Landfill procedure

Operating with the goal of “Realizing sanitary landfills by creating green and eco-friendly environment”, SL Corp. aims to reduce dust and stench in landfills to improve the quality of the environment; to stabilize and reduce hazards in completed landfills; to make advancement in landfill construction technology; and to pursue ecological park business.

Landfill Plan

The goal of Sudokwon Landfill is to minimize the effects of environmental pollution from the waste outputs (of 58 cities, counties and districts) of Seoul, Incheon and Gyeonggi-do through sanitary and safe waste treatment. The 1st Landfill Site started a landfill and completed its process from Feb. 10, 1992 to Oct. 30, 2000 so the 2nd Landfill Site started landfill reclamation from Oct. 13, 2000. Unlike the 1st Landfill Site, the 2nd Landfill Site operates under the Standard for Constructing Wastes Treatment Facilities in “Laws of Waste Management”, by constructing waste water treatment facilities and by implementing proactive sanitary landfill system.

Landfill Process

Waste Landfill

A) Landfill Structure: Semi-Aerobic Landfill Structure

The bottom foundation and separation distance in the slanting banks have added leachate drainage function for rapid drainage and adoptable expanding the aerobic landfill structure.

B) Landfill Method: Cell Landfill Method

The 3rd Landfill Site is divided into a total of 16 blocks, based on an 8-block plan of 400m × 200m each. This layout enables the minimization of leachate generation during the rainy season, facilitates the separation of rainwater and leachate, and allows for efficient landfill and soil covering operations. Waste spreading and compaction are carried out using different methods depending on the layer. To protect base facilities such as the drainage layer and leachate pipelines, the first layer is landfilled using the downstream method, while from the second layer onward, the bottom-up landfill method is used to increase compaction density. The exposed surface of daily landfilled waste is then covered with soil using the Cell landfill method.

C) Each layer of Landfill: Total 8 Layers, each layer height is 40m.

Waste landfill is made up of a total of 8 layers, up to 40m in depth. 1 layer of waste landfill is 5m, consisting of 4.5m of waste and 0.5m of soil covering.

Soil Covering

The soil covering helps minimize environmental pollution of surrounding area and occurrence of leachate, and limits landfill gas and enhances the operation efficiency of waste transport vehicle entry and exit and of landfill equipment.

A) Effects of Soil Covering

• Contribute to minimizing waste exposure area and reducing its stench and waste dispersion.
• Contribute to reducing occurrence of leachate in case of heavy rain.
• Contribute to the loss of pest habitat like flies and mosquitoes.
• Contribute to block landfill gas.
• Contribute to increasing operational efficiency of waste transport vehicles and landfill equipment.

B) Daily Soil Covering

15cm - 20cm of soil is covered immediately after waste disposal is completed per day. Daily soil covering is placed over the waste to prevent dispersion and to minimize stench. At the 2nd Landfill Site, daily soil covering is placed timely (within 3 - 5 hours) after waste disposal

C) Intermediate Soil Covering

According to the “Laws of Waste Management”, if waste is not disposed at the landfill for more than 7 days, 30cm or thicker intermediate cover is required. However, at the 2nd Landfill Site, an intermediate cover of 50cm thickness is placed to isolate exposure to rain, landfill gas and other goals.

D) Final Soil Covering

When a section of the landfill is finished or filled to capacity, it is permanently covered with a combination of a layer of topsoil, drainage layer, barrier layer, separation layer and gas drainage layer. The final soil covering of separation distance is implemented to prevent dispersion of landfill gas and to reduce occurrence of leachate due to rainwater infiltration when landfill is complete. The soil embankment is a generally enforced principle immediately before and after filling of landfill. The construction process is as follows: gas drainage layer, separation layer, barrier layer, drainage layer and topsoil layer.

• Gas Drainage Layer: 30cm laid after 30cm of intermediate layer is taken off
• Separation Layer: 300g/㎡ of non-woven layer laid to separate from gas drainage layer
• Barrier Layer: 45cm layer of soil over areas where coefficient of permeability is less than 1×10-6cm/sec within Sudokwon Landfill Site.
• Drainage Layer: Layer of geotextile (nonwoven 1,000g/㎡) over areas where soil covering load penetrating power is over 3.3×10-5㎡/sec.

Rainwater&Leachate Drainage

A) Rainwater Drainage Treatment

• Rapid leachate drainage plan is implemented to keep safe from formation of leachate accumulation within the layers of the landfill; maintain safety of the water in the outer banks; and minimize leachate leakage.
  • The leachate drainage system is installed in the landfill infrastructure to improve the permeability of the intermediary soil covering. Prior to soil covering, about 20cm of intermediary soil covering is abstracted and used as daily soil covering
  • Rapid leachate drainage is made possible by pilfering all the soil covering beside the internal road just prior to filling the landfill



• In order to minimize occurrence of leachate gas, the landfill is divided in to 300m x 300m blocks. These blocks are re-divided into smaller 150m x 150m mini blacks for landfill purposes.
  • The accumulation layer is reduced by utilizing the vertical drainage wells and vertical gas collection wells.
  • The result of estimating leachate level in the landfill layer is that the maximum level is 11.8m and the average level is 8.49m when an 8 stage landfill is completed. The current leachate level measured with a vertical drainage well in blocks where layers of wastes (2 - 3 stages) are buried is within 20cm or lower level from ground, which is revealing that the leachate drainage is currently functioning very well.
• Key Facilities for Leachate Drainage
  • Vertical Drainage Well: 75 Stations (HDPE Pipe D1200 - D1400)
  • Ground Leachate Drainage Layer: T=60cm crushed stone aggregate layer
  • Ground Leachate Drainage Pipe (Area 1): Pump (HDPE Pipe D300: 7,384m)
  • Internal Leachate Drainage Pipe (HDPE Pipe D400: 7,200m)
  • Leachate Pump Well: Main Pump Well 4 Stations, Relay Pump Well 10 Stations

Landfill Gas Treatment

Landfill gas generated during waste disposal at landfill is installed in horizontal and vertical gas collection pipes, and all amount of landfill gas captured by the power plants (9.88MW in operation, 50MW at December 2006 completion) is then converted from gas to energy in a resource recycling system.

A) Estimated Amount of Gas Generated

• At completion of Landfill Site, the amount of landfill gas generated is estimated at 900㎥ per minute. However, currently at the 3rd Landfill Site. A portion is sent to the power plant and remainder is sent to incineration treatment. The key components of landfill gas are CH4 at 50 - 60%, CO2at 40 - 50% and others. Energy converted is approximately 4,800kcal/㎥, about 46% of LNG.

B) Landfill Gas Collection Facility Status (Total)

• Vertical Collection Pipe
  • Installation Station: 239 Stations
  • Installation Intervals: In equilateral triangular formation at 60m intervals
  • Gas Collection Pipe Dimension: HDPE perforated drainpipe D200/D250mm
  • Rubble Dimension: 25 - 40mm
• Transfer Pipe Lines
  • 1 separate pipeline installed of each collection well (5% or more longitudinal slope)
  • Transfer Pipe Dimension: HDPE imperforated drainpipe D100mm
• External Header Pipe (D400 - D700): L=15.2km
  • Landfill gas is used by separating into 4 districts of vertical collection wells.
  • Stage 2 (Section 2, Section 1 pre-installation), Installation of stage 3 external embankment area
  • The external landfill gas header pipe requires underground construction in the external embankment to minimize reduction in strength resulting from HDPE pipe deterioration, when the header pipe is exposed to drastic changes in temperature and UV rays for extended periods
• Temporary Gas Incinerator: 42