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ILLINOIS INTEGRATED WATER QUALITY REPORT
AND SECTION 303(d) LIST - 2010
Clean Water Act Sections 303(d), 305(b) and 314
Water Resource Assessment Information
and Listing of Impaired Waters
Volume II: Groundwater
December 2011
Illinois Environmental Protection Agency
Bureau of Water
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TABLE OF CONTENTS
EXECUTIVE SUMMARY ................................................................................................. 2
PART A. INTRODUCTION ............................................................................................ 4
A-1. Reporting Requirements ................................................................................................ 4
A-2. Major Changes from Previous Reports ........................................................................ 5
PART B. BACKGROUND ................................................................................................ 7
B-1. Total Waters .................................................................................................................... 8
B-2. Groundwater Protection Programs............................................................................... 8
Illinois Groundwater Quality Standards ..............................................................................8
Groundwater Protection .......................................................................................................8
B-3. Cost/Benefit Assessment ..................................................................................................8
Cost of Pollution Control and Groundwater/Source Water Protection Activities ...............8
Groundwater Improvements ................................................................................................9
PART C. GROUNDWATER MONITORING AND ASSESSMENT ...............10
C-1. Resource-Quality Monitoring Programs .....................................................................10
C-2. Assessment Methodology ..............................................................................................21
C-3. Potential Causes and Potential Sources of Impairment .............................................24
C-4. Monitoring Results ........................................................................................................27
C-5. Use Support Evaluation ................................................................................................40
C-6. Potential Causes of Impairment ...................................................................................42
REFERENCES ......................................................................................................................44
Volume II Appendices:
APPENDIX A – Source Water Data for 2010 Groundwater Use Assessments
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EXECUTIVE SUMMARY
This 2010 Integrated Report continues the reporting format first adopted in the 2006 reporting
cycle. However, for the 2010 cycle the Integrated Report is being divided into two volumes:
Volume I covering surface water and Volume II covering groundwater. Prior to 2006,
assessment information was reported separately in the Illinois Water Quality [Section 305(b)]
Report and Illinois Section 303(d) List. The Integrated Report format is based on federal
guidance for meeting the requirements of Sections 305(b), 303(d) and 314 of the Clean Water
Act (CWA).
The basic purpose of this report (Volume II) is to provide information to the federal government
and the citizens of Illinois on the condition of groundwater in the state. This information is
provided in detail in Section C and in Appendix A.
Groundwater quality and quantity are linked. Analyses of groundwater data collected from 1990
to the present continue to show an overall statistically significant increasing trend of community
water supply (CWS) wells1 with volatile organic compound detections per year. In addition
concentrations of chlorides in the CWS probabilistic network wells utilizing sand and gravel and
shallow bedrock (i.e., Silurian Dolomite) aquifers in Northeastern Illinois (N.E. IL) show a 35
percent increase in concentration compared to the state wide ambient value. These trends
represent an overall increasing trend of groundwater degradation. At the same time, future
groundwater shortages are predicted in N.E. IL (Meyer, Roadcap, et. al., 2009 CMAP, 2010)
A pilot project to assess the Mahomet Aquifer as part of a national effort to design a National
Ground-Water Monitoring Network (NGWMN) has been initiated by a team of state and federal
agencies in Illinois and Indiana. Thus, this report includes a special focus on the quality of
groundwater from CWS probabilistic network wells in the Mahomet-Teays bedrock valley. For
further background on this project see the Advisory Committee on Water Information (ACWI)
Subcommittee on Ground Water (SOGW) web page at: http://acwi.gov/sogw/index.html
1 "Community water supply" means a public water supply which serves or is intended to serve at least 15 service connections used by residents or
regularly serves at least 25 residents.
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The results show that of the 354 CWS probabilistic network wells:
• 28 (8 percent (%) were determined to be Not Supporting (“poor”) due to the elevated
levels of nitrate and VOCs that include trichloroethylene and tetrachloroethylene. All
of these wells draw their water from shallow sand & gravel aquifers, except for one,
which is using a deep well from the Cambrian/Ordovician bedrock aquifer in the
northern part of the state);
• 90 (25%) were determined to be Not Supporting (“fair”) due to statistically significant
increases chloride (Cl-) above background, detections of VOCs, nitrate (total
nitrogen) greater than 3 mg/l, but have not exceeded the health-based Groundwater
Quality Standards (GWQS); and
• 236 (67 %) were determined to be Fully Supporting (“good”), which show no
detections of any of the above analytes.
Additionally, trend analyses for VOC’s also shows that there is a statistically significant
increase in the number of CWS wells with VOC detections, despite the fact that the number of
CWS analyzed for VOC’s over the same time period declined, and the detection limit remained
constant.
Illinois groundwater resources are being degraded. Degradation occurs based on the potential or
actual diminishment of the beneficial use of the resource. When contaminant levels are detected
(caused or allowed) or predicted (threat) to be above concentrations that cannot be removed via
ordinary treatment techniques, applied by the owner of a private drinking water system well,
potential or actual diminishment occurs. At a minimum, private well treatment techniques
consist of chlorination of the raw source water prior to drinking.
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PART A: INTRODUCTION
A-1. Reporting Requirements
The 2010 Integrated Report is based on guidance from United States Environmental Protection
Agency (USEPA) which is intended to satisfy the requirements of sections 305(b), 303(d) and
314 of the Federal Water Pollution Control Act Amendments of 1972 (PL 92-500) and
subsequent amendments (hereafter, collectively called the “Clean Water Act” or “CWA”) in a
single combined report. For this reporting cycle the Integrated Report is being divided into two
volumes: Volume I covering surface water and Volume II covering groundwater.
Accordingly, Section 102 of the CWA requires:
SEC. 102 [33 U.S.C. 1252] Comprehensive Programs for Water Pollution Control:
(a) The Administrator shall, after careful investigation, and in cooperation with other
Federal agencies, State water pollution control agencies, interstate agencies, and the
municipalities and industries involved, prepare or develop comprehensive programs
for preventing, reducing, or eliminating the pollution of the navigable waters and
ground waters and improving the sanitary condition of surface and underground
waters. In the development of such comprehensive programs due regard shall be
given to the improvements which are necessary to conserve such waters for the
protection and propagation of fish and aquatic life and wildlife, recreational purposes,
and the withdrawal of such waters for public water supply, agricultural, industrial,
and other purposes. For the purpose of this section, the Administrator is authorized to
make joint investigations with any such agencies of the condition of any waters in any
State or States, and of the discharges of any sewage, industrial wastes, or substance
which may adversely affect such waters. (Emphasis added)
Further, Section 104(a)(5) of the CWA [33 U.S.C. 1254]) requires:
5) in cooperation with the States, and their political subdivisions, and other Federal
agencies establish, equip, and maintain a water quality surveillance system for the
purpose of monitoring the quality of the navigable waters and ground waters and the
contiguous zone and the oceans and the Administrator shall, to the extent practicable,
conduct such surveillance by utilizing the resources of the National Aeronautics and
Space Administration, the National Oceanic and Atmospheric Administration, the
United States Geological Survey, and the Coast Guard, and shall report on such
quality in the report required under subsection (a) of section 516; and [104(a)(5)
amended by PL 102-285] (Emphasis added)
Section 516 of the CWA requires U.S. EPA to provide a report to Congress on the quality of
water, including groundwater. States are required to report biennially on the quality of water
with an emphasis on navigable waters pursuant to Section 305(b) of the CWA, and compared to
the objectives established in Section 304(a)(1) of the CWA. Section 304(a)(1)(A) of the CWA
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requires that water quality criteria developed must also consider pollutants that originate from
groundwater:
“The Administrator, after consultation with appropriate Federal and State agencies and
other interested persons, shall develop and publish, within one year after the date of
enactment of this title (and from time to time thereafter revise) criteria for water quality
accurately reflecting the latest scientific knowledge (A) on the kind and extent of all
identifiable effects on health and welfare including, but not limited to, plankton, fish,
shellfish, wildlife, plant life, shore lines, beaches, esthetics, and recreation which may be
expected from the presence of pollutants in any body of water, including ground
water…”
Thus, for these reasons, and the hydrologic connection between groundwater and surface water,
that the Illinois EPA has established an integrated monitoring strategy, and includes a volume in
our Section 305(b) Report on ambient groundwater monitoring results.
Illinois reports the resource quality of its waters in terms of the degree to which the beneficial
uses2 of those waters are attained and the reasons (causes and sources) beneficial uses may not be
attained. In addition, states are required to provide an assessment of the water quality of all
publicly owned lakes, including the status and trends of such water quality as specified in
Section 314(a)(1) of the CWA.
Section 303(d) of the CWA and corresponding regulations in Title 40 of the Code of Federal
Regulations, require states to
• Identify water quality-limited waters where effluent limitations and other pollution
control requirements are not sufficient to implement any water quality standard,
• Identify pollutants causing or expected to cause water quality standards violations in
those waters,
• Establish a priority ranking for the development of Total Maximum Daily Load3 (TMDL)
calculations including waters targeted for TMDL development within the next two years,
and,
• Establish TMDLs for all pollutants preventing or expected to prevent the attainment of
water quality standards.
This list of water quality limited waters is often called the 303(d) List.
To the extent possible, this 2010 Illinois Integrated Report is based on USEPA’s Guidance for
2006 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d), 305(b) and
2 Beneficial uses, also called designated uses, are discussed in more detail in Section B-2 Groundwater Protection
Programs, Illinois Groundwater Quality Standards.
3 Total Maximum Daily Load calculations determine the amount of a pollutant a water body can assimilate without
exceeding the state’s water quality standards or impairing the water body’s designated uses.
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314 of the Clean Water Act issued July 29, 2005 and additional guidance contained in USEPA
memorandums from the Office of Wetlands, Oceans and Watersheds regarding Clean Water Act
Sections 303(d), 305(b), and 314 Integrated Reporting and Listing Decisions.
A-2. Major Changes from the 2008 Report Methodology and Format
As stated above, the 2010 Integrated Report was divided into two volumes: Volume I covering
surface water and Volume II covering groundwater. This was done to accommodate the
increased size of the integrated report, which has been greatly expanded to include more water
quality information. This two volume format also improves the organizational structure of the
report and makes it easier for the reader to find the specific information that may be of concern.
In all other aspects Illinois EPA is using the same methodology and format in 2010 as in 2008
with no significant changes.
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PART B: BACKGROUND INFORMATION
B-1. Total Waters
There are approximately 5,534 groundwater dependent public water supplies in the state, of
which 1,022 are community water supplies. The Illinois Department of Public Health estimates
approximately 400,000 residences of the state are served by private wells. To assess the
groundwater resources of the state, the Illinois EPA utilizes three primary aquifer classes that
were developed by O’Hearn and Schock (1984). These three principal aquifers are sand and
gravel, shallow bedrock and deep bedrock aquifers. O’Hearn and Schock defined a principal
aquifer as having a potential yield of 100,000 gallons per day per square mile and having an area
of at least 50 miles. Approximately 58 percent (32,000 square miles) of the state is underlain by
principal aquifers. Of these, about 33 percent (18,500 square miles) are major shallow
groundwater sources. The following are numbers of community water supply (CWS) wells that
withdraw from these aquifers: Out of 3,517 active CWS wells, 46 % (1,619) utilize sand &
gravel aquifer; 27 % (934) utilize a shallow bedrock aquifer; 24 % (825) utilize a deep bedrock
aquifer, and 3% (139) are undetermined.
Table B-1. Illinois Atlas.
Topic Value Scale Source
State Population in year 2009 12,910,409 US Census Bureau
State Surface Area (sq. mi.) 57,918 US Census Bureau
Active CWS Facilities 1,755 N/A SDWIS
Surface Facilities 96 N/A SDWIS
Groundwater Facilities 1,022 N/A SDWIS
Mixed Facilities 7 N/A SDWIS
Purchase Facilities 630 N/A SDWIS
Active CWS Wells 3,517 N/A SDWIS
Confined Wells 2,323 N/A SDWIS
Unconfined Wells 1,194 N/A SDWIS
SDWIS = Safe Drinking Water Information System
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B-2. Groundwater Protection Programs
Illinois Groundwater Quality Standards
Since the inception of the Illinois Environmental Protection Act (Act) (415 ILCS 5) in 1970, it
has been the policy of the State of Illinois to restore, protect, and enhance the groundwater of the
State as a natural and public resource. To this end, Illinois has established the Illinois
Groundwater Standards (35.Ill.Adm.Code 620). For a detailed explanation and listing of Illinois’
Groundwater Standards see the Illinois Pollution Control Board’s webpage at:
http://www.ipcb.state.il.us. Further, Section 12(a) of the Act [415 ILCS 5/12(a)] also applies to
groundwater.
Groundwater Management Zone
Within any class of groundwater, a groundwater management zone may be established as a three
dimensional region containing groundwater being managed to mitigate impairment caused by the
release of contaminants from a site: That is subject to a corrective action process approved by the
Agency; or for which the owner or operator undertakes an adequate corrective action in a timely
and appropriate manner.
Groundwater Protection
For a full description of Illinois’ groundwater protection programs see the Illinois Groundwater
Protection Act Biennial Report at: http://www.epa.state.il.us/water/groundwater/groundwater-protection/
index.html or contact the Groundwater Section at 217/ 785-4787 to obtain a hard
copy.
B-3. Cost/Benefit Assessment
Section 305(b) requires the state to report on the economic and social costs and benefits
necessary to achieve Clean Water Act objectives. Information on costs associated with water
quality improvements is complex, and not readily available for developing a complete
cost/benefit assessment. The individual program costs of pollution control activities in Illinois,
the general surface water quality improvements made, and the average groundwater protection
program costs follow.
Cost of Pollution Control and Groundwater/Source Water Protection Activities
The Illinois EPA Bureau of Water distributed a total of $121.0 million in loans during 2008 for
construction of municipal wastewater treatment facilities. Other Water Pollution Control
program and Groundwater/Source Water Protection costs for Bureau of Water activities
conducted in 2008 are summarized in Table B-6.
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Table B-3. Water Pollution Control Program Costs for the Illinois Environmental
Protection Agency’s Bureau of Water, 2008.
Activity Total
Monitoring $5,277,300
Planning $1,517,400
Point Source Control Programs $14,011,000
Nonpoint Source Control Programs $9,469,000
Groundwater/Source-Water Protection $2,102,400
Total $32,377,100
Groundwater Improvements
Protecting and managing groundwater are critical. Groundwater is an important natural resource
that not only provides Illinois’ citizens water for drinking and household uses, but also supports
industrial, agricultural, and commercial activities throughout the state.
Unfortunately, industrial, agricultural and commercial activities can often produce volatile
organic compounds. They are usually produced in large volumes and are associated with
products such as plastics, adhesives, paints, gasoline, fumigants, refrigerants, and dry-cleaning
fluids. They can reach groundwater through many sources and routes, including leaking storage
tanks, landfills, infiltration of urban runoff and wastewater, septic systems, and injection through
wells. Volatile organic compounds are an important group of environmental contaminants to
monitor and manage in groundwater because of their widespread and long-term use, as well as
their ability to persist and migrate in groundwater.
For a detailed discussion of groundwater protection improvements, please refer to the recently
published Interagency Coordinating Committee on Groundwater Biennial Comprehensive Status
and Self-Assessment Report on Illinois Groundwater Protection Program at:
http://www.epa.state.il.us/water/groundwater/groundwater-protection/index.html.
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PART C: GROUNDWATER MONITORING AND ASSESSMENT
C-1. Resource-Quality Monitoring Program
Hydrologic Background
To assess the groundwater resources of the state, the Illinois EPA utilizes three primary aquifer
classes (O’Hearn and Schock, 1984). These three “principal aquifers” are sand and gravel,
shallow bedrock and deep bedrock aquifers, as illustrated in figures C-1 thru C-3. A principal
aquifer is defined as having a potential yield of 100,000 gallons per day per square mile and
having an area of at least 50 miles.
Figure C-1. Principal Sand and Gravel Aquifers in Illinois
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Figure C-2. Principal Shallow Bedrock Aquifers in Illinois
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Figure C-3. Principal Deep Bedrock Aquifers in Illinois
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Water resource availability can be expressed in a number of ways. In the groundwater field, the
term “potential yield” or “safe yield” is often used (Wehrmann, 2003). Potential aquifer yield is
the maximum amount of groundwater that can be continuously withdrawn from a reasonable
number of wells and well fields without creating critically low water levels or exceeding
recharge (Wehrmann, 2003). Statewide estimates of groundwater availability, based on aquifer
potential yield estimates, were developed in the late 1960s (Illinois Technical Advisory
Committee on Water Resources, ITACWR, 1967). The ITACWR report presented maps of the
estimated potential yields, expressed as recharge rates in gallons per day per square mile
(gpd/mi2), of the principal sand and gravel and shallow bedrock aquifers of Illinois. For
reference, a recharge rate of 100,000 gpd/mi2
is equal to 2.1 inches/year. (Wehrmann, 2003).
The 1967 ITACWR report stated the following:
• The potential yield of the [sic] principal sand and gravel and bedrock aquifers in Illinois are
estimated to be 4.8 and 2.5 billion gallons per day (bgd), respectively;
• The total groundwater potential in Illinois based on full development of either sand and
gravel or bedrock aquifers, whichever has the higher recharge rate, is estimated to be 7.0 bgd;
• Principal sand and gravel aquifers underlie only about 25 percent of the total land area in
Illinois;
• About 3.1 bgd, or about 65 percent of the total potential yield of the principal sand and gravel
aquifers in the state, is concentrated in less than 6 percent of the total land area in Illinois and
is located in alluvial deposits that lie directly adjacent to major rivers such as the Mississippi,
Illinois, Ohio, and Wabash;
• About 0.5 bgd, or about 10 percent of the total potential sand and gravel yield is from the
principal sand and gravel aquifers in the major bedrock valleys of the buried Mahomet valley
in east-central Illinois and in the river valleys of the Kaskaskia, Little Wabash, and Embarras
Rivers in southern Illinois;
• Of the total estimated yield of bedrock aquifers in the State, 1.7 bgd, or 68 percent, is
available from the shallow bedrock aquifers, mainly dolomites in the northern third of the
State;
• The potential yield of the shallow dolomite varies. In areas where the more permeable
shallow dolomites lie directly beneath the glacial drift, the potential yield ranges from
100,000 to 200,000 gpd/mi2;
• In areas where less permeable dolomites lie directly beneath the drift or are overlain by thin
beds of less permeable rocks of Pennsylvanian age, the potential yield ranges from 50,000 to
100, 000 gpd/mi2; and
• Where the overlying Pennsylvanian rocks are thick, the potential yield is less than 50,000
gpd/mi2.”
Future groundwater shortages are predicted in Northeastern Illinois (N.E. IL) (Meyer, Roadcap,
et. al., 2009) and In addition, although shortages are not predicted, the Mahomet Aquifer in
Champaign Urbana shows significant drawn down trends (Roadcap, and Wehrmann, 2009 and
MAC, 2009) .
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Approximately 58 percent (32,000 square miles) of the state is underlain by principal aquifers; of
these, about 33 percent (18,500 square miles) are shallow groundwater sources. The following
are numbers of community water supply wells that withdraw from these aquifers:
Out of 3,517 active CWS wells:
• 46 percent (1,619) utilize a sand and gravel aquifer;
• 27 percent (934) utilize a shallow bedrock aquifer;
• 24 percent (825) utilize a deep bedrock aquifer; and
• 3 percent (139) are undetermined.
There are approximately 5,550 groundwater dependent public water supplies in the state, of
which 1,022 are community water supplies (CWS). The Illinois Department of Public Health
estimates approximately 400,000 residences of the state are served by private wells4.
Water that moves into the
saturated zone and flows
downward, away from the
water table is recharge.
Generally, only a portion of
recharge will reach an
aquifer. The overall
recharge rate is affected by
several factors, including
intensity and amount of
precipitation, surface
evaporation, vegetative
cover, plant water demand,
land use, soil moisture
content, depth and shape of
the water table, distance
and direction to a stream or
river, and hydraulic
conductivity of soil and
geologic materials (Walton,
1965).
Figure C-4 illustrates the
potential for aquifer
recharge, defined as the
probability of precipitation
reaching the uppermost
aquifer. The map is based
on a simplified function of
depth to the aquifer,
4 "Private Water System" means any supply which provides water for drinking, culinary, and sanitary purposes and serves an owner-occupied
single family dwelling. (Section 9(a)(5) of the Illinois Groundwater Protection Act [415 ILCS 55/9(a)(5)])
Figure C-4. Potential for Aquifer Recharge in Illinois
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occurrence of major aquifers, and the potential infiltration rate of the soil. This simplification
assumes that recharge rates are primarily a function of leakage from an overlying aquitard (fine
grained non-aquifer materials). Moreover, recharge may also be occurring from outside of a
watershed boundary. Additionally, pumping stresses from potable water supply wells located
adjacent to watershed boundaries may change the natural groundwater flow directions.
Therefore, aquifer boundaries may not be consistent with surface watershed boundaries.
Additional and more detailed information is
available via Illinois EPA’s Environmental
Facts Online (ENFO):
http://www.epa.state.il.us/enfo/.
Groundwater contribution to stream flow in
the form of base flow was analyzed for 78
drainage basins in Illinois (O’Hearn and
Gibb, 1980). This study determined that
median base flow per square mile of
drainage area generally increases from the
south west to the northeast at all three flow
durations. Figure C-5 shows the 3 year low
flow streams. This provides a good indictor
of groundwater base flow in surface water.
Increased withdrawal of groundwater is
having a direct impact on surface water
quantity. Groundwater modeling studies
conducted in Kane County show that as of
2003 stream flow capture by groundwater
pumping had reduced natural groundwater
discharge to streams in and near Kane
County by about 17 percent (Meyer,
Roadcap, et. al., 2009).
Figure C-5. Three-Year Low Flow
Streams in Illinois
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Illinois Groundwater Monitoring Network
Section 13.1 of the Act (415 ILCS 5/13.1) requires the Illinois EPA to implement a groundwater
monitoring network to assess current levels of contamination in groundwater and to detect future
degradation of groundwater resources. Further, Section 7 of the IGPA (415 ILCS 55/7) requires
the establishment of a statewide ambient groundwater monitoring network comprised of
community water supply wells, non-community water supply wells, private wells, and dedicated
monitoring wells. The ICCG serves as a groundwater monitoring coordinating council. The
following provides a summary of the Illinois EPA’s network of CWS wells.
Prototype Ambient Groundwater Monitoring
The collection of high quality chemical data is essential in assessing groundwater protection
efforts. In 1984, the Illinois State Water Task Force published a groundwater protection
strategy. This strategy lead to the addition of Section 13.1 to the Act (415 ILCS 5/13.1) which
required the Illinois EPA to develop and implement a Groundwater Protection Plan (Plan) and to
initiate a statewide groundwater-monitoring network. In response to these requirements, the
Illinois EPA and the United States Geological Survey (USGS) Illinois District Office, located in
Urbana, began a cooperative effort to implement a pilot groundwater monitoring network (i.e.,
ambient monitoring network) in 1984 (Voelker, 1986). CWS well ambient network design
started with pilot efforts in 1984, moved to implementation of the ISWS network design
(O'Hearn, M. and S. Schock. 1984) for several years, and was followed by sampling all of
Illinois’ CWS wells (3,000+) (Voelker, 1988 and 1989).
The prototype monitoring efforts included development of quality assurance and field sampling
methods. Illinois EPA’s quality assurance and field sampling methods, originally developed in
1984 in cooperation with the USGS, were compiled into a field manual in 1985 (Cobb and
Sinnott,1987 and Barcelona, 1985). This manual has since been revised many times to include
quality improvements. Monitoring at all stations sampled by Illinois EPA is completed by using
Hydrolab® samplers to insure that in situ groundwater conditions are reached prior to sampling.
Water quality parameters include: field temperature, field specific conductance, field pH, field
pumping rate, inorganic chemical (IOC) analysis, synthetic organic compound (SOC), and VOC
analysis. All laboratory analytical procedures are documented in the Illinois EPA Laboratories
Manual.
In the year 2000, the Illinois EPA tasked the USGS to conduct a yearlong independent evaluation
of our groundwater quality sampling methodology. The USGS concluded that Illinois EPA
sampling program (sampling methodology guidelines, water quality meter calibration, and
sampling performance) is considered to provide samples representative of aquifer water quality.
Only minor revisions to the sampling program were suggested (Mills and Terrio 2003). In
addition, Illinois EPA also participates in the annual USGS National Field Quality-Assurance
Program.
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Coordinated Ambient Monitoring
From the experience gained from these prototype networks, implemented pursuant to Section
13.1 of the Act, Illinois EPA designed a probabilistic monitoring network of CWS wells
(Gibbons 1995). The design of this network was completed in coordination with the USGS, the
Illinois State Geological Survey (ISGS), and the ISWS, with USGS performing the detailed
design. The goal of the network is to represent contamination levels in the population of all
active CWS wells. The network wells were selected by a random stratified probability-based
approach using a 95 percent confidence level (CWS probabilistic network). This results in an
associated plus or minus 5 percent precision and accuracy level. Further, the random selection of
the CWS wells was stratified by depth, aquifer type and the presence of aquifer material within
50 feet of land surface to improve precision and accuracy. Illinois EPA used geological well log
and construction log detail to perform this process.
The random stratified selection process included nearly 3,000 CWS wells resulting in 354 fixed
monitoring locations see Figure C-6. Additionally, in order to prevent spatial or temporal bias
17 random groups of 21 wells, with alternates, were selected from all the 354 fixed station wells.
To further assure maximum temporal randomization within practical constraints, the samples
from each sample period are collected within a three-week timeframe.
This probabilistic network is designed to provide an overview of the groundwater conditions in
the CWS wells; provide an overview of the groundwater conditions in the principle aquifers
(e.g., sand and gravel, Silurian, Cambrian-Ordovician, etc.,); establish baselines of water quality
within the principle aquifers; identify trends in groundwater quality in the principle aquifers; and
evaluate the long-term effectiveness of the IGPA, CWA and Safe Drinking Water Act (SDWA)
program activities in protecting groundwater in Illinois. Illinois EPA has also developed an
integrated surface and groundwater monitoring strategy. Figure C-7 shows the probabilistic
groundwater monitoring network wells and the surface water monitoring stations.
During the 1997 monitoring cycle, Illinois EPA initiated a rotating monitoring network of CWS
wells. Illinois EPA rotates every two years from the probabilistic (fixed station) network to
special intensive or regional studies.
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Figure C-6. Active Community Water Supply Wells and Community Water Supply
Probabilistic Network Wells
All CWS Wells in Illinois CWS Probabilistic Network Wells in Illinois
19
Figure C-7. Illinois EPA’s integrated surface and groundwater monitoring network sites
20
A cooperative was established with the USGS to evaluate the occurrence of pesticides and their
transformation products in CWS wells (Mills and McMillan, 2004). A random stratified
statistical method was used to select 117 wells from the 354 well fixed station network to ensure
representation of the major aquifer types in Illinois. For details on the pesticide sub-network of
the CWS probabilistic network, see Illinois Integrated Water Quality Report and Section 303(d)
List-2008 at: http://www.epa.state.il.us/water/tmdl/303-appendix/2008/2008-final-draft-
303d.pdf, and http://www.epa.state.il.us/water/groundwater/publications/herbicides-in-source-water-
report.pdf.
The IGPA required the establishment of a statewide ambient groundwater monitoring network
coordinated by the ICCG, and comprised of CWS wells; non-CWS5 wells; private wells; and
dedicated monitoring wells. Illinois also used a statistically-based approach for designing: a
pilot rural private well monitoring network (Schock and Mehnert, 1992) and the Illinois
Department of Agriculture (IDA) dedicated pesticide monitoring well network (Mehnert et al.
2005) http://www.epa.state.il.us/water/tmdl/303-appendix/2008/2008-final-draft-303d.pdf.
The ICCG also coordinates with the USGS on groundwater monitoring
http://www.epa.state.il.us/water/tmdl/303-appendix/2008/2008-final-draft-303d.pdf.
5 "Non-Community Water System" means a public water system which is not a community water system, and has at least 15 service connections
used by nonresidents, or regularly serves 25 or more nonresident individuals daily for at least 60 days per year. (Section 9(a)(4) of the Illinois
Groundwater Protection Act [415 ILCS 55/9(a)(4)]).
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C-2. Assessment Methodology
Overall Use Support
Though there are many uses of groundwater in Illinois, the groundwater use assessments are
based primarily upon CWS chemical monitoring analyses. The assessment of chemical
monitoring data essentially relies on the Board’s Class I: Potable Resource Groundwater
standards.
The fixed station probabilistic network of CWS is utilized to predict the likelihood of attaining
full use support in the major aquifers in Illinois. As previously described, the overall use support
is based on compliance with Illinois’ Class I GWQS. Class I standards include the
nondegradation standards. The attainment of use support is described as Full and Nonsupport, as
described below:
Full Support
Good - indicates that no detections occurred in organic chemical monitoring data and inorganic
constituents assessed were at or below background levels for the groundwater source being
utilized.
Nonsupport
Fair - indicates that organic chemicals were detected and therefore exceed the nondegradation
standard, but measured levels are less than the numerical Class I GWQS, and inorganic
constituents assessed were above background level (nondegradation standard) but less than the
numerical Class I GWQS.
Poor - indicates that organic chemical monitoring data detections were greater than the Class I
GWQS and inorganic chemicals assessed were greater than both the background concentration
and Class I GWQS.
Organic results in the probabilistic network of CWS wells, which are commonly known to be
anthropogenic in nature, were analyzed by well and year. It was determined that a detection of
an organic contaminant would be recorded and not averaged. In this manor, the Illinois EPA is
able to track the contamination and determine if a trend in that CWS well exists.
22
Individual Use Support
Groundwater in Illinois supports many
uses. For over 50 years, the USGS has
been collecting data on estimated water
withdrawals by state, source of water,
and category. According to the USGS6,
the major uses of groundwater in Illinois
are domestic, public water supply,
agricultural, livestock, industrial, and
thermoelectric.
According to the USGS, Illinois uses
approximately 15.2 billion gallons of
fresh water per day. Only a small
percentage – 1,210 million gallons per
day (MGD), is from groundwater
sources Figure C-13. Irrigation uses
most of the groundwater with over 479
MGD (40%), followed by Public water
supplies use - 406 MGD (34%). Industrial
(self-supplied) withdraws slightly more than
128 MGD (11%), followed by Domestic,
which includes private well usage, 101
MGD (8%), and Livestock/Aquaculture at
44 MGD (3%) Mining (both fresh and
saline) accounts for 41 MGD (3%) and
Thermoelectric sources round off the bottom
of this list with approximately 7 MGD (1%)
of groundwater usage in the State.
In addition, the ISWS conducts an annual
survey of Illinois CWSs as to how much
water they use in a year. These data are
presented in Figure C-14 in MGD. For
purposes of this discussion, only community
CWS use will be considered for the
following assessment. All other uses are
assumed to be full with the exception of
Domestic, which is assessed by the Illinois
Department of Public Health.
The ISWS has updated an analysis of
groundwater use to aquifer potential yield in
Illinois and prepared a report summarizing
6 Based on USGS Circular 1344, 2005, which can be
found at http://pubs.usgs.gov/circ/1344/
Figure C-13. Groundwater Withdrawals in Illinois (USGS 2005)
Public
Supply
34%
Domestic
8%
Irrigation
40%
Livestock
3%
Aquaculture
0%
Industrial
11%
Mining
Fresh
1%
Mining
Saline
2%
Thermo-electric
1%
Figure C-14. Statewide CWS Pumping Rates (ISWS, 2004)
23
the findings (Wehrmann, 2003). This report compared Year 2000 groundwater withdrawals
against estimated aquifer potential yields. The comparison is presented as a ratio of groundwater
use (withdrawals) to groundwater yield (i.e., potential aquifer yield) on a township basis. A high
use-to-yield ratio (e.g., >0.9) suggests an area where groundwater availability problems exist or
could be impending7 (Wehrmann, 2003). For further, detail see the ISWS report at:
http://www.sws.uiuc.edu/pubdoc/CR/ISWSCR2004-11.pdf.
Wehrmann (2003) pointed out that major withdrawals from sand and gravel aquifers can be seen
in the Metro-East area of St. Louis and in Quincy along the Mississippi River; in the Peoria-
Pekin area along the Illinois River, in the Fox River corridor in northeastern Illinois, and in the
Champaign area of east-central Illinois in. Major withdrawals from the shallow bedrock aquifers
can be clearly seen almost solely in northeastern Illinois in southern Cook, Kankakee and Will
Counties for communities such as Crest Hill, Lockport, Manteno, New Lenox, Park Forest, and
Romeoville (Wehrmann, 2003). Major withdrawals from the deep bedrock are found spread
across northern Illinois, particularly in the Rockford area of north-central Illinois, the Fox River
corridor, and farther south in the area of Joliet and the I-55 industrial corridor near Channahon
(Wehrmann, 2003).
In addition, new comprehensive hydrogeologic analysis and demand studies in N.E. IL predict
future water shortages (Meyer, Roadcap, et. al., 2009 and CMAP, 2010). For further detail see,
http://chicagoareaplanning.org/watersupply and
http://www.isws.illinois.edu/iswsdocs/wsp/ppt/NEIL_RWSPG_Mar2009.pdf
Groundwater contributes to stream flow in the form of base flow in many of these river
corridors. Thus, stream flows may also be impacted in areas where the ratio of use to yield is >
0.9. This is especially true in northeastern Illinois due to the following factors: Supreme Court
limitations on Lake Michigan; continued population growth; and a deep aquifer condition
beyond sustainable recharge. It is predicted that these factors will force an increased reliance on
the use of sand and gravel and shallow bedrock aquifer resources. These shallow aquifers are in
direct hydraulic connection to surface waters. Decreased base flow in the stream may have an
impact on surface water quality and stream habitat.
In addition, some groundwater in Illinois is designated as “special resource.” Special Resource
Groundwater is described as the groundwater contributing to highly sensitive areas such as
dedicated nature preserves that supports ecologically sensitive areas such as the Parker Fen in
McHenry County and the Southwest Sinkhole Karst Plain located in Monroe, St. Clair and
Randolph counties.
7 (Note: The delineation of high groundwater use to-yield areas by this method should be considered simply as a
means for calling attention to areas to prioritize on a statewide basis for water resources planning and management
(Wehrmann, 2003).)
24
C-3. Potential Causes and Potential Sources of Impairment
Potential Causes of Impairment
As previously stated, when possible, assessments of overall groundwater use support is based
upon application of Illinois’ GWQS (including non-degradation standards) to water quality
sample measurements from the probabilistic network of CWS wells. Generally, a detection of an
organic contaminant above the laboratory practical quantification limit or the detection of an
inorganic constituent above the naturally occurring background level in a CWS well is
considered a cause of less than full use support.
Potential Sources of Impairment
Illinois EPA used its database of potential sources that have been inventoried as part of well site
surveys, hazard reviews; groundwater protection needs assessments, source water assessments,
and other special field investigations to evaluate potential sources of contamination relative to
CWS WHPAs. Further, the Illinois EPA utilized its Geographic Information System (GIS) to
calculate land use activities proximate to the probabilistic network of CWS wells8. Table C-3
describes the most prevalent (common) potential sources of groundwater contamination in
Illinois relative to CWS WHPAs.
8
County by county land cover grid data for Illinois derived from Thematic Mapper (TM) Satellite data from the Landsat 4
sensor. Dates of the imagery used range from April 1991 to May, 1995.
25
Table C-3. Most Prevalent Potential Sources of Ground Water Contamination9
Contaminant Sources
Occurrence of
Potential Source10
Contaminants11
AGRICULTURAL ACTIVITIES
Agricultural chemical facilities 587 A, B, E
Animal feedlots 66 E, J, K, L
Drainage wells 3 A, B, C, D
Fertilizer applications 323 A, B, E
Irrigation practices 63 A, B, E
Pesticide applications 174 A, B, E
STORAGE AND TREATMENT ACTIVITIES
Land Application 14 A, B, D, E, G, H, J
Material stockpiles 683 G, H
Storage tanks (above ground) 2,249 C, D
Storage tanks (underground) 2,878 C, D
Surface impoundments 236 E, G, H, J, K, L
Waste piles 231 E, G, H
Waste tailings 9 G, H, I, J
DISPOSAL ACTIVITIES
Deep injection wells 9
A, B, C, D, E, F, G, H,
I, M
Landfills 40 C, D, G, H, J
Septic systems 6,290 E, G, H, J, K, L
Shallow injection wells 9
A, B, C, D, E, F, G, H,
J, K, L
OTHER
Hazardous waste generators - A, B, C, D, G, H
Hazardous waste sites 97 A, B, C, D, G, H
Industrial Facilities 1,565 A, B, C, D, G, H
Material transfer operations 232 A, B, C, D, E, F, G, H
Mining and mine drainage 19 G, H, M
Pipelines and sewer lines 111 C, D, E, G, H, J, K, L
Salt storage and road salting 76 G
Salt water intrusion - G
Spills 9 A, B, C, D, E, G, J
Transportation of materials 164 A, B, C, D, E
Manufacturing/repair shops 1,554 C, D, G, H
Urban runoff 1,184
A, B, D, E, G, H, J, K,
L
Other sources (potential routes of contamination such as drainage wells,
improperly abandoned potable water wells, or sand & gravel quarries)
249 A, B, D, E, J, K, L
FACILITY TREATMENT AND RECREATION
Former Storage Facility 113 A, B, C, D, E, G, H
Commercial Waste or Chemical Handling Facility 1,078 C, D, E, G, J
Public Utilities Facility 203 E, F, G, H, J, K, L
Waste Treatment Facility 202 E, G, H, J, K, L
Recreational facility of area 581 J, L
Agriculture Materials Storage and Sales - A, B, E, G, M
9 The basis for the analysis provided in this table is a combination of existing monitoring data and potential source of groundwater contamination
data from the completed CWS well site survey reports which Illinois EPA has conducted over the past 20 years.
10 Occurrences are based solely on the Illinois EPA Groundwater Section’s existing databases. This is only an estimate and should not be used as
anything more than an approximation of potential sources of contamination to CWS wells in Illinois.
11 Contaminants: A. Inorganic pesticides; B. Organic pesticides; C. Halogenated solvents; D. Petroleum compounds; E. Nitrate; F. Fluoride;
G. Salinity/brine; H. Metals; I. Radio-nuclides; J. Bacteria; K. Protozoa; L. Viruses; and M. Other.
26
The Illinois EPA identified 16,354 potential sources of contamination of which 1,163 are
considered threatening. Figure C-15 shows the most threatening potential contamination sources
associated with CWS wells with VOC detects. The most prevalent potential source grouping
was land disposal activities (2,953 sites) and the most threatening potential source grouping was
chemical/petroleum processing/storage (255 sites) facilities.
In addition, ISWS research on CWS wells in Northeastern Illinois has also determined that road
salting is the most threatening potential source causing and contributing to Cl- contamination
above background in Northeastern Illinois. Approximately 16% of the samples collected from
CWS wells in northeastern Illinois in the 1990s had Cl- concentrations greater than 100 mg/L,
and median values were less than 10 mg/L , prior to 1960, before extensive road salting (Kelly
and Wilson, 2004). The 75the quartile value of the sand and gravel CWS probabilistic network
wells in N.E. IL show a 35 percent increase in concentration compared to the state wide ambient
value in the CWS probabilistic network.
The current occurrence of herbicide compounds found in the pesticide sub-network of the CWS
probabilistic network of wells indicates that various factors, along with current agricultural land
use contribute to herbicide occurrence. It appears that many areas that were once rural
agricultural land use have now been encompassed by urban land use. The USGS study of
herbicide transformation and parent products determined:
“… a strong inverse relation (-0.81) between current use of land for corn and soybean
production and the current occurrence of herbicide compounds in underlying aquifers
indicates that various factors, along with current agricultural land use contribute to
herbicide occurrence. These factors include, among others, land-use history, ground-water
age, ground-water flow patterns, geology, soil microbiology, and chemistry and
persistence of the herbicide compounds (Mills and McMillan, 2004).”
Agricultural
Activities
3%
Disposal
Activities
35%
Other
10%
Facility Treatment
and Recreation
25%
Storage and
Treatment
27%
Figure C-15. Most threatening potential contamination sources in community water supply
wells with volatile organic compound detections
27
C-4. Monitoring Results
IDA Dedicated Pesticide Monitoring Well Network Results
For a detailed discussion of the IDA’s dedicated pesticide monitoring well network results see
Illinois Integrated Water Quality Report and Section 303(d) List-2008 at:
http://www.epa.state.il.us/water/tmdl/303-appendix/2008/2008-final-draft-303d.pdf.
CWS Probabilistic Monitoring Network Results
Statistics have a critical role in determining environmental impacts to groundwater quality,
especially with respect to IOCs. The problem is technically interesting: given a new
measurement for a well in the network, drilled in a particular aquifer, and analyzed for a
particular substance, what is the probability that the measurement represents an effect of an
unnatural source (Gibbons, 1995). Thus, this becomes a problem of statistical prediction. Given
a collection of historical or background measurements for a substance, what limit or interval will
contain the new measurement with a desired level of confidence. The wells in the CWS
probabilistic network are not necessarily located in areas geographically removed from potential
sources of contamination, as described above (Gibbons, 1995).
Illinois EPA is using box plots to represent a snapshot of IOC measurement results for network
wells drilled in particular aquifers. As illustrated in Figure 16 a box and whisker plot provides a
statistical prediction of the concentration of a substance bounded by percentiles. In other words,
the box plot shows what concentration occurs between 90, 75, and 25 percent of the time for a
CWS drilled in a particular aquifer. However, because the historical data set for the network
may include measurement results that are due to
unnatural sources, additional regional and/or site
specific evaluation may be needed to determine
if measurements are occurring due to natural
versus unnatural sources.
Figures C-16(a-d) show the IOC results for the
CWS probabilistic network wells drilled in sand
and gravel, shallow bedrock, deep bedrock, and
mixed aquifers. The immediate figure to the left
(Figure C-15) is a key to reading the box plots
that are contained in those figures.
Figure-16. A sample box plot for the
following figures
2 8
Figure C-16a. Inorganic Water Quality Data in Illinois Principal Aquifers
2 9
Figure C-16b. Inorganic Water Quality Data in Illinois Principal Aquifers
3 0
Figure D-16d. Inorganic Water Quality Data in Illinois Principal Aquifers
Figure C-16c. Inorganic Water Quality Data in Illinois Principal Aquifers
31
Northeastern Illinois Chlorides
In addition to the state wide evaluation of inorganic compounds in the CWS probabilistic
network presented in the maps above, Illinois EPA specifically analyzed the
concentrations of chlorides in the network wells utilizing sand and gravel and shallow
bedrock (i.e., Silurian Dolomite) aquifers in N.E. IL (Figure C-17). Table C-4 provides a
comparison of the statistical values between the N.E. IL wells and the state wide CWS
Network wells:
Aquifer Type
Number of
samples
(N)
Mean Median Min Max Q3
Sand and
Gravel
State wide
1258 31.73 17.58 0.50 978.00 37.90
Sand and
Gravel N.E.
Ill
135 51.41 27.00 1.30 928.00 58.20
Aquifer Type
Number of
samples
(N)
Mean Median Min Max Q3
Silurian
State wide
334 57.19 20.15 1.00 843.00 75.58
Silurian N.E.
IL
282 46.75 22.00 1.00 451.00 75.58
The 75th quartile value of the sand and gravel CWS probabilistic network wells in N.E. IL
show a 35 percent increase in concentration compared to the state wide ambient value in
the CWS probabilistic network. In addition, as suspected there are not significant
differences between network wells in the Silurian and N.E. IL since the majority of the
Silurian Dolomite aquifer is in N.E. IL.
Table C-4. Northeastern Illinois and CWS Network Well statistics
3 2
Figure C-17. Northeastern Illinois CWS Network Wells
33
The Mahomet Aquifer
Illinois EPA has done a focused evaluation the CWS probabilistic network wells screened
in the Mahomet Aquifer. The aquifer occupies a portion of the Teays bedrock valley
extending across east‐central Illinois from the Indiana border near Hoopeston to the
Illinois River near. The Mahomet Aquifer is comprised of various unconsolidated
geologic materials as illustrated in the following conceptual model of the hydrogeology
(Figure C-18)
Arsenic is a naturally occurring inorganic compound that has been the subject of
numerous research projects and investigations in the Mahomet Aquifer. The
concentration of arsenic in the CWS probabilistic network wells screened in different
hydrogeologic units in the Mahomet-Teays Bedrock Valley are shown in the box plots in
Figure C-19.
Further, all of the other inorganic compounds present in the Ambient Network of CWS
well screened in the respective geologic formations in the Mahomet-Teays are presented
in Figures C-20(a-e).
Figure C-18 Cross Section of the Mahomet Aquifer (SOI, 2009)
3 4
Figure C-19 Arsenic Levels in the Mahomet Aquifer
3 5
Figure C-20a Iron and TDS Levels in the formations of the Mahomet Aquifer
3 6
Figure C-20b IOC Levels in the Undefined Sand & Gravel of the Mahomet Aquifer
3 7
Figure C-20c IOC Levels in the Glasford Formation of the Mahomet Aquifer
3 8
Figure C-20d IOC Levels in the Banner Formation of the Mahomet Aquifer
3 9
Figure C-20e IOC Levels in the Mahomet Sand of the Mahomet Aquifer
The Illinois EPA included the data on nitrate above from the CWS Ambient Network wells
screened in the Glasford Formation and the data on nitrate and sulfat
Ambient Network wells screened in the Banner Formation but the number of these sample sets
may not be statistically representative.
C-5. Use Support Evaluation
Figure C-21 and C-22 summarize
measurements in the probabilistic network of CWS wells.
CWS probabilistic network wells:
• 28 (8 percent (%)) were determined to be
levels of nitrate and VOCs that include trichloroethylene and
of these wells draw their water from shallow sand & gravel aquifers, except for one,
which is using a deep well from the Cambrian/Ordovician bedrock aquifer in the
northern part of the state);
• 90 (25%) were determined to be
increases chloride (Cl-) above background, detections of VOCs, nitrate (total
nitrogen) greater than 3 mg/l,
Quality Standards (GWQS); and
• 236 (67 %) were determined to be
detections of any of the above analytes
Trend analyses for VOC’s also shows that there continues to be a
number of CWS wells with VOC detections,
for VOC’s over the same time period
75the quartile value of the sand and gravel CWS probabilistic network wells in N.E. IL show a
35 percent increase in concentration of chlorides compared to the state wide ambient value in
the CWS probabilistic network screened in sand and gravel aquifers.
0
50
100
150
200
250
Good Fair
235
91
Figure C-21. Use Support in CWS Network Wells
40
sulfate above from the CWS
use support in the State of Illinois as determined by
abilistic The results show that of the 354
e Not Supporting (“poor”) due to the elevated
tetrachloroethylene
p Not Supporting (“fair”) due to statistically significant
) but have not exceeded the health-based Groundwater
Fully Supporting (“good”), which show no
analytes.
OC’s significant increase in the
despite the fact that the number of CWS
declined, and the detection limit remained constant
obabilistic Poor
28
. e tetrachloroethylene. All
, analyzed
constant. The
41
Figure C-22. Use Support for the CWS Ambient Network Wells within Illinois’ Principal Aquifers
42
C-6. Potential Causes of Impairment
VOCs in CWS Wells
As previously stated, when possible, assessments of groundwater overall use support is based
upon Illinois’ GWQS within the probabilistic network of CWS wells. Generally, a detection of
an organic contaminant above the laboratory practical quantification limit or the detection of an
inorganic constituent above the naturally occurring background level in a CWS well is
considered a cause of less than full use support. Detections of VOCs in CWS wells on a
statewide basis have fluctuated since 1990 showing the lowest concentration of wells with
detections in the early nineties (During the mid-nineties VOC detections exceeded the GWQS a
total of five times. However, the findings of the first long term trend analysis conducted for all
of the CWS wells (not just the fixed station network wells) monitored for VOC results. The
entire data set (1990 to the present) was analyzed and the results are shown in Figure C-23.
VOCs analyses of data collected from 1990 to the present shows a statistically significant
increasing trend of CWS wells with VOC detections per year. The causal data also show total
xylenes and 1,1,1- trichloroethane as the top ranked VOCs detected
Figure C-23. Long-term VOC trend from the full data set
43
Chlorides in CWS Wells
The 75the quartile value of the sand and gravel CWS probabilistic network wells in N.E. IL
show a 35 percent increase in concentration of chlorides compared to the state wide ambient
value in the CWS probabilistic network screened in sand and gravel aquifers. Further, ISWS
research determined that: approximately 16% of the samples collected from CWS wells in
northeastern Illinois in the 1990s had Cl- concentrations greater than 100 mg/L; median values
were less than 10 mg/L prior to 1960, before extensive road salting (Kelly and Wilson, 2004).
Groundwater Degradation
Illinois groundwater resources are being degraded. Degradation occurs based on the potential or
actual diminishment of the beneficial use of the resource. When contaminant levels are detected
(caused or allowed) or predicted (threat) to be above concentrations that cannot be removed via
ordinary treatment techniques, applied by the owner of a private drinking water system well,
potential or actual diminishment occurs. At a minimum private well treatment techniques consist
of chlorination of the raw source water prior to drinking. This groundwater degradation is
exacerbated due to the predicted shortages of drinking water sources in the N. E. IL.
It should be noted that groundwater that is consumed via a CWS has to be treated before it is
delivered to the users. This treatment often includes methods for removing various
contaminants, including the ones previously mentioned in this section. For more information of
waters that are being consumed from CWSs, the public can contact their local CWS or the
applicable Consumer Confidence Report at
http://epadata.epa.state.il.us/water/bowccr/ccrselect.aspx
44
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