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STATE OF COLORADO DIVISION OF MINERALS AND GEOLOC{Y Dcparlmenl ul N'atural Kesowcea 7) I I Sherman 51., Ruum ~ I S Denvyr, Colorado NI~'pt ~~ ~' ~ S I O ~~ O Pnr,ne~. uu II nhh-3s~,- MINERAL S N,n. 13017 Ni'-AIUh GEOLOGY 0.EC LAFIATION MINING•SAF ETT DATE: 3/ I/99 sill oMen, Gmernor TO: Hazfy POSey Greg E. Walther ERecolive Dnenor FROM: Allen Sorenson ~ ~ Michael B. Lang Division Director RE: Ambient Ground Water, Bulldog Mine, Permit No. NI-77-21~ Homes[ake has installed a ground water monitoring well east of the alignment of the 9360 adit projected to the surface. If the hydrogeolo~ic model [hat assumes the primazy ground water flow path in this regime is along the Creede Fm./rhyolite contact is correct. then the adit is downgradient of the well screen. The samples from the well show an ARD chemical signature indicating that the ambient ground water condition is contaminated. The geologic reports from the 1970s supplied by Homestake illustrate the following points: / The Creede Fm, is mineralized in some locations. The Monon Mine, circa 1920, shipped 22,000 tons @ 34.6 oz./I' Ag from an ore body located on the Creede Fm./rhyolite contact. A 3 oz.II' assay was taken in the 9360 adit, from the Creede Fm., near the rhyolite contact. Hole BTc 1 encountered pyrite below 600 feet. I've marked the location of BTc 1 on the Pb/Ag anomaly map. Freeport/Homestake delineated an ore body in the Creede Fm. in Bachelor Mtn., across Windy GI. from the 9700 portal, but it was never mined. / Roeber concludes that the Creede Fm. in the Baker area (that area around the 9700 and 9360 portals) was mineralized, but only in the younger Creede Fm. units that have been eroded away. The remaining, uneroded Creede Fm. in the Baker area vas never minerali;,ed. So the Pb/Ag anomaly map can only be used to indicate the potential for Creede Fm. mineralization in general. but not to show that the Creede Fm. in the vicinity of the monitoring well is mineralized. The following items are discussed per your request: / Find attached a ]one-section of the 9360 adit from daylight curve on the south to the surface trace of the Creede Fm./rhyolite contact on the north. / Two piezometers were installed approximately ]~ feet east of the trace of the infiltration trench on the mine bench. These aze located 300 and X00 feet south o(the 9360 portal, and are drilled into the Creede Fm. They are 17 feet deep and are screened in the lower 10 feet. The piezometers have been essentially dry through the period of infiltration, so it is unlikely that the infiltration trench is the source of the seeps at the toe of the Bulldog Mine dump in Windy Gl. / There is very little mining disturbance located upgradient of the monitoring well screen elevation. What mining disturbance that exists is summarized here: