The reason for the blocks goes back some 12, years, to the end of the last Ice Age, when the Champlain Sea covered much of what are now the St. Lawrence and Ottawa valleys. Some of the former area of this now-vanished sea became covered with what is called Leda clay. Leda clay has a high-water content, which makes it highly compressible.
Putting extra weight on it — such as the weight of a new home — has the potential to squeeze out some of the water, so that the clay compresses. While exposure to the surface has dried out and hardened the upper layers of this clay, the un-weathered soil below still compresses easily. Without proper steps being taken, a house constructed on this type of clay might develop foundation cracks, subside, or even collapse.
Thorough analysis of the soil underneath the building site helps guide the builders regarding what construction methods are needed. It is important to learn the maximum weight the soil will support, and to work within those limitations. Depending on your location in Ottawa, your soil may have some of these soil types listed here from youngest to oldest :.
Some areas of Ottawa, such as the downtown area, have very little soil cover and are primarily composed of bedrock. So before you begin your sprinkler systems plan, it is important to understand what soil your lawn has.
Your lawn and our Ottawa sprinkler systems: An ideal pairing for your soil Can your soil be improved? Regardless of the type of soil, your grass roots need moisture and air to live. Moisture has the role of dissolving the required nutrients for the root system to absorb.
Air prevents the roots from drowning in that water. Air is not a factor you can play with too much; however, the factor of moisture can affect your soil in three ways:. In this case, you will want to install our Ottawa sprinkler systems to give the soil a steady source of moisture.
In addition, a core aeration treatment can alleviate any compaction issues, while adding some healthy topsoil can improve organic content in the soil, as well as its quality.
Across the Ottawa region, the soil composition can be quite varied and the only way to determine the actual soil makeup of your site is by drilling boreholes and taking samples of these materials. However, we can also get a good idea of the types of soil by consulting soil maps published by the Geologic Survey of Canada.
For example, here are the general soil profiles for a few areas in Ottawa:. Random and Engineered Fill Materials Fill materials form the youngest part of the soil profile and consist of soils excavated from their natural location and then transported to another location through human activity.
There are two broad categories of fill materials:. Organic Soils topsoil, peat Recent decomposition of vegetation will form soils that may consist partly or almost entirely of organic matter instead of mineral particles only. Common types of organic soils include:. Sandy Soils silty sand, gravel Sand deposits in the Ottawa area are found in two main areas.
First, in a large triangular patch extending across the Ottawa airport site and the lands to the south, and second, along beaches of old channels of the Ottawa River, such as Mer Bleu, an area southeast of the City. There are also sand deposits in many other areas within the City. The composition of these sand deposits varies greatly from clean, beach-like sand, to silt, silty sand, sandy silt, as well as sand and gravel , but the way that they behave, from an engineering perspective, is similar.
Sensitive Silty Clay 10, years About 10, years ago, eastern Ontario was flooded by the Atlantic Ocean and the Ottawa area was covered by what has been named the Champlain Sea. When this Sea dried up, it left thick deposits of silty clay which now form the geology of eastern Ontario. Since the groundwater level is generally within about 2 to 5 metres of ground surface, the silty clay to that depth has been exposed to air, then oxidized, and finally dried to form a relatively dry and stiff brown or grey-brown crust.
The silty clay below this has never been exposed to air and so has different properties. It is grey, wet and compressible, and it is relatively weak. Glacial Till 12, years About 12, years ago, the glaciers melted and formed our current landscape.
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