Going back to the Technical Report on PFS of 1 August 2018, there is quite a lot that deals with LAC's plans to manage waste and water issues at the proposed Thacker Pass mine.  I admit to doing a slap dab job of gleaning through the document to find items that I thought might be relative to those concerns.  You can no doubt do a better job on your own by reviewing the entire document, but the things that stood out in my very brief overview are below. Heavy type/italic emphasis in the following was done my me and not included in the orignal document. I cited page numbers in only a few locations, but it is all taken from the PFS except for the obvious few comments from me included:

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The life of mine schedule results in 46 years of commercial production mining with two (2) years of preproduction waste stripping. The pre-production stripping can be reduced to a single year; but was scheduled to coincide with plant construction. This allowed for mine waste to be utilized as construction fill, removing the need for imported fill.

 The waste is hauled to the plant and tailings embankment areas, to previously mined portions of the pit, or to the nearby waste dump

An overland ore conveyor is used to transport ore from the pit margin to the plant. A surface miner was chosen to mine the ore due to its ability to selectively and efficiently mine the subhorizontal layers of ore. Surface miners also have the ability to mine the ore without blasting or crushing, while simultaneously producing a crushed ore feed at 100% passing 150 mm. This simplifies the process of using an overland ore conveyor to transport the ore from the pit edge to the process plant.

From the test results in the reports, and the machine excavation of the test pit, it is expected that only the basalt waste material may require blasting, and this was the assumption included in the PFS. This test pit was excavated without blasting. The remaining waste as well as the ore will be mined without explosives. Due to the relatively small quantity of waste requiring blasting, a contractor will be used for the drilling and blasting on site.

 After Ore Preparation, the ore will be transferred as a slurry to the Leaching circuit. Sulfuric acid will be mixed in with the slurry to liberate the lithium from the clay. The leaching process will take place in stirred reactors designed to (a) maximum lithium dissolution from the ore and (b) optimize sulfuric acid consumption. The lithium bearing solution, i.e. “lithium brine”, will be separated from the leach residue by filtration. The filtered residue will be washed to recover any remaining free lithium, and then conveyed to the clay tailings facility. The wash solution will be recycled to the slurry ore in the attrition scrubbers. Crushed limestone and residue from the neutralization filters (Section 17.1.3) will be added to the leach clay residue to produce a geotechnically stable clay tailings.

Each of the two phases of the Thacker Pass Project will require approximately 2,000 acre-feet per year of make-up water from wells described in Section 18.6.

Clay Tailings and Salt Storage:

 The tailings and salt storage strategy is based on consideration of the following aspects of the site plan:  Adoption of filtered stack method of clay tailings disposal, referred to as the Clay Tailings .  Site selectFilter Stack (CTFS).  Fully contained and lined cells for the mineral salts requiring separate storageion for the CTFS and salt cells: the selected location is on relatively flat terrain within the mineral claim area for proper containment, while maintaining close proximity to the process plant.  Surface water management to minimize water entering the tailings area.  Utilization of mine waste rock to provide supplemental perimeter containment of the tailings on the downslope sides and for storage of the mineral salts in fully contained cells.  The salt storage areas are designed for eventual recovery of the salts, driven by market conditions. The stored materials have a market value, and their potential recovery as economic products will be evaluated in later engineering phases. There are two storage cells: one to store magnesium sulfate and the other for potassium and sodium sulfates. These topics are discussed in the following sub-sections. Deposition of filtered tailings, otherwise termed as “dry stack tailings”, is not as common as the conventional slurry method and typically has higher operating costs but has the benefit of improved stability and reduced risk of catastrophic failure and environmental impacts. Figure 18-2 shows the different states of tailings based on water content. At the tailings storage site, it is possible to dewater the tailings to a relatively low water content, but not quite to the degree to which it can be considered a “dry stack” as such. Hence, the term “filter stack” has been adopted for this application as described herein.

Based on limited chemistry testing conducted in conjunction with the process design, it is anticipated that most of the soil overburden and waste rock excavated from the open pit can be used to construct perimeter containment dykes, subject to confirmation of their physical and chemical properties.

A laboratory test program was completed to determine the physical and chemical properties of the tailings. The tests were performed on samples prepared from leach residue, neutralized residue, and residue from solution neutralization.

Following neutralization, the tailings are anticipated to be essentially inert and hence do not pose a hazard to contaminate the groundwater, especially when taking account of the relatively low hydraulic conductivity of the compacted tailings. However, as a precaution for groundwater protection, a basal clay liner is included in the present design. The approach to protecting the groundwater is based on the following factors:  The finest fraction of the tailings is sufficiently fine to severely limit the amount and rate of water infiltration.  The surface of the CFTS can be shaped to direct run-off water into lows or sumps from which collected water can be pumped out, preferably to the process plant; thereby minimizing the hydraulic head and associated gradient and hence the seepage rate and volume.  A clay liner will be placed from clay soil or mudstone rock obtained from the pit excavation. Limited laboratory data indicate the availability of relatively low permeability material (range of 1 x 10-6 to 1 x 10-7 cm/s), thereby minimizing any seepage losses from the CTFS.  It is understood that there is no shallow underlying potable water aquifer close to the ground surface that might potentially be contaminated by any minor seepage potentially penetrating the bottom of the CTFS and the underlying soil deposit. 

For a figure of the stockpile tailings, please go to page 152 of the PFS and refer to:  Figure 18-4 Snapshot of Stockpile Section

Closure Plan One of the most attractive features associated with the filter stack method is the ease of reclaiming and closing the facility at the end of mining. The following guidelines are proposed for CTFS closure:  Contoured as a dry landform conforming as much as possible to the surrounding landscape.  Drainage directed in shallow swales placed at regular intervals (50 m to 100 m spacing) which are vegetated or lined with gravel rockfill for erosion protection on steeper gradients.  The central portion of the deposit is anticipated to settle with time due to long-term consolidation of the tailings.  Placement of a 1.0 m thick mixed grained soil cover and a 300 mm thick layer of topsoil.  Establishment of a native vegetative cover as erosion protection and which is compatible with the surrounding vegetation.  Suitable vegetation should be established that can withstand the relatively arid climate. Clay Tailings Filter Stack Monitoring A geotechnical monitoring program for the CTFS will potentially include:  Regular visual observation of the perimeter dyke and tailings surface for cracks, bulges, slumps etc.  Survey pins along inside crest of perimeter containment dykes on south and east sides of the CTFS. Pin spacing between 50 – 100 m.  Slope inclinometers along inside crest of perimeter containment dykes on south and east sides of the CTFS. Inclinometers to be installed to a minimum depth of 15 m below the original ground surface at stack heights of 10 and 60 m (Figure 18-5) and spaced at 250 m along the dyke crest

Inclinometers are used to monitor subsurface movements and deformations of the tailings stack as well as native ground below the tailings. The applications of the inclinometer for the filter stack will include:  Detecting zones of movement and establishing whether movement is constant, accelerating, or responding to remedial measures.  Checking that deformations are within design limits and that adjacent infrastructure is not affected by ground movements.  Verifying the overall stability of the stack.

 Not reproduced here, but referenced is:  Design of Salt Containment Cells  You can go to page155 for that information and learn of the specifics to be taken to provide containment of produced salts.

Water supply issues are in the PFS on pages 156 and 157, but the source of the water being used is described in the first sentensce under the topic of "Water Supply":  "Raw water is supplied to the plant site via a raw water pipeline from a well or series of wells in the Quinn River Valley to the east of the site."

Sanitary Sewer The sanitary sewer system is planned to use a septic leach field located south of the plant next to the storm water pond in an alluvial fan to handle discharge from the septic and sanitary sewers on site. Meteoric Water Controls The site is being designed to have roof coverage over the process, loading and unloading areas to minimize any potential chance of contamination of meteoric waters by process materials. Storm Water Pond The majority of the meteoric water will fall on site roads, unimproved land and will have no contamination from the process. This water will be directed around the plant using a series of ditches and swales to a small pre-sedimentation pond which discharges then to a large storm water pond (10,600 m3) located south of the plant. This system will settle out suspended solids and contain the water from the site. This pond will then release the clean water back to the local water courses or be used on site.

 Contaminated Storm Water The contaminated storm water system is designed to collect all meteoric water from the site that has been contaminated by contact with process materials. This includes rainwater from process roofs and containment areas. Water stored in this tank will be consumed by the process plant.