Saturday, March 1, 2008

Okanagan Geology - Don't build your house upon the sand

"He shall be likened unto a foolish man, which built his house upon the sand: And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it."

For anyone familiar with this ancient parable you will understand it is a practical example of what happens when you do not build your home upon a strong foundation.

The Okanagan valley is an area of Canada both unique in climate and geology. Ranging from sandy/gravel soils of Canada’s only desert in Osoyoos to the massive silt and sand deposits around Penticton to the ancient volcanic features of Mount Boucherie and Dilworth Mountain in the Kelowna area. These unique features have been a major focal point to attracting people to the valley. But it also causes unique problems for construction. Clay and high sulphate soils have caused severe damage to foundations in the central Okanagan while improper drainage has led to sink hole development in the areas around Penticton. The Okanagan valley is rich in mineral deposits including uranium, which has caused water quality issues in some communities. Several fault lines also cross the Okanagan valley. The Okanagan Fault line is recorded as one of BC’s largest earth structures. These fault lines have resulted in areas in additional code requirements for commercial foundations in the Kelowna area. It has also resulted in the Central Okanagan having high potential for Geothermal heat development. These unique issues only become more relevant as we continue to build in areas that we would have never even thought of developing 5 years ago. Money is a strong motivator to overcoming land issues. That is why I would recommend seeking out the services of professional geoscientist (geotechnical engineer) if you are building anything larger than a garage or adding

Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. Geotechnical engineering includes investigating existing subsurface conditions and materials; assessing risks posed by site conditions; designing earthworks and structure foundations; and monitoring site conditions, earthwork and foundation construction.

A typical geotechnical engineering project begins with a site investigation of soil and bedrock on and below an area of interest to determine their engineering properties including how they will interact with, on or in a proposed construction. Site investigations are needed to gain an understanding of the area in or on which the engineering will take place. Investigations can include the assessment of the risk to humans, property and the environment from natural hazards such as earthquakes, landslides, sinkholes, soil liquefaction, debris flows and rock falls.

A geotechnical engineer then determines and designs the type of foundations, earthworks, and/or pavement subgrades required for the intended man-made structures to be built. Foundations are designed and constructed for structures of various sizes such as high-rise buildings, bridges, medium to large commercial buildings, and smaller structures where the soil conditions do not allow code-based design.

For more information on geoscience and work undertaken by a professional geoscientists, see the Association of Professional Engineers and Geoscientists (APEGBC) website: or check out Wikipedia – Geotechnical Engineering.

If you are interested in leaning more about the Okanagan, I would suggest picking up a copy of Okanagan Geology British Columbia

No comments: