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Memo to Steve Shuey • ? • March 3, 1999 along the vein was any drifting or sloping conducted. The edit continued a[ a 1% grade to the no. 1 winze. • No. 1 winze. This winze connects the 9360 level with all other deeper underground workings from u ~'_'!' '` • : "~: "~' ~` r.'.:^'-:'.i.-. _' rock was mined. The elevation difference between the 9360 edit plug and the 9360 winze is 2~ or more feet. Substantial water w'as encountered in [he mine at the 9200 level, and had to be pumped throughout the duration of the operation. • Mineralized vein below the 9360 edit level. These workings were the source of the vast majority of Bulldog ore. • 9360 level dump. This dump, which lies mostly on the west bank of Windy Gulch and partly within Windy Gulch, holds waste rock from the 9360 edit level and below, and includes Creede Formation, rhyolite bedrock, and mineralized rock. The operator maintains that the static water level has returned to its original elevation, around 9200 feet. Flow from the 9360 portal has low pH and metals. At issue is whether this flow represents natural conditions, or degraded water quality conditions related to underground mining. Possible sources of metals and acid in the 9360 edit include the following: • Mineralized waters delivered from Windv Gulch to the Creede Formation, alone the Creede Formation/Rhyolite bedrock contact. This assumes that surface water in Windy Gulch flows through the 97001eve] waste rock, and that the waste rock is mineralized. Note: We do not have enough information at this stage to either favor or rule out this possibility. We do not know whether surface water flows through the dump and into the Creede, and we do not know whether the 9700 level rock is mineralized or not. Based on conversations with Mack Rober, it seems that hydrothermal alteration around or adjacent to veins in the Creede district was minimal, so pyritic alteration shells should be uncommon. Therefore, our simplest interpretation is that the 9700 level waste rock, being from the 9700 level edit, is essentially unmineralized because the edit runs transverse to the mineralized vein, and so is not an acid metals generator. If this interpretation holds true, then this option for mineralized water can be dismissed. • Mineralized water in the Creede Formation. unaffected by mining, which is naturally acidic and metalliferous due to natural interactions with Creede Formation mineralization. Under ordinary circumstances, such water would flow through Creede Formation to the bedrock contact then along the upper bedrock surface to base level. In this case, the edit would have intersected the flow of groundwater to base level, and should return to normal if the edit plug valve is closed. Based on results of the Creede Formation drill hole sample, taken this year, this option is the most favored one. Acid mine drainage caused by mining-related contamination in the 9360 level edit. In this case, AMD could be caused by interactions between groundwater and either mineralized mine waste on the edit floor, or pyritic exposures along the back and ribs. According to the drift reports, the 9360 edit was basically dry, except for occasional fracture leakage and especially due to significant seepage along the Creede formation/rhyolite bedrock contact. Thus, if the edit was essentially dry, and water is derived mainly from the Creede bedrock contact, then the notion of AMD generation in the edit behind the contact loses plausibility. Acid mine drainage seeping, upward from the mineralized workings below the 9360 edit. This possibility assumes several things, some of which are less plausible than others. It assumes first, that the standing water level has risen above the original 9200 fool level and is now discharging