2015-04-17_REPORT - M1977004 (2)

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Pitch Reclamation Project Colorado Mined Land Reclamation Board — 2014 Annual Reclamation Report understanding of surface water and groundwater flow and geochemical conditions at the Pitch property. A conceptual site model (CSM) was developed to provide an understanding of the natural and anthropogenic sources of uranium as well as the geochemical processes that control uranium concentrations in surface water and groundwater in and around the Pitch property. A summary of the CSM was provided to the WQCD in August 2014. The CSM was used as the basis 'for an alternatives evaluation to begin determining the LPL and associated best management practices (BMPs) that can be implemented to reduce the uranium loading to Indian Creek. With the CSM established, in 2014 an alternatives evaluation was performed to assess viable clean water diversion, uranium source control, in -situ, and passive /semi - passive options to achieve uranium mass load reduction and obtain the LPL for uranium. "Proof, of concept" bench testing performed in 2014 demonstrated that addition of phosphate (as pH- neutralized phosphoric acid) to the Pitch property surface water and groundwater resulted in rapid and near complete immobilization of uranium. As a result, phosphate -based treatment was identified as the principal means of achieving source control in the underground workings and North Pit Lake. Plans are being developed to conduct initial field -scale pilot testing of in -situ source treatability in the Pinnacle Mine underground workings to investigate the viability of in -situ treatment at the high elevation mine site with limited year -round access. The pilot testing is tentatively scheduled to be implemented during 2015 field season (June to early October) to perform a field test as a precursor to a full -scale source treatability by characterizing the physical extent and hydraulic conditions in the underground workings, and identifying the appropriate method for application and distribution of reagent to facilitate source treatment. The knowledge gained from pre- design pilot - testing will be used to design, permit, and implement BMPs to establish a reasonable and defensible LPL for uranium at the discharge POC (SW -33) over the next few years. f Specific activities associated with field -scale pilot testing in 2015 may include: • Develop a pilot testing work plan that details the piezometer installation, hydraulic testing, injection strategy, and long -term monitoring plan. • Obtain regulatory approvals for the 2015 field programs, as needed. • Investigate the suitability of P-4 and P -5 piezometers for reagent and tracer injection /recirculation. • Installation of two new piezometers into the underground workings to expand the injection infrastructure and long -term treatment network. iThese piezometers will be used for injection, circulation, and monitoring during the pilot testing and will serve an important function in the long- term treatment and monitoring program. I • Installation of pressure transducers with on- board') data logging capabilities into each piezometer (Piezometers P-4, P -5, and the new piezometers) to facilitate short-term testing and monitor longer -term trends. The pressure transducers will provide high - resolution data with minimal intervention and will provide a long -term safe solution to monitoring. r • Conduct phosphate injections (as dilute pH- neutralized phosphoric acid and /or sodium phosphate) and concurrent tracer testing under safe low -flow conditions (Fall 2015). • Monitor the success of the treatment approach and assess tracer transport in the underground workings, the North Pit Lake, PP -01, and the surface water discharge point of compliance (SW- 33). 1 Pitch 2014 Reclamation Report 16Apd12015_Cw.Docx 1 28