80 miles out ouch that's a killer in gas, I guess you have to access via a trail I can't remember what the refers to them as. I will try to locate and retype the record account later today.
Your shaft is probably getting water from under the moss if it is present around the portal. Heres our method for a temp portal that is until you or me reach a recoverable amount of gold. Shaft a little more than 4'x4' in the clear four sheets of marine grade plywood with bonded 2x4's liquid nails or similar. Pull your moss back about 2' or so put in your portal with 2" blue foam on the outside. Leave about 1' above the finished surface to keep surface water out. Optimally fill with some thick muck a foot or so pack and then use four bags of betonite (spelling) clay it's impervious to water then fill the remainder of muck. We use a cap of 3/4" plywood with foam mounted on the underside. We have never tried a another trick of cutting 1' wide strips of moss 7' long and draping these over the portal cap to insulate further and keep sunshine off the the lid. Incoming water is a pain we have found even if your shaft is solid permafrost muck the ground acts like a thermal heat sink. The incoming water in summer freezes from the bottom up leaving only the top 2.5' or so liquid.
The first shaft was us reopening an older cribbed shaft the surface around the shaft was already raised by old timers but when the water comes up 2-3 feet 20-30feet wide in the flood plane it's pretty hopeless.
As far as sinking down we have tried a number of methods. Steam thawing, cold water thawing both produce the same results for the material to be removed. Shoveling cold mud is hard as is(suction, weight, removal from shovel and bucket ect). As well as there is the problem with running a boiler and keeping water pumping fuel(wood) going into the boiler.
Actually kind of a funny story there we had a large scavenged steam chest on the stack of our boiler it blew at 130 psi even though we have had it past that a number of times(never hydro tested it as it looked real solid made from 1/4" mild steel. ) Kind of amazing to I think the energy equivalent for each gallon of water at 100 psi or so is equal to 1 stick of dynamite if instantly released. Can't remember where I was reading that but I could believe it. We were about 30ft from the boiler when it let go I will say that it wasn't like dynamite going off but enough to make you mess yourself.
We have gotten away from using steam or water and have switched over to concrete breakers and a genset. Earplugs and full cover ear protection is required for this as you are standing in a solid tube of frozen ground and the pounding can be felt through your entire body. The material slabs up in pieces sometimes as large a 1'x1.5' easy easy easy to shovel. After broken up about a foot in depth it's like shoveling dry coal very light and easy to get out of a bucket. The only drawback is when the material is broken the energy invested into the ground from the breaker point causes some water vapor to be released fogging the shaft some but it rises out of the shaft shortly after starting to shovel. I have a small video of this process but I've never posted a video before.
We considered blasting but getting explosives after 9/11, well it's harder to do. After 9/11 the state required a blasting licenses to purchase from Pacific powder Supply. I've never looked into getting one really, Prior to 9/11 it wasn't that hard to purchase from Pacific Powder Supply state Id and some simple forms plus $$$ for blasting media.
Our 48' of muck is frozen solid no live water old reports confirm this. Funny about 2' down we found a pelvis from a Moose calf the funny thing is there was gravel packed in and around the bones we defrosted these in the cabin and there was fine gold present. It's funny because there isn't any surface gravel to speak of on the claim.
I understand about the weather we keep a digital indoor/outdoor thermometer that records the record highs and lows it has shown 49F below when we went out for a couple of days. Plenty of visits show 30F below. The winter problem we have is the valley we work is narrow about 1 mile +/-. The low winter sun for a couple months never touches the valley floor keeping the temps lower than in town.
P.s. Have fun in town today the morning news said it was -44F. I'll sit at home for the day and force feed the wood stove.