A Big-Picture Approach to Wastewater Management

Detroit-area utility’s wastewater master plan extends well beyond its boundaries.

A Big-Picture Approach to Wastewater Management

Great Lakes Water Authority maintenance technician Hawun Howard services and greases the forebay gates at the Connor Creek Pump Station in Detroit, Michigan. (Photography by Amy Voigt)

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When the Great Lakes Water Authority began developing its 40-year wastewater master plan, a simple reality informed the task: The utility’s 195 miles of sewer lines and an additional 15,000 miles of lines that feed into them from surrounding southeastern Michigan communities are not contained by municipal boundaries.

“The pipes don’t know where one community ends and another one begins,” says Suzanne Coffey, the utility’s chief planning officer. “All of our region’s wastewater infrastructure and assets are connected.

“The master plan effectively removes those boundaries,” she continues, noting that more than 100 stakeholders — including representatives from 79 communities with sewer lines connected to the utility’s system — collaborated on the plan. The 377-page document essentially provides a 40-year road map for the future of the region’s sprawling wastewater collections and treatment system.

“We focused on the concept that this is one large system and looked for the best ways to optimize it. We can achieve more when we function as a region, not individual agencies.

“When you take away those geographic limits, it allows new ideas to bubble up.”

To develop the plan, stakeholders attended more than 100 meetings during the past four years. Believed to be the only one of its kind nationwide, the plan’s goals center on improving water quality as well as prioritizing low-cost, high-impact projects that leverage existing infrastructure while providing the greatest environmental benefits.

“I think the region was really hungry for this kind of collaboration,” Coffey says. “I believe a lot of (neighboring wastewater) operators could see opportunities to do things differently and better, but until we all came together, there was no ability to understand what happens to their flow after it leaves their cities.

“Now we’ve educated our member partners about the layout of the regional system and provided an operational dashboard. So when they think about their community and how it’s operating, they can access this dashboard and understand what’s happening upstream and downstream and make better decisions.

“In a manner of speaking, we’ve turned on the lights so everyone can see what’s going on. It’s similar to using GPS to avoid traffic jams — operators can see where wastewater traffic jams are occurring and deliver flow to treatment facilities more efficiently.”

Sprawling system

The Great Lakes Water Authority’s collections and treatment systems cover 944 square miles in three counties in southeastern Michigan and serve approximately 2.8 million people in 79 communities and municipalities, including the city of Detroit.

The thousands of miles of sanitary sewer lines funnel through 86 separate municipal systems before reaching the utility’s Water Resource Recovery Facility, the largest single-site treatment facility in North America. The facility treats an average of 630 mgd but can handle up to 1.7 bgd.

That treatment capacity is supplemented by nine combined-sewer overflow treatment facilities that can treat up to 17 bgd. The system also includes 1,545 manholes, nine pump stations and a biosolids facility that turns approximately 600 million gallons of biosolids into environmentally friendly fertilizer annually instead of incinerating or landfilling it.

Managing such a massive system poses many challenges, says Navid Mehram, chief operating officer for wastewater operating services.

“In some situations, flows are so low that we have to manage the volume of water coming in and make sure the infrastructure can convey it at such a low velocity,” Mehram explains. “In other cases, we’ve built massive infrastructure that allows us to capture heavy flows we receive from larger tributary areas.

“So we try to manage our collections system in a way that we can capture that differentiation in flow.”

Low flow velocity also increases sedimentation, which creates problems if heavy rains occur. That creates what Mehram calls a major “slug load” — a high volume of solids — at the WRRF.

“We can go from an average loading of 300 dry tons per day of solids to 1,200 dry tons per day during a rain event,” he says.

Improving water quality

Implementation of the master plan will occur in three phases: Optimizing existing infrastructure; adapting to take advantage of opportunities as they arise and expanding pipes and wet-weather facilities to further improve water quality; and then sustaining the improved performance through continued maintenance. Many key phase-one initiatives already are underway.

Moreover, the master plan is not just a road map for regulatory compliance. Instead, it also focuses on improving water quality.

“We want to see real tangible improvement of the quality of water in rivers,” Coffey says. “We’ve already invested more than a billion dollars in the last 25 to 30 years in combined-sewer overflow controls, including wet-weather control facilities that treat and discharge any overflow.”

In addition, the utility has established a water-quality monitoring program in which local streams and rivers get tested regularly, not just during sewer overflows. The testing will be performed with both “grab samples” and by continuous in-stream sampling.

The agency uses Suna nutrient sensors made by Sea-Bird Scientific, and NuLab nutrient sensors developed by Green Eyes.

“So over time, we’ll be able to spot trends and make operational improvements that will keep improving water quality,” Coffey says.

Optimizing assets

The plan, which will be updated every five years, also focuses on optimizing existing infrastructure in order to minimize significant investments in new capital improvements. Coffey says that will help ease one of the biggest barriers to implementing most master plans: funding.

“For us, affordability is always at the forefront. We’d love to obtain more state and federal dollars, but the best thing we can do now is plan well and optimize what we’ve already invested in, which will reduce the need to build new facilities.”

For a good example of optimizing existing assets, consider the connectors, or regulators, that link smaller upstream concrete sewer lines to the Detroit River interceptor, which lies 20 to 50 feet deep and ranges from 9 to 12 feet in diameter. It collects flow from shallower sewers.

Currently those approximately 30 connections narrow where they meet the larger interceptor line, which restricts wastewater flow. But engineers are working on retrofitting those connections to make them larger, which would significantly increase flow to the WRRF and reduce untreated sewer overflows.

In fact, for a relatively small amount of money — about $15 million — compared to a more significant repair option, the utility plans to enlarge these connections so they match the diameter of the upstream sewer lines. That would reduce combined-sewer overflows by roughly 160 million gallons, Coffey says.

“That would eliminate approximately 10% of our untreated overflows from discharging into the Detroit River. It’s a project that provides the best bang for our buck.”

Two regulators have been expanded so far and the GLWA is monitoring their performance to see what kind of difference it makes.

Mindful maintenance

But the biggest operational challenge is sewer maintenance. “It’s a massive network and we have to ensure that conveyance is reliable every day,” Mehram says.

Generally speaking, a team of employees is responsible for inspecting and performing preventive maintenance in what Mehram calls the gravity system — the 195 miles of sewer pipes — as well as the system’s nine pump stations. Employees rely on a camera truck outfitted with inspection cameras built by Telespector Corp. and R.S. Technical Services, with WinCan VX sewer-inspection software.

The GLWA usually hires contractors to repair and/or upgrade its assets, he says.

GLWA recently completed a three-year effort to inspect all of its sewer lines. A key finding: A 12.5-mile-long, 9- to 16-foot-diameter section of the Detroit River interceptor was a high-priority candidate for repairs.

Contractors have been rehabbing the interceptor for about 2 1/2 years. Most of the work, expected to be completed in another year, centers on repairing or regrouting the largely brick structure, along with improvements for enhanced flow control and maintenance.

“It’s one of the bigger sewer rehab projects we’ve taken on,” Mehram says of the $48 million effort. “It’s also one of the most critical sewers marked for rehab.”

Technology-centric operation

The GLWA staff also uses sophisticated software programs to manage its numerous assets. Good examples are Work and Asset Management (WAM) software developed by Oracle, Microsoft Suite products like Power BI (Business Intelligence) and ArcGIS mapping and special analytics software from Esri.

WAM is used to track work orders and as a communication tool between management and front-line workers. “We aggressively use WAM on our vertical assets (pump stations and water resource recovery systems), while Power BI brings that data into a dashboard that allows us to clearly communicate needs to our leadership team,” Mehram says.

Employees use handheld data-collection devices manufactured by Spectra Precision/Trimble Geospatial to collect information for the ArcGIS system, which provides a good overview of where assets are located and their condition, all in graphical form.

Coffey notes that through development of the master plan, GLWA officials have learned that there’s strength in numbers.

“We can do more when we come together and remove boundaries from the equation,” she says. “Think about all the brain power from all the stakeholders that participated. This process has given birth to a whole new family of ideas.

“We’re well-connected with national associations across the industry, and we’ve never seen a master plan quite like this. Developing this plan involved an unprecedented amount of collaboration.

“We knew we achieved something special when one of our member partners proposed redirecting their own capital dollars to a project downstream from their municipal boundary, realizing that it was a better project for improving water quality. I would encourage water utility managers to consider how they could implement a regional approach in their areas. It has brought GLWA cost-effective solutions that otherwise would not have been possible.” 


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