Geological and Soil Hazards Report
PDC Energy
Metcalf Soil Treatment Facility
OA Project No. 013-0036
760 Horizon Drive, Suite 102 | Grand Junction, CO 81506 | TEL 970.263.7800 | FAX 970.263.7456
THIS PAGE LEFT BLANK FOR TWO-SIDED DUPLICATION.
GEOLOGIC AND SOIL HAZARDS REPORT
Introduction
Metcalf Property Management LLC proposes to construct a soil treatment facility to be located
in Section 24, Township 7 South, Range 96 West, of the Sixth Principal Meridian, located west
of the town of Battlement Mesa, east of Interstate 70, and south of the Colorado River, in
Garfield County, Colorado (Fig. V-1).
The proposed Soil Treatment Facility is located in the eastern part of the Piceance Basin south
of the Colorado River on a terrace between Dry Creek and Monument Gulch at the western
base of Battlement Mesa. The proposed location is shown on a map provided (Fig. G-1).
Structural Geology
The proposed project is located in the eastern part of the Piceance Basin; an irregularly-shaped
elongated basin formed by tectonic forces associated with the Laramie orogeny that
downwarped the earth’s crust as a result of the uplift of the Colorado Rocky Mountains. Areas
on all sides of the Piceance Basin have been uplifted by these same tectonic forces.
The Piceance Basin is the major structural geologic feature in the region. It is bound to the east
by the Grand Hogback monocline, the White River Uplift to the northeast, the Gunnison Uplift to
the south, the Uncompahgre Uplift to the southwest, the Douglas Creek Arch to the westnorthwest, and the axial basin uplift to the north (Grout and Verbeek, 1992).
The Grand Hogback monocline is a sinuous feature comprised of Upper Cretaceous age
bedrock of the Mesaverde Group, which includes the Williams Fork Formation and the
underlying Mancos Shale. The Grand Hogback forms part of the boundary between two major
physiographic provinces, the Colorado Plateau and the Rocky Mountain foreland.
Bedrock Geology
Two bedrock units crop out, or are exposed in the Grand Valley Quadrangle, the Tertiary age
(Eocene and Paleocene) Wasatch Formation and (Eocene) Green River Formation. The
Wasatch Formation is at the surface or it underlies surficial deposits in most of the quadrangle.
Rocks of the Green River Formation comprise the main bulk of the uplands of the Roan Plateau
and Battlement Mesa, and are exposed along the steep slopes and cliffs to the east of the
Grand Valley.
Metcalf Property Management LLC.
Metcalf Soil Treatment Facility
January 2013
1
Olsson Associates
Grand Junction, CO
OA Project # 013-0036
The Wasatch Formation is more than 6,000 feet thick, according to geophysical logs of gas
wells within the basin. The Wasatch Formation consists of claystone, mudstone, and siltstone
interbedded with sandstone and conglomerate. Fine-grained sediments predominate the
formation and range in color from very light gray, to brown, olive gray, reddish, and tan.
Claystones and mudstones are poorly to moderately indurated, and sandstones are generally
discontinuous, commonly lenticular and are yellowish gray to olive gray in color. The Wasatch
Formation is prone to landslides as described in the section on geologic hazards (Madole and
Streufert, 2003).
The Green River Formation is comprised of lithified lacustrine sediment deposited in a group of
intermontane freshwater Eocene lake basins in Colorado, Utah, and Wyoming. Over 3,000 feet
of interbedded sandstone, mudstone, siltstone, limestone, dolomite, and marlstone were
deposited in the deep lake known as Lake Uinta in very fine annual layers called varves. The
Green River Formation is comparatively resistant to erosion, and comprises many of the high
cliffs and escarpments several miles to the east of the site.
Surficial Geology
The location for the proposed facility is located in river terrace deposits of the Holocene epoch
(Fig. G-1), which overlie the Wasatch Formation. Battlement Mesa, along the east side of the
quadrangle, consists primarily of the Green River Formation, with large slump blocks of basalt
irregularly veneered with young Pinedale glacial drift.
Alluvial and colluvial deposits consist of silt, sand, gravel, and clay are found in debris fans,
stream channels, flood plains, and adjacent hill slopes along tributary valleys. Depositional
processes in stream channels and on floodplains are primarily alluvial, whereas colluvial and
sheet-wash processes pre-dominate on debris fans, hillslopes, and along the hillslope/valley
floor boundary. An alluvial fan is a fan or cone-shaped deposit of sediment built up by streams
or debris flows. Undifferentiated deposits of older gravels and alluvium underlie terraces and hill
slopes 10 feet to 40 feet above small perennial and intermittent streams.
The maximum thickness of these deposits is up to about 30 feet, and areas may be prone to
sheet wash and rockfall.
Geologic Hazards
The processes of mass wasting, flooding, hydrocompaction, and piping are the principal
geologic hazards in the Grand Valley Quadrangle, with mass wasting processes being the most
widespread hazard. Mass wasting is defined as earth materials transported downslope
primarily by gravity. Mass wasting differs from other modes of sediment transport in that the
materials move as a mass rather than as individual fragments or particles borne along by a
transport medium such as wind or flowing water. Water is an important component in masswasting, and commonly triggers movement, but the water is part of the moving mass rather than
Metcalf Property Management LLC.
Metcalf Soil Treatment Facility
January 2013
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Olsson Associates
Grand Junction, CO
OA Project # 013-0036
the transport agent. Mass wasting may take the form of slope creep, as a slow or imperceptible
and progressive downslope movement, or can be more sudden and dramatic in areas prone to
slumping, debris flows, or landslides. Triggering mechanisms are most commonly the result of
wetting from rain or heavy snowmelt. Most failure occurs on steep slopes and involves
movement of all surficial geological materials (alluvium, colluvium, decomposed bedrock)
overlying competent bedrock.
Debris flows are dense mixtures of sand, silt, clay, rock debris, and lesser amounts of water and
air that move as a fluid mass. Debris flows may resemble wet concrete with variable fluidity
depending on the amounts of debris and water present. Most debris flows become channelized
as they descend to the main valleys regardless of whether the flow was initiated at the valley
heads or on the valley sides. Debris flow deposits are a major constituent of fan-shaped
masses that accumulate where large gullies and tributary valleys converge.
The site for the soil facility is located in an area of Garfield County that has been mapped by
Garfield County for landslides or landslide potential. No major slope hazards have been
identified in the immediate area. Landslides occur in areas that are vulnerable to slope failure
due to a variety of reasons. Weak rocks, high relief, steep slopes, and locally abundant
moisture are all contributing factors in causing landslides. Much of the Wasatch Formation
consists of fine-grained materials that are weakly cemented. These materials are often overlain
by indurated strata that are more resistant to weathering, both within and overlying the Wasatch
Formation, resulting in different erosion rates and over steepening of slopes. The Wasatch
Formation also may contain expansive clay minerals that can reduce rock strength and slope
stability.
Natural events, including intense rainfall, rapid snow melt, groundwater level changes, and
earthquakes, in addition to human activities, may trigger landslides. Human activities which
may cause failure include construction projects, the use of earth fill for construction, cutting
benches into hill slopes, and use of unlined pits or septic systems that change water levels or
add weight to the natural slope, increasing the shear stress.
Floods are another potential hazard in the area, although they are more predictable and more
frequent than landslides and debris flows. Areas subject to debris flows are also subject to flash
floods. The areas that are prone to flooding are smaller as compared to the areas that are
vulnerable to landslides. Mapped flood plain areas are shown along the banks of the Colorado
River near the facility but do not include the facility area itself, as seen in figures F-1 and F-2.
Hydrocompaction occurs in areas underlain by thick deposits of fine-grained sediments that
have a low bulk density and indicate that the sediment contains a relatively high volume of void
space between grains. Hydrocompacted sediments may undergo significant reduction in
volume and collapse when wetted, or when additional weight is added on top of them, or by a
combination of weight and wetting. Hydrocompaction is most common in relatively young, fine-
Metcalf Property Management LLC.
Metcalf Soil Treatment Facility
January 2013
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Olsson Associates
Grand Junction, CO
OA Project # 013-0036
grained sediments deposited by wind, sheet flow, and in some mudflows or debris flows where
entrapped air results in a high percentage of void space. The area of the project site is not
considered to be at risk for hydrocompaction hazard..
According to the Colorado Geological Survey, there have been earthquakes in the eastern part
of Garfield County near Glenwood Springs and New Castle, but there are no recorded
earthquakes or faults shown in the vicinity of the of the soil treatment facility.
Soils
According to information prepared by the Natural Resources Conservation Service Soil Survey,
the predominant soils in this section have been mapped as the Nihill channery loam (46), the
Potts-Ildefonso complex (58), and the Arvada loam (4), with small deposits of Ildefonso stony
loam (34), Torrifluvents (65), and Wann sandy loam (72).
The Nihill channery loam (46) soils cover 40.8 percent of the area in which the Metcalf Soil
Treatment Facility will be located as seen in figure S-1. The soil in this area occupies 1 to 6
percent slopes at elevations ranging from 5,000 to 6,500 feet above mean sea level. The Nihill
channery loam is a deep and well-drained soil that forms on valley sides and alluvial fans. The
capacity of the most limiting layer to transmit water is moderately high to high. Depth to water
table is more than 80 inches. The parent material is alluvium derived from sandstone and
shale.
The Potts-Ildefonso complex (58) soils cover 27 percent of the project area, occupying 12 to 25
percent slopes at elevations ranging from 5,000 to 6,500 feet in elevation. This well-drained soil
forms on valley sides, alluvial fans, and mesas. The capacity of the most limiting layer to
transmit water is moderately high to high. Depth to water table is more than 80 inches. The
parent material is alluvium derived from sandstone and shale.
The Arvada loam (4) soils cover 21.3 percent of the project area, occupying 6 to 20 percent
slopes at elevations ranging from 5,100 to 6,200 feet in elevation. This well-drained soil forms
on terraces and alluvial fans. The capacity of the most limiting layer to transmit water is
moderately low to moderately high. Depth to water table is more than 80 inches. The parent
material is alluvium derived from sandstone and shale.
Radon
Radon is a naturally occurring, odorless and colorless radioactive gas that is produced by the
radioactive decay of radioactive minerals present in the soils and bedrock. According to the
Colorado Department of Public Health and Environment (CDPHE), Colorado has a moderate to
high radon potential. Since the site is a facility that does not have buildings or an area that is
occupied throughout the work day, the potential presence of radon is not expected to represent
a geologic hazard or a significant worker exposure issue.
Metcalf Property Management LLC.
Metcalf Soil Treatment Facility
January 2013
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Olsson Associates
Grand Junction, CO
OA Project # 013-0036
Garfield County Geographic Information System
Olsson personnel have reviewed the relevant county maps prepared by Garfield County’s
Geographic Information System (GIS) Department that pertain to this study. According to the
Flood Plain Profile the 100-year flood plain is indicated immediately along the Colorado River,
and is not shown to be in the immediate vicinity of the proposed soil treatment facility.
According to the Slope Hazard Map provided by Garfield County, Colorado - GIS Department
website, no moderate or major slope hazard is indicated within the vicinity of the proposed soil
treatment facility.
According to the Surficial Geology Map provided by Garfield County, Colorado – GIS
Department website the hazards associated with alluvial fan, landslide, mudflow, mudflow/slide
are low.
Conclusions and Summary
According to the information provided by Garfield County, Colorado - GIS Department pertaining
to the location of the proposed soil treatment facility, the overall geologic and soil hazards
appear to be low.
Stormwater controls and Best Management Practices (BMPs) should take into consideration the
geology and soil types present at this location. These engineering controls and practices should
be used temporarily and permanently to divert stormwater away from the construction areas and
to prevent additional weight which could trigger a debris flow or landslide. Pits are required to
be lined by COGCC rules, but pit liners may also prevent water infiltration into unconsolidated
sediments which could trigger slope failure. Pits and catchment basins should be sited and
designed so as not to add weight to potentially unstable areas.
William Monroe
Project Geologist
Olsson Associates
Metcalf Property Management LLC.
Metcalf Soil Treatment Facility
January 2013
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Olsson Associates
Grand Junction, CO
OA Project # 013-0036
References
Harman, Jerry B. and Murray, Donald J., 1985, Soil Survey of Rifle Area, Colorado, Parts of
Garfield and Mesa Counties, Colorado:
U.S. Department of Agriculture, Soil
Conservation Service, in cooperation with the Colorado Agricultural Experiment Station,
149 p. two plates, and 20 map sheets.
Online References
Colorado Oil and Gas Conservation Commission
http://cogcc.state.co.us/
Natural Resources Conservation Service - Soil Survey
http://www.nrcs.usda.gov/
Garfield County
Slope Hazards: http://garfield-county.com/geographic-informationsystems/documents/6439291200422slopehaz.pdf
Soil Hazards: http://garfield-county.com/geographic-informationsystems/documents/64335291200423soilhaz.pdf
Surficial Geology of Garfield County: http://garfield-county.com/geographic-informationsystems/documents/geologic-hazards/24surfgeo.pdf
Metcalf Property Management LLC.
Metcalf Soil Treatment Facility
January 2013
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Olsson Associates
Grand Junction, CO
OA Project # 013-0036
Qa
Two
Bent C
reek
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ek
te
El
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ra
Pl
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er
Pa
ra
ch
u
Cl
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Ql
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Sto
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Qu
Soil Data provided by NRCS Soil Survey
Legend
Affected Parcel
Geology Type
Highway/Interstate
Qa - Modern alluvium
County Roads
Ql - Landslide Deposits
Two - Wasatch formation and Ohio Creek formation
PROJECT NO:
DRAWN BY:
DATE:
013-0036
Jenna Muhlbach
1/28/13
GEOLOGY MAP
PDC ENERGY
METCALF SOIL TREATMENT
FACILITY
GARFIELD COUNTY, COLORADO
0
250
500
760 HORIZON DRIVE,
SUITE 102
GRAND JUNCTION,
CO 81505
TEL 970.263.7800
FAX 970.263.7456
Feet
1,000
FIGURE
G-1
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3
72
65
73
34
65
Bent C
65
reek
rC
ea
Cl
4
ne
Sto
y
arr
Qu
ra
46
El
do
Pa
56
ra
ch
ut
e
er
ac
Pl
ek
re
46
72
58
34
56
56
56
56
Soil Data provided by NRCS Soil Survey
Legend
Affected Parcel
Highway/Interstate
County Roads
Soil Type
3 - Arvada loam, 1-6% slopes
4 - Arvada loam, 6-20% slopes
34 - Ildefonso stony loam, 6-25% slopes
46 - Nihill channery loam, 1-6% slopes
56 - Potts loam, 6-12% slopes
PROJECT NO:
DRAWN BY:
DATE:
013-0036
Jenna Muhlbach
1/28/13
58
65
72
73
- Potts-Ildefonso complex, 12-25% slopes
- Torrifluvents, nearly level
- Wann sandy loam, 1-3% slopes
- Water
SOILS MAP
PDC ENERGY
METCALF SOIL TREATMENT
FACILITY
GARFIELD COUNTY, COLORADO
0
250
500
760 HORIZON DRIVE,
SUITE 102
GRAND JUNCTION,
CO 81505
TEL 970.263.7800
FAX 970.263.7456
Feet
1,000
FIGURE
S-1
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luf
f
Riv
er
B
6
70
o
Sm
Em
Mahogany
Oro
Rainbow
ge
Bonanza
Tamarack
Cobre
Stone
Quarr
y
Parcel - 240924200158
Floodplain Data provided by Garfield County GIS Department
Legend
Affected Parcel
Parcels
FloodPlain
PROJECT NO:
DRAWN BY:
DATE:
013-0036
Jenna Muhlbach
1/9/13
Highway/Interstate
County Roads
FLOODPLAIN MAP
PDC ENERGY
METCALF SOIL TREATMENT
FACILITY
GARFIELD COUNTY, COLORADO
0
625
1,250
760 HORIZON DRIVE,
SUITE 102
GRAND JUNCTION,
CO 81505
TEL 970.263.7800
FAX 970.263.7456
ueen
d
Ironwe
Empire
Silve
rQ
ar
te
gs
Placer
Eldora
d
al
er
Ced
Pa
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ch
u
ill
Tamarisk
Mineral Sprin
Th Horizon
un
de
rb
er
g
Si
lve
rto
n
Bent Creek
H
key
Feet
2,500
FIGURE
F-1
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Stone Qu
arry
Parcel - 240924200158
Floodplain Data provided by Garfield County GIS Department
Legend
Affected Parcel
Parcels
FloodPlain
PROJECT NO:
DRAWN BY:
DATE:
013-0036
Jenna Muhlbach
1/9/13
Highway/Interstate
County Roads
FLOODPLAIN MAP
PDC ENERGY
METCALF SOIL TREATMENT
FACILITY
GARFIELD COUNTY, COLORADO
0
150
300
760 HORIZON DRIVE,
SUITE 102
GRAND JUNCTION,
CO 81505
TEL 970.263.7800
FAX 970.263.7456
Feet
600
FIGURE
F-2
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