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By Dave Dempsey
Groundwater, a critical part of Michigan’s water cycle, is out of sight—and so is the groundwater pollution that contaminates thousands of drinking water wells and reaches hundreds of rivers and lakes across the state. Despite its invisibility to the naked eye, groundwater contamination sickens Michigan residents. About 45% of the Wolverine State’s population drinks well water.
Among the biggest culprits in degrading Michigan’s groundwater are failing septic systems. Designed to treat household wastewater in areas not served by sewers and buried beneath the land surface, septic systems require proper maintenance if they are to avoid polluting groundwater. Such maintenance includes regular inspections and, when necessary, pumping out of the wastewater. But because there are no inspection and maintenance requirements in most areas of the state, an estimated 130,000 septic systems in our state are failing. That means sewage and associated microorganisms are reaching groundwater, lakes, and streams.
September 20-24 is SepticSmart Week in Michigan and nationally—an opportunity for owners of property with septic systems to learn about the threat failing systems pose to our water resources, and ways to prevent or minimize such pollution. As our allies protecting Crystal Lake in Benzie County, Michigan, point out: Being septic smart can extend the life of a septic system, keep well water safe, protect the environment and prevent accidents at home.
FLOW’s Groundbreaking Reports on Groundwater
As FLOW described in our fall 2018 report on groundwater contamination in Michigan, and a second report we released earlier this year, our state is the only one of the 50 states that lacks a statewide sanitary code requiring regular inspection and maintenance of small, mainly domestic septic systems. Because of the gap in state protections, some counties, townships, cities, and villages are enacting local ordinances in place of statewide requirements, but they are relatively few out of Michigan’s approximately 2,000 local units of government.
Septic systems are small-scale wastewater treatment options, used when a home or complex cannot easily be connected to a municipal sewer system. Raw sewage and wastewater (e.g., bath water and dishwater) are first pumped from the home into the septic tank. This is an underground, sealed, concrete tank where the household waste is treated. Here, solid waste sinks to the bottom of the tank and materials such as oil form a layer of scum on top. Bacteria in the tank break down the solid waste, while the wastewater migrates out of the septic tank and into the drain field. Perforated pipes distribute the liquid wastewater throughout the drain field. Once out of the pipes, the wastewater effluent seeps through a gravel layer, then through the soil. Both filter the wastewater before it flows into the groundwater or nearby surface water.
Leaking or malfunctioning septic systems allow organic wastewater compounds like nitrate and E. coli to percolate through the soil and enter the groundwater. Leakage and effluent runoff are also major contributors to E. coli levels in surface water. The Michigan Department of Environment, Great Lakes, and Energy (EGLE) has identified 196 rivers, lakes, and beaches with E. coli levels over the EPA limit.
Between 2013 and 2014, an estimated 5.7 billion gallons of untreated sewage from failing septic systems were pumped into surface water in Michigan. A 2015 study headed by Dr. Joan Rose, co-director of Michigan State University’s Center for Advancing Microbial Risk Assessment and Center for Water Sciences, sampled 64 river systems that drain approximately 84 percent of the Lower Peninsula for E. coli and the human-specific source tracking marker bacteria called B-theta. The more septic systems in the watershed, the more human fecal source tracking bacteria were found in the water.
Failing septic systems have been correlated with disease. A 2003 study found that septic system densities were associated with endemic diarrheal illness in central Wisconsin.
Septic Systems and Emerging Contaminants
Human wastes are not the only pollutants that failing septic tanks are releasing to groundwater and surface water. So-called emerging contaminants are found in household wastes, whether they discharge to publicly owned sewage systems or septic tanks. Twenty different studies on septic systems have identified 45 contaminants in septic effluent, including pharmaceuticals, personal care product ingredients, chemicals in cleaning products, flame retardants, hormones (both natural and synthetic), and other common substances such as caffeine. Septic systems are somewhat effective at removing chemicals such as acetaminophen, caffeine, and alkylphenols, a common group of ingredients used in cleaning products. But some chemicals remain largely untreated, including the carcinogenic flame retardant TCEP, an anti-epilepsy drug called carbamazepine, and the antibiotic sulfamethoxazole.
One cause of the septic system pollution problem is homeowners’ lack of awareness. A 2018 study of mid-Michigan residents likely to have septic systems, conducted by Public Sector Consultants, found:
- Approximately 30 percent of residents did not know they have a septic system.
- The average age of septic systems was 28 years old.
- Forty-three percent of respondents indicated they had not had their system pumped within the last 5 years, and 25 percent indicated that they did not pump or maintain their system on a regular basis.
- Only 15 percent of residents were aware of the normal lifespan of a septic system.
Only 11 of 83 Michigan counties have ordinances that require septic tank inspection at the time property is sold. Within the first 6 years of implementing their ordinances, two Michigan counties found 1,000 failed septic tanks and 300 homes without any septic system or other wastewater treatment.
Tips for Properly Maintaining Septic Systems
Protect It and Inspect It: Homeowners should generally have their system inspected every three years by a qualified professional or according to their state or local health department’s recommendations. Tanks should be pumped when necessary, typically every three to five years.
Think at the Sink: Avoid pouring fats, grease, and solids down the drain. These substances can clog a system’s pipes and drainfield.
Don’t Overload the Commode: Only put things in the drain or toilet that belong there. For example, coffee grounds, dental floss, disposable diapers and wipes, feminine hygiene products, cigarette butts, and cat litter can all clog and potentially damage septic systems.
Don’t Strain Your Drain: Be water-efficient and spread out water use. Fix plumbing leaks and install faucet aerators and water-efficient products. Spread out laundry and dishwasher loads throughout the day—too much water at once can overload a system that hasn’t been pumped recently.
Shield Your Field: Remind guests not to park or drive on a system’s drainfield, where the vehicle’s weight could damage buried pipes or disrupt underground flow.
Pump your Tank: Routinely pumping your tank can prevent your septic system from premature failure, which can lead to groundwater contamination.
Test Your Drinking Water Well: If septic systems aren’t properly maintained, leaks can contaminate well water. Testing your drinking water well is the best way to ensure your well water is free from contaminants.
Source: Michigan Department of Environment, Great Lakes, and Energy.