HomeMy WebLinkAbout20140449.tiff APPENDIX E
GEOLOGICAL HAZARD DEVELOPMENT PERMIT
ARCAD1S
Infrastructure•WaterWater Environment Buildings Imagine the result
'1 KerrNtrGee
Geological Hazard Assessment
KMG 19-3i Communications Tower Project
sw1/4 SW'/4, Section 3, Ti N, R68W
Prepared for:
Kerr McGee Oil &Gas Onshore LP
1099- 18"Street, Suite 1800
Denver, Colorado 80202
Submittal Date:
September 30, 2013
ARCADIS
Geological Hazard Assessment
KMG 19-3i Communications
Tower Project
Matthew W. Bauer, P.G. (Kansas No. 778)
Staff Geologist
SWY4 SW1/4, Section 3, TIN, R68W
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William J.Zahniser, P.E. (Colorado No. 38996) Highlands Ranch
Principal Engineer Colorado 80129
Tel 720 344 3500
Fax 720 344 3535
Our Ref
CO001847
Date-
September 30,2013
This document is intended only for the use
of the individual or entity for which it was
prepared and may contain information that
is privileged. confidential and exempt from
disclosure under applicable law.Any
dissemination.distribution or copying of
this document is strictly prohibited.
ARCADIS Table of Contents
1. Introduction 1
1.1 Site Location 1
1.2 Site Setting 1
1.3 Proposed Development 2
2. Methods 3
3. Results 4
3.1 Flood Hazard 4
3.2 Landslides 4
3.3 Seismic Activity/Earthquakes/Site Classification 4
3.4 Previous Geotechnical Investigation 5
3.5 Shrinking/Swelling Potential of Soils and Bedrock 6
3.6 Undermining 7
4. Additional Considerations 10
5. Conclusions 11
6. Recommendations 13
7. References Cited 14
Figures
Figure 1 Geological Hazard Development Map
Figure 2 Site Location Map
Figure 3 Mine Workings Map
Appendices
Appendix A Geological Hazard Development Permit Submittal Checklist and
Application
Appendix B Previously Completed Geotechnical Investigation Report
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1. Introduction
ARCADIS U.S Inc., has prepared this geologic hazard assessment on behalf of Kerr
McGee Oil & Gas Onshore LP(Kerr McGee), for their proposed installation of a
communications tower at their existing KMG19-3i Salt Water Disposal (SWD) Facility
located near the towns of Erie/Frederick, in Weld County, Colorado(the site)
(Figure 1). Kerr McGee previously met with Weld County to discuss Site Specific
Development Plan, and Use by Special Review(USR) requirements for this project.
During that meeting Kerr McGee and Weld County determined that, based on the sites
proximity to historical coal mining activity a Geologic Hazard Development Permit
(GHDP)application would need to be included in Kerr McGee's USR submittal
package. In order to adequately consider the GHDP application, Weld County also
requires submittal of a geologic hazard assessment report with emphasis on those
conditions which may impact the proposed development. This report has been
prepared in order to assess the potential geological hazards posed on the proposed
development, and to satisfy the requirements of Section 2, Article 23, Division 7 of the
Weld County Code pertaining to geologic hazard development permits. In order to help
guide the review of a GHDP application, Weld County has developed a GHDP
submittal checklist. A copy of Weld County's GHDP submittal checklist, along with a
completed GHDP application, is provided in Appendix A.
1.1 Site Location
The site is located northeast of the intersection of County Road 12 and County Road 7
in Weld County, Colorado on a 75.78 acre lot located in the W'/6, of the SW'/%of
Section 3, T1 N, R69W (Figure 2). The property on which the site is located is owned
by Kerr McGee's parent company, Anadarko E&P Company LP, and is zoned
agricultural with special purpose improvements (Weld County 2013).
1.2 Site Setting
The site elevation is approximately 5,050 feet above mean sea level (ft amsl) (USGS
1994). The property slopes gently to the north and has a multi-well pad and salt water
disposal facility in the northeast corner with the remainder used for agricultural
purposes. The site has one existing building and a tank battery for the KMG19-3i Salt
Water Disposal Facility in the northeast corner of the property(Figure 1).
The site is located in the Colorado Piedmont(13f)section of the Great Plains province
of the Interior Plains physiographic region (Fenneman 1946). The Colorado Piedmont
lies on the eastern foot of the Rockies between the South Platte and Arkansas Rivers
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which have excavated into the Tertiary sedimentary rock layers of the Great Plains.
The site receives an average of 18 inches per year(NOAA 2011).
While there are no significant drainages on the site, surface water bodies are present
within one mile, and include branches of the Community Ditch irrigation canal and
several perennial and intermittent agricultural ponds. The branches of the Community
Ditch irrigation canal are approximately 3,000 feet to the west and 1,950 feet to the
east of the site. The closest agricultural pond is approximately 500 feet to the
northeast of the site.
1.3 Proposed Development
The proposed structure is an approximately 192 foot tall, pre-fabricated, self-
supporting,cross-braced communication tower. The base of the tower will measure
approximately 35 feet by 35 feet, and will be supported by an engineered foundation.
Final foundation design determinations have not yet been made, but will likely consist
of either a structural mat-and-pier type of foundation, or drilled caisson footers(4 foot
diameter concrete caissons, up to 44 feet deep)at each tower corner.
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2. Methods
ARCADIS has reviewed readily available published materials from the United States
Geological Survey(USGS), Colorado Geological Society(CGS) and the Federal
Emergency Management Agency(FEMA), United States Department of Agriculture
(USDA), the Association of Engineering Geologist(AEG)and Colorado School of
Mines.
ARCADIS also reviewed a geotechnical report that was previously prepared by Ground
Engineering Consultants, Inc. (GROUND)in May 2010 for Kerr McGee in support of
their construction of the KMG 19-3i SWD facility(GROUND 2010). GROUND
previously drilled test holes and collected geotechnical data in support of geological
hazard assessment and offered a number of geotechnical recommendations for
construction that are also applicable to the newly proposed construction of a
communications tower.
Geologic hazards reviewed using these readily available documents for the site
location include flooding, landslides, undermining, seismic activity, and the
shrinking/swelling of soil and bedrock.
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3. Results
This section of the report summarizes the key findings from ARCADIS' review of the
available regional and site specific information. Our assessment of flooding, landslide,
and seismic considerations are based on available literature. Key findings from the
previous GROUND geotechnical investigation summary report (included as
Appendix B)are condensed and summarized in this section of the report for
convenience. The most significant hazards ARCADIS has identified for this site pertain
to the potential for shrink-swell of soils and bedrock heave, as well as subsidence as a
result of historic underground mining activity beneath the site. Additional details
regarding the assessment of these hazards will be provided herein.
3.1 Flood Hazard
The site is defined by the Flood Insurance Rate Maps zone as Zone C which is
described as having a 0.2 percent chance of annual flooding (FEMA 1990). ARCADIS'
opinion is that the flood risk to the proposed development is minimal.
3.2 Landslides
The USGS defines landslides as a "wide range of ground movement, such as rock
falls, deep failures of slopes and shallow debris flows (USGS 2004). The Colorado
Landslide Inventory(CLI), which includes landslides mapped by CGS and USGS, does
not include any mapped landslide areas within one mile of the site. The lack of a
mapped landslide in a given area by the CLI does not imply that a landslide hazard has
not been mapped by an outside private or academic party or that a hazard does not
exist.
The area surrounding the site has an approximate one percent grade and in
ARCADIS's opinion presents an unlikely risk of a naturally occurring landslide.
3.3 Seismic Activity/ Earthquakes/Site Classification
Colorado does have Quaternary age faults located in the Front Range and to the west
but is considered by the USGS to be a region of minor earthquake activity. The
earthquake peak ground acceleration that has a 2 percent chance of being exceeded
in 50 years at the site has a value of between 4 and 8%g (USGS 2012). Two normal
faults, NE-SW and N-S striking, intersect the property on which the site is located
(Tweto 1979). These are examples of the late cretaceous age faults that span the
Boulder-Weld Coal Field and are responsible for the five-fold thickening of the Fox
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Hills sandstone and the availability of minable coal in downthrown blocks of the
Laramie Formation (Davis &Weimer 1976).
A seismic site assessment was performed in accordance with the National Earthquake
Hazards Reduction Program (NEHRP) Recommended Seismic Provisions for New
Buildings and Other Structures 2009. Based on this assessment, ARCADIS has
identified site specific occupancy and seismic design categories for the proposed
communications tower, as follows:
• Occupancy Category- II —The proposed communications tower is defined as
Occupancy Category II. Occupancy Category II is reserved for non-essential
buildings and other structures that represent between a low hazard and a
substantial hazard to human life in the event of failure.
• Seismic Design Category—C—Quantitative determination of the site class in
accordance with the 2009 international building code (ICC 2009) requires
specific actions including, but not limited to testing, analyses, and subsurface
investigation including a 100 foot deep boring. In 2010, two test borings were
advanced to approximately 184 feet below ground surface. Laboratory
analysis was performed on the bottom 20 feet of each boring (GROUND
2010). As per Table 1613.5.2 (ICC 2009), a seismic design category C was
assigned to the site based on soil conditions encountered at the site in 2010.
The 2009 NEHRP Seismic Design Provisions for the above occupancy and seismic
design categories are as follows:
• Ss = 23% g—The mapped, maximum considered earthquake, 5-percent-
damped, spectral response acceleration parameter at short periods (0.2
seconds).
• S1 = 8.1% g—The mapped, maximum considered earthquake, 5-percent-
damped, spectral response acceleration parameter at a period of 1 second.
• Fa = 1.2% g—Site coefficient as a function of site class and mapped spectral
response acceleration at short periods, S-s.
• Fv= 1.7% g - Site coefficient as a function of site class and mapped spectral
response acceleration at a 1 second period,
3.4 Previous Geotechnical Investigation
Anadarko previously hired GROUND to conduct a subsurface investigation and
prepare geotechnical recommendations for the design and construction of foundations
associated with the saltwater disposal facility. A copy of the GROUND investigation
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summary report is included as Appendix B. The investigation entailed the installation
of five test holes to depths ranging between 20 and 35 feet below surface in order
evaluate subsurface conditions, including depths to bedrock and groundwater, and to
retrieve samples for laboratory testing and analysis. Two additional test holes were
advanced to depths of 182 to 184 feet in order to evaluate the possible presence of
mine workings (GROUND 2010).The location of these test holes are shown on
Figure 3.
Pertinent findings from this investigation are summarized below:
• The test holes generally encountered competent bedrock materials within a
few feet of the ground surface. Competent bedrock was overlain by several
feet of alluvium and severely weathered bedrock and/or clayey fill soils.The
bedrock consisted primarily of claystones and siltstones with thin interbeds of
sandstone, and coal beds up to at least 8 feet thick.
• Groundwater was not encountered in the shallower test holes, and was only
encountered irregularly at various depths in the two deeper test holes.
• Laboratory swell-consolidation testing indicated a high to very high potential for
post-construction heave at the site. Measured swells for samples of the
shallow bedrock ranged up to approximately six percent when wetted and
subjected to loads indicative of in-place overburden pressure. Slight
consolidation was measured as well.
• The two deeper test holes encountered zones of broken rock and voids at
depths of about 175 feet below surface. GROUND used data from this
investigation to calculate settlement potential.These calculations estimated
that between three and four inches of differential settlement is likely in areas of
the site underlain by historical mine workings.
• Significant concentrations, up to one percent by weight, of water-soluble
sulfates were measured in selected test-hole samples. Such concentrations
can present a severe environment for sulfate attack on concrete exposed to
these materials.
3.5 Shrinking/Swelling Potential of Soils and Bedrock
The site is located on the Nunn Loam at one to three percent slope. The Nunn Loam
is described as a deep, well-drained soil on terraces at elevations of 4,550 to 5,000
feet. It formed in mixed alluvium. Small, long and narrow areas of sand and gravel
deposits were also included in the areas mapped as the Nunn Loam and may be
present on site. Typically the surface layer of the Nunn Loam is grayish brown loam
about 12 inches thick. The subsoil is light brownish gray clay loam about 12 inches
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thick. The upper part of the substratum is light brownish gray clay loam. The lower
part to a depth of 60 inches is brown sandy loam. Permeability is moderately slow.
Available water capacity is high. The effective rooting depth is 60 inches or more.
Surface runoff is medium, and the erosion hazard is low. The Nunn Loam has fair to
poor potential for urban development. It has moderate to high shrink swell, low
strength, and moderately slow permeability. These features create problems in
dwelling and road construction. Those areas that have loam or sandy loam in the
lower part of the substratum are suitable for septic tank absorption fields and
foundations (Crabb 1980).
The site is underlain by the Laramie Formation and the Fox Hills Sandstone. The
Laramie formation is composed of gray claystone, shale,sandy shale and fine to
medium grained sandstone with coal beds of varying thickness. Slope stability is
generally good in unsaturated slopes of less than 25°. Foundation suitability is
generally good where expansive clay, slope stability and subsidence problems are
absent. The Fox Hills Sandstone is a fine to coarse grained, calcareous,tan
sandstone with interbedded sandy shale. This formation generally has a high bearing
strength (Bildeau, Buskirk, &Biloceau 1987).
As discussed previously, GROUND conducted a subsurface investigation at the site in
2010. Evaluation of soil heave potential from this investigation indicated that the
property has high to very high potentials for post-construction heave in the shallow
onsite bedrock(GROUND 2010).
GROUND's interpretation of samples from borings conducted at the salt water disposal
facility indicated that this portion of the property was on the Laramie Formation
(GROUND 2010). It is likely that the Fox Hills Sandstone lies on the other(western)
side of the cretaceous age faults that intersect the site. Mining in the Puritan Mine
followed coal seams accessible in the downthrown blocks of the Laramie Formation
and did not extend west of the fault intersecting the property(National Fuel 1939).
3.6 Undermining
The Boulder-Weld Coal Field, originally the Northern Field,was mined from 1859 to
1978. 223 coal mines operated in the district removing over 111 million short tons of
coal making it the most mined of the Front Range fields (CGS 2012).
The property on which the communications tower will be located is partially underlain
by the southwest portion of The National Fuel Company's Puritan Mine which operated
from 1908 to its abandonment on May 13, 1939 producing 256,578 tons of coal
(Western 2008, Naitonal Fuel 1939). The Puritan Mine was closed before or
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immediately after the advent of the automated continuous miner and used a modified
room and pillar retreat method. The continuous miner increased extraction rates in
mines which it operated from 50-60 to 60-70 percent or greater(Western 2008). The
western edge of this portion of the Puritan Mine follows the N-S striking fault that
crosses the property on which the site is located. The Puritan Mine removed five to ten
feet of coal at an estimated depth of 175 feet below the surface at the site and was
accessed via a rock tunnel to the hoist shaft in the SEA of Section 34 of T2N, R68W.
Figure 3 depicts the location of the site and property boundary in relation to the original
maps of the Puritan Mine workings. The limitations of surveying methods and the
completeness of the extent of mining surveys should be considered when evaluating
the location of the workings in relation to the site. The portion of the Puritan Mine
underlying the site has had the pillars removed.
Evidence of subsidence above this area of the Puritan Mine was not identified in the
literature search. The nearest located evidence of subsidence is approximately 4,700
feet to the southwest in an area of overlap of the Morrison and Clayton Mines(Ivey
1975).
The site is mapped as having a"low"subsidence hazard,which is described as"areas
in which the rate and magnitude of any surface displacement would be small enough to
warrant repair of damage to existing structures and application of adequate
engineering design to future structures so they can withstand small amounts of
foundation displacement." These areas, below which all or essentially all pillars have
been removed allowing for the possibility of relatively uniform and complete
subsidence to have occurred. Problems in such areas should be reduced to post-
subsidence compaction and related surface settling, and to small-scale effects of sub-
surface shifting resulting from any small residual or secondary voids. The only
restriction placed on land use would be the requirement for adequate structural design
of any structures planned for these areas" (Ivey 1975).
Previous mine subsidence assessments, conducted for subdivision of land, in Section
3 of Ti N, R 68W were reviewed. Collapse was complete in all borings that intersected
the Puritan Mine conducted during these investigations. Drilling fluid loss, when
present,was observed within approximately 20 feet above the mined interval. This
suggests that complete collapse and the rubble zone is confined to 20 feet above the
workings where the formation of a pressure arch has occurred. Theoretical strain
analysis conducted as part of these assessments to estimate a worst case mine
subsidence event of the consolidation of the rubble zone used a"theoretical void"of
approximately 0.5 feet resulting in a maximum of 0.15 percent horizontal strain(Tierra
1983;Western 1999a,b,c; Western 2008).
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As part of GROUND's subsurface investigation two borings, TH-6 &TH-7, (Figure 3
and Appendix A)were advanced to 184 ft bgs and 182 ft bgs. These borings
encountered voids, 2.5 foot and 0.5 foot, at approximately 176 ft bgs. Shoring timbers
and fractures within ten feet of the voids were also encountered. GROUND used data
from these two test holes to calculate settlement potential. These calculations
estimated that between three and four inches of differential settlement is likely in areas
of the site underlain by historical mine workings (GROUND 2010).
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4. Additional Considerations
This geological hazard assessment report was prepared in support of Kerr McGee's
request for a GHDP. Weld County will evaluate this report for completeness using their
GHDP submittal checklist(Appendix A). The GHDP submittal checklist includes a list
of specific topics that, where applicable, should be addressed by this report. The need
for this report is generally addressed under the GDHP submittal checklist.
supplemental requirement number 3. The specific topics this report needed to address
are listed as supplemental requirements 3.A through 3.K. ARCADIS has substantively
addressed each of concerns associated with these topics in this report, where
applicable. The notable exceptions are Items 3.C (poorly consolidated aquifers), and
3.D (wind deposited silts or loess)which we deemed not applicable, due to the
absence of these types geologic materials at the site.
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5. Conclusions
Based upon the results of the literature review completed by ARCADIS the following
conclusions and recommendations can be made.
• The supplemental GDHP checklist requirements have been effectively
addressed by the preparation and submittal of this general geological hazard
assessment report.
o Pursuant to supplemental requirement number 1, a completed application
permit has been prepared, and is included with Appendix A
a Pursuant to supplemental requirement number 2, a site survey has been
conducted by a licensed surveyor, 609 Consulting, LLC. Results of this
survey, along with the supplemental Items 2.A through 2.1 from the
checklist, have been incorporated into Figure 1.
This report effectively addresses the intent of supplemental requirement
number 3, including explanation of features depicted on Figure 1, and the
assessment of potential hazards associated with Items 3.A through 3.K,
where applicable.
• Literature reviews indicate the loamy soils and shallow, weathered bedrock at
the site have a moderate to high shrink-swell potential. This finding is
underscored by site-specific testing that was conducted on test holes from the
site in 2010.
• Laboratory swell-consolidation testing from test-hole samples indicated a high
to very high potential for post-construction heave at the site. Measured swells
for samples of the shallow bedrock ranged up to approximately six percent
when wetted and subjected to loads indicative of in-place overburden
pressure. Slight consolidation was measured as well.
• The Puritan Mine's workings have partially undermined the site. Based upon
original mine maps showing removal of pillars; the near to complete collapse
documented in all subsidence investigation borings in Section 3, Ti N. R 68W;
observations from the previously installed test holes by GROUND; and a lack
of documented surface subsidence in the area it is ARCADIS' opinion that the
site has a low risk for subsidence.
• The extent of undermining at the site is generally understood, and the low
potential for subsidence risk on the proposed development has been
effectively mitigated by Kerr McGee's decision to place the communications
tower several hundred feet to the west of the approximated fault line location,
in an area of the site where undermining did not occur.
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• Significant concentrations, up to one percent by weight, of water-soluble
sulfates were measured in selected test-hole samples. Such concentrations
can present a severe environment for sulfate attack on concrete exposed to
these materials.
• Poorly consolidated aquifers, loess, and fine grained colluvial soils have not
been identified at the site.
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6. Recommendations
Based on our assessment of the geological hazards on the proposed development,
ARCADIS recommends Kerr McGee consult with a qualified geotechnical engineer to
ensure the shrink-swell potential of the soils and shallow bedrock is accounted for in
the design of the proposed communication tower's foundation.
The geotechnical recommendations for foundation systems that were previously
prepared by GROUND in support of the saltwater disposal facility construction are also
applicable to the area of the site where the communications tower will be constructed.
GROUND included recommendations designed to address the shrink-swell potential of
the alluvium soils and shallow bedrock, including recommendations specific to use of
either drilled pier foundations,or shallow foundation systems.The geotechnical report
also included: 1)recommended specifications for sulfate resistant cement for use in
any concrete that is exposed to soils and bedrock; and 2)excavation and backfill
considerations for the installation of utility laterals at the site(Appendix A).
ARCADIS recommends that Kerr McGee's tower design engineer take these past
geotechnical recommendations into account when designing the foundation and utility
connections for the communications tower.
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7. References Cited
Bilodeau, S.W., D.V. Buskirk, &W.L. Biloceau. 1987. Geology of Boulder, Colorado,
U.S.A. Bulletin of the Association of Engineering Geologists, 289-332.
Colorado Geological Society(CGS). 2012. Boulder-Weld Coal Field. November. [Web
Page]. Located at http://geosurvey.state.co.us/minerals/HistoricMiningDistricts/
BoulderHMD/Pages/BoulderWeldCoalField.aspx. Accessed: September
2013.
Crabb, J.A. 1980. Soil Survey of Weld County, Colorado;Souther Part. United States
Department of Agriculture Soil Conservation Service.
Davis,T.and R.Weimer. 1976. Late Cretaceous Gmwth Faulting, Denver Basin,
Colorado. Golden, CO: Profesional Contributions, Colorado School of Mines.
Federal Emergency Managment Agency(FEMA). 1990. Floor Insurance Rate Map
(FIRM), Weld County, Colorado, Unicorporated Areas, Community-Panel
Number 0802660960D.
Fenneman, N.A. 1946. Physical Divisions of the United States. U.S. Geological
Survey.
Ground Engineering Consultants, Inc. (GROUND). 2010. Subsurface Exploration
Program&Geotechnical Recommendations;Anadarko KMG 19-3i Facility;
Weld County, Colorado. Englewood, CO: Ground Engineering Consultants
Inc. May 7.
International Code Council, Inc. (ICC). 2009. 2009 international building code. Country
Club Hills, Ill: ICC. International Code Council, Inc.
Ivey,A.A. 1975. Coal Mine Subsidence and Land Use in Boulder-Weld Coalfield,
Boulder and Weld Counties, Colorado. Denver, Colorado: Colorado Geological
Survey.
National Fuel. 1939. Map of the National Fuel Co's Puritan Mine. Weld County, CO:
National Fuel Company.
National Oceanic Atmospheric Administration (NOAA). 2011. 1981-2010 Climate
Normals;Erie, CO.
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Tierra. 1983. Subsidence Potential Study, Dacono Properly, Weld County, Colorado
(W3). Lakewood, CO: Tierra Consultants Inc.
Tweto, O. 1979. Geologic Map of Colorado; 1:500,000. U.S. Geological Survey.
U.S. Geological Survey(USGS). 1994. 7.5 Minute Quadrangle;Frederick, CO. Reston,
Virginia: U.S. Geological Survey.
USGS. 2004. Landslide Types and Processes. U.S. Geological Survey.
USGS. 2012. Colorado Siesmic Hazard Map. November 2012. [Web Page] Located at
http://earthquake.usgs.gov/earthquakes/states/colorado/hazards.php.
Accessed: August 2013.
Weld County.2013. GIS and Mapping. [Web Page]. Located at http://www.co.weld.co.
us/Departments/GIS/. Accessed: September 2013.
Western Enviromental(Western). 1999a. Mine Subsidence Investigation, Glacier
Industrial Park, Lots 4 and 5, Block 4(W57). Littleton, CO:Western
Environment and Ecology Inc.
Western. 1999b. Mine Subsidence Investigation, Glacier LLC Property(W49). Littleton,
CO:Western Environment and Ecology Inc.
Western. 1999c. Mine Subsidence Investigation, Lot 6, Block 3, Glacier Industrial Park
(W71). Littleton, CO:Western Environment and Ecology Inc.
Western. 2008. Mine Subsidence Assesment, Lot 3 and 4, Block 1, Glacier Buisness
Park, Frederick Colorado(W100). Littleton, CO:Western Environment and
Ecology, Inc.
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ARCAD1S
Appendix A
Geological Hazard Development
Permit Submittal Checklist and
Application
GEOLOGICAL HAZARD DEVELOPMENT PERMIT (GHDP) SUBMITTAL CHECKLIST
APPLICATION REQUIREMENTS:
One (1) original Geologic Hazard Overlay District Development Permit application and required
materials plus two (2) copies; for a total of three (3) copies. (Based upon the number of referral
entities, the planning staff may request additional copies of the packets and maps.)
A map portraying the geologic conditions of the area (see Page 3).
A Geologic Report (see Page 3).
$180.00, Geologic Hazard Overlay District Development Permit Fee
SUPPLEMENTAL REQUIREMENTS:
The following items shall be submitted with an application fora Geologic Hazard Overlay District Developm ent Permit:
1. A completed application form (form attached).
2. A map portraying the geologic conditions of the area with particular attention given to the specific regulated
geologic hazards. The map shall be delineated in drawing ink on mylar or other drafting medium approved
by the Department of Planning Services. The dimensions of the map shall be twenty-four(24)inches bythirty-
six(36) inches. The map shall be prepared at a 1" = 100' scale and shall include the parcel in question, as
well as features within 500 feet of the parcel boundaries. The scale of the map may be reduced or enlarged
upon approval of the Department of Planning Services. Such map shall also include:
A. A certified boundary survey of the property for which appication is made. Bearings and distances of
all perimeter boundary lines shall be indicated outside the boundary lines.
B. The topography of the area at ten (10) foot contour intervals or at intervals as determined by the
Department of Planning Services.
C. Existing structures and landscape features, including the name and location of all watercourses,
ponds, and other bodies of water.
D. Proposed building locations and arrangements.
E. Legend including a complete and accurate legal description as prescribed by the deve lopm ent permit
application form. The description shall include the total acreage of the surveyed parcel.
F. Engineer's Certificate and Surveyor's Certificate.
G Title, scale and north arrow.
H Date, including revision dates,if applicable.
Such additional information as may be required by the Board of County Commissioners or
Department of Planning Services.
3. A geologic report explaining the above maps with particular emphasis on evaluating and predicting the impact
of such geologic conditions on the proposed land-use changes and developments. The report shall also
include recommended mitigating procedures to be employed in meeting the intent and purposes of this
regulation. Applications for development in ground subsidence areas shall include,but not be limited to,the
following information or data,where applicable:
-1-
A. Amount of material removed or materials subject to volume decrease.
B. Interval between the ground surface and the location of void space or materials subject to volume
decrease.
C. In poorly consolidated aquifers, the effect of pore fluid withdrawal.
D. In wind deposited silt (loess) areas, and areas of predominantly fine-grained colluvial sods, the
amount of wetting the area is subject to and its effect.
E. In areas of soluble materials, the effect of wetting.
F. In areas of underground mining, date regarding air shafts, haulage ways, attics, faults, rooms and
pillars, and final mine maps.
G. Building type and proportion.
H. Pertinent geologic and hydrologic factors of the area.
Test hole and well log data.
J. Mitigation techniques that will be employed, including effectiveness and estimated cost of such
techniques.
K. Pertinent historic factors including,but not limited to,part occurrences of ground subsidence in the
area proposed for development.
-2-
GEOLOGIC HAZARD DEVELOPMENT PERMIT (GHDP) PROCEDURAL GUIDE
APPLICATION FEE HEARINGS/MEETINGS PROCESSING TIME
$180.00 Department of Planning Services 60 days
Administrative Staff Review'
Colorado Geological Survey"
'As soon as practicable after a decision has been reached, the Department of Planning Services shall notify the
applicant of the action taken on the Geologic Hazard Overlay District Development Permit application.
The applicant shall pay for any fees requred by the Colorado Geological Survey at the time of submittal of the
application.
An additional investigation fee shall be added to the costof the permitapplication when specific land,uses, buildings,
manufactured homes, mobile homes, and structures that require a permit by the Weld County Code, Chapter 23, are
located, moved, operated,or constructed prior to obtaining a permit. The investigation fee shall be 50% of the fee
established by separate action bythe Board of County Com missioners for land-use applications. The payment of such
investigation fee shall not relieve any persons from fully corn plying with the requirements of the Weld County Code,
Chapter 23, nor from any other penalties
PURPOSE
The purpose of this packet is to provide an applicant with information on the Geologic Hazard Overlay District
Development Permit application process.
INTENT
The purpose of the Geologic Hazard Overlay Distnct Development Permit is to ensure that any proposed building,
development, structure, and use which 's to be located within the Geologic Hazard Overlay District and is subject to
the requirements of the District contained in the Weld County Code, Chapter 23, Article II, Division 7, and Chapter 23,
Article V, Division 2, nor from Geologic Hazards.
A Geologic Hazard Overlay District Development Permit shall not be required if any proposed building, structure, and
use and its accessory uses are allowed by right within the underlying zoning district. Any person applying for a Use
by Special Review, a Major Faciity of a Public Utility, Change of Zone, Subdivision of land including Recorded
Exemptions,and Planned UnitDevelopments within the Geologic Hazard Overlay District shall submit their application
for review to the Colorado Geological Survey. If the Colorado Geological Survey determines that conditions and the
land-use request require further review,the applicant shall apply for and obtain a Geologic Hazard Overlay District
Development Permit before any of these applications are considered for final approval by the Board of County
Commissioners.
A completed application form and supporting materials will enable the Planning Staff to process and reach a decision
based on the merits of the Geologic Hazard Overlay District Development Permit application. The applicant shall
submit the following:
The Weld County Department of Planning Services shall be responsible for processing a Geologic Hazard Overlay
District Development Permit in the unincorporated areas of Weld County in accordance with Section 23-2-570 of the
Weld County Code.
The submission requirements are explained in Section 23-2-590 of the Weld County Code. Geologic Hazard Overlay
District Development Permit applications submitted for review shall include the following information. Applications
containing less than the specified requirements shall not be accepted for review unless the appicant has submitted
to and had approved by the Department of Planning Services written justification as to why a particular requirement
does not pertain to the proposed development.
-3-
STANDARDS
The Department of Planning Services shall not issue a Geologic Hazard Overlay District Permit until it has been
determined that all applicable standards specified in the Weld County Code, Chapter 23, have been met by the
Applicant.
1. Applicants seeking a permit to develop in a regulated geologic hazard area must demonstrate to the
Department of Planning Services through required maps and reports that all significant geologic hazards to
public health and safety and to property shall be minimized by using mitigating techniques. These maps and
reports shall be certified by registered professional engineer who shall certify that the design of the proposal
ensures the protection of human life and property from the adverse impacts of geologic hazards to the
greatest extent possible.
2. Any construction approved by the Department of Planning Services within a regulated geologic hazard area
shall be supervised bya qualified professional engineer. Engineering techniques to mitigate geologic hazard
conditions at the site shall be employed.
QUALIFICATION OF INVESTIGATORS.
All geologic maps and reports required by these regulations shall be prepared by or under the direction of and shall
be signed by a professional geologist as defined by Section 34-1-201, et seq., Colorado Revised Statutes. All
engineering work required by these regulations shall be prepared by orunder the directionof a registered professional
engineer as defined in Section 12-25-101,et seq.,Colorado Revised Statutes.
EXEMPTIONS.
The Geologic Hazard Overlay District Development Permit Regulations shall not apply to land uses which do not
involve any of the following:
A. Human habitation.
B. Concentration of people.
C. Potential hazards to human life or property.
-4-
GEOLOGICAL HAZARD DEVELOPMENT PERMIT (GHDP) APPLICATION
FOR PLANNING DEPARTMENT USE DATE RECEIVED:
RECEIPT/AMOUNT# /$ _ CASE#ASSIGNED: --
APPLICATION RECEIVED BY PLANNER ASSIGNED:
Parcel Number 1 a 6 7 - 0 3 - 3 - 0 0 - 0_ 5 4 _
(12 digit number-found ai Tax I.D.information,obtainable at the Weld County Assessor's Office,or www co.weld.co.us).
Legal Description PT W2SW4 3-1-68 LOT A SUB EXEMPT SE-956(2.37r) Section 3 , Township 1 North, Range68 West
Property Address _, City , State _, Zip _
, Proposed Acres, 75.78 Use Special Purpose P Existing Use Ag w!Fenced Lot'Code,Special Purpose
pose ,
FEE OW NER(S) OF THE PROPERTY:
Name: Ankadarko E&P Company LP
Work Phone#_ Home Phone# Email Address
Address: PO Box 173779
City/State/Zip Code Denver CO 80217-3779
APPLICANT OR AUTHORIZED AGENT(See Below:Authorization must accompany all applicatia,s signed byAulhond Agent)
Name: Kerr McGee ON 8 Gas Onshore LP Elizabeth M.Smith
Work Phone# 720.929.6038 Home Phone# Email Address Elizabeth.Smith@anadarko.com
Address: 1099 18th Street
City/State/Zip Code Denver,Co 80202
ENGINEER:
Name: ARCADIS U.S.Inc William J.Zahniser,P.E.
Work Phone# 720.344.3888 Email Address Bill.Zahniser@arcadis-us.com
Address: 630 Plaza Drive,Suite 100
City/State/Zip Code Highlands Ranch,CO 80129
GEOLOGIST:
Name: ARCADIS U.S.Inc Matthew W.Bauer,P.G.
Work Phone# 303.231.9115 x113 Email Address Matt.Bauer@arcadis-us.com
Address: 1687 Cole Boulevard,Suite 200
City/State/Zip Code Lakewood,CO 80401
I(We) hereby depose and state under the penalties of perjury that afl statements, proposals and/or plans submitted
with or contained within the application are true and correct to the best of my knowledge. Ifan Authorized Agent signs,
a letter of authorization from all fee owners must be included with the application. If a corporation is the fee owner,
notarized evidence must be included showing the signatory has to legal authority to sign for the corporation.
Signature:Owner or Authorized Agent Date Signature: Owner or Authorized Agent Date
ARCADIS
Appendix B
Previously Completed Geotechnical
Investigation Report
Subsurface Exploration Program
and Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
Prepared for:
Anadarko Petroleum
3939 Carson Avenue
Evans, CO 80620
Attention: Mr. Tony Capushion
Job Number: 10-3022 May 7, 2010
1 I I
ENGINEERING CONSULTRNTS INC
41 Inverness Drive East,Englewood,CO 80112-5412 Phone(303)289-1989 Fax(303)289-1686 www.groundeng.com
Office Locations: Englewood • Commerce City • Loveland . Granby • Gypsum • Grand Junction • Casper
TABLE OF CONTENTS
Page
Purpose and Scope of Study 1
Proposed Construction 1
Site Conditions _ 2
Subsurface Exploration 3
Laboratory Testing 3
Subsurface Conditions 4
Seismic Classification 5
Geotechnical Considerations for Design 6
Foundation Systems 8
Tank Floor Systems 15
Below-Grade Tank Walls 15
Fill Station Containment Slab 16
Project Earthwork 18
Water-Soluble Sulfates 21
Soil Corrosivity 22
Buried Utility Lateral Installation 25
Surface Drainage 27
Closure 28
Location Of Test Holes Figure 1
Logs of Test Holes Figure 2
Legend and Notes Figure 3
Log of Test Hole 6 Figure 4
Log of Test Hole 7 Figure 5
Compaction Test Results Figure 6
Summary of Laboratory Test Results Tables 1 and 2
Geotechnical Basis for Recommendations Appendix A
Recommendations for Foundation & Floor System Construction Appendix B
Recommendations for Earthwork Construction Appendix C
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
PURPOSE AND SCOPE OF STUDY
This report presents the results of a subsurface exploration program and laboratory
testing performed by GROUND Engineering Consultants, Inc. (GROUND) to provide
geotechnical recommendations for design and construction of the proposed Anadarko
KMG 19-3i Facility, in Weld County, Colorado. Our services were performed in general
accordance with GROUND's Proposal No. 1002-0247 dated February 10, 2010.
Our proposed scope of service does not include providing geotechnical
recommendations for construction of the proposed access road(s). A separate proposal
can be provided upon request to provide those additional services.
A field exploration program was conducted to obtain information on subsurface
conditions. Material samples obtained during the subsurface exploration were tested in
the laboratory to provide data on the classification and engineering characteristics of the
on-site soils. The results of the field exploration and laboratory testing are presented
herein.
This report has been prepared to summarize the data obtained and to present our
conclusions and recommendations based on the proposed construction and the
subsurface conditions encountered. Design parameters and a discussion of
geotechnical engineering considerations related to the construction of the proposed
facility are included.
PROPOSED CONSTRUCTION
Based on the information provided by the project civil engineer, CH2M Hill Trigon, Inc.,
we understand that the project will consist of the following:
❑ Construction of settling, slop and oil storage tanks approximately 12 feet in
diameter and 20 feet in height.
❑ Construction of elevated cone bottom fiberglass tanks with vertical legs
approximately 20 feet in diameter and 30 feet tall.
U Construction of water storage tanks approximately 50 feet in diameter and 24 feet
tall.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 1
Subsurface Exploration Program
Geotechnicai Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
• Construction of a portable pump injection building on a structural steel skidded
frame. The approximate size of the building is 15 feet wide by 50 feet long. The
building is to be 10 feet in height
❑ A drum filter.
U A transformer.
❑ A concrete containment slab for a truck fill station, approximately 100 feet wide by
100 feet long.
U There are also anticipated to be pumps, a glycol heater, and pipe and cable tray
supports.
Based on the site topography, additional cuts and fills necessary to achieve the finished
grades at the site will be less than 2 feet. We assume that buried drain/fill lines will be
installed for the tanks and that other buried utility lines will be installed to serve the
facility. Geotechnical recommendations for paving were excluded from our scope.
We assume that little or no landscaping will be included in the project. Gravel pathways,
rather than concrete sidewalks will facilitate access between the structures.
If the proposed construction differs significantly from that described above, GROUND
should be notified to re-evaluate the recommendations contained herein.
SITE CONDITIONS
The site consisted of a portion of a cultivated field that had been graded to form an
elongate facility pad surrounded by an approximately 10-foot berm. The pad was nearly
flat, and contained a well. Gravel and small cobbles were common on the ground
surface on the southern half of the pad; about 2 inches of drilling mud covered much of
the north half.
On the west side of the bermed area was an unpaved access road. Another existing
well was noted to the east of the site. Cultivated land surrounded the remainder of the
site, supporting what appeared to be native grasses.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 2
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
SUBSURFACE EXPLORATION
The subsurface exploration for the project was conducted in March, 2010. Five test
holes were advanced using conventional, truck-mounted drilling equipment to depths
from approximately 20 to 35 feet below existing grades to evaluate the subsurface
conditions, including depths to bedrock and groundwater, as well as to retrieve samples
for laboratory testing and analysis. Two additional test holes were advanced to depths
from approximately 182 to 184 feet below existing grades using air-rotary and NX coring
equipment to evaluate the possible presence of mine workings beneath the site. A
GROUND engineer directed subsurface exploration, logged the test holes in the field
and prepared the samples for transport to our laboratory.
Samples of the subsurface materials were retrieved with a 2-inch I.D. "California" -type
liner sampler for the five shallower test holes. The sampler was driven into the substrata
with blows from a 140-pound hammer falling 30 inches. This procedure is similar to the
Standard Penetration Test described by ASTM Method D1566. Penetration resistance
values (blows per distance driven, typically 12 inches), when properly evaluated, indicate
the relative density or consistency of soils and bedrock. Depths at which the samples
were obtained and associated penetration resistance values are shown on the test hole
logs.
Additionally, core samples of the bedrock materials in the depths of historic coal mining
activities were advanced into the bedrock materials using a 5-foot, NX-sized core barrel.
Depths at which the samples were obtained and associated properties of the cores are
also shown on the boring logs.
The approximate locations of the test holes are shown in Figure 1, following the text.
Logs of the test holes are shown in Figure 2 through 4. Legend and Notes are
presented in Figure 5.
LABORATORY TESTING
Samples retrieved from our test holes were examined and visually classified in the
laboratory by the project engineer. Laboratory testing of soil samples obtained from the
subject site included standard property tests, such as moisture content in-placed
density, grain size analyses, and Atterberg limits. Swell-consolidation, unconfined
Job No. 10.3022 GROUND Engineering Consultants,Inc. Page 3
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-31 Facility
Weld County, Colorado
compressive strength, water-soluble sulfate content, corrosivity and hydraulic
conductivity (permeability) tests were performed on selected samples as well.
Compaction (Proctor) characteristics were evaluated from a composite (bulk) sample of
the shallow soils. Laboratory tests were performed in general accordance with
applicable ASTM protocols. Data from the laboratory testing program are summarized
on Tables 1 and 2. Data from the proctor testing are summarized on Figure 6.
SUBSURFACE CONDITIONS
The test holes generally encountered bedrock materials from almost the ground surface.
The bedrock was overlain by a few feet of severely weathered bedrock and/or clayey fill
soils. The bedrock consisted primarily of claystones / clay shales and siltstones / silt
shales (referred to herein as "claystones" and "siltstones") with thin interbeds of
sandstone, and coal beds up to 8 or more feet in thickness.
Published maps, e.g. Ogden Tweto (1979)1, depict the site as underlain by the Upper
Cretaceous Laramie and Fox Hills Sandstone formations. We interpret the bedrock to
be Laramie Formation materials.
The claystones, siltstones, and coals extended to the depths explored. Within those
materials, indications of mined out zones (broken rock, voids filled with rock-water
slurry, timbers, etc.) were encountered at depths of about 176 and 179 feet below
existing grades.
Maps published by the Colorado Geological Survey 2 indicate that the Puritan Mine
extended toward the site from the east, with coal mined from workings at depths of 150
feet or more. We interpret the above findings to indicate that mining extended farther to
the west than mapped.
Fill soils were encountered locally in the test holes. Delineation of the complete lateral
and vertical extents of all fills on the site was beyond our present scope of services. If
fill soil volumes and compositions at the site are of significance, the contractor should
evaluate them using shallow test pits.
Trimble, D.E. and M.N. Machette, 1979, Geologic Map of the Greater Denver Area, Front Range Urban
Comdo,; Colorado, U.S. Geological Survey, Miscellaneous Investigations Series, Map l-656-H.
2 Colorado Geological Survey, 1989,Mining and Surface Features, Boulder-Weld Coal Field.
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 4
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
Fill generally consisted of sands and clays with gravel and cobbles locally. The sand
fractions were fine to coarse. These soils were moist, low to medium plastic, loose to
compact, and light brown in color.
Weathered Claystone and Siltstone was slightly sandy to sandy, low or highly plastic,
moist to wet, stiff to very stiff, and light brown in color. iron oxide staining was noted
locally.
Claystone and Siltstone Bedrock generally consisted of claystones with subordinate
siltstones and coals, and scattered beds of sandstone. The sand fractions were
generally fine. They were low to highly plastic, slightly moist to moist, medium hard to
very hard, and light brown to gray to brown to gray-brown in color. iron oxide staining
was noted locally.
Coal was encountered at various depths in beds ranging from a few inches to at least 8
feet in thickness. The coal was anthracitic, moderately hard, and exhibited numerous
fractures.
Groundwater was not encountered in the shallower test holes at the time of drilling.
The deeper test holes encountered groundwater irregularly at various depths. Methane
gas releases caused episodic bursts of groundwater to the surface from depths of more
than 100 feet at Test Hole 6. Groundwater levels should be anticipated to fluctuate,
however, in response to annual and longer-term cycles of precipitation, applied
irrigation, and surface drainage.
Swell-Consolidation Testing indicated a high to very high potential for post-
construction heave at the site. Measured swells for samples of the shallow claystone
bedrock ranged up to approximately 6.0 percent upon wetting against surcharge loads
that approximated the in-place overburden pressure on that sample. A slight
consolidation was measured, as well. Swell-consolidation test results are summarized
on Table 1.
SEISMIC CLASSIFICATION
According to the 2006/2009 International Building Code® (Section 1613 Earthquake
Loads), "Every structure, and portion thereof, including nonstructural components that
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 5
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
are permanently attached to structures and their supports and attachments, shall be
designed and constructed to resist the effects of earthquake motions in accordance with
ASCE 7, excluding Chapter 14 and Appendix 11A. The seismic design category for a
structure is permitted to be determined in accordance with Section 1613 (2006/2009
IBC) or ASCE 7." Exceptions to this are further noted in Section 1613.
In accordance with the 2006/2009 International Building Code, it is GROUND's opinion
that Seismic Design Category B would be applicable for seismic foundation design,
based on an Occupancy Category of I, II, or III. The Project Structural Engineer should
ultimately determine the Seismic Design Category. Compared with other regions of the
Western United States, recorded earthquake frequency in the project vicinity is relatively
low.
Per 2006/2009 IBC, Section 1613.5.2 Site class definitions, "Based on the site soil
properties, the site shall be classified as either Site Class A, B, C, D, E or F in
accordance with Table 1613.5.2. When the soil properties are not known in sufficient
detail to determine the site class, Site Class D shall be used unless the building official
or geotechnical data determines that Site Class E or F soil is likely to be present at the
site".
As permitted in Table 1613.5.2, in the event the soil shear wave velocity, vs, is not
known, site class shall be determined from standard penetration resistance, N, or from
soil undrained shear strength, su, calculated in accordance with Section 1613.5.5, for the
top 100 feet of subsurface soils.
Based on the soil conditions encountered in the test holes drilled on the site, our review
of applicable geologic maps, as well as our experience within the Project site vicinity,
GROUND estimates that a Site Class C (estimate this using the IBC guidelines)
according to the 2006/2009 IBC classification (Table 1613.5.2) be utilized for design.
GEOTECHNICAL CONSIDERATIONS FOR DESIGN
The proposed facility site is a difficult site geotechnically. The previous earthwork at the
site removed the native soils, resulting in exposure of the Laramie Formation claystones
and siltstones essentially at the ground surface, overlain only by a few feet of
uncontrolled fill, etc. Foundations bearing on the claystones and siltstones will provide
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 6
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
ample bearing support for the project structures. However, the highly expansive nature
of the bedrock claystones and the potential for surface settlement due to consolidation
of former mine workings at depth complicate design of the proposed structures.
Expansive Soils Heave The data obtained for this study suggested high to very high
potentials for post-construction heave in the shallow, on-site bedrock. As discussed in
detail in Appendix A, we estimate that 6 to 8 inches of post-construction movements are
likely where structures are supported directly on the shallow bedrock exposed at the
site.
Mining-Related Subsidence Both of the deeper test holes (Test Holes 6 and 7)
encountered zones of broken rock and voids at depths of about 175 feet beneath the
site. We understand that the injection well drilled on the site also encountered voids.
We interpret those zones to represent former workings of the Puritan Mine that have
partially collapsed. As such, they would indicate that the Puritan Mine workings
apparently extend at least 200 feet farther west than mapped by the Colorado
Geological Survey.2 Based on these subsurface conditions, it is GROUND's opinion that
the mine workings underlie effectively the entire project site. (Further) collapse of those
zones could lead to settlements at the ground surface above or near the area that
collapsed. Numerous incidents of mine-related subsidence have been documented in
the overall Boulder— Weld County coal field area which includes the subject site.
As discussed in Appendix A, we estimate that the likely magnitude of settlement that will
be realized at the facility is 3 to 4 inches, This settlement likely will be differential across
a given structure footprint because we anticipate mine-related subsidence to be realized
irregularly, if at all, across the site.
Drainage Effective drainage is an important tool for mitigating expansive soils heave.
The facility pad, however, has been constructed by lowering grades slightly to provide
material for constructing the enclosing berms. The berms themselves limit run-off away
from the propose facilities. Therefore, effective surface drainage measures should be
incorporated into project design to slow post-construction wetting of the site soils.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 7
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
FOUNDATION SYSTEMS
The following recommendations are applicable to the elevated fiberglass tanks, the at-
grade or below-grade settling, slop, oil storage and water tanks, and the various
ancillary structures. It should be noted that these foundation recommendations were
intended to address the expansive soil conditions at the site. We assumed that the risk
of mine-related subsidence was acceptable to the Anadarko Petroleum and that no
remedial measures will be undertaken to address it. These foundation systems and
associated earthwork will provide little or no benefit with regard to mitigating distress
that could result from mine-related subsidence. Recommendations to address mine-
related subsidence can be provided on request. Note that undertaking such measures
at depths on the order of 175 feet may be costly.
Drilled Pier Foundations Where tolerances for post-construction movements are low,
GROUND recommends that structures be supported on straight-shaft drilled piers
bearing below the depth of wetting. Although drilled pier foundations will not eliminate
the risk of post-construction building movements, if the measures outlined in this report
are implemented effectively, the likelihood of acceptable building performance will be
within the local industry standards for buildings supported on drilled pier foundation
systems on soils of this nature.
The design criteria presented below should be observed for drill pier foundation
systems. Additional geotechnical criteria and considerations for construction of
drilled pier foundations are provided in Appendix B.
It should be noted that the depths discussed herein refer to depths below existing
surface grades at the time of our subsurface exploration. The contractor should make
appropriate allowance for any changes in grades between the time of GROUND's field
exploration and the time of drilled pier installation. Lowering grades may not be
sufficient to reduce drilled pier lengths.
1) Piers should be at least 31 feet in length and should penetrate at least 11 feet
into relatively un-weathered bedrock. Both criteria — minimum total pier length
and minimum bedrock penetration — should be met. In this case, it appears that
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 8
Subsurface Exploration Program
Geotechnlcal Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
the minimum length criterion generally will govern because of the shallow depths
at which bedrock was encountered.
Based on the depths to relatively un-weathered shales encountered in the test
holes, we anticipate that it will be necessary to advance piers to depths of at
least 31 feet to 34 feet below existing grades to meet these geotechnical criteria.
However, the actual pier lengths may be longer, based on the design loads, the
presence of coal beds, the requirement for minimum dead load pressure, etc., as
determined by the structural engineer, and the actual conditions encountered in
the field at each pier location during installation.
Lenses of severely weathered, soft or loose material, or coal, may be identified
within the relatively un-weathered bedrock during drilled pier excavations.
Where materials not suitable for foundation support are identified, it will be
necessary to deepen individual piers.
2) Piers bearing in relatively un-weathered bedrock may be designed for an
allowable end bearing pressure of 30,000 psf.
Even with careful observation of the drilled pier excavations, it likely will not be
possible to be certain that a pier does not bear on a relatively soft or weak coal
lens or bed a short distance below the pier bottom. It will be necessary to
perform supplemental drilling during construction after the drilled pier locations
are known precisely to evaluate the possible presence of coal at bearing
elevations.
We anticipate a 4-inch diameter test hole advanced rapidly at each pier location
to the to the design bearing depth. An SPT sampler would be advanced at that
depth and at approximately 24 to 36 inches below that depth to evaluate the
possible presence of coal. Lengthening individual piers to get below local coal
beds / lenses should be anticipated.
3) The portion of a pier penetrating relatively un-weathered bedrock may be
designed for an allowable skin friction of 3,000 psf. This allowable skin friction
value is applicable both to provide bearing support and resist uplift.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 9
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-31 Facility
Weld County,Colorado
4) Piers also should be designed for a minimum dead load pressure of 12,000 psf
based on pier end area only.
If the minimum dead load requirement cannot be achieved (as commonly it
cannot), the pier lengths should be extended beyond the above minimum length
to make up the dead load deficit. Skin friction in relatively un-weathered bedrock
can be used to resist uplift.
6) A minimum pier diameter of 18 inches is recommended to facilitate proper
cleaning and observation of the pier hole.
7) We suggest that a maximum pier length : diameter ratio of 25 (L) : 1 (d) be
maintained. The actual length : diameter ratio, however, should be determined
by the structural engineer.
8) Groups of relatively closely spaced piers placed to support concentrated loads
will require an appropriate reduction of the estimated capacities.
Reduction of axial capacity can be avoided by spacing piers to a distance of at
least 3 'diameters' center to center. At this spacing or greater, no reduction in
axial capacities or horizontal soil modulus values is required. Pier groups
spaced less than 3 diameters center to center should be studied on an individual
basis to determine the appropriate axial capacity reduction(s).
In-line arrays of drilled piers, however, must be spaced at least 6 diameters
apart, center to center, to avoid reductions in lateral capacity when loaded in line
with the array (parallel to the line connecting the pier centers). Linear arrays of
piers spaced more closely than 6 diameters center to center should be studied to
determine the appropriate lateral capacity reduction(s).
9) Piers should be reinforced for their full length to resist the ultimate tensile load
created by the on-site swelling materials. Adequate reinforcement should be
designed to resist the deficit between the design dead load on a pier and the
uplift pressures acting on the pier perimeter in the upper 20 feet of material
penetrated by the pier.
Job No. 10.3022. GROUND Engineering Consultants,Inc. Page 10
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
Tension may be estimated on the basis of uplift pressure in the upper 20 feet of
material penetrated by the pier, and on the surface area of the pier. An uplift
skin friction of 1,800 psf should be used. Adequate reinforcement should be
designed to resist the deficit between the design dead load on the pier and the
uplift pressures acting on the pier perimeter.
10) Bedrock penetration in pier holes should be roughened artificially to assist the
development of peripheral shear between the pier and bedrock. Artificially
roughening of pier holes should consist of installing shear rings 3 inches high
and 2 inches deep in the lowest 11 feet of each hole. The shear rings should be
installed 18 inches on centers.
The specifications should allow a geotechnical engineer to waive the
requirement for shear rings depending on the conditions actually encountered in
individual pier holes, however.
11) A 12-inch or thicker void should be provided beneath grade beams to prevent the
swelling soil and bedrock from exerting uplift forces on the grade beams and to
concentrate pier loadings. A void should also be provided beneath necessary
pier caps.
12) The parameters tabulated below may be used for analysis of drilled piers
regarding their response to lateral roads using "L-Pile" or other programs using
similar input parameters. The parameters were developed based on the field
and laboratory data obtained for the subject site and GROUND's experience with
similar sites and conditions.
A simplified soil / bedrock profile, unit wet weights (y'), angles of internal friction
t4), cohesion (c), for the earth materials, as well as values for strain at 50
percent of failure stress (C50) and horizontal soil modulus (ku). The estimated
values are tabulated below. Resistance to lateral loads should be neglected in
any soils, including fill soils, shallower than 5 feet. No reduction of lateral
support in cased intervals is recommended, as long as no slurry was placed in
the pier hole to facilitate placement of concrete.
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 11
Subsurface Exploration Program
Geotechnlcal Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
ESTIMATED GEOTECHNICAL PARAMETERS FOR"L-PILE" LATERAL LOAD ANALYSIS
Soil I Bedrock Approximate
Material Depth Range Parameter Range of Valucs Moan Value
120 to 136 pcf 130 pcf
Claystone (13 23 to 29 degrees 24 degrees
Siltstone & 5+ feet
C 3,500 to 8,000 psf 4,500 psf
Sandstone - , ---- - •
Bedrock E50 0.009 to 0.015 0.012
k,, 1,500 to 2,500 pci 2,400 pci
Alternative Shallow Foundations As a higher risk alternative, shallow foundation
systems and/or slab-on-grade concrete floors may be used, together with remedial
earthwork if the owner understands and accepts the associated, increased risk of
adverse post-construction structure movements as discussed in Appendix A and
tabulated below. In such cases, the criteria presented below may be observed for a
spread footing foundation system. Additional geotechnical criteria and
considerations for construction of conventional, shallow foundations are
provided in Appendix B.
1) If shallow foundations are selected for a structure, if the foundations bear on a
section of properly compacted fill soils, the potential for distress resulting from
post-construction foundation movements will be somewhat reduced. Alternative
fill section thicknesses are tabulated below, together with estimated, likely post-
construction vertical movements. The desired fill section thickness should be
selected by the owner based on the degree of post-construction movement
acceptable to him.
Note that if a coal bed or lens is exposed at the bottom of remedial fill section
excavation, the coal should be excavated in entirety if less than 2 feet in
thickness. If the coal is greater than 2 feet in thickness, the remedial excavation
should be deepened into the coal by a minimum of 2 feet.
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 12
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
FILL SECTION OPTIONS BENEATH ALTERNATIVE_. SHALLOW
FOUNDATIONS AND SLABS-ON-GRADE
Estiu ,tad Likely
Fill Section Thfcknc .... I Post-Construction Moveltiynt
_(feet) (inches)
4 under footings (6 under slab) 3.0
6 under footings (8 under slab) 2.5
8 under footings (10 under slab)_ 2.0
I 12 under footings(14 under slab) 1.5
For the selected fill section, in areas proposed for filling, the existing soils —
primarily bedrock -- should be excavated and replaced to a sufficient depth to
allow the recommended fill section to be constructed.
The fill section should underlie a given structure footprint and extend at full depth
laterally beyond the structure perimeter a distance at least equal to the thickness
of the fill section.
Recommendations for placement and compaction of fill soils are provided in the
Project Earthwork section and Appendix C of this report.
2) Footings bearing on properly compacted fill may be designed for an allowable
soil bearing pressure (Q) of 3,000 psf under drained conditions. This value may
be increased by 1/3 for transient loads such as wind or seismic loading.
Based on these recommended allowable bearing pressures, we anticipate post-
construction settlements from direct compression of the foundation soils on the
order of 1 inch. Post-construction heave and mine-related subsidence induce
additional movement beyond that caused by direct compression of the soils.
The allowable bearing capacity provided above is based on the assumption of
well-drained conditions. If foundation soils become wet, the effective bearing
capacity could be reduced and the potential for heave or settlement will be
increased.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 13
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
3) Where possible, footings also should be designed to impose a minimum dead
load of at least 1,000 psf. This minimum loading does not need to be maintained
during transient loading, however.
4) In order to reduce differential settlements between footings or along continuous
footings, footing loads should be as uniform as possible. Differentially loaded
footings will heave or settle differentially.
5) We assume, however, that the portable, steel-framed, pump injection building, is
adjustable and not readily affected by expansive soils heave. Therefore, that
structure may be supported on shallow foundations bearing on firm, existing soils
without a fill section beneath them. Connections to the building of all types must
be flexible and/or adjustable to accommodate the anticipated movement
6) Spread footings should have a minimum footing lateral dimension of 16 or more
inches for linear strip footings and a minimum lateral dimension of 24 or more
inches for isolated pad footings. Actual footing dimensions, however, should be
determined by the structural engineer, based on the design loads.
7) Footings should be provided with adequate soil cover above their bearing
elevation for frost protection. Footings should be placed at a bearing elevation 3
or more feet below the lowest adjacent exterior finish grades. (If frost heave is
not a design concern for the portable, pump injection building, then footings for
that building can bear at a depth of 1.5 feet.)
8) Continuous foundation walls should be reinforced top and bottom to span an
unsupported length of at least 10 feet.
9) The lateral resistance of spread footings will be developed as sliding resistance
of the footing bottoms on the compacted, granular fill. Sliding friction at the
bottom of footings may be taken as 0.30 times the vertical dead load.
10) Compacted fill placed against the sides of the footings should be compacted to
at least 95 percent relative compaction in accordance with the recommendations
in Appendix C.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 14
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
TANK FLOOR SYSTEMS
To provide for the least risk of adverse post-construction tank floor movements that are
at-grade or below grade, GROUND recommends the use of structural floors supported
on drilled piers in a manner similar to the structures and spanning over a void as the
floor system entailing the lowest risk of post-construction floor movements.
Requirements for the number and position of piers to support a floor, etc., will depend
upon the spans, design loads, etc., in the structural design and, therefore, should be
developed by the structural engineer. Geotechnical recommendations for design and
installation of drilled piers are provided in the Foundation Systems section of this report
and in Appendix B.
Drain-fill piping for the tank should be designed to allow for differential movement
between the piping and the tank of up to 8 inches. We suggest that the piping be
provided with flexible connections where the pipes enter the building to accommodate
these differential movements.
BELOW-GRADE TANK WALLS
Where any of the tanks are partially or entirely below-grade, then below-grade tank
walls which are laterally supported and can be expected to undergo only a limited
amount of deflection, i.e., an "at-rest" condition, should be designed to resist lateral
earth pressures computed on the basis of an equivalent fluid unit weight of 82 pcf where
on-site materials are used as backfill.
If CDOT Class 1 Structure Backfill were imported for use as wall backfill, an at-rest
equivalent fluid pressure of 55 pcf could be used. However, we do not recommend use
of a granular backfill without effective drainage that then would require a sump and
pump or other means to remove infiltrating surface water.
These 'at rest' loads are for well-drained conditions with a horizontal upper backfill
surface. The additional loading of an upward sloping backfill, hydrostatic loads if
sufficient drainage is not provided, as well as loads from traffic, stockpiled materials,
etc., should be included in foundation wall design.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 15
Subsurface Exploration Program
Geotechnical Rocommondations
Anadarko KMG 19-3i Facility
Weld County, Colorado
Backfill soils should be placed in accordance with the recommendations provided in the
Project Earthwork section and Appendix C of this report. The contractor should take
care not to over-compact the backfills, which could result in excessive lateral pressures
on the walls.
Some settlement of wall backfills will occur even where the material was placed
correctly. This settlement likely will be differential, increasing with depth of fill. Where
shallowly founded structures and pavements must be placed on backfilled zones,
structural design, pipe connections, etc., should take into account backfill settlement,
including differential movement and the associated risks are understood by the owner.
A geotechnical engineer should be retained to provide recommendations for founding
improvements in such areas.
FILL STATION CONTAINMENT SLAB
GROUND recommends that the truck fill station containment slab be constructed as a
reinforced portland cement concrete slab 7 or more inches in thickness placed on 6
inches of properly compacted CDOT Class 6 Aggregate Base Course.
That slab is subject to comparable expansive soils heave as the other structures at the
site. Therefore, slab+gravel system should be placed over a section of properly
moisture-conditioned and compacted fill to reduce the post-construction heave and
make that heave more uniform. Heave will not be eliminated, however. Fill section
alternatives with associated post-construction movement estimates are provided under
Alternative Shallow Foundations in the Foundation Systems section of this report. It
must be understood that even with a properly placed fill section beneath it, distress to
the relatively lightly loaded containment slab likely will result from post-construction soil
movements.
The containment slab should be adequately reinforced. Recommendations based on
structural considerations for slab thickness, jointing, and steel reinforcement in floor
slabs should be developed by the structural engineer.
An allowable vertical soil modulus (K,) of 45 poi may be used for design of concrete
slabs bearing on a properly prepared fill section.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 16
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
The containment should be provided with effective control joints. ACI recommendations
should be followed regarding construction and/or control joints, at minimum.
Prior to placement of the aggregate base course, a proof roll should be performed to
identify areas beneath the containment slab that exhibit instability and deflection. The
soils in these areas should be removed and replaced with properly compacted fill or
otherwise stabilized.
Effective surface drainage to carry water away from the containment slab should be
incorporated into project civil design.
Concrete Scaling Climatic conditions in the project area including relatively low
humidity, large temperature changes and repeated freeze — thaw cycles, make it likely
that project sidewalks and other exterior concrete will experience surficial scaling or
spalling. The likelihood of concrete scaling can be increased by poor workmanship
during construction, such as 'over-finishing' the surfaces. In addition, the use of de-icing
salts on exterior concrete flatwork, particularly during the first winter after construction,
will increase the likelihood of scaling. Even use of de-icing salts on nearby roadways,
from where vehicle traffic can transfer them to newly placed concrete, can be sufficient
to induce scaling. Typical quality control / quality assurance tests that are performed
during construction for concrete strength, air content, etc., do not provide information
with regard to the properties and conditions that give rise to scaling.
We understand that some municipalities require removal and replacement of concrete
that exhibits scaling, even if the material was within specification and placed correctly.
The contractor should be aware of the local requirements and be prepared to take
measures to reduce the potential for scaling and/or replace concrete that scales.
In GROUND's experience the measures below can be beneficial for reducing the
likelihood of concrete scaling. (These measures are applicable to other project
concrete, as well.) It must be understood, however, that because of the other factors
involved, including weather conditions and workmanship, surface damage to concrete
can develop, even where all of these measures were followed. The mix design criteria
should be coordinated with other project requirements including the criteria for sulfate
resistance presented in the Water-Soluble Sulfates section of this report.
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 17
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
1) Maintaining a maximum water/cement ratio of 0.45 by weight for exterior
concrete mixes.
2) Include Type F fly ash in exterior concrete mixes as 20 percent of the
cementitious material.
3) Specify a minimum, 28-day, compressive strength of 4,500 psi for all exterior
concrete.
4) Include `fibermesh' in the concrete mix may be beneficial for reducing surficial
scaling.
5) Cure the concrete effectively at uniform temperature and humidity. This
commonly will require fogging, blanketing and/or tenting, depending on the
weather conditions. As long as 3 to 4 weeks of curing may be required, and
possibly more.
6) Avoid placement of concrete during cold weather so that it is exposed to freeze-
thaw cycling before it is fully cured.
7) Avoid the use of de-icing salts on given reaches of flatwork through the first
winter after construction.
PROJECT EARTHWORK
The already had been graded at the time of our field exploration. Only limited cuts and
fills are anticipated to achieve final grades. Deeper earthwork will be necessary to
comply with the remedial earthwork criteria discussed herein for project structures, etc.
Use of Existing Fill Soils as Fill Clayey fill soils were encountered locally in select test
holes during subsurface exploration. In general, these appeared suitable for use as
compacted fill if free of trash, organic material, construction debris, and other
deleterious materials.
Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt)
larger than 3 inches in maximum dimension will require special handling and/or
placement to be incorporated into project fills. in general, such materials should be
placed as deeply as possible in the project fills. A geotechnical engineer should be
consulted regarding appropriate recommendations for usage of such materials on a
case-by-case basis when such materials have been identified during earthwork.
Standard recommendations that likely will be generally applicable can be found in
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 18
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
Section 203 of the current CDOT Standard Specifications for Road and Bridge
Construction.
Use of Excavated Bedrock Materials as Fill Excavated claystone, siltstone and
sandstone that are free of coal, trash, and other deleterious materials are suitable, in
general, for placement as compacted fill. Organic materials should not be incorporated
into project fills.
Because of the high swell potentials, excavated bedrock will require a well-coordinated
effort to moisture treat, process, place, and compact properly. In-place bedrock
deposits were dense and relatively dry, and require a significant volume of water to be
mixed into the excavated material to bring it to a uniform moisture content as
recommended in Appendix C. Bedrock fragments larger than 3 inches in maximum
dimension should not be incorporated into project fills. Adequate watering, and
compaction equipment that aids in breaking down the material (e.g., a Caterpillar 825
compactor-roller), likely will be needed. Excavated bedrock will require additional
moisture conditioning and processing in an open area outside of utility trenches or
foundation excavations prior to placement as backfill.
Potential earthwork contractors should be made aware that significant processing and
reprocessing of the on-site materials will likely be required.
Immediately following placement and compaction, drive samples of the fill materials
should be obtained and tested to determine the resultant swell-potential of the in-place
materials. Materials represented by samples exhibiting more than 1 percent swell upon
wetting against a 1,000 psf surcharge should be re-worked at increased moisture
contents and re-compacted in accordance with the recommendations above. In
addition, we suggest that the contractor consider pre-processing bedrock-derived fill
materials prior to placement to facilitate achievement of this heave requirement.
Imported Fill Materials If it is necessary to import material to the site, the imported
soils should be free of organic material, and other deleterious materials. Imported
material should consist of relatively impervious soils that have less than 80 percent
passing the No. 200 Sieve and should have a plasticity index of less than 25.
Representative samples of the materials proposed for import should be tested and
approved by a geotechnical engineer prior to transport to the site.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 19
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
Fill Placement and Compaction Detailed geotechical recommendations for fill
placement and compaction are provided in Appendix C.
Settlements Settlements will occur in filled ground, typically on the order of 1 to 2
percent of the fill depth. If fill placement is performed properly and is tightly controlled,
in GROUND's experience the majority (on the order of 60 to 80 percent) of that
settlement will typically take place during earthwork construction, provided the contractor
achieves the compaction levels recommended herein. The remaining potential
settlements likely will take several months or longer to be realized, and may be
exacerbated if these fills are subjected to changes in moisture content.
Cut and Filled Slopes Permanent site slopes supported by on-site soils up to 3 feet in
height may be constructed no steeper than 2Y2:1 (horizontal : vertical). Minor raveling or
surficial sloughing should be anticipated on slopes cut at this angle until vegetation is
well re-established. Surface drainage should be designed to direct water away from
slope faces.
Excavation Considerations Test holes TH-1 through -5 were advanced to the depths
indicated on the test hole logs by means of conventional truck-mounted drilling
equipment. We anticipate no unusual excavation difficulties, in general, for the
proposed construction in the site soils with conventional, heavy-duty excavating
equipment in good working condition.
However, although no unusually well cemented, hard or resistant sandstone beds were
encountered in the bedrock, although such beds and lenses have been encountered in
the shallow bedrock in the project area. The contractor should be prepared to excavate
beds of very hard resistant sandstone and to handle, process, and, if necessary, export
such materials. Specialized breaking equipment or limited local blasting may be cost
effective to reach project lines and grades, especially for utility installation.
Groundwater was not encountered during subsurface exploration in the shallower test
holes (as deep as 35+ feet). Therefore, groundwater is not anticipated to be a
significant factor for excavating to shallow depths during construction of this project.
Drilled pier holes, however, may encounter groundwater.
Job No. 10.3022 GROUND Engineoring Consultants, Inc. Page 20
Subsurface Exploration Program
Geotochnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
The contractor should take pro-active measures to control surface waters during
construction, to direct them away from excavations and into appropriate drainage
structures. (If seepage or groundwater is encountered in shallow project excavations,
the geotechnical engineer should evaluate the conditions and provide additional
recommendations, as appropriate.)
Temporary Excavation Slopes We recommend that temporary, un-shored excavation
slopes up to 15 feet in height be cut no steeper than 1% :1 (horizontal : vertical) in the
native bedrock in the absence of seepage. Some surficial sloughing may occur on
slope faces cut at this angle. Local conditions encountered during construction such as;
loose, dry sand, soft, wet materials, or seepage will require flatter slopes. Stockpiling of
materials should not be permitted closer to the tops of temporary slopes than 5 feet or a
distance equal to the depth of the excavation, which ever is greater.
Should site constraints prohibit the use of the recommended slope angle, then
temporary shoring should be used. Temporary shoring designed to allow the soils to
deflect sufficiently to utilize the full active strength of the soils may be designed for
lateral earth pressures computed taking an equivalent fluid unit weight of 60 pounds per
cubic foot (pcf) to be characteristic of the site soils for a level adjacent ground condition
in the absence of seepage. In addition to this lateral earth pressure, shoring design
should include surcharge loads exerted by equipment, traffic, seepage forces, material
stockpiles, etc. Actual shoring system(s) should be designed for the contractor by a
registered engineer.
WATER-SOLUBLE SULFATES
The concentrations of water-soluble sulfates measured in selected samples retrieved
from the test holes ranged up to 1.0 percent by weight. (See Table 2.) Such
concentrations of water-soluble sulfates represent a severe environment for sulfate
attack on concrete exposed to these materials. Degrees of attack are based on the
scale of `negligible,' `moderate,' `severe' and 'very severe' as described in the "Design
and Control of Concrete Mixtures," published by the Portland Cement Association
(PCA).
Job No. 10-3022 GROUND Enylnooring Consultants,Inc. Page 21
Subsurface Exploration Program
Geotechnicar Rocommendations
Anadarko KMG 19-31 Facility
Weld County, Colorado
Based on these data and PCA and Colorado Department of Transportation (CDOT)
guidelines, GROUND recommends use of sulfate-resistant cement in all concrete
exposed to site soil and bedrock, conforming to one of the following requirements:
1) Type V, as specified by ASTM C150.
2) Type II with a maximum C3A content of 5 percent and a maximum content of
(C4AF +2[C3A]) of 25 percent.
3) Type II or Type I/II, and 15 to 20 percent of the cement shall be replaced with an
approved Type F fly ash.
4) A blended cement conforming to Type HS, as specified by ASTM C1157.
Other cement types or blends may be acceptable, however, if type-specific test data
demonstrate equal or superior sulfate-resistance to Type V cement. Test data should
be provided to a geotechnical engineer for review, and the cement approved, prior to
use.
All concrete exposed to site soil and bedrock should have a maximum water/cement
ratio of 0.45 by weight. All concrete exposed to site soil and bedrock should have a
minimum compressive strength of 4,500 psi. Concrete mixes should be relatively rich
and should be air entrained.
The contractor should be aware that certain concrete mix components affecting sulfate
resistance including, but not limited to, the cement, entrained air, and fly ash, can affect
workability, set time, and other characteristics during placement, finishing and curing.
The contractor should develop mix(es) for use in project concrete which are suitable with
regard to these construction factors, as well as sulfate resistance. A reduced, but still
significant, sulfate resistance may be acceptable to the owner, in exchange for desired
construction characteristics.
SOIL CORROSIVITY
The degree of risk for corrosion of metals in soils commonly is considered to be in two
categories: corrosion in undisturbed soils and corrosion in disturbed soils. The potential
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 22
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
for corrosion in undisturbed soil is generally low, regardless of soil types and conditions,
because it is limited by the amount of oxygen that is available to create an electrolytic
cell. In disturbed soils, the potential for corrosion typically is higher, but is strongly
affected by soil conditions for a variety of reasons but primarily soil chemistry.
A corrosivity analysis was performed to provide a general assessment of the potential
for corrosion of ferrous metals installed in contact with earth materials at the site, based
on the conditions existing at the time of GROUND's evaluation. Soil chemistry and
physical property data including pH, oxidation-reduction (redox) potential, sulfides, and
moisture content were obtained. Test results are summarized on Table 2.
Reduction-Oxidation: Reduction and oxidation testing indicated negative potentials:
-24 to -55 millivolts. Such a low potentials typically creates a more corrosive
environment.
Sulfide Reactivity: Sulfide reactivity testing for the presence of sulfides indicated a
"trace" and a "positive" result in the native claystones. The presence of sulfides in the
site soils suggests a more corrosive environment.
Soil Resistivity In order to assess the "worst case" for mitigation planning, samples of
materials retrieved from the test holes were tested for resistivity in the laboratory, after
being saturated with water, rather than in the field. Resistivity also varies inversely with
temperature. Therefore, the laboratory measurements were made at a controlled
temperature.
Measurements of electrical resistivity indicated values of approximately 1,502 and 1,168
ohm-centimeters in samples of the site earth materials.
pH Where pH is less than 4.0, soil serves as an electrolyte; the pH range of about 6.5
to 7.5 indicates soil conditions that are optimum for sulfate reduction. In the pH range
above 8.5, soils are generally high in dissolved salts, yielding a low soil resistivity3.
Testing indicated pH values of approximately 7.4 and 7M in the native claystones.
3.3 American Water Works Association ANSI/AWWA C1051A21.5-05 Standard
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 23
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko MG 19-3i Facility
Weld County, Colorado
The American Water Works Association (AWWA) has developed a point system scale
used to predict corrosivity. The scale is intended for protection of ductile iron pipe but is
valuable for project steel selection. When the scale equals 10 points or higher,
protective measures for ductile iron pipe are recommended. The AWWA scale is
presented below. The soil characteristics refer to the conditions at and above pipe
installation depth.
TABLE A.1 SOIL-TEST EVALUATION 2
Soil Characteristic!Value Points
Resistivity
<1,500 ohm-cm .. 10
1,500 to 1,800 ohm-cm 8
1,800 to 2,100 ohm-cm 5
2,100 to 2,500 ohm-cm 2
2,500 to 3,000 ohm-cm 1
>3,000 ohm-cm 0
pH
0 to 2.0 5
2.0 to 4.0 3
4.0 to 6.5 0
6.5 to 7.5 0
7.5 to 8.5 0
>8.5 3
Rectox Potential
< 0 (negative values) 5
0 to+50 rV 4
+50 to+100 mV 31/1
> +100 mV 0
Sulfide Content
Positive 3%
Trace 2
Negative 0
Moisture
Poor drainage, continuously wet 2
Fair drainage, generally moist 1
Good drainage, generally dry 0
If sulfides are present and low or negative redox-potential results (< 50 my)
are obtained, add three points for this range.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 24
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
WoId County, Colorado
We anticipate that drainage at the site after construction will be good. Nevertheless,
based on the values obtained for the soil parameters, the overburden soils/bedrock
appear(s) to comprise a highly corrosive environment for metals.
Corrosive conditions can be addressed by use of materials not vulnerable to corrosion,
heavier gauge materials (increased pipe wall/metal thickness) with longer design lives,
polyethylene encasement, or cathodic protection systems. If additional information or
recommendations are needed regarding soil corrosivity, GROUND recommends
contacting the American Water Works Association or a Corrosion Engineer. It should
be noted, however, that changes to the site conditions during construction, such as the
import of other soils, or the intended or unintended introduction of off-site water, may
alter corrosion potentials significantly.
BURIED UTILITY LATERAL INSTALLATION
Recommendations regarding excavation of utility lateral trenches are provided in the
Project Earthwork section of this report and Appendix C. The resultant voids may be
difficult to backfill with conventional means and methods. Particular care, including the
use of CLSM, may be needed to backfill trenches properly.
On-site soils — primarily bedrock materials — excavated from trenches are suitable, in
general, for use as trench backfill. Backfill soils should be free of vegetation, trash and
other deleterious materials.
Pipe bedding materials, placement and compaction should meet the specifications of
the pipe manufacturer and applicable municipal standards. The contractor should not
anticipate that significant volumes of suitable materials will be available on-site where
relatively free-draining bedding materials are called for. Imported materials proposed for
use as pipe bedding should be tested and approved by a geotechnical engineer prior to
transport to the site.
Trench backfill materials above the pipe bedding zone where CLSM is not used (as
discussed in Appendix C.) should be conditioned to a uniform moisture content, placed
in uniform lifts not exceeding 8 inches in loose thickness, and properly compacted.
Recommendations for backfill placement and compaction are provided in Appendix C.
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 25
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
Bedding should be brought up uniformly on both sides of the pipe to reduce differential
loadings.
Some settlement of trench backfill materials should be anticipated, even where
materials are placed and compacted correctly. To reduce these settlements, the
Contractor should take adequate measures to achieve adequate compaction in the
utility trench backfills, particularly in the lower portions of the excavations and around
manholes, valve risers and other vertical pipeline elements where greater settlements
commonly are observed. However, the need to compact to the lowest portion of the
backfill must be balanced against the need to protect the pipe from damage during
backfilling. Some thickness of backfill may need to be placed at compaction levels
lower than recommended above to avoid damaging the pipe. Likewise, construction
conditions may preclude density testing at specified frequencies in the lower portions of
a trench.
Because of these limitations, we recommend the use of "controlled low strength
material" (CLSM), i.e., a lean, sand-cement slurry, "flowable fill," or similar material in
lieu of compacted soil backfill for areas with low tolerances for surface settlements.
Placement of CLSM in the lower portion of the trench and around risers, etc., likely will
yield a superior backfill and provide protection for the pipe, although at an increased
cost. Other means, e.g., use of smaller compaction equipment, also may be effective
for achieving adequate compaction in these areas.
We assume that surface drainage will direct water away from utility trench alignments.
Where topography, site constraints or other factors limit or preclude adequate surface
drainage, the granular bedding materials should be surrounded by non-woven filter
fabric (e.g., Mirafi° 140N or the equivalent) to reduce migration of fines into the bedding
which can result in severe, local settlements.
Development of site grading plans should consider the subsurface transfer of water in
utility trenches and the pipe bedding. Granular pipe bedding materials can function as
efficient conduits for re-distribution of natural and applied waters in the subsurface. Cut-
off walls in utility trenches or other water-stopping measures should be implemented to
reduce the rates and volumes of water transmitted along utility alignments and toward
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 26
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
tank and other structures where excessive wetting of the underlying soils will be
damaging.
SURFACE DRAINAGE
The following drainage measures are recommended for design, construction, and
should be maintained at all times after the project has been completed:
1) Wetting or drying of the foundation excavations and underslab areas should be
avoided during and after construction as well as throughout the improvements'
design life. Permitting increases/variations in moisture to the adjacent or
supporting soils may result in a decrease in bearing capacity and an increase in
volume change of the underlying soils and/or differential movement.
2) Positive surface drainage measures should be provided and maintained to
reduce water infiltration into foundation soils. The ground surface surrounding
the exterior of each structure should be sloped to drain away from the foundation
in all directions. We recommend that, to the extent possible, a minimum slope of
12 inches in the first 10 feet in the areas not covered with pavement or concrete
slabs, or a minimum 3 percent in the first 10 feet in the areas covered with
pavement or concrete slabs. In no case should water be allowed to pond near or
adjacent to foundation elements or utility trench alignments, etc.
3) The berms surrounding this site will tend to direct water toward the proposed
structures. Area drains or other measures should be included in project design
between structures and the slopes.
4) Roof downspouts and drains should be provided with positive conveyance off-
site for collected waters.
5) We do not anticipate that significant landscaping will be installed around the
proposed structures. If vegetation that requires watering is planted, it should be
located 10 or more feet from structure perimeters or other site improvements.
Landscape irrigation outside that 10-foot limit should be limited to the minimum
quantities necessary to sustain healthy plant growth. Controlling rates of
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 27
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
moisture increase in foundation/subgrade soils should take higher priority than
minimizing landscape plant losses.
6) Plastic membranes should not be used to cover the ground surface adjacent to
foundations. Perforated "weed barrier" membranes that allow ready evaporation
from the underlying soils may be used.
CLOSURE
Geotechnical Review The author of this report should be retained to review project
plans and specifications to evaluate whether they comply with the intent of the
recommendations in this report. The review should be requested in writing.
The geotechnical recommendations presented in this report are contingent upon
observation and testing of project earthworks by representatives of GROUND. If
another geotechnical consultant is selected to provide materials testing, then that
consultant must assume all responsibility for the geotechnical aspects of the project by
concurring in writing with the recommendations in this report, or by providing alternative
recommendations.
Materials Testing Anadarko Petroleum should consider retaining a geotechnical
engineer to perform materials testing during construction. The performance of such
testing or lack thereof, in no way alleviates the burden of the contractor or subcontractor
from constructing in a manner that conforms to applicable project documents and
industry standards. The contractor or pertinent subcontractor is ultimately responsible
for managing the quality of their work; furthermore, testing by a geotechnical engineer
does not preclude the contractor from obtaining or providing whatever services they
deem necessary to complete the project in accordance with applicable documents.
Limitations This report has been prepared for Anadarko Petroleum as it pertains to
design and construction of the KMG 19-3i facility as described herein. It may not
contain sufficient information for other parties or other purposes. The owner or any
prospective buyer relying upon this report must be made aware of and must agree to the
terms, conditions, and liability limitations outlined in the proposal.
Job No. 10.3022 GROUND Engineering Consultants,Inc. Page 28
Subsurface Exploration Program
Geotechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County, Colorado
In addition, GROUND has assumed that project construction will commence by Summer
2011. Any changes in project plans or schedule should be brought to the attention of a
geotechnical engineer, in order that the geotechnical recommendations may be re-
evaluated and, as necessary, modified.
The geotechnical conclusions and recommendations in this report relied upon
subsurface exploration at a limited number of exploration points, as shown on Figure 1,
as well as the means and methods described herein. Subsurface conditions were
interpolated between and extrapolated beyond these locations. It is not possible to
guarantee the subsurface conditions are as indicated in this report. Actual conditions
exposed during construction may differ from those encountered during site exploration.
If during construction, surface, soil, bedrock, or groundwater conditions appear to be at
variance with those described herein, a geotechnical engineer should be advised at
once, so that re-evaluation of the recommendations may be made in a timely manner.
In addition, a contractor who relies upon this report for development of his scope of work
or cost estimates may find the geotechnical information in this report to be inadequate
for his purposes or find the geotechnical conditions described herein to be at variance
with his experience in the greater project area. The contractor is responsible for
obtaining the additional geotechnical information that is necessary to develop his
workscope and cost estimates with sufficient precision. This includes current depths to
groundwater, etc.
The materials present on-site are stable at their natural moisture content, but may
change volume or lose bearing capacity or stability with changes in moisture content.
Performance of the proposed structure will depend on implementation of the
recommendations in this report and on proper maintenance after construction is
completed. Because water is a significant cause of volume change in soils and rock,
Job No. 10-3022 GROUND Engineering Consultants,Inc. Page 29
Subsurface Exploration Program
Gootechnical Recommendations
Anadarko KMG 19-3i Facility
Weld County,Colorado
allowing moisture infiltration may result in movements, some of which will exceed
estimates provided herein and should therefore be expected by the owner.
This report was prepared in accordance with generally accepted soil and foundation
engineering practice in the project area at the date of preparation. GROUND makes no
warranties, either expressed or implied, as to the professional data, opinions or
recommendations contained herein. Because of numerous considerations that are
beyond GROUND's control, the economic or technical performance of the project
cannot be guaranteed in any respect.
GROUND appreciates the opportunity to complete this portion of the project and
welcomes the opportunity to provide the Owner with a cost proposal for construction
observation and materials testing prior to construction commencement.
Sincerely,
GROUND Engineering Consultants, Inc.
Brian H. Reck, P.G T
-1\1 S.,7„
•
• B
• C--)
Reviewed by Jas .E.
Job No. 10-3022 GROUND Engineering Consultants, Inc. Page 30
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ENGONEEF8ING =CONSULTRINTS
LOGS OF TEST HOLES
JOB NO.: 10-3022 FIGURE: 2
CADFILE NAME: 3022LOG.DWG
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT SURFACE ELEV. BORING NO.
10-3022 ANADARKO FACILITY 100 Ft. TH-6
LOGGED BY: LOCATION DEPTH TO GROUNDWATER SHEET
T. ROBERTS, GEC SOUTHWEST CORNER - Ft. 1 OF 8
DATE COORDINATES DEPTH TO BEDROCK HOLE DIAMETER
03/29/10 0 Ft. 2.75 INCH
DRILLER TOTAL DEPTH TREND
VINE LABORATORIES 184 Ft.
DRILL RIG CAD FILE NAME FIGURE: PLUNGE
CANTERRA CT 250 3022DRILLLOG01.DWG 3 90°±1'
SAMPLE DATA CORE DATA
<O w w - FRACTURES = v LITHOLOGIC NOTES ON DRILLING
ga o_a a o o D H > a ao DESCRIPTION CONDITIONS
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GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 3B/ TH-6
3022DRILLLOG02.DWG
SAMPLE DATA CORE DATA
w w z z w o FRACTURES = LITHOLOGIC NOTES ON DRILLING
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GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 3C/ TH-6
3022DRILLLOG03.DWG
SAMPLE DATA CORE DATA
2w w z z w o FRACTURES r = LITHOLOGIC NOTES ON DRILLING
w a az m° DESCRIPTION 9 w <J DESCRIPTION CONDITIONS
,1) rn a w O
w CC
-45 CLAYSTONE BEDROCK: Air Rotary Drilling
Blue to brown to dark brown in
color.
—50
-55
COAL
CLAYSTONE BEDROCK:
Blue-gray to gray in color.
-v5
1
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 3D/ TH-6
3022DRILLLOG04.DWG
SAMPLE DATA CORE DATA
o w w z z w o FRACTURES r = LITHOLOGIC NOTES ON DRILLING
w a az m° DESCRIPTION p w <J DESCRIPTION CONDITIONS
cn rn a w D
w CC
-70 CLAYSTONE BEDROCK: Air Rotary Drilling
Gray to white in color.
--75
-
COAL: Dark gray to light black
in color.
—80
CLAYSTONE BEDROCK:
Gray to light brown in color.
—8
--9c
CCAL
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 3E/ TH-6
3022DRILLLOG05.DWG
SAMPLE DATA CORE DATA
o w w z z w o FRACTURES r = LITHOLOGIC NOTES ON DRILLING
w a az m° DESCRIPTION p w <J DESCRIPTION CONDITIONS
,1) rn a w O
w CC
-95 COAL:Various cracks,black to Air Rotary Drilling
brown in color.
CLAYSTONE BEDROCK:
Light gray to light brown in color.
—100
-105
-1
COAL
-CLAYSTONE BEDROCK:
Light gray in color.
—11j —
IMP
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 3F/ TH-6
3022DRILLLOG06.DWG
SAMPLE DATA CORE DATA
o w z EL o FRACTURES r = LITHOLOGIC NOTES ON DRILLING
w a m o DESCRIPTION 9 o w t._ a J DESCRIPTION CONDITIONS
w
n rn a w 0
—120 CLAYSTONE BEDROCK Air Rotary Drilling
-125
—130
rig
r i
-135 _
-140
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 3G/ TH-6
3022DRILLLOG07.DWG
SAMPLE DATA CORE DATA
o w w z z w o FRACTURES = LITHOLOGIC NOTES ON DRILLING
w a� a z m° DESCRIPTION 9 w cc J DESCRIPTION CONDITIONS
cn rn w w o
w o!
M Mechanical break CLAYSTONE BEDROCK Air Rotary Drilling
P Planarity Index:
1 Planar
2 Somewhat Planar
3 Somewhat Irregular
4 Irregular —
R Roughness Index:
1 Smooth
2 Fairly Smooth
3 Fairly Rough
4 Rough
S Stepped Fracture
Surface —1 J0--
RIC
-155
-160
AIR ROTARY DRILLING
162 R#1 52% 95% CLAYSTONE/SANDSTONE NX CORING
P2R2 / BEDROCK
M
P2R2
R
P2R2 165
M 1 -
P2R2
..........
166.5 R#1 53% 37%
M
M
M
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 3H/ TH-6
3022DRILLLOG08.DWG
SAMPLE DATA CORE DATA
o w w z z w o FRACTURES r = LITHOLOGIC NOTES ON DRILLING
w a� a z m° DESCRIPTION 9 w a J DESCRIPTION CONDITIONS
cn CI) a w �7
w o!
M Mechanical break —170 CLAYSTONE/SANDSTONE
P Planarity Index: BEDROCK
1 Planar
2 Somewhat Planar —.—.
171.5 R#3 8% 0% 3 Somewhat Irregular COAL:Some claystone.
4 Irregular
R Roughness Index:
1 Smooth
2 Fairly Smooth
3 Fairly Rough
4 Rough
S Stepped Fracture
Surface —175
FAVOID Drilling Steel Dropped
A
179 R#4 70% 22% COAL:Some claystone.
—180
END CORE AT 184'
r i
-185
-190
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT SURFACE ELEV. BORING NO.
10-3022 ANADARKO FACILITY 100 Ft. TH-7
LOGGED BY: LOCATION DEPTH TO GROUNDWATER SHEET
T. ROBERTS, GEC NORTHWEST CORNER - Ft. 1 OF 7
DATE COORDINATES DEPTH TO BEDROCK HOLE DIAMETER
03/30/10 1 Ft. 2.75 INCH
DRILLER TOTAL DEPTH TREND
VINE LABORATORIES 182 Ft. -
DRILL RIG CAD FILE NAME FIGURE: PLUNGE
CANTERRA CT 250 3022DRILLLOG09.DWG 4 90°±1'
SAMPLE DATA CORE DATA
<O w w FRACTURES = v LITHOLOGIC NOTES ON DRILLING
ga o_a a o o D w > a~ ao DESCRIPTION CONDITIONS
wLL
w a 'Z m a L 0 DESCRIPTION O
U) rn a 0
w
-o CLAYSTONE BEDROCK: Gray Air Rotary Drilling
to brown in color.
—5 -
�-a
Jasg
—10
-15 _
-,0 - -
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 4B/ TH-7
3022DRILLLOG10.DWG
SAMPLE DATA CORE DATA
o w w z z w o FRACTURES r = LITHOLOGIC NOTES ON DRILLING
w a>- a z m° U DESCRIPTION 9 w <J DESCRIPTION CONDITIONS
w cn V) a c7
w CC
-20 CLAYSTONE BEDROCK: Air Rotary Drilling
Gray to brown in color.
sue,
/./": SANDSTONE BEDROCK:
Red in color.
CLAYSTONE BEDROCK:
Gray to brown in color.
—30-
COAL
-3 - CLAYSTONE BEDROCK:
Gray in color.
--40
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 4D/ TH-7
3022DRILLLOG11.DWG
SAMPLE DATA CORE DATA
o w w z z o o FRACTURES r = LITHOLOGIC NOTES ON DRILLING
w a a z m o DESCRIPTION p w t._ a J DESCRIPTION CONDITIONS
n rn a w o 0
w CC
—45 CLAYSTONE BEDROCK: Air Rotary Drilling
— = Gray to brown in color.
—50
r i
I-
I �
`65 _
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 4E/ TH-7
3022DRILLLOG12.DWG
SAMPLE DATA CORE DATA
o w Li-1 z z o o FRACTURES r -_-_° LITHOLOGIC NOTES ON DRILLING
w a>- a_z m o ° > DESCRIPTION p w T_ <J DESCRIPTION CONDITIONS
cn rn a w O
w CC
70 CLAYSTONE BEDROCK: Air Rotary Drilling
Gray in color.
In
a
r
m
7
H
6
:0
IN
im
COAL
•
is
• CLAYSTONE BEDROCK:
Gray to brown in color.
mi.
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 4F/ TH-7
3022DRILLLOGI3.DWG
SAMPLE DATA CORE DATA
o w luJw z F- FRACTURES FRACTURES = LITHOLOGIC NOTES ON DRILLING
o
w a a z m o DESCRIPTION p w ac)
DESCRIPTION CONDITIONS
n rn w o 0
w cc
—95 CLAYSTONE BEDROCK Air Rotary Drilling
—100
-105 '
r i
I-
I �
-115
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 4G/ TH-7
3022DRILLLOGI4.DWG
SAMPLE DATA CORE DATA
o w w z z w o FRACTURES = LITHOLOGIC NOTES ON DRILLING
lit ILL,w a� z m° - DESCRIPTION 9 w a DESCRIPTION CONDITIONS
(1) n a o
c
w C
mom.-
120 al= 1 CLAYSTONE BEDROCK: Air Rotary Drilling
Gray to brown in color.
COAL
—125
CLAYSTONE BEDROCK:
Gray to brown in color.
—130 - -
-135-
-140��
rte!
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 4H/ TH-7
3022DRILLLOGI5.DWG
SAMPLE DATA CORE DATA
o w w z - w o FRACTURES = LITHOLOGIC NOTES ON DRILLING
w aL. � a z m o DESCRIPTION p w" a cc J DESCRIPTION CONDITIONS
U) rn w o
w o!
•
M Mechanical break —145 CLAYSTONE BEDROCK: Air Rotary Drilling
P Planarity Index: Gray to brown in color.
1 Planar ---- —
2 Somewhat Planar - -
3 Somewhat Irregular
4 Irregular
R Roughness Index: —
1 Smooth
2 Fairly Smooth
3 Fairly Rough
4 Rough
S Stepped Fracture —
Surface —1 50,
-155
AIR ROTARY DRILLING
160 ..........
160 R#1 73% 73% CLAYSTONE/SANDSTONE NX CORING
BEDROCK
M
162 R#2 60% 24% M
M
M
M
M --165
M
167 R#3 67% 33% M _ _
M
M r
P3R2 55° / y
P2R2 70° / - - Extreme shaking of rig
GROUND ENGINEERING CONSULTANTS, INC. BORING LOG
PROJECT NO. PROJECT FIGURE/CAD FILE NAME BORING NO.
10-3022 ANADARKO FACILITY FIGURE 41/ TH-7
3022DRILLLOG16.DWG
SAMPLE DATA CORE DATA
o w w z z w o FRACTURES = LITHOLOGIC NOTES ON DRILLING
_ILLw a a z m° 9. DESCRIPTION p w <J DESCRIPTION CONDITIONS
cn m a �7
w cc
•
—170 ' CLAYSTONE/SANDSTONE Void like structure noted
_.... .. BEDROCK by drillers-observed
water
M
172 R#4 40% 12% M
P2R2 90` I Ni
M
M 175-
VOID 176'-Loss of circulation
177 R#5 100% 8% COAL Gas coming out at 177'
M when pulling up core.6"
wood at bottom of run. 10
M Inches of wood at top of
M run
M
M X180
Timber shoring
M
M encountered.
M
M CLAYSTONE/SANDSTONE
nMn BEDROCK END CORING AT 182'
M Mechanical break
P Planarity Index:
1 Planar
2 Somewhat Planar
3 Somewhat Irregular
4 Irregular
—185_
R Roughness Index:
1 Smooth
2 Fairly Smooth
3 Fairly Rough
4 Rough
S Stepped Fracture
Surface
—190-
LEGEND:
:R.; Fill: Generally classified as sands and clays in Test Hole 5, and as sands and clays with gravels and
Y Y
46 cobbles in Test Hole 4. The sand fractions were fine to coarse in Test Hole 5 and fine to coarse with
gravels and cobbles in Test Hole 4. The fills were low to medium plastic, loose to compact, moist, and
light brown in color.
® Weathered Claystone: Slightly sandy, highly plastic, moist to wet, stiff to very stiff, and light brown in
color with iron stainings.
7 Claystone Bedrock: Generally consisted of claystone with interbedded layers and lenses of sandstone
and siltstone bedrock. The sands were generally fine to occasionally medium. The bedrock was low to
highly plastic, dry to moist, medium hard to very hard, and light brown to gray to brown to gray-brown in
color with occasional iron stainings, and occasional lignite.
Coal
2 Drive sample, 2-inch I.D. California liner sample
Small disturbed sample
23/12 Drive sample blow count, indicates 23 blows of a 140-pound hammer falling 30 inches were
required to drive the sampler 12 inches.
NOTES:
1) Test holes 1 - 5 were drilled on 03/18/10 with 4-inch diameter continuous flight power augers.
2) Test holes 6 and 7 were cored on 03/30/10 with 2.75 air rotary drilling methods.
3) Locations of the test holes were measured approximately by pacing from features shown on
the site plan provided. a site plan provided by CH2M Hill indicates the test holes to be a
at the same elevation. This elevation is labeled 100 on the Logs of Test Holes.
4) Elevations of the test holes were not measured and the logs of the test holes are drawn to
depth.
5) The test hole locations and elevations should be considered accurate only to the degree
implied by the method used.
6) The lines between materials shown on the test hole logs represent the approximate
boundaries between material types and the transitions may be gradual.
7) Groundwater was not encountered during drilling. Groundwater levels can fluctuate seasonally
and in response to landscape irrigation.
GROUND
The material descriptions on this legend are for general ENGs6FaEER0NSi CON5a.ULTSNTS
I
classification purposes only. See the full text of this report for
descriptions of the site materials and related LEGEND AND NOTES
recommendations.
JOB NO.: 10-3022 FIGURE: 5
CADFILE NAME: 3022LEG.DWG
COMPACTION TEST REPORT
Curve No.: 2047
Project No.: (0-3022 Date: 4/SIR)
Project: Anadarko KMG I9-3i Facility
Location: TI-1-4
Elev./Depth: 0-3 Ft. BG Sample No. 2047
Remarks:
MATERIAL DESCRIPTION
Description: Claystonc
Classifications - USCS: (C1,)s AASHTO: A-4(6)
Nat. Moist. = NA% Sp.G. =
Liquid Limit= 28 Plasticity Index = 10
%> No.4= % % <No.200 = 77.0%
TEST RESULTS
Maximum dry density= 111.8 pc!'
Optimum moisture= 15.9%
140 „ _--_- [---' —` Test specification:
ASTM D698 Method A Standard Compaction
130 -
120 ( l I 100%SATURATION CURVES
' - -` - .- FOR SPEC. GRAY. EQUAL TO:
------ --- ------. ._—---— -- _I_ L 2.8
.....------- -- --- --..__.. _.._ - - -.— 2.7
cci ,,,.......
110 �� � 2.6
,7., .............._________ .....
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90 . , -.RR _i_:.. __..
80 ' ' '
70
0 5 10 15 20 25 30 35 40
Water content, %
Figure Co
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APPENDIX A
Geotechnical Basis for Recommendations
GEOTECHNICAL BASIS FOR RECOMMENDATIONS
Geotechnical Risk
The data obtained for this study suggested relatively severe potential for post-
construction heave in the shallow on-site bedrock, as well as a risk of moderate post-
construction settlement from mine-related subsidence. These soil conditions have the
potential to damage the proposed improvements.
Expansive Soils Heave
Various quantitative and semi-quantitative methods are used by geotechnical engineers
in the Colorado Front Range area to estimate post-construction heave of structures,
pavements, etc., as a step toward development of recommendations for foundations,
remedial earthworks, etc. Those typically used are based on practical engineering
experience and judgment using combinations of measured values of soil moisture
content, density and plasticity, one-dimensional swell/consolidation, and/or soil suction.
The recommendations and criteria provided in this report were based on the data
presented herein, and our experience in the general project area with similar structures,
and our engineering judgment with regard to the applicability of the data and methods of
forecasting future performance. A variety of engineering parameters were considered as
indicators of potential future soil movements. Our recommendations were based on our
judgment of "likely movement potentials," (Le., the amount of movement likely to be
realized if site drainage is generally effective, estimated to a reasonable degree of
engineering certainty) as well as our assumptions about the owner's willingness to
accept geotechnical risk. "Maximum possible" movement estimates necessarily will be
larger than those presented herein. They also have a significantly lower likelihood of
being realized in our opinion, and generally require more expensive measures to
address. We encourage the client and owner, upon receipt of this report, however, to
discuss these risks and the geotechnical alternatives with us.
At any point in the design life of a structure, the vertical and lateral extents of future
wetting and expansion of the underlying soils will exert a dominant influence on the
extent and distribution of future uplift experience by improvements constructed on those
soils. Professional experience and opinions differ with regard to depths to which
significant, post-construction, soil moisture and volume changes take place. Differing
assumptions regarding future 'depth of heave' and 'depth of wetting' at a site will give
rise to differing estimates of potential, total, post-construction vertical movements.
Job No. 10-3022 GROUND Engineering Consultants, Inc. A.1
Movement estimates based depths of heave and wetting that are much deeper than
typically estimated will be larger than those based on more typically observed depths.
Engineering consulting and design practice always involves weighing the risks inherent
in a given design approach against the construction costs associated with reducing
those risks. The owner (and subsequent, prospective future owners) must, therefore,
understand the risks and remedial approaches presented in this report (and the risk-cost
trade-offs addressed by the civil engineer and structural engineer) in order to direct his
design team to the portion of the Higher Cost / Lower Risk -- Lower Cost / Higher Risk
spectrum in which this project should be (or was) designed. If the owner does not
understand these risks, it is critical that he request additional information or clarification
so that his expectations reasonably can be met.
Depth of Heave 'Depth of Heave' refers to the depth above which the stresses
exerted by the clay particles as they take up water and expand exceeds the
downward loads imposed by the weight of the overlying soils and improvements.
Below this depth, even when exposed to water the clay particles cannot expand.
This depth varies with clay mineralogy and, therefore, from site to site. Practically, it
is an averaged parameter as the clay mineralogy varies laterally and layer to layer in
the earth materials.
Some geotechnical engineers determine this depth as a percentage of the pressure
needed to re-compress an expanded soil sample back to its pre-wetted thickness in
a one-dimensional swell-consolidation test performed at a relatively light load.
Because of the alterations of the clay mineral structures as water is taken into them,
however, determinations based on this approach, in our experience, typically lead to
over-estimates of the depth of heave. As part of this study, GROUND measured
swells exhibited by samples of the site soils against the approximate overburden
loads applying to the soils in their natural setting, if wetted. Because structural loads
vary across a site and for a limited amount of additional conservatism, the loads
applied by the proposed improvements were ignored. The resultant data set allows
the 'depth of heave' to be estimated for the site.
Based on the swell-consolidation test data that we obtained for this site, it is
GROUND's conclusion that the earth materials at this site are characterized by a
'depth of heave' of about 24 feet, This does not mean that no soil layer at a depth
greater than this depth can swell at all, but that such layers are few and the
contribution of such layers to the total, estimated heave for the site generally is not
significant.
Job No. 10-3022 GROUND Engineering Consultants, Inc. A-2
Depth of Wetting At this site, GROUND estimated a depth of wetting of 20 feet, a
depth that is equal to or greater than the "depth of wetting" found at about 68 percent
of the sites studied by Walsh and others (2006)1, and about 70 percent of the sites
evaluated by Walsh and others (2009).' This "depth of wetting" is appropriately
conservative in our opinion for this project. There is, however, a potential for this
"depth of wetting" to be exceeded, which if considered — other parameters being
equal — would lead to greater estimates of post-construction movements. "Depths of
wetting" of 30, 40 or 70 feet or more have been considered (e.g., Chao and others,
2006)3 and have been encountered locally in the field. These cases, however,
generally are in unusual geologic conditions such as the "Designated Dipping
Bedrock Area" as recognized by Jefferson County, Colorado, or identified
forensically in unusual circumstances such as a pipe leak that has remained un-
repaired for an extended period. However, in more typical geologic settings in this
area, such greater "depths of wetting" are considered only rarely in engineering
consulting practice.
Mine-Related Subsidence
Construction over or near abandoned underground mine workings subject to
consolidation entails a risk of surface subsidence or settlement if the workings collapse
at depth and that volume loss propagates to the surface. The degree of risk depends on
multiple factors. These include the thickness of the mined out seam and the degree to
which consolidation already has been realized — both of which affect the maximum
magnitude of potential surface settlement — and the depth of the mine workings which
affects the extent of the affected area as well as the settlement realized at the ground
surface.
The magnitude of potential, mine-related subsidence commonly is estimated using the
methodology of the National Coal Board (1975)4. That methodology is an empirical
approach based on recorded subsidence at various underground of mines. This
approach can be used to estimate both vertical settlements and secondary horizontal
Walsh, K.D.,C.A. Colby,W.N. Houston and S.A. Houston, 2006,Evaluation of Changes to Soil Suction
Resulting from Residential Development, Unsaturated Soils 2006,American Society of Civil Engineers,
Special Publication No. 147, pp. 203-212.
2 Walsh, K.D., C.A. Colby,W.N. Houston and S.A. Houston,2009, Method for Evaluation of Depth of
Wetting in Residential Areas,Journal of Geotechnical and Geoenvironmentall Engineering, American
Society of Civil Engineers, Vol. 135,No. 2,pp. 169— 176.
s Chao, K-C, D.D. Overton, and J.D. Miller,2006, The Effects of Site Conditions on the Predicted Time Rate
of Heave, Unsaturated Soils 2006,American Society of Civil Engineers, Special Publication No. 147. pp.
2086—2097.
4 National Coal Board, 1975, Subsidence Engineers Handbook, U.S. Bureau of Land Management, Mining
Department.
Job No. 10.3022 GROUND Engineering Consultants, Inc. A-3
strains that result from conventional collapse of underground workings. It is not
applicable to locations where vertical excavations (shafts) are present near the subject
location.
GROUND used the National Coal Board methodology to estimate potential surface
subsidence at this site. This approach is dependent upon several geometric
parameters, principally the depth, and the lateral and vertical extents of mining, and the
position of point in question relative to the surface projection of the mined out volume.
Again, GROUND's recommendations were based on our judgment of "likely potential
settlements," not maximum possible settlements, particularly when some of the input
parameters were estimated. "Maximum possible" estimates of settlement will be larger
than those presented herein.
Whereas expansive soils heave will be realized to at least some extent relatively shortly
after soils or bedrock containing expansive clays has become wetted, estimation of the
likelihood of potential, mine-related subsidence being realized in a given area during a
given period of time (such as the design-life of a structure) is more difficult to estimate.
It does not appear to be a strong function of the potential magnitude of subsidence.
Instead, it appears to depend more on whether shafts for hoisting or ventilation were
excavated near the location of interest, and how shallow the former mine workings are.
For perspective, it should be noted that significant portions of the towns and areas
surrounding Lafayette, Erie, Firestone, etc., have been constructed over mine workings
at similar depths in the Laramie Formation. The great majority of structures in these
areas have not been adversely affected by mine-related subsidence. Nonetheless, the
risk of such subsidence is not zero. Again, we encourage the owner, upon receipt of this
report, however, to discuss these risks and the geotechnical alternatives with us.
Likely Post-Construction Movements
Because soils must be both wetted after construction and capable of heaving against the
load imposed on them in order to lift and damage near-surface structures, the shallower
of the 'depth of heave' and 'depth of wetting' at a site limits estimates of that movement.
GROUND considers the values discussed above to be representative of the site and
appropriate for the proposed construction. However, if the owner prefers a more
conservative (or less conservative) `depth of wetting' (or `depth of heave') to be used to
develop geotechnical parameters for design, GROUND should be contacted to revise
the criteria provided herein.
Job No.10.3022 GROUND Engineering Consultants,Inc. A-4
Utilizing the above assumptions, data obtained for this study, and our experience on
other projects in the vicinity, our estimates indicate post-construction vertical movements
on the order of 6 to 8 inches where building elements are supported directly on the
existing earth materials that become wetted following construction to the depth
described. (Lateral movements would result, as well.)
Because of the timbers recovered in the cores at Test Hole 7, we have assumed that the
mining beneath the site was room-and-pillar type mining, not "long-wall" mining that
removes all the coal. On this basis we have assumed that the width of mined coal
comprising a given `room' was 40 to 60 feet (12 to 18 meters). A depth of 175 feet (53
meters) was used for the depth of mining. Based on the conditions encountered in the
test holes, the thickness of 2 to 3 feet (0.6 to 0.9 meter) was used for the thickness of
the void remaining at depth that could collapse. Using these ranges of input parameters,
potential ground surface settlements of about 1% to 5'/% inches were estimated.
(Because no mine shafts were indicated on the maps reviewed by GROUND in the
vicinity of the project, we consider the likelihood of a severe subsidence event to be very
low.) Base on our experience, we anticipate that surface settlements will be irregular in
occurrence with most areas seeing little or no subsidence. In GROUND's opinion,
settlements of 3 to 4 inches across an area about 100 feet in dimension are likely where
surface settlements are realized. Based on the depth of mining and the lack of mapped
shafts near the site, we consider the likelihood to be moderate of such an area of
settlement developing somewhere within the overall footprint of the subject facility during
its design life. The likelihood of any specific structure being affected is considered low.
Comparison of the two movement mechanisms suggests that the potential for distress
from expansive soils heave is greater than from mine-related subsidence. It is also, in
our opinion, more likely to be realized. Movements of these magnitudes can cause
signficant cosmetic and/or structural distress to the proposed structures. (These same
general potentials for post-construction movement and damage also apply to project
pavements, hardscaping, piping, and all other improvements in contact with the site
earth materials where subject to post-construction wetting.)
General Foundation Types
At the subject site, several types of foundation systems, in conjunction with differing
extents of remedial earthworks, etc., can be employed to support the proposed
structures on the soils and bedrock encountered in the test holes. Each combination
entails a different degree of risk of post-construction foundation movements from
expansive soils heave. These range from utilizing shallow spread footings and slab-on-
Job No. 10-3022 GROUND Engineering Consultants, Inc. A-5
grade concrete floors bearing directly on the native earth materials (entailing the greatest
risk) to supporting the structures, including floors, on deep, drilled pier foundations
bearing in the underlying bedrock at depths of more than 70 feet (entailing the least risk
among typically employed foundation types). Some research, in fact, has concluded that
drilled piers as long as 100 feet or more may be needed to resist uplift in expansive
materials such as_thoseencountered on-site. None of these foundation types can
mitigate the potential for settlement if a portion the site experiences settlement resulting
from consolidation of a portion of the mine workings at depths, however.
GROUND recommends that the proposed buildings and related structures be supported
on drilled pier foundation systems, and the tanks and other structures with floors,
provided with structural floors supported similarly. We assume that 70+ -foot piers are
not practical economically for the subject project because such depths are not required
to support the structural loads. (It should be noted in this regard that many lightly to
moderately loaded commercial and residential structures in the Colorado Front Range
area have been supported successfully in similar materials on 20- to 40-foot piers.)
Therefore, in the absence of direction otherwise from CH2M Hill or Anadarko Petroleum,
we have assumed that the Anadarko Petroleum prefers to consider drilled piers of more
conventional lengths for this project. The geotechnical criteria provided in the Building
Foundations section of this report for design of a drilled pier foundation system were
developed accordingly. Although a drilled pier foundation system incorporating these
criteria will not eliminate the risk of post-construction buildinc.movement, if the measures
outlined in this report are implemented effectively, the likelihood of acceptable building
performance to a reasonable degree of engineering certainty will be within local industry
standards for construction of a drilled pier foundation system on soils and bedrock of this
nature. Based on the conditions encountered in GROUND's test holes, the assumptions
outlined herein, including effective maintenance of site drainage, we estimate post-
construction movements from heave and/or settlement of drilled pier foundations to be
on the order of inch in the absence of mine-related subsidence.
GROUND is available to meet, however, to discuss the risks and remedial approaches
presented in this report, as well as other potential approaches, upon request.
On-Going Maintenance
Irrespective of the foundation system and floor system selected by the City of Lone Tree,
some risk of post-construction building and floor movements will remain, even after
effective implementation of the recommendations in this report. The City of Lone Tree
should understand these risks, as well as the site maintenance measures that are
Job No. 16-3022 GROUND Engineering Consultants,Inc. A-6
necessary to manage them. Other elements of the proposed improvements on this site
(hardscaping, pavements, etc.) will be underlain by expansive earth materials, and likely
will be damaged. Owner tolerances for movement and distress to these appurtenant
improvements typically is greater than for buildings. Nevertheless, periodic maintenance
will be required. To achieve performance similar to that of the building floors, similar
foundation measures will be required. We recommend that maintenance personnel for
the subject buildings familiarize themselves with the measures presented in Noe (2007)5
and implement them at this site. This booklet is available from the Colorado Geological
Survey in Denver, Colorado, and can be purchased from their website.
(www.geosurvey.state.co.us). Although written for residential construction on expansive
soils, the concepts and recommendations outlined therein are generally applicable to
other building types, as well.
5 Noe, D.C.,2007,A Guide to Swelling Soils for Colorado Homebuyers and Homeowners,Colorado
Geological Survey, Special Publication 43, 2n°Edition.
Job No. 10.3022 GROUND Engineering Consultants,Inc. A-7
APPENDIX B
Recommendations for
Foundation and Floor System Construction
FOUNDATION AND FLOOR SYSTEM CONSTRUCTION
Drilled Pier Foundations
I. Because groundwater was encountered locally and groundwater conditions can
fluctuate, the contractor should be prepared to complete the piers in the presence of
groundwater, including the use of casing. In no case, should concrete be placed in
more than 3 inches of water, unless placed through an approved tremie method.
II. Pier holes should be properly cleaned prior to placement of concrete.
III. Concrete utilized in the piers should be a fluid mix with sufficient slump so that it will
fill the void between reinforcing steel and the pier hole wall. We recommend the
concrete have a minimum slump in the range of 5 to 7 inches. Concrete should be
placed by an approved tremie or other method to reduce mix segregation.
IV. Where water or slurry is present in the drilled pier hole, including outside of a casing
that will be withdrawn from the hole, the concrete placed for the pier should have
sufficient slump and be placed with sufficient head maintained above groundwater
levels so that the concrete is not displaced in the body of the pier by water, soil,
slurry, etc., leading to effective voids in the pier. Slurry, if used, must be fully
displaced by the concrete.
V. Concrete should be placed in piers the same day they are drilled. Failure to place
concrete the day of drilling will normally result in a requirement for additional bedrock
penetration. The presence of groundwater or caving soils may require that concrete
be placed immediately after the pier hole drilling is completed.
VI. The contractor should take care to prevent enlargement of the excavation at the tops
of piers, which could result in mushrooming of the pier top. Mushrooming of pier
tops can increase uplift pressures on the piers.
VII. GROUND recommends that sonic integrity testing be performed for an appropriate
percentage of the drilled piers to assess the effectiveness of the pier construction
methods for installing the piers in accordance with project plans and specifications.
VIII. Although not encountered in the test holes, beds and lenses of very hard, resistant
bedrock materials are known to be present. Difficult to very difficult drilling conditions
Job No.09-3045 GROUND Engineering Consultants,Inc. 8.1
may be encountered during pier hole drilling. The contractor should be prepared to
core lenses and beds of highly cemented materials.
IX. In general, the pier-drilling contractor should mobilize equipment of sufficient size
and operating capability to achieve the required penetration into the bedrock. We
suggest the pier drilling contractor advance a test hole with-the proposed equipment
at least to the minimum anticipated depth prior to beginning pier installation to
assess whether the equipment can reach the target depths. This test drilling should
be performed sufficiently early in the construction process so that more powerful
equipment can be mobilized if necessary without delaying to the project. If refusal is
encountered in these materials either during the test program or during actual
installation, the geotechnical engineer should evaluate the conditions to establish
that true refusal has been met with adequate drilling equipment.
X. A geotechnical engineer should be retained to observe pier drilling operations on a
full time basis.
Shallow Foundations
I. The contractor should take care while making foundation excavations not to
compromise the bearing or lateral support for nearby improvements.
II. At each structure, the contractor should take care to construct a fill section beneath
the building of uniform depth and composition to reduce differential post-construction
foundation movements. A differential fill beneath a structure will tend to increase
differential settlements.
III. The contractor should provide surveyed data of the excavations beneath the
buildings verifying that the remedial excavations were advanced to at least the
selected depths and lateral extents.
IV. The soils exposed at the surface on which the foundation fill section will be
constructed should be tested for swell potential prior to placement of fill there.
Additional excavation and replacement may be necessary in some areas.
Job No, 09.3045 GROUND Engfneering Consultants, Inc. B•2
V. Care should be taken when excavating the foundation to avoid disturbing the
supporting materials. Hand excavation or careful backhoe soil removal may be
required in excavating the last few inches.
VI. Footing excavation bottoms may expose debris, loose or wet materials, organic or
otherwise deleterious materials. Firm materials may be disturbed by the excavation
process. All such unsuitable materials should be excavated and replaced with
properly compacted fill. Recommendations for fill placement and compaction are
provided in Appendix C.
VII. Foundation soils may be disturbed or deform excessively under the wheel loads of
heavy construction vehicles as the excavations approach footing levels.
Construction equipment should be as fight as possible to limit development of this
condition. The use of track-mounted vehicles is suggested because they exert lower
contact pressures. The movement of vehicles over proposed foundation areas
should be restricted.
VIII. All footing areas should be compacted with a vibratory plate compactor prior to
placement of concrete.
IX. Compacted fill placed against the sides of the footings should be compacted to at
least 95 percent relative compaction in accordance with the recommendations in
Appendix C.
X. A geotechnical engineer should be retained to observe and test all footing
excavations prior to placement of reinforcing steel or concrete.
Job No.09-3045 GROUND Engineering Consultants, Inc. B-3
APPENDIX C
Recommendations for
Earthwork Construction
EARTHWORK CONSTRUCTION
General Considerations
Prior to earthwork construction, existing structures, vegetation and other deleterious
materials should be removed and disposed of off-site. Relic underground utilities should
be abandoned in accordance with applicable regulations, removed as necessary, and
capped at the margins of the property.
Excavations
The contractor should take care when making excavations not to compromise the
bearing or lateral support for the foundations of the adjacent, existing pavements or
other improvements.
Good surface drainage should be provided around temporary excavation slopes to direct
surface runoff away from the slope faces. A properly designed drainage swale should
be provided at the top of the excavations. In no case should water be allowed to pond at
the site. Slopes should also be protected against erosion. Erosion along the slopes will
result in sloughing and could lead to a slope failure.
Excavations in which personnel will be working must comply with all OSHA Standards
and Regulations particularly CFR 29 Part 1926, OSHA Standards-Excavations, adopted
March 5, 1990. The contractor's "responsible person" should evaluate the soil exposed
in the excavations as part of the contractor's safety procedures. GROUND has provided
the information in this report solely as a service to the City of Lone Tree, and is not
assuming responsibility for construction site safety or the contractor's activities.
Fill Platform Preparation
Prior to filling, the top 8 to 12 inches of in-place materials on surfaces on which fill soils
will be placed should be scarified, moisture conditioned and properly compacted in
accordance with the recommendations below to provide a uniform base for fill
placement.
If surfaces to receive fill expose loose, wet, soft or otherwise deleterious material,
additional material should be excavated, or other measures taken, to establish a firm
platform for filling. The surfaces to receive fill must be effectively stable prior to
Job No. 10.3022 GROUND Engineering Consultants,Inc. C-1
placement of fill. The contractor should anticipate encountering several feet of soft/loose
and wet soils that typically will be unstable along the swale traversing the site.
Fill Placement
Fill materials should be thoroughly mixed to achieve a uniform moisture content, placed
in uniform lifts not exceeding 8 inches in loose thickness, and properly compacted. Soils
that classify as GP, GW, GM, GC, SP, SW, SM, or SC in accordance with the USCS
classification system (granular materials) should be compacted to 95 or more percent of
the maximum modified Proctor dry density at moisture contents within 2 percent of
optimum moisture content as determined by ASTM D1557, the "modified Proctor." Soils
that classify as ML, MH, CL or CH, as well as all excavated bedrock materials, should be
compacted to 95 percent of the maximum standard Proctor density at moisture contents
from optimum moisture content to 4 percent above the optimum as determined by ASTM
D698, the "standard Proctor."
No fill materials should be placed, worked, rolled while they are frozen, thawing, or
during poor/inclement weather conditions. Where soils supporting foundations or on
which foundation will be placed are exposed to freezing temperatures or repeated freeze
— thaw cycling during construction — commonly due to water ponding in foundation
excavations — bearing capacity typically is reduced and/or settlements increased due to
the loss of density in the supporting soils. After periods of freezing conditions, the
contractor should re-work areas affected by the formation of ice to re-establish adequate
bearing support.
Care should be taken with regard to achieving and maintaining effective moisture
contents during placement and compaction. We anticipate that the commonly silty site
soils may exhibit significant pumping, rutting, and deflection at moisture contents above
the optimum. In our experience, achieving and maintaining compaction in such soils can
be very difficult if water contents are not monitored closely. The contractor should be
prepared to handle soils of this type, including the use of chemical stabilization, if
necessary.
Compaction areas should be kept separate, and no lift should be covered by another
until relative compaction and moisture content within the recommended ranges are
obtained.
Job No. 10-3022 GROUND Engineering Consultants,Inc. C•2
Use of Squeegee
Relatively uniformly graded fine gravel or coarse sand, i.e., "squeegee," or similar
materials commonly are proposed for backfilling foundation excavations, portions of
utility trenches and other areas where employing compaction equipment is difficult. In
general, GROUND does not recommend this procedure for the following reasons:
Although commonly considered "self compacting," uniformly graded granular
materials require densification after placement, typically by vibration. The
equipment to densify these materials is not available on many job-sites.
Even when properly densified, uniformly graded granular materials are
permeable and allow water to reach and collect in the lower portions of the
excavations backfilled with those materials. This leads to wetting of the
underlying soils and resultant potential loss of bearing support as well as
increased local heave or settlement.
GROUND recommends that wherever possible, excavations be backfilled with approved,
on-site soils placed as properly compacted fill. Where this is not feasible, use of
"Controlled Low Strength Material" (CLSM), i.e., a lean, sand-cement slurry ("fiowable
fill") or a similar material for backfilling should be considered.
Where "squeegee" or similar materials are proposed for use by the contractor, the
design team should be notified by means of a Request for Information (RFI), so that the
proposed use can be considered on a case-by-case basis. Where "squeegee" meets
the project requirements for pipe bedding material, however, it is acceptable for that use.
Utility Trench Backfilling
The recommendations above for fill placement and compaction are applicable to
construction of trench backfills.
Some settlement of trench backfill materials should be anticipated, even where materials
are placed and compacted correctly. To reduce these settlements, the contractor should
take adequate measures to achieve adequate compaction in the utility trench backfills,
particularly in the lower portions of the excavations and around manholes, valve risers
and other vertical pipeline elements where greater settlements commonly are observed.
Job No. 10-3022 GROUND Engineering Consultants, Inc. C-3
However, the need to compact to the lowest portion of the backfill must be balanced
against the need to protect the pipe from damage during backfilling. Some thickness of
backfill may need to be placed at compaction levels lower than recommended in this
report to avoid damaging the pipe. Likewise, construction conditions may preclude
density testing at specified frequencies in the lower portions of a trench. Such backfilling
methods will lead to increased surface settlements.
Because of these limitations, we recommend the use of "controlled low strength
material" (CLSM), i.e., a lean, sand-cement slurry, "flowable fill," or similar material in
lieu of compacted soil backfill for areas with low tolerances for surface settlements.
Placement of CLSM in the lower portion of the trench and around risers, etc., likely will
yield a superior backfill and provide protection for the pipe, although at an increased
cost. Other means, e.g., use of smaller compaction equipment, also may be effective for
achieving adequate compaction in these areas.
Settlements
Settlements will occur in filled ground, typically on the order of 1 to 2 percent of the fill
depth. For a 6-foot fill, for example, this corresponds to settlement on the order of 1
inches, without imposition of foundation loads. If fill placement is performed properly
and is tightly controlled, in GROUND's experience the majority of that settlement will
take place during earthwork construction. The remaining potential settlements likely will
take several months or longer, to be realized.
Job No. 10-3022 GROUND Engineering Consultants,Inc. C4
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