November 2011

The preliminary alternatives were developed with input from the Community Working Group (CWG), project team, resource agencies, and the public.  The alternatives included north-south Build Alternatives.   In addition, a No-Build Alternative, a Transportation System Management (TSM)/ Travel Demand Management (TDM), a transit alternative, and an east-west only alternative were included in the range of alternatives considered.

The alternatives are narrowed down through a five-step alternative evaluation process.  The first three steps in the process are complete.  A brief summary of each step is below.

1) Initial Screening  

Description

All of the alternatives identified above were included in the Initial Screening.  The Initial Screening eliminates unrealistic or non-feasible options.  Three criteria were included in this evaluation:

• Does the alternative directly impact state of federally protected areas? If yes, eliminate alternative from further consideration.
• Does the alternative meet the horizontal and vertical clear zone requirements for the Central Illinois Regional Airport? If no, the alternative is eliminated from further consideration.
• Does the alternative divide or isolate a neighborhood or community?  This criterion was assessed using guidance from IDOT’s Community Impact Assessment Manual.  If yes, the alternative is eliminated from further consideration.  

Results

Thirty-six (36) alternatives were eliminated in this step due to dividing and/or isolating a community or neighborhood.

2) Purpose & Need Evaluation 

 Description

 The remaining 93 Build Alternatives, in addition to the East-West Only Alternative, the TSM/TDM Alternative, the Transit Alternative, and the No-Build Alternative were carried through to the Purpose and Need (P&N) Screening. The P&N Evaluation criteria are   based  on the Purpose and Need Statement defined for the project. Eight criteria were included in this evaluation:

• Is the alternative compatible with adopted land use plans?
• Does the alternative restrict/reduce opportunities for uncontrolled, or leapfrog development?
• Does the alterative reduce congestion in the study area?
• Does the alternative improve north/south travel efficiencies?
• Does the alternative improve east/west travel efficiencies?
• Does the alternative improve travel efficiency to the Interstate System?
• Does the alternative improve north/south and east/west travel efficiencies to/from major travel nodes?
• Does the alternate improve network wide travel efficiencies?

Results

Eight Build Alternatives were less consistent with meeting P&N criteria and were eliminated from further consideration.  The transit alternative was also eliminated at this step.  The P&N Screening evaluation of the TSM/TDM Alternative is on-going and has not yet   been completed.

3) Macro Analysis

Description

The remaining 85 Build Alternatives, in addition to the East-West Only Alternative, and the No-Build Alternative were carried through to the Macro Analysis. In this step, alternatives were evaluated to ensure that those carried forward minimized impacts to the  natural and human environment. Impacts to the resources were calculated for a 500 foot wide footprint for all alternatives with the exception of the East-West Only Alternative, which had a 200 foot wide footprint. Alternatives with the greatest resource impacts were eliminated in a stepwise fashion to avoid or minimize the environmental effects.

The resources considered in the Macro Analysis included the following:

Resource Impacts were assessed in three general categories. 1) Resources that were not impacted by any of the corridors under consideration. 2) Resources that were impacted equally or within the same general range by all corridors, or where only preliminary data was available. 3) Resources where impacts varied widely among corridors. Resources in the third category were considered differentiating criteria used for corridor elimination. Forty-five (45) alternatives with disproportionality high impacts to residences or prime & important farmland were eliminated during this step of the analysis.  The East-West Only Alternative was eliminated in this step due to high residential impacts.

4) Alignment Analysis

The remaining 40 Build Alternatives and the No-Build Alternative were carried through to the Alignment Analysis. Impacts to the resources were calculated for a 250 foot wide footprint for all alternatives.  Similar to the Macro Analysis, alternatives with the greatest resource impacts were eliminated in a stepwise fashion to avoid or minimize the environmental effects.

The resources considered in the Alignment Analysis included all those evaluated in the Macro Analysis plus these additional criteria:

Resource Impacts were assessed in three general categories similar to the Macro Analysis as described above. Residences, prime and important farmland, tract severances, farms otherwise affected, termini connections, constructability, area of new pavement, riparian areas, highly erodible soils, and bike/pedestrian access were considered differentiating criteria used to reduce the number of alignments.   Through a step-wise elimination process, the forty alignments were narrowed to four.  These four alignments will be carried into step five, the Environmental Assessment Analysis.   To see the four remaining alignments on an interactive map click here.

5) Environmental Assessment Analysis

The Environmental Assessment is the final step of the alternative evaluation process.  A detailed analysis of the remaining alternatives is conducted in this step.  The single Preferred Alternative that best addresses the Purpose & Need and minimizes impacts to the socioeconomic and natural environment is identified in this step.