|Title||Establishment of Eco Park|
1. The Waste Dumping Site Stabilization Work
As various wastes were piled up in this site unsanitarily for 15 years, the rotted wastes generated leachate, odor and harmful gas, and thus contaminating the Han river and atmosphere, while deteriorating the surrounding ecology. The goal of the stabilization work was to restore the environment, while keeping the huge garbage heaps as it is. In other words, the goal was to identify source of environmental pollution in the dumping site as it is and to restore the abandoned land of the Nanjido into an environment-friendly park. The stabilization work included installation of the impermeable wall in order to prevent leakage of leachate from dumping site, the treatment of leachate, the collection and treatment of landfill gas, slope stabilization to manage side of waste heaps, and the construction of grassland after covering the top of landfill with soil. A shielding wall was installed to prevent leakage of leachate from sides and bottom part of the dumping site. The leachate were collected and sent to the leachate treatment facility for purification. Sheet pile and slurry walls were installed as measures to prevent leakage of leachate and pollution.
Also, 31 leachate collection wells were installed on the inside of shielding wall to collect the planned amount of leachate (1,860 tons/day). Collected leachate was transported to the leachate treatment facility. In order to remove the foul odors and dangers of explosion due to landfill gas, the upper part of the dumping site was covered with a blocking layer consisting of soil and shielding sheet. The 106 landfill gas collection wells were installed on the upper part and sides of the landfill to extract landfill gas from waste heaps, and collected landfill gas was transferred to the treatment facility through a 14,050m long gas pipe. Landfill gas was used as fuel of regional heating system and remaining gas was incinerated in the gas stack. The upper part of the landfill had a 4% or higher degree slope to ensure rainwater runoff. The upper lot of Landfill 1 and landfill 2 were divided into 10 blocks to help rainwater runoff and site rearrangement was planed accordingly. The upper parts of the landfills were covered with soil to restrict emission of landfill gas and also with a blocking layer (HDPE) to prevent rainwater penetration and underground water pollution by leachate later. On the uppermost part, a vegetation layer (30cm) and surface layer (30cm) was constructed to help vegetation restoration without rainwater permeation. Side-gutter was installed at the slope of landfill to collect and drain of surface water ran off from the upper part. Rainwater pipes (plume pipes, PE pipes, slope waterway, hume pipes, etc) were installed to drain rainwater from the landfill slopes and maintenance roads.
Slope collapse and scour protection were prevented by installing slope safety devices, such as GEO CELL, slope collection and drainage pipes, reinforced retaining walls, etc. It was necessary to monitor leachate leaks, landfill gas emissions, contamination level, stability of landfill slope, subsidence behavior analysis in final cover layer of upper part, and activity destruction. In order to achieve this purpose, the 66 surface settlement plates were installed on the upper part of the landfill. And other monitoring equipments were installed as follows; 21 inclinometers on upper parts and sides of the landfill, 17 pore water-pressure gauge, 62 underground water level gauges inside and outside of leachate impermeable wal, 6 underground water contamination monitoring wells outside of the landfill, and 6 landfill gas monitoring wells inside and outside of the leachate impermeable wall. Furthermore, installation of landfill gas collection wells and landfill gas discharge wells was carried out after diagnosis on environmental status of ground level beside two waste heaps. ##3D_LAYER##In particular, collected landfill gas has been burned in a gas stack to remove foul odors and harmful substances.##3D_TEXT:In detail information about Nanjido waste dump site stabilization work is available from “Nanjido waste dump site stabilization work white book”(Seoul City Government Construction Safety Department, 2003). The white book includes waste landfill history, stabilization work designs, stabilization work procedures, stabilization work participants, and so on.##3D_LAYER_END##
Source: Seoul City Government Construction Safety Department