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However, there may be situations where, due to technical issues, twin pit latrine with shallow pits is not feasible. In such cases, other technological options will have to be considered. Keeping these facts in view, Dhamaka toilet design will have to be evaluated. In this evaluation, the hydrogeological factors will be very important. Further it would be necessary to decide whether alternative designs are possible. If that is not possible, what modifications would be necessary to convert it to a sanitary toilet? 9. Geohydrological data for soil As seen above, the geological characteristics of soil strata would be an important criteria for the suitability of pit latrine, of any design. Aquifers transmit water, as well as store water. This is affected by two factors i. porosity ii. permeability Unconsolidated granular sediments in the soil such as sands, silt, clay etc. contain pore space between the grains. The proportion of pore spaces to the total volume of sediments is known as porosity. In sand, porosity can extend to above 30 %. The water transmitting characteristic is known as its permeability. Well connected pore spaces between the grains of sand and gravel increase their permeability. However, clays which have high porosity, but very little connection between the pores because of very small grains and compactness, transmit water very poorly, resulting into very low permeability.

Grain sizes of a range of sediment types from ‘Guidelines for Assessing the Risk to Groundwater from Onsite sanitation’ DFID 2001. Naturally, in soils with low permeability, the travel time for contaminations will increase. The greater the travel tie the greater the opportunity for contaminant attenuation. 9

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...