GEOLOGICAL SOCIETY OF THE PHILIPPINES
GEOLOGICAL AND GEOPHYSICAL SURVEY ON THE PROPOSED SOLID WASTE DISPOSAL SITE OF LASAM, CAGAYAN
Rey A. Taylan, Ronald Philip B. Ramirez, Ronald Jose T. Zipagan and Albert Johann B. Jacildo
The rapid growth in population and the increased economic activity has considerably increased solid waste generation in the Municipality of Lasam. Incidence of irresponsible garbage dumping along Zinundungan River is already a cause for alarm as this environmentally critical body of water traverses the Poblacion area passing through the back of the Municipal Public Market. Pollution of this river will also adversely affect the rich fishing ground in the vicinity of Magapit Lallo Cagayan where this river joins the the main stream – the Cagayan River. This part of the river is identified as the spawning/breeding ground of the endangered “Ludong – a rare fish specie noted for its seasonal occurrence and good taste whose price of PhP 1500 – PhP 2000 per kilo made it more famous in the Cagayan Valley Region.
Environmental awareness of the residents and the Local Government (LGU) of Lasam coupled with insufficient Solid Waste Disposal Sites (SWDS) to serve the town prompted them to prioritize technical evaluation of initially identified potential disposal sites within the 75 hectares of public land in Barangay Minanga Norte. This paved the way for the LGU of Lasam to enter into a Memorandum of Agreement with the Mines and Geosciences Bureau in the conduct of a geological and Georesistivity survey at the proposed SWDS.
Geological mapping confirmed earlier findings that rocks underlying the area consist of tuffaceous sedimentary beds principally sandstone, siltstone and shale. However, the mapped shale interbeds within the siltstone and sandstone units represents semi-impervious layer that will help retard further downward percolation of leachate. These attributes, notwithstanding the wide buffer zones and ridge crests serving as natural boundaries to contain the solid waste, only indicate a favorable geo-environment that could lessen engineering intervention problems associated with a poorly selected SWDS.
The geo-resistivity survey on the other hand, suggested a thick deposit of sedimentary beds mostly fine to medium grained sediments. Geo-resistivity survey results further indicate that the groundwater depth at the time of the survey occur at a depth of 34m, with resistivity values suggesting principally mudstone, shale and siltstone.
The objective of the survey is to validate the suitability of the proposed site for development into a SWDS using the Presidential Task Force on Waste Management Site Screening Criteria. The factors considered in the assessment of the site were focused on the accessibility, topography, surface and groundwater condition and availability of soil cover.
The activity also endeavors to recommend measures to mitigate the possible adverse effect of SWDS to the environment, particularly surface and groundwater as well as on the residents living in the adjacent barangays. Results of the survey suggest that the area could host a SWDS provided that the conferred recommendations are strictly followed.
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Geological Society of the Philippines
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