Implementation of Subsoil Sodium Adsorption Ratio Guidelines into the Alberta Environment Subsoil Salinity Tool

Tony Knafla
GL 09-9189-50

Salinity impacts have the largest total foot-print and potential environmental liability of all oil and gas-related impacts to soil and groundwater. The Subsoil Salinity Tool currently provides benefit to oil and gas companies, environmental consultants, government environmental agencies, and landowners due to the ability to provide standardized assessment and remediation of the chloride aspect of salinity impacts. It would be of value to extend these benefits to sodicity (SAR), another important aspect of salinity impacts. Subsoil SAR currently has inadequately refined guidelines which may lead to over-remediation of certain sites or the inability to generate effective remediation or risk management plans on other sites due to a lack of appropriate, risk-based guidelines. Having subsoil SAR guidelines implemented in the SST in a similar manner to subsoil chloride guidelines will provide enhanced efficiency for site investigation, guideline derivation, and SST user training. Industry would benefit from this project in terms of reduced investigation and remediation costs as well as improved environmental performance. This could ultimately result in the accelerated return of historically salt-impacted land to productive use while maximizing soil conservation and the effectiveness of remediation resources.

This project does not include additional laboratory research, and focuses on algorithm development, software implementation, and finalization of subsoil SAR guidelines. Previous and current research projects performed by Equilibrium Environmental in conjunction with PERD, AUPRF, Alberta Environment, and industry in-kind funding have generated a proposed framework for subsoil SAR guidelines. The framework would be based on combinations of multiple relevant factors (SAR, EC, soil texture, water table depth, lateral and vertical impact dimensions, infiltration rate) producing an output of subsoil SAR guidelines that are not associated with an unacceptable risk of potential adverse effects. The Subsoil Salinity Tool provides an effective mechanism to collect site-specific input parameters relevant to subsoil SAR impacts, apply appropriate mathematical algorithms, and produce subsoil SAR guidelines on a Tier 2 basis. This project proposes to implement additional SAR-related data input into the SST, and implement suitable algorithms following a regulatory approval process in order to produce subsoil SAR Tier 2 guidelines on a site-specific basis by operators of the SST. This will allow the simultaneous generation of subsoil chloride and SAR guidelines from one execution of the SST, in addition to focusing remediation efforts on the salinity parameter of concern (remediation depth analysis will simultaneously assess changes in chloride and SAR guidelines).