Mains, Trains, and Automobiles: Utilizing Fort Worth’s Risk Assessment Data to Drive Sanitary Sewer Rehabilitation

For nearly a decade, the city of Fort Worth has been systematically evaluating their sanitary sewer interceptors as part of the Interceptor Condition Assessment Program or ICAP. The data collection for the program has consisted of the deployment of a floating platform which includes a high-resolution video camera, a light detection and ranging (LIDAR) head to evaluate the pipe wall above the water surface, and a sonar head to evaluate pipe wall and lodged debris below the water surface. The data is compared to standard inner diameters for their respective pipe classes to determine the extent of pipe corrosion. Pipe segments (from manhole to manhole) are ranked best to worst on a scale of 1–5. Given the large amount of data to process for a collection system spanning the 350-square-mile city, condition ratings were assigned based on the worst corrosion found anywhere along a segment, requiring further analysis to determine the extent of necessary rehabilitation work. Kimley-Horn was tasked with interpreting the city’s findings for over 10,000 linear feet of three sanitary sewer interceptors ranging in size from 24-inches to 54-inches throughout its Clear Fork Basin. Most of the lines in this basin are more than 50-year-old reinforced concrete pipe. Additionally, access to these interceptors for maintenance is very difficult given their locations traversing the Union Pacific Davidson Railyard, a commercial district, a major arterial road, multiple highways, and the city’s premiere park. This paper will discuss how the risk assessment data was evaluated to pinpoint portions of the pipelines with the greatest failure risk, reducing necessary rehabilitation to less than 5,000 linear feet of pipe and saving the city approximately $3,000,000 dollars. The paper will also explore design challenges related to the installation of cured-in-place pipe (CIPP) in very difficult locations. Construction is anticipated to begin in the spring of 2019.