Keefe Environmental Services Superfund site is a former chemical waste storage and bulking facility whose operations lasted from 1978-1981 and resulted in chlorinated volatile organic compounds and emerging contaminants (i.e., 1,4-dioxane) impacts to groundwater. As New Hampshire Department of Environmental Services’ trusted advisor and holder of this contract for 24 years, Weston took over this project Site in 2014. Re-evaluation of the selected remedy (groundwater extraction and treatment) was required as its effectiveness diminished and costs to operate and maintain the pump and treat system could no longer be justified. The Amended Record of Decision selected monitored natural attenuation (MNA) of 1,4-dioxane as the new remedy, an approach that had not previously been approved by EPA. The case for MNA, including a 10-year evaluation period, was made successfully by Weston as part of the Focused Feasibility Study due to the development of multiple lines of evidence including refinement of the Conceptual Site Model. Weston is now performing long term monitoring at the Site, as the property owner is in the process of returning the site to beneficial reuse as a solar farm.