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. LOWER SANGAMON RIVER . ~.'. ~ '. ' " ~T", , _.~.. . .' AREA ASSESSMENT
'~
OEP.-,RTMENT Of NATURAL RESOURCES LOWER SANGAMON.RIVER AREA ASSESSMENT
VOLUME 1: GEOLOGY
Illinois Department ofNatural Resources Office of Scientific Research and Analysis State Geological Survey Division 615 East Peabody Drive Champaign, Illinois 61820 (217) 333-4747
2000
300 Printed by the authority of the State of Illinois . . Other CTAP Publications
Lower Sangamon River Area Assessment Vol. 2 Water Resources Vol. 3 Living Resources Vol. 4 Socio-Economic Profile, Environmental Quality, Archaeological Resources The Lower Sdngamon River Basin: An Inventory ofthe Region's Resources - 22-page color booklet
Descriptive inventories and area assessments are also available for the following regions: Rock River Lower Rock River Cache River Sinkhole Plain Mackinaw River Sugar-Pecatonica Rivers Illinois Headwaters VermiIion River Illinois Big Rivers Upper Sangamon River Fox River Du Page River Kankakee River Thorn Creek Kishwaukee River Prairie Parklands Embarras River Kaskaskia River Upper Des Plaines River Lower Des Plaines River Illinois River Bluffs Calumet Area Spoon River Lower Des Plaines River Driftless Area
Also available: Illinois Land Cover, An Atlas, plus CD-ROM Inventory ofEcologically Resource-Rich Areas in Illinois EcoWatch '98, Annual Report of the Illinois EcoWatch Network Illinois Geographic Information System, CD-ROM of digital geospatial data
All CTAP and Ecosystems Program documents are available from the DNR Clearinghouse at (217) 782-7498 or TDD (217) 782-9175. Selected publications are also available on the World Wide Web at http://dnr.state.il.us/ctap/ctaphome.htm, or http://dnr.state.il.us/c2000/manage/partner.htm, as well as on the EcoForum Bulletin Board at I (800) 528-5486 or (217)782-8447.
For more information about CTAP, call (217) 524-0500 or e-mail [email protected]; for information on the Ecosystems Program call (217) 782-7940 or e-mail [email protected].
The Illinois Department of Natural Resources does not discriminate based upon race, color, national origin, age, sex, religion or disability in its programs, services, activities and facilities. If you believe that you have been discriminated against or if you wish additional information, please contact the Department at (217) 785-0067 or the U.S. Department of the Interior Office of Equal Employment, Washington, D.C. 20240. About This Report
The Lower Sangamon River Area Assessment examines 4,575 square miles in central lllinois. Because significant natural community and species diversity has been found in the watershed, a portion of the assessment area has been designated a state "Resource Rich Area." 1
This report is part of a series of reports on areas of Illinois where a public-private partnership has been formed to protect natural resources. The assessments provide information on the natural and human resources of the area as a basis for managing and improving its ecosystems. The determination of resource rich areas and development of ecosystem-based . information allg management programs in lllinois are the result of three processes - the Critical Trends Assessment Program, 'Conservation Con@'e!;s', aIidWaterResources-and _. Land Use Priorities Task Force.
Background
The Critical Trends Assessment Program (CTAP) documents changes in ecological conditions. In 1994, using existing information, the program provided a baseline of ecological conditions.2 Three conclusions were drawn from the baseline investigation:
1. the emission and discharge of regulated pollutants over the past 20 years has declined, in some cases dramatically, 2. existing data suggest that the condition of natural ecosystems in llIinois is rapidly declining as a result of fragmentation and continued stress, and 3. data designed to monitor compliance with environmental regulations or the status of individual species are not sufficient to assess ecosystem health statewide.
Based on these findings, CTAP has begun to develop methods to systematically monitor ecological conditions and provide information for ecosystem-based management. Five components make up this effort:
1. identify resource rich areas, 2. conduct regional assessments, 3. publish an atlas and inventory of llIinois landcover, 4. train volunteers to collect ecological indicator data, and 5. develop an educational science curriculum which incorporates data collection
At the same time that CTAP was publishing its baseline findings, the llIinois Conservation Congress and the Water Resources and Land Use Priorities Task Force were presenting their
1 See Inventory ofResource Rich Areas in Illinois: An Evaluation ofEcological Resources 2 See The Changing Illinois Environment: Critical Trends, summary report and volumes 1-7.
iii respective findings. These groups agreed with the CTAP conclusion that the state's ecosystems were declining. Better stewardship was needed, and they determined that a voluntary, incentive-based, grassroots approach would be the most appropriate, one that recognized the inter-relatedness ofeconomic development and natural resource protection and enhancement.
From the three initiatives was born Conservation 2000, a program designed to reverse ecosystem degradation, primarily through the Ecosystems Program, a cooperative process of public-private partnerships that merge natural resource stewardship with economic and recreational development. To achieve this goal, the program provides financial incentives and technical assistance to private landowners.
At the same time, CTAP identified 30 Resource Rich Areas (RRAs) throughout the state. In RRAs and areas where Ecosystem Partnerships have been formed, CTAP is providing an assessment of the area, drawing from ecological and socio-economic databases to give an ~ overview of the region's resources- geologic,~daphig,hydrologic, biotic, and socio economic. Although several ofthe analyses are somewhat r~stricted by spatial and/or temporal limitations of the data, they help to identifY information gaps and additional opportunities and constraints to establishing long-term monitoring programs in the partnership areas.
The Lower Sangamon River Area Assessment
The Sangamon River basin drains 5,419 square miles and forms the largest watershed of any of the tributaries of the Illinois River. The mainstem of the Sangamon flows more than 240 miles. The assessment area encompasses more than 2,927,900 acres and includes the lower Sangamon River watershed (which includes parts of McLean, Piatt, DeWitt, Macon, Shelby, Christian, Sangamon, Montgomery, Macoupin, Morgan, Menard, Logan, Tazewell, Mason, and Cass counties) and some Illinois River tributaries. Major tributaries to the Sangamon, such as South Fork Sangamon River and Salt Creek, are included. Five natural divisions are encompassed - Grand Prairie (Grand Prairie and Springfield sections), Upper Mississippi River and Illinois River Bottomlands, Illinois , River and Mississippi River Sand Areas, Western Forest-prairie, and Southern Till Plain. Parts or all of four sub-basins on the northwestern edge of the area are designated Resource Rich Areas because they contain signific'ant natural community diversity.
This assessment is comprised of four volumes. In Volume I, Geology discusses the geology, soils, and minerals in the assessment area. Volume 2, Water Resources, discusses the surface and groundwater resources and Volume 3, Living Resources, describes the natural vegetation communities and the fauna of the region. Volume 4 contains three parts: Part I, Socio-Economic Profile, discusses the demographics, infrastructure, and economy of the area; Part II, Environmental Quality, discusses air and water quality, and hazardous and toxic waste generation and management in the area; and Part III, Archaeological Resources, identifies and assesses the archaeological sites known in the area.
IV t 1
Scale 1:2700000 '",,"======.'i;;iOOM... ,,'======,:.i1601tl1Dm1lt•.
Drainage basins from 1:24000 scale watershed boundaries as delineated by the U.S.G.S. Water Resource. Division.
Mlijor drainage basins oflilinois and location of the Lower Sangamon River Assessment Area ------_.- -
I
Scale I:982080 j r ~...... __;,oo...... __...... ~50 Kilometers
Subbasins in the Lower Sangamon River Assessment Area. Subbasin boundaries depicted are those determined by the Illinois Environmental Protection Agency. Contributors
Introduction: Influence of Geology and Soil on EcosystemDevelopment ...... MymaM. Killey and William W. Shilts Part 1: The Natural Geologic Setting BedrockGeology ...... C. Pius Weibel Glacial and Surficial Geology ...... MymaM. Killey with contributions by Lisa R. Smith and ChristopherC. Goldsmith Modem Soils and the Landscape-Influences on Habitat and Agriculture...... Michael L. Barnhardt with contributions by LisaR. Smith and ChristopherC. Goldsmith Landscape Features and Natural Areas with Geologic Features oflnterest MymaM. Killey with contributions by Lisa R. Smith and ChristopherC. Goldsmith Land CoverInventory...... DonaldE. Luman with contributions by Lisa R. Smith and ChristopherC. Goldsmith
Part 2: Geology and Society
Mineral Resources ...... VijuIpe with contributions by Lisa R. Smith and ChristopherC. Goldsmith AquiferDelineation ...... Ross D. Browerand Robert C. Vaiden Potential for Contamination ofGroundwaterResources ...... Donald A. Keefer Regional Earthquake History ...... Timothy H. Larson with contributions by LisaR. Smith and Christopher C. Goldsmith
Landslides ...... Robert A. Bauer with contributions by LisaR. Smith and ChristopherC. Goldsmith Coal Mine Subsidence and Acid Drainage ...... Robert A. Bauer
Additional Readings ...... Lynne E. Raymond Appendix A: Overview ofDatabases . . . LisaR. Smith AppendixB: Land Coverby Subbasin...... DonaldE. Luman
vii Table of Contents
Introduction: Influence of Geology and Soils on Ecosystem Development...... 1
Part 1: The Natural Geologic Setting. 7 Bedrock Geology ...... 8 Glacial and Surficial Geology ...... 14 Modem Soils and the Landscape-Influences on Habitat and Agriculture . 22 Landscape Features and Natural Areas with Geologic Features of Interest. 31 Land Cover Inventory ...... 34
Part 2: Geology and Society 57 Mineral Resources...... 58 Aquifer Delineation . . . . . 66 Potential for Geologic Hazards. 71 Potential for Contamination of Groundwater Resources . 71 Regional Earthquake History ...... 77 Landslides 80 Coal Mine Subsidence and Acid Mine Drainage . 83 Additional Readings ...... 87 Appendix A: Overview of Databases . 91 Appendix B: Land Cover by Subbasin. 94
List ofFigures Introduction: Influence of Geology and Soils on Ecosystem Development Figure 1. Lower Sangamon River Assessment Area ...... 5
Part 1: The Natural Geologic Setting Bedrock Geology Figure 2. Generalized Geologic Column for Illinois...... 9 Figure 3. Bedrock Geology...... 10 Figure 4. Bedrock Topography and Buried Valleys 12
viii Glacial and Surficial Geology Figure 5. Timetable of Events in the lee Age in Illinois. 15 Figure 6. Glacial Geology . 16 Figure 7. Drift Thickness . . . . . 19
Modern Soils and the Landscape Figure 8. Topography . 24 Figure 9. Soils . . . . . 25
Landscape Features Figure 10. Physiographic Divisions of Illinois...... 32
Land Cover Inventory Figure 11. Subbasins in the Assessment Area...... 43 Figure 12. Subbasins As Percentage of Total Assessment Area .44 Figure 13. Principal Land Cover . .45 Figure 14. Agricultural Land by Subbasin . .46 Figure 15. Cropland Cover . .47 Figure 16. Cropland & Rural Grassland by Subbasin. .48 Figure 17. Rural Grassland Cover...... 49 Figure 18. Forest and Woodland Cover .... 50 Figure 19. Forest and Woodland by Subbasin. 51 Figure 20. Urban and Built-Up Land . 52 Figure 21. Urban Land by Subbasin . 53 Figure 22. Urban Built-Up & Open Space by Subbasin. 54 Figure 23. Wetland Cover .... 55 Figure 24. Wetland by Subbasin. 56
Part 2: Geology and Society Mineral Resource Figure 25. Active Sand and/or Gravel Pits, Limestone Quarries and Coal Mines ...... 59 Figure 26. Potential Mineral Resources in the Lower Sangamon River Assessment Area...... 60
Potential for Geologic Hazards Figure 27. Potential for Contamination from Pesticides (Aquifer Sensitivity) in the Lower Sangamon River Assessment Area ...... 75 Figure 28. Earthquakes in the Lower Sangamon River Assessment Area 78 . Figure 29. Landslides in the Lower Sangamon Assessment Area. 81 Figure 30. Coal Mines in the Lower Sangamon Assessment Area . . . . 82
ix List of Tables Part 1: The Natural Geologic Setting Landscape Features and Natural Areas Table 1. Natural Areas with Features of Geologic Interest ...... 33
Land Cover Inventory Table 2. Land Cover of the Lower Sangarnon River Assessment Area...... 37 Table 3. Land Cover of Illinois...... 38 Table 4. Principal Land Cover of the Lower Sangarnon River Assessment Area. 39
Part 2: Geology and Society Mineral Resources Table S. Mineral Producers...... 62
x Introduction: Influence of Geology and Soils on Ecosystem Development
Geology is ... the original source ofinorganic chemical nutrients for the biosphere andprovides the abiotic physical environment ofthe biosphere. Through knowledge ofrock type mineralogy, the geologist can predict the amount and variety oftoxic or beneficial inorganic chemical nutrients present. ... Geological processes modifying geologic materials create landforms that are commonly a basisfor land unit hierarchies. Geologists can increase understanding ofland unit hierarchies in ecosystem studies .... Geologists can be critical players in understanding ecosystems.]
The 'Natural Divisions ofIllinois' is a classification ofthe natural envi ronments and biotic communities ofIllinois based on physiography, flora, andfauna. ... Factors considered in delimiting the 14 natural divisions are topography, soils, bedrock, glacial history, and the distribution of plants and animals.2
In the few areas of the earth that have not been modified by human settlement, the patterns of vegetation and the animals that interact with vegetation are directly influenced by geo logical factors. In fact, in undisturbed areas, surficial geology and to some extent bedrock geology can be mapped using inferences drawn from vegetation patterns observed on air photographs and satellite images and during field observations. For exarnple, in the pris tine terrains of northern North America, ecosystem variations were used to infer and eventually map underlying geological conditions.
The geological characteristics that most influence ecosystem development are soil moisture and composition, topography (including slope angle, slope direction, and local drainage), and texture of the parent material. In some places, geological events such as earthquakes, glacial advances and retreats, and volcanic eruptions exert a strong control over the eco system. Even animal activities that are seemingly removed from geological control are influenced by geological factors such as availability of salt for migrating herds, availabil ity of suitable vegetation for food, or-in the case of carnivores-suitable colonies of prey that congregate near geologically controlled food sources.
1 P. Hughes, A geologic response to the Seventh American Forest Congress and Round Tables: Environ mental Geology 28 (I) July 1996, p. 52-53.
2 Comprehensive Plan for the minois Nature Preserves System, Part 2, The Natural Divisions of minois, John E. Schwegman, principal author, 1984, Illinois Nature Preserves Commission, p. 3.
I In uninhabited areas of the glaciated North American Arctic, ridges of gravel (eskers) left behind by retreating glaciers served as transportation routes for early humans and animals alike. The ridges provided ease of footing, vantage points for hunters or the hunted, and protection from ravenous insects that prefer the calmer air of low-lying areas. Even in modern America, roads in New England are often constructed on these ridges. These examples clearly illustrate the dominant role local geologic factors can play in ecosystem development.
Before human settlement, the whole panoply of Illinois' ecological components was in equilibrium with the geology and climate of an area. The original ecological systems were closely attuned to the variety of-near-surface conditions that are generated by the distribution of glacial deposits and by spatial variations in bedrock units.
The glacial moraines (arc-shaped ridges) in the northeastern part of the state provided well-drained soils for forest growth and refuge for forest-dwelling animals. The low, flat plains are sites where shallow lakes were dammed between moraines and became poorly drained seas of herbaceous plants whose luxuriant growth provided the biomass for the thick organic-rich soils that support so much agriculture. lllinois' soils developed on tills or thick loess that are mixtures of crushed bedrock particles. These soil parent materials, formed and homogenized by the grinding action of glaciers, supply abundant nutrients vital to crops that are the agricultural basis of our society.
Where glaciers did not cover the terrain, the topography, soils, and vegetation differed significantly. The soils are directly related to the composition of the immediately under lying bedrock from which they were formed by chemical and physical weathering. The contrasts in our ancient ecosystems can be imagined by observing the ways modem soci ety has adjusted to the differences between the soils of the glaciated and unglaciated parts of the state: except on alluvial plains, crops are not a major source of income outside the large area of the state that was glaciated.
On our modern landscape, original ecosystems cannot be restored or maintained without respecting the geologic factors that generated the original complex plant and animal inter relations. For instance, attempting to reestablish a wetland consisting of acid-loving plants that require periodic drying will not succeed in depressions actively fed by ground water that passes through alkaline glacial till. Likewise, reestablishing certain types of forest vegetation on an unstable terrain underlain by thick, easily erodible glacial loess is likely to fail.
Land on a high terrace ofthe Illinois River, about 100feet above the river channel, was purchased for wetlands restoration. The permanent water table was nine feet below the surface, and the sandy'soils were highly permeable. Wetlands plants installed at the site died and were replaced naturally by uplandplant species tolerant ofthe dry conditions. Had read ily available information on geology and hydrogeology ofthe area been taken into consideration, it would have clearly indicated that this site was inappropriate as a potential wetlands compensation site. Given that the
2 existence ofwetlands depends on hydrology, and hydrology depends on geologic and geomorphic factors, such information identifies areas most favorable for the occurrence ofwetlands or wetland mitigation. -Michael V. Miller, Illinois State Geological Survey
Hine's emerald dragonfly, a federally listed endangered species, is associ ated with seep areas that receive groundwaterflows from dolomitic limestone formations. The exact habitat requirements oflarvae and adults are still unclear. -Illinois Natural History Survey Annual Report, 1995-1996, p. 10.
Notice that these two examples of the interrelationships between geology and ecosystem elements illustrate the four geologic factors considered by the Illinois Nature Preserves Commission (Schwegman 1984) in delimiting the 14 natural divisions of the state: topog raphy (high terrace of a river channel), soils (sandy permeable soils), bedrock (dolomitic limestone formations), and glacial history (the Illinois River channel's location and con figuration are due largely to the area's glacial history).
Topography influences the biota of Illinois by controlling the diversity of habitats: gener ally, the more rugged the topography, the greater the diversity of habitats. The type of bedrock is often reflected by a characteristic topography (for example, sandstone is typi cally hard and resistant, forming bluffs and ledges, whereas shale is soft and erodible, forming smooth slopes). Bedrock also exerts a control on plant life because of the thin soils that commonly are developed in it. A crucial factor in controlling soil type is the geologic material in which the soil developed (parent material); the diversity of soil par ent materials is partly responsible for tlie varied environments and biota within ecosys tems. Glacial history has played a major role in shaping the topography of the landscape: the subdued, irregular topography characteristic of recently glaciated areas generally is poorly drained, resulting in an abundance of aquatic habitats (Schwegman 1984).
Another interesting example ofthe interrelationships between geology and ecosystems is an observation made at certain landfills in which the water table assumes a mounded shape within the landfill. Cattails have been observed to grow where the water table is high, and cattails help clean up the water by taking some ofthe pollutants out ofthe leachate. -Keros Cartwright, Illinois State Geological Survey
The preceding examples all mention water as a crucial element. Water is also an inherent aspect of the four geologic factors used to delineate natural divisions: topography deter mines drainage, soil moisture is a function of soil texture, bedrock types determine resis tance to erosion, and glacial materials, which range from clayey glacial tills (see Glacial Geology section) to sands and gravels, vary widely in texture and moisture-holding capac ity and their ability to yield moisture to plants (Schwegman 1984)......
3 The geologic foundation of the Lower Sangamon River Assessment Area is bedrock and glacially derived sediments that lie directly beneath the soils and modem sediments at the land surface. The topography of the bedrock surface partly determined the type and distri bution of the overlying glacial deposits. These sediments, in tum, store the area's ground water resources, form the parent materials of the region's rich soils, and playa role in.the development of wetland areas. Sand and gravel deposited by streams of glacial meltwater supports an ongoing industry important to the region's economy. Together, these geologic factors affect the development of the entire range of plant and animal communities within the watershed.
Geology provides the foundation for understanding the complex interactions between the plants and animals and the surface processes we see in the Lower Sangamon River Assess ment Area. Geologic factors also playa fundamental role in how humans use the land. For example, about 88% of the land in the Lower Sangamon River Assessment Area is devoted to agriculture largely because of the abundant fertile soils that developed in the windblown silts that blanket the landscape.
Part 1 of this volume, The Natural Geologic Setting, is organized "from the bottom up"-that is, we begin by describing the bedrock geology, then work our way upward from the bedrock surface and describe the sediments and features that stack on top of each other until we reach the landscape on which we live. This approach may seem counter intuitive to many readers: why don't we begin at the surface, with the geology we can see, and work our way"downward? We believe the opposite strategy is a more logical·and natural approach for two reasons: (1) it reflects the chronological order in which geologic materials were emplaced, and (2) it better describes how the bedrock geology and glacial deposits influence each other and how they combine to create the geologic template upon which life exists on the surface.
Part 2 of this volume, Geology and Society, examines the use of geologic resources within the assessment area and some of the impacts related to resource extraction. It also describes some of the dominant natural and society-induced geologic hazards that can occur in the assessment area.
The following discussions and accompanying maps are generalized for the entire Lower Sangamon River Assessment Area (Figure 1) and cannot be used for site-specific purposes. Users needing more detailed information should contact the authors at .
illinois State Geological Survey Natural Resources Building 615 East Peabody Drive Champaign, 1L 61820-6964 217-333-4747
The maps reproduced in this volume are small-scale versions of preliminary work maps used by the authors in preparation of their sections. The level of detail in these maps is limited by the page size and type and quality of printing available for the reproduction of
4
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0tl===j'0••••21'0'====3p Miles
D assessment area assessment area boundary ! • surface water N county boundary j river or stream
Figure 1. Lower Sangamon River Assessment Area this report. In general, these maps are suitable for general planning and information pur poses. Higher-detail and higher-resolution maps suitable for more specific applications and assessments can be consulted or obtained by contacting the authors at the Il1inois State Geological Survey.
The databases used in this report are discussed in Appendix A.
The fact that Il1inois is incorporating geologic data into this report on the Lower Sanga mon River Assessment Area, and into reports on other assessment areas in the state, is an appropriate recognition of the necessity of integrating geologic and biological data into efforts to preserve our natural heritage.
6 Part 1: The Natural Geologic Setting
Imagine that you are standing on the valley side overlooking the floodplain of the Lower Sangamon River. In the distance you see broad, flat plains, gently roIling hills, and perhaps a tributary valley. Now imagine that 100 feet below that surface (more or less, depending on where you are standing), lies another landscape, complete with roIling hills, flat plains, and valleys. This is the bedrock surface. Every aspect of this surface-its shape, its com position, its stability, or lack of it-and every aspect of the layers of glacial and surficial materials above the bedrock surface exerts some control on life at the surface of the earth. The nature of the geologic framework below us plays a key role in where flora and fauna prefer to grow, where streams flow, where humans build their homes, factories, cities, and where land is set aside for parks and natural areas. Part 1 discusses the geologic framework of the Lower Sangamon River Assessment Area and, where possible, describes how the geology relates to ecosystems and habitat.
7 Bedrock Geology
Description of Materials
Bedrock beneath the Quaternary mantle of unconsolidated glacial material in the Lower Sangamon River Assessment Area consists of sedimentary rocks of middle Mississippian (Valmeyeran) and Pennsylvanian age (Figure 2). The middle Mississippian (lower, middle, and upper Valmeyeran) rocks are dominated by limestone and siltstone. Pennsylvanian strata consist of many relatively thin layers of sandstone, siltstone, shale, limestone, and coal. Sandstone, siltstone, and shale are the dominant lithologies (rock types). Within this assessment area, the Pennsylvanian strata are separated into five formations (Kosanke and others 1960, Willman and others 1967, Greb et a1. 1992) which are generally similar. Each formation is differentiated by key beds (rock layers with diagnostic features) and is characterized by general lithologic differences between minor lithological components. The oldest and lowermost Pennsylvanian formation in the area, which is now called the Tradewater Formation, is characterized by thin, widespread limestone and coals. The over lying Carbondale Formation contains the thickest coal beds in lllinois (The Colchester Coal Member, considered to be one of the most extensive coal beds in the United States, is found in the Carbondale Formation [Hopkins and Simon 1975]; see Coal Mine Subsidence and Acid Mine Drainage section below). The Modesto Formation, which overlies the Carbondale Formation, contains widespread, relatively thicker, argillaceous (clayey) limestones and thin coals, whereas the next youngest Pennsylvanian unit, the Bond Formation, is charac terized by several thick, pure limestones. The youngest and uppermost Pennsylvanian formation, the Mattoon Formation, is characterized by widespread, thin limestones and discontinuous, thin coals. Almost all of the bedrock subcrop (bedrock that occurs directly beneath glacial sediment) in the assessment area is of Pennsylvanian age (Figure 3). Mississippian-age bedrock subcrops only along the northwest edge of the assessment area below and adjacent to the Illinois River Valley. Throughout the assessment area, the bedrock strata generally are tilted gently east-southeastward toward the central, deeper part of the Illinois Basin. As a consequence, the strata at the bedrock surface are progressively younger in age from the northwest edge of the assessment area toward the east-southeast, where the youngest strata (Pennsylvanian Mattoon Formation) occur. This general struc tural trend is interrupted by several local anticlines and synclines, most of which occur in the eastern part of the assessment area (Figure 3). These structures are responsible for some of the outliers of the Pennsylvanian formations within the area, but otherwise have little effect on the rocks at the bedrock surface.
8 13 Period or System 0 Age Era and Thickness .t (years ago) General Types of Rocks , " Holocene Recent- alluvium in river valleys'·>}:>~ :5 Quaternary ~ ~I~ 10,000 Glacial till, glacial outwash, gravel, sand, silt, r.;;~~.•·~.;·.:;. 1: '" 0-500' g0; lake deposits of clay and silt, loess and sand ~ ~ ]l·u dunes; covers nearly all of state except north- : .•:',':;.": ...,;, ~ ~ £a west comer and southem tip :"","",<.11;: () ~ f----~\-P-li-oce=n-=e+[ a;::] Chert grav".l, ~resent in northem, southern and ;0'; .~.~:<".\ <5 a 36:6 m f.-:lIltitmJ'JIIiIllllinLOis..n'" -l4i;·:,.;·A~'·41:o\ l:j ~ Tertiary ~ Mostly micaceous sand with some silt and clay; -:"';~-.C.~:C.7 ZUJ 0-500' ,)' presently only in southern Illinois " Largely shale and sandstone with beds of coal, limestone, and clay ("Coal Measures") 320m Black and gray shale at base, middle zone of MiSSissippian thick limestone that grades to siltstone 0-3,500' chert, and shale; upper zone of interbedded sandstone, shale, and limestone 360m Thick limestone, minor sandstones and shales; Devonian largely chert and cherty limestone in southern 0-1,500' lI1inois; black shale at top 408m 7 7 / // Silurian Principally dolomite and limestone 0-1,000' / / j 438m .c ~ Ordovician Largely dolomite and limestone but contains ~ 500-2,000' sandstone, shale, and siltstone fonnations '0 " If f------jl- 505m +------j:z::~~;lfl, Cambrian Chiefly sandstones with some dolomite and shale; 1,500-3,000' exposed only in small areas in north-central .:.::: :.;. . lI1inois :. . .i/:· I·::·:·::::::: 570m Precambrian Igneous and metamorphic rocks; known in Illinois only from deep wells Figure 2. Generalized Geologic Column for Illinois 9 ------_. -~- ID I . I - ---l / o 10 20 30 I I Miles geologic [J Pennsylvanian formation Mattoon lPmal boundary Bond (Pbl Modesto (Pml fault Carbondale (Pcl I Tradewater (Pt) -+- anticline N Mississippian syncline j Upper Valmeyeran (Mvu) -+- . Middle Valmeyeran (Mvm) assessment area • Lower Valmeyeran (Mvl) boundary county boundary Figure 3. Bedrock Geology (modified after Willman and Others 1967; Nelson 1995) Bedrock Topography The top of the bedrock surface in the Lower Sangamon River Assessment Area is a complex topography of buried valleys, lowlands, and uplands (Figure 4). Buried bedrock valleys generally contain coarse-grained sediments (sands and gravels) that form important, pro ductive aquifers (Horberg 1945). The buried bedrock surface was originally shaped by the well-developed regional drainage system that persisted for several million years during the late Tertiary Period. This old surface, however, was profoundly modified during the repeated episodes of continental glaciation in the past 1.5 million years (Kempton and others 1991). For the most part, the sediments deposited by the glaciers almost completely hide the shape of the underlying bedrock surface. Portions of several large, buried valleys on the bedrock surface traverse the assessment area (Horberg 1950). The largest of the buried valleys is the Lower IIIinois-Mackinaw-Middle Illinois Bedrock Valley; which traverses the northernmost part of the assessment area. One of its major tributaries, the Mahomet Bedrock Valley, crosses the northeastern part of the assessment area in southeast Tazewell County, southwest McLean County, and central De Witt County. A smaller tributary, the Middletown Bedrock Valley, parallels the Mahomet Bedrock Valley and crosses the central part of the area before joining the Lower IIIinois Mackinaw Bedrock Valley in south-central Mason County. A second smaller tributary, the Athens Bedrock Valley, also joins near this intersection. The path of the Athens Valley generally parallels that of the north-south portion of the modem Sangamon River in Menard County. Outcrops of the bedrock are exposed in only a few areas where modem rivers have eroded through the cover ofglacial sediments. Pennsylvanian strata crop out in central Logan County, southern Menard County, central Sangamon County, and central and northwestern Christian County. 11 o 10 20 30 I I MOes Elevations are feet above mean sea level county 500to550 600 to 650 • greater than 700 o boundary N! I o 550to600 • 650to700 -- buried valley axes assessment area - boundary Figure 4. Bedrock Topography and Buried Valleys (modified after Herzog and Others 1994) References Greb, S.F., D.A. Williams, and A.D. Williamson, 1992, Geology and Stratigraphy of the Western Kentucky Coal Field: Kentucky Geological Survey, Series XI, Bulletin 2, 77 p. Herzog, B.L., B.J. Stiff, C.A. Chenoweth, K.L. Warner, J.B. Sieverling, and C. Avery, 1994, Buried Bedrock Surface of Illinois: lllinois State Geological Survey Map 5. Hopkins, M.E., and J.A. Simon, 1975, Pennsylvanian System, in H.B. Willman, et aI., Handbook of Illinois Stratigraphy: Illinois State Geological Survey Bulletin 95, 261 p. Horberg, L., 1945, A major buried valley in east-central lllinois and its regional relationships: Journal of Geology, v. 53, p. 349-359. Horberg, L., 1950, Bedrock Topography of Illinois: Illinois State Geological Survey Bulletin 73, III p. Kempton, J.P., W.H. Johnson, P'.C. Heigold, and K. Cartwright, 1991, Mahomet Bedrock Valley in east-central Illinois-Topography, glacial drift stratigraphy and hydrogeol ogy, in W.N. Melhorn and J.P. Kempton, eds., Geology and Hydrogeology of the Teays-Mahomet Bedrock Valley System: Geological Society of America Special Pa per 258, p. 91-124. Kosanke, R.M., J.A. Simon, H.R. Wanless, and H.B. Willman, 1960, Classification of the Pennsylvanian Strata of Illinois: Illinois State Geological Survey Report of Investigations 214, 84 p. Nelson, W.J., 1995, Structural Features in Illinois: Illinois State Geological Survey Bulletin 100, 144 p. Willman, H.B., J.C. Frye, J.A. Simon, K.B. Clegg, C. Collinson, J. A. Lineback, and T.C. Buschbach, 1967, Geologic Map of Illinois: Illinois State Geological Survey, 1:500,OOO-scale map. 13 Glacial and Surficial Geology Description of Materials Most of the unlithified sediments that overlie the bedrock in the Lower Sangamon River Assessment Area were deposited by the succession of continental glaciers that advanced across the area during the Pleistocene Epoch, or Great Ice Age (Figure 5). These sediments fall into two major categories: till (sometimes called diamicton by geologists) and outwash. Much of the outwash has been re-worked by the wind into sand dunes. Less common types of deposits include lacustrine (lake) sediments and, in a few places, organic-rich debris (peat). Overlying the deposits of glacial origin is a windblown silt, or loess (pro nounced "luss") of late glacial and post-glacial age. Collectively, glacial sediments are called glacial drift. Knowledge about these deposits is especially important because they strongly influence land use, ecosystem development, landscape processes that can affect ecosystems (see also Modem Soils and the Landscape-Influences on Habitats and Agri~ culture section below), and the effects of geologic hazards. Till is a mixture of all sizes of rocks and ground-up rock debris, ranging from the smallest clay particles to the largest boulders. Most till is a compact mixture of clay, silt, and sand particles that provides the matrix that surrounds and supports larger grains, such as pebbles, cobbles, and boulders. Some till was deposited across the pre-existing landscape at the base of the glacier as it moved forward; other till is sediment that flowed as a muddy mass of material off the front of the melting ice sheet or through crevasses (cracks) that devel oped within the ice. Each layer (or bed) of till may represent a particular glacial advance, particularly if it can be recognized over large regions. These layers help identify major groups of sediment associated with particular glacial episodes. When exposed in stream banks, the dense, compact till can be involved in slumping and minor landslides (see Landslides subsection below). During the infrequent earthquakes experienced in the area, however, till is less likely to enhance seismic energy than the loose, water-saturated sediments found along river floodplains. Outwash is sand and gravel that literally "washed out" from the ice in meltwater streams along the front of a glacier. Outwash is found in (l) stream valleys that served as meltwater outlets in front of, or beneath, the glacier, (2) fan-shaped deposits in front of end moraines (the arc-shaped ridges of till that built up on the landscape where the ice margin temporarily sta bilized), and (3) occasionally as isolated hillocks and ridges on the landscape that formed where meltwater carrying rock debris plunged through crevasses in the ice. Where exten sive layers of outwash are associated with particular tills, the identification of the tills in drillholes helps geologists predict the occurrence of major bodies of outwash that can serve as aquifers. 14 1,600,000 and older Figure 5, Timetable of Events in the Ice Age in Illinois (from Killey 1998) 15 0 10 20 30 I I Miles ~ Cahokia Alluvium tea) ~ liskilwa Fm 0 bedrook at or near ablation facies (ta) surface (nQ) Grayslake Peat (gl) till facies (tt) Piatt Mbr {tp. BIDl surface mined Q Peoria and/or Roxana Silts (pta) Delavan Mbr (tdl - water (w) 0 Equality (eq) Teneriffe Silt (t8) assessment area boundary Henry Fm - 0 Pearl Fm - Parkland facies (hpll - Hagarstown Mbr (peh) county boundary N! Mackinaw facies (hml Batavia facies (hb) -0 Glasford Fm river or stream j Wasco facies (hw) Radnor ril' (gr) Hulick Till (ghk) stratigraphic unit Lemont Fm Vandalia Till Cgv) boundary Batestown Mbr lib) KeJlerviJIe Till (gk) - Yorkville Mbr (IV) Figure 6. Glacial Geology in the Lower Sangamon River Assessment Area Outwash is a potential resource for construction sand and gravel (see Mineral Resources section below). Layers (or beds) of outwash also occur within the glacial sediments between bedrock and today's land surface. Such sand and gravel deposits are generally porous and permeable; that is, fluids such as water can move easily among the grains. When thick enough, these deposits can be excellent aquifers (see Aquifer Delineation section below). Lacustrine (lake) deposits generally consist of fine-grained sediments such as silt and clay deposited in temporary lakes that commonly formed along the margin of the ice as it melted or between a moraine and the melting ice front. These sediments commonly are poorly drained and may cause water problems in construction projects. Organic-rich layers of sediment that sometimes occur between layers of glacial sediment in some places can serve as important marker beds that represent major intervals of warmer climate between glaciations during which soils developed and vegetation grew. Organic deposits that separate major sequences of glacial sediments help geologists inter pret the sequence of deposits and predict where outwash may occur below the surface. The low bearing capacity (weight the ground can safely support) of organic soils can affect construction. Loess, a windblown silt, blankets much of the landscape in the assessment area. It has important properties that make it an excellent parent material for the region's productive soils: it crumbles easily when lightly squeezed, drains well yet has good moisture-holding capacity, and contains no pebbles or cobbles to interfere with plowing. Loess is derived from sediments that were deposited along the major meltwater valleys, such as the lllinois River Valley, by sediment-laden meltwater flowing from the melting glaciers to the northeast. Prevailing westerly winds picked up the finer sediments-silt, fine sand, and some clay-from the floodplain and blew them across the landscape. Loess is thickest immediately east of the major valleys and thins rapidly with distance eastward. Regional Glacial History Hundreds of records (logs) and samples of sediments from borings drilled throughout the Lower Sangamon River Assessment Area are stored and catalogued at the Illinois State Geological Survey. Deep borings that penetrated the entire sequence of glacial sediments 'overlying bedrock provide the records from which the general glacial history of the region can be interpreted. The sediments left by the earliest (pre-Illinoian) glaciers in this area are not shown in Figure 6 because they are either buried beneath younger deposits or are eroded away (Willman and Frye 1970). The early sediment record is therefore less clearly defined than that of the more recent llIinois Episode (between approximately 300,000 and 125,000 years ago; see Figure 5) and the most recent Wisconsin Episode of glaciation (between approxi mately 25,000 and 13,500 years ago; see Figure 5) (Hansel and Johnson 1996, Killey 1998). Nevertheless, pre-lliinoian glaciers and their meltwaters probably deepened the pre-existing I7 bedrock valleys in the area. One of the largest of these, the Mahomet Bedrock Valley, extends westward and northwestward across the northern part of the assessment area from De Witt County to the Illinois River. Its tributary. the Middletown Bedrock Valley, trends through the northeastern comer of Sangamon County and the southwestern part of Logan County, and joins the Mahomet Bedrock Valley in the vicinity of the junction of the Menard, Logan, and Mason County lines (Figure 4). Remnants of sediments depos ited during pre-Illinoian glaciations exist in the deeper parts of the bedrock valleys (Kempton and others 1991); coarse-textured units such as sands and gravels associated with pre-llIinoian glaciations are preseni and serve as aquifers for communities lying above them. Tills deposited directly by pre-Illinoian glaciers are collectively named the Banner Formation (Willman and Frye 1970) but do not appear on the surficial geologic map of the assessment area (Figure 6) because they are buried. The Yarmputh Soil, a major buried soil that developed in the pre-Illinoian till and loess, was formed during a long warm interval between major glacial advances; the soil is still preserved in places on the upper surface of Banner Formation sediments. Even where the Yarmouth Soil is absent, a weathered surface can sometimes help us trace the physical record of this major time interval between glacial episodes. Above the Banner Formation and Yarmouth Soil are sediments deposited by glaciers of the Illinois Episode of glaciation. These sediments occur directly beneath the loess blanket in most of the central and southern parts of the assessment area (Figure 6). The tills are members of the Glasford Formation (Willman and Frye 1970). The Radnor Till (symbol "gr" on the glacial geology map) is a gray, compact silty till, and the Vandalia Till (symbol "gv" on the map) is a hard, compact sandy till. Major and minor beds of sand and gravel associated with Glasford Formation tills are present, some of which serve as important aquifers for some communities in the assessment area (see Aquifer Delineation section below). The Teneriffe Silt (map symbol "ts"), a unit composed primarily of silt and clay with some beds of sand, was deposited in large proglacial lakes associated with Illinois Episode glaciers. A major area of Teneriffe Silt occurs just beneath the loess in central Sangamon County (Figure 6). Northeast, east, and southeast of the area mapped as Teneriffe Silt are some scattered ridges and hillocks of sand and gravel; this sediment is classified as the Hagarstown Member of the Pearl Formation (map symbol "peh"; Killey and Lineback 1983). These distinctive ridges and hillocks may have originated as deposits from glacial meltwater during the waning stages of one of the advances of the lllinois Episode glacier into the area, or as deposits between two coalescing lobes of Illinois Episode glaciers (Jacobs and Lineback 1969, Killey 1998). Another major buried soil, the Sangamon Soil, and associated weathering surfaces com monly occur at the top of Illinoian sediments. The Sangamon Soil represents the major warm interval between the Illinois and Wisconsin Episodes of glaciation. The Sangamon Soil and the widespread, overlying silts called the Roxana Silt (distinctive for its pinkish tan color) and the Robein Silt (distinctive for its high organic content) form important subsurface marker beds that predate the advance of Wisconsin Episode glaciers. 18 ------_. --- 0 10 20 30 I I Miles 0 Jess than 25 feet 300 - 400 feet 0 25 - 50 feet • 400 - 500 feet , 50 -100 feet • open water N 100 - 200 feet assessment area i • • boundary • 200 - 300 feet county boundary • river or stream Figure 7. Drift Thickness in the Lower Sangamon River Assessment Area In the northeastern segment and the easternmost part of the southeastern segment of the assessment area, tills deposited during the Wisconsin Episode of glaciation overlie llJinois Episode sediments. These tills belong to the Wedron Group (Hansel and Johnson 1996) and compose the major landforms seen on the present land surface in this area, primarily end moraines (arc-shaped ridges) and ground moraine (the gently rolling land surface be tween end moraines). The till that lies at or near the surface over most of this area is the Delavan Member of the Tiskilwa Formation (map symbol "td"); the Delavan consists of gray to pinkish gray, sandy silty till. Along the border of the northeastern segment of the assessment area, the gray silty till of the Batestown Member of the Lemont Formation (map symbol "lb") has been mapped. Water-laid sediments deposited during the Wisconsin Episode include sand and gravel outwash of the Henry Formation. The assessment area includes a broad swath of Henry Formation outwash (Mackinaw facies; map symbol "hm") that extends along the Illinois River from the Sangamon River across much of Mason County into the southwestern part ofTazewell County (Figure 6). Broad areas ofoutwash within this swath have been reworked by the wind into sand dunes, classified as Parkland facies (map symbol "hpl"). Elsewhere in the assessment area, Henry Formation outwash occurs as fans and sheets of sand and gravel along the fronts of end moraines (Batavia facies; map symbol "hb"), although other minor areas of outwash also occur, including some reworked dune sand beyond the Wisconsin glacial margin on the Glasford surface. Loess, classified as Peoria and Roxana Silts (map symbol "prs"), blankets nearly all the land surface except for areas along streams. It is mapped as a separate unit only where its thickness exceeds 20 feet (primarily in Cass, northern Menard, and eastern Mason Counties). Elsewhere in the assessment area, it thins eastward to less than 10 feet thick and therefore is not shown on the map. Minor areas of Grayslake Peat (map symbol "gl") occur in the westernmost tip of the assessment area. Stream deposits (alluvium) belong to the Cahokia Formation (map symbol "ca"; Willman and Frye 1970). Thickness of Materials Glacial deposits range from less than 25 feet to more than 400 feet thick within the assess ment area (Figure 7; Piskin and Bergstrom 1975). Generally, the glacial deposits are relatively thin (100 feet thick or less) in approximately the southern one-third of the area, but they are mostly 100 feet thick or more across the northern two-thirds. The thickest deposits, 300 to 400 feet thick, coincide with the Mahomet Bedrock Valley in De Witt, southwestern McLean, and Tazewell Counties, and its tributary, the Middletown Bedrock Valley in eastern Sangamon and southwestern Logan Counties. One small area with more than 400 feet of drift is located in southwestern De Witt County. Most ofthe'drift consists of tills; but thick outwash deposits occur in many of the bedrock valleys, and lacustrine deposits make up the rest. 20 References Hansel, A.K., and W.H. Johnson, 1996, Wedron and Mason Groups-Lithostratigraphic Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area: Illinois State Geological Survey Bulletin 104, 116 p. Jacobs, A.M., and J.A. Lineback, 1969, Glacial Geology ofthe Vandalia, Illinois, Region: Illinois State Geological Survey Circular 442, 24 p. Kempton, J.P., W.H. Johnson, P.C. Heigold, and K. Cartwright, 1991, Mahomet Bedrock Valley in east-central lllinois-Topography, glacial drift stratigraphy, and hydrogeology, p. 91-124, in W.N. Melhorn and J.P. Kempton, 1991, Geology and Hydrogeology of the Teays-Mahomet Bedrock Valley System: Geological Society of America Special Paper 258, 128 p. Killey, M.M., 1998, llIinois' Ice Age Legacy: Illinois State Geological Survey Geoscience Education Series 14,66 p. Killey, M.M., and J.A. Lineback, 1983, Stratigraphic Reassignment of the Hagarstown Member in Illinois, in Geologic Notes: Illinois State Geological Survey Circular 529, p. 13-16. Lineback, J.A., 1979, Quaternary Deposits of Illinois: Illinois State Geological Survey, 1:500,OOO-scale map. Piskin, K., and R.E. Bergstrom, 1975, Glacial Drift in Illinois: Thickness and Character: lllinois State Geological Survey Circular 490, 35 p. Willman, H.B., and J.e. Frye, 1970, Pleistocene Stratigraphy of Illinois: Illinois State Geological Survey Bulletin 94, 204 p. 21 Modern Soils and the Landscape-Influences on Habitat and Agriculture The Lower Sangamon River Assessment Area contains some very productivesoils, as indicated by the extensive distribution of agricultural land cover (Figures 13 and 14). Soil development in the area is strongly influenced by geologic, topographic, and biologic .factors. The influences of geology and topography on soil development are discussed here. Geology, topography, and soil types combine to produce different types of habitat that are conducive to the development and survival of various natural plant and animal communities. Geologic Factors Loess, till, outwash, eolian sand, and alluvium are the dominant parent materials of the soils in this assessment area. These materials differ significantly in their permeability, erodibility, and physical and chemical characteristics. By affecting water table elevation, erosion, sedimentation, and water chemistry, these differences create localized habitats. Soil texture, acidity, and other physical and chemical characteristics are very important in determining land use and land cover (see Land Cover Inventory section below). This assessment area contains an exceptionally large number of soil associations (23) because the landscape is complex. The complexity derives from the presence of the terminal moraine for the Wisconsin Episode glaciers (northeastern part of the area), the extensive outwash sand and gravel along the drainages, the large expanse ofeolian sand in Mason County, the strongly weathered Illinoian till plain, and the variable thickness of windblown silt (loess) over the entire assessment area. Loess is the initial parent material for most of the soils in the Lower Sangamon River Assessment Area. The overall thickness of windblown silt (loess), in which modern soils have developed, varies across the assessment area, but its distribution across the landscape is rather continuous, as are its physical and chemical characteristics. The loess is generally thickest in the southern and western part of the assessment area and thins toward the north and east, where it may be less than 3 feet thick. Also affecting soil development are the materials underlying the loess. Silty clay loam till is found throughout the area, but it may be loamy to sandy in some areas. Most of the soils have developed partially into the under lying till, especially in local areas where erosion has removed the overlying loess cover (Figure 6). Outwash and eolian sand in the western part of the assessment area have provided the sediment for sand dune development. 22 Topographic Factors Topographic influences (Figure 8) on drainage, erosion, and deposition are important in the long-term development of the landscape. Differences in the frequency, rate, and mag nitude of surficial geologic processes have created many combinations of slope angle, slope length, and slope orientation that influence local drainage, erosion, and sedimentation. Modifications by human activities are also creating significant changes in surficial processes (discussed in Soil Erosion and Sedimentation subsection below). The upland areas between tributary drainages are commonly level and poorly to somewhat poorly drained. Prime farmland is located in these areas, as shown by Figure 15. Down stream portions of each subbasin, however, commonly have greater amounts of pasture and forest cover. This increase demonstrates the effect topography and soil erosion have on land use. The physiography of the Lower Sangamon River Assessment Area is sub divided into four general units by the positions of large end moraines and the large expanse of sand in Mason County. The moraines occur in McLean County and along the Logan De Witt-McLean county boundaries and are clearly shown on the drift thickness and surface topography maps (Figures 7 and 8) of this area. This relationship is also shown well in the figures in the Land Cover Inventory section of this report. . Soil Classification The soils in the Lower Sangamon River Assessment Area are classified predominantly into two soil orders, Alfisols and Mollisols. Alfisols and Mollisols can be differentiated by the accumulation of organic matter in the upper soil horizon: Mollisols are rich in organic matter and have a darker soil color (black to dark brown), whereas Alfisols are not as organic rich and have thinner upper soil horizons. In general, Mollisols have devel oped under natural prairie or marsh vegetation, whereas Alfisols have developed under forest vegetation. Prairie grassland soils (MolIisols) tend to be more fertile. Poorly and very poorly drained Mollisols and Alfisols are common along drainages, floodplains, and flat upland areas and can play an important role in the development and maintenance of localized habitats. There may also be scattered occurrences of Entisols and Inceptisols on floodplains and sandy outwash and eolian areas, and along steeper, eroded uplands. Entisols and Inceptisols are soils with minimal soil horizon development. They occupy small acreages in the area, but are still significant because. they help create niche communities (for example, where exceptionally sandy sediments exist). Twenty-three soil associations are found in the Lower Sangamon River Assessment Area (Figure 9). The thick to moderate loess cover has provided relatively uniform parent materials, and topography associated with stream incision has controlled the pattern of ·erosion. The most widespread associations include the Ipava, Sable, Tama, Herrick, Virden, and Piasa soils. Significant occurrences of the Plainfield, Bloomfield, Sparta, and Oakville 23 ------ Topography of a land surface is the physical configuration of the land in terms of the difference in elevations. Topographic features are commonly illustrated by means of contour lines. Contour lines represent the same elevation along their entire length. The relative proximity of adjacent contours depicts the slope of an area. For example, the closer together the contours, the steeper the land surface; the farther apart the contour lines, the flatter the land. o 10 20 30 I I Miles [J assessment area Surface elevation ranges from about 443 feet (135 meters) assessment area to 919 feet (280 meters~ above N! boundary sealevel. j county boundary topographic contour (5 meter interval or 16 feet) Figure 8. Topography in the Lower Sangamon River Assessment Area I 1 1 I WOODFORD CO. _ .J 1 f ~ ---I 1 1 '- -., I- __ r J 1 L --.., I 1 1 1 1 I gJ I I :rIo I ::>"'I"<: I ~I~ o01 3u. ~I ---1, 1 _ SCHUYLER CO .. ---I I .1 81 i5' ~I ::< I I -- ,.....-----,I PIATT CO. J ,-1 8·1 1 ~I ~I - ::> I 01 1--, ::<1 1 1 -.,, , I ---I 1 r 1 l .J-- I I I I ______...J1 -- LSHELBYCO.------ o 10 20 30 I I Miles IIIIIlIII IPAVA-SABLE-TAMA(lLOO3) JASPER-LA HOGUE-SELMA (IL023) PLAINFIELD-BLOOMFIELD-SPARTA (lL056) [jjjjji] HERRICK-VIRDEN-PIASA (lL004) -[jjjjji] GILFORD-MAUMEE-SPARTA (lL0241 -PLAINFIELD-SPARTA-OAKVILLE (lL0711 [jjjjji] COWDEN-OCONEE-DARMSTADT (lLOO5) IlIIIIlI SAWMILL-GENESEE-LAWSON (lL028) -IPAVA-VIRDEN-HERRICK (lL072) 0 BROADWELL-LAWNDALE-ONARGA (lLOO9) 0 BEAUCOUP-LAWSON-DARWIN (lL029) -CATLIN-DANA-TAMA (lL073) 0 FLANAGAN-DRUMMER-CATLIN (lL010) ROZETTA-FAYETTE-HICKORY (lL034) -ASHKUM-CHENOA-GRAYMONT (lLOB1) DRUMMER-PLANO-ELBURN (lL012) ROZETTA-KEOMAH-HICKORY (lL0361 WATER - -assessment area WORTHEN-L1TTLETON-EL8URN (lL013) 0 MIDDLETOWN-ALVIN-SYLVAN (IL04l1 -0 - -boundary rzzJ SAYBROOK-DRUMMER-PARR (lL014) FINCASTLE-SABINA-8IRKBECK (lL045) county boundary [3 ELLlO"FASHKUM-VARNA (lL016) 0 MIAMI-STRAWN-HENNEPIN (lL046) - river or stream Figure 9. Soils in the Lower Sangamon River Assessment Area soils are found in Mason County. The more productive soils have developed in thicker loess areas and tend to be MolIisols, which owe their fertility, in part, to their high organic matter content. Many have more than 4.5% organic matter in the plow zone. The upland subbasins devoted to row-crop agriculture are dominated by the Tama, Virden, Sable, Ipava, Drummer, and other very productive Mollisols (see Figure 9). In general, the soils classified within the same soil association will behave in a similar fashion and can be treated as a single unit for general planning purposes. Differences in drainage class are often the reason for differences in soil characteristics on a local scale. Soil Erosion and Sedimentation In areas where slopes of less than 5% (5 vertical feet in 100 horizontal feet) predominate, the potential for soil erosion is generally low. The general lack of drainage dissection in parts of the flat upland and floodplain areas, however, combined with the slow permeability of the relatively fine textured underlying sediments, makes high water tables, wet soils, severe stream and channel erosion, and sedimentation in streams and lakes a problem across the area. Flat upland and floodplain areas may be prime wildlife and wetland areas if they have not been cleared for cultivation. Steeper slopes adjoining the floodplains of the streams are commonly susceptible to severe soil erosion through sheetwash and the development of extensive gully networks. This eroded sediment is often transported into small local channels and, ultimately, into the larger drainages. Uncontrolled erosion and sedimentation can seriously damage biologic.com munities that live in the channel or along streambanks by altering water tables, channel capacity, and channel geometry. The extensive distribution and thickness of loess across the assessment area further contrib utes to the erosion hazard. Loess is easily picked up (entrained) and carried by moving water or wind. When dry, loess has the consistency of talcum powder and, if unprotected, is easily carned by wind. Loess is also particularly susceptible to erosion by running water because of its low shear resistance. It is rapidly incised and develops into a deeply dis sected landscape characterized by rills and gullies that are difficult to control. On topographic maps, this characteristic drainage pattern is shown as highly crenulated (sinuous) topo graphic contour lines (see Figure 8). Where loess overlies less permeable geologic mate rials such as fine-textured tills, the contrast in permeability and erodibility creates problems in land management, especially where the overlying loess unit is dissected or eroded and the less-permeable underlying materials are exposed at or near the land surface. Further increasing the erodibility of loess is the tendency for piping to develop within the soil. Piping is common when surface water penetrates to the subsurface and flows along macropores, such as open channels formerly occupied by roots, or along other natural fractures in the ground. These linear "pipes" may enlarge and ultimately collapse, causing the ground surface to subside and form small surface drainage channels. These channels 26 ------then begin to collect and transport sediment and water as they are integrated into the local drainage system. Areas with sloping, forested soils are especially susceptible to piping and are where hillside gullies often begin, even when the ground surface has not been disturbed by deforestation or cultivation. Once begun, these small rills and gullies can quickly enlarge and erode upstream, extending the drainage network and directing increased water and sediment into the existing drainage system. The increased water and sediment discharge can initiate streambank erosion and streambed changes that are detrimental to the biologic communi ties that inhabit the stream channels. The more widespread areas of grassland and forested land cover remaining in the Lower Sangamon River Assessment Area (Figures 17 and 18) are generally found along stream valleys and indicate the difficulty of cultivating the steeper, more dissected and eroded landscape associated with major drainageways. These grassland and forested areas con tribute to the existing prime wildlife habitat in the region. Most of the eroded soils in the assessment area are located on slopes adjacent to stream channels, especially along the larger tributaries. The increase in slope angle and slope length in these areas creates a high potential for erosion. Because of their topographic position, low wetland areas commonly receive accelerated deposition of sediment eroded from adjacent upland areas that have been in, or are currently in, cultivation or are in transition from undisturbed natural vegetation. This inundation of sediment can degrade wildlife food supplies and fill stream channels, decreasing their capacity to transport water and increasing the frequency of discharges of floodwater over the banks of streams. Pools along the streams are especially prone to damage from sedimenta tion. Pesticides and other agricultural chemicals adsorbed to the sediment may also be deposited in channels and pools. The physical load of sediment can accumulate quickly enough to bury part of the modem soil. Buried modem soils can be seen in some vertical soil profiles exposed along stream courses where a dark-colored former soil horizon lies beneath recently deposited, lighter colored sediments. Such buried modem soils are evidence of accelerated erosion resulting from human activity and are environmental indicators of current and potential problems in a drainage system. Land Management Practices Sound land use and management practices are especially important in controlling erosion on loessial soils. Damaged land should quickly be remediated, and appropriate erosion control measures should be implemented to prevent additional damage to the landscape. It is unlikely that severe erosion caused by gullying on hillslopes will repair itself quickly enough to prevent extensive damage to adjacent land. Gullies that develop in loess can quickly become too deep for farm equipment to cross and eliminate through tillage. 27 Farming along narrow ridgetops is generally not advisable due to the lack of transition zones along field edges to keep water from running off the field and entering hillside drainage channels. The moderately slow penneability of many of the soils in the assessment area creates conditions conducive to flooding and standing water during periods of high water table or heavy precipitation. Some of the soils in the assessment area respond well to tiling, and field drainage has increased the volume and rate of runoff from cultivated fields. The increased stream discharge that results from tiling, however, is causing extensive erosion problems through channel widening and bank failure along many of the drainages. In summary, the potential for water and wind erosion and the slow penneability of soil are the major management problems faced by land users in this area. The many potential problems created by the predominance of silty soil and variable topography can be allevi ated by appropriate conservation tillagepractices and tiling. County Soil Survey Reports The Lower Sangamon River Assessment Area covers parts of fourteen counties, with most of the area being in McLean, De Witt, Logan, Mason, Menard, Cass, Christian, and Sangamon Counties. The assessment area is covered by modern soil surveys, and digital soil surveys are in progress in McLean, Christian, Macoupin, and Sangamon Counties. The infonnation from these reports, however, is available to interested individuals by contact ing the Natural Resources Conservation Service (NRCS) office in that county. Using the appropriate software, these digital products can provide increased versatility in applying soil characteristics in environmental planning. As always, individuals or groups seeking to plan environmental restoration or conservation projects should contact local federal, state, and county offices to determine the nature of the soils and consult other appropriate environmental databases. The maps presented in this assessment report are too small in scale (not detailed enough) to provide for more than a cursory or reconnaissance level of interpretation. They are for general planning and infonnation purposes only. Many county soil survey reports are being updated and converted to digital fonnal. Although this process will take some years to complete, interested individuals and groups should check with their local NRCS agent to learn what materials and information are available for their specific location. The individual soil maps presented in each county soil survey report are published at a scale of I: 15,840, or I inch equals 1,320 feet (0.25 miles). A smaller-scale soil association map is also included, usually at a scale of about 1:250,000, or I inch equals about 4 miles. The scale of the soil association map is too small (contains too little detail) for site-specific planning and analysis, but the individual soil sheets are ideal for this purpose. Even these maps, however, lack the detail necessary for specific site assessments for construction, but they are valuable for most environmental-scale planning. 28 ,\ The large-scale soil maps in county soil survey reports are valuable sources of information regarding local conditions. Tabulated information within the report summarizes the capabilities and limitations of each soil series for various land uses as well as their physical and chemical characteristics. There are also tables with information concerning the suitabil ity and capability of soils for supporting wildlife and woodland habitats. References Alexander, J.D., and R.G. Darmody, 1991, Extent and Organic Matter Content of Soils in lllinois Soil Associations and Counties: Department of Agronomy, College of Agriculture, University of Illinois at Urbana-Champaign, Agronomy Special Report 1991-03, 64 p. Berning; G.V., 1994, Soil Survey of Christian County, Illinois: U.S. Department of Agriculture, Soil Conservation Service and Illinois Agricultural Experiment Station, University of Illinois at Urbana-Champaign, 200 p. Calsyn, D.E., 1995, Soil Survey of Mason County, lllinois: U.S. Department of Agriculture, Soil Conservation Service and lllinois Agricultural Experiment Station, University of Illinois at Urbana-Champaign, 211 p. Fehrenbacher, J.B., I.J. Jansen, and KR. Olson, 1986, Loess Thickness and Its Effect on Soils in Illinois: University of Illinois at Urbana-Champaign, Agricultural Experiment Station, Bulletin 782, 14 p. Fehrenbacher, J.B., J.D. Alexander, I.J. Jansen, R.G. Darmody, R.A. Pope, M.A. Flock, E.E. Voss, J.W. Scott, W.F. Andrews, andL.J. Bushue, 1984, Soils oflllinois. University of Illinois at Urbana-Champaign, Agricultural Experiment Station, Bulletin 778, 85 p. Gotsch, KA., 1996, Soil Survey of Shelby County,lllinois: U.S. Department of Agriculture, Soil Conservation Service and llIinois Agricultural Experiment Station, University of Illinois at Urbana-Champaign, 189 p. Hansel, A.K, and W.H. Johnson, 1996, Wedron and Mason Groups-Lithostratigraphic Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area: Illinois State Geological Survey Bulletin 104, 116 p.; plate 1: Quaternary Deposits of Illinois (map). Hudelson, G.W., 1974, Soil Survey of Logan County, Illinois: U.S. Department of Agriculture, Soil Conservation Service and Illinois Agricultural Experiment Station, University of Illinois at Urbana-Champaign, 99 p. Martin, W.S., 1991, Soil Survey of Piatt County,lllinois: U.S. Department of Agriculture, I Soil Conservation Service and Illinois Agricultural Experiment Station, University of lllinois at Urbana-Champaign, 131 p. I 29 ", Teater, W.M., 1996, Soil Survey of Tazewell County, Illinois: U.S. Department of Agriculture, Soil Conservation Service and Illinois Agricultural Experiment Station, University of Illinois at Urbana-Champaign, 2lOp. United States Department of Agriculture, 1994, State Soil Geographic (STATSGO) Data Base, Data Use Information: Natural Resources Conservation Service, National Soil Survey Center Misc. Publication no. 1492 [1994 revision], 35 p., plus appendices. Wascher, H.L., J.D. Alexander, B.W. Ray, A.H. Beavers, and RT. Odell, 1960, Characteristics of Soils Associated with Glacial Tills in Northeastern Illinois: University of Illinois at Urbana-Champaign, Agricultural Experiment Station Bulletin 665, 155 p. Wascher, H.L., B.W. Ray, lD. Alexander, lB. Fehrenbacher, A.H. Beavers, and RL. Jones, 1971, Loess Soils of Northwest lllinois: UniversitY of Illinois at Urbana-Champaign, Agricultural Experiment Station Bulletin 739, 112 p. Windhorn, RD., 1998, Soil Survey of McLean County, Illinois: U.S. Department of Agriculture, Soil Conservation Service and Illinois Agricultural Experiment Station, University of Illinois at Urbana-Champaign, 277 p. 30 Landscape Features and Natural Areas with Geologic Features of Interest Landscape Features The landscape features of the Lower Sangamon River Assessment Area result from the multiple glacial advances across the area. The northeastern segment of the assessment area, along with a narrow band along the east border of the southeastern segment, falls within the physiographic division called the Bloomington Ridged Plain (Figure 10). The remain der of the area falls with the Springfield Plain. Both the Bloomington Ridged Plain and the Springfield Plain are subdivisions of the Till Plains Section of the Central Lowland Province (Leighton and others 1948). The Bloomington Ridged Plain is characterized by a succession of end moraines (the "ridges" referred to in the name of this physiographic division) that arc across the land surface. In the Lower Sangamon River Assessment Area, the Shelbyville Moraine represents the farthest southward terminus of the Wisconsin Episode glacier. Other moraines behind the Shelbyville include the southern part of the Bloomington Morainic System, a group of several major and minor moraines that trend generally east-southeast across the southern part of McLean County. The Springfield Plain includes the generally level portion of the landscape covered by Illinois Episode glaciers in central and south-central Illinois. The topography has both uplands and lowlands. Most of the land in the Lower Sangamon River area is in uplands, the extensive higher ground that includes the end moraines and ground moraine in the assessment area. The major area of Henry Formation outwash and sand dunes east of the lllinois River is informally called the "Havana Lowlands" (after the town of Havana on the east bank of the Illinois River), and may be considered lowlands because the outwash was deposited along a broad lowland area of what is now the Illinois River Valley. Elsewhere in the area, the limited lowlands occur mostly along stream valleys, floodplains, and similar areas of alluvial deposition. Because of the brief time since the retreat of the last glaciers, the Lower Sangamon River area has undergone relatively little erosion, and the uplands between stream valleys remain comparatively broad and flat. Natural Areas with Geologic Features of Interest According to Illinois Natural History Survey records, four natural areas containing features of geologic interest occur within the Lower Sangamon River Assessment Area. 31 WI~7i~~~~S_'fc'T::IL:.::L-,-P.::LA:...I~N.S:-"S::E_C:.T.:.I.O.:.:N.: ,..,~ ..,-G_R.E....A....T, LAKE S eTlaN ~ 'r -~~. ~~'~r~-+: ·;J;~I--M(\laiflal-- ,:\ CentrallhwlRnd Province Ozark Plateaus Province Cnterior lnw Plateaus Province Co~tal Plain P1'ovince - province boundary physiographic section boundary section subdivision boundary county boundary Lnwer Sangamon • Ass8ssmentArea Scale 1:3,000,000 :J~d!..-4::lINTERIOR LOW 0 50 Miles ,~~~~~~, PLATEAUS o 60 Kilometers , ! '""""~~I-. PROVINCE COASTAL PLAIN PROVINCE Figure 10. Physiographic Divisions of Illinois (from Leighton, Ekblaw, and Horberg 1948) Table 1. Natural Areas with Features of Geologic Interest Name Geologicalfeature Type ofownership Cass County . Cottonwood Geological Loess fonnations Private Area Mason County Quiver Prairies Sand dunes (No infonnation available) Menard County . Bobtown Hill Prairie Exposed glacial materials Private in excavation* Sangamon County Carpenter Park Sandstone outcrop Public * Potential for residential development References Illinois Natural Areas Inventory, 1978: Department of Landscape Architecture, University of Illinois at Urbana-Champaign, and Natural Land Institute, Rockford, IL, 3 vols. Leighton, M.M., G.E. Ekblaw, and c.L. Horberg, 1948, Physiographic Divisions of Illinois: lllinois State Geological Survey Report of Investigations 129, 19 p. 33 Land Cover Inventory Introduction Land is the "raw material" of Illinois. Current and detailed information regarding this fundamental natural resource is essential for making wise decisions affecting the land and ensuring good stewardship. Land can be described in terms of a number of biological, geological, and hydrological characteristics. This section focuses on land cover, a principal factor of a region's land resource. The following paragraphs introduce and explain some basic concepts. Land use refers to human activities on the land and emphasizes the principal role of land in describing a region's economic activities. Since the concept describes human activity, land use is not always directly observable; that is, we often cannot "see" the specific use of a parcel of land. For example, the ·presence of forested land in an aerial photograph or .satellite image does not convey the possible multiple uses of that land, which may include recreation, wildlife refuge, timber production, or residential development. Land cover refers to the vegetation and manmade features covering the land surface, all of which can be directly observed using remote sensing imagery. I Whereas land use is abstract, land cover is tangible and can be determined by direct inspection of the land surface; it is the visible evidence ofland use (Campbell 1987). In association with other geologic data (such as aquifer location, distribution of water wells, and soil characteristics), geologists can use land cover and land use maps to infer geologic conditions in an area. For example, knowledge of land cover (such as location and extent of urban lands and cropland) is essential to accurately assess the potential for groundwater contamination. Land cover information is also important for resource conservation. In areas where natural vegetation predominates, land cover maps can be used as substitutes for ecosystems in conservation evaluation because vegetation effectively integrates many physical and biological factors in a geographic area (Scott 1993). Remote Sensing Products Land use and land cover maps are derived directly from remote sensing imagery. Geologists use a variety of data sources to derive information concerning surface and near-surface 1 Remote sensing is the science of deriving infonnation about an object or phenomenon at or near the sur face of the earth through the analysis of data acquired by a camera or sensor system located in an aircraft or orbiting satellite. 34 conditions, and the usefulness of remote sensing imagery for mapping geologic features has been long recognized (USGS 1994). For assessments at the site level (for example, sample sites or plots) or small regions (for example, county-level), land cover information is typically derived from the interpretation of aerial photography. At the statewide level, land cover information is usually derived from the analysis of satellite imagery, and the resulting inventory offers accurate, regional level information regarding surface cover characteristics. Although agricultural lands dominate three-fourths of the surface of Illinois, and many landscape features have been obscured as a result of 175 years of European settlement, under optimum ground conditions, remote sensing imagery can show subtle changes in the uppermost few feet of materials that are similar in detail to soils maps. Factors of biodiversity associated with resource quality, richness, and quantity can be estimated with remotely-sensed data, principally because a remote sensing approach can compare changes in land use over time (Stoms and Estes 1993). In 1996, the Illinois Department of Natural Resources published Illinois Land Cover: An Atlas (IDNR 1996) and Illinois Land Cover: An Atlas on Compact Disc (IDNR 1996), which present the most recent and comprehensive inventory of the state's surface cover. Multitemporal, Landsat Thematic Mapper satellite imagery acquired during 1991-1995 . was the principal data source. All of the land cover information presented in this section is derived from Illinois Land Cover: An Atlas on. Compact Disc. Land Cover Statistical Summary The most pervasive change to the natural vegetative cover within the state has been the emergence and growth of agricultural land use, and this is best seen on the broad, flat glaciated uplands in Illinois where most of the Lower Sangamon River Assessment Area is situated. Landsat Thematic Mapper satellite imagery acquired on October 3 and 12 and June 13, 1992, and May 27, 1994, were the primary data source for the interpretation of the land cover informationwithin the Lower Sangamon River Assessment Area (IDNR 1996). The type and extent of land cover within the assessment area is presented in Table 2, and for purposes of comparison, a statewide summary of land cover is provided in Table 3. In addition, Appendix B provides an inventory of land cover for each subbasin; the original 18 categories shown in Table 2 have been consolidated to 9 principal land cover categories (see Table 4) to facilitate subbasin comparisons. 35. Location and Area The following are the principal statistics about the land cover of the assessment area. • Originating in McLean County, the Sangamon River flows for approximately 200 miles southwest, then north and west to its confluence with the Illinois River near Beardstown. It drains approximately 5,400 square miles from portions of 16 counties in central Illinois. Salt Creek and South Fork are the major tributaries, with Salt Creek draining the north and central portions of the basin and South Fork draining the south and southeast portions of the drainage area (IEPA 1994). • The Sangamon River is divided into three segments: (1) the lower Sangamon, extending from its confluence with South Fork to the lllinois River; (2) the middle Sangamon, which extends between the South Fork confluence and Lake Decatur; and (3) the upper Sangamon River, which extends above Lake Decatur. • The Lower Sangamon River Assessment Area, encompassing the largest of the three segments, includes portions of 15 central Illinois counties: Cass, Christian, De Witt, Logan, McLean, Macon, Macoupin, Mason, Menard, Montgomery, Morgan, Piatt, Sangamon, Shelby, and Tazewell Counties (Figure 11). • The assessment area is extensive, encompassing a surface area of 4,574.8 square miles (2,927,864 acres), which represents approximately 8.1 % of the total surface area of Illinois. • Fifty-one subbasins compose the assessment area (Figure II), ranging in size from 590.2 square miles (212,467 acres) (Kickapoo Creek Subbasin) to only 0.3 square mile (192 acres) (Mosquito Creek Subbasin). • Figure 12 gives the area of each subbasin as a percentage of the total assessment area, with the subbasins ordered left-to-right on the graph by decreasing basin area. Examination of the graph shows three different parts based upon changes in the slope of the line: (I) Subbasins I to 7; (2) Subbasins 8 to 32; and (3) Subbasins33 to 51. The subbasins composing part I of the graph account for nearly 32% of the total assessment area, those in part 2 for nearly 55% of the total assessment area, and part 3 for 13% of the total assessment area. Beginning with Subbasin I, Kickapoo Creek (212, 467 acres), it is also interesting to note that the subbasin area decreases by approximately one-half at the part 2 and 3 boundaries. Agricultural Land Agricultural cover is composed of two principal categories, Cropland and Rural Grassland. As a principal land cover category, Cropland is an aggregate of three classes: Row Crops (corn, beans, and other row-tilled crops), Small Grains (oats, wheat, barley, etc.), and OrchardslNurseries (Table 2). Rural Grassland incorporates permanentpastureland, alfalfa, hay, roadsides and fencelines, waterways, and other grassland cover located in rural areas. 36 Table 2. Land Cover of the Lower Sangamon River Assessment Area* Land Cover Category Sq. Mi. Acres Area % Agricultural 4,005.5 2,563,540 87.6 Row Crops 3,251.3 2,080,809 71.1 Small Grains 187.1 119,736 4.1 Orchards & Nurseries 0.3 199 0.0 Rural Grassland 566.9 362,796 12.4 Forest and Woodland 218.9 140,105 4.8 Deciduous, closed canopy 177.6 113,651 3.9 Deciduous, open canopy 36.0 23,034 0.8 Coniferous 5.3 3,420 0.1 Urban & Built-Up Land 156.9 100,389 3.4 High Density 19.3 12,336 0.4 Medium Density 34.7 22,213 0.8 Low Density 18.3 11,685 0.4 Transportation 34.4 21,998 0.8 Open Space 50.2 32,157 1.1 Wetland 119.7 76,590 2.6 Shallow MarshlWet Meadow 9.9 6,359 0.2 Deep Marsh 4.2 2,713 0.1 Forested 82.4 52,731 1.8 Shallow Water 23.1 14,786 0.5 Other Land 73.8 47,241 1.6 Lakes & Streams 73.1 46,81 1.6 Barren & Exposed 0.7 430 0.0 Totals 4,574.8 2,927,864 100.0 ·Small errors in totals are due to rounding. • Agricultural Land is extensive and the predominant land cover within the Lower Sangamon River Assessment Area, composing 87.6% of the entire assessment area (Figure 13). This amounts to slightly more than 2.5 million acres (approximately 4,000 square miles) (Table 4). Land devoted to agricultural use amounts to 77.5% of the surface area of lllinois (Table 3). • The area covered by agricultural land in the Lower Sangamon River Assessment Area accounts for 9.2% of all agricultural land use within Illinois. The potential for agricultural nonpoint pollution is therefore high within the assessment area. • Figure 14 shows that, with few exceptions, at least 85% of the entire surface area of Subbasins 1 to 32 is devoted to agricultural land uses, underscoring the perva sive nature of upland agricultural land within the assessment area. Over one-third 37 Table 3. Land Cover of Illinois (IDNR 1996)* Land Cover Category Sq. Mi. Acres Area % Agricultural 43,638.8 27,928,797 77.5 Row Crops 30,600.4 19,584,247 54.3 Small Grains 3,166.0 2,026,268 5.6 Orchards & Nurseries 9,847.5 6,302,371 17.5 Rural Grassland 24.9 15,911 0.0 Forest and Woodland 6,388.5 4,088,623 11.3 Deciduous, closed canopy 5,618.0 3,595,538 10.0 Deciduous, open canopy 657.8 421,013 1.2 Coniferous 112.6 72,072 0.2 Urban & Built-Up Land 3,261.6 2,087,396 5.8 High Density 476.7 305,065 0.8 Medium/High Density 186.5 119,352 0.3 Medium Density 729.5 466,894 1.3 Low Density 392.5 251,180 0.7 Transportation 492.0 314,866 0.9 Open Space 84.4 630,038 1.8 Wetland 1,829.0 1,170,550 3.2 Shallow MarshlWet Meadow 219.8 140,664 0.4 Deep Marsh 54.5 34,855 0.1 Swamp 18.3 11,726 0.0 Forested 1,264.0 808,987 2.2 Shallow Water 272.4 174,318 0.5 Other Land 1,228.7 786,361 2.2 Lakes & Streams 1,203.4 770,183 2.1 Barren & Exposed 25.3 16,178 0.1 Totals 56,346.5 36,061,727 100.0 *Small errors in totals are due to rounding. (34.5%) of all the agricultural land cover within the assessment area is concen trated in Subbasins 1 to 7. • Cropland is the dominant, principal land cover in the assessment area, accounting for 75.2% of the entire surface of the assessment area (Table 4 and Figure 15). At the subbasin level, Cropland averages between 55% to slightly over 90% of the total surface area in Subbasins 1 to 32 (Figure 16). • Rural Grassland is the second most common land cover in the assessment area, representing 12.4% of the total surface area (Table 4). At the subbasin level, Rural Grassland averages from 5% to 20% of the surface area of each subbasin (Figure 16). Figure 17 shows that Rural Grassland cover is closely associated with the principal 38 Table 4. Principal Land Cover of the Lower Sangamon River Assessment Area* Land Cover Category Sq. Mi. Acres Area % Agricultural 4,005.5 2,563,540 87.6 Cropland 3,438.7 2,200,744 75.2 Rural Grassland 566.9 362,796 12.4 Forest and Woodland 218.9 140,105 4.8 Urban and Built-Up Land 156.9 100,389 3.4 Built-Up 106.6 68,232 2.3 Open Space 50.2 32,157 1.1 Wetland 119.7 76,590 2.6 Forested 82.4 52,731 1.8 Nonforested 37.3 23,858 0.8 Other Land 73.8 47,241 1.6 Lakes & Streams 73.1 46,811 1.6 Barren & Exposed 0.7 430 0.0 Totals 4,574.8 2,927,864 100.0 'Small errors in totals are due to rounding. stream network within the assessment area, and serves as buffers between the break in-slope between upland tracts with extensive Cropland and areas with greater stream dissection. The spatial distribution of Rural Grassland tracts defines the dendritic stream pattern in many of the subbasins and provides distinct evidence of the homo geneous nature of the underlying surficial materials. • Analysis of the original satellite imagery used to derive the land cover information· indicates that conservation tillage methods such as crop residue management are widespread throughout the assessment area, but the increased use of pesticides nec essary with residue management also poses a greater potential for surface and groundwater contamination. Forest and Woodland Forest and Woodland is defined as land predominantly covered with trees and woody vegetation. This principal land cover category is an aggregate of three classes (Table 2), Deciduous (trees that undergo seasonal change), closed-canopy; Deciduous, open-canopy; and Coniferous (wooded areas dominated by pine and other coniferous trees). • 4.9% of the assessment area is covered by Forest and Woodland cover, amounting to 218.9 square miles (140,105 acres) (Table 4). Forest and Woodland cover accounts for 11.3% of the surface area of lllinois (Table 3). 39 • Figure 18 shows that Forest and Woodland cover is primarily restricted to areas containing slopes too steep for cultivation, with the largest concentration situated along the dissected bluffs adjacent to the Sangamon River floodplain in Cass County. • At the subbasin level, Forest and Woodland averages less than 5% of the total surface area of Subbasins 1 to 32 (Figure 19), which is indicative of the low local relief and low slopes within the assessment area that have resulted in extensive tracts of agricultural lands. Urban and Built-Up Land Urban and Built-Up Land comprises land areas covered with manmade structures, as well as open space that is incorporated within urban areas. This principal land cover category is composed of two broad categories, UrbanlBuilt-Up Land and Open Space. Urbani Built-Up Land includes land surfaces that have been developed, or "built-up" with struc tures such as buildings, roadways, parking lots, driveways, and other such structures that form impervious surfaces. UrbanlBuilt-Up Land is subdivided into subclasses based upon the relative amount of impervious surface area, ranging from High Density (all or nearly all of the land surface is covered with manmade structures) to LowDensity (only a portion of the land is covered with manmade structures, intermixed with other cover such as grassland, wooded lands, etc.) (Table 2). Open Space includes residential lawns, parks, golf courses, and other managed grassland in urban and built-up areas. • The Lower Sangarnon River Assessment Area is predominantly rural, with only 3.4% of the total area devoted to Urban and Built-Up Land. This amounts to 156.9 square miles (100,389 acres) (Table 4 and Figure 20). By comparison, 5.8% of Illinois' surfac€; area is composed of Urban and Built-Up Land (Table 3). • At the subbasin level, Urban and Built-Up Land cover typically accounts for only 2% to 3% of the surface area of each subbasin (Figure 21). The two isolated peaks shown in Figure 21 for Subbasins 12 to 24 are associated with the two principal urbanized areas in the assessment area, Springfield (12, Spring Creek Subbasin) and Bloomington-Normal (24, Sugar Creek #1 Subbasin). Those Subbasins contained within part 3 are significantly smaller in basin area, and the large amounts of Urban and Built-Up Land shown in Figure 21 for Subbasins 47 to 49 are associated with small basins that have a significant portion of their catchment area within the Springfield (Sugar Creek #3 Subbasin), Bloomington-Normal (Goose Creek Subbasin), and Taylorville (Panther Creek #2 Subbasin) urbanized areas. Within Subbasins 12,24, and 47 to 49, there is a greater potential for adverse impacts to the natural cover, drainage, and groundwater from urban land use. • Within the assessment area, Built-Up Land cover is about twice the area of Open Space cover (Table 4). However, at the subbasin level, Figure 22 shows that there is a significant amount of Open Space within the two major urbanized areas of Springfield and Bloomington-Normal. 40 Wetland The Wetland principal land cover category is divided into two broad types, Forested Wetland and Nonforested Wetland. Forested Wetland includes swamps (forested wetlands with a permanent or semi-permanent water regime) and bottomland forests (forested wetlands that are temporarily or seasonally flooded). Nonforested Wetland includes shallow marsh/wet meadow (areas characterized by standing water or saturated soils for brief to moderate periods during the growing season), deep marsh (areas characterized by standing water or saturated soils on a semipermanent or permanent basis during the growing season), and shallow water wetland (permanently flooded areas less than 20 acres in extent and less than 2 meters deep). • Wetland comprises 2.6% of the total land cover within the assessment area, amount ing to 119.7 square miles (76,590 acres) (Tables 2 and 4). Wetland accounts for 3.2% of the total surface area of Illinois (Table 3). • Of all the Wetland cover within the assessment area, 68.9% is Forested Wetland, and 31 % is Nonforested Wetland types (Table 4). Most of the Wetland cover is concen trated along the floodplain areas of the llIinois and Lower Sangamon Rivers, as well as the Sugar Creek, Kickapoo Creek, Salt Creek, and South Fork tributaries (Figure 23). The concentration of Forested Wetland within the Sanganois State Wildlife Area at the confluence area of the Illinois and Sangamon Rivers north of Beardstown is most notable. • At the subbasin level, Wetland cover averages less than 2% of the total surface area of most of the subbasins (Figure 24). Two of the isolated peaks shown on Figure 24 are associated with the Sanganois wetland complex in the Illinois River #3 and Sangamon River #1 Subbasins (Subbasins 5 and 41). The shallow water, nonforested wetland complexes in the Illinois River #1 Subbasin (Subbasin 28) are the third of the four peaks. Of all the Wetland cover within the assessment area, 43% is contained within these three subbasins. The fourth subbasin is very small, with some 18% of the area in wetland. • The paucity of wetland habitat on the upland areas attests to the broad, extensive areas of cultivated lands within the Lower Sangamon River Assessment Area. Notes on Land Cover Maps In addition to Illinois Land Cover: An Atlas (IDNR 1996), two other publications relating to the statewide land cover inventory ·are available from the lllinois Department of Natural Resources: (1) Illinois Land Cover: An Alias on Compact Disc (IDNR 1996), which con tains the statewide land cover digital database; and (2) Land Cover ofIllinois (IDNR 1996), a printed 1:500,000-scale map. All are available through DNR Conservation 2000 Publications (524 South Second Street, Springfield, IL 62701-1787; telephone: 217-782-7940). Land cover information and data are also available through the DNR website at http://dnr.state.il.us/ctapllandmap.htm 41 It is useful to discuss appropriate mapping scales that should be used as guidelines with applications involving the statewide land cover database. Using standardized map scales and associated National Map Accuracy Standards (NMAS) established by the U.S. Geological Survey, maps developed from the land cover database can range from 1:62,000 (l inch = I mile) to I: 100,000 (l inch =1.6 miles) and still maintain NMAS standards for ' raster data possessing a ground spatial resolution of 28.5 meters (93.5 feet). Of course, any smaller scale maps (for example, 1:250,000) will also maintain NMAS accuracy standards. Given these guidelines, the lllinois land cover database can support regional applications but should not be expected to fulfill the needs of site specific projects. References Campbell, J.B., 1987, Introduction to Remote Sensing: The Guilford Press, New York, 551 p. lllinois Environmental Protection Agency, 1994, lllinois Water Quality Report, 1992-1993, Volume ll: IEPA Bureau of Water, Springfield, IL, 181 p. lllinois Land Cover-An Atlas, 1996: illinois Department of Natural Resources, Springfield, Illinois, IDNRlEEA-96/05, 157 p. Illinois Land Cover-An Atlas on Compact Disc, 1996: Illinois Department of Natural Resources, Springfield, Illinois. Land Cover of Illinois, 1996: Illinois Department of Natural Resources, Springfield, Illinois, Illinois Scientific Surveys Joint Report 3; 1:500,000-scaie map. Scott, J.M., F. Davis, B. Csuti, R. Noss, B. Butterfield, C. Groves, H. Anderson, S. Caicco, F. D'Erchia, T.e. Edwards, Jr., J. Ulliman, and R.G. Wright, 1993, Gap Analysis-A Geographic Approach to Protection of Biological Diversity: Wildlife Monograph, No. 123,41 p. Starns, D.M., and J.E. Estes, 1993, A remote sensing research agenda for mapping and monitoring biodiversity: International Journal of Remote Sensing, v. 14, p. 839-1860. United States Geological Survey, 1994, Airborne Remote Sensing for Geology and the Environment-Present and Future, K. Watson and D.H. Knepper (eds.): USGS Bulletin 1926, 43 p. 42 I I I ---j \ I--, I 1 --, I 1 1 I 01 U I Ilo c:JIU I => z I ~Ig Cl°1 5" ~I I ----j 1 -j I I C 1 SCHUYLER co. - -( 1 1 1 I I I -'1 1 I I / I I ,- I I __ L~E..L:~C~__ o 10 20 30 1 1 Miles D assessment area county boundary I assessment area subbasin boundary r boundary Figure 11. Subbasins in the Lower Sangamon River Assessment Area ~ 4 10 9 8 7 ", 6 c \ -Q) !:! 5 a.Q) 4 '- 3 \...... 2 ~ , , ~ o 1 j 1 1 1 _.1. . .I ..L.L.L.L._ _I. _I._I. _ . ____ L_L _____ . _1. __,- _____1. ____ . .I. ____ ..._._.L.L L.L.J. Subbasin ____ Basin Size 1. Kickapoo Creek 13. Prairie Creek #1 26. Horse Creek 39. Pike Creek 2. Salt Creek #3 14. S. Fork Sangamon River #2 27. Deer Creek 40. Lake Springfield 3. Flat Branch 15. N. Fork Salt Creek 28. Illinois River #1 41. Sangamon River #1 4. Quiver Creek 16. Sangamon River #5 29. Sugar Creek #2 42. S. Fork Sangamon River #1 5. Illinois River #3 17. Salt Creek #1 30. Lake Sangamon 43. Jobs Creek 6. Sangamon River #3 18. Buckhart Creek 31. Salt Creek #2 44. Panther Creek #1 7. Sangamon River #4 19. Bear Creek 32. S. Lake Fork 45. Cox Creek 8. Lick Creek 20. Crane Creek 33. Illinois River #2 46. Coon Creek 9. Sangamori River #2 21. M. Fork Sugar Creek 34. Richland Creek 47. Sugar Creek #3 10. S. Fork Sangamon River #3 22. Sugar Creek #4 35. Brush Creek 48. Panther Creek #2 11. Lake Fork 23. W. Fork Sugar Creek 36. Ten Mile Creek 49. Goose Creek 12. Spring Creek 24. Sugar Creek #1 37. Prairie Creek #2 50. Clear Creek 25. N. Lake Fork 38. Timber Creek 51. Mosquito Creek Figure 12. Subbasin as Percentage of Total Lower Sangamon River Assessment Area '. ' Urban Land Wetland (3.40%) (2.60%) Forested Land (4,80%) Agricultural Land (87.60%) Figure 13. Principal Land Cover of the Lower Sangamon River Assessment Area ..l:>. er 100 I\. ~ M r-..~ ,.,,/\/ 90 . J{ ,., . ". W' .... ~ \l ! .. ~ 60 /V ~ I r ~I 70 ~ • ~ 8 60 _. c ,,' " ~ 50 c: - - 2l 40 ~ <1l - tl. 30 20 10 0 J J. .l, J 1, ! .J, c!. ,J" on" .l., ... 4A4"'.".I,.o.b ...... ,I• ..,I"..}.. .,IA"><;...I::...,1,..,'1I ..O'l.n.,I...'?+.,.,'A':l<;'l.1::: ..7 ___ Agricultural Land 1. Kickapoo Creek 13. Prairie Creek #1 26. Horse Creek 39. Pike Creek 2. Salt Creek #3 14. S. Fork Sangamon River #2 27. Deer Creek 40. Lake Springfield 3. Flat Branch 15. N. Fork Salt Creek 28. Illinois River #1 41. Sangamon River #1 4. Quiver Creek 16.. Sangamon River #5 29. Sugar Creek #2 42. S. Fork Sangamon River #1 5. Illinois River #3 17. Salt Creek #1 30. Lake Sangamon 43. Jobs Creek 6. Sangamon River #3 18. BUckharl Creek 31. SaltCreek#2 44. Panther Creek #1 7. Sangamon River #4 19. Bear Creek 32. S. Lake Fork 45. Cox Creek 8. Lick Creek 20. Crane Creek 33. Illinois River #2 46. Coon Creek 9. Sangamon River #2 21. M. Fork Sugar Creek 34. Richland Creek 47. Sugar Creek #3 10. S. Fork Sangamon River #3 22. Sugar Creek #4 35. Brush Creek 48. Panther Creek #2 11. Lake Fork 23. W. Fork Sugar Creek 36. Ten Mile Creek 49. Goose Creek 12. Spring Creek 24. Sugar Creek #1 37. Prairie Creek #2 50. Clear Creek 25. N. Lake Fork 38. Timber Creek 51. Mosquito Creek Figure 14. Agricultural Land by Subbasin for the Lower Sangamon River Assessment Area I I ----j-- / \ I--, I I --~ I CO· I I ~<;.o~\p.. I 01 U . :1:/0 ::J",U z ~Ig 0/5 u. ~,° ---j I 1 _ SCHUYLER CO ___ I 1 ~ I #). I~'~ ci ---- i51 ~I ::<1 I rdolUI''''S~ PIATT CO. J I_- Terre creek ~- ---1 I I r- dl ~I I~ I L ~I 1 ::J -[ 01 I I I ::<1 _ Jl~TI ~.-..L MORGAN CO, --T-- 10 d U ulz ~I~ llilg "'1« '" ;:; / LittJ~ _ I Wabuh I - River '-.J o 10 20 30 I I Miles assessment area river or stream • Cropland D other boundary j subbasin boundary 1 • surface water county boundary Figure 15. Cropland Cover in the Lower Sangamon River Assessment Area 1< ~...."..~ ~ 100 90 80 70 ~ ll) > 8 60 "0 ffi 50 ...J ~ C ~ 40 ~ ll) a. 30 20 10 0 ___ Cropland ...... - Rural Grassland - .. - 1. Kickapoo Creek 13. Prairie Creek #1 26. Horse Creek 39. Pike Creek 2. Salt Creek #3 14. S. Fork Sangamon River #2 27. Deer Creek 40. Lake Springfield 3. Flat Branch 15. N. Fork Salt Creek 28. Illinois River #1 41. Sangamon River #1 4. Quiver Creek 16. Sangamon River #5 29. Sugar Creek #2 42. S. Fork Sangamon River #1 5. Illinois River #3 17. Salt Creek #1 30. Lake Sangamon 43. Jobs Creek 6. Sangamon River #3 18. Buckhart Creek 31. Salt Creek #2 44. Panther Creek #1 7. Sangamon River #4 19. Bear Creek 32. S. Lake Fork 45. Cox Creek 8. Lick Creek 20. Crane Creek 33. Illinois River #2 46. Coon Creek 9. Sangamon River #2 21. M. Fork Sugar Creek 34. Richland Creek 47..Sugar Creek #3 10. S. Fork Sangamon River #3 22. Sugar Creek #4 35. Brush Creek 48. Panther Creek #2 11. Lake Fork 23. W. Fork Sugar Creek 36. Ten Mile Creek 49. Goose Creek 12. Spring Creek 24. Sugar Creek #1 37. Prairie Creek #2 50. Clear Creek 25. N. Lake Fork 38. Timber Creek 51. Mosquito Creek Figure 16. Cropland &Rural Grassland by Subbasin for the Lower Sangamon River Assessment Area I I \ I--., I - ---r ----- I P!!,Tl~·lJ I_- I I I I I I I I- r I KiI3kaskia Litt/~ _ I I River "''''''h I __ L~~~C~_ _ Rivet' --.J o 10 20 30 I I Miles county boundary Rural Grassland other D river or stream . assessment area ! surface water N • - boundary subbasin boundary I • Figure 17. Rural Grassland Cover in the Lower Sangamon Assessment River Area .- , 1 \ ---j I I --~ I I 81 :I:ld U ~"'I z ~Ig giG?'-' ~, I ---1 I , --j 1 _ 1 I SCHUYLER CO ___ I I ~o " I~~~ CASS ~c~o-,~-":'~~.l:~S; ------~I 81 ~I I ~- P!6T1C-2'lJ ,- I I I I 1 1 -I I 1 I 1- (' I K..k..ki. Litt/r _ I I "River W.b;uh 1 __ L f!!:iE!:.B'!:CE: _ - Rio..,. -.J o 10 20 30 I 1 • Miles county boundary Forest and Woodland other D river or stream assessment area ! surface water N • - boundary subbasin boundary j • Figure 18. Forest and Woodland Cover in the Lower Sangamon River Assessment Area ---V\ 100 90 80 70 ~ 8 60 "0 lij 50 ....I -~ 40 ~ OJ a. 30 20 10 0 ~ Forest&Woodland 1. Kickapoo Creek 13. Prairie Creek #1 26. Horse Creek 39. Pike Creek 2. Salt Creek #3 14. S. Fork Sangamon River #2 27. Deer Creek 40. Lake Springfield 3. Flat Branch 15. N. Fork Salt Creek 28. Illinois River #1 41. Sangamon River #1 4. QUiver Creek 16. Sangamon River #5 29. Sugar Creek #2 42. S. Fork Sangamon River #1 5. Illinois River #3 17. Salt Creek #1 30. Lake Sangamon 43. Jobs Creek 6. Sangamon River #3 18. Buckhart Creek 31. Salt Creek #2 44. Panther Creek #1 7. Sangamon River #4 19. Bear Creek 32. S. Lake Fork 45. Cox Creek 8. Lick Creek 20. Crane Creek 33. Illinois River #2 46. Coon Creek 9. Sangamon River #2 21. M. Fork Sugar Creek 34. Richland Creek 47. Sugar Creek #3 10. S. Fork Sangamon River #3 22. Sugar Creek #4 35. Brush Creek 48. Panther Creek #2 11. Lake Fork 23. W. Fork Sugar Creek 36. Ten Mile Creek 49. Goose Creek 12. Spring Creek 24. .Sugar Creek #1 37. Prairie Creek #2 50. Clear Creek 25. N. Lake Fork 38. Timber Creek 51. Mosquito Creek Figure 19. Forest & Woodland by Subbasin for the Lower Sangamon River Assessment Area ------~------~ - ...- I I DCa. \ ---j I I --::I I I t)°1 . rio "'It):0 Z 010 Z !:J gl~ ~I I ----j I --j I 1 _ I SCHUYLER CO I ___ I I #)." I~~" ~I 81 ~I I PIATT CO. I I _ _ '-'-"---'=-"' ,1- ---1 I I I- I I~ I I I L 1 -I I I I I I _ Jl~lJ: ~.---L MORGAN CO. . --T-- 10 °It)t) Z ~I§ ttllS "'I""::;; '" I Little __ I W.b;uh I _____Riyer --1 o 10 20 30 I I Miles assessment area river or stream Urban Built-Up surface water boundary subbasin I county boundary boundary N • Urban Grassland • other j D Figure 20. Urban and Built-Up Land in the Lower Sangamon River Assessment Area VI \..oJ 100 90 80 70 ~ Q) i5 () 60 "0 c: 10 50 ..J c: -Q) 0 40 ~ Q) [l. 30 20 - /' K 10 1...... - ~ 1 \---- ~ I. I 0 -./'l -~1~lf~~'&~~h1~1~1~1bb1~4~~~~~~~*.'~~h~~ ••f .k~~kk~~k~kk~~ Subbasin -.....- Urban Land 1. Kickapoo Creek 13. Prairie Creek #1 26. Horse Creek 39. Pike Creek 2. Salt Creek #3 14. S. Fork Sangamon River #2 27. Deer Creek 40. Lake Springfield 3. Flat Branch 15. N. Fork Salt Creek 28. Illinois River #1 41. Sangamon River #1 4. Quiver Creek 16. Sangamon River #5 29. Sugar Creek #2 42. S. Fork Sangamon River #1 5. Illinois River #3 17. . Salt Creek #1 30. Lake Sangamon 43. Jobs Creek 6. Sangamon River #3 18. Buckhart Creek 31. Salt Creek #2 44. Panther Creek #1 7. Sangamon River #4 19. Bear Creek 32. S. Lake Fork 45. Cox Creek 8. Lick Creek 20. Crane Creek 33. Illinois River #2 46. Coon Creek 9. Sangamon River #2 21. M. Fork Sugar Creek 34. Richland Creek 47. Sugar Creek #3 10. S. Fork Sangamon River #3 22. Sugar Creek #4 35. Brush Creek 48. Panther Creek #2 11. Lake Fork 23. W. Fork Sugar Creek 36. Ten Mile Creek 49. Goose Creek 12. Spring Creek 24. Sugar Creek #1 37. Prairie Creek #2 50. Clear Creek 25. N. Lake Fork 38. Timber Creek 51. Mosquito Creek Figure 21. Urban Land by Subbasin for the Lower Sangamon River Assessment Area ~ 100 . 90 80 70 ~ _ 0 60 "0 C ~ 50 C e ~ l! ~7 10 • I~ I. -~~A b .. o --"" AJL ...... 1 2 3 4 , /; I /; S 101112"'415'6'7'~1'9:ioid12 24252~z,m2~3b:J13'2""34:!s,\;:IT:Js:Jo4041 ;'4344454647 4~4~ b51 Subbasin _____ Built-Up Land Open Space 1. Kickapoo Creek 13. Prairie Creek #1 26. Horse Creek 39. Pike Creek 2. Salt Creek #3 14. S. Fork Sangamon River #2 27. Deer Creek . 40. lake Springfield 3. Flat Branch 15. N. Fork Salt Creek 28. Illinois River #1 41. Sangamon River #1 4. Quiver Creek 16. Sangamon River #5 29. Sugar Creek #2 42. S. Fork Sangamon River #1 5. Illinois River #3 17. Salt Creek #1 30. lake Sangamon 43. Jobs Creek 6. Sangamon River #3 18. Buckhart Creek 31. Salt Creek #2 44. Panther Creek #1 7. Sangamon River #4 19. Bear Creek 32. S. lake Fork 45. Cox Creek 8. lick Creek 20. Crane Creek 33. Illinois River #2 46. Coon Creek 9. Sangamon River #2 21. M. Fork Sugar Creek 34. Richland Creek 47. Sugar Creek #3 10. S. Fork Sangamon River #3 22. Sugar Creek #4 35. Brush Creek 48. Panther Creek #2 11. lake Fork 23. W. Fork Sugar Creek 36. Ten Mile Creek 49. Goose Creek 12. Spring Creek 24. Sugar Creek #1 37. Prairie Creek #2 50. Clear Creek 25. N. lake Fork 38. Timber Creek 51. Mosquito Creek Figure 22. Urban Built-Up & Open Space by Subbasin for the Lower Sangamon River Assessment Area ------,------_. _. - ___ I 1 \ ----/ I 1 --::1 I I 0/ U :>:10 U "'IOJ z Z°1° !::l gl~ ~I ----j I 1 _ SCHUYLER CO ___ I I/ tl'J0 " I~'" ~I 81 ~t I eL PIATT---1 CO. J ,-I I I I I -I I I I 1- r" I K..ka.ki. I I River WaAuh I - _ L ~~BI-~'_ _ Rivet' -.J o 10 20 30 I I Miles county boundary Wetland other , D river or stream assessment area surface water t{ • boundary subbasin boundary j • Figure 23. Wetland Cover in the Lower Sangamon River Assessment Area ...J\ ~ 50 45 40 . ~ 35 ~ 30 8 - - _.- . 1::l c: ~ 25 c e20 Q) a. 15 10 5 ~ -"" ~ o - l..tV\ - 3031323'J34353637383'g~ 113 15.7, 910,11213141516,7,Bl.2bi,222324'5 4142434445"\;4148405051 Subbasin __ Wetland 1_ Kickapoo Creek 13. Prairie Creek #1 26. Horse Creek 39. Pike Creek 2. Salt Creek #3 14. S. Fork Sangamon River #2 27. Deer Creek 40. Lake Springfield 3. Flat Branch 15. N. Fork Salt Creek 28. Illinois River #1 41. Sangamon River #1 4. Quiver Creek 16. Sangamon River #5 29. Sugar Creek #2 42. S. Fork Sangamon River #1 5. Illinois River #3 17. Salt Creek #1 30. Lake Sangamon 43. Jobs Creek 6. Sangamon River #3 18. Buckhart Creek 31. Salt Creek #2 44. Panther Creek #1 7. Sangamon River #4 19. Bear Creek 32. S. lake Fork 45. Cox Creek 8. Lick Creek 20. Crane Creek 33. Illinois River #2 46. Coon Creek 9. Sangamon River #2 21- M. Fork Sugar Creek 34. Richland Creek 47_ Sugar Creek #3 10. S. Fork Sangamon River #3 22. Sugar Creek #4 35. Brush Creek 48. Panther Creek #2 11. Lake Fork 23. W. Fork Sugar Creek 36. Ten Mile Creek 49. Goose Creek 12. Spring Creek 24. Sugar Creek #1 37. Prairie Creek #2 50. Clear Creek 25. N. Lake Fork 38. Timber Creek 51. Mosquito Creek Figure 24. Wetland by Subbasin for the Lower Sangamon River Assessment Area Part 2: Geology and Society Most of us live, work, and play on the surface of the Earth. But what we often fail to recog nize is that beneath the office building or factory where we work, beneath the home where we live, or beneath the park where we play, is a framework of geology that supports our lives on the surface. The geologic framework contains the mineral resources that are the raw ingredients of most of the manufactured materials that furnish our homes, offices, and playgrounds; and it provides the water that flows freely from the faucets we tum on and off daily. At the same time, the contamination of water resources, the slumping of banks along our roads, or damage froJ;IJ earthquakes are hazards that we don't think about until they happen-let alone realize that a supporting framework of geologic materials and processes affects why they occur. The interrelatedness between geology and human society is so intimate and intricate that it is more easily ignored than understood. Nevertheless, to understand and wisely use the natural heritage we value, we must consider the geological factors that affect our daily lives. Some ofthe major ways geologic materials (resources) and geologic processesaffect modem society are discussed below. 57 Mineral Resources Sand and gravel, industrial sand, stone, and coal are mined in the Lower Sangamon River Assessment Area. Eighteen pits produce sand and gravel, two pits produce industrial sand, . and four quarries produce stone; two coal mines operate in the assessment area (Figure 25). Table 5 lists the mineral industry operations in the assessment area. Data on production and employment at individual pits and quarries or for the assessment area as a whole are not available. Although stone and sand and gravel are bulk commodities with low unit values, they are vital inputs for the construction industry. In 1998, the average price of construction sand was $4.41 per ton, and that of crushed stone was $5.89 per ton. Since these commodities have low unit values, efficiency in extraction and transportation is important. Known or expected deposits of useful mineral resources are possible sources for future exploitation (Figure 26). This assessment area contains many sand and gravel deposits along and near the floodplains and valley trains of the Sangamon River (Lineback 1979, Masters 1983). The primary sources of sand and gravel are the glacial-age Mackinaw Member of the Henry Formation, the Hagarstown Member of the Pearl Formation, and the Cahokia Alluvium. The most extensive deposits of the Henry Formation are located in the low terraces and in the floodplains of the Sangamon River, but an abundant supply of sand and fine gravel also is available in terraces on many of the streams tributary to the Sangamon River. Less well-sorted deposits of the Cahokia Alluvium are also found along the floodplains and channels. There is good potential for mining sand and gravel from the glacial outwash that occurs locally within the lllinoian-age Pearl Formation, especially along valley sides where overburden is thin. Sand dunes (Parkland Sand) scattered along the uplands bordering the Sangamon River have potential for use as fill sand, mason sand, molding sand, and possibly sources of quartz and feldspar (Masters 1983). Two industrial sand mines, producing fill sand and raw material for glass foundries, are currently operating in Mason County. Pennsylvanian-age limestones are potential sources of near-surface stone reserves in some of the counties in this assessment area. Several quarries currently mine the Pennsylvanian Lonsdale and Millersville Limestones in Logan, Menard, Christian, and Montgomery Counties. Thin limestone beds outcrop in several areas in Logan, Menard, and Sangamon Counties and in a few spots in Tazewell County. Where present, the thickness of these shallow Pennsylvanian limestone units rarely exceeds 25 feet. Thick limestone and dolomite units are present at greater depths, but these deeper units cannot presently be mined economically. Underground mining of these limestones may be possible in the future, depending on the market conditions and emerging technologies. In addition to stone and sand and gravel, coal resources underlie much of the Lower Sangamon River Assessment Area (Figure 26). The principal resources are in the Herrin, 58 51 / I OCO. \ ----i I I --:I I 1 01 U :rIo Silngamon ",/U River :> :z I ~I{:! I 0,5 I ~I'" "- ~T~EWELI:C~. -.J ---j I LOGAN CO. I I #;'" (, 'XI S~HUYLERco - 01; I ~~- • MASON CO. -, ·\il.·'/"'-,....-,.,_J rl / \ San aIPo I g 1 I I@ ---I I ~o~ 1;2 ·I__ J_~ I;): . I~ol'$ o J '- -- L - ."p""," ___ 9'~.£0-,- __ iSl ~I =<1 ~ I I- I -I I I r' \ Kaskaskia Little _ I } Riller HlWuh I __ L~~~C~_ - River -.J o 10 20 30 I I Miles assessment area • limestone coal mine boundary I sand and/or gravel surface water county boundary N • • river or stream I 'X industrial sand •D other Figure 25. Active Sand and/or Gravel Pits, Limestone Quarries and Coal Mines , I I I , I WOODFORD CO. _ .. I ( ~ ---I 1 I ---. / I J / I co. t -L __ r --I / I ~,,-Ol'\" ) I I I I I 81 I I :>;Id / OJ",u z I ~I~ 0 o 1"3 :if , _"':-j I 1 -I I SCHUYLER,----- CO 1 I I I I / I ---I I 1 I .1 I 81 I i51 1 ~I ~I I - I PIATT CO. I 1-- .------1 1 I ., / , 8 1 1 !!!I L, "'I~- -I 01 --,1 ~I .!!~lJ: ~.l --r---:~~~IIII~i~~ I - MORGAN CO. I /0 diU --, / U z ---I !;\! , ~ I :""",0<:5~ I tli 18 l?r , :51~ t LU I- l- I I ~ d I -J Ii=! U I I I 1 Ji5 I I ~-- I ~ -- LSHELBYCO.------______.J o 10 20 30 I I Miles potential source of potential source of surface water I D coal m stone assessment area potential source of no potential mineral • boundary r sand and gravel D resources within • aSSessment area boundary county boundary Figure 26. Potential Mineral Resources in the Lower Sangamon River Assessment Area Springfield, and Danville Coals of the Carbondale Formation, with a minor amount in the Assumption Coal in the underlying Tradewater Formation. The Herrin Coal is present throughout the area, but is thickest in the southern part of the area in Christian, Macoupin, Montgomery, Morgan, and Sangamon Counties. The Herrin Coal has been mined exten sively in Christian and southern Sangamon Counties and is currently mined at the Crown IT Mine near Virden. The Springfield Coal is also present throughout the area, but is thickest in the northern'two-thirds of the area, especially in Cass, De Witt, Logan, McLean, and Menard Counties and northern Sangamon County. The Springfield Coal has been mined at numerous locations throughout this area and is currently mined at the Turris Mine near Elkhart: Although potentially surface-mineable near where they crop out in Morgan and Cass Counties, these two seams are most likely to be mined by underground methods. Demand for these resources is currently weak because of their high sulfur content. How ever, the relatively thick, shallow seams can be mined at a competitive cost and will be attractive for mining if the market for high-sulfur coal improves. Resources of the Danville Coal have been mapped in portions of Christian and McLean Counties, and the Assumption Coal has been mapped in Christian County. Both coals lie at depths that will require under ground mining. Although the Assumption Coal was mined during the first part of the 20th Century, neither the Assumption nor the Danville Coal is thick enough to be economically mined at this time. 61 Table 5. Mineral Producers in the Lower Sangamon River Assessment Area Sand and Gravel 1. Bicket Pit SW 6. DownsNE Rowe Construction Company Stark Materials, Inc. P.O. Box 609 1805 West Washington 1523 N. Cottage Street P.O. Box 3756 Bloomington, IL 61702-0609 Bloomington, IL 61701 Mineral: Sand and Gravel Mineral: Sand and Gravel County: McLean County: McLean Location: SW 32 22N 2E Location: NE 5 22N 3E Phone: (309) 827-0091 Phone: (309) 828-5034 2. Buckhart Sand & Gravel 7. Given Sand Pit Buckhart Sand & Gravel Inc. Given Sand and Gravel P.O. Box 156 2027-1350 Avenue Mechanicsburg, IL 62545 Lincoln, IL 62656 Location: NW 16 15N 3W Mineral: Sand and Gravel County: Sangamon County: Logan Mineral: Sand and gravel Location: SE 5 20N 2W Phone: (217) 525-1752 Phone: Not available 3. Builders Sand and GravelIne. 8. Hurley Pit 1200 Jostes Rd. R.A. Cullinan & Son, Inc. Rochester, IL 62563 P.O. Box 166 County: Sangamon Tremont, IL 61568 Location: NW I 15N 4W Mineral: Sand and Gravel Mineral: Sand and gravel County: Tazewell Phone: (217) 498-7263 Location: SE 14 24N 6W Phone: (309) 925-2711 4. Carmichael NW Mine Rowe Construction Company 9. Lane Construction Co. P.O. Box 609 14897 County Rd. 1523 N. Cottage Street Bath, IL 62617 Bloomington, IL 61702-0609 County: Mason Mineral: Sand and Gravel Mineral: Sand and Gravel County: McLean Location: NE 3 19N 9W Location: NW 12 21N IE Phone: Not available Phone: (309) 827-0091 10. Lincoln Sand & Gravel 5. Downs 2NE Mine Mineral: Sand and Gravel Stark Materials, Inc. P.O. Box 67 1805 West Washington Lincoln, IL 62656 P.O. Box 3756 County: Logan Bloomington, IL 61701 Mineral: Sand and Gravel Mineral: Sand and Gravel Location: S I 19N 3W County: McLean Phone: (217) 735-3815 Location: NE 33 23N 3E Phone: (309) 828-5034 62 II. Menard County Highway Department Mine 15. Sangamon Dredge R.R. 3, P.O. Box 497 Sangamon Valley Sand & Gravel Petersburg, IL 62675 232 S. Old Covered Bridge Ln. County: Menard Springfield, IL 62707 Location: NE 25 18N 7W County: Sangamon Mineral: Sand and Gravel Location: NW I 15N 4W Phone: (217) 632-2722 Mineral: Sand and gravel Phone: (217) 787-1882 12. Mine # 13 Ralston PurinaCompany 16. Sellards Pit NE 300 Airport Urban Sand and Gravel Company Cape Girardeau, MO 63701 P.O. Box 3193 County: Mason Champaign, IL 61826 Mineral: Sand and Gravel Mineral: Sand and Gravel Location: SW 319M 9W County: McLean Phone: Not available Location: NE 6 21N 2E Phone: (217) 586-4991 13. Nail Trucking Service Mine Nail Trucking Service 17. Site 105 R.R. 2, Chanderville Rowe Construction Company IL 62627 P.O. Box 609 Mineral: Sand and Gravel 1523 N. Cottage Street County: Mason Bloomington, IL 61702-0609 Location: NW 33 20N 8W Mineral: Sand and Gravel Phone: (309)546-2300 County: McLean Location: NW 5 22N IE 14. New Plant Phone: (309) 827-0091 Clear Lake Sand & Gravel Company P.O. Box 2609 18. Smith Excavating Inc. Springfield, IL 62708 1610 W. Sangamon Rd. County: Sangamon Taylorville, IL 62568 Location: SE 22 16N 4W Mineral: Sand and gravel Mineral: Sand and Gravel Location: NE 33 13N 2W Phone: (217) 629-7631 County: Christian Industrial Sand 1. East Side Sand Pit 2. West Side Sand Pit Manito Investment Company Manito Investment Company 22285 N. County Rd. 22285 N. County Rd. Topeka, IL 61567 Topeka, IL 61567 Mineral: Industrial Sand Mineral: Industrial Sand County: Mason County: Mason Location: SE 29 21N 5W Location: SE 5 22N 7W Phone: (309) 535-2357 Phone: (309) 535-2357 63 Stone 1. Nokomis Quarry 3. Yard #12-Rocky Ford Nokomis Quarry Co. of Illinois Material Service Corporation Box No. 90 4226 Lawndale Ave. Nokomis, IL 62075 Lyons, IL 60534 Location: NE 3 toN 2W County: Logan County: Montgomery Mineral: Limestone Mineral: Limestone Location: S 5 19N 3W Phone: (217) 563-2011 Phone: (708) 442-4624 2. Pana Quarry 4. Yard #17-Indian Point Martin Marietta Aggregates Material Service Corporation th 1980 East ll6 St. 4226 Lawndale Ave. Suite 200, Box 549 Lyons, IL 60534 IN Carmel, 46032 . County: Menard Location: SE 18 llN IW Mineral: Limestone County: Christian Mineral: Limestone Location: SW 18 18N 5W Phone: (317) 776-4460 hone: (708) 442-4624 Coal Mines 1. Turns Coal Co. 2. Freeman United Coal Mining Co. Elkhart, IL 62634 P.O. Box 261 County: Logan Virden, IL 61440 Phone: (217) 947-2952 County: Macoupin Phone: (217) 965-5461 64 References Bergstrom, R.E., K. Piskin, and L.R. Follmer, 1976, Geology for Planning in the Springfield Decatur Region: lllinois: Illinois State Geological Survey Circular 47,76 p. Hester, N.C., 1970, Sand and Gravel Resources of Sangamon County, Illinois: Illinois State Geological Survey Circular 452, 22 p. Hester, N.C., and R.C. Anderson, 1969, Sand and Gravel Resources of Macon County, Illinois: Illinois State Geological Survey Circular 446, 16 p. Hester, N.C., and T.C. Labotka, 1970, An Investigation of Sands on the Uplands Adjacent to the Sangamon River Floodplain-Possibilities as a "Blend Sand" Resource: Illinois State Geological Survey Industrial Minerals Note 42, 10 p. Krey, F., and I.E. Lamar, 1925, Limestone Resources of Illinois: lllinois State Geological Survey Bulletin 46, 392 p. Lineback, 1.A., 1979, Quaternary Deposits of Illinois: Illinois State Geological Survey, 1:500,OOO-scale map. Masters, 1.M., 1983, Geology of Sand and Gravel Aggregate Resources ofIllinois: TIlinois State Geological Survey Illinois Mineral Notes 88, lOp. Masters, 1.M., V.C. Ipe, and M. Falter, 1999, Directory of Illinois Mineral Producers, and Maps of Extraction Sites 1997: Illinois State Geological Survey Illinois Minerals 117,86 p. 65 Aquifer Delineation An aquifer is a body of saturated earth materials capable of yielding sufficient ground water to a spring or small- or large-diameter well for its intended use. An aquifer will also yield water to any stream intercepting it. Aquifers in Illinois are generally composed of saturated sand and gravel, fractured or jointed limestone and dolomite, or permeable sandstone. Fine-grained earth materials such as silt, clay, shale, or till may restrict the flow of groundwater through and between aquifers. Among aquifers, yield variability is greatest in limestone and dolomite aquifers found in the bedrock. The rock units making up the bedrock tend to be relatively uniform in char acter in the horizontal plane and have their greatest variability in character in the vertical direction. Bedrock aquifers in lllinois are found in shallow and intermediate-depth dolo mites, limestones, and sandstones, and in deeply buried sandstones. Shales and unfractured limestones or dolomites restrict the vertical movement of groundwater between bedrock . aquifers. Aquifer thicknesses and distributions tend to be most variable in glacial deposits. Sand and gravel deposits in the glacial drift commonly formed in stream channels and where glacial meltwaters flowed over the landscape during and following successive advances and retreats of glacial ice. Although sand and gravel may be the dominant lithology locally, the bulk of the glacial drift consists of till, silt, and clay, materials that are not aquifers. Glacial drift aquifers are broadly categorized as basal, interbedded, and surficial. The rock units making up the bedrock tend to be relatively uniform in character horizon tally and have their greatest variability in character in the vertical direction. Bedrock aqui fers are found in the shallow dolomites, intermediate-depth dolomites and sandstones, and deeply buried sandstones. Shales and unfractured dolomites restrict the vertical movement of groundwater between bedrock aquifers. . Bedrock Aquifers The availability of usable groundwater from bedrock aquifers in the assessment area is extremely limited. Even small groundwater supplies are not generally developed from early Paleozoic rocks throughout the assessment area. These older, deeply buried rocks (of Cambrian, Ordovician, Silurian, Devonian, and Mississippian age) are predominantly limestone, dolomite, and sandstone (Figure 2). Although these rocks are potable aquifers in many other parts of the state, the bedrock formations within the Lower Sangamon River area do not yield water of usable quality because of the great depth of these rocks. Water quality generally deteriorates with increased depth, and at depths of 200 to 400 feet below land surface in lllinois, most groundwater becomes highly mineralized and undrinkable 66 (Herzog et al. 1995). Water in the deepest formations is therefore unusable for most purposes. Groundwater of acceptable quaHty may be obtained from Mississippian-age rocks at the extreme west edge of the area in the Havana Lowland. Generally, these aquifers are not used because of the abundant yields of the glacial drift aquifers in that area. Throughout virtually all of the assessment area, the early Paleozoic rocks are overlain by younger Pennsylvanian-age strata. These rock units, predominantly composed of shale interbedded with thin, discontinuous layers of sandstone, limestone, and coal, may yield small quantities of relatively poor-quality groundwater. The upper part of the Pennsylvanian age bedrock may be considered as a source only of small, fair-quality local supplies in the assessment 'area. In general, the bedrock yields only small amounts of poor-quality ground water, and some areas lack sufficient drift and bedrock resources even for domestic use. Glacial Drift Aquifers The primary glacial drift aquifers in the Lower Sangamon River Assessment Area are (1) deeply buried deposiis of sand and gravel within the confines of the Mahomet Bedrock Valley in the northern part of the assessment area; (2) thick, extensive surficial deposits of sand and gravel east of the Illinois River, predominantly in the Havana Lowland in Mason County; and (3) smaller deposits in the valleys of tributary creeks of the Sangamon River and, in a few areas, within the Sangamon River Valley itself. Small groundwater supplies are obtained from thinner, less-extensive aquifers that are present in many localities in the northern part of the assessment area, or in smaller bedrock valleys throughout the area. Outside of these areas, groundwater yield potential is very limited for the glacial drift, and even domestic supplies may be difficult to obtain. The Mahomet Aquifer is an extensive sand and gravel deposit located within the Mahomet Bedrock Valley, which stretches across much of the northern edge of the assessment area (Figure 4). High-capacity municipal and irrigation wells have developed groundwater yields of 2,000 to 3,000 gallons per minute (gpm) from the Mahomet Aquifer. Lesser yields are obtained near the edge of the valley and in some areas where the aquifer is less extensive. The Mackinaw Bedrock Valley enters the far northern part of the area in Tazewell and McLean Counties and joins the Mahomet Bedrock Valley. Moderate to possibly large supplies may be obtained from the Mackinaw Bedrock Valley in that area (Figure 4). The thick wedge of glacial outwash sand deposited primarily in Mason County is a pro ductive aquifer extensively used for irrigation (Figure 6). Yields of 1,000 gpm or more are often obtained. This aquifer is particularly vulnerable to contamination because it lies at or near the land surface. 67 The valleys of tributaries of the Sangamon River (the Sugar, Kickapoo, and Salt Creeks in particular) contain, in some areas, relatively thick deposits of sand and gravel of limited extent. These deposits may yield 50 to 100 gpm, and up to as much as several hundred gpm in limited areas. Several communities obtain their water supply from these deposits. Limited areas in the Sangamon River Valley may provide small to possibly moderate groundwater supplies. Small bedrock valleys tributary to the Mahomet are found in parts of Logan, Menard; McLean, and other Counties. Moderate groundwater supplies may be obtained from these deposits in some areas. In the northern part of the assessment area, shallower deposits with a scattered distribution within the Glasford-age drift, although thinner and less con tinuous than Mahomet Valley deposits, commonly yield small to moderate groundwater supplies to drilled wells. These deposits are not present in some areas, and are virtually absent in the southern part of the area, particularly in Sangamon County. Generally, drift thickness decreases toward the south, and in most of this area, ground water supplies are difficult to obtain where the glacial drift is thin. In very limited areas, particularly in Logan County, the presence of "ridged drift" deposits offers the prospect of a domestic, or possibly larger water supply; however, these deposits are elevated above the surrounding landscape and therefore may be partially drained in some areas. In the parts of the assessment area where the thin glacial drift yields little or no groundwater to a small-diameter drilled well, large-diameter bored wells are commonly used to provide water supplies. These wells provide very limited and sometimes seasonal yields, requiring careful control of water usage. Water Quality The water from glacial drift aquifers is generally of good quality, with relatively low total dissolved solids (TDS), although the iron content and hardness are commonly high. Water obtained from the Mississippian- and Pennsylvanian-age bedrock varies widely in quality; the quality of the water that is available from the Pennsylvanian is generally marginal. Summary In summary, major aquifers capable of reliably producing large water supplies are encountered only in deeply buried deposits of sand and gravel within the Mahomet Bedrock Valley and the Mackinaw Bedrock Valley, and in thick, extensive surficial deposits of sand and gravel in the Havana Lowland east of the Illinois River. Sand and gravel deposits in creek valleys, within the Sangamon River Valley, and in other buried bedrock valleys may provide small to moderate groundwater supplies. 68 --_._------ Some domestic supplies can be obtained from thinner, less extensive aquifers that may be present in the northern part of the assessment area or in smaller bedrock valleys. In much of the southern part of the assessment area, groundwater yields from the glacial drift are small, and even domestic supplies may be difficult to obtain. Throughout the area, bedrock aquifers generally yield only small amounts of poor quality water. References Hansel, A.K., and W.H. Johnson, 1996, Wedron and Mason Groups-Lithostratigraphic . Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area: Illinois State Geological Survey Bulletin 104, 116 p.; plate 1: Quaternary Deposits of Illinois (map). Heigold, P.C., V.L. Poole, K. Cartwright, and R.H. Gilkeson, 1985, An Electrical Earth Resistivity Survey of the Macon-Taylorville Ridged Drift Aquifer: Illinois State Geological Survey Circular 533, 23 p. Heriog, B.L., et aI., 1994, Buried Bedrock Surface of Illinois: Illinois State Geological Survey and U.S. Geological Survey, ISGS lllinois Map 5. Herzog, B.L., et aI., 1994, Hydrogeology and Groundwater Availability in Southwest McLean and Southeast Tazewell Counties. Part I-Aquifer Characterization: ~llinois State Geological SurveylIllinois State Water Survey Cooperative Groundwater Report 17, 70 p., 37 figs., 12 tables. Horberg, L.,1950, Bedrock Topography of Illinois: Illinois State Geological Survey Bulletin 73, III p. Illinois State Water Plan Task Force, 1997, The Mahomet Bedrock Valley Aquifer System-Knowledge Needs for a Vital Resource: University oflllinois Water Resources Center Special Report 21, 49 p., 9 figs. Nelson, W.J., 1995, Structural Features of Illinois: Illinois State Geological Survey Bulletin 100, 144 p. Piskin, K., and R.E. Bergstrom, 1975, Glacial Drift in lllinois-Thickness and Character: lllinois State Geological Survey Circular 490, 35 p. Public-Industrial-Commercial Supplies Database (PICS), 1996: lllinois State Water Survey. Selkregg, L.F., and J.P. Kempton, 1958, Groundwater Geology in East-Central Illinois: Illinois State Geological Survey Circular 248, 36 p. 69 Selkregg, L.P., W.A. Pryor, and J.P. Kempton, 1957, Groundwater Geology in South Central Illinois: Illinois State Geological Survey Circular 225, 30 p. Walker, W.H, R.E. Bergstrom, and W.C. Walton, 1965, Preliminary Report on Ground-Water Resources of the Havana Region in West-Central Illinois, Cooperative GroundwaterlResources Report 3, 61 p., 44 figs., II tables. Willman, H.B., J.e. Frye, J.A. Simon, K.E. Clegg, K.H. Swann, E. Atherton, e. Collinson, J.A. Lineback, and T.e. Buschbach,1967, Geologic Map of Illinois: Illinois State Geological Survey. Willman, H.B., J.e. Frye, 1970, Pleistocene Stratigraphy oflllinois: llIinois State Geological Survey Bulletin 94, 204 p. 70 Potential for Geologic Hazards Detennining appropriate land use in the Lower Sangamon River Assessment Area requires an understanding of the potential natural and society-induced geologic hazards inherent to the area. Geologic hazards develop through interactions between geologic materials and natural forces and can be influenced by human activities. This section will sensitize readers to some of the potential geologic hazards, including groundwater contamination, that can occur in the assessment area. Site-specific geologic conditions or hazards are not comprehensively discussed. For a broader view of geologic hazards and what measures to take when they occur, consult The Citizen's Guide to Geologic Hazards. Prepared by the American Institute of Professional Geologists, this publication covers both hazards that arise from naturally occurring geologic materials (such as radon and asbestos) and from geologic processes (such as earthquakes, landslides, and flooding). In addition, its appendices list sources of help from professional geologists and insurance professionals. The publication may be ordered by contacting: American Institute of Professional Geologists 7828 Vance Drive Suite 103 Arvada, CO 80003 Telephone: (303) 431-0831 Potential for Contamination of Groundwater Resources Groundwater contamination can arise from many sources. These sources are generally grouped into two classes, point or nonpoint, on the basis of the size of the area where a chemical is applied or spilled, or a waste material is deposited. Point sources of contami nation include many types of facilities and activities, such as landfills, chemical storage tanks (both above and below ground surface), individual septic systems, homeowner dis posal of unwanted chemicals (for example, paint or used motor oil), the over-application of lawn fertilizers and pesticides at individual residences, and the facilities of pesticide and fertilizer dealers or applicators, etc. The primary nonpoint source of potential contamination in lllinois is the agricultural use of pesticides and fertilizers. Urban and suburban sources of groundwater contamination, such as septic systems and overuse of lawn fertilizers and pesticides, can also become nonpoint problems if a significant concentration of these sources occurs in a subdivision or other area. Groundwater contamination can be defined as the presence of a chemical at or below the water table in concentrations that exceed federal or state acceptable levels. Flowing 71 groundwater is the means of transporting these dissolved contaminants away from their source. Responsible chemical use and prompt cleanup of spills can prevent the degradation or contamination of groundwater. In addition, it can be helpful to restrict or closely monitor activities that can contribute to groundwater contamination, particularly when they are conducted in or near the setback zone of a water supply well. The Il1inois EPA provides information on the delineation of setback zones and the evaluation of activities within these areas (Cobb and others 1995). The potential for groundwater contamination depends on a complicated combination of hydrogeologic properties, environmental processes, and the quantity and nature of the con taminant in question. In general, as depth to the top of the uppermost aquifer increases, the sensitivity to contamination of that particular aquifer decreases. Greater depth from the ground surface affords an aquifer greater protection, due to the increased opportunity for adsorption, microbial degradation, and dilution of a spilled contaminant before it can reach the aquifer. The validity of this statement, however, depends on several other factors. The effects of these various factors on contaminant fate and transport are discussed below. Effects of Climatic Variables on the Fate of the Contaminant Four climatic variables (precipitation, temperature, humidity, and wind spee~) help deter mine the fate of subsurface chemicals through their impact on several different processes. The amount and intensity of rain helps to determine the amount of runoff from the soil surface and, consequently, the amount of water infiltrating the soil surface. Temperature, humidity, and wind speed influence water and chemical movement through their effects on the processes of evaporation, transpiration, volatilization, and condensation. Evaporation of water from the soil and transpiration of water from plants both reduce the amount of water in the soil that percolates downward to the water table. Depending on the depth of the water table and the depth and distribution of plant roots, plants can even remove water from below the water table. Volatilization is the process whereby a chemical in a liquid state is heated enough to convert it to a gaseous state. Gasoline is one example of a chemical that can volatilize at temperatures normally found in the soil during Illinois summers. Condensation is the process whereby gaseous chemicals are cooled into a liquid state. Once condensed, the chemical may become dissolved in water and leach to the groundwater system. Thus, chemicals which have been volatilized and remain trapped as gases in soil can condense back to a liquid form and leach to groundwater. Effects of Quantity and Chemical Characteristics of the Fate of the Contaminant The quantity and nature of a chemical spill or application, as well as the chemical properties of the contaminant, also help determine whether groundwater contamination will occur and the amount of groundwater that will become contaminated. The larger the quantity of contaminant that is released, the more likely it is that some fraction of the chemical will leach to groundwater. In addition, the depth from the land surface to the aquifer and the 72 area of land exposed to the chemical will also affect the likelihood of groundwater contami nation. For example, a herbicide applied to the land surface at a rate of 3 pounds per acre, over 640 acres will have a much lower likelihood of causing significant groundwater con tamination than a leaking gasoline storage tank that is 15 feet below land surface. Several chemical properties affect the fate of a chemical in the subsurface. These properties include, but are not limited to, water solubility (the amount of a chemical that can dissolve in water) and the adsorption coefficient (a measure of the tendency for a chemical to stick to the outside of soil particles). Many chemicals applied to agricultural fields are removed by runoff and soil erosion during rainfalls. The water solubility of a chemical helps control how readily the chemical mixes, or dissolves, in water. Less-soluble compounds will generally not move as rapidly as more-soluble compounds. Adsorption is the process whereby a molecule of a chemical sticks to the surface of a soil particle. Like solubility, adsorption is important in helping to control the rate of chemical movement in the subsur face. Many organic chemicals found in pesticides or used in solvents are strongly adsorbed by the organic matter or clay minerals in soil, which slows their flow to groundwater resources. Nitrate, however, does not adsorb to soil particles, and so moves much more rapidly in groundwater than do pesticides. In addition to solubility and adsorption characteristics, potential contaminants are also characterized by their half-life. The half-life of a chemical is a measure of the speed with which it can be degraded by microbial organisms or by exposure to other natural processes. In general, these processes break the chemical down into smaller compounds that may be less toxic or even nontoxic. Effects of Geologic Materials Whether groundwater becomes contaminated also depends heavily upon the hydrogeologic characteristics of the area. Groundwater flow is largely controlled by the hydraulic con ductivity of the geologic materials and the hydraulic gradient of the system. Hydraulic conductivity is a measure of the ability of water to flow through a geologic deposit. For example, sand and gravel deposits generally have high hydraulic conductivity values, whereas clayey diamictons generally have low hydraulic conductivity values. Some geologic materials are fractured, and depending on the size and spacing of the fractures, hydraulic conductivities in these units can be much higher than unfractured materials. Hydraulic gradient is the difference in groundwater pressure between two points. Under a large hydraulic gradient (or a large difference in pressure), water and dissolved contaminants will move more quickly through a given geologic material than under a small hydraulic. gradient. Because the measurement of hydraulic conductivity and hydraulic gradient requires signifi cant commitments of time and money, other methods have been developed to estimate the potential for groundwater contamination. 73 Potential for Groundwater Contamination Most discussions of groundwater contamination do not distinguish between groundwater contamination and aquifer contamination. This distinction can have very important practical consequences. Technically, any time a chemical leaches into the water table to a concentra tion above a level established by a state or federal agency, groundwater is contaminated. In most of lllinois, however, contamination of shallow groundwater would not necessarily result in contamination of the uppermost aquifer because the uppermost aquifer commonly lies deeper than 20 feet from the surface. Most water supplies that use groundwater rely on the water in aquifers for that supply. For this reason, most concerns regarding ground water quality generally refer to the protection of the water quality in aquifers rather than all groundwater. In regions without aquifers, private water supplies may have to draw water from nonaquifer materials with low hydraulic conductivities by using large-diameter dug or bored wells. Residents of these regions must be concerned with the contamination of any groundwater. The contamination potential of shallow aquifers is estimated using information on the occurrence and depth of shallow sand and sand and gravel deposits, and on the leaching chaJ:acteristics of mapped soils (Keefer 1995). It is important to recognize that, by defini tion, aquifers are geologic deposits that are saturated with water. Sand and gravel deposits may not be aquifers when they are saturated only partially or seasonally. The statewide prediction of contamination potential by Keefer (1995) recognized these factors, but noted that the relative contaminant transport properties of aquifer and nonaquifer materials did not change significantly when the materials were unsaturated. For this reason, all mapped deposits of aquifer material (i.e., sand, sand and gravel, fractured limestone or dolomite, sandstone) were treated as aquifers by Keefer (1995), and are treated similarly in this discussion. To create the aquifer sensitivity map of the assessment area (Figure 27), the soils of the assessment area were first classified according to their predicted pesticide leaching charac teristics (Keefer 1995). Soils with greater organic-matter contents were generally classi fied as having lower leaching potential (greater ability to retain contaminants and prevent aquifer contamination) than soils with smaller organic-matter contents. In addition, soils with smaller hydraulic conductivities or poor drainage characteristics were classified as having lower leaching potential than soils with larger hydraulic conductivities and better drainage. These aquifer sensitivity classifications are based only on the generalized characteristics of the mapped geologic materials. Water quality information was not used because no suit able information was available. This map was designed to be used for statewide screening purposes. These limitations should be considered, however, before using the aquifer sensitivity interpretations for anything other than broad screening decisions at the watershed or subbasin level. 74 I I I I I I vi o /1 \' I PIATT---1 CO. J 01 ~I ,,"'I"!::;, ~:J" 01 J I':; 0 10 20 30 I I Miles Excessive GJ Very limited High Disturbed land! • surface water Moderate assessment area , • • boundary N GJ Somewhat limited county boundary I river or stream UJ Limited Figure 27. Potential for Contamination from Pesticides (Aquifer Sensitivity) in the Lower Sangamon River Assessment Area Aquifer Contamination Potential in the Lower Sangamon River Assessment Area For the Lower Sangamon River Assessment Area (Figure I), approximately 42% of the almost 3 million acres of land area has been mapped as having aquifer materials within 50 feet ofland surface. Using Keefer's (1995) mapping of aquifer sensitivity to contami nation by pesticide leaching, approximately two-thirds of these areas were mapped with an aquifer sensitivity rating of Excessive or High. The remaining 58% of the assessment area does not have mapped aquifers within 50 feet of land surface; the vast majority of these areas are mapped with an aquifer sensitivity rating of Very Limited. Detailed analysis of Figure 27 indicates that areas with Excessive aquifer sensitivity occupy . approximately 280,000 acres (approximately 10%) of the total land area. These areas have aquifer materials within 20 feet of land surface and have a soil leaching class of Exces sive to Moderate (Keefer 1995, Berg and Kempton 1988). Areas with Excessive aquifer sensitivity occur throughout Mason County and in the southeastern portions of Tazewell County. In these areas, thick sand is present from the surface to depths greater than 50 feet. Smaller areas with Excessive aquifer sensitivity are present in the assessment area along floodplains of the major streams wherever sand is within 20 feet of the surface and where the soils are generally well drained (Berg and Kempton 1988). Areas with High aquifer sensitivity occupy over 500,000 acres (approximately 17%) of the Lower Sangamon River Assessment Area. Large areas with High aquifer sensitivity occur in several places throughout the assessment area. In the northwestern portion of the assessment area, areas with High aquifer sensitivity occur in the Crane Creek, Illinois River, and Quiver Creek Subbasins. In these areas, the shallow geologic materials generally con sist of sand or sand and gravel deposits that are more than 50 feet thick (Berg and Kempton 1988). The soil leaching class for these areas is either Somewhat Limited or Limited (Keefer 1995). In the north-central and northeastern parts of the assessment area, High aquifer sensitivity is mostly associated with sand and gravel deposits in stream floodplains and associated terraces where sand and gravel lies within 20 feet of land surface. In the southern and south-central portions of the assessment area, High aquifer sensitivity again is associated with floodplain and terrace deposits of the major streams and with sand and gravel deposits of the Pearl Formation (Figure 6) (Berg and Kempton 1988, Willman and Frye 1970). The Pearl Formation is not generally associated with modem stream channels, and tends to occur more commonly in broad deposits. Some examples of this occurrence can be found in the Lake Fork Subbasin and again around the Brush Creek Subbasin. All of these sand and gravel deposits occur within 20 feet of land surface and have soil leach ing characteristics that range from Somewhat Limited to Limited (Keefer 1995). Areas of Moderate aquifer sensitivity are found in almost 145,000 acres (approximately 5%) of the assessment area. Most of these areas are associated with the floodplain of the Illinois River and the Sangamon River near its confluence with the Illinois River. In these areas, the sand and gravel is generally within 20 feet of land surface. The soil leaching characteristic of these areas is Very Limited. In the remainder of the assessment area, areas of Moderate aquifer sensitivity occur along the floodplains of other major streams, including the South Fork of the Sangamon, Salt Creek, Quiver Creek, and Lake Fork. In these areas, 76 the aquifers are also generally within 20 feet of land surface, and the soil leaching class is Very Limited (Berg and Kempton 1988, Keefer 1995). Areas with Somewhat Limited aquifer sensitivity,cover almost 250,00 acres (just over 8%) of the assessment area. Most of these areas occur in the central part of the assessment area, between Salt Creek and the Sangamon River, but smaller areas are scattered throughout the assessment area. Geologic materials in these locations consist of a thin, sometimes discontinuous sand and gravel deposit that generally lies between 20 and 50 feet below land surface (Berg and Kempton 1988). This sand and gravel is over- and underlain by lllinoian till of the Glasford Formation (Willman and Frye 1970). The soil leaching classes in these areas range from Somewhat Limited to Very Limited (Keefer 1995). Areas with Limited aquifer sensitivity cover almost 300,000 acres (10%) of the land in the assessment area. These areas all correspond to locations with no aquifer materials within the upper 50 feet and soil leaching class ratings of Excessive or High (Berg and Kempton 1988, Keefer 1995), Areas mapped with Limited aquifer sensitivity in the northern half of the assessment area include areas with geologic materials in the upper 50 feet that include fine-grained deposits of loess and till (Berg and Kempton 1988). In the southern half of the area, where glacial deposits are thin, some Pennsylvanian shale bedrock is exposed at the land surface, primarily in lowland areas (Berg and Kempton 1988); these areas also have limited aquifer sensitivity. Areas with Very Limited aquifer sensitivity to contamination cover approximately 1,400,000 acres (or 48%) of the assessment area. The Very Limited rating was assigned to areas where there is no aquifer material within 50 feet of the land surface, and where the soil leaching characteristics are rated as Moderate to Very Limited (Berg and Kempton 1988, Keefer 1995). In this assessment area, these locations are characterized by loess deposits overlying tills that are greater than 50 feet thick with soil leaching characteristics that range from Moderate to Very Limited (Berg and Kempton 1988). In this assessment area, these areas generally occur in uplands with flat to gently sloping land surfaces. Regional Earthquake History July 19, 1909 It is reported from Mason City, lll., that nearly all the inhabitants felt the tremor and about a thousand persons were on the streets shortly afier ward discussing the disturbance. Springfield also reported a slight shock. -The St. Louis Post Dispatch Earthquakes are more of an occasional curiosity than a dangerous hazard in the Lower . Sangamon River Assessment Area. Small earthquakes are known to occur on rare occasions in the area. The 1909 earthquake that startled the citizens of Mason City is a good example. 77 ~ I I I I WOODFORD CO. _ -J ----j (1937 \ -~-, / 1 I 1- L __ r J --I I I cO' ( 3 I I ~P'<-\~ ,) I I I 1956 I I 81 • 3.7 I I :x: I u0 1885 I :>"I z . 010 3.4 I z !::; g/2 • ~I I I ----j --- -.McLEAN-- CO..-...., --r I . DEWI17TCO. .. ('. -l I r I , I I SCHUYlERCO. -( 1 • I 1 1952 : 1 1 3.4 I f---~-- I ---I I I I I I I I I 0 1 I - 9'~S£O_'__ __ ...... ul I I SANGAMON CO. -- z 01 U « I I ::;~ __P~Tl~· J f k..t,r-r I 1 1- I I • :.....::..J I I L 1 r .:--' 1977 -I I I I' 2.3 I I I 1 I _ ~ee2TJ: ee2.---L MORGAN CO. I --T-- ---I -- I 1928 • ~ 10 ~ 1 3.4 -, I u°lu z 1 ~--I ~!~ 1982 I, I I HilS I I 11: ", 2.6 (, 1 I- f-- " I ::; I : 1982 I 1- I j I 2.6 I r-- I I MONTGOMERY CO. __ L~E.!:~C£______-1 o 10 20 30 I I Miles • epicenter 3.4 approximate magnitude r! 1952 year of earthquake D Prairie Parklands Assessment Area Figure 28. Earthquakes in the Lower Sangamon Assessment Area (St. Louis University Earthquake Center Database, 1996) Larger, more frequent earthquakes in the more seismically active regions of southeastern and southern Illinois, Missouri, and Tennessee, can also shake the area. Only nine small earthquakes have been reported over the last century from the counties in and adjacent to the assessment area (Figure 28). Most of these small earthquakes occurred before seismometers were installed in the region in the 1960s, so we can only estimate that their magnitudes were somewhere between 3.0 and 4.5. None of these small earthquakes were known to have caused any damage within the assessment area, and only the ones with estimated magnitudes of 4.0 or greater were even felt throughout the area. For example, the small tremor in western Fulton County was felt in Canton but not in Peoria. But the stronger 1909 earthquake was felt at least from north ofFulton County to St. Louis in the south and as far east as Logan County. More recently, seismographs located in St. Louis and Chicago have enabled scientists to accurately locate even smaller earthquakes that probably were not felt more than a few miles from their epicenters. These occasional, small earthquakes could possibly reach magnitudes as great as 5.0. At that size, minor damage such as broken chimneys and cracked or broken plaster walls 'could be expected. The Wabash Valley Seismic Zone, about 50 to 100 miles to the southeast, spawns mag nitude 5 earthquakes about every 10 years. The magnitude 5.0 earthquake of 1987 and the magnitude 5.2 earthquake of 1968 were felt by most people in the area, and rattled windows and knocked objects off shelves. The Wabash Valley area could produce earthquakes as large as Richter magnitude 6.5. These larger quakes might cause damage to chimneys and older brick structures in the assessment area, but the likelihood of their occurring in the near future is very low. The New Madrid Seismic Zone in far southern lllinois, Missouri, and Tennessee is capable of producing very powerful earthquakes, but because it is 150 or more miles to the south, the resulting ground motions in the assessment area are not expected to be dangerous. A magnitude 6.2 earthquake that occurred in the northern part of the New Madrid Zone in 1895 reportedly awakened guests at a hotel in Vermont and sickened people in Canton. It caused no damage in the Lower Sangamon River Assessment Area, but it caused severe damage in southern Illinois towns. A similar earthquake, with similar effects, is expected to occur in the New Madrid Seismic Zone sometime in the next 15 years. An even stronger series of earthquakes occurred in the New Madrid Seismic Zone in 1811-1812. Devastating earthquakes, possibly as large as Richter magnitude 8 occurred three times that winter. There is no record of the ground motions in the Lower Sangamon River Assessment Area from those earthquakes, but it is estimated that the motions would probably have been strong enough to damage masonry structures. Fortunately, such large earthquakes are not expected to recur within the next several hundred years. 79 Landslides When most people think of landslides, they usually envision a massive body of boulders, gravel; sand and dirt crashing down a hillside, destroying everything in its path. Rightly so: for that type of "mass wasting," as geologists call it, commonly occurs in landscapes dominated by very high, steep slopes. Several such landslides have been documented in Illinois and have caused hundreds of thousands of dollars in property damage, but these are rare. In the relatively young, low-relief, glacially sculpted landscape common to most of Illinois, more subtle mechanisms of mass wasting can be just as threatening and costly as their more extreme but less common counterparts. Nearly 60% of the landslides documented thus far in lllinois have been classified as "slumps" (Killey and others 1985). A slump is a mass of rock or earth (glacial material) that moves down along one or more underground surfaces or slip planes within the mass or along the contact between the underlying bedrock and the glacial material. Slump-type landslides may be recognized by one or more of the following characteristics: • A sharp cliff (also called a "scarp") found at the top of the slide can be several inches or feet high that results from the initial downward movement • One or more additional scarp faces resulting from successive slump movement • Ponding of water or marshy, wet areas in the landslide due to large blocks of earth tilting back toward the slope • Tilting of trees, fence posts, and utility poles • Earth bulging and rolling over the original ground surface at the base of the landslide Most landslides in Illinois involve stream erosion or road construction that impacts the lower part of the slope, triggering the landslide. Two landslides have been reported in this watershed (Figure 29). Both are earth slumps along roadway improvements. The earth slump in McLean County is along the interchange of 1-74 and U.S. Highway 51. It has since been regraded. The earth slump in Sangamon County is along 1-72 in a drainage way that collects outflow from farm fields. Information on landslides in Illinois is contained in Landslide Inventory ofIllinois (Killey and others 1985), produced by the Illinois State Geological Survey in cooperation with the United States Geological Survey. This publication contains historical photos of land slides that have occurred in lllinois and provides information on landslide classification, factors contributing to landslide potential, and what can be done to stabilize landslides. It can be purchased from the Illinois State Geological Survey at (217) 333-ISGS. 80 ------ I -- I \ ---1 I I - -::I I I U°1 . :>:10 U ::>"'I z I z°1°!S I glee , ~I I TAZEWELL CO. -.J ~ -.-,- LOGANCo. - ~ ----1 I I I ....._-- , SCHUYLER CO .MASON CO...... ,--+-.:../ 1 1 I ___ I I I 01'). " I~~-.J_·_I Is'" J ' _ _ _ _ CASS CO. -~--- ----,-- I I I I 1- r'" Middle Fork I K../IDki. Shoaler.. I Ri.., '-. __ L~~~C~_ o 10 20 30 I I Miles assessment area assessment area D boundary open water N! county boundary j location of society ~ river or stream • induced landslide location of naturally • induced landslide Figure 29. Landslides in the Lower Sangamon Assessment Area .- I 1 \ ---I I I - ~:-T I I 01 U. :rIo u :>z"I I 010 Z !j I gl~ I ,,~.. ~I ~T~ZEWEL.!o C~. --.J ~. I 1 I LOGAN CO. ~~ ~ I,!c~~ ~O. ----1 --j I : DEWITT CO. 1 _ ,if I I I SCHUYLER CO. o#i MASON CO. ~.er ;--"""....,._'" I D ~ Ig &urfac9 • I 10 mil106 0;:'-/ , 1;2 . I PIATT---1 CO. J dl ~I L ~I 1 :> 01 I ::;;1 I _ ~~lJ: ~'--L MORGAN CO. --T-- 10 diU U Z ~I~ ~18 ""'I'" ::;; 1- I (' I Kaskaakia Little _ 1 River w..ba. o 10 20 30 I I Miles 1,,0-» underground mine river or stream county boundary ! • surface mine assessment area r • open water boundary Figure 30. Coal Mines in the Lower Sangamon Assessment Area Coal Mine Subsidence and Acid Mine Drainage The coal industry has long been an important component of the Illinois economy. In this assessment area, which covers all or parts of fifteen counties, coal mining has occured in eight of them: Christian, Logan, McLean, Macoupin, Menard, Montgomery, Sangamon, and Shelby (Figure 30). Information on the mining type, acreage mined out, and coal seam mined is given in Guither et al. (1985). In Christian County about 52,269 acres (83.3 square miles) were mined out underground. All of these areas except 275 acres (0.43 square miles) used the room-and-piIIar mining method in the Herrin Coal; the exception was one long wall mine in the Colchester Coal. In Logan County, about 4,333 acres (6.8 square miles) were mined out underground in the Springfield Coal. These acres represent only the area of the abandoned mines and do not include the active Turris Coal mine. Of the total area undermined, about 77 acres (0.12 square miles) were mined using the longwall mining method, whereas the room-and-pillar mining method was used for the rest. In McLean County, only one mine operated, using the longwall mining method in both the Springfield and Colchester Coals. Seams were mined out from the same 499 acres (0.78 square miles). In Macoupin County, about 5,440 acres (8.5 square miles) were mined out underground using the room-and-pillar mining method in the Herrin Coal. In Menard County, about 2,016 acres (3.15 square miles) were undermined, almost all in the Springfield Coal, except for 38.4 acres (0.06 square miles) that were in the Herrin Coal. All of the mining used room and-pillar mining methods. In Montgomery County, about 11,000 acres (17 square miles) have been undermined in the watershed. These mines operated in the Herrin Coal and used room-and-pillar mining methods. In Sangamon County, about 60,537 acres (94.6 square miles) were undermined using the room-and-pillar mining method; 22,976 acres (35.9 square miles) were in the Herrin Coal and 37,568 acres (58.7 square miles) in the Springfield Coal. In Shelby County, about 307 acres (0.48 square miles) were undermined using room-and pillar mining methods in the Springfield Coal. Exact mine locations and coal mine niaps, catalogued by county, are available at the ISGS. County-based maps at a scale of I: 100,000, or I inch equals about 1.6 miles, show the general outlines of the mines. Each map is accompanied with a county directory, which lists company names, mine names and numbers, type of mining method used, years of operation, coal seam mined, and mine location. More detailed maps at a scale of 1:24,000 are available for some of the quadrangles in some of the counties in this assessment area. Mine subsidence (the sinking ofland surface either as an intentional result of modem long wall mining, or from unintentional failure of the mine underground) has occurred over the mines in Christian, Logan, and McLean Counties, which used longwall mining methods to remove all the coal. The old longwall mining method removed all the coal by hand as mining moved away from the vertical shaft entrance. Roadways from the operating face back to the shaft were held open by packing rock along the entryway and by cutting out some of the roof rock to maintain head room. Subsidence was part of this mining process and occurred at the time of mining. The ground surface would have been lowered several feet over the entire mined area. 83 The other mines in this assessment area used room-and-pillar mining methods, which left large blocks (pillars) of coal to support the mine roof and ground surface. Where underground mining is deep and the room-and-pillar mining method was used, failure of stability of pillars underground can produce a depression on the ground surface hundreds of feet across and 1 to 3 feet deep near the center. This is the type of subsidence that can occur over the other mines in this assessment area, as shown by the reports by Quade (1933, 1934 a,b) for Christian, Montgomery, and Sangamon Counties. The Christian County report shows about 40 subsidence events scattered over most of the mines in the county. The Montgomery County report shows subsidence over the mine in the northeast part of the county. Most of the mines in the northwest part of the county mostly did not exist in the early 1930s. The Sangamon County report shows about 170 subsidence events over about 80% of the mines in the county. Two essential publications for land-use planners and homeowners who want to learn more about coal mine subsidence are Planned Coal Mine Subsidence in Illinois, A Public Infor mation Booklet and Mine Subsidence in Illinois: Factsfor Homeowners. These booklets contain information on coal-mine reserves in Illinois, coal-mining methods, the history of subsidence in Dlinois, what to do if subsidence occurs, and sources for additional information. Contact the Dlinois State Geological Survey at (217) 333-ISGS to request these publications. Despite its obvious economic contributions, coal production can also threaten other natural resources. Mine subsidence over abandoned coal mines can damage structures and affect farmland productivity. Unreclaimed mine wastes can pollute air and water resources and can be another source for coal. Achieving a balance between the advantages and disadvan tages of coal production can be aided when citizens are knowledgeable about past and present coal mining methods, and how these methods affect natural resources. Piles of mining waste, often called "gob piles," can contribute to groundwater contamination. Composed mostly of shale (clay-rich rock) and poorer quality coal, the waste commonly contains sulfur-rich minerals, particularly pyrite and marcasite. These minerals react with rainfall and air to produce sulfuric acid; eventually, the sulfuric acid may drain or percolate into surface water and groundwater resources. The resulting increase in the acidity of the surface water can affect aquatic life and weaken concrete structures such as bridge piers, retainer walls, utility pipes, and well casings (Nuhfer et al., 1993). In some areas these piles are reprocessed to take additional coal out. It is important to distinguish between "pre-law" and "post-law" mining activities and to describe the responsibilities that federal and state laws have placed on Illinois coal mining. Since the late 1970s, Dlinois has had one of the nation's strictest and best enforced programs for regulating surface strip mining. To obtain a mining permit, companies must file a detailed report on the proposed mine area. The report must demonstrate that the strip min ing activity will have no environmental impact outside the mine area and that after mining the land can and will be reclaimed to a condition equal to or better than before mining. To support their reclamation plans, companies must post with the state a bond for an amount deemed sufficient to reclaim the land. As the land is reclaimed, the bond is returned. If the company fails to reclaim the land properly, the bond is forfeited, and the state uses the 84 money to do the reclamation work. Most companies find it cheaper to do the reclamation work properly themselves than to forfeit the bond. All mines must report annually to the state on their mining and reclamation activities, and state inspectors regularly visit the mines to ensure that all activities are in compliance with the permit issued by the state. Underground mines also require permits to mine either with a plan that will not subside the ground surface or a plan that has subsidence as part of the mine plan. Mines are not allowed to subside the ground surface unless they have acquired the right to do so from a previous or current land owner. Even then, they may not subside the surface unless they present a plan on how the land and structures will be handled and how the land will be repaired and that the land will be returned to a condition that is able to sustain the same land use as before mining. Companies are also liable for any future damage from subsidence even after an area is no longer actively mined. The Lands Unsuitable for Mining Program includes procedures allowing residents to petition that certain areas (such as special natural or historical sites) be declared "unsuitable for mining." The law also requires companies to contribute to a fund for cleaning up abandoned mine sites that are environmental or safety hazards. The fund will also cover future prob lems on abandoned mine properties. .References Berg, R.C., and J.P. Kempton, 1988. Stack-Unit Mapping of Geologic Materials in Illinois to a Depth of 15 Meters: Illinois State Geological Survey Circular 542, 23 p. Cobb, R.P., H.A.Wehrmann, and R.c. Berg, 1995, Guidance Document for Groundwater Protection Needs Assessments: Illinois Environmental Protection Agency, Report No. IEPAlPWS/95-01, 96 p. Guither, H.D., J. Hines, and R.A. Bauer, 1985, The Economic Effects of Underground Mining Upon Land Used for Illinois Agriculture: Illinois Department of Energy and Natural Resources Document No. 85/01, 185 p. Hansel, A.K., and W. H. Johnson, 1996, Wedron and Mason Groups-Lithostratigraphic Relationships of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area: Illinois State Geological Survey Bulletin 104, 116 p. Keefer, D.A., 1995. Potential for Agricultural Chemical Contamination of Aquifers in lllinois: 1995 Revision: Illinois State Geological Survey Environmental Geology 148,28 p. Nuhfer, E.B., R.J. Proctor, and P.H. Moser, 1993, Citizens' Guide to Geologic Hazards: American Institute of Professional Geologists, Arvada, CO 134 p. Quade, J.C., 1933, Preliminary Report on Subsidence Investigation, Christian County, Illinois: For the Federal Land Bank of St. Louis. 85 Quade, J.e., 1934a, Preliminary Report on Subsidence Investigation, Montgomery County, Illinois: For the Federal Land Bank of St. Louis. Quade, J.e., 1934b, Preliminary Report on Subsidence Investigation, Sangamon County, Illinois: For the Federal Land Bank of St. Louis. Willman, H.B., and J.C. Frye, 1970, Pleistocene Stratigraphy of Illinois: lllinois State Geological Survey Bulletin 94, 204 p. I 86 Additional-Readings Berggren, D., and C.S. Hunt, 1979, A Guide to the Geology of the Farmer City Area, De Witt County, Illinois: Illinois State Geological Survey Field Trip Guide Leaflet 1979-B, 27 p. Bergstrom, R.E., K. Piskin, and L.R. Follmer, 1976, Geology for Planning in the Springfield-Decatur Region: Illinois State Geological Survey Circular 497, 76 p. Berning, G.V., 1994, Soil Survey of Christian County, Illinois: University of Illinois Agricultural Experiment Station Soil Report 143, 200 p. Calsyn, D.E., 1995, Soil Survey of Mason County, Illinois: U.S. Department of Agriculture, Natural Resources Conservation Service, University of lllinois Agricultural Experiment Station Soil Report 146,211 p. Calsyn, D.E., K.P. Black, and J.K. Witt, 1989, Soil Survey ofCass County, Illinois: U.S. Department of Agriculture, Natural Resources Conservation Service, University of Illinois Agricultural Experiment Station Soil Report 129, 195 p. Chrzastowski, MJ., M.M. Killey, RA. Bauer, P.B. DuMontelle, A.L. Erdmann, B.L. Herzog, J.M. Masters, and L.R Smith, 1994, The Great Flood of 1993-Geologic Perspectives on Flooding along the Mississippi River and Its Tributaries in Illinois: Illinois State Geological Survey Special Report 2, 45 p. Cross, P.G., M. Bittinger, R. Mazrim, and T.J. Wood, 1997, Prehistoric and Historic Occupation of Fork Prairie. Phase I -Archeological Survey for the Proposed Route 29 Project: Contract Archeology Program, Center for American Archeology, 1 vol., maps. Follmer, L.R, D.P. McKenna, and J.E. King, 1986, Quaternary Records of Central and Northern'Illinois, American Quaternary Association Ninth Biennial Meeting, 31 May 6 June, 1986: Illinois State Geological Survey Guidebook 20, 84 p. Follmer, L.R, 1985, Surficial Geology and Soils of the Rhoads Archeological Site near Lincoln, Illinois: American Archeology, v. 5, p. 150--160; Illinois State Geological Survey Report 1986-R Hajic, E.R., and D.S. Leigh, 1984, Shallow Subsurface Geology, Geomorphology and Limited Cultural Resource Investigations of the Meredosia Village and Meredosia Lake Levee . and Drainage Districts, Scott, Morgan, and Cass Counties, Illinois: St. Louis District Resource Management Report No. 17, 165 p. 87 Hallberg, G.R, J.A. Lineback, D.M. Mickelson, J.C. Knox, J.E. Goebel, H.C. Hobbs, J.W. Whitefield, RA. Ward, J.D. Boellstorf, J.B. Swinehart, V.H. Dreeszen, G.M. Richmond, D.S. Fullerton, and A.e. Christiansen, 1991, Quaternary Geologic Map of the Des Moines 4 0 x 6 0 Quadrangle, United States: U.S. Geological Survey Miscellaneous Investigations Series I, I: 1,000,000 scale. Hansel, A.K., and W.H. Johnson, 1986, Quaternary Records ofNortheastern Illinois and Northwestern Indiana: Illinois State Geological Survey Guidebook 22, 106 p. Hester, N.C., 1970, Sand and Gravel Resources of Sangamon County, Illinois: Illinois State Geological Survey Circular 452, 17 p. Hunt, C.S., and J.P. Kempton, 1977, Geology for Planning in De Witt County, Illinois: Illinois State Geological Survey Environmental Geology Note 83, 42 p. lllinois Environmental Protection Agency, 1998, Lower Sangamon River Watershed: Illinois Environmental Protection Agency, I map. lllinois Environmental Protection Agency, 1998, Salt Creek of Sangamon River Watershed, Illinois Environmental Protection Agency, I map. . Labotka, T.e., and N.e. Hester, 1971, Sand and Gravel Resources ofMason County, Illinois: Illinois State Geological Survey Circular 464, 18 p. Lee, M.T., 1982, Sediment Conditions in the Sanganois Conservation Area, Cass and Mason Counties, Illinois: Illinois State Water Survey Contract Report 290, 10 p. Masters, E.L., 1942, The Sangamon: Urbana, Illinois, University of Illinois Press, (reprint, 1988), 258 p. Miller, J.A., 1973, Quaternary History of the Sangamon River Drainage System: Illinois State Museum, Reports of Investigations 27, 36 p. Miller, J.A., 1972, Quaternary History of the Sangamon River Drainage System, Central Illinois: Master's Thesis, University of Illinois, Urbana-Champaign, 68 p. Nelson, R.S., and D.L. Reinertsen, 1984, A Guide to the Geology of the Pontiac-Streator Area: llIinois State Geological Survey Field Trip Guide Leaflet 1984-C, 16 p. O'Hearn, M., and T.L. Williams, 1982, A Summary of Information Related to the Com prehensive Management of Groundwater and Surface Water Resources in the Sangamon River Basin, Illinois: Illinois State Water Survey Contract Report 299, 145 p. Reinertsen, D.L., J.M. Masters, L.R. Follmer, A.K. Hansel, P.C. Reed, RH. Howard, and S.T. Whitaker, 1991, Guide to the Geology of the Decatur Area, Macon and Christian Counties: Illinois State Geological Survey Field Trip Leaflet 1991-C, 41 p. 88 Reinertsen, D.L., L.R. Follmer, and K. Piskin, 1978, Geological Science Field Trip, . Springfield Area, Sangamon County, Illinois, New City, Springfield East, Springfield West, and Williamsville 7.5-Minute Quadrangles: Illinois State Geological Survey Field Trip Guide Leaflet 1978-A, 53 p. Roper, D.C., 1974, The Distribution of Middle Woodland Sites within the Environment. of the Lower Sangamon River, lllinois: Illinois State Museum, Report of Investigations No. 30,22 p. Shaver, R.H., and J.A. Sunderman (eds.), 1983, Field Trips in Midwestern Geology: Indiana Geological Survey, Indiana University and Purdue University, 491 p. Springfield (IL) Water, Light, and Power Dept., Illinois Natural History Survey Division, 1993, Hunter Lake Environmental Studies: Springfield (IL) Water, Light, and Power Dept., Illinois Natural History Survey Division, maps. Stamer, J.K., and D.M. Mades, 1982, Work Plan for the Sangamon River Basin, Illinois: U.S. Geological Survey Open-File Report 82-0693, 31 p. Steinkamp, J.F., 1980, Soil Survey of Sangamon County, Illinois: University of Illinois Agricultural Experiment Station Soil Re~ort Ill, 139 p. Tucker, W.J., and W.H. Ettinger, 1975, A Biological Investigation of the South Fork, Sangamon River and Tributaries: Illinois Environmental Protection Agency, Division of Water Pollution Control, 56 leaves. U.S. Geological Survey, 1980, Land Use and Land Cover, 1973-76, Decatur, lllinois, Land Use and Land Cover Map L-181: American Geological Institute, scale: 1:250,000. U.S. Geological Survey, 1979, Land Use and Land Cover and Associated Maps for Decatur, Illinois: U.S. Geological Survey Open-File Report 79-0267, scale: 1:250,000. U.S. GeologiCal Survey, 1979, Land Use and Land Cover and Associated Maps for Quincy, lllinois, Missouri: U.S. Geological Survey Open-File Report 79-0266, scale: 1:250,000. U.S. Geological Survey, 1979, Land Use and Land Cover and Associated Maps for Burlington, Iowa, Illinois, Missouri: U.S. Geological Survey Open-File Report 79-1550, scale: 1:250,000. University of lllinois Agricultural Experiment Station, 1974, Soil Survey of Logan County, lllinois: University of Illinois Agricultural Experiment Station Soil Report 92, 99 p. Willman, H.B., 1973, Geology Along the Illinois Waterway-A Basis for Environmental Planning: Illinois State Geological Survey Circular 478,48 p. 89 Whitfield, J.W., R.A. Ward, J.E. Denne, D.F. Holbrook, W.V. Bush, J.A. Lineback, K.V. Luza, K.M. Jensen, and W.D. Fishman, 1993, Quaternary Geologic Map of the Ozark Plateau 4° x 6° Quadrangle, United States, G.M. Richmond (ed.): U.S. Geolog ical Survey Miscellaneous Investigations Series I, scale: 1: I,000,000. 90 ------Appendix A: Overview ofDatabases 1IIinois Wetlands Inventory This digital database contains the location and classification of wetland and deepwater habitats in Illinois. Following U.S. Fish and Wildlife Service definitions, the Illinois Natural History Survey (INHS) compiled the information from interpretations of I :58,000-scale high-altitude photographs taken between 1980 and 1987. Identifiable wetlands and deepwater habitats were represented by points, lines, and polygons on 1:24,000-scale U.S. Geological Survey (USGS) 7.5- minute quadrangle maps. These data were digitized and compiled into the Illinois Wetlands Inventory. Because no wetland or deep-water habitats smaller than 0.01 acres were included, many farmed wetlands are not in the database. This database is appropriate for analysis on a local and regional scale; due to the dynamics of wetland systems, however, boundaries and classifications may change over time. For detailed explanation of wetland classification in Illinois, see Wetland Resources of Illinois: An Analysis and Atlas (Suloway and Hubbell 1994). Quaternary Deposits of Illinois Originally automated in 1984, this database is the digital representation of the I :500,OOO-scale map Quaternary Deposits in Illinois (Lineback 1979). Because these data, modified by Hansel and Johnson (1996), represent a generalization of the glacial sediments that lie at or near the land surface, this database is most appropriate for use at a regional scale. For further information about surficial deposits in llIinois, see Wedron and Mason Groups: Lithostratigraphic Reclassification ofthe Wisconsin Episode, Lake Michigan Lobe Area .(Hansel and Johnson 1996). Thickness of Loessin Illinois This database contains 5-foot-interval contour lines indicating loess thickness on uneroded upland areas in Illinois. These data were originally automated in 1986 from the I :500,000-scale map in Glacial Drift in Illinois-Thickness and Character (Piskin and Bergstrom 1975, plate I). This database is most appropriate for use at a regional scale. Thickness of Surficial Deposits This database contains polygons delineating glacial and stream materials throughout the state, with thicknesses ranging from less than 25 feet to greater than 500 feet. The data were originally automated in 1986 from the 1:500,OOO-scale map in Glacial Drift in Illinois-Thickness and Character (Piskin and Bergstrom 1975, plate I). This database is most appropriate for use at a regional scale. Noncoal Minera/lndustry Database Compiled by the ISGS from lllinois Office of Mines and Minerals permit data and informa tion from the ISGS Directory of Illinois Mineral Producers, this database contains the locations of mineral extraction operations (other than coal, oil, and gas producers) in 91 Illinois. The database contains both active and inactive sites and is updated every year. The 1996 data include 7 active underground mines and 449 active surface pits and quarries. This is a point database and is appropriate for analysis on a local to regional scale. For more information on the current locations of noncoal mineral extraction sites or on the location of potential noncoal mineral resources, contact the Industrial Minerals Section of the liIinois State Geological Survey. 1:100,OOO-Scale Topography ofl1Iinois Depicting the general configuration and relief of the land surface in Illinois, this database was compiled by the ISGS from I: lOO,OOO-scale digital line graph (DLG) format data files, originally automated by the USGS from USGS I: IDO,DOO-scale 30- by 60-minute quadrangle maps. The USGS collected the land surface relief data for Illinois from stable base manuscripts, photographic reductions, and stable-base composites of the original I: 100,000 map separates using manual, semiautomatic, and automatic digitizing systems. The contour interval of this topographic data is 5.0 meters (16.4 feet). These digital data are useful for the production of intermediate- to regional-scale base maps and for a variety of spatial analyses, such as determining the slope of a geographic area. DLG format topo graphic data are available from the USGS and can be down loaded on the Internet from http://edcwww.cr.usgs.gov/glislhyper/guide/IOOkdlgfig/statesffl.html A full description of the DLG format can be found in the Digital Line Graphs from J:JOO,OOO-Scale Maps-Data Users Guide 2 produced by the USGS. These data are also available from the ISGS in ARC format. State Soil Geographic (STA TSGO) Data Base for l1Iinois The Illinois STATSGO was compiled by the USDA Natural Resources Conservation Service (NRCS). The database is the result of generalizing available county-level soil surveys into a general soil association map. Ifno county survey was available, data on geology, topography, vegetation, and climate were assembled along with Land Remote Sensing Satellite (LANDSAT) images. Soils of like areas were studied, and the probable classification and extent of the soils were determined. The data were compiled at 1:250,000-scale using USGS 1- by 2- degree quadrangle maps. This database was designed to be used primarily for regional, multistate, state, and river basin resource planning, management, and monitoring. It is not intended to be used at the county level. Illinois STATSGO data are available in DLG, ASCII, or ARC format and can be down loaded on the Internet from http://www.gis.uiuc.edulnrcs/soil.html The data are also available from the ISGS in ARC format. For more information visit the USDA web site or contact the Natural Resources Conservation Service, 1902 Fox Drive, Champaign, IL 61820. 92 Land Cover Database of Illinois Compiled for the IDNR Critical Trends Assessment Project by the INHS, the land cover database is intended as a base line for assessment and management of biologic natural resources in Illinois. Twenty-three major land cover classes were defined using Thematic Mapper (TM) Satellite data. Dates of the imagery range from April 1991 to May 1995. Ancillary data used to interpret the TM imagery include the 1992 Topologically Integrated Geographic Encoding and Referencing System (TIGER) line files, the Illinois Wetlands Inventory, NRCS county crop compliance data, 1988 National Aerial Photography Program (NAPP) photography, and USGS transportation and hydrography data. This database is most appropriate for use at medium and regional scales. For more information on land cover in Illinois see Illinois Land Cover-An Atlas (Illinois Department of Natural Resources 1996). References Hansel, A.K., and W.H. Johnson, 1996, Wedron and Mason Groups-Lithostratigraphic Reclassification of Deposits of the Wisconsin Episode, Lake Michigan Lobe Area: Illinois State Geological Survey Bulletin 104, 116 p.; plate I, Quaternary Deposits of Illinois. Revised map. lllinois Land Cover-An Atlas, 1996: lllinois Department of Natural Resources, Springfield, . Illinois, IDNRJEEA-96/05, 157 p. Lineback, J.A., compiler, 1979, Quaternary Deposits of Illinois: Illinois State Geological Survey 1:500,000 scale map. Piskin, K., and R.E. Bergstrom, 1975, Glacial Drift in Illinois-Thickness and Character: lllinois State Geological Survey Circular 490, 35 p. Suloway, L., and M. Hubble, 1994, Wetland Resources of Illinois-An Analysis and Atlas: Illinois Natural History Special Publication 15,88 p. 93 Appendix B. Principal Land Cover by Subbasin* Kickapoo Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 192,003 90.4 6.6 Cropland 158,376 74.5 5.4 Rural Grassland 33,626 15.8 1.1 Forested Land 5,102 2.4 0.2 Urban Land 9,553 4.5 0.3 Built-Up 6,607 3.1 0.2 Open Space 2,945 1.4 0.1 Wetland 2,891 1.4 0.1 Forested 2,060 1.0 0.1 Nonforested 831 0.4 0.0 Other Land 2,919 1.4 0.1 Lakes & Streams 2,860 1.3 0.1 Barren & Exposed 59 0.0 0.0 Totals 212,467 100.0 7.3 Salt Creek #3 Land Cover Category Acres Subbasin % Area % Agricultural Land 164,474 87.7 5.6 Cropland 140,877 75.1 4.8 Rural Grassland 23,597 12.6 0.8 Forested Land 8,914 4.8 0.3 Urban Land 3,852 2.1 0.1 Built-Up 3,024 1.6 0.1 Open Space 828 0.4 0.0 Wetland 3,048 1.6 0.1 Forested 2,299 1.2 0.1 Nonforested 749 0.4 0.0 Other Land 7,253 3.9 0.2 Lakes & Streams 7,253 3.9 0.2 Barren & Exposed 0 0.0 0.0 Totals 187,540 100.0 6.4 • Small errors in totals are due to rounding. 94 Flat Branch Land Cover Category Acres Subbasin % Area % Agricultural Land 167,149 94.5 5.7 Cropland 154,015 87.1 5.3 Rural Grassland 13,133 7.4 0.4 Forested Land 1,905 1.1 0.1 Urban Land 2,975 1.7 0.1 Built-Up 2,164 1.2 0.1 Open Space 8Il 0.5 0.0 Wetland 3,252 1.8 0.1 Forested 2,493 1.4 0.1 Nonforested 759 0.4 0.0 Other Land 1,510 0.9 0.1 Lakes & Streams 1,510 0.9 0.1 Barren & Exposed 0 0.0 0.0 Totals 176,791 100.0 6.0 Quiver Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 123,100 91.3 4.2 Cropland 109,191 81.0 3.7 Rural Grassland 13,909 10.3 0.5 Forested Land 8,037 6.0 0.3 Urban Land 1,739 1.3 0.1 Built-Up 1,373 1.0 0.0 Open Space 367 0.3 0.0 Wetland 975 0.7 0.0 Forested 547 0.4 0.0 Nonforested 428 0.3 0.0 Other Land 944 0.7 0.0 Lakes & Streams 944 0.7 0.0 Barren & Exposed 0 0.0 0.0 Totals 134,797 100.0 4.6 95 Illinois River #3 Land Cover Category Acres Subbasin % Area % Agricultural Land 76,558 65.2 2.6 Cropland 63,255 53.9 2.2 Rural Grassland 13,303 11.3 0.5 Forested Land 10,988 9.4 0.4 Urban Land 2,139 1.8 0.1 Built-Up 1,696 1.4 0.1 Open Space 443 0.4 0.0 Wetland 21,498 18.3 0.7 Forested 16,854 14.3 0.6 Nonforested 4,644 4.0 0.2 Other Land 6,281 5.3 0.2 Lakes & Streams 6,281 5.3 0.2 Barren & Exposed 0 0.0 0.0 Totals 117,466 100.0 4.0 Sangamon River #3 Land Cover Category Acres Subbasin % Area % Agricultural Land 81,451 78.5 2.8 Cropland 60,892 58.7 2.1 Rural Grassland 20,559 19.8 0.7 Forested Land 14,177 13.7 0.5 Urban Land 2,907 2.8 0.1 Built-Up 1,608 1.5 0.1 Open Space 1,299 1.3 0.0 Wetland 3,571 3.4 0.1 Forested 2,658 2.6 0.1 Nonforested 913 0.9 0.0 Other Land 1,681 1.6 0.1 Lakes & Streams 1,666 1.6 0.1 Barren & Exposed 15 0.0 0.0 Totals 103,787 100.0 3.5 96 Sangamon River #4 Land Cover Category Acres Subbasin % Area % Agricultural Land 78,695 86.2 2.7 Cropland 63,636 69.7 2.2 Rural Grassland 15,059 16.5 0.5 Forested Land 4,392 4.8 0.1 Urban Land 4,646 5.1 0.2 . Built-Up 2,788 3.1 0.1 Open Space 1,859 2.0 0.1 Wetland 2,675 2.9 0.1 Forested 2,072 2.3 0.1 Nonforested 603 0.7 0.0 Other Land 898 1.0 0.0 Lakes & Streams 898 1.0 0.0 Barren & Exposed 0 0.0 0.0 Totals 91,306 100.0 3.1 Lick Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 83,505 93.8 2.9 Cropland 71,955 80.8 2.5 Rural Grassland 11,550 13.0 0.4 Forested Land 2,114 2.4 0.1 Urban Land 1,799 2.0 0.1 Built-Up 1,014 1.1 0.0 Open Space 785 0.9 0.0 Wetland 1,093 1.2 0.0 Forested 614 0.7 0.0 Nonforested 479 0.5 0.0 Other Land 511 0.6 0.0 Lakes & Streams 511 0.6 0.0 Barren & Exposed 0 0.0 0.0 Totals 89,022 100.0 3.0 97 Sangamon River #2 Land Cover Category Acres Subbasin % Area % Agricultural Land 70,537 .83.3 2.4 Cropland 56,499 66.7 1.9 Rural Grassland 14,037 16.6 0.5 Forested Land 9,439 11.1 0.3 Urban Land 620 0.7 0.0 Built-Up 460 0.5 0.0 Open Space 159 0.2 0.0 Wetland 2,693 3.2 0.1 Forested 2,082 2.5 0.1 Nonforested 611 0.7 0.0 Other Land 1,387 1.6 0.0 Lakes & Streams 1,387 1.6 0.0 Barren & Exposed 0 0.0 0.0 Totals 84,677 100.0 2.9 . S. Fork Sangamon River #3 Land Cover Category Acres 'Subbasin % Area % Agricultural Land 77,290 94.1 2.6 Cropland 71,954 87.6 2.5 Rural Grassland 5,337 6.5 0.2 Forested Land 1,125 1.4 0.0 Urban Land 1,190 1.4 0.0 Built-Up 800 1.0 0.0 Open Space 390 0.5 0.0 Wetland 772 0.9 0.0 Forested 439 0.5 0.0 Nonforested 333 0.4 0.0 Other Land 1,785 2.2 0.1 Lakes & Streams 1,561 1.9 0.1 Barren & Exposed 224 0.3 0.0 Totals 82,163 100.0 2.8 98 Lake Fork Land Cover Category Acres Subbasin % Area % Agricultural Land 77,276 96.0 2.6 Cropland 68,613 85.2 2.3 Rural Grassland 8,663 10.8 0.3 Forested Land 751 0.9 0.0 Urban Land 1,440 1.8 0.0 Built-Up 1,008 1.3 0.0 Open Space 432 0.5 0.0 Wetland 541 0.7 0.0 Forested 435 0.5 0.0 Nonforested 106 0.1 0.0 Other Land 508 0.6 0.0 Lakes & Streams 508 0.6 0.0 Barren & Exposed 0 0.0 0.0 Totals 80,516 100.0 2.8 Spring Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 58,505 75.9 2.0 Cropland 47,766 61.9 1.6 Rural Grassland 10,739 13.9 0.4 Forested Land 3,412 4.4 0.1 Urban Land 13,578 17.6 0.5 Built-Up 9,006 11.7 0.3 Open Space 4,571 5.9 0.2 Wetland 1,108 1.4 0.0 Forested 658 0.9 0.0 Nonforested 450 0.6 0.0 Other Land 526 0.7 0.0 Lakes & Streams 526 0.7 0.0 Barren & Exposed 0 0.0 0.0 Totals 77,128 100.0 2.6 99 Prairie Creek #1 Land Cover Category Acres Subbasin % Area % Agricultural Land 69,532 97.2 2.4 Cropland 63,447 88.7 2.2 Rural Grassland 6,085 8.5 0.2 Forested Land 273 0.4 0.0 Urban Land 1,004 1.4 0.0 Built-Up 795 1.1 0.0 Open Space 209 0.3 0.0 Wetland 133 0.2 0.0 Forested 94 0.1 0.0 Nonforested 39 0.1 0.0 Other Land 558 0.8 0.0 Lakes & Streams 558 0.8 0.0 Barren & Exposed 0 0.0 0.0 Totals 71,500 100.0 2.4 S. Fork Sangamon River #2 Land Cover Category Acres Subbasin % Area % Agricultural Land 61,465 87.3 2.1 Cropland 53,887 76.5 1.8 Rural Grassland 7,578 10.8 0.3 Forested Land 2,454 3.5 0.1 Urban Land 2,500 3.6 0.1 Built-Up 1,794 2.5 0.1 Open Space 706 1.0 0.0 Wetland 3,261 4.6 0.1 Forested 2,911 4.1 0.1 Nonforested 350 0.5 0.0 Other Land 717 1.0 0.0 Lakes & Streams 717 1.0 0.0 Barren & Exposed 0 0.0 0.0 Totals 70,396 100.0 2.4 100 N. Fork Salt Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 63,041 90.6 2.2 Cropland 51,550 74.0 1.8 Rural Grassland 11,491 16.5 0.4 Forested Land 3,738 5.4 0.1 Urban Land 1,600 2.3 0.1 Built-Up 1,031 1.5 0.0 Open Space 569 0.8 0.0 Wetland 330 0.5 0.0 Forested 176 0.3 0.0 Nonforested 154 0.2 0.0 Other Land 907 1.3 0.0 Lakes & Streams 907 1.3 0.0 Barren & Exposed 0 0.0 0.0 Totals 69,616 100.0 2.4 Sangamon River #5 Land Cover Category Acres Subbasin % Area % Agricultural Land 59,992 88.4 2.0 Cropland 45,608 67.2 1.6 Rural Grassland 14,384 21.2 0.5 Forested Land 2,437 3.6 0.1 Urban Land 1,207 1.8 0.0 Built-Up 795 1.2 0.0 Open Space 412 0.6 0.0 Wetland 3,207 4.7 0.1 Forested 2,635 3.9 0.1 Nonforested 573 0.8 0.0 Other Land 990 1.5 0.0 Lakes & Streams 986 1.5 0.0 Barren & Exposed 4 0.0 0.0 Totals 67,833 100.0 2.3 101 Salt Creek #1 Land Cover Category Acres Subbasin % Area % Agricultural Land 60,135 93.0 2.1 Cropland 51,224 79.2 1.7 Rural Grassland 8,911 13.8 0.3 Forested Land 1,566 2.4 0.1 Urban Land 1,203 1.9 0.0 Built-Up 863 1.3 0.0 Open Space 341 0.5 0.0 Wetland 1,228 1.9 0.0 Forested 1,059 1.6 0.0 Nonforested 169 0.3 0.0 Other Land 539 0.8 0.0 Lakes & Streams 539 0.8 0.0 Barren & Exposed 0 0.0 0.0 Totals 64,672 100.0 2.2 Buckhart Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 61,093 96.2 2.1 Cropland 54,276 85.5 1.9 Rural Grassland 6,817 10.7 0.2 Forested Land 553 0.9 0.0 Urban Land 648 1.0 0.0 Built-Up 530 0.8 0.0 Open Space 118 0.2 0.0 Wetland 648 1.0 0.0 Forested 369 0.6 0.0 Nonforested 279 0.4 0.0 Other Land 545 0.9 0.0 Lakes & Streams 534 0.8 0.0 Barren & Exposed 10 0.0 0.0 Totals 63,487 100.0 2.2 102 Bear Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 60,103 95.3 2.1 Cropland 56,686 89.9 1.9 Rural Grassland 3,417 5.4 0.1 Forested Land 1,083 1.7 0.0 Urban Land 962 1.5 0.0 Built-Up 616 1.0 0.0 Open Space 346 0.5 0.0 Wetland 669 1.1 0.0 Forested 505 0.8 0.0 Nonforested 164 0.3 0.0 Other Land 243 0.4 0.0 Lakes & Streams 243 0.4 0.0 Barren & Exposed 0 0.0 0.0 Totals 63,060 100.0 2.2 Crane Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 55,789 90.2 1.9 Cropland 47,384 76.6 1.6 Rural Grassland 8,405 13.6 0.3 Forested Land 5,050 8.2 0.2 Urban Land 252 0.4 0.0 Built-Up 214 0.3 0.0 Open Space 38 0.1 0.0 Wetland 344 0.6 0.0 Forested 123 0.2 0.0 Nonforested 220 0.4 0.0 Other Land 392 0.6 0.0 Lakes & Streams 392 0.6 0.0 Barren & Exposed 0 0.0 0.0 Totals 61,827 100.0 2.1 103 M. Fork Sugar Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 57,772 94.3 2.0 Cropland 50,687 82.8 1.7 Rural Grassland 7,085 11.6 0.2 Forested Land 832 1.4 0.0 Urban Land 1,457 2.4 0.0 Built-Up 894 1.5 0.0 Open Space 563 0.9 0.0 Wetland 530 0.9 0.0 Forested 391 0.6 0.0 Nonforested 138 0.2 0.0 Other Land 646 1.1 0.0 Lakes & Streams 646 I.l 0.0 Barren & Exposed 0 0.0 0.0 Totals 61,236 100.0 2.1 Sugar Creek #4 Land Cover Category Acres Subbasin % Area % Agricultural Land 53,675 91.5 1.8 Cropland 47,804 81.5 1.6 Rural Grassland 5,871 10.0 0.2 Forested Land 1,308 2.2 0.0 Urban Land 2,739 4.7 0.1 Built-Up 1,790 3.1 0.1 Open Space 948 1.6 0.0 Wetland 507 0.9 0.0 Forested 319 0.5 0.0 Nonforested 189 0.3 0.0 Other Land 446 0.8 0.0 Lakes & Streams 446 0.8 0.0 Barren & Exposed 0 0.0 0.0 Totals 58,674 100.0 2.0 104 ~' I;:\j 'i\1l.' l;i1' ",~, ~"l': '~~, ;' ;'~~i ',{li,;' , ',.~;fl , W. Fork Sugar Creek :~! ,I Subbasin % Area % ' <"t , Acres '1 Land Cover Category 1.8 :l'ii§ 53,121 94.3 Agricultural Land 1.6 ',"""'~ 46,353 82.3 '_"~ Cropland 12.0 0.2 ''; 6,769 ' ~''7( Rural Grassland 0.0 , 1,123 2.0 Forested Land 1.7 0.0 Urban Land 978 0.0 646 1.1 Built-Up 0.6 0.0 Open Space 332 0.0 440 0.8 Wetland 0.6 0.0 " Forested 316 0.0 124 0.2 Nonforested 0.0 680 1.2 Other Land 0.0 680 1.2 Lakes & Streams 0.0 0.0 Barren & Exposed 0 1.9 56,343 100.0 Totals Sugar Creek #1 Subbasin % Area % Land Cover Category Acres 69.4 1.3 Agricultural Land 38,475 1.1 30,929 55.8 Cropland 13.6 0.3 Rural Grassland 7,545 0.1 2,329 4.2 Forested Land 0.4 13,104 23.6 Urban Land 0.3 9,165 16.5 Built-Up 7.1 0.1 Open Space 3,939 0.0 845 1.5 Wetland 0.0 506 0.9 Forested 0.0 339 0.6 Nonforested 0.0 662 1.2 Other Land 0.0 662 1.2 Lakes & Streams 0.0 0 0.0 Barren & Exposed 1.9 55,415 100.0 Totals 105 N. Lake Fork Land Cover Category Acres Subbasin % Area % Agricultural Land 50,900 96.9 1.7 Cropland 47,506 90.5 1.6 Rural Grassland 3,394 6.5 0.1 Forested Land 140 0.3 0.0 Urban Land 873 1.7 0.0 Built-Up 654 1.2 0.0 Open Space 219 0.4 0.0 Wetland 256 0.5 0.0 Forested 47 0.1 0.0 Nonforested 209 0.4 0.0 Other Land 332 0.6 0.0 Lakes & Streams 332 0.6 0.0 Barren & Exposed 0 0.0 0.0 Totals 52,502 100.0 1.8 Horse Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 49,292 94.0 1.7 Cropland 44,436 84.8 1.5 Rural Grassland 4,856 9.3 0.2 Forested Land 1,500 2.9 0.1 Urban Land 687 1.3 0.0 Built-Up 592 1.1 0.0 Open Space 95 0.2 0.0 Wetland 534 1.0 0.0 Forested 439 0.8 0.0 Nonforested 95 0.2 0.0 Other Land 411 0.8 0.0 Lakes & Streams 411 0.8 0.0 Barren &; Exposed 0 0.0 0.0 Totals 52,424 100.0 1.8 106 Deer Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 48,738 96.7 1.7 Cropland 44,668 88.6 1.5 Rural Grassland 4,069 8.1 0.1 Forested Land' 69 0.1 0.0 Urban Land 1,098 2.2 0.0 Built-Up 815 1.6 0.0 Open Space 283 0.6 0.0 Wetland 80 0.2 0.0 Forested 63 0.1 0.0 Nonforested 17 0.0 0.0 Other Land 442 0.9 0.0 Lakes & Streams 442 0.9 0.0 Barren & Exposed 0 0.0 0.0 Totals 50,426 100.0 1.7 Illinois River #1 Land Cover Category Acres Subbasin % Area % Agricultural Land 32,153 65.5 1.1 Cropland 27,244 55.5 0.9 Rural Grassland 4,909 10.0 0.2 Forested Land 6,999 14.3 0.2 Urban Land 402 0.8 0.0 Built-Up 206 0.4 0.0 Open Space 196 0.4 0.0 Wetland 9,008 18.4 0.3 Forested 1,880 3.8 0.1 Nonforested 7,128 14.5 0.2 Other Land 523 1.1 0.0 Lakes 8i: Streams 484 1.0 0.0 Barren & Exposed 39 0.1 0.0 Totals 49,086 100.0 1.7 107 Sugar Creek #2 Land Cover Category Acres .Subbasin % Area % Agricultural Land 43,753 93.9 1.5 Cropland 38,256 82.1 1.3 Rural Grassland 5,497 11.8 0.2 Forested Land 1,005 2.2 0.0 Urban Land 428 0.9 0.0 Built-Up 405 0.9 0.0 Open Space 22 0.0 0.0 Wetland 800 1.7 0.0 Forested ·690 1.5 0.0 Nonforested 110 0.2 0.0 Other Land 597 1.3 0.0 Lakes & Streams 597 1.3 0.0 Barren & Exposed 0 0.0 0.0 Totals 46,582 100.0 1.6 Lake Sangamon Land Cover Category Acres Subbasin % Area % Agricultural Land 41,929 91.2 1.4 Cropland 39,628 86.2 1.4 Rural Grassland 2,302 5.0 0.1 Forested Land 781 1.7 0.0 Urban Land 554 1.2 0.0 Built-Up 503 1.1 0.0 Open Space 51 0.1 0.0 Wetland 280 0.6 0.0 Forested 72 0.2 0.0 Nonforested 209 0.5 0.0 Other Land 2,419 5.3 0.1 Lakes & Streams 2,368 5.2 0.1 Barren & Exposed 52 0.1 0.0 Totals 45,964 100.0 1.6 108 Salt Creek #2 Land Cover Category Acres Subbasin % Area % Agricultural Land 37,322 85.6 1.3 Cropland 31,257 71.7 1.1 Rural Grassland 6,065 13.9 0.2 Forested Land 2,573 5.9 0.1 Urban Land 1,262 2.9 0.0 Built-Up 940 2.2 0.0 Open Space 321 0.7 0.0 Wetland 1,498 3.4 0.1 Forested 1,221 2.8 0.0 Nonforested 277 0.6 0.0 Other Land 965 2.2 0.0 Lakes & Streams 938 2.2 0.0 Barren & Exposed 27 0.1 0.0 Totals 43,620 100.0 1.5 S. Lake Fork Land Cover Category Acres Subbasin % Area % Agricultural Land 42,096 98.1 1.4 Cropland 39,552 92.1 1.4 Rural Grassland 2,544 5.9 0.1 Forested Land 70 0.2 0.0 Urban Land 639 1.5 0.0 Built-Up 374 0.9 0.0 Open Space 264 0.6 0.0 Wetland 86 0.2 0;0 Forested 0 0.0 0.0 Nonforested 86 0.2 0.0 Other Land 34 0.1 0.0 Lakes & Streams 34 0.1 0.0 Barren & Exposed 0 0.0 0.0 Totals 42,924 100.0 1.5 109 Illinois River #2 Land Cover Category Acres Subbasin % Area % Agricultural Land 25,371 75.3 0.9 Cropland 21,696 64.4 0.7 Rural Grassland 3,676 10.9 0.1 Forested Land 4,661 13.8 0.2 UrbanLand 1,542 4.6 0.1 Built-Up 1,257 3.7 0.0 Open Space 286 0.8 0.0 Wetland 1,306 3.9 0.0 Forested 930 2.8 0.0 Nonforested 376 I.I 0.0 Other Land 829 2.5 0.0 Lakes & Streams 829 2.5 0.0 Barren & Exposed 0 0.0 0.0 Totals 33,711 100.0 1.2 Richland Creek· Land Cover Category Acres Subbasin % Area % Agricultural Land 27,450 88.6 0.9 Cropland 21,799 70.4 0.7 Rural Grassland 5,651 18.2 0.2 Forested Land 2,579 8.3 0.1 Urban Land 488 1.6 0.0 Built-Up 362 1.2 0.0 Open Space 127 0.4 0.0 Wetland 327 1.1 0.0 Forested 199 0.6 0.0 Nonforested 128 0.4 0.0 Other Land 139 0.4 0.0 Lakes & Streams 139 0.4 0.0 Barren & Exposed 0 0.0 0.0 Totals 30,984 100.0 1.1 IIO Brush Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 28,097 92.3 1.0 Cropland 24,518 80.6 0.8 Rural Grassland 3,579 1l.8 0.1 Forested Land 978 3.2 0.0 Urban Land 739 2.4 0.0 Built-Up 654 2.1 0.0 Open Space 86 0.3 0.0 Wetland 263 0.9 0.0 Forested 140 0.5 0.0 Nonforested 123 0.4 0.0 Other Land 360 1.2 0.0 Lakes & Streams 360 1.2 0.0 Barren & Exposed 0 0.0 0.0 Totals 30,438 100.0 1.0 Ten Mile Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 25,083 89.3 0.9 Cropland 21,289 75.8 0.7 Rural Grassland 3,794 13.5 0.1 Forested Land 1,194 4.3 0.0 Urban Land 1,292 4.6 0.0 Built-Up 959 3.4 0.0 Open Space 333 1.2 0.0 Wetland 212 0.8 0.0 Forested 125 0.4 0.0 Nonforested 87 0.3 0.0 Other Land 299 1.1 0.0 Lakes & Streams 299 1.1 0.0 Barren & Exposed 0 0.0 0.0 Totals 28,079 100.0 1.0 III Prairie Creek #2 Land Cover Category Acres Subbasin % Area % Agricultural Land 24,521 95.2 0.8 Cropland 21,647 84.0 0.7 Rural Grassland 2,874 11.2 0.1 Forested Land 773 3.0 0.0 Urban Land 90 0.3 0.0 Built-Up 90 0.3 0.0 Open Space 0 0.0 0.0 Wetland 268 1.0 0.0 Forested 170 0.7 0.0 Nonforested 98 0.4 0.0 Other Land 117 0.5 0.0 Lakes & Streams 1I7 0.5 0.0 Barren & Exposed 0 0.0 0.0 Totals 25,769 100.0 0.9 Timber Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 20,020 88.5 0.7 Cropland 15,901 70.3 0.5 Rural Grassland 4,1I8 18.2 0.1 Forested Land 1,068 4.7 0.0 Urban Land 826 3.7 0.0 Built-Up 617 2.7 0.0 Open Space 209 0.9 0.0 Wetland 402 1.8 0.0 Forested 358 1.6 0.0 Nonforested 44 0.2 0.0 Other Land 295 1.3 0.0 Lakes & Streams 295 1.3 0.0 Barren & Exposed 0 0.0 0.0 Totals 22,611 100.0 0.8 1I2 Pike Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 21,569 95.8 0.7 Cropland 18,671 83.0 0.6 Rural Grassland 2,898 12.9 0.1 Forested Land 608 2.7 0.0 Urban Land 34 0.2 0.0 Built-Up 34 0.2 0.0 Open Space 0 0.0 0.0 Wetland 80 0.4 0.0 Forested 28 0.1 0.0 Nonforested 53 0.2 0.0 Other Land 215 1.0 0.0 Lakes & Streams 215 1.0 0.0 Barren & Exposed 0 0.0 0.0 Totals 22,507 100.0 0.8 Lake Springfield Land Cover Category Acres Subbasin % Area % Agricultural Land 10,678 49.8 0.0 Cropland 7,590 35.4 0.3 Rural Grassland 3,089 14.4 0.1 Forested Land 1,997 9.3 0.1 Urban Land 4,636 21.6 0.2 Built-Up 1,960 9.1 0.1 Open Space 2,6'77 12.5 0.1 Wetland 158 0.7 0.0 Forested 34 0.2 0.0 Nonforested 124 0.6 0.0 Other Land 3,993 18.6 0.1 Lakes & Streams 3,993 18.6 0.1 Barren & Exposed 0 0.0 0.0 Totals 21,463 100.0 0.7 113 Sangamon River #1 Land Cover Category Acres Subbasin % Area % Agricultural Land 14,160 67.3 0.5 Cropland 11,638 55.3 0.4 Rural Grassland 2,522 12.0 0.1 Forested Land 3,490 16.6 0.1 Urban Land 8 0.0 0.0 Built-Up 8 0.0 0.0 Open Space 0 0.0 0.0 Wetland 2,842 13.5 0.1 Forested 2,303 10.9 0.1 Nonforested 539 2.6 0.0 Other Land 541 2.6 0.0 Lakes & Streams 541 2.6 0.0 Barren & Exposed 0 0.0 0.0 Totals _ 21,041 100.0 0.7 S. Fork Sangamon River #1 Land Cover Category Acres Subbasin % Area % Agricultural Land 17,894 87.6 0.6 Cropland 13,297 65.1 0.5 Rural Grassland 4,597 22.5 0.2 Forested Land 1,305 6.4 0.0 Urban Land 178 0.9 0.0 Built-Up 123 0.6 0.0 Open Space 55 0.3 0.0 Wetland 766 3.8 0.0 Forested 668 3.3 0.0 Nonforested 98 0.5 0.0 Other Land 288 1.4 0.0 Lakes & Streams 288 1.4 0.0 Barren & Exposed 0 0.0 ·0.0 Totals 20,431 100.0 0.7 114 Jobs Creek I Land Cover Category Acres Subbasin % Area % Agricultural Land 13,308 71.5 0.5 I Cropland 9,592 51.5 0.3 Rural Grassland 3,716 20.0 0.1 Forested Land 4,817 25.9 0.2 Urban Land 112 0.6 0.0 Built-Up· 111 0.6 0.0 Open Space 1 0.0 0.0 Wetland 149 0.8 0.0 Forested 99 0.5 0.0 Nonforested 49 0.3 0.0 Other Land 236 1.3 0.0 Lakes & Streams 236 1.3 0.0 Barren & Exposed 0 0.0 0.0 Totals 18,622 100.0 0.6 Panther Creek #1 Land Cover Category Acres Subbasin % Area % Agricultural Land 12,218 69.4 O. Cropland 8,536 48.5 0.3 Rural Grassland 3,682 20.9 0.1 Forested Land 4,911 27.9 0.2 Urban Land 121 0.7 0.0 Built-Up 88 0.5 0.0 Open Space 33 0.2 0.0 Wetland 148 0.8 0.0 Forested 40 0.2 0.0 Nonforested 108 0.6 0.0 Other Land 215 1.2 0.0 Lakes & Streams 215 1.2 0.0 Barren & Exposed 0 0.0 0.0 Totals 17,613 100.0 0.6 115 Cox Creek Larid Cover Category Acres Subbasin % Area % Agricultural Land 13,370 80.6 0.5 Cropland 10,280 62.0 0.4 Rural Grassland 3,090 18.6 0.1 Forested Land 3,046 18.4 0.1 Urban Land 0 0.0 0.0 Built-Up 0 0.0 0.0 Open Space 0 0.0 0.0 Wetland 39 0.2 0.0 Forested 17 0.1 0.0 Nonforested 22 0.1 0.0 Other Land 133 0.8 0.0 Lakes & Streams 133 0.8 0.0 Barren & Exposed a 0.0 0.0 Totals 16,589 100.0 0.6 Coon Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 9,988 79.6 0.3 Cropland 8,417 67.1 0.3 Rural Grassland 1,571 12.5 0.1 Forested Land 742 5.9 0.0 Urban Land 1,455 11.6 0.0 Built-Up 1,060 8.5 0.0 Open Space 394 3.1 0.0 Wetland 215 1.7 0.0 Forested 180 1.4 0.0 Nonforested 35 0.3 0.0 Other Land 144 I.1 0.0 Lakes & Streams 144 1.1 0.0 Barren & Exposed 0 0.0 0.0 Totals 12,544 100.0 0.4 116 Sugar Creek #3 Land Cover Category Acres Subbasin % Area % Agricultural Land 4,917 39.8 0.2 Cropland 3,135 25.4 0.1 Rural Grassland 1,781 14.4 0.1 Forested Land 1,106 9.0 0.0 Urban.Land 5,749 46.5 0.2 Built-Up 3,492 28.3 0.1 Open Space 2,257 18.3 0.1 Wetland 455 3.7 0.0 Forested 297 2.4 0.0 Nonforested 158 1.3 0.0 Other La"d 126 1.0 0.0 Lakes & Streams 126 1.0 0.0 Barren & Exposed 0 0.0 0.0 Totals 12,352 100.0 0.4 Panther Creek #2 Land Cover Category Acres Subbasin % Area % Agricultural Land 3,639 61.0 0.1 Cropland 3,095 51.9 0.1 Rural Grassland 544 9.1 0.0 Forested Land 208 3.5 0.0 Urban Land 2,041 34.2 0.1 Built-Up 1,552 26.0 0.1 Open Space 489 8.2 0.0 Wetland 50 0.8 0.0 Forested 43 0.7 0.0 Nonforested 7 0.1 0.0 Other Land 29 0.5 0.0 Lakes & Streams 29 0.5 0.0 Barren & Exposed 0 0.0 0.0 Totals 5,966 100.0 0.2 117 Goose Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 34 2.6 0.0 Cropland 33 2.5 0.0 Rural Grassland I 0.1 0.0 Forested Land 196 14.9 0.0 Urban Land 1,042 78.9 0.0 Built-Up 694 52.5 0.0 Open Space 348 26.4 0.0 Wetland 27 2.0 0.0 Forested 0 0.0 0.0 Nonforested 27 2.0 0.0 Other Land 21 1.6 . 0.0 Lakes & Streams 21 1.6 0.0 Barren & Exposed 0 0.0 0.0 Totals 1,320 . 100.0 0.0 Clear Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 121 31.4 0.0 Cropland 34 8.8 0.0 Rural Grassland 87 22.6 0.0 Forested Land 188 48.6 0.0 Urban Land 0 0.0 0.0 Built-Up 0 0.0 0.0 Open Space 0 0.0 0.0 Wetland 70 18.1 0.0 Forested 63 16.3 0.0 Nonforested 7 1.8 0.0 Other Land 7 1.8 0.0 Lakes & Streams 7 1.8 0.0 Barren & Exposed 0 0.0 0.0 Totals 386 99.9 0.0 118 Mosquito Creek Land Cover Category Acres Subbasin % Area % Agricultural Land 175 91.4 0.0 Cropland 157 81.6 0.0 Rural Grassland 19 9.7 0.0 . Forested Land 1 0.7 0.0 Urban Land o 0.0 0.0 Built-Up . o 0.0 0.0 Open Space o 0.0 0.0 Wetland 9 4.8 0.0 Forested 9 4.8 0.0 Nonforested o 0.0 0.0 Other Land 6 3.2 0.0 Lakes & Streams 6 3.2 0.0 Barren & Exposed o 0.0 0.0 Totals 192 100.0 0.0 119