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How to design a Ranney Well/ Jack well? Instructions, designs for the same would be helpful. Asraful Islam email@example.com
Ranney well design has been dealt with here with a very useful diagram: http://www.ranneymethod.com/index.html
What about Ranney wells in India?
Ranney well, also called jack well or radial collector well, is named after its inventor Leo Ranney. He was born in USA in 1884 and graduated in Geology from Northwestern University near Chicago in 1912. He introduced this new-well technology initially for oil wells and later extended it to water wells. He installed the first such well for water production in London in 1934 when the city was facing severe water shortage and then in a number of cities in Spain to France to Germany to Czechoslovakia. He then built the first such well in USA in 1936. Today, these wells are in use all over the world including India, with about 250 located within USA. The individual well yields range from 400 kl to 150 thousand kl per day http://www.ranneymethod.com/index.html
Ranney well produces best results in large alluvial aquifers in and adjacent to rivers or in soft rocks such as cavernous limestone (karst) formations. Construction of a Ranney well involves sinking of a central reinforced concrete caisson by the open-end caisson sinking method until the lower section of the caisson reaches a specified depth in the aquifer. A bottom sealing plug is poured to make the caisson water-tight. One or more lateral perforated pipes (screens) are driven into the aquifer with a hydraulic jack kept inside the well in a lateral or radial pattern at one or more elevations to collect water into the well. The caisson is then extended above known or anticipated flood elevations and completed with pumping equipment, controls and conveyance system. Such a well is called ‘radial collector well’ because the cassion acts as a collector of groundwater from the radial screens; and called ‘jack well’ as a hydraulic jack is used to drive the laterals.
In the method used by Ranney, perforated pipes were simply directly driven into the aquifer. A Swiss engineer modified this method in 1940’s by driving first a solid projection pipe into which a well screen (usually of stainless-steel wire-wound design) was installed and later the projection pipe was withdrawn. In the 1950’s, some German engineers refined the screen installation process further to allow an artificial gravel-pack filter to be placed around the well screen. The number of laterals of a Ranney well can be as high as 20 with an aggregate length of several hundreds of metres. Several refinements were introduced by Prof. J.A. Taraporevala, which include use of push-pull method of driving laterals into the aquifer in an efficient and cost-effective manner and use of automatic flap valves instead of ordinary sluice valves to regulate entry of water into the cassion from the screens. These advances allowed construction of these wells with high yields in a large range of geological settings. The life of a Ranney well is around 50 years. As Ranney well draws water from a very large area of the aquifer at depth, the US EPA considers it to be the most environmentally sound intake system having no direct impact on the aquifer.
A lecture on “Design of radial well” delivered by Prof. Vinod S. Patel, Consulting Engineer on 15th November 2000 at Vadodara in Gujarat for Indian Water Works Association and Institute of Engineers was published in the Journal of Indian Water Works Association, v. 35, no. 4, October-December 2003. A reprint of the article could be requested from him at firstname.lastname@example.org. Besides giving design details of two Ranney wells constructed in Mahi and Tapi rivers, the article highlights the superiority of Ranney wells over other high-yielding intake structures such as infiltration galleries, infiltration wells and heavy-duty deep tube wells from the point of view of cost, water quality and life of the intake structures. He also gave design details of two Ranney wells constructed in Mahi and Tapi rivers to give a discharge of around 45,000 cubic metres a day.
Contrary to the functioning of Ranney wells in Gujarat as described above, their functioning in the National Capital Territory (NCT) of Delhi by the Delhi Jal Board (DJB) is not that satisfactory. The contribution of water supply from Ranney wells is just 101 thousand cubic metres a day, accounting for 35% of total groundwater supplied and 2.5% of total surface & ground water supplied. Contrary to the general belief that Ranney well water should be of good chemical and bacteriological quality, some of those in NCT Delhi are of poor quality with high ammonia, iron and faecal pollution http://www.adb.org/Documents/Events/2004/WAP/IND/Delhi/Tripathi_presenta...
Dr D.K. Chadha, the then Chairman of the Central Ground Water Authority, expressed in 1998 that deep tube wells rather than Ranney wells are more cost-effective to develop groundwater in NCT Delhi http://www.expressindia.com/ie/daily/19980718/19951464.html
Our work in Sri Venkateswara University has indicated that sanitary infiltration wells could be best constructed in the most cost-effective manner to discharge very large quantities of good quality groundwater free of turbidity and bacteriological impuries. The design of a conventional infiltration well is such that a sand cushion is kept underneath the well kerb for entry of groundwater into the well during pumping. When there is excessive groundwater pumping, there will be excessive welling of sand into the well leading to its collapse. Contrary to this, we have designed a sanitary infiltration well in such a way that its kerb rests at the junction between sand and the underlying rock. The well walls are embedded with permeable well blocks of high hydraulic conductivity for lateral flow of groundwater into the well. The junction between the well walls and the aquifer is filled with sieved coarse sand shrouding. Detailed geological, geophysical and test boring studies have been carried out to pinpoint the well site at a place where sand of high hydraulic conductivity extends to maximum depth. A picture of one such well designed by us in the ephemeral Swarnamukhi river bed near Tirupati can be viewed athttp://www.indiawaterportal.org/blog/wp-content/uploads/2008/01/infiltra... The discharge from this well was found to be 10,000 cubic metres a day. As the cost of this well is at least 20 times less than that of a Ranney well, construction of many such wells could be taken up in preference to a single Ranney well.
Sanitary infiltration wells constructed in the Tungabhadra River near Kurnool in Andhra Pradesh on the other hand gave discharges of more than 40,000 cubic metres a day.
Dr. R. Jagadiswara Rao
Retired Professor of Geology
Sri Venkateswara University
Tirupati, AP email@example.com
R. Jagadiswara Rao, Professor of Geology Retired, Sri Venkateswara University, Tirupati, AP 517502, India firstname.lastname@example.org
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