The AS&T Program has a critical role in our mission to fulfill DOE’s post-closure responsibilities and to ensure the future protection of human health and the environment. Given the long half-lives of some radionuclides, our sites will require LTS&M for hundreds or even thousands of years. Incorporating improvements in scientific understanding and technology applications into site management and remediation strategies improves cleanup effectiveness, protectiveness, and sustainability and can decrease long-term costs. The overriding goal of AS&T is to incorporate advances in science and technology to improve capabilities toward fulfilling the LM mission. AS&T strives to move the “state of the science” in long-term stewardship strategies and methods into the “state of the practice” at LM sites.