Protecting Your Well From Contamination

Probably the most important asset on your property is your water well. Unfortunately it is often misunderstood and taken for granted. This lack of understanding increases the risk of contamination to the groundwater. Contamination can be a health risk to both people and livestock. Groundwater is an important resource that needs to be protected.

Contamination of groundwater is hard to detect in early stages. By the time the problem is obvious, there is little that can be done to remove the contaminant from the system. It can take a very long time for contaminants to be flushed out, often decades or longer. Prevention of pollution is the only effective approach.

Often the biggest contamination threats are things in your own backyard. The following are examples of potential problems and some ways to prevent them.



Poor Well Construction

• The fastest way to contaminate groundwater is through a well. A well provides a direct path for contamination to travel from the surface to the aquifer.
• A proper well casing or formation seal effectively prevents surface water or contaminated groundwater from seeping along the outside of the casing and entering your well (see Figure 1, Annulus or Casing Seal).
• Multi-aquifer well completion allows mixing of water from several aquifers which may have significantly different water qualities (see Figure 2, Multi-Aquifer Well Completion).

Figure 2 Multi-Aquifer Well Completion

• Old wells that are poorly constructed or have rusted steel casing can lead to contamination of an aquifer. Nearby wells, completed in that aquifer, may eventually become contaminated.

• Well pits provide a place for contaminated surface water or shallow groundwater to collect. When this water sits in the pit, it can contaminate the aquifer by seeping around the outside of the well casing or flowing into the well. This type of construction also makes it very susceptible to contamination by small animals and insects (see Figure 3, Well Pit). For this reason well pits are no longer allowed.
• Well pits can also be a deadly safety hazard. With changes in atmospheric pressure, air from within the well casing can displace "normal" air in the well pit. Well gases or low oxygen content resulted in human deaths, even recently. People entering the well pit can be asphyxiated.

• Methane gas buildup can cause explosions.

Figure 3 Well Pit

Figure 4 Pitless Adaptor

• Hydrants are designed to prevent freezing by draining water back down the well whenever they are shut off. This means that the contents of the stand pipe and hose will syphon back into the well. If the hose is directly connected to the water in a tank, this water will also be syphoned down the well (see Figure 5, Farm Water Hydrant). The contents of stock tanks, sprayers, etc. are definite contaminants.
• Shallow groundwater can be contaminated by poorly designed, installed or operating sewage systems (see Figure 6, Poor Sewage Systems). Cesspools constructed over the years have been specifically identified as a greater risk.

Prevention: Properly design, locate and install sewage systems. (See Module 3 "Design and Construction of Water Wells" for minimum distance requirements.) (See Module 11 "Contacts for More Information" Alberta Human Resources and Employment, for requirements.)

Figure 6 Poor Sewage Systems

Seismic Shot Holes

• Improperly plugged shot holes can be a direct path for contamination to groundwater. Shot holes are typically 15-18 m (50-60 ft.) deep and are plugged by installing a plastic plug (with identification) into the hole, at a depth of not less than 1 m (3 ft.) below ground level, followed with bentonite pellets and firmly tamped borehole cuttings placed progressively upwards to the ground surface.

• Manure or fertilizer that is applied to land at a greater rate than growing crops can utilize the nutrients can result in nitrates leaching into groundwater. Fertilizer that is applied to lawns or gardens at excessive rates may also contribute.

• Storage of manure concentrates nutrients in one location which can increase risk of contamination.

• Leaking fuel can contaminate your water supply with hydrocarbons by penetrating water distribution lines or seeping directly into your aquifer.

• The most common reason pesticide contamination of wells occurs is poor pesticide handling in the area around the well.
• The highest contamination risk involving field application is when the following factors all come together:
• persistent pesticides
• high water table
• highly permeable soils
• high pesticide application rate.

• Properly rinse and dispose of empty pesticide containers.

• Wells can easily become contaminated with bacteria when pumps, piping and equipment are laid on the ground prior to placement into the well or during maintenance procedures.
• Pumps, piping and equipment should be thoroughly disinfected and the well shock chlorinated.

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