Lessons Learned from Seven Years of MSI

The North Texas Municipal Water District (NTMWD) is a regional wholesale provider to 24 communities spread between Collin, Dallas, Denton, Kaufman, and Rockwall Counties in North Central Texas, which are some of the fastest growing areas in the country. The service population is approximately 1.2 million people. NTMWD currently owns and operates:

*About 139 miles of gravity mains ranging in diameter from 8-inch to 60-inch

*About 96 miles of force mains ranging in diameter from 14-inch to 60-inch

*25 lift stations

*14 wastewater treatment plants This presentation will focus on methods and results of Years 1 (FY2017) through 7 (FY2023) of the 10-year Condition Assessment Program (CAP). In 2016, NTMWD began the CAP project with the goal to conduct a multi-sensor inspection of all large diameter gravity mains, condition inspection of all manholes, and condition inspection of all lift stations during the project cycle to develop a baseline condition score for each asset to compare in future inspections. The project team conducted several desktop analyses to identify the expected condition of the assets and prioritized the inspection of the assets based on consequence of failure and available funding. Each gravity pipeline is inspected using the RedZone Robotics Multi-Sensor Inspection Program (MSI) to measure the inside dimensions of the pipeline for comparison to the original specifications. This data is used to grade the pipe segment on a 1 to 5 scale with 5 representing the worst condition pipes in need of immediate attention. Through FY2023 of the program, the team has inspected approximately 593,753 linear feet (LF) of large diameter gravity lines with 35,318 LF (6%) receiving a score of 4 or 5. FY2024 is currently in progress and includes the inspection of approximately 96,789 LF of gravity lines and approximately 14,329 LF of force main inspections. It is anticipated that a detailed discussion of the gravity and force main inspections will be available at the time of the conference. NTMWD is concurrently working through a program to inspect each of their manholes using the RapidView IBAK PANORAMO(R) SI 3D Optical Manhole Scanner system. Through FY2023, the team has inspected 761 manholes. FY2024 will include inspections for at least 27 additional manholes. Each inspected asset is assigned a renewal action based on the observed and measured condition of the asset. For pipelines, these actions include replacements, point repair, O&M work, or re-inspection. Similarly, manholes receive either replacement, lining, point repair, O&M, or re-inspection recommendations. In addition to the inspection work, NTMWD is surveying all of the wastewater manholes and force main valves. During CAP FY2017, inaccurate manhole location data led to issues locating manholes to conduct inspections. Additionally, numerous manholes were identified during the pipeline inspections that were not present in the District's geographical information system (GIS). During surveying, it was found that some of the actual manhole locations were a considerable distance away from where the District's GIS indicated the manholes were located. As part of the survey process, inverts were measured for each pipe connecting to the manholes. The location and invert information presented in the placemark file used by Google Earth, Keyhole Markup language Zipped (KMZ), will assist the District in updating the GIS and their hydraulic model. What the team expected to find during this project was large diameter lines in fair condition with occasional defects. Instead, most of the lines (+90%) were observed to be in relatively good condition with minimal defects. The real surprise came from the difference between field verified, GIS, and as-builts records. Through the inspections:

*84 (and counting) previously unrecorded manholes have been identified,

*Significant changes in a few manhole locations,

*Several differences between as-builts and laser measured diameters have been identified,

*And connectivity discrepancies in the hydraulic model have been identified. As part of the FY2023 program, an updated risk-based assessment was performed to prioritize future inspections and re-inspections based on observations and recommendations from historical inspection data. A wastewater model of NTMWD's conveyance system was developed using the Innovyze InfoAsset Planner software to simulate an asset's likelihood of failure (LOF) and consequence of failure (COF). A total risk score was assigned to each wastewater line by multiplying the LOF and COF scores. LOF was based on an assets RUL score, material, age, maintenance history, and surcharged status, while COF was defined by the asset's accessibility, depth, redundancy, and traffic, potential environmental, potential I/I, and outage impact. The result was a maximum risk score of 100 with higher scores representing lines of very poor quality and extreme criticality. The wastewater line total risk scores were then grouped into ranges, and descriptive scores of Very Low to Very High were assigned. The results of the risk assessment showed that 93.26% of gravity mains and 79.92% of force mains have a risk grade of Very Low or Low. 1.19% of gravity mains and 8.02% of force mains are scored with a risk grade of High or Very High. The highest gravity main and force main total risk scores are 73 and 80.96, respectively. These results were then analyzed to update NTMWD's 10-year workplan.