I have an old house in the mid Hudson Valley area of NY.  In addition to a modern "driven" well, it has an old dug well, aka "cistern".  This is an old style well, where tubular pre-cast concrete sections were placed on the ground, and some poor soul had to dig out under them, and let them sink into the ground, as they dug.  As they deepened, another section was placed on top, and so on.

The last section was left above ground, with a round concrete "hat" with an access hole.

The last riser, above ground, is deteriorating to the point I am worried about safety.  It is still useful, for garden watering and other uses.  Besides, it would be quite a job to fill it in.

Problem is, no one seems to have these pre-fab sections, in this size.  Approximately 44.5 inches, O.D.  Around 3-4 inches thick.

So, I am seriously considering doing a pour in place, using my own on site created forms.  I am thinking along the lines of using some rather thin material, such as "masonite" or formica, well braced, obviously, as this would make it easier to form a reasonable circle.   Reinforcing wire would, naturally, be inserted.

How mad an idea is this?  Other suggestions?

Have you thought about making the 'hat' out of fiberglass?

Is it deteriorated to the point that a parge coating would provide little benefit?

DIY parge coating

What about brick or stone cemented around the column?

Something like this:  Brick well or stone well

It's pretty bad. I let it go for some time, the house being un-occupied, it was easy to forget.

Some areas are clear through with only the reinforcing wire showing. I *might" be able to parge, with enough care and . . . whatever those latex (?) adhesion products are called, but it almost seems like more trouble than it's worth.

I had considered a stone or brick replacement. Depending on how difficult building a form appears, that may be the way to go.

The outer form does not appear too difficult, as it will be sitting on solid ground. The inner one, however, presents a few challenges, given how easy it would be to "fall in".