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More on Septic Systems and Lakesby Peter Kallin Last week we reviewed a bit about the history of septic systems in Maine and provided a basic overview of the components of a typical system. This week we will discuss some common misperceptions about septic systems, explain what kind of maintenance is required and how often, and provide some recommendations for making existing rules more protective of Maine lakes. As we mentioned last week, Maine's plumbing code provides guidance for installing systems but once the system is installed, maintenance is up to the homeowner, many of whom have little understanding of what is required. Many a homeowner believes "septics are forever," that the septic system should last as long as the house. In fact, systems are generally engineered for a 20-25-year life cycle, and periodic maintenance is required to keep them functioning properly. The most important maintenance that must be done is pumping of the tank when the level of solids reaches about a third to half of the volume of the tank. Because of the baffle arrangement in the tank, if the solids level reaches the baffle (about a third of the distance from the top), solids will be siphoned directly into the leach field, which will lead to plugging and greatly shortened life.
So how do we know when the tank is a third full? One way is to open the tank and measure the level with a stick, but most homeowners don't do this. Instead they rely on estimates of average use or simply pump every three years or so. The table at right shows that it really isn't quite that simple. A typical tank for a year round residential system is 1000 to 1250 gallons. For a family of four, the table shows that three years is a reasonable interval, unless you are using a garbage disposal in which case you should pump twice as often. If your system was designed for a seasonal camp and is only 500 gallons and you have all your kids and grandkids there all summer (averaging 6-7) your system will be filled in one season and should be pumped every year. Just as you have your mechanic look over your car when you get your oil changed, you should have a certified septic system inspector do an inspection of your system when you pump your tank. The inspector should check the level of the scum line to verify no major leaks in the tank, do a visual inspection of the baffles to make sure they are in place and operating correctly, and should both visually inspect the leach field area for indications of leaks (odors, tall lush grass, etc) and do a few small test borings in the leach field to determine if the water level in the field is at the same level throughout the field, which indicates consistent drainage. Most haulers who are licensed inspectors will do this inspection for little or no extra cost because it can potentially lead to additional repair work for them. It is in your interest to do this because relatively minor problems can be detected and repaired before the whole system fails and must be replaced. When a property is sold, a more in-depth point-of-sale inspection should be done, especially if the system is over 20 years old. This inspection should include opening up the distribution box to insure proper drainage and scoping the laterals and other pipes with a camera to look for leaks or blockages. This is required in most states but not in Maine, except in the coastal zone where the clam and worm fishermen successfully lobbied for this. There are a few towns that have local ordinances requiring this but not enough. For example, of the thirteen towns in the Belgrade Lakes Watershed, only Smithfield has such an ordinance in place. If your system is over 20 years old, it is like owning a 15-year old car with over 150,000 miles on it. If you have babied it and changed the oil religiously, it could go another 150,000. If you have been towing your boat, loaning it to all your relatives, and neglecting routine maintenance, be prepared to buy a new car any time. You wouldn't buy a used car like that without having a mechanic give it a thorough check, you shouldn't buy a septic like that without the same precaution. Another common misconception about septic systems is that they break down and treat all wastes dumped into them. A properly functioning system will do a good job of breaking down organic waste and killing or trapping bacteria as the system was designed to do, but even a properly operating system only removes a portion of the nitrogen and phosphorous nutrients that are a threat to our lakes. Some of the nitrogen is removed through the process of denitrification in the anaerobic tank and bubbles off as nitrogen gas, but most flows through to the leach field and eventually reaches the groundwater below as soluble nitrate. About a quarter of the phosphorous is removed in particulate form if the tank is pumped regularly, but the rest flows through the system as dissolved orthophosphate. A typical family of four deposits about 6 pounds a year of phosphorus into their tank — more if they use phosphate soaps and detergents — of which approximately a pound is removed by regular pumping. This means that about five pounds a year of dissolved orthophosphate (the most bio-available) is discharged to the soil absorption system (SAS) that we talked about last week. Aluminum and iron minerals in the native soils will trap most of this phosphorus as long as the soil is aerobic but these minerals eventually become saturated and once the plume reaches the groundwater table this process is much less efficient. Under current Maine code, in the shoreland zone there can be as little as 12 inches of native soil between the bottom of the leach field and the groundwater table. Most states require a minimum of four feet. This narrow zone of adsorption is insufficient to protect lakes with significant development around them. If there are 500 septic systems around the lake, 2500 pounds of phosphate a year is being discharged to the soil around the lake. Eventually some of this will end up in the lake. The Maine Congress of Lake Associations (Maine COLA) has recommended that Maine amend the plumbing code to require two feet of native soils below septic systems in the shoreland zone of lakes at risk from development to ensure that more of this phosphorus will be trapped before reaching the groundwater and eventually the lakes. The issues discussed above deal with properly operating systems built to code. Older, grandfathered systems are even less likely to be effective at removing phosphorus and more likely to have phosphorus-saturated soils beneath them. Most Maine municipalities have no septic management ordinances in place. York, and soon China, are exceptions. In places where such programs were put in place or where they have done random sampling of operating systems, 15 to 30% of existing systems were not fully functioning. Common problems include clogged leach fields, roots in pipes, cracked pipes or faulty joints where pipes enter or leave tanks, broken baffles in tanks, etc. Systems that are malfunctioning are even more of an issue for both the lakes and for public health. The best way to minimize the impact on the lakes is to keep your system operating in peak condition. Keep it pumped, inspect it regularly, and don't put anything in it other than human waste. Flushing cigarettes, tampons, or household chemicals down the toilet shorten the life of your system and decrease its efficiency. Remember that microbes are doing the dirty work in your system and stuff that kills microbes (bleach, paint thinner, etc.) will kill the microbes in your tank and biomat. Don't drive or park on your leach field — you risk crushing the pipes or compacting the soil and decreasing drainage capacity. Don't let woody plants, especially trees grow on your field. They will grow roots right into your drainage pipes and plug them. Please stop into the BRCA office if you have questions about your system. We have lots of information that can help you. Or check out the septic system publications from the University of Maine Cooperative Extension. Peter Kallin, Executive Director of the Belgrade Regional Conservation Alliance (BRCA), can be contacted at | ||
