Illinois Department of Transportation, Erica Borggren, Acting Secretary
Patrick J. Quinn, Governor
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Environmental Information

The project team will include a variety of environmental studies in the planning to improve U.S. 20/I-39. These studies will identify important local environmental and historical resources so the roadway can be planned with as little disruption as possible to the natural environment and historic character of the area.

Studies will focus on natural resources which are protected by law, including wetlands; threatened and endangered species of plants and animals; and historic structures and archaeological resources.


Wetlands are areas that are frequently saturated by water and have developed plant life adapted to wet soil conditions. There are three elements an area must contain to be classified as wetlands:

  • Wetland vegetation, which includes plants that usually occur in wet environments;
  • Hydric soils, which are soils that have been saturated over a long period of time and have developed unique characteristics such as a grey color, a rotten-egg odor and various mineral deposits; and
  • Wetland hydrology, which is indicated by high-water marks on trees, drift lines of flood debris, and other signs of frequent flooding.

An area is classified as a regulatory wetland only if all three indicators are present. Wetlands include naturally occurring areas such as backwater swamps; man-made areas where surface flow has been blocked and ponds form for a few to several weeks during the growing season; and silted-in farm ponds with vegetation growing in them.

Threatened and endangered species

One aspect of the field studies will be the search for animals and plants on either the federal or state Endangered and Threatened Species List. Studies will include a review of records of previous sightings of threatened or endangered species within the study corridor or in other areas of similar habitat in eastern Illinois.

Areas where the animals or plants are likely to live are identified on project aerial photos. These areas were then field surveyed using special methods to locate the plants or animals.

Noise Study

The study will also include an analysis of predicted noise levels at locations along U.S. 20/I-39 using the Federal Highway Administration’s Traffic Noise Prediction Model. Noise receptors will include noise sensitive areas such as residences, schools, parks, recreation areas and nursing homes. The predicted noise levels (in decibels) for each receptor will be compared with the existing noise levels and the FHWA noise abatement criteria. Noise abatement measures will be considered for locations that have predicted noise levels greater than the noise abatement criteria. Noise abatement considerations will include height and length of barriers, estimated costs and projected decibel reductions.

For additional information regarding highway traffic noise, including properties of noise, noise measuring, noise modeling, and abatement approaches, please see the Highway Traffic Noise section of IDOT's website at the following link: Highway Traffic Noise

I-39/U.S. 20 Improvement Project

Project Description
Project Location
Purpose and Need
Public Involvement
The Study Process
Project Exhibits
Traffic Projections
Aerial Photography
Environmental Information
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