Open File Report 2009-04

Open File Report 2009-04

OFR 2009-04

Description of the Process for Defining the Base of Groundwater Protection

Author(s) Lemay, T.G. Date 2009-07-13

This report describes the methods used to map the base of groundwater protection for Alberta and discusses the results.

In 2005, Alberta Environment (AENV) commissioned the Alberta Geological Survey (AGS) to map the base of groundwater protection (BGP) across Alberta Alberta Geological Survey updated Statistical Series 55 (ST-55) through the completion of Statistical Series 55-2007 using a geostatistical mapping process where the unit being protected was a bedrock unit. Stratigraphic information was used as the basis for the interpretation. Where the unit being protected was the drift, AGS used available bedrock topography or drift thickness information as the basis for the interpretation.

The BGP is the best estimate of the depth at which saline groundwater (water with a total dissolved solids concentrations = 4000 mg/L) is likely to occur. In the original ST-55 document, the formations where non-saline groundwater could be found were identified over most of the province. In an effort to be conservative, and to maximize the protection of non-saline groundwater, AGS, in consultation with the Energy Resources Conservation Board (ERCB) and AENV, chose to map to the base of these designated formations. Where formations were not designated, the decision was made to select the formations where non-saline groundwater was likely to be found in, and to map to the base of those formations.