The distribution, type, popularity, size and availability of river-run gravel and crushed stone for use in land drainage systems and their suitability for mineral soils in Ireland

The performance of land drainage systems installed in mineral soils in Ireland is highly variable, and is dependent on, amongst other factors, the quality and suitability of the aggregate used. In Ireland, aggregate for land drainage systems is usually river-run gravel and crushed stone. This study classified the distribution, type, popularity, size and availability of aggregates for land drainage systems throughout Ireland and quantified their suitability for use in mineral soils. Eighty-six quarries were surveyed. Limestone and river-run gravel (80% of lithologies) are widespread throughout the country. The quarry aggregate sizes (“Q sizes”), reported by the quarries as either a single size, that is, “50 mm”, or a graded size, that is, 20–40 mm, were variable, changed across lithology and region and were, in most cases, larger than what is currently recommended. A particle size distribution analysis of 74 samples from 62 quarries showed that individual Q sizes increased in variability with increasing aggregate size. In some regions, the aggregate sold does not meet current national regulations, which specify an aggregate size ranging from 10 to 40 mm. The suitability of these aggregates for drainage in five soils of different textures was compared using three established design criteria. It was found that the aggregate in use is too large for heavy soil textures and is therefore unsuitable as drainage envelope material. Guidance for contractors, farmers and quarry owners will be required, and investment may be needed by quarries to produce aggregate that satisfies design criteria. An aggregate size, based on one or a combination of established aggregate design criteria, where an analysis of the soil texture is conducted and an appropriate aggregate is chosen based off its 15% passing size, is required.