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Gilder Assceiates Irte. <br />'OO Union Fowevrn, S~_,te 5C0 <br />~Kewac a. CU USA 80224 <br />Tef epnene ;303) 9c0-Optic <br />~a (303) 9B5.2C'80 <br />April 13, 1994 <br />A~~lde~~aii~s <br />VII. Allen SOIERSOn <br />Division of Mineral and Geology <br />Department of Naturd] Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Past-It" brans tax transmitt~.l memo 7~'t • o+Fnge. • - <br />7b ~ I! rpm <br />1/. <br />~. P ~a ~ <br />p.Pp Ph°n• n <br />Fa: r Faa a <br />RE: LO W STRESS, GEODiI:'1VIBRANE/SUIL LINER 11vTERFACE DIRECT <br />SHEAR TESTIlti1G <br />Dear Mr. Sorenson: <br />Mr. ]ohn Hardaway, Manages of Environment Affairs for the Pikes Peak Mining Company <br />(PPMC), has asked Older Associates Inc. (Golder) to perform additional duect shear <br />interface; testing at low stress ranges. This letter presents the results of the testing. <br />LS ~L'."L ~n <br />Initially, interface dizect shear testing was performed on compacted Ironclad tailingsJsntoot6 ~, <br />80-mil VLDP)r geomembrane/-1.5-itch drain cover fill at 50, 100, 150, and 300 psi normal -~i•~-ti <br />stress ranges with only tkle overlying drain cover fill saturated during shearing. Concerns <br />azose during third party review that Otis may not be representative of low stress conditions. <br />4n additional concern was that Cne upper portion of the soil liner fill may become saturated , : , ;~ <br />due to condensation at the soil linerJgeomembt2ae interface. Thererore, additional interface -~ <br />shear testing was performed at low normal stress levels with the soil liner thoroughly wetted ,~, • .. .. <br />prior to placement of the genrnembrane into the sheaz de~tice. Additionally, the entirti sheaf : ~. <br />boz was flooded during shearing to simulate worst case conditions. The lower normal stress "' <br />loads •.vere selected as 15 and 30 psi. <br />A summary of tY~e i..terpretations of the test resulu are presented in the following table. <br />~ -_ <br />Tvpe <br />Angle of <br />Cohesion <br /> Internal <br /> Fricaion <br /> (°) (PSI) <br />Low stress data only, best tit line between origi.-t (U 29.8 0 <br />psis and l~ psi data point <br />Low stress data only, 13est lit line with y-intercept ; 37.4 0 <br />through nrisin. <br />Low stress data only, 3est fit line with y-intercept 46.5 -7.2 <br />computed. <br />All data, Best fit line with y-intercept computed. ~ 28.8 6.8 <br />All data, Best fit line with y•!ntercept through origin. ~ 30.2 0 <br />...._ <br />n.~ .,, <br />-_ <br />,.+,. <br />.L.•. . `.'.' . <br />OFFICES .N AUSrfL:C~q. CANADA vER~b1AfJV, kGh.~ARJ, RACY, 5': JED6N. UNIIEL' KINGDC;I, lil~.Tri: $iATS$ <br />