The mineralization at ESM has been classified as sedimentary exhalative (Sedex) in origin. The composition of the mineralization is unique, composed of primarily massive sphalerite and only minor galena and pyrite. Massive and semi-massive sphalerite-bearing deposits occur in siliceous dolomitic and evaporite-bearing marbles of the Upper Marble Formation of the Balmat-Edwards marble belt. These zinc-sulphide deposits lie in the core of the Sylvia Lake Syncline, a major poly- deformed fold lying between Balmat and Edwards. Zinc mineralization tends to follow evaporate deposition in the stratigraphic sequence. The region has experienced multiple metamorphic and intrusive events and large-scale ductile structures are common.

The property contains 14 known zones of sphalerite mineralization. Three clusters have been defined consisting of three to five deposits each. Geometry of mineralization varies, ranging from tabular to podiform and shallow to steeply dipping. Areas defined to date contain tonnages ranging from roughly 0.5 Mt to over 10 Mt. Typical thickness ranges from 2 ft to 12 ft thick. Mineralization tends to be very continuous along strike, ranging from 50 ft to 800 ft Plunge-lengths may exceed 6,000 ft.

There are two mineralization styles recognized in the district. Stratiform high-grade massive sphalerite is interpreted as primary mineralization contemporaneous with deposition of the Upper Marbles. Discordant breccia-like “durchbewegung” texture ........

The mine utilizes a combination of selective longhole stoping, modified or stepped room and pillar and mechanized Cut and Fill as mining methods, based on the geometry and the grade of the mineralized zones:
- Longhole stoping (“LH”) for mining blocks dipping steeper than 45°, which represents about 50% of the mine plan tonnage. This is the preferred mining method from a productivity and operating cost perspective;
- Mechanized Cut and Fill (“C&F”), for mining blocks with dips of less than 45° and zones not amenable to LH stoping, is more selective and represents about 7% of the mine plan tonnage;
- Modified or Stepped Room and Pillar (“RP”), for mining blocks with dips of less than 45° and grades, do not warrant the application of a fill to permit multiple panel extraction, representing 11% of the mine plan tonnage.

The mine plan tons at the ESM deposit will be extracted using a combination of longitudinal retreat stoping (LGS), Cut and Fill (C&F), Panel Mining – Primary and Secondary (PAP & PAS), and development drifting underground mining methods with rock backfill. Longhole backstopes (BCK) are also used in the design where applicable. The proposed combined underground and open pit mine plan is expected to reach an initial target production rate of 1,200 t/d for 2021 and ramp up to 1,800 t/d in 2022. Open pit mining will be completed in Year three (2024). The overall mine life will be seven years.

Underground
The ESM deposit will ........

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Non-potable water will be supplied by a 6 hp, 9-stage, 460 V, Goulds Model 55 GS 30 well pump which is capable of 50 gallons per minute (gal/m) at 65 psi. This well is located near the fence line at the front gate location. The water will run through an underground 2” Sclairpipe (HDPE) to the vehicle storage building where it will be treated by a Magnum CY 962 water softener before it will enter one of two 1,000 gal holding tanks.

Mill process and cooling water (non-potable) for the site will be pumped from the Sylvia Lake pump house with (3) Worthington 14-135-2, 75 hp pumps rated at 1,500 gal/m. The third pump will constitute excess capacity and the other two cycle off and on. Pump discharge will be through a 10” pipe to two 100,000 gal tanks. Each of the concrete deluge tanks (a concentrator water tank and a fire pump storage tank) are near the concentrate storage building / rail loadout shed. Water is pumped from the reservoir tanks to the concentrator. Mine water will be pumped from the booster pump house via the 4” shaft water line to the various mine levels.

Grey water from the surface facilities, surface run-off, water from the facility catch basins, and overflow from the reservoir tank will be directed to the mill holding pond. Waste water from the holding pond will be either recycled in the mill or pumped to the tailings dam through a pipeline comprising of 5,000 ft of 14” diameter Sclairpipe.

Mine water balances are calculated seasonally for May to October (summer) and November to April (winter) conditions. During the operating summer months, a total of 851,000 gal/d of fresh water is drawn from Sylvia Lake.

During winter months, the water inflows into ESM increase to 491,000 gal/d. Also, during winter, the fresh-water intake from Sylvia Lake increases to 889,000 gal/d average.