Feature Article January 15, 2003
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How well is your well?by Gray MerriamYour well is not turned off for the winter. Ground water is still warm and moving. Your well needs care year round. First on your list is to take a sample for testing every month or two for older or dug wells, and oftener during periods of melt and runoff. For newer, well-sealed wells, test every year. Each test should take weekly samples for three weeks. Check with your Health Unit to get proper sample bottles and to learn when they will accept samples. Follow the instructions and take only fresh, cool samples to them.
The test will tell whether your well has high counts of total coliform bacteria and of fecal coliforms. Most coliform bacteria are not harmful and can come from any vertebrate animal - toads to pigeons. However, high numbers may indicate that you might have some source contaminating your well. Because a few types of E. coli, like the ones in Walkerton and in some hamburgers, can be deadly, you should react when your test is over the limit - especially if repeated tests are high. Your Health Unit will help interpret the results.
If your well is contaminated, find and eliminate the source and disinfect your well and water system.
Surface drainage getting in past your well cap is one entry for contamination. So are leaky casings. And no casing protects a dug well. Groundwater contamination can also happen where surface water enters the soil and rock to recharge the groundwater. If your well is drilled in limestone, any input of contamination is likely to spread to many wells through the solution channels in the limestone. Look nearby for the most likely source of contamination. But do not assume that it can only come downhill. Groundwater follows slopes and pressures in the bedrock, not on the surface. It can also follow channels created along old buried pipes.
When you have stopped the source of contamination, disinfect your well. Use only real bleach, not a chlorine-free substitute. For drilled wells pour in 5 oz. (142 ml.) of 4% household bleach for every 25 feet of water depth in the well. For dug wells 3 feet in diameter, pour in 1 quart ( 1 L.) of household bleach for every 5 feet (1.5 m) of water depth. Let the bleach mix to bottom of the well for an hour. Then turn on an outside tap and let it run (not on your plants) until you smell bleach. When you smell bleach from the hose, turn it into the top of the well and rinse down the casing or cribbing for 30 minutes. This may also wash some sediment into the well which will show up when you turn on the inside taps. Do not be alarmed by it. Turn off the hose and turn on all inside taps and let run until you smell bleach. Turn off all taps and let the system sit without use for 24 hours. Then turn on the outside tap (to keep as much bleach as possible out off your septic system) and let run until you no longer smell bleach.
Take another sample for testing after 48 hours and take another after one week.
Remember that testing by your Health Unit does not deal with objectionable tastes or bad smells that are common in some wells or iron staining or with hardness that is a problem in limestone wells. For these problems or chemical contamination, heavy metals or road salt, seek professional laboratory testing and advice.
For more information see: Best Management Practices, Water Wells (ISBN 0-7778-6149-6 - Agriculture Canada and Environmental Living: Protecting the Environment at the Cottage, Vol. 4 (ISBN 0-7778-1072-7 V.4 - Ont. Ministry of the Environment.
