Borewell 462 feet, pump installed at 330 feet, we get muddy water after initial 2- 3 mins when it is switched on - Need help

We drilled a borewell sometime in February 2009 and in Chikmagalur, Karnataka. The diameter is 6 inches, total depth is 462 feet, casing is done till 90 feet later we hit with a rock. We have installed a 1.5 HP submersible pump at 330 feet.

According to the driller we got water of around 1 inch at 150 feet, but we further proceeded with drilling hoping for more water. After drilling 200+ feet he said there is one more water point of 0.5 to 1 inch. Then there was a rock we came across and continued drilling hoping for water, we took a chance and asked him to drill till 450 feet so that rock drilling may end and we can get good water below that.

From the day one after installing the pump we are facing a muddy water problem. When we switch on the pump we get a clean water for 2 to 3 minutes. Then suddenly muddy water starts pouring for another 2 to 3 minutes. Water is so muddy that you can't use it for any purpose. But after that again clean water starts pouring out. If we switch on the pump everyday then the quantity of muddy water is less but the quality increases progressively with number of days taken to switch on the pump.

Initially we thought, this problem may go off eventually but it is been four years now but the problem continues. I would be glad if some expert let me know, the reasons for this problem  and if there are possible solutions.

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