When you have time, review reports that mention the bridge. Let us know what you learn.
You mentioned the rail line had been graded along Montevallo Road from Brock's Gap to Grace's Gap. Montevallo Road crosses Red Mountain at Grace's Gap, named for Jefferson County Sheriff Bayless Grace. South of Red Mountain the road is called Oxmoor because it led past Oxmoor Furnace during the war. Further south the roadway disappears, but we know that it led over Ross Bridge and thence to Brock's Gap in Shade's Mountain. In antebellum times this was a well-traveled highway, leading past the resort on the crest of Shades Mountain where Bluff Park now exists. Before the war the Jefferson-Shelby line ran through present-day Bluff Park.