Abstract

Little work has been published that compares actual yields from sand and gravel excavations with reserve calculations based on drilling. To do so sites must meet criteria of clear identification; in-house site investigation; full drilling; and properly recorded production. There are several potential sources of difference between calculated and actual figures.

Twenty-six sites were investigated, yielding from 63.64% to 152.400f calculated reserves. The mean of the results is 104.37%, the median 104.31% and the mode group 107.0–109%. This analysis confirms that, in a majority of cases, the measurement of reserves using conventional techniques is accurately carried out. A variance of ± 5 0s suggested as the geologist's target.