Ada County Highway District

Three Cities River Crossing

General Description:



On Wednesday, July 21, 2010 the ACHD Commission voted to recommend a No Build Alternative, but left open the option to revisit the project in the future if funding becomes available. The Commission could not support the Build Alternative at this time because the environmental and cost impacts were more significant than the traffic benefits.

The Environmental Impact Statement will be finalized with the No Build Alternative. Once the Environmental Impact Statement receives agency review and approval it will then be published for public comment, which is expected to occur in about a year.

 Three Cities River Crossing study was initiated to evaluate an alignment for a proposed future link across the Boise River to connect State Street, where it meets Highway 55 north to McCall, with Chinden Boulevard (U.S. 20/26) on the south.  A river crossing was first envisioned in 1961 as part of the Major Thoroughfares Plan conducted by the Ada County Zoning Commission.  In 1995 the ACHD Bench/Valley Transportation Study identified the need for a river crossing between Glenwood Street and Eagle Road to accommodate forecasted growth in the county. 

Connecting these roads would provide an additional route across the Boise River, provide more direct access to neighborhoods and relieve congestion on Eagle and Glenwood roads. The project has considered environmental impacts, traffic patterns and neighborhood concerns, evaluated the continuing practicality of the proposal and identified a preferred alignment.

Over the four-mile span between Glenwood and Eagle Road, there exists no north-south link over the Boise River. This gap forces traffic to travel east-west on Chinden and State Street in order to go north or south creating increased congestion, travel time and air pollution. Part of the study evaluated whether the benefits of increased connectivity would overcome the costs and environmental impacts associated with undertaking a major bridge project.

In 2006 the ACHD Commission recommended Alternative 6 as the preferred alignment for federal highway officials to consider, the recommendations is in the Draft EIS. However, Alternative 6 was evaluated equally with Alternatives 1 (the No-Build Alternative),4, 7A, 8, and 9, in the Draft EIS that resulted in a February 2008 public hearing. The 2006 cost estimates are available for viewing. An updated cost estimate on Alternative 6 can be seen below under "What will the project cost?". 


Funding realities

When the Three Cities River Crossing project was initiated in 2003, the vision was a project that would be funded with some combination of local and federal funds, or some other creative funding mechanism. ACHD always understood that the project cost would overwhelm our budget if it was 100% locally funded. The funding landscape has changed dramatically since that time. Federal funding is tighter every year. Any potential for public/private partnerships that depend on development are unlikely for a number of years. As we approach the end of the Environmental Impact Statement process, the ACHD Commission must decide if the benefits of the project are sufficient to proceed, given the cost and impacts. 

One important question: With limited funds we must make choices - the optimal countywide road system is unaffordable. How important is building the Three Cities River Crossing in comparison to widening Fairview Avenue, widening State Street or building a high capacity transit system?


New traffic projections

Communities in Motion (CIM) is a regional long-range transportation plan for the Treasure Valley that estimates what transportation needs and traffic volumes will be 25 years in the future. The information from CIM helps us understand how future traffic volumes will be impacted by building or not building the Three Cities River Crossing.

The traffic projections in the Draft Environmental Impact Statement for the Three Cities River Crossing project are based on forecasts from the 2006 CIM, which estimated traffic growth to 2030; we extrapolated growth to 2035 because that was assumed to be 20 years from construction.

The CIM has been recently updated to forecast growth to 2035. Click on the following tables to see how other roadways will be impacted with or without the Three Cities River Crossing.


What will the project cost?

The following 2010 cost estimates are for Alternative 6, which is the Commission's preferred alternative if the project is built (project will require either the east or west crossing, not both).

  • East River Crossing:   $65,500,000
  • West River Crossing:  $82,500,000


Can the cost be reduced or managed?

ACHD looked at three options for reducing or managing costs: 

  1. Reducing the project footprint would save about 10% ($5 - $7 million). ACHD could change the proposed drainage system to reduce the right of way needed. This would likely preclude any widening in the future.
  2. ACHD could recommend Alternative 4, which connects from the SH44/SH55 intersection on the north to Cloverdale Rd. and is estimated to cost $55 - $70 million. However the benefits to Eagle Rd. and Glenwood St. are reduced.
  3. The project could be phased to spread the financial impact over a longer period, however phasing would not reduce the overall cost. Right of way could be purchased over 10 to 15 years ($19 - $24 million) and the project could be built in four logical segments (the range in costs depends on which river crossing is selected):
    • SH44/SH55 intersection to just north of the river: $2 - $3 million
    • River crossing to Mulberry Ave.: $25 - $48 million
    • Mulberry Ave. to Chinden at near Mountain View Dr.: $6 - $7 million
    • Mulberry Ave. to Cloverdale Rd.:  $6 million


If we build the Three Cities River Crossing project with local funds, how will it affect other projects?

If ACHD builds the Three Cities River Crossing project with local funds it would cost the equivalent of about two years of our entire capital budget. While the costs could be spread over a number of years, this is a substantial impact. Construction and right of way costs could easily use up all impact fees collected for 6 or 7 years. Construction alone would use the projected impact fees for the Northeast Service Area for more than 20 years. This means that about two-thirds of the projects planned in the Northeast Service Area would not be built or would be delayed by 20 years.


How could  traffic flow be improved and congestion be reduced in this area if the Three Cities River Crossing is not built? 

Special high volume intersections or grade separations would be required to address traffic demand for these four intersections:

  • Glenwood/State,
  • Chinden/Glenwood,
  • Chinden/ Eagle, and
  • Eagle/Eagle Alternate Route 

*Please note that these intersections are under the jurisdiction of the Idaho Transportation Department (ITD) and only Chinden/Eagle is currently in the approved Long Range Transportation Plan.

If the Three Cities River Crossing is built intersection improvements would still be necessary but may be delayed and/or the treatment may not be as extensive.

What would these alternative solutions cost?

Approximate Costs Table 

Background on Alternatives and 2005 Public Meeting Materials:

Input from the public involvement in late 2005 played an important part in winnowing the options and forming a recommended alternative. Nearly 400 people came out to public meetings on November 29th and December 1st, commenting on the potential alignments still under consideration. A strong majority favored the alignments featuring multiple connections to Chinden Boulevard.

The Ada County Highway District examined this input, along with environmental and traffic analysis and feedback gleaned from elected officials of Ada County, Boise City, Eagle and Garden City, to make the recommendation to federal officials about the possible bridge.


Improvements to be Constructed

No immediately buildable improvements are anticipated to spring from the study, but the process could lead to a bridge-building project within the next 15 to 20 years if the crossing is determined to be in the community's interest.


Time Frame

Start Date:
End Date:

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