I wish you a safe trip back.

I have been thinking about the design and construction of the bulkhead extension.

I would begin by measuring the height, width, and depth of the 174 School St. bulkhead extension (which I believe to be identical with that installed on Nantucket), and use these measurements as a guide to designing the bulkhead extension on Nantucket. I would plan to extend the steel sides of the new bulkhead (with their outward turned flanges) by securely clamping to the side of the steel bulkhead horizontal pieces of 2x8 treated lumber using 1/4" diameter 5" long stainless steel carriage bolts with flat washers and locking washers.  On each side of the bulkhead, to serve as legs, I would bolt to these horizontal pieces of treated lumber, vertical pieces of 2x8 2x6 or 2x4 treated lumber extending down to the concrete foundation.  I would make a cover for the opening extending 1 1/2 inches over the lateral edges and 1 inch over the front of the opening by bolting together three congruent pieces of 3/4" treated plywood. At each of the lateral sides of this cover, I would insert two eye bolts to be tethered to the vertical legs on the sides of the bulkhead extension. Thus the cover would be removable and permit installation at some later date of a pulley to help hoist large objects, bicycles for instance, into and out of the basement.

We can discuss details and options if you wish, but I'm not offended if you choose to proceed on your own without further consultation.