Old School Sewer Evaluation

By Lawrence F. Lihosit

Only 100 years ago, the average American citizen lived 47 years compared with today's average of 78.1 The most dramatic improvement had nothing to do with fancy medicines, Flash Gordon medical machinery, or changes in the national diet, but just the simple introduction of underground sewer collection and potable water pipes. Between 1900 and 1930 (prior to the discovery of antibiotics and the common use of electric power in rural American homes), the average life expectancy improved to 60 years. With the introduction of underground potable water and sewer collection systems, the incidence of waterborne cholera and typhoid decreased by a third.2 One hundred years ago, these two diseases were the fourth and eighth top killers in the country.3


Although a few cities experimented with sanitary sewers in the 19th century, disease and filth were the rule, not the exception, until the beginning of the 20th century. Today, many of these same systems are in use even though the expected replacement age is 60 to 80 years for vitrified clay (standard sewer pipe material circa 1900) and 50 years for lead or copper (standard water pipe materials circa 1900-1950). These pipes are quietly disintegrating under our feet. Increasingly, citizens are suffering from the effects of waterborne disease that had been nearly eliminated for earlier generations.4

The smell of an overflowing manhole or cleanout usually catches our attention. Unfortunately, sometimes the problem goes unnoticed until local hospitals begin to report an increasing number of patients with cholera, salmonellosis, typhoid fever, hepatitis, meningitis, pneumonia, giardiasis, or undiagnosed dysentery and respiratory problems. We can unknowingly come in direct contact with untreated sewage as it runs down streets, flows into basements, yards, or even into swimming areas.

American urban planners tend to shy away from public works, the backbone of all modern urban settlements. Why be timid? Especially in small towns, urban planners have the opportunity to roll up their sleeves and work alongside their engineering counterparts. Working together is the basis for teamwork.

This article focuses on the sewer collection system, the pipes that take effluent from our home to a treatment plant, and identifies four maps that help to evaluate the system with a minimum investment, so important in hard times. If you work in a city, you may have sewer information on a GIS system. These maps could serve as additional "layers" (attribute files). If you work for a hamlet or town without GIS, use to-scale maps so the information can be transferred to an electronic format in the future. Contact the public works and engineering departments to acquire paper copies of the most accurate sewer maps available. If manholes are numbered for GIS, or future GIS application, use them in your work.


The idea is very simple. Urban planners aid the engineers by making a methodical review of key elements that indicate the need for removal or rehabilitation. The key elements are a thorough understanding of the system, pipe age, and incidence of recent problems. The first part is actually the easiest as all towns will have maps of their collection system. Most probably, your town has a master map in sections with the location of lines, diameter, materials, and key elevations (invert and flow line). Invert refers to the elevation at the bottom of a pipe while flow line refers to the actual elevation of the effluent flow.

Perhaps there is already a map that distinguishes the main lines. If not, you can create one by simply paying attention to the plans. For an illustrative example, see Figure 1. Older residential lines are normally 6 inches in diameter while newer lines are generally 8 inches. These will lead to larger diameter lines often called interceptors, which range from 8 to 12 inches in diameter. Like tree branches, they lead to sewer trunk lines that are larger still. Water flows downhill, so check the elevations. Color code an existing map with arrows showing direction of flow and ask the engineer if you have noted them all. Also note lift stations. A lift station is an electrically powered pump that sucks effluent from one pipe and pushes it along another at a higher elevation. Before the advent of electricity, all sewer systems relied totally on gravity. (Sewer collection pipes were used as early as 1500 B.C. on the island kingdom of Minoa.5) The location of lift stations will be important later as you check line performance.

Interceptors and Trunklines
Figure 1    
Interceptors and Trunklines    

Using the same scale as the first map, you will now prepare a map illustrating sewer service areas by era (see Figure 2). The second map relies on research, an urban planner's greatest strength. The best sources of information are old dated maps that illustrate the sewer system, like snapshots of a particular moment in time. If none exist, another valuable source is the expansion plan. Search your archives for old, dated maps. Each time a new line was added, an engineer created plans showing what existed and what was proposed for construction.

Using these maps, you can simply delineate the neighborhoods served. Often, historical photos tell the same stories, whether aerials or taken at ground level. Towns often hire consultants to prepare reports that accompany plans for expansion. These also may be archived by the city or even the local library. Libraries usually have microfilm or microfiche of old newspapers. Water and sewer expansion projects are always big news. Even if the article has no map, it will normally list streets and the length of line to be installed. The finance department also might have descriptions of such expansions if a bond was involved.

Lastly, there is physical evidence. Once you have an idea about installation dates (even by general era), contact the field crew foreman. Accompanied by someone from the field crew who regularly flushes lines, pop some selected manhole covers and ask questions. Are any of the manholes built of masonry? If so, they are probably pre-World War II. Are any of the lines themselves built of masonry? If so, they probably date back to before 1920. In addition, where do storm drainage inlets drain into the sewer system? If there are any, they probably also denote a collection portion that dates back before World War II. The reason for going to the field is that the crew often is not used to working with maps. Once you go out to familiar territory, they will have all kinds of useful information. If your field crew has been on the job for years, they can offer incredible insight. Take notes.

The result of all this research should be one simple to-scale map (e.g., Figure 2) that outlines approximate dates of installation. It is not necessary to show each line, just the area. Each general zone should correspond with an era like 1900 to 1920, 1921 to 1944, or whatever dates are convenient based on your own materials.

Service Areas by Era
Figure 2    
Service Areas by Era    

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