WINDSOR, Ont. -- The Detroit River Tunnel Partnership (DRTP) says it will begin an environmental assessment within a few weeks for a proposed double-stacked rail tunnel across the Detroit River between Windsor and Detroit.

The project originally proposed to convert the existing rail tunnel into a truck route across the border, but that plan fizzled shortly after governments on both sides of the border announced they would instead support building a new bridge in southwest Windsor and Detroit.

The DRTP has since focused on expanding rail car capacity through the tunnel.

"We’re not going to end up with two rail tunnels," spokesman Mike Rohrer Rohrer told the Windsor Ontario News. "We’re replacing the one that’s been there for 101 years."

The new $400 million tunnel would be built either immediately parallel to the existing tunnel, Rohrer says.

Meanwhile, Rohrer told the paper he had no comment on DRIC's project to build a new bridge. "We have no horse in the DRIC race."

A few years ago, though, the DRTP blasted DRIC for backing the bridge process.

The project is a partnership between the Ontario Municipal Employees Retirement System (OMERS) and Canadian Pacific Railway (CPR).

More details will be available at the end of March.