In Malaysia we place a precast reinforced concrete (RC) cylinder upright on the site. We start digging on the inner ground and the heavy cylinder will lower by itself into the ground. When the cylinder is level with the ground place another cylinder on top and so on until clean water at the deeper level is obtained. Water will seep in between the cylinders into the well. The top few cylinder joints can be joined with sealant to prevent dirty water of top levels seeping in. No danger of wall collapse.Using those folding sacks is a lot more efficient than filling buckets like most builders would use. Good idea to speed things up and save a lot of shovel work.