By contrast, several tanks found on the site did not show a vein, so were abandoned. The tank shown at right occurs not far from the north opencast and was probably intended to find the limits of the deposit located in the adjacent opencast (Tank A in the schematic diagram below). It clearly didn't find the vein, and was thus abandoned. The water supply may have been obtained from a small leat run from a stream up the main Cothi valley before the much larger aqueduct was constructed.