The Dollars and Sense for Adopting Optimized O&M Processes: The Demonstrated Successes of Three Utilities

Accepted Practices for Mitigating SSOs For decades, utilities have established and implemented the EPA CMOM guidance of regular, scheduled cleaning 1. It recommends that the total collection system be cleaned on an ongoing basis, annually for smaller systems and on a multi-year cadence for larger systems. Additionally, it states that collection systems which have segments where rapid build-up occurs, often referred to as 'hot spots', and that could result in blockages, should be cleaned at higher frequencies e.g., monthly, bi-monthly, and quarterly. To establish the cleaning frequency rate, utilities relied on the known history of a given segment's build-up and established a schedule to stay well ahead of the historical trend 2. Of note, in order to stay ahead of potential blockages, some or many segments are cleaned on a high frequency schedule. This occurs irrespective of the actual segment conditions and results in overcleaning - cleaning pipes that do not require it. The primary reason for this rest with the field maintenance team not knowing segment conditions for a segment. Yet, while it might be wasteful of resources, the high frequency cleaning approach has proven effective for reducing SSOs 3/4. Unprecedented Disruption There may be no adequate way to describe the disruption that the pandemic brought to our lives, business, and so much more, with virtually no element being untouched. Water and wastewater were no exception. During the initial weeks, shutdowns occurred in rapid succession. Yet, water/wastewater operations had to continue, as they were deemed an essential industry by the Department of Homeland Security and in conjunction with EPA in 20155. Keeping in mind that utilities built their processes, staffs, and resources such as trucks and equipment around the EPA CMOM cleaning guidelines, the pandemic created widespread challenges. The Water Environment Federation (WEF), for example, sponsored a series of online webinars in May and June of 2020 whereby utilities outlined a confluence of challenges: - securing personal protective equipment (PPE), - managing reduced staffs due to the necessity to implement staff isolation Moreover, a significant increase in sewer-unfriendly objects started to appear in the collections system and pump stations. So-called flushable wipes, face masks, and latex gloves accumulated in these structures increasing the amount and severity of blockages 6. To illustrate this, one Tennessee utility would normally clean a wastewater pump station once per month and now found that cleaning was required twice per week, an eight-fold increase. The occurrences of rapid and unexpected sewer system build-up only added more pressure on already challenged maintenance teams. It was the perfect storm of less available resources and more challenges to meet. An Emerging Hypothesis Over the course of the past five years, a small but growing number of utilities have been studying and adopting new O&M cleaning processes. Their goal was to gain increased insights into actual remote segment conditions and use this information to determine when a segment needed to be cleaned. They hypothesized that they could conserve maintenance resources and vector these to other urgent tasks or projects. In effect, they were seeking increased productivity. In order to test this hypothesis, utilities (three cited herein) adopted a smart technology approach where sensors were installed at remote locations, capable of continuous communication of flow-depth to web-enabled devices. Supervisory and managerial staff had continuous access to sensor-site data showing actual segment conditions. Using available predictive, machine learning analytics, a staff member could be notified of locations that would need cleaning and, doing so, well in advance of any possible blockage developments or issues that could lead to an SSO. Testing the Hypothesis Examples of three utilities demonstrate how the application of smart technology as the determinant of when to clean, enabled them to supplant their older schedule-driven process. As stated, field maintenance resources were potentially being wasted as these teams cleaned a pipe segment strictly based on the requirement of a schedule to do so. They lacked visibility of the segment's actual condition and could well be cleaning already clean pipes. The new approach enabled continuous visibility of flow-depth behavior. [Note: hydrographs will be shown.] All of the pilot studies were set-up in similar fashion. High frequency cleaning locations were chosen (usually monthly frequencies but in one pilot weekly locations were included). Monitors were installed at each location with depth measurement frequencies set at 15-minute intervals. These were communicated to a cloud-based software that also contained analytics capable of detecting depth measurement pattern anomalies, indicative of the development of a future blockage. If detected, a dashboard displayed the location and urgency for action. In this case, the cognizant staff member would create a work order to clean, having days or even weeks for scheduling. Results The earliest pilot was comprised of ten (10) test locations for a duration of six-months. Using the older, schedule-driven method, the utility would have cleaned 60-times during this period (6-monthly x 10 locations). Upon completion of the pilot, the utility cleaned a total of 12-times, an 80% reduction. The second pilot tested twenty (20) locations. Eight (8) of the locations were scheduled to be cleaned weekly, while twelve (12) were on a monthly schedule. The pilot duration was four (4) months and during that time scheduled cleaning was reduced by 94% for all 20 locations. The third utility installed monitoring at 25-monthly locations. In the first year alone, scheduled cleaning was reduced by 92%. The common result for these three utilities was a dramatic decrease in cleaning and with no SSOs at any location. All were able to allocate their maintenance resources to other tasks. Thus, with the same total resources, each utility was able to accomplish more and realize increased productivity. One Unexpected Benefit The subject of the pandemic, raised earlier, illustrated how smart technology had a significant and positive effect on otherwise difficult challenges. The aforementioned third utility maintains almost 3,000 miles of gravity sewer. To do this they have more than 20 combination (cleaning) trucks. They employ both a first and second shift plus a smaller third-shift that's primarily dedicated to urgent cleaning. When the pandemic shutdown started, operations had to be cut-back severely for three weeks. All regular scheduled cleaning stopped as all employees were instructed to shelter in-place (at home). They had a single team to respond to emergencies-only. Yet, this utility had already implemented the 'Optimized Cleaning' process using monitors at their critical locations. Over the course of the three weeks of lock-down, the supervisor reported that he was at ease knowing that the critical locations were monitored. Moreover, if any needed attention he had advanced notice and could schedule his single team to performance maintenance. In fact, during that time, two sites indicated that cleaning was necessary. Moreover, potential SSOs were avoided. Final Thoughts What these three examples demonstrate is that through knowing actual segment conditions, effectiveness and utilization of maintenance resources increases. Moreover, the sudden and drastic changes created by the pandemic underscored that in the face of extremely limited maintenance capacity, smart technology offers an alternative that minimally protects from SSOs but can also right-size maintenance demands. For utility managers, there is a fundamental advantage for updating old O&M processes when their organization can increase productivity and, in the case of severe challenges, gain peace of mind. References 1.Guide for Evaluating Capacity, Management, Operation, and Maintenance (CMOM) Programs at Sanitary Sewer Collection Systems, United States Environmental Protection Agency, Office of Enforcement and Compliance Assurance (2224A), EPA 305-B-05-002, pp.2-29/30, January 2005. 2.I&I Magazine, Cole Publishing, January 2019; Jay Boyd and Paul Forsthoefel. 3.Sanitary Sewer Overflows: What They are and How to Reduce Them, Environmental Protection Agency, Office of Wastewater Management, EPA 832-K-96-001, p. 5, Summer 1996. 4.Sewer System Management Plan, Central Contra Costa Sanitary District, CIWQS WDID: 2SSO10105, Nov. 2017. 5.Water and Wastewater Systems Sector-Specific Plan, US Department of Homeland Security and United States Environmental Protection Agency, per Presidential Policy Directive 21; 2015. 6.Epidemic of Wipes and Masks Plagues Sewers, Storm Drains, Associate Press Release, June 4, 2020; Claudia Lauer, and John Flesher.