Break out the card and go see the librarian. Request, through interlibrary loan, a copy of John Gross Barnard's Seacoast Fortifications. Barnard was chief engineer of the Army of the Potomac, detail designer of the attack plan up the Mississippi River apon works he had once commanded, as well as author of the failed Peninsula campaign, through McClellan. Barnard can answer your questions better than I ever could.

One interesting seacoast fortification I'd run across was on Amelia Island, Florida. It was the work of the survey party under R.E. Lee, a mortar pit. That work never had a tube in it, the 10" mortars that were being made for the area were dumped in a canal in New Orleans apon the capture of the city in April, 1862.