Federal authorities are concerned about the environmental impacts that a new Interstate 5 bridge between Portland and Vancouver, Wash., might have on endangered salmon.

More study is needed about the impacts of nearby development, bridge construction and stormwater runoff, according to the National Marine Fisheries Service.

The agency's concern, which echo those raised by local environmental groups, add another layer to the already complicated Columbia River Crossing project.

The $4.2 billion proposal would replace the six-lane Interstate Bridge with a new 12-lane bridge, light rail extension to Vancouver and improvements to six highway interchanges.

Carley Francis, a spokeswoman for the CRC project, told The Oregonian that bridge planners are aware of the fisheries service's concerns and will address them.

The fisheries service's comments affirm criticism by local environmental groups and growth watchdogs that the bridge project could result more farmland converting into subdivisions.

Such development creates areas where rain will bring pollution into streams.

The fisheries service says initial environmental plans didn't properly analyze the effects of development outside of urban growth boundaries.

Bridge planners assumed that local governments would prevent stormwater runoff from impacting salmon, but the fisheries service is skeptical of those promises. And they say more documentation is needed about how the project will avoid or mitigate pollution in creeks where salmon are found.

The fisheries service also urged bridge planners to consider a bridge design that would attach light rail below the highway deck, reducing the number and size of piers in the water and minimizing construction disruption.

But such a design would intrude into federally protected airspace for Pearson Field, a small historic airport just east of I-5 in Vancouver.

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