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TM <br /> Fj 1 11 <br /> APR 2 -: 1989 <br /> SIERRA-CRETEROADBASE & STRUCTURAL FILL <br /> ENVIRONMENTAL/REGULATORY DATA <br /> "Sierra-Crete" is a manufactured rather than a natural <br /> product. It is composed of hydrated, cemented metal oxides <br /> (principally iron) . As an inorganic material , the only potential <br /> environmental concern would be the leaching of any of the metals <br /> present. <br /> Du Pont worked closely with the California Department of <br /> Health Services (DOHS) to confirm "'Sierra-Crete's" environmental <br /> soundness. The DOHS, based on certified laboratory data (see <br /> Attachment I) , first determined that the only metals which might pose <br /> a potential problem were chromium and vanadium. In response, we had <br /> 15 randomly-selected additional samples of routine production <br /> evaluated for extractable chromium and vanadium using California' s <br /> aggressive WET (citric acid leach) procedure. All samples easily <br /> passed the stringent State limits, 560 mg/l for chromium and 24 mg/.l <br /> for vanadium, demonstrating these metals are tightly bound or fixed <br /> in the cemented oxide matrix. (See Attachment II for results . ) <br /> Based on the above data, with its demonstration of routinely <br /> reliable performance, David Leu, Chief of the Alternative Technology <br /> Section, Toxic Substances Control Division, Department of Health <br /> Services, in a March 11 , 1987 , letter, stated that "Sierra-Crete" is <br /> "non-hazardous according to the standards and methods contained <br /> the California Administrative Code (CAC) Division 4 , Title 22 <br /> regulations". <br /> aUPON1 <br />