Error Involved in Estimation of Site Sensitivity Index (SSI) for Land filling of Municipal Solid Waste

An environmental Index known as Site Sensitivity Index (SSI) was developed by Central Pollution Control Board (CPCB) in association with National Environmental Engineering Research Institute (NEERI), India to quantify and compare the sensitivity of different sanitary landfill sites on the basis of accessibility, receptor, environmental, socio-economic, waste management practices, climatological and geological criteria. The SSI integrates parametric effects of all attributes about suitability of site for landfilling and generates a single number expressing the sensitivity of the site for municipal solid waste disposal. The index is based on the impact of 32 attributes and their relative significance as assessed by a group of experts. It therefore necessitates ascertaining all 32 attributes for the selected sites and then compare their respective suitability based on SSI. In case, data related with any or a few attribute(s) are not available, comparing and finalization of landfill site is not possible using this approach. This paper attempts to estimate and report the error introduced in the value of SSI due to unavailability of such required data. An attempt has been made to classify attributes into high, medium and low weight categories based upon their significance in finding the SSI. The SSIs have been calculated for two sites of Varanasi, one site of Bangalore and one arbitrarily selected most sensitive site. The analysis of this study indicates that the error may be high (>10%) if more than two data of high weight category are not available, whereas a marginal error (5–10%) is incurred ifup to 10 parameters having low or middle weights are not available. A software program has been developed in Visual Basic to calculate SSI based on available data and guide the user about the importance of the missing attributes.