Okay, off to a good start. When I first looked at the name, I said, this must be an aviation engineer unit and I was correct.
http://renfrew.typepad.com/army_engineers/
There are boxed unit records at the Eisenhower Museum. Here's the index which lists the info. Consult page three.
http://www.eisenhower.archives.gov/research/finding_aids/pdf/US_Army_Unit_Records_Index.pdf
Here is Chapter Nine from the Army Airforce -THE AVIATION ENGINEERS IN AFRICA AND EUROPE
http://www.ibiblio.org/hyperwar/AAF/VII/AAF-VII-9.html
Darn, was going to refer you to my buddy's page - IX Engineer Command, for he has info on the 835th, but that particular link and several others on his page, are no longer functioning. Hope this isn't bad news. I sent him a note and will see if he replies.
Proud Daughter of Walter (Monday) Poniedzialek
540th Engineer Combat Regiment, 2833rd Bn, H&S Co, 4th Platoon
There's "No Bridge Too Far"