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The hydrologic component that is being encouraged to infiltrate to the Grassy Valley feeder is <br />• the infiltration that would enter the ECOSA through the engineered cover. As stated in <br />Appendix 1, Attachment 1, p.2 of the MLE Project Application, this infiltration rate is <br />expected to be approximately 5 inches per year for approximately half the year. The hydraulic <br />conductivity of the underlying materials exceeds this value, so the infiltration capacity of the <br />underlying material exceeds this infiltration rate. Therefore the underlying material has the <br />carrying capacity to conduct any potential the flow of water to the underlying diatremal <br />bedrock by gravity flow (under unit hydraulic gradient). <br />The purpose of the roughening of the surface of the ECOSA prior to placement of overburden <br />material is to ensure that there is no preferential pathway along the underlying material to <br />the base of the placed overburden, and therefore to ensure that any potential flow of water that <br />may result from heavy precipitation (particularly during construction and prior to placement <br />of the cover) does not flow rapidly downhill to the base of the facility. Instead, water would be <br />contained in the depressions created by the roughening, and gradually infiltrate to the <br />underlying bedrock. The roughening is not intended to, nor is it expected to, inhibit <br />saturation of the ECOSA; rather the reverse, it is designed to encourage temporary saturation <br />of the underlying soil or rock within the depressions so created, to allow time for any potential <br />water to infiltrate into the underlying bedrock. <br />The infiltration of water from the surface area within the footprint of the ECOSA to the <br />bedrock is demonstrated by water level data collected from the recently installed pressure <br />transducers in the OSABH piezometers. The OSABH piezometers (1, 2, 4, and 6) show <br />• seasonal saturation and infiltration in 2007 and 2008. Concurrent measurements in three <br />downgradient piezometers (5, 7, and 8) show unsaturated conditions during the seasonal <br />saturation of the upgradient piezometers. These data strongly suggest that local infiltration <br />from the surface to the bedrock in the ECOSA footprint is dominant compared to lateral flow <br />in the colluvium. <br />DRMS is correct that the advantage of channeling infiltration to the feeder is to facilitate <br />capture within the diatremal rockmass; that is, by allowing time for all of the potential water <br />that may infiltrate through the cover to continue to flow through the underlying subsoil and <br />into the diatremal rockmass. <br />C. The DRMS is not fully convinced that all the drainage from the Grassy Valley area will <br />report to the diatreme, and benefit from the reported abundance of neutralization potential <br />before discharging through the Carlton Tunnel. In order for the DBMS, to be comfortable <br />with your conclusions, please provide a detailed deep drill core data correlation that shows <br />the deep drill core data from Grassy Valley area is similar to deep drill core data from other <br />areas with in the diatreme. <br />Response. <br />CC&V drills coreholes only to determine geotechnical conditions relevant to slope stability. <br />As no potential surface mine is planned in the ECOSA area at this time, no deep drill holes <br />• have been cored in this area. Accordingly, CC&V cannot provide the requested correlation. <br />23