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The A-Groove and B-Groove Aquifers are approximately 40 feet thick, comprise the entire <br /> A-Groove and B-Groove lean stratigraphic zones, and are found at depths of approximately <br /> 1,440 and 1,640 feet, respectively. The Dissolution Surface Aquifer can be as much as 50 to 70 <br /> feet thick, extending approximately 50 to 70 feet above the DS. In the area of the NS sodium <br /> leases, the top of the Dissolution Surface Aquifer is found at a depth of approximately 1,890 <br /> feet in the upper L-5 Zone. The Perched, A-Groove, B-Groove, and Dissolution Surface Aquifers <br /> are classified as underground sources of drinking water (USDW) by the EPA. The Dissolution <br /> Surface (DS) Aquifer is density stratified with the lower part of the aquifer having a higher <br /> concentration of total dissolved solids (TDS) than the upper. The upper part of the DS Aquifer <br /> meets the EPA definition of a USDW. NS obtained an Aquifer Exemption for the L-5 Zone, which <br /> includes the DS Aquifer. Additional details regarding historical operations and the geology and <br /> hydrology of the NS sodium leases can be found in the NS Mine Plan and Environmental <br /> Monitoring Plan. <br /> 3 Sampling Protocol <br /> Qualified personnel experienced in water quality sampling activities will supervise all field <br /> operations. Sampling procedures can be found in Appendix B. Water level measurements and <br /> field parameters (conductivity, pH and temperature) will precede groundwater sample <br /> collection events. These procedures also apply to the collection of field parameters and <br /> samples of the injectate. Water level measurements will precede field parameter data <br /> collection. <br /> Groundwater samples from most of the monitoring wells are collected from relatively deep, <br /> tight formations. These deep, tight formations limit the types of monitoring equipment and <br /> methodology which can be employed. Generally, NS uses nitrogen lift pump (NLP) systems for <br /> groundwater sampling. In addition, bailing and discrete interval sampling may be used where <br /> appropriate. The practice of purging/bailing 1-3 well bore volumes of fluid prior to sampling <br /> has proven impractical due to the typically large volume of well bore water, tight nature of the <br /> formations, and resulting slow recharge rate, as such, NS will typically purge the fluid volume of <br /> the NLP sampler and sample tubing prior to sample collection. <br /> Daub &Associates, Inc. 4 NS LLC 2022 SAP <br />