TARP System is located, passed an ordinance in 1997 (Chicago Municipal Code 11–8–390) that effectively precludes 

groundwater use for public water supply. However, there are 

51 water-supply wells within 5 mi of the TARP System but 

outside of the Chicago City limits that obtained water from the 

Silurian aquifer from 1999 through 2015. Of these 51 wells, 

18 have been abandoned and 4 are inactive, leaving 29 active 

water-supply wells within 5 mi of the TARP System that were 

sampled by the IEPA in 2015 (fig. 29). This sampling is part of 

the routine statewide monitoring effort performed by the IEPA 

in selected water-supply wells and is not part of the TARP 

System monitoring effort.

More than 4,850 total coliform analyses (which includes 

FC) were performed on samples of raw water from these 

water-supply wells beginning in 1999 and continuing through 

the time of report preparation (March 2015). These samples 

(taken prior to treatment and before water enters the distribution system for transmission to the public) were analyzed 

only for the presence or absence of total coliform; the number 

of colonies was not counted. Total coliform was detected in 

145 samples, including 14 wells with repeat detections in the 

northern part of Cook County and west of the future McCook 

Reservoir (fig. 29). 

More than 2,600 samples of raw water from these 

water-supply wells were tested for Escherichia coli (E. coli), 

resulting in 28 detections (fig. 29). E. coli were detected in 

more than one sample from an abandoned well in east-central 

DuPage County about 6.5 mi northwest of the future McCook 

reservoir and from two active wells about 0.4 mi east of the 

Majewski Reservoir (fig. 2). 

Some of the water-supply wells with detections of total 

coliform and E. coli are in the LaGrange area, where sampling 

indicates increasing concentrations of chloride and TDS in the 

Silurian aquifer that predates construction of the TARP System 

(Gibb and O’Hearn, 1980). These increased concentrations 

were attributed to the application of road salts, but their presence indicates that other anthropogenic compounds applied 

at or near the land surface—such as septic wastes—may be 

capable of migrating to the Silurian aquifer in parts of northeastern Illinois.

Implications for Future Monitoring

Data analysis presented in this report indicates that most 

of the samples collected during the 1995–2013 monitoring 

period were affected by the chemistry of the Silurian aquifer 

in the vicinity of the monitoring well. Anomalous values of 

most of the analytes were detected in all of the monitoring 

wells, particularly those with a high frequency of detection 

for FC (table 7), but typically during less than 5 percent of 

the sampling events (fig. 12, table 5). Dates during which 

anomalous values of an analyte were detected in a well (or in 

multiple wells) usually were not associated with the detection 

of anomalous values of other analytes, especially FC. Therefore, many of the identified anomalies in analyte values may 

not have been caused by CSF migration into the aquifer. These 

data indicate that CSF-affected water was present in a small 

percentage of the samples collected from most of the monitoring wells. This result is likely due to the fact that monitoring 

occurred on a fixed schedule, which would only occasionally 

coincide with the random CSF events. 

CSF discharge to the aquifer is expected to occur over a 

smaller part of the TARP System for shorter periods of time 

once the Thornton and McCook reservoirs are connected to the 

TARP System. Improved efficiency of the monitoring effort 

will be needed to define the (likely) smaller future spatial and 

temporal effects of CSF on the water quality of the aquifer.

The efficacy of the monitoring program could be 

improved by focusing future sampling efforts on those wells 

where analytes related to the presence of CSF were detected in 

a substantial number of samples during the 1995–2013 sampling period. Groundwater levels and FC populations are clear 

indicators of the presence (and to a lesser degree absence) of 

CSF effects. Chloride, TDS, EC, ammonia, and DOC concentrations can indicate the presence of CSF in a sample but typically only on a periodic or seasonal basis or in a small number 

of wells where the difference between their concentration in 

aquifer water and the CSF is particularly high. Hardness, sulfate, pH, and temperature (measured at the well head) provide 

limited insight into the effects of CSF events on groundwater 

quality. 

Data from wells located at the boundaries of the monitoring system nearest water-supply wells might yield more 

valuable information than data from wells in the middle of the 

TARP System as a result of their proximity to potential points 

of exposure. In addition, many of the wells showing greater 

CSF effects are located in similar areas, often the downstream 

parts of the tunnel systems, and yield data with a high degree 

of correlation. Sampling from a few representative monitoring wells during CSF events may be a more effective use of 

resources than sampling all wells on a fixed schedule. 
60 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

66/0 80/1

69/0

59/0

88/0

87/0

84/0

84/0

0/0

0/0

60/0

2/0

0/0 77/0

93/1 0/0

86/0

78/0

75/0

11/0

27/4

16/0

88/0

73/0

87/0

1/0

90/1

110/9

1/0 66/0

0/0

52/0

75/0

74/0

0/0

89/1

86/0

50/0

0/0

87/0

0/0

0/0

88/0

105/11

0/0

0/0

15/0

1/0

82/4 66/0

159/2

148/2

160/3

112/2

119/0

151/0

2/0

6/2

66/0

9/0 123/6

185/13 1/0

117/1

81/0

78/0

16/0

50/9

16/0

165/1

74/0

164/3

76/0

135/3

76/0 139/0

128/26

263/0

1/0

172/3

204/24

40/0 156/2

4/0

91/4

164/7

80/0

1/0

182/1

70/1 178/0

1/0

179/1

24/0

48/0

196/0

198/18 1/0

121/7

15/0

0 5 10 MILES

0 5 10 KILOMETERS

Base from U.S. Geological Survey 1:100,000-scale

digital data. Albers Equal-Area Conic Projection 

Standard parallels 45° and 33°, central meridian -89°

LAKE

MICHIGAN

ILLINOIS

INDIANA

COOK COUNTY

DU PAGE COUNTY

DU PAGE COUNTY

WILL COUNTY

COOK COUNTY

WILL COUNTY

LAKE COUNTY

COOK COUNTY

MAINSTREAM

SYSTEM

UPPER

DES PLAINES

SYSTEM

DES PLAINES

SYSTEM

CALUMET

SYSTEM

EXPLANATION

Reservoir

Tunnel

Water-supply well with number of total coliform samples/number 

 of total coliform detected (top), number of E. coli samples/number 

 of E. coli detected (bottom)

Status in 2015

Active

 Inactive

 Abandoned

70/1

50/0

88° 87°

42°

41°40'

Figure 29. Location of water-supply wells open to the Silurian aquifer within 5 miles of the Tunnel and Reservoir Plan (TARP) System, 

northeast Illinois, with results of total coliform and Escherichia coli (E.coli) analysis in raw water prior to treatment before entering

the water-distribution system, 1999−2015.

Figure 29. Location of water-supply wells open to the Silurian aquifer within 5 miles of the Tunnel and Reservoir Plan System, 

northeast Illinois, with results of total coliform and Escherichia coli (E coli) analyses in raw water prior to treatment and before 

entering the water-distribution system, 1999–2015.
Implications for Future Monitoring 61

Table 7. Summary of water-quality data indicating the presence of combined sewer flow effects in monitoring wells in which fecal 

coliform was detected in 10 percent or more of the samples, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

Well

Percentage of 

samples with 

fecal coliform 

detections

Analyte with anomalously 

high values1

Analyte displaying 

seasonality2

Analyte with elevated 

geometric mean 

concentration

MW–5 22 Chloride, total dissolved solids Chloride, total dissolved solids None

MW–6 19 Chloride None None

MW–7 17 None None None

MW–8 31 None Chloride None

QD–27 15 Ammonia, dissolved organic carbon, 

hardness, sulfate, total dissolved 

solids

None Ammonia, dissolved 

organic carbon

QD–29 17 Dissolved organic carbon Total dissolved solids None

QD–30 10 Chloride, hardness None None

QD–31 30 Groundwater elevation, total dissolved 

solids

None None

QD–34 14 Dissolved organic carbon Total dissolved solids None

QD–36 11 Chloride, dissolved organic carbon Total dissolved solids None

QD–46 13 Groundwater elevation, chloride, 

dissolved organic carbon, hardness, 

total dissolved solids, sulfate

None None

QM–61 33 Chloride, groundwater elevation, electrical conductivity, hardness, ammonia, 

sulfate, total dissolved solids 

None None

QM–62 54 Chloride, electrical conductivity, 

hardness, sulfate, total dissolved 

solids

Chloride None

QM–63 36 Hardness, total dissolved solids, 

dissolved organic carbon

None Ammonia

QM–64 48 Chloride, hardness, sulfate, total 

dissolved solids, dissolved organic 

carbon

None Ammonia

QM–65 26 Chloride, hardness, sulfate, total 

dissolved solids, dissolved organic 

carbon

Total dissolved solids Ammonia, dissolved 

organic carbon

QM–67 81 Chloride, hardness, ammonia, sulfate, 

total dissolved solids, dissolved 

organic carbon

Chloride Ammonia, dissolved 

organic carbon

QM–68 32 Dissolved organic carbon Chloride None

QM–75 24 Groundwater elevation, hardness, pH, 

dissolved organic carbon

Total dissolved solids None

QM–77 29 Groundwater elevation, total 

dissolved solids, dissolved organic 

carbon

Total dissolved solids None

QC–2 63 Hardness, sulfate, total dissolved solids None None

QC–4 22 None None None

QC–17 15 Total dissolved solids, dissolved organic 

carbon

None None

1

Anomalously high values detected in multiple wells on a given sampling date or anomalously high values of multiple analytes in a particular sample. 

2

Analytes demonstrating seasonal variation in concentration.
62 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Finally, the efficacy of the monitoring program would be 

improved by sample collection during and after CSF events 

rather than on a fixed schedule. Improvement of the timing 

of sample collection would be aided by hourly measurement 

of water levels in the tunnel systems; continuous monitoring 

of water temperature, water level, specific conductance, and 

perhaps organic carbon using devices located within the open 

interval of selected monitoring wells; and real time reporting 

of that data. These water-quality data need to be combined 

with some initial intensive data collection to verify the utility 

of these analytes in the detection of CSF effects on the aquifer 

(from initial to maximum effect to the eventual return to background conditions). 

Summary and Conclusions

The U.S. Geological Survey, in cooperation with the 

Metropolitan Water Reclamation District of Greater Chicago 

(MWRDGC), performed statistical analysis of samples collected from 106 Tunnel and Reservoir Project (TARP) System 

monitoring wells sampled by the MWRDGC from 1995 

through 2013. This analysis was done to assess the efficacy of 

the monitoring effort. Analysis was performed on groundwater 

levels, pH, temperature, electrical conductivity, total dissolved 

solids, hardness, ammonia as nitrogen (ammonia), dissolved 

organic carbon, chloride, sulfate, and fecal coliform data. 

Groundwater typically drains from the Silurian aquifer into the TARP tunnels, inducing flow within the aquifer 

towards the tunnel system over a distance of thousands of 

feet. As a consequence, analyte values in the samples from the 

monitoring wells are primarily affected by their values in that 

part of the aquifer draining to the tunnels being monitored by 

a particular well. If a precipitation event induces combined 

sewer flow (CSF) in the tunnel system in excess of about 

80 million gallons per day, the hydraulic pressure in the tunnel 

system can be large enough to overcome the normal hydraulic 

gradient and induce flow from the tunnels to the Silurian aquifer for a period of hours to days. These effects appear to occur 

throughout the TARP System but are particularly substantial in 

the downstream part of the tunnel systems.

Tunnel-to-aquifer flow can cause analytes dissolved in 

the CSF to migrate into the aquifer, resulting in high levels of 

fecal coliform, chloride, hardness, ammonia, total dissolved 

solids, dissolved organic carbon, and electrical conductivity 

in parts of the aquifer, but typically less than 5 percent of the 

samples from a particular well contained elevated values of 

these analytes because of the inefficiency of the fixed sampling schedules. Migration of analytes from the tunnels to 

the nearby monitoring wells may occur within 2 weeks of a 

CSF event. Once the aquifer-to-tunnel hydraulic gradient is 

reestablished, the temporarily elevated values of the analytes 

emplaced in the aquifer during the CSF event return to background levels. Groundwater levels tend to return to background levels within 2 weeks of a CSF event. Fecal coliform 

populations can to return background levels within about 4 

to 6 weeks, whereas chloride concentrations can take 4 to 

6 months to return to background levels.

Values of electrical conductivity, sulfate, and dissolved 

organic carbon showed a statistically significant decrease in at 

least 60 percent of the TARP wells from 1995 through 2013. 

The trend in dissolved organic carbon concentrations may be 

related to an upgrade of the device used to quantify dissolved 

organic carbon concentrations during the period of analysis. 

Values of hardness, chloride, total dissolved solids, ammonia, and pH did not show a statistically significant increase 

or decrease in more than 50 percent of the wells from 1995 

through 2013. Water quality in the Silurian aquifer is spatially 

variable owing to a variety of natural and non-TARP anthropogenic processes. Therefore, the trend in the values of an 

analyte at a well likely was primarily a reflection of the spatial 

variation in the value of the analyte within that part of the 

Silurian aquifer draining to the tunnel near the well. 

In addition to the water quality-effects associated with 

drainage from the Silurian aquifer to the tunnel at a well, there 

were short-term effects associated with the periodic migration of CSF into the aquifer. Depending on the well and the 

analyte, these short-term effects could be observed during only 

one or two sampling events or repeated on a seasonal basis for 

several years. Short-term CSF events appear to have affected 

fecal coliform populations in at least one sample collected 

from 77 of the 106 wells sampled from 1995 through 2013. 

Clearly identifiable CSF effects in the form of fecal coliform 

detections were present in 23 wells during 10 percent or more 

of the sampling events; only 3 wells had fecal coliform populations during most of the sampling events. The wells with 

fecal coliform present in at least 10 percent of the samples 

tend to be in the upper part of the Upper Des Plaines System, 

the downstream parts of the Des Plaines and Mainstream 

Systems near the Stickney Water Reclamation Plant and the 

future McCook Reservoir, and near the Thornton Reservoir in 

the Calumet System. 

The movement of groundwater and CSF between the 

tunnel system and the Silurian aquifer is dependent on a 

number of factors, including the relative hydraulic pressure in 

the aquifer and the tunnel system, the integrity of the tunnel 

liner, and the hydraulic properties of the aquifer between the 

tunnel and the well. Migration of CSF into the Silurian aquifer 

is likely to be greatest in the downstream parts of most of the 

tunnel systems because these parts of the tunnel system tend to 

contain CSF-affected water under the highest pressure for the 

longest periods of time. The amount of CSF movement into 

the aquifer is expected to be reduced when the McCook and 

Thornton Reservoirs are connected to the tunnel systems.

Temperature (if measured outside of the well, as per this 

monitoring effort), pH, sulfate, and hardness were of limited 

value for identifying the presence of CSF because they were 

affected by atmospheric interaction or have values that did not 

differ appreciably between the CSF and groundwater. Chloride, electrical conductivity, total dissolved solids, ammonia, 
References Cited 63

and dissolved organic carbon can indicate the presence of 

CSF, but separating analyte values related to CSF from those 

related to background water quality in the Silurian aquifer can 

be difficult. Future temperature measurements taken within 

the open interval of the well, if attempted, may be useful for 

identifying the presence of CSF.

High groundwater levels appear to be a good indicator of 

the initiation of a CSF event, but the relation between groundwater levels and analyte values is indirect, and groundwater 

levels are elevated for a short period of time (days) relative to 

the duration of water-quality effects (weeks to months). As a 

consequence, groundwater levels cannot be used to assess the 

full nature (analyte, concentration, duration) of CSF effects.

Because of its natural absence from the Silurian aquifer, fecal coliform is the only analyte whose detection can be 

attributed solely to the presence of water affected by CSF. 

The absence of fecal coliform in a sample is a good, but not 

conclusive, indication that CSF is not affecting water quality. 

Of the analytes tested, fecal coliform is the most useful for 

assessing the effects of CSF in the Silurian aquifer near the 

TARP System. The lack of correlation between fecal coliform 

populations and the values of other analytes indicates that the 

other analytes cannot be used as a surrogate for fecal coliform 

to identify the presence of CSF effects. Fecal coliform populations within the various tunnel systems tend to be highly correlated between wells in which fecal coliform was detected in 

at least 10 percent of the samples. 

Acknowledgments

The author thanks Dave Lorenz of the U.S. Geological 

Survey for his guidance with the statistical software used to 

obtain the results presented in this report. 

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 65

Appendix 1. Summary statistics for analytes and physical 

properties, by well, Tunnel and Reservoir Plan System, 

1995–2013

Each appendix has four Tunnel and Reservoir Plan Systems, each with multiple tables of varing sizes.

Table 1–1 to table 1–34. Summary statistics for analytes and physical properties in samples from wells, 

Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois.

Table 1–35 to table 1–74. Summary statistics for analytes and physical properties in samples from wells, 

Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois. 

Table 1–75 to table 1–98. Summary statistics for analytes and physical properties in samples from wells, 

Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois. 

Table 1–99 to table 1–107. Summary statistics for analytes and physical properties in samples from wells, 

Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois.
66 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–1. Summary statistics for analytes and physical properties in samples from monitoring well QC–1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 259 1,505 7.0 669 0.69 8.9 585 1,204 13.0 21.0 -86

Minimum value 37 286 <1 62 0.16 6.4 30 384 1.0 7.2 -248

Geometric mean value 49 925 na 543 0.35 7.4 248 830 4.0 12.3 -125

Arithmetic mean value 51 949 na 551 0.36 7.5 253 837 4.4 12.4 -126

Standard deviation 20 189 na 63 0.059 0.32 40 96 2.1 1.3 18

Coefficient of variation 0.39 0.19 na 0.11 0.16 0.043 0.16 0.11 0.47 0.11 -0.14

Number of samples 263 263 263 263 263 263 263 263 263 263 263

Number of detections 263 263 3 263 263 263 263 263 263 263 263

Percent detections 100 100 1 100 100 100 100 100 100 100 100
Appendix 1 67

Table 1–2. Summary statistics for analytes and physical properties in samples from monitoring well QC–2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 391 1,091 28,000 579 3.0 8.9 258 850 57 22.0 -85

Minimum value <15 210 <1 25 0.050 6.1 0.34 204 <1 6.8 -314

Geometric mean value 41 462 19 94 0.46 7.6 29 399 3.2 13.0 -259

Arithmetic mean value 2 551 1,086 112 0.67 7.8 31 415 3.8 13.1 -262

Standard deviation 23 121 3,362 57 0.30 0.42 23 72 3.6 1.7 31

Coefficient of variation 0.54 0.22 3.1 0.51 0.45 0.054 0.74 0.17 0.94 0.13 -0.12

Number of samples 294 294 294 294 294 294 294 294 294 294 294

Number of detections 293 294 185 294 294 294 294 294 293 294 294

Percent detections >99 100 63 100 100 100 100 100 >99 100 100
68 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–3. Summary statistics for analytes and physical properties in samples from monitoring well QC–2.1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 97 870 84 100 0.85 8.7 40 744 9.0 17.1 -271

Minimum value 5 276 <1 39 0.040 6.6 <0.4 366 0.8 9.0 -296

Geometric mean value 34 561 na 61 0.50 7.7 5.3 545 3.5 12.8 -278

Arithmetic mean value 36 582 na 61 0.52 7.7 9.5–9.6 548 4.1 12.9 -290

Standard deviation 10 152 na 8.4 0.13 0.41 9.0–9.1 62 2.8 1.8 4.9

Coefficient of variation 0.29 0.26 na 0.14 0.25 0.054 1.1 0.11 0.68 0.14 -0.02

Number of samples 226 226 226 226 226 225 226 226 226 226 226

Number of detections 226 226 14 226 226 225 191 226 225 226 226

Percent detections 100 100 6 100 100 100 85 100 100 100 100
Appendix 1 69

Table 1–4. Summary statistics for analytes and physical properties in samples from monitoring well QC–2.2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 53 1,436 1,100 574 1.49 9.1 493 866 21.0 16.0 -122

Minimum value 12 251 <1 12 0.03 6.7 3 172 0.9 9.0 -288

Geometric mean value 16 496 na 44 0.42 8.2 37 389 3.1 12.7 -227

Arithmetic mean value 17 514 na 51 0.46 8.2 46 395 3.8 12.7 -231

Standard deviation 8.2 154 na 59 0.19 0.55 53 79 2.8 1.5 37

Coefficient of variation 0.47 0.30 na 1.2 0.41 0.067 1.2 0.20 0.73 0.12 -0.16

Number of samples 87 87 87 87 87 87 87 87 87 86 87

Number of detections 84 87 8 87 87 87 87 87 87 86 87

Percent detections 97 100 9 100 100 100 100 100 100 100 100
70 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–5. Summary statistics for analytes and physical properties in samples from monitoring well QC–3, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 30 694 220 96 1.43 8.7 50 528 9.0 16.0 -99

Minimum value 3 238 <1 54 0.02 6.7 19 368 0.4 9.0 -267

Geometric mean value 12 502 0.79 64 0.35 7.8 27 420 2.1 12.5 -227

Arithmetic mean value 12 512 3.7–4.6 64 0.39 7.9 27 422 2.7 12.5 -229

Standard deviation 3.7 101 25.5–25.6 5.4 0.16 0.48 6.3 30 1.7 1.3 24

Coefficient of variation 0.30 0.20 5.5–6.9 0.085 0.40 0.061 0.23 0.071 0.64 0.10 -0.10

Number of samples 75 75 75 75 75 75 75 75 75 75 75

Number of detections 74 74 9 74 74 74 74 74 73 74 74

Percent detections 99 99 12 99 99 99 99 99 97 99 99
Appendix 1 71

Table 1–6. Summary statistics for analytes and physical properties in samples from monitoring well QC–4, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed, e, estimated]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 20 703 96 17 1.72 9.0 48 518 7.0 18.3 -196

Minimum value 1 339 <1 9 0.06 6.9 8 392 0.4 10.0 -262

Geometric mean value <11 523 1.3 11 0.12 8.1 16 442 1.9 12.3 -237

Arithmetic mean value <12 534 82–83 11 0.16 8.1 19 442 2.8 12.3 -235

Standard deviation <3.5 107 624 1.6 0.18 0.58 10 27 2.6 1.4 12

Coefficient of variation 0.29e 0.20 7.5–7.6 0.15 1.1 0.072 0.53 0.062 0.93 0.11 -0.050

Number of samples 87 88 89 88 89 88 89 89 89 88 87

Number of detections 77 88 20 88 86 88 85 89 74 88 87

Percent detections 89 100 22 100 97 100 96 100 83 100 100
72 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–7. Summary statistics for analytes and physical properties in samples from monitoring well QC–5, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 39 1,334 <1 16 0.41 9.0 43 726 15 15.0 -129

Minimum value <15 357 <1 1 <0.01 6.8 2 458 1 9.0 -267

Geometric mean value 26 766 na 9.0 0.10 8.1 11 599 2.6 12.2 -225

Arithmetic mean value 27 785 na 10 0.13 8.1 13 601 3.4 12.2 -226

Standard deviation 3.8 167.5 na 2.3 0.07 0.53 7.8 45 2.6 1.2 25

Coefficient of variation 0.14 0.21 na 0.23 0.54 0.065 0.58 0.075 0.76 0.10 -0.11

Number of samples 86 87 87 87 87 87 87 87 87 87 87

Number of detections 85 87 0 85 81 87 84 87 85 87 87

Percent detections 99 100 0 98 93 100 97 100 98 100 100
Appendix 1 73

Table 1–8. Summary statistics for analytes and physical properties in samples from monitoring well QC–6, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 35 950 8 51 0.60 9.0 564 674 12 16.0 -151

Minimum value 13 318 <1 8 0.02 6.7 4 186 1 7.5 -259

Geometric mean value 18 661 na 23 0.33 8.1 21 522 2.8 12.4 -218

Arithmetic mean value 19 678 na 25 0.35 8.1 38 527 3.5 12.4 -219

Standard deviation 4.7 145 na 10 0.076 0.55 83 66 2.4 1.2 21

Coefficient of variation 0.25 0.21 na 0.41 0.22 0.067 2.2 0.13 0.70 0.10 -0.10

Number of samples 87 86 87 86 87 86 87 87 87 86 86

Number of detections 83 86 4 86 87 86 83 87 87 86 86

Percent detections 95 100 5 100 100 100 95 100 100 100 100
74 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–9. Summary statistics for analytes and physical properties in samples from monitoring well QC–7, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 27 859 <1 501 0.70 9.1 32 1,130 10 18.0 -101

Minimum value 2 312 <1 5 0.11 6.4 0.40 322 0.9 10.0 -189

Geometric mean value 11 579 na 13 0.26 8.1 3.7 441 2.8 12.4 -155

Arithmetic mean value 11 589 na 18 0.27 8.1 6.7 446 3.3 12.5 -156

Standard deviation 3.1 104 na 55 0.080 0.58 7.0 88 1.9 1.3 16

Coefficient of variation 0.27 0.18 na 3.0 0.30 0.071 1.0 0.20 0.56 0.10 -0.10

Number of samples 80 80 81 80 81 80 81 81 81 80 80

Number of detections 80 80 0 80 81 79 67 81 80 80 80

Percent detections 100 100 0 100 100 99 83 100 99 100 100
Appendix 1 75

Table 1–10. Summary statistics for analytes and physical properties in samples from monitoring well QC–9, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed; e, estimated]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 26 731 5,800 107 0.77 9.6 49 550 7.0 18.0 -75

Minimum value 6 248 <1 44 0.11 6.4 10 268 0.7 9.2 -255

Geometric mean value <10 411 na 61 0.41 8.0 25 328 1.9 12.7 -191

Arithmetic mean value <10 418 na 62 0.49 8.0 26 330 2.3 12.8 -194

Standard deviation <2.6 77 na 6.7 0.22 0.53 8.5 38 1.4 1.3 37

Coefficient of variation 0.26e 0.18 na 0.11 0.45 0.067 0.32 0.11 0.60 0.10 -0.19

Number of samples 74 75 75 75 75 75 75 75 75 75 75

Number of detections 64 75 3 75 73 75 75 75 75 75 75

Percent detections 86 100 4 100 97 100 100 100 100 100 100
76 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–11. Summary statistics for analytes and physical properties in samples from monitoring well QC–10, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed; e, estimated] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 40 1,132 <1 21 0.37 9.4 64 506 10.0 18.0 -124

Minimum value 24 190 <1 9 0.02 7.0 <1 286 0.3 10.0 -250

Geometric mean value 31 498 na 12 0.078 8.2 <5.2 405 1.5 12.5 -219

Arithmetic mean value 31 512 na 12 0.097–0.098 8.2 <8.5 407 2.0 12.6 -220

Standard deviation 2.6 125 na 2.1 0.058–0.059 0.5 <9.6 37 1.8 1.2 21

Coefficient of variation 0.084 0.24 na 0.17 0.59–0.61 0.07 1.1e 0.091 0.90 0.10 -0.093

Number of samples 88 88 88 88 88 88 88 88 88 88 88

Number of detections 88 88 0 88 77 88 67 88 68 88 88

Percent detections 100 100 0 100 88 100 76 100 77 100 100
Appendix 1 77

Table 1–12. Summary statistics for analytes and physical properties in samples from monitoring well QC–11, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 40 565 <1 26 0.19 9.1 30 452 7.0 15.0 -186

Minimum value 14 289 <1 11 <0.01 7.1 <0.4 214 0.2 11.0 -241

Geometric mean value 23 403 na 21 0.10 8.1 <2.1 306 1.0 12.8 -221

Arithmetic mean value 23 408 na 21 0.10 8.2 5.4–5.5 309 1.4 12.8 -222

Standard deviation 4.2 65 na 2.6 0.039 0.57 7.3 39 1.5 1.1 13

Coefficient of variation 0.18 0.16 na 0.12 0.39 0.070 1.3–1.4 0.13 1.1 0.084 -0.058

Number of samples 52 52 52 52 52 52 52 52 52 52 52

Number of detections 52 52 0 51 50 52 32 52 37 52 52

Percent detections 100 100 0 98 96 100 62 100 71 100 100
78 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–13. Summary statistics for analytes and physical properties in samples from monitoring well QC–12, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 47 1,500 15 286 0.56 8.6 844 1,088 10.0 25.0 -209

Minimum value 23 526 <1 21 <0.01 6.6 28 574 0.3 5.4 -274

Geometric mean value 37 991 na 155 0.24 7.7 282 891 1.4 12.6 -242

Arithmetic mean value 37 1021 na 167 0.27 7.7 304 896 2.1 12.8 -242

Standard deviation 4.6 245 na 54 0.10 0.43 109 96 2.1 2.4 15

Coefficient of variation 0.12 0.24 na 0.32 0.37 0.056 0.36 0.11 1.0 0.19 -0.062

Number of samples 52 52 52 52 52 52 52 52 52 52 52

Number of detections 52 52 2 52 51 52 52 52 37 52 52

Percent detections 100 100 4 100 98 100 100 100 71 100 100
Appendix 1 79

Table 1–14. Summary statistics for analytes and physical properties in monitoring well QC–13, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 63 890 <1 2,692 0.25 9.6 70 554 8.0 15.1 -210

Minimum value 21 300 <1 21 0.05 7.1 8.0 304 0.5 10.0 -285

Geometric mean value 42 559 na 39 0.15 7.9 35 444 1.4 13.0 -246

Arithmetic mean value 43 572 na 90 0.16 7.9 38 447 1.9 13.0 -246

Standard deviation 11 120 na 376 0.049 0.51 12 50 1.7 1.1 19

Coefficient of variation 0.26 0.21 na 4.2 0.31 0.064 0.32 0.11 0.89 0.086 -0.075

Number of samples 50 50 50 50 50 50 50 50 50 50 50

Number of detections 50 50 0 50 50 50 50 50 39 50 50

Percent detections 100 100 0 100 100 100 100 100 78 100 100
80 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–15. Summary statistics for analytes and physical properties in samples from monitoring well QC–13, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 63 890 <1 2,692 0.25 9.6 70 554 8.0 15.1 -210

Minimum value 21 300 <1 21 0.05 7.1 8.0 304 0.5 10.0 -285

Geometric mean value 42 559 na 39 0.15 7.9 35 444 1.4 13.0 -246

Arithmetic mean value 43 572 na 90 0.16 7.9 38 447 1.9 13.0 -246

Standard deviation 11 120 na 376 0.049 0.51 12 50 1.7 1.1 19

Coefficient of variation 0.26 0.21 na 4.2 0.31 0.064 0.32 0.11 0.89 0.086 -0.075

Number of samples 50 50 50 50 50 50 50 50 50 50 50

Number of detections 50 50 0 50 50 50 50 50 39 50 50

Percent detections 100 100 0 100 100 100 100 100 78 100 100
Appendix 1 81

Table 1–16. Summary statistics for analytes and physical properties in samples from monitoring well QC–14, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 312 1,040 <1 164 0.32 9.2 34 3,982 9.0 16.0 -19

Minimum value 19 442 <1 12 0.02 6.8 0.4 330 1.9 8.0 -248

Geometric mean value 66 644 na 73 0.17 7.8 0.97–2.6 598 3.1 12.7 -205

Arithmetic mean value 83 665 na 90 0.19 7.8 7.6 659 3.4 12.7 -212

Standard deviation 53 172 na 47 0.079 0.5 9.4 486 1.6 1.3 29

Coefficient of variation 0.64 0.26 na 0.52 0.42 0.06 1.2 0.74 0.47 0.10 -0.14

Number of samples 53 53 53 53 53 53 53 53 53 53 53

Number of detections 53 53 0 53 52 53 36 53 53 53 53

Percent detections 100 100 0 100 98 100 68 100 100 100 100
82 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–17. Summary statistics for analytes and physical properties in samples from monitoring well QC–15, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 54 679 <1 62 0.28 9.2 48 464 7.0 18.8 -215

Minimum value 12 249 <1 5 0.01 7.0 <0.4 244 0.7 10.9 -240

Geometric mean value 15 418 na 14 0.18 8.1 1.4 337 1.6 12.9 -217

Arithmetic mean value 16 426 na 15 0.20 8.1 5.8–5.9 339 2.6 13.0 -227

Standard deviation 6.6–7.0 84 na 7.2 0.053 0.5 10 38 2.0 1.5 7.3

Coefficient of variation 0.41–0.44 0.20 na 0.47 0.27 0.07 1.8 0.11 0.77 0.11 -0.032

Number of samples 50 50 50 50 50 50 50 50 50 50 50

Number of detections 47 50 0 50 50 50 28 50 42 50 50

Percent detections 94 100 0 100 100 100 56 100 84 100 100
Appendix 1 83

Table 1–18. Summary statistics for analytes and physical properties in samples from monitoring well QC–16, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 253 999 1 126 0.95 9.0 219 1,148 8.0 17.8 -5

Minimum value 8 329 <1 7 0.01 6.7 15.0 354 0.4 9.0 -262

Geometric mean value 19 629 na 76 <0.073 7.8 54 531 1.7 12.1 -191

Arithmetic mean value 22 647 na 78 0.088 7.8 57 536 2.2 12.2 -200

Standard deviation 26 147 na 11.5 0.11 0.4 22 82 1.7 1.6 40

Coefficient of variation 1.2 0.23 na 0.15 1.3 0.06 0.39 0.15 0.77 0.13 -0.20

Number of samples 85 85 85 85 85 85 85 85 85 85 85

Number of detections 85 85 1 85 66 85 85 85 75 85 85

Percent detections 100 100 1 100 78 100 100 100 88 100 100
84 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–19. Summary statistics for analytes and physical properties in samples from monitoring well QC–17, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 20 835 51 198 0.37 8.6 222 980 8.3 23.0 -130

Minimum value 3 263 <1 17 0.09 6.2 10 388 0.5 9.0 -207

Geometric mean value <8.0 574 0.89 160 0.25 7.7 178 538 1.2 12.5 -170

Arithmetic mean value 8.4 594 2.1–3.0 166 0.26 7.8 186 542 1.7 12.6 -170

Standard deviation 5.1–5.2 147 7.9–8.1 27 0.047 0.48 30 74 1.7 1.9 15

Coefficient of variation 0.61–0.62 0.25 2.6–3.9 0.16 0.18 0.062 0.16 0.14 1.0 0.15 -0.087

Number of samples 47 47 47 47 47 47 47 47 47 47 47

Number of detections 35 47 7 47 47 47 47 47 35 47 47

Percent detections 74 100 15 100 100 100 100 100 74 100 100
Appendix 1 85

Table 1–20. Summary statistics for analytes and physical properties in samples from monitoring well QC–18, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 124 723 5 76 0.25 9.4 63 744 6.9 21.5 -188

Minimum value 2 260 <1 5 0.02 6.8 25.0 358 0.3 6.0 -229

Geometric mean value 8.1 485 na 9 0.073 8.3 38.0 416 1.1 12.3 -210

Arithmetic mean value 10 497 na 11 0.089 8.4 39 421 1.5 12.5 -211

Standard deviation 17 106 na 13 0.043–0.044 0.70 8.9 71.2 1.6 2.0 11

Coefficient of variation 1.7 0.21 na 1.2 0.48–0.49 0.083 0.23 0.17 1.1 0.16 -0.054

Number of samples 50 50 50 50 50 50 50 50 50 50 50

Number of detections 36 50 1 50 43 50 50 50 34 50 50

Percent detections 72 100 2 100 86 100 100 100 68 100 100
86 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–21. Summary statistics for analytes and physical properties in samples from monitoring well QC–19, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed; e, estimated] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 53 787 1 160 1.58 9.1 206 1,040 12.6 15.0 -87

Minimum value 1 266 <1 6 <0.10 6.6 64.6 366 0.5 7.5 -183

Geometric mean value 4.9 562 na 119 0.26 7.9 164 481 1.5 12.0 -128

Arithmetic mean value <5.3 573 na 123 0.28 7.9 165 484 2.1 12.1 -129

Standard deviation <6.0 112 na 19 0.16 0.53 18 71 2.0 1.2 16

Coefficient of variation 1.1e 0.20 na 0.15 0.57 0.066 0.11 0.15 0.95 0.10 -0.12

Number of samples 78 79 79 79 79 79 79 79 79 79 79

Number of detections 64 79 1 79 78 79 79 79 66 79 79

Percent detections 82 100 1 100 99 100 100 100 84 100 100
Appendix 1 87

Table 1–22. Summary statistics for analytes and physical properties in samples from monitoring well QC–20, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater 

level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 33 730 1 158 0.25 9.2 108 606 7.3 18.9 -217Maximum value 33 730 1 158 0.25 9.2 108 606 7.3 18.9 -217Geometric mean value 18 357 na 22 0.13 8.1 <6.6 300 1.4 12.5 -271Arithmetic mean value 18 365 na 27 0.15 8.1 10 304 1.5–1.7 12.6 -271

Standard 

deviation

3.0 86 na 25 0.042 0.60 22 58 1.2–1.4 1.7 9.9

Coefficient of variation 0.16 0.24 na 0.93 0.28 0.074 2.2 0.19 0.71–0.93 0.13 -0.036

Number of samples 46 46 46 46 46 46 46 46 46 46 45Number of 

detections

46 46 2 46 45 46 28 46 35 46 45

Percent 

detections

100 100 4 100 98 100 61 100 76 100 100
88 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–23. Summary statistics for analytes and physical properties in samples from monitoring well QC–21, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 29 679 1 114 0.63 9.1 126 582 18.0 20.2 -43

Minimum value 12 212 <1 6 0.01 6.6 <0.4 102 0.7 11.0 -280

Geometric mean value 17 400 na 16 0.088 8.0 <4.7 330 2.6 13.0 -256

Arithmetic mean value 17 409 na 24 0.11 8.0 9.8 340 3.5 13.1 -261

Standard deviation 3.1 89 na 24 0.088 0.63 20 79.0 3.2 1.6 31

Coefficient of variation 0.18 0.22 na 1.0 0.80 0.078 2.0 0.23 0.91 0.13 -0.12

Number of samples 58 58 58 58 58 58 58 58 58 58 58

Number of detections 58 58 1 58 49 58 46 58 58 58 58

Percent detections 100 100 2 100 84 100 79 100 100 100 100
Appendix 1 89

Table 1–24. Summary statistics for analytes and physical properties in samples from monitoring well QC–22, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 19 465 <1 57 0.34 9.0 537 414 9.0 15.0 -27

Minimum value 10 153 <1 10 0.08 6.8 0.4 172 0.5 10.0 -299

Geometric mean value 14 323 na 27 0.19 7.9 <3.6 269 2.1 12.4 -242

Arithmetic mean value 14 328 na 28 0.20 8.0 13 271 2.4 12.5 -252

Standard deviation 1.8 61 na 7.4 0.056 0.53 70 34.3 1.4 1.3 43

Coefficient of variation 0.13 0.18 na 0.26 0.29 0.066 5.4 0.13 0.57 0.11 -0.17

Number of samples 59 59 59 59 59 59 59 59 59 59 59

Number of detections 58 59 0 59 59 59 43 59 59 59 59

Percent detections 98 100 0 100 100 100 73 100 100 100 100
90 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–25. Summary statistics for analytes and physical properties in samples from monitoring well QC–23, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 28 581 <1 17 0.24 9.5 14 508 7.3 16.3 -22

Minimum value 14 268 <1 4 0.01 7.0 <0.4 292 <0.3 11.0 -249

Geometric mean value 20 413 na 6 0.090 8.4 <2.7 348 <1.2 12.4 -216

Arithmetic mean value 20 420 na 6 0.10 8.4 2.8–2.9 350 1.5 12.5 -227Standard deviation 1.9 76 na 1.5 0.051 0.70 3.6–3.7 35 1.5 1.1 41Coefficient of variation 0.093 0.18 na 0.24 0.51 0.083 1.2–1.3 0.10 1.0 0.087 -0.18

Number of samples 63 63 63 63 63 63 63 63 63 63 63

Number of detections 63 63 0 63 56 63 37 63 44 63 63

Percent detections 100 100 0 100 89 100 59 100 70 100 100
Appendix 1 91

Table 1–26. Summary statistics for analytes and physical properties in samples from monitoring well QC–24, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 49 993 <1 40 0.87 9.2 11 490 9.6 15.0 -22

Minimum value 23 215 <1 8 0.07 7.1 <0.4 198 0.2 10.8 -241

Geometric mean value 27 316 na 12 0.14 8.2 <3.4 270 <1.0 12.5 -206

Arithmetic mean value 28 325 na 13 0.16 8.2 0.16 273 2.3–2.5 12.5 -220Standard deviation 3.5 100 na 4.2 0.10 0.61 0.10 41.5 3.2–3.3 0.92 46Coefficient of variation 0.13 0.31 na 0.33 0.63 0.075 0.63 0.15 1.3–1.4 0.073 -0.21

Number of samples 63 63 63 63 63 63 63 63 63 63 63

Number of detections 63 63 0 63 62 63 29 63 45 63 63

Percent detections 100 100 0 100 98 100 46 100 71 100 100
92 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–27. Summary statistics for analytes and physical properties in samples from monitoring well QC–25, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 20 377 <1 48 0.29 9.6 30 352 7.5 22.4 -17

Minimum value 11 194 <1 8 0.01 6.9 <0.4 178 <0.2 10.8 -243

Geometric mean value 14 274 na 17 0.14 8.1 <4.0 236 <1.0 13.0 -215

Arithmetic mean value 14 277 na 17 0.15 8.1 5.1 238 1.3 13.1 -225

Standard deviation 1.8 43 na 6.5 0.048 0.63 5.9 31.1 1.4 2.0 38

Coefficient of variation 0.12 0.15 na 0.37 0.32 0.078 1.2 0.13 1.1 0.15 -0.17

Number of samples 58 58 58 58 58 58 58 58 58 58 58

Number of detections 54 57 0 57 57 57 47 57 40 57 57

Percent detections 93 98 0 98 98 98 81 98 69 98 98
Appendix 1 93

Table 1–28. Summary statistics for analytes physical properties in samples from monitoring well QC–26, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 36 468 <1 68 0.97 9.3 17 1,322 10.9 14.0 -15

Minimum value 10 218 <1 4 <0.01 7.1 1.0 214 0.2 10.0 -246

Geometric mean value 12 326 na 7.3 <0.086 8.3 <3.2 297 <1.0 12.3 -197

Arithmetic mean value 13 331 na 8.7 0.10 8.3 3.0–3.2 308 1.1 12.4 -211

Standard deviation 4.2 59 na 10 0.12 0.59 4.3–4.4 138 1.6 0.92 49Coefficient of variation 0.33 0.18 na 1.2 1.2 0.071 1.3–1.5 0.45 1.5 0.075 -0.23

Number of samples 61 61 61 61 61 61 61 61 61 61 61

Number of detections 56 61 0 61 50 61 34 61 39 61 61

Percent detections 92 100 0 100 82 100 56 100 64 100 100
94 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1-29. Summary statistics for analytes and physical properties in samples from monitoring well QC–27, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 43 502 <1 48 0.29 9.2 12 352 6.0 16.0 -136

Minimum value 13 188 <1 10 0.06 6.8 <0.4 204 0.2 10.0 -248

Geometric mean value 30 327 na 26 0.15 8.0 1.0 276 1.1 12.6 -204

Arithmetic mean value 31 333 na 26 0.16 8.0 2.4–2.6 278 1.1 12.7 -205Standard deviation 5.6 65 na 5.3 0.048 0.52 3.2–3.3 34 1.1 1.1 20Coefficient of variation 0.18 0.20 na 0.20 0.29 0.066 1.2–1.4 0.12 1.0 0.087 -0.10

Number of samples 60 60 60 60 60 60 60 60 60 60 60

Number of detections 59 60 0 60 59 60 28 60 41 60 60

Percent detections 98 100 0 100 98 100 47 100 68 100 100
Appendix 1 95

Table 1–30. Summary statistics for analytes properties in samples from monitoring well QC–28, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 38 870 <1 34 0.25 8.9 589 408 6.0 17.0 -49

Minimum value 11 166 <1 8 <0.01 6.4 <0.4 228 0.8 10.7 -255

Geometric mean value 15 326 na 16 <0.064 8.0 <3.6 284 1.9 13.1 -227

Arithmetic mean value 15 339 na 16 0.071–0.072 8.0 15 286 2.1 13.1 -232

Standard deviation 4.8–5.2 112 na 3.3 0.062–0.063 0.59 4.8–5.2 36 1.1 1.3 37

Coefficient of variation 0.32–0.35 0.33 na 0.20 0.86–0.89 0.073 0.32–0.35 0.12 0.54 0.10 -0.16

Number of samples 58 58 58 58 58 58 58 58 58 58 58

Number of detections 54 58 0 58 42 58 33 58 57 58 58

Percent detections 93 100 0 100 72 100 57 100 98 100 100
96 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–31. Summary statistics for analytes and physical properties in samples from monitoring well QC–29, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 228 1,480 <1 518 0.80 8.2 203 1,102 6.5 15.3 0

Minimum value 9 260 <1 40 0.27 6.7 33 342 0.5 7.0 -78

Geometric mean value 97 708 na 222 0.58 7.4 122 711 1.3 12.0 -44

Arithmetic mean value 127 760 na 262 0.60 7.4 130 739 1.5 12.1 -56

Standard deviation 63 274 na 120 0.14 0.32 41 194 1.0 1.3 19

Coefficient of variation 0.50 0.36 na 0.46 0.23 0.043 0.31 0.26 0.68 0.10 -0.33

Number of samples 63 64 64 64 64 64 64 64 64 63 64

Number of detections 62 64 0 64 64 64 64 64 63 63 64

Percent detections 98 100 0 100 100 100 100 100 98 100 100
Appendix 1 97

Table 1–32. Summary statistics for analytes and physical properties in samples from monitoring well QC–30, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed; e, estimated]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 161 700 49 352 0.77 8.7 175 892 10.2 24.1 -6

Minimum value 5 220 <1 42 <0.02 6.8 1.0 204 0.7 5.0 -150

Geometric mean value 11 434 na 59 0.22 7.9 65.1 418 1.4 11.9 -115

Arithmetic mean value <14 446 na 64 0.28 7.9 71.3 425 1.9 12.0 -128

Standard deviation <21 102 na 45 0.15 0.42 24 84 1.8 2.2 34

Coefficient of variation 1.5e 0.23 na 0.70 0.54 0.053 0.34 0.20 0.96 0.18 -0.27

Number of samples 60 61 60 61 61 61 61 61 61 61 61

Number of detections 38 61 4 61 58 61 61 61 47 61 61

Percent detections 63 100 7 100 95 100 100 100 77 100 100
98 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–33. Summary statistics for analytes physical properties in samples from monitoring well QC–31, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 37 941 9 264 1.10 8.8 229 636 7.3 17.1 -1

Minimum value 8 280 <1 182 0.59 6.8 81 482 0.6 10.0 -122

Geometric mean value 16 559 0.66 230 0.96 7.6 178 557 1.3 12.7 -65

Arithmetic mean value 17 577 na 230 0.96 7.6 179 558 1.5 12.7 -79

Standard deviation <6.4 147 na 16 0.10 0.30 19 28 1.2 1.3 27

Coefficient of variation 0.35e 0.25 na 0.069 0.10 0.039 0.11 0.05 0.83 0.10 -0.35

Number of samples 65 66 65 66 66 66 66 66 66 66 66

Number of detections 60 66 3 66 66 66 66 66 61 66 66

Percent detections 92 100 5 100 100 100 100 100 92 100 100
Appendix 1 99

Table 1–34. Summary statistics for analytes and physical properties in samples from monitoring well QC–37, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2010. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 milliliter)

Hardness 

(milligrams 

per liter as 

CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 35 1,399 <1 25 0.41 9.5 121 1,126 53 15.0 -47

Minimum value 24 355 <1 11 0.01 6.9 15 662 1.7 8.8 -136

Geometric mean value 28 860 na 17 0.13 8.1 57 912 6.5 12.4 -119

Arithmetic mean value 28 919 na 17 0.17 8.1 66 924 12 12.6 -123

Standard deviation 3.1 323 na 4.8 0.10 0.73 31 153 15 2.1 24

Coefficient of variation 0.11 0.35 na 0.28 0.59 0.090 0.47 0.17 1.26 0.17 -0.20

Number of samples 12 12 12 11 12 12 12 12 12 12 12

Number of detections 12 12 0 11 12 12 12 12 12 12 12

Percent detections 100 100 0 100 100 100 100 100 100 100 100
100 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–35. Summary statistics for analytes and physical properties in samples from monitoring well QD–21, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 372 2,627 <1 1,002 0.3 8.2 482 1,802 15.0 18.0 -29

Minimum value 103 523 <1 616 0.1 6.4 190 1,006 0.7 10.0 -92

Geometric mean 

value

253 1,546 na 790 0.23 7.2 307 1,464 2.8 12.6 -75

Arithmetic mean 

value

258 1,613 na 794 0.23 7.2 312 1,474 3.7 12.6 -76

Standard deviation 46 431 na 77 0.056 0.34 59 162 2.8 1.1 8.7

Coefficient of 

variation

0.18 0.27 na 0.10 0.24 0.05 0.19 0.11 0.75 0.086 -0.12

Number of 

samples

87 87 87 87 87 87 87 87 87 87 87

Number of 

detections

87 87 0 87 87 87 87 87 87 87 87

Percent detections 100 100 0 100 100 100 100 100 100 100 100
Appendix 1 101

Table 1–36. Summary statistics for analytes and physical properties in samples from monitoring well QD–22, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 159 2,100 87 902 38 8.0 1,038 1,534 12.0 21.1 0Minimum value 87 470 <1 510 0.22 6.1 107 772 0.6 10.0 -42Geometric mean 

value

126 1,214 na 779 0.39 7.3 292 1,224 2.7 12.6 -31.9

Arithmetic mean 

value

127 1,256 na 782 0.79 7.3 299 1,232 3.6 12.7 -33

Standard 

deviation

15 303 na 58 4.0 0.32 88 135 2.5 1.4 5.6

Coefficient of 

variation

0.12 0.24 na 0.074 5.0 0.044 0.29 0.11 0.71 0.11 -0.17

Number of 

samples

91 91 91 91 91 91 91 91 91 91 91

Number of 

detections

91 91 4 91 91 91 91 91 91 91 91

Percent detections 100 100 4 100 100 100 100 100 100 100 100
102 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–37. Summary statistics for analytes and physical properties in samples from monitoring well QD–23, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 313 870 84 100 0.85 8.7 40 744 9.0 17.1 -271

Minimum value 5 276 <1 39 0.040 6.6 <0.4 366 0.8 9.0 -296

Geometric mean 

value

34 561 na 61 0.50 7.7 5.3 545 3.5 12.8 -278

Arithmetic mean 

value

36 582 na 61 0.52 7.7 9.5-9.6 548 4.1 12.9 -290

Standard 

deviation

10 152 na 8.4 0.13 0.41 9.0-9.1 62 2.8 1.8 4.9

Coefficient of 

variation

0.29 0.26 na 0.14 0.25 0.054 1.1 0.11 0.68 0.14 -0.02

Number of 

samples

226 226 226 226 226 225 226 226 226 226 226

Number of 

detections

226 226 14 226 226 225 191 226 225 226 226

Percent detections 100 100 6 100 100 100 85 100 100 100 100
Appendix 1 103

Table 1–38. Summary statistics for analytes and physical properties in samples from monitoring well QD–24, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 168 1,562 48 810 0.76 8.0 830 1,798 14.0 14.0 89

Minimum value 14 185 <1 66 <0.01 6.1 91 634 1.0 9.0 -12

Geometric mean 

value

95 978 na 565 0.35 7.4 194 934 3.7 11.5 14

Arithmetic mean 

value

99 1,020 na 580 0.40 7.4 203 952 4.4 11.5 14

Standard 

deviation

24 265 na 100 0.14 0.33 79 193 2.7 1.0 10

Coefficient of 

variation

0.24 0.26 na 0.17 0.35 0.044 0.39 0.20 0.60 0.087 0.69

Number of 

samples

91 91 91 91 91 91 91 91 91 91 91

Number of 

detections

90 91 4 91 90 91 91 91 91 91 91

Percent detections 99 100 4 100 99 100 100 100 100 100 100
104 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–39. Summary statistics for analytes and physical properties in samples from monitoring well QD–25, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 527 2,220 <1 798 0.82 8.2 1,031 1,870 19.0 24.7 32

Minimum value 114 575 <1 393 0.02 6.5 127 474 1.0 9.0 8

Geometric mean 

value

344 1,582 na 655 0.62 7.3 237 1,421 4.2 11.3 25

Arithmetic mean 

value

353 1,623 na 660 0.66 7.3 246 1,443 5.2 11.4 25

Standard 

deviation

77 344 na 84 0.13 0.31 94 219 3.3 1.9 3.4

Coefficient of 

variation

0.22 0.21 na 0.13 0.19 0.043 0.38 0.15 0.64 0.17 0.14

Number of 

samples

89 88 89 89 89 89 89 89 89 89 89

Number of 

detections

89 88 0 89 89 89 89 89 89 89 89

Percent detections 100 100 0 100 100 100 100 100 100 100 100
Appendix 1 105

Table 1–40. Summary statistics for analytes and physical properties in samples from monitoring well QD–26, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 83 1,405 25 755 3.53 8.2 237 1,330 8.0 16.1 -8

Minimum value 4 355 <1 326 0.23 6.7 <0.4 424 0.4 10.0 -108

Geometric mean 

value

22 719 na 443 0.35 7.4 112 613 <2.5 12.2 -18

Arithmetic mean 

value

24 760 na 446 0.40 7.4 120 619 <3.2 12.2 -20

Standard 

deviation

12 250 na 55 0.43 0.28 27 97 <2.1 1.1 12

Coefficient of 

variation

0.50 0.33 na 0.12 1.1 0.038 0.22 0.16 <0.66 0.090 -0.59

Number of 

samples

87 87 87 87 87 87 87 87 87 87 87

Number of 

detections

83 87 3 87 87 87 86 87 74 87 87

Percent detections 95 100 3 100 100 100 99 100 85 100 100
106 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–41. Summary statistics for analytes and physical properties in samples from monitoring well QD–27, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 429 3,120 260 600 34 8.9 301 1,460 51 16 -36

Minimum value 212 353 <1 283 0.12 6.5 6 870 2 7 -258

Geometric mean 

value

314 1,477 0.85 508 22 7.4 54 1,236 22 12.1 -192

Arithmetic mean 

value

316 1,616 4.2–5.1 511 24 7.4 61 1,240 24 12.2 -194

Standard 

deviation

36 584 26.2–26.4 47 5.2 0.37 34 90 9.2 1.4 20

Coefficient of 

variation

0.11 0.36 5.1–6.3 0.093 0.22 0.050 0.56 0.072 0.39 0.12 -0.10

Number of 

samples

114 114 113 114 114 114 114 114 113 114 114

Number of 

detections

114 114 17 114 114 114 114 114 113 114 114

Percent detections 100 100 15 100 100 100 100 100 100 100 100
Appendix 1 107

Table 1–42. Summary statistics for analytes and physical properties in samples from monitoring well QD–28, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 378 2,063 1 804 0.97 8.3 327 1,834 10.0 16 -40

Minimum value 138 505 <1 101 0.45 6.4 94 634 0.8 4.1 -153

Geometric mean 

value

228 1,333 na 659 0.67 7.3 236 1,259 2.6 12.5 -131

Arithmetic mean 

value

239 1,371 na 669 0.68 7.3 239 1,275 3.3 12.6 -132

Standard 

deviation

72 297 na 83 0.13 0.32 37 201 2.2 1.5 16

Coefficient of 

variation

0.30 0.22 na 0.12 0.19 0.043 0.15 0.16 0.68 0.12 -0.12

Number of 

samples

89 89 89 89 89 89 88 89 89 88 89

Number of 

detections

89 89 1 89 89 89 88 89 89 88 89

Percent detections 100 100 1 100 100 100 100 100 100 100 100
108 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–43. Summary statistics for analytes and physical properties in samples from monitoring well QD–29, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 157 1,579 2,200 865 0.61 8.0 416 1,410 9.0 17 -142

Minimum value 75 551 <1 591 0.15 6.3 197 960 1.0 6.1 -206

Geometric mean 

value

118 1,123 24 715 0.35 7.2 287 1,149 3.1 12.6 -184

Arithmetic mean 

value

120 1,154 44–45 717 0.36 7.3 290 1,153 3.6 12.7 -185

Standard deviation 19 257 258 62 0.082 0.35 47 100 2.0 1.4 14

Coefficient of 

variation

0.16 0.22 5.7–5.9 0.087 0.23 0.048 0.16 0.087 0.56 0.11 -0.076

Number of 

samples

88 88 88 88 88 88 88 88 88 88 88

Number of 

detections

88 88 15 88 88 88 88 88 88 88 88

Percent detections 100 100 17 100 100 100 100 100 100 100 100
Appendix 1 109

Table 1–44. Summary statistics for analytes and physical properties in samples from monitoring well QD–30, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 367 1,840 37 939 2.5 8.3 495 1,634 15 15 -109

Minimum value 85 260 <1 28 0.09 6.5 0.81 996 0.6 9.0 -194

Geometric mean 

value

131 1,182 0.79 747 0.30 7.3 336 1,263 2.7 11.8 -134

Arithmetic mean 

value

134 1,249 1.5–2.4 774 0.37 7.3 365 1,270 3.6 11.8 -134

Standard deviation 36 358 5.8–6.0 120 0.39 0.31 78 133 2.9 1.0 14

Coefficient of 

variation

0.27 0.29 2.4–4.0 0.15 1.1 0.042 0.21 0.10 0.80 0.087 -0.10

Number of 

samples

80 80 80 80 80 80 80 80 80 80 80

Number of 

detections

80 80 8 80 80 80 80 80 80 80 80

Percent detections 100 100 10 100 100 100 100 100 100 100 100
110 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–45. Summary statistics for analytes and physical properties in samples from monitoring well QD–31, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 507 1,722 7,600 882 2.58 8.4 402 1,358 13.0 15.0 -118

Minimum value 102 483 <1 222 0.09 6.8 146 206 0.3 9.8 -200

Geometric mean 

value

120 1,183 1.5 317 0.20 7.6 210 956 2.1 11.6 -181

Arithmetic mean 

value

123 1,219 186–187 328 0.24 7.6 213 967 2.9 11.6 -183

Standard deviation 43 269 1050 96 0.26 0.27 38 108 2.5 1.0 23

Coefficient of 

variation

0.35 0.22 5.6 0.29 1.1 0.036 0.18 0.11 0.86 0.085 -0.12

Number of 

samples

87 87 87 87 87 87 87 87 87 87 87

Number of 

detections

87 87 26 87 86 87 87 87 73 87 87

Percent detections 100 100 30 100 99 100 100 100 84 100 100
Appendix 1 111

Table 1–46. Summary statistics for analytes and physical properties in samples from monitoring well QD–32, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 576 3,510 360 427 0.58 9.6 335 2,854 36.0 16.0 -115

Minimum value 122 221 <1 17 0.03 6.8 149 420 0.3 9.0 -218

Geometric mean 

value

480 2,149 na 33 0.15 8.4 220 1,894 2.0 11.6 -156

Arithmetic mean 

value

487 2,283 na 38 0.18 8.4 222 1,924 3.8 11.7 -161

Standard deviation 67 629 na 43 0.082 0.56 28 274 4.7 1.2 38

Coefficient of 

variation

0.14 0.28 na 1.1 0.46 0.067 0.13 0.14 1.2 0.10 -0.24

Number of 

samples

85 85 85 85 85 85 85 85 85 85 85

Number of 

detections

85 85 7 85 80 85 85 85 68 85 85

Percent detections 100 100 8 100 94 100 100 100 80 100 100
112 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–47. Summary statistics for analytes and physical properties in samples from monitoring well QD–33, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 567 2,731 3,300 82 3.04 9.1 252 2,046 26.0 19.9 -98

Minimum value 327 481 <1 17 0.06 6.8 24 1,474 0.2 5.9 -205

Geometric mean 

value

362 1,767 na 27 0.21 8.1 197 1,692 1.3 12.1 -155

Arithmetic mean 

value

363 1,881 na 28 0.30 8.1 200 1,694 2.8 12.2 -157

Standard deviation 26 562 na 6.1 0.44 0.46 24 90 3.7 1.5 25

Coefficient of 

variation

0.072 0.30 na 0.22 1.5 0.056 0.12 0.053 1.3 0.12 -0.16

Number of 

samples

113 113 113 113 112 113 113 113 113 113 113

Number of 

detections

113 113 8 113 110 113 113 113 85 113 113

Percent detections 100 100 7 100 98 100 100 100 75 100 100
Appendix 1 113

Table 1–48. Summary statistics for analytes and physical properties in samples from monitoring well QD–34, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 150 1,741 1,000 1,011 0.55 8.1 768 1,642 14.0 15.0 -92

Minimum value 95 372 <1 651 0.14 6.4 216 1,040 0.6 4.2 -129

Geometric mean 

value

116 1,080 0.86 780 0.34 7.3 349 1,269 2.1 12.3 -109

Arithmetic mean 

value

116 1,146 16–17 784 0.34 7.3 357 1,276 2.7 12.4 -110

Standard deviation 13 359 120 81 0.067 0.34 81 132 2.3 1.5 8.2

Coefficient of 

variation

0.12 0.31 6.7–7.1 0.10 0.20 0.047 0.23 0.10 0.85 0.12 -0.075

Number of 

samples

70 70 70 70 70 70 69 70 70 70 70

Number of 

detections

70 70 10 70 70 70 69 70 70 70 70

Percent detections 100 100 14 100 100 100 100 100 100 100 100
114 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–49. Summary statistics for analytes and physical properties in samples from monitoring well QD–35, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 138 1,821 1 1,011 0.40 8.5 496 1,702 12.0 18.0 -86

Minimum value 89 539 <1 494 0.10 6.4 98 946 1.1 9.6 -134

Geometric mean 

value

111 1,146 na 746 0.28 7.2 335 1,226 3.2 12.5 -108

Arithmetic mean 

value

111 1,189 na 753 0.29 7.2 345 1,236 3.8 12.5 -108

Standard deviation 9.7 307 na 105 0.071 0.34 76 160 2.3 1.3 8.5

Coefficient of 

variation

0.087 0.26 na 0.14 0.25 0.048 0.22 0.13 0.61 0.10 -0.079

Number of 

samples

78 78 78 78 78 78 78 78 78 78 78

Number of 

detections

78 78 1 78 78 78 78 78 78 78 78

Percent detections 100 100 1 100 100 100 100 100 100 100 100
Appendix 1 115

Table 1–50. Summary statistics for analytes and physical properties in samples from monitoring well QD–36, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 168 1,941 290 1,089 0.55 8.0 545 1,880 11.0 15.0 -91

Minimum value 13 429 <1 588 0.08 6.1 275 1,044 0.8 9.0 -135

Geometric mean 

value

127 1,241 1.1 854 0.26 7.2 390 1,389 2.7 11.8 -117

Arithmetic mean 

value

129 1,299 5.1–6.0 861 0.27 7.2 398 1,401 3.3 11.8 -118

Standard deviation 18 357 32 113 0.071 0.36 79 187 2.1 1.1 9.3

Coefficient of 

variation

0.14 0.27 5.3–6.3 0.13 0.27 0.050 0.20 0.13 0.64 0.095 -0.079

Number of 

samples

91 91 91 91 91 91 91 91 91 91 91

Number of 

detections

91 91 10 91 91 91 91 91 91 91 91

Percent detections 100 100 11 100 100 100 100 100 100 100 100
116 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–51. Summary statistics for analytes and physical properties in samples from monitoring well QD–37, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 372 2,330 7 969 26 8.4 567 2,282 30.0 16.3 -7

Minimum value 213 384 <1 1 <0.01 6.6 66 820 0.3 4.7 -244

Geometric mean 

value

279 1,442 na 403 0.28 7.5 331 1,446 1.4 12.6 -196

Arithmetic mean 

value

280 1,537 na 446 0.96 7.5 341 1,452 2.7 12.7 -201

Standard deviation 32 481 na 144 2.9 0.35 70 127 4.1 1.2 23

Coefficient of 

variation

0.11 0.31 na 0.32 3.0 0.05 0.20 0.087 1.5 0.10 -0.11

Number of 

samples

112 111 112 112 112 112 112 112 112 112 112

Number of 

detections

112 111 1 112 108 112 112 112 84 112 112

Percent detections 100 100 1 100 96 100 100 100 75 100 100
Appendix 1 117

Table 1–52. ummary statistics for analytes and physical properties in samples from monitoring well QD–38, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 319 1,702 <1 437 0.60 8.4 253 1,534 10.0 16.0 -53

Minimum value 21 451 <1 59 0.02 6.7 9 562 0.3 4.3 -236

Geometric mean 

value

202 1,135 na 244 0.31 7.6 115 888 1.5 12.0 -167

Arithmetic mean 

value

207 1,194 na 249 0.34 7.6 121 895 2.2 12.1 -171

Standard deviation 34 343 na 41 0.079 0.34 37 114 1.7 1.4 32

Coefficient of 

variation

0.16 0.29 na 0.17 0.23 0.045 0.30 0.13 0.76 0.11 -0.19

Number of 

samples

90 90 90 90 90 90 90 90 90 90 90

Number of 

detections

90 90 0 90 89 90 90 90 77 90 90

Percent detections 100 100 0 100 99 100 100 100 86 100 100
118 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–53. Summary statistics for analytes and physical properties in samples from monitoring well QD–39, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 77 1,600 3 532 0.32 9.2 349 1,242 10.0 14.3 3

Minimum value 20 526 <1 15 <0.01 7.1 24 760 0.3 9.0 -159

Geometric mean 

value

31 1,048 na 23 <0.096 8.2 103 866 1.6 11.9 -94

Arithmetic mean 

value

32 1,072 na 38 0.073–0.074 8.3 108 870 2.5 11.9 -74

Standard deviation 9.9 221 na 87 0.057–0.060 0.48 40 92 2.4 1.0 68

Coefficient of 

variation

0.31 0.21 na 2.3 0.77–0.82 0.058 0.37 0.11 0.97 0.082 -0.93

Number of 

samples

52 52 52 52 52 52 52 52 52 52 52

Number of 

detections

52 52 2 52 33 52 52 52 38 52 52

Percent detections 100 100 4 100 63 100 100 100 73 100 100
Appendix 1 119

Table 1–54. Summary statistics for analytes and physical properties in samples from monitoring well QD–40, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 140 1,285 <1 27 0.65 9.8 445 878 4.0 15.0 -50

Minimum value 9 525 <1 12 <0.01 7.0 167 502 0.5 10.0 -112

Geometric mean 

value

16 1,027 na 22 <0.10 8.7 369 764 1.6 12.3 -68

Arithmetic mean 

value

20 1,049 na 22 0.12 8.8 374 767 1.7 12.4 -70

Standard deviation 22 192 na 3.6 0.11 0.76 51 60 0.80 1.0 16

Coefficient of 

variation

1.1 0.18 na 0.16 0.92 0.087 0.14 0.078 0.46 0.078 -0.23

Number of 

samples

39 39 39 39 39 39 39 39 39 39 39

Number of 

detections

39 39 0 39 35 39 39 39 39 39 39

Percent detections 100 100 0 100 90 100 100 100 100 100 100
120 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–55. Summary statistics for analytes and physical properties in samples from monitoring well QD–41, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 132 1,640 <1 555 0.37 9.2 493 1,090 9.0 20.0 -116

Minimum value <10 373 <1 18 <0.10 6.9 96.7 752 0.9 9.0 -216

Geometric mean 

value

18 941 na 398 0.26 7.6 352 852 2.4 12.4 -130

Arithmetic mean 

value

20 969 na 436 0.27 7.6 358 854 3.0 12.5 -131

Standard deviation 17 225 na 95 0.048 0.35 54 72 1.8 1.4 15

Coefficient of 

variation

0.83 0.23 na 0.22 0.18 0.05 0.15 0.084 0.62 0.11 -0.12

Number of 

samples

50 50 50 50 50 50 50 50 50 50 50

Number of 

detections

48 50 0 50 49 50 50 50 49 50 50

Percent detections 96 100 0 100 98 100 100 100 98 100 100
Appendix 1 121

Table 1–56. Summary statistics for analytes and physical properties in samples from monitoring well QD–42, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 47 1,116 1 806 0.43 9.6 324 1,108 10.0 14.4 -97

Minimum value 13 303 <1 352 0.13 6.8 235 742 0.6 10.0 -138

Geometric mean 

value

18 827 na 417 0.29 7.6 285 803 2.0 11.8 -127

Arithmetic mean 

value

19 853 na 420 0.29 7.6 285 805 2.6 11.9 -127

Standard deviation 4.6 188 na 62 0.055 0.45 20 63 2.1 0.85 7.1

Coefficient of 

variation

0.24 0.22 na 0.15 0.19 0.059 0.068 0.078 0.82 0.072 -0.06

Number of 

samples

53 53 53 53 53 53 53 53 53 53 53

Number of 

detections

53 53 2 53 53 53 53 53 53 53 53

Percent detections 100 100 4 100 100 100 100 100 100 100 100
122 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–57. Summary statistics for analytes and physical properties in samples from monitoring well QD–43, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 79 1,087 <1 701 0.37 8.0 423 960 13.0 14.8 2

Minimum value 16 8 <1 394 0.01 6.9 157 598 0.7 10.0 -162

Geometric mean 

value

34 723 na 464 0.24 7.5 228 746 1.9 11.8 -142

Arithmetic mean 

value

36 805 na 466 0.26 7.5 230 749 2.6 11.8 -141

Standard deviation 11 233 na 51 0.071 0.24 38 66 2.5 1.0 28

Coefficient of 

variation

0.31 0.29 na 0.11 0.27 0.032 0.17 0.088 0.94 0.087 -0.20

Number of 

samples

50 50 50 50 50 50 50 50 50 50 49

Number of 

detections

50 50 0 50 50 50 50 50 48 50 49

Percent detections 100 100 0 100 100 100 100 100 96 100 100
Appendix 1 123

Table 1–58. Summary statistics for analytes and physical properties in samples from monitoring well QD–44, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 158 961 230 715 0.53 8.9 273 898 7.0 15.0 -3

Minimum value 7 250 <1 79 0.19 6.4 92 392 0.7 9.0 -172

Geometric mean 

value

15 611 na 268 0.31 7.7 197 602 1.7 11.6 -15

Arithmetic mean 

value

18 640 na 282 0.32 7.7 201 608 2.1 11.6 -19

Standard deviation 20 184 na 87 0.059 0.44 36 86 1.5 1.2 22

Coefficient of 

variation

1.1 0.29 na 0.31 0.18 0.057 0.18 0.14 0.69 0.10 -1.2

Number of 

samples

55 55 55 55 55 55 55 55 55 55 55

Number of 

detections

54 55 3 55 55 55 55 55 51 55 55

Percent detections 98 100 5 100 100 100 100 100 93 100 100
124 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–59. Summary statistics for analytes and physical properties in samples from monitoring well QD–45, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 42 1,064 2 417 0.37 9.2 269 730 7.0 15.0 5

Minimum value 12 290 <1 64 0.11 6.8 185 502 0.7 10.0 -27

Geometric mean 

value

17 678 na 95 0.27 8.2 214 588 1.7 11.8 -13

Arithmetic mean 

value

17 708 na 101 0.28 8.2 215 589 2.0 11.8 -14

Standard deviation 4.7 193 na 58 0.057 0.53 19 44 1.3 1.1 7.6

Coefficient of 

variation

0.27 0.27 na 0.57 0.21 0.065 0.090 0.075 0.65 0.091 -0.55

Number of 

samples

48 48 48 48 48 48 48 48 48 48 48

Number of 

detections

48 48 1 48 48 48 48 48 48 48 48

Percent detections 100 100 2 100 100 100 100 100 100 100 100
Appendix 1 125

Table 1–60. Summary statistics for analytes and physical properties in samples from monitoring well QD–46, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 151 1,755 470 700 0.74 8.8 277 1,296 10.0 16.0 -70

Minimum value 8 443 <1 21 0.01 6.4 95 540 0.4 9.9 -194

Geometric mean 

value

15 797 0.75 93 0.21 7.8 141 650 1.9 12.1 -174

Arithmetic mean 

value

19 824 0.81–1.7 107 0.23 7.9 144 656 2.5 12.2 -175

Standard deviation 20 225 3.6–3.8 96 0.087 0.41 32 108 2.0 1.2 16

Coefficient of 

variation

1.1 0.27 2.1–4.7 0.90 0.37 0.052 0.23 0.17 0.79 0.10 -0.09

Number of 

samples

87 88 88 87 88 88 88 88 88 88 87

Number of 

detections

84 88 11 87 88 88 88 88 79 88 87

Percent detections 97 100 13 100 100 100 100 100 90 100 100
126 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–61. Summary statistics for analytes and physical properties in samples from monitoring well QD–47, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 58 4,680 <1 281 0.46 9.3 202 620 9 17.0 7

Minimum value 11 296 <1 130 0.14 7.0 127 484 1 10.0 -20

Geometric mean 

value

17 640 na 237 0.25 7.7 151 537 1.7 13.2 -2

Arithmetic mean 

value

17 713 na 238 0.25 7.7 151 538 2.2 13.2 -2

Standard deviation 6.1 580 na 19 0.051 0.33 14 28 1.6 1.3 7.3

Coefficient of 

variation

0.35 0.81 na 0.081 0.20 0.043 0.10 0.052 0.75 0.10 -4.5

Number of 

samples

52 52 52 52 52 52 52 52 52 52 52

Number of 

detections

52 52 0 52 52 52 52 52 48 52 52

Percent detections 100 100 0 100 100 100 100 100 92 100 100
Appendix 1 127

Table 1–62. Summary statistics for analytes and physical properties in samples from monitoring well QD–48, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 47 1,030 13 467 0.61 8.8 356 826 8.0 18.0 1

Minimum value <10 260 <1 101 0.10 6.8 194 428 1.0 10.0 -187

Geometric mean 

value

13 646 8.8 292 0.26 7.9 271 618 1.8 13.2 -69

Arithmetic mean 

value

13–15 688 10 302 0.28 7.9 273 624 2.1–2.2 13.3 -112

Standard deviation 6.9–9.1 230 4.9 73 0.11 0.41 30 86 1.5–1.6 1.6 74

Coefficient of 

variation

0.46–0.70 0.33 0.52 0.24 0.38 0.052 0.11 0.14 0.68–0.76 0.12 -0.66

Number of 

samples

45 45 45 45 45 45 45 45 45 45 45

Number of 

detections

34 45 2 45 45 45 45 45 41 45 45

Percent detections 76 100 4 100 100 100 100 100 91 100 100
128 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–63. Summary statistics for analytes and physical properties in samples from monitoring well QD–49, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 28 1,210 170 517 0.60 8.9 333 836 11.0 23.5 16

Minimum value 9 280 <1 8 <0.10 7.0 172 460 <1 10.0 -186

Geometric mean 

value

15 711 na 309 0.31 7.8 233 626 2.3 13.3 -133

Arithmetic mean 

value

16 752 na 338 0.35 7.8 236 632 3.0 13.5 -93

Standard deviation 3.2 228 na 93 0.15 0.46 33 87 2.3 2.5 80Coefficient of 

variation

0.20 0.30 na 0.27 0.43 0.059 0.14 0.14 0.77 0.19 -0.87

Number of 

samples

44 44 44 44 44 44 44 44 44 44 44

Number of 

detections

41 44 3 44 43 44 44 44 41 44 44

Percent detections 93 100 7 100 98 100 100 100 93 100 100
Appendix 1 129

Table 1–64. Summary statistics for analytes and physical properties in samples from monitoring well QD–50, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 215 1,158 1 497 0.48 10.0 321 762 9.0 15.0 -58

Minimum value 1 394 <1 <0.5 <0.01 6.6 116.0 374 0.7 9.0 -140

Geometric mean 

value

14 841 na 7.8 0.078 8.6 252 681 2.0 12.0 -100

Arithmetic mean 

value

18 867 na 14 0.098–0.099 8.6 255 685 2.4 12.1 -103

Standard deviation 23 195 na 54 0.060–0.061 0.83 33 60 1.5 1.1 27Coefficient of 

variation

1.3 0.23 na 3.8 0.60–0.62 0.10 0.13 0.087 0.63 0.091 -0.26

Number of 

samples

84 84 84 84 84 84 84 84 84 84 84

Number of 

detections

80 84 1 83 70 84 84 84 81 84 84

Percent detections 95 100 1 99 83 100 100 100 96 100 100
130 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–65. Summary statistics for analytes and physical properties in samples from monitoring well QD–51, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 52 1,030 6 39 0.15 9.8 272 764 8.0 15.0 4

Minimum value 1 300 <1 4 <0.01 6.9 24 466 0.7 10.0 -120

Geometric mean 

value

12 683 na 5.4 <0.059 8.5 122 570 2.1 12.0 -89

Arithmetic mean 

value

13 703 na 6.1 0.053–0.055 8.6 125 572 2.6 12.1 -87

Standard deviation 6.7 156 na 4.6 0.040–0.043 0.78 29 52 1.6 1.0 22Coefficient of 

variation

0.53 0.22 na 0.75 0.73–1.1 0.091 0.23 0.092 0.62 0.087 -0.25

Number of 

samples

84 84 84 84 84 84 84 84 84 84 84

Number of 

detections

81 84 1 83 53 84 84 84 83 84 84

Percent detections 96 100 1 99 63 100 100 100 99 100 100
Appendix 1 131

Table 1–66. Summary statistics for analytes and physical properties in samples from monitoring well QD–52, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 32 918 840 26 0.20 9.7 265 686 6.0 16.1 25

Minimum value 1 325 <1 8 <0.01 6.8 58 198 0.7 9.0 -106

Geometric mean 

value

15 647 na 18 0.078 8.3 137 500 2.0 13.2 -58

Arithmetic mean 

value

15 660 na 19 0.097–0.098 8.4 139 503 2.3 13.3 -53

Standard deviation 3.1 122 na 4.3 0.049–0.051 0.68 24 53 1.3 1.2 21Coefficient of 

variation

0.20 0.18 na 0.23 0.50–0.53 0.081 0.17 0.11 0.55 0.093 -0.41

Number of 

samples

82 82 82 82 82 82 82 81 82 82 82

Number of 

detections

82 82 2 82 71 82 82 81 79 82 82

Percent detections 100 100 2 100 87 100 100 100 96 100 100
132 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–67. Summary statistics for analytes and physical properties in samples from monitoring well QD–53, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 38 1,030 920 15 0.20 9.7 251 680 9.0 17.1 -18

Minimum value 13 354 <1 2 <0.01 6.7 12 520 0.9 9.0 -169

Geometric mean 

value

19 766 na 8.2 <0.050 8.4 118 603 2.5 12.8 -116

Arithmetic mean 

value

19 780 na 8.7 0.037–0.040 8.4 136 604 3.0 12.9 -125

Standard deviation 3.9 142 na 2.7 0.039–0.042 0.70 50 34 1.9 1.5 39Coefficient of 

variation

0.20 0.19 na 2.7 0.98–1.1 0.70 50 34 1.9 1.5 -0.33

Number of 

samples

83 83 83 83 83 83 83 83 83 83 83

Number of 

detections

83 83 3 83 43 83 83 83 82 83 83

Percent detections 100 100 4 100 52 100 100 100 99 100 100
Appendix 1 133

Table 1–68. Summary statistics for analytes and physical properties in samples from monitoring well QD–54, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 60 1,216 3,700 61 0.37 9.6 443 582 6 19.0 34

Minimum value 10 336 <1 20 <0.01 6.7 70 404 0.4 5.0 -33

Geometric mean 

value

17 598 na 40 0.19 8.3 140 460 1.5 12.1 -21

Arithmetic mean 

value

19 613 na 40 0.21 8.3 145 461 1.8 12.2 -21

Standard deviation 8.6 139 na 8.4 0.066 0.73 42 33 1.2 1.6 12Coefficient of 

variation

0.46 0.23 na 0.21 0.31 0.087 0.29 0.071 0.64 0.13 -0.60

Number of 

samples

83 83 83 83 83 83 83 83 83 83 83

Number of 

detections

83 83 2 83 82 83 83 83 71 83 83

Percent detections 100 100 2 100 99 100 100 100 86 100 100
134 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–69. Summary statistics for analytes and physical properties in samples from monitoring well QD–55, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 28 947 6 231 0.47 10.5 477 848 7.0 15.4 33

Minimum value 10 288 <1 83 0.13 4.6 34 302 0.4 5.0 -147

Geometric mean 

value

16 602 na 168 0.34 7.9 160 480 2.1 11.8 -131

Arithmetic mean 

value

16 616 na 172 0.34 7.9 171 485 2.4 11.9 -126

Standard deviation 2.9 127 na 38 0.062 0.78 57 67 1.3 1.5 40

Coefficient of 

variation

0.18 0.21 na 0.22 0.18 0.10 0.33 0.14 0.55 0.13 -0.31

Number of 

samples

83 83 83 83 83 83 83 83 83 83 83

Number of 

detections

83 83 1 83 83 83 83 83 81 83 83

Percent detections 100 100 1 100 100 100 100 100 98 100 100
Appendix 1 135

Table 1–70. Summary statistics for analytes and physical properties in samples from monitoring well QD–56, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 64 875 <1 123 0.94 9.5 257 534 8.0 14.0 34

Minimum value 9 210 <1 19 <0.01 6.4 2 256 0.3 6.0 -83

Geometric mean 

value

12 474 na 48 0.19 8.0 12 354 1.6 11.3 -52

Arithmetic mean 

value

13 487 na 50 0.22 8.0 20 357 2.2 11.4 -48

Standard deviation 6.8 112 na 12 0.10 0.60 35 48 1.7 1.3 22

Coefficient of 

variation

0.54 0.23 na 0.23 0.46 0.074 1.8 0.13 0.79 0.11 -0.45

Number of 

samples

83 83 83 83 83 83 83 83 83 83 83

Number of 

detections

79 83 0 83 82 83 81 83 67 83 83

Percent detections 95 100 0 100 99 100 98 100 81 100 100
136 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–71. Summary statistics for analytes and physical properties in samples from monitoring well QD–57, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 105 1,010 7 238 0.50 9.6 363 848 9.0 14.2 32

Minimum value 8 230 <1 16 0.14 6.5 47 278 0.6 9.0 -120

Geometric mean 

value

12 572 na 38 0.27 8.0 89 432 1.8 11.4 -85

Arithmetic mean 

value

13 598 na 58 0.28 8.0 110 439 2.2 11.5 -81

Standard deviation 11 174 na 54 0.085 0.58 77 89 1.5 1.1 34

Coefficient of 

variation

0.82 0.29 na 0.94 0.31 0.07 0.70 0.20 0.67 0.10 -0.42

Number of 

samples

74 74 74 74 74 74 74 74 74 74 74

Number of 

detections

73 74 2 74 74 74 73 74 65 74 74

Percent detections 99 100 3 100 100 100 99 100 88 100 100
Appendix 1 137

Table 1–72. Summary statistics for analytes and physical properties in samples from monitoring well QD–58, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 49 620 <1 145 0.96 8.9 38 602 8.0 16.0 32

Minimum value 1 170 <1 90 0.14 6.9 0.4 180 0.20 9.0 -112

Geometric mean 

value

12 386 na 121 0.28 7.7 <5.7 294 1.2 11.6 -89

Arithmetic mean 

value

14 395 na 121 0.29 7.8 7.1 299 1.7 11.6 -84

Standard deviation 8.3 82 na 8.8 0.10 0.40 7.2 60 1.5 1.1 33Coefficient of 

variation

0.60 0.21 na 0.073 0.32 0.051 1.0 0.20 0.84 0.090 -0.39

Number of 

samples

75 75 75 75 75 75 75 75 75 75 75

Number of 

detections

74 75 0 75 75 75 60 75 62 75 75

Percent detections 99 100 0 100 100 100 80 100 83 100 100
138 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–73. Summary statistics for analytes and physical properties in samples from monitoring well QD–59, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 190 1,080 <1 446 0.55 8.8 139 796 9.0 14.0 36

Minimum value 10 230 <1 162 0.05 6.6 5 246 0.4 9.0 -66

Geometric mean 

value

90 622 na 283 0.30 7.6 44 491 1.2 11.6 -38

Arithmetic mean 

value

108 652 na 288 0.32 7.6 54 510 1.7 11.7 -35

Standard deviation 50 196 na 54 0.090 0.36 29 133 1.5 0.95 20

Coefficient of 

variation

0.46 0.30 na 0.19 0.28 0.05 0.53 0.26 0.84 0.081 -0.57

Number of 

samples

77 77 77 77 77 77 77 77 77 77 77

Number of 

detections

77 77 0 77 77 77 77 77 66 77 77

Percent detections 100 100 0 100 100 100 100 100 86 100 100
Appendix 1 139

Table 1–74. Summary statistics for analytes and physical properties in samples from monitoring well QD–60, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units 

per 100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 114 818 <1 300 0.45 8.5 190 966 8.0 16.0 20

Minimum value 39 284 <1 223 0.01 6.6 44.0 318 0.2 10.0 -131

Geometric mean 

value

47 559 na 260 0.33 7.6 101 445 <1.1 12.2 -110

Arithmetic mean 

value

48 575 na 260 0.35 7.6 103 450 1.4 12.2 -106

Standard deviation 10 126 na 17 0.066 0.35 18 76 1.6 1.1 33Coefficient of 

variation

0.22 0.22 na 0.065 0.19 0.046 0.17 0.17 <1.1 0.091 -0.31

Number of 

samples

82 82 82 82 82 82 82 82 82 82 82

Number of 

detections

82 82 0 82 82 82 82 82 62 82 82

Percent detections 100 100 0 100 100 100 100 100 76 100 100
140 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–75. Summary statistics for analytes and physical properties in samples from monitoring well QM–53, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 35 513 <1 165 0.43 9.1 59 500 13.7 15 -22

Minimum value 10 150 <1 100 0.01 6.8 27 12 0.3 8.8 -62

Geometric mean 

value

15 267 <1 138 0.08 7.9 37 210 1.1 11.6 -40

Arithmetic mean 

value

16 276 na 138 0.10 8.0 37 225 1.5 11.7 -41

Standard deviation 3.6 74 na 14 0.070 0.50 6.0 73 1.9 1.2 5.6

Coefficient of 

variation

0.23 0.27 na 0.10 0.69 0.063 0.16 0.32 1.3 0.10 -0.14

Number of 

samples

54 52 54 52 54 52 55 55 55 52 52

Number of 

detections

53 52 0 52 50 52 55 55 42 52 52

Percent detections 98 100 0 100 93 100 100 100 76 100 100
Appendix 1 141

Table 1–76. Summary statistics for analytes and physical properties in samples from monitoring well QM–56, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 47 505 1 145 0.54 8.5 37 462 5 17.0 -71

Minimum value 29 218 <1 97 0.37 6.6 3 188 0.3 10.0 -79

Geometric mean 

value

36 359 na 120 0.45 7.8 12 270 1.4 13.4 -76

Arithmetic mean 

value

36 364 na 120 0.46 7.8 13 274 1.8 13.5 -76

Standard deviation 3.3 63 na 11 0.036 0.44 6.1 49 1.3 1.4 2.0

Coefficient of 

variation

0.091 0.17 na 0.088 0.079 0.056 0.46 0.18 0.71 0.10 -0.026

Number of 

samples

40 38 40 38 40 38 40 40 40 38 38

Number of 

detections

40 38 1 38 40 38 40 40 37 38 38

Percent detections 100 100 3 100 100 100 100 100 93 100 100
142 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–77. Summary statistics for analytes and physical properties in samples from monitoring well QM–58, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 56 897 <1 324 1.9 8.7 214 598 6.0 16.0 -63

Minimum value 12 218 <1 126 0.53 7.0 39 202 0.7 11.0 -177

Geometric mean 

value

16 585 na 283 1.0 7.9 173 466 2.3 13.0 -109

Arithmetic mean 

value

17 602 na 286 1.0 7.9 176 471 2.6 13.0 -110

Standard deviation 6.6 124 na 36 0.15 0.43 23 63 1.2 1.2 14

Coefficient of 

variation

0.40 0.21 na 0.13 0.14 0.054 0.13 0.13 0.47 0.090 -0.13

Number of 

samples

53 53 53 53 53 53 53 53 53 53 53

Number of 

detections

53 53 0 53 53 53 53 53 53 53 53

Percent detections 100 100 0 100 100 100 100 100 100 100 100
Appendix 1 143

Table 1–78. Summary statistics for analytes and physical properties in samples from monitoring well QM–61, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 163 1,240 >20,000 320 1.1 8.7 81 736 8.0 24.3 -79

Minimum value 41 220 <1 108 0.19 6.9 5 262 0.6 6.8 -186

Geometric mean 

value

70 579 4.9 146 0.34 7.8 21 391 2.0 13.3 -168

Arithmetic mean 

value

75 630 1,204 150 0.37 7.8 27 402 2.6 13.4 -169

Standard deviation 29 260 4,190 37 0.19 0.38 19 102 1.9 2.0 15

Coefficient of 

variation

0.39 0.41 3.5 0.24 0.51 0.049 0.69 0.25 0.74 0.15 -0.092

Number of 

samples

83 81 83 81 83 81 83 83 83 81 81

Number of 

detections

83 81 27 81 83 81 83 83 77 81 81

Percent detections 100 100 33 100 100 100 100 100 93 100 100
144 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–79. Summary statistics for analytes and physical properties in samples from monitoring well QM–62, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 254 1,143 720,000 870 3.8 9.2 689 1,238 9 18.0 -86

Minimum value 27 320 <1 132 0.26 6.9 17 252 1.1 10.0 -201

Geometric mean 

value

50 554 15 170 0.54 7.8 35 402 2.8 13.8 -186

Arithmetic mean 

value

54 566 14,010 183 0.6 7.8 46 418 3.2 13.8 -188

Standard deviation 31 125 93,760 112 0.49 0.41 86 163 1.9 1.4 19

Coefficient of 

variation

0.58 0.22 6.7 0.61 0.79 0.05 1.9 0.39 0.59 0.10 -0.10

Number of 

samples

59 59 59 59 59 59 59 59 59 59 59

Number of 

detections

59 59 32 59 59 59 59 59 59 59 59

Percent detections 100 100 54 100 100 100 100 100 100 100 100
Appendix 1 145

Table 1–80. Summary statistics for analytes and physical properties in samples from monitoring well QM–63, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 78 2,205 >20,000 1,051 10.47 9.1 4,277 2,070 11.8 17.0 -68

Minimum value 38 317 <1 156 <0.01 6.8 30 394 1.4 10.0 -217

Geometric mean 

value

51 1,253 3.8 760 1.6 7.5 746 1,478 2.9 13.4 -179

Arithmetic mean 

value

51 1,327 629 787 1.8 7.5 822 1,524 3.2 13.5 -181

Standard deviation 5.0 413 2,821 166 1.1 0.33 402 310 1.4 1.3 20

Coefficient of 

variation

0.10 0.31 4.5 0.21 0.59 0.04 0.49 0.20 0.45 0.10 -0.11

Number of 

samples

113 113 112 113 113 113 113 113 113 113 113

Number of 

detections

113 113 40 113 112 113 113 113 113 113 113

Percent detections 100 100 36 100 99 100 100 100 100 100 100
146 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–81. Summary statistics for analytes and physical properties in samples from monitoring well QM–64, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 151 993 >20,000 860 3.0 8.2 763 1,424 10 18.0 -107

Minimum value 45 281 <1 162 1.5 7.0 24 162 0.9 10.0 -199

Geometric mean 

value

57 616 3.3 228 2.0 7.6 46 483 2.4 13.7 -165

Arithmetic mean 

value

58 635 663 236 2.0 7.6 56 493 2.9 13.7 -165

Standard deviation 13 152 2,522 86 0.31 0.23 77 119 2.0 1.3 10

Coefficient of 

variation

0.23 0.24 3.8 0.36 0.15 0.031 1.4 0.24 0.68 0.10 -0.061

Number of 

samples

112 112 111 112 112 112 112 112 112 112 112

Number of 

detections

112 112 53 112 112 112 112 112 111 112 112

Percent detections 100 100 48 100 100 100 100 100 99 100 100
Appendix 1 147

Table 1–82. Summary statistics for analytes and physical properties in samples from monitoring well QM–65, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 524 3,350 8,700 731 14.7 8.1 262 1,736 31 16 -103

Minimum value 84 260 <1 221 0.85 6.6 50 174 2.2 9.0 -214

Geometric mean 

value

386 1,642 1.3 576 8.2 7.3 194 1,381 10 12.9 -191

Arithmetic mean 

value

392 1,769 95–96 580 8.7 7.3 197 1,411 11 12.9 -192

Standard deviation 62 594 870 63 2.6 0.32 29 212 5.7 1.1 16

Coefficient of 

variation

0.16 0.34 9.1–9.2 0.11 0.30 0.043 0.15 0.15 0.50 0.088 -0.081

Number of 

samples

100 95 100 95 100 95 100 98 97 95 95

Number of 

detections

100 95 26 95 100 95 100 98 97 95 95

Percent detections 100 100 26 100 100 100 100 100 100 100 100
148 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–83. Summary statistics for analytes and physical properties in samples from monitoring well QM–67, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 324 1,975 6,600 836 12.64 9.0 285 1,726 14 18.0 -60

Minimum value 18 563 <1 205 <0.01 6.6 1.4 330 <1 9.0 -202

Geometric mean 

value

179 1,118 49 425 1.8 7.4 51 915 4.9 13.5 -161

Arithmetic mean 

value

187 1,172 571 464 5.3 7.4 101 942 5.6 13.6 -161

Standard deviation 50 346 1,111 185 4.4 0.37 88 217 2.9 1.4 13

Coefficient of 

variation

0.27 0.30 1.9 0.40 0.82 0.050 0.87 0.23 0.52 0.11 -0.079

Number of 

samples

118 114 117 115 118 114 116 118 116 114 114

Number of 

detections

118 114 95 115 112 114 116 115 115 114 114

Percent detections 100 100 81 100 95 100 100 97 99 100 100
Appendix 1 149

Table 1–84. Summary statistics for analytes and physical properties in samples from monitoring well QM–68, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 379 670 2,300 212 1.9 9.0 244 550 12.7 17.0 -110

Minimum value 12 166 <1 142 0.23 6.7 0.5 178 0.3 10.0 -185

Geometric mean 

value

23 334 1.9 174 0.61 7.8 34 274 1.3 13.0 -131

Arithmetic mean 

value

29 344 63 175 0.65 7.8 41 280 1.7 13.0 -132

Standard deviation 44 88 293 18 0.26 0.49 27 63 1.9 1.3 9.9

Coefficient of 

variation

1.5 0.26 4.6 0.10 0.40 0.063 0.65 0.22 1.1 0.10 -0.075

Number of 

samples

70 69 69 69 70 69 70 70 70 69 69

Number of 

detections

70 69 22 69 70 69 70 70 54 69 69

Percent detections 100 100 32 100 100 100 100 100 77 100 100
150 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–85. Summary statistics for analytes and physical properties in samples from monitoring well QM–69, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 75 754 460 213 1.1 8.8 84 472 11.8 15.0 -16

Minimum value 32 246 <1 134 0.81 6.6 36 290 <1 9.0 -139

Geometric mean 

value

37 434 na 170 0.93 7.8 54 347 1.3 11.5 43

Arithmetic mean 

value

37 449 na 171 0.93 7.8 55 349 2.6 11.5 -46

Standard deviation 5.1 114 na 17 0.047 0.48 12 33 1.6 1.3 21

Coefficient of 

variation

0.14 0.25 na 0.10 0.051 0.061 0.22 0.094 0.61 0.11 -0.45

Number of 

samples

89 87 88 87 89 87 88 88 89 87 87

Number of 

detections

89 87 3 87 89 87 88 88 88 87 87

Percent detections 100 100 3 100 100 100 100 100 99 100 100
Appendix 1 151

Table 1–86. Summary statistics for analytes and physical properties in samples from monitoring well QM–70, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 65 740 5.0 181 0.57 8.8 71 412 10.6 19.1 -52

Minimum value 44 240 <1 127 0.3 6.8 49 218 0.7 9.0 -93

Geometric mean 

value

49 439 na 156 0.39 7.9 56 337 1.5 11.7 -72

Arithmetic mean 

value

50 454 na 156 0.40 7.9 56 338 2.1 11.8 -73

Standard deviation 3.9 115 na 11 0.05 0.42 5.53 30 1.9 1.5 11

Coefficient of 

variation

0.078 0.25 na 0.074 0.14 0.054 0.098 0.09 0.92 0.12 -0.16

Number of 

samples

44 43 44 43 44 43 43 43 44 43 43

Number of 

detections

44 43 3 43 44 43 43 43 32 43 43

Percent detections 100 100 7 100 100 100 100 100 73 100 100
152 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–87. Summary statistics for analytes and physical properties in samples from monitoring well QM–71, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 144 997 1.0 238 0.56 9.2 89 588 6.7 15 -52

Minimum value 48 218 <1 159 0.24 6.8 33 314 0.4 9 -126

Geometric mean 

value

124 557 na 204 0.44 7.8 70 489 1.2 11.5 64

Arithmetic mean 

value

125 594 na 205 0.44 7.8 71 492 1.6 11.6 -65

Standard deviation 12 209 na 16 0.048 0.43 9.5 51 1.2 1.2 12

Coefficient of 

variation

0.10 0.35 na 0.080 0.11 0.055 0.13 0.10 0.75 0.10 -0.19

Number of 

samples

51 51 51 51 51 51 50 50 51 51 51

Number of 

detections

51 51 1 51 51 51 50 50 37 51 51

Percent detections 100 100 2 100 100 100 100 100 73 100 100
Appendix 1 153

Table 1–88. Summary statistics for analytes and physical properties in samples from monitoring well QM–72, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 147 899 1 272 34 9.4 102 560 10.6 16.0 -65

Minimum value 118 242 <1 176 0.08 6.7 0.34 274 0.40 9.0 -95

Geometric mean 

value

130 538 na 221 0.34 7.7 3.3 434 1.5 11.5 -81

Arithmetic mean 

value

130 562 na 221 0.71 7.7 6.4 438 1.9 11.6 -81

Standard deviation 5.8 152 na 14 3.5 0.48 11 57 1.4 1.2 7.1

Coefficient of 

variation

0.045 0.27 na 0.064 5.0 0.063 1.8 0.13 0.74 0.11 -0.09

Number of 

samples

91 87 90 87 91 87 91 91 91 87 87

Number of 

detections

91 87 1 87 90 87 77 91 81 87 87

Percent detections 100 100 1 100 99 100 85 100 89 100 100
154 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–89. Summary statistics for analytes and physical properties in samples from monitoring well QM–73, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 57 584 1 169 0.45 9.3 61 442 11.0 20.9 -86

Minimum value 16 254 <1 48 0.15 5.2 0.64 244 0.7 9.0 -167

Geometric mean 

value

39 420 na 146 0.27 7.8 3.6 317 2.3 12.3 -137

Arithmetic mean 

value

40 431 na 148 0.28 7.8 6.6 320 3.1 12.4 -139

Standard deviation 7.5 96 na 18 0.065 0.51 10 42 2.6 1.7 21

Coefficient of 

variation

0.19 0.22 na 0.12 0.23 0.065 1.5 0.13 0.84 0.14 -0.15

Number of 

samples

50 50 50 50 50 50 50 50 50 50 50

Number of 

detections

50 50 1 50 50 50 41 50 50 50 50

Percent detections 100 100 2 100 100 100 82 100 100 100 100
Appendix 1 155

Table 1–90. Summary statistics for analytes and physical properties in samples from monitoring well QM–74, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 66 457 2 117 0.34 8.9 50 562 8.9 14.7 -6

Minimum value 10 232 <1 63 0.12 5.4 0.31 226 0.9 9.0 -68

Geometric mean 

value

48 350 na 96 0.22 7.9 3.3 276 2.0 11.8 -25

Arithmetic mean 

value

49 357 na 97 0.22 7.9 6.3 280 2.2 11.9 -28

Standard deviation 8.7 70 na 8.8 0.047 0.61 8.7 58 1.4 1.1 14

Coefficient of 

variation

0.18 0.20 na 0.091 0.21 0.077 1.4 0.21 0.62 0.094 -0.49

Number of 

samples

48 48 48 48 48 48 48 48 48 48 48

Number of 

detections

48 48 1 48 48 48 41 48 47 48 48

Percent detections 100 100 2 100 100 100 85 100 98 100 100
156 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–91. Summary statistics for analytes and physical properties in samples from monitoring well QM–75, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 47 402 2,600 707 0.61 8.9 42 428 10 15 -35

Minimum value 8.6 140 <1 20 0.10 5.1 2.7 166 0.40 7.7 -81

Geometric mean 

value

13 294 1.3 63 0.25 7.9 11 237 1.1 11.8 -62

Arithmetic mean 

value

14 301 71–72 70 0.26 7.9 12 239 1.4 11.8 -62

Standard deviation 4.8 60 386 75 0.062 0.59 5.1 35 1.5 1.1 9.0

Coefficient of 

variation

0.34 0.20 5.4 1.1 0.24 0.075 0.42 0.15 1.0 0.090 -0.14

Number of 

samples

74 74 74 74 74 74 74 74 74 74 74

Number of 

detections

70 74 18 74 74 74 74 74 50 74 74

Percent detections 95 100 24 100 100 100 100 100 68 100 100
Appendix 1 157

Table 1–92. Summary statistics for analytes and physical properties in samples from monitoring well QM–76, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 47 608 19 162 0.36 9.2 97 564 7 16.0 -97

Minimum value <10 241 <1 12 0.09 5.6 4 234 0.5 9.0 -188

Geometric mean 

value

12 418 na 47 0.23 8.1 49 347 1.5 12.4 -151

Arithmetic mean 

value

13 428 na 50 0.24 8.2 56 351 1.9 12.4 -155

Standard deviation 5.7–6.1 89 na 21 0.066 0.74 23 58 1.4 1.3 32

Coefficient of 

variation

0.44–0.47 0.21 na 0.43 0.28 0.091 0.41 0.16 0.71 0.10 -0.21

Number of 

samples

49 48 49 48 49 48 49 49 49 48 48

Number of 

detections

45 48 4 48 49 48 49 49 43 48 48

Percent detections 92 100 8 100 100 100 100 100 88 100 100
158 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–93. Summary statistics for analytes and physical properties in samples from monitoring well QM–77, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 18 329 8,700 51 0.22 8.8 29 378 12.7 15.1 -6

Minimum value 3.6 135 <1 37 0.04 6.2 1.0 92 0.4 10.0 -185

Geometric mean 

value

11 234 1.9 43 0.12 8.0 3.8 188 1.4 11.7 -155

Arithmetic mean 

value

11 239 316 43 0.13 8.0 6.2 193 2.0 11.8 -164

Standard deviation 2.7 46 1,497 3.4 0.041 0.6 7.0 48 2.0 1.2 29

Coefficient of 

variation

0.24 0.19 4.7 0.080 0.31 0.07 1.1 0.25 1.0 0.10 -0.17

Number of 

samples

51 50 51 50 51 50 51 51 51 50 50

Number of 

detections

46 50 15 50 46 50 41 51 41 50 50

Percent detections 90 100 29 100 90 100 80 100 80 100 100
Appendix 1 159

Table 1–94. Summary statistics for analytes and physical properties in samples from monitoring well QM–78, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 55 855 15 782 0.31 9.4 135 540 10.1 19 -21

Minimum value 8 131 <1 3 0.02 6.2 35 198 0.1 6.4 -166

Geometric mean 

value

13 421 na 11 0.069 8.3 55 335 0.72 11.5 -116

Arithmetic mean 

value

15 440 na 21 0.08 8.3 57 340 1.1 11.5 -128

Standard deviation 7.9 131 na 89 0.042 0.6 18 62 1.7 1.5 46

Coefficient of 

variation

0.53 0.30 na 4.28 0.50 0.08 0.32 0.18 1.6 0.13 -0.36

Number of 

samples

75 75 75 75 75 75 75 75 75 75 75

Number of 

detections

68 75 3 75 64 75 75 75 47 75 75

Percent detections 91 100 4 100 85 100 100 100 63 100 100
160 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–95. Summary statistics for analytes and physical properties in samples from monitoring well QM–79, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 33 740 11 415 0.25 9.5 50 1,458 11 20.7 -15

Minimum value 15 190 <1 7 <0.01 6.9 14 198 0.4 9.1 -215

Geometric mean 

value

19 438 na 11 <0.052 8.3 21 358 1.1 11.5 -115

Arithmetic mean 

value

19–20 455 na 18 0.051 8.4 21 375 1.7 11.5 -125

Standard deviation 3.3–4.0 122 na 49 0.039 0.69 6.7 157 2.1 1.4 37

Coefficient of 

variation

0.17–0.21 0.27 na 2.8 0.76 0.08 0.31 0.42 1.3 0.12 -0.29

Number of 

samples

72 72 72 72 72 72 72 72 72 72 72

Number of 

detections

71 72 1 72 53 72 72 72 47 72 72

Percent detections 99 100 1 100 74 100 100 100 65 100 100
Appendix 1 161

Table 1–96. Summary statistics for analytes and physical properties in samples from monitoring well QM–80, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 30 471 6 44 0.14 9.3 244 7,690 9.7 23 -23

Minimum value 11 130 1 12 <0.01 7.0 0.37 172 0.1 9.9 -157

Geometric mean 

value

14 273 2.4 21 <0.034 8.1 4.0 230 0.77 12.2 -127

Arithmetic mean 

value

14 280 3.5 21 0.039 8.2 11 327 1.0 12.3 -131

Standard deviation 2.4–3.3 60 3.5 3.1 0.026 0.59 32 857 1.4 1.7 23

Coefficient of 

variation

0.17–0.24 0.22 1.01 0.15 0.67 0.072 2.9 2.62 1.4 0.14 -0.18

Number of 

samples

77 77 76 77 77 77 77 77 77 77 77

Number of 

detections

71 77 2 77 53 77 63 77 47 77 77

Percent detections 92 100 3 100 69 100 82 100 61 100 100
162 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–97. Summary statistics for analytes and physical properties in samples from monitoring well QM–81, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 39 842 760 37 0.27 9.1 55 598 5 16.0 -32

Minimum value 13 191 <1 8 0.02 6.7 7 196 0.2 10.0 -152

Geometric mean 

value

21 336 na 27 0.062 8.0 16 256 1.3 12.4 -120

Arithmetic mean 

value

22 348 na 27 0.077 8.0 18 261 1.7 12.5 -125

Standard deviation 5.7 110 na 4.7 0.048 0.59 8.9 59 1.1 1.1 26

Coefficient of 

variation

0.26 0.32 na 0.17 0.62 0.073 0.49 0.23 0.66 0.089 -0.21

Number of 

samples

87 84 87 84 87 84 87 87 87 84 84

Number of 

detections

86 84 2 84 74 84 87 87 76 84 84

Percent detections 99 100 2 100 85 100 100 100 87 100 100
Appendix 1 163

Table 1–98. Summary statistics for analytes and physical properties in samples from monitoring well QM–82, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 46 545 <1 28 0.15 9.2 800 3,956 10.8 15.1 -141

Minimum value 14 150 <1 3 <0.01 7.1 <5 226 0.7 11.0 -200

Geometric mean 

value

29 381 na 13 <0.053 8.2 13 314 1.7 12.6 -171

Arithmetic mean 

value

30 392 na 13 0.050–0.051 8.2 28 363 2.2 12.7 -172

Standard deviation 4.0 87 na 3.1 0.032–0.034 0.57 102 473 1.8 1.1 17

Coefficient of 

variation

0.14 0.22 na 0.24 0.63–0.68 0.069 3.6 1.3 0.85 0.08 -0.10

Number of 

samples

60 59 60 59 60 59 60 60 60 59 59

Number of 

detections

60 59 0 59 44 59 59 60 56 59 59

Percent detections 100 100 0 100 73 100 98 100 93 100 100
164 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–99. Summary statistics for analytes and physical properties in samples from monitoring well MW–1, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 248 1,075 11 571 0.81 8.5 587 1,576 10.0 21.0 33

Minimum value <10 310 <1 374 0.14 6.8 273 684 0.6 10.9 -27

Geometric mean 

value

33 825 na 439 0.31 7.6 351 812 1.6 14.0 18

Arithmetic mean 

value

35 848 na 440 0.32 7.6 353 816 2.0 14.0 19

Standard deviation 25 181 na 28 0.085 0.39 35 91 1.7 1.5 12

Coefficient of 

variation

0.71 0.21 na 0.064 0.27 0.052 0.10 0.11 0.85 0.11 0.65

Number of 

samples

98 99 99 99 99 99 98 98 99 99 99

Number of 

detections

97 99 5 99 99 99 98 98 84 99 99

Percent detections 99 100 5 100 100 100 100 100 85 100 100
Appendix 1 165

Table 1–100. Summary statistics for analytes and physical properties in samples from monitoring well MW–2, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.[CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 1,149 1,324 39 605 0.63 8.7 583 1,042 6.0 18.0 45

Minimum value 7 328 <1 398 0.15 6.8 343 792 0.6 11.0 33

Geometric mean 

value

25 828 na 462 0.52 7.8 407 865 1.7 13.6 40

Arithmetic mean 

value

41 872 na 463 0.53 7.9 408 866 2.0 13.7 40

Standard deviation 132 249 na 30 0.06 0.42 35 46 1.1 1.1 2

Coefficient of 

variation

3.2 0.29 na 0.064 0.12 0.053 0.087 0.053 0.56 0.081 0.051

Number of 

samples

73 73 73 73 73 73 72 73 73 73 73

Number of 

detections

73 73 3 73 73 73 72 73 70 73 73

Percent detections 100 100 4 100 100 100 100 100 96 100 100
166 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–101. Summary statistics for analytes and physical properties in samples from monitoring well MW–3, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 99 1,130 24 487 0.67 8.6 588 1,576 9.0 19.8 89

Minimum value 6 316 <1 363 0.04 6.8 339 756 0.4 11.0 30

Geometric mean 

value

13 789 na 437 0.29 7.7 423 836 1.2 14.3 37

Arithmetic mean 

value

15 817 na 437 0.30 7.7 424 839 1.5 14.3 37

Standard deviation 11 199 na 19 0.074 0.37 34 81 1.1 1.2 5.1

Coefficient of 

variation

0.73 0.24 na 0.044 0.25 0.05 0.081 0.10 0.74 0.086 0.14

Number of 

samples

119 119 119 119 119 119 118 119 119 119 119

Number of 

detections

113 119 5 119 119 119 118 119 95 119 119

Percent detections 95 100 4 100 100 100 100 100 80 100 100
Appendix 1 167

Table 1–102. Summary statistics for analytes and physical properties in samples from monitoring well MW–4, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.[CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 97 1,347 4 649 2.24 8.8 649 2,486 9.0 21.5 21

Minimum value <10 357 <1 482 <0.01 6.8 311 820 0.3 10.0 -75

Geometric mean 

value

52 938 na 558 0.091 7.6 382 965 1.3 13.6 -6.5

Arithmetic mean 

value

54 973 na 559 0.11 7.6 383 972 1.8 13.7 -6

Standard deviation 9.9–10.4 239 na 36 0.21 0.29 38 152 1.5 1.4 10

Coefficient of 

variation

5.1–5.4 0.25 na 0.064 1.9 0.039 0.10 0.16 0.86 0.10 -1.8

Number of 

samples

113 113 113 113 113 113 112 113 113 113 113

Number of 

detections

112 113 7 113 92 113 112 113 87 113 113

Percent detections 99 100 6 100 81 100 100 100 77 100 100
168 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–103. Summary statistics for analytes and physical properties in samples from monitoring well MW–5, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 961 1,830 1,700 607 0.48 9.0 476 2,166 7.0 19.0 -25

Minimum value 9 333 <1 66 <0.01 6.8 15 606 0.4 11.0 -122

Geometric mean 

value

108 1,005 0.96 319 0.081 7.8 286 897 1.7 14.2 -48

Arithmetic mean 

value

140 1,046 20 340 0.010 7.8 303 917 2.1 14.3 -49

Standard deviation 128 275 173 118 0.11 0.46 80 224 1.3 1.5 10

Coefficient of 

variation

0.92 0.26 8.7 0.35 11 0.059 0.27 0.24 0.61 0.11 -0.21

Number of 

samples

96 96 96 96 96 96 95 96 96 96 96

Number of 

detections

96 96 21 96 76 96 95 96 90 96 96

Percent detections 100 100 22 100 79 100 100 100 94 100 100
Appendix 1 169

Table 1–104. Summary statistics for analytes and physical properties in samples from monitoring well MW–6, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.[CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 93 1,304 480 572 0.62 8.9 472 1,044 9.0 18.1 64

Minimum value 15 218 <1 240 0.31 6.3 55 412 0.3 6.0 12

Geometric mean 

value

38 764 0.96 392 0.48 7.7 322 777 1.8 13.3 54

Arithmetic mean 

value

38 812 6.7–7.5 394 0.48 7.7 328 782 2.2 13.4 55

Standard deviation 7.7 251 45 47 0.052 0.42 54 93 1.2 1.5 7.6

Coefficient of 

variation

0.20 0.31 6.0–6.7 0.12 0.11 0.055 0.16 0.12 0.56 0.11 0.14

Number of 

samples

117 117 117 117 117 117 116 117 117 117 117

Number of 

detections

117 117 22 117 117 117 116 117 115 117 117

Percent detections 100 100 19 100 100 100 100 100 98 100 100
170 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–105. Summary statistics for analytes and physical properties in samples from monitoring well MW–7, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 99 1,236 6,000 652 1 8.1 492 1,220 7 18.0 67

Minimum value 21 354 <1 375 0.30 6.8 32 454 0.4 9.8 5

Geometric mean 

value

35 814 1.3 526 0.49 7.5 393 928 1.2 14.7 15

Arithmetic mean 

value

36 855 142 528 0.50 7.5 402 932 1.5 14.8 16

Standard deviation 8.0 250 843 47 0.066 0.30 55 89 1.3 1.3 6.5

Coefficient of 

variation

0.22 0.29 5.9 0.089 0.13 0.04 0.14 0.10 0.85 0.086 0.42

Number of 

samples

86 86 86 86 86 86 86 86 86 86 86

Number of 

detections

86 86 15 86 86 86 86 86 69 86 86

Percent detections 100 100 17 100 100 100 100 100 80 100 100
Appendix 1 171

Table 1–106. Summary statistics for analytes and physical properties in samples from monitoring well MW–8, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.[CaCO3, calcium carbonate; <, less than; na, not analyzed]

Chloride 

(milligrams 

per liter)

Electrical 

conductivity 

(micromhos 

per 

centimeter)

Fecal 

coliform 

(colony 

forming 

units per 

100 

milliliter)

Hardness 

(milligrams 

per liter 

as CaCO3)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 352 1,318 3,700 502 0.48 8.9 680 1,536 35 16.9 19

Minimum value 18 366 <1 90 <0.01 6.9 25 360 0.6 10.0 -63

Geometric mean 

value

51 769 1.4 345 0.064 7.9 286 756 1.4 14.5 -44

Arithmetic mean 

value

58 802 25–26 359 0.073–0.075 8.0 307 770 1.9 14 -40

Standard deviation 45 228 123 85 0.10 0.50 94 151 3.7 1.0 23

Coefficient of 

variation

0.76 0.28 4.7–4.9 0.24 1.3–1.4 0.063 0.31 0.20 1.9 0.072 -0.57

Number of 

samples

85 85 85 85 85 85 85 85 85 85 85

Number of 

detections

85 85 26 85 57 85 85 85 79 85 85

Percent detections 100 100 31 100 67 100 100 100 93 100 100
172 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 1–107. Summary statistics for analytes and physical properties in samples from monitoring well MW–9, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [CaCO3, calcium carbonate; <, less than; na, not analyzed] Chloride (milligrams per liter) Electrical conductivity (micromhos per centimeter) Fecal coliform (colony forming units per 100 milliliter) Hardness (milligrams per liter as CaCO3

)

Ammonia 

(milligrams 

per liter)

pH 

(standard 

units)

Sulfate 

(milligrams 

per liter)

Total 

dissolved 

solids 

(milligrams 

per liter)

Dissolved 

organic 

carbon 

(milligrams 

per liter)

Temperature 

(degrees 

Celsius)

Groundwater level 

(feet from 

City of 

Chicago 

Datum)

Maximum value 81 1,136 6 465 1 8.5 737 1,536 10 18.0 4

Minimum value 3 360 <1 250 <0.02 6.8 209 542 0.7 11.0 -73

Geometric mean 

value

34 771 na 392 0.35 7.7 342 800 1.5 14.3 -5

Arithmetic mean 

value

36 800 na 394 0.37 7.7 345 805 1.7 14.3 -4

Standard deviation 9.2 207 na 37 0.077 0.32 53 105 1.4 0.93 8.1

Coefficient of 

variation

0.26 0.26 na 0.094 0.21 0.041 0.15 0.13 0.79 0.065 -1.9

Number of 

samples

90 90 90 90 90 90 90 90 90 90 90

Number of 

detections

90 90 6 90 89 90 90 90 88 90 90

Percent detections 100 100 7 100 99 100 100 100 98 100 100
Appendix 2 173

Appendix 2. Results of temporal trend analysis of analytes 

and physical properties, by well, Tunnel and Reservoir Plan 

System, 1995–2013

Each appendix has four Tunnel and Reservoir Plan Systems, each with multiple tables of varing sizes.

Table 2–1 to table 2–33. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical 

properties, by well, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois. 

Table 2–34 to table 2–73. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical 

properties, by well, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois. 

Table 2–74 to table 2–97. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical 

properties, by well, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois.

Table 2–98 to table 2–106. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical 

properties, by well, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois.
174 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–1. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 2.1 -31 1.2 -3.3 0.00 0.00 -1.5 — -0.16

— -0.44

p>0.05

—

—

—

—

—

—

— -0.51

— 0.00

—

Table 2–2. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.38 -12

— -2.2 -0.020 -0.030 -0.35

—

—

— -1.1

p>0.05

—

— 1.1

—

—

—

— -0.82 -0.16 0.00

—

Table 2–3. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–2.1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.25 -24 3.2 0.52 0.010 -0.040 -1.5 -3.3 -0.18

— -3.5

p>0.05

—

—

—

—

—

—

—

—

— 0.000

—
Appendix 2 175

Table 2–4. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–2.2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.10 -13 — 0.59 -0.010 -0.020 -1.5 -3.4 -0.18 — -3.1p>0.05 — — 0.69 — — — — — — 0.000 —

Table 2–5. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–3, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.12 -20 -2.1 0.19 0.35 -0.040 — — -0.21 — 2.9

p>0.05 — — — — — — 0.00 -1.1 — 0.00 —

Table 2–6. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–4, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.20 -11.0 -3.1 0.00 0.000 — -0.94 -2.1 -0.36 — 1.4p>0.05 — — — — — 0.000 — — — 0.00 —
176 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–7. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–5, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

— -19 na -0.10 0.00

— -0.98 -3.7 -0.24

— 3.0

p>0.05 0.00

— na

—

— 0.00

—

—

— 0.00

—

Table 2–8. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–6, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.60 -20 -1.2 -1.4 0.00

— -3.9 -7.8 -0.22

— 3.2

p>0.05

—

—

—

—

— 0.00

—

—

— 0.00

—

Table 2–9. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–7, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -10 na

—

— -0.030 -1.4 -2.2 -0.18

— -1.6

p>0.05 0.00

— na 0.00 0.00

—

—

—

— 0.00

—
Appendix 2 177

Table 2–10. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–9, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -6.3 — — -0.40 -0.02 1.1 — -0.11 — -0.45

p>0.05 0.010 — 0.10 0.00 — — — 0.00 — 0.00 —

Table 2–11. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–10, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -10 na — 0.00 — -1.4 — -0.20 — 1.8

p>0.05 0.00 — na 0.00 — -0.01 — 0.00 — 0.00 —

Table 2–12. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–11, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.20 -4.2 na -0.12 0.00 — -1.3 — -0.20 — -0.99

p>0.05 — — na — — -0.02 — -0.66 — 0.00 —
178 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–13. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–12, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

— -17 -14

— 0.01

— 5.4 5.3 -0.32

— 1.6

p>0.05 0.00

—

— 2.20

— 0.00

—

—

— 0.00

—

Table 2–14. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–13, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 1.7 -6.9 na 0.40 0.00

—

—

— -0.19

— 2.1

p>0.05

—

— na

—

— -0.02 0.00 1.6

— 0.10

—

Table 2–15. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–14, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 7.0 11 na 0.84 0.01 -0.41 -1.1 20

— 0.00 0.92

p>0.05

—

— na

—

—

—

—

— 0.00

—

—
Appendix 2 179

Table 2–16. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–15, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -6.5 na — — — -1.5 — -0.17 — 0.81

p>0.05 -0.063 — na 0.00 0.00 -0.027 — -1.2 — 0.00 —

Table 2–17. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–16, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.69 -14 na 0.46 -0.01 -0.02 1.1 — -0.19 0.09 -5.6

p>0.05 — — na — — — — -1.0 — — —

Table 2–18. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–17, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -13 — — 0.00 — -1.4 — -0.17 0.048 —

p>0.05 0.28 — 0.31 -0.39 — 0.00 — -0.49 — — -0.89
180 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–19. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–18, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

— -8.0 na

—

—

— -1.3 -1.8 -0.20 0.055 1.1

p>0.05 0.00

— na 0.00 0.00 0.023

—

—

—

—

—

Table 2–20. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–19, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.22 -13 na -2.4

—

— -1.4 -1.9 -0.23

— 1.2

p>0.05

—

— na

— 0.00 0.000

—

—

— 0.00

—

Table 2–21. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–20, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

—

— na 0.28 0.00 -0.05

—

— 0.00

— 0.50

p>0.05 0.00 0.00 na

—

—

— 0.00 0.00

— 0.052

—
Appendix 2 181

Table 2–22. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–21, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.37 — na 2.3 0.00 -0.065 — 6.4 0.11 — —

p>0.05 — 4.6 na — — — 0.00 — — 0.00 0.00Table 2–23. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–22, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.26 — na 0.88 — -0.049 -0.28 — -0.10 — —

p>0.05 — 1.6 na — 0.00 — — 0.77 — 0.00 -0.27Table 2–24. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–23, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — — na — -0.01 — -0.64 -1.7 -0.29 — -1.3

p>0.05 0.00 -2.5 na 0.00 — 0.00 — — — 0.00 —
182 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–25. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–24, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

—

— na 0.19 0.00

— -1.0 -3.1 -0.15

— -0.90

p>0.05 0.00 -1.5 na

—

— 0.00

—

—

— 0.00

—

Table 2–26. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–25, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

—

— na 0.77 0.00

—

—

— -0.17

— -1.1

p>0.05 0.00 -0.58 na

—

— 0.00 0.12 0.00

— 0.00

—

Table 2–27. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–26, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

—

— na

— 0.01

— -0.79

— -0.15

— -0.51

p>0.05 0.00 -1.1 na 0.00

— -0.01

— -1.3

— 0.00

—
Appendix 2 183

Table 2–28. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–27, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.37 — na -0.39 — — -0.94 -4.1 -0.13 — -0.86

p>0.05 — -3.6 na — -0.17 0.00 — — — 0.01 —

Table 2–29. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–28, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013 [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.18 — na — -0.01 — -0.51 — -0.12 — -0.86

p>0.05 — -0.25 na 0.00 — 0.00 — -0.13 — 0.00 —

Table 2–30. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–29, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. . [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 18 38 na 35 0.039 -0.032 12 56 — 0.049 —

p>0.05 — — na — — — — — 0.000 — -0.73
184 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–31. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–30, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

—

—

— 0.91

— 0.048 1.3

— -0.15

—

—

p>0.05 -0.47 -0.066 -0.53

— 0.00

—

— -0.57

— 0.00 0.00

Table 2–32 Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–31, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.68

—

—

— 0.015 0.018

— 3.8 -0.042

— 4.1

p>0.05

— -3.8 0.00 0.97

—

— 0.66

—

— 0.00

—

Table 2–33. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QC–37, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2010. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

—

— na 1.3

—

—

— 47 -1.4

— -2.0

p>0.05 -0.38 59 na

— 0.010 0.080 6.0

—

— -0.38

—
Appendix 2 185

Table 2–34. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–21, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -44 na — — -0.026 — — -0.27 — 0.69

p>0.05 1.6 — na -1.5 0.00 — 0.52 0.00 — 0.00 —

Table 2–35. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–22, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 1.4 -38 8.7 -5.8 0.00 — -2.8 — -0.28 — 0.21

p>0.05 — — — — — -0.01 — -3.8 — 0.00 —

Table 2–36. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–23, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013 [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 3.4 -26 na -3.7 0.00 — — — -0.24 0.00 0.28

p>0.05 — — na — — 0.00 0.00 3.5 — — —
186 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–37. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–24, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

— -26 0.00 -7.6 0.014

— -3.8

— -0.25 0.00 0.35

p>0.05 0.66

—

—

—

— -0.068

— -0.12

—

—

—

Table 2–38. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–25, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 11

— na -10 0.0038

— -5.2

— -0.39

— 0.13

p>0.05

— -10 na

—

— 0.00

— 6.6

— 0.00

—

Table 2–39. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–26, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -1.4 -33 2.7 -7.0

— -0.012 -3.0 -8.2 -0.28

— -0.50

p>0.05

—

—

—

— 0.0011

—

—

—

— 0.00

—
Appendix 2 187

Table 2–40. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–27, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 1.6 -50 — -2.0 0.51 -0.015 -2.3 — -1.1 — -1.0

p>0.05 — — 0.000 — — — — -2.2 — 0.000 —

Table 2–41. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–28, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 9.6 — na — -0.011 -0.012 — 17 -0.22 0.080 1.0

p>0.05 — -9.1 na -0.93 — — -1.3 — — — —

Table 2–42. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–26, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 3.0 -29 -3.9 -7.2 0.0095 — -6.7 — -0.13 0.020 —

p>0.05 — — — — — -0.011 — -2.8 — — 0.000
188 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–43. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–30, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 1.5 -40

— -12 0.0069

— -8.3 -12 -0.20

—

—

p>0.05

—

— -1.5

— 0.000

—

—

— 0.075 0.000

Table 2–44. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–31, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.90 -29

— -11

— -0.015 -4.3 -5.4 -0.31

— -0.62

p>0.05

—

— 0.000

— 0.000

—

—

—

— 0.000

—

Table 2–45. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–32, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 4.0 -31

—

— 0.0030

—

— 8.0 -0.47

— -4.5

p>0.05

—

— 0.000 0.13

— 0.000 0.74

—

— 0.000

—
Appendix 2 189

Table 2–46. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–33, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.95 -33 — — 0.0038 — -0.61 -5.1 -0.41 — -1.7

p>0.05 — — 0.000 0.000 — -0.011 — — — 0.000 —

Table 2–47. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–34, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 1.4 -30 — -12 0.0069 -0.015 -9.7 -12 -0.15 — 1.0

p>0.05 — — 0.000 — — — — — — 0.073 —

Table 2–48. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–35, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.76 -37 na -16 0.0051 — -11 -18 -0.091 — —

p>0.05 — — na — — 0.000 — — — 0.000 0.000
190 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–49. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–36, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

— -45

— -16 0.0055

— -12 -20 -0.18

—

—

p>0.05 0.10

— -0.18

—

— 0.000

—

—

— 0.000 0.000

Table 2–50. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–37, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -2.9 -42 na 17 0.012 -0.012 6.0 2.7 -0.37

— -0.70

p>0.05

—

— na

—

—

—

—

—

— 0.000

—

Table 2–51. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–38, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -3.9 -50 na

—

—

— -1.8 -7.9 -0.21

— -4.6

p>0.05

—

— na -0.30 0.000 0.000

—

—

— 0.000

—
Appendix 2 191

Table 2–52. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–39, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -24 na — — — -2.0 — -0.34 — -5.1p>0.05 0.000 — na 0.000 0.000 -0.011 — -0.67 — 0.000 —

Table 2–53. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–40, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.47 -17 na — 0.0017 — -3.2 -3.2 -0.096 — -2.1p>0.05 — — na 0.12 — 0.0058 — — — 0.10 —

Table 2–54. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–41, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -22 na -5.0 — — -3.9 -6.6 -0.19 0.026 -1.0p>0.05 0.000 — na — 0.000 0.0080 — — — — —
192 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–55. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–42, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 0.11 -16 na -3.3

— 0.023

— -1.8 -0.18 0.000 0.60

p>0.05

—

— na

— 0.0015

— -0.50

—

—

—

—

Table 2–56. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–43, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 1.2 -21 na -2.3 0.0066 -0.012 -2.8

— -0.18

— 1.7

p>0.05

—

— na

—

—

—

— -1.2

— 0.000

—

Table 2–57. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–44, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.50 -19

—

— 0.0025 -0.018

—

— -0.15

— 0.98

p>0.05

—

— -0.21 0.16

—

— -0.85 0.60

— 0.000

—
Appendix 2 193

Table 2–58. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–45, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.15 -17 na 0.75 0.0041 — -1.4 — -0.11 — 1.1p>0.05 — — na — — -0.022 — -0.16 — 0.013 —

Table 2–59. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–46, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -21 — -2.3 — -0.027 -1.8 -1.2 -0.19 — 0.92p>0.05 0.080 — 0.000 — 0.000 — — — — 0.000 —

Table 2–60. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–47, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.15 -17 na — — — — — -0.16 — 0.89p>0.05 — — na 0.14 0.000 0.000 0.000 -0.78 — 0.000 —
194 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–61. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–48, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 -0.42 -28 na -3.5 -0.41 0.021

—

— -0.14

— -8.0

p>0.05

—

— na

—

—

— -0.44 -3.2

— 0.000

—

Table 2–62. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–49, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.12 -35 16

— -0.015

— -3.1

— -0.17

— -11

p>0.05

—

—

— -3.4

— 0.0000

— -2.8

— 0.072

—

Table 2–63. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–50, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.072 -22 na 0.11 0.0026

— 2.5

— -0.18

— -3.6

p>0.05

—

— na

—

— -0.020

— -0.74

— 0.000

—
Appendix 2 195

Table 2–64. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–48, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.074 -17 na — — — — -4.4 -0.19 — -2.8

p>0.05 — — na 0.000 -0.0013 -0.010 0.000 — — 0.000 —

Table 2–65. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–49, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -12 na 0.59 0.0039 — 0.70 -3.3 -0.15 — -1.9p>0.05 0.000 — na — — -0.0079 — — — 0.000 —

Table 2–66. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–50, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.12 -14 128 0.34 — — 6.2 -1.7 -0.23 0.018 -5.9p>0.05 — — — — -0.0023 0.0000 — — — — —
196 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–67. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–54, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 0.21 -7.7 460 -0.41 0.0045

—

—

— -0.16 0.000 -0.23

p>0.05

—

—

—

—

— -0.014 0.69 -0.57

—

—

—

Table 2–68. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–55, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.35 -8.3 na

— 0.0033

— 5.5 3.4 -0.14 0.048 -0.62

p>0.05

—

— na 0.88

— -0.014

—

—

—

—

—

Table 2–69. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–56, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -15 na -0.31

—

— -0.47 -4.8 -0.31

— -1.9

p>0.05 0.000

— na

— 0.0015 -0.0061

—

—

— 0.000

—
Appendix 2 197

Table 2–70. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–57, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.16 -26 na -6.0 0.0099 — -8.4 -8.2 -0.17 0.024 -3.0p>0.05 — — na — — 0.000 — — — — —

Table 2–71. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–58, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -8.5 na -0.99 — -0.019 -1.2 -1.8 -0.20 — -2.6p>0.05 0.000 — na — 0.0020 — — — — 0.000 —

Table 2–72. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–59, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -8.5 na -0.99 0.0020 -0.019 -1.1 -1.8 -0.20 — -2.6p>0.05 0.00 — na — — — — — — 0.000 —
198 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–73. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QD–60, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

— -10 na -2.5

—

—

—

— -0.18

— 1.0

p>0.05 0.14

— na

— 0.00 -0.012 0.00 -0.39

— 0.00

—
Appendix 2 199

Table 2–74. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–53, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -5.8 na — -0.0026 -0.020 — — -0.10 — 0.20p>0.05 0.000 — na -0.36 — — -0.16 -0.17 — 0.000 —

Table 2–75. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–56, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.32 -5.7 na 1.3 — -0.044 — 3.0 -0.19 — -0.11

p>0.05 — — na — 0.0021 — 0.00 — — 0.000 —

Table 2–76. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–58, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2008.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.26 -12 na -3.9 — -0.046 -1.6 -2.9 -0.14 — 1.6p>0.05 — — na — 0.00 — — — — 0.00 —
200 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–77. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–61, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 -3.1 -38 7.1 -4.1

— -0.030 2.1 -13 -0.19

— -0.31

p>0.05

—

—

—

— -0.0026

—

—

—

— 0.00

—

Table 2–78. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–62, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -4.8

— 1.3 0.012 -0.023

—

— -0.13

—

—

p>0.05 0.085

— 1.2

—

—

— 0.082 1.8

— 0.000 -0.19

Table 2–79. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–63, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -24

— 13 0.043 0.021 16 25 -0.088

— -0.42

p>0.05 0.00

— 0.81

—

—

—

—

—

— 0.00

—
Appendix 2 201

Table 2–80. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–64, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.48 -16 0.94 -4.4 -0.032 — -1.1 -3.7 -0.19 — -0.30p>0.05 — — — — — 0.000 — — — 0.000 —

Table 2–81. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–65, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2010. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -54 -0.91 -6.7 — — — — -0.81 — 0.62

p>0.05 1.8 — — — 0.0080 0.000 -0.99 -1.8 — 0.000 —

Table 2–82. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–67, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 4.4 -42 22 -30 0.74 — -15 -32 -0.31 — 0.29p>0.05 — — — — — 0.000 — — — 0.000 —
202 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–83. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–68, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 0.99

—

— 2.2

— -0.041 -0.33 4.6 -0.10 0.033

—

p>0.05

— 1.9 0.42

— 0.0019

—

—

—

—

— 0.000

Table 2–84. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–69, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -14 na -2.6

— -0.022 -1.9 -3.2 -0.13

— 1.0

p>0.05 0.00

— na

— -0.0012

—

—

—

— 0.00

—

Table 2–85. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–70, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -13 na -0.70

— -0.025 -0.55 -2.2 -0.13

— 1.8

p>0.05 -0.11

— na

— 0.00

—

—

—

— 0.000

—
Appendix 2 203

Table 2–86. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–71, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -20 na -1.6 — -0.018 -0.83 -2.5 -0.12 — 0.73p>0.05 -0.23 — na — 0.000 — — — — 0.000 —

Table 2–87. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–72, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -15 na -1.3 0.0031 -0.032 -0.80 — -0.11 — 1.1p>0.05 -0.18 — na — — — — -1.8 — 0.000 —

Table 2–88. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–73, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.57 -10 na — — — -0.68 -3.3 -0.15 0.032 -2.2p>0.05 — — na 0.28 -0.0018 -0.0081 — — — — —
204 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–89. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–74, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05

— -6.1 na

—

—

— -0.80

— -0.087

— 1.1

p>0.05 0.000

— na 0.31 -0.0022 -0.0073

— -0.96

— 0.000

—

Table 2–90. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–75, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -4.9 2.0

—

—

— -0.37 -1.6 -0.14

— -1.3

p>0.05 0.000

—

— 0.054 0.00 -0.012

—

—

— 0.00

—

Table 2–91. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–76, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -10

—

—

—

—

—

— -0.13

— -1.9

p>0.05 0.000

— 0.14 0.53 0.000 -0.028 0.000 -2.0

— 0.0056

—
Appendix 2 205

Table 2–92. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–77, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.13 -5.3 4.8 — -0.0026 -0.024 -0.82 -2.0 -0.11 0.085 -1.7p>0.05 — — — -0.11 — — — — — — —

Table 2–93. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–78, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.19 -18 na 0.000 -0.0031 — -2.4 -6.9 -0.17 0.000 -3.7p>0.05 — — na — — 0.012 — — — — —

Table 2–94. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–79, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.33 -16 na — — — -0.68 -6.9 -0.23 0.045 -4.1p>0.05 — — na 0.000 0.000 0.014 — — — — —
206 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–95. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–80, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 -0.055 -5.8 na

— -0.0019

— -0.72 -2.4 -0.14

— -1.0

p>0.05

—

— na 0.000

— 0.000

—

—

— 0.000

—

Table 2–96. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–81, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.25 -5.1 na 0.52

—

— -0.93

— -0.14

—

—

p>0.05

—

— na

— -0.0015 -0.022

— -0.35

— 0.000 -0.15

Table 2–97. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well QM–82, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 -0.10 -6.6 na 0.31

—

— -0.73 -3.3 -0.16 0.016 -2.6

p>0.05

—

— na

— 0.000 0.000

—

—

—

—

—
Appendix 2 207

Table 2–98. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–1, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1994–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -16 na -1.3 — -0.026 0.86 1.3 -0.12 0.00 -0.73p>0.05 0.08 — na — 0.00 — — — — — —

Table 2–99. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–2, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1994–2010. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 1.8 -24 na — 0.0023 -0.043 — 2.7 -0.10 — —

p>0.05 — — na -1.0 — — 0.23 — — 0.0 0.0

Table 2–100. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–3, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1994–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.21 -20 na — 0.0057 -0.025 1.2 1.7 -0.11 0.00 0.00p>0.05 — — na 0.00 — — — — — — —
208 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 2–101. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–4, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1994–2013. [<, less than; >, greater than; na, not analyzed; —, no data] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level p<0.05 0.91 -21 na -3.5

—

— -1.2

— -0.18

— -0.44

p>0.05

—

— na

— 0.00 0.00

— -1.1

— 0.00

—

Table 2–102. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–5, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1994–2010. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 6.8 -19

— -17 0.00

— -12 -6.9 -0.11

—

—

p>0.05

—

— 0.21

—

— -0.012

—

—

— 0.00 0.00

Table 2–103. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–6, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1994–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05

— -27 1.9 -4.5

— -0.02 -3.0 -6.0 -0.11

— 0.50

p>0.05 0.00

—

—

— 0.00

—

—

—

— 0.00

—
Appendix 2 209

Table 2–104. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–7, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1998–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 0.28 -26 — -7.6 0.00 -0.04 -5.2 -10 -0.15 — —p>0.05 — — 0.77 — — — — — — 0.00 0.08

Table 2–105. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–8, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1997–2013. [<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -24 5.3 -10 -0.01 — -5.8 -9.2 -0.09 — -3.3p>0.05 0.50 — — — — 0.02 — — — 0.00 —

Table 2–106. Kendall’s tau correlation coefficient with slope estimator for overall trends in analytes and physical properties, monitoring well MW–9, Upper Des Plaines System, Tunnel and Reservoir Plan system, Cook County, Illinois, 1997–2013.[<, less than; >, greater than; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Ground- water level

p<0.05 — -23 — -5.2 — — -1.4 -4.0 -0.10 — 0.45p>0.05 -0.09 — 0.00 — 3.2 0.00 — — — 0.00 —
210 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013

Appendix 3. Seasonality of analytes and physical properties, 

by well, Tunnel and Reservoir Plan System, 1995–2013

Each appendix has four Tunnel and Reservoir Plan Systems, each with multiple tables of varing sizes.

Table 3–1 to table 3–33. Seasonality of analytes and physical properties in samples from wells, Calumet System, 

Tunnel and Reservoir Plan System, Cook County, Illinois.

Table 3–34 to table 3–73. Seasonality of analytes and physical properties in samples from wells, Des Plaines System, 

Tunnel and Reservoir Plan System, Cook County, Illinois.

Table 3–74 to table 3–97. Seasonality of analytes and physical properties in samples from wells, Mainstream System, 

Tunnel and Reservoir Plan System, Cook County, Illinois.

Table 3–98 to table 3–106. Seasonality of analytes and physical properties in samples from wells, Upper Des Plaines System, 

Tunnel and Reservoir Plan System, Cook County, Illinois.
Appendix 3 211

Table 3–1. Seasonality of analytes and physical properties in samples from monitoring well QC–1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.51 0.27 na 0.75 0.60 0.65 0.58 0.46 0.77 <0.00 0.09

Table 3–2. Seasonality of analytes and physical properties in samples from monitoring well QC–2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.32 0.39 na 0.51 <0.00 0.71 0.17 0.46 0.66 <0.00 na

Table 3–3. Seasonality of analytes and physical properties in samples from monitoring well QC–2.1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.84 0.24 na <0.00 0.80 0.52 na 0.67 na <0.00 0.69

Table 3–4. Seasonality of analytes and physical properties in samples from monitoring well QC–2.2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value <0.00 0.47 na 0.69 0.41 0.75 na 0.35 0.96 <0.00 0.83
212 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–5. Seasonality of analytes and physical properties in samples from monitoring well QC–3, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.54 0.49 na 0.82 0.45 0.79 0.92 0.48 na <0.00 0.19 Table 3–6. Seasonality of analytes and physical properties in samples from monitoring well QC–4, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.72 na 0.37 na 0.62 na 0.18 na <0.00 0.10 Table 3–7. Seasonality of analytes and physical properties in samples from monitoring well QC–5, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.65 na 0.28 na 0.36 na 0.23 na <0.00 0.79 Table 3–8. Seasonality of analytes and physical properties in samples from monitoring well QC–6, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.77 na 0.95 0.45 0.64 na 0.35 0.71 <0.00 0.23
Appendix 3 213

Table 3–9. Seasonality of analytes and physical properties in samples from monitoring well QC–7, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.67 0.63 na 0.27 0.99 0.81 na 0.10 na <0.00 0.74

Table 3–10. Seasonality of analytes and physical properties in samples from monitoring well QC–9, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.66 na 0.73 na 0.97 0.90 0.06 0.91 <0.00 0.62

Table 3–11. Seasonality of analytes and physical properties in samples from monitoring well QC–10, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.97 0.89 na 0.30 na 0.46 na 0.14 0.91 <0.00 0.01

Table 3–12. Seasonality of analytes and physical properties in samples from monitoring well QC–11, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.33 0.76 na 0.83 na 0.15 na 0.50 na <0.00 0.95
214 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–13. Seasonality of analytes and physical properties in samples from monitoring well QC–12, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.31 0.90 na 0.24 na 0.19 0.39 0.47 na <0.00 0.86 Table 3–14. Seasonality of analytes and physical properties in samples from monitoring well QC–13, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.80 0.29 na 0.38 0.50 0.27 0.52 0.79 na <0.00 0.78 Table 3–15. Seasonality of analytes and physical properties in samples from monitoring well QC–14, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.78 <0.00 na 0.87 na 0.95 na 0.37 0.88 <0.00 0.36 Table 3–16. Seasonality of analytes and physical properties in samples from monitoring well QC–15, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.50 na 0.76 0.24 0.92 na 0.52 na <0.00 0.44
Appendix 3 215

Table 3–17. Seasonality of analytes and physical properties in samples from monitoring well QC–16, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.71 0.69 na 0.41 na 0.82 0.52 0.22 na <0.00 0.29

Table 3–18. Seasonality of analytes and physical properties in samples from monitoring well QC–17, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.77 na 0.38 0.75 <0.00 0.48 0.85 na <0.00 0.89

Table 3–19. Seasonality of analytes and physical properties in samples from monitoring well QC–18, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.40 na 0.52 na 0.06 0.27 0.46 na <0.00 0.97

Table 3–20. Seasonality of analytes and physical properties in samples from monitoring well QC–19, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.45 na 0.50 na 0.58 0.79 0.32 na <0.00 0.94
216 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–21. Seasonality of analytes and physical properties in samples from monitoring well QC–20, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.41 0.46 na 0.43 na 0.19 na 0.49 na <0.00 0.58 Table 3–22. Seasonality of analytes and physical properties in samples from monitoring well QC–21, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.82 0.36 na 0.62 na 0.53 na 0.10 0.96 <0.00 0.43 Table 3–23. Seasonality of analytes and physical properties in samples from monitoring well QC–22, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.91 na 0.61 0.13 0.82 na <0.00 0.63 <0.00 0.31 Table 3–24. Seasonality of analytes and physical properties in samples from monitoring well QC–23, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.25 0.97 na 0.54 na 0.64 na <0.00 0.92 <0.00 0.36
Appendix 3 217

Table 3–25. Seasonality of analytes and physical properties in samples from monitoring well QC–24, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.99 0.91 na 0.05 na 0.86 na <0.00 0.92 <0.00 0.31

Table 3–26. Seasonality of analytes and physical properties in samples from monitoring well QC–25, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.75 na 0.49 0.36 0.89 na 0.17 na <0.00 0.89

Table 3–27. Seasonality of analytes and physical properties in samples from monitoring well QC–26, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.49 na 0.21 na 0.44 na 0.74 na <0.00 0.76

Table 3–28. Seasonality of analytes and physical properties in samples from monitoring well QC–27, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.16 na 0.97 na 0.16 na 0.21 na <0.00 0.69
218 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–29. Seasonality of analytes and physical properties in samples from monitoring well QC–28, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.32 na 0.19 na 0.59 na 0.12 na <0.00 0.57 Table 3–30. Seasonality of analytes and physical properties in samples from monitoring well QC–29, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.48 na 0.68 0.81 0.76 0.63 0.51 na <0.00 0.70 Table 3–31. Seasonality of analytes and physical properties in samples from monitoring well QC–30, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.72 na 0.16 na 0.64 0.69 <0.00 na <0.00 0.16 Table 3–32. Seasonality of analytes and physical properties in samples from monitoring well QC–31, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.85 na 0.87 0.42 0.06 0.09 0.52 na <0.00 0.50
Appendix 3 219

Table 3–33. Seasonality of analytes and physical properties in samples from monitoring well QC–37, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2010. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.82 0.74 na 0.36 0.39 0.34 0.61 0.51 0.84 <0.00 0.74
Appendix 3 221

Table 3–34. Seasonality of analytes and physical properties in samples from monitoring well QD–21, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.16 0.63 na 0.04 0.97 0.31 <0.00 <0.00 0.99 <0.00 0.78

Table 3–35. Seasonality of analytes and physical properties in samples from monitoring well QD–22, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.32 0.54 na 0.73 0.55 0.16 <0.00 <0.00 0.97 <0.00 0.79

Table 3–36. Seasonality of analytes and physical properties in samples from monitoring well QD–23, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.85 0.23 na 0.94 0.83 0.43 <0.00 <0.00 0.98 <0.00 <0.00

Table 3–37. Seasonality of analytes and physical properties in samples from monitoring well QD–24, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.30 na 0.48 na 0.64 0.43 <0.00 0.82 <0.00 0.23
222 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–38. Seasonality of analytes and physical properties in samples from monitoring well QD–25, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.02 0.72 na 0.28 0.89 0.80 0.35 <0.00 0.66 <0.00 0.31 Table 3–39. Seasonality of analytes and physical properties in samples from monitoring well QD–26, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.71 na 0.65 0.44 0.69 na 0.64 na <0.00 0.01 Table 3–40. Seasonality of analytes and physical properties in samples from monitoring well QD–27, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.75 0.40 na 0.89 0.92 0.49 0.29 0.73 0.91 <0.00 0.88 Table 3–41. Seasonality of analytes and physical properties in samples from monitoring well QD–28, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.51 0.58 na 0.19 0.29 0.24 na <0.00 0.88 <0.00 0.15
Appendix 3 223

Table 3–42. Seasonality of analytes and physical properties in samples from monitoring well QD–29, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.75 0.69 na 0.21 0.47 0.45 0.40 <0.00 0.48 <0.00 0.50

Table 3–43. Seasonality of analytes and physical properties in samples from monitoring well QD–30, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.73 0.74 na 0.45 0.26 0.82 0.39 0.10 0.59 <0.00 0.71

Table 3–44. Seasonality of analytes and physical properties in samples from monitoring well QD–31, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.27 0.98 na 0.78 na 0.87 0.75 0.17 na <0.00 0.60

Table 3–45. Seasonality of analytes and physical properties in samples from monitoring well QD–32, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.37 0.52 na 0.65 0.66 0.87 0.81 0.14 na <0.00 0.91
224 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–46. Seasonality of analytes and physical properties in samples from monitoring well QD–33, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.50 0.28 na 0.08 na 0.96 0.57 0.26 na <0.00 0.68 Table 3–47. Seasonality of analytes and physical properties in samples from monitoring well QD–34, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.46 0.03 na 0.31 0.47 0.32 0.38 <0.00 0.51 <0.00 0.78 Table 3–48. Seasonality of analytes and physical properties in samples from monitoring well QD–35, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.67 0.41 na 0.89 0.40 0.18 0.72 <0.00 0.51 <0.00 0.28 Table 3–49. Seasonality of analytes and physical properties in samples from monitoring well QD–36, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.74 0.39 na 0.59 0.50 0.99 na <0.00 0.99 <0.00 0.41
Appendix 3 225

Table 3–50. Seasonality of analytes and physical properties in samples from monitoring well QD–37, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.21 0.67 na 0.47 na 0.36 0.95 0.80 na <0.00 0.47

Table 3–51. Seasonality of analytes and physical properties in samples from monitoring well QD–38, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.53 0.93 na 0.19 na 0.28 0.55 0.52 na <0.00 0.57

Table 3–52. Seasonality of analytes and physical properties in samples from monitoring well QD–39, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.82 0.35 na 0.69 na 0.96 0.65 <0.00 na <0.00 0.51

Table 3–53. Seasonality of analytes and physical properties in samples from monitoring well QD–40, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.74 0.35 na 0.47 na 0.36 0.51 0.23 0.81 <0.00 0.50
226 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–54. Seasonality of analytes and physical properties in samples from monitoring well QD–41, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.29 na 0.58 na 0.16 0.27 0.04 na <0.00 0.93 Table 3–55. Seasonality of analytes and physical properties in samples from monitoring well QD–42, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.42 0.60 na 0.31 0.44 0.50 0.51 0.03 0.56 <0.00 0.49 Table 3–56. Seasonality of analytes and physical properties in samples from monitoring well QD–43, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.98 0.35 na 0.19 0.44 0.18 0.87 0.03 na <0.00 0.35 Table 3–57. Seasonality of analytes and physical properties in samples from monitoring well QD–44, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.35 na 0.06 0.03 0.96 0.10 0.22 na <0.00 0.15
Appendix 3 227

Table 3–58. Seasonality of analytes and physical properties in samples from monitoring well QD–45, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.87 0.56 na 0.68 0.99 0.82 0.69 0.06 0.16 <0.00 0.49

Table 3–59. Seasonality of analytes and physical properties in samples from monitoring well QD–46, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.85 na 0.44 0.41 0.93 0.51 0.13 na <0.00 na

Table 3–60. Seasonality of analytes and physical properties in samples from monitoring well QD–47, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.51 0.32 na 0.43 0.96 0.68 0.65 0.60 na <0.00 0.99

Table 3–61. Seasonality of analytes and physical properties in samples from monitoring well QD–48, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.37 na 0.21 0.99 0.98 0.07 0.30 na <0.00 0.98
228 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–62. Seasonality of analytes and physical properties in samples from monitoring well QD–49, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.51 na 0.25 na 0.81 0.89 0.20 na <0.00 0.53 Table 3–63. Seasonality of analytes and physical properties in samples from monitoring well QD–50, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.23 na na na 0.49 0.84 0.71 na <0.00 0.05 Table 3–64. Seasonality of analytes and physical properties in samples from monitoring well QD–51, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.81 na na na 0.12 0.67 0.80 na <0.00 0.06 Table 3–65. Seasonality of analytes and physical properties in samples from monitoring well QD–52, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.50 0.26 na 0.69 na 0.21 0.11 0.13 na <0.00 0.09
Appendix 3 229

Table 3–66. Seasonality of analytes and physical properties in samples from monitoring well QD–53, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.20 0.61 na 0.23 na 0.16 0.37 0.25 na <0.00 0.07

Table 3–67. Seasonality of analytes and physical properties in samples from monitoring well QD–54, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.50 0.70 na 0.94 na 0.41 0.68 0.88 na <0.00 0.11

Table 3–68. Seasonality of analytes and physical properties in samples from monitoring well QD–55, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.92 0.56 na 0.99 0.52 0.28 0.37 0.11 na <0.00 0.25

Table 3–69. Seasonality of analytes and physical properties in samples from monitoring well QD–56, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.50 0.26 na 0.69 na 0.21 0.11 0.13 na <0.00 0.09
230 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–70. Seasonality of analytes and physical properties in samples from monitoring well QD–57, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.51 na 0.77 0.87 0.69 na 0.80 na <0.00 0.79 Table 3–72. Seasonality of analytes and physical properties in samples from monitoring well QD–59, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.34 0.25 na 0.74 0.69 0.99 0.24 0.46 na <0.00 0.71 Table 3–71. Seasonality of analytes and physical properties in samples from monitoring well QD–58, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value na 0.42 na 0.33 0.93 0.67 na 0.96 0.44 <0.00 0.51 Table 3–73. Seasonality of analytes and physical properties in samples from monitoring well QD–60, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.22 0.24 na 0.74 0.47 0.81 0.47 0.87 na <0.00 0.86
 231

Table 3–74. Seasonality of analytes and physical properties in samples from monitoring well QM–53, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.93 na 0.28 na 0.36 0.38 0.16 na <0.00 0.22

Table 3–75. Seasonality of analytes and physical properties in samples from monitoring well QM–56, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.36 0.23 na 0.95 0.44 0.71 0.55 0.09 na <0.00 0.53

Table 3–76. Seasonality of analytes and physical properties in samples from monitoring well QM–58, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2008. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.96 0.90 na 0.68 0.42 0.08 0.15 0.03 0.19 <0.00 0.35

Table 3–77. SSeasonality of analytes and physical properties in samples from monitoring well QM–61, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.10 0.83 na 0.49 0.91 0.60 na 0.69 0.77 <0.00 0.08
232 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–78 Seasonality of analytes and physical properties in samples from monitoring well QM–62, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.01 0.26 na 0.45 0.64 0.37 0.95 0.96 0.39 <0.00 0.90 Table 3–79. Seasonality of analytes and physical properties in samples from monitoring well QM–63, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.23 0.28 na 0.63 na 0.19 0.79 0.81 0.84 <0.00 0.25 Table 3–80. Seasonality of analytes and physical properties in samples from monitoring well QM–64, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.16 0.41 na 0.75 0.48 0.12 0.89 0.15 nc <0.00 0.42 Table 3–81. Seasonality of analytes and physical properties in samples from monitoring well QM–65, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.07 0.04 na 0.12 0.96 0.28 0.60 0.05 0.88 <0.00 0.19
 233

Table 3–82. Seasonality of analytes and physical properties in samples from monitoring well QM–67, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value <0.00 0.75 na 0.46 na 0.89 na 0.49 na <0.00 0.41

Table 3–83. Seasonality of analytes and physical properties in samples from monitoring well QM–68, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.05 0.17 na 0.05 0.99 0.18 0.41 0.15 na <0.00 0.32

Table 3–84. Seasonality of analytes and physical properties in samples from monitoring well QM–69, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.78 0.48 na 0.58 0.69 0.97 0.69 0.84 na <0.00 0.84

Table 3–85. Seasonality of analytes and physical properties in samples from monitoring well QM–70, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.15 0.85 na 0.26 0.70 0.31 0.66 0.41 na <0.00 0.86
234 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–86. Seasonality of analytes and physical properties in samples from monitoring well QM–71, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.80 0.88 na 0.43 0.10 0.10 0.58 0.07 na <0.00 0.06 Table 3–87. Seasonality of analytes and physical properties in samples from monitoring well QM–72, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.51 0.76 na 0.64 na 0.40 na <0.00 na <0.00 0.99 Table 3–88. Seasonality of analytes and physical properties in samples from monitoring well QM–73, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.99 0.64 na 0.19 0.53 0.94 na 0.77 0.84 <0.00 0.99 Table 3–89. Seasonality of analytes and physical properties in samples from monitoring well QM–74, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.37 0.74 na 0.60 0.12 0.48 na 0.31 0.51 <0.00 0.74
 235

Table 3–90. Seasonality of analytes and physical properties in samples from monitoring well QM–75, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.12 na 0.59 0.53 0.94 0.75 <0.00 na <0.00 0.74

Table 3–91. Seasonality of analytes and physical properties in samples from monitoring well QM–76, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.56 na 0.36 0.58 0.31 0.31 0.42 na <0.00 0.57

Table 3–92. Seasonality of analytes and physical properties in samples from monitoring well QM–77, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.78 0.84 na 0.28 na 0.96 na 0.04 na <0.00 0.18

Table 3–93. Seasonality of analytes and physical properties in samples from monitoring well QM–78, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.78 na 0.66 na 0.33 0.55 0.17 na <0.00 0.86
236 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–94. Seasonality of analytes and physical properties in samples from monitoring well QM–79, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.32 0.76 na 0.34 na 0.77 0.27 0.54 na <0.00 0.57 Table 3–95. Seasonality of analytes and physical properties in samples from monitoring well QM–80, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.02 0.83 na 0.92 na 0.85 na 0.14 na <0.00 0.42 Table 3–96. Seasonality of analytes and physical properties in samples from monitoring well QM–81, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.99 0.32 na 0.63 na 0.92 0.61 0.09 na <0.00 0.68 Table 3–97. Seasonality of analytes and physical properties in samples from monitoring well QM–82, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.78 0.75 na 0.47 na 0.94 na 0.19 na <0.00 0.96
Appendix 3 237 23

Table 3–98. Seasonality of analytes and physical properties in samples from monitoring well MW–1, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.20 0.77 na 0.99 0.40 0.32 0.95 0.52 na <0.00 0.71

Table 3–99. Seasonality of analytes and physical properties in samples from monitoring well MW–2, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2010. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.45 0.24 na 0.92 0.56 0.62 0.76 0.09 na <0.00 0.03

Table 3–100. Seasonality of analytes and physical properties in samples from monitoring well MW–3, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value na 0.16 na 0.40 0.38 0.63 0.67 <0.01 na <0.00 0.01

Table 3–101. Seasonality of analytes and physical properties in samples from monitoring well MW–4, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.92 0.24 na 0.91 na 0.59 0.60 0.33 na <0.00 0.33
238 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 3–102. Seasonality of analytes and physical properties in samples from monitoring well MW–5, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2010. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value <0.01 0.06 na 0.37 na 0.45 0.41 0.02 na <0.00 0.12 Table 3–103. Seasonality of analytes and physical properties in samples from monitoring well MW–6, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.50 0.48 na 0.40 0.09 0.34 0.04 0.06 na <0.00 0.10 Table 3–104. Seasonality of analytes and physical properties in samples from monitoring well MW–7, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1998–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance] Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level p value 0.19 0.02 na 0.69 0.89 0.31 0.54 0.67 na <0.00 0.41 Table 3–105. Seasonality of analytes and physical properties in samples from monitoring well MW–8, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1997–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value <0.01 0.12 na 0.32 na 0.33 0.85 0.20 na <0.00 0.77
Appendix 3 239 23

Table 3–106. Seasonality of analytes and physical properties in samples from monitoring well MW–9, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1997–2013. [<, less than; na, data not analyzed; underline denotes seasonality indicated to 95 percent or higher level of significance]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature Groundwater level 

p value 0.02 0.08 na 0.31 na 0.68 0.22 0.04 na <0.00 0.42

Appendix 4 241

Appendix 4. Analyte and physical property correlations, 

by well, Tunnel and Reservoir Plan System, 1995–2013

Each appendix has four Tunnel and Reservoir Plan Systems, each with multiple tables of varing sizes.

Table 4–1 to table 4–33. Kendall’s tau-b correlation coefficient for analytes and physical properties, by well, 

Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois.

Table 4–34 to table 4–73. Kendall’s tau-b correlation coefficient for analytes and physical properties, by well, 

Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois.

Table 4–74 to table 4–97. Kendall’s tau-b correlation coefficient for analytes and physical properties, by wells, 

Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois. 

Table 4–98 to table 4–106. Kendall’s tau-b correlation coefficient for analytes and physical properties, by wells, 

Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois.
242 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–1. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.01

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.16 0.22 na

—

—

—

—

—

—

—

Ammonia -0.03 0.19 na 0.07

—

—

—

—

—

—

pH -0.09 0.08 na 0.18 -0.08

—

—

—

—

—

Sulfate 0.23 0.11 na -0.08 0.16 -0.08

—

—

—

—

Total dissolved solids

0.11 0.12 na 0.03 -0.02 0.04 -0.06

—

—

—

Dissolved organic carbon

-0.12 0.26 na 0.39 0.04 0.05 0.01 0.05

—

—

Temperature -0.01 0.05 na 0.07 0.04 -0.03 -0.03 0.09 -0.03

—

Groundwater level -0.02 -0.21 na -0.16 0.06 -0.07 -0.11 -0.07 -0.23 -0.04
Appendix 4 243

Table 4–2. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.24 — — — — — — — — —

Fecal coliform 0.22 -0.02 — — — — — — — —Hardness 0.47 0.28 0.12 — — — — — — —

Ammonia 0.37 0.12 0.34 0.31 — — — — — —

pH 0.03 0.06 0.05 0.16 0.19 — — — — —

Sulfate 0.15 0.07 0.04 0.11 0.07 0.04 — — — —

Total dissolved solids

0.12 0.17 0.02 0.11 -0.03 -0.08 -0.01 — — —

Dissolved organic carbon

0.29 0.23 0.04 0.37 0.17 0.11 0.10 0.20 — —

Temperature -0.03 -0.08 0.11 -0.02 0.14 0.03 0.04 -0.03 -0.01 —

Groundwater level 0.31 0.09 0.34 0.25 0.50 0.10 0.16 0.03 0.25 0.11
244 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–3. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–2.1, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.16

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.02 -0.10 na

—

—

—

—

—

—

—

Ammonia -0.12 -0.18 na 0.21

—

—

—

—

—

—

pH 0.05 0.15 na -0.04 -0.11

—

—

—

—

—

Sulfate 0.29 0.25 na -0.21 -0.27 0.17

—

—

—

—

Total dissolved solids

0.06 0.19 na 0.00 -0.15 0.03 0.08

—

—

—

Dissolved organic carbon

0.07 0.20 na -0.10 -0.18 0.08 0.23 0.22

—

—

Temperature -0.06 0.00 na 0.02 -0.02 0.00 0.01 -0.02 -0.07

—

Groundwater level 0.15 0.35 na -0.27 -0.17 0.25 0.44 0.10 0.20 -0.02
Appendix 4 245

Table 4–4. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–2.2, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.15 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.02 -0.11 na — — — — — — —

Ammonia 0.15 0.10 na -0.37 — — — — — —

pH -0.01 0.14 na -0.03 0.01 — — — — —

Sulfate 0.02 0.31 na -0.19 0.05 0.19 — — — —

Total dissolved solids

0.24 0.14 na 0.04 0.06 0.09 0.22 — — —

Dissolved organic carbon

0.12 0.28 na -0.08 0.09 0.24 0.34 0.30 — —

Temperature -0.20 0.02 na 0.03 0.08 0.00 0.04 0.00 -0.07 —

Groundwater level 0.04 0.04 na -0.31 0.36 0.05 0.23 0.05 0.27 0.03
246 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–5. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–3, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.05

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.03 -0.11 na

—

—

—

—

—

— -

Ammonia 0.12 -0.33 na 0.07

—

—

—

—

—

—

pH -0.15 0.14 na -0.03 -0.17

—

—

—

—

—

Sulfate 0.22 0.01 na -0.06 0.00 -0.04

—

—

—

—

Total dissolved solids

0.27 0.26 na -0.04 -0.03 -0.03 0.13

—

—

—

Dissolved organic carbon

-0.23 0.24 na -0.12 -0.23 0.22 0.06 0.12

—

—

Temperature 0.04 0.09 na 0.02 0.07 -0.07 0.00 -0.03 -0.14

—

Groundwater level -0.04 -0.07 na 0.05 0.22 -0.07 -0.23 -0.16 0.20 0.20
Appendix 4 247

Table 4–6. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–4, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.12 — — — — — — — — —

Fecal coliform -0.06 0.13 — — — — — — — —

Hardness -0.10 0.13 0.10 — — — — — — —

Ammonia 0.14 -0.07 -0.08 -0.12 — — — — — —pH 0.03 0.00 0.05 0.18 -0.10 — — — — —

Sulfate 0.11 0.25 0.14 0.22 -0.19 0.00 — — — —

Total dissolved solids

0.07 0.32 0.05 0.11 -0.11 -0.03 0.29 — — —

Dissolved organic carbon

0.15 0.34 0.17 0.11 -0.03 -0.11 0.42 0.30 — —

Temperature -0.05 -0.04 0.02 -0.06 -0.09 0.10 0.03 -0.01 -0.20 —

Groundwater level -0.04 -0.17 0.13 -0.22 0.12 -0.13 -0.20 -0.14 -0.24 0.03
248 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–7. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–5, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.01

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.28 0.21 na

—

—

—

—

—

—

—

Ammonia -0.09 -0.20 na -0.08

—

—

—

—

—

—

pH -0.05 -0.01 na 0.11 -0.07

—

—

—

—

—

Sulfate 0.04 0.28 na 0.28 -0.16 0.04

—

—

—

—

Total dissolved solids

0.02 0.22 na 0.18 -0.22 -0.06 0.26

—

—

—

Dissolved organic carbon

-0.07 0.28 na 0.20 -0.09 -0.02 0.31 0.25

—

—

Temperature -0.03 0.03 na -0.04 -0.05 0.12 0.02 0.07 -0.13

—

Groundwater level -0.04 -0.34 na -0.28 0.19 -0.06 -0.40 -0.26 -0.39 0.03
Appendix 4 249

Table 4–8. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–6, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.35 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.59 0.43 na — — — — — — —

Ammonia 0.22 0.11 na 0.24 — — — — — —

pH 0.01 0.03 na 0.04 -0.07 — — — — —

Sulfate 0.62 0.47 na 0.72 0.23 0.01 — — — —

Total dissolved solids

0.53 0.43 na 0.56 0.15 -0.05 0.57 — — —

Dissolved organic carbon

0.37 0.37 na 0.50 0.22 0.00 0.48 0.45 — —

Temperature 0.08 0.10 na 0.06 -0.02 0.11 0.05 0.08 -0.05 —

Groundwater level -0.39 -0.39 na -0.48 -0.18 -0.10 -0.54 -0.38 -0.41 0.09
250 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–9. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–7, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.10

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.03 0.13 na

—

—

—

—

—

—

—

Ammonia -0.06 0.08 na 0.07

—

—

—

—

—

—

pH 0.00 0.08 na -0.08 -0.06

—

—

—

—

—

Sulfate -0.04 0.25 na -0.01 -0.14 0.37

—

—

—

—

Total dissolved solids

0.10 0.14 na 0.08 -0.03 0.14 0.15

—

—

—

Dissolved organic carbon

-0.10 0.28 na 0.07 0.11 0.15 0.34 0.02

—

—

Temperature -0.05 -0.03 na 0.05 -0.04 0.01 -0.01 0.12 -0.20

—

Groundwater level -0.19 0.28 na 0.13 0.11 0.07 0.31 0.05 0.40 -0.09
Appendix 4 251

Table 4–10. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–9, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.04 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.16 0.04 na — — — — — — —

Ammonia -0.04 0.18 na -0.20 — — — — — —

pH -0.01 0.04 na 0.00 0.34 — — — — —

Sulfate 0.07 -0.31 na -0.11 -0.27 -0.18 — — — —Total dissolved solids

-0.03 -0.18 na 0.09 -0.05 0.05 0.03 — — —

Dissolved organic carbon

-0.04 0.19 na 0.03 0.33 0.19 -0.35 0.07 — —

Temperature -0.19 -0.08 na 0.09 -0.17 -0.03 0.12 0.23 -0.09 —

Groundwater level -0.02 0.23 na -0.07 0.30 0.05 -0.31 -0.05 0.35 -0.09
252 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–11. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–10, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.09

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.05 0.15 na

—

—

—

—

—

—

—

Ammonia -0.16 -0.18 na -0.03

—

—

—

—

—

—

pH -0.03 0.08 na 0.05 0.08

—

—

—

—

—

Sulfate 0.00 0.31 na 0.07 -0.14 0.14

—

—

—

—

Total dissolved solids

0.05 -0.02 na -0.05 0.07 -0.01 0.02

—

—

—

Dissolved organic carbon

-0.02 0.24 na 0.03 -0.16 -0.09 0.42 0.06

—

—

Temperature -0.04 -0.02 na -0.01 0.06 0.09 -0.01 0.05 -0.10

—

Groundwater level 0.09 -0.19 na -0.03 0.07 -0.08 -0.44 -0.01 -0.24 -0.10
Appendix 4 253

Table 4–12. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–11, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.09 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.01 0.06 na — — — — — — —

Ammonia -0.22 -0.02 na -0.02 — — — — — —

pH -0.04 0.01 na -0.14 0.06 — — — — —

Sulfate 0.13 0.24 na 0.18 -0.18 0.23 — — — —

Total dissolved solids

0.19 0.06 na 0.04 -0.12 -0.06 0.06 — — —

Dissolved organic carbon

0.20 0.27 na 0.29 -0.17 0.13 0.57 0.22 — —

Temperature 0.08 -0.08 na 0.02 -0.05 0.14 0.00 0.09 0.06 —Groundwater level -0.18 -0.36 na -0.13 0.03 -0.03 -0.39 -0.18 -0.33 0.12
254 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–13. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–12, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.06

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.17 -0.12 na

—

—

—

—

—

—

—

Ammonia 0.12 -0.18 na 0.15

—

—

—

—

—

—

pH -0.02 -0.20 na -0.12 0.04

—

—

—

—

—

Sulfate 0.15 0.02 na 0.55 0.28 -0.10

—

—

—

—

Total dissolved solids

0.09 0.02 na 0.61 0.29 -0.17 0.69

—

—

—

Dissolved organic carbon

-0.10 0.28 na -0.08 -0.51 -0.06 -0.23 -0.18

—

—

Temperature -0.11 0.02 na 0.02 -0.05 0.01 -0.11 -0.04 0.13

—

Groundwater level -0.29 -0.26 na 0.01 0.34 0.07 0.04 -0.05 -0.48 0.04
Appendix 4 255

Table 4–14. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–13, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.21 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.30 -0.05 na — — — — — — —Ammonia 0.40 -0.07 na 0.30 — — — — — —pH -0.12 0.04 na -0.07 -0.03 — — — — —

Sulfate 0.07 0.03 na 0.24 0.17 -0.04 — — — —

Total dissolved solids

0.19 -0.07 na 0.08 -0.03 -0.26 0.33 — — —

Dissolved organic carbon

-0.58 0.22 na -0.38 -0.22 0.07 -0.14 -0.18 — —

Temperature 0.19 -0.19 na 0.09 0.01 0.14 -0.02 0.09 -0.12 —Groundwater level 0.53 -0.25 na 0.19 0.26 -0.14 0.09 0.19 -0.45 0.25
256 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–15. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–14, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.29

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.85 0.29 na

—

—

—

—

—

—

—

Ammonia 0.64 0.20 na 0.58

—

—

—

—

—

—

pH -0.36 -0.18 na -0.39 -0.43

—

—

—

—

—

Sulfate -0.61 -0.38 na -0.67 -0.51 0.46

—

—

—

—

Total dissolved solids

0.68 0.18 na 0.70 0.49 -0.27 -0.51

—

—

—

Dissolved organic carbon

-0.08 -0.10 na -0.06 0.03 0.13 0.14 -0.06

—

—

Temperature 0.28 0.26 na 0.31 0.19 -0.12 -0.33 0.32 -0.01

—

Groundwater level 0.32 0.22 na 0.29 0.19 -0.18 -0.25 0.24 -0.11 0.24
Appendix 4 257

Table 4–16. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–15, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.02 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.21 -0.13 na — — — — — — —

Ammonia -0.08 0.08 na 0.02 — — — — — —

pH -0.07 0.12 na -0.07 0.15 — — — — —

Sulfate -0.06 0.35 na -0.13 0.03 0.34 — — — —

Total dissolved solids

0.23 -0.06 na -0.11 0.02 -0.07 0.20 — — —

Dissolved organic carbon

-0.07 0.28 na -0.08 0.21 0.25 0.47 0.14 — —

Temperature -0.17 -0.02 na -0.05 0.10 0.10 -0.15 0.02 0.01 —

Groundwater level 0.06 -0.19 na -0.20 -0.03 -0.05 -0.32 -0.21 -0.31 0.07
258 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–17. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–16, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.19

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.18 0.00 na

—

—

—

—

—

—

—

Ammonia -0.24 0.11 na -0.06

—

—

—

—

—

—

pH -0.19 0.04 na -0.02 0.06

—

—

—

—

—

Sulfate 0.35 -0.04 na 0.31 -0.02 -0.11

—

—

—

—

Total dissolved solids

-0.01 0.03 na 0.14 -0.04 0.06 0.00

—

—

—

Dissolved organic carbon

-0.52 0.10 na -0.33 0.12 0.22 -0.41 0.00

—

—

Temperature 0.16 -0.03 na 0.15 -0.12 -0.05 0.22 0.01 -0.22

—

Groundwater level -0.60 0.15 na -0.22 0.22 0.15 -0.38 0.02 0.39 -0.22
Appendix 4 259

Table 4–18. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–17, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.25 — — — — — — — — —

Fecal coliform 0.12 0.06 — — — — — — — —

Hardness 0.27 0.07 -0.04 — — — — — — —

Ammonia 0.13 -0.33 0.23 -0.10 — — — — — —pH -0.15 0.13 0.07 0.02 -0.18 — — — — —

Sulfate 0.01 0.10 0.03 0.18 -0.04 0.02 — — — —

Total dissolved solids

0.27 0.10 0.08 0.24 0.06 -0.10 0.10 — — —

Dissolved organic carbon

-0.33 0.29 0.19 0.07 -0.20 0.04 0.30 0.06 — —

Temperature 0.00 -0.16 0.10 0.01 0.12 -0.03 -0.03 -0.18 -0.14 —Groundwater level 0.46 -0.04 0.04 0.23 0.00 -0.13 0.17 0.35 0.01 -0.08
260 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–19. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–18, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.06

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.01 -0.15 na

—

—

—

—

—

—

—

Ammonia -0.09 -0.37 na 0.18

—

—

—

—

—

—

pH -0.01 -0.14 na 0.04 0.06

—

—

—

—

—

Sulfate 0.03 0.20 na -0.01 -0.02 -0.04

—

—

—

—

Total dissolved solids

0.04 0.06 na 0.08 0.14 -0.02 0.20

—

—

—

Dissolved organic carbon

-0.16 0.25 na 0.00 -0.02 -0.05 0.49 0.39

—

—

Temperature -0.10 0.06 na 0.05 0.00 -0.08 -0.25 -0.03 -0.20

—

Groundwater level -0.20 -0.32 na 0.16 0.04 0.03 -0.37 -0.25 -0.21 0.03
Appendix 4 261

Table 4–20. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–19, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.07 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.23 0.40 na — — — — — — —

Ammonia -0.12 -0.14 na 0.05 — — — — — —

pH -0.15 -0.08 na -0.01 -0.01 — — — — —

Sulfate -0.10 0.36 na -0.08 -0.02 -0.08 — — — —

Total dissolved solids

-0.11 0.17 na -0.06 0.01 -0.06 0.28 — — —

Dissolved organic carbon

-0.19 0.23 na 0.05 0.00 0.05 0.38 0.20 — —

Temperature -0.15 -0.01 na 0.15 -0.05 0.15 -0.04 -0.03 -0.02 —

Groundwater level 0.12 -0.03 na -0.11 -0.11 -0.11 0.09 -0.06 -0.12 0.04
262 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–21. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–20, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. 

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.07

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.23 0.40 na

—

—

—

—

—

—

—

Ammonia -0.12 -0.14 na 0.05

—

—

—

—

—

—

pH -0.15 -0.08 na -0.01 -0.01

—

—

—

—

—

Sulfate -0.10 0.36 na -0.08 -0.02 -0.08

—

—

—

—

Total dissolved solids

-0.11 0.17 na -0.06 0.01 -0.06 0.28

—

—

—

Dissolved organic carbon

-0.19 0.23 na 0.05 0.00 0.05 0.38 0.20

—

—

Temperature -0.15 -0.01 na 0.15 -0.05 0.15 -0.04 -0.03 -0.02

—

Groundwater level 0.12 -0.03 na -0.11 -0.11 -0.11 0.09 -0.06 -0.12 0.04
Appendix 4 263

Table 4–22. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–21, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013. [Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.15 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.41 0.21 na — — — — — — —

Ammonia -0.29 -0.11 na -0.33 — — — — — —

pH -0.35 -0.04 na -0.14 0.15 — — — — —

Sulfate 0.06 0.13 na 0.16 -0.08 0.13 — — — —

Total dissolved solids

0.32 0.19 na 0.49 -0.17 -0.15 0.28 — — —

Dissolved organic carbon

0.26 0.24 na 0.24 -0.14 -0.12 0.31 0.33 — —

Temperature -0.03 0.14 na 0.06 -0.06 0.11 0.09 0.20 0.09 —

Groundwater level -0.01 -0.03 na 0.03 -0.01 -0.05 0.19 0.08 0.06 0.09
264 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–23. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–22, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.15 - - - - - - - - -

Fecal coliform na na - - - - - - - -

Hardness 0.22 0.10 na - - - - - - -

Ammonia -0.26 -0.13 na -0.02 - - - - - -

pH -0.30 -0.16 na -0.04 0.23 - - - - -

Sulfate -0.27 0.07 na -0.13 0.04 0.03 - - - -

Total dissolved solids

0.15 0.07 na 0.08 0.04 0.16 -0.01 - - -

Dissolved organic carbon

-0.29 -0.05 na -0.22 0.14 0.13 0.12 0.00 - -

Temperature -0.01 0.06 na -0.03 0.14 0.10 0.04 0.21 0.01 -

Groundwater level -0.32 0.04 na 0.01 0.25 0.28 0.17 0.16 0.21 0.14
Appendix 4 265

Table 4–24. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–23, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.03 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.06 0.05 na — — — — — — —

Ammonia -0.03 0.10 na 0.03 — — — — — —

pH 0.02 0.07 na -0.10 0.08 — — — — —

Sulfate 0.01 0.02 na 0.20 0.15 0.09 — — — —

Total dissolved solids

0.01 -0.03 na 0.04 0.16 0.19 0.21 — — —

Dissolved organic carbon

-0.09 -0.03 na 0.05 0.22 -0.08 0.20 0.11 — —

Temperature -0.20 0.05 na -0.11 0.10 0.11 0.02 0.23 -0.03 —

Groundwater level -0.16 0.11 na 0.14 0.31 0.11 0.22 0.23 0.35 0.17
266 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–25. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–24, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.09

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.06 0.05 na

—

—

—

—

—

—

—

Ammonia -0.10 0.09 na -0.04

—

—

—

—

—

—

pH -0.16 0.09 na 0.09 0.14

—

—

—

—

—

Sulfate -0.10 0.10 na -0.27 0.06 0.03

—

—

—

—

Total dissolved solids

0.13 0.12 na -0.14 0.02 -0.07 0.11

—

—

—

Dissolved organic carbon

-0.05 -0.02 na -0.31 0.20 -0.07 0.37 0.26

—

—

Temperature -0.01 0.10 na 0.02 0.13 -0.03 0.01 0.17 0.11

—

Groundwater level -0.12 0.05 na -0.08 0.26 0.16 0.17 0.22 0.35 0.08
Appendix 4 267

Table 4–26. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–25, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.01 - - - - - - - - -

Fecal coliform na na - - - - - - - -

Hardness 0.10 -0.06 na - - - - - - -Ammonia -0.16 0.12 na -0.24 - - - - - -

pH -0.32 -0.07 na -0.05 0.11 - - - - -

Sulfate -0.32 0.24 na 0.05 -0.04 0.22 - - - -

Total dissolved solids

0.16 0.07 na -0.06 -0.02 -0.12 0.15 - - -

Dissolved organic carbon

0.01 0.02 na -0.54 0.22 -0.11 -0.17 0.09 - -

Temperature 0.03 -0.11 na 0.16 -0.07 0.03 -0.04 0.02 -0.02 -Groundwater level -0.18 0.04 na -0.58 0.30 0.17 -0.02 -0.04 0.41 -0.04
268 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–27. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–26, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.09

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.10 0.10 na

—

—

—

—

—

—

—

Ammonia -0.18 0.07 na 0.08

—

—

—

—

—

—

pH -0.07 -0.02 na -0.13 0.23

—

—

—

—

—

Sulfate -0.21 -0.01 na 0.05 0.14 0.08

—

—

—

—

Total dissolved solids

0.16 0.02 na -0.13 -0.06 0.03 0.10

—

—

—

Dissolved organic carbon

-0.11 0.02 na -0.04 0.37 0.00 0.19 0.04

—

—

Temperature 0.16 0.07 na 0.04 -0.01 -0.06 -0.08 0.11 0.05

—

Groundwater level -0.29 0.21 na 0.14 0.35 0.07 0.33 0.00 0.36 0.01
Appendix 4 269

Table 4–28. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–27, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.11 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.35 0.22 na — — — — — — —

Ammonia 0.12 0.13 na 0.17 — — — — — —

pH -0.10 0.00 na -0.13 0.02 — — — — —

Sulfate 0.08 0.11 na 0.26 0.27 0.06 — — — —

Total dissolved solids

0.15 0.23 na 0.28 0.03 -0.07 0.26 — — —

Dissolved organic carbon

0.21 0.15 na 0.36 0.16 -0.07 0.30 0.36 — —

Temperature -0.03 0.17 na 0.05 0.02 -0.14 0.15 0.30 0.24 —

Groundwater level 0.28 0.13 na 0.41 0.19 -0.05 0.37 0.31 0.35 0.11
270 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–29. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–28, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1999–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.06

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.02 0.13 na

—

—

—

—

—

—

—

Ammonia -0.03 0.10 na -0.02

—

—

—

—

—

—

pH -0.12 0.18 na -0.01 0.14

—

—

—

—

—

Sulfate -0.17 0.09 na -0.23 0.26 0.07

—

—

—

—

Total dissolved solids

0.20 0.03 na -0.05 0.15 0.04 0.17

—

—

—

Dissolved organic carbon

0.16 -0.05 na 0.03 0.21 -0.15 0.25 0.17

—

—

Temperature 0.04 0.14 na -0.10 0.03 0.04 0.17 0.17 -0.04

—

Groundwater level -0.04 0.11 na -0.13 0.45 0.24 0.20 0.17 0.23 -0.04
Appendix 4 271

Table 4–30. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–29, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.32 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.82 0.35 na — — — — — — —

Ammonia 0.75 0.35 na 0.80 — — — — — —

pH -0.26 -0.10 na -0.27 -0.30 — — — — —

Sulfate 0.76 0.35 na 0.82 0.78 -0.29 — — — —

Total dissolved solids

0.80 0.31 na 0.86 0.79 -0.26 0.79 — — —

Dissolved organic carbon

0.02 -0.36 na 0.03 0.04 -0.14 0.05 0.08 — —

Temperature 0.11 0.20 na 0.15 0.15 0.00 0.16 0.15 0.06 —

Groundwater level -0.35 -0.20 na -0.26 -0.29 0.18 -0.29 -0.31 0.11 0.02
272 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–31. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–30, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.19

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.14 0.04 na

—

—

—

—

—

—

—

Ammonia -0.17 -0.09 na 0.07

—

—

—

—

—

—

pH -0.05 0.04 na -0.03 0.15

—

—

—

—

—

Sulfate 0.05 0.02 na 0.38 0.31 0.09

—

—

—

—

Total dissolved solids

0.20 -0.08 na 0.28 0.10 -0.17 0.29

—

—

—

Dissolved organic carbon

0.10 -0.14 na -0.22 0.10 -0.02 -0.11 0.11

—

—

Temperature 0.18 0.15 na 0.21 -0.01 0.05 0.09 0.19 -0.04

—

Groundwater level -0.20 -0.05 na 0.02 0.14 -0.12 0.13 0.06 -0.01 0.05
Appendix 4 273

Table 4–32. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–31, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.12 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.10 -0.03 na — — — — — — —Ammonia -0.20 -0.23 na 0.25 — — — — — —

pH -0.17 -0.07 na 0.01 0.01 — — — — —

Sulfate -0.24 -0.08 na 0.05 0.11 0.25 — — — —

Total dissolved solids

-0.01 -0.21 na 0.37 0.41 0.01 0.07 — — —

Dissolved organic carbon

-0.10 -0.21 na 0.04 0.07 -0.17 0.05 0.00 — —

Temperature 0.00 0.06 na -0.01 -0.03 0.00 -0.10 0.12 -0.08 —

Groundwater level -0.50 -0.10 na -0.11 0.16 0.00 0.02 0.00 0.10 0.11
274 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–33. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QC–37, Calumet System, Tunnel and Reservoir Plan System, Cook County, Illinois, 2003–2010.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.03

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.09 0.42 na

—

—

—

—

—

—

—

Ammonia -0.05 0.23 na 0.37

—

—

—

—

—

—

pH 0.03 0.06 na -0.17 -0.20

—

—

—

—

—

Sulfate -0.16 -0.05 na 0.15 -0.25 0.11

—

—

—

—

Total dissolved solids

0.12 0.35 na 0.83 0.23 -0.12 0.26

—

—

—

Dissolved organic carbon

0.09 -0.06 na -0.17 0.14 -0.31 -0.44 -0.18

—

—

Temperature -0.31 0.08 na -0.24 -0.13 0.00 -0.06 -0.21 0.18

—

Groundwater level 0.30 -0.45 na -0.53 -0.09 -0.22 -0.44 -0.51 0.48 0.15
Appendix 4 275 27

Table 4–34. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QD–21, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.06 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.11 0.10 na — — — — — — —

Ammonia 0.23 -0.01 na 0.14 — — — — — —pH -0.08 0.06 na 0.01 -0.13 — — — — —

Sulfate 0.13 -0.04 na 0.45 -0.05 -0.01 — — — —Total dissolved solids

0.21 0.07 na 0.43 0.13 -0.04 0.33 — — —

Dissolved organic carbon

-0.11 0.32 na 0.01 0.00 0.26 -0.11 -0.10 — —

Temperature -0.22 0.01 na 0.16 0.00 -0.05 0.15 0.32 -0.04 —

Groundwater level 0.00 -0.14 na -0.03 -0.15 -0.14 0.05 0.01 -0.25 0.05
276 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–35. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–22, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.24

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.21 0.28 na

—

—

—

—

—

—

—

Ammonia 0.23 -0.17 na -0.07

—

—

—

—

—

—

pH -0.03 0.06 na -0.01 -0.01

—

—

—

—

—

Sulfate 0.06 0.20 na 0.24 -0.02 0.07

—

—

—

—

Total dissolved solids

0.02 0.19 na 0.18 -0.06 -0.10 0.13

—

—

—

Dissolved organic carbon

-0.24 0.35 na 0.36 -0.13 0.09 0.21 0.08

—

—

Temperature 0.04 -0.03 na 0.04 0.07 -0.19 0.03 0.42 -0.07

—

Groundwater level -0.01 -0.13 na -0.05 -0.12 -0.08 -0.03 0.02 -0.22 0.13
Appendix 4 277 27

Table 4–36. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–23, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.25 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.20 0.12 na — — — — — — —

Ammonia 0.11 -0.11 na -0.06 — — — — — —pH -0.15 0.00 na -0.01 -0.07 — — — — —

Sulfate 0.01 0.02 na 0.16 -0.01 -0.01 — — — —

Total dissolved solids

0.18 0.04 na 0.19 0.05 -0.08 0.12 — — —

Dissolved organic carbon

-0.39 0.24 na 0.14 -0.10 0.15 -0.04 -0.10 — —

Temperature 0.13 0.03 na 0.05 0.10 -0.15 0.02 0.37 -0.14 —

Groundwater level 0.32 -0.09 na 0.14 -0.09 -0.07 0.21 0.22 -0.23 0.12
278 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–37. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–24, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.08

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.33 0.18 na

—

—

—

—

—

—

—

Ammonia 0.22 -0.13 na -0.01

—

—

—

—

—

—

pH -0.13 -0.17 na -0.13 -0.14

—

—

—

—

—

Sulfate 0.33 0.21 na 0.57 -0.03 -0.02

—

—

—

—

Total dissolved solids

0.40 0.16 na 0.56 0.17 -0.12 0.52

—

—

—

Dissolved organic carbon

0.08 0.25 na 0.39 -0.15 0.05 0.26 0.22

—

—

Temperature -0.07 -0.07 na -0.13 0.08 -0.07 -0.10 0.05 -0.17

—

Groundwater level -0.09 -0.18 na -0.18 0.20 -0.15 -0.22 -0.12 -0.22 0.22
Appendix 4 279 27

Table 4–38. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–25, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.02 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.25 0.15 na — — — — — — —

Ammonia 0.23 -0.07 na 0.01 — — — — — —pH -0.05 -0.12 na -0.02 -0.01 — — — — —

Sulfate -0.22 0.09 na 0.43 -0.02 -0.02 — — — —

Total dissolved solids

0.32 0.08 na 0.17 0.20 -0.04 0.12 — — —

Dissolved organic carbon

-0.47 0.13 na 0.41 -0.19 0.01 0.28 -0.09 — —

Temperature 0.17 0.13 na -0.02 0.12 -0.10 0.08 0.40 -0.13 —

Groundwater level 0.25 0.04 na 0.00 0.27 -0.06 -0.01 0.18 -0.18 0.21
280 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–39. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–26, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.31

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.38 0.44 na

—

—

—

—

—

—

—

Ammonia -0.05 -0.02 na -0.08

—

—

—

—

—

—

pH 0.11 0.08 na 0.20 0.06

—

—

—

—

—

Sulfate 0.51 0.37 na 0.47 -0.17 0.15

—

—

—

—

Total dissolved solids

0.65 0.37 na 0.49 -0.07 0.08 0.52

—

—

—

Dissolved organic carbon

0.41 0.32 na 0.39 -0.03 0.01 0.34 0.40

—

—

Temperature -0.19 0.06 na -0.04 -0.05 -0.14 0.00 -0.11 -0.18

—

Groundwater level 0.26 0.36 na 0.32 -0.13 0.06 0.31 0.31 0.10 0.14
Appendix 4 281 28

Table 4–40. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–27, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.01 — — — — — — — — —

Fecal coliform -0.02 0.02 — — — — — — — —

Hardness 0.14 0.13 -0.14 — — — — — — —

Ammonia 0.42 -0.13 0.04 0.11 — — — — — —pH -0.14 -0.06 0.14 0.08 -0.08 — — — — —

Sulfate -0.14 0.21 -0.04 0.08 -0.41 0.14 — — — —

Total dissolved solids

0.55 0.18 0.01 0.34 0.26 -0.07 0.07 — — —

Dissolved organic carbon

-0.14 0.27 0.04 0.25 -0.23 0.15 0.40 0.16 — —

Temperature 0.14 0.13 -0.03 -0.01 0.03 -0.22 -0.06 0.11 -0.08 —Groundwater level -0.07 0.33 0.03 0.16 -0.29 0.03 0.32 0.09 0.27 0.04
282 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–41. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–28, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.01

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.15 0.06 na

—

—

—

—

—

—

—

Ammonia -0.24 0.11 na 0.02

—

—

—

—

—

—

pH -0.08 -0.06 na 0.01 0.11

—

—

—

—

—

Sulfate -0.08 0.15 na 0.29 -0.07 -0.02

—

—

—

—

Total dissolved solids

0.47 0.07 na 0.16 -0.21 -0.05 -0.01

—

—

—

Dissolved organic carbon

-0.38 0.04 na 0.00 0.42 0.19 -0.09 -0.29

—

—

Temperature 0.10 0.06 na -0.01 -0.20 -0.22 -0.04 0.32 -0.20

—

Groundwater level 0.31 -0.09 na 0.01 -0.27 -0.01 -0.04 0.31 -0.32 0.33
Appendix 4 283 28

Table 4–42. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–29, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.34 — — — — — — — — —

Fecal coliform -0.11 0.14 — — — — — — — —

Hardness -0.27 0.28 0.23 — — — — — — —

Ammonia 0.47 -0.20 0.01 -0.15 — — — — — —pH -0.22 -0.15 -0.08 -0.08 -0.21 — — — — —

Sulfate -0.37 0.26 0.16 0.42 -0.29 0.02 — — — —

Total dissolved solids

-0.03 0.06 0.13 0.15 0.02 -0.10 0.09 — — —

Dissolved organic carbon

-0.24 0.15 0.19 0.32 -0.05 0.01 0.27 0.12 — —

Temperature 0.14 -0.06 0.07 -0.07 0.08 -0.17 -0.17 0.35 -0.05 —Groundwater level -0.04 0.04 -0.19 -0.03 -0.16 -0.04 -0.02 -0.04 -0.03 0.10
284 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–43. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–30, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.10

—

—

—

—

—

—

—

—

—

Fecal coliform -0.08 -0.02

—

—

—

—

—

—

—

—

Hardness -0.11 0.31 0.02

—

—

—

—

—

—

—

Ammonia 0.32 -0.19 -0.04 -0.14

—

—

—

—

—

—

pH 0.02 -0.13 0.03 0.08 -0.03

—

—

—

—

—

Sulfate -0.11 0.28 0.10 0.68 -0.15 0.10

—

—

—

—

Total dissolved solids

0.07 0.28 0.11 0.53 -0.07 -0.04 0.51

—

—

—

Dissolved organic carbon

-0.19 0.32 0.26 0.32 -0.12 -0.08 0.28 0.20

—

—

Temperature -0.05 0.04 0.10 -0.11 0.02 -0.09 -0.12 0.08 -0.08

—

Groundwater level 0.00 -0.09 0.10 0.02 0.02 -0.04 0.09 0.10 -0.07 -0.04
Appendix 4 285 28

Table 4–44. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–31, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.12 — — — — — — — — —

Fecal coliform -0.12 0.06 — — — — — — — —

Hardness -0.23 0.46 0.02 — — — — — — —

Ammonia 0.07 0.06 0.02 0.06 — — — — — —

pH -0.16 -0.01 -0.02 0.13 -0.03 — — — — —

Sulfate -0.23 0.34 -0.05 0.61 0.05 0.08 — — — —

Total dissolved solids

0.13 0.29 -0.03 0.49 0.02 0.06 0.37 — — —

Dissolved organic carbon

-0.24 0.41 0.13 0.46 0.07 0.12 0.34 0.21 — —

Temperature 0.07 -0.06 -0.01 0.00 0.00 -0.04 -0.01 0.06 -0.02 —

Groundwater level -0.27 0.14 -0.04 0.15 -0.14 0.09 0.15 -0.03 0.23 0.06
286 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–45. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–32, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.13

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.38 0.11 na

—

—

—

—

—

—

—

Ammonia 0.24 0.02 na 0.31

—

—

—

—

—

—

pH 0.02 0.14 na -0.09 0.06

—

—

—

—

—

Sulfate 0.32 0.08 na 0.30 0.14 0.06

—

—

—

—

Total dissolved solids

0.58 0.03 na 0.34 0.25 0.01 0.20

—

—

—

Dissolved organic carbon

-0.26 0.11 na -0.06 -0.08 -0.15 -0.15 -0.22

—

—

Temperature -0.02 -0.01 na -0.09 -0.07 0.00 -0.02 0.00 0.01

—

Groundwater level -0.17 0.11 na -0.02 0.04 -0.16 0.03 -0.13 0.42 0.01
Appendix 4 287 28

Table 4–46. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–33, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.10 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.11 -0.13 na — — — — — — —

Ammonia -0.07 -0.03 na 0.14 — — — — — —

pH 0.05 0.11 na -0.15 -0.06 — — — — —

Sulfate 0.11 0.14 na -0.05 -0.07 0.15 — — — —

Total dissolved solids

0.15 0.09 na 0.06 -0.04 0.08 0.08 — — —

Dissolved organic carbon

0.29 0.22 na -0.12 -0.17 0.11 0.16 0.33 — —

Temperature -0.06 0.10 na 0.07 -0.03 0.03 -0.05 -0.02 -0.02 —

Groundwater level 0.30 0.09 na -0.07 -0.09 -0.05 0.10 0.20 0.43 -0.14
288 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–47. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–34, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.18

—

—

—

—

—

—

—

—

—

Fecal coliform 0.05 -0.01

—

—

—

—

—

—

—

—

Hardness -0.54 0.40 -0.14

—

—

—

—

—

—

—

Ammonia 0.32 -0.24 0.18 -0.45

—

—

—

—

—

—

pH -0.23 -0.10 -0.09 0.11 -0.19

—

—

—

—

—

Sulfate -0.47 0.35 -0.05 0.61 -0.48 0.06

—

—

—

—

Total dissolved solids

-0.33 0.22 -0.21 0.47 -0.25 0.14 0.35

—

—

—

Dissolved organic carbon

-0.17 0.32 0.03 0.36 -0.12 0.04 0.23 0.26

—

—

Temperature -0.12 0.06 -0.03 0.04 0.01 -0.14 0.01 0.22 -0.08

—

Groundwater level 0.21 -0.18 0.04 -0.18 0.32 -0.22 -0.30 0.02 0.01 0.09
Appendix 4 289 28

Table 4–48. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–35, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.15 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.31 0.35 na — — — — — — —

Ammonia 0.03 -0.22 na -0.21 — — — — — —pH 0.01 -0.25 na 0.04 -0.02 — — — — —Sulfate -0.21 0.39 na 0.60 -0.20 0.02 — — — —

Total dissolved solids

-0.16 0.24 na 0.47 -0.12 0.11 0.43 — — —

Dissolved organic carbon

-0.21 0.10 na 0.21 -0.13 0.07 0.21 0.20 — —

Temperature 0.09 0.05 na -0.01 0.05 -0.13 -0.02 0.18 0.12 —

Groundwater level -0.14 -0.10 na 0.02 0.00 -0.01 -0.06 0.07 -0.07 0.11
290 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–49. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–36, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.09

—

—

—

—

—

—

—

—

—

Fecal coliform -0.01 0.05

—

—

—

—

—

—

—

—

Hardness 0.10 0.43 0.08

—

—

—

—

—

—

—

Ammonia 0.04 -0.26 -0.03 -0.21

—

—

—

—

—

—

pH 0.02 -0.20 -0.12 -0.11 -0.04

—

—

—

—

—

Sulfate 0.12 0.36 0.05 0.60 -0.24 -0.03

—

—

—

—

Total dissolved solids

0.08 0.32 0.15 0.50 -0.06 -0.12 0.45

—

—

—

Dissolved organic carbon

0.04 0.26 0.09 0.33 -0.12 0.05 0.34 0.30

—

—

Temperature -0.11 0.05 0.07 0.01 0.03 -0.03 -0.03 0.25 -0.04

—

Groundwater level -0.41 -0.11 -0.02 -0.11 -0.02 -0.04 -0.11 -0.07 0.06 0.00
Appendix 4 291 29

Table 4–50. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–37, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.18 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.44 -0.27 na — — — — — — —

Ammonia -0.16 -0.27 na 0.42 — — — — — —

pH -0.03 0.00 na -0.13 -0.17 — — — — —

Sulfate -0.36 -0.19 na 0.49 0.34 -0.19 — — — —

Total dissolved solids

0.03 -0.04 na 0.19 0.18 -0.03 0.22 — — —

Dissolved organic carbon

0.36 0.23 na -0.35 -0.06 0.08 -0.42 -0.14 — —

Temperature -0.13 0.10 na 0.05 0.07 0.01 0.09 0.17 -0.10 —

Groundwater level 0.18 0.19 na -0.22 -0.04 0.03 -0.19 -0.13 0.36 -0.05
292 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–51. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–38, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.40

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.19 0.06 na

—

—

—

—

—

—

—

Ammonia 0.01 0.09 na 0.21

—

—

—

—

—

—

pH -0.08 0.11 na -0.02 -0.01

—

—

—

—

—

Sulfate 0.45 0.36 na 0.08 0.01 -0.13

—

—

—

—

Total dissolved solids

0.67 0.27 na 0.19 -0.04 -0.10 0.35

—

—

—

Dissolved organic carbon

0.49 0.44 na 0.06 0.03 -0.08 0.43 0.37

—

—

Temperature -0.06 -0.09 na 0.01 0.04 0.11 -0.03 -0.05 -0.07

—

Groundwater level 0.47 0.51 na -0.03 -0.05 -0.03 0.41 0.32 0.55 -0.08
Appendix 4 293 29

Table 4–52. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–39, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.07 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.15 0.15 na — — — — — — —

Ammonia -0.10 -0.09 na -0.01 — — — — — —

pH -0.23 0.24 na 0.02 0.03 — — — — —

Sulfate 0.03 0.34 na 0.11 0.08 0.05 — — — —

Total dissolved solids

0.00 0.09 na 0.29 -0.08 -0.09 0.01 — — —

Dissolved organic carbon

-0.09 0.51 na 0.13 0.12 0.22 0.50 -0.04 — —

Temperature -0.12 0.04 na 0.17 0.10 0.03 0.03 0.23 0.05 —

Groundwater level -0.05 0.31 na 0.06 0.15 0.08 0.32 0.00 0.57 0.12
294 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–53. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–40, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.31

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.04 -0.10 na

—

—

—

—

—

—

—

Ammonia 0.01 -0.05 na 0.18

—

—

—

—

—

—

pH -0.27 0.11 na 0.13 0.00

—

—

—

—

—

Sulfate -0.33 0.23 na -0.05 -0.20 -0.04

—

—

—

—

Total dissolved solids

-0.23 0.22 na 0.04 -0.18 -0.05 0.32

—

—

—

Dissolved organic carbon

-0.38 0.42 na 0.03 0.05 0.06 0.20 0.28

—

—

Temperature 0.04 -0.23 na -0.01 0.21 0.04 -0.12 -0.24 -0.14

—

Groundwater level -0.29 0.32 na -0.04 0.08 0.10 0.19 0.27 0.54 -0.04
Appendix 4 295 29

Table 4–54. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–41, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.14 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.10 0.42 na — — — — — — —

Ammonia 0.03 -0.03 na -0.12 — — — — — —pH -0.07 0.16 na 0.11 -0.11 — — — — —

Sulfate -0.10 0.36 na 0.37 -0.20 0.10 — — — —

Total dissolved solids

-0.02 0.31 na 0.36 0.02 -0.05 0.33 — — —

Dissolved organic carbon

-0.13 0.37 na 0.43 0.10 0.11 0.39 0.32 — —

Temperature 0.09 -0.17 na -0.21 -0.03 -0.18 -0.32 -0.14 -0.32 —Groundwater level 0.19 0.32 na 0.27 -0.04 -0.02 0.31 0.27 0.40 -0.21
296 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–55. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–42, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.33

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.30 0.40 na

—

—

—

—

—

—

—

Ammonia 0.03 -0.20 na -0.18

—

—

—

—

—

—

pH -0.10 0.25 na 0.29 -0.15

—

—

—

—

—

Sulfate 0.04 0.09 na 0.14 -0.17 0.04

—

—

—

—

Total dissolved solids

-0.12 0.24 na 0.32 -0.36 0.13 0.18

—

—

—

Dissolved organic carbon

-0.34 0.35 na 0.44 -0.06 0.04 0.19 0.23

—

—

Temperature 0.06 -0.16 na -0.09 0.07 0.06 -0.05 0.03 -0.09

—

Groundwater level 0.14 -0.28 na -0.37 0.02 -0.12 -0.10 -0.21 -0.35 0.13
Appendix 4 297 29

Table 4–56. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–43, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.27 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.19 0.16 na — — — — — — —

Ammonia 0.54 -0.34 na -0.12 — — — — — —pH -0.21 0.22 na 0.15 -0.33 — — — — —

Sulfate -0.38 0.36 na 0.38 -0.28 0.10 — — — —

Total dissolved solids

-0.06 0.05 na 0.49 -0.01 0.04 0.29 — — —

Dissolved organic carbon

-0.36 0.30 na 0.35 -0.27 0.06 0.45 0.24 — —

Temperature 0.05 -0.11 na 0.13 0.06 -0.12 -0.03 0.23 -0.08 —Groundwater level 0.30 -0.35 na -0.35 0.32 -0.13 -0.39 -0.18 -0.52 0.03
298 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–57. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–44, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.29

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.18 0.04 na

—

—

—

—

—

—

—

Ammonia 0.25 -0.14 na -0.06

—

—

—

—

—

—

pH -0.06 -0.06 na -0.02 -0.14

—

—

—

—

—

Sulfate -0.20 0.08 na 0.45 -0.06 0.09

—

—

—

—

Total dissolved solids

-0.07 0.08 na 0.35 0.03 -0.15 0.37

—

—

—

Dissolved organic carbon

-0.33 0.29 na -0.10 -0.13 0.22 0.09 -0.11

—

—

Temperature -0.04 -0.01 na -0.04 0.08 -0.04 -0.10 -0.01 0.03

—

Groundwater level 0.22 -0.31 na 0.00 0.08 -0.25 -0.08 0.00 -0.43 0.03
Appendix 4 299 29

Table 4–58. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–45, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.12 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.04 -0.14 na — — — — — — —Ammonia 0.07 -0.23 na 0.10 — — — — — —pH -0.31 0.19 na 0.07 -0.20 — — — — —

Sulfate 0.03 0.15 na -0.07 -0.11 0.07 — — — —

Total dissolved solids

0.04 0.09 na 0.19 0.02 0.04 0.10 — — —

Dissolved organic carbon

-0.27 0.25 na -0.15 -0.20 0.16 0.37 0.13 — —

Temperature -0.04 -0.12 na 0.22 0.07 0.02 0.00 0.27 -0.25 —

Groundwater level 0.15 -0.28 na 0.23 0.19 -0.12 -0.38 0.00 -0.44 -0.01
300 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–59. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–46, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.08

—

—

—

—

—

—

—

—

—

Fecal coliform 0.06 0.00

—

—

—

—

—

—

—

—

Hardness -0.13 0.31 -0.08

—

—

—

—

—

—

—

Ammonia 0.04 0.07 -0.09 0.08

—

—

—

—

—

—

pH -0.12 0.15 0.11 0.26 -0.13

—

—

—

—

—

Sulfate 0.10 0.30 -0.21 0.47 0.21 0.11

—

—

—

—

Total dissolved solids

0.47 0.13 -0.04 0.01 0.06 -0.08 0.25

—

—

—

Dissolved organic carbon

-0.01 0.28 -0.02 0.29 -0.03 0.32 0.19 0.20

—

—

Temperature -0.15 0.01 0.13 -0.01 0.07 -0.02 -0.11 -0.02 -0.02

—

Groundwater level 0.05 -0.07 -0.13 -0.27 0.12 -0.27 -0.12 0.09 -0.23 0.09
Appendix 4 301 30

Table 4–60. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–47, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.22 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.26 -0.04 na — — — — — — —

Ammonia 0.06 0.00 na 0.01 — — — — — —

pH -0.01 0.08 na 0.00 -0.08 — — — — —

Sulfate 0.12 -0.07 na -0.09 0.27 -0.25 — — — —Total dissolved solids

0.17 0.13 na -0.06 0.16 -0.17 0.05 — — —

Dissolved organic carbon

0.32 0.40 na 0.07 0.12 0.01 0.08 0.27 — —

Temperature 0.02 0.00 na -0.19 -0.02 0.08 -0.10 0.01 -0.12 —

Groundwater level -0.23 -0.36 na 0.03 0.21 0.00 0.06 -0.04 -0.46 0.09
302 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–61. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–48, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.30

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.16 0.30 na

—

—

—

—

—

—

—

Ammonia 0.26 0.36 na -0.01

—

—

—

—

—

—

pH -0.34 -0.10 na -0.19 -0.09

—

—

—

—

—

Sulfate 0.02 0.00 na 0.21 -0.03 -0.03

—

—

—

—

Total dissolved solids

0.20 0.26 na 0.58 -0.05 -0.23 0.16

—

—

—

Dissolved organic carbon

0.48 0.46 na 0.21 0.39 -0.14 0.06 0.14

—

—

Temperature -0.01 0.01 na 0.00 0.08 0.05 -0.15 0.07 -0.04

—

Groundwater level 0.42 0.28 na 0.00 0.40 -0.05 -0.03 -0.08 0.57 0.11
Appendix 4 303 30

Table 4–62. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–49, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.22 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.24 0.27 na — — — — — — —

Ammonia 0.34 0.32 na 0.31 — — — — — —

pH -0.02 -0.01 na 0.04 0.09 — — — — —

Sulfate 0.11 0.33 na 0.12 0.12 -0.12 — — — —

Total dissolved solids

0.11 0.30 na 0.67 0.17 0.01 0.08 — — —

Dissolved organic carbon

0.22 0.48 na 0.32 0.43 -0.04 0.39 0.28 — —

Temperature -0.07 -0.21 na 0.03 -0.27 -0.07 -0.09 0.13 -0.18 —

Groundwater level 0.15 0.55 na 0.21 0.39 -0.03 0.42 0.23 0.57 -0.12
304 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–63. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–50, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.03

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.19 -0.09 na

—

—

—

—

—

—

—

Ammonia -0.02 -0.02 na 0.27

—

—

—

—

—

—

pH -0.07 0.08 na 0.06 0.07

—

—

—

—

—

Sulfate -0.17 -0.19 na 0.30 0.22 0.03

—

—

—

—

Total dissolved solids

0.15 0.15 na 0.01 0.02 0.12 0.11

—

—

—

Dissolved organic carbon

0.21 0.38 na -0.17 -0.13 0.16 -0.31 0.12

—

—

Temperature -0.07 -0.16 na 0.00 0.00 0.16 0.08 0.01 -0.15

—

Groundwater level 0.18 0.38 na -0.23 -0.11 0.07 -0.31 0.10 0.61 -0.13
Appendix 4 305 30

Table 4–64. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–51, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.20 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.03 0.03 na — — — — — — —

Ammonia -0.14 0.14 na 0.11 — — — — — —

pH -0.16 0.06 na 0.05 0.00 — — — — —

Sulfate -0.05 -0.05 na 0.18 0.15 0.06 — — — —

Total dissolved solids

-0.07 0.15 na 0.13 0.08 0.08 0.18 — — —

Dissolved organic carbon

-0.29 0.25 na 0.17 0.10 0.09 -0.01 0.39 — —

Temperature -0.14 -0.03 na -0.03 0.08 0.09 -0.08 -0.01 -0.02 —

Groundwater level -0.20 0.34 na 0.13 0.03 0.00 0.04 0.35 0.58 -0.16
306 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–65. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–52, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.08

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.19 -0.29 na

—

—

—

—

—

—

—

Ammonia -0.07 0.05 na 0.17

—

—

—

—

—

—

pH 0.14 0.00 na -0.24 0.00

—

—

—

—

—

Sulfate -0.19 -0.06 na 0.26 0.22 -0.05

—

—

—

—

Total dissolved solids

-0.02 0.19 na -0.21 -0.13 0.06 -0.04

—

—

—

Dissolved organic carbon

-0.13 0.26 na -0.22 -0.18 0.05 -0.08 0.29

—

—

Temperature 0.08 -0.12 na -0.07 0.00 0.05 0.04 0.21 -0.11

—

Groundwater level -0.06 0.14 na -0.06 -0.14 -0.14 -0.11 0.18 0.41 -0.10
Appendix 4 307 30

Table 4–66. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–53, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.06 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.31 -0.19 na — — — — — — —Ammonia 0.10 0.25 na -0.12 — — — — — —

pH -0.10 0.09 na -0.15 0.08 — — — — —

Sulfate 0.31 -0.28 na 0.46 -0.04 -0.04 — — — —Total dissolved solids

-0.14 0.16 na -0.22 0.03 0.12 -0.22 — — —

Dissolved organic carbon

-0.10 0.41 na -0.22 0.20 0.00 -0.43 0.20 — —

Temperature -0.06 -0.18 na -0.01 -0.10 -0.03 0.15 0.05 -0.19 —

Groundwater level -0.18 0.29 na -0.38 0.07 -0.06 -0.52 0.13 0.55 -0.18
308 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–67. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–54, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.11

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.12 -0.04 na

—

—

—

—

—

—

—

Ammonia 0.16 0.01 na 0.14

—

—

—

—

—

—

pH -0.05 0.04 na -0.11 -0.07

—

—

—

—

—

Sulfate 0.19 -0.08 na 0.41 0.18 -0.21

—

—

—

—

Total dissolved solids

0.12 0.00 na 0.21 0.14 -0.20 0.25

—

—

—

Dissolved organic carbon

-0.28 0.32 na 0.06 -0.15 -0.04 -0.13 0.13

—

—

Temperature 0.04 -0.15 na -0.02 0.00 0.00 0.04 -0.05 -0.23

—

Groundwater level 0.07 0.08 na 0.15 -0.02 -0.10 0.20 0.24 0.23 -0.16
Appendix 4 309 30

Table 4–68. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–55, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.09 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.25 0.05 na — — — — — — —

Ammonia 0.22 0.00 na 0.38 — — — — — —

pH -0.26 -0.08 na -0.32 -0.10 — — — — —

Sulfate 0.50 -0.09 na 0.33 0.25 -0.24 — — — —Total dissolved solids

0.34 0.06 na 0.38 0.25 -0.22 0.46 — — —

Dissolved organic carbon

-0.28 0.33 na 0.11 0.04 -0.06 -0.21 -0.01 — —

Temperature 0.08 -0.10 na -0.05 0.04 -0.05 0.09 0.07 -0.29 —Groundwater level -0.17 0.08 na -0.22 -0.17 0.23 -0.27 -0.10 0.13 -0.07
310 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–69. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–56, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.02

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.15 0.09 na

—

—

—

—

—

—

—

Ammonia -0.04 -0.05 na 0.12

—

—

—

—

—

—

pH -0.10 0.13 na 0.10 -0.03

—

—

—

—

—

Sulfate -0.10 0.22 na 0.22 -0.20 0.33

—

—

—

—

Total dissolved solids

0.07 0.37 na -0.05 -0.04 -0.08 0.10

—

—

—

Dissolved organic carbon

-0.08 0.45 na 0.15 0.01 -0.02 0.12 0.39

—

—

Temperature -0.01 -0.11 na 0.12 -0.03 0.04 0.13 -0.03 -0.16

—

Groundwater level 0.16 0.37 na 0.14 0.10 0.00 0.19 0.35 0.44 -0.10
Appendix 4 311 31

Table 4–70. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–57, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.32 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.40 0.52 na — — — — — — —

Ammonia -0.31 0.36 na 0.49 — — — — — —

pH -0.05 0.08 na 0.23 0.18 — — — — —

Sulfate -0.33 0.49 na 0.52 0.39 0.13 — — — —

Total dissolved solids

-0.27 0.52 na 0.51 0.33 0.03 0.40 — — —

Dissolved organic carbon

-0.27 0.46 na 0.36 0.27 -0.18 0.36 0.40 — —

Temperature -0.04 -0.17 na -0.02 0.01 0.11 -0.13 -0.18 -0.25 —

Groundwater level -0.21 0.51 na 0.53 0.40 0.02 0.52 0.46 0.46 -0.12
312 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–71. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–58, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.05

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.20 0.28 na

—

—

—

—

—

—

—

Ammonia -0.05 0.04 na -0.03

—

—

—

—

—

—

pH -0.11 0.12 na 0.14 0.00

—

—

—

—

—

Sulfate -0.10 0.35 na 0.40 -0.15 0.28

—

—

—

—

Total dissolved solids

0.18 0.17 na 0.03 0.01 -0.01 0.13

—

—

—

Dissolved organic carbon

-0.09 0.47 na 0.41 -0.06 0.13 0.48 0.29

—

—

Temperature -0.10 -0.14 na 0.04 0.08 0.00 -0.08 -0.11 -0.07

—

Groundwater level -0.11 0.43 na 0.43 -0.08 0.19 0.65 0.18 0.56 -0.06
Appendix 4 313 31

Table 4–72. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–59, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.06 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.21 0.28 na — — — — — — —

Ammonia -0.05 0.04 na -0.03 — — — — — —

pH -0.12 0.12 na 0.14 0.00 — — — — —

Sulfate -0.15 0.36 na 0.45 -0.14 0.28 — — — —

Total dissolved solids

0.18 0.17 na 0.03 0.01 -0.02 0.14 — — —

Dissolved organic carbon

-0.10 0.47 na 0.41 -0.06 0.13 0.50 0.29 — —

Temperature -0.10 -0.14 na 0.04 0.08 0.00 -0.02 -0.11 -0.07 —

Groundwater level -0.11 0.43 na 0.43 -0.08 0.19 0.65 0.18 0.56 -0.06
314 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–73. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring QD–60, Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1996–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.01

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.16 0.22 na

—

—

—

—

—

—

—

Ammonia -0.03 0.19 na 0.07

—

—

—

—

—

—

pH -0.09 0.08 na 0.18 -0.08

—

—

—

—

—

Sulfate 0.23 0.11 na -0.08 0.16 -0.08

—

—

—

—

Total dissolved solids

0.11 0.12 na 0.03 -0.02 0.04 -0.06

—

—

—

Dissolved organic carbon

-0.12 0.26 na 0.39 0.04 0.05 0.01 0.05

—

—

Temperature -0.01 0.05 na 0.07 0.04 -0.03 -0.03 0.09 -0.03

—

Groundwater level -0.02 -0.21 na -0.16 0.06 -0.07 -0.11 -0.07 -0.23 -0.04
Appendix 4 315

Table 4–74. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–53, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.01 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.13 0.32 na — — — — — — —

Ammonia 0.04 0.46 na 0.22 — — — — — —

pH -0.12 0.27 na 0.15 0.15 — — — — —

Sulfate -0.03 0.11 na 0.16 0.07 0.00 — — — —

Total dissolved solids

0.11 0.16 na 0.15 0.07 0.00 0.05 — — —

Dissolved organic carbon

-0.07 0.25 na 0.25 0.23 0.29 0.13 0.27 — —

Temperature 0.08 0.04 na 0.20 0.07 0.01 0.00 0.27 0.15 —

Groundwater level 0.19 -0.09 na -0.18 0.05 -0.15 -0.16 -0.09 -0.28 -0.11
316 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–75. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–56, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2009.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.21

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.44 -0.10 na

—

—

—

—

—

—

—

Ammonia 0.11 0.07 na 0.28

—

—

—

—

—

—

pH -0.28 0.06 na -0.36 -0.31

—

—

—

—

—

Sulfate -0.07 -0.06 na 0.07 -0.11 -0.17

—

—

—

—

Total dissolved solids

0.32 -0.09 na 0.14 0.19 -0.29 -0.03

—

—

—

Dissolved organic carbon

-0.25 0.15 na -0.27 -0.11 0.25 -0.16 -0.05

—

—

Temperature -0.26 0.24 na -0.20 0.04 -0.03 -0.12 0.13 0.12

—

Groundwater level -0.31 0.26 na -0.28 0.00 0.10 0.00 -0.09 0.27 0.15
Appendix 4 317

Table 4–76. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–58, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2008.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.22 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.37 0.26 na — — — — — — —

Ammonia 0.02 0.07 na 0.00 — — — — — —

pH -0.20 0.06 na 0.28 -0.03 — — — — —

Sulfate -0.24 0.10 na 0.34 0.00 0.13 — — — —

Total dissolved solids

-0.10 0.14 na 0.36 -0.05 -0.05 0.33 — — —

Dissolved organic carbon

-0.41 0.15 na 0.30 0.11 0.32 0.23 0.10 — —

Temperature -0.06 -0.06 na 0.07 -0.34 -0.14 0.06 0.25 -0.18 —

Groundwater level 0.20 -0.39 na -0.20 -0.06 -0.08 -0.23 -0.12 -0.22 0.07
318 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–77. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–61, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.42

—

—

—

—

—

—

—

—

—

Fecal coliform 0.07 -0.08

—

—

—

—

—

—

—

—

Hardness 0.70 0.52 0.09

—

—

—

—

—

—

—

Ammonia 0.25 0.09 0.18 0.24

—

—

—

—

—

—

pH 0.16 0.28 -0.17 0.22 -0.08

—

—

—

—

—

Sulfate 0.62 0.40 0.18 0.57 0.15 0.16

—

—

—

—

Total dissolved solids

0.75 0.51 0.01 0.64 0.23 0.13 0.56

—

—

—

Dissolved organic carbon

0.38 0.51 -0.01 0.45 0.28 0.16 0.40 0.44

—

—

Temperature -0.09 0.05 0.14 -0.02 -0.01 0.16 0.05 0.00 0.03

—

Groundwater level 0.25 0.18 0.37 0.28 0.31 0.03 0.30 0.25 0.25 0.20
Appendix 4 319

Table 4–78. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–62, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.18 — — — — — — — — —

Fecal coliform 0.02 -0.03 — — — — — — — —Hardness 0.32 0.06 0.25 — — — — — — —

Ammonia 0.38 0.09 0.14 0.45 — — — — — —

pH 0.00 -0.05 -0.17 -0.20 -0.22 — — — — —Sulfate -0.07 0.00 0.46 0.26 0.08 -0.12 — — — —

Total dissolved solids

0.33 0.11 0.14 0.45 0.36 -0.13 0.14 — — —

Dissolved organic carbon

-0.02 0.16 -0.12 -0.14 -0.22 0.26 -0.07 -0.09 — —

Temperature -0.20 -0.08 0.22 0.07 -0.03 0.00 0.23 0.03 -0.06 —

Groundwater level 0.10 -0.10 0.31 0.07 0.02 -0.01 0.29 0.01 -0.07 0.08
320 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–79. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–63, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.09

—

—

—

—

—

—

—

—

—

Fecal coliform 0.01 -0.11

—

—

—

—

—

—

—

—

Hardness 0.13 0.00 -0.13

—

—

—

—

—

—

—

Ammonia 0.08 -0.03 -0.02 0.56

—

—

—

—

—

—

pH -0.02 0.10 -0.08 -0.20 -0.21

—

—

—

—

—

Sulfate 0.13 0.02 -0.13 0.66 0.54 -0.23

—

—

—

—

Total dissolved solids

0.20 -0.06 -0.01 0.71 0.59 -0.24 0.66

—

—

—

Dissolved organic carbon

0.03 0.05 -0.07 -0.18 -0.35 0.03 -0.31 -0.21

—

—

Temperature -0.05 0.01 0.11 0.07 0.07 -0.04 0.07 0.15 -0.04

—

Groundwater level 0.04 -0.11 0.15 -0.28 -0.31 0.08 -0.30 -0.31 0.13 -0.07
Appendix 4 321

Table 4–80. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–64, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.17 — — — — — — — — —

Fecal coliform 0.06 -0.09 — — — — — — — —Hardness 0.40 0.38 -0.08 — — — — — — —

Ammonia 0.45 0.27 -0.05 0.54 — — — — — —

pH 0.08 -0.10 0.04 0.07 -0.04 — — — — —Sulfate 0.12 0.33 -0.12 0.43 0.18 0.03 — — — —

Total dissolved solids

0.15 0.16 -0.07 0.17 0.15 -0.07 0.17 — — —

Dissolved organic carbon

0.06 0.38 -0.11 0.41 0.37 -0.03 0.31 0.17 — —

Temperature 0.00 -0.08 0.09 -0.02 0.05 -0.04 -0.09 0.04 0.02 —Groundwater level 0.16 0.02 -0.02 0.16 0.08 0.05 0.17 0.01 0.03 0.03
322 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–81. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–65, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2010.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.13

—

—

—

—

—

—

—

—

—

Fecal coliform -0.15 0.13

—

—

—

—

—

—

—

—

Hardness 0.31 0.20 -0.14

—

—

—

—

—

—

—

Ammonia 0.62 0.15 -0.05 0.29

—

—

—

—

—

—

pH -0.10 -0.13 0.07 -0.07 -0.10

—

—

—

—

—

Sulfate -0.18 -0.15 -0.12 0.05 -0.30 0.08

—

—

—

—

Total dissolved solids

0.67 0.13 -0.14 0.43 0.51 -0.05 -0.12

—

—

—

Dissolved organic carbon

0.24 0.28 0.03 0.51 0.39 -0.03 0.00 0.28

—

—

Temperature 0.09 -0.02 0.05 -0.07 0.00 -0.05 -0.05 0.09 -0.11

—

Groundwater level 0.00 -0.12 0.08 -0.08 -0.06 -0.13 0.00 0.00 -0.12 0.28
Appendix 4 323

Table 4–82. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–67, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.20 — — — — — — — — —

Fecal coliform 0.19 -0.26 — — — — — — — —Hardness -0.25 0.49 -0.37 — — — — — — —

Ammonia 0.34 -0.41 0.41 -0.64 — — — — — —pH 0.06 -0.11 0.16 -0.19 0.06 — — — — —Sulfate -0.36 0.45 -0.36 0.74 -0.73 -0.07 — — — —

Total dissolved solids

-0.13 0.47 -0.38 0.75 -0.59 -0.13 0.66 — — —

Dissolved organic carbon

-0.30 0.33 -0.26 0.50 -0.38 -0.27 0.47 0.46 — —

Temperature 0.14 0.14 -0.04 0.04 -0.02 -0.04 -0.03 0.09 0.02 —

Groundwater level 0.02 -0.06 0.05 -0.07 0.13 -0.07 -0.11 -0.08 0.12 0.00
324 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–83. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–68, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.11

—

—

—

—

—

—

—

—

—

Fecal coliform -0.08 -0.05

—

—

—

—

—

—

—

—

Hardness 0.49 0.05 0.00

—

—

—

—

—

—

—

Ammonia 0.15 0.00 -0.21 0.06

—

—

—

—

—

—

pH -0.36 0.00 0.03 -0.34 0.02

—

—

—

—

—

Sulfate -0.26 -0.05 -0.04 -0.26 0.00 0.20

—

—

—

—

Total dissolved solids

0.49 -0.06 0.02 0.42 0.12 -0.27 -0.24

—

—

—

Dissolved organic carbon

-0.46 0.05 -0.13 -0.35 0.03 0.39 0.29 -0.25

—

—

Temperature 0.12 -0.01 0.13 0.17 -0.16 -0.09 -0.13 0.26 -0.17

—

Groundwater level -0.04 0.09 0.38 -0.02 0.00 0.13 0.02 0.09 0.02 0.11
Appendix 4 325

Table 4–84. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–69, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.02 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.01 0.30 na — — — — — — —

Ammonia -0.03 0.03 na 0.01 — — — — — —

pH -0.04 0.04 na 0.11 0.11 — — — — —

Sulfate 0.05 0.42 na 0.47 0.16 0.16 — — — —

Total dissolved solids

0.15 0.19 na 0.36 0.03 0.04 0.41 — — —

Dissolved organic carbon

0.04 0.26 na 0.37 0.08 0.10 0.45 0.30 — —

Temperature 0.01 -0.09 na -0.05 0.04 0.00 -0.09 -0.07 -0.16 —Groundwater level 0.07 -0.42 na -0.41 -0.14 -0.08 -0.51 -0.26 -0.28 0.13
326 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–85. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–70, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.05

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.08 0.16 na

—

—

—

—

—

—

—

Ammonia -0.01 -0.08 na 0.01

—

—

—

—

—

—

pH -0.13 0.30 na 0.17 -0.05

—

—

—

—

—

Sulfate 0.16 0.39 na 0.25 0.04 0.25

—

—

—

—

Total dissolved solids

0.11 0.30 na 0.17 -0.06 0.30 0.34

—

—

—

Dissolved organic carbon

0.08 0.28 na 0.49 0.10 0.26 0.49 0.27

—

—

Temperature -0.11 -0.13 na -0.15 -0.01 -0.18 -0.17 -0.04 -0.16

—

Groundwater level -0.20 -0.51 na -0.37 0.06 -0.24 -0.62 -0.36 -0.60 0.26
Appendix 4 327

Table 4–86. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–71, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.02 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.08 0.16 na — — — — — — —

Ammonia -0.10 0.00 na 0.15 — — — — — —

pH 0.06 0.26 na 0.14 0.06 — — — — —

Sulfate 0.10 0.20 na 0.33 -0.04 0.13 — — — —

Total dissolved solids

0.02 0.02 na 0.22 0.10 0.14 0.24 — — —

Dissolved organic carbon

0.07 0.16 na 0.38 0.18 0.09 0.35 0.19 — —

Temperature -0.06 -0.04 na 0.04 0.18 -0.02 -0.07 0.20 -0.07 —

Groundwater level -0.09 -0.15 na -0.20 -0.09 -0.15 -0.19 -0.05 -0.43 0.09
328 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–87. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–72, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.00

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.07 0.15 na

—

—

—

—

—

—

—

Ammonia -0.07 -0.09 na -0.19

—

—

—

—

—

—

pH 0.15 0.16 na 0.17 -0.35

—

—

—

—

—

Sulfate 0.16 0.12 na 0.34 -0.23 0.41

—

—

—

—

Total dissolved solids

0.02 0.09 na 0.06 0.07 0.04 0.12

—

—

—

Dissolved organic carbon

0.13 0.29 na 0.36 0.01 0.23 0.36 0.12

—

—

Temperature -0.04 -0.04 na -0.02 0.02 0.06 -0.03 0.32 -0.04

—

Groundwater level -0.03 -0.21 na -0.38 0.29 -0.34 -0.53 -0.10 -0.41 0.01
Appendix 4 329

Table 4–88. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–73, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.26 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.16 -0.03 na — — — — — — —Ammonia 0.14 0.27 na 0.17 — — — — — —

pH 0.14 0.08 na -0.11 0.02 — — — — —

Sulfate 0.31 0.35 na -0.06 0.18 0.23 — — — —

Total dissolved solids

0.28 0.29 na -0.08 0.29 0.06 0.39 — — —

Dissolved organic carbon

0.45 0.35 na 0.02 0.13 0.07 0.36 0.24 — —

Temperature -0.19 -0.19 na -0.09 -0.04 -0.05 -0.18 -0.10 -0.08 —

Groundwater level 0.26 0.30 na -0.04 0.16 0.02 0.21 0.26 0.42 -0.09
330 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–89. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–74, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.21

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.07 -0.08 na

—

—

—

—

—

—

—

Ammonia 0.06 0.10 na 0.17

—

—

—

—

—

—

pH -0.05 0.09 na -0.01 -0.15

—

—

—

—

—

Sulfate 0.11 0.31 na 0.05 0.22 0.08

—

—

—

—

Total dissolved solids

0.07 0.12 na 0.01 0.09 -0.15 0.21

—

—

—

Dissolved organic carbon

0.08 0.18 na 0.12 0.35 0.06 0.40 0.23

—

—

Temperature 0.03 -0.08 na 0.07 -0.11 0.06 0.00 0.21 0.01

—

Groundwater level -0.11 -0.30 na 0.08 -0.13 -0.11 -0.27 -0.13 -0.24 0.09
Appendix 4 331

Table 4–90. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–75, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.08 — — — — — — — — —

Fecal coliform 0.01 -0.07 — — — — — — — —Hardness -0.17 -0.13 -0.04 — — — — — — —

Ammonia 0.10 0.06 0.00 -0.02 — — — — — —

pH -0.02 0.00 -0.05 -0.05 -0.08 — — — — —Sulfate 0.05 0.18 -0.18 0.01 -0.07 0.13 — — — —

Total dissolved solids

0.07 -0.07 -0.16 -0.03 0.18 0.13 0.19 — — —

Dissolved organic carbon

-0.04 0.22 -0.14 0.07 0.04 0.08 0.43 0.29 — —

Temperature 0.08 -0.01 0.21 -0.21 -0.04 0.06 0.00 0.17 0.10 —Groundwater level 0.10 0.24 -0.11 -0.07 0.04 0.04 0.34 0.15 0.35 -0.01
332 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–91. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–76, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.03

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.11 -0.03 na

—

—

—

—

—

—

—

Ammonia -0.04 -0.08 na -0.39

—

—

—

—

—

—

pH 0.05 0.22 na -0.40 0.13

—

—

—

—

—

Sulfate -0.11 -0.04 na 0.43 -0.43 -0.14

—

—

—

—

Total dissolved solids

-0.08 0.14 na 0.17 -0.27 0.04 0.29

—

—

—

Dissolved organic carbon

-0.16 0.24 na -0.11 0.08 0.14 -0.08 0.09

—

—

Temperature 0.08 0.02 na 0.08 -0.17 -0.10 -0.01 0.01 -0.13

—

Groundwater level -0.09 0.20 na -0.15 0.15 0.12 -0.03 -0.05 0.43 -0.14
Appendix 4 333

Table 4–92. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–77, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.23 — — — — — — — — —

Fecal coliform -0.22 -0.17 — — — — — — — —

Hardness 0.09 0.16 0.01 — — — — — — —

Ammonia 0.28 0.07 -0.10 -0.02 — — — — — —pH 0.09 0.32 -0.10 -0.03 0.08 — — — — —Sulfate 0.26 0.40 -0.06 0.28 0.06 0.11 — — — —

Total dissolved solids

0.24 0.07 -0.18 -0.03 0.19 -0.04 0.15 — — —

Dissolved organic carbon

0.13 0.34 -0.03 0.04 0.15 0.19 0.31 0.18 — —

Temperature -0.26 -0.18 0.17 -0.11 -0.28 -0.10 -0.28 0.05 -0.23 —

Groundwater level 0.35 0.37 -0.21 0.15 0.22 0.21 0.40 0.21 0.19 -0.28
334 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–93. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–78, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.24

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness 0.01 0.20 na

—

—

—

—

—

—

—

Ammonia 0.13 0.28 na 0.20

—

—

—

—

—

—

pH -0.15 0.09 na 0.08 0.06

—

—

—

—

—

Sulfate 0.33 0.45 na 0.23 0.30 -0.13

—

—

—

—

Total dissolved solids

0.24 0.22 na 0.12 0.15 -0.01 0.44

—

—

—

Dissolved organic carbon

0.18 0.42 na 0.22 0.43 0.05 0.56 0.41

—

—

Temperature -0.17 -0.02 na -0.13 -0.11 0.18 -0.16 0.04 -0.12

—

Groundwater level 0.31 0.34 na 0.17 0.27 -0.01 0.48 0.53 0.46 -0.01
Appendix 4 335

Table 4–94. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–79, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.50 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.12 0.00 na — — — — — — —

Ammonia 0.12 0.11 na -0.01 — — — — — —

pH -0.13 0.05 na 0.05 0.09 — — — — —

Sulfate 0.31 0.42 na 0.18 0.00 -0.07 — — — —

Total dissolved solids

0.38 0.39 na -0.08 0.26 0.04 0.36 — — —

Dissolved organic carbon

0.27 0.32 na -0.02 0.22 -0.04 0.41 0.44 — —

Temperature -0.13 -0.07 na 0.07 -0.08 0.01 -0.08 -0.10 -0.14 —

Groundwater level 0.44 0.46 na -0.10 0.07 -0.09 0.46 0.42 0.54 -0.12
336 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–95. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–80, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.15

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.17 -0.04 na

—

—

—

—

—

—

—

Ammonia 0.06 0.17 na -0.01

—

—

—

—

—

—

pH -0.11 0.16 na 0.14 -0.03

—

—

—

—

—

Sulfate 0.18 0.33 na 0.19 0.15 0.18

—

—

—

—

Total dissolved solids

0.03 0.17 na -0.05 0.12 0.07 0.26

—

—

—

Dissolved organic carbon

0.06 0.39 na 0.17 0.31 0.06 0.37 0.37

—

—

Temperature -0.18 0.03 na -0.01 -0.04 -0.07 -0.17 0.04 -0.05

—

Groundwater level 0.28 0.23 na -0.05 0.19 -0.15 0.20 0.22 0.35 0.00
Appendix 4 337

Table 4–96. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–81, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.08 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness 0.22 -0.26 na — — — — — — —Ammonia 0.18 -0.09 na 0.06 — — — — — —pH -0.21 0.08 na -0.02 -0.17 — — — — —

Sulfate -0.19 0.20 na -0.40 -0.11 0.12 — — — —

Total dissolved solids

0.10 -0.02 na 0.04 0.20 -0.06 0.00 — — —

Dissolved organic carbon

-0.15 0.10 na -0.26 0.25 0.07 0.39 0.11 — —

Temperature 0.10 0.02 na 0.04 -0.05 0.09 -0.06 0.08 -0.26 —

Groundwater level -0.17 0.35 na -0.27 -0.12 0.03 0.18 -0.05 0.00 0.01
338 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–97. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well QM–82, Mainstream System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1995–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.24

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.27 -0.26 na

—

—

—

—

—

—

—

Ammonia -0.01 -0.07 na 0.03

—

—

—

—

—

—

pH 0.08 0.18 na -0.03 0.09

—

—

—

—

—

Sulfate 0.24 0.28 na -0.34 0.03 0.11

—

—

—

—

Total dissolved solids

0.22 0.17 na -0.50 0.02 0.11 0.28

—

—

—

Dissolved organic carbon

0.25 0.17 na -0.55 0.02 0.02 0.26 0.39

—

—

Temperature -0.07 0.08 na 0.18 -0.02 0.03 -0.12 0.03 -0.13

—

Groundwater level 0.30 0.24 na -0.62 -0.02 0.06 0.38 0.45 0.56 -0.18
Appendix 4 339

Table 4–98. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–1, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.13 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.19 0.23 na — — — — — — —

Ammonia -0.04 0.06 na -0.01 — — — — — —

pH 0.03 0.07 na 0.11 -0.07 — — — — —

Sulfate 0.00 -0.11 na -0.08 -0.08 -0.05 — — — —Total dissolved solids

-0.04 -0.03 na -0.10 -0.07 -0.06 0.09 — — —

Dissolved organic carbon

-0.11 0.34 na 0.20 0.13 0.17 -0.10 -0.08 — —

Temperature -0.12 -0.11 na 0.02 -0.08 -0.15 -0.03 0.01 -0.08 —

Groundwater level -0.01 0.21 na 0.05 0.20 0.09 -0.13 -0.04 0.38 -0.12
340 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–99. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–2, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2010.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.26

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.26 0.09 na

—

—

—

—

—

—

—

Ammonia 0.14 0.03 na -0.12

—

—

—

—

—

—

pH -0.30 0.24 na 0.04 -0.03

—

—

—

—

—

Sulfate -0.04 -0.09 na 0.10 -0.23 -0.03

—

—

—

—

Total dissolved solids

0.29 -0.15 na 0.00 -0.10 -0.11 0.06

—

—

—

Dissolved organic carbon

-0.51 0.29 na 0.17 0.04 0.27 -0.10 -0.24

—

—

Temperature 0.08 -0.11 na 0.03 0.12 -0.12 -0.03 0.16 -0.07

—

Groundwater level -0.12 0.12 na -0.16 0.17 0.11 -0.17 -0.30 0.10 -0.02
Appendix 4 341

Table 4–100. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–3, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.03 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.01 0.00 na — — — — — — —

Ammonia 0.16 -0.25 na 0.04 — — — — — —pH -0.18 0.20 na 0.15 -0.16 — — — — —

Sulfate -0.02 -0.14 na -0.05 0.15 0.03 — — — —

Total dissolved solids

0.18 -0.07 na -0.08 0.10 -0.15 0.01 — — —

Dissolved organic carbon

-0.11 0.30 na -0.01 -0.16 0.20 -0.23 -0.10 — —

Temperature -0.06 -0.02 na 0.01 0.05 -0.01 0.06 0.06 -0.18 —

Groundwater level 0.11 -0.06 na -0.01 0.16 -0.06 0.11 0.14 -0.12 0.30
342 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–101. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–4, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.24

—

—

—

—

—

—

—

—

—

Fecal coliform na na

—

—

—

—

—

—

—

—

Hardness -0.21 0.29 na

—

—

—

—

—

—

—

Ammonia -0.03 0.03 na 0.04

—

—

—

—

—

—

pH 0.02 0.10 na 0.08 -0.04

—

—

—

—

—

Sulfate -0.22 0.06 na 0.15 0.08 0.03

—

—

—

—

Total dissolved solids

-0.07 0.08 na 0.09 0.08 -0.03 0.03

—

—

—

Dissolved organic carbon

-0.45 0.34 na 0.37 0.12 0.04 0.19 0.17

—

—

Temperature 0.10 -0.02 na -0.03 -0.05 0.03 0.01 0.12 -0.05

—

Groundwater level -0.35 0.19 na 0.21 0.04 0.07 0.13 0.11 0.39 0.06
Appendix 4 343

Table 4–102. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–5, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2010.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.16 — — — — — — — — —

Fecal coliform 0.14 0.17 — — — — — — — —

Hardness -0.25 0.25 -0.02 — — — — — — —

Ammonia -0.18 -0.07 0.01 0.12 — — — — — —

pH 0.02 0.04 -0.03 -0.05 -0.01 — — — — —Sulfate -0.24 0.19 -0.07 0.66 0.09 0.03 — — — —

Total dissolved solids

0.29 0.38 0.13 0.39 -0.04 -0.04 0.33 — — —

Dissolved organic carbon

-0.35 0.03 -0.14 0.29 0.12 0.01 0.24 -0.03 — —

Temperature -0.02 0.04 0.23 0.04 0.08 -0.03 -0.02 -0.03 0.06 —

Groundwater level -0.30 0.06 -0.11 0.31 0.04 -0.10 0.19 -0.01 0.38 0.07
344 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–103. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–6, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1994–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.00

—

—

—

—

—

—

—

—

—

Fecal coliform -0.14 -0.21

—

—

—

—

—

—

—

—

Hardness 0.02 0.46 -0.34

—

—

—

—

—

—

—

Ammonia 0.20 0.01 0.01 0.07

—

—

—

—

—

—

pH -0.05 0.23 -0.11 0.20 -0.12

—

—

—

—

—

Sulfate 0.05 0.23 -0.28 0.41 0.14 0.03

—

—

—

—

Total dissolved solids

0.10 0.31 -0.23 0.43 0.14 0.11 0.38

—

—

—

Dissolved organic carbon

-0.14 0.23 -0.09 0.32 0.01 0.17 0.13 0.22

—

—

Temperature -0.10 -0.05 0.22 0.02 0.10 -0.06 0.08 0.10 -0.06

—

Groundwater level -0.05 -0.39 0.28 -0.48 0.01 -0.13 -0.39 -0.43 -0.34 -0.05
Appendix 4 345

Table 4–104. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–7, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1998–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

-0.19 — — — — — — — — —

Fecal coliform 0.16 0.10 — — — — — — — —

Hardness -0.24 0.28 -0.10 — — — — — — —

Ammonia 0.16 -0.17 0.20 -0.27 — — — — — —pH -0.12 0.22 -0.06 0.28 -0.32 — — — — —

Sulfate -0.22 0.29 -0.07 0.48 -0.31 0.30 — — — —

Total dissolved solids

-0.20 0.28 0.05 0.43 -0.19 0.26 0.37 — — —

Dissolved organic carbon

-0.20 0.31 0.08 0.41 -0.02 0.10 0.31 0.32 — —

Temperature -0.10 0.09 0.13 -0.02 -0.03 -0.04 0.06 0.10 0.07 —

Groundwater level 0.19 0.07 -0.02 0.08 0.02 0.02 -0.06 0.02 -0.05 0.08
346 Hydrogeology and groundwater quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 Table 4–105. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–8, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1997–2013.

[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.00

—

—

—

—

—

—

—

—

—

Fecal coliform -0.06 -0.12

—

—

—

—

—

—

—

—

Hardness -0.16 0.29 -0.18

—

—

—

—

—

—

—

Ammonia 0.01 0.20 -0.07 0.15

—

—

—

—

—

—

pH 0.08 -0.06 0.07 -0.18 0.07

—

—

—

—

—

Sulfate -0.16 0.17 -0.22 0.55 -0.04 -0.18

—

—

—

—

Total dissolved solids

0.03 0.29 -0.24 0.61 0.23 -0.09 0.45

—

—

—

Dissolved organic carbon

-0.01 0.26 -0.13 0.22 0.23 -0.09 0.19 0.22

—

—

Temperature -0.04 0.09 0.24 0.03 -0.03 0.13 -0.06 0.01 0.08

—

Groundwater level 0.04 0.22 -0.33 0.41 0.25 -0.10 0.27 0.34 0.40 -0.03
Appendix 4 347

Table 4–106. Kendall’s tau-b correlation coefficient for analytes and physical properties, monitoring well MW–9, Upper Des Plaines System, Tunnel and Reservoir Plan System, Cook County, Illinois, 1997–2013.[Bold denotes tau-b greater than 0.25 or less than -0.25; na, not analyzed; —, no data]

Chloride Electrical conductivity Fecal coliform Hardness Ammonia pH Sulfate Total dissolved solids Dissolved organic carbon Temperature 

Electrical conductivity

0.00 — — — — — — — — —

Fecal coliform na na — — — — — — — —

Hardness -0.07 0.34 na — — — — — — —

Ammonia -0.22 0.06 na 0.18 — — — — — —

pH -0.03 0.05 na 0.13 0.06 — — — — —

Sulfate -0.18 0.05 na 0.26 0.10 0.05 — — — —

Total dissolved solids

0.10 0.24 na 0.33 0.18 0.03 0.14 — — —

Dissolved organic carbon

0.07 0.27 na 0.33 0.07 0.07 0.07 0.22 — —

Temperature -0.02 0.03 na -0.04 0.09 0.03 -0.07 0.06 0.05 —

Groundwater level -0.01 -0.11 na -0.11 0.03 0.10 -0.04 0.07 0.35 0.16


Kay—Hydrogeology and Groundwater Quality, Tunnel and Reservoir Plan System, Cook County, Ill., 1995–2013 —Scientific Investigations Report 2015–5186, ver. 1.1

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155186