Purchase of even a small amount of right of way may add several months to a project. If the project involves environmentally sensitive areas such as wetlands, historic sites, or archaeological sites, considerable additional time is needed. A major construction project on new location can take five to ten years to complete the feasibility, location, and environmental studies, conduct public hearings, and make soil and hazardous material surveys. Preparation of construction plans, purchase of right of way, and moving utilities such as power lines, water mains, etc., can take another one to two years before the project can be advertised and awarded for construction. Where the proposed highway location involves wetlands, public parks, or other unique environmentally sensitive areas, several years can be added to the process.
Public opposition can defer construction for years or block the project altogether.
IDOT will not undertake highway improvements unless there is a strong level of public support. Even replacement of an existing deteriorated bridge can take one to three years to bring the project to a construction letting. Hydraulics of the stream or river, soil conditions, and impact on navigable streams have to be investigated. Where a proposed replacement bridge would disturb wildlife habitat or have an adverse impact on endangered species, additional time is required to develop a mitigation plan. The published multi-year programs may be overprogrammed by about five percent to allow for unforeseen delay in bringing a project to a construction letting.