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underground sources of drinking water (USDW) by the EPA, while the total dissolved solids <br />(TDS) within the Dissolution Surface Aquifer are too elevated to be a USDW. Additional details <br />regarding historical operations and the geology and hydrology of the NS sodium leases can be <br />found in the NS Mine Plan and Environmental Monitoring Plan. <br />3 Sampling Protocol <br />Groundwater samples from many 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 that can be employed. Generally, NS uses bladder pumps or nitrogen lift systems <br />for groundwater sampling. In addition, bailing may be used where appropriate. The practice of <br />purging/bailing 1-3 well bore volumes of fluid prior to sampling has proven impractical due to <br />the typically large volume of well bore water, tight nature of the formations, and resulting slow <br />recharge rate. <br />Qualified personnel experienced in water quality sampling activities will supervise all field <br />operations. All sampling procedures can be found in Appendix B. Water level measurements <br />and field parameters (conductivity, pH and temperature) will precede groundwater sample <br />collection events. Water level measurements will precede field parameter data collection. <br />Whenever possible, purging and sampling will be accomplished with a low -flow method that <br />involves pumping at a low -flow rate. The slow pumping rate allows water to flow directly from <br />the formation to the pump intake. The slow pumping rate results in minimal mixing with the <br />stagnant water column above and/or below the pump intake, minimal pumping -induced <br />turbidity, and minimal disturbance of sediment accumulated in the bottom of the well. Using <br />the low -flow sampling protocol will provide the highest quality sample (Puts and Barcelona, <br />1996). Refer to Sections B.6, "General Considerations for the Sampling of Liquids," and B.8, <br />"Standard Practice for Purging of Monitoring Wells," in Appendix B for specific guidance. <br />The following low -flow methodology is described with the understanding that the nature of <br />equipment and formation limitations make strict adherence to any sampling methodology <br />difficult. Bladder and nitrogen lift pump equipment will be set-up and operated in accordance <br />with instructions and settings provided during equipment installation. <br />As described in Section B.7 (Appendix B), "Standard Test Method for the Measurement of <br />Water Levels in Groundwater Monitoring Wells", depth to water will be measured with an <br />electric sounder immediately prior to purging. The initial pumping rate should not exceed <br />500 milliliters per minute (mL/min) (Puts and Barcelona, 1996). At the start of pumping, the <br />water level should be monitored continuously to determine if drawdown is occurring. If <br />drawdown is occurring at the initial pumping rate, the pumping rate should be decreased until <br />Daub & Associates, Inc. 4 NS LLC 2015 S A P Rev. 2 <br />