Culvert Construction Dates
I am conducting a survey of the features of the Niles Canyon Railway, which as you probably know was a portion of the original Transcontinental Railroad built by the Western Pacific and Central Pacific Railroads.
Some of the culverts appear to date to the line's original construction in 1866, and feature battered coursed-ashlar sandstone headwalls and rectangular culverts. The stones are split-faced and are generally about 1' high and of varying lengths. There are other stone culverts on the line that use smaller stones with dressed faces. I have assumed that these were built later, but I have no idea how to date them.
Later culverts use clay or concrete pipe with cast-in-place concrete headwalls. The headwalls often feature a simple projecting cornice of about 2" deep by 6" tall. I am assuming that the corniced headwalls pre-date the un-corniced headwalls, but this is just a guess that the railroad would have simplified the design to save costs after determining that the rain-shedding benefit of the cornice was unwarranted on a culvert headwall.
Other culvert types include creosoted wood box culverts and corrugated steel pipe.
I am hoping to establish a range for the construction dates of these structures. I have exactly one piece of evidence that dates the construction of a wood box-culvert to 1916 (this culvert was replaced by the PLA in 2007). I believe the SPRR did not use concrete in earnest until around 1910, but I am not certain of this. I am also curious as to what decision process led to the selection of one construction technology over another when options were available. Wood would seem a poor choice at any time. Corrugated steel pipe was introduced in 1896, but I do not think the SPRR started using it until much later, and even when galvanized, they are not expected to last for 40 years.
Any thoughts, speculation, or actual fact-based knowledge would be appreciated.
Randolph R. Ruiz
150 Haight Street #501
San Francisco CA 94102