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<br /> <br /> <br />I~ <br /> <br /> <br /> <br />1 <br /> <br /> <br />1 <br /> <br />1 <br /> <br /> <br />1 <br /> <br />1 <br />the specific flow path from dre tailings area to the Rito Seco, there should be <br />more sampling. Therefore, M-4, M-10 and RS-4 should be roptirrcly sampled <br />until the hydrologic gradient is established and until other down-gradieru monitor <br />wells are installed. <br />RESPONSE: Regionally, it can be determined that the ground water gradient in the Santa Fe <br />aquifer is generally from east to west, based on water level elevations irr M-1, M- <br />4 and M-9. While locally it is possible that, if there were a leak in the tailings <br />facility, some water could flow to the north towards to M-4, given the maximum <br />head differential between the tailings pond elevation and the watef level elevation <br />in M-4 (approximately 60 feet), the distance from the tailings facility to M-4 <br />(5,800 feet) and an aquifer permeability of 3.8 feet per day, the Seepage velocity <br />in the Santa Fe Formation is only approximately 0.1 foot per day. Given this <br />velocity, even if the tailings facility started leaking the first day there was water <br />in the facility, and a saturation front was immediately established, water from the <br />tailings facility could not have reached M-4 at this time. Thereffore, bi-weekly <br />sampling of M-4 and M-10 at this time wuuld not provide the additional <br />information identified in the comment. If the further studies related to <br />establishing asite-specific gradient near the tailings facility indicate a gradient to <br />the north, appropriate additional monitoring measures would be taken at that time. <br />Surface water station RS-4 monitors a dry tributary to Ritp Seco, and is <br />monitoring a different sub-basin than what the tailings facility is Ipcated in. BMR <br />does not believe that there is merit in bi-weekly monitoring of station RS-4 and, <br />in any event, no samples have ever been obtained from RS-4, as ii Iras never been <br />observed to flow. <br />3. Chain of custody should begin wid: dre commercial laboratory tltnr prepares the <br />sample containers forficld sampling pcrsatrtcl. 77tird parry smnp>rrs and vendors <br />should supply all collectiat devices, sample containers, and ren~enrs including <br />wash solutions. <br />RESPONSE: Section 2.1.1 of the Protocol document states that "[E]mpty sample containers <br />and laboratory water will be received in coolers. Achain-of-custody form will <br />be received with the above-mentioned items." Therefore, the protocol document <br />provides that the chain-of-custody is initiated with the commercial laboratory. <br />While BMR agrees that the collection devices and the reagents, including wash <br />solutions, should be provided by the samplers, the sample containers (and their <br />associated preservatives) are provided, and should be provided, by the analytical <br />laboratory. <br />-2- <br /> <br />