5.6 GEOLOGY AND SOILS
This section evaluates the potential environmental effects related to geology and soils associated with
the implementation of the proposed Project.
5.6.1 EXISTING CONDITIONS
The Project is located in the western edge of the Basin and Range Geomorphic Province. 1 Within
California, this geomorphic province encompasses an area that extends approximately 270 miles along
the eastern flank of the Sierra Nevada and north of the Mojave Desert Province, and covers portions of
Mono, Inyo, Kern, and San Bernardino Counties. The Basin and Range Province is characterized by
north–south trending fault-block mountain ranges (Sierra Nevada, Inyo Mountains, and Panamint
Mountains), and elongated, relatively narrow valleys (Owens Valley, Panamint Valley, and Death
Valley).2
The Owens River and its tributaries run throughout the Project area.
Regional Climate
The Sierra Nevada greatly influences the climate of the Owens Valley. As described in Section 5.9,
Hydrology and Water Quality, the climate is generally semiarid to arid, characterized by low
precipitation, abundant sunshine, frequent winds, moderate to low humidity, and high potential
evapotranspiration. Most precipitation occurs within the Project area between December and March;
average monthly precipitation for the Project area can be found in Table 5.9-1, Monthly Precipitation
Data for Bishop (Weather Station No. 35)—Years 1984–2013, and Table 5.9-2, Monthly Precipitation
Data for Owens Valley North (Weather Station No. 183)—Years 2003–2013.
Regional Geology
Inyo County is characterized by extremes in topographic features consisting of high mountain ranges
contrast with deep intervening valleys. The geology of the mountain ranges differs greatly from that of
the neighboring valleys. These fault-block ranges were formed when large blocks of earth bounded by
faults in the Earth’s crust were uplifted during periods of tectonic activity. Valleys were formed between
1
2
U.S. Geological Survey (USGS) and California Division of Mines and Geology (now California Geological Survey [CGS],
“Geologic Map of California,” National Geologic Map Database (1966).
California Geological Survey (CGS) “California Geomorphic Provinces, (2002). Based on the Geomorphic Map of California
prepared by Olaf P. Jennings, 1938; revisions of the text by D. L. Wagner, 2002, http://www.conservation.ca.gov/cgs
/information/publications/cgs_notes/note_36/Documents/note_36.pdf.
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these ranges as a result of the relative downward movement of the valley floor, combined with the
uplift of the surrounding mountains. 3
The Sierra Nevada, composed largely of granitic rock, flanks the western Owens Valley, composed of
slightly to moderately consolidated sedimentary material (alluvium) and areas of volcanic flow rock. The
White-Inyo Mountains are made up largely of granite, sandstone, shale, conglomerate, and volcanic
flow rock. Alluvial material dominates neighboring Saline Valley. Conglomerate rock, with smaller
amounts of sandstone-shale-limestone rock formations and volcanic flow rock, dominates the Panamint
Mountains east of Saline Valley, whereas Death Valley to the east is underlain by layers of alluvium. 4
Local Geology
Within the upper Owens Valley area of Inyo County are the unincorporated communities of Aberdeen,
Big Pine, Independence, Lone Pine, and the City of Bishop. The Owens Valley is a deep north–south
trending fault bounded basin lying between the Sierra Nevada on the west and the Inyo-White
Mountains on the east. 5 The bedrock beneath the Owens Valley is covered with thousands of feet of
sediment. The fill of the Owens Valley is particularly thick east of the Alabama Hills near Lone Pine. 6
These sedimentary deposits are formed of multiple layers of fine sand, silt, and clay.
Figures 5.6-1 through 5.6-7, Geologic Units in the Project Area show the localized geology of the areas
of the proposed routes. These include:
•
The City of Bishop and surrounding areas (Figures 5.6-1 and 5.6-2) lie directly on alluvial fill, and
proposed routes extending outward from the City primarily cross over quaternary alluvium deposits,
Pleistocene nonmarine deposits, and some pyroclastic deposits. There are smaller portions of the
Precambrian Wyman Formation, the Cambrian Deep Springs Formation, and Mesozoic granite
underlying the routes farthest from the City center.
•
The Aberdeen Area (Figure 5.6-3) generally lies across Quaternary alluvium deposits, with small
amounts of basalt and rhyolite flows. Big Pine Area (Figure 5.6-4) lies predominantly on Quaternary
alluvium deposits, with some routes crossing over Mesozoic granite, Pleistocene nonmarine
deposits, and basalt and rhyolite flows.
•
The Death Valley Road Area (Figure 5.6-5) is primarily underlain by Pleistocene nonmarine deposits,
with some small sections passing across the Precambrian Wyman Formation.
3
4
5
6
Inyo County General Plan, “Public Safety Element,” 9-37 (2001).
Inyo County General Plan, “Public Safety Element,” (2001).
Darla Heil, “Owens Valley Geology,” Owens Valley Committee (n.d.), http://www.ovcweb.org/owensvalley/geology.html.
Heil, “Owens Valley Geology.”
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•
Independence Area (Figure 5.6-6) lies on Quaternary alluvium deposits, with some Cambrian
Tamarack Canyon Dolomite and Mississippi-Pennsylvanian Rest Springs Shale.
•
Lone Pine Area (Figure 5.6-7) lies on Quaternary alluvium deposits and Quaternary lake deposits,
with some Mesozoic granite interspersed.
Faulting and Seismicity
The California Geologic Survey (CGS) classifies active faults as those that have, or are suspected to have,
ruptured within the Holocene epoch, which is within the last 11,700 years. CGS classifies potentially
active faults as those that have evidence of activity within the Quaternary period (last 1.6 million years),
but give no indication of Holocene seismic events. Active faults are typically identified based on
recorded seismic events or by radiocarbon dating of recent (Holocene) sediments that have been offset
during prior earthquakes.
The geologic forces that helped shape Inyo County are also responsible for the numerous faults
traversing the valleys and mountain ranges. The Project area is located in an active seismic region.
According to the USGS, low-magnitude earthquakes occur almost daily throughout Inyo County, and
earthquakes of highly destructive magnitudes have been recorded in recent geologic history. 7
The Basin and Range Province is traversed by a group of subparallel normal faults trending roughly
north–south. 8 The lengths of the Owens Valley, Death Valley, and Panamint Valley are underlain by fault
zones extending several miles. The Sierra Nevada, White-Inyo, and Panamint ranges contain localized
networks of faults, many of which have been active in the recent geologic past. 9
The Owens Valley Fault, the nearest active fault to the Project area, is capable of generating an
earthquake of a magnitude of 8.0 or greater. The fault passes through Lone Pine near the eastern base
of the Alabama Hills and follows the floor of the Owens Valley northward to the Poverty Hills, where it
steps 3 kilometers to the left and continues northward across Crater Mountain and through Big Pine.10
Data suggests an average slip rate for the Owens Valley Fault of between 1.5 and 2mm/yr for the last
Inyo County General Plan, “Public Safety Element,” 9-39 (2001).
USGS, “Geologic Provinces of the United States: Basin and Range Province,” USGS Geology in the Parks (2000),
http://www.nature.nps.gov/geology/usgsnps/province/basinrange.html.
9 State of California Department of Conservation, “Inyo County Regulatory Map,” http://www.quake.ca.gov/gmaps
/WH/regulatorymaps.htm.
10 Sarah Beanland and Malcolm M. Clark The Owens Valley Fault Zone, Eastern California, and Surface Faulting Associated
with the 1872 Earthquake, US Geological Survey Bulletin (Denver: US Geological Survey, 1982).
7
8
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300,000 years. The fault zone passes directly underneath the proposed network of combined-use routes
in these areas.
Liquefaction
Liquefaction occurs most often where groundwater is within 30 feet of the surface, but it may also occur
in areas where groundwater is located up to 50 feet beneath the surface. Liquefaction is the loss of
strength in generally cohesionless, saturated soils when the pore-water pressure induced in the soil by a
seismic event becomes equal to or exceeds the overburden pressure. The primary factors that influence
the potential for liquefaction include the groundwater table elevation, the soil type and grain size
characteristics, the relative density of the soil, the overburden or confining pressure, and the intensity
and duration of ground shaking. The depth within which the occurrence of liquefaction may impact
surface improvements is generally identified as the upper 50 feet below the existing ground surface.
The presence of a high groundwater table (within 50 feet of the ground surface) is a main factor in
liquefaction potential.
Slope Stability
A landslide occurs when slopes become unstable and collapse. Natural factors, such as fractured or
weak bedrock, heavy landfall, erosion, earthquake activity, and fire, as well as human alteration of
topography and water content, cause landslides or slope instability. Portions of the upper Owens Valley
are near the base of the Inyo-White Mountains; rock avalanches and debris flows have been
documented in this area and have caused road closures. For example, severe thunderstorms in July 2013
resulted in landslides, debris flows, and major rockfalls. As a result, a number of roads, including Wyman
Canyon Road, Division Creek Road, and Mazourka Canyon Road, became unpassable to vehicles. 11
Forest roads, especially those on steeper slopes (40 percent), are subject to failure through mass
wasting processes. 12
Soils
Soils in the upper Owens Valley area can generally be differentiated according to their texture.
Mountainous areas contain gravelly and sandy soils. Valleys that historically did not contain lakes are
generally loamy in texture, whereas areas with historic lake-type environments are generally clayey.
11 U.S. Forest Service, Inyo National Forest, “Severe Thunderstorms Cause Road and Trail Damage on the National Forest in
Inyo County,” news release, July 31, 2013.
12 U.S. Forest Service, Final Environmental Impact Statement: Inyo National Forest Motorized Travel Management (Bishop,
CA: 2009).
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Areas in Inyo County with coarse-textured soils include the Sierra Nevada and the White-Inyo, Coso, and
Panamint Mountains. Loamy soils predominate in Saline Valley and on alluvial fans. Portions of Death
Valley and the Owens area are underlain by clayey soils as a result of the historic presence of water in
these areas. 13
Erosion that exceeds normal geologic erosion becomes destructive and is called accelerated erosion.
This type of erosion occurs when the soil and natural vegetation are disturbed by human activity. Soils
that are susceptible to erosion include soils with low water infiltration capability, soils with low organic
matter content, soils with poor (unstable) structure, soils on steep hills (especially in regions of high
rainfall), and soils with hydrophobic characteristics (usually intensified by fire). 14 Soils most susceptible
to erosion include dry coarse and loamy textured sands. Well-drained and clayey-textured soils are less
susceptible to erosion.
Soil surveys provide a landscape scale assessment of soil properties, behaviors, and inherent limitations
or hazards. As described in the soil survey for the Inyo National Forest Area, Eastern Part, the area over
which the Project network of proposed routes spans, the composition of the underlying rock determines
the composition of the soil. In turn, the composition of the soil determines how well the soil will
compact, how well it drains, which in turn contribute to how resistant to erosion it is. 15 The effects of
off-highway vehicle (OHV) use on soils are most evident in desert soils and other easily eroded soil types
such as the granitic-based soils underlying the Project area. 16
The eastern side of the Inyo National Forest can be broken up into three regions with respect to soil
types: alluvial plains, temperate uplands, and cold uplands.
Soils of the alluvial plains make up 8 percent of the area and have a depth that ranges from 14 inches to
greater than 60 inches. Elevations range from 3,800 to 10,100 feet, and soil temperature regimes are
generally mesic to frigid. 17 A description of typical soils found on the alluvial plains can be found in
Table 5.6-1, Soil Types in the Project Area (Alluvial Plains).
Soils of the temperate uplands make up 81 percent of the area, and soil depths range from 4 inches to
greater than 60 inches. Elevations range from 4,100 to 12,700 feet, and temperature regimes are
13 Inyo County General Plan “Public Safety Element,” (2001).
14 University of British Columbia, Faculty of Land and Food Systems, “Soil Management,” SoilWeb200 (n.d.),
(http://www.landfood.ubc.ca/soil200/soil_mgmt/soil_erosion.htm#312.
15 USDA Soil Conservation Service, “Soil Survey, Inyo National Forest Area, Eastern Part, California and Nevada (1994).
16 USDA Forest Service, “Unmanaged Motorized Recreation,” position paper (n.d.), http://www.fs.fed.us/publications/policyanalysis/unmanaged-recreation-position-paper.pdf.
17 USDA Soil Conservation Service, “Soil Survey, Inyo National Forest Area, Eastern Part” (1994).
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generally mesic to frigid. 18 In addition to Xerollic Haplargids, typical soils are described in Table 5.6-2,
Soil Types in the Project Area (Temperate Uplands).
Soils of the cold uplands comprise 11 percent of the East Inyo National Forest Survey Region. Elevations
range from 8,800 to 14,250 feet, and soil depth ranges from 39 to over 60 inches; 19 the temperature
regime is cryic. Typical soils include are described in Table 5.6-3, Soil Types in the Project Area (Cold
Uplands).
Existing Road Network
The County’s existing roadway network, as described in Section 4.0, Environmental Setting, links the
unincorporated communities of Aberdeen, Big Pine, Independence, and Lone Pine and the City of
Bishop. Of the total 1,226 miles of County- and City-maintained roads, 588.6 miles are unpaved. Regular
vehicles already utilize the existing roadway network for a variety of purposes. Current illegal nonstreet-legal vehicle usage in relation to the percentage of total Average Daily Traffic (ADT) on paved and
unpaved portions of the proposed routes can be found in Table 5.6-4, Current Illegal Non-Street-Legal
Vehicle Usage of Proposed Combined-Use Routes. It is important to note that this table was derived
from the observations of County staff.
Groundwater
The Owens Valley Groundwater Basin has a surface area of 661,000 acres. The Basin is bound by the
Benton Range on the north, the Coso Range on the South, the Sierra Nevada on the west, and the White
and Inyo Mountains on the east. This system of valleys is drained by several creeks to the Owens River,
which flows southward into the Owens Lake, a closed-drainage depression in the southern part of the
Owens Valley. 20 The water-bearing materials of this basin are sediments that fill the valley and reach at
least 1,200 feet thick. The primary productive unit is Quaternary in age and is separated into upper,
lower, and middle members, composed respectively of unconsolidated coarse alluvial fan material, finegrained fluvial and lacustrine material, and Bishop Tuff, fluvial, and lacustrine material. 21
18 USDA Soil Conservation Service, “Soil Survey, Inyo National Forest Area, Eastern Part” (1994).
19 USDA Soil Conservation Service, “Soil Survey, Inyo National Forest Area, Eastern Part” (1994).
20 South Lahontan Hydrologic Region, “Owens Valley Groundwater Basin,” California’s Groundwater, Bulletin 118 (2004),
http://www.water.ca.gov/pubs/groundwater/bulletin_118/basindescriptions/6-12.pdf.
21 USGS. c. 1998.
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Table 5.6-1
Soil Types in the Project Area (Alluvial Plains)
Soil Type
Typic/Xeric
Torriorthents
Parent Material Texture
Alluvium
Coarsederived from
loamy
granitic and
mixed rocks
Depth and
Common
Typical
Drainage
Shallow to
deep; well
drained
Location
Low hills, inset
fans, stream
terraces
Vegetation
Annual grasses
and forbs
Slope
Gentle to
steep
Xeric
Alluvium
Torripsamments derived from
granitic and
mixed rocks
Little clay
Very deep,
and organic excessively
matter,
drained
resulting in
loose soil
Alluvial fans,
Sagebrush
stream terraces,
inset fans, fan
piedmonts,
mountain valleys
Typic
Alluvium
Xeropsamments derived from
granitic rocks
Loamy sand,
with 0 to 10
percent of
surface
covered by
coarse gravel
Mountain slopes Annual grasses, 5 to 75
and valleys,
shrubs, scattered percent
alluvial fans, flood oaks
plains
Xerollic
Haplargids
Moderately Very deep; well Inset fans and fan Grasses and
coarse upper drained
skirts
sagebrush
layer,
mediumtextured
middle layer,
coarse and
gravelly
lower layer
Zero to
35
percent
Typic Durargids Alluvium
derived from
granitic and
mixed rocks
Gravelly,
Shallow, well
moderately drained
coarse upper
layer;
moderately
fine textured
lower layer
over
indurated
hardpan
Gentle to
strong
Typic
Camborthids
Gravelly
desert
pavement
underlain by
clayey to
sandy loam
Lacustrine
deposits
Alluvium
derived from
mixed rocks
Very shallow,
somewhat
excessively
drained
Piedmont slopes
Very dry;
Alluvial plain
contain little
organic matter
or water
Annual grasses
0 to 15
percent
Grasses and forbs Gentle to
very
strong
Sources: USDA Soil Conservation Service, Soil Survey of Eureka County Area, Nevada; Soil Survey of Storey County Area, Nevada; Soil Survey of
Inyo National Forest Area, Eastern Part, California and Nevada (1994).
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Table 5.6-2
Soil Types in the Project Area (Temperate Uplands)
Depth and
Soil Type
Parent Material
Texture
Typical
Drainage
Common Location
Very shallow
to shallow;
well drained
Mountain slopes
Grasses and 15 to 75
percent
shrubs,
juniper,
bitterbrush
Lithic
Volcanic,
Loamy-skeletal Shallow; well
Torriorthents limestone,
drained
dolomite,
marble, plutonic,
and/or
noncarbonated
sedimentary and
metamorphic
rocks
Mountain slopes
Grasses and
shrubs
Aridic
Argixerolls
Back slopes, colluvial
Grasses and
slopes, mountain-valley sagebrush
fans
Aridic/Lithic Residuum
Loamy sand
Haploxerolls weathered from
schist and/or
metasedimentary
rock
Volcanic,
limestone,
dolomite,
marble, plutonic,
and/or
noncarbonated
sedimentary and
metamorphic
rocks
Gravelly,
Moderately
moderately
deep to deep
coarse textured
upper layer,
medium- to
moderately fine
textured lower
layer
Vegetation
Slope
30 to
50
percent
Gentle
to
steep
Sources: USDA, Soil Conservation Service, Soil Survey of Eureka County Area, Nevada; Soil Survey of Storey County Area, Nevada; Soil Survey of
Inyo National Forest Area, East Part, California.
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Table 5.6-3
Soil Types in the Project Area (Cold Uplands)
Depth and
Soil Type
Parent Material
Texture
Vegetation
Slope
Pergelic
Plutonic,
sedimentary
and/or
metamorphic
rock
Silt/sandy loam Permafrost
Colluvial and/or alluvial
when moist, or positions on high
dry frost if no mountains
excess water
Goldenbrush,
bluegrass,
lupine,
bristlecone
pine
Steep
Loamy
Goldenbrush,
bluegrass,
lupine,
bristlecone
pine
Steep
Typic
Plutonic,
Cryoborolls sedimentary
and/or
metamorphic
rock
Drainage
Typical
Common Location
Shallow to
deep; well
drained
Colluvial and/or alluvial
positions on high
mountains
Sources: USDA Soil Conservation Service, Soil Survey of Eureka County Area, Nevada; Soil Survey of Storey County Area, Nevada; Soil Survey of
Inyo National Forest Area, East Part, California.
Table 5.6-4
Current Illegal Non-Street-Legal Usage of Proposed Combined-Use Routes
Road
Percentage on
Paved Portion
Percentage on
Dirt Portion Route(s)
Airport Road
<1
–
Bishop No. 2, 3, 4
Baker Creek Road
~5
–
Big Pine No. 3
Barlow Lane
<1
–
Bishop No. 9
Begone Street
<1
–
Lone Pine No. 5
Bir Road
<1
–
Bishop No. 9
Birch Creek Road
–
~5
Aberdeen No. 1
Black Canyon Road
–
~25
Bishop No. 18
Bruce Street
<1
–
Bishop No. 3
Casa Diablo Road
–
~10
Bishop No. 8
Chalk Bluff Road
–
<1
Bishop No. 8
Clay Street (south)
<1
–
Independence No. 1
Coats Street
<1
–
Bishop No. 2
County Road
~5
~5
Big Pine No. 1
Coyote Valley Road
–
~25
Bishop No. 10
Crocker Avenue
<1
–
Big Pine No. 1, 2, and 3
Death Valley Road
<1
–
Death Valley Road No. 1, 2, and 3
Division Creek Road
–
~10
Aberdeen No. 3
Dolomite Loop Road
–
~5
Lone Pine No. 3
<10
–
Bishop No. 1, 2, 3, 4, 5, 15, and 18
Eastside Road
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Road
Percentage on
Paved Portion
Percentage on
Dirt Portion Route(s)
Ed Powers Road
<1
–
Bishop No. 7
Foothill Road
~5
~5
Independence No. 3, 4, and 6
Gene Autry Lane
<1
–
Lone Pine No. 2
Glacier Lodge Road
<1
–
Big Pine No. 2 and 3
Hanby Avenue
<1
–
Bishop No. 2, 3, and 4
Haul Road
–
~10
Bishop No. 2, 3, and 4
Hogback Road
–
~10
Lone Pine No. 7
Horseshoe Meadow Road
<1
–
Lone Pine No. 1, 2, 4, and 5
Horton Creek Road
<1
–
Bishop No. 6
Jackson Street (Independence)
<1
–
Independence No. 3
Jackson Street (Lone Pine)
<1
–
Lone Pine No. 5
Jean Blanc Road
–
~15
Joe Smith Road
~1
–
Bishop No. 14, 15, and 16
Kearsarge Street
<1
–
Independence No. 6
Keough’s Hot Springs Road
<1
–
Big Pine No. 1
Laws Poleta Road
~10
–
Bishop No. 15
Line Street, East
<1
–
Bishop No. 1, 2, 3, and 4
Lone Pine Avenue
<1
–
Lone Pine No. 6
Lone Pine Narrow Gauge Road
<1
–
Lone Pine No. 3
Lubkin Canyon Road
<1
–
Lone Pine No. 1
MacIver Street
<1
–
Bishop No. 4
Market Street
<1
–
Independence No. 3, 4, and 6
Mazourka Canyon Road
<5
~5
Independence No. 1 and 2
McMurray Meadows Road
–
~10
Big Pine No. 2 and 3
Movie Road
<1
~5
Lone Pine No. 2, 4, 5, and 7
Onion Valley Road
<1
–
Independence No, 3, 4, and 6
Owenyo–Lone Pine Road
~5
~5
Lone Pine No. 3
Park Street (Bishop)
<1
–
Bishop No. 3
Park Street, East (Independence)
<1
–
Independence No. 1 and 3
Pine Street
<1
–
Big Pine No. 3
Pleasant Valley Dam Road
<1
–
Bishop No. 6, 7, and 8
Poleta Road
~5
–
Bishop No. 1, 2, 3, 4, and 15
Poplar Street
<1
–
Big Pine No. 3
Redding Canyon Road
–
~10
Round Valley Road
<1
–
Bishop No. 6
Sawmill Road
<1
–
Bishop No. 6 and 7
Schober Lane
<1
–
Bishop No. 9
School Street
~5
–
Big Pine No. 1 and 3
Short Street
<1
–
Bishop No. 1
Silver Canyon Road
~5
~25
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Bishop No. 14
Bishop No. 1, 2, 3, 4, 5, 15, and 18
Bishop No. 11, 12, and 16
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Percentage on
Paved Portion
Road
Percentage on
Dirt Portion Route(s)
Sneden Street
<1
–
Bishop No. 1
Spruce Street
<1
–
Bishop No. 2, 3, and 4
Statham Way
<1
–
Lone Pine No. 4
Sunland Drive
<1
–
Bishop No. 5
Sunset Drive
<1
–
Lone Pine No. 2, 4, 5, and 6
Taboose Creek Road
–
~10
Aberdeen No. 2
Tinemaha Road
~5
<5
Aberdeen No. 1, 2, and 3
Tungsten City Road
–
~5
Bishop No. 7
Tuttle Creek Road
<1
–
Lone Pine No. 4, 5, and 6
Washington Street (Independence)
<1
–
Independence No. 4 and 6
Washington Street (Lone Pine)
<1
–
Lone Pine No. 2 and 4
Wall Street
<1
–
Independence No. 4
Warm Springs Road
~5
~5
Bishop No. 5
Whitney Portal Road
<1
~10
Lone Pine No. 2, 4, 5, and 6
Wye Road (City)
<1
–
Bishop No. 2, 3, and 4
Wye Road (County)
~5
–
Bishop No. 2, 3, and 4
Wyman Canyon Road
–
~25
Bishop No. 12 and 17
Yaney Street
<1
–
Bishop No. 2, 3, and 4
Source: Inyo County Planning Department (2014).
5.6.2 REGULATORY SETTING
5.6.2.1
Federal Regulations
National Forest Management Act of 1976: Renewable Resource Program
The National Forest Management Act of 1976 was passed as an amendment to the Forest and
Rangeland Renewable Resources Planning Act of 1974, which called for the management of renewable
resources on national forest lands. 22 The National Forest Management Act seeks to recognize the
fundamental need to protect and, where appropriate, improve the quality of soil, water, and air
resources. 23 With respect to transportation systems throughout national forests, the act specifies that
roads shall be designed to standards appropriate for the intended uses, considering safety, cost of
transportation, and impacts on land and resources. 24
22 Forest and Rangeland Renewable Resources Planning Act of 1974, 16 USC 36 (1974).
23 National Forest Management Act of 1976, 4.
24 National Forest Management Act of 1976, 8.
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Inyo National Forest Land and Resource Management Plan
The Inyo National Forest Land and Resource Management Plan (LRMP) contains standards and
guidelines that set minimum resource conditions that must be maintained throughout Inyo National
Forest. The Inyo National Forest LRMP includes the following management direction related to soil
resources: 25
•
Reduce accelerated erosion resulting from management activities to natural background levels
within three years after the soil-disturbing activity.
•
Conserve the surface mineral and/or organic layer of the soils by minimizing soil disturbance to
maintain long-term soil productivity.
•
Require an interdisciplinary review to avoid or mitigate adverse impacts for any projects or activities
proposed in areas identified in the soil resource inventories as having an erosion hazard rating of
nine or greater.
•
Limit land disturbance to no more than five percent per decade on that portion of a management
area characterized by steep slopes, very high erosion potential or high instability.
•
Avoid the use of soil-disturbing equipment, OHVs, and trampling by livestock on wet and poorly
drained soils whenever possible.
•
Locate roads and trails on natural benches or ridges well away from stream courses and other water
bodies where possible. Avoid constructing roads and trails that parallel or cross tributaries to a main
stream.
•
Use the steepest permissible pitches and grades to avoid paralleling the stream at stream crossings.
Design to maintain the existing width: depth ratio of the stream.
•
Wild and Scenic Rivers (Management Area 8)—Scenic Segment: Allow camping and OHV use at
locations at least 100 feet from the river’s edge. 26
25 USDA Forest Service, Inyo National Forest Land and Resource Management Plan (1988), 94–96.
26 USDA Forest Service, Inyo National Forest Land and Resource Management Plan (1988), 128.
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5.6.2.2 State Regulations
Soil Conservation Standards and Guidelines of 2008
The California State Parks Off-Highway Motor Vehicle Recreation Division updated the 1991 Soil
Conservation Guidelines and Standards in 2008 to establish a generic and measurable soil conservation
standard. 27 The standard and supporting guidelines are intended to ensure appropriate resource
management and maintenance in areas of OHV use. Specifically, OHV recreation facilities will be
managed for “sustainable long-term prescribed use without generating soil loss that exceeds
restorability, and without causing erosion or sedimentation which significantly affects the resource
values beyond the facilities.” 28 Topography, climate, geology and soils, vegetation, hydrology, air
quality, and wildlife should all be considered in the management of an OHV area. When areas or trails
cannot be maintained to established standards for sustained long-term use, they will be closed to use
and repaired to prevent accelerated erosion.
5.6.2.3
Local Regulations
Inyo County General Plan
The Public Safety Element of the Inyo County General Plan seeks to minimize exposure to hazards and
structural damage from geologic and seismic conditions. 29 The goal for geologic and seismic hazards as
listed in the Public Safety Element includes the following policies: 30
Policy GEO-1.1
Development Hazard Constraints. Restrict development of inhabitable
structures in areas that are subject to severe geologic hazards, such as AlquistPriolo Special Studies Zones, liquefaction zones, landslide areas, and seismically
induced unstable soils.
Policy GEO-1.3
Disaster Preparedness. Promote and provide education to prepare inhabitants
of the County for disaster events.
The Conservation/Open Space Element of the Inyo County General Plan seeks to maintain the
productivity of Inyo County’s soils, in addition to recognizing development limitation of soil types in
27 California State Parks Off-Highway Motor Vehicle Recreation Division, “2008 Soil and Conservation Standard and Guidelines”
(n.d.), http://ohv.parks.ca.gov/pages/1140/files/2008%20soil%20cons.%20standard%20and%20guidelines.pdf.
28 California State Parks Off-Highway Motor Vehicle Recreation Division, “2008 Soil and Conservation Standard and
Guidelines” (n.d.).
29 Inyo County General Plan, “Public Safety Element,” 9-29 (2001).
30 Inyo County General Plan, “Public Safety Element,” 9-29 (2001).
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review and approval of future development projects. 31 The Conservation/Open Space Element includes
the following policies regarding soil and erosion: 32
Policy S-2.1
Soil Erosion. Minimize soil erosion from wind and water related to new
development.
Policy S-2.3
Soil Instability. In areas of unstable soils and/or steep terrain, the County shall
limit the intensity of development in order to minimize the potential for erosion
and landform instability.
City of Bishop General Plan
The Safety Element in the City of Bishop General Plan is consistent with the goals and policies set forth in
the Inyo County General Plan. The purpose of the Safety Element is “to reduce loss of life, injuries, and
damage to property resulting from natural and man-caused public safety hazards.” 33 The City of Bishop
General Plan includes provisions for soil disturbance including erosion. Applicable policies include:
•
Geologic conditions of the area, as well as the characteristics of the soil must be carefully managed
to assure that no disruption to sensitive watershed areas occurs.
5.6.3 THRESHOLDS OF SIGNIFICANCE
In order to assist in determining whether a project would have a significant effect on the environment,
CEQA identifies criteria for conditions that may be deemed to constitute a substantial or potentially
substantial adverse change in physical conditions. Specifically, Appendix G of the State CEQA Guidelines
(Environmental Checklist Form) lists the following thresholds, under which a project may be deemed to
have a significant impact on geology and soils if it would:
•
Result in substantial soil erosion or the loss of topsoil.
Potential geology and soil impacts that were determined to be less than significant or have no impact
are discussed in Section 7.1, Effects Found Not to Be Significant.
31 Inyo County General Plan, “Conservation/Open Space Element,” 8-4 (2001),
32 Inyo County General Plan, “Conservation/Open Space Element,” 8-4 (2001),
33 City of Bishop General Plan, “Safety Element,” 10-4, (1981).
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METHODOLOGY
5.6.4 PROJECT IMPACTS
The environmental impact analysis presented below is based on determinations made in the Initial
Study (IS) for impacts considered to be potentially significant and for impacts identified by reviewing
agencies, organizations, or individuals commenting on the Notice of Preparation (NOP) as potentially
significant (see Responses to NOP, Appendix 2.0-d).
5.6.4.1
Result in substantial soil erosion or loss of topsoil
Impact Analysis
Erosion is an impact caused by human activity and disturbance of surface soil, and can naturally occur by
wind and water. Roads are considered the principal cause of accelerated erosion in forests throughout
the western United States. 34 Use of combined-use roadways by OHVs may increase the amount of
erosion bordering existing roads and creek crossings due to the following factors: the alteration of soil
properties (soil compaction in particular); removal or displacement of protective topsoil, including the
alteration of natural soil structure (biotic and abiotic crusts) and desert pavement (fine gravel surfaces)
that would otherwise stabilize soils; diminished soil fertility; and the changing of the soil microclimate. 35
Increased OHV activity on the proposed routes may increase soil compaction due to multiple passes of
heavy vehicles across the same area, diminishing the natural rehabilitation ability of the soil. Soil
compaction destroys soil stabilizers and inhibits water infiltration, resulting in less soil moisture available
to vegetation so that soil fertility, root growth, and vegetative cover is diminished, further exacerbating
the soil’s susceptibility to erosion. In turn, precipitation runoff increases in volume and velocity, even
further accelerating erosion and sedimentation. Indicators of soil compaction as a result of OHV use
include soil bulk density (weight per unit of volume), soil strength (the soil’s resistance to deforming
forces), and soil permeability (the rate at which water or air infiltrates soil). 36 Generally, soil bulk density
and strength increase with compaction, whereas permeability decreases with compaction. Factors
affecting soil’s susceptibility to compaction include soil type, texture, structure, porosity, and depth.
Loamy, coarse-textured, gravelly soils such as those found over much of the Project area are more
vulnerable to compaction, and therefore to erosion, than are sandy or clayey soils.
34 Leslie M. Reid and Thomas Dunne, “Sediment Production from Forest Road Surfaces,” Water Resources Research 20 no. 2
(November 1984).
35 Hermann Gucinski et al., Forest Roads: A Synthesis of Scientific Information. USDA Forest Service General Technical Report
PNW-GTR-509 (Portland, OR: May 2001), http://www.fs.fed.us/pnw/pubs/gtr509.pdf.
36 Douglas S. Ouren et al., Environmental Effects of Off-Highway Vehicles on Bureau of Land Management [BLM] Lands, US
Geological Survey Open-File Report 2007-1353 (Reston, VA: US Department of the Interior and US Geological Survey, 2007).
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OHV activity can result in the removal of protective topsoil as tires destabilize the delicate top layer of
soil. Continued OHV use inhibits plant growth in the absence of fertile topsoil, resulting in further soil
erosion. The loss of topsoil can also increase raindrop splash erosion because there are fewer plant
leaves to absorb the raindrop impacts. 37 A study of erosion from OHV trails on national forest lands
classified trails into three OHV disturbance classes (low, medium, and high) and used rainfall simulations
to measure hydraulic conductivity and erosion. 38 Generally, hydraulic conductivity decreases with an
increasing level of disturbance class and erosion generally increases with increasing level of disturbance.
Soil types tested ranged from gravelly to sandy loam, which are similar to soil types found throughout
the Project area. The study found that sites with loamy soils experienced an increase in runoff, with
erosion and sediment loss increasing in proportion to increased runoff. Gravelly soil sites experienced
increased erosion, which would be expected to be exacerbated by OHV traffic. The removal of
protective topsoil also creates conditions favorable to wind erosion. 39 Where disturbance exposes
individual particles and soil aggregates to the wind, or when physical or biological crusts are broken
apart, particle movement begins at lower wind speeds. 40
Although the majority of the proposed combined-use routes are on existing paved roads, many
proposed segments are on unpaved dirt roads, as shown in Tables 5.6-5 to 5.6-10, Paved and Unpaved
Roads in the Project Areas.
Certain proposed routes, or segments of routes, include more unpaved segments than do others. In the
Aberdeen Area, all three proposed routes include significant unpaved segments. Aberdeen Routes 2 and
3 both contain more unpaved than paved roadway.
In Big Pine, the majority of Route 1 is paved. However, County Road contains a 1-mile dirt segment. Big
Pine Routes 2 and 3 are primarily unpaved, with both routes involving 5.9 miles on McMurray Meadows
Road. With the exception of Route 1, routes in the Big Pine area contain unpaved segments of significant
length.
Routes concentrated within the center of Bishop are generally paved; these routes include Bishop
Routes 1 through 6, 9, and 15. Bishop Route 7 is split between paved and unpaved segments, but
37 Randy B. Foltz, “Erosion from All Terrain Vehicle (ATV) Trails on National Forest Lands,” paper no. 068012, presented at the
2006 American Society of Agricultural and Biological Engineers (ASABE) Annual International Meeting, 9–12 July 2006
(Portland, OR: ASABE, 2006), http://forest.moscowfsl.wsu.edu/engr/library/Foltz/Foltz2006e/ASABE2006e.pdf.
38 Foltz, “Erosion from All Terrain (ATV) Trails” (2006).
39 T. Adam Switalski and Allison Jones, Best Management Practices for Off-Road Vehicle Use on Forestlands, (Salt Lake City,
UT: Wild Utah Project, 2008), http://www.wildlandscpr.org/files/ORV_BMP_2008.pdf.
40 USDA Natural Resources Conservation Science, “Rangeland Soil Quality—Wind Erosion,” Soil Quality Information Sheet,
Rangeland Sheet 10 (2001), http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052501.pdf.
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contains a significant unpaved 2.7 mile segment on Tungsten City Road. The remaining routes in the
Bishop Area contain significant dirt or unpaved route segments. Bishop Routes 8, 12, 14, and 18 are
mostly unpaved, and Routes 10, 11, and 17 are completely dirt. The segments of dirt road on Bishop
Route 8 are 5.9 miles on Chalk Bluff Road and 1.4 miles on Casa Diablo. Route 12 involves 7.4 miles on
Wyman Canyon Road; Route 14 involves 3.6 miles on Jean Blanc Road and 1.4 miles on Casa Diablo
Road. Bishop Route 18 includes 5.6 miles on Black Canyon Road. Finally, Bishop Route 10 involves 2.1
miles on Coyote Valley Road, Route 11 involves 7.1 miles on Silver Canyon Road, and Route 17 involves
3.2 miles on Wyman Canyon Road.
All proposed combined-use routes within the Death Valley Road area are paved.
Table 5.6-5
Paved and Unpaved Roads in the Bishop Area
Route
Bishop Route 1
Road
Short Street
Sneden Street
East Line Street
Poleta Road
Eastside Road
Redding Canyon Road
Total
Paved Distance
0.1
0.1
0.4
4.0
0.7
–
5.3
Dirt Distance
–
–
–
–
–
0.6
0.6
Bishop Route 2 Alternative Coats Street
A
Yaney Street
Spruce Street
Wye Road
Haul Road
Airport Road
Poleta Road
Eastside Road
Redding Canyon Road
Total
0.1
0.5
0.4
0.8
–
0.3
3.1
0.7
–
5.9
–
–
–
–
1.2
–
–
–
0.6
1.8
Coats Street
Bishop Route 2 Alternative Yaney Street
B
Hanby Avenue
East Line Street
Poleta Road
Eastside Road
Redding Canyon Road
Total
0.1
0.7
0.5
0.3
4.0
0.7
–
6.3
–
–
–
–
–
–
0.6
0.6
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Route
Road
Coats Street
Yaney Street
Bishop Route 2 Alternative Spruce Street
C
Hanby Avenue
East Line Street
Poleta Road
Eastside Road
Redding Canyon Road
Total
Paved Distance
0.1
0.5
0.3
0.4
0.3
4.0
0.7
–
6.3
Bishop Route 3 Alternative Park Street
A
Bruce Street
Spruce Street
Wye Road
Haul Road
Airport Road
Poleta Road
Eastside Road
Redding Canyon Road
Total
Park Street
Bishop Route 3 Alternative Bruce Street
B
Spruce Street
Yaney Street
Hanby Avenue
East Line Street
Poleta Road
Eastside Road
Redding Canyon Road
Total
–
0.2
0.5
0.8
–
0.3
3.1
0.7
–
5.6
–
0.2
0.06
0.1
0.6
0.3
4.0
0.7
–
5.96
–
–
–
–
1.2
–
–
–
0.6
1.8
–
–
–
–
–
–
–
–
0.6
0.6
Park Street
Bruce Street
Bishop Route 3 Alternative Spruce Street
C
Hanby Avenue
East Line Street
Poleta Road
Eastside Road
Redding Canyon Road
Total
–
0.2
0.2
0.4
0.3
4.0
0.7
–
5.8
–
–
–
–
–
–
–
0.6
0.6
Bishop Route 4 Alternative MacIver Street
A
Spruce Street
Wye Road
Haul Road
Airport Road
0.2
0.3
0.8
–
0.3
–
–
–
1.2
–
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Dirt Distance
–
–
–
–
–
–
–
0.6
0.6
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5.6 Geology and Soils
Route
Road
Poleta Road
Eastside Road
Redding Canyon Road
Total
Paved Distance
3.1
0.7
–
5.4
Dirt Distance
–
–
0.6
1.8
Bishop Route 4 Alternative MacIver Street
B
Spruce Street
Yaney Street
Hanby Avenue
East Line Street
Poleta Road
Eastside Road
Redding Canyon Road
Total
0.2
0.1
0.1
0.6
0.3
4.0
0.7
–
6.0
–
–
–
–
–
–
–
0.6
0.6
MacIver Street
Bishop Route 4 Alternative Spruce Street
C
Hanby Avenue
East Line Street
Poleta Road
Eastside Road
Redding Canyon Road
Total
0.2
0.4
0.4
0.3
4.0
0.7
–
6.0
–
–
–
–
–
–
0.6
0.6
Bishop Route 5
Schober Lane
Sunland Drive
Warm Springs Road
Eastside Road
Redding Canyon Road
Total
0.5
1.5
5.3
1.7
–
9
–
–
–
–
0.6
0.6
Bishop Route 6
Pleasant Valley Dam Road
Round Valley Road
Horton Creek Road
Total
1.2
4.2
0.8
6.2
–
–
–
–
Bishop Route 7
Pleasant Valley Dam Road
Sawmill Road
Ed Powers Road
Tungsten City Road
Total
1.2
–
1.7
0.8
–
3.7
–
–
2.7
2.7
Bishop Route 8
Pleasant Valley Dam Road
Chalk Bluff Road
Casa Diablo Road
Total
0.8
–
–
0.8
–
5.9
1.4
7.3
Bishop Route 9
Schober Lane
Barlow Lane
1.5
0.5
–
–
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Route
Road
Bir Road
Total
Paved Distance
1.7
3.7
Dirt Distance
–
–
Bishop Route 10
Coyote Valley Road
Total
–
–
2.1
2.1
Bishop Route 11
Silver Canyon Road
Total
–
–
7.1
7.1
Bishop Route 12
Silver Canyon Road
Wyman Canyon Road
Total
1.9
–
1.9
–
7.4
7.4
Bishop Route 14
Joe Smith Road
Jean Blanc Road
Casa Diablo Road
Total
1.1
–
–
1.1
–
3.6
1.4
5.0
Bishop Route 15
Joe Smith Road
Silver Canyon Road
Laws Poleta Road
Poleta Road
Eastside Road
Redding Canyon Road
Total
0.2
0.5
2.9
1.1
0.7
–
5.4
–
–
–
–
–
0.6
0.6
Bishop Route 16
Joe Smith Road
Silver Canyon Road
Total
0.2
0.5
0.7
–
5.9
5.9
Bishop Route 17
Wyman Canyon Road
Total
–
–
3.2
3.2
Bishop Route 18
Redding Canyon Road
Eastside Road
Black Canyon Road
Total
–
1.7
–
1.7
0.6
–
5.6
6.2
Source: Inyo County Planning Department (2013).
Note: Distance is calculated in miles.
Table 5.6-6
Paved and Unpaved Roads in the Big Pine Area
Paved
Route
Big Pine Route 1
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Crocker Avenue
School Street
County Road
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Distance
0.2
0.5
7.0
Dirt Distance
–
–
1.0
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Paved
Route
Big Pine Route 2
Big Pine Route 3
Road
Keough’s Hot Springs
Total
Distance
0.3
8.0
Crocker Avenue
Glacier Lodge Road
McMurray Meadows Road
Total
0.5
2.0
–
–
–
5.9
2.5
5.9
0.1
0.1
0.2
0.2
0.3
2.0
–
–
–
–
–
–
–
5.9
2.9
5.9
Pine Street
Poplar Street
Baker Creek Road
School Street
Crocker Avenue
Glacier Lodge Road
McMurray Meadows Road
Total
Dirt Distance
–
1.0
Source: Inyo County Planning Department (2013).
Note: Distance is calculated in miles.
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Table 5.6-7
Paved and Unpaved Roads in the Death Valley Road Area
Paved
Route
Death Valley Route 1
Road
Death Valley Road
Total
Distance
2.1
2.1
Dirt Distance
–
–
Death Valley Route 2
Death Valley Road
Total
5.8
5.8
–
–
Death Valley Route 3
Death Valley Road
Total
3.8
3.8
–
–
Source: Inyo County Planning Department (2013).
Note: Distance is calculated in miles.
Table 5.6-8
Paved and Unpaved Roads in the Aberdeen Area
Route
Road
Tinemaha Road
Division Creek Road
Total
Paved Distance
2.8
1.6
4.4
Aberdeen Route 2
Tinemaha Road
Taboose Creek Road
Total
1.6
–
1.6
–
2.6
2.6
Aberdeen Route 3
Tinemaha Road
Birch Creek Road
Total
1.5
–
1.5
2.1
1.5
3.6
Aberdeen Route 1
Dirt Distance
–
2.0
2.0
Source: Inyo County Planning Department (2013).
Note: Distance is calculated in miles.
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Table 5.6-9
Paved and Unpaved Roads in the Independence Area
Paved
Route
Independence Route 1
Road
East Park Street
South Clay Street
Mazourka Canyon Road
Total
Distance
0.1
0.2
6.4
6.7
Dirt Distance
–
–
1.8
1.8
Independence Route 2
Mazourka Canyon Road
Total
–
–
4.0
4.0
Independence Route 3
Park Street
Jackson Street
Kearsarge Street
Washington Street
Market Street
Onion Valley Road
Foothill Road
Total
0.1
0.3
0.1
0.1
0.1
4.2
–
4.9
–
–
–
–
–
–
2.8
2.8
Independence Route 4
Wall Street
Washington Street
Market Street
Onion Valley Road
Foothill Road
Total
0.1
0.1
0.2
4.2
–
4.6
–
–
–
–
2.8
2.8
Independence Route 6
Kearsarge Street
Washington Street
Market Street
Onion Valley Road
Foothill Road
Total
0.1
0.1
0.2
4.2
–
4.6
–
–
–
–
2.8
2.8
Source: Inyo County Planning Department (2013).
Note: Distance is calculated in miles.
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Table 5.6-10
Paved and Unpaved Roads in the Lone Pine Area
Paved
Route
Road
Lubkin Canyon Road
Horseshoe Meadows Road
Total
Distance
3.4
0.9
4.3
Lone Pine Route 2
Gene Autry Lane
Washington Street
Whitney Portal Road
Tuttle Creek Road
Sunset Drive
Horseshoe Meadows Road
Whitney Portal Road
Movie Road
Total
0.03
0.2
0.5
3.9
0.3
2.1
0.4
0.3
7.73
–
–
–
–
–
–
–
–
–
Lone Pine Route 3
Lone Pine Narrow Gauge Road
Owenyo – Lone Pine Road
Dolomite Loop Road
Total
3.3
–
–
3.3
–
5.3
0.04
5.34
Lone Pine Route 4
Statham Way
Washington Street
Whitney Portal Road
Tuttle Creek Road
Sunset Drive
Horseshoe Meadows Road
Whitney Portal Road
Movie Road
Total
0.02
0.2
0.5
3.9
0.3
2.1
0.4
0.3
7.72
–
–
–
–
–
–
–
–
–
Lone Pine Route 5
Begole Street
Jackson Street
Whitney Portal Road
Tuttle Creek Road
Sunset Drive
Horseshoe Meadows Road
Whitney Portal Road
Movie Road
Total
0.03
0.2
0.6
3.9
0.3
2.1
0.4
0.3
7.83
–
–
–
–
–
–
–
–
–
Lone Pine Route 1
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Dirt Distance
–
–
–
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Paved
Route
Lone Pine Route 6
Lone Pine Route 7
Road
Lone Pine Avenue
Whitney Portal Road
Tuttle Creek Road
Sunset Drive
Horseshoe Meadows Road
Total
Hogback Road
Movie Road
Total
Distance
0.1
0.7
3.9
0.3
2.2
7.2
–
–
–
Dirt Distance
–
–
–
–
–
–
4.0
5.2
9.2
Source: Inyo County Planning Department (2013).
Note: Distance is calculated in miles.
In Independence, proposed routes are generally split between paved and unpaved segments. Route 2 is
the only proposed combined-use route that is completely unpaved in this area, involving 4.0 miles on
Mazourka Canyon Road. The remaining routes in this area are split between paved and dirt: Route 1
includes 1.8 miles on unpaved Mazourka Canyon Road; Routes 3, 4, and 6 include 2.8 miles on the
unpaved Foothill Road.
Finally, the majority of roads in the Lone Pine area are paved. The exceptions are Lone Pine Route 3,
with 5.3 miles of dirt segment on Owenyo–Lone Pine Road; and Lone Pine Route 7, which is all unpaved
but split between 4.0 miles on Hogback Road and 5.2 miles on Movie Road.
Surface erosion is greater on unpaved routes than on paved routes and is closely correlated to traffic
volume. Effects of erosion may be compounded on the routes with significant dirt segments, as
previously explained, because unpaved roads have less surface protection from both OHV tires and
precipitation. As discussed in Section 5.15, Transportation and Traffic, the proposed Project would
contribute an additional 1,406 average daily trips over the six areas during peak seasons (March 21
through June 21, and September 1 through October 31), and an additional 805 average daily trips over
the six areas during off-peak seasons (June 22 through August 31, and November 1 through March 20).
This corresponds to an average increase in OHV use throughout the proposed network of combined-use
routes of approximately 2.7 percent during peak season, and 1.35 percent during the off-peak season.
While minor, this increase in traffic volume means that soil would be more susceptible to disturbances
and will have less time to recover. Erosion and sedimentation problems are compounded in wet
weather, when OHVs can cause deep ruts and permanently damage trail treads. The months between
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ATV Adventure Trails of the Eastern Sierra
July 2014
5.6 Geology and Soils
December and March generally involve the wettest weather, since most precipitation occurs during this
period. Knobby and cup-shaped protrusions from OHV tires that aid the vehicles in traversing various
landscapes are responsible for major direct erosional losses of soil. 41 As the tire protrusions dig into the
soil, forces exceeding the strength of the soil are exerted to allow the vehicles to move forward.
Precipitation can saturate the earth, contributing to soil instability by adding weight and reducing the
cohesion of earthen materials. 42 Tread erosion may cause significant damage to trails to the extent that
they are no longer usable for vehicular passage. One of the main Project objectives is to provide
increased access to the Project area on a unified linkage of combined-use trails. In the event that a route
becomes unusable by OHVs due to accelerated erosion, the Project goals of increased access and
combined-use route connectivity would not be met. However, effects are reduced when OHV travel is
limited to roads and trails located and designed for motorized use, especially on paved roads. The
proposed Project would involve the designation of existing roads (both paved and unpaved) designed
for motorized use for combined use with OHVs.
There is no construction, development, grading, or other new ground-disturbing activities proposed with
the Project. The routes being evaluated in this analysis already exist on the ground. Proposed combineduse routes, especially those on paved roads, already have some degree of compaction, soil
displacement, and general lack of vegetation. The designation of existing routes for combined use by
OHVs is not expected to substantially alter existing topography. In terms of soil productivity, the
proposed routes are already considered nonproductive even though some are likely to have some
degree of soil productivity as evidenced by vegetation growth within the area directly surrounding the
route.
As previously mentioned, erosion is accelerated in wet weather, which generally occurs between
December and March in the Project area. The season of peak OHV-use overlaps with the wet weather
period during the end of March and through the month of April. Therefore, during these months
erosional impacts would increase further.
Impacts would be potentially significant.
Mitigation Measures
The following mitigation measure is identified to reduce significant soil erosion and loss of topsoil:
41 T. Adam Switalski and Allison Jones, Best Management Practices for Off-Road Vehicle Use (2008).
42 Salix Applied Earthcare and Geosyntec Consultants, OHV BMP Manual for Erosion and Sediment Control (Sacramento, CA:
California Department of Parks and Recreation, Off-Highway Motor Vehicle Recreation Division, 2007).
Meridian Consultants
052-001-13
5.6-26
ATV Adventure Trails of the Eastern Sierra
July 2014
5.6 Geology and Soils
MM-GEO-1
Implement a monitoring program throughout the month of March, during which time
the peak wet-weather season corresponds with the peak OHV-use season, on the
portions of unpaved roads susceptible to wet-weather damage by motor vehicles.
Increased monitoring and associated route maintenance would reduce the rutting and
subsequent channeling of surface water runoff that occurs predominantly during the
monsoon season. If a route includes any unpaved segment or combination of unpaved
segments exceeding 1 mile, the route would be subject to this mitigation measure. In
the Bishop Area, Routes 2 (Alternative A), 3 (Alternative A), 4 (Alternative A), 7, 8, 10–
12, 14, and 16–18 would require monitoring. All proposed routes in the Independence
Area would need monitoring. Finally, Lone Pine Routes 3 and 7 would require
monitoring.
Based on the results of the monitoring program and should substantial soil erosion
occur on said routes, the County would provide recommendations for soil treatment.
Treatment would include but not be limited to the options of adding a surface
treatment to the road to reduce erosion or decommissioning the combined-use routes
by not allowing the continued use of OHVs.
Level of Significance after Mitigation
Impacts would be less than significant.
5.6.5 INDIRECT IMPACTS
Impact Analysis
As discussed in Section 5.15, Transportation and Traffic, the proposed Project would contribute an
additional 1,406 average daily trips during peak seasons (March 21 through June 21, and September 1
through October 31) over the Project area, and an additional 805 average daily trips during off-peak
seasons (June 21 through August 31, and November 1 through March 20). This corresponds to an
average increase in OHV use throughout the proposed network of combined-use routes of
approximately 2.7 percent during peak season, and 1.35 percent during the off-peak season. These
additional OHV trips would be dispersed throughout the proposed combined-use routes.
As stated previously, the months between December and March generally involve the wettest weather,
since most precipitation occurs during this period. Protrusions from OHV tires that aid the vehicles in
traversing various landscapes are responsible for major direct erosional losses of soil. Tread erosion may
cause indirect damage to roads in surrounding lands to the extent that they are no longer usable for
vehicular passage.
Meridian Consultants
052-001-13
5.6-27
ATV Adventure Trails of the Eastern Sierra
July 2014
5.6 Geology and Soils
While the potential for indirect impacts to soil would exist, under the proposed Project, OHV users
would be limited to combined-use routes designated as part of the proposed Project, and OHV use in
nearby surrounding lands would be subject to the operating restrictions (hours of use) specified by their
appropriate jurisdiction. Restrictions may include road maintenance or decommissioning of roads as
determined by landowners or agencies responsible for those areas.
Indirect impacts would be less than significant.
Mitigation Measures
No mitigation is required.
Level of Significance after Mitigation
Cumulative impacts would be less than significant.
5.6.6 CUMULATIVE IMPACTS
Impact Analysis
As discussed above, the Project would result in less than significant impacts, with mitigation
incorporated, relative to soil and geologic resources. These impacts, although individually less than
significant, may be considered cumulatively significant if they would make a considerable contribution
to what would be deemed a significant increase in geologic hazards or soil erosion resulting from the
combined effects of the Project and any other past, present, and reasonably foreseeable projects.
The nature of the primary impact, soil erosion, is generally considered site specific and dependent on
local conditions. Therefore, the geographic context for the analysis of potential cumulative geology and
soil impacts consists of individual development sites. Although cumulative development in the County
may include numerous projects with geologic and soil impacts, as identified on Table 4.0-8, Related
Projects, these impacts would affect each individual project, rather than resulting in an additive
cumulative effect. Two of the related projects are located within 2 miles of proposed combined-use
routes: the Northland Power Independence Solar Project, and the Fort Independence Hotel and Casino.
All projects must be designed in accordance with State and City building standards.
The designation of existing road segments for combined-use by OHVs will increase access to the Project
area, resulting in a potential increase in recreation and the overall number of OHVs that utilize the
roads. Related projects will include construction of facilities, which could lead to an increase in traffic on
a temporary basis during construction, and on a permanent basis upon completion.
Meridian Consultants
052-001-13
5.6-28
ATV Adventure Trails of the Eastern Sierra
July 2014
5.6 Geology and Soils
Cumulative development would result in a less than significant cumulative impact related to geology
and soil hazards.
Mitigation Measures
No mitigation measures are required.
Level of Significance after Mitigation
Cumulative impacts would be less than significant.
Meridian Consultants
052-001-13
5.6-29
ATV Adventure Trails of the Eastern Sierra
July 2014
C?
Qal
LAWS
END ROUTE 15
BEGIN ROUTE 14,16
Qpvp
END ROUTE 11
BEGIN ROUTE 12
ROUTE 14
Qt
Qc
ROU TE 16
BLANCO MOUNTAIN
ROU TE 8
LAWS
Qal
Qt
Qpvp
Qpvp
Qpvp
FISH SLOUGH
ROVANA
END ROUTE 8
BEGIN ROUTE 6,7
C
FISH SLOUGH
END ROUTE 14
BEGIN ROUTE 8
C
R O UT E 11
END ROUTE 16
BEGIN ROUTE 11
ROUTE 6
C Qal
Qt
ROUTE 15
RO U T E 1 2
Qal
RO U
TE 7
Qt
ROVANA
FISH SLOUGH
TUNGSTEN HILLS
BISHOP
LAWS
Qal
BEGIN ROUTE 2,3,4
BLANCO MOUNTAIN
POLETA
CANYON
WESTGARD PASS
END ROUTE 7
BEGIN ROUTE 1
Qal
Qc
ROUTE 5
END ROUTE 9
POLETA
CANYON
Qc
BISHOP
Qc
END ROUTE 1,2,3,4,5,15
BEGIN ROUTE 18
E9
gr
gr
Qc
POLETA
CANYON
BISHOP
TUNGSTEN HILLS
UT
ROUTE 5,18
O
R
Qc
ROUTE 1,2,3,4,15
BEGIN ROUTE 5,9
Qal
BEGIN ROUTE 10
ROUTE 1,2,3,4
WESTGARD PASS
END ROUTE 6
END ROUTE 10
Qc
Locator Map
Death Valley
Road
Bishop
Qt - nonmarine terrace deposits
Independence
Ql - Quaternary lake deposits
Qc - Pleistocene non-marine depostis
Big Pine
Aberdeen
Lone Pine
Qpvb - basalt and rhyolite flows
Qpvp - pyroclastic deposits
³
CM - Mississippian Perdido Formation
SOURCE: Applied Earthworks, Inc - 2014
CP - Mississippian-Pennsylvanian Rest Springs
Shale
O - Ordovician Barrel Spring Formation, Johnson
Spring Formation, and Ely Springs Dolomite
C - Cambrian Tamarack Canyon Dolomite, Lead
Gulch Formation, Bonanza King Dolomite, Campito
Formation, Poleta Formation, Harkless Formation,
Emigrant, and Monola Formations
JTRv - Jurassic to Triassic metamorphosed
basaltic to rhyolitic tuffs and flows
bi - diorite and gabbro
gr - Mesozoic granite
C? - Cambrian Deep Springs Formation
ms - quartzite, hornblende, and marble
lpC - Precambrian Wyman Formation
END ROUTE 18
Basemap: California 7.5' USGS Quadrangles
Legend
Qal - Quaternary alluvium deposits
C?
0
N
0.5
1
2
APPROXIMATE SCALE IN MILES
FIGURE
5.6-1
Geologic Units in the Project Area (Bishop Routes 1-11, 14-16, 18)
052-001-13
C?
RO UT E 1 2
C
C?
lpC
CROOKED CREEK
BLANCO MOUNTAIN
C?
Qal
C
END ROUTE 12
BEGIN ROUTE 17
C
Qal
gr
END ROUTE 11
BEGIN ROUTE 12
END ROUTE 17
C
Locator Map
Death Valley
Road
Bishop
Qal - Quaternary alluvium deposits
Qt - nonmarine terrace deposits
Independence
Ql - Quaternary lake deposits
Qc - Pleistocene non-marine depostis
Big Pine
Aberdeen
Basemap: California 7.5' USGS Quadrangles
Legend
Lone Pine
Qpvb - basalt and rhyolite flows
Qpvp - pyroclastic deposits
³
CM - Mississippian Perdido Formation
SOURCE: Applied Earthworks, Inc - 2014
CP - Mississippian-Pennsylvanian Rest Springs
Shale
O - Ordovician Barrel Spring Formation, Johnson
Spring Formation, and Ely Springs Dolomite
C - Cambrian Tamarack Canyon Dolomite, Lead
Gulch Formation, Bonanza King Dolomite, Campito
Formation, Poleta Formation, Harkless Formation,
Emigrant, and Monola Formations
JTRv - Jurassic to Triassic metamorphosed
basaltic to rhyolitic tuffs and flows
bi - diorite and gabbro
gr - Mesozoic granite
C? - Cambrian Deep Springs Formation
ms - quartzite, hornblende, and marble
lpC - Precambrian Wyman Formation
0
N
0.5
1
2
APPROXIMATE SCALE IN MILES
FIGURE
5.6-2
Geologic Units in the Project Area (Bishop Routes 11, 12, 17)
052-001-13
TINEMAHA
RESERVOIR
BLACKROCK
TINEMAHA
RESERVOIR
Qpvb
FISH
SPRINGS
ms
TE
3
ROUTE 2,3
Qpvb
Qpvb
Qal
BEGIN ROUTE 2,3
END ROUTE 1
Qal
Qpvb
ms
gr
ms
RO U T E 1 2
ROUTE 2
Qal
BLACKROCK
ABERDEEN
U
RO
gr
Qpvb
ABERDEEN
END ROUTE 2
FISH SPRINGS
END ROUTE 3
Qpvb
gr
END ROUTE 1
Locator Map
Death Valley
Road
Bishop
Qal - Quaternary alluvium deposits
Qt - nonmarine terrace deposits
Independence
Ql - Quaternary lake deposits
Qc - Pleistocene non-marine depostis
Aberdeen
Lone Pine
³
Big Pine
Basemap: California 7.5' USGS Quadrangles
Legend
SOURCE: Applied Earthworks, Inc - 2014
Qpvb - basalt and rhyolite flows
Qpvp - pyroclastic deposits
CM - Mississippian Perdido Formation
CP - Mississippian-Pennsylvanian Rest Springs
Shale
O - Ordovician Barrel Spring Formation, Johnson
Spring Formation, and Ely Springs Dolomite
C - Cambrian Tamarack Canyon Dolomite, Lead
Gulch Formation, Bonanza King Dolomite, Campito
Formation, Poleta Formation, Harkless Formation,
Emigrant, and Monola Formations
JTRv - Jurassic to Triassic metamorphosed
basaltic to rhyolitic tuffs and flows
bi - diorite and gabbro
gr - Mesozoic granite
C? - Cambrian Deep Springs Formation
ms - quartzite, hornblende, and marble
lpC - Precambrian Wyman Formation
N
0
0.5
1
2
APPROXIMATE SCALE IN MILES
FIGURE
5.6-3
Geologic Units in the Project Area (Aberdeen Routes 1-3)
052-001-13
BEGIN ROUTE 1,2,3
RO
gr
UT
E
2 ,3
Qc
RO UT E 1 2
BIG PINE
gr
FISH SPRINGS
BIG
PINE
POLETA
CANYON
Qal
gr
Qpvb
END
ROUTE 2,3
Qal
gr
RO
bi
BIG PINE
FISH SPRINGS
COYOTE FLAT
COYOTE FLAT
Locator Map
Death Valley
Road
Bishop
Qt - nonmarine terrace deposits
Independence
Ql - Quaternary lake deposits
Qc - Pleistocene non-marine depostis
Big Pine
Aberdeen
Basemap: California 7.5' USGS Quadrangles
Legend
Qal - Quaternary alluvium deposits
Lone Pine
Qpvb - basalt and rhyolite flows
Qpvp - pyroclastic deposits
³
CM - Mississippian Perdido Formation
SOURCE: Applied Earthworks, Inc - 2014
SPLIT MOUNTAIN
SPLIT MOUNTAIN
gr
BISHOP
BISHOP
Qc
E1
COYOTE FLAT
POLETA
CANYON
END
ROUTE 1
UT
CP - Mississippian-Pennsylvanian Rest Springs
Shale
O - Ordovician Barrel Spring Formation, Johnson
Spring Formation, and Ely Springs Dolomite
C - Cambrian Tamarack Canyon Dolomite, Lead
Gulch Formation, Bonanza King Dolomite, Campito
Formation, Poleta Formation, Harkless Formation,
Emigrant, and Monola Formations
JTRv - Jurassic to Triassic metamorphosed
basaltic to rhyolitic tuffs and flows
bi - diorite and gabbro
gr - Mesozoic granite
C? - Cambrian Deep Springs Formation
ms - quartzite, hornblende, and marble
lpC - Precambrian Wyman Formation
N
0
0.5
1
2
APPROXIMATE SCALE IN MILES
FIGURE
5.6-4
Geologic Units in the Project Area (Big Pine Routes 1-3)
052-001-13
BEGIN ROUTE 2
Qc
Qal
C
END ROUTE 3
COWHORN
VALLEY
UHLMEYER
SPRING
RO UT E 1 2
Qal
C?
lpC
ROUTE 1
Qc
lpC
lpC
lpC
BEGIN ROUTE 1
END ROUTE 2
R
O
U
TE
3
lpC
lpC
R OU
UHLMEYER SPRING
TE 1
BEGIN ROUTE 3
END ROUTE 1
TINEMAHA
RESERVOIR
Death Valley
Road
Bishop
Aberdeen
WAUCOBA
MOUNTAIN
Basemap: California 7.5' USGS Quadrangles
Legend
Qal - Quaternary alluvium deposits
Qt - nonmarine terrace deposits
Independence
Ql - Quaternary lake deposits
Qc - Pleistocene non-marine depostis
Big Pine
lpC
WAUCOBA
MOUNTAIN
TINEMAHA
RESERVOIR
Locator Map
COWHORN
VALLEY
Lone Pine
Qpvb - basalt and rhyolite flows
Qpvp - pyroclastic deposits
³
CM - Mississippian Perdido Formation
SOURCE: Applied Earthworks, Inc - 2014
CP - Mississippian-Pennsylvanian Rest Springs
Shale
O - Ordovician Barrel Spring Formation, Johnson
Spring Formation, and Ely Springs Dolomite
C - Cambrian Tamarack Canyon Dolomite, Lead
Gulch Formation, Bonanza King Dolomite, Campito
Formation, Poleta Formation, Harkless Formation,
Emigrant, and Monola Formations
JTRv - Jurassic to Triassic metamorphosed
basaltic to rhyolitic tuffs and flows
bi - diorite and gabbro
gr - Mesozoic granite
C? - Cambrian Deep Springs Formation
ms - quartzite, hornblende, and marble
lpC - Precambrian Wyman Formation
0
N
0.5
1
2
APPROXIMATE SCALE IN MILES
FIGURE
5.6-5
Geologic Units in the Project Area (Death Valley Road Routes 1-3)
052-001-13
K
C
E
C
O
KR EN
AC ND
BL PE
E
D
IN
K
K
C
O
EA
KR A P
AC RK
U
BL
O
AZ
M
AK
PE E
E
C
N
G
R DE
A
S
N
AR PE
KE DE
IN
RO UT E 1 2
RO
UT
AK N
PE O
E MS
G
R L IA
SA IL
AR T W
KE UN
O
M
E3
,4,
6
BEGIN
ROUTE 1,3,4,6
END ROUTE 2
Qal
CP
END ROUTE 1
BEGIN ROUTE 2
END ROUTE 3,4,6
UT
E2
CM
N
M
KA
R
U
S
O AK
G
AZ PE RIN N
SP YO
E AN
BE C
SO
AM
LI
IL
AR
W AN
T
Z
N
U
AN
O
M
M
RO
O
R
E
O
U
T
E
1
IN
D
C
EN S
D
G
IN
R N
SP YO
N
E
A
BE C
EP
EN
IN
C
D
E
C
EN
D
R
EN NA
EP NZA
A
M
Locator Map
Death Valley
Road
Bishop
Qal - Quaternary alluvium deposits
Qt - nonmarine terrace deposits
Independence
Ql - Quaternary lake deposits
Qc - Pleistocene non-marine depostis
Big Pine
Aberdeen
Basemap: California 7.5' USGS Quadrangles
Legend
Lone Pine
Qpvb - basalt and rhyolite flows
Qpvp - pyroclastic deposits
³
CM - Mississippian Perdido Formation
SOURCE: Applied Earthworks, Inc - 2014
CP - Mississippian-Pennsylvanian Rest Springs
Shale
O - Ordovician Barrel Spring Formation, Johnson
Spring Formation, and Ely Springs Dolomite
C - Cambrian Tamarack Canyon Dolomite, Lead
Gulch Formation, Bonanza King Dolomite, Campito
Formation, Poleta Formation, Harkless Formation,
Emigrant, and Monola Formations
JTRv - Jurassic to Triassic metamorphosed
basaltic to rhyolitic tuffs and flows
bi - diorite and gabbro
gr - Mesozoic granite
C? - Cambrian Deep Springs Formation
ms - quartzite, hornblende, and marble
lpC - Precambrian Wyman Formation
N
0
1
2
4
APPROXIMATE SCALE IN MILES
FIGURE
5.6-6
Geologic Units in the Project Area (Independence Routes 1-4, 6)
052-001-13
UNION WASH
Qal
NEW YORK BUTTE
MANZANAR
UNION WASH
E7
RO
UT
MANZANAR
WILLIAMSON
gr
gr
JTRv
MANZANAR
UNION WASH
MOUNT LANGLEY
ROUTE 7
END
ROUTE 3 BEGIN
DOLOMITE
Qal
ROUTE 4,5 BEGIN
RO UT E 1 2
Qal
MOUNT LANGLEY
WHITNEY
NEW YORK BUTTE
LONE PINE
ROUTE 7 BEGIN
ROUTE 2,4,5 END
ROUTE 2,6 BEGIN
gr
Qal
Ql
UT
RO
E
3
Qal
gr
RO
UT
E2
,4 ,
5, 6
gr
R
U
O
2 ,4
DOLOMITE
LONE PINE
LONE PINE
,5
ROUTE 3 END
ROUT E 1,6
MOUNT LANGLEY
TE
Qal
ROUTE 1
BEGIN
ROUTE 1
gr
gr
ROUT E 1,6
JTRv
ROUTE 1,6
END
Locator Map
Death Valley
Road
Bishop
Qal - Quaternary alluvium deposits
Qt - nonmarine terrace deposits
Independence
Ql - Quaternary lake deposits
Qc - Pleistocene non-marine depostis
Big Pine
Aberdeen
Basemap: California 7.5' USGS Quadrangles
Legend
Lone Pine
Qpvb - basalt and rhyolite flows
Qpvp - pyroclastic deposits
³
CM - Mississippian Perdido Formation
SOURCE: Applied Earthworks, Inc - 2014
CP - Mississippian-Pennsylvanian Rest Springs
Shale
O - Ordovician Barrel Spring Formation, Johnson
Spring Formation, and Ely Springs Dolomite
C - Cambrian Tamarack Canyon Dolomite, Lead
Gulch Formation, Bonanza King Dolomite, Campito
Formation, Poleta Formation, Harkless Formation,
Emigrant, and Monola Formations
JTRv - Jurassic to Triassic metamorphosed
nasaltic to rhyolitic tuffs and flows
bi - diorite and gabbro
gr - Mesozoic granite
C? - Cambrian Deep Springs Formation
ms - quartzite, hornblende, and marble
lpC - Precambrian Wyman Formation
0
N
1
2
4
APPROXIMATE SCALE IN MILES
FIGURE
5.6-7
Geologic Units in the Project Area (Lone Pine Routes 1-7)
052-001-13