CHARLESTON, W.Va. -- A recent trip to Petersburg sent me on a trip down memory lane.Actually, it sent me on two of the originally proposed routes for Appalachian Highway Corridor H, the road that someday will link Interstate 79 near Weston with Interstate 81 near Harrisonburg, Va.As I drove alone through the mountains, I had lots of time to think about the impacts road construction sometimes has on rivers and streams. Anticipating those impacts, and allowing for them, can turn a potential environmental nightmare into a road that lies more gently on the watersheds it crosses.That's exactly what happened with Corridor H.The highway's original "preferred routing" would have seen it follow essentially the same route as U.S. 33 between Elkins and Seneca Rocks. Proof of that can be seen today by driving Route 33 between Elkins and Bowden.Scenically, it's a beautiful little 10-mile stretch of four-lane that climbs to the top of Cheat Mountain and follows the sweep of Shavers Fork to the foot of Shavers Mountain. As soon as the road crosses Shavers Fork, it reverts to two lanes.Today's travelers probably wonder why highway engineers would build such a short segment of limited-access highway and have it end essentially in the middle of nowhere.The answer can be found in the creeks and rivers that drain the six valleys between Elkins and Seneca Rocks. All of them are trout streams, and some of those streams are among the very best West Virginia has to offer.Back in the late 1970s and early 1980s, highways officials hoped to extend the existing Corridor H stub to Seneca Rocks and beyond. They didn't, however, factor in the impact trout fishermen and other outdoor recreation buffs would have on the road's eventual routing.Members of Trout Unlimited and The Highlands Conservancy took a good close look at highway officials' "preferred alternative" and didn't like what they found. The road would have had a significant impact on a couple of miles of Glady Fork, a minimal impact on Laurel Fork, a significant impact on a couple of miles of Dry Fork, a huge impact on the lower reaches of Seneca Creek, and devastating impacts on a handful of smaller native brook-trout streams.White's Run, for example, would have been routed through an 8- by 8-foot concrete "box culvert" for a substantial portion of its length, effectively eliminating its fishery.Opposition to the road built quickly. Opponents pointed out that construction of the Elkins-to-Bowden stretch had ruined one of the two springs that fed the Bowden Fish Hatchery - something that wasn't supposed to have happened.Eventually, highways officials abandoned the "southern route" and went with an alternative that went northeast from Elkins to Parsons and eastward from there over Mount Storm and on toward Moorefield and Wardensville.Some of the road has been built. The stretch from the eastern side of Mount Storm to Wardensville is complete, is a joy to drive, and was built without causing any major environmental problems.Construction crews are currently working on the segment between Mount Storm and Thomas. According to the state Department of Highways' website, construction should begin in 2018 on a 13 1/2-mile segment between Kerens and Parsons, and in 2025 on the final 9-mile stretch between Parsons and Thomas.Environmental planning for the Parsons-Thomas unit has been particularly dicey because the mountain to be traversed contains habitat for the endangered Northern Virginia flying squirrel.Here's hoping engineers can find a route for the highway that not only preserves the squirrels, but also the integrity of any trout streams it might happen to cross.