fact sheet nevada gold mines llc aa block project …

FACT SHEET

(Pursuant to Nevada Administrative Code (NAC) 445A.401)

Permittee Name: Nevada Gold Mines LLC

Project Name: AA Block Project

Permit Number: NEV0090060 Review Type/Year/Revision: Renewal 2020, Fact Sheet Revision 00

A. Location and General Description of Facility

Location:

The AA Block is a portion of the Nevada Gold Mines Goldstrike facilities located

in the Little Boulder Basin adjacent to the Tuscarora Mountain Range on the county

line between Elko and Eureka Counties, approximately 27 miles northwest of the

community of Carlin, Nevada. The facilities are located in Sections 23, 24, 25, 26,

27, 34, 35, and 36, Township 36 North (T36N), Range 49 East (R49E), and Sections

19, 20, 28, 29, and 30, T36N, R50E, Mount Diablo Baseline & Meridian.

The AA Block encompasses an area of approximately 2,854 acres. The private

lands, approximately 2,591 acres, are owned or controlled by Nevada Gold Mines

LLC (Permittee) and the unpatented mining claims, approximately 263 acres, are

held by Permittee on U.S. Bureau of Land Management administered lands.

The Goldstrike facilities can be accessed from Interstate 80 via the Carlin exit, Exit

280 and traveling northwest on the Nevada State Route SR766 for approximately

27 miles.

General Description:

This site is in permanent closure. The AA Block currently consists of the AA Block

Heap Leach Facility (AA Block HLF, which includes AA, Phases I, II, III, and

IIIA), AA Barren Solution Pond, one pumpback well, numerous groundwater

monitoring wells, the AA Tailings Impoundment, AA Tails Seepage Collection

Pond, Mill 4 Tailings Storage Facility 1 (Mill 4) and Seepage Collection Pond, and

the Bazza Waste Rock Disposal Facility (WRDF). With the closure of the heap

leach pad, most of the adsorption, desorption, recovery (ADR) process components

have been dismantled, and the buildings converted into a metallurgical testing lab.

B. Synopsis

Water Pollution Control Permit (WPCP) NEV0090060 (Permit) was first issued to

Barrick Goldstrike Mines, Inc. and became effective 3 August 1991. The Permit

was renewed in 1997, 2007, 2013, 2018, and 2020.

Nevada Gold Mines LLC

AA Block Project

Permit No. NEV0090060 (Renewal 2020, Fact Sheet Rev. 00)

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20201005km_0090060_NOD_FactSheet_Rev00.docx

In 2008, the AA Block WPCP was reorganized along with the North Block WPCP

(NEV0091029) such that active mine components were consolidated into

NEV0091029 while components in closure or projected to be in closure in the near

future were consolidated into NEV0090060. The following components were

transferred to NEV0091029 during this process:

o AA Barren Solution Pond,

o Wet Mill/Autoclave Process Facilities,

o Valdez Pond,

o Autoclave Stockpile Pads,

o AA Block Carbon Reactivation Facilities.

Historical information and past test results for these components may be found in

previous Permit documents and reports for NEV0090060.

In July 2019, Nevada Gold Mines LLC (NGML), a joint venture between Barrick

Gold Corporation and Newmont Goldcorp Corporation was created. NGML

represents the combination of various Nevada operations, of which the AA Block

Project is included. Revision 01 of the 2018 Permit reflects the transfer of the

Permit from Barrick Goldstrike Mines Inc. to NGML.

In February 2020, the Permittee submitted a document entitled Final Plans for

Permanent Closure (FPPC) of the AA Block Project. As the AA Block Project

represents components that are either in closure or projected to be in closure in the

near future, the FPPC represents a compilation of previously submitted FPPCs.

This FPPC has been reviewed and was approved by the Division in August 2020.

This FPPC includes the following facilities:

o AA Heap Leach Pad

AA, Phase I, II, III, & IIIA Heap Leach Pads

o AA Tailings Storage Facility

o AA Seepage Collection Pond

o LPOP-10 and other monitoring ports

o AA Pump-back Well and Piping

o Mill 4 Tailings Storage Facility 1

Mill4 Seepage Collection Pond, pumps, sumps, valves, ditches,

pipelines

o Other associated Pipes, Valves, and Piping

In May 2020, at the request of the Division, the Permittee submitted an engineering

design change (EDC) to transfer the AA Barren Solution Pond (aka Lab Pond) from

the NEV0091029 Permit back to the NEV0090060 Permit. Transfer of the pond

was to satisfy the BMRR Closure Branch policy of having a draindown collection

pond uniquely associated with a process component, specifically the AA HLF.


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AA Block Heap Leach Facility (AA Block HLF which includes AA Pad, Phases

I, II, III, and IIIA)

The AA Block HLF is one large heap leach pad segmented into five component

leaching areas: the AA Pad (2.2 million sq.ft.); the Phase I Pad (1.9 million sq.ft.);

the Phase II Pad (1.2 million sq.ft.); the Phase III Pad (2.6 million sq.ft.); and the

Phase IIIA Pad (1.8 million sq.ft.), resulting in a total area of 9.7 million sq.ft.

(approximately 223 acres).

Leach ore was primarily hauled directly from the Betze-Post Pit to the leach pads

as run-of-mine for leaching. However, a portion of the ore was crushed and

agglomerated with lime and cement prior to placement on the AA Pad.

The original AA Pad was lined with a single 60-mil High Density Polyethylene

(HDPE) liner over compacted soil. The Phases I and II leach pad expansions were

lined with 80-mil HDPE over a prepared base of compacted, in-place soil meeting

a permeability specification of 1.0 x 10-6 centimeters per second (cm/sec). The

Phase III leach pad expansion was lined with 80-mil Very Low Density

Polyethylene (VLDPE) which overlays a minimum thickness of 12 inches of

compacted soil meeting a permeability specification of 1.0 x 10-6 cm/sec. A sand

leak detection layer incorporating an electronic leak detection system exists

between the synthetic liner and compacted soil layers of the Phase III expansion.

The Phase IIIA leach pad expansion was lined with 80-mil VLDPE, over a

secondary liner consisting of a minimum thickness of 12 inches of compacted soil

meeting a permeability specification of 1.0 x 10-6 cm/sec. A sand leak detection

layer incorporating an electronic leak detection system exists below this compacted

soil layer. The sand layer in turn overlies a lower liner consisting of a minimum

thickness of 12 inches of compacted soil meeting a permeability specification of

1.0 x 10-6 cm/sec. Table 1 provides a description of the liner materials utilized for

the various AA Leach Pad and subsequent expansions.

Table 1: AA Heap Leach Pad and Subsequent Expansion Liner Composition

Details

Leach Pad Synthetic Liner Soil Layer Size

AA Leach Pad 60-mil HDPE Compacted Soil 2,200,000 ft2

Phase I Expansion 80-mil HDPE Soil 10-6 cm/sec 1,900,000 ft2

Phase II Expansion 80-mil HDPE Soil 10-6 cm/sec 1,200,000 ft2

Phase III Expansion 80-mil VLDPE 12” Soil 10-6 cm/sec 2,600,000 ft2

Phase IIIA Expansion 80-mil VLDPE (2) 12” Soil 10-6 cm/sec 1,800,000 ft2

Following the 1997 Permit renewal, the AA Block HLF entered permanent closure

and the leach pad was reclaimed (Final Plan for Permanent Closure [FPPC],

February 2000). The FPPC for the AA Block HLF included placement of a fine

textured soil cover vegetated similar to the natural vegetation on adjacent

undisturbed areas. The 4-foot thick soil cover has a sufficiently finer particle size

distribution and reduced permeability to provide a capillary break between the

material on the leach pad and the cover. It was designed to be of sufficient thickness


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to store water during the period of maximum precipitation for elimination by

evaporation and transpiration during periods of minimum precipitation.

Reclamation plans included reshaping to provide natural morphology, eliminate the

potential for ponding water, provide a natural looking and naturally functioning

drainage network and reduce erosion and sediment yield from the surface of the

cover to levels comparable to the existing natural landforms of the area. The cover

and drainage network are also designed to minimize the risk of a localized breach

of the cover and exposure of the underlying spent ore material. The stormwater

drainage system around the perimeter of the re-contoured heap leach pad has been

redesigned to safely accept the additional stormwater runoff from the covered leach

pad area.

One-dimensional and two-dimensional hydrologic models indicate that the

percolation rate through the covered AA Block HLF is small because precipitation

is significantly less than potential evaporation in the region. Based on the analyses

performed, a 4-foot cover thickness was selected as the optimum cover design. A

4-foot thick capillary/evapotranspiration (ET) cover constructed of Carlin

Formation siltstones effectively minimizes water percolating through the

recontoured AA Block HLF. The ET cover is expected to be stable under all

conditions anticipated in the proposed re-contouring design. The design also

incorporates a high transmissivity toe drain beneath the ET cover to convey

draindown and/or post-closure flow to the existing downgradient AA ponds.

Toe Drain

As described above, the ET cover was designed for minimal flux of precipitation

through the ET cover. Nonetheless, a high transmissivity toe drain was incorporated

beneath the ET cover, located along the downgradient (western) margins of the

heap, and conveys any potential draindown or post-closure flows that may drain

through the spent heap material to the AA ponds. The toe drain-flow is collected

in a sump consisting of a minimum 22-cubic feet of non-calcareous drain rock

encapsulated in filter fabric, with an 8-inch diameter perforated drainpipe. The

sump is designed for a flow rate up to of 710 gallons per minute (gpm); as of the

fourth quarter 2017, the current draindown rate ranges between 4 – 6 gpm. This

toe drain flow represents the heap draindown and correlates well with the modeled

draindown rate.

Water Balance Model and Results

In order to design a capillary cover for the AA Block HLF, hydrologic simulations

(modeling) were conducted. The daily evapotranspiration data along with the daily

potential soil evaporation and precipitation were used to develop a spreadsheet

model to simulate water fluxes through soil layers covered with vegetation

according to a seed mix developed for the site. The model was run to study water

fluxes under developing vegetative cover, in dry and wet years and under varying

soil thicknesses.


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The water balance model was run for local area conditions and configured with two

back-to-back wet years. The spreadsheet model determined a cover thickness of 3

feet would be adequate to prevent deep percolation after the effective vegetation

cover reached about 33% (year 4), with percolation (leakage through cover) of 2.82

inches (37 gpm) in year 1. If cover thickness were increased to 4 feet, the leakage

potential decreased to 0.49 inches (7 gpm) in year 1. The use of a 5-foot cover

thickness eliminated the leakage potential in year 1 but provided no benefit beyond

the second year. Based on the marginal reduction in flux, the 4-foot cover thickness

was selected as the optimum cover thickness.

Draindown Solution Management

Draindown solution from the AA Pad flows to the AA Barren Pond. Solutions from

the Phase I, II, III, and IIIA (Phase) leach pads, Leach Pad Observation Port

(LPOP)-10 (pad leak detection) and the AA Pumpback Well (AA PBW) are

directed to the Phase Composite Box (PCB). The PCB is a double-containment

structure, with the manifold collection box primary containment being constructed

of mild steel, surrounded by a precast concrete box for secondary containment.

Solution return pipes from the AA Block HLF to the PCB and from the PCB to the

AA Barren Pond are buried pipe-in-pipe. Any leakage occurring from the AA

Block HLF pipe reports to the PCB primary containment box, whereas leakage

from the PCB outlet pipe reports to the AA Barren Pond.

The Permittee submitted a plan, which was subsequently approved by the Nevada

Division of Environmental Protection (Division) in November 2013, to construct

an ore stockpile on the northwestern portion of the HLP. The stockpile is located

approximately 100 yards from LPOP-10. During 2014, flows to LPOP-10

temporarily increased from approximately 5 gallons per day (gpd) to 155 gpd. With

this flow increase, certain constituents of concern, i.e. pH, arsenic, magnesium,

manganese, nitrate, selenium, sulfate, and total dissolved solids, also increased.

Due to the increased flow rate, the Permittee increased monitoring frequency to

monthly, which continued through the fourth quarter of 2014 following a noticeable

decrease in flow rate. In general, the flows have decreased, having a yearly average

of approximately 1.75 gpd in 2019.

Monitoring:

The following sections describe the monitoring of heap draindown, leach pad leak

detection, and site groundwater.

Draindown

The PCB secondary containment is monitored weekly for fluid accumulation and

reported as average daily accumulation in gallons per day (Permit monitoring point

PCB). Discrete flow rate measurements and water quality samples are collected

for LPOP-10, AA PBW, and the co-mingled Phase solutions.

Due to the location of the PCB, i.e., downgradient and associated with the AA HLP

stormwater diversion channel, the secondary containment would receive


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stormwater flows, thereby resulting in occasional exceedances in the PCB leak

detection Permit limits. To alleviate this situation, the Permittee submitted an

Engineering Design Change (EDC) in August 2016 to reconstruct the lower portion

of the existing diversion resulting in essentially blocking the PCB with the channel

berm. The Division approved the EDC in October 2016. The improvements were

completed in April 2017.The AA Pad Inlet (AAPI) and Phase Composite (PC)

draindown flows are monitored individually at end-of-pipe for flow rate and water

quality as the solution enters the AA Barren Solution Pond.

Beginning in 2018, the PCB began to exceed the annual leak detection rate of 50

gpd as allowable per Part I.G.4 of the Permit. Ongoing investigation and evaluation

of the PCB line has resulted in a list of potential leak sources and repair approach

proposals. Although the Permittee has proactively investigated the leakage, the

Division has included a Schedule of Compliance item in the 2020 Permit renewal

to complete all investigations and repair/resolve the PCB leakage.

Leach Pad Observation Ports (LPOPs)

Leak detection systems for the AA and Phases I and II pads are provided by LPOPs

which were constructed to detect any solutions that may escape through the

synthetic liner.

LPOPs 6 and 8 are downgradient of the leach pad on the western toe of the AA pad.

LPOPs 9, 10, 11, and 12 are located on the western toe of the Phase pads on the

northern end of the facility. LPOPs are monitored weekly for fluid accumulation

and reported as average daily accumulation in gallons per day. As part of the

closure of Post Pad #1 and the construction of the Bazza WRDF, LPOPs 1 thru 5,

were either closed out or buried. LPOP-7 was abandoned during the closure of the

AA Block HLF.

The leak detection systems that are part of the Phases III and IIIA pad liners were

monitored with an Electronic Leak Detection System (ELDS), as well as physical

leak detection ports beneath the solution collection ditches. The ELDS was taken

out of service during closure of the AA Block HLF and has not been monitored

since that time.

Ground Water Observation Ports (GWOPs)

GWOPs are monitoring wells used to monitor groundwater elevation and quality in

the vicinity of the leach pads. GWOPs are monitored quarterly for Profile I

parameters. GWOPs 9 and 12 are located on the eastern side upgradient of the

Phase leach pads for establishing background groundwater quality. GWOP-13a is

located west of the Phase leach pads for monitoring downgradient groundwater

quality. GWOP-16b is downgradient of the solution ponds on the northwest side.

GWOP-17b is located upgradient of the remaining solution pond on the southeast

end to establish groundwater quality upgradient of the ponds. GWOPs 1 thru 4

were closed/buried during construction of the Bazza WRDF; GWOPs 5 through 8

and 14 were abandoned during closure of the AA Block HLF. There is no record

of GWOP-19 and it is believed it was never constructed and the number was simply


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overlooked. GWOPs 10A, 11A, and 15A are associated with the AA Tailings

Impoundment.

Cutoff Trench

Cutoff Trench North Side (CTNS) and Cutoff Trench South Side (CTSS) were

constructed downgradient of the four phased leach pads during commissioning of

the Phase I ponds to intercept shallow groundwater drainage originating upgradient

of the leach pads. Each trench has a monitoring point (CTNS and CTSS) located

on the north and south ends, respectively, of the cutoff trench to monitor fluid flow

rate and, if present, water quality of that flow. To date, no solution from any source

has ever reported to these trenches.

LPOP-10 and Associated Corrective Action

In January 2008, the Permittee informed the Division that LPOP-10 had exceeded

the permitted average daily flow over the fourth quarter of 2007 of 75 gpd and the

permitted average daily flow for calendar year 2007 of 25 gpd. The Permittee

submitted a Corrective Action Plan (CAP) as required by the Division in February

2008. The CAP included the installation of a permanent pumping system in LPOP-

10 to minimize head on the secondary layer. The CAP also required installation

and monitoring of a new groundwater monitoring well (GWOP-18), located

immediately downgradient of LPOP-10.

In May 2008, the Permittee submitted an EDC for the construction of a double

contained (pipe-in-pipe) drain line to convey the solution from LPOP-10 to the

PCB. The EDC was approved by the Division and constructed, which allowed

continuous pumping of the fluid rather than periodic evacuation to a water truck.

In February 2009, the Division required submittal of a second CAP which was

approved by the Division in June 2009. The second CAP expanded the

groundwater investigation and included the addition of two new monitoring wells:

GWOP-20, installed near the existing GWOP-12 to provide additional upgradient

groundwater data, and GWOP-21, a vadose zone well, which was installed in

November 2009 near GWOP-18 but at a 45 degree angle to extend under the heap

leach pad. Soil samples taken during the drilling of GWOP-21 were used to

evaluate the vadose zone below LPOP-10 for evidence of leakage through the

LPOP-10 secondary layer.

The analyses of water sampled from GWOP-18 and GWOP-21 indicate the

presence of process solution derived exceedances, of Division Profile I reference

values, for arsenic, magnesium, manganese, nitrate, selenium, sulfate, and total

dissolved solids (TDS). As a result, a Finding of Alleged Violation and Order

(Order) was issued to the Permittee in April 2010. The Order required submittal of

a revised CAP which included the installation of AA PBW and an additional

downgradient monitoring well (GWOP-22).

AA PBW was constructed approximately 40 feet downgradient of GWOP-18 to a

depth of 215 feet and is screened over the interval from 155 feet to 215 feet (see


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Table 1 below for well construction details). AA PBW commenced operation on

19 October 2010. In general, groundwater quality exceeds Profile I reference

values for arsenic, manganese, nitrate, and selenium. Table 2 provides the monitor

a well construction and groundwater details.

Table 2. – Monitor well construction and depth to water details.

Well ID

Collar

Elevation

(ft. AMSL)(a)

Total

Depth

(feet)

Well Bottom

(ft. AMSL) (a)

Depth to

water

(ft.

below

collar)

Groundwater

Elevation

(ft. AMSL) (a)

Screen

Interval

(feet)

GWOP-18 5616.99 200 5416.99 163.99 5453.00 175 - 195

GWOP-21

(as vertical) 5616 140 5476 131.5 5430.50

69.25 –

99.25

AA PBW 5616.25 227 5389.25 177 5439.25 155 - 215

GWOP-22 5613.94 185 5428.94 165.22 5448.72 155 – 195

(a) AMSL = Above Mean Sea Level

GWOP-22 is located approximately 100 feet downgradient of GWOP-18.

Table 3 below provides solution concentrations only for constituents considered of

interest or currently elevated. Average LPOP-10, GWOP-18, GWOP-21, AA

PBW, and GWOP-22 solution concentrations are based on an average of all

available analyses from initial well construction (first sampling) through the first

quarter of 2020. The range reflects the lowest and highest values from all sampling

events. GWOP-18, GWOP-21, AA PBW, and GWOP-22 wells have been

monitored for water quality and depth to water since construction. LPOP-10

chemistry represents heap draindown chemistry of the Phase (PC) leach pads.

Table 3. – Comparison of Concentrations of Constituents of Concern (COC),

Inception to First Quarter 2020

COC Division

Profile I

R.V.

Average

LPOP-10

Average

GWOP-18

Average

GWOP-21

Average AA

PBW

Average

GWOP-22

Arsenic,

mg/L

0.01 0.089

(0.021 – 0.231)

0.023

(0.007 – 0.052)

0.060

(0.008 – 0.154)

0.040

(ND – 1.17)

0.011

(0.004 -0.015)

Magnesium,

mg/L

150 238

(150 – 330)

151

(25 – 290)

315

(150 – 450)

48

(0.797 - 275)

36

(11 – 48)

Manganese,

mg/L

0.10 24

(13-39)

0.017

(0.005 - 0.061)

0.083

(0.007 – 0.234)

0.42

(0.005 – 26)

0.010

(0.005 – 0.347)

Nitrate,

mg/L

10 330

(96 – 430)

106

(5.4 – 160)

268

(99 – 380)

32

(0.19 – 140)

8.4

(1.13 – 18)

pH, s.u. 6.5 – 8.5 3.47

(3.01 – 4.70)

7.58

(6.25 – 8.21)

7.26

(6.31 – 7.84)

7.79

(6.68 – 9.05)

7.61

(6.91 – 8.32)

Selenium,

mg/L

0.05 1.27

(0.26 – 1.65)

0.399

(0.021 – 0.68)

1.10

(0.49 – 1.4)

0.094

(ND – 0.28)

0.025

(0.007 - 0.085)

Sulfate,

mg/L

500 3,368

(2,700- 5,500)

769

(142 – 1,400)

2,331

(960 – 3,700)

232

(7.1 – 2,390)

100

(38 – 220)

TDS, mg/L 1,000 6,900

(5,100 – 8,700)

1,856

(936 – 2,600)

4,960

(2,300 – 19,900)

593

(68-4,140)

450

(310 – 640)

# Data Pts. 80 85 66 105 59 mg/L = milligrams per liter; ND = non-detect; R.V. = Reference Value; s.u. = standard units; TDS = Total Dissolved Solids


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In August 2011, the Permittee submitted “Addendum 1 Final Permanent Closure

Plan AA Heap Leach Pad Seepage” (Plan). This Plan included a fate and transport

model and described additional proposed closure actions to address the observed

seepage associated with the AA Block HLF. These actions consist of continued

operation of the pumpback system, continued monitoring with revision as

necessary, and review of the pumping systems effectiveness. This Plan was

approved by the Division in February 2012.

Prior to 2018, groundwater sampled in GWOP-22 had only rarely exceeded Profile

I reference values and was considered to be representative of background

groundwater quality. However, beginning in the first quarter of 2018, the total

nitrogen (N(T)) concentration exceeded the Profile I R.V. of 10 mg/L and has

continued to increase to the current level (2Q20) of 18 mg/L. Also beginning in

the second quarter of 2018, the concentration of nitrate+nitrite (as N), exceeded the

Profile I R.V. of 10 mg/L and has continued to increase to the current level (2Q20)

of 18 mg/L. Additionally, as noted during the review of the 2019 annual report,

although concentrations are currently below Profile I R.V.s’, the Division noted

that selenium, sulfate, and TDS concentrations indicate an increasing trend. With

these exceedances, the Division is requiring an evaluation of the

effectiveness/efficacy of the PBW in capture and containment of the LPOP-10

plume and a CAP to address the contamination observed in GWOP-22. As such,

the Division has included a Schedule of Compliance item in the 2020 Permit

renewal.

Following submittal and review of the mitigation portion of the Plan, the

enforcement action was closed on 1 December 2011, while remediation and

monitoring continue.

Monitoring wells related to the AA HLP and HLP Seepage, which are monitored

on a minimum quarterly basis, consist of the following:

AA-PBW, LPOP-10, GWOP-9, GWOP-12, GWOP-13a, GWOP-16b,

GWOP-17b, GWOP-18, GWOP-20, GWOP-21, and GWOP-22.

AA Enrichment Solution and Freshwater Ponds

A total of six leach solution ponds were associated with the AA Block HLF. There

were four ponds within the AA Pad leach system and two solution ponds within the

Phase I II, III, and IIIA (Phase) expansions. The AA Enrichment Solution pond

and the freshwater pond were closed in September 2012. The remaining four ponds

were either closed or transferred to WPCP NEV0091029 following closure

activities beginning in February 2000.

An FPPC for the AA Enrichment pond and the freshwater pond was submitted in

February 2012 and approved by the Division in April 2012. The pond FPPC

consisted of cutting the pond liners and folding the liner into the center of the pond

to encapsulate any sludge that remains. The entire area was then backfilled with


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clean non-Potentially Acid Generating (non-PAG) waste material, compacted,

brought up to an elevation of 5,500 feet above mean sea level (AMSL), leveled,

and eventually utilized for parking. The closure of the ponds, with the exception

of backfilling to the 5,500 foot AMSL elevation, was completed in September 2012.

The AA Barren Solution Pond, per the March 2020 EDC, was transferred back from

the North Block Permit (NEV0091029) to the AA Block Permit and is now

uniquely associated with the AA HLF. The pond is double-lined, consisting of 80-

mil HDPE for both the primary and secondary liners, with a capacity of 2.5 million

gallons, and is being used as a temporary flow-through catchment for the current

4 - 6 gallons per minute (gpm) of AA Block HLF solution draindown. Draindown

solutions ultimately report to the process water system of the North Block

operations (WPCP NEV0091029). Draindown is expected to continue to decline

to less than 1 gpm by 2040. At that time, the pond will be converted to an

evaporation cell (E-Cell). A TPPC for the conversion/construction of an e-cell is

in progress and planned for submittal in the fourth quarter of 2020.

AA Tailings Impoundment

The Carbon-in-Leach (CIL) tailings slurry has been historically routed to the two

tailings impoundments - the AA Tailings Impoundment (AA Tails) and the North

Block Tailings Disposal Facility (NBTDF). Only the AA Tails is included in

WPCP NEV0090060. The NBDTF and Tailings Storage Facility 3 (TSF3) are

included in WPCP NEV0091029 and now receive all tailings produced.

Active tailings deposition ceased at the AA tailings storage facility (TSF) in 1997,

when the NBTDF was commissioned (except for a period in 2007 when tailings

were deposited to consume the remaining storage capacity). The AA Tails is lined

with native materials. In areas where the in-place soils have permeability greater

than 1 x 10-6 cm/sec, a 12-inch thick compacted clay liner (permeability <1 x 10-7

cm/sec) has been installed. A 1-foot thick sand/gravel blanket drain overlays all but

an approximately 80-foot wide strip along the upper reaches of the entire clay liner.

The clay liner is located in the deeper parts of the impoundment. A minimum of 2

feet of compacted material with a permeability of less than 1 x 10-5 cm/sec was

placed over the blanket to minimize the hydraulic head imposed on the drain. A

synthetic liner was placed over higher permeability zones within the north

embankment area.

In May/June 2014, during construction of the TCM Tailings Thickener,

containment of the AA Tails was breached by a power pole anchor and two

foundation drain pipes that collect non-contact subsurface water. Upon realization

of the breach, the Permittee requested a reduction of the AA Tails freeboard

reference elevation to 5718.5 feet AMSL. In November 2014, the Division

approved the Permittee request to a reduction in the AA Tails freeboard elevation.

In February 2015, the Permittee submitted an EDC to repair the liner damage and

reconstruct the drain sump to prevent the non-contact surface water from entering

the AA Tails. This EDC also provided for a future request to re-instate the

previously approved freeboard elevation for the potential future use of the AA Tails


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for water storage due to operational issues with the TCM plant – this request was

denied by the Division based on the AA Tails not meeting pond design criteria per

NAC 445A.435.1, and because of degradation of groundwater at GWOP-10A and

GWOP-15A. Following denial of the request to increase freeboard elevation to

allow use of AA Tails for the TCM, a tentative plan for permanent closure (TPPC)

for the AA Tails was submitted in July 2015 and updated in December 2015.

GWOP-10A/GWOP-15A

Beginning in the second quarter of 2007, groundwater chemistry at GWOP-15A,

located on the southern edge of the impoundment, indicated trace weak acid

dissociable (WAD) cyanide, and elevated concentrations of sulfate and TDS.

Similar constituent exceedances were discovered in 1994 at GWOP-15 (which was

replaced by GWOP-15A in 2002). At that time, the Permittee conducted an

investigation consisting of installing seven new monitoring wells, data collection

and analysis, and performing a geological evaluation of the area. The investigation

concluded that excess water located in the southeast corner of the AA tails dam was

infiltrating into a contact zone between the Carlin Formation and the underlying

Vinini Formation allowing for a preferential flow path from the tails dam to

GWOP-15.

This investigation resulted in a plan to deposit tails in the southeast corner above

the contact zone to develop a protective beach sealing off the infiltration area and

confine the supernatant pond to the northeast quadrant of the tails. By 1998, water

levels in GWOP-15 had dropped, precluding a clean sampling zone due to

sedimentation close to the base of the well. GWOP-15 was closed and relocated to

its current location as GWOP-15A. Initial sampling conducted from the second

quarter of 2001 through the second quarter of 2002 (2Q01 thru 2Q02) indicated

decreasing levels of sulfate and TDS, suggesting that the plan was working.

However, beginning in the second quarter of 2007 and continuing through 2017,

both sulfate and TDS began to increase and have remained at relatively stable

levels, i.e. 1,300 mg/L sulfate and 2,200 mg/L TDS, respectively.

Also in the second quarter of 2007 and continuing through 2017, at GWOP-10A,

located downgradient of the impoundment, both sulfate and TDS concentrations

began to increase, and, in the first quarter of 2011, concentrations of both exceeded

the Division Profile I reference values. Trace WAD cyanide was also indicated.

In the first half of 2009, in correspondence to the Division, the Permittee theorized

that the chemistry trends were coincident with the supernatant pond approaching

the south and east embankments of the impoundment. In 2010, as an interim

stabilization measure to minimize solution impoundment in the southeast corner as

well as reduce the amount of windborne dust originating from the AA Tails surface,

the Permittee placed a nominal 2-foot thick cover of waste rock over the south and

east portion of the tailings beach. The Permittee believes that the placement of the

cover will aid in reversing the groundwater degradation.


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Additionally, the Permittee has actively reduced the supernatant pond volume, with

only direct meteoric water collecting on the impoundment surface. In the short

term, the 2015 TPPC proposed to begin closure–related activities consisting of the

following steps:

o Removal of the water pool to allow stabilization of the tailings and facilitate

cover placement;

o Removal of the TCM construction laydown yard (completed January 2016);

o Design, permit and construction of new secondary containment for the RIL

tailings distribution, decant/reclaim return pipelines and the tails thickener

pipe corridor overflow which currently reports to the AA tailing storage

facility (AATSF) (WPCP NEV0091029);

o Design, permit, and construction of a location to run evaporators at TSF 3

(WPCP NEV0091029);

o Permit and construct a pad for disposal of spill related material on the North

Block Tails Dam (WPCP NEV0091029); and

o Development of an FPPC.

The long-term proposal included the following:

o Completion and submittal of an FPPC (completed July 2019);

o Formulation of a budget and commencing the budgeting process;

o Complete a schedule of work;

o Stockpile cover material (scheduled for 4Q2020); and

o Begin closure construction activities (1Q2021).

Following elimination of process solution inflows, reduction of the supernatant

pool, and placement of the 2-inch waste rock cover on the south and east beaches,

quarterly water quality data monitored at GWOP-10A and GWOP-15A from the

fourth quarter of 2017 to the first quarter 2020 indicates that the chemistry appears

to be stable or slightly decreasing for the constituents of concern. Table 4 below

provides discrete data points for the aforementioned quarterly monitoring.

Table 4 - Comparison of Concentrations of Constituents of Concern (COC),

GWOP-10A and GWOP-15A, Fourth Quarter 2017 and First Quarter 2020

COC Division

Profile I

R.V.

GWOP-10A

2017

GWOP-10A

2020

GWOP-15A

2017

GWOP-15A

2020

Arsenic, mg/L 0.01 0.014 0.015 <0.005 <0.005

Magnesium,

mg/L

150 82 68 140 140

Nitrate, mg/L 10 1.4 1.4 3.3 1.9

pH, s.u. 6.5 – 8.5 7.72 7.32 7.4 6.73

Sulfate, mg/L 500 640 570 1,300 1,300

TDS, mg/L 1,000 960 1,000 2,400 1,600

WAD cyanide,

mg/L

0.2 0.025 0.019 0.016 0.022


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AA TSF Tentative and Final Plans for Permanent Closure

An updated TPPC was received in December 2015 and approved by the Division

in April 2016. The Permittee submitted an FPPC to the Division in June 2017. The

FPPC was revised and resubmitted in February 2018. The Division reviewed and

approved the revised FPPC in April 2018. In July 2019, the Permittee submitted

Revision 2 of the FPPC, which was subsequently was reviewed and approved by

the Division in March 2020.

AA Tails draindown, AA-TDD, which represents seepage from the tailings blanket

drain, embankment blanket drain, and embankment toe drain, currently reports to

the vault located above the Seepage Collection Pond (SCP) via a seepage collection

trench. Solution is currently pumped from the vault to the tailings surface via a 6-

inch diameter HDPE pipe. AA-TDD is sampled quarterly for NDEP Profile I and

flowrate at the vault. The 6-inch pipe extends up the downstream (west)

embankment face, under the AA TSF crest road, and terminates approximately 275

feet onto the tailings surface. Historic flows (2019) averaged approximately 23

gpm.

AA TDD will ultimately be managed by constructing a series of E-Cells in the

vicinity of the existing SCP, per the approved FPPC. In the interim, the permittee

was directed by the Division to end recirculation of the tailings draindown to the

AA TSF surface. Per a January 2020 approved EDC submitted for the North Block

Project (NEV0091029), the Permittee plans to tie the AA TSF seepage return pipe

into both of the two new reclaim pipes (primary and backup) that will convey

process water from the NBTDF to the Autoclave area Wet Mill in a pipe-in-pipe

arrangement. The NBTDF reclaim pipes will be contained in the RIL to CIL

Pipeline Corridor, which will entail utilizing existing lined corridors/facilities

where possible and constructing a new lined channel to connect the existing

containment areas. One-way check valves will be installed so reclaim water cannot

flow back into the seepage return pipe. Construction is due to be completed by

September 2020.

The approved FPPC includes regrading and covering the TSF with a minimum 4-

foot thick engineered soil cover. Beginning in 2020, the Permittee will begin an

accelerated schedule of waste rock cover placement to be completed in 2023 with

the final cover placement. Stormwater diversion channels will be constructed to

convey the 500-year 24-hour storm event converging in a spillway which outfalls

into the existing Brush Creek Diversion.

Approximately 3 acres of the AA Tails surface will be utilized for temporary

stockpiles of highly mineralized ore and magnetic separation concentrate. The

stockpiles will remain for approximately 5 years from initial placement of

material(s). The highly mineralized ore stockpile was constructed in January 2012

and decommissioned in January 2017. Prior to construction and loading of the

stockpile, two vibrating wire piezometers (VWP) monitoring points (AA-VWP-11-

01 and AA-VWP-11-02 in the Permit) were installed directly beneath the ore

stockpile footprint. The VWPs were installed a minimum of 6 feet deep in the base


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tailing material. Following decommissioning of the Mineralized Ore Stockpile,

piezometers AA-VWP-11-01 and AA-VWP-11-02 were removed. Only stockpiled

cover material remains on the AA Tails surface.

AA Tails Seepage Collection Pond

The AA Tails Seepage Collection Pond is designed to collect seepage from the AA

Tails (AA – UCP) embankment drains. This pond is lined with 40-mil HDPE which

overlays a 12-inch layer of low-permeability clay and has a leak detection system.

This pond only contains solution during periods of heavy rainfall or power upsets.

The AA Tails Seepage Collection Pond also has the required capacity to contain

the 100-year, 24-hour storm event. As of August 2020, under normal operating

conditions, solution reporting from the embankment drains is pumped to the surface

of the AA Tails and represents the impounded tails draindown (reclaim) solution

(supernatant), AA-TR. However, pursuant to the January 2020 EDC submitted for

the North Block Project (NEV0091029) and described above, the Permittee plans

to eliminate recirculation of the draindown to the surface by tying the AA TSF

seepage return pipe into the process circuit for the North Block Project facilities

until such time as E-cell construction is completed in the vicinity of the SCP. AA-

TR will continue to be monitored semi-annually for Profile I and the depth of the

supernatant on the impoundment surface.

Solution Pond Observation Ports (SPOPs) are used to monitor the leak detection

systems in this collection pond. The SPOPs consist of 12 inches of coarse sand

between the synthetic liner and the low-permeability clay layer with a network of

perforated HDPE pipes draining to the east and west ends. SPOPs are monitored

using riser pipes located at the lower corners of each pond for the accumulation of

fluids and reported as an average daily accumulation.

SPOP-3 is located west of the AA Barren Solution Pond; SPOP-5 and SPOP-9 are

located south of the seepage collection pond and west of the AA Tails (downstream

toe of the embankment). GWOPs 10a and 11a are located downgradient (west) of

the AA Tails to monitor groundwater quality. GWOP-15a is on the southern end

of the tailings facility. These monitoring wells are monitored quarterly for Division

Profile I parameters and groundwater elevation.

SPOP-2 was abandoned as part of closure activities in 2012 related to the AA

Enrichment Solution and Freshwater Ponds. SPOPs 6 through 8 were abandoned

during the AA Facility HLF closure activities in 2000. SPOP-1 was abandoned

during closure of the Post Pad #1 in 1991. SPOP-4 was transferred to WPCP

NEV0091029 in 2008.

Mill 4 Facility

The original WPCP for the Mill 4 Facility (NEV0089015) was incorporated into

the Mill 4 Tailing Storage Facility 1 WPCP (NEV0092100) in June of 2001. The

Mill 4 Facilities were constructed during the period 1988-1989. The mill building,

a Caro’s Acid system, and all ancillary pipes, tanks, and valves were located within

secondary containment. All mill facilities have been closed and removed; the site


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has been in post-closure monitoring since August 2004. Newmont Mining

Corporation sold the Mill 4 Facility and Mill 4 Tailings Storage Facility to the

Permittee in late 2005. The Permittee submitted an EDC in December 2009 for

transfer of these facilities from Permit NEV0092100 to Permit NEV0090060;

Permit transfer was completed in May 2010.

Mill 4 Tailings Storage Facility 1 (Mill 4 TSF1) and Seepage Collection Pond

Construction of Mill 4 TSF1 began 13 March 1989, and deposition of tailings began

1 June 1989. Although a pre-regulation facility, the design meets the applicable

requirements of the NAC 445A regulations for tailings storage facilities, including

the 12-inch thick low permeability soil layer (1 x 10-6 cm/sec maximum

permeability). Mill 4 TSF1was constructed over compacted low permeability soils

with draindown water being conveyed through an underdrain blanket to an

underdrain collection pond constructed with primary and secondary 80-mil HDPE

liners. A geonet between the liners provides a flow path to convey leakage to the

leak detection sump. Initially, the Mill 4 TSF1 starter embankment extended to an

elevation of 5,505 feet AMSL and was subsequently raised to 5,530 feet AMSL in

1990, and 5,559 feet AMSL in 1991. Mill 4 TSF1 covers approximately 102 acres

and contains some 12 million tons of material. The facility was used regularly for

tailings disposal until June 1993, after which its use was limited to brief periods

when required for maintenance of the Mill 4 Tailings Storage Facility 2 prior to the

acquisition of Mill 4 by the current Permittee.

The Mill 4 TSF1 embankment was constructed to withstand a 100-year, 24-hour

precipitation event with an initial upstream slope of 2.5H:1V (horizontal to vertical)

and an initial downstream slope of 2H:1V. This is an earth- and rock-fill structure

consisting of two zones, ‘A’ and ‘S’. Zone ‘A’, the retaining structure, was

constructed of random fill (mine waste material rock consisting of clayey silt to

fractured rock), delivered and compacted in 24-inch thick layers by haul trucks.

Zone ‘S’, the seal zone, on the upstream face, is constructed of quality-

assurance/quality-control (QA/QC)-documented, low permeability (1 x 10-6

cm/sec), fine-grained soils (silts and sandy silts) that were borrowed from within

the Mill 4 TSF1 basin area, moisture conditioned, bentonite- or clay-amended as

required, and compacted in nominal 12-inch thick lifts. Density and moisture tests

were performed by nuclear density and sand cone methods. Zone ‘S’ is 20 feet

wide and was extended a minimum 2 feet into low-permeability, over-consolidated

silts along the entire length of the embankment to form a cut-off trench. Zone ‘S’

was ultimately covered with a layer of 10-ounce geotextile to minimize erosion

prior to deposition of a protective layer of tailings material.

The tailings storage basin is covered with 12 inches of QA/QC-documented, low-

permeability (1 x 10-6 cm/sec), fine-grained soils borrowed from within the Mill 4

TSF1 basin area, moisture-conditioned, bentonite- or clay-amended as required,

and compacted to 95% modified Proctor density in nominal 6-inch thick lifts. The

area beneath the supernatant pond received 18 inches of the same low permeability

soil to further enhance containment. The entire prepared Mill 4 TSF1 basin is


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covered with a nominal 12 inches of drainage blanket material containing 3.9-

12.7% minus 200-mesh fines. A network of 8-inch, 6-inch, and 4-inch diameter

corrugated polyethylene tube (CPT) underdrain pipe was installed within v-

trenches cut into the drainage blanket on 30-foot centers. A layer of 6-ounce

geotextile covers the drainage blanket in the supernatant pool area to prevent

migration of fines.

Draindown solution (UCP), currently flowing at less than 0.25 gpm, as of the

second quarter of 2020, reports to the Mill 4 Seepage Collection Pond (UCPRL)

and is pumped to the North Block seepage collection pond (WPCP NEV0091029).

The Mill 4 Seepage Collection Pond has an operating volume of 330,000 gallons

with 3 feet of freeboard and a total volume of 480,000 gallons. The seepage

collection pond base and embankment are constructed in a 2-foot-deep cut area

which was backfilled with waste rock and covered with fine-grained soils. The

base and embankments were moisture conditioned and compacted to a minimum

95% of maximum dry density prior to being covered with a layer of 6-ounce

geotextile. The geotextile was then covered with a 60-mil HDPE secondary liner,

overlain by geonet, which was in turn covered with a primary liner of 60-mil HDPE.

The interstitial geonet is hydraulically linked by a 6-inch diameter poly-vinyl

chloride (PVC) pipe to the external Leak Collection and Recovery System (LCRS)

sump, Underdrain Collection Pond Leak Detection Sump (UCPS), and equipped

with a submersible pump. Any fluid reporting to the sump is pumped back to the

UCPRL.

Groundwater quality in the area of Mill 4 TSF1 was monitored by upgradient wells

MW-8, MW-9D, and MW-9S. Downgradient monitoring wells included MW-1D,

MW-1S, MW-6, MW-7, MW-10, TB-5, and TB-9. As a result of the pit dewatering

program, all wells have been dry since at least June 2005. In March 2011, the

Permittee submitted an EDC for removal and abandonment of eight of the ten

monitoring wells: MW-1S, MW-6, MW-7, MW-9S, MW-9D, MW-10, TB-5, and

TB-9. The Division approved the EDC in May 2011; well abandonment was

completed in November 2011. Also in May 2011, monitor wells MW-8 and MW-

1D were formally transferred to WPCP NEV0091029. No direct monitoring of the

Mill 4 TSF1 groundwater wells will be performed in the AA Block Permit.

Monitoring is addressed in WPCP NEV0091029.

Fluid head pressures in the Mill 4 TSF1, which are to be maintained below an

average of 2 feet of hydraulic head, are measured by a network of vibrating wire

piezometers. Mill 4 TSF1 utilizes two underdrain piezometers (P2 and P5) and two

piezometers within the tailings solids (P3 and P4). All piezometer data indicate

stable head pressures at well below 2 feet.

An FPPC for Mill 4 TSF1 was submitted in December 2012 and approved by the

Division in February 2015. The FPPC consists of converting the existing open

pond into an evaporation cell (e-cell) and constructing an infiltration gallery

northwest of the e-cell to allow for a controlled discharge in the event of an

overflow.


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In preparation for permanent closure of the Mill 4 TSF1 facility, in 2012 the

Permittee began stockpiling Carlin Formation (Carlin) materials from the Tailings

Storage Facility 3 (TSF3, WPCP NEV0091029) excavation on the surface of Mill

4 TSF1 for closure of the facility with a Carlin cap. This area will also be utilized

to temporarily stockpile additional colluvium and Carlin material that will be used

as buffer zone materials for the phased construction of TSF3 over the next few

years. The total area the stockpiles will encompass is approximately 14 acres.

The Permittee submitted plans to expand the existing stockpiles on Mil 4 TSF1 by

5.3 acres and 16.5 acres. The Division approved these expansions in June 2014 and

December 2014, respectively.

In June 2020, the Permittee submitted an EDC for a modification to the closure

spillway. The proposed modification modified the spillway design to ultimately

terminate outside the TSF3 haul road, flowing along the existing ground before

flowing by gravity to its discharge point in the Betze-Post Pit. Although the

Division is typically not receptive to storm event flows purposely being directed to

an open pit, as per NAC 445.429. 2, the alternate option of pumping from the

spillway outlet to access either Bell Creek or Rodeo Creek to route around the pit

has been demonstrated to be a much less desirable option and the Division

determined this alternative is not practical or in the best interest of a long-term

passive closure scenario. Therefore, discharge to the Betze-Post pit was approved

and applies only to the Mill 4 TSF closure spillway. (See correspondence entitled

Mill 4 TSF Closure Storm Water Management Options, dated 28 April 2016).

Based on its location relative to other existing process components and their

specific closure strategies, and the previous approval, the Division approved the

proposed spillway modifications in August 2020.

Mill 4 TSF1 is protected from storm run-on by a diversion berm placed between

the tailings embankment and Brush Creek.

Post Pad #1

Prior to construction of the Bazza WRDF, the Post Pad #1 heap leach facility was

operated by Western States Minerals in the approximate southeast corner of the

current Bazza location. The heap, which encompassed an area of approximately 19

acres, was operated from August 1986 to July 1989. The heap was detoxified using

sodium hypochlorite and hydrogen peroxide as rinse solution until the WAD

cyanide concentration was less than 0.2 mg/L.

Two process ponds were associated with this facility. The ponds were constructed

of 40-mil HDPE liner over a compacted low-permeability soil layer with a 6 inch

sand layer leak detection system. Draindown solution was transported by water

truck to the AA Tails for disposal. By the latter part of 1990, draindown flow had

decreased to almost zero. The ponds were permanently closed in 1991.

The Post Pad #1 was closed by the Permittee in 1991 and covered by construction

of the Bazza WRDF. Newmont acquired the effluent pipe discharge in a land


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exchange with the Permittee in 1999 and assumed responsibility for management

of the Post Pad #1 draindown solution as part of its North Area Leach Permit WPCP

NEV0087065. Following the formation of the Nevada Gold Mines joint venture in

July 2019, the Permittee assumed responsibility for the permanent closure and

management of the draindown solution under WPCP NEV0087065. The Permittee

has constructed and is currently operating an evapotranspiration cell for long-term

solution management.

Bazza Waste Rock Disposal Facility

The Bazza WRDF has a surface area of approximately 2,500 acres and is located

west and southwest of the Betze-Post Pit. The Bazza WRDF received waste rock

from the Betze-Post Pit as well as minor amounts from the underground operations

at the Meikle and Rodeo Creek mines. The Bazza WRDF was designed and

operated to comply with applicable mining and reclamation requirements and to

prevent the degradation of waters of the State.

Beginning in the early 1990s, an in-pit geochemical testing and classification

program was initiated to facilitate selective handling of Potentially Acid-

Generating (PAG) and non-PAG waste rock. The program of waste rock

classification, segregation, and selective placement was designed to reduce the

occurrence of acid rock drainage and to prevent releases of surface runoff, seepage,

or infiltration that may have a potential to degrade waters of the State. The program

was based on data from more than 140 humidity cell tests on a variety of waste rock

types and static tests on over 30,000 composite exploration drill hole samples

within the Betze-Post Pit. Results from testing indicate a correlation between the

acid neutralization potential/acid generating potential (ANP/AGP) ratio, net

carbonate value (NCV), and sulfide sulfur. The results indicate that waste rock

having an ANP/AGP ratio greater than 1.2 will not produce acid, which is therefore

classified as non-PAG. Material with an ANP/AGP ratio less than 1.2 and with a

sulfide sulfur value greater than 0.3% is classified as PAG.

PAG and non-PAG waste rock disposal has been facilitated through computerized

truck dispatching, recording, and verification systems. Monitoring components

associated with waste rock management have included ongoing acid-base

accounting on waste rock samples collected from the mining operations and annual

composite samples of PAG and non-PAG material. Meteoric Water Mobility

Procedure (MWMP)-Profile I analyses have been performed annually on the

composite samples as well to further characterize the waste rock.

A conceptual closure design of the Bazza facility was included in the 2004 Waste

Rock Management Plan (WRMP) update. The Bazza WRDF FPPC, submitted in

March 2007, incorporates an ET cover into the design. Specifically, the 2007 FPPC

update included the following elements:

- Use of a layered cover comprised of topsoil and Carlin Formation

(Fm) materials designed to minimize or eliminate infiltration of

water and oxygen;


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- A multi-layer cover consisting of 6 feet of Carlin Fm and topsoil

material to be placed over the approximately 498 acres of

encapsulated PAG cells;

- A minimum of 12 inches of cover consisting of either run-of-mine

Carlin Fm material or a combination of topsoil and Carlin Fm

material over the non-PAG remainder of the waste rock facility.

Results of modeling of the soil cover, based on the modeling code VADOSE/W

calibrated to the AA Block HLF cover, indicated that the proposed Bazza WRDF

soil cover would provide an effective barrier to movement of meteoric water into

PAG waste rock. Additionally, monitoring of the AA Block HLF cover over the

last approximately 12 years indicates that the cover is functioning as designed and

evaluation of available geologic materials indicates that this design approach can

be applied to the Bazza WRDF.

The Bazza WRDF reached the end of its operational life in 2009 and has since been

closed. Waste rock disposal has shifted to the Clydesdale Waste Rock Facility (a

component of WPCP NEV0091029).

Portions of the Bazza WRDF have been utilized for other mining related activities,

i.e., the bioremediation cell, several ore stockpiles, and replacement transformer

storage. Closure requirements for the bioremediation cell are addressed in WPCP

NEV0091029. Per a 2 October 2019 mutually-agreed upon decision, although the

Bazza WRDF is a closed facility under WPCP NEV0090060, the ore stockpiles are

not closed and are managed under WPCP NEV0091029. Current plans for use of

the Bazza surface consist of a temporary storage area for new transformers and the

existing Class III waivered landfill, which shall remain in-place until final

Goldstrike Mine closure (currently estimated to be 2050).

Tanks and Bins

All tanks and bins that contain fuel, chemicals, or process solutions are managed

under WPCP NEV0091029.

Figure 1 below provides a site map indicating all monitoring locations specific to

the AA Block Project. Monitoring location identifiers are presented in capital

letters. Specific process components are also identified. The North Block Tailings

Impoundment and Tailings Storage Facility 3 are monitored in WPCP

NEV0091029; North Area Leach Pad is monitored in WPCP NEV0087065 and are

included for relative location only.


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Figure 1. – Permit monitoring locations, highlighted in all capital letters, specific to the

AA Block Project.


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C. Receiving Water Characteristics

The Permittee’s mining and processing operations are located on the southwest

flank of the Tuscarora Mountains in north-central Nevada. The facilities lie in the

Little Boulder Basin, which is a topographic feature that contains the Brush, Rodeo,

and Bell Creek drainages. In the Goldstrike area, which includes the AA Block

Project, elevations range from about 5,100 feet to 5,926 feet AMSL. The terrain in

the vicinity of the Project is typical of the Basin and Range physiographic province,

and is dominated by north-trending fault-block mountain ranges that expose

sedimentary rocks.

Surface Hydrology

A detailed description of the regional surface hydrology can be found in the

Assessment of Area of Review for the AA Block. A detailed description of the

site-specific surface hydrology can also be found in referenced documents listed in

the WPCP application.

In general, surface runoff from the AA Block Project area flows west and southwest

via Brush and Rodeo creeks. The Rodeo Creek diversion, which diverts Rodeo

Creek around the Betze-Post Pit and associated facilities, flows northeasterly

through the Project before bending west and southwest through the North Block

Project (WPCP NEV0091029). The water quality of these creeks has been

established via Permit requirements. In general, Brush Creek background water

quality constituent concentrations meet Profile I reference values. Rodeo Creek

typically shows higher arsenic, iron, and manganese background concentrations.

Surface flow in these drainages infiltrates into the alluvium beneath and adjacent

to the creeks. The Division has not designated beneficial uses or established

numerical surface water quality standards for Brush Creek or Rodeo Creek.

Hydrogeology

Shallow alluvial deposits are found primarily adjacent to drainages within the

Project area. Subsurface drainage within these deposits generally appears to follow

the course of these drainages to Rodeo Creek or into the underlying or adjacent

Carlin Formation. The alluvial deposits generally consist of interbedded clay, silt,

sand, and gravel deposited by channel and overbank flows of the creek. The

permeability of the alluvium ranges from 1 x 10-4 cm/sec to 8 x 10-2 cm/sec.

The Carlin Formation, which is found east and north of Rodeo Creek, underlies the

Little Boulder Basin regionally and extends under the AA Tails, Mill 4 TSF1, and

the AA Block HLF. This formation has a regional thickness of 600 feet and consists

of materials that generally exhibit low permeability. In the AA Block Project area,

the Carlin Formation permeability ranges from 5.2 x 10-6 cm/sec to 8.3 x 10-5

cm/sec. The variable nature of the formation results in lenses of more permeable

material along the bedding planes within the formation. Very little vertical flow

occurs and the Carlin Formation acts as an aquitard, producing locally confined

conditions within the underlying Vinini Formation. Most of the recharge of the

Carlin Formation is derived from direct infiltration of precipitation and snow melt


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from the Tuscarora Mountains. This source of local recharge is directly responsible

for variations in groundwater quality in the Carlin Formation as opposed to

underlying metasediments.

The original groundwater gradient beneath this area was northeast to southwest,

with a pre-mining groundwater elevation of approximately 5,320 feet AMSL.

However, dewatering operations have reduced local groundwater elevations to

approximately 3,596 feet AMSL below mining operations and have resulted in a

localized zone of groundwater depression that is observed west-southwest of the

AA Block facilities. Continued dewatering activities in the Project area are

expected to maintain the water table at depth (approximately 2,500 to 3,500 feet

below ground surface) in the AA Block area.

GWOP-9, GWOP-12, and GWOP-20 are located on the eastern side of the property

upgradient of the AA HLP and are most representative of background groundwater

quality. Background water quality in the Carlin Formation is generally good,

meeting all Division Profile I reference values, with an occasional exceedance of

arsenic.

However, beginning in the fourth quarter of 2004, GWOP-12 has indicated

exceedances of chloride and TDS. In March 2015, following ongoing discussions

with the Division, the Permittee conducted an investigation of the area surrounding

GWOP-12 as well as developing historical concentration plots of the correlation

between chloride and magnesium. The historical plots identified that a strong

correlation exists between the chloride and magnesium trends over the span of the

entire dataset. The model output indicated an R2 value of 0.98.

Given the strong statistical correlation between chloride and magnesium and the

proximity of an upgradient stormwater feature to GWOP-12, the Permittee believes

that magnesium chloride used as a dust suppressant on nearby roads is the source

of elevated chloride and TDS in GWOP-12. Since no other constituents are present

in concentrations above background conditions at this location, as compared to

GWOP-9 and GWOP-20, the Permittee believes the well is still functioning

adequately to provide background groundwater data relevant to the AA HLP and

will continue to monitor this well quarterly. In late 2015, the Permittee modified

the stormwater diversion controls to divert stormwater away from this location.

Additionally, to eliminate the contaminant source, the Permittee switched from the

use of magnesium chloride to lignin sulfonate for dust suppression and, with the

construction of TSF3, the access road that parallels the GWOP-12 location is no

longer used as a main access road. Although sporadic, both the chloride and TDS

trends appear to be decreasing.

Well Locations in the Project Area

Numerous groundwater monitoring wells and piezometers exist within the Project

area. The locations of the wells within the AA Block area can be found in the

WPCP application. These wells are monitored, sampled, and results are submitted

as required by the Permit.


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Well EW-14 provides potable water to the AA Block facilities.

D. Procedures for Public Comment

The Notice of the Division’s intent to issue a Permit authorizing the facility to

construct, operate and close, subject to the conditions within the Permit, is being

published on the Division website: https://ndep.nv.gov/posts/category/land. The

Notice is being mailed to interested persons on the Bureau of Mining Regulation

and Reclamation mailing list. Anyone wishing to comment on the proposed Permit

can do so in writing within a period of 30 days following the date the public notice

is posted to the Division website. The comment period can be extended at the

discretion of the Administrator. All written comments received during the

comment period will be retained and considered in the final determination.

A public hearing on the proposed determination can be requested by the applicant,

any affected State, any affected intrastate agency, or any interested agency, person

or group of persons. The request must be filed within the comment period and must

indicate the interest of the person filing the request and the reasons why a hearing

is warranted.

Any public hearing determined by the Administrator to be held must be conducted

in the geographical area of the proposed discharge or any other area the

Administrator determines to be appropriate. All public hearings must be conducted

in accordance with NAC 445A.403 through NAC 445A.406.

E. Proposed Determination

The Division has made the tentative determination to issue the renewed Permit.

E. Pathway to Final Closure and Permit Termination

See Section I of the Permit.

In accordance with NAC 445A.409 and 445A.446, for final closure and Permit

termination the Permittee must demonstrate to the Division that: 1) all sources at

the facility have been stabilized, removed, or mitigated; 2) any applicable

requirements in NAC 445A.429, 445A.430, and 445A.431 have been achieved; and

3) sufficient post-closure monitoring has occurred to verify the adequacy of these

actions to ensure the long-term protection of waters of the State, human health, and

wildlife under the physical, chemical, and climatic conditions reasonably expected

to occur at the site. If the facility includes a long-term trust and/or requires

perpetual treatment or maintenance, post-closure monitoring may never be reached

and the Division may not be able to terminate the Permit.

The pathway to final closure and Permit termination at this facility includes the

following specific actions:

• Submit a Tentative Plan for Permanent Closure (TPPC) for conversion of the

AA Barren Pond to an E-Cell;

• Complete approved permanent closure actions on the AA HLF and E-Cell, AA

TSF, and Mill4 TSF1;


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• Submit a final closure report for the AA HLF and E-Cell, AA TSF, and Mill4

TSF1, ;

• Complete remedial activities at LPOP-10 and GWOP-22 locations in

accordance with the approved CAP;

• Monitor the facility through major storms and large winter/spring seasons to

verify that closed components and the fluid management system remain

functional with no potential for degradation of waters of the State;

• Discuss with the Division whether the facility is ready for final closure and

Permit termination. If so, submit for review and approval a request for final

closure and Permit termination including a demonstration of compliance with

all applicable closure requirements (e.g., NAC 445A.379, 445A.409,

445A.424, 445A.429, 445A.430, 445A.431, 445A.446, 445A.447).

The Division may require additional actions if warranted in accordance with site

conditions and applicable statutes, regulations, orders, and Permit conditions.

G. Rationale for Permit Requirements

Ongoing closure-related investigations and remediation activities continue and the

results of these investigations/remediation activities may induce changes to existing

component closure plans and WPCP rationale/requirements.

Seepage occurring at the AA Block HLF will continue to be actively pumped and

monitored. These activities will occur until it can be demonstrated that water

quality is stable, meets Profile I reference values and will not degrade waters of the

State.

With the expedited closure of the AA Tailings Facility, i.e., elimination of process

water from the tails surface, water quality monitored at GWOP-10A and GWOP-

15A is expected to improve; monitoring of the wells will continue until it can be

demonstrated that water quality is stable, meets Profile I reference values and will

not degrade waters of the State. Based on the results of this monitoring, additional

mitigation actions may be required.

The facility is located in an area where annual evaporation is greater than annual

precipitation. Therefore, it must operate under a standard of performance which

authorizes no discharge(s) except for those accumulations resulting from a storm

event beyond that required by design for containment.

The primary methods used for identification of escaping process solution will be

required routine monitoring of leak detection systems, as well as routine sampling

of downgradient monitoring wells. Specific monitoring requirements can be found

in Part I.D of the Permit.

Facilities will be monitored and operated in accordance with the Permit conditions

and the operating plans.


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H. Federal Migratory Bird Treaty Act

Under the Federal Migratory Bird Treaty Act, 16 U.S. Code 701-718, it is unlawful

to kill migratory birds without license or permit, and no permits are issued to take

migratory birds using toxic ponds. The Federal list of migratory birds (50 Code of

Federal Regulations 10, 15 April 1985) includes nearly every bird species found in

the State of Nevada. The U.S. Fish and Wildlife Service is authorized to enforce

the prevention of migratory bird mortalities at ponds and tailings impoundments.

Compliance with State permits may not be adequate to ensure protection of

migratory birds for compliance with provisions of Federal statutes to protect

wildlife.

Open waters attract migratory waterfowl and other avian species. High mortality

rates of birds have resulted from contact with toxic ponds at operations utilizing

toxic substances. The Service is aware of two approaches that are available to

prevent migratory bird mortality: 1) physical isolation of toxic water bodies through

barriers (e.g., by covering with netting), and 2) chemical detoxification. These

approaches may be facilitated by minimizing the extent of the toxic water. Methods

which attempt to make uncovered ponds unattractive to wildlife are not always

effective. Contact the U.S. Fish and Wildlife Service at 1340 Financial Boulevard,

Suite 234, Reno, Nevada 89502-7147, (775) 861-6300, for additional information.

Prepared by: Karl W. McCrea

Date: 05 October 2020

Revision 00: Renewal; Permit effective date 28 October 2020.

fact sheet nevada gold mines llc aa block project …

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