Environmental stewardship is an important aspect of Lockheed Martin Corporations commitment to the communities in which the Corporation operates. Accordingly, the Corporation has assumed responsibility for the assessment and cleanup of environmental impacts for the Lockheed West Seattle Superfund Site as part of this continuing stewardship. This Executive Summary presents the results of the Remedial Investigation and the findings of the Feasibility Study for the Lockheed West Seattle Superfund Site (Lockheed West Site or the Site). The Remedial Investigation provides the information on the nature and extent of contamination, the risks to human health and the environment, the nature of ongoing sources of contamination, and the physical and chemical properties that influence the fate and transport of contaminants found at the Site. The results of the Remedial Investigation culminate in the identification of risks and definition of the study area boundary to be used in the Feasibility Study. Therefore, the Remedial Investigation uses the historical lease area boundaries and the Feasibility Study uses the study area boundary defined in the Remedial Investigation. The Feasibility Study contains a description and evaluation of a range of remedial alternatives for addressing the Site risks identified during the Remedial Investigation through remediation of sediment contamination at the Site and identifies a best-supported alternative for a final remedy. The investigation and study were both completed under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and the Administrative Settlement Agreement and Order on Consent (U.S. Environmental Protection Agency (EPA) Docket No. CERCLA 10-2006-0321) and associated Statement of Work for the Site.