| 1974–1997 |
AEC/DOE managed FUSRAP; surveys and investigations conducted at Tonawanda properties, including Seaway. |
| 1993 |
DOE completed a Remedial Investigation (RI) and Feasibility Study (FS) and issued a Proposed Plan (PP) for on-site disposal of contaminants. |
| 1994 |
DOE suspended decision-making to re-evaluate alternatives due to community concerns. |
| 1998 |
FUSRAP responsibility transferred from DOE to USACE under the Fiscal Year 1998 Energy and Water Development Appropriations Act (Pub. L. 105-62); separate plans and decisions issued for other Tonawanda sites. |
| 2008 |
USACE issued a Feasibility Study addendum and revised Proposed Plan, identifying contaminated soils and confirming groundwater/leachate were not impacted. |
| 2009 |
Record of Decision (ROD) approved; selected remedy was containment with limited off-site disposal, including capping and excavation. |
| 2016 |
USACE completed excavation and off-site disposal of contaminated soil from Seaway Northside. |
| 2017 |
USACE delineated contamination in Seaway Southside. |
| 2021 |
Contract awarded for engineered cap design and planning. |
| 2022 |
First five-year review of the selected remedy completed in accordance with CERCLA requirements. |
| 2023 |
Contract awarded for engineered cap installation. |
| 2024 |
Installation of the engineered cap began. |
| 2025 |
Engineered cap completed in December 2025. |