Black sand particles from borewell - Indore
Submitted by ankurshrimali on August 20, 2010 - 11:43
We recently (mid of July 2010) digged 6" borewell up to 455 ft in Indore location. Casing installed is 22 ft. According to the Boring Agent water stuck is 2".We are done with installation of 2HP 26 stage pump with 1.25" pipe. However even after 1 month usage we are continuously getting black sand like particles 10-15 in number in a bucket. We are also getting some patch of muddy water means 10-15 seconds of muddy water intermittently(although not so frequent). We have installed pump at depth of 420 ft. Before installation we measured borewell which was 437 ft(actual drilled depth was 455 according to pipes inserted by rig) and water level was at a depth of 55 ft.
Can any one please suggest how to resolve this? Is this going to create problem to submersible pump? Please suggest.
- Borwell dug in July 2010
- Location: Indore
- Depth: 437 ft (actual drilled depth was 455 according to pipes inserted by rig)
- Time of borewell: July 2010
- Casing: Upto 22 ft
- Water stuck is 2" thick
- Pump in use: 2HP 26 stage pump with 1.25" pipe at depth of 420 ft
We now are witnessing black sand like particles 10-15 in number in a bucket of water.
We also get some patch of muddy water in 10-15 seconds intervals
Can any one please suggest how to resolve this? Is this going to create problem to submersible pump?
Comments
1. Dear Ankur, I just come to
Dear Ankur,
I just come to the notable points that logically help you or readers to judge.
Water level is 55 feet. Pump installed depth is 420 feet. H. P. is 2 and stage is 26
Since the bore's yield is stated as 2 inches which experience show is about a minimum of 40 Litres per minutes. Please note that this depends on at what depth you struck the under ground spring and the geo-spatial location in the mini or macro ground water basin and other characteristics beyond the scope of this discussion.
If you have obtained the 2 inches yield beyond the depth of 120 feet then, if your requirements is about 2000 liters per day, your pump will give this in a maximum of one hour near Indore.
Then what is the need for inserting lengthy pipes till 420 feet. Just 180 or 200 feet level is enough. Your bore well at 200 feet, for your static water level of 55 feet, again in peak dry season say 80 feet will supply about roughly 850 to 1000 litres from dead storage. Since yield is 2 inches I recommend to re install the pump at 200 feet depth.
The Black granules and the mud swing is due to the close proximity of pump intake being located in the settling zone of your disturbed disintegrated particles that come down and settle at the bottom.
May be some part of the formation is soft and the block granules is trickling when you disturb while pumping and ground water movement causes, may be this fall. The red mud indicates that the yielding zone of the contacts between two formations and it is the geo-hydrological aspects.
I hope the recommendation stated will get you Clear water. If you do not pull up the pump higher over the period the bore depth will get reduced due to the selling colloids and you may loose the pump.
Further due to aberration the pump's impeller gets damaged and the discharge will reduce and also more Amperage may result.
With best regards and wishes,
A. RAJAMOHAMED AMBALAM GEOPHYSICIST COASTAL ENERGY Pvt Ltd, CHENNAI +919443619352
2. Dear Ankur, The borewell has
Dear Ankur,
The borewell has not been developed properly.
Proper development with compressor would clean the well and subsequently the pump may be lowered.
With regards,
D. Chakraborty
Scientist
Central Ground Water Authority (CGWA)
New Delhi
3. Black sand particles from borewell - Indore
Dear Ankur,
You have given the following Information regarding your borewell
And recently, end of august you have been witnessing black sand like particles 10-15 in number in a bucket of water-also get some patch of muddy water in 10-15 seconds intervals -
till this date the water was clean I presume
What I think from this information is that, probably the casing installed has a small crack or has been not installed properly and there is a small gap & you have had rainfall which has saturated the uncofined near surface zone down to 22ft B.g.l., and the static water level in the borewell is way above the 55ft mark which was the case when you first installed the pump.
Please confirm this.
If what I have predicted visualized is correct, it will be advisiable to try and insert a smaller diameter casing inside the existing casing and try to grout the area bettween the two casing with concrete pumped in with pressure.
Or arrange to get the existing casing removed and re-instlled, ensuring that the casing is lowered a bit more say down till 30 ft and to be on the safe side grout it with cement.
If this is not done, probably the quantity of muddy water and sand content will increase, the particles which cannot pass through the pump strainer will get deposited in the well, and would probably accumulate over a period of time and finally the pump would get totally burried in this and may also get clogged and stuck in the borewell.
You have not mentioned the depth at which you have encountered the aquifer ( 2 inches of water) if that is at a higher elevation My advise would be to pull the pump up to a point just below this depth, rather than lowering in to almost the base of the borewell.
In anycase, mud entering the borewell suddenlly after a month or so can only point to a damaged casing, and increased saturation in that region due to rains.
With Regards
Dr. Anil Lalwani
www.wellwaterworks.com
4. Thanks all for providing
Thanks all for providing valuable comments.Further I want to clarify below points:
From responses provided will pulling pump above for 10-20ft suffice the purpose?? We are worried of getting dry borewell during summer season so hoping that we do not have to pull pump further.
5. Rainwater Harvesting
Dear Ankur,
In order to overcome summer water security you must consider supplementing water by harvesting rainwater.
And recharging the rainwater to the borewell would also improve the groundwater levels.
Regards,
Arun
India Water Portal Team
6. Thanks all for providing new - Black sand particles from borewe
Dear Sir,
The underground water spring occurred at a depth between 360 to 380 feet and when you happened to install the pump the water level has rose up to a level of 55 feet.
This is due to the hydrostatic pressure of the prevailing pressure potential of your sub system in that area. I understand that you might have been pumping water not upto even one hour duration at a stretch. Even if have pumped for 2 hours the water level will not fall below a depth of, from 55 feet to 150 feet due to the instantaneous recharge and pressure head of your strata.
The black nudles are from the soft rock that has been disturbed while pumping and minor water holding and slowly water oozing strata in your geohydrological set up. Probably from hard ash bed that may be forming different contact zone of the petrolgic features, that trickles down from top along with the oozing water and also that got dismantled from its position during the vertical and downward zidding movement of water in your bore.
If you are reluctant to pull up the pump. Try to keep the pump level at 250 meter depth and observe whether the black nuddles are coming again. Latter during summer depend upon the requirement you may insert down your pump level.
I guess since your requirement may be about maximum of 35 minutes of pumping, the water level fall during pumping may be about 80 feet and in summer it may be about 110 feet, at the worst. Hence yu can try and this may avoid the sucking of black nudles by your pump intake. Or else you may tie a nice screen at the contact between pump and motor. Many nylon and steel screens are available, even similar to nylon cloth of water resistant variety may suffice the need. What ever it is the pump level should be at least some 10 feet above your yielding strata of 360 feet or so
With best wishes,
A. RAJAMOHAMED AMBALAM GEOPHYSICIST COASTAL ENERGY Pvt Ltd, CHENNAI +919443619352
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