REV12101 - Laserfiche WebLink

Home Browse Search

Memo to Steve Shuev 2 June 15.1998 ground-water quality shall be maintained for each pazameter at whichever of the following levels is less restrictive: (A) existing ambient quality as of January 31, 1994, or (B) that quality which meets [he most stringent criteria set forth in Tables 1 through 4 of "The Basic Standards for Ground Water." As discussed previously, the 9360 adit water is contaminated beyond the criteria set forth in the Basic Standards for Ground Water. However, there is currently insufficient information available to compare the 9360 adit water quality to existing ambient quality as of January 31, 1994, and it is towazd characterizing ambient quality that the Operator's efforts should be directed. An acceptable procedwe for characterizing ambient ground water quality relative to the 9360 adit water would be to drill a monitoring well or wells into the formation above the 9360 adit from which the inflows to the adit are derived. Ground water samples collected from such wells would be acceptable to the Division as representative of water quality on January 31, 1994 because there have been no new or increased sowces of ground water contamination initiated in the azea in question subsequent to that date. The Operator's current hydrogeologic model for the formation above the 9360 adit is that no continuous static water table will be present. As such, the drilling targets will have to be carefully designed to maximize the potential for collection of a water sample representative of the water that eventually percolates through the formation and drips or flows into the 9360 adit. If representative sampling of water from the superjacent formation indicates that water quality is similar to 9360 adit water, then the Division can approve closing the valve on the concrete bulkhead seal and forcing reinfiltration to the formation of the 9360 adit water. If, on the other hand, sampling of the superjacent formation ground water reveals water quality is superior to the 9360 adit water, this would be regarded as evidence that the presence of the adit is causing degradation of water quality, and a ground water protection program would have to be established in accordance with Rule 3.1.7 before the valve on the concrete bulkhead could be closed. The essential elements of any such program would be to asswe that the Interim Narrative Standard for ground water is achieved at some point o[ points of compliance. There are a number of mechanisms that could contribute to the adit being the causative agent for ground water contamination. These include: The presence of the adit would modify ground water flow paths and flow rates by acting as a ground water drain. Even if the adit were to be plugged, this effect could potentially persist if the adit were to seasonally refill and drain in response to snowmelt. The driving of the adit and subsequent caving have caused and increase in rock surface area exposed to weathering.