DETROIT — Another government agency is punching holes in an Environmental Assessment (EA) prepared for the U.S. Coast Guard regarding a twin span for the Ambassador Bridge between Detroit and Michigan.

In a recent review, the Michigan Division of the Federal Highway Administration (FHWA) described the environmental stamp of approval for the bridge company’s twin “enhancement project” a “largely qualitative document” that “does not perform a rigorous quantitative analysis of several topical areas.”

The FHWA found several problems with the previous analysis, including the air quality impact assessment, which according to the FHWA was very limited in scope. “The air quality is a transboundary impact. The analysis needs to be done right,” wrote Division Administrator James J. Steele to the Coast Guard.

… “Impacts in Canada from the proposed enhancement project will be studied by Transport Canada and need to be considered in the U.S. Coast Guard’s analysis before a decision is reached.”

A cable-stayed span could end up next, or in place of, the Ambassador.
But the state highway authority wants to see a better impact analysis first.

The Detroit International Bridge Co. (DIBC) is working on building a cable- stayed toll bridge over the Detroit River next to the 77 year-old Ambassador.

The EA to the Coast Guard appears to demonstrate that the project will have little significant social or environmental impacts, while providing a positive economic benefit for the operation of the border crossing. But the FHWA review contends that this rosy picture is based on a limited overview of DIBC’s entire plans.

“The analysis is too narrow in its scope in that it only looks at the proposed bridge and ignores other improvements discussed and publicly presented by the DIBC, such as further expansion of the U.S. plaza beyond the footprint of the Ambassador Gateway plaza.”

Construction on the Gateway plaza is expected to begin this summer.

The FHWA found many other aspects of the EA to be incomplete or in need of further details:

“The analysis draws on data from the DRIC study, specifically the traffic data for border crossing trips. This is the extent of the traffic analysis performed. In our review of the document, it appears that the traffic was only analyzed for the air quality analysis. No attempt is made to refine the DRIC traffic data for the future proposed enhancement bridge.”

A refinement, says FHWA, would include the eventual operation of a new bridge at the DRIC location to address future capacity needs and show projected traffic at the Ambassador location. “No analysis of current or future traffic could be found.”

Also questioned by the FHWA was the proposed length of the new span, which at 685 meters would, according to the administration, be significantly longer than any current cable-stayed bridge in North America. The height of the proposed support tower could also interfere with operations of the Windsor Airport, the FHWA speculated.

Based on the track record of even longer links in places like China, the span-length proposed may be reasonable, says FHWA. “However, there is no indication that an engineering consultant experienced in such a record setting long-span cable-stayed structure was involved in determining the feasibility of the proposed bridge.”

There are significant structural security vulnerabilities associated with suspension and cable-stayed bridges, the administration continued. “The opportunity exists to mitigate some of these vulnerabilities when designing new bridges of these types. This opportunity should not be ignored for such a critical structure.”

The FHWA also commented on lack of variety in the supporting documents submitted by the DIBC for the Coast Guard report.

“It was noted in our review that many of these letters say almost exactly the same thing, word for word,” states the FHWA report. “They appear to be a form letter prepared by the DIBC to support the proposed project and provided to the groups to send back to the DIBC.”

— CORRECTION: A Previous version of this story stated the U.S. Coast Guard prepared the original Environmental Assessment recently reviewed by FHWA. In fact the DIBC commissioned the EA for submission to the Coast Guard. We regret the error.