«D’Undra» (the lower bisse) was for the inhabitants of the municipality Ausserberg of high importance, which explains also why people spoke formerly of «dr’ Wasserleita» (the water pipe), so each resident knew, which one of the Suone was meant. «D’Undra» was first documented in 1377, and served until 1939 as well as for drinking water supply for the residents. Therefore the bisse had to be maintained even in harsh winter months till up to the catchement of the wild river Baltschieder in the rugged valley Baltschiedertal. The “Sander” was responsible for these risky works. He was hired by the municipality for the maintenance of the bisse. His name derives from one of his main activities, the removal of sand.