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Environmental, social, and energy conservation considerations are integral elements in transportation investments. Beyond the construction and maintenance of transportation projects IDOT is proactive in protecting and preserving the environment and maintaining or improving quality of life for Illinois residents. All transportation projects, involving the use of state and federal funds are required to follow formal procedures designed to protect the natural and social environment, this includes wetlands, plants, animals, air and water quality, archaeological and historic sites, agriculture, and communities.

IDOT strives to reduce or eliminate adverse environmental impacts and as appropriate to identify mitigation or remediation actions to achieve the best possible outcome during project development, design, and construction. Environmental regulations encompass air quality, traffic noise, community impacts such as relocations and access changes, natural resources including protected species and habitats, cultural resources such as pre-historic and historic sites, and land and water contamination issues.

In order to ensure the transportation projects are in compliance with state and federal environmental laws and regulations, IDOT uses special technical expertise to conduct surveys, review and/or prepare portions of environmental documents, and coordinate projects with state and federal resource agencies.  IDOT also oversees and coordinates the activities of University of Illinois scientists and specialists located within the Illinois Natural History Survey, the Illinois State Archaeological Survey, and the Illinois State Geological Survey who conduct a variety of scientific surveys.

Please visit the Consultant Resources webpage (toward bottom of page) to view Environmental resources as the Environmental Survey Request (ESR) form, which initiates the Phase 1 review process.

Natural Resources

Water Quality

IDOT maintains approximately 60,000 bridges over streams and rivers. During the construction or rehabilitation of bridge structures, IDOT must comply with the Clean Water Act, the National Environmental Policy Act (NEPA), the Fish and Wildlife Coordination Act, and other related laws and regulations. To comply with these regulations IDOT conducts environmental surveys. These field surveys range from the identification of federal and state listed endangered and threatened species to the characterization of the physical (substrate), biological (fish, mussels, aquatic macroinvertebrates), and chemical (concentrations of heavy metals, chloride, dissolved oxygen) components of streams. The results of these surveys are used to obtain permits (section 404 and 401 of the Clean Water Act) from the Corps of Engineers, Illinois Environmental Protection Agency (IEPA) and/or to meet the requirements of NEPA.

IDOT looks at rivers on the National Wild and Scenic River System and the Nationwide Rivers Inventory and coordination may occur for work on these streams with the National Park Service. IDOT uses IEPA Illinois Integrated Water Quality Report and Section 303(d) List to determine streams or lakes water quality standards, the designated uses of these water bodies, and the IEPA assessment of these uses.

Highways may impact water quality through storm water runoff. IDOT is involved in activities to control and reduce contamination from highway runoff (see Storm Water Management Program on this website). Deicing materials used for snow and ice removal flow into area streams via roadside ditches and/or storm sewers. In addition, a portion of road salt that remains on the pavement may be dispersed into the air due to the motion of traffic. In order to analyze atmospheric dispersal of salt, IDOT, in conjunction with the Illinois State Tollway Authority and the Federal Highway Administration initiated studies that were performed by the Illinois Water Survey.

The 1987 Illinois Groundwater Protection Act was implemented to protect groundwater resources from degradation. The Act allows for the establishment of both regulated groundwater recharge areas and groundwater protection areas. For transportation projects groundwater is assessed in terms of recharge areas to identify the potential for proposed highway corridors to contaminate shallow aquifers. Groundwater studies using monitoring wells are often performed in areas that are considered sensitive because they support plant communities containing endangered or threatened species or land areas that have been designated as Natural Areas or Nature Preserves. Potential impacts to these resources can involve interruption and/or change in groundwater flow patterns. Areas featuring karst topography are especially subject to groundwater contamination because these areas do not contain the usual filtering layers provided by soil so that surface water contamination can flow directly into the groundwater.

An aquifer is an area containing saturated (with groundwater) soils and geologic materials that are sufficiently permeable to readily yield economically useful quantities of water to wells, springs, or streams under ordinary hydraulic gradients. A sole-source aquifer is one which supplies at least 50 percent of the drinking water consumed in the overlying area with no practicable alternative drinking water source. While Illinois has no designated sole-source aquifer at the present time, it has many shallow (sand and gravel) and deep (bedrock) aquifers. Public well water supplies are regulated through set back zones established by IEPA.

Every two years the IEPA issues an “Illinois Integrated Water Quality Report and Section 303(d) List”. Information on groundwater standards and groundwater quality can be found in this report.

Floodplains are areas of land that could be inundated by floodwaters from any source. Floodplains usually occur adjacent to streams, rivers, and lakes. Transportation projects are assessed for the potential for impacts to floodplains, more specifically encroachments into the 100-year floodplain. The 100-year floodplain is defined as an area that has a 1 percent or 1 chance in 100 of experiencing a flood condition that exceeds any previous 1 year period. Coordination with the U.S. Army Corp of Engineers and the Department of Natural Resources Office of Water Resources (IDNR-OWR) is required to obtain the necessary permits for work within floodplains. A regulated floodway is the channel of the stream plus any adjacent floodplain areas. These areas must be kept free of encroachment so that the 1 percent chance annual flood can occur without substantial increases in flood heights. Depending upon the location of the regulated floodplain, the regulatory authority may be the community within which the floodway is located, FEMA or IDNR-OWR. Bridge structures located over major rivers such as the Mississippi must be coordinated with the U.S. Coast Guard to ensure that pier placement does not affect shipping channels.


IDOT assesses potential impacts to wildlife and their habitats while planning and designing transportation facilities. To comply with the National Environmental Protection Act and other state and federal environmental laws and regulations, special studies and assessments are conducted, and coordination with state and federal natural resource agencies is initiated. Project impacts to wildlife are identified and evaluated and consideration is given to implementing practical measures to avoid, minimize, and mitigate any adverse impact to these valuable resources. To accommodate wildlife connectivity and to increase safety to the motoring public, IDOT includes wildlife crossing structures such as underpasses, culvert extension, and fencing within project designs in environmentally sensitive locations that feature quality habitat. These measures not only reduce wildlife mortality and the number of vehicle-animal collisions but help to ensure that species populations remain viable. In addition, IDOT considers effects on area sensitive migratory birds during project development and evaluates the potential for habitat fragmentation.

IDOT is one of many state and local agencies, and environmental groups involved in the “Illinois Wildlife Action Plan.” This initiative was developed to address the particular needs of wildlife species in an effort to stabilize and reverse trends in declining populations. The plan can be accessed here.

Other sources of information about this topic include:

  • The 2006 publication “Eco-Logical: An Ecosystem Approach to Developing Infrastructure Projects” is a guide for making infrastructure more sensitive to wildlife and ecosystems through greater interagency cooperation. More information on the “Eco-Logical” approach can be found here.
  • “The North American Breeding Bird Survey” is a major landscape-level survey of the birds of North America. It is an on-going cooperative program sponsored jointly by the U.S. Fish and Wildlife Service and the Canadian Wildlife Service. The main purpose of this roadside survey is to estimate population trends of the many species of birds that nest in North America and migrate across international boundaries. More information can be found on the U.S. Fish & Wildlife Service website or the North American Breeding Bird Survey page.
  • The Illinois Natural History Survey website contains extensive information regarding all aspects of vertebrate and invertebrate species in Illinois. The “Inventory of Resource Rich Areas,” a watershed based land cover survey that identifies areas within the state that contain high quality habitat such as large tracts of woodlands and nearly one-half of the remaining wetlands can be found on the Illinois Natural History Survey Research webpage.
  • Information regarding wildlife – vehicle collisions can be found on the Deer Vehicle Crash Information Clearinghouse webpage. This national study details the causes and impacts to wildlife-vehicle collisions. The site is a deer crash information clearinghouse that contains accident data and suggested countermeasures and strategies to reduce the number of deer-vehicle accidents.

Threatened and Endangered Species

Under the Endangered Species Act of 1973 and the Illinois Endangered Species Act, IDOT is required to consult with the U.S. Fish and Wildlife Service (U.S. FWS) and the Illinois Department of Natural Resources (IDNR) to insure that the department’s projects are not likely to jeopardize the continued existence of any endangered and threatened species (listed species). IDOT Division of Highways, Bureau of Design and Environment (BDE) procedures for consulting with the U.S. FWS and IDNR on these two Acts are detailed in Chapters 26 (section 26-9) and 27 (section 27-1) of the BDE manual.

The department utilizes in-house expertise together with other sources of geographic information to screen project areas for the presence of habitats that may contain or be suitable for a listed species. In the event a listed species is present or there is suitable habitat within a project area, IDOT will conduct surveys through a statewide contract with the Illinois Natural History Survey (INHS) to determine the continued presence of the species and suitable habitat in the area which aids the department in avoiding impacts, minimizing impacts, and as a last case scenario mitigating impacts. More information can be found on the INHS website.

There are occasions where the department will request INHS through the statewide contract to conduct surveys throughout the state or a specific region to gather more data to further streamline consultation with the agencies. One example of that is the survey work performed in District 1 for the Indiana bat. More information can be found under the Indiana Bat (below).

Indiana Bat

IDOT’s BDE, Illinois State Toll Highway Authority, and Chicago office of the U.S. FWS developed a plan in 2006 for a mist-netting survey in northeastern Illinois to determine if the federally endangered Indiana Bat (Myotis Sodalis) occurs in the region. The U.S. FWS staff produced a list of 20 survey areas, primarily in public ownership, in Cook, DuPage, Kane, Kankakee, Lake, McHenry, and Will counties that were deemed to provide high-quality summer habitat for the Indiana Bat. Most of these areas included multiple netting sites. INHS conducted the survey during the summers of 2006 and 2007. Mist netting was conducted for 87 nights at 43 sites. This represented a 176 net-nights of effort (1 net-night = 1 net checked for one night). Following this effort, no Indiana Bats were captured by the INHS. The Indiana Bat collected in Chicago in September 1928 remains the only record for the area. Results of the 2006-2007 survey suggest that the Indiana Bat is extinct from the northeast corner of the state. Survey results will be used by the U.S. FWS to clear a number of transportation projects over the next several years that involve impacts to suitable habitat for the Indiana Bat.

Below are the results for the 2006 and 2007 mist netting surveys:

Further Information

Web Links



IDOT complies with Section 404 of the Clean Water Act (CWA) and the Illinois Interagency Wetland Policy Act of 1989 (IWPA). Departmental procedures for ensuring compliance with the CWA and IWPA are detailed in the IDOT Wetlands Action Plan, Bureau of Design and Environment Manual, Chapter 26-8. Under the CWA and IWPA, IDOT must demonstrate that all measures were taken to first avoid and then minimize impacts to wetlands to the fullest extent practicable. Unavoidable impacts are mitigated by way of wetland compensation through either restoration or creation of wetlands.

IDOT. The INHS and Illinois State Geological Survey provide technical assistance to IDOT in locating, evaluating and monitoring compensatory wetlands. More information on the Wetlands Group can be found on INHS’s Wetland Science Program webpage.

IDOT Wetland Compensation Sites

CountySite NameRoute and FAP #ISGS#Status
AlexanderEast Cape GirardeauIL 146, FAP 31281Active
ColesI-57/TR1000N InterchangeTR1000N, TR41N/AActive
EffinghamGreen CreekIL33, FAP 77475Active
FranklinSugar Camp CreekIL 3, FAP 31274Inactive
HancockHancock County near CarthageUS 136, FAP 315 & 1042Active
HendersonGulfportUS 34, FAP 31329Inactive
HenryJoslinIL 92, FAP 58523Inactive
JacksonCarbondaleUS 51, FAP 33265Inactive
JacksonDe SotoUS 51, FAP 33268Inactive
Jo DaviessGalena River Bridge, West Stagecoach TrailFAS 6746Inactive
JohnsonMax CreekIL 147, FAS 93280Active
LakeNorth ChicagoIL 47, FAP 326; IL 56, FAP 365N/AActive
MaconDecaturUS 51, FAP 32227Active
MadisonSand RoadUS 267, FAP 31015Inactive
MadisonFormer Luehmann Property, New River CrossingFAP 99951Inactive
MercerEdwards River, Mercer CountyUS 67, FAP 31050Inactive
PerryPyatts BlacktopIL 13 & 127, FAP 4267Inactive
PerrySwan RoadTR 22286Active
PikeHannibal BridgeUS 36, FAP 31910Inactive
Rock IslandMilan Beltway, Airport RoadFAU 582217Active
Rock IslandMilan Beltway, Phase 1 Green RockFAU 582244Active
Rock IslandMilan Beltway, Phase 2 Green RockFAU 582244Inactive
Rock IslandMilan Beltway, Rock Island SiteFAU 5822N/A*Active
SalineHarrisburgUS 45, FAP 33263Active
SalineHarrisburg, Site 2IL 14, FAP 857N/A*Active
SalineHarrisburg Site 3IL 13, FAP 331N/A*Active
SalineSaline CountyIL 13, FAP 33118Active
SangamonVeteran's Parkway, SpringfieldFAP 6629Inactive
SangamonSpringfieldIL 29, FAP 65854Inactive
SangamonBuckhartTR 478, FAS 163758Inactive
StephensonOrangevilleIL 26, FAP 31616Inactive
StephensonJane Addams TrailUS 20, FAP 30172Active
StephensonWeber PropertyN/A79Active
UnionTammsIL 127, FAS 190771Active
WillGrant Creek NorthI-55, FAI 55N/A*Active
WinnebagoPecatonica River Forest PreserveHarrison Avenue Extension73Inactive

Wetland Mitigation Bank Sites

The link below will provide electronic copies of base-line studies, instruments and monitoring reports for IDOT bank sites and multi-use compensation sites.

IDOT Wetland Mitigation Bank Sites

Further Information

Web Links

Roadside Maintenance

Please navigate to Roadside Maintenance to view more information.

Cultural Resources


In 1956, the Illinois Department of Transportation established a policy for the preservation of cultural properties found in proposed highway rights-of-ways and currently partners with the Illinois State Archaeological Survey (ISAS) for specialized services, such as archaeological surveys and excavations, field work and reports and documentation to name a few.

Historic Bridges

IDOT partners with the Illinois State Archaeological Survey (ISAS) to maintain Historic Bridge Survey inventories to maintain an inventory of the State's Historic Bridges, which are at least fifty years old and of historical significance. 

IDOT Guidance for Photographing Historic Structures


I-LAST: Illinois Livable and Sustainable Transportation Rating System and Guide

In the years since the National Environmental Policy Act was signed into law in 1970, the range of concerns about the relationship between the highway and its associated effects on the surrounding environment has expanded. The approach of sustainability and I-LAST is to incorporate a broader range of issues into the development and completion of state highway projects.

This document is titled Illinois Livable and Sustainable Transportation (I-LAST) Rating
System and Guide and is a sustainability performance metric system developed by the Joint
Sustainability Group of the Illinois Department of Transportation (IDOT), the American Council of Engineering Companies (ACEC) and the Illinois Road and Transportation Builders Association (IRTBA). The intent is that this rating system and guide will be revised as the state of the art evolves – utilizing the input of industry users.

Community Impact Assessment

Community Impact Assessment (also referred to as Socio-economic Assessment) is a process used to evaluate the effects of transportation projects on community residents and their quality of life. Typically these effects may include changes in access, business and residential relocations, environmental justice issues, cohesion impacts, affects on public facilities and services, development and growth patterns, land use changes and other potential results associated with improvements in infrastructure. The assessment process is an integral part of project planning and development. Public involvement during the early stages of project development can ensure that the community residents are not only aware of the planned improvement but play an active role in achieving the greatest possible benefit for the most people. These processes are in place to facilitate beneficial results for the community.

IDOT’s Community Impact Assessment Manual has been developed for use in the identification and assessment of socioeconomic impacts. This manual provides a description of the community impacts that may occur as a result of a transportation project, and specifies methods, techniques and data requirements for conducting a community study. Also included are procedures for presenting the results of the assessment in environmental documents and a description of mitigation measures that can be applied if adverse impacts are unavoidable.

Section 4(f) Documents

Section 4(f), which is implemented under 23 CFR 774 (Code of Federal Regulations), is the federal act that protects publicly owned parks, recreation areas, and wildlife and waterfowl refuges.

To submit a comment on a Section 4(f) Document, please click here.

Storm Water Management Program

IDOT’s Storm Water Management Program is governed by several activities. To learn more please click a topic below:

  1. Storm Water Management Plan
  2. Erosion and Sediment Control

Traffic Noise

IDOT Noise Policy and Analysis Requirements

It is the policy of the Illinois Department of Transportation (IDOT) to assess traffic noise impacts on proposed transportation projects such as highways on new location or the addition of through travel lanes. Land uses evaluated for noise impacts include residential areas, schools, libraries, and parks or other recreational areas which may be affected by highway traffic noise. During the project development stage traffic noise studies are performed. The Federal Highway Administrations’ (FHWA) Traffic Noise Model (TNM) is used to predict traffic noise impacts. If the predicted noise levels approach or exceed FHWA’s noise abatement criteria, noise abatement measures are considered. Abatement measures such as noise walls or berms are effective in reducing traffic noise that will result from the transportation improvement. While landscaping can be used as an effective visual barrier, studies have shown that trees and shrubbery alone do not provide significant reduction in noise levels and are not approved as a noise abatement measure.

IDOT’s Highway Traffic Noise Assessment Manual describes techniques and procedures for analyzing and reporting traffic noise impacts, and includes a discussion of abatement measures which can be incorporated into project designs to mitigate traffic noise impacts. This guidance manual is issued in an effort to ensure that studies and reports on traffic noise prepared by or for IDOT are consistent with existing laws and regulations and are technically accurate and sufficient.

For more information about the FHWA Highway Noise Program, please visit https://www.fhwa.dot.gov/environment/noise/.

Traffic Noise - Resources and Frequently Asked Questions (FAQ)

Residents, business owners, and community groups often have questions about traffic noise and the tools available to IDOT for managing the impacts of highway traffic noise near where people live, work, and play.  The IDOT environmental team has developed resources to aid in the understanding of the nature of noise in general, specific issues associated with highway traffic noise, and IDOT policies regarding traffic noise abatement.  Click on the links below to view resources including a four-part YouTube video series, informational handouts, a glossary of key terms, and a document of frequently asked questions (FAQ) related to highway traffic noise.

Traffic Noise Informational Videos

Noise 101

Measuring and Predicting Noise

Studying Traffic Noise Abatement

What Is Your Role?

Other Resources for Understanding Traffic Noise

Noise Fundamentals

Noise Abatement

Noise Analysis

Informational Brochure - Understanding How Weather Affects Traffic Noise Levels in Your Community

Glossary of Important Noise-Related Terms

Traffic Noise Frequently Asked Questions (FAQ)

Air Quality

Air pollution is derived from numerous sources. These include: stationary sources such as power plants, large industrial sources, metals, and chemical processing as well as small businesses such as print shops, gas stations, and dry cleaning shops; mobile sources including cars, trucks, buses, planes, trains, as well as construction and lawn equipment; natural sources such as dust, volcanoes or fires including forest and wild fires, controlled burns such as prairies; and finally, other combustion sources including furnaces in our homes, plants, and fires from wood-burning fire places, etc. All these sources contribute to and release different pollutants and incomplete combustion emissions into the atmosphere. The chart below depicts the air pollutants by emission category.


Source: U.S. EPA, Our Nation’s Air Status and Trends Through 2008, February 2010.
*(Particulate Matter (PM); Ammonia (NH 3); Sulfur Dioxide (SO 2); Nitrogen Oxides (NO x); Volatile Organic Compounds (VOC); Carbon Monoxide (CO)) 

Air emissions from these source categories are regulated by the U.S. Environmental Protection Agency (U.S. EPA) and state and local air agencies. U.S. EPA has developed health-based air standards which are known as the National Ambient Air Quality Standards (NAAQS) for six criteria pollutants. These include: carbon monoxide, lead, nitrogen dioxide, particulate matter (PM2.5 and PM10), ozone, and sulfur oxide.

According to the Federal Highway Administration (FHWA), “Transportation contributes to four of the six criteria pollutants: ozone, carbon monoxide, particulate matter, and nitrogen dioxide.” Currently in Illinois, two areas of the State do not achieve the NAAQS for the 8-Hour ozone standard and PM2.5 annual standard: the Chicago Metropolitan Area and the Metro East St. Louis area. The exhibits below depict Illinois’ PM2.5 and ozone 8-hour non-attainment areas. The Illinois EPA Annual Air Quality Report includes additional information.


To fulfill specific air quality requirements under the Clean Air Act (CAA), IDOT partners and works closely with the U.S. Department of Transportation, U.S. and Illinois Environmental Protection Agency (EPA), and Metropolitan Planning Organizations (MPO), to deal with regional as well as micro-scale air quality issues. To help achieve transportation air quality planning goals and to attain the NAAQS, IDOT works through the inter-agency consultation process to ensure that the Long Range Plans and Transportation Improvement Programs, developed by MPOs, conform with air quality improvement plans.

IDOT also evaluates and documents various micro-scale air quality issues such as carbon monoxide and particulate matter hot-spot analyses, in our environmental documents to fulfill National Environmental Policy Act (NEPA), CAA, and other air quality requirements. Chapters 24 to 26 of the Bureau of Design and Environment (BDE) Manual outlines various highway-related air quality issues that are documented in IDOT NEPA documents. 

In addition, air quality emissions from construction-related activities are also addressed. To address potential dust concerns, Dust Control requirements are outlined in IDOT’s Standard Specifications for Road and Bridge Construction.

IDOT has developed additional construction-related specifications and contract special provisions dealing with the use of cleaner diesel fuel, idling reduction requirements for construction equipment, and the installation of emission control devices on contractor vehicles. Construction air quality specifications (cleaner diesel fuel and idling reduction requirements) are contained in Article 107.41 of the Standard Specifications for Road and Bridge Construction.

IDOT has also included a special provision for the installation of emission control devices on contractor vehicles.

IDOT has also sponsored various Air Quality meetings and Peer Exchanges to discuss emerging air quality issues and state-of-the-art air quality practices. Representatives from state DOT’s, FHWA, MPOs, U.S. and Illinois EPA have attended and participated in these meetings. Proceedings from these meetings are provided below: