Board of Water Supply. City Water Tunnel No. 2. Patrick McGovern, Inc., contractor. This special wooden form was assembled to construct the concrete lining where a 21-foot diameter shaft meets City Water Tunnel No. 2. It was built in the contractor's yard and designed so it could be taken apart in sections for transportation. Here the ribs are in place, to later be completely covered with wooden strips that were steamed and bent to the required curvature. This photograph is a view taken during the construction and shows only the circular and elliptical ribs which will later be completely covered with wooden lagging. March 10, 1932.