According to the scientific exploration and partial excavation, much metal is present in the underground palace and it also features a very good drainage system. Sima Qian’s text indicates that during its construction the tomb may have reached groundwater, and the water table is estimated to be at a depth of 30 meters. An underground dam and drainage system was discovered in 2000 and the tomb appeared not to have been flooded by the groundwater.[14] Anomalously high levels of mercury in the area of the tomb mound were found.[15] This gives credence to the Sima Qian’s account that mercury was used to simulate waterways and the seas in the Mausoleum of the First Qin Emperor. However, some scholars believe that if the underground palace is excavated, the mercury will quickly volatilize.