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.~ •. DIVISION Of MINERALS AND GEOLOGI' Depanmcm of nawral Rrsourmi I:.15 Shormar. C; Ruom '_l i i?cnco~. QdpraAo BO'_0] I'h~~nC.I .U?i Nbh Sib: r:~~ ,~ea~+u~ slo(, interoffice MEA'IORANDUA'1 llEi'.ARTtt1Ef\'T OF NATURAL RESOURCES °, Ft,mr, Govr~n°: to: Janet Binns Inmec i. Lnchheed e.~~°~~rr Dnraor ~„~t nlichnrl tl LnnG from• }rgr~G. \>,~alker °"i`'°" °"r""` subject: Grassy Gap Inspection date: June 30. 1995 Reference: Memo, Binns to',~%alker, June 11, 1995, same subject .At your request, I accompanied you on an inspection of a slide at Grassy Gap. The inspection \\~as made on I6 3une 1998. ~'~ Bather \\'as overcast. The purpose of the inspection \\~as to detemtine if there was a relationship bet\veen a sedimentation pond and the slide. I suspect there is a relationship beltveen the two. The pond is located at the crest of a steep slope (approximately 3~ °, or 70%). It is located directly above the slide inspected; and a previous but not so extensive a slide. Relati\'e locations are sho\\n in Pictures 3, 4 and d. ,a.tt o\'ervie\e' of the site is provided in Picture Z. There uas some water in the pond. The \\ater surface \\as below the primary spillway riser. This portion of the mine is on the \vest flanl: of a north-plunging anticline. The formations likely dip approximately 14` to 16° to the west in the vicinity of the slide (Pemtit, pace ILD-~l. These beds outcrop under a thin mantle of soil and [alus debris t\here they intersect \\•ith the 70°.0 slopes of the valley. There are indications of.vater seepa_e at such intersections at the elevation of the crest of the slides. Dote the vegetation lint on Picturz'_ extendine to the south around the nose of the of the rider. ]n addition. there is an unidentified linear feature that runs to the north from the crest of the slide (see Pictures 1 and 2~. This linear feature mi_ht have been a ditch (no\\ obliterated b\' in-fillin_' 1. capturine spring \\ater from the precise location of the slide crest. Inherent seepaee is also inferred b~ the seepage in the slide area at the time of the inspection (see \\'at:r seepage in Picture 6i. The pond is located directly above the slide area and close to the edge of the steep slop; s. The pond extends across the area (north to southl of bo[h slides. The older of the slides. the less e~aensive one, is located to the north (left in Picture ;) of the one that resulted in the inspection. The tree ero~+th located belo~\ the no-n end of the pond in Picture ;locates the cast area of this STATE OF COLORADO