A Package Plan

Bundling tasks and methodical approaches helps a southern city reap the benefits of I&I reduction.

A Package Plan

The Mobile Area Water and Sewer System team includes, from left, Donald Seltzer, John Connelly, Robert Johnson, Matt Welch (public service supervisor I), Charles Benning, Calressia Clark (director of field operations and logistics), Jordan Brown, Joseph Tuite (public service supervisor II), Dominick Pettway, Rico Thomas, and Jason Saxon.

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Inflow and infiltration itself is anything but consistent and methodical, but if you’re going to mitigate it successfully, those are some of the most important qualities your utility can possess.

By incorporating a blend of flow monitoring, a highly systematic approach, robust investigation activities and consistent follow-through to client feedback, the Mobile (Alabama) Area Water and Sewer System has successfully reduced I&I while creating a comprehensive plan to improve overall collection system health and performance that is affordable, sustainable and scalable.

MAWSS serves a population of approximately 200,000 citizens, which equates to approximately 90,000 customer accounts throughout the metropolitan area of Mobile. Established through a legislative act in the early 1950s, the utility is responsible for delivering water and sanitary services — along with wastewater treatment at two centralized plants and three decentralized plants — which collectively process approximately 40 mgd. The sanitary collection system is comprised of 1,246 miles of gravity sewer, 28,859 manholes, 99,200 service laterals and 233 miles of force mains.

The utility has established a robust inflow and infiltration remediation program through its in-house staff of 13 dedicated employees to finding sources of I&I, 13 lift station employees, 10 video investigation employees, 27 sewer repair employees and six construction inspectors. It also has the help of an outside consulting engineer for larger capital projects. All maintenance, inspection, smoke testing and flow monitoring is handled internally. The department has benefited from an extraordinarily strong customer response and service approach. Through its preventive maintenance program and customer response teams, much of the information it has been able to derive regarding the health of its system has come from its field and video investigative teams.

Although some of the work MAWSS does do is reactive — to be expected in a city of this size — the department does have a well-staffed and progressive, proactive investigation department that operates three CUES-equipped CCTV mainline video and lateral-launching trucks out in the field daily. In addition to its regularly scheduled CCTV inspections and rotations, this field investigation department also handles the monitoring and assessment of data. This comes in from 75 ADS TRITON+ flow monitors and 20 Mission Communications rain gauges positioned in pivotal areas of the city.

MAWSS also has a smoke testing team, which prior to the COVID-19 pandemic was performing smoke testing daily. “We were able to resume our smoke testing, which was really good news,” says Calressia Clark, director of field operations and logistics for MAWSS. “We know private laterals do contribute to I&I, and smoke testing is an excellent way for us to pinpoint the exact location and get our customers involved in helping us to stop I&I and overflows through the use of the Private Lateral Program.”

MAWSS performs private lateral investigations and will repair issues in these laterals on the public side. To be proactive, the utility also sends notifications to property owners.

The intention is to get information out to the public, alerting them when there are plumbing issues on their property that need to be repaired. Using Infor as the asset management and work order system, in conjunction with ArcView GIS from Esri, allows the utility to input, analyze and carefully monitor all data. This enables Clark to develop projects for the department while determining whether they can use internal annual contracts for repair or pass the project on to consultants for design, bid and build projects.

Better use of data

When Clark joined the utility in 2007, there were 67 flow monitors in the system. Although data was being collected, not much was being done with it to determine next steps for system maintenance. As the years progressed, it was decided that MAWSS needed to expand and add some other investigative techniques to better understand the sources of I&I. The department launched a smoke-testing program that included a private lateral program and — analyzing the data from smoke testing, manhole inspections, CCTV inspections and flow monitoring — it was able to more accurately compare dry versus wet weather flows. This enabled it to prioritize problem areas, which are typically 75,000 to 150,000 feet of isolated areas upstream of the flow monitors. Clark and her team were now better equipped to pinpoint areas to address within each of the system’s basins.

Working inward

When Clark puts together a rehab project, she approaches it in a very systematic way, beginning work up-stream of the prioritized monitoring areas in an effort to repair/rehabilitate the issues that smoke testing has revealed. Everything within that section of the basin will be rehabilitated to seal the system. This includes the mains, manholes and laterals, all in one comprehensive project.

“The best way to deal with I&I issues is, if you can’t replace it all, rehab it all, and try to get the system sealed as much as possible,” says Clark. Bundling the projects in each basin and taking care of all the assets within it prevents the potential of groundwater migrating and entering through another unsealed area of the system. Rehabbing all the elements together also provides MAWSS with great economy of scale, while ensuring less disruption to the community.

The biggest benefit is the knowledge that when the project is complete, the team has pretty much taken care of any possible I&I issues for that area for the foreseeable future.

As a case in point, there was an area along the Dog River just south of Interstate 10 where a basin was being influenced by tidal aspects of the river. Even after the sewer main had been rehabilitated using CIPP, the utility continued to experience system overflows after rain events, as well as when the area experienced a high tide, due to leaky laterals.

BLD Services was the contractor awarded to work with MAWSS on this project. They quickly discovered that during a normal tide in the area, there still was too much water coming in to allow for CIPP installations. They had to find workarounds to deal with Mother Nature on some of the repairs. MAWSS had the option of using well-point dewatering/replacement for the project, but was reluctant due to the added cost. 

BLD’s team discussed the option of holding off on rehabilitating these lines until the winter, hoping that cold fronts with strong north winds could blow the water out of the Dog River and surrounding waterways. This would effectively lower the tide and reduce the infiltration entering the service laterals, allowing time for CIPP rehab work. The winter waiting worked, and over the course of a few years — with seasonal timing — the laterals in the Dog River area were rehabbed and overflows were reduced. 

Accountability tracking

For every project, Clark and her team perform accountability tracking to determine how successful the rehab and remediation of I&I has been. Flow monitoring has been especially helpful in auditing how well a rehab project has performed in any given area.

Although inflow is much more difficult to remove from a system than infiltration, Clark has been able to glean valuable insight from monitor data collected during rain events. She found that when an area in the system recovers quickly after a rain event, the utility’s approach of working from the upstream in to seal all parts of the system is more effective — the gain in the amount of I&I mitigation is greater and faster.

Another thing the utility has learned while working to mitigate I&I is that correlation doesn’t equal causation when it comes to wet-weather events. After one line overflowed during a wet-weather event, Clark noticed a nearby manhole was still overflowing long after the rain had stopped the following day. She began to question if the issue was truly related to the wet-weather event, or if it was some other cause. These are the types of things that Clark and her team are now beginning to examine more closely. They’re focusing on doing the extra work to determine the true sources of infiltration to prevent spending resources chasing flawed assumptions.

The right mix of fix

MAWSS has found that utilizing traditional felt-and-resin CIPP trenchless rehabilitation from a variety of manufacturers such as BLD Services and LMK Technologies for mains and laterals has been most advantageous. Trenchless technology in many forms has great benefits for an older city such as Mobile, since replacement-type projects require extensive and cost-prohibitive restoration to comply with the latest regulations in the right-of-way of restoration from sidewalk to sidewalk.

“I’m pushing trenchless rehab so hard because you can do so much more with so much less,” says Clark. For its manhole rehabilitations, MAWSS has been using a combination of cementitious or spray-applied polyurethane solutions from manufacturers like Sprayroq, StrongLite and Quadex.

Staying the course

The old figurative question “How do you eat an elephant?” is answered: “One bite at a time.” That’s exactly the approach Clark has taken. With MAWSS’ board continuing to fund improvements, Clark is staying dedicated to the cause. MAWSS has been able to reduce I&I, but she admits it is not always easy.

“It’s so easy to get sidetracked off your I&I issues, because you often run into structural issues in your system that have to be repaired now, while I&I only appears to be a problem when it’s raining. It’s like that ‘If a tree falls in the forest and nobody hears it, did it really make a sound?’ scenario,” Clark says.

For her and her team, what is buried is always in the forefront. Fortunately, management shares the dedication and vision for reducing I&I, and budgets operation and maintenance funding between $800,000 and $1 million each year to address the I&I investigative effort alone. This cost does not include initiating new technology integrations and putting together projects that can really make a difference now, and for generations to come. With operations and maintenance, annual contracts and capital projects costs, MAWSS spends approximately $6 million per year. 



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