Should You Repair or Replace Aging Sewer & Septic Systems?

There’s a question communities of all ages often ask themselves: if a sewage pumping system needs constant repairs or is showing its age, is it better to repair or replace it? There are often many factors to consider, including balancing the needs of the users, the lifespan of the infrastructure, and the profitability of the existing wastewater or treatment plants. Can a repair help the system continue to meet the growing needs of businesses and residents and truly solve the underlying problem? What environmental factors make replacing all or part of the system a better choice? Finally, what is the impact on the bottom line? It can be a large investment that requires time, planning, and resources to make it happen.

More contemporary than ever

Communities across the country are growing and expanding. After hitting an all-time low in 20091, housing starts in the United States have more than tripled since then. This explosion has resulted in community resources that are often strained beyond their limits. According to the American Society of Civil Engineers (ASCE) 2021 Infrastructure Report Map, the nation’s more than 16,000 wastewater treatment plants are operating, on average, at 81% of their design capacity, while 15% are at or above it. Most of the country’s wastewater treatment plants are designed to have an average lifespan of 40 to 50 years, so the systems built in the 1970s around the passage of the Clean Water Act in 1972 are reaching the end of their lives. About 20% of Americans rely on septic tanks and face similar problems. Commonly used in rural and recreational areas near freshwater resources, these systems have a similar lifespan of 40 years.

Industry experts have been working on multi-million dollar projects to improve systems, fix channel overflows and other crises. However, these projects have largely maintained the status quo: in 2017, the ASCE rated the country’s wastewater infrastructure D+. In 2021, that grade stayed the same. Overcoming the status quo and objectively evaluating existing systems can help the industry prepare for the future. There are a few factors to consider.

Current service costs

When considering service costs, it is important to consider time, materials, labor and downtime. When it comes to work considerations, think about how a repair person’s time could be put to better use. If you’re constantly busy fixing outdated equipment, what routine maintenance isn’t getting done? When it comes to downtime, consider the hard and soft costs. The inconvenience and disruption to homeowners and local businesses can lead to escalating PR scenarios. Water and wastewater departments operate in the business of trust and reliability – and when failures occur, both are at risk.

The East Cedar Creek Fresh Water Supply District (ECCFWSD), located about 50 miles southeast of Dallas, has recently faced mounting service issues and has had to re-evaluate its current system. The community serves approximately 6,500 water customers and 5,000 sewage customers adjacent to the banks of a 1,000-square-mile reservoir. Built primarily in the 1960s and 1970s, the equipment has been upgraded over the years, but the number of nuisance calls related to pump problems continued to increase. Current pumps would seize up or burn out, circuit breakers would trip for no apparent reason, and maintenance issues became the norm. In fact, in one weekend alone, ECCFWSD logged 28 hours of overtime repair work. The time added up and with it the cost of repairing pumps that weren’t grinding efficiently enough. In addition, the municipality’s 80 lift stations had to be serviced continuously.

The district knew that initially replacing 5,000 pumps plus lift stations would be prohibitively expensive. However, the continuous repair of faulty systems was not sustainable in terms of service repair hours.

After evaluating the capabilities of new automatic and manual 208-230 volt/single-phase macerator pumps, ECCFWSD recognized how the updated equipment could provide multiple benefits. The units easily coped with the demands of grinding domestic wastewater and the cutting system was designed not to clog even if a pump stops running at the end or in the middle of a grinding cycle. The heavy duty shaft would also help prevent the pump from seizing at the beginning/end of a run cycle.

ECCFWSD immediately specified the pumps for known problem areas: approx. 150 pumps in the first year. Service calls were also answered with a new protocol: If a pump couldn’t be fixed on the first try, it was sent to the county pump graveyard and a new pump installed in its place. Since April 2018, nearly 700 new mills have been installed in individual residences with minimal service calls or required maintenance. The district has also set up new pumps in 15 lift stations. It is planned to replace all pumps in the future.

Not only is this a good example that service cost is an important metric to include in the repair versus replacement argument, but it also underscores that replacing a system doesn’t have to be “all or nothing.” A phased approach with the right plan can be a realistic solution.

Lifetime cost of a new system

If the status quo has taught the industry anything, it’s that no system will last forever. In addition to the initial upfront costs of purchasing and installing a new system, operators should weigh the lifetime cost of ownership of the existing vs. potential. In some cases, lifetime service and maintenance costs can wipe out any savings from a seemingly “cheap” system.

For example, when it comes to the big picture of an entire wastewater management system, the underlying technology of collecting and distributing water has not changed dramatically over the years. What has evolved are many of the parts and components. Today’s heavy-duty pumps are built with installation and maintenance in mind.

For example:

  • Sewage systems with preformed inlets and outlets in the tank help reduce installation time and keep the tank cleaner throughout the life of the unit.
  • Floats that connect and disconnect more easily allow for streamlined service and replacement.
  • Pumps with individual parts that can be replaced as they wear out rather than replacing the entire unit provide a more serviceable system over the years.
  • When units like these are specified for a project, the total cost of ownership (TCO) can often be lower than others that offer a lower initial cost.

FIGURE 2: A recreational lake community installed low-pressure sewage collection systems in numerous residences to meet the community’s changing wastewater needs.

When a city sewerage agency near a lakeside recreation community decided to replace their sewage system, they examined what they had and realized they needed a different solution. For this established community, a gravity fed system was simply no longer feasible and would pose a high risk of inflow and infiltration problems. The soil on the plots was no longer compatible with the sewage treatment plants, which increased the risk of groundwater contamination in the community. Instead, the community opted for a low-pressure sewage collection system to meet residents’ changing wastewater needs.

However, since 8.5 linear miles of the entire pipe were required and the longest segment was over 4 miles long, friction losses were an issue. Adding to the challenge was the general ability to design the best system for the area. After conducting a hydraulic analysis of the area using a low pressure system, the agency was confident that the solution would be suitable for the community given the challenging location and topography. As an added benefit, the combination of the 180 degree drop inlet access design with the flexible drain pipe and directional drilling simplified installation and eliminated the need for road digging.

environmental factors

Both of the above examples had one element in common: proximity to fresh water sources. Whether for drinking water, recreation, or both, protecting environmental resources remains critical to communities and wastewater professionals. Inflow and infiltration (I&I) is often an important consideration when addressing end-of-life concerns of an existing system. Testing water bodies for high levels of contamination can indicate whether a problem is present or imminent and indicate the need for change. In areas near water sources, during heavy rains, a large amount of I&I can occur and overload a sewage treatment plant. For the city sewer company mentioned above, local residents were already aware of the need to “save the lake”. This made the investment and personnel costs of housing replacement more palatable. For ECCFWSD, the nearby reservoir was also a major consideration and concern.

These examples also prove another point: no two situations are the same. The needs of homeowners and businesses, the age and lifespan of the existing facility, maintenance and service costs, and the topography of the area are just a few of the considerations that come into play. In the fix versus replace debate, the best solution is one that is tailored to specific needs and built to last for decades to come.

references

US Census Bureau and US Department of Housing and Urban Development, New Privately Owned Housing Units Started: Total Units [HOUST], retrieved from FRED, Federal Reserve Bank of St. Louis; fred.stlouisfed.org/series/HOUST, 14 November 2021.

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