POTENTIAL RISK
There are potential risks associated with developments close to a landfill site due to sub-surface migration of landfill gas. Under Annex 7 of the EIAO-TM, an evaluation of the potential risk posed by landfill gas is required for and development which is proposed within 250m of the edge of waste, know as landfill Consultation Zone.
As the Extension Site falls within the SENT Landfill Consultation Zone, a Qualitative Landfill Gas Hazards Assessment (QLFGHA) will be required to assess the potential risk due to landfill has migration from the SENT Landfill to the Extension.
The QLFGHA assessment shows that landfill gas risk posed by the SENT Landfill and the Extension is medium to high within the Extension Site boundary during both the construction and operation phases. Whereas the risk posed by the Extension to the adjacent developments ranges from very low to low depending on the nature and location of the adjacent developments.
Qualitative Assessment of Landfill Gas Hazard Associated with the Extension
| Source | Pathway | Pathway | Qualitative Risk |
SENT landfill – potential for gas generation over time, but comprehensive and proven mitigation installed (category: medium) |
Surface soil, reclamation fill materials, part of the work site piggyback onto the waste slope of SENT Landfill and the existing infrastructure area with potential direct anthropogenic conducts, distance to waste boundary <50m (category: very short/direct) |
Target 1 (Construction Site of the Extension) – Open cut construction method, may have deep excavation, working in confined space by trained workers. (category: medium sensitivity target) |
Medium |
SENT landfill – potential for gas generation over time, but comprehensive and proven mitigation installed SENT landfill – potential for gas generation over time, comprehensive and proven mitigation to be installed (category: medium) |
Surface soil, reclamation fill materials, part of the tipping face piggyback onto the waste slope of SENT Landfill and the existing infrastructure area with potential direct anthropogenic conducts, distance to waste boundary <50m (category: very short/direct) |
Target 2 (Tipping face of the Extension) – waste tipping in the open air, absence of confined space, access by drivers/operators of waste collection vehicles who may not have knowledge on landfill gas hazards. (category: medium sensitivity) |
Medium |
The Extension – potential for gas generation over time, comprehensive and proven mitigation to be installed (category: medium) |
Surface soil, reclamation fill materials, potential direct anthropogenic conducts, distance to waste boundary <50m (category: very short/direct) |
Target 3 (Infrastructure are of the Extension) – Ground level offices and pump rooms of unrestricted staff access, underground confined spaces with restricted access, some with source of ignition. (category: medium to high sensitivity) |
Medium to High |
Surface soil, reclamation fill materials, no direct anthropogenic conducts • Distance to waste boundary <50 (category: very short/direct)• Distance to waste boundary between 50m to 100m (category: moderate short/direct) • Distance to waste boundary >100m (category: long/indirect) |
Target 3 (Infrastructure are of the Extension) – Ground level offices and pump rooms of unrestricted staff access, underground confined spaces with restricted access, some with source of ignition. (category: medium to high sensitivity) |
Very Low to Low |