Rehabilitation of Saravan dumpsite in Rasht, Iran: geotechnical characterization of municipal solid waste

Accepting and landfilling municipal solid waste, MSW, in non-engineered conditions since 1984, has made the Saravan dumpsite as one of the biggest environmental concerns in northern Iran. Due to a lack of any type of coverage, precipitation is infiltrated into the waste piles, increasing the amount of leachate production. The average annual discharge rate of leachate is estimated to be 7 L per second, which all are discharged to the downstream rivers and creeks. To reduce the produced leachate, the construction of soil cover, leachate drainage system, gas collection systems and other requirements were planned. To construct the soil cover, stability analyses to reach a safe side slope were necessary; therefore, geotechnical evaluation of MSW was vital. MSW samples with different age and conditions were collected, and geotechnical tests such as moisture and organic content, composition, grain size distribution and direct shear tests were performed. Back-calculation analyses performed on unstable slopes at the site resulted in situ shear strength of MSW, comparable with those achieved in laboratory tests. Results showed that the soil-like fraction, moisture and organic content decrease with depth and age, leading to an increase in foil-like contents and reduction in shear strength of MSW. Direct shear tests with different shearing rates showed that the MSW in Saravan dumpsite exhibits higher strength at higher rates of shearing which means a higher safety factor for slopes during seismic condition could be expected.