HomeMy WebLinkAbout4.9.2 Slope Stability Rpt PkgSTORAGE FACILITIES
PAD 697-16-16
PAD 604-12-13
ROCKSLIDE & LANDSLIDE ASSESSMENT
MEMORANDUM
Prepared by:
Donald J Berger, P.E.
January 29, 2015
Prepared for:
OXY USA INC.
oX
195 Lodgepole Circle, Parachute, CO 81635
Office: (970) 903-3028 Fax: (970) 712-5715
Rockslide & Landslide Assessment
OXY USA INC. Pads 697-16-16 & 604-12-13
January 31, 2015
STORAGE FACILITIES, PAD 697-16-16 & PAD 604-12-13
ROCKSLIDE & LANDSLIDE ASSESSMENT
ASSESSMENT OVERVIEW
The risk to personnel and infrastructure from rockslides or landslides on the Storage Pads 697-16-16 &
Pad 604-12-13 is minimal. These facilities are oil and gas drill pads that have been converted over to
storage facilities and as such have been designed to minimize the risk associated with rockslides and
landslides. Both pads were constructed around 2010 and both have cut slopes in the shale bedrock and
fill slopes constructed from the excavated shale materials. The design, construction, location and
utilization of the storage facilities in conjunction with the frequency of exposure to personnel, in our
opinion, indicate that the potential risk is minimal.
BACKGROUND INFORMATION
The storage facilities are located on the top of the Roan Plateau within the Piceance basin on OXY USA
INC property. Access to the sites is via the OXY USA INC Cascade Creek road system which has
limited access to only OXY employees and their contractors. A location map developed by Olsson &
Associates (attached) provides the location of the two (2) storage areas within their private, limited access
roadway system. Olsson Associates have conducted a review of the access roadway to the sites (Garfield
County Roadway Standards Assessment, January 2015, Project No. 013-0655). The pads are located
geologically in what is considered the main body of the Unita Formation (Hail & Smith 1997) that is
"mostly brown dominantly tuffaceous sandstone and siltstone, but also includes interbedded dolomitic
marlstone, shale, oil shale, mudstones and minor limestone, claystone and minor tuff beds. The
sandstone beds are highly variable in lithology." The bedding layers within the area of the sites are
generally horizontal to slightly dipping. The nearly horizontal bedding found within the rock formations
allows the dramatic vertical cliffs to form in the vicinity of the storage facilities. The excavated slopes
for the sites have been designed and excavated in a manner to preserve the integrity of the cuts slopes via
controlled blasting techniques. The fill slopes were initially pushed slopes constructed from the
excavated shale material. These fill slopes have had time to consolidate under self weight to become
fairly stable slopes as well.
Rock Solid Solutions (RSS) has worked with OXY USA INC over the past 10 years to design and
construct and to evaluate rockslide and landslide hazards within the limits of their property. The two
storage facilities have been designed and constructed to provide for safe access to and from the pads as
well as for use in drilling, operations and storage of materials.
604-12-13 Storage Pad
The 604-12-13 Pad is a large single level pad with the no active wells, however, separators and
condensate tanks are stored on it. The perimeter of the pad near the cut slope has been used for the
storage of empty tanks and miscellaneous piping and other materials as well.qop
ROCK SOLID
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Rockslide & Landslide Assessment
OXY USA INC. Pads 697-16-16 & 604-12-13
January 31, 2015
t OXY USA WTP LP
wiry 750 Horizon Drive, Suite 101
Grand Junction, CO 81506
Figre 1 - Overview Map for Garfield
County Road Standards Assessment
Updated: Jandary 19, 2015 Garfield County, Colorado
0 0.3 0.6 0.9 12 1.S
Mgrs
604-12-13 Storage Area
697-16-16 Storage Area
- Stara Sites
r,W Oxy Guard Shack
Oxy Roadway Section
/Mesa Road Segment
% . Mountain Road Segment
• Valley Road Segment
•"A4 Unimproved Public Road
' Gravel Public Road
'�rPavad Public Road
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Rockslide & Landslide Assessment
OXY USA INC. Pads 697-16-16 & 604-12-13
January 31, 2015
Photo #1 — 604-12-13 Pad Overall Site View with Pipeline Corridor
Photo #2 — 604-12-13 Pad South Facing Cut & Fill Slopes
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Rockslide & Landslide Assessment
OXY USA INC. Pads 697-16-16 & 604-12-13
January 31, 2015
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Photo #3 — 604-12-13 Pad NE Corner Cut Slope
The storage of materials located on the perimeter of the cut slope have generally been placed a distance
of 15 to 20 -ft from the near vertical excavated cut slope. This is in accordance with the recommendations
of the Ritchie Ditch criteria followed by CDOT and FHWA for rockfall catchment zones for this height
of slope.
The distance materials are placed from the crest of the fill slopes are generally greater than a 111: 1V
from the toe of the fill slope sections as well. This practice has been followed by OXY USA INC on
most all of their facilities and pads in the Piceance Basin as well.
697-16-16 Storage Pad
The 697-16-16 Pad is a two tiered pad with the lower pad having active wells, separators and condensate
tanks located on it while the upper tier has been used for the storage of empty tanks, miscellaneous piping
and other materials.
At first glance the location of the empty storage tanks on the SW edge of the pad appears close, however, the
weathered shale material placed above the cut slope into bedrock is fairly thin and the offset distance from the fill
slope is sufficient to maintain stability of the pad (see photos #5 and #6).
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Rockslide & Landslide Assessment
OXY USA INC. Pads 697-16-16 & 604-12-13
January 31, 2015
Photo #4 — 697-16-16 Pad Overall Site Location
Photo #5 — 697-16-16 Pad SW Cut Slope; Note Bedrock in Face
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Rockslide & Landslide Assessment
OXY USA INC. Pads 697-16-16 & 604-12-13
January 31, 2015
Photo #6 — 697-16-16 Tank Storage Adjacent to Cut Slope; Offset 15+ ft
Photo #7 — 697-16-16 Entrance to Pad from NW Corner
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Rockslide & Landslide Assessment
OXY USA INC. Pads 697-16-16 & 604-12-13
January 31, 2015
SUMMARY
In general, storage pads 604-12-13 and 697-16-16 are located in very stable geologic sites. They have
been designed and constructed to take advantage of the local geology, topography and access road system
to allow for safe access by OXY USA INC employees and their contractors. Access to these pads is
limited to only those personnel OXY USA INC has provided access rights to and have been trained
and/or informed of the inherent risk and nature of the geologic conditions found on the Roan Plateau
within the Piceance basin. Therefore, in our opinion, the risk to personnel and facilities to rockfall and
landslide hazards on the two (2) storage pads is minimal.
Thank you for the opportunity to work on this project.
Respectfully,
Donald J. Berger, P.E.
Rock Solid Solutions
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