3. AFFECTED ENVIRONMENT
3.1. Geology and Mineral Resources
3.1.1. Geological Setting
The Project mine and process area is located in southeast California
within the Colorado Desert portion of the Basin and Range physiographic
province along the southwestern flank of the Chocolate Mountains (Norris
and Webb 1976). The southeastern portion of the Chocolate Mountains consists
largely of Jurassic age (180 to 135 million years ago) gneisses and
schists overlain by Tertiary age (65 to 1 million years ago) basalts, fanglomerates,
and Quaternary age (1 million years ago to present) alluvium (see Figure 3.1).
A thin veneer of flood basalt caps the gravel and forms distinct ridges
and land forms (Clark 1970).
About 95 percent of the Project mine and process area consists of Quaternary
age alluvium (in the active ephemeral stream channels) and older alluvium
(in the upland areas), which vary in thickness from 10 to 1,000 feet.
Below the Quaternary age sediments, the geologic section in the Project
mine and process area consists of the Jurassic schist and gneiss units unconformably
overlain by Tertiary andesite and basalts (see Figure 3.2).
The lowermost unit that would be exposed during mining activities is an
undifferentiated Jurassic gneiss which forms the footwall to the orebody
(Personal Communication, Dan Purvance, Chemgold, 1996). Generally above
the undifferentiated gneiss is a biotite gneiss which has sericitic schist
zones that appear to be structurally and/or hydrothermally localized. The
biotite gneiss varies from a white quartzo-feldspathic rock to a dark gray
hornblende-biotite gneiss. Often the biotite gneiss has a shatter-breccia
texture that is variably cemented by iron oxides, clays and less commonly
quartz or carbonate. The sericitic schist is a white, red-to-tan iron-oxide-stained
rock composed predominantly of sericite with quartz. The sericite schist
is weak and highly foliated.
A discontinuous horizon of Tertiary basalt flows and volcanicistic mudflows
(and/or paleosoil horizons) with basaltic fragments rest unconformably on
the Jurassic rocks (Personal Communication, Dan Purvance, Chemgold, 1996).
This volcanic unit is discontinuous and thin, ranging from zero (0)
to 100 feet in thickness within the Project mine and process area.
A Tertiary age conglomerate overlies the volcanics, or lies directly on
the Jurassic metamorphics where the volcanics are absent. The conglomerate
is typically a moderately well indurated, clay/carbonate/iron oxide-cemented
material with coarse, subangular gneissic fragments in a moderate- to coarse-grained
sand matrix with considerable mica component. Zones of finer-grained material,
including silty sands and silts, are present locally.
Dominant regional structural features include the Chocolate Mountains
thrust fault, which placed basal gneissic rocks over the younger Orocopia
Schist (see Figure 3.1), and the San Andreas fault system. The
Project mine and process area is structurally aligned and equidistant between
the Picacho Mine and Mesquite Mine gold deposits. A complex geologic setting
exists within the area as evidenced by detachment fault features identified
at the Picacho Mine and American Girl Mine and intricate strike-slip fault
systems identified at the Mesquite Mine (Tosdal, et al. 1991). Structural
patterns within the Project mine and process area identified by exploration
drilling to date consist of west-northwest to northwest trending faults
cut by northeast trending high angle faults (Personal Communication, Dan
Purvance, Chemgold, 1996). A south-southwest dipping low angle fault bounds
the orebody at its base and along the north side (see Figure 3.2).
The Imperial Valley is at the southern end of the San Andreas Fault system,
probably the most studied and best known fault system in the United States.
The San Andreas system transects the northeastern margin of the Imperial
Valley approximately 63 miles northwest of the Project mine and process
area (see Figure 3.3). Other major Holocene age (10,000 years
ago to present) faults also shown within the region on Figure 3.3
include several faults which parallel, or are "en echelon"
to, the southern section of the San Andreas Fault, most notably the reported
East Mesa Fault, the East Highline Canal lineament, the Imperial-Brawley
Seismic Zone, the Superstition Hills Fault (San Jacinto Fault Zone), and
the Elsinore Fault. Some geologic references for the area also indicate
the possible existence of a postulated fault (Sand Hills Fault) beneath
the Algodones Sand Dunes, which may represent the inactive eastern boundary
of the Salton Trough spreading center (Heath 1992). No evidence has been
documented to indicate that the Sand Hills Fault has been active in Holocene
time. The active faults currently associated with the eastern boundary of
the Salton Trough are now coincident with the East Mesa Fault and possibly
the East Highline Lineament (Heath 1992). Figure 3.4 shows that
the Project area itself is located in a relatively aseismic portion of Imperial
County (BLM and ICPBD 1993b).
Geologic relationships in the nearby Mesquite Mine indicate that northwest-
and northeast-trending faults which control mineralization are known to
be pre-Holocene in age (greater than 10,000 years old). The Miocene-Pliocene
Age (3 to 11 million year old) Bear Canyon Conglomerate has been
cut by a northeast-trending system that is no younger than late Pleistocene
Age (about 10,000 to 60,000 years old). Faults mapped in the Mesquite
Mine pits have not ruptured the 35,000 to 40,000 year old alluvial surfaces
within the Mesquite project vicinity (Tosdal, et al. 1991).
3.1.2. Mineral Resources
The Project mine and process area is located midway between the historic
Mesquite, Picacho, Tumco and Cargo Muchacho gold mining districts south
of the Chocolate Mountains in eastern Imperial County, California (see Figure 3.5).
The first gold mining in the region is attributed to early Spanish communities
in the Cargo Muchacho Mountains in 1780 (Clark 1970). Mining interest in
the region increased soon after the Mexican War in 1848 and the advent of
the California Gold Rush in 1849, and peaked between 1870 and 1930. Production
from the mines at Picacho, Tumco, and American Girl peaked in the early
1900's, producing a cumulative total of approximately 500,000 ounces
of gold. Scattered, small-scale dry wash placer operations were attempted
throughout the region and many small tailings piles from these operations
are still visible. Increasing gold prices and bulk tonnage leaching technology
developed in the 1970's led to exploration and subsequent development of
open pits at the Picacho Mine in 1979, and the Mesquite and American Girl
mines in 1980.
Little mining history exists for the Project mine and process area itself.
Bedrock exposed in limited locations on the north side of the Project mine
and process area was first prospected by Dick and Alice Singer (Personal
Communication, Steve Baumann, Chemgold, 1995). Between 1982 and 1985, Gold
Fields Mining Corporation conducted a regional exploration program comprised
of aeromagnetic, gravity and resistivity surveys and stream wash geochemical
studies. Gravity anomalies, low-grade mineralization in exposed bedrock,
and a very limited drilling program led to the discovery of minor mineralization
in the fringe areas of the current Imperial Project mine and process area.
In 1987, Glamis Gold Exploration, Inc. (GGX) acquired the mining claims
and began exploration drilling through a joint venture agreement with a
third party. In 1994, GGX became the sole owner and operator of the claims
and initiated an accelerated development drilling and pre-feasibility program.
This program ultimately culminated in the delineation of the three (3) ore
bodies designated by the proposed East Pit, Singer Pit and West Pit. In
1997, all of the claims were assigned to Glamis Imperial Corporation (Personal
Communication, Steve Baumann, Glamis Imperial, 1997).
Gold and silver mineralization at the Project mine and process area occurs
in Jurassic-age granitic gneiss in the upper plate of the Chocolate Mountains
thrust (see Figure 3.1). The thrust has an estimated throw of
48 kilometers to the northeast, moving gneiss and intrusive rocks over
greenschist facies schists. Analysis of drill information indicates that
the deposit's geology is similar to that observed at the nearby Picacho
Mine and Mesquite Mine gold deposits. The mineralization occurs in sub-tabular
blocks averaging 200 to 300 feet thick and is structurally controlled
by the intersection of low-angle and high-angle shear zones which are localized
to the ore body (see Figure 3.2) (Personal Communication, Dan
Purvance, Chemgold, 1996).
Gold and silver are associated with limonite and hematite in highly sheared
and brecciated gneiss, and minor hydrothermal alteration is present as a
weak form of sericitization. Oxidation extends to depths in excess of 1,500 feet
below ground surface and, to date, no pyrite or other sulfide minerals have
been observed in the ore or waste rock, other than oxidized remnants of
pyrite in some drill cuttings.
No other economically recoverable mineral resources are known within the
Project area.
3.2. Soil Resources
A report of the soil inventory conducted for the Project mine and process
area was prepared in June, 1995 (Bamberg and Hanne 1995a; see Attachment D
to Appendix A). The inventory report identified the various soil series
mapped in the Project mine and process area, discussed the salvage potential
and suitability of the soil material for reclamation activities, and contained
recommendations for reclamation and revegetation activities in the area.
Most of the Project mine and process area is covered by desert pavement.
The dominant mapped soil units are generally representative of relic paleosoils
which formed under cool, moist conditions, not the hot, arid conditions
of the current climate. A summary of the principal characteristics of the
four (4) soil units identified in the Project mine and process area
are presented in Table 3.1. The most notable
aspects of the four (4) major types of soil are: coarse texture with
large fragments; low organic matter and few available nutrients; high salts
and excess alkalinity; and, in some of the soils, high concentrations of
other chemicals, such as boron and nitrates. Soil depths vary from as shallow
as two (2) inches to generally less than 24 inches.
Table 3.1
Taxonomic
and Mapping Unit |
Classification |
Topographic Position |
Unit Salvageable
(percent) |
Salvage Volume
(cu.yd.) |
Soil Depth
(in.) |
Primary Salvage Limitations |
A
(Laprosa/Rock outcrop complex) |
Exposed weathered gneiss and sandy-skeletal, mixed, lithic Haplocalcids |
Low ridges, dissected |
0 |
0 |
0-20 |
Rock outcrop, surface rubble |
| B |
Sandy-skeletal, mixed hyperthermic, Torriopsamments |
Recent alluvial fans and washes |
50 |
16,800 |
0-20 |
Gravel texture, rock |
| C |
Sandy-skeletal, mixed hyperthermic Torriopsamments |
Shallow washes along drainages |
65 |
26,200 |
18-24 |
Shallow, narrow extent |
| D |
Sandy-skeletal, mixed, hyperthermic Petrocalcids |
Old alluvial upland flats and slopes |
3 |
69,200 |
0-24 |
Salt content, mixed alluvium, rock |
Source: Bamberg and Hanne 1995a
3.3. Hydrologic Resources
3.3.1. Surface Waters
In addition to other changes, this section has been modified from the
November 1996 Draft EIR in response to comments to: include a discussion
of flood zones; add a discussion of the small, ephemeral seeps located in
the vicinity of the Project ground water well field area; and add a new
delineation of "waters of the United States."
The Project area is located within the Salton Sea Drainage, a closed hydrologic
basin in which all surface flows drain toward the Salton Sea, a saline water
body which has no outlet. However, surface water which flows from or through
the general vicinity of the Project area (herein termed the "Indian
Wash Drainage Basin") is prevented from reaching the Salton Sea by
the Algodones Sand Dunes, a natural topographic constraint located approximately
12 miles downstream of the Project mine and process area to the southwest
(see Figure 3.5). Surface flows either evaporate or infiltrate
into the wash bottoms or outwash areas east of the Algodones Sand Dunes.
There are no free-standing surface waters present within the Project area
or vicinity. There are no springs, seeps or streams within the Project area.
The region's low precipitation rate, coupled with the high evaporation rate
and the presence of highly permeable soils in the washes, preclude the formation
of perennial or intermittent streams. The perennial water source located
closest to the Project mine and process area is the Colorado River, approximately
seven (7) miles northeast of the Project mine and process area at its closest
point, which is outside of the Salton Sea Drainage Basin, on the other side
of the Chocolate Mountains. The perennial water sources located within the
Salton Sea Drainage Basin closest to the Project mine and process area are
the All American Canal, approximately sixteen (16) miles south, and
the Coachella Canal, a branch of the All American Canal, approximately nineteen (19)
miles southwest, on the other side of the Algodones Sand Dunes. The All
American Canal, which transports water from the Colorado River, is the primary
source of water within the Salton Sea Drainage Basin.
Several small, isolated, ephemeral water seeps are located northwest to
southwest of the Project ground water well production area, in the vicinity
of or adjacent to the Algodones Sand Dunes, at a distance of five (5)
miles or more from the Project water production well area and more than
eight (8) miles from the Project mine and process area (Personal Communication,
Randy Rister, ICFGC, June 26, 1997). The source of the water for the
seeps has not been identified in any area hydrologic studies; however, because
the depth to ground water in the Project ground water well field area is
several hundred feet below ground surface, it is believed that the seeps
result from near-surface flows of water as sub-flow in ephemeral stream
channels, or the seepage of precipitation which falls on the Algodones Sand
Dunes.
3.3.1.1. Surface Flows
Surface water drainages within the Project area consist of a series of
subparallel ephemeral washes which are fed by precipitation from infrequent
winter storms and summer thunderstorms. Four (4) primary washes flow
into the Project mine and process area (herein named the West Pit West,
West Pit East, East Pit West, and East Pit East). Two (2) of these
washes (West Pit East and East Pit West) flow together within the Project
mine and process area, such that only three (3) major washes (West
Pit West, Central, and East Pit East) exit the Project mine and process
area (see Figure 3.6). Central Wash and East Pit East Wash flow
into Indian Wash approximately two (2) miles downstream of the Project
mine and process area, and West Pit East and Indian Wash each eventually
end in individual areas of infiltration on the eastern edge of the Algodones
Sand Dunes (see Figure 3.5).
The local catchment areas for these four (4) washes were determined
(see Figure 3.7), and estimates of peak flow in each of the washes
at the upstream boundary of the Project mine and process area calculated,
through use of a simple computer model, for the 100-year, 6- and 24-hour,
and the 500-year, 24-hour storm events (Hanson 1997a; Hanson 1997c). Table 3.2 presents these catchment areas and
peak flow estimates for these storms for each of the four (4) washes.
Table 3.2
| Storm Event |
Precipitation
(inches) |
Peak Runoff by Diversion
(cubic feet per second) |
| West Pit West |
West Pit East |
Singer Pit |
East Pit West |
East Pit East |
| Catchment Basin Area |
| 3.00 miles2 |
0.974 miles2 |
0.27 miles2 |
1.30 miles2 |
0.684 miles2 |
| 100-year/6-hr |
N/A |
2,121 |
888 |
N/A |
1,025 |
518 |
| 100-year/24-hr |
4.8 |
2,043 |
727 |
364 |
925 |
492 |
| 500-yr/24-hr |
N/A |
2,927 |
1,083 |
N/A |
1,394 |
704 |
Source: Hanson 1997a; Hanson 1997b
3.3.1.2. Water Quality
No direct data regarding the quality of the surface waters which occasionally
flow through the Project area are available. Because water flows in these
washes only during infrequent storm events, and because there is no substantial
surface disturbance nor unusual natural sources of contaminants located
upstream, the quality of the water flows are assumed to be typical of similar
desert washes (i.e. very high in suspended solids and variable in dissolved
solids). Based upon observations made in the field (EMA 1996a), the principal
throughgoing stream channels appear to be currently undergoing very little
geomorphic change.
3.3.1.3. Flood Zones
Federal Emergency Management Agency (FEMA) National Flood Insurance Program
Flood Insurance Rate Map (FIRM) for Imperial County, California (Unincorporated
Areas), Panel 700 of 1175, Community-Panel Number 060065 0700 B,
Effective Date: March 15, 1984, provides National Flood Insurance Program
designations for flood hazard areas in and around the Project area at a
scale of 1:24,000. In the immediate vicinity of the Project area, only two (2)
flood hazard zones are designated: Zone C, "Areas of minimal flooding;"
and Zone A, "Areas of 100-year flood, base flood elevations and
flood hazard factors not determined." Based upon an evaluation of the
FEMA map, all areas in the vicinity of the Project area are labeled as "Zone C"
except for two (2) narrow areas: one (1) along the ephemeral stream
channel adjacent to and northwest of Indian Pass Road; and one (1)
along the ephemeral stream channel which, in its upper reaches, is located
immediately southeast of the Project mine and process area (see Figure 3.8).
Executive Order 11988, effective May 24, 1977, requires federal
agencies to take certain actions to reduce the risk of flood loss, to minimize
the impact of floods on human safety, health and welfare, and to restore
and preserve the natural and beneficial values served by floodplains, which
are defined in the same manner as FEMA. Section 3(d) requires each
agency, in any right-of-way to be granted in or across a floodplain, to
reference in the conveyance those uses that are restricted under identified
federal, state or local floodplain regulations, and attach other appropriate
restrictions to the uses of the land properties or withhold the grant.
3.3.1.4. "Waters of the United States"
The U.S. Army Corps of Engineers (ACOE),
under Section 404 of the Clean Water Act, regulates the discharge of
dredged or fill material into "waters of the United States" (33 USC 1251-1376).
Permits must be obtained from the ACOE prior
to initiating discharges into jurisdictional "waters of the United
States." Pursuant to applicable regulations (40 CFR 230.10),
no permit for the discharge of dredged or fill material would be granted
by the ACOE if: there is a practicable alternative
to the proposed discharge which would have less adverse impact on the aquatic
ecosystem; or if the discharge causes or contributes, after consideration
of disposal site dilution and dispersion, to violations of any applicable
state water quality standard; violates any applicable toxic effluent standard
or prohibition; jeopardizes the continued existence of species listed as
endangered under the federal Endangered Species Act; causes or contributes
to substantial degradation of the "waters of the United States";
or unless appropriate and practicable steps have been taken which would
minimize potential adverse impacts of the discharge on the aquatic ecosystem.
Pursuant to 33 CFR 325.4, the ACOE
may take into account the existence of controls imposed under other federal,
state, or local programs which would achieve the objective of the desired
condition, or the existence of an enforceable agreement between the applicant
and another party concerned with the resource in question.
"Waters" are broadly defined at 33 CFR 328.2 to include
non-tidal waters, including intermittent watercourses (commonly known as
>isolated waters=) (33 CFR 328.3(a)(3)) and tributaries to
such watercourses (33 CFR 328.3(a)(5)). "Isolated waters
of the United States" include "All other waters such as intrastate
lakes, rivers, streams (including intermittent streams), mudflats, sandflats,
wetlands, sloughs, prairie potholes, wet meadows, playa lakes, or natural
ponds, the use, degradation, or destruction of which could affect interstate
or foreign commerce...", including those "which are or would be
used as habitat by birds protected by Migratory Bird Treaties; or which
are or would be used as habitat by other migratory birds which cross state
lines; or which are or would be used as habitat for endangered species;
or used to irrigate crops sold in interstate commence" (51 FR 41217).
The limits of ACOE jurisdiction on "non-tidal
waters of the United States" extend to the "ordinary high water
mark" (OHWM), in the absence of adjacent wetlands (33 CFR 328.4©(1));
or beyond the OHWM to the limits of the adjacent wetlands, when adjacent
wetlands are present (33 CFR 328.4©(2)); or to the limits
of the wetlands when only wetlands are present (33 CFR 328.4©(3)).
Surveys were performed to identify "waters of the United States,"
including wetlands, in and around the Project mine and process area (LSA
1997a [see Appendix D]). The surveys inventoried each of the principal
throughgoing ephemeral washes within the Project mine and process area,
as well as all tributaries, to determine which met the criteria of "waters"
and "waters of the United States" (see Figure 3.9).
No wetlands were identified within the Project mine and process area. However,
114.5 acres of land within the Project mine and process area were determined
to be within the OHWM of the washes, and thus were determined to be "waters"
under the applicable definitions (LSA 1997a). All of the 114.5 acres
were determined to qualify as "waters of the United States," although
some upland areas (i.e. islands within braided systems) were included that
were not within the jurisdictional "waters of the United States"
as a matter of expediency. It is expected that were a detailed, intensive
survey of all areas encompassing Awaters of the United States@ to be conducted,
it would reveal that the actual extent of ACOE
jurisdictional "waters" is less than 114.5 acres (LSA 1997a).
This delineation has been submitted to the ACOE
for concurrence; however, as of September 1997, the ACOE
has not responded (Personal Communication, Jack Easton, LSA Associates,
Inc., September 12, 1997).
The 114.5-acre jurisdictional "waters of the United States" area
consists of ephemeral drainage courses and their tributaries which have
the following characteristics (LSA 1997a):
- An "ordinary high water mark" (OHWM), which is evident along
each of the jurisdictional drainage courses.
- Support, or are tributary to areas that support, vegetation that may
be used as habitat by birds that are protected under Migratory Bird Treaties.
Further, the vegetation supported by the intermittent streams is substantially
different from the vegetation of the adjacent upland areas.
- Are non-tidal, not a part of a surface tributary system to interstate
or navigable waters, and not adjacent to such tributary water bodies.
Based on these three (3) factors, identified drainage courses on
the Project mine and process area are considered to meet the definition
of "isolated waters of the United States," and are, therefore,
subject to the jurisdiction and permitting authority of the ACOE.
Tributaries to "isolated waters of the United States" are also
subject to the ACOE's jurisdiction and permitting
authority. Due to the absence of any hydrophytic vegetation, none of the
jurisdictional drainage courses meet the definition of "wetlands."
3.3.2. Ground Waters
In addition to other changes, this section has been modified from the
November 1996 Draft EIR in response to comments to: clarify the relationship
of the ground waters in the Project area to the Colorado River aquifer; and reduce the estimated quantity of water
seeping from All American Canal to the Amos-Ogilby-East
Mesa Basin.
The Project area is located within what has recently been termed the Amos-Ogilby-East
Mesa ground water basin (Environmental Solutions, Inc. 1993a; WESTEC, Inc.1996a),
which is roughly equivalent to the "Sand Hills Area" and "East
Mesa Area" described by Dutcher, et. al. (1972). The basin is a northwesterly
trending, elongated area of approximately 860 square miles within the
southeastern portion of Imperial County, California, but which likely extends
for hundreds of additional square miles into northern Mexico. It is bounded
on the northeast by the Chocolate Mountains, on the north by the surface
drainage/ground water divide which separates the Amos Basin from the East
Salton Sea Basin, on the west by the finer sediments in the irrigated portion
of the Imperial Valley, and to the south by the arbitrary political boundary
with Mexico (see Figure 3.10). The alluvial sediments which
make up the water-bearing aquifer range in
thickness from zero (0) feet on the eastern boundary at the Chocolate
Mountains to as much as 10,000 feet at the western boundary in the
Imperial Valley (Environmental Solutions, Inc. 1993a).
3.3.2.1. Ground Water Quantity
The principal historic source of recharge to the water-bearing deposits
within the Amos-Ogilby-East
Mesa Basin has been reported to be from the Colorado River and, more
recently, leakage from the All American and Coachella Canals (see Figure 3.10).
An estimated 20,000 afy enters the basin
from the Colorado River as underflow between the Cargo Muchacho Mountains
and Pilot Knob. In addition, the USGS (Loetz 1975) estimated that in the
late 1960's, the All American and Coachella Canals contributed about 100,000
and 130,000 afy, respectively, to the ground
water basin. Relatively little recharge comes from infiltration of local
precipitation and runoff. Since the lining of the first 45 miles of
the Coachella Canal in the 1980's essentially eliminated leakage from the
Coachella Canal, total recharge to the basin was roughly estimated in 1993
at 100,000 afy (Environmental Solutions,
Inc. 1993a). However, it is currently believed that the distribution of
low permeability materials to the north and east of the All American Canal,
as well as the extensive pumping of ground water south of the All American
Canal in Mexico, may limit the seepage of ground water from the All American
Canal into the Amos-Ogilby-East Mesa basin (Personal Communication, Carol
Brown, United States Bureau of Reclamation [USBR], April 21, 1997;
Watt 1991). Therefore, the annual recharge into the Amos-Ogilby-East Mesa
Basin may be more correctly conservatively estimated at approximately 30,000 afy; 20,000 afy
of seepage from the Colorado River and 10,000 afy
of leakage from the All American Canal.
Although the principal source of recharge to the Amos-Ogilby-East
Mesa Basin is reported to be from the Colorado River and leakage from
the All American Canal, the United States Geological Survey (USGS) recently
determined that the Project mine and process area is outside of the Colorado
River aquifer (Wilson, et al. 1994); that
is, it is outside of that area from which ground water production would
be replaced by Colorado River water, and thus no federal water appropriations
permit would be required if ground water was produced from this area. However,
this USGS study evaluated the Colorado River system only from Hoover Dam
to Laguna Dam, and although the Project mine and process area is clearly
within the boundary of the USGS study area, the Project ground water test
well PW-1 and the Project ground water well field are located immediately
to the west (outside) of the boundary of this USGS study. The U.S. Bureau
of Reclamation has recently terminated its study of the boundary of the
Colorado River aquifer outside of the area
studied by the USGS, and the USGS has no immediate plans to expand the area
of their previous study (Personal Communication, Jeff Adagio, USBR, July 1,
1997).
The water currently in storage within the nonmarine deposits of late Tertiary
and Quaternary age of the Amos-Ogilby-East
Mesa Basin to a depth of 3,000 feet is estimated at approximately
230,000,000 acre-feet (Environmental Solutions, Inc. 1993a). Ground
water stored in the Amos-Ogilby portion of this basin only is estimated
at approximately 126,000,000 acre-feet (BLM
and ICPBD 1995). Lower stratigraphic units found in the western portions
of the Amos-Ogilby-East Mesa
Basin and under the East Mesa area frequently produce geothermal waters
of elevated temperature (Dutcher, et. al. 1972).
The area of the local catchment upgradient of the Project ground water well
field area has been estimated at approximately 30,000 acres. Since
the average annual rainfall at the neighboring Gold Rock Ranch is approximately
3.60 inches (or 0.3 feet) (GSi/Water 1993), a conservative average
of 9,000 afy of precipitation falls within
the catchment area. However, since nearly all of the precipitation falling
within the catchment area evaporates or is consumed by plants in the vegetated
portions of the basin, relatively little precipitation infiltrates and actually
provides basin recharge (Environmental Solutions, Inc. 1993a). Estimates
of the infiltration percentage range from one (1) to ten (10)
percent, which translates to 90 to 900 afy
of ground water recharge into the basin upgradient of the Project well field
production area (GSi/Water 1993).
The Project area is underlain by undifferentiated alluvial and lacustrine
deposits of Quaternary and Tertiary age which rapidly thicken from the Chocolate
Mountains towards the desert floor to the southwest (Personal Communication,
Dan Purvance, Chemgold, 1996). The alluvium within the Project mine and
process area ranges from 10 feet to as much as 1,000 feet in places
(WESTEC, Inc. 1996a).
Ground water beneath the Project area occurs within three (3) different
aquifers (see Figure 3.11
and Figure 3.12): an unconfined alluvial aquifer
(the uppermost aquifer, which has a water table which is open to direct infiltration);
a confined alluvial aquifer (which is bounded
both above and below by relatively low permeability (impermeable) beds);
and a bedrock aquifer. The alluvial aquifers consist of consolidated and unconsolidated
sands and gravels. The bedrock aquifer is
comprised of fractured and jointed gneissic and granitic rocks (WESTEC,
Inc. 1996a).
Ground water flow within the Project area generally follows the topographic
gradient, from the higher elevations toward the alluvial basin of the valley
floor, and the ground water gradient is generally from the northeast to
the southwest (WESTEC, Inc. 1996a).
Two (2) ground water monitoring wells, thirteen (13) piezometer
holes, and one (1) ground water production test well were installed
by Glamis Imperial and its consultants in order to obtain more specific
information regarding the characteristics of the alluvial and bedrock aquifers in the Project area (WESTEC, Inc. 1996a,
and EMA 1996c; see Appendix E-1 and Appendix E-2 of this EIS/EIR).
Figure 3.13 is a map of the locations of these holes and wells
and the static ground water level (potentiometric) surface derived from
these holes and wells. Table 3.3 provides
the physical data (name, location, depth to ground water, and aquifer)
for those holes and wells from which water quality data has been obtained.
Table 3.3
| Hole Number |
Location |
Total Depth |
Depth to Static Water |
Aquifer |
| (ft bgs) |
| Piezometer Holes |
| H-1 |
Mine and Process Area |
1,000 |
657.2 |
Alluvial (unconfined) |
| H-2 |
Abandoned |
N/A |
N/A |
N/A |
| H-3 |
Mine and Process Area |
1,100 |
695.0 |
Bedrock |
| H-4 |
Ancillary Area |
1,000 |
545.0 |
Alluvial (confined) |
| H-5 |
Ancillary Area |
1,080 |
595.0 |
Alluvial (unconfined) |
| H-6 |
North of Ancillary Area |
920 |
631.0 |
Alluvial (confined) |
| H-7 |
Ancillary Area |
950 |
528.0 |
Alluvial (confined) |
| H-8 |
Indian Pass/Ogilby Rd. |
950 |
480.0 |
Alluvial (confined) |
| ER-2 |
Mine and Process Area |
930 |
522.0 |
Bedrock |
| EC-5 |
Mine and Process Area |
800 |
720.0 |
Bedrock |
| WR-1 |
Mine and Process Area |
910 |
734.0 |
Bedrock |
| WR-31 |
Mine and Process Area |
900 |
682.0 |
Alluvial (unconfined) |
| WC-5 |
Mine and Process Area |
800 |
606.0 |
Bedrock |
| WR-2 |
Mine and Process Area |
945 |
694.5 |
Alluvial (unconfined) |
| Monitoring Wells |
| MW-1 |
Mine and Process Area |
640 |
479.7 |
Conglomerate (bedrock) |
| MW-2 |
Mine and Process Area |
880 |
626.2 |
Bedrock |
| Test Production Well |
| PW-1 |
Water Supply Area |
960 |
544.4 |
Alluvial (confined) |
Source: WESTEC, Inc. 1996a; EMA 1996c
Static ground water elevations measured in the wells completed in the
alluvial aquifers (94H-1, WR-2, and PW-1)
ranged from a high of 360 feet AMSL immediately
northeast of the Project mine and process area to a low of 70.5 feet
AMSL in the southwest corner of the Project
mine and process area, which produces a gradient from northeast to southwest.
Variations in measured static water levels were attributed to the wells
being completed in the different aquifers
(WESTEC, Inc. 1996a; EMA 1996c).
Static ground water elevations measured in the wells completed in the bedrock
aquifer (EC-5, WC-5, and MW-2) ranged from
a high of 211 feet AMSL in the area of
the proposed West Pit to a low of 85.5 feet AMSL
approximately two (2) miles southwest of the Project mine and process
area. With the exception of the elevation in the West Pit, all of the bedrock
aquifer measurements produced an essentially
flat surface; the anomalously high West Pit bedrock aquifer
elevation was attributed to either the fracture-controlled nature of the
aquifer or an unknown ground water barrier
between the two (2) proposed pits (WESTEC, Inc. 1996a).
Aquifer testing was performed in the Project area to evaluate the hydrogeologic
characteristics of the underlying geologic materials (WESTEC, Inc. 1996a;
see Appendix E-1 of this EIS/EIR). Slug tests were conducted in the
piezometer wells completed in the confined alluvial and bedrock aquifers. Falling head tests were conducted in the
bedrock piezometers; however, falling head tests could not be performed
in the alluvial piezometers due to the increased permeability of the alluvial
material that would not allow a sufficient column of water to be maintained
in the well during the tests. Slug and falling head tests generally yield
data that are of low confidence; however, the multiple tests conducted do
give some indication of the permeability of the alluvial and bedrock aquifers. The results of the slug and falling
head tests are shown in Table 3.4.
Table 3.4
| Hole Number |
Test |
Hydraulic Conductivity |
Aquifer Formation |
| cm/sec |
ft/day |
| H-4 |
Slug |
2.8 x 10-3 |
7.9 |
alluvial |
| EC-5 |
Slug |
3.8 x 10-7 |
1.1 x 10-3 |
bedrock |
| WC-5 |
Slug |
8.4 x 10-7 |
2.4 x 10-3 |
bedrock |
| EC-5 |
Falling Head |
3.5 x 10-7 |
9.9 x 10-4 |
bedrock |
| WC-5 |
Falling Head |
1.4 x 10-6 |
4.0 x 10-3 |
bedrock |
| H-5 |
Slug |
1.05 x 10-2 |
29.8 |
bedrock |
Source: WESTEC, Inc. 1996a; EMA 1996c
Well H-5 was screened in highly fractured bedrock and the hydraulic conductivity
calculated from the slug test is much higher than those calculated from
slug tests conducted on wells EC-5 and WC-5. In addition, wells EC-5 and
WC-5 are both located in the mine and process facilities area and well H-5
is located approximately 3.3 miles to the southwest of the mine area.
The different locations of the wells could account for fracture heterogeneities
in the bedrock and the differences in the calculated hydraulic conductivities.
A constant rate pump and recovery test was conducted in the production test
well (PW-1) completed in the confined alluvial aquifer.
The pump test was conducted to evaluate the transmissivity
and storage coefficient of the alluvial sediments in the vicinity of PW-1,
which is located approximately 3.5 miles southwest of the Project mine
and process area. A pumping test was conducted for 48-hours at a constant
pumping rate of 500 gallons per minute (gpm). Ground water was produced
from approximately 200 feet of saturated alluvial sediments, equivalent
to the length of the screened interval, at a depth between 718 and 918 feet
below ground surface (bgs). Piezometer H-4, located
91 feet west of PW-1, was used as an observation well to measure the
drawdown effects of the pumping test on PW-1. The depth to ground water
in PW-1 and H-4 was measured throughout the entire time the pumping test
was being conducted. Total drawdown of ground water in PW-1 at the end of
the 48-hour pumping test was 130 feet, most of which occurred during
the first five (5) minutes of the test. The water level data collected
during the pumping test were used to calculate the hydraulic characteristics
of the confined alluvial aquifer using the
Theis and Jacob methods (Kruseman 1991). The drawdown curve, showing the
change in drawdown of the ground water in the observation well versus time,
was matched with a Theis Curve for a confined aquifer
showing leakage through one of the confining layers. The transmissivity
(T), storativity (S), and hydraulic conductivity (K) of
the confined alluvial aquifer, calculated
from the pumping test and assuming a saturated thickness of 200 feet,
are shown in Table 3.5.
Table 3.5
| Method |
Well |
T (ft2/day) |
S |
K (ft/day) |
K (cm/sec) |
| Theis |
H-4 |
1,645 |
0.03 |
8.0 |
2.8 x 10-3 |
| Cooper-Jacob |
H-4 (drawdown) |
2,701 - 5,403 |
0.003 - 0.02 |
14 - 27 |
4.9x10-3 - 9.5x10-3 |
| Cooper-Jacob |
PW-1 (drawdown) |
965 - 5,017 |
not calculated |
5.0 - 25 |
1.8x10-3 - 8.8x10-3 |
| Cooper-Jacob |
H-4 (recovery) |
2,680 - 5,696 |
0.001 |
13 - 28 |
4.6x10-3 - 9.9x10-3 |
| Cooper-Jacob |
PW-1 (recovery) |
1,737 - 4,438 |
not calculated |
9.0 - 22 |
3.2x10-3 - 7.8x10-3 |
Source: WESTEC, Inc. 1996a
There is currently no ground water being produced from beneath the Project
area. Limited pumping of ground water occurs from the Amos-Ogilby-East Mesa
Basin in the immediate vicinity of the Project area, this from: a well located
at Gold Rock Ranch (approximately four and one-half (4.5) miles southwest
of the Project ground water well field area); two (2) wells located
at the American Girl Mine (approximately eight (8) miles south of the
Project ground water well field area); and three (3) production wells
for the Mesquite Mine located southeast of the Mesquite Mine itself (and
approximately eight (8) miles west-northwest of the Project ground
water well field area) (see Figure 3.10). The produced ground
water is authorized for mining and domestic uses.
The well at the Gold Rock Ranch is used to supply domestic water for the
ranch. Current usage is estimated at 5,000 gallons per day (gpd) [less
than six (6) afy], with an estimated historic
maximum usage rate of 12,000 gpd (less than fourteen (14) afy), as estimated by the owner (BLM
1994a). Ground water usage for the American Girl Mine operations was reported
as less than 200 afy (U.S. Bureau of Land
Management 1994b). However, American Girl Mine has recently curtailed mining
and milling operations and has substantially reduced its water consumption.
The rate of production of water from the Mesquite Mine wells was reported
at approximately 1,500 afy (Environmental
Solutions, Inc. 1993a).
3.3.2.2. Ground Water Quality
Ground water quality within the Amos-Ogilby-East
Mesa Basin consistently shows levels of total dissolved solids (TDS),
chloride, and fluoride which exceed drinking water standards (Environmental
Solutions, Inc. 1993a). TDS concentrations range from 1,100 mg/l in
the Mesquite Mine wells to greater than 3,000 mg/l in the Glamis and
Boardman wells (WESTEC, Inc. 1996a). In general, the ground water is not
suitable as drinking water without prior treatment, although the quality
is sufficient for use in mining operations.
Table 3.6 provides water quality data for
the Project ground water monitoring and production wells. Filtered samples
from the upgradient monitoring well (MW-1) met all primary drinking water
standards, but exceeded the secondary drinking water standards for TDS and
manganese. The downgradient monitoring well (MW-2) met all primary drinking
water standards except for arsenic, and exceeded secondary drinking water
standards for chloride, manganese, sulfate, and TDS. The production test
well (PW-1) met all primary drinking water standards except for fluoride,
and exceeded secondary drinking water standards for chloride, iron, and
TDS. TDS levels were at the lower end of the range for wells completed within
the basin, and the water quality appears to be suitable for non-potable
uses (WESTEC, Inc. 1996a) [see Appendix E-1]. Stiff and Piper diagrams
(see Figure 3 in Appendix E-2) indicate that the dominant cation
species are sodium and potassium, while the dominant anion varies from sulfate
and carbonate/bicarbonate near the Project mine and process area to chloride
and sulfate in the alluvial basin.
Table 3.6
| Element |
Units |
Current Drinking Water Quality Standards |
Well Number |
MW-1 |
MW-1 |
MW-1 |
MW-1 |
MW-1 A |
MW-1 B |
MW-2 |
MW-2 |
MW-2 A |
MW-2 B |
PW-1 |
| Collection Date |
08/30/95 |
11/28/95 |
04/22/96 |
08/15/96 |
08/29/96 |
08/29/96 |
07/11/96 |
08/15/96 |
08/29/96 |
08/29/96 |
11/19/95 |
| Field Filtering |
unfiltered |
unfiltered |
unfiltered |
unfiltered |
filtered |
unfiltered |
unfiltered |
unfiltered |
filtered |
unfiltered |
filtered |
| Alkalinity |
mg/l |
|
138 |
183 |
183 |
171 |
163 |
186 |
246 |
169 |
95 |
195 |
32 |
| Aluminum |
mg/l |
1.0 (1)
0.02 (2) |
0.5 |
1.7 |
<0.1 |
0.3 |
<0.02 |
1.37 |
0.7 |
1.3 |
<0.02 |
4.03 |
<0.1 |
| Antimony |
mg/l |
0.006 (1) |
<0.5 |
<0.5 |
<0.04 |
<0.003 |
<0.005 |
<0.005 |
<0.003 |
<0.003 |
<0.005 |
<0.005 |
<0.002 |
| Arsenic |
mg/l |
0.05 (1) |
<0.005 |
0.005 |
0.02 |
<0.005 |
<0.01 |
0.01 |
<0.005 |
<0.005 |
0.09 |
0.11 |
0.009 |
| Barium |
mg/l |
1.0 (1) |
0.2 |
<0.1 |
0.2 |
<0.1 |
0.17 |
0.21 |
0.1 |
0.1 |
0.04 |
0.08 |
<0.1 |
| Beryllium |
mg/l |
0.004 (1) |
<0.1 |
<0.1 |
<0.002 |
<0.002 |
<0.001 |
0.001 |
<0.002 |
<0.002 |
<0.001 |
0.002 |
<0.0002 |
| Bismuth |
mg/l |
|
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<1 |
<1 |
<0.1 |
<0.1 |
<1 |
<1 |
<0.1 |
| Boron |
mg/l |
|
|
|
|
|
0.50 |
0.53 |
|
|
4.95 |
5.06 |
|
| Cadmium |
mg/l |
0.005 (1) |
0.0004 |
0.0006 |
<0.0002 |
<0.002 |
<0.005 |
<0.005 |
<0.002 |
<0.002 |
<0.005 |
<0.005 |
<0.0002 |
| Calcium |
mg/l |
|
83 |
38 |
53 |
34 |
49.4 |
57.1 |
64 |
80 |
67.3 |
108 |
57 |
| Chloride |
mg/l |
250 (2) |
92 |
110 |
91 |
39 |
56.1 |
61.1 |
130 |
120 |
641 |
606 |
320 |
| Chromium |
mg/l |
0.05 (1) |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.01 |
0.03 |
<0.1 |
<0.1 |
<0.01 |
0.07 |
<0.1 |
| Cobalt |
mg/l |
|
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.03 |
<0.03 |
<0.1 |
<0.1 |
<0.03 |
<0.03 |
<0.1 |
| Field Conductance |
Fmhos/cm |
|
|
|
|
|
832 |
832 |
|
|
2460 |
2460 |
|
| Copper |
mg/l |
1.0 (2) |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.01 |
<0.01 |
<0.1 |
<0.1 |
<0.01 |
0.03 |
<0.1 |
| Fluoride |
mg/l |
1.4 (1) |
0.2 |
0.5 |
0.2 |
0.3 |
0.6 |
0.6 |
0.2 |
0.2 |
0.6 |
0.6 |
1.6 |
| Gallium |
mg/l |
|
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.5 |
<0.5 |
<0.1 |
<0.1 |
<0.5 |
<0.5 |
<0.1 |
| Iron |
mg/l |
0.3 (2) |
1.4 |
3.4 |
<0.1 |
0.2 |
<0.03 |
4.39 |
0.5 |
1.7 |
<0.03 |
6.64 |
0.4 |
| Lead |
mg/l |
|
0.009 |
0.015 |
<0.002 |
<0.005 |
<0.003 |
0.049 |
<0.003 |
<0.005 |
<0.003 |
0.024 |
<0.002 |
| Lithium |
mg/l |
|
<0.1 |
<0.1 |
<0.1 |
<0.1 |
0.04 |
0.06 |
<0.1 |
<0.1 |
0.58 |
0.67 |
0.1 |
| Magnesium |
mg/l |
|
31 |
6 |
6.7 |
3.4 |
5.3 |
5.7 |
28 |
31 |
19.0 |
27.5 |
1.5 |
| Manganese |
mg/l |
0.05 (2) |
<0.1 |
0.3 |
0.1 |
<0.1 |
0.70 |
1.10 |
<0.1 |
0.20 |
0.09 |
0.50 |
<0.1 |
| Mercury |
mg/l |
0.002 (1) |
<0.0005 |
<0.0005 |
<0.0005 |
<0.0005 |
<0.0002 |
<0.0002 |
<0.0005 |
<0.0005 |
<0.0002 |
<0.0002 |
<0.0005 |
| Molybdenum |
mg/l |
|
<0.5 |
<0.5 |
<0.1 |
<0.1 |
<0.05 |
<0.05 |
<0.1 |
<0.1 |
0.12 |
0.06 |
<0.5 |
| Nickel |
mg/l |
0.1 (1) |
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.04 |
0.04 |
<0.1 |
<0.1 |
<0.04 |
0.08 |
<0.1 |
| Nitrate Nitrogen |
mg/l |
10 (1) |
0.1 |
0.6 |
<0.1 |
<0.1 |
0.13 |
0.05 |
0.2 |
0.3 |
0.07 |
<0.05 |
1.9 |
| pH |
mg/l |
6.8 - 8.5 |
7.99 |
7.6 |
7.47 |
7.29 |
7.69 |
7.51 |
7.79 |
7.49 |
7.70 |
7.64 |
8.2 |
| Phosphorous |
mg/l |
|
<0.1 |
0.3 |
<0.1 |
<0.1 |
0.09 |
0.31 |
<0.1 |
<0.1 |
0.03 |
0.80 |
<0.1 |
| Potassium |
mg/l |
|
6 |
6.9 |
4.7 |
4.1 |
6 |
10 |
8.6 |
5.9 |
10 |
20 |
0.1 |
| Scandium |
mg/l |
|
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.01 |
<0.01 |
<0.1 |
<0.1 |
<0.01 |
<0.01 |
<0.1 |
| Selenium |
mg/l |
0.05 (1) |
<0.001 |
<0.001 |
<0.001 |
<0.001 |
<0.01 |
<0.01 |
<0.001 |
0.001 |
<0.01 |
<0.01 |
<0.001 |
| Silver |
mg/l |
0.1 (2) |
<0.0005 |
<0.0005 |
<0.0005 |
<0.002 |
<0.01 |
<0.01 |
<0.002 |
<0.002 |
<0.01 |
<0.01 |
<0.0005 |
| Sodium |
mg/l |
|
130 |
200 |
160 |
150 |
159 |
135 |
140 |
150 |
537 |
463 |
260 |
| Strontium |
mg/l |
|
1.8 |
1.2 |
4.5 |
0.3 |
4.28 |
4.19 |
1.3 |
1.3 |
2.57 |
2.61 |
0.8 |
| Sulfate |
mg/l |
250 (2) |
290 |
200 |
210 |
160 |
230 |
211 |
320 |
270 |
360 |
230 |
180 |
| TDS |
mg/l |
500 (2) |
799 |
712 |
656 |
529 |
620 |
640 |
728 |
804 |
1780 |
1690 |
906 |
| Thallium |
mg/l |
0.002 (1) |
<1 |
<1 |
<0.0005 |
<0.001 |
<0.002 |
<0.005 |
<0.001 |
<0.001 |
<0.002 |
<0.005 |
0.001 |
| Tin |
mg/l |
|
<1 |
<1 |
<1 |
<0.5 |
<0.05 |
<0.05 |
<1 |
<0.5 |
<0.05 |
<0.05 |
<1 |
| Titanium |
mg/l |
|
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.01 |
<0.01 |
<0.1 |
0.1 |
<0.01 |
0.01 |
<0.1 |
| Vanadium |
mg/l |
|
<0.1 |
<0.1 |
<0.1 |
<0.1 |
<0.05 |
<0.05 |
<0.1 |
<0.1 |
<0.05 |
<0.05 |
<0.1 |
| Zinc |
mg/l |
5.0 (2) |
0.3 |
0.9 |
<0.1 |
<0.1 |
<0.01 |
0.06 |
<0.1 |
0.1 |
<0.01 |
0.26 |
<0.1 |
(1) California Primary Maximum Contaminant Limit
(2) California Secondary Maximum Contaminant Limit
Source: WESTEC, Inc. 1996a; Personal Communication, Dan Purvance, Glamis
Imperial, 1997
3.4. Air Resources
3.4.1. Regulatory Framework
Ambient air quality and the emission of air pollutants are regulated
under both federal and California laws and regulations. In addition, there
are local requirements and standards which provide regulation of both air
quality and the emission of air pollutants in the Project area.
The federal Clean Air Act (CAA), and the subsequent Clean Air Act Amendments
of 1990 (CAAA), requires the U.S. Environmental
Protection Agency (USEPA) to identify national ambient air quality standards
(NAAQSs) to protect public health and welfare. NAAQSs have been established
for six (6) pollutants, known as "criteria" pollutants because
the standards satisfy "criteria" specified in the CAA. A list
of the criteria pollutants regulated by the CAA, and the NAAQSs set by the
USEPA for each, are listed in Table 3.7.
Table 3.7
| Criteria Pollutant |
Averaging Period |
California Standards |
Federal Standards |
| Concentrationa |
Primarya |
Secondarya |
| Ozone (O3) |
1-Hour |
90 ppbv (180 Fg/m3) |
120 ppbv (235 Fg/m3) |
Same as Primary Standards |
| Carbon Monoxide (CO) |
8-Hour |
9 ppmv (10 mg/m3) |
9 ppmv (10 mg/m3) |
- |
| 1-Hour |
20 ppmv (23 mg/m3) |
35 ppmv (40 mg/m3) |
- |
| Oxides of Nitrogen (NOx) as Nitrogen Dioxide (NO2) |
Annual |
- |
53 ppbv (100 Fg/m3) |
Same as Primary Standards |
| 1-Hour |
250 ppbv (470 Fg/m3) |
- |
- |
| Sulfur Dioxide (SO2) |
Annual |
- |
30 ppbv (80 Fg/m3) |
- |
| 24-Hour |
40 ppbv (105 Fg/m3) |
140 ppbv (365 Fg/m3) |
- |
| 3-Hour |
- |
- |
500 ppbv (1,300 Fg/m3) |
| 1-Hour |
250 ppbv (655 Fg/m3) |
- |
- |
| Particulate Matter # 10 Microns in Diameter (PM10) |
Annual Geometric Mean |
30 Fg/m3 |
- |
- |
| 24-Hour |
50 Fg/m3 |
150Fg/m3 |
Same as Primary Standards |
| Annual Arithmetic Mean |
- |
50 Fg/m3 |
- |
| Sulfates (SO4) Lead (Pb) |
24-Hour |
25 Fg/m3 |
- |
- |
| 30-Day |
1.5 Fg/m3 |
- |
- |
| Calendar Quarter |
- |
1.5 Fg/m3 |
Same as Primary Standards |
| Hydrogen Sulfide (H2S) |
1-Hour |
30 ppbv (42 Fg/m3) |
- |
- |
aEquivalent units given in parentheses are based upon a reference
temperature of 25EC and a reference pressure of 760 mm mercury. Measurements
of air quality are corrected to a reference temperature of 25EC and a reference
pressure of 760 mm mercury (1,013.2 millibar); ppmv and ppbv
in this table refer to parts by million by volume and parts per billion
by volume, respectively, or micro-moles of pollutant per mole of gas. µg/m3 / micrograms per cubic
meter (CARB 1994).
In addition to the NAAQSs listed in Table 3.7,
on July 16, 1997 the USEPA adopted revisions to the current primary
NAAQSs for particulate matter less than 10 microns in diameter (PM10)
and ozone (O3) (62 Federal Register 38652-38760;
62 Federal Register 38856-38896). Under these newly adopted
standards, the USEPA will be phasing out the current 1-hour O3
standard (once an area is meeting the 1-hour standard) and adopting a new,
0.08 ppm, 8-hour O3 standard, effective September 15,
1997, to protect against longer exposures. In addition, the USEPA has added
two (2) new primary standards for particulate matter less than 2.5 microns
in diameter (PM2.5); a 15 µg/m3,
three (3)-year, annual arithmetic mean standard; and a 65 µg/m3, 24-hour average, standard
meeting the 98th percentile, averaged over three (3) years.
USEPA is also adjusting the current 24-hour PM10 standard from
a 1-expected-exceedence to a 99th percentile form, averaged over
three (3) years. The annual mean PM10 standard would remain
unchanged.
At present, a USEPA-accepted monitoring network for ambient PM2.5
does not exist, and as such it is expected to take until the year 2003 before
sufficient ambient PM2.5 measurements can be obtained to allow
the USEPA to establish attainment status designations. Depending upon the
status of compliance with the current NAAQSs for PM10 and the
pace with which ambient PM2.5 concentrations are established
and compliance plans developed and adopted, states may have up to the year
2017 to meet these new PM2.5 standards.
The California Air Resources Board (CARB), which is part of the California
Environmental Protection Agency (Cal-EPA
), is the California state agency to which the USEPA has delegated primary
responsibility for implementation within California of those portions of
the CAA, as amended, which entail the day-to-day regulatory functions and
contacts with source operators. Under '40002 of the California Health &
Safety Code, jurisdiction for air quality and regulation of emissions from
all sources other than motor vehicles within Imperial County, including
the Project area, has been delegated to the Imperial County Air Pollution
Control District (ICAPCD).
The CARB also has the responsibility for establishing California Ambient
Air Quality Standards (CAAQS ) under the California
Clean Air Act (CCAA). The CAAQS are generally
equal to or more stringent than the NAAQSs. A list of the California "criteria"
air pollutants, and the CAAQS adopted for each,
are also included in Table 3.7.
Pursuant to the CAA, the USEPA has developed classifications for distinct
geographic regions known as air basins. Under these classifications, for
each federal criteria pollutant, each air basin (or portion of an air basin,
known as a "planning area") is classified as in "attainment"
(if the air basin (or planning area) has "attained" compliance
with (that is, not exceeded) the adopted NAAQS for that pollutant), or is
"non-attainment" (if the levels of ambient air pollution exceed
the NAAQS for that pollutant). Air basins which have not received sufficient
analysis for certain criteria pollutants are designated as "unclassified"
for those particular pollutants. Air basins located within California also
receive similar designations with respect to the CAAQS
.
In addition to the NAAQSs, the CAA requires the
USEPA to place each airshed within the United States into one (1) of
three (3) classes, which are designed to limit the deterioration of
air quality when it is below the NAAQSs. Class I is the most restrictive
air quality category, and was created by Congress to prevent further deterioration
of air quality in national parks and wilderness areas of a given size which
were in existence prior to 1977 or have since been designated under federal
regulations (40 CFR 52.21). All remaining areas outside of the
Class I area boundaries were designated as Class II airsheds,
which allows a relatively greater deterioration of air quality over that
in existence in 1977, although still below NAAQSs. No Class III areas,
which would allow air quality to degrade down to the NAAQSs, have been designated.
Federal Prevention of Significant Deterioration (PSD) regulations require
that the maximum allowable increase in ambient particulate matter in a Class I
airshed resulting from a major stationary source is 5 µg/m3
(annual geometric mean) and 10 µg/m3
(24-hour average). Specific types of facilities which emit, or have the
potential to emit, 100 tons per year or more of PM10, or any
facility which emits, or has the potential to emit, 250 tons per year or
more of PM10, is considered a major stationary source. However,
most fugitive emissions are not counted as part of the calculation of emissions
for PSD.
There are no designated Class I airsheds within 100 kilometers
of the Project mine and process area; the nearest Class I airshed is
the Joshua Tree National Park Class I airshed, which is located approximately
110 kilometers northeast of the Project mine and process area at its
closest point (USEPA 1997). Neither of the two (2) wilderness areas
recently established in the vicinity of the Project mine and process area
were designated a Class I airsheds.
3.4.2. Meteorological Setting
The Project area is a desert environment characterized by very hot summers
and mild winters. Humidity in the area is very low, with the exception being
July and August, when humid winds may blow in from the Gulf of California,
located southeast of the Project area (BLM and
ICPBD 1994a). Precipitation in the area is low, with the average annual
rainfall measured at the neighboring Gold Rock Ranch being only approximately
3.60 inches per year (GSi/Water 1993).
Two (2) general wind patterns exist in the region (BLM
and ICPBD 1994a). From October to May, the prevailing winds are out of the
west and northwest, and it is during these periods that humidity is at its
lowest. Summer wind patterns, especially during July and August, are dominated
by heat-induced low-pressure areas formed over the California desert, which
draw air from the Gulf of California and the northern portion of Mexico.
During these conditions, humidity is at its highest. The months of June
and September are transitional months. Wind speeds in the region tend to
be moderate, ranging from 5 to 8 mph at night (weakest in the late
spring and strongest in the winter) to daytime winds averaging between 9
and 13 mph (strongest in the winter and early spring, weakest in the
fall). These wind speeds tend to promote mixing, and generally transport
locally generated air emissions away from the area (BLM
and ICPBD 1994a).
3.4.3. Air Quality
The Project area is located within the Imperial County portion of the
newly designated Salton Sea Air Basin (SSAB) (formerly the southern section
of the Southeast Desert Air Basin (SEDAB)). The Imperial County portion
of the SSAB is entirely under the jurisdiction of the Imperial County Air
Pollution Control District (ICAPCD). That portion of Imperial County west
of the crest of the Chocolate Mountains, which includes the Project area,
is designated as "moderate non-attainment" under the NAAQS, and
"non-attainment" under the CAAQS
, for particulate matter less than 10 microns in diameter (PM10).
Imperial County is being re-evaluated for designation under the NAAQS for
ozone (O3), and is currently designated "moderate non-attainment/Transitional"
for O3. In addition, all of Imperial County is designated "non-attainment"
under the CAAQS for ozone (O3),
and is designated as "attainment" for sulfates/sulfur dioxide (SO4/SO2),
oxides of nitrogen (NOx), and lead (Pb). A small portion
of Imperial County (the city of Calexico) is classified as "non-attainment"
for carbon monoxide (CO); the remainder of the County, including the
portion in which the Project area is located, is designated "unclassified/attainment"
under the NAAQS and CAAQS for CO. Imperial
County is also designated as "unclassified" relative to the CAAQS for hydrogen sulfide (H2S).
The ICAPCD-run stations for monitoring atmospheric pollutants located in
California nearest the Project area are in El Centro and Brawley, California,
approximately 46 miles west-southwest and 42 miles west, respectively,
of the Project mine and process area. Both O3 and PM10
are measured at the El Centro station, whereas only PM10 is measured
at the Brawley station. Since 1985, four (4) PM10 monitoring
stations have been operated by the operators of the Mesquite Mine, located
approximately ten (10) miles northwest of the Project mine and process
area. These four (4) stations are located within, or immediately adjacent
to, the Mesquite Mine boundary. In addition, through 1996, two (2)
PM10 monitoring stations were operated by the operators of the
American Girl Mine; one (1) at the mine, located about seven (7)
miles south of the Project mine and process area, and one (1) at Gold
Rock Ranch, located approximately seven (7) miles southwest of the
Project mine and process area.
During the 1988-1993 period, daily averages for PM10 measured
at Brawley exceeded the CAAQS a total of 141 days
(CARB 1989-1994). The highest number of exceedence days (35) in
a single year was recorded in 1989, with 676 µg/m3
being the highest recorded 24-hour PM10 concentration. Similarly,
daily averages for PM10 measured at El Centro during the same
period exceeded the CAAQS a total of 122 days.
The highest number of exceedence days (31) in a single year was also
recorded in 1989, with 287 µg/m3
being the highest recorded 24-hour PM10 concentration (BLM and ICPBD 1994a). PM10 monitoring at the
Mesquite Mine during 1991 indicated that the 24-hour CAAQS
for PM10 was likely exceeded a total of 27 days that year
(BLM and ICPBD 1994a). The NAAQS was never exceeded
at the Mesquite Mine during that year, although measurements taken at Brawley
and El Centro did exceed the NAAQS (BLM and ICPBD
1994a). Background (annual) PM10 levels calculated from the PM10
measured at the Mesquite Mine during 1991 and 1992 are reported as 19.9 Fg/m3
(arithmetic mean) and 18.1 Fg/m3 (geometric mean) (BLM and ICPBD 1994a). Background (annual) PM10
levels calculated from the PM10 measured at Gold Rock Ranch by
the American Girl Mine for the year 1996 were 19.0 Fg/m3
(arithmetic mean) and 17.5 Fg/m3 (geometric mean). No data
are currently available regarding the existing ambient PM10 concentrations
in or immediately adjacent to the Project mine and process area.
Sources of PM10 in Imperial County are both natural and anthropogenic
(that is, related to the activities of man). The primary source of PM10
and the related pollutant, total suspended particulates (TSP), in Imperial
County is fugitive dust from area sources, principally vehicular traffic
on unpaved roads and wind erosion of cultivated agricultural land, although
PM10 and TSP transported into the Imperial Valley from Mexico
are also substantial (Pechan & Associates 1993). PM10
can also be created indirectly in the atmosphere from chemical reactions
that convert gaseous precursors into small particles. These PM10
precursors, which are predominantly products of man-made combustion, include
NOx, reactive organic gases (ROGs), and oxides of sulfur (SOx).
Principal existing PM10/TSP sources in the vicinity of the Project
area are wind erosion from disturbed areas, vehicular traffic on unpaved
roads, and fugitive and point source emissions from other mining operations
in the area.
Ozone (O3) is a photochemical oxidant which is not typically
emitted directly into the atmosphere, but is formed in the atmosphere through
chemical reactions among emission precursors and ultraviolet light. Imperial
County is classified as "transitional/attainment" by the USEPA
for O3 since recent ambient air monitoring for O3
at the El Centro station has not indicated any exceedences of the NAAQS
for O3. However, between 1988 and 1993 there were a total of
45 exceedence days (139 hours) of the lower CAAQS
for O3 (CARB 1989-1994). The highest number of exceedence days
(25) in a single year was recorded in 1993, with 150 ppbv being the
highest recorded 24-hour O3 concentration. A substantial portion
of the O3 measured in Imperial County is believed to be transported
into the basin from other areas, principally from the South Coast Air Basin
and Mexico, and these sources are likely the cause of at least some of the
measured exceedences of the CAAQS for O3
(BLM and ICPBD 1994a).
Hydrocarbons, or more specifically ROGs (also known as reactive organic
compounds (ROCs)), are not strictly criteria air pollutants, but are recognized
as precursors of photochemical oxidants, including O3, and are
also precursors to atmospheric particulate matter, both of which are criteria
air pollutants. In addition, oxides of nitrogen (NOx) and
oxides of sulfur (SOx), some forms of which are criteria
pollutants, are also precursors to photochemical oxidants and atmospheric
particulate matter. Table 3.8 presents
a list of the criteria pollutants which can be created by secondary reactions
from emissions of the precursors ROGs (ROCs), NOx, and SOx.
Table 3.8
| Precursor |
Secondary (Criteria) Pollutants |
| Reactive Organic Gases (ROGs) |
a) photochemical oxidants (ozone) |
| b) the organic fraction of suspended particulate matter |
| Oxides of Nitrogen (NOx) |
a) nitrogen dioxide (NO2) |
| b) the nitrate fraction of suspended particulate matter |
| c) photochemical oxidants (ozone) |
| Oxides of Sulfur (SOx) |
a) sulfur dioxide (SO2) |
| b) sulfate (SO4) |
| c) the sulfate fraction of suspended particulate matter |
Source: South Coast Air Quality Management District 1994.
Principal sources of ROGs in the atmosphere include vehicular and industrial
emissions and unsaturated hydrocarbon emissions from trees and other vegetation.
No data are currently available regarding the levels of hydrocarbons in
the ambient air in the Project area or immediate vicinity, but they are
presumed to be negligible due to the lack of substantial emissions sources,
including nearby existing mining operations (which typically have few sources
of ROGs except for internal combustion engines). Similarly, no data are
available regarding existing levels of sulfur dioxide (SO2) and
nitrogen dioxide (NO2) in the ambient air in the immediate Project
area, although the levels of these pollutants are also presumed to be small
because of the absence of local sources.
3.5. Biological Resources
3.5.1. Regulatory Framework
3.5.1.1. Federal Endangered Species Protection
The federal Endangered Species Act of 1973, as amended (ESA), provides
the general regulatory framework for the protection of threatened or endangered
(T/E) plant and animal species and critical habitat which are formally listed
under the ESA. The ESA defines the following terms:
- Endangered species: "... any species which is in danger
of extinction throughout all or a significant portion of its range ..."
- Threatened species: "... any species which is likely to
become an endangered species within the foreseeable future..."
- Critical habitat: "... the specific areas within the geographical
area occupied by the species ... on which are found those physical or biological
features (I) essential to the conservation of the species and (II) which
may require special management considerations or protection ..."
The ESA is administered by the U.S. Fish and Wildlife Service (USFWS),
in consultation with other federal agencies (see Section 3.5.2).
In addition to listed T/E species, the USFWS identifies another group of
species known as special status species (formerly "candidate species").
Special status species are not specifically afforded the same protection
under the ESA as T/E species, but federal agencies are required to consider
special status species in their planning and decision-making processes.
The BLM evaluates special status species in a
manner analogous to T/E species, and the BLM
is required to deny approval of any project that may lead to the listing
of special status species.
3.5.1.2. California Endangered Species Protection
The California Endangered Species Act of 1984 (CESA) and the California
Native Plant Protection Act of 1977 (CNPPA) provide the framework for protection
of California listed rare or endangered plant or animal species. The state
also affords protection to candidate species which have been accepted for
state review for potential listing as rare, threatened or endangered species.
CESA status definitions include:
- Endangered: A native species or subspecies of a bird, mammal,
fish, amphibian, reptile, or plant which is in serious danger of becoming
extinct throughout all, or a significant portion, of its range due to one
or more causes, including loss of habitat, change of habitat, overexploitation,
predation, competition, or disease.
- Threatened: A native species or subspecies of a bird, mammal,
fish, amphibian, reptile or plant that, although not presently threatened
with extinction, is likely to become an endangered species in the foreseeable
future in the absence of the special protection and management efforts
required by this chapter (California Fish and Game Code Chapter 1.5).
- Rare: A species, subspecies or variety is rare when, although
not presently threatened with extinction, it is in such small numbers throughout
its range that it may become endangered if its present environment worsens.
- Candidate: A native species or subspecies of a bird, mammal,
fish, amphibian, reptile, or plant that the California Fish and Game Commission
has formally noticed as being under review by the California Department
of Fish and Game (CDFG) for addition to either the list of endangered species
or the list of threatened species, or a species for which the California
Fish and Game Commission has published a notice of proposed regulation
to add the species to either list.
- Species of Special Concern: Native species or subspecies that
have become vulnerable to extinction because of declining population levels,
limited ranges, or rarity. The goal is to prevent these species from becoming
endangered by addressing the issues of concern early enough to secure long
term viability for these species.
The CEQA process requires state lead agencies to consult with the CDFG if
proposed projects would adversely impact T/E species or their critical habitat
(see Section 3.5.3).
3.5.1.3. BLM Sensitive Species
Plant and animal species are listed by the BLM
as sensitive species if the species
has been identified as a proposed T/E species or a special status species
by the USFWS, or if the species has been designated as sensitive by the
BLM State Director from information obtained
from the California Native Plant Society (CNPS), California Natural Diversity
Data Base (CNDDB), or other authoritative sources. The purpose of this listing
is to provide increased management attention to species which may subsequently
be listed as a federal or state T/E species as a result of declining populations
or habitat.
3.5.1.4. California Native Plant Society
The CNPS is a professional society of plant biologists, scientists, and
associated professionals which has accumulated a statewide data base on
California native plants and their distribution. The CNPS has created four
categorical listings of plants to identify their respective concern for
these species as potential rare, threatened, or endangered species. These
listings do not afford legal status or protection for the species, but the
lists are utilized by agencies in their planning processes for activities
which may impact the species or habitat. The listing categories include:
- CNPS 1A: Plant species presumed to be extinct in California.
- CNPS 1B: Plant species presumed to be rare, threatened, or endangered
in California or elsewhere.
- CNPS 2: Plant species presumed to be rare, threatened, or endangered
in California but common elsewhere.
- CNPS 3: Plant species for which more information is needed to
be properly categorized, and includes an assemblage of taxa that have been
transferred from other lists or have been suggested to CNPS for consideration.
- CNPS 4: Plant species which are not currently threatened or
vulnerable but are considered to have limited distribution in California
and, because of their uncommon status, should be monitored.
3.5.1.5. California Natural Diversity Data Base
The CNDDB is a computerized inventory of information on the general location
and condition of California's rare and threatened animals, plants, and natural
communities maintained by the CDFG. The species inventoried by the CNDDB
are listed (both state and federal) endangered, threatened, and rare animals
and plants. The CNDDB also includes species that the scientific community
considers deserving of official listing. Sensitive species proposed for
federal listing, USFWS special status species (formerly candidate species),
and state candidate species are also identified by the CNDDB. The CNDDB
includes information for reported sightings only, and it may not cover every
project location. Therefore, site-specific biological surveys are typically
also required.
3.5.1.6. Migratory Bird Treaty Act
Provisions of the Migratory Bird Treaty Act (16 USC 701-718h)
are applicable to birds within the Project area. The Act establishes a comprehensive
federal regulatory system governing the taking of all migratory birds, but
makes no provisions for the killing of any migratory birds by mining operations
or cyanide heap leaching processes. Activities which repeatedly or negligently
fail to prevent migratory bird mortality could be prosecuted under the Act.
Nearly all birds found within the Project area are considered migratory
under the Act. Raptors and many other birds are protected from hunting under
the Act.
3.5.1.7. Bald Eagle Protection Act
Amendments to the Bald Eagle Protection Act (PL 92-535) provide
additional federal protection to the golden eagle. The golden eagle (Aquila
chrysaetos) is not listed under the federal ESA as a threatened or endangered
species, but the golden eagle is a fully protected species in California
as a look-alike species.
3.5.1.8. Protection of Wetlands
Executive Order 11990 (Protection of Wetlands), effective May 24,
1977, is an overall wetlands policy for all agencies managing federal lands,
sponsoring federal projects, or providing federal funds to state or local
projects. This executive order requires federal agencies to follow avoidance/mitigation/preservation
procedures, with public input, before proposing new construction in wetlands.
When federal lands are proposed for lease to non-federal parties, the executive
order requires that restrictions be placed in the lease to protect and enhance
the wetlands on the property.
3.5.2. U.S. Fish and Wildlife Service Consultation
The ESA requires that the USFWS be formally consulted by federal agencies
for those actions proposed by the federal agency which may adversely affect
listed T/E species or their critical habitats. Protection under the ESA
also extends to species and habitat proposed for listing, and the BLM extends protective status to species and habitat
identified by the USFWS as candidates for listing. The ESA prohibits the
"take" (i.e., killing, harming, or harassment) of listed T/E species
without special exemptions. Section 7(a) of the ESA requires that federal
agencies responsible for authorizing projects (authorizing agencies) which
may adversely affect a listed species, or may adversely modify listed critical
habitat designated for such a species, undertake consultation with the USFWS.
As discussed below, consultation may be informal or formal.
Informal consultation is a process that includes all discussions and correspondence
between the authorizing agency and USFWS and is designed to determine if
formal consultation is required. Unless it is readily apparent that formal
consultation is necessary, the authorizing agency would typically first
consult informally on all actions that may affect a listed species or its
listed critical habitat. The authorizing agency would also typically seek
recommendations for modification of actions that would avoid the likelihood
of adverse effects and contribute to achieving recovery objectives for the
listed species or its critical habitat.
Formal consultation is initiated by the authorizing agency through the preparation,
and submittal to the USFWS, of a Biological Assessment prepared by the authorizing
agency for the "proposed action." This Biological Assessment would
be utilized in association with other informational resources by the USFWS
to prepare the Biological Opinion. The Biological Opinion would determine
if the "proposed action" is likely to jeopardize the continued
existence of a listed species. A section of the Biological Opinion would
specify the terms and conditions under which the listed species may be taken.
This section also determines appropriate levels of take, as defined by individuals
of the species killed, injured, or moved, and the amount of critical habitat
subject to temporary and/or permanent disturbance. If the USFWS= Biological
Opinion determines that the "proposed action" may jeopardize the
continued existence of a listed species, then the authorizing agency must
notify the USFWS in writing prior to its final decision on the "proposed
action."
The consultation process is terminated by: the issuance of a biological
opinion by the USFWS; notification by the authorizing agency that the "proposed
action" is not likely to occur; or a determination by the authorizing
agency (with the concurrence of the USFWS) that the "proposed action"
is not likely to adversely affect any listed species.
3.5.3. California Department of Fish and Game
Consultation
3.5.3.1. State Listed Species
The CESA also prohibits the "take" of any state listed species.
If a state agency is acting as the CEQA lead agency, it is required to consult
with the CDFG to determine if proposed projects are likely to jeopardize
the continued existence of any T/E species or result in the destruction
or adverse modification of habitat essential to the continued existence
of any T/E species. However, if a local agency, such as the ICPBD, is the
CEQA lead agency, such consultation is not required. The CDFG has instead
historically authorized exceptions to the "take" prohibition to
individuals which would allow the "take" of state listed species
for management purposes under Section 2081 of the California Fish and
Game Code. This practice, although recently under judicial review, has now
been reaffirmed with the passage and approval of SB 879, effective
January 1, 1998. Where applicable, the Section 2081 process establishes
measures for the protection of the affected T/E species and their habitat
during project actions, and SB 879 adds that any required compensation
must be roughly proportional to the impacts on the species. Where a species
is both federal and state listed, and a project is subject to both NEPA
and CEQA, the CDFG is encouraged to participate to the extent practical
in the federal consultation process and adopt a coordinated biological opinion
with the USFWS that reflects consistent and compatible findings between
state and federal agencies. With the passage and approval of AB 21,
effective January 1, 1998, the federal ESA Section 7 "take"
authorization for a project would preclude the necessity for a state Section 2081
permit, if the Section 7 authorization is approved by CDFG as consistent
with CESA.
Fourteen (14) animal and three (3) plant state-listed species
have been identified by the CDFG within Imperial County (CDFG 1995). Project
impacts on each of these species and their habitat must be considered by
the CDFG under Section 2081.
3.5.3.2. Stream Alteration Agreement
Entities which propose to divert, obstruct or change the natural flow
or the bed, channel or bank of any river, stream or lake in which there
is at any time an existing fish or wildlife resource, must first notify
the CDFG prior to the activity (California Fish and Game Code '1603). When
an existing fish or wildlife resource may be "substantially adversely
affected by the project or activity," the CDFG must respond to the
notice by providing a description of the resource which would be affected
and submitting a proposal for measures necessary to protect fish and wildlife.
The affected entity is provided an opportunity to accept the CDFG proposal
or through consultation reach a mutual agreement on measures necessary to
protect fish and wildlife (i.e., Stream Alteration Agreement). If no agreement
can be reached, then a panel of arbitrators is established with the power
to settle disagreements and make binding decisions regarding fish and wildlife
modifications. The project or activity may not proceed unless it is conducted
in conformance with a Stream Alteration Agreement or the decisions of the
panel of arbitrators.
The CDFG has stated that a Stream Alteration Agreement is required to conduct
Project activities within the ephemeral drainage channels within the Project
mine and process area. Of concern are the effects of the Project on the
wildlife and the wash habitat.
3.5.4. Biological Setting
3.5.4.1. Project Location
The area of the Proposed
Action is located in an Eastern Colorado Desert environment in southeastern
Imperial County. The Project mine and process area is located on a broad
south and west facing alluvial plain southwest of Indian Pass, between the
Cargo Muchacho Mountains (located approximately four (4) miles south)
and Black Mountain (located approximately five (5) miles north). The elevation
over the Project mine and process area ranges from about 760 feet to
925 feet AMSL with the lower, and nearly
flat, elevations in the south and southwest. Elevations gradually increase
to the north and northeast with topography characterized by a series of
gently rolling ridges separated by interconnecting drainages generally trending
from northeast to southwest.
Soils within the Project mine and process area are dominated by desert pavement
in the upland areas with gravel-based alluvial soil in the major drainages
and the west-central portion of the Project mine and process area (see Section 3.2).
Soils of the upland landscape support very little vegetation. A soil resource
evaluation of the Project mine and process area was conducted by Bamberg
and Hanne (1995a) and is provided as Attachment D to Appendix A
of this report.
There are no springs, seeps, permanently wet areas, wetlands, nor standing
surface water within the Project area. Three (3) primary, sub-parallel,
ephemeral, stream channels traverse the Project mine and process area (see
Section 3.3.1). The largest ephemeral stream channel is located
near the western boundary of the Project mine and process area (the West
Pit West channel) and parallels Indian Pass Road (see Section 3.3.1.1
and Figure 3.6). Two (2) branches of a second ephemeral
channel (the West Pit East and East Pit West channels) enter the north-central
portion of the Project mine and process area, merge, and exit the south-central
portion of the Project mine and process area as a single ephemeral stream
channel. The third ephemeral steam channel (East Pit East channel) is located
in the east portion of the Project mine and process area. Precipitation
in the Colorado Desert tends to occur in short, intense events and average
annual precipitation in the Project area is only approximately 3.6 inches
(see Section 3.4.2). The infrequent rain events result in temporary
flow in the channels across the Project area which quickly infiltrates in
the sandy and gravelly wash bottoms, providing some residual moisture to
the wash vegetation between storm events.
Fluvial processes in the washes affect the rate of deposition and type of
material deposited on the wash bottoms. Fluvial processes also affect nutrient
cycling and biogeochemical processes in soils and water. These processes
affect the vegetation and plant communities which can establish in the washes.
As discussed in Section 3.3.1.2, the principal throughgoing
stream channels appear to be currently "in balance;" that is,
the reaches of the principal washes within the Project mine and process
area are not dominated by either erosion or deposition, but both processes
are occurring at approximately the same rate. The majority of the Project
area has been subject to very slow erosional deflation by wind, which has
produced a well-developed desert pavement. Wash bottoms have a veneer of
recently deposited gravelly rock with sand and gravel along the banks. This
erosional material moves through the Project mine and process area by the
flushing action of water flow following infrequent storm events (Bamberg
and Hanne 1995a).
Surface runoff from this region, which comprises a portion of the Chocolate
Mountains basin area, and includes the Project area, drains into individual
isolated areas along the eastern edge of the Algodones Sand Dunes, providing
moisture to pockets of microphyll vegetation (see Figure 3.5).
3.5.4.2. Special Biological Resource Management
Areas
The Project area is located within the BLM's
California Desert Conservation Area (CDCA) and is subject to the applicable
plans and goals of the CDCA Plan. The CDCA Plan (1980) indicates that a
prescriptive Habitat Management Plan (HMP) would be prepared by the BLM for the Indian Wash area, which includes the
Project area. The long-term goals for the Indian Wash HMP stated in the
CDCA Plan were to protect, stabilize, and/or enhance wildlife resource values
in the area. The Indian Wash HMP would set forth management actions to meet
these goals, including: control of vehicle use; restriction of camping and
parking; and increasing surveillance in the area. The BLM
has not yet prepared or implemented the Indian Wash HMP (Personal Communication,
Nancy Nicolai, BLM, July 1, 1996).
Two (2) wilderness areas, Indian Pass Wilderness Area and Picacho Peak
Wilderness Area, are located within one and one-half (12) and one-half (2)
miles of the Project mine and process area, respectively (see Figure 3.14).
While not specifically developed as biological resource management areas,
substantial protection to plants and animals within these areas is afforded
by their designation as wilderness.
The USFWS has designated specific areas as desert tortoise critical habitat
in an effort to manage the recovery of this species. The nearest desert
tortoise critical habitat to the Project area is the Chuckwalla Unit, located
at its closest approximately two (2) miles northwest of the Project
mine and process area (see Figure 3.14).
3.5.5. Vegetation
Vegetation within the Project area is characterized by: tree/shrub vegetation
in and adjacent to the ephemeral stream channels; and shrub/scrub vegetation
on the upland areas between the stream channels (Bamberg and Hanne 1995b).
Vegetation associations within the Project area are shown on Figure 3.15.
All of the vegetation is highly adapted to be able to succeed in the harsh
environment.
Dominant species within the wash channels include ironwood (Olneya
tesota) and palo verde (Cercidium floridum), with a diverse plant
association containing cat's-claw (Acacia greggii), purple heather
(Krameria erecta), desert lavender (Hyptis emoryi), Anderson
thornbush (Lycium andersonii) and yellow felt-plant (Horsfordia
newberryi). Dominant desert scrub species include creosote bush (Larrea
tridentata), burrobush (Ambrosia dumosa), ocotillo (Foaquieria
splendens), and brittlebush (Encelia farinosa). Several sparsely
populated cactus species are found within this habitat, including Bigelow
cholla (Opuntia bigelovii), cottontop cactus (Echinocactus polycephalus),
beavertail cactus (Opuntia basalaris), diamond cactus (Opuntia
ramosissima), and California barrel cactus (Ferocactus cylindiceus).
A quantitative, site-specific, baseline vegetation survey of the entire
Project mine and process area and a buffer zone (total of approximately
1,700 acres) was conducted in June, 1995 by Bamberg and Hanne (1995b).
The report of the vegetation survey is provided as Appendix F to this
EIS/EIR. The survey report notes that the weather during the spring of 1995
included substantial rains which provided abundant moisture and the washes
had flowed for a short period of time. In addition, the previous three (3)
years had also been a wet cycle with periods of heavy rain that resulted
in extremely favorable conditions for plant growth and productivity in the
Project mine and process area. This was evident in the good growth observed
in perennial trees and shrubs, and by herbaceous annuals, during the survey.
Vegetative growth was reported to have been higher over the immediately
previous three (3) years (1993-1995) than it had been in the previous
15-20 years.
In addition to the baseline vegetation survey of the Project mine and process
area and buffer zone, a quantitative wash vegetation and habitat survey
was conducted in May, 1997 by Bamberg and Associates (Bamberg 1997b). The
report of the wash vegetation survey is provided as Appendix G to this
EIS/EIR. Sections of washes proposed to be diverted or otherwise disturbed
by Project activities within the Project mine and process area were sampled
up- and down-gradient from the diversions. Additionally, complete censuses
of microphyllous tree species were conducted along reaches of the main washes
which traverse the Project mine and process area. The wash survey followed
a two-year period of extremely dry weather conditions. Less than 0.25 inches
of rain fell since the baseline survey was completed in 1995 (22 months).
Vegetation within both the Project mine and process area and the Project
ancillary area are categorically creosote shrub type, but for the purposes
of the survey the vegetation was subdivided into shrub/scrub vegetation
observed on the open, drier alluvial flats and slopes; and tree/shrub vegetation
observed on the sides of washes and drainages. The tree/shrub type can be
easily distinguished from the shrub/scrub type on aerial photographs of
the Project mine and process area and vicinity (see Figure 3.16).
Approximately 95 percent of the Project mine and process area and the
Project ancillary area is the shrub/scrub type with an almost non-existent
vegetative ground cover. These upland areas were further subdivided into
three (3) topographic subtypes as summarized below:
- Desert pavement: Covers an estimated 35 percent of the
uplands; vegetation is extremely scarce; water and seeds cannot generally
penetrate the surface; estimated vegetative ground cover at the time of
the 1995 survey ranged from 0 to 0.5 percent.
- Alluvial flats and slopes: Covers an estimated 64 percent
of the uplands; characterized as areas within the desert pavement that
have had their alluvial surfaces disturbed in the last 1,000 years
by erosion or deposition; spacing of plants by clumping in favorable areas;
vegetative ground cover estimated at the time of the 1995 survey ranged
from 7 to 9 percent.
- Rock outcrop/thin soil: Occurs in a small (1 percent) upland
area in the north-central portion of the Project mine and process area;
characterized by vegetation growing in cracks and between rocks; vegetation
density is very low and clumped; vegetative ground cover estimated at the
time of the 1995 survey was 2 to 4 percent.
The tree/shrub vegetation type occurs on the sides and banks of the washes,
and represents a total of approximately five (5) percent of the
Project mine and process area and the Project ancillary area. Two (2)
topographic subtypes were identified as follows:
- Broad major washes: Drainages which cross the Project mine and
process area and continue out onto the broad alluvial flats southwest of
the Project area toward the Algodones Sand Dunes; characterized as washes
ranging from almost no depth to fifteen (15) feet deep and eight (8)
to 225 feet (average 40 feet) wide; plant cover at the time of
the 1995 survey ranged from 0 percent in the sandy bottom areas to
66 percent on some sides and mid-wash clumps (islands).
- Shallow subsidiary washes: Narrower (average 30 feet) than
the broad major washes and not as deep; finer soils washed or deposited
within them; fewer and smaller trees with additional species present; plant
cover at the time of the 1995 survey was irregular on the bottoms and the
sides of these secondary drainages and averaged 35 to 45 percent.
The average cover measured in the baseline vegetation survey (Bamberg and
Hanne 1995b) was seven (7) percent in the shrub/scrub community and
45 percent cover in the tree/shrub community. Diversity averaged seven
and six-tenths (7.6) species per transect, indicating the low number of
perennial species and wide spacing of individual plants. Average density
of all plants in the shrub/scrub community was 136 plants per acre,
and 1,058 plants per acre in the tree/shrub community. Because of the
three (3) consecutive wet years and favorable conditions prior to the 1995
survey, the results of this vegetation survey were interpreted to represent
the highest cover and diversity possible in the Project mine and process
area, with more than four times (>4x) the cover which would be expected
following a series of dry years.
The mean vegetative cover in the washes measured in the 1997 wash vegetation
and habitat survey (Bamberg 1997b) ranged from 33 to 76 percent. Plant
species diversity was measured at nine (9) to 16 perennial plant
species per sample site. Perennial plants alone occurred in a range of densities
from 36 to 580 individuals per acre.
During the vegetation surveys evidence of previous human disturbance within
the Project mine and process area was observed, including roads and access
trails and some previous trenching for exploration in the rock outcrop area.
Plants had been periodically collected or cut; in particular, many of the
older ironwood trees had been cut and were left as old stumps or resprouted
bases on the sides of washes throughout the Project mine and process area.
Rado (1995) observed heavy prior cutting of ironwood trees in all of
the washes in an area extending for at least one and one-half (12) miles
in each direction from the Project mine and process area. This was evidenced
by old ironwood stumps and discarded branches. The reason for the heavy
cutting of ironwood trees is believed to be historic harvesting for fuel,
and it has probably resulted in the loss of many ironwood trees, reduced
the tree canopy and degenerated the microphyll woodland habitat in the area.
Little regeneration of the ironwoods has occurred (Personal Communication,
Ted Rado, February 9, 1996).
No perennial streams, riparian habitat, or wetland areas exist on or adjacent
to the Project area (see Section 3.3.1 and Section 3.3.1.4).
Further, no star dunes, sheet dunes, wind-accumulated sand deposits or other
aeolian sand deposits exist within the Project area (Rado 1995).
3.5.5.1. Special Status Species
A total of 22 federal- or state-listed or proposed T/E plant species;
USFWS special status species (e.g., former C2 or C3 candidate species);
and BLM sensitive plant species were identified
from lists which are known to occur in the general vicinity of the area of the Proposed Action (Rado
1997). These species are identified in Table 3.9.
However, eleven (11) of these identified plant species do not have
potential habitat within the area
of the Proposed Action. These include: Pierson's milk-vetch (Astragalus
Magdalena var. Piersonii), Algodones Dunes sunflower (Helianthus
nivens ssp. tephrodes), giant Spanish needle (Palafoxia
arida var. gigantea), Borrego milk-vetch (Astragalus
lentiginosus var. borreganus), Hardwood's milk-vetch (Astragulus
insularis var. harwoodii), Wiggins cholla (Opuntia wigginsii),
sand food (Pholisma sonorae), and Wiggin's croton (Croton wigginsii),
all of which are typically found in sand dunes; rock nettle (Eucnida
rupestris), which is confined to an isolated occurrence in California
located 60 miles west of the Project mine and process area; Glandular
ditaxis (Ditaxis clariana), which is found only in Mojave scrub or
Sonoran desert scrub/sandy soils not present in the area
of the Proposed Action; and Munz's cholla (Opuntia munzii), which
is found in lower fans and plains.
Table 3.9
Common Name |
Scientific Name |
Statusa |
| Pierson's milk-vetch |
Astragalus magdalena var. Piersonii |
BLM/FPE/SE/CNPS-1Bb |
| Borrego milk-vetch |
Astragalus lentiginosus var. borreganus |
CNPS-4/SPb |
| Hardwood's milk-vetch |
Astagalus insularis var. hardwoodii |
CNPS-2b |
| Ribbed cryptantha |
Cryptantha costata |
CNPS-4/SP |
| Winged cryptantha |
Cryptantha holoptera |
CNPS-4/SP |
| Fairy duster |
Calliandra eriophylla |
CNPS-2/SP |
| Rock nettle |
Eucnida rupestris |
CNPS-2/SPb |
| California ditaxis |
Ditaxis California |
BLM/USFWS/CNPS-1B |
| Glandular ditaxis |
Ditaxis clariana |
CNPS-2b |
| Hairy stickleaf |
Mentzelia hirsutissima |
USFWS/CNPS-2/SP |
| Slender-lobed four o=clock |
Mirabilis tenuiloba |
CNPS-4/SP |
| Wiggin's cholla |
Opuntia wigginsii |
BLM/USFWS/CNPS-3/SPb |
| Sand food |
Pholisma sonorae |
BLM/CNPS-1Bb |
| Foxtail cactus |
Escobaria vivipara var. alversonii |
BLM/USFWS/CNPS-1B/SP |
| Algodones Dunes sunflower |
Helianthus niveus ssp. tephrodes |
BLM/USFWS/SE/CNPS-1B/SPb |
| Munz's cholla |
Opuntia munzii |
BLM/USFWS/CNPS-1B/SPb |
| Giant spanish needle |
Palafoxia arida var. gigantea |
BLM/USFWS/CNPS-1B/SPb |
| Orocopia sage |
Salvia greatei |
BLM/USFWS/CNPS-1B/SP |
| Wiggin's croton |
Croton wigginsii |
BLM/USFWS/SR/CNPS-3/SPb |
| Desert unicorn plant |
Proboscidia althaefolia |
CNPS-4 |
| Thurber's pilostyles |
Pilostyles thurberi |
CNPS-4 |
| Crown-of-thorns |
Koebeslina spinosa |
CNPS-2 |
aLegend:
FPE: Federal proposed for endangered status
SE: California state listed as endangered
SR: California state rare species
CNPS: California Native Plant Society;
1B - Taxa determined to be rare, threatened or endangered;
2 - Species rare or endangered in California but common elsewhere;
3 - More information on status needed; and
4 - Species of limited distribution.
SP: California Special Plant
USFWS: Designated as a Special Status Species by the U.S. Fish and Wildlife
Service
BLM: Designated a BLM
Sensitive Species
bNo potential habitats for species present within the area
of the Proposed Action
Source: Rado 1997
The following plant species have geographic ranges and preferred habitats
that indicate that they may potentially occur within or near the area of
the Proposed Action. Descriptions of these species are provided below.
Foxtail cactus: Foxtail cactus is a small cactus associated with
rocky alluvial slopes and hills. The distribution of the species ranges
from approximately western Joshua Tree National Park southeast to the Chuckwalla
Mountains of southeastern California (Munz 1974). In appearance, the foxtail
cactus consists of one (1) to a few stems that branch from a common
base to a height of about eight (8) inches. The identifying characteristic
of this species are the elongated spines that are white at the base, but
transitionally change color to red or purple near the tip, giving the plant
an appearance like a fox's tail. Flowers are purple to magenta in coloration
and bloom in May and June (Munz 1974; USBR 1996). The species is threatened
by collecting (Skinner and Pavlik 1994).
Ribbed cryptantha: The ribbed cryptantha is a small annual in the
Borage family characterized by ashen stems and leaves, with "ribbed"
sepals (Jaeger 1941). Flowers are white, and bloom between April and May.
It is uncommonly distributed in California on sandy soils and gravelly alluvial
fans in the Colorado Desert between Palm Springs and Yuma below 1,500 feet
in habitats dominated by creosote bush (Jaeger 1941; Munz 1974).
Winged cryptantha: The winged cryptantha is also a small annual in
the Borage family, characterized by rough-hairy herbage, and a "completely
winged" seed (Jaeger 1941). The species grows upright and may reach
a height of about two (2) feet. White flowers bloom in March-April
(Skinner and Pavlik 1994). It is irregularly distributed from the vicinity
of Palm Springs to the Colorado River in California, present in gravelly
and rocky habitats dominated by creosote bush below 2,000 feet (Munz
1974). The winged cryptantha is found in ephemeral stream channels and washes
throughout the Colorado Desert, in the eastern Mojave Desert of California
and Nevada, and in the Sonoran Desert of Arizona. The plants are not considered
"rare" but are uncommon enough that CNPS recommends that their
status be monitored. It has been previously recorded during area surveys
for other projects in the area (Pritchett 1984; BLM
and ICPBD 1995).
Fairy duster: Fairy duster is a low, rounded shrub with dark green
acacia-like leaves. Flowers are scarlet and white, and bloom in January
through March (Skinner and Pavlik 1994). It is closely associated with the
edges of smaller washes in southeastern California desert regions (Jaeger
1941). It has been noted during botanical surveys of this general area (Environmental
Solutions 1987; Office of Arid Lands Studies 1993).
California ditaxis: California ditaxis is a woody perennial herb,
approximately eighteen (18) inches in height, associated with
sandy washes and canyons distributed between the Santa Rosa Mountains and
the southern side of the Eagle Mountains in Riverside County and San Diego
County (Munz 1974; Skinner and Pavlik 1994). Distribution of plants appears
to be spotty, with fewer than twenty (20) known occurrences, most consisting
of few plants (Skinner and Pavlik 1994). Flowers are white in color. The
California Desert Plan (BLM 1980) records a population
of California ditaxis near Picacho Peak, approximately ten (10) miles
east of the Project mine and process area. This may represent an error,
since the record is substantially southeast of the known geographic range
(Munz 1974), and subsequent literature (CNPS 1988; Skinner and Pavlik 1994)
do not address this locality. California ditaxis was not documented during
surveys of the area of the Proposed Action (Rado 1997), nor in neighboring
project sites (Office of Arid Lands Studies 1992; BLM
1994a). It is considered a "Special Status Species" by the USFWS
and is a Category 1B taxon (i.e., plants rare, threatened or endangered
in California and elsewhere) by the CNPS (Skinner and Pavlik 1994).
Hairy stickleaf: This is an annual blazing star, consisting of erect
stems rising to ten (10) or more inches in height. The orange-colored
flowers bloom in March-April. It is closely associated with coarse rock
rubble and rocky slopes in creosote bush habitats below 2,000 feet.
The geographic range in California is principally confined to Imperial County
and eastern San Diego County. Localities include Box Canyon, Palm Canyon
and Mountain Springs grade (Munz 1974). It has been previously recorded
from this general area (CNPS 1988).
Slender-lobed four o=clock: Slender-lobed four o=clock is a perennial
herb, with many branches extending from a base to a height of about 1.5 feet
(Jaeger 1941). Flowers are white and bloom in March through May. The plant
is closely associated with rocky slopes below 1,500 feet elevation
in creosote bush habitats (Munz 1974). The geographic range extends from
the western edge of the Colorado Desert south into Baja California (Jaeger
1941).
Orocopia sage: Orocopia sage is a sparsely-distributed spiny-leaved
shrub associated with gravelly washes below 600 feet in elevation in
the Orocopia Mountains and Chocolate Mountains areas of southeastern California
(Jaeger 1941; Munz 1974). Its lavender flowers bloom in March to April.
Desert unicorn plant: Desert unicorn plant is a coarse spreading
perennial species, associated with creosote bush scrub habitats in Imperial,
San Diego and Riverside Counties in California. The geographic range of
this taxon also includes portions of Sonora, Mexico; Baja California, Mexico;
and the state of Arizona (CNPS 1988). Flowers are yellow to orange, with
maroon streaking on the lower lobe and spotted along the sides of the "throat."
It is uncommonly distributed throughout its range, and associated with sandy
substrates (Munz 1974; Hickman 1993). It was not documented in the area
of the Proposed Action during surveys (Rado 1997) and has not been recorded
during surveys of the nearby Mesquite Mine (Office of Arid Lands Studies
1992) or American Girl Oro Cruz Project sites (BLM
1994a). Desert unicorn plant has no federal or state status. It is listed
by the CNPS as a List 4 species (i.e., a "watch list"
species).
Thurber's pilostyles: Thurber's pilostyles is a stem parasite associated
with indigobush (Dalea, especially Dalea emoryi)(Munz 1974).
Distribution of this plant in California is confined to creosote bush scrub
habitats in Riverside, San Diego, and Imperial Counties in California.
The geographic range of this plant also includes Arizona, Nevada, Texas,
and Baja California (CNPS 1988; Hickman 1993). The plant, in appearance,
is quite small, with scale-like leaves and flowers. Flowers are brown in
coloration and minute in size (Munz 1974). The preferred host plant species,
Dalea emoryi, was not documented during surveys of the area of the
Proposed Action (Rado 1997). Thurber's pilostyles has not been documented
during surveys of the Mesquite Mine (Office of Arid Lands Studies 1992)
or the American Girl Oro Cruz Project (BLM 1994a).
Thurber's pilostyles has no federal or state status. It is listed by the
CNPS as a List 4 species (i.e., a "watch list" species).
Crown-of-thorns: Crown-of-thorns is a nearly leafless deciduous shrub
consisting of pale green, spine-tipped branchlets (Munz 1974). Flowers are
small and greenish white in coloration. The species is present in washes
in creosote bush scrub. It has been reported from the Chocolate Mountains
in Imperial County (Munz 1974) east into parts of Sonora, Mexico; Arizona;
and Texas (Munz 1974; Hickman 1993). In California it is known from fewer
than ten (10) occurrences (Skinner and Pavlik 1994). Crown-of-thorns
is highly visible and readily identified in areas where it occurs, but it
was not documented during surveys of the area
of the Proposed Action (Rado 1995), or during surveys of the Mesquite
Mine area (Office of Arid Lands Studies 1992) or the American Girl Oro Cruz
Project site (BLM 1994a). Crown-of-thorns has
been listed by the CNPS as a List 2 taxon (i.e., plants rare, threatened,
or endangered in California but more common elsewhere). It is not a federal-
or state-listed species.
3.5.5.2. Botanical Survey Findings
Systematic pedestrian botanical surveys of the entire Project area, including
the Project mine and process area, the Project ancillary area, and alternate
transmission line corridors, including buffer zones, were conducted during
multiple visits to the Project area in July, August, and September 1994
and in February, April, and May 1995 (Rado 1995). In addition, incidental
observations of sensitive botanical species were made during the pedestrian
biological survey of the overbuilt 92 kV/34.5 kV transmission
line corridor in August and September of 1995 (Rado 1997; see Section 3.5.6.2).
A total of 116 plant taxa were identified within the survey area. This
includes a few introduced species of plants, mainly annuals such as mustards
and grasses. Plants observed during the surveys were reported as typical
of wash and desert scrub plant associations in the Colorado Desert (Rado
1995; Burk 1977). The botanical survey included collection of prior data
from the area, California Native Plant Society (CNPS) data ( Skinner and
Pavlik 1994; CNPS 1988), and a review of prior biological survey reports
conducted in the general area (Turner et al. 1980b; Pritchett 1984; Kiva
Biological Consulting 1991; Office of Arid Lands Studies 1993; Environmental
Solutions 1987; BLM undated; BLM
1994a). A detailed discussion of the findings and observations made during
the botanical surveys is provided in the biological survey report (Rado
1995), which is attached as Appendix H.
The biological survey report indicates that no state or federal listed,
proposed, or special status species were observed on the surveyed lands.
No state or federal listed, proposed, or special status species have been
reported to exist within the area
of the Proposed Action (Rado 1997). A single sensitive plant species,
the fairy duster, was observed within the Project mine and process area.
The presence of fairy duster was common in virtually all of the ephemeral
stream channels throughout the Project mine and process area. This species
was restricted to the ephemeral stream channels, where it was generally
present along wash edges and banks. It was most commonly observed in the
smaller channels; those between approximately two (2) and eight (8)
feet in width. A total of 285 individual plants were observed, and
the actual number present within the Project mine and process area probably
exceeds 500 (Rado 1997).
One CNPS List 4 (i.e., "watch" list) species, winged cryptantha
(Cryptantha holoptera), was found in larger stream channels throughout
the Project mine and process area. A total of 53 individual plants
were observed, and it was assumed that the actual number of plants was higher
(Rado 1997). The plants were distributed along the edges of the larger washes
within the Project mine and process area.
Foxtail cactus, ribbed cryptantha, California ditaxis, hairy stickleaf,
slender-lobed four o=clock, orocopia sage, desert unicorn plant, Thurber's
pilostyles, and crown-of-thorns were not documented during the biological
surveys of the area of the
Proposed Action (Rado 1995; Rado 1997).
3.5.6. Wildlife
In addition to other changes, this section has been modified from the
November 1996 Draft EIR in response to comments to: document the results
of a survey of the Project mine and process area for bats; document the
results of a survey of the southernmost end of the overbuilt 92 kV/34.5 kV
transmission line corridor for flat-tailed horned lizard or sign; and provide
additional information on desert deer and bighorn sheep.
Wildlife found within the vicinity of the area
of the Proposed Action are characteristic of the Eastern Colorado Desert
(Rado 1995). Bamberg and Hanne (1995b) roughly estimated that 95 percent
of the Project mine and process area is comprised of desert scrub habitat
with predominantly scrub vegetation and relatively little succulent vegetation.
The remaining estimated 5 percent of the Project mine and process area,
restricted to the wash bottoms and adjacent areas, is comprised of tree/shrub
vegetation, generally equivalent to microphyll woodland or desert dry wash
woodland habitat. Independently, Rado (1995) utilized aerial photographs
to map the two (2) major habitat associations (see Figure 3.14).
Based upon the Rado map, approximately 139 acres of microphyll woodland
habitat exists within the revised boundaries of the Project mine and process
area (about 8.9 percent of the Project mine and process area). This
estimate includes both vegetated areas along the banks and slopes of the
drainages, and the less vegetated wash bottoms. Microphyll woodland is considered
sensitive habitat by the CDFG.
Oblique aerial photographs taken in July, 1997 of the Project ancillary
area and the overbuilt 92 kV/34.5 kV transmission line corridor
were analyzed, together with the applicable USGS 7.5 minute series
topographic maps, to estimate the microphyll woodland habitat within these
areas. Approximately one-quarter (3) mile of microphyll woodland habitat
occurs within the alignment of the new transmission line/water pipeline
within the Project ancillary area. Assuming disturbance occurs within a
60-foot wide corridor in the Project ancillary area, and providing a 20 percent
methodology error, this translates to about 2 acres of microphyll woodland
habitat which would be disturbed (or about 5.8 percent of the total
of 38 acres of disturbance) within the Project ancillary area. An estimated
sixteen (16) of the overbuilt 92 kV/34.5 kV transmission
line poles would be/are located in microphyll woodland habitat. Assuming
an approximately 50-foot-square area of disturbance around each power line
pole, and providing again a 20 percent methodology error, this translates
to approximately 1 acre of microphyll woodland habitat which would
be disturbed (or about 5 percent of the total 22 acres of disturbance)
along the overbuilt 92 kV/34.5 kV transmission line corridor.
The following common species inhabit or occasionally visit the area of the
Proposed Action:
Reptiles: zebra-tailed lizard (Callisaurus draconoides),
side-blotched lizard (Uta stansburiana), western whiptail (Cnemidophorus
tigris), and desert iguana (Dipsosaurus dorsalis);
Birds: Using microphyll woodland habitat - mourning doves (Zenaida
macroura), Gambels= quail (Lophortyx gambelii), Say's phoebes
(Sayornis saya), and black-tailed gnatcatchers (Polioptila melanura);
Using desert succulent scrub habitat - black-throated sparrow (Amphispiza
bilineata), loggerhead shrike (Lanius ludovicianus), and cactus
wren (Campylorhynchus brunnecapillus);
Raptors: Multiple raptor species would be expected to periodically
forage or migrate through the area, including: golden eagle (Aquila chrysaetos),
red-tailed hawk (Buteo jamaicensis), sharp-shinned hawk (Accipiter
striatus), American kestrel (Falco sparverius), prairie falcon
(Falco mexicanus), northern harrier (Circus cyaneus), western
screech-owl (Otus kennicottii), great horned owl (Bubo virginianus),
and turkey vulture (Cathartes aura).
Mammals: antelope ground squirrel (Ammospermophilus leucurus),
Merriam kangaroo rat (Dipodomys merriami), desert woodrat (Neotoma
lepida), black-tailed jackrabbit (Lepus californicus), deer (Odocoileus
hemionus), kit fox (Vulpes macrotis), coyote (Canis latrans),
American badger (Taxidea taxa), and wild burro (Equus asinus).
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