2. ALTERNATIVES INCLUDING THE PROPOSED ACTION
2.1. Proposed Action
This section has been modified from the November 1996 Draft EIR to reflect
changes made in the Proposed Action, including the proposed Reclamation
Plan, by Glamis Imperial, some of which were made in response to public
comments on the November 1996 Draft EIR. The principal revisions to the
Proposed Action since the November 1996 Draft EIR are listed in Table 1.3.
2.1.1. Introduction
The Proposed Action consists of two (2) general components: the
Imperial Project, a proposed open-pit, heap-leach, precious metal mine;
and the "overbuilding" of a sixteen (16)-mile section of
an existing 34.5 kV utility electrical transmission line with 92 kV
conductors to deliver the necessary electrical power to the Imperial Project.
The Imperial Project (Project) would include: mining gold and silver ore
and waste rock at a typical daily mining rate of 130,000 tons per day
(which would range from zero (0) to 200,000 tons per day); constructing
and operating facilities to administer the operation and maintain all mining
and related equipment; processing the ore utilizing conventional heap leach
methods; stockpiling the waste rock; developing and producing ground water
for use in processing operations and dust control; conducting geological
survey activities within the Project mine and process area; implementing
environmental impact reduction measures; and implementing reclamation measures,
all of which have been designed to meet the anticipated permit requirements
of the various federal, state and local agencies which regulate mining in
the area.
As discussed throughout this document, the "Project area," in
which all of the specific components of the Project would be located, consists
of a "Project mine and process area" and a "Project ancillary
area." Figure 2.1 shows the boundaries of the Project mine
and process area and the Project ancillary area.
Specific Project components located within the Project mine and process
area, and shown in Figure 2.2, include:
- Three (3) open pits, identified as the West Pit, East Pit and
Singer Pit, and the Associated Areas of Disturbance adjacent to some of
the pits;
- Two (2) waste rock stockpiles, identified as the East Waste Rock Stockpile
and the South Waste Rock Stockpile;
- Two (2) soil stockpiles, identified as the West Soil Stockpile
and the East Soil Stockpile;
- Five (5) stream drainage diversion channels, identified as the West
Pit West Diversion, the West Pit East Diversion, the Singer Pit East Diversion,
the East Pit West Diversion, and the East Pit East Diversion;
- One (1) administration office and equipment maintenance (shop)
facility area;
- Ore processing facilities, including a lime bin, heap leach pad, and
process solution (barren and pregnant) ponds;
- One (1) precious metal recovery plant;
- One (1) electrical power substation; and
- A system of roads (and associated electrical distribution lines);
Specific Project components located within the Project ancillary area include:
- One (1) ground water well field, consisting of up to four (4)
production wells, designed to produce ground water at a combined peak yield
of approximately 1,200 acre feet per year (afy)
- A buried water pipeline to convey the water from the ground water well
field to the Project mine and process area;
- An approximately 3.7-mile section of new 92 kV/13.2 kV transmission
line; and
- Relocated portions of Indian Pass Road, including the permanent realignment
of the intersection of Indian Pass Road and Ogilby Road and the temporary
relocation of an approximately 6,000-foot portion of Indian Pass Road,
which would be moved approximately 1,000 feet to the west of its current
location to provide continuous, safe public access to areas northeast of
the Project mine and process area during the completion of Project activities.
Up to 150 million tons of ore would be mined and leached as part of
the Project, and up to 300 million tons of waste rock would be mined
and deposited in the waste rock stockpiles or the mined-out portions of
the West Pit and Singer Pit. Mining activities, performed 24 hours
per day and seven (7) days per week, would commence in 1998. Operations
would terminate around the year 2017, although completion of all reclamation
activities would continue beyond this date if necessary.
In addition to the Project components described above, the Proposed Action
includes the "overbuilding" of a sixteen (16)-mile section
of existing 34.5 kV utility electrical transmission line with 92 kV
conductors to deliver the necessary electrical power to the Imperial Project.
All activities associated with the "overbuilding" of this transmission
line would occur within the "overbuilt 92 kV/34.5 kV transmission
line corridor," located outside of the Project area, as shown in Figure 1.2.
"Overbuilding" the existing 34.5 kV utility transmission
line would include: blading the existing access road, as necessary; establishing
an equipment lay down area; delivery of new, taller pole(s) to the site
of each existing pole; adding insulators and cross arms, as necessary, to
each of the new poles; leaning the existing wooden poles out of the current
transmission line alignment; setting the new, taller, wooden poles in the
same transmission line alignment; stringing new 92 kV wire conductors
near the top of the new poles and new 34.5 kV wire conductors below
the 92 kV conductors on the new poles; energizing the new conductors;
and removing the existing 34.5 kV conductors, poles and any other waste
materials.
The Proposed Action would create a maximum of approximately 1,340 acres
of new surface disturbance within the Project area, and approximately 22 acres
of additional disturbance within the overbuilt 92 kV/34.5 kV transmission
line corridor during the "overbuilding" of the 92 kV/34.5 kV
transmission line, for a total of approximately 1,362 acres of surface
disturbance within the "area
of the Proposed Action." An itemized list of the estimated surface
disturbance for each of the major Project facilities and overbuilt 92 kV/34.5 kV
transmission line, together with the undisturbed and reclaimed acreage within
the Project mine and process area, is presented in Table 2.1.
2.1.2. Construction
Construction of Project facilities would commence once necessary approvals
were obtained from the appropriate regulatory agencies. The initial construction
phase of the Project would take up to six (6) months. Additional construction
activities would also occur during the mine life, particularly during the
completion of the later phases of the heap leach pad construction (see Section 2.1.8.1).
Equipment necessary for construction activities would include a portable
screen plant and crusher, scrapers, dozers, rollers, graders, portable generators,
and other related equipment. As discussed in Section 2.1.9.1,
employment of up to approximately 225 workers would be necessary to
complete initial construction activities within the Project area. Construction
activities which would occur during the routine mining operations would
require up to 40 workers. Construction activities related to the overbuilding
of the 92 kV/34.5 kV transmission line, which are discussed in
Section 2.1.9.3.1, would require up to 30 workers.
Table 2.1
| COMPONENT |
DISTURBED ACRES |
RECLAIMED ACRES |
UNDISTURBED ACRES |
| ON-SITE |
OFF-SITEa |
| PROJECT AREA |
| Project Mine and Process Area |
| Mining Area |
1 |
West Pit |
110 |
110 |
|
|
| 2 |
East Pit |
198 |
0 |
165 |
|
| 3 |
Singer Pit |
33 |
33 |
|
|
| 4 |
Associated Areas of Disturbance |
38 |
38 |
|
|
| Pad Facilities |
5 |
Leach Pad |
334 |
334 |
|
|
| 6 |
Process Area |
24 |
24 |
|
|
| 7 |
Lime Bin Area and Fresh Water Pond |
9 |
9 |
|
|
| Waste Rock Stockpiles |
8 |
East Waste Rock Stockpile |
135 |
135 |
|
|
| 9 |
South Waste Rock Stockpile |
232 |
232 |
|
|
| Soil Stockpiles |
10 |
West Soil Stockpile |
20 |
20 |
|
|
| 11 |
East Soil Stockpile |
10 |
10 |
|
|
| Support Facilities |
12 |
Office/Maintenance/Parking/ Power Facilities |
21 |
21 |
|
|
| 13 |
Haul and Ancillary Roads |
94 |
94 |
|
|
| 14 |
Drainage Diversions |
44 |
44 |
|
|
Project Mine and Process Area Subtotal: |
1,302 |
1,104 |
165 |
269 |
Project Mine and Process Area Total: |
1,302 |
1,269 |
269 |
TOTAL PROJECT MINE AND PROCESS AREA ACREAGE: |
1,571 |
| Ancillary Area |
| Ancillary |
15 |
County Road Realignment |
7 |
7 |
|
|
| 16 |
Powerline/Water Pipeline |
27 |
27 |
|
|
| 17 |
Water Wells and Access Roads |
4 |
4 |
|
|
Project Ancillary Area Subtotal: |
38 |
38 |
0 |
Not Applicable |
Project Ancillary Area Total: |
38 |
38 |
Not Applicable |
TOTAL PROJECT ANCILLARY AREA ACREAGE: |
38 |
PROJECT AREA ACREAGE SUBTOTAL: |
1,340 |
1,142 |
165 |
269 |
PROJECT AREA ACREAGE TOTAL: |
1,340 |
1,307 |
269 |
TOTAL PROJECT AREA ACREAGE: |
1,609 |
| a As compensation for the 165 acres of East Pit slopes which
would not be reclaimed, Glamis Imperial has offered to reclaim under an
MOA developed with the BLM up to 165 acres
of lands located off-site which were previously disturbed by others. |
| OVERBUILT 92 kV/34.5 kV TRANSMISSION LINE CORRIDOR |
Overbuilt 92 kV/34.5 kV Transmission Line |
22 |
22 |
0 |
Not Applicable |
TOTAL OVERBUILT TRANSMISSION LINE CORRIDOR ACREAGE: |
22 |
| |
| AREA OF THE PROPOSED ACTION SUMMARY |
Proposed Action Subtotal: |
1,362 |
1,164 |
165 |
269 |
Proposed Action Total: |
1,362 |
1,329 |
269 |
TOTAL PROPOSED ACTION ACREAGE: |
1,631 |
2.1.3. Mining
"Ore" is an economic term used to describe a resource which
can be profitably mined and processed. The size and configuration of the
proposed pits is defined by the precious metals content, depth of mineralization,
metallurgy and other geologic, geotechnical and economic factors. Based
on the results of exploration and development drilling, three (3) ore
zones have been delineated. These would be mined as the West Pit, Singer
Pit, and East Pit (see Figure 2.2). The estimated pit dimensions
resulting from development of the currently known ore zones are listed in
Table 2.2.
Table 2.2
| PIT |
PROJECTED PIT DIMENSIONS |
PIT FLOOR ELEVATION (ft Above Mean Sea Level) |
| LENGTH (ft) |
WIDTH (ft) |
DEPTH (ft) |
| West Pit |
2,700 |
2,700 |
760 |
-60 |
| East Pit |
4,700 |
2,700 |
880 |
-60 |
| Singer Pit |
1,000 |
2,000 |
400 |
460 |
In the waste rock stockpile and leach pad areas, exploratory "condemnation"
drilling was conducted on approximately 2,000-foot centers to identify possible
open pit-type reserves. Drilling results from the waste rock stockpile and
heap areas indicated that no continuity between assays or holes were identified
which would indicate the presence of a minable resource at those areas.
Mining of the ore zones would employ conventional open pit mining techniques.
The mining sequence would be phased, with the West Pit mined first, followed
by the Singer Pit, and then mining of the East Pit. Figure 2.3
shows the projected final configuration of the West Pit following the completion
of mining of that pit.
Mined waste rock would be placed on the waste rock stockpiles, located adjacent
to the pits, or, as mining proceeds from one pit to the next, into the previously
mined-out open pits. As mining progresses, the West Pit and Singer Pit would
be backfilled. Figure 2.4 shows the projected final configuration
of the East Pit and the backfilled and reclaimed West Pit and Singer Pit
following final reclamation. Figure 2.5 shows the same final
configuration and final contours in relation to the topography in the vicinity
of the Project mine and process area.
The overburden thickness above the ore zones ranges from 40 to 350 feet
and consists mostly of alluvial gravels (both unconsolidated and cemented)
and minor amounts of volcanic rock. Mining of the unconsolidated gravels
may not require blasting; however, the cemented gravels are expected to
require blasting prior to excavation. Ore and some waste rock are comprised
of weakly-altered gneiss. All of this material is expected to require drilling
and blasting prior to excavation.
For blasting, mobile rotary blast hole drills would drill 6-3/4-inch
to 12-inch diameter blast holes spaced on between 16- and 35-foot centers.
The rock would be blasted with a conventional ammonium nitrate/fuel oil
(ANFO) blasting agent, although an emulsion
blasting agent may be used in the event water is found in the drill holes.
Blasting would occur only during daylight hours. The blasted rock would
be loaded, using an electric shovel or diesel front-end loader(s)/shovel(s),
into 320-ton capacity haul trucks. No crushing of the ore is proposed, and
run-of-mine (ROM) ore would be hauled by the haul trucks directly to the
heap leach pad. Waste rock would also be hauled directly to a waste rock
stockpile, or hauled to one of the pits to be backfilled (see Section 2.1.5).
Haulage ramps in the pits have been designed with a minimum width of 120 feet
and a maximum gradient of 10 percent. Minor sections of temporary ramping
may be steeper and narrower. Haulage roads outside of the pit areas would
be 120 feet wide, and in some areas would be 150 feet wide to
allow for surface drainage areas and separate lanes for support vehicle
traffic.
Haul roads adjacent to the pits may need to be relocated as the mining of
the pits proceeds to ensure proper gradients and adequate separation for
safety. Also, additional geological surveys, including drilling, are likely
to occur in the areas located between the pits (see Section 2.1.10).
To conservatively estimate the surface disturbance which may result from
these activities, those areas located between the pits not otherwise disturbed
by specific Project components have been designated as "associated
areas of disturbance" (see Figure 2.2), and the associated
acreage included in the estimated areas of disturbance in Table 2.1.
Engineering analyses indicate that the ultimate pit walls would have overall
slope angles varying from 40 to 50 degrees (1 horizontal to 0.8 vertical
[1H:0.8V] to 1H:1.2V), depending on location of the slope in each of the
pits. Pit walls would have safety benches constructed at regular vertical
intervals to contain minor rock spills. An additional stability study would
be conducted for each of the deeper pits (West Pit and East Pit) after one (1)
year of mining to ensure stability and confirm the accuracy of the original
study. Following those studies, pit wall slopes may be changed slightly
as actual mining conditions and geotechnical and safety factors warrant,
although any changes would not disturb any lands not otherwise already proposed
for disturbance under the Proposed Action.
Piezometer and exploration drill holes drilled in the projected locations
of the bottoms of the East Pit and the West Pit have encountered ground
water at depths of 88 feet above mean sea level (AMSL)
and 211 feet AMSL, respectively, which
is above the anticipated floor of the respective pits. As such, it is possible
that ground water would enter either or both of these pits during mining
operations. However, tests conducted to date have indicated that the hydraulic
conductivity of the bedrock formation is very low, and total ground water
inflow has been estimated at only 1.5 gpm for the West Pit and 0.7 gpm
for the East Pit. Should ground water be encountered in the pits during
mining operations, it would be utilized in dust control operations, or collected
and used in process operations. No ground water is anticipated to be encountered
in the Singer Pit.
Since the West Pit and the Singer Pit would be backfilled with waste rock
mined from the East Pit, this would prevent the formation of a pit lake
in either of these pits. Calculations conducted for the East Pit indicate
that the estimated annual evaporation rate is approximately 170 times
the annual estimated ground water and precipitation inflow rates, indicating
that the formation of a pit lake in the bottom of the East Pit after the
cessation of mining activities is not probable. However, Glamis Imperial
would conduct an assessment at the end of mining to determine if ground
water encountered in the East Pit may enter the pit in sufficient quantities
to create a pit lake in spite of evaporation. If this assessment indicates
that the formation of a pit lake is likely, Glamis Imperial would then place
sufficient backfill into the open East Pit
to raise the floor of the pit to a level higher than the level of any pit
lake which may be eventually predicted to form from the inflow of ground
water.
2.1.4. Geochemical Characteristics of Mined Materials
Some types of waste rock, leached ore, or fresh ore can acidify contacting
water when exposed to the atmosphere and ground or rain water. This ability
is characterized as a rock's "acid potential." Generally, rock
with a high acid potential contains disseminated sulfide minerals which
can react with water and atmospheric oxygen to produce sulfuric acid. The
generated acid may then leach potentially toxic metals and other constituents
from the waste materials. Other waste rock, leached ore, or fresh ore may
be acid-neutralizing under the same conditions. This is a rock's "neutralization
potential." Waste rock materials with low acid potential and high neutralizing
potential are generally environmentally benign.
Geochemical characterization analyses were conducted on waste rock and leached
ore samples from the Project mine and process area to determine whether
the ore and waste rock materials would have the potential to be acid generating,
to determine the chemical characteristics of the potential leachate generated
from these materials under various conditions, and to assess the potential
interactions which may occur between the waste rock which may be backfilled
into the pits and ground water (EMA 1995, see Appendix C-1; EMA 1996b;
see Appendix C-2). The sampling and analyses procedures used to characterize
the waste generated from the Project, as described in the following sections,
were based on procedures generally accepted by the California Regional Water
Quality Control Board, Colorado River Basin Region (CRWQCB
) for characterizing mine waste material.
2.1.4.1. Static Test Analyses
As part of the Acid Neutralization Potential (ANP)
analysis, the total sulfur content of each sample was determined to evaluate
its acid potential (AP). The neutralization potential
(NP) of each sample was also determined by titrometric methods. The ratio
of NP:AP is the sample's acid neutralization potential
(ANP). Based on these analyses, the potential
for the Project waste rock and spent ore material to be acid generating
was found to be low to very low. These findings are consistent with observations
made by Glamis Imperial geologists that the ore and waste rocks are devoid
of sulfide minerals.
2.1.4.2. Geochemical Characteristics
Metal analyses, using total metal and acidic rain water extraction methodologies
(the latter using the U.S. Environmental Protection Agency (USEPA) Synthetic
Precipitation Leaching Procedure (SPLP) (Method 1312)), were conducted
on samples of waste rock and ore material. The SPLP is designed to simulate
the concentrations of metals and other compounds which could be leached
from waste materials exposed to acidic rainfall. Ore samples were first
subjected to leaching by dilute cyanide solution to remove precious metals,
then neutralized, to be representative of the leached ore material which
would remain on the heaps following completion of Project activities.
None of the total extracted metal concentrations from the samples exceeded
the State of California Total Threshold Concentration Limits (TTLCs) for
characteristically toxic hazardous waste for any constituents tested, and
most metal concentrations were an order of magnitude or more below the respective
TTLC values. Metal concentrations detected in the solution extracted from
samples using the SPLP method were all consistently very low (EMA 1995,
see Appendix C-1; EMA 1996b; see Appendix C-2).
2.1.5. Waste Rock Stockpiles
Two (2) waste rock stockpiles are proposed: one (1) located south
of the West Pit (the South Waste Rock Stockpile); and one (1) located
north of the East Pit (the East Waste Rock Stockpile). The waste rock stockpile
locations were selected to minimize disturbed acreage, stockpile height,
and haulage distance. Up to 300 million tons of waste rock would be
mined and placed onto the waste rock stockpiles or placed into the previously
mined West Pit and Singer Pit. As described in Section 2.1.3,
most of the waste rock consists of cemented and uncemented alluvial gravels,
although some bedrock (Jurassic Age gneiss and minor amounts of Tertiary
Age volcanic rock) would also comprise waste rock. No segregation of waste
material is planned for the waste rock stockpiles.
The South Waste Rock Stockpile would be constructed first, followed by construction
of the East Waste Rock Stockpile. These waste rock stockpiles would be constructed
in successive 50-foot to 100-foot lifts, to a maximum height of 300 feet,
and would be ultimately reclaimed to have overall 2 horizontal to 1 vertical
(2H:1V), or 30 degree, final slopes. The waste rock stockpiles would
be developed by end-dumping from the haul trucks, with the active face of
each lift lying at the angle of repose of the waste rock (typically 1.5H:1V,
or about 42 degrees).
As mining proceeds from the West Pit to the Singer Pit, and from the Singer
Pit to the East Pit, waste rock would be placed into the previously mined-out
West Pit and, ultimately, the Singer Pit.
2.1.6. Soil Stockpiles
Soil would be salvaged from the surface of disturbed wash areas within
the Project mine and process area for use during reclamation (see Section 2.1.11.3.1)
and would be stockpiled at one of two (2) proposed sites: the East
Soil Stockpile, located to the east of the leach pad; and the West Soil
Stockpile, located to the southwest of the West Pit (see Figure 2.2).
The soil stockpiles would be clearly identified with signs to assure that
the material was not misidentified as waste rock material. Both soil stockpiles
would be located well away from surface water channels, and standard erosion
control methods would be used to route any storm flows away from the stockpiles
to natural drainages to minimize erosion (see Section 2.1.9.7).
2.1.7. Temporary Storage Areas and Construction
Sites
The top surfaces of waste rock stockpiles and other areas approved for
disturbance would be temporarily utilized for equipment storage, assembly
and erection; and for the stockpiling of construction materials and aggregates
produced on-site. The stockpiled construction materials and aggregates would
be hauled from the temporary storage areas to mobile crushing and screening
systems which would be brought to the Project mine and process area as necessary
over the life of the Project to construct the sequential phases of the leach
pad facility (see Section 2.1.8).
2.1.8. Ore Processing Facilities
Ore would be processed using conventional heap leach methods. This methodology
is currently utilized by Chemgold, Inc., Glamis Imperial's sister company,
at its Picacho Mine, located eight (8) miles east of the Project mine
and process area; by other companies at the two (2) other mines located
in the vicinity of the Project mine and process area; and at numerous other
mines throughout the western United States. The process involves stacking
the ore on an engineered, synthetically-lined, impervious pad. The surface
of the ore heap is then wetted with an alkaline solution containing low
concentrations of cyanide. This solution percolates through the ore, producing
a soluble, precious metal-cyanide complex, known as the "pregnant"
solution. The pregnant solution drains through the heap to the pad liner,
then flows within a pipe drainage system to the pregnant solution storage
pond. The gold/silver-bearing pregnant solution is then pumped from the
pregnant pond to the processing facility, where the precious metals are
extracted from the solution by way of a carbon adsorption process. The resultant
"barren" solution, from which the gold/silver has been removed,
then flows to the barren solution
storage pond for the addition of makeup water, sodium hydroxide, and sodium
cyanide, as necessary, before being pumped back to the heap to begin the
cycle again.
The carbon from the adsorption process is stripped of its gold/silver by
a stripping solution, from which the gold/silver is then electroplated onto
steel wool or stainless steel cathodes. The gold/silver-bearing cathode
material is shipped off-site for final refinement.
Development of the proposed ore processing facilities would include the
construction of a 334-acre heap leach pad, a lime bin area, and a fresh
water pond (the latter two (2) together comprising a total of approximately
nine (9) additional acres). Associated processing buildings, process
solution ponds, and a storm water retention pond would comprise approximately
an additional 24 acres (see Figure 2.2 and Table 2.1). The heap leach pad, as well as the
collection channels and process ponds, would be designed as lined, zero-discharge
facilities with leak detection systems, in conformance with California Code
of Regulations (CCR), Title 27, Division 2, Subdivision 1
regulations (formerly Title 23, Division 3, Chapter 15) and
the CRWQCB Waste Discharge Requirements (WDRs ) which would be prepared and adopted for
the Project (see Section 2.1.8.1, Section 2.1.8.2
and Section 2.1.8.3).
2.1.8.1. Heap Leach Facility
The heap leach facility pad would be designed to hold up to 150 million
tons of ore. The run-of-mine ore would be stacked at an approximate rate
of 12 million tons per year. The leach pad liner and associated facilities
would be constructed in three (3) to four (4) phases as space
is required for new ore. A portable crusher and screen plant would be utilized
to develop the aggregates for the liner system, which would come from the
waste rock mined during normal mining activities. The construction materials
would be temporarily stockpiled and then hauled to the liner system for
installation. It is anticipated that liner system construction activities
would occur once every two (2) to four (4) years.
As part of the leach pad construction, the site to be constructed would
be graded to ensure solution drainage from the leach pad to the solution
ponds. In addition, the heap benches and berms would be constructed to provide
for 100 percent containment of the precipitation from the 1-hour probable
maximum precipitation (PMP) design storm event (4.65 inches, which
is the average of the 1-hour PMP from El Centro and Yuma) in order to minimize
runoff from the heap piles and maximize infiltration of storm water into
the heap piles. A service road and containment berm would be constructed
around the perimeter of the pad to assure that process solution and rain
which falls onto the heap drains to the pregnant solution pond. Interceptor
ditches would be constructed to divert upstream surface runoff around the
heap leach facilities. A six (6)-foot high, metal, chain-link fence,
topped with one (1) foot of barbed wire ("process fence")
would surround the entire leach pad and process area.
The heap leach pad liner would be designed to serve as an engineered alternative
to the prescriptive standard for a Group B mining waste, waste pile,
as contained in Title 27, Division 2, Subdivision 1, Article 7
of the CCR (formerly Title 23, Division 3, Chapter 15, Article 7),
and may be approved, or modified, by the CRWQCB
in the WDRs for the Project. The first portion
of the leach pad, consisting of approximately 4.4 million square feet
(designed to accommodate approximately 30 million tons of ore), would
be constructed with a liner consisting of a composite of 40-mil polyvinyl
chloride (PVC) primary and 20-mil PVC secondary geomembrane liners placed
directly on a minimum of four (4) inches of compacted, fine-grained,
bedding material (see Figure 2.6). Similar liners were approved
by the CRWQCB and constructed by others at
the nearby American Girl mine in 1995. Third-party construction quality
assurance/quality control (QA/QC) would be provided to ensure that lining
and bedding materials and containment facilities were constructed in accordance
with design specifications approved by the CRWQCB
. If low permeability clay materials are developed in the West Pit, the
subsequent phases of the leach pad liner may be constructed with a composite
liner of 40-mil PVC geomembrane liner overlying twelve (12) inches
of compacted, low-permeability clay materials with a maximum permeability
of 1 x 10-6 cm/sec. If low permeability clay materials
are not available, these later leach pad liners would be constructed similar
to the liner for the first unit.
An engineered drain pipe network to collect the leach solution and convey
it to the process ponds would be placed on top of the liner system for all
four (4) phases of leach pad construction. Following the placement
of one (1) layer of ten-ounce geofabric and one (1) layer of sixteen-ounce
geofabric above the 40-mil PVC geomembrane liner, a 12-inch layer of minus
3-inch screened/crushed, free-draining gravel would be placed on top of
the liner system to protect the liner, facilitate the collection and removal
of leach solution, and minimize the hydraulic head on the synthetic liner
(see Figure 2.6). The screened gravel would be placed at a thickness
of 24 inches in localized areas to anchor and protect the engineered
drain pipe network.
A containment berm, with a minimum height of six (6) feet, would be
constructed around the perimeter of the ore heap. The ore heap would be
typically set back eighteen (18) feet from the inside crest of the
berm. The leach pad system would be designed such that pregnant solution
would drain internally to the central pipe network and into the pregnant
solution pond. No exposed solution ditches would be present. A containment
berm for the 24-inch solution pipes would be installed along the downhill
toe of the leach pad. Containment berms and other higher-sloped areas would
be constructed with a minimum of 6 inches of compacted, fine grained
bedding material.
The first lift of run-of-mine ore would be loaded onto the heap leach pad
directly over the protective layer of free-draining gravel. The ore would
be loaded onto the pad, without prior crushing, by end-dumping from the
haul trucks. Approximately two (2) pounds of lime per ton of ore would
be placed onto the trucks at the lime bin location prior to dumping. The
ore would be spread and scarified by a bulldozer to produce a heap pile
with relatively uniform thickness and percolation characteristics.
The proposed heap leach facilities would be constructed in progressive lifts
to a maximum height of 300 feet above existing grade. Overall exterior
slopes would not exceed 2H:1V (30 degrees), and would be designed for
operational stability, decommissioning, and final reclamation (see Section 2.1.11.2.5).
Barren solution would be applied to the ore using conventional drip emitter
irrigation technology. Sprinklers would be used to apply water during decommissioning
and rinsing of the heaps, and possibly to apply barren cyanide solution
after major storm events to facilitate evaporation of excess water.
Monitoring of the heap for ponding of the cyanide solution and equipment
malfunction would be conducted at least once per shift, seven (7) days
per week. Any discovered mechanical malfunction in the solution emitters,
pipelines or other equipment would be repaired immediately. Should any ponding
of the cyanide solution on the heap leach pad be found, the area would be
repaired by reducing the number of emitters in the area (thereby reducing
solution flow), or by removal of the emitters, scarification of the heap
surface under the emitters, and reinstallation of the emitters.
2.1.8.2. Barren, Pregnant and Storm Water Ponds
The barren and pregnant process solution ponds and storm water overflow
pond would be constructed immediately down-slope of the leach pad. Leach
solution and rain which falls on the heap would drain by gravity through
the heap to the liner, then drain directly to the process ponds. The combined
process and overflow ponds have been designed to hold the working volume
of solution, and the rainfall run-off from the heap resulting from a maximum
probable one (1)-hour storm event occurring simultaneously with a 24-hour
power outage, while maintaining a two-foot freeboard. The working capacity
of the pregnant and barren solution
ponds, approximately 10.7 million gallons each, would together be sufficient
to store the storm water runoff (including a two (2)-foot freeboard) for
the first phase of the leach pad without construction of the overflow
pond. The approximately 22.4 million gallon storm water overflow pond
would be constructed during the construction of the second phase of the
leach pad, and would provide sufficient additional storm water capacity
(including a two (2)-foot freeboard) for both the second and third phases
of the heap leach pad. If the fourth phase of the heap leach pad is constructed,
the storm water pond would be expanded to meet the storm water runoff requirements
for the additional pad space.
All pond liner systems are currently proposed to consist of an inner 40-mil
thick PVC liner and an outer 45-mil thick polypropylene liner, separated
by geonet on the pond sides and a geotextile layer on the pond bottom. The
geonet/geotextile is part of the leachate collection and recovery system
(LCRS), which also includes a sump, consisting of select drain fill placed
at the lowest corner of each pond between the geomembrane liners. A leak
detection well, consisting of 8-inch diameter, Schedule 80 PVC
pipe, would be placed in the sump and "daylighted" at the top
of the pond for monitoring any fluid which reached the sump. The well pipe
would be screened in the sump material.
The pregnant and barren solution
ponds would be constructed with solution pond covers consisting of small-mesh
nets. Similar netting systems have been used successfully to date by Chemgold,
Inc., Glamis Imperial's sister company, at its Picacho Mine, and at many
other mines operating throughout the Western United States. Discharge of
leach solution and precipitation from the leach pad to the ponds would occur
in pipelines within the netted area of the ponds.
2.1.8.3. Vadose Zone and Ground Water Monitoring
A vadose (unsaturated ground water) zone monitoring system would be installed
to detect potential leaks in the pad lining system. This vadose
zone monitoring system is currently designed to consist of perforated
liquid collection pipes in a gravel bed installed beneath the liner system
and above a 20-mil PVC sheet (see Figure 2.6). This vadose zone monitoring system would underlay
approximately 25 percent of the leach pad liner, and be located directly
under the main process solution collection pipes, the lowest points of the
heap leach pad liner.
Two (2) monitoring wells, one (1) located at the upgradient boundary and
one (1) located at the downgradient boundary of the Project mine and process
area near the heap, have already been installed by Glamis Imperial, and
quarterly samples of the ground water are being taken. A ground water monitoring
program for these would be implemented by Glamis Imperial to sample and
test the ground water passing beneath the leach pad and ponds to detect
leakage, if any, from these facilities into this ground water.
2.1.9. Support Facilities
Support facilities located within the Project mine and process area would
include: office buildings with approximately 7,000 square feet of floor
space; an approximately 80-foot tall maintenance shop of approximately 20,000 square
feet on a reinforced concrete slab; telephone facilities, including a microwave
communications antenna; explosives magazines; an ammonium nitrate storage
facility; a lime storage facility; chemical storage areas; diesel fuel storage
areas; water storage facilities; an electrical substation and electrical
distribution powerlines; an emergency electrical power generator; a temporary
hazardous waste storage area; equipment wash facilities; a laboratory; roads;
and surface flow and erosion control structures. Project support facilities
located within the Project ancillary area would include: water supply wells
and connecting pipeline; electrical power lines; and the realignments of
portions of Indian Pass Road. Project support facilities located outside
of the Project area would consist only of the overbuilt 92 kV/34.5 kV
electrical transmission line.
2.1.9.1. Manpower
Approximately 225 workers may be required to construct the Project
facilities; however, only a percentage of these workers would be employed
at the Project mine and process area at any given time. Contractor personnel
would be hired to: construct the leach pad liner systems, ponds, process
plant and related facilities; perform civil construction, concrete work,
liner installation and quality assurance/quality control; install electrical
utilities and communication systems; and complete other miscellaneous tasks.
Glamis Imperial employees would be utilized for: construction management;
technical services; pre-stripping the orebodies; earth moving; and facility
preparation.
When in full production, the mine would employ approximately 120 full-time
employees. Mining and processing operations would be conducted up to 24 hours
per day, up to 365 days a year. The work force would likely be predominantly
from Imperial County, California and Yuma County, Arizona. It is anticipated
that the 40 current Picacho Mine employees would transfer to the Project
after the completion of mining at the Picacho Mine. Employment levels for
the Project would remain relatively constant for the life of the mining
operations, then be reduce during implementation of final reclamation. Employees
would be encouraged by Glamis Imperial to carpool to the Project area.
2.1.9.2. Water Supply and Distribution System
Development of a water supply system would be required to supply water
to the Project sufficient to operate the heap leach and related facilities,
and provide water for dust control. Peak water consumption for the Project
is expected to average approximately 1,200 acre feet per year.
Water used in the heap leach process would be recycled back onto the leach
pad (see Section 2.1.8). Evaporation losses from the heap leach
process would be minimized through the use of drip irrigation emitters,
and the absence of open flow ditch channels. Approximately 75 percent
of the total Project water consumption would be for the heap leach process,
including capillary retention of water within the heap. Dust suppression,
reclamation activities, domestic use, and construction would account for
the remaining 25 percent of Project water consumption.
Glamis Imperial is proposing to develop a ground water well field to provide
the Project water requirements. Production of the water would require drilling
and completion of up to four (4) water wells within the Project ancillary
area. A test well has been completed, and this well (PW 1)would be
upgraded to a production well for the Project if approved by the County
of Imperial. A location for the second well (PW 2) has been defined,
and it is expected that these two (2) wells should be sufficient to
provide the necessary water for the Project. Should additional well(s) be
required, they would be located in the Project ancillary area adjacent to
Indian Pass Road next to the water pipeline right-of-way within 1.5 miles
of the initial test well (see Figure 2.1). The water would be
pumped to the surface from a depth of 800 to 1,000 feet below ground
surface (bgs) by electrical pumps. The water
would be conveyed by buried 12-inch pipeline from the wells to above-ground
water storage and distribution tanks, or to the fresh water storage pond,
constructed within the Project mine and process area. Both the buried pipeline,
and any required electric power distribution line needed to power each of
the well pumps, would be constructed within the right-of-way, adjacent to
the access road to each well. An area of less than approximately one (1)
acre would be disturbed by each well and its associated access road. An
area of substantially less than one (1) acre around each well would
be fenced to control access to the well-head equipment.
2.1.9.3. Electric Power Supply and Utilities
2.1.9.3.1. Electrical Power
Peak electrical power requirements for the Project would be approximately
8 MW, which would be supplied from the utility power system. To deliver
this power to the Project, an existing 34.5 kV transmission line owned
by the local electrical utility, the Imperial Irrigation District (IID),
would be "overbuilt" with a new 92 kV transmission line,
to also be owned by the IID (see Figure 2.7). Approximately
sixteen (16) miles of this 34.5 kV transmission line would be overbuilt,
from immediately south of Interstate Highway 8 and immediately east
of Sidewinder Road to Indian Pass Road near Ogilby Road. This new 92 kV/34.5 kV
transmission line would be connected to the existing IID 92 kV "C-Line,"
located immediately south of Interstate Highway 8. At the point where
the existing 34.5 kV transmission line crosses Indian Pass Road, a
new 92 kV transmission line would be built adjacent to the south side
of Indian Pass Road to a 92 kV/13.2 kV mine substation located
within the Project mine and process area (see Figure 2.7). The
new substation would be constructed to transform the electrical power to
the 13.2 kV voltage used by the Project. A 13.2 kV distribution
line would be "underbuilt" on the same poles as the new 92 kV
transmission line running adjacent to Indian Pass Road to provide power
as necessary to the ground water well pumps located adjacent to Indian Pass
Road in the Project ancillary area. Special devices would be installed on
this new transmission line at each point where the direction that the transmission
line changes which would be visible at night only to military pilots using
night vision devices to prevent collisions with ground-following aircraft
(see Section 3.9.2).
The mine substation would be enclosed within a fenced area approximately
100 feet by 100 feet in size located inside the Project mine and
process area at the entrance near the parking facility. Emergency power
requirements for essential loads and services for the Project during periods
of utility service interruption would be provided by a "750 kW,
diesel-powered, electric generator located near the processing facility
in the Project mine and process area. "Overbuilding" the existing
34.5 kV transmission line with the 92 kV transmission line would
entail the following: (1) regrading the existing access road as necessary
to accommodate truck-trailer traffic; (2) establishing an equipment
lay down area for the temporary storage of equipment and materials; (3) delivery
of new pole(s) to the site of each existing pole; (4) "framing"
each of the new poles (adding insulators and cross arms, as necessary);
(5) leaning the existing wooden poles to the west to move the electrical
conductors out of the current transmission line alignment; (6) setting
new, taller, wooden poles in the same transmission line alignment; (7) stringing
the new 92 kV wire conductors near the top of the new poles and new
34.5 kV wire conductors below the 92 kV conductors on the new
poles; (8) energizing the new conductors; (9) removing the existing
conductors; and (10) removing the existing poles and any other waste materials.
Construction of the new 92 kV/13.2 kV transmission line would
require the same steps as construction of the "overbuilt" 92 kV/34.5 kV
transmission line except for steps (5), (9), and (10), since there is no
existing transmission line to lean or remove.
The 92 kV/34.5 kV transmission line would be constructed by
the IID under an amendment to the current 20-foot wide right-of-way granted
by the BLM and the easements obtained from the
private landowners near Interstate Highway 8 for the existing 34.5 kV
transmission line to allow the installation of the taller poles and two (2)
conductor sets. Approximately 22 acres would be disturbed during the construction
of the overbuilt 92 kV/34.5 kV transmission line.
Construction of the new approximately 3.7 mile-long 92 kV/13.2 kV
transmission line along Indian Pass Road to the Project mine and process
area has been conservatively estimated as disturbing a total of 27 acres
(3.7 miles times the entire width of the requested 60 foot right-of-way).
This would include the disturbance from the construction of the buried water
pipeline within the same right-of-way. Actual disturbance required to build
the new transmission line and pipeline is expected to be much less.
Principal access for construction of the new 92 kV/13.2 kV transmission
line would be Indian Pass Road itself. However, short access spur roads
from Indian Pass Road to the transmission line/pipeline corridor would be
constructed at three locations along the 3.7 mile length in those areas
where the corridor is separate from Indian Pass Road by as much as 250 feet.
The IID would own and operate the new 92 kV transmission line, and
would also construct, own and operate the approximately 100-foot by 100-foot
substation within the Project mine and process area. The surface disturbance
that would be created by this new construction for the transmission line,
pipeline, and electric substation are included as part of the Proposed Action
within the Project area.
2.1.9.3.2. Telephone Service
Telephone service would be provided to the offices and maintenance shop
by an FCC-approved microwave telephone system. A transmitter-receiver (low
height) would be constructed within the Project mine and process area, which
would beam the signal to existing facilities located on Black Mountain,
which then connects to the land-based telephone system; no new facilities
would be constructed outside of the Project mine and process area. Field
communications would be provided by an FCC-approved FM mine communication
system.
2.1.9.3.3. Exterior Lighting
Exterior lighting would be the minimum necessary, consistent with safety
requirements and 24-hour-per-day operations. Low-intensity "street"
lighting would be installed in the administration area; in the process area
on the precious metal recovery plant, and on the lime bin. Portable 35 hp
diesel-powered light plants would be used in the Project mine and process
area to illuminate the active working areas during nighttime hours; two (2)
plants in the active pit, one (1) on the active waste rock stockpile,
and one (1) on the heap leach pad. All of the haul trucks, light-weight
trucks, and operating earth-moving equipment would be equipped with headlights.
2.1.9.4. Chemical Use and Storage
Numerous chemicals would typically be transported to, stored at, and
used by, the Project (see Appendix A for a complete list of chemicals
stored and used). These can be generally categorized as heap leach processing
chemicals; mine chemicals/explosives; maintenance facility/power generation
chemicals; and laboratory chemicals. Approximately three (3) truck
loads of chemicals would be delivered per day. All chemicals would be transported
and stored in conformance with local, state and federal regulations and
company safety policies.
Miscellaneous laboratory chemicals would be maintained in small quantities
only and kept in containers in the on-site laboratory. Most of the bulk
chemicals would be stored in closed, weather-proof containers in secured,
open-air storage areas.
Heap Leach Processing Chemicals:
The principal heap leach processing chemical, sodium cyanide, would be shipped
and received in the manufacturer's dry bulk trucks. Solid sodium cyanide,
in the form of briquettes, would be put into solution directly from the
dry bulk trucks at the Project mine and process area process facility by
circulating an alkaline solution through the truck until the briquettes
have dissolved. The resulting solution, about 30 percent cyanide and
at a pH of about 13, would be stored in one (1) of two (2) 20,000
gallon storage tanks. All cyanide would be stored within the lined portion
of the Project process area, immediately adjacent to the process ponds,
and surrounded by a security fence. Sodium cyanide solution would be metered
directly into the barren solution
in the pipes leaving the barren solution
pond for application to the heap. The cyanide concentration of the barren
solution applied to the heap would be maintained at the desired 200 to 350 parts
per million (ppm) for effective leaching of the ore. Similar cyanide handling
practices are currently utilized at the Picacho Mine, and are standard in
the precious metal processing industry. Annual sodium cyanide usage for
the Imperial Project is anticipated to be approximately 1,750 tons.
Other heap leach processing chemicals, including sodium hydroxide (for cyanide
solution pH control) and hydrochloric acid (for carbon cleansing), would
be stored in a secured, lined containment area, near the process facility.
Acids would never be stored near cyanide. Calcium oxide (lime), which would
be added directly to each haul truck prior to loading the ore on the heap
leach pad, would be stored in silos on the north end of the heap leach loading
ramp. Anti-scalants (principally polymaleic acid) would be stored adjacent
to the process ponds. Calcium hypochlorite [Ca(ClO)2@4H2O]
would be kept on the Project mine and process area to neutralize any small
spills of liquid NaCN. Annual usage of these chemicals is estimated at 150 tons
for sodium hydroxide; 212 tons for hydrochloric acid; 16,500 tons
for lime; and 150 tons for polymaleic acid.
Mine Chemicals/Explosives:
The mine chemicals/blasting agents and associated explosives which are necessary
for mining operations would be stored in magazines in compliance with U.S. Bureau
of Alcohol, Tobacco and Firearms (ATF), and Mine
Safety and Health Administration (MSHA), safety standards. The ammonium
nitrate used in blasting would be stored in bulk in silos adjacent to the
lime bin facility. Annual consumption of the bulk ammonium nitrate would
be approximately 7,500 tons.
Maintenance Facility/Power Generation Chemicals:
The maintenance facility/power generation chemicals stored and used in the
greatest quantities would be diesel fuel, unleaded gasoline, and motor oil,
all of which would be stored in above-ground tanks located within a containment
structure located next to the maintenance shop. Annual consumption of gasoline
is estimated at approximately 40,000 gallons, and annual lubricant
consumption is estimated at 31,000 gallons. Annual diesel fuel consumption
for blasting and fueling on-site equipment and use in the emergency generator
is estimated at 4 million gallons.
2.1.9.5. Waste Disposal
Septic treatment systems with leach drain fields would be installed near
the office and shop facility, adjacent to the processing and laboratory
facilities, and adjacent to the lime storage facility. Glamis Imperial would
contract with local disposal service companies for the pumping of septic
tanks and the removal of other non-mining waste (trash) from the Project
area for disposal in an approved landfill. These wastes are estimated at
one (1) ton per day, based upon historic Picacho Mine and Mesquite Mine
data. Regulated wastes, such as used antifreeze, spent solvents, batteries,
and used oils and oil filters, would be transported off-site by a company
authorized to recycle these regulated wastes. These wastes would be recycled
or disposed of in conformance with all applicable local, state and federal
laws and regulations, and in a manner approved by the responsible regulatory
agencies. These wastes are also estimated to be approximately one (1) ton
per day, based on historic Picacho Mine data.
Major maintenance of equipment would be conducted within the concrete-paved
and bermed areas of the maintenance yard to the extent possible to minimize
accidental discharges of waste lubricants and other materials to the ground.
All mining equipment would be equipped with the "EVA" servicing
system, which allows quick, "leak-free" lubricant servicing from
mobile and stationary servicing equipment.
2.1.9.6. Roads
Haul roads constructed to haul mined material within the Project mine
and process area would typically be approximately 120 feet wide, although
in some areas would be as much as 150 feet wide to allow for surface
drainage areas and separate lanes for support vehicle traffic. Service or
maintenance roads within the Project mine and process area would be approximately
30 feet wide. A service road would be constructed inside the perimeter
fence around the perimeter of the Project mine and process area to provide
access for maintenance and security; in some locations, this perimeter road
would be coincident with constructed haul roads. All road crossings of ephemeral
stream channels would be at existing grade.
Access to the Project would be from Ogilby Road, a county-maintained two-lane
paved road, via Indian Pass Road, a county-maintained gravel road (see Figure 2.8).
Project traffic on Ogilby Road and Indian Pass Road is estimated at approximately
47 light-weight vehicle round trips per day during normal operations,
which assumes, based upon the experience of other mines in the area, that
approximately 25 percent of workers carpool to work. Heavy truck traffic
is estimated at approximately 3.5 round trips per day.
Small numbers of light vehicles (less than one (1) per day) may also
occasionally access the Project area from Chemgold, Inc.'s Picacho Mine,
located eight (8) miles to the east of the Project area, via BLM Route A278, Hyduke Road. Neither Hyduke Road
nor the BLM open routes of travel in the vicinity
of the Project mine and process area would be used for heavy truck or equipment
traffic. Occasional use of Hyduke Road by light-weight vehicles would continue
until final closure and reclamation of the Picacho Mine in approximately
the year 2003.
The approximately 6,000-foot section of Indian Pass Road located within
the Project mine and process area would be relocated prior to mining the
West Pit, as the pit would occupy the road's current location (see Figure 2.2).
Figure 2.2 shows the proposed relocation of Indian Pass Road,
which would shift the road approximately 1,000 feet to the west of
its current location to allow safe, continued public access to areas north
of the Project mine and process area. Construction of the realigned section
of Indian Pass Road would begin immediately following receipt of approvals
to proceed with the Project and would require approximately one (1)
month to complete. The entire length of Indian Pass Road would be maintained
open to the public during this construction.
The intersection of Indian Pass Road and Ogilby Road would also be re-engineered
and realigned to have Indian Pass Road meet Ogilby Road at a right angle,
rather than the acute angle which the intersection now has. This would be
accomplished by constructing a new intersection approximately 330 feet
south of the current intersection of Ogilby Road and Indian Pass Road, and
connecting the current alignment of Indian Pass Road with this new intersection
through a 60E turn with a radius of approximately 105 feet. The abandoned
section of Indian Pass Road would be regraded and reclaimed.
The relocated portion of Indian Pass Road would cross the western ephemeral
stream channel "at grade" in two (2) locations. Signs would be
posted at the two (2) wash crossings along the relocated portion of
Indian Pass Road warning drivers not to cross the wash when flooded. Glamis
Imperial would undertake repair and maintenance, as may be necessary and
authorized by Imperial County, to Indian Pass Road if it is damaged by flooding
where it crosses existing ephemeral stream channels. Water and/or an environmentally
acceptable chemical dust inhibitor such as sodium lignosulfonate (a non-toxic
non-hazardous, co-product of cellulose produced from trees), would be applied
to Indian Pass Road from its intersection with Ogilby Road to the boundary
of the Project mine and process area. Glamis Imperial plans no other alterations
to Indian Pass Road to accommodate mine-related traffic.
Because the two (2) "at grade" crossings of the western ephemeral
stream channel of the relocated portion of Indian Pass Road present a long-term
maintenance issue, the Imperial County Public Works Department has requested,
and Glamis Imperial has committed, to return Indian Pass Road to the east
side of the western ephemeral stream channel. After the completion of mining
of the West Pit, waste rock stripped from the sequential mining of the Singer
Pit and East Pit would be placed in the mined-out West Pit. Indian Pass
Road would then be returned to a location east of and approximately parallel
to the diverted West Pit West Diversion channel. At that time, the area
disturbed by the relocated segment of Indian Pass Road would be regraded
and reclaimed (see Figure 2.4).
As part of Glamis Imperial's operations, water sprays and/or chemical treatments,
which do not contain petroleum or petroleum by-products, would be used to
minimize the generation of dust from disturbed surfaces within the Project
mine and process area. Water, and/or an environmentally acceptable chemical
dust inhibitor, such as magnesium chloride, would be applied to the haulage
and other roads in sufficient quantities to minimize dust emissions. Water
would generally be applied on those roads used only temporarily, while the
chemical dust inhibitor would be routinely applied to the more heavily traveled
areas.
2.1.9.7. Surface Flow Diversions
All surface drainages in the area are ephemeral, with flows occurring
only during, and immediately following, major precipitation events. Several
ephemeral drainages would be permanently diverted around the facilities
located within the Project mine and process area. Each of the diversion
channels has been designed to safely convey all runoff flows from the 100-year,
6- and 24-hour precipitation events, and to direct water back into the same
major drainage system from which it was diverted (see Figure 2.9).
The drainage diversions permanently route five (5) washes (identified as
the West Pit West Diversion, the West Pit East Diversion, the Singer Pit
East Diversion, the East Pit West Diversion, and the East Pit East Diversion)
around the mine pits. In each case, all diversion channels would channel
surface flows either back into the same drainage channel, or into another
existing nearby drainage channel which flows back into the same drainage
channel within the Project mine and process area. These diversion channels
would be built to approximate the original drainage system in both gradient
and channel geometry (see Figure 2.10). During the period that
an adjacent pit is open, a diversion channel may be temporarily lined with
high density plastic or clay protected by rip rap to prevent subsurface
flows into the open pit. Additionally, any areas of the diversion channels
which might be especially susceptible to erosion from surface flows would
be bermed and/or rip-rapped to prevent erosion and potential damage during
the period when an adjacent pit is open. Once the pits have been backfilled
(see Section 2.1.3), or mining is complete, any rip rap or temporary
plastic liners installed in a diversion channel would be removed and the
channel regraded. Once all construction activity within a diversion channel
has been completed, stockpiled soil from disturbed washes would be spread
along diversion channel banks. The channel slopes and banks would be planted
with wash vegetation directly transplanted from other disturbed drainages
and/or selectively planted with young ironwood and palo verde trees or seedlings
to begin to reestablish microphyll woodland habitat similar to that removed
by excavation of the original stream channel.
2.1.9.8. Fences
Prior to the initiation of operations, fencing would be installed around
Project facilities to protect the public and wildlife. A 3-strand, 4-foot
high, smooth-wire fence would be erected along the entire Project mine and
process area boundary, and the southern portion of the central drainage,
except as noted below. Along the entire western boundary of the Project
mine and process area, generally along the boundary adjacent to Indian Pass
Road, a 6-foot high chain-link fence would be constructed (see Figure 2.2).
In addition, those portions of the Project mine and process area boundary
coincident with the ore leach pad or process facilities would be fenced
with six (6)-foot high, metal, chain-link fencing topped with one (1) foot
of barbed wire (see Figure 2.2). In areas where the fence crosses
an ephemeral stream channel, the fence would be designed to minimize damage
during storm events. These sections of fence would be inspected immediately
following a flow event and appropriate repairs undertaken in the event that
the fence is damaged to prevent public or wildlife access to the Project
mine and process area.
Tortoise-exclusion fencing would be installed coincident with the entire
perimeter fence. The tortoise-proof fence construction, and material specification,
would be approved by the BLM prior to installation.
Typical fence construction would consist of 1.5 feet of 0.5-inch mesh
hardware cloth above the ground surface. An additional one (1) foot
of the mesh would either be buried below ground level, or bent at a right
angle towards the outside of the fence and covered with gravel and rocks
to prevent animals from burrowing under the fence. The uppermost portion
of the hardware cloth would extend not more than two (2) inches above
the lowermost wire strand. T-posts, or other suitable anchoring posts, would
be placed at appropriate intervals (usually 10- to 16-foot spacing).
The entire ore leach pad and process facilities, and the fresh water pond,
would be fenced with 6-foot high, metal, chain-link fencing topped with
one (1) foot of barbed wire (see Figure 2.2).
Signs would be posted on the perimeter fence at any locations which could
pose a threat to public safety, as required by regulation. Fencing constructed
for the Project operations would be maintained in-place until revegetation
is complete and determined successful for bond release by the BLM
and Imperial County. At that time, all fencing would be removed.
2.1.10. Geological Surveys
Continuing geological activities to complete condemnation or confirmation
of mineralization are planned for the Project mine and process area. These
activities, which may include geophysical surveying, geochemical sampling,
mapping, drilling, and bulk sampling, would occur only in areas already
proposed for disturbance under the Proposed Action, and be concentrated
within and adjacent to the proposed open-pit areas. No additional surface
disturbance would be created within the Project mine and process area, and
no geological surveys for the condemnation, exploration, or confirmation
of mineralization outside of the Project mine and process area are proposed,
or would be authorized, under the Proposed Action.
Condemnation or confirmation holes would be drilled using either reverse-circulation
or core-drilling methods. Large diameter holes would be drilled for metallurgical
samples. The drilling equipment would be serviced by a water truck/pipe
truck/crane truck. Water requirements for drilling activities would be supplied
by Glamis Imperial's proposed water supply system. All drill holes would
be capped and/or plugged in accordance with applicable state law.
2.1.11. Proposed Reclamation
Section 2.1.11 is a summary of the Reclamation Plan prepared
by Glamis Imperial for the Imperial Project, which is provided as Appendix A
to this joint EIS/EIR. Those readers wishing more detailed information on
the Reclamation Plan proposed by Glamis Imperial are encouraged to read
Appendix A in its entirety.
2.1.11.1. Reclamation Goals
Glamis Imperial has proposed to conduct reclamation activities in accordance
with SMARA and the regulations found at 43 CFR 3809.1-3(d) and
14 CCR 3500. In general, the proposed Reclamation Plan includes
measures for: protecting wildlife and the public; minimizing erosion and
mass failure potential; demolishing structures and neutralizing process
components; regrading selected side and cut-and-fill slopes; revegetation;
and, where feasible, providing for the resumption of pre-mining land uses.
The proposed post-mining reclamation goals are to: reclaim the Project mine
and process area to a stable, functioning landscape unit/ecosystem to allow
for similar land uses as currently exist; establish conditions that would
promote the long-term development of a vegetation community typical of the
local area; and produce reclaimed areas that are visually and functionally
compatible with the surrounding topography. Implementation of the proposed
Reclamation Plan would not limit the future development of mineral resources
in the area, although some mineralization may be concealed after placement
of waste rock in the West and Singer Pits. Currently uneconomic precious
metal resources within the walls and floors of the East Pit would remain
largely accessible for future development. In addition, material in the
waste rock stockpiles would be available for future development.
The Reclamation Plan relies primarily on natural processes and requires
little intervention once preparation is complete. Reclamation procedures,
as stated in the Reclamation Plan, are to:
Establish stable topographic surfaces and drainage conditions
that are compatible with the surrounding landscape and serve to control
erosion.
Regrade waste rock stockpiles and the leach pad slopes to no greater
than 2H:1V and install catchment basins to promote revegetation.
Backfilling the West Pit and Singer Pit.
Provide a technical review of the groundwater flows and levels
encountered in the East Pit. If the results of the review indicate a pit
lake may form, backfill that portion of
the floor of the East Pit to above the level of any projected pit lake.
Establish, on waste rock stockpiles, haul roads, pit bottoms and
facilities, soil conditions conducive to a stable plant community through
grading and reapplication of suitable growth material containing seeds.
Revegetate disturbed areas using native plant species endemic
to the area in order to establish a long-term productive biotic community
compatible with proposed post-mining land uses and capable of self-regeneration
without the long-term dependency on maintenance, soil amendments, or fertilizers,
including;
- Planting and transplanting young ironwood (Olneya tesota), palo verde
(Cercidium floridum) trees or seedlings and shrub species along the channels
which divert the throughgoing washes to reestablish the microphyll woodland
habitat in acreage roughly equivalent to that acreage currently found along
these channels within the Project mine and process area;
- Transplant ocotillo, barrel cactus and species of cholla into catchment
basins;
- Adding seeds of the California Native Plant Society (CNPS)-listed,
but locally common, endemic fairy duster (Calliandra eriophylla) and winged
forget-me-not (Cryptantha holoptera) to the revegetation seed mix.
For specific details on the reclamation methods and ultimate physical
condition of the Project mine and process area, see Section 6.6 of
the Reclamation Plan.
The reclamation effort would consist of different methods to be applied,
as appropriate, to reclaim different types of surface disturbance (see Table 2.3). Figure 2.11 shows which
areas of the Project mine and process area would be subject to the specific
reclamation methods outlined above.
2.1.11.2. Reclamation Activities
The reclamation plan addresses all surface disturbance created by the
Project. In general, the reclamation plan includes measures for: protecting
wildlife and the public; minimizing erosion and mass failure potential;
demolishing structures and neutralizing process components; regrading selected
side and cut-and-fill slopes; revegetation; and, where feasible, providing
the resumption of pre-mining land uses. The post-mining reclamation goals
at the Project are to reclaim the area to a stable, functioning landscape
unit/ecosystem to allow for similar, but not identical, land uses, including
wildlife habitat and recreation, as currently exist, consistent with the
applicable reclamation standards of the California Code of Regulations,
Article 9, Title 14 (Reclamation Standards), and the surface management
regulations under the general mining law found in the Code of Federal Regulations,
Title 43, Group 3800. The final land forms of the Project mine and process
area cannot be reclaimed to the original contours. Thus the goal of the
Plan is not to restore and revegetate to the original land form, but to
a natural state that blends in with the existing undisturbed terrain.
The reclamation effort consists of different methods to be applied, as appropriate,
to reclaim different types of surface disturbance. These methods are the
construction and reclamation of diversion channels; demolition of structures
and removal of facilities; rinsing and neutralization of residual leach
solution in the solution ponds and heap; backfilling of selected pit(s);
the construction of boulder barricades for public safety and to exclude
vehicle access; design and construction of stable slopes; rough regrading;
surface preparation through fine grading, ripping to loosen soil, topsoiling,
and/or construction of water catchments for vegetation; tree and cactus
transplantation; reseeding and revegetation; or natural revegetation.
Table 2.3
| MINE FACILITY COMPONENT |
RECLAMATION METHODS TO BE APPLIED |
S
T
R
U
C
T
U
R
E
D
E
M
O
L
I
T
I
O
N
F
A
C
I
L
I
T
Y
R
E
M
O
V
A
L |
N
E
U
T
R
A
L
I
Z
A
T
I
O
N |
V
E
H
I
C
L
E
A
C
C
E
S
S
E
X
C
L
U
S
I
O
N |
S
L
O
P
E
S
T
A
B
I
L
I
Z
A
T
I
O
N |
R
E
G
R
A
D
I
N
G |
S
U
R
F
A
C
E
P
R
E
P
A
R
A
T
I
O
N |
B
A
C
K
F
I
L
L |
N
A
T
U
R
A
L
V
E
G
E
T
A
T
I
O
N |
R
E
V
E
G
E
T
A
T
I
O
N |
T
R
A
N
S
P
L
A
N
T
V
E
G
E
T
A
T
I
O
N |
| Mine and Process Area |
| Pits |
West & Singer Pits (see also Waste Rock Stockpiles) |
|
|
|
|
X |
X |
X |
|
X |
|
| East Pits-Bottom |
|
|
X |
|
|
X |
|
|
X |
|
| East Pits-Slopes |
|
|
X |
X |
|
|
|
X |
|
|
| Process Facilities |
Heap Leach Pad-Top |
|
X |
|
|
X |
X |
|
|
X |
|
| Heap Leach Pad-Slopes |
|
X |
|
X |
X |
X |
|
|
X |
X |
| Process Facility Area (Solution Ponds and Process Facilities) |
X |
X |
|
|
X |
X |
|
|
X |
|
| Lime Bin Area and Fresh Water Pond |
X |
|
|
|
X |
X |
|
|
X |
|
| Waste Rock Stockpiles |
Waste Rock Stockpiles-Top |
|
|
|
X |
X |
X |
|
|
X |
|
| Waste Rock Stockpiles-Slopes |
|
|
|
X |
X |
X |
|
|
X |
X |
| Topsoil Stockpiles |
Soil Stockpiles Sites |
|
|
|
|
X |
X |
|
X |
|
|
| Support Facilities |
Office/Maintenance/Parking/Emergency Power Area |
X |
|
|
|
X |
X |
|
|
X |
|
| Haul and Maintenance Roads |
|
|
|
|
X |
X |
|
|
X |
|
| Drainage Diversions |
|
|
|
|
X |
X |
|
|
X |
X |
| Ancillary Area |
| County Road Realignment-Temporary |
|
|
|
|
X |
X |
|
|
X |
|
| Powerline, Water Wells |
X |
|
|
|
X |
X |
|
|
X |
|
| Pipeline Route |
|
|
|
|
X |
X |
|
|
X |
|
Concurrent Reclamation:
Concurrent reclamation activities would begin with construction of the necessary
diversion channels, and the stabilization and erosion control of the soil
stockpiles during the construction phase of the mine and leach pad complexes.
During initial construction, constructed diversion channels would be reclaimed
with soil, vegetation and trees removed from existing wash areas disturbed
by Project-related construction. As operations progress, areas no longer
needed for mining activities become available for concurrent reclamation.
Concurrent reclamation would focus on the stable diversion of surface water,
as well as the stabilization of new or upgraded access roads, side and final
cut-and-fill slopes, and final waste rock stockpiles. The interim reclamation
of soil stockpiles generally consists of grading for stabilization and allowing
natural germination from seeds present in the soil. Soil stockpiles would
be placed in field determined locations away from washes that provide protection
from water erosion. The sandy and stony nature of the soils would prevent
significant wind erosion after placement. Large trees and shrubs would either
be removed and appropriate specimens transplanted before soil stripping,
or buried in soil stockpiles and waste rock stockpiles. Small shrubs and
surface litter including seeds would be incorporated into the soil stockpiles.
Roads constructed for drilling may be reclaimed concurrent with mining operations
when it is determined that the roads are outside the influence of further
geological surveying or mining operations.
Reclamation of the diversion channels would be done concurrently with diversion
channel construction. Reclamation of the remainder of the disturbed areas
would be initiated when individual components are no longer required for
mine operations or when facilities are decommissioned and closure begins.
Removal of facilities, rough grading, and scarifying activities may occur
at any time during the Project life.
Closure and Post-Closure Reclamation:
Closure and post-closure reclamation would commence when the ore reserves
are exhausted and mining has ceased. Leaching operations would cease after
uneconomic recovery rates are reached. It is foreseeable that the heap leaching
activities would remain active after mining activities have stopped, due
to the length of time required to complete leach cycles. In this case, open
pit and some related facility reclamation and closure activities would occur
in advance of leach pad reclamation and closure.
It is estimated that the closure and post-closure phase of reclamation would
take one (1) to three (3) years to complete following cessation
of leaching. Post-closure monitoring of revegetation success is expected
to account for an additional five (5) years.
2.1.11.2.1. Backfilling and Grading
Waste rock and overburden would be placed on waste rock stockpiles adjacent
to the pits or, as mining proceeds, into the previously mined-out West Pit
and Singer Pit. The West Pit and Singer Pit would be backfilled. Subsequent
backfill may be necessary to raise the floor
of the East Pit to a level higher than the level of any pit lake which may
be eventually predicted to form from the inflow of ground water.
During active mining, reclamation in and around the open pits would be limited
to controlling erosion of the haul roads and slopes. Upon the completion
of mining and any appropriate or necessary backfilling, the remaining open
pits would be reclaimed by regrading (and revegetating) the haul roads and
floors and leaving the slopes in a stable condition. Stable angles of the
final pit highwalls would be determined by an engineering analysis which
would be completed after one full year of mining in each of the West Pit
and East Pit. Results of these studies would then be incorporated into open
pit designs.
All disturbed areas except the open pit slopes would be regraded and revegetated,
when no longer required for mine operations. This reclamation would create
undulating land forms that are stable, do not allow for any pooling or ponding
of water, and blend with the surrounding undisturbed topography. Final regrading
on the tops and accessible slopes of the waste rock stockpiles and the leach
pad, the bottoms of the open pits, the haul roads, and the areas disturbed
for the soil stockpiles would be conducted to minimize erosion potential
and additional surface disturbance and facilitate the establishment of post-mining
vegetation. Sharp edges would be rounded and straight lines altered to provide
contours which are visually and functionally compatible with the surrounding
terrain. In addition, regrading would entail the construction of small catchment
basins to facilitate the revegetation of the disturbed areas. Regrading
of other areas disturbed by facilities and roads would be fine-graded to
enhance moisture retention for reclamation and revegetation.
2.1.11.2.2. Stable Slopes
Stable topographic surface and drainage conditions would be established
that would control erosion, prevent sedimentation, and be compatible with
the surrounding landscape. Slopes would depend on the type of material,
material erodability, and the practical considerations of the mining process.
Overall pit slopes would range from: 0.8H:1V (40 degrees) to 1H:1.2V
(50 degrees); 2H:1V (30 degrees) for waste rock stockpile slopes;
2H:1V (30 degrees) for leach pad slopes; and near-flat along the tops
of waste rock stockpiles, heap, haul and maintenance roads, and pit bottoms.
Pit wall slopes would be constructed during mining at angles consistent
with long-term stability. Engineering analysis and the experience of Glamis
Imperial's sister company, Chemgold, Inc. at the Picacho Mine, indicates
that the slope of the ultimate pit walls would be 40 degrees to 50 degrees
to provide the required factor of safety for long-term slope stability.
Each pit is to be developed in separate phases, which allows verification
of slope stability parameters. In addition, after one full year of mining
in each of the East Pit and West Pit a slope stability analysis would be
performed. Results of the study for each pit would be incorporated into
the design of that open pit. Due to the limited depth, size, and life of
the Singer pit (less than 6 months), no additional slope stability
analysis is planned for the Singer Pit.
Pit walls would have safety benches at regular vertical intervals to contain
minor rock spills. Pit wall slopes may increase if actual mining conditions
and geotechnical factors indicate that pit wall integrity could sustain
steeper slopes. After closure, pit highwalls remaining in areas not utilized
for waste rock stockpiling would be left in a stable configuration, subject
to natural processes, and barricaded with large boulders around the rim
of the pit to prevent vehicular access and discourage pedestrian access
by the public over slopes which could constitute a hazard. The barricade
would consist of boulders averaging approximately four (4) feet in
diameter, which would be stacked into a continuous wall no less than eight (8)
feet high. This "wall" would be set back from the edge of the
pit by no less than 100 feet. In addition, the uppermost ten (10)
feet of the pit slope would slope no greater than 2H:1V (30 degrees),
and would terminate at its lower side into a horizontal bench no less than
ten (10) feet wide.
Overall final slope grades of the waste rock stockpiles would not exceed
2H:1V (30 degrees). Upon final mine closure, the tops and accessible
slopes of the waste rock stockpiles would be rough-graded and ripped to
prevent water pooling, ponding, and erosion, and to create small catchment
basins to facilitate the revegetation of the disturbed areas. Stockpiled
soil material would be distributed on the tops and the accessible level
portions of the waste rock stockpile prior to broadcast seeding with the
proposed seed mixtures.
The heap would be constructed with no greater than 2H:1V (30 degree)
overall slopes to provide for final reclamation. The sharp contours of the
top and bottom of the leach pad would be rounded and softened, and the graded
material extended outward far enough to overlap the perimeter berm that
encircles the leach pad during active operations. Grading of the pad would
leave in place the interceptor ditch around the pad, thereby diverting all
runoff away from the pad area. Upon final mine closure, the top and slopes
of the leach pad would be rough-graded and ripped to prevent water pooling,
ponding, and erosion, and to create small (4,000 to 5,000 square foot)
catchment basins to facilitate the revegetation of the disturbed areas.
2.1.11.2.3. Drainage Reestablishment and
Erosion Control
All surface drainages in the area are ephemeral, with flows occurring
only during and following major precipitation events. Those sections of
these existing washes which could convey storm waters around or through
the Project mine and process area without impacting Project facilities would
not be altered by the Project and would continue to carry storm flows through
and around the Project mine and process area. However, several of these
ephemeral drainages must be permanently diverted around the facilities located
within the Project mine and process area. Each of the diversions has been
designed to direct water back into the same major drainage system from which
it was diverted. At no time would flows be diverted into other major drainage
systems.
All diversion channels have been designed to safely convey all runoff flows
from the 100-year, 24- and 6-hour precipitation events, and would be built
to approximate the original drainage system gradient and channel geometry.
During the period that the pits are open, the diversion channels may be
temporarily lined with high density plastic or cement grout and protected
by rip rap to prevent subsurface flows into the open pits. Areas of the
diversion channels not lined would be reclaimed concurrent with initial
diversion channel construction. All diversion channels would re-connect
with the same wash system at a point just downstream of the open pits. Additionally,
any areas of the diversion channels which may be especially susceptible
to erosion from surface flows would be bermed and/or rip-rapped to prevent
erosion and potential damage during the period when the pits are open. All
bermed and/or rip-rapped areas would be maintained while the open pits are
being mined to prevent wash erosion. Diversion channel slopes and banks
would have suitable microphyll woodland species directly relocated from
the disturbed drainage and would be selectively planted with young ironwood
and palo verde trees or seedlings to begin to reestablish microphyll woodland
habitat.
To minimize erosion and the production of sediment, all undisturbed areas
and adjacent ephemeral wash vegetation which is not to be directly impacted
by the construction of Project facilities would be left intact and undisturbed.
To minimize impacts from erosion on the Project area and down surface-gradient
areas, all mine facilities, such as the heap leach facility, waste rock
stockpiles, soil stockpiles, and roads, would be designed and constructed
with appropriate erosion control features designed to meet the performance
standards of 14 CCR 3706. Additionally, in accordance with the
Storm Water NPDES General Permit requirements, Glamis Imperial would prepare
and implement a Storm Water Pollution Prevention Plan (SWPPP), which is
a site-specific plan to control drainage and erosion. Surface runoff and
drainage from disturbed areas within the Project mine and process area would
be controlled, collected, conveyed to sediment basins, and infiltrated (or
consumed in mining or the heap leach process).
Methods to be employed, if necessary, to reduce or prevent the generation
of sediment from within the Project mine and process area would include
berms, sediment ponds, rip rap, check-dams, sand bags, silt fences, or other
temporary techniques to minimize impacts. All surface runoff generated from
disturbed areas within the Project mine and process area would be collected
in the active pit(s), collected in the heap leach system and added to the
process solution volume, or collected and directed to sedimentation basins
for infiltration. No runoff from disturbed areas within the Project mine
and process area would be directed into the existing drainage system during
the life of the Project. Erosion control methods would be designed to handle
in excess of a 20-year/one-hour intensity storm event, in accordance with
standards established by 14 CCR 3706(d) (SMARA regulations).
2.1.11.2.4. Structure Demolition and Facility
Removal
The main haul roads and all other Project roads, including roads constructed
for drilling holes for geological surveying, and abandoned sections of the
county road within the mine and process area would be regraded, scarified,
and revegetated. The relocated section of Indian Pass Road would be reconstructed
adjacent and parallel to the West Pit West Diversion channel following the
completion of backfilling of the West Pit.
Buildings and ancillary facilities would be reclaimed by having all portable
and salvageable structures removed and taken off-site. Any permanent below-grade
structures and all foundations would be removed. All surplus materials,
storage containers and trash would be transported to a landfill authorized
to accept this material. The remaining waste products, and all surplus fuel
oil and other materials, would be removed from the Project mine and process
area and disposed of according to then-current state and federal regulations.
The on-site electric substation, the 92 kV/13.2 kV transmission
line, and the ground water well pumping facilities would be removed following
the completion of reclamation of the Project mine and process area. Areas
disturbed during powerline construction within the project ancillary area
would be reclaimed shortly after the powerline is in place, and again after
removal. The overbuilt 92 kV/34.5 kV transmission line, owned
by the IID, would remain in place. Disturbed areas created by overbuilding
the 92 kV/34.5 kV line which would not be used for regular maintenance
would be raked shortly after the powerline is constructed and naturally
revegetated.
Ground water production and monitoring wells would be plugged and abandoned
in conformance with applicable regulatory requirements (14 CCR 3713(a)).
The buried ground water pipeline from the ground water well field to the
Project mine and process area would be abandoned in-place. The buried water
pipeline construction corridor would be reclaimed after pipeline installation
is completed.
Fencing constructed for Project operations would be maintained in-place
until revegetation is completed and determined successful for bond release
by the BLM and Imperial County. At that time,
fencing would be removed.
2.1.11.2.5. Contaminant Control
The leach pad and process ponds would be designed as lined, zero-discharge
facilities with leak detection systems, in conformance with CRWQCB
requirements. The process ponds, and storm water overflow pond, would be
designed with sufficient capacity to contain the normal operating volume
of solution, together with the rainfall run-off from the heap following
a maximum probable one (1)-hour storm event occurring simultaneously
with a 24-hour power outage, while maintaining a two (2)-foot freeboard.
Process chemicals would be stored in secured areas in weather-proof containers,
in accordance with local, state and federal regulations and company safety
policies.
At the completion of leaching, the spent ore on the heap leach pad and sediment
contained within solution ponds would be neutralized, regraded, and small
catchment basins installed and seeded. Prior to initiation of reclamation,
neutralization of the heap leach pile would be accomplished by rinsing with
fresh water to reduce cyanide levels to meet the requirements of the WDRs to be issued by the CRWQCB
before use of the leach facility can commence. A neutralizing agent may
be added to the process waters and rinse solutions to reduce the cyanide
level to meet CRWQCB standards. Sampling and
laboratory testing would be conducted to evaluate and verify completion
of the neutralization process at the conclusion of heap rinsing. This would
likely require twelve (12) months of rinsing (based on Chemgold, Inc.'s
experience to date with the successful closing of four (4) heaps at the
Picacho Mine).
All neutralized process waters and rinse solutions would be evaporated in
the ponds or by sprinklers on the heaps, or land applied. Process water
ponds would then be reclaimed, but the final neutralization and reclamation
of the ponds would not occur until the neutralization of the heaps is complete
to the satisfaction of the CRWQCB .
Any soil material contaminated by spills of regulated waste materials, such
as fuel oil, waste lubricants or gasoline, would be collected, contained,
and either remediated within the Project mine and process area (if permissible
under then-current regulations) or removed and disposed of in conformance
with then-current regulations.
To ensure containment of sediment erosion during mining, several sediment
traps have been designed around the waste rock stockpiles to contain the
sediment and runoff which may be generated by the 100-year, 24-hour storm
event. Sediment from surface runoff from the Project facilities would be
contained on-site. Project surface runoff would remain separated from throughgoing
runoff flow in the diversion channels during the life of the Project.
2.1.11.3. Revegetation Activities
Revegetation activities would include: salvaging and stockpiling of available
soil; contouring and shaping accessible disturbed areas; reapplying soil
materials as necessary; preparing seedbeds; seeding and transplanting; optimizing
seed mixtures and rates by using locally collected seed; conducting revegetation
test plots; and monitoring and reporting.
2.1.11.3.1. Soil Salvage and Stockpile
Most of the Project mine and process area is located on old piedmont
surfaces consisting principally of desert pavement which has a poorly developed
soil profile and which is not suitable for salvage and use in reclamation.
However, a few areas within the Project mine and process area, principally
in the shallow washes and adjacent slopes, have shallow soils with suitable
texture which can be salvaged. Stripping of these soils to the greatest
depth practicable (generally 12-18 inches) would lead to the salvage
of an estimated maximum of 112,200 cubic yards of soil. Salvaged soil
would be stockpiled at two (2) soil stockpile sites. Construction of
the stockpiles would be done to enhance stability of the side slopes and
divert surface run-on. Best management practices (BMPs)
would be used to contain any sediment which may be liberated due to precipitation
directly on the soil stockpiles.
2.1.11.3.2. Contouring and Grading
All disturbed areas except the pit slopes would be regraded and revegetated,
when no longer required for mine operations. This reclamation would create
undulating land forms that are stable, do not allow for any pooling or ponding,
and blend with the surrounding undisturbed topography. Final regrading on
the tops and slopes of the waste rock stockpiles and the leach pad, the
bottoms of the open pits, and haul roads would be conducted to minimize
erosion potential and facilitate the establishment of post-mining vegetation.
Sharp edges would be rounded and straight lines altered to provide contours
which are visually and functionally compatible with the surrounding terrain.
Final regrading would entail the construction of catchment basins to facilitate
the revegetation of the disturbed areas.
Rough grading would blend the top edges and crests of the waste rock stockpiles
and the heap and would be used during the construction of the diversion
channels. Final grading would construct the small catchment basins for revegetation
on the waste rock stockpiles and leach pad. Potential drainage and erosion
processes would be important considerations in the design for shape and
size of these small catchment basins. In general, most flat or gently sloping
areas, less than 2H:1V slopes, would have catchment basins constructed on
them. This would include the entire leach pad and waste rock stockpiles.
2.1.11.3.3. Revegetation Test Plots
In order to provide the basis for specific reclamation methods and techniques
which would be used at the Project, revegetation test plots would be set
up early in the mine life. The objective of the test plot program is to
provide long-term plots which would be evaluated throughout the mine life,
and to utilize test plot results to modify and continue developing reclamation
methods.
All revegetation treatments would be based on the Project test plots developed
for the site-specific conditions of the Project area. Treatment may be the
same as have been used elsewhere, such as at American Girl or Picacho Mines,
but would be designed for environmental conditions specific to the Project.
Ongoing monitoring of Picacho Mine reclamation, and Imperial Project concurrent
and interim reclamation, would provide additional information for refining
the Project seeding and revegetation plan, which would be updated with new
information subject to the concurrence of the BLM
and Imperial County, prior to the start of final reclamation and decommissioning
of the Project area.
Revegetation testing would be conducted during the life of the Project when
areas become available. A seed collection program was initiated in 1996
and would continue to be conducted periodically throughout the life of the
Project. This would provide a seed bank of native, acclimatized vegetation
for the revegetation effort. To aid in the revegetation of the Project mine
and process area, the naturally vegetated areas between the disturbed areas,
such as between roads and pits and the undisturbed, fenced portion of the
central wash, would be managed as undisturbed buffers to serve as a natural
seed sources and provide protection for small mammals, birds, and reptiles.
2.1.11.3.4. Soil Reapplication
A minimal amount of useful soil (growth media) exists within those portions
of the Project mine and process area to be disturbed. However, salvaged
and stockpiled soils which remain after completion of diversion channel
reclamation would be distributed as equitably as possible to all the areas
to be revegetated. Revegetation experience at the Picacho Mine indicates
that the neutralized leached ore on the heap is excellent in-place growth
media. Based on this experience, little or no soil is needed on the leach
pad to achieve revegetation success. With that in mind, the remaining stockpiled
soil would be used as needed to reclaim waste rock stockpiles, haul roads
and ancillary facilities areas.
Where necessary, areas of compacted material would be ripped prior to application
of the salvaged soil. Soil would be placed on prepared areas in the early
fall or immediately after final grading, just prior to seeding. Soil placement
would be monitored to ensure that a sufficient depth of material is being
placed. The surface would be left in a rough or furrowed state to reduce
wind and water erosion and to increase available moisture in the surface
soil layer.
2.1.11.3.5. Seedbed Preparation
Following catchment basin construction, stockpiled topsoil placement
and final grading, seedbed preparation, seeding, and transplant efforts
would be performed as follows:
- Compacted surfaces would be loosened and left in a rough condition
by ripping.
- The surfaces would be contoured into catchment basins which enhance
moisture, promote seed germination and plant growth, and provide for stabilization
of the surface material from wind and erosion.
2.1.11.3.6. Seeding, Planting and Transplanting
The intended seeding mixture would be collected from the natural sources
located on surrounding areas and the Project area. The revegetation seeding
rates recommended would be based on test plots from the Project, the Picacho
Mine, and in consultation with the BLM, Imperial
County, and the California Department of Fish and Game (CDFG) (as to deer
browse). Glamis Imperial, or Glamis Imperial's contractors, would collect,
prepare, and store native seed for use in reclamation. During final reclamation,
the seed mixture would include native plant seeds collected in the local
area designed to increase available browse for deer. Any substitutions to
the approved native seed would require reapproval by the BLM
and Imperial County prior to use.
Surface conditions for sowing seed are best immediately after surface preparation
and/or soil placement since the surface is loose and friable, allowing the
seed to be covered with no raking or harrowing. Seeds would be hand broadcast,
or broadcast by rotary spreaders. For broadcast applications, equipment
such as a "cyclone" spreader would be used to distribute collected
seed immediately after grading, when surfaces are rough. The rate of sowing
would be adjusted, by volume, depending on the visible seeds present. Generally,
about one-half (2) cup of seed-containing material per catchment basin
would be used, which is estimated at a rate of which about 8 to 10 pounds
of native seed per acre.
Plants deemed valuable for transplanting that meet the transplant criteria
outlined in the Reclamation Plan, such as cactus, ocotillo, young ironwood
and palo verde trees, would be collected from those areas of the Project
area schedule for surface disturbance prior to surface disturbance. Additionally,
seedlings of some species may be grown from seeds collected from the area
or equivalent sources. These plants would be carefully placed into prepared
locations. Selected cacti species which occur within the disturbed areas
of the Project area would be transplanted to a holding area south of the
leach pad within the Project mine and process area. The holding area would
serve to temporarily hold plant specimens prior to placement during final
reclamation. The holding area would be sized to hold approximately 250 transplant
specimens. The area would be prepared using salvaged soil and would be watered
as necessary.
2.1.11.3.7. Schedule
Soil distribution and revegetation activities are limited by the time
of year during which they can be effectively implemented. Table 2.4
outlines the anticipated annual revegetation activities schedule on a monthly
basis which would be followed to achieve the reclamation goals and adequate
revegetation. Site conditions and/or yearly climatic variations may require
that this activities schedule be modified to achieve revegetation success.
Table 2.4
| TECHNIQUES |
MONTH |
| J |
F |
M |
A |
M |
J |
J |
A |
S |
O |
N |
D |
| Soil Distribution |
|
|
|
|
|
|
|
|
|
|
|
|
| Regrading/Seedbed Preparation |
|
|
|
|
|
|
|
|
|
|
|
|
| Seeding |
|
|
|
|
|
|
|
|
|
|
|
|
| Transplanting from Storage |
|
|
|
|
|
|
|
|
|
|
|
|
| Note: Regrading, transplanting or seeding activities could occur year round. |
By sowing seed and planting in the fall/winter and utilizing the available
soil moisture accumulated during winter, growth would be encouraged for
most seeds in the seed mix of endemic species. Two kinds of germination
are common: (1) fall or winter annuals and shrubs; and (2) spring
or early summer germinators, generally shrubs and trees. Some native plant
seed have been observed to germinate at any time of year after a substantial
rain. Reclamation has a better chance for success in years with average
and above-average precipitation, especially if adequate moisture is available
during the November through April time period.
Milestone dates for the completion of certain mining and reclamation activities
are presented in Table 2.5. The completion
dates of the various elements shown are based upon final completion of leaching,
neutralization of the heap, and mining activities. Early or late completion
dates in any of the activities for a leach pad would result in a corresponding
change in the timing of the subsequent dates.
Table 2.5
YEAR |
RECLAMATION ACTIVITIES PLANNED |
| 1 |
West Pit diversion channels installed and concurrently reclaimed.
Remaining West Pit area soils salvaged and stockpiled.
Sediment catchment basins installed around Project facilities.
Selected plant specimens transplanted to temporary holding area.
Transmission line and water pipeline areas reclaimed. |
| 2 |
Reclamation test plots installed in wash habitat.
West pit slope stability reanalyzed. |
| 3 |
Singer Pit and East Pit East diversion channels installed and concurrently
reclaimed.
Singer Pit and East Pit area soil salvaged and stockpiled. |
| 4 |
East waste rock stockpile completed with revegetation test plots.
Selected plant specimens transplanted to temporary holding area.
East pit slope stability reanalyzed. |
| 5 |
Backfilling West Pit completed.
Revegetation test plots and reclamation on south slopes of the South
waste rock stockpile started. |
| 6 |
Singer Pit backfill completed.
East Pit West diversion channel installed and concurrently reclaimed.
East Pit West wash channel area soil salvaged and stockpiled. |
| 6-10 |
On-going reclamation testing and monitoring.
Indian Pass Road returned to location parallel to and east of the
West Pit West diversion channel.
Relocated portion of Indian Pass Road reclaimed. |
| 10-15 |
Heap leach facility neutralized
Initial heap leach pad reclamation.
Slopes reduced, catchment basins installed, and undulating land forms
constructed on South waste rock stockpile. |
| 15-20 |
Final reclamation of heap leach pad.
All remaining facilities removed and/or reclaimed.
Reclamation success monitored and final bond release. |
2.1.11.3.8. Weed Control
Weed control in this extreme desert climate has not proven to be a problem
at the nearby Picacho Mine or at other mines in the Cargo Muchacho Mountains.
As the revegetation process progresses, the natural succession of species
would tend to foster those species best adapted to a particular site. Weed
species in revegetated areas would be managed when they threaten the success
of the proposed reclamat |
