Final impediment is the thirtieth and final level of the Present difficulty in the Genesis/Mega Drive port of Lemmingsand the fourth level of SUNSOFT in the Super NES port of Lemmings as SUNSOFT SPECIAL 4.
Strategy[]
Deploy the second Lemming as blocker above thick enough terrain, anticipating that we'll unfoot this blocker later. The first Lemming will dig at the far right of the platform, and dig down as far as possible to build toward the right. Stretch each bridge on the way to the right side of the level. Build another bridge to close the digger's hole and bash to cut off early. If you've done this correctly, you will be able to walk across this bridge and not touch the flame thrower.
Unfoot the blocker with either a digger/basher or a miner, and build to cut off early if necessary. Build a left-bound bridge to the exit, and bash to cut off early if necessary. Raise the release rate, and we are complete.