> Port added the money, if approved, would go to install a 5 to 6-foot-wide pipe between Market Square and the Merrimack River.

It’s not 5-6 feet long, it’s 5-6 feet wide.

You need heavy machinery to move those culvert sections into place, heavy machinery to dig the trench, you can only get a couple 20’ sections of 5-6’ diameter concrete culvert on a semi so factor in lots of freight costs too. If you cross any roads or sidewalks, those need to be sawcut and removed, and then replaced afterwards. $655k sounds reasonable to me, if you include all the engineering/utility/heavy machinery/manpower/material costs.