well house to water holding tank conversion

Let's see if I can explain this. I bought property that already has a well in place. The existing well is actually the second well that the previous land owner had drilled. The reason he had to drill another well is because the first one hit a coal seam (at least I was told) and produced crummy water. So at the original well site (~500' uphill from the newer, existing well) the drilling company built a well house with the expectation it would be next to the well itself. Since the well was moved, it is basically out in the middle of nowhere but uphill of the rest of the land. Being uphill of everything could be very beneficial for a gravity feed system. The well house is nothing more than a 8' diameter corrugated steel colvert dropped into the ground about 8 feet. So basically, it's a big water tank should one fill it with water. The previous owner went ahead and used the underground well house by running a 500' of pex (in addition to 500' of electrical line for the pressure switch) to a pressure tank in the well house. I built a home last year and it doesn't use the existing well house, pex line or electrical line. I ran a separate line to a pressure tank in my house.

So here's what I'm thinking, using the old pex line from the well to the well house, I could transport water from the well to the old well house (I'll call it a tank from here on out because that's what it'll be). The water will slowly accumulate via a slow solar pump (or windmill or hamsters in a wheel or something) until the tank is full. Because the tank is above the apple orchard and everything else, I can then use the water for a small gravity feed system when things get dry.

My issue is that the ground where I live is very, very sandy and rocky. So much so, dirt had to be brought in for my leech field. If I fill the tank as is, I know it will percolate through the dirt ground within a day. Is there a way to gley or seal the bottom of the well house such that I can use it for a retainer? This is an off-the-beaten-path type project, so any suggestions are appreciated. Thanks!

It sounds like you have a metal ring with no bottom. That would be pretty useless as a water tank. You could get an insert to place within the ring, but you may want to put your tank closer to your well. 500' uphill doesn't give the elevation gain, just the distance from the well. Make sure your pump is rated to pump the water to whatever elevation you want it to be (height difference from the pump at the bottom of the well to the top of the tank). If you do get a galvanized tank, make sure it is epoxy coated on the inside, or it will rust through in 15-20 years.