Underground sewer infrastructure is an often-forgotten piece of the public infrastructure puzzle that creates the opportunity for us to live and build strong, happy communities. Although it’s not something we think about daily, it is one thing that provides value to the quality of our daily lives. We don’t worry about sewer infrastructure on a daily basis because it’s typically out of sight, unlike roadways and buildings; however, the underground infrastructure is just as important. Just as the condition of our cars requires maintenance and may even deteriorate over time without it, so does the condition of our sewer infrastructure.
It is important to have an up-to-date inventory of all the sewer infrastructure within the gravity collection system to perform a quality evaluation of its condition. An inventory including the age, size, elevation, and material for all sewer pipes and manholes will allow for the most thorough and accurate evaluation. Once an initial inventory is taken, data should be continuously updated for the collection system. The updates should include routine closed-circuit television (CCTV) inspection, manhole inspections, smoke testing, flow monitoring, and logging sanitary sewer overflows (SSO’s).
In one recent project with the Knoxville Utilities Board (KUB), LDA engineers experienced the advantages of KUB’s advanced and comprehensive sewer inventory. The project involved the Loves Creek mini-basin, which is an individual wastewater collection system owned by KUB. The KUB Asset Replacement and Rehabilitation Program identified issues along a 6,000 linear feet section of the Loves Creek sewer trunkline and worked with LDA Engineering to address reducing rain-derived inflow/ infiltration (RDII) and structural or maintenance problems that may cause blockage related overflows and/ or require increased frequency of blockage abatement activities. There was also concern for surcharge in the area upstream from the Loves Creek Wastewater Treatment Plant. LDA used inventory and inspection data provided by KUB, as well as an internal survey, to provide sanitary solutions for this collection system.
More specifically, the Loves Creek sewer trunkline had numerous design challenges to improving the performance of the collection system. The project area included six creek crossings, a railroad crossing, inaccessible manholes, and a state highway crossing. After further investigating the conditions of the collection system, LDA also found issues including, corrosion, pipe sagging, fractures in pipe, infiltration, intruding roots, obstacle blockage, obstacles intruding the pipe, pipe deformation, and broken pipe. LDA provided design solutions for these challenges by method of pipe bursting rehabilitation, open cut point repair, jack and bore, pipe rerouting via open cut installation, cured in place pipe (CIPP), and pipe upsizing.
As a result of their proactive assessment of the sanitary collection system, KUB was able to pinpoint critical areas and find sanitary solutions to keep the Loves Creek mini-basin collection system performing well. It is vital to collect and maintain up-to-date data for your sanitary sewer collection system inventory to identify the areas of concern before it’s too late. The data can be used to find the best solution for each issue. Although many of the sanitary solutions LDA provided for the Loves Creek mini-basin may be underground and out of sight, the positive impact of these sanitary solutions can be seen every day in our strong, happy communities.
Taylor Hagood, E.I., is an engineer at LDA Engineering in Nashville, TN. He is a 2015 graduate from the University of Tennessee, Knoxville with a B.S. in Civil Engineering in pursuit of his PE license. Taylor is an active member of professional organizations including the American Water Works Association (AWWA) and the American Public Works Association (APWA).