Regional officials are starting to blanch at the potential costs of drilling a new light-rail tunnel into the West Hills.

As WW reported Tuesday, Portland City Commissioner Steve Novick and others have asked regional planning agency Metro to slow down on studying possible tunnels under Oregon Health and Sciences University, as part of a new transit line to Tualatin.

Novick warned local governments would foot half the bill on a tunnel—which could reach $2 billion in costs, if it extends underneath the Hillsdale neighborhood.

But others are asking Metro to resurrect an even longer tunnel, which was briefly abandoned last summer as too expensive.

That long tunnel could run more than 4 miles, and have at least 3 underground stations, including beneath the Portland Community College Sylvania Campus, before emerging at the Barbur Transit Center.

"The estimated cost of the long tunnel, in 2014 US dollars, is $1.86 billion," says Metro public affairs specialist Juan Carlos Ocaña-Chíu. "Keep in mind that the actually construction of the tunnels would start in 2022 at the earliest, so the cost is very likely to increase by the time it would be built."

WW has previously reported on how large capital projects have eaten into Portland's transportation funds—and how the tunnels of the SW Corridor project offer another test of priorities.

But where exactly would these tunnels run? A Metro draft design from this March offers possible routes for the SW Corridor High Capacity Transit line. (Officials haven't decided whether it will be a MAX line or bus rapid transit).

And here's a close-up of the possible tunnel options. (The tunnels are noted with dotted lines; the longest, $1.86 billion version is in red.)

UPDATE, 4:10 pm:
mileage of each tunnel option.