Killycronaghan Landfill, Killycronaghan, Smithborough, County Monaghan

Section 22 register number: S22-02296

Grid Reference: 256923 E and 328618 N

The site covers an area of 9 ha.

Quantity of waste at facility: Approximately 147,784 tonnes. 106,000 m3

Killycronaghan historic landfill is not owned by Monaghan County Council (landowner is a local farmer)

The site is located almost 7km north-east of Clones on privately owned land and covers an area of 9ha.

The site is surrounded by agricultural lands and is bounded by the Kilgormly river to the
south-east, east and north, and by the Magheramey river to the north-west.

There are poultry houses adjacent to the north-east of the site and three dwellings within 500m of the site boundary, the nearest of which is located 230m from the north-eastern boundary.

The landfill was operational from 1970 to circa 1984 and comprises of approximately 147,784 tonnes of municipal solid waste (MSW).

An appropriate assessment of the activity was carried out as it was determined that there is a hydrological connection between the closed landfill and one SPA site and two SAC sites, the nearest of which is located 16.2km south-west of the closed landfill.

Post remedial works, Monaghan County Council intend to use the site for low intensity grazing.

The risk assessment has categorised the site as High risk (Class A) with high scoring pollutant linkages identified as:
– Leachate migration into groundwater, and, via groundwater, to surface waterbodies;
– Migration of leachate, via groundwater, to Surface Water Body Protected Areas;
– Migration of leachate, via surface water drainage/runoff, to surface water bodies;
– Human health exposure pathway of off-site lateral migration of landfill gas into nearby buildings; and
– Vertical landfill gas migration.

The Technical Commitee notes that the Tier 1 and Tier 2 assessment determined the overall risk score for the closed landfill as high due partly to the risk of migration of landfill gas into the adjacent buildings i.e. the poultry houses, located to the north east, and the farm buildings, situated to the east of the site. The TC further notes that modelling showed that landfill gas will continue to be generated for several years although in minimal quantities. As landfill gas monitoring is carried out in the existing groundwater monitoring boreholes, the TC considers it prudent that monitoring is carried out in the additional boreholes to be installed for groundwater monitoring as required under condition 3.1(i).

The TC notes the high-risk classification of the site is partially due to the risk to the groundwater aquifer from the migration of leachate from the waste body. The TC also notes that the site investigations determined that the groundwater table likely transects the waste body and that groundwater monitoring results show that leachate is having a deleterious effect on groundwater quality.

The site investigations carried out as part of Tier 1, 2 and 3 assessments established the following facts:
– the closed landfill has been capped with soil but the cap allows rainfall to infiltrate into the waste body;
– the landfill is unlined;
– there is migration of landfill leachate into groundwater;
– the landfill is contributing to a deterioration in groundwater quality;
– the waste material is deposited in a single infill area tending west to east in the centre of the site and between approximately 150m in length and 130m in width;
– the average thickness of the waste body is 5m and there is a layer of leachate contaminated sands and gravels below waste;
– the groundwater table appears to be intersecting the waste body;
– leachate seepage was observed near the centre of the site;
– landfill gas is being generated;
– there are two wells present on-site. The Council believes these to be old methane wells;

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