Thompson Rivers University
Thompson Rivers University

Ground Water

Ground Water

Definition

Ground water occurs when runoff and precipitation seep through the soil and are collected in underground reservoirs called aquifers. Aquifers can be a few hectares to thousands of square kilometres in area, and a few metres or hundreds of metres deep. Ground water is the technical name for well water.

Ground water comes in two general forms: deep and shallow.

Deep ground water is less susceptible to contamination from natural and human sources and generally does not need treatment for biological hazards.

Contamination Risks

Minimizing Contamination Risks

Keeping a water source safe starts at the point where your system first contacts the water. The following are some basic steps you can take at the source to minimize hazards to water quality.

Construction

Poorly constructed wells can lead to the contamination of a ground water source that supplies many users.

If you are hiring people to work on your water system, make sure they are trained and qualified. Most provinces have a registration process or require certification for contractors who construct water systems, and many only allow registered or certified well installers to drill or dig wells.

A professionally drilled well will have a well log that records the water level and the soil conditions. This information will help you determine the amount of water, the water quality, and the degree of source protection you can expect.

More information on the construction standards and guides in your province is available from your local Ministry of Environment or Ministry of Health.

Well Sealed

A common issue with wells is improper well seals after construction. If a well is not sealed properly with clay (surface seal) and a secure cover (well seal) is not fitted, contaminants such as animal droppings and runoff can enter into the groundwater.

In coastal areas, salt water can seep into well water, which can be costly to treat.

NB: If an aquifer has been contaminated, it may take decades before it produces drinkable water again, since there is no easy way to flush out contaminants

Shallow Wells

Shallow wells are usually dug, are often low in dissolved minerals, and often produce good quality water if protected from biological hazards.

Shallow wells can be influenced by nearby surface water and are more likely to contain biological hazards than deep wells.

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General Construction Tips for Wells

Surface Seals

Make sure that the area between the well casing and the ground is sealed.

To make a surface seal for a well:

  1. Make well hole a third to a half metre (1–2 feet) larger than well casing.
  2. Place dried clay or bentonite (a highly absorbent clay) alongside casing.

The clay absorbs water and expands to act as a seal that prevents surface runoff and pathogens from entering through the outside of the well.

Well Seal

Well caps should have a tight-fitting seal to prevent contaminants from entering the well.

On large-diameter dug wells it may be necessary to construct a lid. It should be fitted with a rubber seal to prevent contamination by rodents, insects, or surface water.

If a vent cap is necessary, it should be fitted with a fine-mesh screen.

Pump House

An important part of construction is the well or pump house. The pump house should be vented to allow the escape of gases that may come from the well, and the vents should be screened against rodents and insects.

Pump houses with unsealed doors and windows make wonderful winter homes for rodents whose droppings can be the source of disease.

The pump or well house should not be used for storage of paint, gardening chemicals, oil or other possible pollutants. These substances can be very harmful even in small quantities if they enter your well.

Floodproofing

The well casing should extend a third to a half metre (1–2 feet) above the ground to prevent any chance of floodwater overflowing the top or running down the outside of the well.

Deep Wells

A deep well usually requires drilling and, if constructed properly, is usually protected from most biological hazards. Go to the topic Minimizing Contamination for construction tips.

Deep wells, however, often contain dissolved minerals that can affect water quality:

  • High levels of calcium and magnesium create hard water.
  • High levels of arsenic or fluoride can be harmful to health.
  • High levels of iron, manganese, or sulphur can stain plumbing fixtures and laundry and affect the taste and smell of the water.
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General Construction Tips for Wells

Surface Seals

Make sure that the area between the well casing and the ground is sealed. To make a surface seal for a well:

  1. Make well hole a third to a half metre (1–2 feet) larger than well casing.
  2. Place dried clay or bentonite (a highly absorbent clay) alongside casing.

The clay absorbs water and expands to act as a seal that prevents surface runoff and pathogens from entering through the outside of the well.

Well Seals

Well caps should have a tight-fitting seal to prevent contaminants from entering the well. Sanitary well seals are available for most sizes of drilled wells. The lid should be fitted with a rubber seal to prevent contamination by rodents, insects, or surface water.

If a vent cap is necessary, it should be fitted with a fine-mesh screen.

Pump House

An important part of construction is the well or pump house. The pump house should be vented to allow the escape of gases that may come from the well, and the vents should be screened against rodents and insects.

Pump houses with unsealed doors and windows make wonderful winter homes for rodents whose droppings can be the source of disease.

The pump or well house should not be used for storage of paint, gardening chemicals, oil or other possible pollutants. These substances can be very harmful even in small quantities if they enter your well.

Floodproofing

The well casing should extend a third to a half metre (1–2 feet) above the ground to prevent any chance of floodwater overflowing the top or running down the outside of the well.