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t <br />• 6.1.5 Monitoring Wells <br />Dedicated monitoring wells were constructed in 1990-91 to monitor four water " <br />bearing zones, Dissolution Surface, B-Groove, A-Groove and Perched aquifers, see <br />Figure 2-1 for location. Immediately down-gradient, monitoring wells were <br />established six months prior to mining (April, 1990! to collect baseline water <br />quality and level data. Up-gradient wells and additional down-gradient monitoring <br />I <br />wells were dril{edlrecompleted during the summer and fall of 1990. An additional <br />monitoring well was completed in 1991, utilizing the recompleted IRI-5 well as <br />Perched aquifer. <br />The plan is to equip each monitoring well with a nitrogen gas, air lift water sampler <br />'. to obtain water quality samples from a discrete zone. Sand and bentonite are <br />• utilized to isolate the sampler, A pressure transducer is placed approximately 20 <br />feet below the water surface with water level information recorded continuously at <br />a surface data acquisition system (see Comprehensive Monitoring Plan, February <br />27, 1991 for more details on monitoring). <br />Dedicated Monitoring Wells Immediately Down-Gradient <br />Wells utilized to establish baseline conditions were: <br />Well Aquifer <br />Na26-EX-2 Dissolution Surface <br />Na26-89-1 B-Groove <br />Na26-89-2 A-Groove <br />Na26-89-3 Perched <br /> <br />50 <br />