Regarding the bridge you are talking about (and the yard that it used to lead to), I have found two references that give a clue to when it was built:
In Fairport, Painesville & Eastern's Time Table #1, it shows that there was a Bulletin issued on Sept. 24, 1929 that said:
"Effective at 12:01 P. M. September 25th, 1929, the crossing target signal at the F. P. & E. Railroad Crossing, at grade with the Baltimore and Ohio, F. P. & E. Railroad Main track and the lead track to the new B. &. O. Railroad Coal Storage Yard, Fairport, Ohio, will be moved to a point mid-way between the Baltimore & Ohio Crossings."
Then when I was doing a Google search the other day, I came across this blurb from a Railway Age magazine dated January 3, 1931, which said:
"New coal-storage yard and drawbridge over Grand river, Fairport, Ohio, $364,000 (completed)."
So based on these little bits of info, I think it is safe to assume that this secondary line between Painesville and Fairport--of which this bridge was a part--was built between 1929 and 1930.
I call this line the 'secondary line' because the main line went over the bridge that TrapperY is talking about. Although I believe that later, after A.E. Staley shut down their facility in Grand River in 1969, the secondary line became the main line.
Anyway, if you go to this webpage ... http://www.multimodalways.org/archives/rrs/B&O/B&O.html
... then click on the Track Chart file named "B&O Akron-Chicago Div TC 1966.pdf" and then go to page 31 of that document, then you can see how the track layout was in that area--though it is difficult to get oriented since it is not geographically correct. Basically, the bridge you are talking about is on the line that shifts to the right.
Hope this helps!