20120403211048_thorn-creek-watershed-based-plan

              Thorn Creek Watershed Based Plan
December 2005
Thorn Creek Watershed Based Plan December 2005
i
TABLE OF CONTENTS
Section Page
List of Figures.............................................................................................................................................................v
List of Tables..............................................................................................................................................................vi
Acknowledgments ..................................................................................................................................................vii
Executive Summary..................................................................................................................................................ix
1. Introduction....................................................................................................................................................... 1-1
1.1. Overview ................................................................................................................................................. 1-2
1.1.1. Plan Organization......................................................................................................................... 1-2
1.2. Model Watershed Planning Strategy .................................................................................................... 1-4
1.2.1. Methodology................................................................................................................................. 1-5
1.2.1.1. Identify and Assemble Stakeholders ................................................................................ 1-5
1.2.1.2. Establish Goals..................................................................................................................... 1-6
1.2.1.3. Inventory Watershed Resources and Conditions ........................................................... 1-6
1.2.1.4. Assess Existing Watershed Problems and Threats ......................................................... 1-7
1.2.1.5. Recommend Objectives and Management Practices for Prevention
and Remediation ................................................................................................................. 1-7
1.2.1.6. Develop an Effective Action Plan...................................................................................... 1-8
1.2.1.7. Implement Plan and Monitor Success .............................................................................. 1-8
1.2.2. Evaluation of Plan Conformity to the Nine Minimum Elements ........................................... 1-9
1.3. Stakeholders ...........................................................................................................................................1-11
1.4. Initial Concerns and Goals for the Thorn Creek Watershed.............................................................1-14
1.4.1. List of Issues and Concerns from meeting December 8, 2003 ................................................1-14
1.4.2. Goals and Objectives for the Thorn Creek Ecosystem Partnership
as noted in A Watershed Plan for Thorn Creek ............................................................................1-15
1.5. Thorn Creek Goals and Objectives.......................................................................................................1-17
1.5.1. Overall Goal .................................................................................................................................1-17
1.5.2. Resource Based Goals ..................................................................................................................1-17
1.5.2.1. Habitat and Natural Resources ........................................................................................1-17
1.5.2.2. Water Quality......................................................................................................................1-17
1.5.2.3. Water Supply ......................................................................................................................1-18
1.5.2.4. Recreation and Access .......................................................................................................1-18
1.5.2.5. Flooding..............................................................................................................................1-19
1.5.3. Watershed Coordination Goals ..................................................................................................1-19
1.5.3.1. Communication, Coordination, and Governance..........................................................1-19
1.5.3.2. Education and Stewardship..............................................................................................1-20
2. Thorn Creek Watershed Resource Inventory ............................................................................................... 2-1
2.1. Climate ..................................................................................................................................................... 2-2
2.2. Geology and Physiography................................................................................................................... 2-3
2.2.1. Bedrock and Glacial Geology....................................................................................................... 2-3
2.2.2. Topography and Stream Gradient .............................................................................................. 2-3
2.2.3. Soils................................................................................................................................................. 2-4
2.2.4. Aquifer Sensitivity........................................................................................................................ 2-5
Thorn Creek Watershed Based Plan December 2005
ii
2.3. Hydrology and Waterbodies.................................................................................................................. 2-6
2.3.1. Streams........................................................................................................................................... 2-6
2.3.2. Lakes..............................................................................................................................................2-10
2.4. Water Quality Assessment ....................................................................................................................2-12
2.4.1. Illinois EPA Water Quality Assessments ..................................................................................2-12
2.4.1.1. Lakes ...................................................................................................................................2-13
2.4.1.2. Streams................................................................................................................................2-14
2.4.2. NIPC Water Quality Assessments .............................................................................................2-17
2.4.2.1. NIPC Water Quality Empirical Analysis ........................................................................2-17
2.4.2.2. NIPC Land Use Pollutant Loading Analysis..................................................................2-19
2.4.3. Results of NIPC Water Quality Assessments ...........................................................................2-23
2.4.3.1. Fecal Coliform.....................................................................................................................2-23
2.4.3.2. Dissolved Oxygen ..............................................................................................................2-24
2.4.3.3. Biological Oxygen Demand ..............................................................................................2-24
2.4.3.4. Total Dissolved Solids .......................................................................................................2-25
2.4.3.5. Sulfate .................................................................................................................................2-26
2.4.3.6. Total Phosphorus and Chlorophyll a...............................................................................2-27
2.4.3.7. Nitrogen..............................................................................................................................2-28
2.4.3.8. pH........................................................................................................................................2-29
2.4.3.9. Metals..................................................................................................................................2-30
2.4.3.10. Total Suspended Solids ...................................................................................................2-31
2.4.4. Additional Data on Water Quality in Thorn Creek .................................................................2-32
2.4.4.1. Thorn Creek Stream Inventory and Opportunity Assessment ....................................2-32
2.4.4.2. Illinois EPA-identified Impairments Not Captured in NIPC Assessments ...............2-32
2.5. Fish and Biotic Indicators ......................................................................................................................2-33
2.5.1. Sampling Locations ......................................................................................................................2-33
2.5.2. RiverWatch Program Macroinvertebrate Data.........................................................................2-34
2.5.3. Illinois EPA and Thorn Creek Basin Sanitary District Macroinvertebrate Data..................2-34
2.5.4. Illinois DNR and Illinois EPA Fish Data ...................................................................................2-36
2.6. Channel and Riparian Conditions........................................................................................................2-40
2.7. Natural Resources .................................................................................................................................2-43
2.7.1. Current and Presettlement Land Cover ....................................................................................2-43
2.7.2. Wetlands .......................................................................................................................................2-44
2.7.3. Natural Communities ..................................................................................................................2-44
2.7.4. Natural and Protected Areas ......................................................................................................2-45
2.8. Trails and Greenways ............................................................................................................................2-48
2.9. Flooding, Stormwater Management, and Drainage ..........................................................................2-49
2.9.1. Topography and Floodplains .....................................................................................................2-49
2.9.2. Central Basin Tunnel and Reservoir Project .............................................................................2-49
2.9.3. Stormwater Management Efforts ...............................................................................................2-50
2.10. Municipal and Industrial Discharge and Water Use .......................................................................2-51
2.10.1. Toxic Release Inventory.............................................................................................................2-51
2.10.2. National Pollutant Discharge Elimination System ................................................................2-52
2.10.3. Water Use ...................................................................................................................................2-53
2.11. Socio-Economic and Human Resources ............................................................................................2-57
2.12. Past, Ongoing, and Proposed Watershed Projects ...........................................................................2-58
Thorn Creek Watershed Based Plan December 2005
iii
3. Water Quality Assessment Conclusions and Recommendations............................................................. 3-1
3.1. General Conclusions and Recommendations ...................................................................................... 3-2
3.1.1. Key Water Quality Constituents ................................................................................................. 3-2
3.1.2. Relationship of Water Quality Assessment Conclusions and Recommendations to
Watershed Resource Inventory ................................................................................................ 3-2
3.2. Specific Water Quality Conclusions and Recommendations ............................................................ 3-3
3.2.1. Pathogenic Contamination........................................................................................................... 3-3
3.2.2. Organic Enrichment / Low Dissolved Oxygen.......................................................................... 3-4
3.2.3. Hydrologic Disturbance / Flow Alterations............................................................................... 3-5
3.2.4. Dumping and Debris .................................................................................................................... 3-5
3.2.5. Aquatic Life Toxicity (Total Dissolved Solids, Chlorides, and Sulfates) ............................... 3-5
3.2.6. Nutrients and Algal Growth........................................................................................................ 3-7
3.2.6.1. Phosphorus.......................................................................................................................... 3-7
3.2.6.2. Nitrogen............................................................................................................................... 3-7
3.2.6.3. Recommendations for Addressing Nutrients.................................................................. 3-8
4. Thorn Creek Watershed Improvement Plan................................................................................................. 4-1
4.1. Watershed Management Recommendations....................................................................................... 4-2
4.1.1. Policy and Planning ...................................................................................................................... 4-2
4.1.2. Structural ....................................................................................................................................... 4-3
4.1.3. Non-Structural ............................................................................................................................... 4-4
4.1.4. Coordination and Education........................................................................................................ 4-5
4.1.5. Summary of Impairments, Causes, and Sources....................................................................... 4-7
4.2. Watershed Management Recommendations for Water Quality Improvement.............................4-11
4.2.1. Policy and Planning Recommendations....................................................................................4-11
4.2.2. Structural Recommendations......................................................................................................4-14
4.2.3. Non-Structural Recommendations ............................................................................................4-17
4.3. Expected Pollutant Load Reduction Estimates...................................................................................4-21
4.4. Cost Estimates........................................................................................................................................4-22
4.5. Thorn Creek Watershed Short Term Action Plan ..............................................................................4-23
4.6. Implementation Partners .......................................................................................................................4-24
4.7. Potential Funding Sources for Watershed Restoration Activities....................................................4-28
4.8. Information and Education in the Thorn Creek Watershed.............................................................4-38
4.8.1. Goals and Objectives of the Information and Education Strategy.........................................4-38
4.8.2. Target Audiences.........................................................................................................................4-38
4.8.3. Possible Partnering Organizations.............................................................................................4-39
4.8.4. Ideas for Implementing the Thorn Creek Information and Education Strategy.................4-40
4.8.5. Evaluating the Outreach Plan.....................................................................................................4-43
4.8.6. Watershed Information and Education Resources ..................................................................4-44
4.8.7. Sources of Impairment and Outreach Strategy ........................................................................4-47
4.9. Action Plan Summary for Water Quality Improvement...................................................................4-48
5. Plan Implementation Evaluation.................................................................................................................... 5-1
5.1. Monitoring Water Quality Improvement............................................................................................. 5-2
5.1.1. Purpose of Monitoring.................................................................................................................. 5-2
5.1.2. Analytical Monitoring................................................................................................................... 5-2
5.1.3. Visual and Anecdotal Monitoring............................................................................................... 5-2
5.1.4. Quality Assurance Project Plans (QAPP)................................................................................... 5-3
Thorn Creek Watershed Based Plan December 2005
iv
5.2. Watershed Management Recommendation Implementation Monitoring Strategy....................... 5-4
5.3. Water Quality Objective Monitoring Strategy..................................................................................... 5-6
5.4. Evaluation of Education Strategy.......................................................................................................... 5-8
Appendix A: Selected Figures............................................................................................................................ A-1
Appendix B: NIPC Water Quality Assessment ................................................................................................. B-1
B-1. Water Quality Empirical Analysis ....................................................................................................... B-1
B-2. Land Use Pollutant Loading Analysis ................................................................................................ B-4
Appendix C: Effectiveness of Best Management Practices ..............................................................................C-1
Thorn Creek Watershed Based Plan December 2005
v
LIST OF FIGURES
Page
Figure 1-1. Thorn Creek Watershed Municipalities.......................................................................................... A-2
Figure 2-1. Thorn Creek Watershed Digital Elevation Model and 100 Year Floodplains........................... A-3
Figure 2-2. Longitudinal Profile of Thorn Creek.............................................................................................. A-4
Figure 2-3. Thorn Creek Watershed Selected Soil Types................................................................................. A-5
Figure 2-4. Thorn Creek Watershed Main Stem and Tributaries ................................................................... A-6
Figure 2-5. Thornton Mean Annual Flow 1949–2002........................................................................................ 2-8
Figure 2-6. Mean Annual Flow, Thornton Ten Year Averages 1949–2002..................................................... 2-8
Figure 2-7. Monthly Mean Streamflow at Thornton......................................................................................... 2-8
Figure 2-8. Glenwood Mean Annual Flow 1949–2002...................................................................................... 2-9
Figure 2-9. Mean Annual Flow, Glenwood Ten Year Averages 1949–2002................................................... 2-9
Figure 2-10. Monthly Mean Streamflow at Glenwood ..................................................................................... 2-9
Figure 2-11. Thorn Creek Historical Flow Analysis, Glenwood, Illinois (USGS 05536215),
Mean Daily Flow by Decade ........................................................................................................2-10
Figure 2-12. Subbasins and Water Quality Sampling Locations in the Thorn Creek Watershed..............2-19
Figure 2-13. Thorn Creek Subwatershed Percent Imperviousness. ...............................................................2-22
Figure 2-14. Total BOD Loading by Watershed Land Use and Percent of BOD Load by Subbasin .........2-25
Figure 2-15. TDS Loading by Watershed Land Use and Percent of TDS Load by Subbasin......................2-26
Figure 2-16. Total P Loading by Watershed Land Use and Percent of TP Load by Subbasin ...................2-28
Figure 2-17. Total N Loading by Watershed Land Use and Percent of TN Load by Subbasin..................2-29
Figure 2-18. Total Copper Loading by Watershed Land Use and Percent of Copper Load
by Subbasin.....................................................................................................................................2-30
Figure 2-19. Total Zinc Loading by Watershed Land Use and Percent of Zinc Load by Subbasin...........2-31
Figure 2-20. TSS Loading by Watershed Land Use and Percent of TSS Load by Subbasin........................2-32
Figure 2-21. Biological and Habitat Sampling Locations . ..............................................................................2-33
Figure 2-22. Thorn Creek Watershed 1997 Land Cover. ................................................................................. A-7
Figure 2-23. Thorn Creek Watershed Presettlement Land Cover. ................................................................. A-8
Figure 2-24. Thorn Creek Watershed Northeastern Illinois Regional Greenways and Trails Plan........... A-9
Figure 2-25. Thorn Creek Watershed Forest Preserves ................................................................................. A-10
Thorn Creek Watershed Based Plan December 2005
vi
LIST OF TABLES
Page
Table 1-1. Relation between Seven-Step Watershed Planning and
USEPA Nine Minimum Elements................................................................................................... 1-5
Table 2-1. 1971-2000 Temperature Normals for Chicago Midway Airport ................................................... 2-2
Table 2-2. 1971-2000 Mean Precipitation Normals for Chicago Midway Airport......................................... 2-2
Table 2-3. Description of Trophic State Index...................................................................................................2-14
Table 2-4. Water Quality Impairments in Reach HBD 04 of Thorn Creek....................................................2-15
Table 2-5. Water Quality Impairments in Reach HBD 05 of Thorn Creek....................................................2-15
Table 2-6. Illinois EPA Use Assessment and Potential Causes and Sources of Impairment
for Thorn Creek .................................................................................................................................2-16
Table 2-7. Illinois EPA Use Assessment and Potential Causes and Sources of Impairment
for Deer, Butterfield, and North Creeks ..........................................................................................2-17
Table 2-8. Sampling Locations and Data Sources for NIPC Water Quality Empirical Analysis ...............2-18
Table 2-9. Standards for Total Dissolved Solids and Sulfate for Select Reaches of Thorn Creek ..............2-19
Table 2-10. Relation between Watershed Quality and Impervious Land Cover .........................................2-21
Table 2-11. Average Chlorophyll a Concentrations in Thorn Creek, 1997-2004...........................................2-27
Table 2-12. Illinois DNR RiverWatch Data Summary, Thorn Creek, 1997–2003..........................................2-34
Table 2-13. Illinois EPA Macroinvertebrate Data, Thorn Creek, 2001 ...........................................................2-35
Table 2-14. MBI Values Above and Below Thorn Creek Basin Sanitary District Plant, 1988-1999............2-36
Table 2-15. Illinois DNR Fish Community Data, Thorn Creek, 1998.............................................................2-37
Table 2-16. Illinois DNR and Illinois EPA Fish Community Data, Thorn Creek at
HBD 05, 2001 ....................................................................................................................................2-37
Table 2-17. TCBSD Fish Survey Data, Thorn Creek, 1999 ...............................................................................2-38
Table 2-18. Stream Conditions, Thorn Creek from Butterfield Creek Confluence to
Paarlberg Farm, 2002........................................................................................................................2-40
Table 2-19. Habitat Observations, Thorn Creek at HBD 05, 2001 ..................................................................2-41
Table 2-20. Channel Conditions, Thorn Creek, 1999........................................................................................2-42
Table 2-21. Current and Presettlement Land Cover in the Thorn Creek Watershed ..................................2-43
Table 2-22. CTAP Professional Scientists Monitoring — Bird Species ..........................................................2-45
Table 2-23. CTAP Professional Scientists Monitoring — Plant Species.........................................................2-45
Table 2-24. Natural Areas within the Thorn Creek Watershed......................................................................2-46
Table 2-25. Nature Preserves within the Thorn Creek Watershed.................................................................2-46
Table 2-26. Toxic Release Inventory Facilities within the Thorn Creek Watershed ....................................2-51
Table 2-27. NPDES Permits Granted to Facilities within Thorn Creek Watershed .....................................2-52
Table 2-28. 1990 Water Use within the Thorn Creek Watershed....................................................................2-54
Table 2-29. Projected 2020 Non-Cooling Water Demand by Township........................................................2-56
Table 2-30. Demographic Projections for Municipalities in the Thorn Creek Watershed ..........................2-57
Table 3-1. Reductions Needed to Meet Fecal Coliform Target........................................................................ 3-3
Table 3-2. Reductions Needed to Meet Phosphorus Target............................................................................. 3-7
Table 3-3. Reductions Needed to Meet Nitrogen Target.................................................................................. 3-8
Table 4-1. Expected Effect of Watershed Management Recommendations on Pollutant Loading ...........4-21
Table 4-2. Cost Estimates for BMPs....................................................................................................................4-22
Thorn Creek Watershed Based Plan December 2005
vii
Table B-1. Exceedance Frequency of Water Quality Constituents above State Standards in
Thorn Creek, 1997-2004....................................................................................................................... B-2
Table B-2. Average Water Quality Constituent Concentrations in Thorn Creek, 1997-2004....................... B-3
Table B-3. Land Use Pollutant Loading Model Assumptions ......................................................................... B-4
Table C-1. Effectiveness of BMPs Recommended for Thorn Creek................................................................C-1
Table C-2. Pollutant Removal Efficiencies for Selected Groups of BMPs ......................................................C-2
Table C-3. Pollutant Removal Efficiencies for BMPs (Center for Watershed Protection)............................C-3
Table C-4. Pollutant Removal Efficiencies for BMPs (Illinois EPA)................................................................C-3
Table C-5. Effectiveness of Riparian Buffers in Reducing Pollutant Loading...............................................C-4
Thorn Creek Watershed Based Plan December 2005
viii
ACKNOWLEDGMENTS
This report was prepared using U.S. Environmental Protection Agency funds under Section 319 of the
Clean Water Act distributed through the Illinois Environmental Protection Agency. The findings and
recommendations contained herein are not necessarily those of the funding agencies.
Partners in the development of the Thorn Creek Watershed Based Plan included the Thorn Creek Ecosystem
Partnership and the Thorn Creek Restoration Coalition. Numerous individuals helped shape this
Watershed Based Plan through their service on the Steering and Technical Advisory Committees for the
Thorn Creek Watershed Planning process. They are listed in Section 1.3. The Northeastern Illinois
Planning Commission (NIPC) provided staff support and drafted the Watershed Based Plan document.
NIPC staff members who worked on the plan include Laura Barghusen, Michael Carter, Dennis Dreher,
Jesse Elam, Jessica Higgins, Holly Hudson, Jason Navota, Sarah Nerenberg, Suzanne Thorsen, Jennifer
Welch, and Jeff Wickenkamp.
Thorn Creek Watershed Based Plan December 2005
ix
EXECUTIVE SUMMARY
Location and Conditions
Thorn Creek flows northward about 20 miles from its origin in
eastern Will County to its confluence with the Little Calumet River in
southern Cook County, running along the way through the
municipalities of University Park, Park Forest, South Chicago
Heights, Chicago Heights, Glenwood, Thornton, and South Holland.
Thorn Creek and its tributaries—Deer Creek, Butterfield Creek, and
North Creek—form a 107 square mile watershed (about 104 square
miles of which are in Illinois). The Thorn Creek Watershed Based Plan
focuses on a smaller area than this, the main stem Thorn Creek
subwatershed, which is 32.2 square miles or 20,614 acres in size.
Urbanized land, at 48 percent, makes up a
plurality of the entire Thorn Creek watershed,
with another 48 percent comprised of forested
cover (primarily along the major drainageways),
grassland, and cropland (mainly in the
southwest two thirds of the watershed). The
subwatershed has a dual character in other
ways as well. For instance, the northeastern
third extends into the Chicago Lake Plain, a flat
expanse formed by the same glacier that created
Lake Michigan, while the origin of the stream in
the southwest lies in a rolling landscape of
glacial moraines, the hills created by sediments
deposited during glacial retreat. Thorn Creek
flows from an area of hills and ravines with
farms and forest cover into a much flatter, more
urbanized landscape.
Water quality has been declining in Thorn Creek for the past several decades, largely due to the effects of
land conversion. With conversion to cropland and urban cover, prairie has declined from an estimated
70 percent in pre-settlement times to less than 12 percent within the grassland areas. As a result,
increased stormwater runoff has carried a significant pollutant burden into the stream. Aquatic
communities have suffered as well, although conditions vary along the stream course. Studies at certain
locations have shown poor fish diversity and a preponderance of pollution tolerant organisms. With its
array of different habitat types, however, the Thorn Creek watershed still supports a large number of
species for its size, made possible in large part by the conservation of natural areas in forest preserve
lands along the stream. The fraction of pre-settlement forest remaining in the Thorn Creek watershed
(about 83 percent) is much higher than in Illinois overall (about 30 percent). Several rare and threatened
species make their home in the watershed, and there is a great diversity of birds and plants despite the
degradation of the aquatic community.
Thorn Creek Watershed Based Plan December 2005
x
Background and Goals
With funding from the Illinois Environmental Protection Agency obtained in 2003, the Northeastern
Illinois Planning Commission sought to employ its Model Watershed Planning Strategy in a threatened
watershed in the region while also piloting new federal guidelines for Watershed Based Plans. The U.S.
Environmental Protection Agency now calls for more thorough quantification of water quality problems
and establishment of rigorous measures of success to help assure the effectiveness of federal assistance.
For a variety of reasons, the Thorn Creek watershed stood out as a candidate, not least because of the
capacity of the Thorn Creek Ecosystem Partnership and the Thorn Creek Restoration Coalition as
collaborating organizations.
The most pressing watershed issues emerged from early meetings with stakeholders. This list was
combined with additional information to develop a set of goals and objectives for the watershed that
were categorized as either resource-based goals, such as habitat restoration, or watershed coordination
goals, such as improved education and outreach. The Thorn Creek Watershed Based Plan focuses closely on
the goal of protecting and enhancing surface water quality to support uses designated for Thorn Creek by
the Illinois Environmental Protection Agency. This is so because improving water quality is the intent of
the funding behind the plan, yet the plan also provides a doorway for considering the other important
goals identified by watershed stakeholders. In order of priority, these include the resource-based goals of
protecting and restoring aquatic and terrestrial habitat, protecting and enhancing groundwater quality
and quantity, reducing flooding and flood damages. The watershed coordination goals include
improving cooperation among actors in the watershed, such as businesses, universities, and
governments, and educating stakeholders about their role in protecting the watershed.
Findings of Water Quality Assessment
Water quality sampling data from several sources were analyzed to determine the extent of impairment
by various contaminants. A land use pollutant loading model also was employed to relate water quality
problems back to the mix of land uses and the amount of impervious surface in the watershed.
Watershed stakeholders reviewed the results and concluded that the water quality constituents most in
need of attention include the presence of pathogenic organisms (as indicated by fecal coliforms), low
dissolved oxygen, hydrologic modification, dumping and debris, and road salt runoff.
Recommendations and Evaluation
A set of Watershed Management Recommendations (WMRs) was developed to address the goals
stakeholders identified as most important to them. From there, a smaller subset of WMRs directed at
surface water quality was selected for further elaboration, with estimates of their effectiveness and cost to
implement. Stakeholders then prioritized these water quality related WMRs. Several steps to take most
immediately were:
• Enact and enforce ordinances to protect floodplains, riparian buffer areas, flood prone areas,
natural depressional storage areas, and other natural retention and drainage features. Acquire
and protect floodplains for flood prevention, open space, and environmental enhancement along
the mainstem and tributaries.
• Utilize natural drainage and infiltration measures to reduce runoff volumes, filter pollutants from
runoff water, and improve stormwater infiltration into the ground. Implement lot level BMPs to
Thorn Creek Watershed Based Plan December 2005
xi
capture stormwater. Maintain, restore, and enhance natural drainage and storage systems that
can serve multiple objectives such as stormwater conveyance, storage, and habitat.
• Conduct stream cleanups to improve aesthetics, remove trash and debris, and maintain channel
flow. Leave some natural elements as habitat features.
• Improve road maintenance practices to remove potential pollutants, such as through regular
street sweeping, and reduce the use of road salt in winter.
• Adopt and enforce ordinances, programs, and practices that protect natural areas and sensitive
features from new development and human activities and that minimize unavoidable
disturbances of high quality natural areas.
• Collect current baseline scientific data for the watershed, including information on the location,
capacity, and impact of retention/detention within the watershed. Develop detailed short and
long term watershed monitoring strategies and a standard list of indicators.
• Eliminate illicit sanitary/industrial/commercial connections to storm sewers.
• Develop comprehensive plans for watershed management, stormwater management, land use,
and flood hazard mitigation for Thorn Creek and all significant tributaries and incorporate into
local plans and policies.
In turn, these general WMRs were rendered into a Short Term Action Plan that included phasing
implementation, estimating costs, and identifying responsible parties.
Thorn Creek Watershed Based Plan December 2005
1–1 Introduction
1. INTRODUCTION
Thorn Creek Watershed Based Plan December 2005
1–2 Introduction
1.1. Overview
Thorn Creek flows north from its origin near Monee in eastern Will County to its confluence with the Lit-tle
Calumet River in South Holland in Cook County (Figure 1-1, Appendix A). Thorn Creek and its tribu-taries
— Deer Creek, Butterfield Creek, Third Creek, and North Creek — form a 107 square mile sub-watershed
of the Little Calumet watershed. Thorn Creek itself runs through the municipalities of Univer-sity
Park, Park Forest, South Chicago Heights, Chicago Heights, Glenwood, Thornton, and South Hol-land.
Although the watershed is largely urban, it supports a diversity of terrestrial and aquatic wildlife, and the
substantial portion located in the Cook County Forest Preserve is somewhat protected from many of the
negative effects of urbanized land use found within other parts of the watershed. Even so, water quality
has declined over the past few decades. The natural hydrology of the stream has been altered, and con-centrations
of several pollutants substantially exceed Illinois standards.
Using funding from the Illinois Environmental Protection Agency, the Northeastern Illinois Planning
Commission (NIPC) set out in 2003 to develop a pilot Watershed Based Plan in the region. The dedica-tion,
track record, and organizational capacity of the Thorn Creek Ecosystem Partnership and the Thorn
Creek Restoration Coalition made them excellent partners for this pilot project.
This Watershed Based Plan focuses on nonpoint source pollution, particularly in the 26 square mile wa-tershed
of the Thorn Creek mainstem. While the Watershed Resource Inventory in Section 2 of this docu-ment
delves into a broad range of issues — for example, recreation, habitat restoration, etc. — the rec-ommendations
of this Watershed Based Plan concentrate on water quality.
1.1.1. PLAN ORGANIZATION
This organization of this document follows the organization of the planning process, which is described
further under Model Watershed Planning Strategy (Section 1.2) below. The sections of this plan are as fol-lows:
Section 1 — Introduction. This section outlines the Model Watershed Planning Strategy the North-eastern
Illinois Planning Commission employs and relates it to the U.S. Environmental Protection
Agency’s specifications for watershed plans. A self-assessment of the Thorn Creek Watershed Based Plan
relative to the USEPA guidelines is also presented. Goals and objectives for the Thorn Creek water-shed
from stakeholder input are documented.
Section 2 — Watershed Resource Inventory. This section summarizes general physical conditions in
the watershed, such as climate and soil type, and reviews available hydrological and water quality
data. Causes and sources of water quality impairment are discussed. The Inventory presents the re-sults
of a predictive analysis associating land use and surface imperviousness with water quality, as
well as an empirical analysis of water quality data. These results are interpreted further in Section 3,
where specific conclusions are drawn from them. Information on natural areas, land cover, runoff
management, and projects affecting the watershed, among other things, is also presented in the In-ventory.
Section 3 — Water Quality Assessment Conclusions and Recommendations. This section concen-trates
on a set of key water quality constituents identified as watershed priorities by stakeholder
Thorn Creek Watershed Based Plan December 2005
1–3 Introduction
committees. Pollutant loading reductions needed to meet water quality standards are presented for
priority constituents, followed by recommended next steps.
Section 4 — Thorn Creek Watershed Improvement Plan. This section draws from the data in the
Inventory and the water quality assessment of Section 3 to derive recommendations and implementa-tion
steps to improve water quality in Thorn Creek. First this section relates general watershed man-agement
practices, and then selects those that best meet the identified water quality objectives of wa-tershed
stakeholders (described in Section 1). These Watershed Management Recommendations
(WMRs) are then described in more detail, with a discussion of cost and expected pollutant reduc-tions.
Supporting evidence for the effectiveness of certain WMRs is also presented. An action plan is
presented in which groups of potential partners in the watershed and how they could contribute to
implementation are identified, strategies for enacting the WMRs are provided, and potential funding
sources are outlined. Finally, the framework of an informational outreach and education program is
also presented.
Section 5 — Plan Implementation Evaluation. This section describes monitoring needs for tracking
the success of WMR implementation.
Maps and other figures are divided between the text and an appendix. The Watershed Resource Inven-tory
has several maps in line with the text for easier reference.
Thorn Creek Watershed Based Plan December 2005
1–4 Introduction
1.2. Model Watershed Planning Strategy
Watershed planning is performed in numerous ways in varying contexts throughout Illinois. The ap-proach
used in any particular watershed should reflect the issues, interest groups, technical complexity,
resources, and size of the watershed. While flexibility is important, there also are some basic elements
that should be included in any watershed planning process. Historically, most successful watershed
plans have included the following seven steps:
1. Identify stakeholders
2. Establish goals
3. Inventory watershed resources and conditions
4. Assess waterbody/watershed problems
5. Recommend management practices for prevention and remediation
6. Develop an effective action plan (who, what, when)
7. Implement plan and monitor success
This basic approach was employed in the development of the Thorn Creek Watershed Based Plan. It is
consistent with the watershed assessment approach described in the Illinois Environmental Protection
Agency’s (IEPA) biennial Illinois Water Quality Report (also known as the “305(b) Report”). It has also
been recommended by the IEPA for the development of watershed plans, and is the foundation for a wa-tershed
based planning manual currently under development for the State of Illinois by the Northeastern
Illinois Planning Commission.
New directives for Watershed Based Plans from the U.S. Environmental Protection Agency (USEPA) call
for thorough quantification of identified problems, measures of success, and documentation of the man-ner
in which plan implementation will be monitored. In essence, the agency is requiring more assurance
that federal grant dollars invested in watershed projects will result in measurable improvements in water
quality and waterbody uses. The new guidelines can be found in “Supplemental Guidelines for the
Award of Section 319 Nonpoint Source Grants to States and Territories in FY 2003”.1 This guidance was
developed specifically for watershed entities interested in Section 319 funding to help implement their
plans. USEPA’s objective is to ensure that federally funded projects make effective progress towards re-storing
waters impaired by nonpoint source pollution.
Plans that result from this process will be called Watershed Based Plans. The new plans, while broadly
following the seven-step approach described above, must include nine elements. Table 1-1 shows how the
seven-step and nine-element approaches relate to one another and where the nine elements are addressed
in this plan. The following section presents the recommended seven-step watershed planning process in
more detail and indicates how it incorporates the nine EPA-required elements (indicated by the use of the
notation (Element #) in boldface). Section 1.2.2 below presents an evaluation of this plan’s conformance to
the nine USEPA elements of a Watershed Based Plan.
1 See http://www.epa.gov/owow/nps/Section319/319guide03.html; also Federal Register, October 23, 2003, Vol. 68, No. 205, p. 60659.
Section 319 is part of the federal Clean Water Act.
Thorn Creek Watershed Based Plan December 2005
1–5 Introduction
Table 1-1. Relation between Seven-Step Watershed Planning and USEPA Nine Minimum Elements
1.2.1. METHODOLOGY
1.2.1.1. Identify and Assemble Stakeholders
One of the most important considerations in a successful watershed planning process is the level of in-volvement
and commitment of key individuals, or stakeholders, that reside or work in the watershed.
Ideally, local stakeholders will drive the planning process and will utilize outside resource agencies for
technical support, coordination, and funding. With the early and ongoing involvement of local commu-nity
members and local government officials, such “bottom-up” plans are more likely to be implemented
than “top-down” plans that are driven primarily by outside agencies and organizations.
Watershed Planning
Approach USEPA Minimum Elements
Section of This
Plan in Which
Addressed
1. Identify Stakeholders 1.3
2. Goals and Objectives
1.4
1.5
3. Inventory Watershed
Resources and Conditions
4. Assess Waterbody/
Watershed problems
1. Identify causes and sources that will need to be controlled to
achieve load reductions estimated within the plan
2.
3.
4.1.5.
2. Estimate load reductions expected for proposed nonpoint
source pollution management measures
4.2.
4.3.
5. Recommend
Management Practices 3. Describe the NPS management measures that need to be im-plemented
in order to achieve the load reductions estimated in
step 2; and identify critical areas
4.2.
4.3.
4.5.
4. Estimate technical and financial assistance needed, costs, and
the sources and authorities (e.g., ordinances) that will be relied
upon to implement the plan
4.4.
4.6.
4.7.
4.9.
5. Information and public education component; and early and
continued encouragement of public involvement in the design
and implementation of the plan
4.8.
5.4.
6. Implementation schedule 4.9.
7. Interim, measurable milestones 5.2.
6. Develop Action Plan
8. Criteria to measure success and, if necessary, reevaluate the
plan
5.3.
7. Implement
Plan and Monitor
9. Monitoring component 5.3.
Thorn Creek Watershed Based Plan December 2005
1–6 Introduction
Another key element of stakeholder involvement is strong leadership, particularly at the community
level. In many cases, leadership comes down to one or two key individuals who can convey their enthu-siasm
and knowledge to potential stakeholders and outside agencies. Continuity in leadership is also
critical, as planning and implementation can take many years to complete. With consistent internal sup-port,
momentum and enthusiasm are maintained. Without it, the planning process can wither and die.
Typical Steps:
• Assemble stakeholders in an initial meeting.
• Discuss known watershed characteristics and problems.
• Identify a preliminary list of watershed issues and concerns.
• Identify an initial planning structure to engage stakeholders and resource experts in future meet-ings
(e.g., setting up policy and technical advisory committees).
1.2.1.2. Establish Goals
Before any detailed analysis of the watershed is conducted, it is important that the watershed stake-holders
identify a preliminary set of goals. These goals should reflect the concerns and desired outcomes
of people living and working in the watershed. While the initial goals may change over time as more in-formation
becomes available, they provide the basic direction for the planning steps that follow.
While the focus of this watershed planning guidance is on water quality and waterbody uses, it is also
desirable at this stage of the planning process to identify related concerns and goals. For example, flood-ing
problems are often associated with water quality problems and should be identified if they are sig-nificant
concerns in the watershed.
As a note of caution, there is often a tendency to rush to identify detailed problems and solutions in the
early meetings of the stakeholders. While some discussion along these lines may be inevitable, partici-pants
should be directed to identify goals that reflect desired outcomes for the watershed. For example,
improved water quality, improved fishing, and enhanced recreational access all are appropriate goal
categories. In contrast, better stormwater management, improved education, and stream restoration are
potential solutions, but are not goals.
Typical Steps:
• Identify impartial facilitator.
• Identify a range of potential watershed goals.
• Discuss and prioritize key goals.
1.2.1.3. Inventory Watershed Resources and Conditions
Watershed inventories are needed to document existing conditions and problems in the watershed. The
inventories should be directed specifically at factors related to the previously identified goals. Invento-ries
are sometimes done on an iterative basis — the quality and thoroughness of readily available infor-mation
will determine whether more in-depth data collection may be necessary.
Typical Steps:
• Assemble any readily available data from reports, particularly the Illinois Water Quality Report.
Thorn Creek Watershed Based Plan December 2005
1–7 Introduction
• Map any available spatial information (e.g., land use, wetlands, and other natural resources).
• Visually evaluate key waterbodies and natural resources (particularly the stream corridor), docu-menting
simple physical characteristics and problems.
1.2.1.4 Assess Existing Watershed and Waterbody Problems and Threats
An effective watershed planning process requires a logical, understandable procedure to process poten-tially
large quantities of information about watershed problems. The Illinois EPA has documented such a
process in its biennial Illinois Water Quality Report. The logic of this process starts with a consideration of
desired waterbody uses and their impairments and proceeds to an analysis of causes of impairment and
sources of pollution. The assessment approach should consider not only existing problems, but also
those problems that can be predicted to arise if watershed conditions (e.g., land use) change.
The assessment should utilize appropriate analytic tools such as geographic information systems (GIS)
and pollutant load spreadsheets. Depending on the complexity of issues in the watershed, water quality
models also may be appropriate.
Typical Steps:
• Identify potential uses and use impairments from 305(b) Report.
• Utilizing local resource experts, update the IEPA assessment to the level of detail necessary to
understand the watershed.
• Identify and quantify the causes and sources or groups of similar sources that will need to be
controlled to achieve estimated pollutant load reductions (Element 1).
• Identify critical areas for protection and/or remediation.
1.2.1.5. Recommend Management Practices for Prevention and Remediation
Based on the previously identified causes of use impairment and the specific sources that are contribut-ing,
appropriate control objectives and best management practices (BMPs) should be identified. While
there is sometimes a tendency to simply borrow lists of BMPs from published guides or other watershed
plans, it is important that recommended practices be tailored to the specific conditions, needs, and priori-ties
of the watershed.
Typical Steps:
• Identify specific objectives necessary to address the causes and sources of impairment (e.g.,
phosphorus reduction, flow rate control, streambank stabilization).
• Estimate of the pollutant load (or flow) reductions expected to achieve the objectives (Element 2).
• Describe the nonpoint and point source management measures that will need to be implemented
to achieve the load reductions estimated above and an identification (using a map or a descrip-tion)
of the critical areas in which those measures will be needed to implement this plan (Element
3).
• In addition to BMPs necessary to reduce existing impairments, identify practices needed to pre-vent
or minimize future problems (e.g., those associated with new development) as well as
measures needed to maintain existing high quality conditions (e.g., ongoing stewardship and
management of natural areas).
Thorn Creek Watershed Based Plan December 2005
1–8 Introduction
1.2.1.6. Develop an Effective Action Plan
An action plan is needed to translate the quantitative recommendation of various BMPs into specific, im-plementable
actions and programs. Some of the critical considerations of an action plan are what specifi-cally
needs to be done, who will do it, and when it should be accomplished. It is essential to have broad
stakeholder involvement in developing the action plan. In particular, both the resource experts who have
identified recommended actions and the recommended implementers (e.g., local government officials
and major landowners) must be involved. In a successful planning process, there will be considerable in-teraction
and feedback during this part of the process, resulting in mutual education of the participants
and an action plan that is both implementable and effective.
Typical Steps:
• Identify specific recommendations for BMPs and implementation programs.
• Where appropriate, compare these to ongoing practices and programs (e.g., watershed develop-ment
ordinances) already in place in the watershed.
• Identify responsible parties to undertake recommended actions.
• Identify the amount of technical and financial assistance needed, the associated costs, and/or the
funding sources and authorities that will be relied upon to implement the plan (Element 4).
• Develop an information/education component, particularly targeting local residents, landowners,
and local government officials (Element 5).
• Develop an implementation schedule for the various action plan recommendations (Element 6).
• Describe interim, measurable milestones for determining whether recommendations are being
implemented (Element 7).
• Develop a set of criteria that can be used to determine whether pollutant loading reductions and
related plan objectives are being achieved over time (Element 8).
• Develop a monitoring component to evaluate the effectiveness of the implementation efforts over
time, measured against the criteria referenced above (Element 9).
1.2.1.7. Implement Plan and Monitor Success
If the preceding steps have been rigorously pursued, there should be a strong likelihood of implementa-tion
success. Nonetheless, the planning process needs to continue well after the action plan has been
completed. In particular, a mechanism needs to be in place to report back to stakeholders and implemen-ters
about implementation progress.
Typical Steps:
• Identify an entity from the stakeholder group to track plan implementation.
• Following the criteria and milestones referenced above, track plan implementation activities on a
regular basis (e.g., annually).
• Contact stakeholders and implementers if progress is lacking.
• Inventory and monitor changes (i.e., improvements) in resource conditions with respect to crite-ria
identified above (e.g., chemical, physical, and biological conditions.
• Periodically compare implementation success to plan goals, recommendations, and criteria to de-termine
whether new actions need to be added to the plan, or whether the plan’s goals and objec-tives
need to be revised.
• Revise plan accordingly.
Thorn Creek Watershed Based Plan December 2005
1–9 Introduction
1.2.2. EVALUATION OF PLAN CONFORMITY TO THE NINE MINIMUM ELEMENTS
This section assesses the performance of the Thorn Creek Watershed Based Plan (TCWBP) with respect to the
USEPA nine minimum elements. On the whole, this plan follows the guidelines, although there are areas
that would benefit from an upgrade in the future. The best assembled and most time intensive part of the
TCWBP probably is the Watershed Resource Inventory (Section 2), which assesses water and habitat qual-ity
with considerable thoroughness and addresses Element 1. The most significant shortcoming in the
TCWBP relates to Element 3 because of the plan’s lack of specificity about BMP installation sites, overall
costs and pollutant load reductions, and responsible parties.
The identification of causes and sources of impairments called for in Element 1 of the guidelines can also
be found in summary form in Section 4.1.5. This table is comprehensive and integrates the major areas of
the plan by looking back to the goals and objectives of the stakeholders and forward to the application of
the Watershed Management Recommendations (WMRs). While the Watershed Resource Inventory in
Section 2 describes the impairments and causes quantitatively and in detail, so that this portion of the
plan is on solid footing, the Water Quality Assessment in Section 3 is not as conclusive with regard to the
sources. Further study is needed to isolate the sources of several impairments, and Section 3 specifies the
types of study required and watershed locations to target.
The WMRs in this plan are a generalized list of nonpoint source pollution management measures, as re-quired
in Element 3. Those most appropriate for the watershed were selected in consultation with stake-holders,
after which priority (geographic) areas, estimated costs, and expected pollutant load reductions
were then developed for each WMR. For the most part, however, the recommendations remain general.
Critical areas are no more specific than the subbasin level, whereas — for structural BMPs at least — spe-cific
sites should be selected. Estimated costs are on a per-unit basis, and expected pollutant load reduc-tions
(Element 2) are given on a percentage basis for particular pollutant sources (Section 4.3. and 4.4.).
The exception to this generality is the Short Term Action Plan, presented in Section 4.5., which outlines a
set of WMRs to implement over the next three years. These activities are mostly presented in numerical
terms, so that the total cost and, to an extent, the pollutant load reduction can be estimated. However, the
TCWBP does not evaluate the relative pollutant contribution of, for example, outdated dry bottom deten-tion
basins, then quantify the benefit of retrofitting a specified number of them. Not only does the plan
provide too little information to select the most cost-effective WMRs, it does not attempt to determine es-timated
pollutant reductions on an absolute or mass-balance basis. Again, however, it is difficult to reach
this level of specificity when the sources of impairment and their relative contributions to water quality
problems are not known with great certainty. The TCWBP is an evolving document written in the absence
of this certainty, and so it takes the approach of establishing a framework for more detailed planning. The
Short Term Action Plan provides an example of how to specify the work to be performed, although it
does not provide specific BMP installation sites.
Identification of the responsible parties and financial assistance required to implement watershed projects
is required by Element 4. Various implementation partners are associated with the WMRs in a matrix
given in Section 4.9 (Action Plan Summary for Water Quality Improvement). Financial assistance, in turn,
is covered in Section 4.7 with an up-to-date list of potential funding sources that concentrates mainly on
project grants as opposed to planning grants. While the territory within Element 4 has been covered, not
all the connections have been made. Places, projects, people, and funding have not been connected to-gether
at a level of detail beyond the Short Term Action Plan.
Thorn Creek Watershed Based Plan December 2005
1–10 Introduction
Element 5, the information and education component, was approached in an integrative way, as a micro-cosm
of the entire plan. Goals and objectives for the education campaign were developed through stake-holder
input, general methods of outreach were described and evaluated, and a specific strategy that
identified target audiences and messages was developed with assignment of priorities and responsible
parties (Section 4.8). An evaluation mechanism was also developed for the education strategy (Section
5.4).
Element 6 requires an implementation schedule for nonpoint source control measures, the water quality-related
WMRs in this plan. This was done on both a short- and longer-term basis. In Section 4.9, the Ac-tion
Plan Summary for Water Quality Improvement, the general priority of each of the WMRs was
ranked by timeframe for implementation, which in turn suggested the most important or highest priority
WMRs to feed into the Short Term Action Plan (implementation over three years). Milestones to measure
interim progress were developed to guide and monitor activities to be undertaken from three to 15 years
hence (Section 5.2, Watershed Management Recommendation Implementation Monitoring Strategy), as
required by Element 7. These are oriented toward tracking the implementation of the WMRs. Achieve-ment
of water quality objectives (i.e., outcomes) is dealt with in matrix form in Section 5.3. This table ad-dresses
Elements 8 and 9 by establishing indicators and milestones for reaching water quality objectives.
Thorn Creek Watershed Based Plan December 2005
1–11 Introduction
1.3. Thorn Creek Watershed Stakeholders
The following 107 individuals volunteered or were invited to participate in the Thorn Creek Watershed
Planning process. Several also participated in the Technical Advisory Committee (TAC) or Steering Com-mittee
(SC).
Name Organization TAC SC
Ders Anderson Openlands Project
Katie Armstrong Former Village Trustee, Village of Park Forest
Marcus Arnold Transportation Planner, South Suburban Mayors & Managers Associa-tion
Steve Aultz
Cindy Bakkom Superintendent of Public Programs and Education, Forest Preserve Dis-trict
of Will County
●
Diane Banta National Park Service
Janet Basek
James Bilotta Board Member, Will County
Lynn Boerman C2000 Ecosystem Administrator, Illinois Department of Natural Re-sources
Region 2
●
Tim Bradford Assistant to Supervisor, Rich Township
Scott Bullard Forest Preserve District of Cook County ●
Margaret Burns-
Westmeyer
Beautification Committee, Chicago Heights ●
Steven M. Bylina Jr. General Superintendent, Forest Preserve District of Cook County
Roland Carlson Village of Thornton ●
Mary Carrington Governors State University
Joseph Christofanelli Manager, Village of Glenwood
Karen D'Arcy Governors State University ● ●
James Daugherty District Manager, Thorn Creek Basin Sanitary District ● ●
Don De Graff President, Village of South Holland
Kristi DeLaurentiis South Suburban Coordinator, Metropolitan Planning Council ●
Anthony DeLuca Mayor, City of Chicago Heights
Marcy DeMauro Forest Preserve District of Will County
Donna Dettbarn Supervisor, Monee Township
Rose Marie DeWitt Will/South Cook Soil & Water Conservation District ●
Charles Dieringer
Judy Dolan-Mendelson
Kerry Durkin Village of Glenwood
Stuart Fagan President Governors State University
Stina Fish URS Corporation
Bud Fleming Cook County Department of Planning & Development
Mark Franz Manager, Village of Homewood
Mary Ann Gearhart Will County Board
Thorn Creek Watershed Based Plan December 2005
1–12 Introduction
Deutsch
Carl Glassford Open Space Alliance/Sauk Calumet Sierra Club ●
Timothy Good Forest Preserve District of Will County
Jeffrey D. Greenspan
Chuck Gruberman Village of Homewood
Michael Grubermann Administrator, Village of Monee ●
Rob Gunther Village of Park Forest
David Guritz Irons Oaks Environmental Learning Center
State Senator Debbie
Halvorson
Andy Hawkins J. F. New & Associates, Inc. ●
Andre Haynes Cook County Highway Department
Hall Healy
Jennifer Hindel Thorn Creek Basin Sanitary District ●
Richard Hofeld President, Village of Homewood
Jean Hurrle
Robert Jankowski District Conservationist, US Department of Agriculture/Natural Re-source
Conservation Service
John Joyce Village of Park Forest
Karen Kaempf Thorn Creek Audubon
Nancy Kaszak Executive Director, CorLands
Anne Kawaters
Bill Keonig Forest Preserve District of Cook County
Mary Kilday Cook County Highway Department
Dave Kircher Forest Preserve District of Cook County ●
Kenneth W. Kramer Trustee, Village of Park Forest ● ●
Jeanne Maggio Mayor, Village of Glenwood
Al Marconi
Chris Marinovich Superintendent of Conservation, Forest Preserve District of Cook
County
Dave Mauger Forest Preserve District of Will County ● ●
Larry McClellan
Sally McConkey Professional Scientist, Illinois Department of Natural Resources / Illi-nois
State Water Survey
Alvin McCowan President, Village of University Park
Jon Mendelson Governors State University ●
Jeff Mengler Botanist/Wetland Ecologist, U.S. Fish and Wildlife Service
Greg Meyer Director, Homewood-Flossmoor Park District
Peter Miller HDR Engineering
Jim Morley Supervisor, Rich Township
Janet Muchnik Former Village Manager, Village of Park Forest
Joan Murphy Commissioner, Cook County Building
Thorn Creek Watershed Based Plan December 2005
1–13 Introduction
Jason Navota Northeastern Illinois Planning Commission, Project Manager
David Niemeyer
Leon Norwood South Suburban COPE
Timothy O'Donnell President, Village of Monee
Mary Orlick City of Chicago Heights ●
John Ostenburg President,Village of Park Forest
David Owen President, Village of South Chicago Heights
Edward Paesel Executive Director, South Suburban Mayors & Managers Association
Michael Pasteris Executive Director, Forest Preserve District of Will County
Paul Peterson Administrator, Village of South Chicago Heights ●
James Phillips Forest Preserve District of Cook County
Scott Ristau Illinois Environmental Protection Agency
Steve Rodgers
Richard Rosenthal President, The Land Group ●
Max Salmon Village of Thornton ● ●
Bill Saylor Illinois State Water Survey
John Schaefer Director of Public Works, Village of Homewood
Jean Sellar US Army Corps of Engineers
Connor B. Shaw Possibility Place Nursery
Elbert Shaw Village Manager, Village of University Park
Deborah Simms Commissioner, Cook County Building
Thomas Somer Supervisor, Bloom Township
John Spomar Norco Cleaners, Inc. ●
Jack Swan President, Village of Thornton
Glenn Sweeny
Renee Thakali Midewin National Tall Grass Prairie
Paul Vicari Project Manager, J. F. New & Associates Inc.
Amy Walkenbach Illinois Environmental Protection Agency
Tyson Warner Planning Division, Will County Land Use Department
Tammy Watson Division of Ecosystems, Illinois Department of Natural Resources
Bill White Peoria Field Office, Illinois State Water Survey
Jeff Wickenkamp Northeastern Illinois Planning Commission ●
Valencia Williams Director of Planning, City of Chicago Heights
Nancy Williamson Illinois Department of Natural Resources, Region 2
Dr. Mary V Woodland Storm Water Resource Committee
John Yunger
Richard Zimmerman Village Administrator, Village of South Holland
Frank Zuccarelli Supervisor, Thornton Township
Thorn Creek Watershed Based Plan December 2005
1–14 Introduction
1.4. Initial Concerns and Goals for the Thorn Creek Watershed
1.4.1. LIST OF ISSUES AND CONCERNS FROM MEETING DECEMBER 8, 2003
1. Lack of recognition for good actions — businesses who comply on their own
2. Negative images — self-perpetuating
3. Lack of stormwater management
4. All parties should be represented
5. Habitat fragmentation
6. Development pressure on the habitat
7. Degraded streambanks of public and privately-owned land
8. The need for “real” outreach programs
9. Implementation-making sure things happen in areas that need action.
10. Enforcement of state laws
11. Intra-governmental conflicts
12. Loss of aquatic biodiversity
13. Decaying infrastructure — locating and repairing
14. Protection of Thorn Creek headwaters
15. Maintenance of high-quality natural habitats
16. Acquisition of open space — low cost of land in south suburbs
17. Exotic species
18. Being satisfied with progress in small steps: acceptance of restoration management practices
19. Public buy-in: proving that environmental improvements will provide an economic benefit and
represent progress
20. Degraded streambanks
21. Lack of water in the upstream portion of the creek
22. Past BMP performance/local applicability
23. Ordinance adoption in line with watershed goals
24. Ineffectual planning that is not implemented
25. Lack of citizen involvement
26. Competition for funding (Butterfield and Thorn Creeks) — coordination
27. Public education
28. Lack of bike trails
29. Aquifer protection
30. Wellhead protection
31. Public education about the aquifer
32. Conservation of sensitive natural areas
33. Educating decision-makers about watershed conservation
34. Educating the private sector (e.g. builders)
35. Involving all watershed communities in protection efforts
Thorn Creek Watershed Based Plan December 2005
1–15 Introduction
36. Access to the creek at appropriate locations
37. Inter-governmental competition may impede cooperation on watershed protection
38. Water quality
39. Debris in the stream
40. Incorporating infrastructure into the plan (e.g.26th Street Dam)
41. Mitigation planning and stormwater management — should be used together
42. Greenways
43. Infrastructure projects — should consider watershed impacts
44. Stormwater detention — removal or rehabilitation of dysfunctional or poorly engineered facilities
45. Errors on watershed maps
46. Inability of organisms to migrate in the stream
47. Monitoring of point sources (e.g. Thorn Creek Basin Sanitary District)
48. Inclusion of the private sector
49. NPDES Phase II regulation — should be incorporated into the process
50. Wetland restoration process as related to stormwater
51. Inability of native species to re-colonize
52. Ubiquitous application of herbicides and pesticides
53. “Not my problem” — ownership of stormwater infrastructure repairs and maintenance
54. Conflicts among environmental organizations
55. Streambank stabilization
56. Flooding
1.4.2. GOALS AND OBJECTIVES FOR THE THORN CREEK ECOSYSTEM PARTNERSHIP AS
NOTED IN A WATERSHED PLAN FOR THORN CREEK
Goals
• To ensure the preservation, protection, and restoration of natural landscapes and to enhance eco-system
processes.
• To integrate the watershed’s natural resources into the life and future of the community.
• To foster and facilitate increased intergovernmental, interagency and private sector cooperation
within the Thorn Creek watershed.
• To foster and facilitate increased citizen involvement within the Thorn Creek watershed.
Objectives
• To protect critical open space remaining in the watershed.
• To restore, enhance, and maintain open spaces and natural areas.
• To improve water quality, hydrology and hydraulics in watershed streams, lakes, and wetlands.
• To improve environmental education, public outreach, and scientific research.
• To improve conservation / environmental practices related to sustainable development.
Thorn Creek Watershed Based Plan December 2005
1–16 Introduction
• To encourage the use of natural resources to create an (socio) economic benefit to local communi-ties.
Thorn Creek Watershed Based Plan December 2005
1–17 Introduction
1.5. Thorn Creek Goals and Objectives
The following set of goals and objectives was developed using the information collected and identified in
Section 1.4.
1.5.1. OVERALL GOAL
Preserve open space and habitat that serve multiple functions such as flood damage reduction, water
quality improvement, habitat, and recreation, especially permeable soils, depressional storage, wetlands,
and hydric soils. Create a culture in which water (wetlands, waterways, lakes, ponds) is treated as a re-source
rather than a waste product.
1.5.2. RESOURCE BASED GOALS
1.5.2.1. Habitat and Natural Resources
Issues and Concerns
• Habitat fragmentation and degradation
• Loss of aquatic biodiversity
• Open space protection
• Exotic species
• Aquatic migration
• Degraded streambanks
• Lack of water flow in the upstream portion of the creek
• Unprotected headwaters
• Wetlands as stormwater facilities
• In-stream debris
Goal (Priority 1)
Protect and restore terrestrial and aquatic habitat quality and quantity within the watershed.
Objective
1. Protect, manage, and restore important habitat areas, biological diversity, buffers, green corri-dors,
and “stepping stones” between habitat areas.
1.5.2.2. Water Quality
Issues and Concerns
• Aquifer and wellhead protection (groundwater)
• Lack of point sources monitoring
• Overapplication of herbicides and pesticides
• Lack of good stormwater management and detention
• Joint mitigation planning and stormwater management
Thorn Creek Watershed Based Plan December 2005
1–18 Introduction
Goal (Priority 2)
Protect and enhance surface water quality to support uses designated for Thorn Creek by the Illinois
Environmental Protection Agency.
Objectives
1. Reduce contamination (bacteria, fecal coliform, pathogens) from urban runoff, sanitary sewer
overflows or aging infrastructure (leakage, and/or failure of connections, lift stations, etc.), illicit
connections of sanitary sewers or other waste discharge pipes to storm sewers, and animal waste
including pets, horses, and urban wildlife (geese, other birds, raccoons, deer).
2. Reduce organic enrichment / low dissolved oxygen problems from urban runoff; sanitary sewer
overflows or aging infrastructure (leakage, and/or failure of connections, lift stations, etc.); illicit
connections of sanitary sewers or other waste discharge pipes to storm sewers; and animal waste
including pets, horses, and urban wildlife (geese, other birds, raccoons, deer).
3. Reduce nutrient loads (phosphorous and nitrogen) and algal growth from urban runoff; point
source discharges / illicit stormsewer connections; and agricultural activity.
4. Reduce aquatic life toxicity (primarily total dissolved solids, chlorides, and sulfates) from urban
runoff, road salt and storage / highway maintenance and runoff, and point discharges / illicit
stormsewer connections.
5. Reduce fly dumping and debris loads in the stream.
6. Reduce hydrologic disturbance / flow alterations from hydrologic modification and urban devel-opment.
1.5.2.3. Water Supply
Issues and Concerns
• Aquifer and wellhead protection (groundwater)
Goal (Priority 3)
Protect and enhance ground water quality and quantity.
Objective
1. Identify and protect important groundwater recharge areas, infiltration areas, and areas of high
aquifer sensitivity / susceptibility to pollution, including wellhead protection areas.
1.5.2.4. Recreation and Access
Issues and Concerns
• Greenways
• Lack of sufficient bike trails
• Access to the creek at appropriate locations
Goal (Priority 4)
Thorn Creek Watershed Based Plan December 2005
1–19 Introduction
Increase, improve, and promote recreational resources, opportunities, and access throughout the wa-tershed
for social and economic benefits.
Objectives
1. Identify and prioritize areas for recreational enhancement including trails, trail access, and alter-native
transportation networks.
2. Promote the creek and increase demand for natural resource-based recreation activities.
1.5.2.5. Flooding2
Issues and Concerns
• Flooding
Goal (Priority 5)
Reduce flooding and flood damages.
Objectives
1. Reduce flow rates and volumes from existing developed areas.
2. Minimize increases in runoff rates and volumes associated with new development.
3. Manage drainage ways to preserve stormwater conveyance.
1.5.3. WATERSHED COORDINATION GOALS
1.5.3.1. Communication, Coordination, and Governance
Issues and Concerns
• Lack of ordinances and enforcement
• Intra- and inter-governmental and organizational conflicts and competition
• NPDES Phase II regulation
• Infrastructure maintenance and construction
• Inaccurate maps
• Ineffectual plans
Goal (Priority 1)
Increase coordination, cooperation, research, and informed decision-making among governments,
agencies, non-profits, and the private sector.
Objectives
1. Create public/private partnerships to implement the Watershed Based Plan and pursue funding
opportunities.
2. Improve decision-making by encouraging watershed communities to share accurate information
and pursue technical assistance from appropriate agencies.
2 Additional stormwater-related goals and objectives are included under Water Quality, Section 1.5.2.2.
Thorn Creek Watershed Based Plan December 2005
1–20 Introduction
3. Provide technical assistance to those seeking guidance in the design and/or implementation of
best management practices.
4. Coordinate recreational, flood control, habitat, and water quality objectives.
Goal (Priority 4)
Improve procedures and ordinances so that they are up to date, aligned with watershed protection
goals, aligned with adopted plans, and enforced/enforceable.
Objectives
1. Strengthen and enforce existing regulations, especially those regulations related to non-point
source pollution.
2. Cooperate watershed-wide to coordinate and achieve regulatory goals such as NPDES require-ments.
3. Coordinate / incorporate watershed management plans and strategies into local plans and poli-cies.
1.5.3.2. Education and Stewardship
Issues and Concerns
• Negative perceptions of creek / public buy-in
• Inadequate outreach and public education
• Lack of citizen involvement
• Lack of understanding / acceptance of restoration management practices
• Lack of involvement of all watershed communities and private sector
• Recognition for good actions
Goal (Priority 2 — tie)
Educate the public, public officials, community leaders, businesses, and developers about the wa-tershed
and their impact and role in protecting watershed resources.
Objectives
1. Develop and disseminate watershed planning and protection information to the public and com-munity
leaders and decision-makers.
2. Develop public relations and media strategies to educate, involve, and invigorate the public and
community leaders and decision-makers.
Goal (Priority 2 — tie)
Increase involvement in watershed leadership, stewardship, monitoring, and volunteer activities.
Objectives
1. Encourage stewardship, coordination, cooperation, and best management practice implementa-tion
with key corporate and political entities.
Thorn Creek Watershed Based Plan December 2005
1–21 Introduction
2. Create and implement short and long-term maintenance, management and monitoring plans for
all protected open space including uplands, wetlands, waterways, stormwater conveyance and
detention/retention facilities and lakes.
Thorn Creek Watershed Based Plan December 2005
2–1 Watershed Resource Inventory
2. THORN CREEK WATERSHED RESOURCE INVENTORY
Thorn Creek Watershed Based Plan December 2005
2–2 Watershed Resource Inventory
2.1. Climate
The climate of the Thorn Creek watershed is continental, with wide temperature fluctuations during the
course of each year. Summer maximum temperatures are generally in the eighties and low nineties
(Fahrenheit degrees) with lows in the fifties and sixties, while high temperatures in winter are generally
in the twenties to thirties with lows in the teens and twenties. Precipitation is usually heaviest in the
growing season and lightest in midwinter, with the greatest amounts of snowfall coming in December
through March and rarely exceeding 12 inches in depth.
The most in-depth climate history data near the Thorn Creek watershed is from Midway Airport (Tables
2-1 and 2-2). Average and extreme temperatures and precipitation levels should be fairly consistent
throughout the area.
Table 2-1. 1971-2000 Temperature Normals for Chicago Midway Airport (degrees F)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
High 30.7 36.1 47.4 59.2 71.3 80.8 84.7 82.3 75.1 63.2 48 35.6 59.5
Low 16.2 21.3 30.6 40.2 50.9 60.7 66.3 65 56.7 44.9 33.6 22.2 42.4
Mean 23.5 28.7 39 49.7 61.1 70.8 75.5 73.7 65.9 54.1 40.8 28.9 51
Days >90 0 0 0 0.1 1.3 4.6 8.4 5 1.9 0.1 0 0 21.4
Days <32 16.3 10.7 3.4 0.1 0 0 0 0 0 0 1.9 10 42.6
Table 2-2. 1971-2000 Mean Precipitation Normals for Chicago Midway Airport (inches)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Precipitation 1.95 1.78 2.83 3.82 3.86 4.16 3.82 3.91 3.45 2.79 3.22 2.76 38.3
Snowfall 12.9 10.3 6 1.4 0 0 0 0 0 0.1 2.3 10.1 43.1
Days with
>0.1
5 4.6 6.6 7.2 7.1 6.4 6.1 6.3 5.5 5.6 6.7 5.3 72.5
Source: Illinois State Climatologist’s Office, a part of the Illinois State Water Survey, www.sws.uiuc.edu/atmos/ statecli.
Thorn Creek Watershed Based Plan December 2005
2–3 Watershed Resource Inventory
2.2. Geology and Physiography
2.2.1. BEDROCK AND GLACIAL GEOLOGY
The bedrock of the Thorn Creek watershed is primarily comprised of Silurian dolomite and Ordovician
Maquoketa shale. Outcrops of Silurian dolomite of the Thornton Reef formation are generally restricted
to artificial exposures like Thornton Quarry, but a few bedrock outcrops are found near Glenwood Road
in Glenwood and Margaret Street in Thornton. The features of the bedrock surface topography generally
include coarse grained sediments such as sands and gravels that form important productive aquifers. On
top of the bedrock lies a mantle of glacial material. The surface geology of the Thorn Creek watershed,
like that of the Great Lakes area as a whole, was formed largely by glacial action.
The land surface of the Thorn Creek watershed is made up of two distinct physiographic regions. The
northeastern third of the watershed occupies the Chicago Lake Plain, marking the furthest advance of the
Wisconsin Glacier, which formed Lake Michigan. The land here is very level, interrupted only by a pair
of beach ridges, the Glenwood and the Calumet. This area is composed of lacustrine deposits, fine
grained sediments which were once the base of temporary lakes that often formed along the margin of
the glacier. Lacustrine sediments are usually poorly drained and may cause water problems for construc-tion
projects.
The southwestern two-thirds of the watershed lies on a broad upland composed of the Tinley Moraine,
the Westmont Moraine, which is the innermost moraine of the Valparaiso system in the area, and associ-ated
ground moraine. The topography is rolling, but in many places, particularly forested areas near
Thorn Creek, deep ravines have developed. This area is composed primarily of till, a compact mix of
clay, silt, and sand particles that form a matrix around larger particles.
Moraines are formed when a glacial margin advances and melts back several times, depositing till at the
glacier’s base or allowing sediment to flow off the melting edge of the mass of ice. The hills left after each
advance are called end moraines, and a number of notable examples of this geographic feature are lo-cated
in the watershed. The Westmont and Clarendon moraines on the southern border of the watershed
form the divide between the Great Lakes/North Atlantic watershed and the Mississippi River/Gulf of
Mexico watershed. Here also is the divide between the Thorn Creek Watershed, with its north flowing
streams, and Black Walnut Creek flowing south to the Kankakee, the Illinois, and eventually the Missis-sippi
River. The Tinley moraine forms the hills of Chicago Heights.
Across the landscape, on top of these glacial deposits, lies a layer of windblown silt called loess. Loess is
the parent material of the region’s rich soils. It is derived from sediments that flowed into major melt-water
valleys and were blown from the floodplain. In the Thorn Creek watershed, loess tends to be less
than two feet thick over the coarser outwash, tills, and lacustrine sediments.
2.2.2. TOPOGRAPHY AND STREAM GRADIENT
The fairly narrow watershed of the main stem of Thorn Creek follows a general orientation from south-west
to northeast. Significant areas of floodplains occur generally above Sauk Trail Lake and in the lower
reaches of the main stem (approximately the lower half of the watershed).
Thorn Creek itself begins in the Valparaiso moraine near Crete-Monee Road, runs along the western
margin of glacial period Lake Steger, crosses the Tinley moraine at a low point in Chicago Heights, and
enters the Little Calumet River after traversing about 6 miles of the Lake Chicago plain. In the moraine,
some of the valley bluffs are 35 and 40 feet high, while on the lake plain the average is only 15 feet. Fig-
Thorn Creek Watershed Based Plan December 2005
2–4 Watershed Resource Inventory
ure 2-1 (Appendix A) provides a color-classified map of elevations, as well as floodplains, within the wa-tershed.
The elevation change from the headwaters, at 790 feet above sea level, to the mouth, at 585 feet,
is a little more than 200 feet along a horizontal distance of about 20 miles, an average gradient of 10 feet
per mile. The general shape of the profile (Figure 2-2, Appendix A) illustrates the substantial differences
in stream gradient between the upper morainal portion of the watershed, where the gradient is over 17
feet per mile, and that of the Lake Chicago Plain to the north, where it is less than 3 feet per mile.1
2.2.3. SOILS
There are two soil associations in the upper (southern) morainal portion of the Thorn Creek watershed,
one formed in silty clay loam till, the other in heavier till of silty clay texture (Figure 2-3, Appendix A). A
common soil of the latter association is Bryce silty clay (235), a hydric soil of small depressions and drain-ageways,
formed under wet prairie or marsh vegetation. Another common soil of this association is
Frankfort silty clay loam (320A–C soil type), an upland soil of level or gently rolling terrain. Frankfort
probably supported prairie and/or savanna vegetation. Two other soils, Napanee silt loam (228B-C) and
Chatsworth silty clay (241D–F) are found along the wooded slopes of the upper Thorn Creek Valley.
Soils of the silty clay loam association are widely distributed in this part of the watershed. The common
hydric soil is Ashkum silty clay loam (232), found in small drainageways and wet spots throughout. Two
soils, Blount silt loam (23) and Morley silt loam (194C–F), are characteristic of the extensive woodlands of
this area. Blount is found on level uplands, while Morley is the soil of slopes. Two other widely distrib-uted
soils, Beecher silt loam (298) and Markham silt loam (531), are also located on uplands, but probably
originated under prairie and/or savanna vegetation. They are the loamy analogues of Frankfort.
The major soil of the Thorn Creek floodplain is Sawmill silty clay loam (107). It occurs both in the upper,
morainal reaches of the creek and in the floodplain of Thorn Creek as it traverses the Chicago Lake Plain.
Within the watershed, the boundary between the Tinley ground moraine and Chicago Lake Plain runs in
an arc from just south of Route 30 at the Indiana state line in the southeast to the intersection of 183rd
Street and Chicago Road in the northwest.
Two groups of soils are characteristic of the Chicago Lake Plain: soils of the lake plain proper, and those
of the two beach ridges associated with lake plain. Additionally, soils developed on bedrock outcrops
may be found in several places, most notably in the vicinity of the Thornton Quarry.
Major soils of the lake plain itself are Milford silty clay loam (69), Martinton silt loam (189), and Del Rey
silt loam (192). Milford is a poorly drained soil of flats, shallow depressions and drainageways. Martinton
and Del Rey occur at slightly higher elevations, and are somewhat better drained. Martinton developed
under prairie vegetation; Del Rey may have originally supported savanna or open woodland. Morley, a
principal forest soil of the moraines, also occurs on lake plain, in narrow strips along the wooded slopes
of the Thorn Creek valley. Conversely, Milford, Martinton and Del Rey are found in the morainal region,
occupying the basin of Glacial Lake Steger, an ice-front lake, whose basin lies between the Tinley moraine
and Valparaiso ground moraine.
1 Sources: Thorn Creek: An Inventory of the Region’s Resources, 2000. Illinois Department of Natural Resources, Critical Trends As-sessment
Program. Bretz, J. Harlan. 1955. Geology of the Chicago Region. Part II – The Pleistocene. Illinois State Geological Survey Bulle-tin
65.
Thorn Creek Watershed Based Plan December 2005
2–5 Watershed Resource Inventory
Oakville fine sand (741) and Wesley fine loamy sand (141) are the principal soils of the Glenwood Beach,
the outermost of the Chicago Lake Plain beach ridges. Oakville is found on the ridge tops, while Wesley
occupies the flanks of the ridge. Watseka loamy fine sand (49) is the major soil of the Calumet Beach. Gil-ford
fine sandy loam (201) is found on flats either within or adjacent to the beach ridge. Rockton loam
(503B) is the main soil overlying the dolomite outcrops. It is found primarily in the vicinity of the Thorn-ton
Quarry.2
2.2.4. AQUIFER SENSITIVITY
The groundwater in the Thorn Creek watershed is ample and of good quality, and 1,543 private wells and
26 public water supply wells make use of this resource.3 Anecdotal evidence suggests that a previously
discovered cone of groundwater depression in Chicago Heights disappeared when the village switched
from groundwater to Lake Michigan water in 2003. Ford Heights switched to lake water in the same year
as well.
The watershed’s groundwater is drawn from relatively shallow bedrock fissures that are covered by thick
surface soils. These thick overlying soils help protect the groundwater from contamination by pollutants
that might leech through the surface into the groundwater supply.4
2 Sources: Soil Survey of DuPage and Part of Cook Counties, Illinois, USDA, Soil Conservation Service. Soils of DuPage and parts of Cook
County, Illinois. 1979. Illinois Agricultural Experiment Station Report No.108. Wascher, H.L., J. D. Alexander, B. W. Ray, A. H. Bea-vers,
and R. T. Odell. 1960. Characteristics of soils associated with glacial tills in northeastern Illinois. University of Illinois College of Ag-riculture
Bulletin 665. Will County Soils, advance sheets. 1980. Willman, H. B. and J. Lineback. 1970. Surficial Geology of the Chicago
Region, map in Willman, H. B. 1971. Summary of the Geology of the Chicago Region. Illinois State Geological Survey, Circular 460.
3 USGS figures from 1990 indicate that 36.33 million gallons per day of groundwater were withdrawn out of 293.4 mgd (12.4%) of to-tal
water use for the Thorn Creek basin.
4 Sources: Thorn Creek: An Inventory of the Region’s Resources, 2000. Illinois Department of Natural Resources, Critical Trends As-sessment
Program. Private well information from the Illinois State Water Survey private well database; public well information
from Illinois Water Inventory Program.
Thorn Creek Watershed Based Plan December 2005
2–6 Watershed Resource Inventory
2.3. Hydrology and Waterbodies
2.3.1. STREAMS
The main stem of Thorn Creek runs approximately 20 miles from its origin to its confluence. Three major
tributaries join the Creek during its course (Figure 2-4, Appendix A). Deer Creek flows into Thorn Creek
about 7.84 miles upstream from its confluence with the Little Calumet. Butterfield and North Creeks flow
into Thorn Creek further to the north, at miles 7.32 and 4.97 respectively.
Two sites on Thorn Creek have been regularly monitored for streamflow by the United States Geological
Survey (USGS): Glenwood (station #05536215) and Thornton (station #05532675). The Glenwood site is
approximately one mile upstream from the Deer Creek confluence and one half mile below the Thorn
Creek Basin Sanitary District outfall. The Glenwood station records Thorn Creek streamflow above the
confluence with Butterfield, Deer, and North Creeks, and includes effluent flow from the Thorn Creek
Basin Sanitary District (TCBSD) wastewater treatment plant. The Thornton site is approximately one half
mile below the confluence with North Creek and two miles above the confluence with the Little Calumet
River. The Thornton site records streamflow of Thorn Creek mainstem, Butterfield, Deer, and North
Creeks, and effluent flow from the TCBSD and the wastewater treatment plant on Deer Creek. The
graphs in Figures 2-5 through 2-10 present mean annual flow, ten year averages of mean annual flow,
and mean monthly flow for all years on record, illustrating the general temporal and seasonal trends for
Thorn Creek streamflow.
It is interesting to view the change in mean annual streamflow over the period of record from 1950 to
2002. At Glenwood, the trend lines for total flow and baseflow (here meaning total flow minus effluent
from the wastewater treatment plant) indicate a fairly constant baseflow of approximately 22 CFS and an
increase in total flow from 30 CFS to approximately 50 CFS, owing primarily to flow from the wastewater
treatment plant. Ten year averages show a similar trend. Monthly streamflow shows a seasonal varia-tion
from the highest flow in April to the lowest flow in October. Data for Thornton show similar pat-terns
except that the baseflow trendline shows a slight increase over the period of record and total flow is
two to three times that at Glenwood, due to the Butterfield, Deer, and North Creek tributaries.
Fairly constant baseflows at Glenwood may indicate that urban development of the main stem Thorn
Creek watershed over the period of record has not resulted in an overall increase in baseflow volume, as
might be expected due to increased amounts of impervious surface and reduced infiltration of stormwa-ter.
Several factors may contribute to this result. Significant portions of the watershed were developed
prior to 1949. Secondly, some of the increased flow due to impervious areas is being delivered to the
sanitary plant because of wet weather inflow and infiltration. A slight increase in base flow at Thornton
may be indicative of increasing urbanization and runoff in tributary watersheds, or possibly to increasing
wastewater contributions from plants located on these tributaries, but it is difficult to conclude with cer-tainty.
What is not captured by these data is the increasing flashiness or rapid variability in streamflows due to
storm events that are perhaps a more damaging impairment than an increase in overall volume. Without
comparing hydrographs for identical storm events at similar locations over time, it is difficult to prove
that the creeks are more “flashy” due to urbanization. As a partial substitute for analyzing hydrographs,
existing streamflow data can be broken into wet weather and dry weather flows to demonstrate that flow
during wet weather increased substantially over the past 50 years while dry weather flows went up rela-tively
moderately (Figure 2-11). Flows were analyzed for the Glenwood stream gauge by grouping his-torical
daily flows from 1953 through 2002 into five decades. Wet weather flows were approximated as
the top 25 percent of flows in each decade and dry weather flows as the bottom 75 percent.
Thorn Creek Watershed Based Plan December 2005
2–7 Watershed Resource Inventory
Increased dry weather flow is largely due to increased baseline plant discharge. However, the highest
flows show an increase that exceeds that which is attributable to baseline plant discharge. Over the 50-
year period, the volume of water delivered to Thorn Creek in wet weather or high flow events has in-creased
by over 55 percent. While baseline plant discharge has increased over the 50-year time period,
this accounts for less than half of the flow increase during high flow events. During the same time peri-ods,
average precipitation increased by only 16 percent. Some of the stormwater during rain events is de-livered
to the plant, and from there to Thorn Creek. No matter the source, however, the conclusion re-mains
that much more water enters the stream during a rain event now as compared to 50 years ago,
suggesting increased flashiness. Much of the increase in high flows is attributable to the increased ur-banization
in the watershed, where expanding infrastructure such as impervious surfaces, storm sewers,
and sanitary sewers all work to increase the rate and volume of runoff from the land surface. These
changes have modified the natural hydrology of the creek.
The Illinois Environmental Protection Agency’s Illinois Water Quality Report, 2004 (IEPA, 2004) identifies
“other flow alterations” as a cause of impairment in the upper reaches of Thorn Creek due to hydomodi-fication
(upstream impoundment, flow regulation/modification). In the lower reaches of Thorn Creek,
“physical−habitat alteration” is cited as a cause of impairment due to hydromodification (channelization)
and habitat modification (streambank modification/destabilization) (see Table 2-6). These causes and
sources can be at least partially attributed to the changes in streamflow during storm events due to ur-banization.
It appears, therefore, that altered hydrology resulting in streamflow changes is a source of
impairment needing attention and remediation.
Thorn Creek Watershed Based Plan December 2005
2–8 Watershed Resource Inventory
Monthly Mean Streamflow at Thornton
0
50
100
150
200
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Month
Cubic Feet per Second
Mean Annual Flow
Thornton Ten Year Averages 1953 - 2002
0
20
40
60
80
100
120
140
'1953-62 1963-72 1973-82 1983-92 1993-02
Decade
Cubic Feet per Second
Total Flow
Base Flow
Figure 2-5.
Figure 2-6.
Figure 2-7.
Thornton Mean Annual Flow 1949 - 2002
0
50
100
150
200
250
1953
1957
1961
1965
1969
1973
1977
1981
1985
1989
1993
1997
2001
Year
Cubic Feet per Second
Total Flow
Base Flow
Note: Here “Base flow” means Total Flow less flow from the TCBSD plant.
Note: Here “Base flow” means Total Flow less flow from the TCBSD plant.
Thorn Creek Watershed Based Plan December 2005
2–9 Watershed Resource Inventory
Glenwood Mean Annual Flow 1949 - 2002
0
10
20
30
40
50
60
70
80
1950
1953
1956
1959
1962
1965
1968
1971
1974
1977
1980
1983
1986
1989
1992
1995
1998
2001
Year
Cubic Feet per Second
Total Flow
Base Flow
Monthly Mean Streamflow at Glenwood
0
10
20
30
40
50
60
70
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Month
Cubic Feet per Second
Mean Annual Flow
Glenwood Ten Year Averages 1953 - 2002
0
10
20
30
40
50
60
'1953-62 1963-72 1973-82 1983-92 1993-02
Decade
Cubic Feet per Second
Total Flow
Base Flow
Figure 2-9.
Figure 2-8.
Figure 2-10.
Note: Here “Base flow” means Total Flow less flow from the TCBSD plant.
Note: Here “Base flow” means Total Flow less flow from the TCBSD plant.
Thorn Creek Watershed Based Plan December 2005
2–10 Watershed Resource Inventory
Thorn Creek Historical Flow Analysis
Glenwood, Illinois (USGS 05536215)
Mean Daily Flow by Decade
0
20
40
60
80
100
120
140
1953-1962 1963-1972 1973-1982 1983-1992 1993-2002
Decade
Mean Daily Flow (CFS)
Dry weather flows
Wet weather flows
Source: U.S. Geological Survey, Illinois Water Resources Data, Water Year 2002. http://waterdata.usgs.gov/IL/nwis/
Note: Wet weather flows are approximated as those that made up the top 25 percent of observed mean daily flows in each decade.
Dry weather flows were approximated as the lower 75 percent of observed mean daily flows.
2.3.2 LAKES
While there are no large lakes within the Thorn Creek watershed, there are nine lakes between 20 and 50
acres in size, primarily created via sand and gravel mining. In addition to these, there are more than 100
small lakes and ponds in the area, most of which are less than two acres in size.5 Four Illinois EPA 305(b)6
assessed lakes fall within the Thorn Creek watershed and all are located in Cook County: Lake George,
Lake Lynwood, Sauk Trail Lake, and Wampum Lake. Sauk Trail and Wampum Lakes are within Forest
Preserve District of Cook County (FPDCC) preserves and are considered to be significant publicly-owned
water bodies by the Illinois EPA. See Section 2.4.1.1 for water quality information for these lakes.
Created in 1930 when 26th Street was extended to Western Avenue, Sauk Trail Lake is a 28.8-acre online
lake located in South Chicago Heights. A dam and spillway were built across Thorn Creek as a part of
this extension. In 1953, the lake was drained and, along with pools on Thorn Creek, treated with rote-none
to remove the carp and bullhead that had over-populated the lake. In 1954 and 1959—the year a
natural gas pipeline was installed across the lakebed—the lake was stocked with largemouth bass. How-ever,
due to turbidity and a history of winterkills, attempts to establish a sport fishery have been unsuc-
5 Source: IDNR, 1999: Thorn Creek Area Assessment, Volume 2: Water Resources
6 Section 305(b) of the Clean Water Act provides for a National Water Quality Inventory Report to Congress to be developed by U.S.
EPA in conjunction with the states. The reports are available at http://www.epa.gov/305b/.
Figure 2-11.
Thorn Creek Watershed Based Plan December 2005
2–11 Watershed Resource Inventory
cessful. The FPDCC has no immediate plans to establish a healthy fishery in the lake. In 1966, when the
Illinois State Water Survey examined Sauk Trail Lake, the water volume of the lake was 120 acre-feet, the
sediment volume was 13 acre-feet, and the maximum and average depths were 6.4 and 4.0 feet, respec-tively.
7
Wampum Lake, created as a borrow pit in 1953-54 for the construction of the Calumet Expressway, is 35
acres in size and lies within the Thorn Creek Preserve just north of Thornton-Lansing Road and east of
Thorn Creek. Following creation of the lake, it filled slowly and reached its full water level in 1959—a
water level four to five feet higher than originally planned. The lake now has a maximum depth of 13
feet and an average depth of 10.8 feet. It exhibits some shoreline erosion problems for which a shoreline
restoration plan recently has been developed. In 1956, Wampum Lake was initially stocked with ap-proximately
25 smallmouth bass which successfully reproduced. However, the lake became dominated
by goldfish and black bullhead and was subsequently treated with rotenone in 1972 . Largemouth bass,
smallmouth bass, and bluegill were restocked, and fishing remains a popular pastime.8
7 Sources: Jim Phillips, Forest Preserve District of Cook County, 2004 personal communication
8 Sources: Jim Phillips, Forest Preserve District of Cook County, 2004 personal communication. Illinois EPA Water Quality Report,
2000. See http://www.epa.gov/305b/. Vidal, P.J. and H.L. Wight. 1975. Cook County Surface Water Resources. Illinois Dept. of Conser-vation,
Div. of Fisheries. Springfield, IL.
Thorn Creek Watershed Based Plan December 2005
2–12 Watershed Resource Inventory
2.4. Water Quality Assessment
As a major part of the development of the Watershed Based Plan for Thorn Creek, NIPC and the stake-holders
group collected water quality assessment information from a variety of sources, primarily the Il-linois
Environmental Protection Agency (EPA), the Thorn Creek Basin Sanitary District wastewater treat-ment
plant, and the Chicago Metropolitan Water Reclamation District. The ecological health of a water
body can be evaluated in part by examining a variety of chemical parameters that contribute to overall
water quality. Evaluations are made relative to the “General Use” standards defined by the Illinois Pollu-tion
Control Board, which are designed to protect waters for aquatic life, wildlife, agricultural uses, pri-mary
contact, secondary contact, and most industrial purposes. Fish and biotic indicators and habitat as-sessments
also provide important information regarding the health of a stream system and potential for
restoration. Those topics are covered in Section 2.5.
2.4.1. ILLINOIS EPA WATER QUALITY ASSESSMENTS
The biennial Illinois Water Quality Report prepared by the Illinois EPA describes water quality conditions
in terms of the degree to which waters attain their applicable designated uses. Streams and lakes are as-sessed
for the designated uses of aquatic life, fish consumption, primary contact (swimming), indigenous
aquatic life, and public water supply. Lakes are also assessed for secondary contact (recreation) and
“overall” uses. The degree to which the designated uses are attained (supported) in a waterbody is de-termined
by an analysis of all available information, including biological, physical/chemical, habitat, and
toxicity data. Illinois EPA assesses Thorn Creek for aquatic life and primary contact uses. The Thorn
Creek tributaries Deer, Butterfield, and North Creeks are assessed for aquatic life use. Aquatic life use as-sessments
are based on biotic and abiotic data, including fish and macroinvertebrate indices, water chem-istry,
and instream physical habitat. Primary contact (swimming) use impairments are based on fecal
coliform levels and the concentration of total suspended solids. The degree to which waters attain their
applicable designated uses are defined as follows:
• Full Support: Water quality meets the needs of all designated uses protected by applicable water
standards.
• Full Threatened: Water quality is presently adequate to maintain designated uses, but if a declin-ing
trend continues, only partial support may be attained in the future.
• Partial Support/Minor Impairment: Water Quality has been impaired, but only to a minor de-gree.
These may be minor exceedences in applicable water quality standards or criteria for ad-dressing
the designated use attainment.
• Partial Support/Moderate Impairment: Water quality conditions are impaired to a greater de-gree
inhibiting the waterbody from meeting all the needs for designated use.
• Nonsupport: Water Quality is severely impaired and not capable of supporting the designated
use to any degree.
For a waterbody assessed as having less then full overall support, causes and sources of the impairment
are identified at the following magnitudes:
• Slight (S): A cause/source that is one of multiple causes/sources for non- or partial support and is
judged to contribute relatively little to this non-attainment.
• Moderate (M): A cause/source that is the only one responsible for partial support, predominates
over other causes/sources of partial support, or is one of multiple causes/sources of nonsupport
that have a significant impact on designated use attainment.
Thorn Creek Watershed Based Plan December 2005
2–13 Watershed Resource Inventory
• High (H): A cause/source that is the only one responsible for nonsupport or predominates over
other causes/sources.
All of the following water quality assessments are from the Illinois Environmental Protection Agency’s
biennial Illinois Water Quality Report (also known as the “305(b) Report”).
2.4.1.1. Lakes
Both Sauk Trail Lake and Wampum Lake were assessed by the Illinois EPA using 1997 data for publica-tion
in the Illinois Water Quality Report 2000. At that time, Sauk Trail Lake was rated as partial support for
aquatic life and nonsupport for recreational, swimming, and overall use. The causes to which these im-pairments
were attributed were PCBs, nutrients (specifically phosphorus and ammonia), siltation, or-ganic
enrichment, and low dissolved oxygen9, suspended solids, and excessive algal growth. The sources
of these causes were identified as agriculture (in the form of non-irrigated crop production), construction
and land development, urban runoff/storm sewers, flow regulation and modification, and contaminated
sediments from forests, grasslands, and parklands. In the Illinois Water Quality Report 2002 and 2004,
Sauk Trail Lake received exactly the same ratings. Due to these findings, in 2002 Sauk Trail Lake became
listed as a 303(d) medium priority water body by the Illinois EPA.
In both the Illinois Water Quality Report 2000 and 2002, Wampum Lake was assessed as full support for all
uses. In the Illinois Water Quality Report 2004, the lake was assessed as full support for overall, aquatic
life, and primary contract (swimming), but partial support for secondary contact (recreation). Potential
causes for recreation impairment were attributed to habitat assessment. The potential sources of impair-ment
were urban runoff/storm sewers and forest/grassland/parkland. Hence, Wampum Lake was placed
on the medium priority 303(d) list in 2004.
Previous 305(b) reports provide some additional information about the condition of these two lakes. In
older reports, each lake was assigned a mean Trophic State Index (TSI), and aquatic life and recreational
use impairments were attributed to either sediments or macrophytes. The TSI is a measure of the eutro-phication
of a body of water, the process by which lakes are enriched with nutrients, increasing the pro-duction
of rooted aquatic plants and algae. The extent to which this process has occurred is reflected in a
lake's trophic classification or state (Table 2-3). The mean Trophic State Index is determined using a com-bination
of measures of water transparency/turbidity10 (using Secchi disk depth recordings), chlorophyll a
concentrations, and total phosphorus levels. TSI values range from 20 to 110. A very high TSI value,
which indicates excessive nutrients and low transparency, can contribute to use impairments. A TSI of
less than 50 usually indicates little or no impairment, while a TSI greater than 70 is a sign of significant
impairment.
9 Dissolved oxygen is a primary factor in determining a water body’s ability to support life and can be affected by photosynthetic
activity, wind and wave action, decomposition of organic matter, water flow and temperature.
10 Turbidity is a measure of suspended materials (e.g., algae, silt) in the water that impact transparency. Low transparency results
in less sunlight available to aquatic organisms, inability for aquatic plants to conduct photosynthesis, and a general reduction in
plant and animal diversity.
Thorn Creek Watershed Based Plan December 2005
2–14 Watershed Resource Inventory
Table 2-3. Description of Trophic State Index
Trophic State TSI Characteristics
Oligotrophic < 40
Nutrient poor, maximum transparency, minimum chlorophyll a, minimum
phosphorus
Mesotrophic 40 – 50 Moderately productive
Eutrophic 50 – 70 Very productive and fertile
Hypereutrophic > 70
Excessive nutrient concentrations, minimum transparency, maximum chlorophyll a,
maximum phosphorus
Aquatic life and recreation use impairments for the older 305(b) reports are based on the TSI in combina-tion
with the concentration of nonvolatile suspended solids (sediments) and the percent of the lake sur-face
area covered by macrophytes. These parameters were reported in the Illinois Water Quality Report
1998 for Sauk Trail and Wampum Lakes. Sauk Trail Lake was hypereutrophic with a TSI of 70. The
lake’s aquatic life and recreational use impairments were attributed to high levels of sediment and slight
macrophyte impairment. These measurements were taken in 1997 when Sauk Trail Lake received par-tial/
moderate support ratings for overall and swimming uses, nonsupport for recreational use, and full
support for aquatic life use. Wampum Lake was examined in 1992 and was mesotrophic with a TSI of 47.
There were no sediment or macrophyte problems detected, and Wampum received full support ratings
for every use.
2.4.1.2. Streams
Thorn Creek has been assessed by Illinois EPA at three locations along its main stem: HBD 04, HBD05,
and HBD 06. While data from all three locations were used for NIPC’s water quality assessment, de-scribed
in Section 2.4.2, only HBD 04 and HBD 05 were reported in the Illinois EPA Water Quality As-sessment.
Both of the assessed stretches are listed by the Illinois EPA as medium priority water bodies in
the Illinois 2002 Section 303(d) List. A summary of the data provided on these stretches is given in Tables
2-4 and 2-5.
The 7.84 mile HBD 04 reach starting at the confluence with the Little Calumet River and running up-stream
was examined by Illinois EPA in 1997 and 1998. The stream was rated as partial/minor support
for overall use, partial/minor support for aquatic life, and nonsupport for swimming. A second stretch of
the stream (HBD 05) was analyzed in 1997 as well. This 10.15 mile section at about the middle of the run
of Thorn Creek was rated as partial/moderate support for both overall use and aquatic life use and as
nonsupport for swimming use. The causes and degree of impairments of the designated uses of the
stream are shown in Tables 2-4 and 2-5.
Results of Illinois EPA’s most recent assessments (from the Illinois Water Quality Report 2004) of Thorn
Creek and three of its tributaries (Deer, Butterfield, and North Creeks) are provided in Tables 2.6 and 2.7,
respectively.
Thorn Creek Watershed Based Plan December 2005
2–15 Watershed Resource Inventory
Table 2-4. Water Quality Impairments in Reach HBD 04 of Thorn Creek
Cause of Impairment Degree of Impairment
Habitat alterations Moderate
Metals (specifically copper) Slight
Nutrients (phosphorus, ammonia, nitrates) High
pH Slight
Salinity Slight
Pathogens High
Suspended solids None reported
Priority organics None reported
PCBs None reported
Cyanide None reported
Source of Impairment Degree of Source of Impairment
Municipal Moderate
Construction Slight
Land development Slight
Urban runoff and storm sewers Moderate
Hydromodification Slight
Channelization Slight
Bank modification and destabilization Slight
Source: Illinois Water Quality Report, 2004 (Illinois EPA, 2004)
Table 2-5. Water Quality Impairments in Reach HBD 05 of Thorn Creek
Cause of Impairment Degree of Impairment
Metals Slight
Nutrients (ammonia) Slight
Organic enrichment/low dissolved oxygen Slight
Habitat and flow alterations Moderate
Oil and grease Slight
Siltation Moderate
Source of Impairment Degree of Source of Impairment
Construction Moderate
Land development Moderate
Urban runoff and storm sewers Slight
Hydromodification Slight
Channelization Slight
Upstream impoundment None reported
Flow regulation and modification None reported
Streambank modification and destabili-zation
Slight
Source: Illinois Water Quality Report, 2004 (Illinois EPA, 2004)
Thorn Creek Watershed Based Plan December 2005
2–16 Watershed Resource Inventory
Table 2-6. Illinois EPA Use Assessment and Potential Causes and Sources of Impairment for Thorn Creek
Segment ID Designated Use Use Support Causes Sources
Thorn Creek
HBD 03 Aquatic Life Not Assessed (not assessed) (not assessed)
Total Dissolved Solids Urban Runoff/Storm Sewers
HBD 05 Aquatic Life Partial
Other Flow Alterations
Hydromodification, Upstream Im-poundment,
Flow Regulation/
Modification
Silver, Total Nitrogen as
N, Total Phosphorus
Municipal Point Sources, Major
Municipal Point Sources
Aquatic Life Partial Dissolved Oxygen (none listed)
Aldrin, Dieldrin, Hexa-chlorobenzene
HBD 06 Contaminated Sediments
Primary Contact Partial
Total Fecal Coliform
Bacteria
Municipal Point Sources, Major
Municipal Point Sources, Urban
Runoff/Storm Sewers
Zinc, Silver, Dissolved
Oxygen
Municipal Point Sources, Major
Municipal Point Sources, Urban
Runoff/Storm Sewers
Fluoride (none listed)
Total Nitrogen as N, To-tal
Phosphorus
Municipal Point Sources, Major
Municipal Point Sources
Physical-Habitat Altera-tions
(none listed)
Total Suspended Solids Urban Runoff/Storm Sewers
Aquatic Life Partial
Aldrin, Chlordane, DDT,
Dieldrin, Endrin, Hexa-chlorobenzene,
PCBs
Contaminated Sediments
HBD 02
Primary Contact Nonsupport
Total Fecal Coliform
Bacteria
Urban Runoff/Storm Sewers
HBD 04
Aquatic Life,
Primary Contact
Partial (for
Aquatic Life),
Nonsupport
(for Primary
Contact)
Zinc, Silver, Fluoride,
Total Nitrogen as N,
Dissolved Oxygen,
Physical Habitat Altera-tions,
Total Fecal Coli-form
Bacteria, Total
Suspended Solids,
Aldrin, Chlordane, DDT,
Dieldrin, Endrin, Hexa-chlorobenzene,
PCBs,
Total Phosphorus
Municipal Point Sources, Urban
Runoff/Storm Sewers, Hydromodi-fication,
Channelization, Habitat
Modification, Bank Modifica-tion/
Destabilization, Contaminated
Sediments, Source Unknown
Segment IDs are arranged from the creek’s headwaters (segment HBD 03) and proceed downstream. Segment HBD
05 lies downstream of Sauk Trail Lake and upstream of the Thorn Creek Basin Sanitary District. Segments HBD 06–
HBD 04 are downstream of the TCBSD.)
Source: Illinois Water Quality Report, 2004 (Illinois EPA, 2004)
Thorn Creek Watershed Based Plan December 2005
2–17 Watershed Resource Inventory
Table 2-7. Illinois EPA Use Assessment and Potential Causes and Sources of Impairment for Deer, Butterfield,
and North Creeks
Segment ID Designated Use Use Support Causes Sources
Deer Creek
HBDC Aquatic Life Partial
Unspecified Nutrients,
Nitrate Nitrogen, Physi-cal-
Habitat Alterations,
Total Phosphorus
Municpal Point Sources, Urban
Runoff/Storm Sewers, Hydromodi-fication,
Channelization
Sedimentation/Siltation Urban Runoff/Storm Sewers
Other Flow Alterations
Hydromodification, Flow Regula-tion/
Modification
HBDC02 Aquatic Life Partial
Total Phosphorus Municipal Point Sources
Butterfield Creek
Dissolved Oxygen Urban Runoff/Storm Sewers
Other Flow Alterations
Hydromodification, Flow Regula-tion/
Modification
HBDB03 Aquatic Life Partial
DDT Contaminated Sediments
North Creek
HBDA01 Aquatic Life Partial
Sedimentation/Siltation,
Dissolved Oxygen, Non-
Native Animals, Aldrin,
Hexachlorobenzene
Urban Runoff/Storm Sewers, Hy-dromodification,
Flow Regulation/
Modification, Contaminated Sedi-ments,
Forest/Grassland/Parkland
Source: Illinois Water Quality Report, 2004 (Illinois EPA, 2004)
2.4.2. NIPC WATER QUALITY ASSESSMENTS
2.4.2.1. NIPC Water Quality Empirical Analysis
NIPC gathered water quality data from the Illinois EPA, Thorn Creek Basin Sanitary District (TCBSD),
and the Metropolitan Water Reclamation District of Greater Cook County (MWRD) to assess the water
quality of Thorn Creek. TCBSD and MWRD data, which were more extensive and more consistent than
Illinois EPA data, were used for the majority of the analysis. The analysis examined the percentage of in-stances
in which Illinois Pollution Control Board (IPCB) standards of sampled constituents were ex-ceeded
at each sampling location (Table B-1, Appendix B). For constituents lacking an IPCB standard, a
generally accepted guideline was used to screen data. For those constituents and locations with excur-sions
(exceedences) of greater than 5 percent of the samples, the data were graphed to screen for temporal
patterns such as seasonal or long term trends. In addition to excursion frequency, we examined average
concentrations from the headwaters of the Thorn Creek mainstem to the outfall at the Little Calumet
River (Table B-2, Appendix B). Correlating the data with sampling points and subbasin boundaries al-lowed
us to assess which subbasins may contain causes and sources of impairment.
The following fifteen water quality constituents were assessed at twelve sampling sites along the main
stem of Thorn Creek:
• Total Suspended Solids (TSS)
• Total Phosphorus (TP)
• Ammonia Nitrogen (NH3)
• Biological Oxygen Demand (BOD)
• Dissolved Oxygen (DO)
• Copper (Cu)
Thorn Creek Watershed Based Plan December 2005
2–18 Watershed Resource Inventory
• Zinc (Zn)
• Arsenic (As)
• Silver (Ag)
• Iron (Fe)
• Total Dissolved Solids (TDS)
• Fecal Coliform (FC)
• Sulfate (SO4)
• Chlorophyll a (Chl A)
• pH
The sampling points and major flow contributors are listed in Table 2-8 from upstream to downstream.
Figure 2-12 shows the location of sampling and reference points along Thorn Creek. Locations of sam-pling
points for biotic data are given in Section 2.5.1.
Table 2-8. Sampling Locations and Data Sources for NIPC Water Quality Empirical Analysis
Subbasin Sampling Point / Reference Point Location Data
Source
SB100 Stuenkel Stuenkel Road TCBSD
Western Western Avenue TCBSD
SB200+300 HBD 05 Route 30 bridge IEPA
SB400+500 Above East of Halsted Street TCBSD
SB600 Wastewater Treatment Plant
Loc54/Orr Rd Joe Orr Road MWRD
Below Joe Orr Road TCBSD
Glenwood USGS station #05536215 TCBSD
SB700 HBD 06 195th Street IEPA
Deer and Butterfield Creek Confluence
Glenwood School Main Street TCBSD
North Creek Confluence
Thornton USGS station #05536275 TCBSD
HBD 04 Thornton (Thornton Lansing Rd) IEPA
SB800+900 Loc97/170th St. 170th Street MWRD
Thorn Creek Watershed Based Plan December 2005
2–19 Watershed Resource Inventory
Figure 2-12. Subbasins and Water Quality Sampling Locations in the Thorn Creek Watershed
Sampling frequency and the number of years of sampling data varies by constituent. In general this as-sessment
used monthly sampling data from 1997 to 2004. Assessment of the data was made using IPCB
standards for water quality. However, following the establishment of a wastewater discharge connection
from the Rhodia silica plant in 1995, the IPCB granted the Thorn Creek Basin Sanitary District treatment
plant relief from both the total dissolved solids and sulfate standards for portions of Thorn Creek down-stream
from the plant to Thornton (water quality sampling points are indicated by boldface notation in
the main text). The revised standards for these reaches are given in Table 2-9. Although Illinois EPA may
be examining other standards for revision—including total dissolved solids, sulfate, dissolved oxygen,
and phosphorus—the existing standards were used for this assessment.
Table 2-9. Standards for Total Dissolved Solids and Sulfate for Select Reaches of Thorn Creek
Reach TDS (mg/L) SO4 (mg/L)
Old New Old New
Joe Orr Road to Deer Creek confluence 1,000 2,650 500 1,350
Deer Creek to Thornton (USGS 055362775) 1,000 2,620 500 1,340
Thornton to Little Calumet River 1,000 2,360 500 1,160
Thorn Creek Watershed Based Plan December 2005
2–20 Watershed Resource Inventory
2.4.2.2. NIPC Land Use Pollutant Loading Analysis
NIPC also examined land use in the Thorn Creek subbasins to assess whether water quality impairments
might be attributable to prevalent land use types. Different land uses have specific pollutant loading
characteristics due to differences in imperviousness and the types of activities associated with those land
uses (see Table B-2, Appendix B, for pollutant export coefficients by land use). NIPC assessed whether
particular subbasins may be more responsible for specific pollutants than others, potentially making it
possible to recommend different suites of best management practices for each subbasin. While the land
use assessment can point to possible source areas of pollutants, it does not account for point sources,
natural pollutant sinks, or other variations attributable to variability in the landscape and urban fabric.
As such, the model has limitations as a predictor of pollutant loading and should not be relied upon as a
single source for assessing water quality except where no empirical data exist, and the model should still
be used with caution in any case. Empirical data should be relied upon when possible.
Watershed imperviousness is an important indicator of expected watershed and water quality impair-ment.
High quality resources are generally supportable in watersheds with up to approximately 10 per-cent
impervious area. As imperviousness increases beyond 10 percent, watershed quality decreases sig-nificantly.
The Center for Watershed Protection has developed a general guide, reproduced in Table 2-10,
for assessing watershed resource quality based on imperviousness.11 This characterization is important
for watershed restoration and management. Watershed conditions can reasonably be expected to im-prove
from one classification to the next higher classification if maximum effort is applied. However, it is
highly unlikely that watershed conditions can be improved to pristine conditions, let alone an improve-ment
to more than one classification higher than current conditions.
In order to assess land use impacts, the mainstem watershed of Thorn Creek was divided into nine sub-basins
based on USGS Hydrologic Unit Codes. These subbasins are numbered from 100 to 900 from up-stream
to downstream (Figure 2-12). The imperviousness of Thorn Creek subbasins ranges from ap-proximately
14 percent upstream to approximately 40 percent in the middle subbasins, falling to ap-proximately
27 percent downstream (Figure 2-13). Seven of twelve sub