Wow, ran across this beauty this morning while performing research for a new friend. Can't believe I hadn't run across this reference material until today. It's a great source of information on numerous units, covering the time period from Operation Overlord through the end of the war in Europe.
Armed Forces Oral History - World War II Combat Interviews
According to this reference guide, these materials are located at the Washington National Records Center - Operated by the National Archives (NARA) in Suitland, Maryland.
Each reference specifies a number such as CI-370. The CI stands for Combat Interviews, but as the user guide points out, the documentation includes narrative histories, operation reports, official journals, etc.
The reference covers the gamut of military units including engineers. Yes you read that right - engineer units! We are not forgotten. 
Proud Daughter of Walter (Monday) Poniedzialek
540th Engineer Combat Regiment, 2833rd Bn, H&S Co, 4th Platoon
There's "No Bridge Too Far"