Water resources programs benefit from sewer history
Jon C. Schladweiler, P.E.
Historian, Arizona Water and Pollution Control Association
Trustee, Public Works Historical Society
Over the past 5,500 years, as the evolutionary development of our present-day sanitary sewers progressed, there were indeed good times and bad; high points and (very) low ones. Some would liken the "pattern" of those changes over time to a "biorhythm"; more specifically:
Open-topped drain/sewer in the ancient Roman City of Priene (modern-day Turkey) (Photo by Paul Brians, Washington State University, World Civilizations Image Repository)
Historians believe that the first sewers were constructed by the occupants of Mohenjo-daro, a city of upwards of 30,000 people in the Indus River Valley (in modern-day Pakistan) in 3,500 BCE. Their primary need was to get stormwater away from their earthen buildings. They created a system of open-topped (at the surface level) rectangular or square cross-sectioned drains to convey stormwater runoff away from their homes. On day "one" those drains (sewers) were storm sewers. On day "two" (and thereafter) they were combined sewers—as virtually all other wastes (human, animal and garbage) were thrown into the street, awaiting the next storm event to flush them away. Therein lie the roots of our modern-day sewers.
Soon, the sewers were being covered or buried. Even 3,000 years or more before the Common Era, it was realized that the accumulation of grit in the sewer would cause problems and that people would put almost anything they could down into the sewers; thus, precipitating the need to have a way to access those sewers for maintenance. Certain of the stones used to cover the original open-topped sewers were made larger and more removable than the others. Therein lie the roots of our present-day manholes.
During those same times, the City/State of Babylon flourished—near Baghdad, in present-day Iraq. Babylon is given credit as the birthplace of "pipe." The pipe was made of clay/terra cotta, with bell and spigot joints (no seals/gaskets). It was initially used primarily for the conveyance of water.
The involved biorhythm continued over the next 3,000 years in an upward sweep. The "concept" of building sewers spread (by traders, travelers, etc.) throughout the Middle East and on into Europe and Egypt.
A peak in the biorhythm is reached: the City of Rome and the Roman Empire. The City of Rome developed an intensive physical infrastructure of roads, buildings, aqueducts and sewers during the times of its rise from a "marsh" in 600 BCE to its fall in approximately 350 CE. The Cloaca Maxima ("main drain") sewer was initially started in 550 BCE to drain the marshy area on which the Forum was eventually built.
The main drain's initial purpose was to drain a marsh on day "one," but on day "two" it became a combined system. Why? Because (and still) virtually all other wastes were being thrown into the streets—waiting for either the next rainstorm or, for Rome's highly organized street washing program (using water brought in via the City's over 70 linear miles of aqueducts), to flush the wastes into the sewers and on out to the Tiber River.
In approximately 350 CE, the Roman Empire fell. The downward sweep of the biorhythm started. The Dark Ages, followed by the Middle Ages, were entered. During those times, almost all of what had been learned about sewers during the previous 40 centuries was forgotten. It was an age of "mess, stench, filth and disease." For those living in those times, people were lucky to reach the age of 30; even then, the likely cause of death was plagues/disease. These times were indeed the "low" point in the biorhythmic progression of the evolutionary development of sanitary sewers.
As times progressed (1200s-1700s) certain cities began structurally covering natural drainage ditches (that carried all types of wastes); not because they wanted to create a "sewer" per se, but instead to cover the ditch so they could utilize the land area above it to build more roads and buildings. Unbeknownst to them, the art of building sewers was slowly being reinstated. Meanwhile, disease/plagues continued to sweep across Europe throughout the Middle Ages, causing the deaths of millions.
With the act of beginning to structurally cover open ditches, an upsweep in the evolutionary development of sewers' biorhythm was once again occurring. People were beginning to realize that it was not good to mix wastes with their water supply—although they still didn't know the exact reason.
One of the major European cities to bring on a strong upswing in the biorhythm was Paris, France. Starting in the mid-1800s, a system of nearly 400 km of sewers was built over a 45-50 year period, resulting in a sewer under almost every street in Paris. The primary purpose of these sewers was to get storm runoff to the Seine River. Again, on day "one," this system was a storm sewer; on day "two" it became a combined system. Why? Because (and still) almost all other wastes (chamber pot contents, garbage, etc.) were thrown into the street awaiting the next rain event. Other European cities (London, Hamburg, Prague, etc.) all embarked on combined systems, each on their own "schedule"; some earlier on, some at nearly the same time as Paris.
Jumping over to the United States, immediately following the end of the Civil War, cities/towns throughout the country were faced with the return home of soldiers. Up until then, most homes (especially in inland areas) had relatively large lots; each with a privy in one corner of the yard and a water well in another corner. As housing densities increased, these two vital facilities (privies and water wells) got too close to each other. Disease was becoming all too prevalent.
Cities like Memphis, TN were faced with tough decisions regarding "sewers." They could install "combined" systems, along with their inherent issues—larger sewers, larger costs, and more time and disruption to install, etc. Such systems were often the system of choice for the eastern seaboard cities, ones that had different (flatter) terrain and climate more suited for combined systems. Or, the idea that started in England 30 years before ("separate" sanitary sewers) might be a viable option. Col. George Waring brought the separate sanitary sewer idea to Memphis' town fathers. Such an approach would be less costly, be built faster and with less disruption, and the rolling terrain of Memphis could adequately take care of stormwater via "surface" runoff. Memphis chose the separate sanitary sewer approach in the early 1870s.
The first sewering phase for the City of Memphis utilized six-inch diameter gravity clay pipe with lampholes (not manholes). The City soon found out that the system was prone to blockages from a combination of the grit (a problem known to adversely impact sewers since Mohenjo-daro) and the content of the liquid wastes being flushed into it. The lampholes did not provide access for tools to clean the sewers. Thus, the only way to mitigate these blockages was to dig up the sewer pipe, break into it, clean it, repair the pipe and backfill the excavation. The city fathers said something had to change; the first-phase sewers were too difficult and expensive to maintain!
Col. Waring made two significant changes (design-wise) before proceeding with the next phase. Eight-inch diameter gravity clay sewer pipe was now being used (not six-inch) and manholes were positioned at all changes in slope and changes in pipe direction; thus, providing viable access for people and tools to clean the sewers. The revised concept worked much better. The separate sanitary sewer idea spread from Memphis across the United States.
And, the upswing of the biorhythm continued...and, it continues even today.
With an appropriate level of support, respect and funding, the betterment of our sewer systems (separate and combined) will continue to improve. Along with these continuing improvements will come a better way of life, health and welfare for everyone involved; and, the well-being of their water resources.
Jon C. Schladweiler can be reached at (520) 297-7904 or firstname.lastname@example.org.