DESIGN AND DESIGN SPECIFICATIONS FOR SANITARY LANDFILLS

The basic steps in designing SLFs are the following:

  1. Establishing of the site boundary and topo-mapping at 1:500 scale with 1 meter contour interval
    1. The produced map should also indicate the land uses/owners of adjacent properties. With an NTP issued to the surveyor, this work should be completed within a month.
  1. Generation and analysis of basic design data to include
    a. WACS analysis and projections on the residual wastes
    b. Permeability (hydraulic conductivity) of the natural soil-on site.
    c. Borehole to determine soil formation
    d. Hydrometeorological studies on rainfall, flood occurrence, groundwater, and other related parameters of significance at the site
    e. Access to the site
    f. After use of the landfill site
  1. Drafting of the Site Development Plan

There are three major events in a conventional landfill operation which should be considered in site development planning- subsidence, gas generation, and leachate generation.

The other consideration in site development planning is the functionality of the landfill facility components such as the access gates, cells, internal road network for efficient flow of traffic within the facility, maintenance and operations buildings/equipment such as the guardhouse/weigh bridge, admin and maintenance building, utilities—water, electricity and communication, and the possible inclusions of SWM related facilities such as MRF with or without composting, and the THW facility. And majorly, the size requirement for the landfill area.

PERMITTING

The permits required towards establishing SLFs are as follows

1. Letter of Endorsement

    1. Once the site is suitable, the LGU will request a LOE from the DENR for them to proceed with the next steps. This will open the gates for FS and later on the preparation of the OEE documents. The FS will have the general design of the SLF facility and this will be subjected to impact assessment
  1. ECC
    1. Is not technically a permit but a planning tool. Using a checklist the IEE document could be drafted by an in-house group (TWG) or with the help of a service provider. The IEE document is submitted to the Regional EMB for review and evaluation. An ECC is issued with conditionalities once the document is found to merit such an issuance. Else, the document will literate between the prepared and EMB until all requirements are satisfied. With the ECC the project can now proceed at full speed.
  2. The other permits are issued by the LGU—building permits for the construction of the facility, sanitation permits, among others.
  3. With the operation of the leachate collection and treatment component, the SLF operator needs to get a DISCHARGE PERMIT for the discharge of the treated leachate to a receiving body of water or land.

CONSTRUCTION PHASE

There are generally 3 phases of constructing a SLF Facility:

Phase 1: MOBILIZATION

  1. With the contract, permits, and NTP, the contractor mobilizes its resources for the construction of the SLF
  2. Temporary construction camp is set-up inside the SLF site. The location of the camp should be strategically located for ease of transport of materials and workers. It should be located in a place which is not designated for the construction of any SLF components. The camp should be able to accommodate the full complement of key construction personnel, materials, and equipment.
  3. To maintain sanitation and prevent localized environmental degradation. Sanitary facilities will also be temporarily established.
  4. Basic utilities such as water supply, electric power and communications should also be set-up.

Phase 2: CONSTRUCTION AND CONSTRUCTION SUPERVISION

Based on the site development plan, design specifications and approved timetable, the contractor will commence with the actual construction of the facility with the following proposed sequence:

  1. Establishment of control gate and perimeter fence. Together with this activity is the delineation and initial planting of the vegetative buffer strip.
  2. Land grading and construction of internal road network from the gate of the remotest facility component. Land grading for the landfill cell
  3. Simultaneous or phase construction of facility components
    1. Landfill cells
    2. Leachate collection, storage, and treatment
    3. Storm drainage
    4. Guard house
    5. Admin and Maintenance building
    6. Water supply system
    7. Electric power system

      Phase 3: DEMOBILIZATION

Once the facility is completed, demobilization commences with the demolition of temporary structures and facilities. Clean-up of the site of any debris and proposer closure of temporary sanitary facilities and utilities like pit toilets and dug wells.

OPERATION AND MAINTENANCE

The following summarizes the operations of SLFs:

A. SLF Cell Operation

  1. Delivery inspection and data logging at the entrance gate. Access to the SLF facility requires the following inspection and validation:
    1. The accreditation of the delivery vehicle and the delivery crew.
    2. The source. Volume/weight of the wastes should be recorded.
    3. The quality of the waste is inspected
    4. All other pertinent data on delivery are properly logged
  1. Delivery of the wastes to the working face of the SLF is closely coordinated and directed by a SLF spotter. Proper sequencing of delivery vehicles that are queuing for delivery is a must to avoid accidents and traffic jams. The location of the working face is determined by the road access to the cell. The working face could start at the toe of the cell or at the heel.
  1. After delivery, the vehicles are cleaned at the wash bay before leaving the facility.

    B. Leachate Collection, Conveyance, and Storage/Treatment
  1. A network of perforated pipes laid at the bottom of the cell collects the leachate and convey this gravity to the leachate collection and storage tank which is located at the toe of the landfill. The tank is provided with a submersible pump operated on an auto cycle or manually to recirculate the leachate to the cell or the leachate is used to water plants in and around the SLF. The accumulated solids at the bottom of the tank is pumped out periodically using a sludge pump. Before the effluent out fall, a simple wooden flashboard with concrete guide is places to trap floating solids which are removed manually and disposed of properly of the SLF cell.
  2. The tank provides some treatment like settling of heavy carryover particles, exposure to the UV Radiation from the Sun and stabilization of trace organizes by microorganisms growing in the wastewater.
  1. Emissions Control
  1. To mitigate further emissions, the leachate collection pipes can be extended up to the top of the side slopes of the cell with an elbow-cap with screen. This will make the SLF semi-aerobic and this will allow partial treatment of the leachate while it is still in the cell.

MONITORING AND EVALUATION

A. SUBSIDENCE

This should be monitored periodically to avoid ponding in some filled sections of the facility. Ponding will induce more rainfall infiltrating and percolating into the waste pile hence leachate generation is increased. Ponded sections could also become breeding places for pathogenic microorganisms. The softening of the cell section with ponded water could start the breaching of the compacted soil cover.

B. GROUNDWATER AND SURFACE WATER MONITORING

Monitoring of the quality of the groundwater from a monitoring well downstream should be dine on a quarterly basis while the treated leachate and the receiving body of water should be monitored for pH and TSS on a weekly basis. A combination of pH, TDS, and TSS electronic analyzer could be used for this activity

C. SLOPE STABILITY

The side slopes of the rising mound of covered waste in SLF should be monitored for stability. Any damage should be repaired immediately to reduce danger of collapse or severe erosion