I have a borewell in my house at Naini which is having a depth of 210ft. We hit rock at 80-90ft and the casing has been done to that level. The submersible pump has been fixed at 100ft. Prior to fixing of submersible pump we used to pump water (for construction of the said house) . At that time I used to get clear water. But after some time we started getting water with sand. We got the  borewell cleanedand then fixed the submersible pump, however, from then onwards I am getting muddy water every 2 to 3 months gap. If the muddy water is pumped for 2-3 hours then I can get clear water for that day. Again next day when the motor is switched on muddy water starts coming. I even got the borewell cleaned for the second time and at the end of the bore well there is no soil base and the base is very hard with rock content as we can hear and feel the hardness of the rock at the bottom of the borewell. Please advise and help me how to get good water from this borewell.