Mud in borewell water due to rain - Is it temporary? Any suggestions?
Submitted by foubevin on February 16, 2010 - 09:36
Facts: We have dug the borewell in the month of August 2009 for 260 ft. and fixed the submersible pump at 250 ft. Upto november 2009, the water was clear when the rain started. After the rain, the water became muddy.
Actions taken: 1. Stopped drawing water from the borewell for few days in order for the mud to settle down.
2. Water was released to our gardens at a rate of 5 hours per day for a few days.
3. Due to the above actions, the level of mud in the water reduced, though not fully during the months of December, 2009 and January, 2010.
4. On February 15th, Lifted the pump by 25 ft. above and noticed the same level of mud in the water.
Suggestion Received: We have been suggested to flush out the borewell using compressor, to remove the after effects of rain.
Questions: 1.Is the suggestion valid?
2.Are there any other solutions?
3.Is this a temporary problem?
4.We have an alternate well to meet our water requirements. Hence, suggest long term as well as short term solutions.
P.S. The digging of borewell was properly supervised and there could be less chances of any defect in the bore.
Comments
1. Dear Friend, Your location
Dear Friend,
Your location might give us an idea of the source of your mud.
What is "muddy"? Is your water turbid? Opaque-muddy like chai? Translucent-muddy like bad white wine? Muddy all the time? Muddiness clears with some pumping?
Muddiness could be from the deep formations, due to improper well cleaning after finishing drilling (i.e. improper development) both in hard-rock wells and in alluvial wells. In a hard rock well, it can be expected to "eventually" clear up. But your muddiness started from after the rains. That is an indications that the space between the well and the casing pipe is probably not sealed properly and that surface water is entering your well. This is the most likely cause, though there could be other reasons. Do you remember how much casing pipe was put in? Did the driller put a cement seal or a pour a cement slurry grout into the annular space? Did he at least allow drill cuttings to pack into the space? Do you have a concrete apron about 1 m to 2 m diameter, dug to 10 cm below the ground level, around your borehole?
If my guess is correct, you might have a very shallow casing (2m to 3m deep), with no seal on the surface, and with a possibility of surface water flowing around your well or in close vicinity during the rains, then the problem is from the surface. If the casing can be pulled out and a deeper casing set in, good, especially with a seal. Otherwise digging around the casing (1mx1mx1m) and packing it thoroughly with coarse and fine sand (like a filter) with an apron at the surface, preventing surface and making sure that surface runoff does not come too close (at least 3 m from the well), might help.
If you have deep casing (6 m or more), a fully cased well with a screen, then the problem is from the formation. Flushing, well development, compressed air might work in this case, but I think not.
Let me know how it turns out.
Raj Kumar Daw
2. Mud in Bore well
Dear Sir,
In response to what you have described, it is obvious that the problem is due to some sort of movement of water from shallow level into your bore well.
The fact that you were getting clear water until it started to rain, is in itself the answer to your question.
Had you mentioned the length of casing installed, the level at which you struck first water (was your soil saturated during the time of drilling) etc.. it would have been easier to answer your questions.
Howver, with the limited data provided I will try answer the questions raised by you...as regards the other suggestions viz. flushing
Suggestion Received: We have been suggested to flush out the borewell using compressor, to remove the after effects of rain.
Questions: 1.Is the suggestion valid?
The answer is true,but not eh ideal solution in your case.
2.Are there any other solutions?
Probably, if you are open to accepting that there may be a problem while digging itself.
3.Is this a temporary problem?
This will be a recurring problem, with you having to flush out the bore-well every year after the rains, and slowly but steadily there will be effects of soil settling observed due to the movement of soil in the subsurface, due to the presence of water.
4.We have an alternate well to meet our water requirements. Hence, suggest long term as well as short term solutions.
In tht short term, lift the pump a bit, throw in some sodium hexameta phosphate and then reinstall the pump at a slightly higher level. and try to ensure that the level does not drop by controlling the discharge.
You could also try and put a coir rope filter around the inlet but this will have to be periodically cleaned and changed.
If the casing is not to deep I would suggest, either reinstall the casing or install as smaller diameter casing inside the exisint casing and seal the annular opening by cement.
The difficult part is to get some one to lower the casing in such a way that the base of it is not open, but in contact with the existing casing.
Hoe I sound convincing enough to gie it a try..
With Kidn regards
Dr. Anil Lalwani
www.wellwaterworks.com
3. Mud in borewell water due to rain
Dear Sir,
You have drilled the bore well in August and after the rains, that is after November, the mud started entering into you bore well. Where is your bore well located. Like Bangalore, Chennai, Vijawada Hyderabad etc. From the narration I understand that you might have used the DTH rig. What is your depth of casing. Like 50, 60, 20, 30 feet. If you provide these particulars I may be able to suggest something for rectification.
But I guess your casing depth may not be sufficient. Normally in the north east monsoon dominating areas we find the water table at the deepest level in the season during August. And hence at the time of drilling your bore well you might have encountered dry zone in the unsaturated part of the terrain. I also understand or guess your bore well tap ground water from both water table and semi-confined aquifers.
Immediately after the rain, water try to infiltrate and percolate down. Your top part of the aquifer might be also forming a recharge zone and the soaked in rain water percolate and try to reach the water table level in the vicinity of your bore well. And also due to probably, an insufficient length of casing, which might not have provided a sealing of the unconsolidated formation, the trickling and percolating recharge rain water carried colloidal mud along with it and entered into your bore. This action will continue as long as the water level fall below the unconsolidated formation. This is due to raise and fall of water table in the vicinity of bore well at the time of pumping and pump off.
If the casing depth level did not cross the complete unconsolidated and unsaturated formation there is more likelihood that the rain water will trickle down with faster velocity immediately below the casing level.
This is only the possibility for the cause of mud flow. Except guessing that your bore well is situated in the North-East monsoon prevailing area and the casing depth is insufficient, I am unable to provide a solution. Even if I provide it will be trivial and and may not fully attempt to solve problems and doubts. If you can provide more details I will guess out something and try to suggest to the best of my knowledge and expertise.
With best wishes,
A. Raja Mohamed
Geophysicist
Coastal Energy Pvt Ltd, Chennai
bismi1234786@gmail.com 09443619352
A. RAJAMOHAMED AMBALAM GEOPHYSICIST COASTAL ENERGY Pvt Ltd, CHENNAI +919443619352
4. Borewell dry without water
Dear Sir,
When I constructed my house in Vidyaranyapura, Bangalore, we had a borewell dug, we had plenty of water till the construction was done. After moving in, we are facing water problems with the borewell. Water is muddy and very less and the compressor motor makes a lot of noise. The contractor had the borewell dug for us.
1. I want to change the motor as the neighbors are complaining of the sound. If so what motor can I use in its place which is noiseless.
2. Should I get my borewell flushed out. The pipes used are collapsible in the borewell.
3. Approx. how much would it cost for flushing and if you could suggest any company.
Thanks
Anand
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