Groundwater is water that is held underground in cracks or pore spaces in rocks (porosity). Rock and loose sediment units such as sands and gravels, that allow groundwater to move through them easily (permeability) are called aquifers. Groundwater in Alberta moves underground through aquifers, not underground rivers, and typically flows very slowly.
Source: ACWADAM, 2010
Fresh water aquifers in the vicinity of Primrose/Wolf Lake Oil Sands Project (PAW) that may have been affected by the bitumen flow to surface only exist within shallower, Quaternary-aged geologic units. The Quaternary is a geologic time period that spans from 2 million years ago to the present day, typified by periodic glaciations where large continental ice sheets formed and receded. These glaciations have resulted in the deposition of the Quaternary-aged geologic units which consist of layers of sands, gravels, silt and clays.
The layers have been mapped and named by geologists across Alberta. Below is an image which shows the typical Quaternary geology at the PAW flow to surface sites.
The sand and gravel units, which are permeable and porous, allow for groundwater to pass through them easily, and are called aquifers. They are separated by silt and clay rich till units called aquitards which do not allow water to pass through them easily.
Primrose South Regional Quaternarty Cross-Section
Canadian Natural’s geologists have mapped the aquifers and aquitards across the entire PAW area. The mapping helps in the understanding of aquifer impacts in different areas. For example, only one aquifer, the Ethel Lake Aquifer, has been identified and mapped in the area of the flow to surface site in Primrose South. This aquifer is about 85 m deep, and is not in direct contact with any surface water bodies.
Click here to see a larger image.