2010-07-31_REVISION - M1977300 - Laserfiche WebLink

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Whetstq"e ASSOC/ates Technical Memorandum The phrase "potential pathways in low-permeability bedrock" was intended to include structural features such as the Schwartz Trend and the West Rogers Fault. It is an unsubstantiated assertion to call these geologic features "structural conduits." Faults can act as barriers or conduits to groundwater flow. Permeability testing conducted on Schwartz Trend rocks indicated that the hydraulic conductivity of the Schwartz Trend (GBG) rocks ranged from <1.Ox10"7 cm/sec to 6x106 cm/sec, which is not indicative of a high-permeability conduit. That said, the text on page 7-3 has been modified as follows: Issues related to the flooded mine workings include water chemistry in the mine, flow rates from the mine, potential interaction with water in Ralston Creek, and potential pathways in low-permeability bedrock including potential conduits or barriers to groundwater flow such as faults (including the East Rogers Fault, West Rogers Fault, and Illinois Fault) and lithologic units (including the garnet- biotite-horneblende gneiss, mica schist, and garnet-biotite gneiss and quartzite rock of the Schwartz Trend). These topics are discussed in Sections 8(e)(ii)and 14(b). SECTION 8. GROUND WATER INFORMATION 3) Operator states on pg. 8-7 "Two bedrock wells are proposed for drilling in 2010, MW13 and MW14. " Please indicate the proposed locations of these wells on a map, and please provide proposed total depths and locations/depths of screened intervals. Section 15(c) of the April 19, 2010 EPP gave the proposed locations, completion depths, hydrologic conceptual model, and sampling methods for the two new bedrock wells. Section 15(d) provides a construction schedule in accordance with Rule 6.4.20(15), and is believed to be the most appropriate location in the EPP to describe proposed monitoring well construction activities. A figure has been added to Section 15(c) showing the proposed well locations. These locations are identical to those provided to DRMS in the March 19, 2010 meeting with DRMS, the Operator, and the Operator's consultants. The text on page 8-7 has been expanded to refer the reader to proposed well locations and depths provided in Section 15. The revised text in Section 8 is as follows: Two bedrock wells are proposed for drilling in 2010: MW13 and MW14. The proposed locations, depths, and completion intervals are provided in Section 15(c) Mitigation Options and Construction Schedule: Monitoring Well Installation. The total depth and screened intervals of the new monitoring wells will be determined in the field based on the levels of groundwater encountered during drilling. The deepest well is expected to be 300 feet deep and the shallower well is expected to be 80 to 120 feet deep, however these depths are yet to be determined. 4109C.100731 2