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Below this top layer of clay, sand layer is present. For this sand layer, the porosity may be even to the extent of 30%. This layer would be very permeable with relatively less travel time. Hence leaching of water from this layer would be better. This justifies the depth of pit in Dhamaka toilet. This sand layer is a part of aquifer, as indicated in the maps. Further, the subsoil water levels, as indicated in map, have been found in both districts to vary between 30ft to 120ft. In potable water zone, water levels are nearer the surface. In northern region of Sriganganagar District, depth of water level is less than 20 M in NW region and between 20-40 M in northern and SW region. In northern region, nitrate distribution is below 50mg/Lt. In Hanumangarh district, the depth of water level is less than 20 M in northern region and between 20-40 M in central and NW region. In the same region, nitrate distribution is below 50 mg/Lt. As far as the evaluation of Dhamaka toilets is concerned, all this geological data would be important for foreseeing the ground water contamination effects due to generalized use of Dhamaka toilets. 11. Relevance of this data in technology selection These hydrogeological conditions in these two districts (and perhaps in areas of adjacent districts in Rajasthan, Hariyana and Punjab) become an important consideration in selection of on site sanitation technology. Although twin pit latrine with shallow pit is a generally accepted technology, in these two districts, it would not be appropriate. Water from the shallow pits will not leach out because of the clay layer with very low permeability. Hence shallow pit latrine is not likely to function properly in this zone. When leaching of water from the pit is expected, deeper pit reaching the sand layer where permeability is higher, will be the only suitable technology in such situation. Septic tank technology also will not be appropriate, because the issue of management of effluent from septic tank would be problematic due to top clay layer. In one village near Sriganganagar, some families had opted for a change over from ‘Kui’ or ‘Dhamaka’ latrine to septic tank. The effluent from septic tank was let out to surface drain. This surface drain ended in a small cess pool like tank resembling ‘johad’. The bore well adjacent to this tank showed both microbial and chemical contaminations. Therefore it is felt that this kind of changeover from Dhamaka to septic tank should be discouraged.

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Dhamaka latrines in Rajasthan, India.  
Dhamaka latrines in Rajasthan, India.  

Study about appropriateness of design, possibility of conversion to sanitary latrine and extent of groundwater pollution caused Dhamaka lat...

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