Identify Wet-Weather Sanitary System Problems by Combining Field Investigation with Computer Modeling

The combination of field investigation and hydraulic modeling is an effective tool to identify the causes of basement flooding. Field investigation (closed conduit televising) provides detailed information on conditions of sanitary sewer system, while computer model assists a better understanding on overall system performance. During the Livingston/James inflow and infiltration project (City of Columbus, Ohio), over 700,000 linear feet (130 miles) of sanitary sewer was cleaned and televised, 273 homes were tested to identify the sources of I/I contribution. The information gathered from field investigation was used as resources for model calibration and QA/QC. Meanwhile, a hydraulic model (including sanitary sewer with diameter 8 inches and larger) was applied to quantify the impacts of operation and maintenance and system capacity deficiency.

By comparing the area with deficient sewer carrying capacity with the patterns of historical water-in-basement complaints, the authors summarized the causes of the complaints into two categories: system capacity deficiencies and localized insufficiency of operation and maintenance (e.g. Roots, deposits, etc.). Based on the causes, the recommended solutions include both system capacity increment (replacement pipes, parallel relief pipes, etc) and local solutions (back flow prevention device, root treatment, cleaning, etc.). This paper discussed the potential improvement would have been without routine sewer maintenance and demonstrated that either field investigation or modeling approach alone is insufficient to fully understand and identify wet-weather sanitary system problems, but the combination proved to be the best approach.