Spending as much as to replace Brooklyn’s dilapidated Gowanus Expressway truck-and-car tunnel may be seem like a wild idea. But consider the alternative the state Department of Transportation has long been bent on bulling through: $1 billion to reconstruct the elevated highway, bringing South Brooklyn traffic to a halt for most of decade.

“Then, you would still have the overcrowded Gowanus, giving us nothing more than we have now,” says Buddy Scotto, a member of the Gowanus Expressway Community Coalition, the group that has managed to muster political support for their cause–blocking the state project until at least a more comprehensive environmental review is completed.

Instead of overhauling the 56-year old structure, re-routing the 175,000 trucks and cars that use it every day, the white shoe Regional Plan Association joined the community activists and local politicians last month to issue a detailed feasibility study of the tunnel option. The report was commissioned by City Councilman Kenneth Fisher.

“Dollar for dollar it’s a better investment than rebuilding the Gowanus,” says Al Appleton, the form Kenneth Fisher.

“Dollar for dollar it’s a better investment than rebuilding the Gowanus,” says Al Appleton, the former city commissioner of environmental protection, who helped author the report. Up front-costs would be recouped in “lower life cycles,” the RPA says, because it would require less maintenance than the weather-beaten highway. The tunnel would also open up unrestricted access to a broad swath of the Brooklyn waterfront.

The activists say it’s been a brawl just to get the state DOT to even consider changing its construction priorities. For now, though, the state agency seems to have withdrawn for its full throttle support of demolition and reconstruction, shelving a 1995 environmental assessment that dealt solely with the contingencies of rebuilding the highway.

State officials says the RPA’s cost estimate for the tunnel too low, however. DOT spokesperson Alex Dudley says the agency estimates the real big price tag at $5 to $6 billion, and will release its own analysis of the alternatives this fall.