Main Street sewer construction in Biddeford, Maine, circa 1914. This and the following two photographs show construction combining a brick invert with cast-in-place concrete. Photographer: Robert Henry Gay.

Source: Used with permission of the McArthur Public Library photo collection. All rights reserved. Image 7429 of the Maine Memory Network.

Main street sewer construction in Biddeford, Maine, circa 1914. Possibly Summer Street. See above. Photographer: Robert Henry Gay.

Source: Used with permission of the McArthur Public Library photo collection. All rights reserved. Image 7442 of the Maine Memory Network.

Main street sewer construction in Biddeford, Maine, circa 1914. Close-up of oval sewer. Sewer runs from White's Wharf up Main to Alfred and up to Summer Street. See above. Photographer: Robert Henry Gay.

Source: Used with permission of the McArthur Public Library photo collection. All rights reserved. Image 7443 of the Maine Memory Network.

Circular arch and circular invert of large radius. Design used in the new sewer constructed in connection with the founding of the Union Depot buildings in Chicago, circa 1916.

Source: J. F. Springer, "Methods of Concrete Sewer Construction," Municipal Engineering, Volume LI, No. 2 (August 1916), p. 49.

A design used in New York involving a circular invert with large radius, vertical side-walls and flat slab top, circa 1915.

Source: J. F. Springer, "Methods of Concrete Sewer Construction," Municipal Engineering, Volume LI, No. 2 (August 1916), p. 49.

A section of the Mill Creek sewer, St. Louis, MO, where the sewer has a semi-circular arch, vertical side-walls and an invert which is almost flat, circa 1916.

Source: J. F. Springer, "Methods of Concrete Sewer Construction," Municipal Engineering, Volume LI, No. 2 (August 1916), p. 50.

An egg-shaped sewer laid alongside the subway construction in Seventh Avenue, Manhattan borough, New York City, of monolithic concrete. Circa 1916.

Source: J. F. Springer, "Methods of Concrete Sewer Construction," Municipal Engineering, Volume LI, No. 2 (August 1916), p. 50.

Junction of horse-shoe shaped sewer, on the left, with a circular sewer, on the right, circa 1915.

Source: J. F. Springer, "Methods of Concrete Sewer Construction," Municipal Engineering, Volume LI, No. 2 (August 1916), p. 51.

Lowering concrete pipe lined with clay liner plates into trench, 1930s.

Source: National Clay Pipe Institute.

Monolithic reinforced-concrete conduit, circa 1938.

Source: W. A. Hardenbergh, Water Supply and Purification, 1st edition (Scranton, Pennsylvania: International Textbook Company, 1938), p. 145.