In November 2005, the United States Department of Energy requested that Sandia National Laboratories provide a technical review and evaluation of proposed changes in the Montana Water Quality Standards related to Coal Bed Natural Gas produced water treatment and discharge. The goal of Sandia's technical evaluation was to assist the Department of Energy in understanding the technical feasibility and costs associated with meeting the proposed standards and the potential impact on coal bed natural gas production in the region and impacts on natural gas production and supplies nationally. This report summarizes the results of the Sandia review of the proposed standards, with a focus on the technical issues associated with coal bed natural gas produced water reinjection and treatment. Based on our review, there appear concerns with the proposed new standards. These concerns include inconsistencies in treated water constituent standards, identification of treatment standards for arsenic and other constituents that are not currently attainable, lack of the use of EPA recommended methods to assess innovative treatment technology cost and performance impacts, limitations on the use of commonly recognized alternative water management options, and identification of water treatment levels that will make the treated water highly reactive and negatively impact use for irrigation and wildlife. The results of the Sandia review and the technical evaluations of various parts of the proposed standards are summarized in this report.