I have a few comments...first, the over flow may be clogged.....or your well/cistern has turned into a "creek".? Judging by all the surrounding water in one of your photos, it is possible that the bottom of your well has "blown" out.? In other words, a constant flow of water thru the bottom of it.? Some of the below suggestions can help you determine this.? If you discover a blow out....move on....the goodies will be somewhere in the water table, probably miles from the well.
I would be concerned about contaminated water and more importantly contaminated air or lack of it.? I have seen many dead critters in the bottoms of wells.? Yes, dead bodies have been pulled out as well.? Many men have died in these wells due to lack of fresh air.? And yes, some have drowned because they thought that they could get out before the water rose.? Some have died as a result of a combination of these two things.? Wear a hard hat, debris happens!? A quality light source both with you and above you.? Widening the entrance would be nice but I doubt that you have that option.? Be prepared to pull ALOT of debris off the bottom.? It would be wise to hard probe the bottom (rebar) to determine the depth of the muck.?
A solids handling trash pump, get some of the muck out.? If you go this route, rent, buy or borrow the biggest inlet/out you can.? These pumps can only digest solids half as big as those measurements.? If you have the luxury, a pump that has easy access to the volute is a plus, you will clog the pump.? Even better would be to have a fresh water source (lots of volume) to pump down into the well as you're pumping out to get the solids in better suspension.? It will help you get more of the muck out and will also keep the volute cleaner.
To do it right, a tripod over the opening and your butt in a harness.? It will affect your mobility but could save your life.? Make sure your helper can crank your weight out of the hole.? Two would be better than one because if you come out of the bottom unconscious, it will be difficult to get your limp body back thru the narrow opening.? Don't unhook the harness until your feet are back on terra firma.
Wait until winter.? The air and water temps remain fairly constant in these things and if there is a snake or two in the area, this is where you will find it, especially if there is a snake food source close by (frogs, etc).?
If you haven't already, completely cover the opening with something solid to keep out this years leaf fall.? Make sure you have a cell phone that gets reception at the site....test this before you arrive to dig.? I promise, if you show up prepared to go in and the phone isn't working, you're gonna go in anyway (I would!).?
If you can afford it or borrow it, secure a submersible drop camera/TV, black and white, not color.? I've seen them as cheap as $90.? I bought one from Cabela's ($200 shipped) and it is good.? You don't get much depth perception with them but it will give you an idea of what's down there.?
Good soles on your shoes.? You will encounter nails and broken glass.? An updated tetanus shot wouldn't hurt!? Alot of wells back in the day had gazebo type roofs over them and the support for them was usually 2x2's or 4x4's and those supports were sunk into the well. Some are still standing but will be just below the water level.? If you have a legit concrete cistern, the floor will most likely be concrete so you won't have to worry about the roof supports.
Plan and rehearse.? Do a "dry run".? If you use a hoist, test it.? Also simulate an unconscious extraction.? Oh yeah, take a ladder long enough to get you out in the event the harness/tripod fails.? Talk to your companions the entire time you're on the bottom.? Verbalize every move.? This will make them feel more comfortable as you work, they won't be able to see you good.? And, if you are encountering a bad air situation, they may pick up clues by hearing changes in your voice.? You won't realize if you're being overcome by a contaminent but your body will begin to shut down.? You may continue to work but your speech will drop off dramatically.? This would be a clue for your buddies to get you out.
I'd say that it's not a very deep well based on the water table description that you've given, unless the well was dug during a dry spell.? Wells predate cisterns for the most part but wells were often converted into cisterns, no telling how old.
I realize alot of this sounds morbid but you are taking on a serious risk.? I would contemplate as many bad scenarios with your helper and formulate solutions and talk them out loud.? ?Seconds will count if something goes wrong and the last thing you need your helpers doing is thinking of what to do to save your life....plan it out so that they already know what to do and won't waste precious seconds trying to figure it out on their own.?
Will you find something?? Yes.? Have you heard of the well in Rome that was excavated a few years ago?? Over 14,000 coins in it, jewelry, ivory, you name it.? It was a public well so your results will probably vary!? Is it worth it?? Yes.? It is fun, even if you find nothing.? If you find nothing, don't be discouraged, move on to the next well...they are everywhere and eventually you will hit some good stuff.?
I forgot to address how to remove the contents.....sorry,? this is dependent upon how much working room you have in the bottom.? There are many solutions but my general advice would be for you to be out of the well when the debris is coming out.? Small shovels and 5 gallon buckets will serve you well but you will have to modify the bucket (handle) so that you can drop a hook/line into the well to retrieve/pull them out.? I do not suggest filling a bucket, unbuckling your harness, friends pulling bucket up then relowering bucket, then rebuckling.? Chances are, you will start feeling comfortable and make a decision to stay unbuckled.
Best of luck and can't wait to see you finds posted later this year.? For what it's worth, decide before digging who gets what or what percentage share each of you will get.? If you're lucky, you'll have some help that is just plain ole interested in what you do but that seldom happens.? Make sure that if you pull up a bar of gold, tell your help there's another one down there but you need to come up for some fresh air first, chances are they won't abandon you while you're down in the well!? It is proper protocol that nothing gets looked at until the digger is out of the hole.? This is what I like about the "pull the buckets out later" approach.? In my opinion, the digger is taking the risk and should be rewarded with the best find or a slightly bigger percentage.? If you find some goodies, your help will want to accompany you on future digs and then you can get into a rotation of digging and splitting the goods.? Don't forget, you can't do it without them, no way.? And if you do find some good stuff, make sure you have dug all the wells/cisterns within 100 miles 'cause everyone will be doing it.? It would also be kind of you to leave some form of communication that you have excavated the well.? I wouldn't put my name on it but not a bad idea since this is a risky hobby.? You would want to know that a well had been excavated before you go thru all that trouble and risk injury/death. It's also a good way to "hold" a recently discovered well that you may want to dig in the future (slick ain't I!).
I did stay at a Holiday Inn Express last night.......
