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III IIIIIIIIIIIIIIII <br /> San Juan County Mining Ventura 999 <br /> Sunnyside Mine <br /> Washington Mining Co. -Operator <br /> P.O.Box 177 <br /> Silverton, CO 81433 <br /> C[ZjVeL) <br /> (Ph. 303-387-5533 FAX 387-5310) � . <br /> VAIPP <br /> April 17 , 1991 <br /> Fti/ --jecj' �a3 9t <br /> Mr . John <br /> rfer <br /> Reclamation eSpecialist �0�'l r�10tiOn [)ivlsroR <br /> Mined Land Reclamation Division 4o <br /> 1313 Sherman St. , Rm. 423 <br /> Denver, CO 80203 <br /> Re: file M-77-"378 �� <br /> Technical Revision N"o. 11 Addendum <br /> Dear Mr . Doerfer; <br /> Your letter dated March 29 , 1991 lists several items that must be <br /> addressed prior to approval of Technical Revision Request No. 11 . <br /> These items are addressed below for inclusion in the TR request . <br /> I Overburden layer thickness <br /> The February 18 , 1991 Technical Revision request states: <br /> The entire pond area will be covered with approximately one <br /> foot of overburden. This sentence should be replaced with: <br /> The entire pond area will be covered with overburden to a <br /> minimum depth of 12 inches . To achieve a minimum depth of <br /> 12 inches (given the type of material) , the actual thickness <br /> will probably range from 12 to 18 inches . <br /> 2. Up-land runoff diversion <br /> A diversion ditch is currently in place above Tailings Pond <br /> No. 2 . This ditch will be reconstructed in accordance with <br /> the attached drawing to provide a relatively impermeable <br /> diversion structure . This design is adequate to carry the <br /> flow expected from a 100 year thunderstorm event (see <br /> attached FM Fox hydrogr.aph for drainage) . The top foot of <br /> the diversion ditch will be composed of overburden material <br /> from the borrow area. This layer will be compacted to a <br /> minimum of 950 of its maximum dry density (ASTM D-1557 ) . <br /> Tests performed on similar material obtained from the same <br /> area yielded permeabilities ranging from 1 . 9 x 10 cm/sec to <br /> 5.0 x 16-7 cm/sec (see attached soils test results - sand and <br /> gravel soil description) . This ditch will serve to divert <br /> upslope runoff away from the oile. <br />