SOILS OF BRITISH COLUMBIA
Here in British Columbia, we have a fairly wide array of types of soils that can range from hard pan or composed rock to silt or riverbed sand. Here in layman's terms is an overview of these types of soils.
Expansive Clay Soils will swell and heave when wet, then contract and consolidate when dry thus allowing anything whether it is a building, fence, tree, sidewalk, or plant to move as these moisture conditions change.
Rock will erode and expand slightly if in some slope conditions such as faults or fractures and only in these conditions. However faults and fractures do have a wide berth line depending on the density of shale.
Sand has continuity when moist or dry and does not expand or contract but will allow underground water to move it into voids left by other types of soil conditions and cause horizontal movement.
Loam or Select Fill will not change much with any type of moisture variation unless erosion occurs which will change the capacity of this soil.
Canada has developed its own system of soil classification. Here is a brief description of the four types of soils that can commonly be found in B.C.
Brunisol is a normally immature soil commonly found under forested ecosystems. The most identifying trait of these soils is the presence of a B horizon that is brownish in color. The soils under the dry pine forests of south-central British Columbia are typically brunisols.
Luvisol is another type of soil that develops under forested conditions. This soil, however, has a calcareous parent material which results in a high pH and strong eluviations of clay from the A horizon.
Organic soil is mainly composed of organic matter in various stages of decomposition. Organic soils are common in fens and bogs. The profiles of these soils have an obvious absence of mineral soil particles.
Regosol is any young underdeveloped soil. Immature soils are common in geomorphically dynamic environments. Many mountain river valleys in British Columbia have floodplains with surface deposits that are less than 3000 years old. The soils in these environments tend to be regosols.
These are soils with the potential to shrink or swell are found mostly along the coast and southern British Columbia. Soils with this condition create difficult performance problems for buildings constructed on these soils. As the soil water content increases, the soil swells and heaves upward. As the soil water content decreases, the soil shrinks and the ground surface recedes and pulls away from the foundation. These problems are of particular concern in buildings with shallow foundations.
Buildings are normally not built in areas where the soil conditions are perfect. The developer selects land for various reasons, which may include availability, cost, proximity to industrial areas, and proximity to schools. Here in this province it is the view of the mountains, ocean or lake that draws developers into these types of soil conditions.
The best way to find out if the soil beneath your building is expansive is to ask a geo technical engineer. He or she will make soil borings on your site and take samples so these soil samples can be tested for expansiveness. These samples will show how expansive the soil is and at what depths. The geotechnical engineer will provide a written report on his findings.
When a structure is supported by various soil conditions, the building may move differentially. As an example, if one half of the foundation sits upon expansive clay and the other half bears on select fill and/or rock, the amount of seasonal movement will vary from one half to the other half. If the foundation system is not properly designed, the differential movement may cause damage to the foundation and structure. Many times building pads will be cut and/or filled so the bearing soil is all of the same type.
Population growth and urban sprawl means there is not much development land left in many areas, and what is left is not very good. A lot of homes are being built on expansive soil - earth that swells when it rains - without adequate safeguards.
Swelling soil isn't the only problem. Take for example the North Vancouver landslide which claimed a life a few years ago and the Ptarmigan landslide in Mission only a year ago. Both of these landslides were caused by unstable soil that gave way. These homes were built on organic soils that have decayed over the years.
Before you do anything else, remember that these 3 steps will save you money in the long run:
- Call in a Geo Technical Engineer to assess your soil conditions.
- Call in a Structural Engineer to assess any structural damage.
- Call in Mainland Concrete Lifters Inc. to provide a complete turn key assessment of damage in conjunction with both engineers to find a repair solution.
If you need assistance in locating these engineers, please call our office 1-800-231-3132
~ FOUNDATIONS FOR LIFE ~
