Borewell drilled parallel to drainage pipe resulting in foul odour black and green particles in water - Need help to fix it

Hi,

We have a problem with our bore water, it is having bad smell and a kind of black and green particles in it.

The borewell details are as follows:

• Borewell drilled : Sometime in December 2009
• Bore depth: 180 feet
• Usage : 5 family in our Apartment were using
• Status : Unused for the past 3.5 years
• Bore loacation : Front side of the apartment.

It was drilled near and parallel to the drainage and septic tank.  The septic tank is a covered area and drainage is open which is of 5 feet depth. The water was good initially when the usage had just started with only 2 families at that time. but after 3 months (when the usage got increased), the above problem started.

We are assuming that the drainage water is getting mixed with borewell water. Some of the plumbers are saying the same. Can you please advise on the reasons why we are having this problem and the solutions to fix this? Please let us know if you need more information.

Thanks
Rajesh
9884102319