i would drive that point so you have 10' of water over the screen. Where is the water level at now? You can use a gas pump to pump the well off.The time for the water to clear depends on how fine the material is and how big the slot size is on your screen. A well pumped sand free at a high rate will pump sand free at a low rate so try to pump it a level higher than what you are normaly going to use for. To check the flow rate get a five gallon bucket and time it to see how long it takes to fill. Take that time and divide it into 60 and then multiply it by five. Whatever you come up with from that is your GPM. You definitely want to make sure that screen is plenty deep beyond the water table. The water level might be high now but come drought season it can drop. I always say the best time to put in a new well is during a drought.