Laserfiche WebLink
Excerpts from Email response from David Bird to Russ Means on groundwater well location and depth issues. <br />Italics text is questions and remarks posed by Russ Means. Red / bold text is responses from David Bird on the <br />well and depth issues. <br />From your remarks it appears you have questions regarding the proposed depth and location of the wells. Looking <br />at it the proposed locations 1 think they can move JB -01 and maybe JB -02 to the north side of the portal. This would <br />be up gradient although close to the rim of the canyon. <br />Response #1: <br />[I can see from the strat section on Fig 4 that the location would be upgradient stratigraphically, but are we <br />certain that it is upgradient hydrologically? I don't see enough hydrologic data in the material submitted to <br />support that assumption. That is an important concept that will control the locations of baseline monitoring <br />and compliance points. Until they provide data that better define the hydrologic regime at the site, we won't <br />know what is upgradient and what is downgradient. I am skeptical of the hydrologic flow regime shown on <br />Fig.4. Hydrologic recharge zones are usually found in topographically higher areas like mountains and discharge <br />zones are in topographically lower areas, like streams. Fig 4 shows the recharge occurring on the cliff face and <br />flowing down dip to the SSW, towards the area of higher topography. If that is the case, where does the <br />water ultimately discharge? To complete the hydrologic cycle, it has to come out somewhere - it can't just <br />continue to migrate deeper into the earth. I think the more likely scenario is for recharge somewhere off the <br />left side of the map, with infiltration vertically downward through permeable strata or cross - cutting <br />structures... most discharge likely occurs when the infiltration hits impermeable strata and migrates laterally to <br />emerge as seeps and springs along geologic contacts, with a lesser component gaining depth via structures and <br />following broader regional gradients to eventually emerge in the valley floor. Obviously, this scenario, with <br />ground water having to migrate up dip to find its discharge zone, can lead to perched ground water zones] <br />JB -02 could also be located midpoint between 1 and 3 and 4. Knowing the site the main ore body is some 1800 feet <br />to the south /southwest. /think thatJB -3 and 4 should be satellite pads at least at the southern end of this zone <br />which it appears is proposed. Strike and dip actually has any potential for charging a potential aquifer up gradient <br />out in free space of the canyon. The site is very close to the canyon rim. So one up gradient, one midpoint and two <br />or three down gradient should have us covered would you agree? <br />Response #2: <br />[I think if they locate 3 -4 holes in a pattern surrounding the mine, and drill down into the Navajo (that's only <br />about 600 -800 ft according to Fig 4), logging and measuring all water occurrences intersected, then that will be <br />an adequate start to comply with 6.4.20(8)(b) - identification of all known aquifers. They may have to pull drill <br />rods and run a pump test when they hit water - bearing zones. Also might have to install nested monitoring wells <br />to allow collection of the data needed to monitor potential impacts] <br />As for depth, the most likely contact, if any, with GW would be at the Salt wash /Summerville contact. However, <br />from your comments it appears that you're thinking the depth down to the Summerville /Entrada or deeper. My <br />thinking is that JB -4 could be drilled to Entrada and 1, 2 and 3 to Summerville. The most possible known aquifer is <br />probably in the Navajo formation where La Sal Creek is which is some 1000 feet below the mine workings and three <br />other formations so impacts are not likely except through a direct conduit like a well. <br />Response #3: See Response #2 <br />