The recent release of the Subsoil Salinity Tool Version 3.0 represents a substantial upgrade and update to the previous Version 2.5.3, and incorporates technological and protocol advancements in many areas. These include harmonization of many parameters with Tier 1 protocols, upgrades to the drainage rate algorithms, upgrades and refinements to the dugout algorithms, more elaborate modeling for aquatic life, and more a refined multi-step mixing model for the DUA pathway. It also includes incorporation of Tier 2 subsoil SAR and sodium guidelines based on previous Alberta research. A high-level description of all these updates and upgrades have already been provided in the SST Version 3.0 User Manual, but due to the complexity of many of the topics they were touched upon mainly at a high-level to allow software operation but not necessarily an in-depth understanding of the underlying technical details. This project involves creating a companion “Technical Manual” to go with the already-existing “User Manual”, and will go into substantially more depth outlining the methodology, modeling techniques, and modeling assumptions used in the SST Version 3.0. This will provide an important additional reference source for both consultants and regulators (has been requested by both AEP and AER), and will help ensure transparency of the tool and an in-depth understanding of those using or reviewing assessments created using the tool. It could also contain a section describing potential techniques to adjust and apply the guidelines generated from the tool to other nearby relevant jurisdictions such as Saskatchewan which have similar salinity issues and a compatible underlying regulatory framework. The inclusion of relevant case-studies could also serve as a useful learning tool and update/refresher for practitioners using the tool.