Central Park Boulevard Interchange alternatives were developed by the project team. Alternatives were based on work already conducted as part of the I-70 East DEIS.

In addition, these alternatives were developed to allow for constructability within the existing corridor and meet multi-modal transportation needs. The following alternatives were developed for the Environmental Assessment:

Alternative 1: No Action – The No Action alternative assumes that Central Park Boulevard would be built over the existing I-70 corridor.   The associated I-70 and I-270 ramps connecting Central Park Boulevard would not be built.

Alternative 2: Transportation System Management (TSM) – Alternative 2 includes measures to improve intersection operations and safety and reduce travel demand. This alternative would include the building of a new bridge without connections to I-70.

Alternative 3a: New Bridge (Single on/off ramps) – Alternative 3a would include six main-lanes across the bridge with adjacent bike-lanes and sidewalks in both the north and south-bound directions.

Alternative 3b: New Bridge (Two Consecutive on/off ramps) – Alternative 3b would include six main-lanes across the bridge with adjacent bike-lanes and sidewalks in both the north and south-bound directions.

Alternative 4a: Cargo Bridge (no widening) (Single on/off ramps) – This alternative assumes the use of the Cargo bridge in its existing condition.

Alternative 4b: Cargo Bridge (no widening) (Two Consecutive on/off ramps) – This alternative assumes the use of the Cargo bridge in its existing condition.

Alternative X: Other

The a and b variation of Alternatives 3 and 4 were developed to identify the best operational solution for the Central Park Boulevard Interchange. These concepts are variations of the ultimate braided option that were compared to each other to evaluate the operational effectiveness of the proposed interchange. 

Screening Process

The next steps in the process included screening the alternatives in order to identify a preferred alternative. Two levels of screening were applied to the proposed alternatives. The initial level of screening was based on “fatal flaw” screening criteria. The remaining alternatives were retained for the second level of “detailed screening” that evaluated each alternative against a series of engineering, traffic engineering, environmental, and policy related criteria. The No Action alternative was carried forward through the entire screening process for detailed comparison to the Preferred Alternative.

Identification of a Preferred Alternative

As part of the Environmental Assessment process for the Central Park Boulevard Interchange, a Preferred Alternative (Alternative 3B: New Bridge) was identified.  This alternative best meets the purpose and need of the project and has minor impacts and/or mitigation.  The proposed improvements include a new bridge over I-70, immediately east of the existing Cargo Bridge. Central Park Boulevard would overpass I-70 via a diamond interchange with braided ramps to the west to accommodate I-270. 

Environmental impacts identified in the Environmental Assessment include:

·         Impacts to Black-tailed prairie dogs in the NW and SE Quadrants

·         Floodplain impacts in the SW Quadrants

·         Potential for encountering contaminated soil and/or groundwater during construction

·         Impacts to on wetland feature identified in the project area totaling 0.146 acres