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TR-34 to Permit M-1977-342 Environmental Protection Plan 7. ENVIRONMENTAL PROTECTION FACILITIES An EPF is defined in the Rules as "...a structure...for control or containment of designated chemicals, acid mine drainage,or toxic or acid-forming materials...". EPFs,as defined,are present and operational at both the Mine site and the Mill site and are discussed below. Routine water quality monitoring to assess the overall effectiveness of many of the EPFs discussed in this section is performed in accordance with the approved GWMP. The GWMP includes narratives and maps to describe site locations, sample designators, sample parameters, sampling frequency, media being sampled, method of sampling and analysis applied, and reporting date, as required per Rule 6.4.21(7)(d). 7.1. Mine Environmental Protection Facilities EPFs at the Henderson Mine site involve: • The conveyance of impacted underground mine water,which is treated at the URAD WTP, the stormwater diversion system and a pond approved for high-density sludge (HDS) storage; and • Designated chemical storage facilities. The related EPFs are defined and evaluated in Section 7.1.1 and 7.1.2, respectively. Surface features of these EPFs are shown on Figure 1. Leaks, spills, or any other accidental or unauthorized releases are immediately addressed and reported as described in the Henderson Mine IRM (Appendix B). In addition, Henderson has contracted with a spill response contractor to provide third party emergency services who is available to assist in the event of an accidental release. 7.1.1. Mine Environmental Protection Facilities Mine EPF 1.1 — Mine Water & URAD Water Treatment System: Mine water is collected underground and pumped to various settlers for solids removal. A non-toxic flocculant may be added into the settlers to aid precipitation, if necessary. A non-toxic scale inhibitor is added at various sites to keep piping clear. Mine water is pumped to the surface through the#2 shaft. Once at the surface,the Mine water is pumped to a holding tank which is subsequently conveyed to the URAD WTP via 12" and 14" high density polyethylene (HDPE) pipelines and appurtenances. Solids from the settlers are generally sent to the Mill for processing. Some solids have been stored in mine drifts in the past; however, this material is of similar composition to the native ore and may be mined out in the future. Water conveyed from the Mine to the URAD WTP is delivered to the Buffer Pond (1 Pond) where it is held until it is pumped into the treatment system. The URAD WTP utilizes a lime based HDS process. This process treats incoming water using lime to raise the pH, followed by oxidation, settling and final pH adjustment. The HDS process recirculates sludge to improve coagulation and settling, and minimize reagent use. As the pH is raised with lime to alkaline conditions, metals are oxidized and precipitated. A flocculant is also added to promote precipitation. The resulting precipitate or sludge is thickened and removed from the HDS Climax Molybdenum Company August,2021 Henderson Operations Page 17 of 45