P a c i f i c Northwest L a b o r a t o r y (PNL) i s i n v e s t i g a t i n g t h e use o f a r o c k armoring b l a n k e t ( r i p r a p ) t o m i t i g a t e wind and water e r o s i o n o f an earthen radon suppression cover a p p l i e d t o uranium m i l l t a i l i n g s . The purpose o f t h i s earthen cover i s t o reduce radon-222 e x h a l a t i o n f r o m t h e t a i l i n g s and t o prov i d e long-term s t a b i l i t y f o r t h e t a i l i n g s impoundments. Because o f t

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... e l e n g t h o f t i m e t h e cover must remain i n t a c t (up t o 1000 y e a r s o r l o n g e r ) , t h e s o i l must be p r o t e c t e d from n a t u r a l e r o s i o n a l f o r c e s , hence t h e need f o r a longt e r m m i t i g a t i o n technique such as a r i p r a p b l a n k e t . A t t h e same time, t h i s r o c k b l a n k e t must i t s e l f w i t h s t a n d n a t u r a l weathering processes t h a t promote d e t e r i o r a t i o n o f t h e rock. Should weathering cause t h e r i p r a p t o f a i l , t h e radon suppression cover would be exposed t o e r o s i o n a l f o r c e s and i t s e f f e c t i v eness thereby reduced. An e a r l y task i n t h i s study i s t o review c u r r e n t s t a t eo f -t h e -a r t i n f o r m a t i o n on r o c k weathering and r i p r a p d u r a b i l i t y . T h i s r e p o r t , prepared f o r t h e U.S. Nuclear R e g u l a t o r y Commission, i s designed t o p r o v i d e an i n t r o d u c t i o n t o t o p i c s i n geology r e l e v a n t t o weathering processes and t o d e s c r i b e methods c u r r e n t l y used t o e v a l u a t e rock d u r a b i l i t y . Weathering Resistance and S u s c e p t i b i l i t y Related t o Weathering Type and Rock P r o p e r t i e s . . 70 0 0 'INE *% ' CALCIC PLAGIOCLASE \ +> % + S 4 " % J 0 " CALC-ALKALIC Mg PYROXENE PLAG IOCLASE \ * % , % J ALKALIC-CALCIC Ca, Mg PYROXENE PLAG IOCLASE