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TECHNICAL MEMORANDUM <br />To: Bill Lyle <br />Date: October 19, 2007 <br />Page 7 <br />precipitation were responsible for fluoride retention. Fluorite precipitation occurred in the <br />surface soils, but only after the fluoride adsorption sites became saturated. <br />4.0 CONCLUSIONS <br />The baseline soil chemistry evaluation indicates that the Salazar Ranch soils are non- <br />saline, non-sodic soils developed in alluvium, with sandy loam surface textures and <br />calcareous subsoils. Soil DTPA-extractable metal concentrations were relatively consistent <br />with depth, except for cadmium, copper, iron, manganese, nickel, and lead which associate <br />naturally with organic matter and tend to be slightly elevated in surface soils. The <br />concentrations of DTPA-extractable metal concentrations are below phytotoxic levels, and <br />the water-extractable arsenic, boron, and selenium concentrations are also low. <br />Upon irrigation with West Pit ground water, fluoride concentrations in the Salazar Ranch <br />soils will be initially controlled by adsorption to metal oxide and clay mineral surfaces <br />such that fluoride concentrations in the soil solution should remain at or below <br />approximately 1 mg/L. The removal of fluoride by surface adsorption in soils is directly <br />analogous to the use of activated alumina to remove fluoride in commercial water <br />treatment systems (Clifford, 1990). Prior studies have also shown that the presence of <br />secondary carbonates minerals in the soil will also act to precipitate fluorite if the fluoride <br />adsorption capacity is exceeded. Manganese concentrations in the soils are also initially <br />controlled by adsorption to mineral surfaces and/or organic matter. Under normal <br />agricultural conditions, manganese mobility in soils will be limited by the formation of <br />insoluble manganese oxides. <br />P:IProjecisL?11-Nmmon[(SanLurs)LSa=LuislFam-Shalom RanchlSoilsL%I=ar Cha ter gon_fimldoc