Anytime native rock must be removed from below grade for construction, hopefully this work was anticipated and accounted for as it is a costly and resource intensive construction activity. Underground rock removal is typically a contentious situation, particularly if construction contracts or documents don’t accurately address how the rock removal will be handled or paid for, leaving the engineer, project owner, and contractor to hash things out. Local engineers and contractors however will typically be aware of the different geographical regions where rock has been encountered in the past. In these cases a monetary contingency is often set aside for rock excavation. Otherwise, the most common way to foresee underground rock prior to construction is by way of a geotechnical engineer performing soil borings at predetermined locations. The geotechnical engineers report will typically include profiles designating the areas that were bored and the depths at which the augur began to refuse its descent any further in the ground. These reports also typically include the type of bedrock encountered.
Some rock types are less resource intensive to remove than others, epsecially if they are expected to simply be fractured/loose rock not requiring breaker and chipper excavator attachments. As extensive as these reports may seem, it’s next to impossible to be able to foresee where all the rock will exist. The report can indicate typical conditions, but is only as accurate the point locations it identifies.
Typically at least an excavator and hydraulic hammer attachment is required for rock removal. One operator for the excavator with the hammer, one operator for the excavator that removes the material from the trench, and an optional operator if a rubber loader is desired to move large amounts of material longer distances more efficiently. The laborer provides visual assistance to the operators if needed.
As rock is typically a massive structure, it will need to be broken first then removed and loaded onto trucks for site removal. As many rock formations requiring removal are unforeseen, significant time and money can be added to a project and its schedule. Sometimes rock encountered during construction can be left in place if they do not conflict with other construction items line closely underneath future pavements or buildings.