16th Street Bridge Construction Superintendent goes missing in 1921 and no trace ever found

I have always been a fan of narrator and author David McCullough  who is from Pittsburgh  I even use to buy from his family's electrical supply business before it closed and when the 16th street bridge which goes from  Pittsburgh Strip District to North Side  was being named for him   The Post Gazette did some research on the bridges history and  came across the mysterious disappearance of M. C. Sparks the superintendent in charge of building the bridge .

http://www.post-gazette.com/opinion/Op-Ed/2013/07/07/Next-Page-As-Pittsburgh-s-16th-Street-Bridge-is-renamed-missing-man-s-mystery-remains-unsolved/stories/201307070194

I never knew about till I read it in the Post Gazette.
but people going missing along our 3 rivers or drowning in them is nothing new.
When I worked for  Burns International detective Agency as a guard  one of the places was an old forge  that went out of business and before that it was the Pressed Steel Car Company which made rail cars and had a horrendous reputations for accidents and deaths.While working the assignment you would find all types of people walking up the railroad tracks along the river beside the plant. Kids playing teens up to no good the homeless,drifters and vagrants and other undesirables  . You always had to stay on your guard its like that today and in when the 16th street bridge was being built.

It seems like the rivers just attract this bunch just like Walmarts do.
and in M.C.Sparks case it was even more dangerous time along the rivers in 1921  with labor strife everywhere.
did he fall off into the river very possible they did not have the harnesses and safety systems in place like today.Did he commit suicide its possible he was a shell shocked WWI vet  Was he attacked killed and then dumped in river that's more likely. But we will never know till remains are found some day and thats highly unlikely .
Like I always say the storys these 3 rivers would tell if ever dried up and dug up.