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<br />Memo to Steve Shuev ~ March 4. 1999 <br />• In the unlikely event that the mine is flooded to the collar elevation of the no. 1 winze or the A-59 <br />raise, upon plugging and flooding the adit the design pressure at the bulkhead (1 1 psi) would be <br />exceeded and the contingency measure opening the valve in the plug would be enacted. <br />Another possible source of the ground water contamination detected at the Creede formation monitoring <br />well is the 9700 adit dump. This dump is located in Windy Gulch at the contact of the Creede formation <br />and the rhyolite. The point where Windy Gulch crosses the contact is a likely recharge area for the <br />ground water flow path intersected by the monitoring well screen, and the 9700 dump is located directly <br />over this possible recharge point. If sulfide minerals in the dump are contaminating the water before it <br />infiltrates at the contact, then the dump could be a source for the contamination detected in the monitoring <br />well. However, it is clear that from a regulatory standpoint the contaminated ground water condition is <br />the ambient condition, even if the contamination is caused by the 9700 dump. This conclusion is based <br />primarily on the definition of ambient ground water quality in Rule 1.1(5), which states that ambient <br />quality is that quality that was present on January 31, 1994. If the 9700 dump were contaminating ground <br />water, the contamination would have occurred prior to this regulatory date. <br />Considering al] the available information, I believe the Division should find that the ambient ground <br />water feeding the 9360 adit is contaminated to [he point that it would be unsuitable for domestic or <br />agricultural use. As such, closing the valve on the 9360 adit plug and forcing the infiltration of the 9360 <br />adit water to the ground water regime would not cause an adverse impact to the potential uses of the <br />ground water. I would recommend that as a condition to the Division's approval to close the valve, we <br />require Homestake to continue monitoring the water table elevation in the Creede monitoring well and <br />maintain the well such that future water quality samples may be collected if necessary. The continuing <br />water table elevation data should be reported with the tracer study data required under technical revision <br />TR-07. <br />cc: Harry Posey <br />c:\windows\personal\buldog valve closure <br />