The Maribyrnong River and Moonee Ponds Creek could be partially dammed while two bridges are built across them as part of a new toll road through Melbourne's west, planning documents show.

High-voltage transmission towers beside the West Gate Freeway will also be moved or rebuilt so the freeway can be widened to 12 lanes between the Western Ring Road and Williamstown Road as part of the $5.5 billion Western Distributor project.

The high-voltage power lines could either be shifted closer to homes in Brooklyn and Yarraville, or buried.

Fresh detail on how the Western Distributor will be built and the impact it will have on nearby areas is revealed in documents Victoria's Transport Department has submitted to the federal Environment Department.