Delineation of leachate plumes at two waste disposal sites, Selangor

Abstract

This paper discusses the results of two-dimensional (2D) direct current resistivity imaging surveys, which were conducted to identify and delineate the extent of contaminated land and leachate plumes as well as to assess the capability of the 2D resistivity as a pre-characterization tool for tracing the properties of disposed waste and its severity underneath capped landfill sites. The study was confined to two different municipal waste disposal sites, namely Ampar Tenang open- tipping site and Bukit Kemuning capped landfill. There are a total of eleven 2D- resistivity survey lines. Depending on site specification, the lines were distributed as 2 and 9 lines at the Bukit Kemuning and Ampar Tenang sites, respectively. In this study, the 2D resistivity imaging was carried out using SAS1000 & SAS4000 resistivity meters and ABEM LUND automatic electrode selector system. The objectives of the study were to delineate the locations of the contaminated subsoil and groundwater in terms of leachate plumes. Generally, the results of measured resistivity values obtained from the two sites defined the contaminated leachate plumes as electrically conductive anomalies of relatively low resistivity value of less than 10 Ωm. In addition, the observed resistivity values of 2D image profile, which were measured at the top of an excavated part of the Bukit Kemuning landfill, were found to be in a good agreement with the actual profile as regards to characteristics, degree of decomposition, depth and thickness of the disposed wastes, as well as thicknesses of both the cap and liner of the landfill. This proves the efficiency of using the 2D direct current resistivity technique in waste disposal site investigations. Abstrak: Kertas kerja ini membincangkan keputusan survei keberintangan geoelektrik dua dimensa yang dijalankan untuk mengenal pasti and menentukan tahap pencemaran tanah serta larut lesap disamping menilai keberkesanan kaedah keberintangan 2-D sebagai alat pencirian awal untuk mengkaji sifat sisa buangan serta tahap pencemarannya dibawah permukaan tapak buangan tertutup. Kajian ini tertumpu hanya kepada dua tapak buangan iaitu Tapak buangan sampah terbuka Ampar Tenang dan tapak buangan sampah tertutup Bukit Kemuning. Sebanyak 12 garis survei keberintangan telah dibuat iaitu dua di Bukit Kemuning dan 9 garis di Ampar Tenang. Dalam kajian ini, survei keberintangan telah dilakukan dengan menggunakan meter keberintangan SAS1000 dan SAS4000 dan sistem pemilih elektrod LUND ABEM. Matlamat kajian telah dapat dicapai dalam menentukan kedudukan tanah dan air bawah tanah yang tercemar. Secara umumnya daripada pengukuran keberintangan didua tapak pembuangan sampah, di dapati nilai keberintangan larut lesap menunjukan anomali kekonduksian elektrik dengan nilai keberintangan yang relatif rendah daripada 10 Ωm. Selain itu profil imej keberintangan geoelektrik 2-D yang diukur di tapak pembuangan sisa Bukit Kemuning didapati bersesuaian dengan profil sebenar dari aspek pencirian, darjah penguraian, kedalaman dan ketebalan sisa buangan serta ketebalan tanah penutup dan lain-lain maklumat operasi lampau tapak tersebut. In dengan sendirinya telah memboktikan keberkesanan teknik keberintangan geoelektrik 2-D untuk penyiasatan tapak pembuangan sampah.