Wu-Shan-Tau Dam is operated for more than 70 years since 1920. Till now, according to four safety evaluation reports, improving repair is not necessary in the short time. However, for the need to investigate the existence of Liao-Chia fault and overall improvement for the co-operating with Zeng-Wen reservoir, an overall safety study is hold.
Non-destructive geophysical testing methods were proceed by NHMRC in order to assist the study of land slide in the slope over dam. 700 m ERT survey lines and 720 m MASW survey lines were used to investigate the sub-ground characterization. According to both the results of ERT and MASW, there were weak soils existing in the elev. 40m and 60m. The existence of the weak soils may be one of the reason causing landslide after raining.