Immigration and Environmental Impact Statements

Dumb question here from somebody who knows little about the EPA- but before Congress passes immigration reform, might they not be required to do an environmental impact statement?  Wikipedia has this to say about EIS’s:  they are required for actions by the federal government “significantly affecting the quality of the human environment”.

Given that snail darters have in the past derailed government actions, and given that immigration reform could add a few tens of millions of new residents to the US, with their associated environmental impact, shouldn’t the government do an EIS prior to passing immigration reform?  Shouldn’t that EIS go through the usual process of review, comment and (possible) litigation?