Excavation

Excavation is the process by which soil or rock is removed in order to reach the required line and level. If the overall quantities of earthworks material for the scheme are in balance, the material resulting from such excavation will be employed as engineering fill for embankment construction. When the material is unacceptable, or the overall earthworks quantities are in deficit, acceptable fill material may be excavated from specially designated areas either close to the route corridor or from a greater distance, often termed ‘borrow pits’. Even when the earthworks are in balance and the material is predominantly acceptable, on some earthworks contracts it may be more cost effective to excavate borrow pits locally in order to meet the overall construction programme, as haul distances are prohibitive or parts of the scheme are inaccessible. The latter is usually the case where the route corridor is traversed by major rivers, roads or railways, where additional local excavation is more cost effective when compared to the cost and programme time required to construct a temporary crossing.