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Work Plan, PFAS Site Inspection Naval Computer and Telecommunications Station Stockton, California Background Information 2-11 DCN: TRBW-0202-5183-0010 the six AOCs, which is referred to as Site 3 and was used by the Navy as a Firefighting Training Area. Potential sources of PFAS contamination at each PFAS AOC are as follows: • Site 3 previously contained four former ASTs with open tops (open tanks), a former Burn Pit and a former fuel storage area; • Site 45 and Site 19 store stockpiles which are known to contain or potentially contain AFFF-contaminated soil/debris from Site 3; • AOC 01 and AOC 02 are known to formerly store or potentially store AFFF, as well as potentially conduct firefighting training activities using AFFF; and • AOC 03 is located in the southwestern corner of RRI, at the outlet for the island’s drainage channel system where AFFF or PFAS accumulation may have occurred in sediment. 2.5.2 Contaminant Migration Pathways Soil, sediment, and groundwater are considered the environmental media of interest in this SI. PFAS are readily soluble in aqueous solution and therefore have potential for migration to groundwater from soil and with groundwater flow to off -site locations. A series of drainage channels were constructed to transmit groundwater and stormwater from all portions of the islan d to the lowest point on the island (towards AOC 03 – Stormwater Pump House Area). Rainfall runoff and shallow groundwater are intercepted by the island’s interior drainage channel system, which was excavated from native soils and is mostly unlined. Contaminated groundwater may have infiltrated the drainage channels and impacted sediment. 2.5.3 Potential Receptors and Exposure Pathways Human exposure to PFAS can occur through direct contact with environmental media impacted by PFAS. PFAS present a potential hazard to wildlife by direct and dietary exposure on both individual and population levels. Numerous studies have shown PFAS are globally present in wildlife and may bioaccumulate in birds, fish, and mammals (including livestock). Ecological receptors include living organisms other than humans, the habitats that support such organisms, and/or natural resources that could be adversely affected by environmental contaminants from a release or migration from an identified location. Previous and current land use at RRI is designated as industrial; therefore, current and anticipated receptors include commercial/industrial composite workers and construction workers who could be exposed to soil, sediment and/or groundwater through dermal contact, inhalation, incidental ingestion and use of groundwater as drinking water. Residential land use is prohibited by the 2011 Consent Agreement, although future residential receptors will be evaluated in environmental investigations for consistency and completeness.