Hampton Roads environmental groups are alarmed over a proposed federal decision that they say could undermine decades of local tidal wetlands restoration and protection.The U.S. Army Corps of Engineers and Virginia’s Department of Environmental Quality are moving toward approval of a new wetland mitigation bank in Prince George County — 50 miles upstream from Hampton Roads — that would allow developers to purchase mitigation credits from outside the region.Wetland mitigation banks are designed to compensate for environmental damage caused by permitted development projects. Developers buy credits from these banks to offset the impacts, typically by funding the creation or restoration of similar wetlands nearby.The plan to outsource part of the process has prompted fierce opposition from conservationists, who warn that exporting these credits could lead to the continued loss of local saltwater tidal wetlands without restoring equivalent benefits in the region.