1. MTCA Science Advisory Board Presentation Establishing Moderate Soil Levels for Arsenic October 23, 2006

2. Tacoma Smelter

5. Pesticide Applications

6. Yakima County Historic Orchards

9. Arsenic and Lead Mobility Metal concentration Metal speciation Soil redox and pH conditions Precipitation Soil composition and permeability Other (i.e., application of phosphate fertilizers)

11. Arsenate Column Experiment

12. Arsenite Column Experiment

14. Field Data as an Indicator of Arsenic and Lead Mobility

15. Soil Profiles Near the Tacoma Smelter LeadArsenic

16. Soil Profiles – Central, WA

18. Old Yakima Orchard Concentrations w/ Depth

20. Groundwater Data No Specific combined GW/Soil study However on Vashon – lots of soil data and lots of GW Data 22 Group A systems 137 Group B systems 50 to 75 % of Group A and B systems receive water from 25 ft or less DOH and King County Databases

21. WDOH Database

23. Equilibrium Partitioning Model Where: C s = Soil Concentration (mg/kg) C w = Groundwater concentration or cleanup level (μg/L) USF= Unit conversion factor (1 mg/1,000 μg) DF= Dilution factor (dimensionless: 20 for unsaturated zone soil) K d = Distribution coefficient (L/kg) θ w = Water-filled soil porosity (mL water/mL soil: 0.3 for unsaturated soil) P b = Dry soil bulk density (1.5 kg/L)

24. K d - Distribution Coefficient Soil (mg/kg) Water (mg/L) Container K d = Water (mg/L) Soil (mg/kg) = L/kg

25. K d - Arsenic Examples of K d values reported in literature reviews

26. K d - Lead Examples of K d values reported in literature reviews

27. Equilibrium Partitioning Model C W (K d of 29, MTCA) = 43 μg/L C W (K d of 2512, EPA median) = 0.50 μg/L C W (K d of 1585, EPA mean) = 0.79 μg/L C W (K d of 1825, Sauve median) = 0.68 μg/L C W (K d of 13119, Sauve mean) = 0.10 μg/L Arsenic (C S = 25 mg/kg)

28. Equilibrium Partitioning Model C W (K d of 2,510) = 5 μg/L Arsenic (C S = 251 mg/kg)