Atlantic PIRI developed and released Version 1 of the Atlantic RBCA process, User Guidance and the Atlantic RBCA Tool Kit in 1999. Version 1 of the Atlantic RBCA Tool Kit was based on the ASTM Standard E 1739-95, Standard Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites. Atlantic RBCA was revised in 2003 to reflect changes recommended for harmonization with Canada Wide Standards for Petroleum Hydrocarbons (CWS PHC) developed by the Canadian Council of Ministers of the Environment (CCME) in 2001. Atlantic RBCA Version 2 was subsequently updated to reflect the ASTM Standard E2081-00 and continues to be based on the carbon fractionation data published by the US TPH Criteria Working Group. In January 2008, CCME completed their five year review of the CWS PHC for soil. Where each of the Atlantic Environment Ministers had signed the CCME Harmonization Agreements respecting environmental standards, they are each bound to ensure an equivalent level of environmental protection with CCME standards. As a result, Atlantic PIRI conducted an internal review of the 2008 CWS-PHC and supporting documents and recommended several changes to Atlantic RBCA Version 2. The changes incorporated into Atlantic RBCA Version 3 primarily reflect a number of default modeling parameter values revised in the 2008 CWS PHC report. Atlantic PIRI subsequently commissioned Groundwater Services Inc. (GSI) to complete the required changes to the Atlantic RBCA Tool Kit. The result is the revised Atlantic RBCA (Version 3) software Tool Kit for Atlantic Canada, this updated User Guidance document, and supporting documentation (Appendices 1-8). Provincial regulators may also update their policies and guidelines as required to support these changes.