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' Mr. Dustin Czapla <br />Page 6 of 8 <br />between 20 and 100 ft, but anticipated to coincide with the location of the underground <br />workings and therefore are dependent on drilling conditions. It is not anticipated that a <br />sand filter pack will be used in the open underground mine workings. However, if <br />piezometers are completed in collapsed underground workings, or in fractured bedrock, <br />a sand filter pack as needed, may be emplaced to a depth of 5 -ft above the well screen. <br />' Piezometers will be grouted in place using a hydrated bentonite seal above the screen <br />and a cement and bentonite mixture grout. A grout cone or cementing packer will be <br />used to hold grout above open underground mine workings. <br />Infection Activities: <br />A maximum of 25,000 gallons of groundwater will be recirculated through the <br />underground mine workings using the existing and new piezometers. Water from the <br />underground workings will be pumped into storage/mixing tanks, mixed with the <br />reagents, and then injected by gravity feed at a maximum flow rate of 6 gallons per <br />minute. Sodium or potassium bromide will be injected at a maximum constant <br />concentration of 100 milligrams per liter (mg/L, as bromide). Sodium fluorescein (visual <br />' tracer) will be injected at a maximum constant concentration of 100 mg/L. Sodium or <br />potassium monobasic phosphate salts and phosphoric acid will be injected at a <br />maximum phosphate dosing concentration of 2,000 mg/L as phosphate and a pH > 4. <br />The high alkalinity calcium carbonate -type groundwater in the underground mine <br />workings (approximately 400 to 500 mg CaCO3/L) will buffer the pH, thereby <br />maintaining the near neutral to alkaline pH conditions. <br />Phosphate will precipitate in the underground mine workings and adjacent country rock <br />as uranyl phosphate and calcium phosphate and, if present, be further diluted in the <br />North Pit Lake from seepage from the Chester fault springs. It is anticipated that <br />' reagents that do not precipitate within the underground mine workings (including the <br />conservative tracers and low levels of residual phosphate) will discharge into the North <br />Pit Lake where additional phosphate mineral precipitation will occur. Injections will be <br />' controlled so that the injected phosphate is consumed prior to reaching the discharge <br />POC (SW -33). No negative effects to groundwater quality are anticipated as a result of <br />the pilot testing. Compliance with the CDPS permit (# CO -0022756) conditions and <br />Water Quality Control Commission Regulation 85 (Nutrient Management Control <br />Regulations) will be maintained at SW -33. <br />The first round of injection is tentatively scheduled to begin in August 2015 and continue <br />through the 2015 field season (early October) as needed. <br />Performance Monitoring: <br />Active injections and performance monitoring will continue through the 2015 field <br />season and monthly compliance monitoring required by CDPS permit # CO -0022756 <br />will continue to provide long-term performance monitoring data. Monitoring will be used <br />to evaluate the effectiveness of the pilot testing and determine if full-scale treatment <br />460 West 50 North, Suite 500, Salt lake City, Utah 84101 TEL(801)99D-3746 <br />