As mandated by section 19 of the Protecting our Infrastructure of Pipelines and Enhancing Safety Act of 2016 (Pub. L. 114-183), PHMSA will amend the definition of an unusually sensitive area (USA) to explicitly include the Great Lakes, coastal beaches, and marine coastal waters as USA ecological resources for the purposes of determining whether a pipeline is in a high consequence area (HCA), as defined by 49 CFR 195.450. To address this mandate, PHMSA must change the definition of USA and further define what is included in "coastal beaches" and "marine coastal waters." In this rulemaking, PHMSA will solicit broad input from the pipeline industry and other stakeholders, propose definitions and geographic extents for the new terms to be included in the revised USA definition, and understand industry implications and concerns with the proposed revisions.