Boulder Canyon Grading?

Hello,
Was hiking in the Western half of Eldorado Canyon State park a few weeks ago and noticed a substantial roadbed near the bottom of the canyon near South Boulder Creek (this is several miles West of Eldorado Springs). I know there was some form of a toll road that ran west from Eldorado Springs, but the grade we were walking on seemed much more substantial then a toll road would warrant; one part cut through a rock wall and there was a 10+ foot high fill.
My ghost railroads book has a blurb that says the Denver, Utah, and Pacific railroad graded into "Boulder Canyon and beyond" from 1881-1887; does anyone have information about where this was, or what is still visible? Specifically, what are the sections of grade along the creek that intersect the Eldorado Canyon/Walker Ranch Loop trail? Railroad grade or toll road?
Thanks,
Chris Weaver
weaverc@colorado.edu