Board of Water Supply. City Water Tunnel No. 1. Geological test borings on the corner of Madison Street and Clinton Street. Sheds like the one on the right popped up on the Lower East Side in 1910, housing drill rigs that collected core samples of rock from hundreds of feet under the busy sidewalks. These geological investigations were essential in planning the path of City Water Tunnel No. 1. March 21, 1910.