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AR226-2347 Relevance of Soil Sampling in Screening Level Assessments PFOA October 22,2003 Discussion Topics Review soil sampling key learning^ Present site screening level assessmen conceptual model Messages For Today Soil sampling is not critical to site scre level assessments designed to evaluate overall human and environmental expo at a PFOA use facility. Water monitoring should focus on site boundaries, key discharge points, or wh potential exposure is occurring. PFOA P/C Characteristics PFOA displays high water solubility - 1000 mg/L (Kissa, 1994) - >10% (3M,2001) PFOA displays low adsorption capacity in a types (3M & APME Studies) - Similar to other highly mobile chemicals (see chart) ^ a o M 01 ~j Ul U Koc Comparison Comparison of Koo's for PFOA and Other Chemicals 4-------- Cape Fear (APME, 2003) -4' Drummer (APME, 2003) -- Hidalgo (APME, 2003) 4----^ Keyport (APME, 2003) " Wilmington Sludge (APME, 2003) Methylene Chloride 1978)______ Brill Sandy Loam (3M, 0 200 400 600 Koc (mL/g) Napthalene 800 1000 Soil Sampling Key Learning Our extensive soil sampling database from Washington Works shows: - Overall low concentrations, won't build-up - Air deposited PFOA readily dissolves and migra water movement (sw/gw) Most surface soils <50 ug/kg - All results significantly below CATT screening 240,000 ug/kg Site Screening Level Assessm Conceptual Model PFOA Site Screening Lev Assessment Conceptual Mo - Compiled using extensive modeling and monitoring conducted at Washington Work - Considers realistic potential exposure poin focus screening level assessment monitorin Facility water discharges Groundwater at site or discharge boundaries - Soil is not a key monitoring point SCREENING LEVEL ASSESSMENT MODE AIR EMISSIONS C==> CS& *SWMU = SOLID WASTE MANAGEMENT UNIT POTENTIAL SCREENING LEVEL ASSESSM Q) FACILITY AQUEOUS DISCHARGE (2) SURFACE WATER (RIVERS, PON (3) GROUNDWATER (MONITORING PRODUCTION WELLS ETC.)