Feature Article February 20, 2002
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Rain, your septic system, and your well - Part 3by Gray Merriam, Landscape EcologistOn the limestone to the south along Road 38, if a septic system (or several) is not working properly, the overflow can easily get into the water channels in the limestone. Because those channels are all interconnected, the pollution can flow down and sideways across a very large area and get into everyones wells. Sydenham knows about this. Up north on the granite of the Canadian Shield, there are fewer cracks letting the surface water flow into the groundwater deep in the bedrock. Instead, there are many lakes, creeks and ponds on the surface, and poorly built septic systems and privies discharge their liquid waste along the surface of the rock and into these surface waters. Only in the very rare circumstance of having some depth of soil with lots of small plants growing on it, will there be a chance of intercepting the liquid septic waste. Even when drilled in granite, if the well casing is not tight and properly sealed, waste from septic systems, privies or manure piles can flow down along the casing into the well. Walkerton knows about this. We can also get a bad experience from wells drilled deep in granite if the drill happens to hit a vein or a deposit of minerals containing a lot of iron or of sulfur. The Sharbot Lake schools and the Learning Centre know about this. Your well can be connected to your septic system if you are not careful its almost unavoidable down on the limestone. Your well is almost always connected to the rain also. Unless you are pumping fossil water, the level in your well goes up and down with rain and drought. On the granite, it takes some time for the rain to soak everything else on the surface and then gradually start filling up the lakes. This past summer, there was a lag of several weeks between when it started to rain and when the lakes started to rise. It takes additional time before the water flows into the cracks in the rock and eventually gets to the bottom of your well casing; but it does, thank goodness. A year ago, when everything on the surface was already wet and the lakes already full, a week of heavy rain brought the water in our 180-foot well right up to overflow from the casing stand pipe. This well is drilled into a chimney of rock fractured by two intersecting faults, and the water flow up this chimney is almost artesian. We are lucky because we can pump 20 gallons per minute into a heat exchanger which heats our whole house.Fortunately, it also takes time for a drought to have an effect on the water in your well in the granite. Many were glad of this last summer. On the limestone, the time between rain and rising water in wells is much shorter, because it is so easy for the rain to recharge the channels in the limestone. In some places where big channels, called sinkholes open right to the surface in limestone, heavy rains form temporary creeks that gush right into the sinkholes, and one big storm can refill all the water channels. Unfortunately, droughts can also affect wells in limestone more quickly unless the wells are drilled deeply enough to draw on the big, deep underground rivers in the limestone. So, your well not only pumps groundwater up and turns it into surface runoff, but it is also connected to the water which evaporates from the oceans and returns to the land as rain - and your well also is connected to the flow of water that you have used and dumped back into the water cycle. Treating bad water by chlorination and filtering only treats the symptoms, such as bad smell and bacteria; you have to think about the interconnecting flows of the water cycle if you want to get at the real causes of bad water, and if you want to keep it out of your well.
This is the third article in a four-part series. Gray Merriam is a retired professional ecologist, and is a member of our Editorial Advisory Committee.
