Series 6: Blueprints, circa 1897-circa 1935, inclusive; 1914-1927, bulk

The series includes blueprints for tunnels, regulators, sewer and manhole placement on streets and at railroad crossings, technical details of sewers, and other related matter. Much of the material is labeled as being either a superseded plan or as a plan having no special structure. Some specific structures included are plans for a "biological plant" in the 26th Ward and a 1907 tunnel for improving the sanitary conditions of the Gowanus Canal.

The plans are printed on cloth, folded, with pencilled descriptions on the backing.