HomeMy WebLinkAboutSoils Report 04.19.2002Gtech
Hepworth-Pawlak Geotechnical, Inc.
5020 County Road 154
Glenwood Springs, Colorado 81601
Phone: 970-945-7988
Fax: 970-945.8454
hpgeo@hpgeotech.com
PRELIMINARY GEOTECHNICAL STUDY
PROPOSED CALLICOTTE RANCH
COUNTY ROADS 112 AND 103
GARFIELD COUNTY, COLORADO
JOB NO. 101 821
APRIL 19, 2002
RECEIVE° APR 2 2 2002
PREPARED FOR:
MAGNA CASA, INC.
ATTN: JACK MANCINI
1700 E. LAS OLAS BOULEVARD, SUITE 206
FORT LAUDERDALE, FLORIDA 33301
HEPWORTH - PAWLAK GEOTECHNICAL, INC.
April 19, 2002
Magna Casa, Inc.
Attn: Jack Mancini
1700 E. Las Olas Boulevard, Suite 206
Fort Lauderdale, Florida 33301
Job No. 101 821
Subject: Report Transmittal, Preliminary Geotechnical Study, Proposed Callicotte
Ranch, County Roads 112 and 103, Garfield County, Colorado
Dear Mr. Mancini:
As requested, we have conducted a geotechnical study for the proposed development at
the subject site.
The property is suitable for the proposed development based on geologic and
geotechnical conditions. There are several conditions of a geologic nature the should be
considered in project planning and design. These conditions should not require major
modifications to the proposed development plan, but mitigation should be considered for
some.
Subsoils encountered in the exploratory throughout the property excavated generally
consist of relatively stiff, sandy silty clay soils and dense basalt fragments up to boulder
size in a sandy silt and clay matrix. Dense gravel alluvium was encountered below the
fine-grained soils at Pit 10. Groundwater was not encountered in the pits and the soils
are slightly moist to moist.
Spread footings placed on the natural subsoils and designed for an allowable bearing
pressure of 1,500 psf to 3,000 psf appear suitable at the building sites. The water tank
foundation should be designed for an allowable pressure of 1,500 psf, excluding the
weight of the water. There could be post construction settlement/heave if the fine-
grained bearing soils become wetted. Percolation testing indicates the subsoils are
generally suitable for infiltration septic disposal systems.
The report which follows describes our investigation, summarizes our findings, and
presents our recommendations suitable for planning and preliminary design. It is
important that we provide consultation during design, and field services during
construction to review and monitor the implementation of the geotechnical
recommendations.
If you have any questions regarding this report, please contact us
Sincerely,
HEPWORTH - PAWLAK GEOTECHNICAL, INC.
L
Trevor L. Knell
Rev. by: DEH
TLIC/'ksw
TABLE OF CONTENTS
PURPOSE AND SCOPE OF STUDY - 1
PROPOSED DEVELOPMENT 1
SITE CONDITIONS 2
GEOLOGIC SETTING 2
FORMATION ROCK 3
EVAPORITE DEFORMATION AND SOLUTION FEATURES 4
SURFICIAL SOIL DEPOSITS 4
FIELD EXPLORATION 5
SUBSURFACE CONDITIONS 5
GEOLOGIC SITE ASSESSMENT 6
CONSTRUCTION RELATED SLOPE INSTABILITY 6
POTENTIALLY EXPANSIVE FOUNDATION CONDITIONS 7
REGIONAL EVAPORITE DEFORMATION AND SINKHOLES 7
EXCAVATION DIFFICULTIES 8
EARTHQUAKE CONSIDERATIONS 8
PRELIMINARY DESIGN RECOMMENDATIONS 8
FOUNDATIONS 9
WATER TANK 9
FLOOR' SLABS 9
UNDERDRAIN SYSTEM 10
SITE GRADING 10
PAVEMENT SUBGRADE 10
SURFACE DRAINAGE 11
PERCOLATION TESTING 11
LIMITATIONS 12
REFERENCES 13
FIGURES 1 & 2 - GEOLOGIC MAP AND LOCATION OF EXPLORATORY
PITS
FIGURE 3 - LOGS OF EXPLORATORY PITS
FIGURE 4 - LEGEND AND NOTES
FIGURES 5 & 6 - SWELL -CONSOLIDATION TEST RESULTS
TABLE I - SUMMARY OF LABORATORY TEST RESULTS
TABLE II - PERCOLATION TEST RESULTS
PURPOSE AND SCOPE OF STUDY
This report presents the results of a preliminary geotechnical study for the
proposed CaIlicotte Ranch to be located at County Roads 112 and 103, Garfield County,
Colorado. The project site is shown on. Figs. 1 & 2. The purpose of the study was to
evaluate the geologic and subsurface conditions and their impact on the project. The
study was conducted in accordance with our proposal for geotechnical engineering
services to Land Design Partnership, dated November 28, 2001.
A field exploration program consisting of a reconnaissance, exploratory pits and
percolation testing was conducted to obtain information on the site and subsurface
conditions. Samples of the subsoils obtained during the field exploration were tested in
the laboratory to determine their classification, compressibility or swell and other
engineering characteristics. The results of the field exploration and laboratory and
percolation testing were analyzed to develop recommendations for project planning and
preliminary design. This report summarizes the data obtained during this study and
presents aur conclusions and recommendations based on the proposed development and
subsurface conditions encountered.
PROPOSED DEVELOPMENT
The 180 acre Callicotte Ranch will be subdivided into twenty-nine, large
residential Iots with an average lot size of about 4 acres, see Figs. 1 and 2. A network
of interior streets will provide primary access to the tots. The development will have a
central water distribution system. Each lot will have an individual waste disposal
system. The streets will be constructed by the developer. Building site preparation and
driveways will be the responsibility of the individual lot owners. It is expected that the
residences will be relatively large structures with outbuildings. At the time of this
study, grading plans for the streets and individual Iots was not available.
If development plans change significantly from those described, we should be
notified to re-evaluate the recommendations presented in this report.
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2 -
SITE CONDITIONS
The project site is located on a rolling basalt plateau to the north and east of the
Roaring Fork River. The property covers parts of Sections 13 and 24, T. 7 S., R. 88
W. and is located about 3 miles northeast of Carbondale. Crystal Springs Road borders
the property on the east. The topography at the project site is shown by the contour
lines on Figs. 1 and 2. The narrow Crystal Springs Creek valley borders the property
on the south and a small tributary valley crosses through the property. Slopes along
these two valley sides are steep, typically in the range of 30% to 50%. Slopes on the
adjacent uplands are typically in the range of 10 % to 20%. Crystal Springs Creek is a
small perennial stream and a small perennial stream is also present in the southern part
of the tributary valley, but the upper reaches of this stream are ephemeral and only have
surface flow following heavy precipitation. The perennial streams are spring fed and
several contact springs and seeps are also present on the northern Crystal Springs valley
side near the contact of the Eagle Valley Evaporite and overlying basalt flows, see Fig.
2. The property was undeveloped ranch land at the time of this study. Much of the
property is irrigated hay fields. What appears to be a reclaimed borrow area is located
in the proposed open space near the northeast corner of the property. Vegetation
outside the irrigated fields is juniper trees with sage and other brush.
GEOLOGIC SETTING
The basalt plateau in the project area is a structural bench between the White
River uplift to the north and the Roaring Fork syncline to the south. These regional
geologic structures were formed during the Laramide orogeny about 40 to 70 million
years ago. Regional mapping indicates that basalt flows that overlie the Eagle Valley
Evaporite are the near surface formation rock in the project area (Kirkham and
Widmann, 1997). Surfcial soil deposits are mostly colluvium with some valley floor
alluvium. The principle geologic features in the project area are shown on Figs. 1 and
2. The basalt plateau in the project area lies near the center of the Carbondale
evaporite collapse center. The collapse center is a roughly a circular region with a
H -P GEOTECH
3
diameter of about 16 miles and an area of about 200 square miles (Kirkham and
Widmann, 1997). As much as 4,000 feet of regional subsidence has occurred in the
collapse center as the result of dissolution and flowage of evaporite beneath the area.
Much of this subsidence may have occurred within the past 10 million years (Kirkham
and Widmann, 1997). If this is the case, the long-term average subsidence rate was
about 0.5 inch per 100 years. There is some local evidence of evaporite deformations
as recently as the late Pleistocene in the Carbondale collapse center, but no definitive
evidence of deformations during the post -glacial times, within about the past 15,000
years (Widmann and Others, 1998).
FORMATION ROCK
The Pennsylvanian -age Eagle Valley Evaporite (Pee) crops out locally on the
lower valley sides in the southwestern part of the property but basalt flows (Tb and
Tdb) underlie most of the project site.
Eagle Valley Evaporite: The Eagle Valley Evaporite is a thick sequence of
sedimentary rocks that are largely evaporite deposited in the central Colorado trough
about 300 million years ago. The evaporite consists of gray and tan gypsum, anhydrite
and locally occurring halite interbedded with siltstone, claystone and dolomite. The
rock varies from cemented and bard to non-cemented but firm. The bedding is usually
complexly folded because of flow in the plastic gypsum and anhydrite. The evaporite is
relatively soluble in fresh water and subsurface voids and associated sinkholes are
sometimes present in areas where the evaporite is near the surface in the region.
Basalt Flows: The Eagle Valley Evaporite in the project area is overlain by late
Miocene -age basalt flows. Radiometric age dates of the flows in the project area are
between 8.7 and 9.7 million years (Kirkham and Widmann, 1997). Relatively intact
basalt (Tb) -is present in the in the southern part of the project area but the flows are
deformed and broken (Tdb) in the north part. The transition from intact to deformed
basalt is gradational. The intact basalt consist of multiple flows from 5 to 25 feet thick
of very dense and very bard basalt with secondary fracturing. The deformed basalt is
H -P GEOTECH
4
very fractured and broken. It typically consists of large boulder sized, angular basalt
blocks with a sandy clay matrix. At the exploratory pits, intact and deformed basalt
was from less than one foot to greater than ten feet deep. The total thickness of the
basalt at the project site is uncertain in most areas but at least 100 feet of basalt is
present in the northwestern part of the property.
EVAPORITE DEFORMATION AND SOLUTION FEATURES
Regional geologic mapping shows the project site is located along the eastern
limb of a structural sag that starts in Heuschkel Park about two mules to the west and
curves just to the west of the project site and terminates to the northwest (Kirkham and
Widmann, 1997). The axis of the sag in the project area is shown on Figs 1 and 2.
Outcrops in the project area indicate that the basalt flows are tilted and have dips
between 22° and 28°, see Fig. 2. In the Heuschkel Park area, small displacement
normal faults parallel the sag axis, but faults have not been mapped in the project area
(Kirkham and Widmann, 1997).
A sinkhole in the deformed basalt is evident about 1,300 feet to the west of the
northwestern property corner on aerial photographs of the area we reviewed, see Fig. 2.
This sinkhole is also shown of the regional geology map (Kirkham and Widmann,
1997). Evidence of sinkholes was not observed on the property during our site
reconnaissance nor were sinkholes apparent on the aerial photographs reviewed.
SURFICIAL SOIL DEPOSITS
Valley floor alluvium (Qal) is present along the narrow valley floors of Crystal
Springs Creek and its tributary in the project area. Thin colluvium (Qc) is usually
present below the uplands elsewhere on the property. At the exploratory pits, from
less than one foot to greater than ten feet of colluvium was present above the intact and
deformed. basalt. The colluvium is a low plasticity, sandy clay with scattered basalt
fragments from gravel to boulder size. Our laboratory tests show that the colluvium has
a moderate swell potential when wetted.
H -P GeOTECH
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FIELD EXPLORATION
The field exploration for the project was conducted on December 27, 2001,
EIeven exploratory pits were excavated at the locations shown on Figs. 1 and. 2 to
evaluate the subsurface conditions. The pits were dug with a Cat 420D backhoe and
logged by a representative of Hepworth-Pawlak Geotechnical, Inc.
Samples of the subsoils were taken with relatively undisturbed and disturbed
sampling methods. Depths at which the samples were taken are shown on the Logs of
Exploratory Pits, Fig. 3. The samples were returned to our laboratory for review by
the project engineer and testing.
SUBSURFACE CONDITIONS
Graphic logs of the subsurface conditions encountered at the site are shown on
Fig. 3. The subsoils generally consist of up to about 2 feet of organic topsoil overlying
relatively stiff, sandy silty clay soils and dense basalt fragments up to boulder size in a
sandy silt and clay matrix. Dense gravel alluvium was encountered below the clay in
Pit 10. Between 21/2 and 51/2 feet of clay overlies the basalt colluvium in Pits 1, 3, 4, 6,
8, 9 and 11. Digging in the dense basalt gravel with backhoe equipment was difficult
due to the cobbles and boulders and refusal to digging was encountered in the deposit at
Pits 1, 3, 6 and 8.
Laboratory testing performed on samples obtained from the pits included natural
moisture content and density, percent finer than sand size gradation analyses and
Atterberg limits testing. Results of swell -consolidation testing performed on relatively
undisturbed liner samples, presented on Figs, 5 & 6, indicate low compressibility under
existing moisture conditions and light loading and showed a low to moderate expansion
potential when wetted. The sainiale from Pit 7 at 5 feet showed a minor collapse
potential (settlement under a constant load) when wetted and moderate settlement with
increased loading. The laboratory testing is 51 Jmrnarized in Table I.
No free water was encountered in the pits at the time of excavation and the
subsoils were slightly moist to moist.
H -P GEOTECH
6
GEOLOGIC SITE ASSESSMENT
There are several conditions of a geologic nature that should be considered in
project planning and design. These conditions should not require major modifications
to the proposed development plan, but engineered mitigation should be considered for
some. The geologic conditions and their anticipated influence on the project are
described below.
CONSTRUCTION RELATED SLOPE INSTABILITY
The regional geology map shows a landslide on the south side of the Crystal
Spring Creek valley to the south of the project area (Kirkham and Widmann, 1997).
The landside appears to be in the Eagle Valley Evaporite where contact springs
discharge near the contact with the overlying basalt flows. Similar conditions are
locally present on the north side of the valley in the project area. AIthough a landside
has not occurred on the north valley side, in our opinion, this area may be near a
critical stability state and development is not recommend on the steep northern Crystal
Creek valley side in the vicinity of the springs and seeps, see Fig. 2. The preliminary
development plans show the questionable area to be open space and the southwestern
part of Lot 28. Suitable building sites are present on Lot 28 on the plateau top to the
northeast of the steep valley side.
EIsewhere on the property we do not anticipate major problems with
construction related slope instability if the proposed grading is engineered and extensive
grading is not done on steep slopes. We should review the grading plans for the
common streets when the plans are available. Individual lot owners should not locate
buildings or driveways on slopes steeper than about 30% unless site specific
geotechnical studies are performed to evaluate the feasibility of the proposed grading.
Preliminary grading considerations are presented in the Preliminary Design
Recommendations - Site Grading section of this report.
H -P GEOTECH
7
POTENTIALLY EXPANSIVE FOUNDATION CONDITIONS
Our laboratory tests show that the colluvium on the property has a low to
moderate swell potential when wetted. Preliminary recommendations to mitigate the
expansion potential for building foundations are discussed in the Preliminary Design
Recommendations - Foundations section of this report.
REGIONAL EVAPORITE DEFORMATION AND SINKHOLES
The project site is in an area where regional ground deformations have been
associated with evaporite solution and flow in the geologic past. These deformations
probably started about 10 million years ago, but it is uncertain if the deformations are
still active or if deformations have stopped. If deformations are still active, it appears
to be taking place over a broad area and there is no evidence of rapid deformation rates.
Because of this, the risk of problems with typical residential buildings appears to be
low. We are not aware of problems associated with regional evaporite deformations in
the area.
Sinkholes were not observed on the property in the field or on the aerial
photograph reviewed. However, a sinkhole is located about 1,300 feet to the west of
the northwestern property corner and sinkholes are present elsewhere in the region and
the property should not be considered sinkhole risk free. The sinkhole risk on the
property is viewed to be low and no greater than that present in many other parts of
Garfield County where the evaporite is near the surface. The potential for shallow
subsurface voids that could develop into sinkholes should be considered when pt nning
site specific geotechnical studies at specific building sites. If conditions indicative of
sinkhole related problems are encountered, the building site should be moved or the
feasibility of mitigation evaluated. Mitigation measures could include:
• Stabilization by Grouting
• Stabilization by Excavation and Backfig
• Deep Foundation Systems
• Structural Bridging
• Mat Foundations
H -P GEOTECH
S
Water features such as landscape ponds are not recommended near building sites
unless evaluated on a site specific basis. Home owners should be advised of the
sinkhole potential, since early detection of foundation distress and timely remedial
actions are important in reducing the cost of remediation, should a sinkhole start to
develop after construction.
EXCAVATION DIFFICULTIES
Dense, hard basalt is likely present at relatively shallow depths throughout the
project area. Difficult excavations should be expected, particularly in confined
excavations such as trenches, Ripping and blasting may be needed in some part of all
excavations that encounter dense, hard basalt.
EARTHQUAKE CONSIDERATIONS
The project area could experience moderately strong earthquake related ground
shaking. Modified Mercalli Intensity VI ground shaking should be expected during a
reasonable service life for the development, but the probability for stronger ground
shaking is low. Intensity VI ground shaking is felt by most people and causes general
alarm, but results in negligible damage to structures of good design and construction.
Occupied structures should be designed to withstand moderately strong ground shaking
with little or no damage and not to collapse under stronger ground shaking. The region
is in the Uniform Building Code, Seismic Risk Zone 1. Based on our current
understanding of the earthquake hazard in this part of Colorado, we see no reason to
increase the commonly accepted seismic risk zone for the area.
PRELIMINARY DESIGN RECOMNIENDATIONS
The conclusions and recommendations presented below are based an the
proposed development, subsurface conditions encountered in the exploratory pits, and
aur experience in the area. The recommendations are suitable for planning and
preliminary design but site specific studies should be conducted for individual lot
development.
H -P GEOTECH
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FOUNDATIONS
Bearing conditions vary depending on the specific location of the building on the
property. Based on the nature of the assumed construction, spread footings bearing on
the natural subsoils should be suitable at the building sites. We expect the footings can
be sized for an allowable bearing pressure in the range of 1,500 psf to 3,000 psf.
Expansive clays encountered in building areas may need to be removed or the footings
designed to impose a minimum dead load pressure to limit potential heave. Excavation
difficulty could be encountered at site with basalt boulders. Nested boulders and loose
matrix soils may need treatment such as enlarging footings or placing compacted fill or
concrete backfill. Foundation walls should be designed to span Iocal anomalies and to
resist lateral earth loadings when acting as retaining structures. Below grade areas and
retaining walls should be protected from wetting and hydrostatic loading by use of an
underdrain system. The footings should have a minimum depth of 42 inches for frost
protection.
WATER TANK
The water tank is proposed to be an above ground, steel structure 24 feet high
with a diameter'of 36 feet and a 200,000 gallon capacity located on the site as shown on
Fig. 1. The foundation for the tank should bear on undisturbed native soils designed for
an allowable bearing pressure of 1,500 psf, excluding the weight of the water. We
should review the preliminary design plans and perform additional analysis as needed.
FLOOR SLABS
Slab -on -grade construction should be feasible for bearing on the natural soils.
There could be some post construction slab movement at sites with collapsible matrix or
expansive clays. To reduce the effects of some differential movement, floor slabs
should be separated from all bearing walls and columns with expansion joints.. Floor
slab control joints should be used to reduce damage due to shrinkage cracking. A
minimum 4 -inch. thick layer of free -draining gravel should underlie basement level slabs
to facilitate drainage and provide support.
H -P GEOTECH
-10-
UNDERDRAIN SYSTEM
Although free water was not encountered in the exploratory pits, it has been our
experience in the area that Local perched groundwater can develop during times of heavy
precipitation or seasonal runoff. An underdrain system should be provided to protect
below -grade construction, such as retaining walls, crawlspace and basement areas from
wetting and hydrostatic pressure buildup. The drains should consist of drainpipe
surrounded above the invert level with free -draining granular material. The drain
should be placed at each level of excavation and at least 1 foot below lowest adjacent
fnish grade and sloped at a minimum 1% to a suitable gravity outlet.
SITE GRADING
The risk of construction -induced slope instability at the site appears low provided
the buildings are located in the less steep parts of the property and cut and fill depths are
Iimited. Cut depths for the building pads and driveway access should not exceed about
10 feet. Fills should be limited to about 10 feet deep, especially where they encroach -
steep downhill sloping areas. Embankment fills should be compacted to at least 95 % of
the maximum standard Proctor density near optimum moisture content. Prior to fill
placement, the subgrade should be carefully prepared by removing all vegetation and
topsoil. The fill should be benched into the portions of the hillside exceeding 20%
grade. The on-site soils excluding oversized rock and topsoil should be suitable for use
in embankment fills.
Permanent unretained cut and fill slopes should be graded at 2 horizontal to
1 vertical or flatter and protected against erosion by revegetation, rock riprap or other
means. Oversized rock from embankment fill construction will tend to collect on the
outer face. This office should review site grading plans for the project prior to
construction.
PAVEMENT SUBGRADE
The on-site medium plastic clay soils have an AASHTO classification of A-6
with Group Indices of 14 and 18. These soils are considered poor for support of
pavement sections. The Hveem stabilometer `R' value test resulted in a value of 5. An
H-� GEOTECH
-11-
`R' value of 5 can be assumed for design of pavements in clay subgrade areas. The `R'
value should be considerably higher in the basalt fragment deposit areas. A subbase
material such as an import aggregate could be used in improve the clay subgrade. The
subgrade conditions at roadway grade should be evaluated for pavement design at the
time of construction.
SURFACE DRAINAGE
The grading plan for the subdivision should consider runoff from steep uphill .
slopes through the project and at individual sites. Water should not be allowed to pond.
which could impact slope stability and foundations, To limit infiltration into the bearing
soils next to buildings, exterior backfill should be capped with 1 to 2 feet of finer -
grained soils, be well compacted and have a positive slope away from the budding fora
distance of 10 feet. Roof downspouts and drains should discharge well beyond the limits
of all backfill.
PERCOLATION TESTING
Percolation tests were conducted on December 28, 2001 to evaluate the
feasibility of an infiltration septic disposal systems at various locations across the
property. Percolation holes were excavated adjacent to the exploratory pits at the
locations shown on Figs. 1 and 2. The test holes (nominal 12 inch diameter by 12 irtch
deep) were hand dug at the bottom of shallow backhoe pits and were soaked with water
and covered with rigid foam insulation ane day prior to testing. The soils exposed in the
percolation holes are similar to those exposed in the adjacent exploratory pits (see Fig.
2). Average percolation rates ranged from about 10 to 30 minutes per inch. The
percolation test results are presented in Table II. Based on the subsurface conditions
encountered and the percolation test results, tested areas should be suitable for a
conventional infiltration septic disposal system. A civil engineer should design the
infiltration septic disposal system.
H -P GEOTECH-H
12-
L]METATIONS
This study has been conducted according to generally accepted geotechnical
engineering principles and practices in this area at this time. We make no warranty
either expressed or implied. The conclusions and recommendations submitted in this
report are based upon the data obtained from the field reconnaissance, review of
published geologic reports, the exploratory pits located as shown on Figs. 1 and 2,
percolation testing, the proposed type of construction and our experience in the area.
Our findings include interpolation and extrapolation of the subsurface conditions
identified at the exploratory pits and variations in the subsurface conditions may not
become evident until excavation is performed. If conditions encountered during
construction appear different from those described in this report, we should be notified
so that re-evaluation of the recommendations may be made.
This report has been prepared for the exclusive use by our client for planning and
preliminary design purposes. We are not responsible for technical interpretations by
others of our information. As the project evolves, we should provide continued
consultation, conduct additional evaluations and review and monitor the implementation
of our recommendations. Significant design changes may require additional analysis or
smodifications to the recommendations presented herein. We recommend on-site
observation of excavations and foundation bearing strata and testing of structural fill by
a representative of the geotechnical engineer.
Respectfully Submitted,
HEPWORTH - PAWLAIC GEOTECHNICAL, INC.
Trevor L. Knell
Reviewed by:
Daniel E. Hardin, P.
TLK/ksw
cc: High Country
Land Design Partn
oger Neal
on Liston
H -P GEOTaCH
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REFERENCES
Kirkham, R.M. and Widmann, B.L., 1997, Geology Map of the Carbondale
Quadrangle, Garfield County Colorado: Colorado Geological Survey Open File
97-3.
Widmann B. L. and Others, 1998, Preliminary Quaternary Fault and Fold Map and
Data Base of Colorado: Colorado Geological Survey Open File Report 98-3.
H -P GEOTECH
Explanation:
of Man -Placed FIR:
Road NI, olher fill and ground
disturbed by grading.
Qc Colluvlum
Qai Valley Floor Alluvium
Qls Landslide
QTdb Deformed Basalt
Tb Basalt Flows
Fee Eagle Valley Evaporite
101 821
HEPWORTH-PAWLAK
GEOTECHNICAL, Inc.
Contact:
Appraudmata boundary of map units.
Structural Sag:
Approximate axle of structural sag.
Sinkhole
Springs & Seeps
Strike and Dip:
(degrees)
a 500f.
�_I E
Scale:1 in.: 500 it
Contour interval: 2 ft.
Exploratory Pit & Percolation Test Site:
Approxdrneta location.
Caliicotte Ranch Development - Northern Part
Geology Map and Exploratory Pit Locations
Fig. 1
Explanation:
of Man -Placed Fill:
Road fill, other RA and ground
disturbed by grading.
Qc Colluvlum
Dal Valley Floor Alluvium
as Landslide
QTdb Deformed Basalt
Tb Basalt Flows
Pee Eagle Valley Evaporlte
Contact:
Approximate boundary of map units.
Structural Sag:
Approximate axis of structural sag.
C Sinkhole
0 500 It.
«. Springs & Seeps Scale: 1 In. 500 t
Contour Interval: 2 tit.
2i/ Strike and Dip:
(degrees)
Pi
e Exploratory Pit & Percolation Test Site:
Approximate location.
101 821 I HEPWORTH-PAWLAK
GEOTECHNICAL, Inc.
Callicotte Ranch Development - Southern Part Fig. 2
Geology Map and Exploratory PR Locations
C
Y
0
r_ 5
10
0
5
— 10
pig
0
1L
5
• E 10
101 821
PIT 1 PIT 2
Y=11.8
DD -103
WC= 41.8
DD -70
-2003275
PIT 5 R T 6
PIT 9
—7
-1
I WC -8.8
I -200x92
_ ! Ll=.37
PI -20
Ra5
WC -11.6
DD -103
we -321
/ / 00-102
-200.87
P17
P1-17
•
rti
.: 0•r
PIT 3
PIT 4
PiT 7 PIT
PIT 10 PIT 11
/
/
/
•
• of
WC -9.B
DD -81
WC -10.6
DD -77
-200-70
Note: Explanation .of syrnbois is shown on Fiq. 4.
HEPWORTH—PAWLAK
GEOTECHNICAL, INC.
LOGS OF EXPLORATORY PITS
WC=16.1
00-91
0
5
10
0
5
10 —
0 �y
Depth — Feet
Depth — Feet
Depth — Feet
C
LEGEND:
•
T
NOTES:
TOPSOIL; organic sandy silt and clay, dark brown.
CLAY (CL); silty, sandy, very stiff to hard, slightly moist to moist, brown to Light brown, blocky,
calcareous with depth, low to medium plasticity.
BASALT GRAVEL, COBBLES AND BOULDERS (GM); sandy silt and day matrix, medium dense,
slightly moist, light brown, calcareous.
GRAVEL AND COBBLES (GM -GP); .silty, sandy, medium dense, slightly moist, brown, rounded rock
Pit 10 only.
2" Diameter hand driven liner sample.
Disturbed bulk sample.
Practical digging refusal with Cat 4200 backhoe.
1. Exploratory pits were excavated on December 27 and 28, 2001 with a backhoe.
2. Locations of exploratory pits were measured approximately by pacing from features on the site plan
provided.
3. Elevations of the exploratory pits were obtained by interpolation between contours on the site plan
provided.
3. Elevations of exploratory pits were not measured and logs of exploratory pits are drawn to depth.
4. The exploratory pit locations and elevations should be considered accurate only to the degree implied
by the method used. _
5. The lines between materials shown on the exploratory pit logs represent the approximate boundaries
between material types and transitions may be gradual.
6. No free water was encountered in the pits at the time of excavating. Fluctuations In water level may
occur with time.
7. Laboratory -Testing Results:
WC = Water Content (% )
DO = Dry Density ( pcf )
+4 = Percent retained on No. 4 sieve
-200 = Percent passing No. 200 sieve
LL = Liquid Limit()
Pi = Plasticity index ( %
R = Fiveern Stabilometer .' R" Value
101 821
HEPWORTH — PAWLAK
GEOTECHNICAL, INC.
LEGEND AND NOTES
Fig. 4
1
Compression — Expansion %
Compression — Expansion
1
0
1
2
3
2
1
0
1
2
0.1
1.0 10
APPLIED PRESSURE — ksf
Moisture Content = 16.1 percent
Dry Density = 91 pcf
Sample of:Sandy Clay Matrix
From: Pit 4 at 3 Feet
J
Expansion
upon
wetting
0.1
1.0 0
APPLIED PRESSURE — ksf
100
100
101 821
HEPWORTH—PAWLAK
GEOTECHNICAL, INC.
SWELL CONSOLIDATION TEST RESULTS
Fig. 5
i
Moisture Content = 11.8 percent
Dry Density = 103 pcf
Sample of: Sandy Clay
From: Pit 1 at 2.5 Feet
71----.1:1-\\
--....-_,'
____,..._-_L....o-•
Expansion
upon
wetting•
0.1
1.0 10
APPLIED PRESSURE — ksf
Moisture Content = 16.1 percent
Dry Density = 91 pcf
Sample of:Sandy Clay Matrix
From: Pit 4 at 3 Feet
J
Expansion
upon
wetting
0.1
1.0 0
APPLIED PRESSURE — ksf
100
100
101 821
HEPWORTH—PAWLAK
GEOTECHNICAL, INC.
SWELL CONSOLIDATION TEST RESULTS
Fig. 5
1
a
.N
c
a
a
1 1
0
co
L 2
E
0
U
3
Compression %
0
1
2
3
4
IMoisture
Content = 11.6 percent
.Dry Density = 103 pcf
Sample of: Sandy Clay
From: Pit 5 at 7 Feet
F
Expansion
upon
wetting_
9
1111
-�
_
J
0.1
LO 10
APPLIED PRESSURE — ksf
100
Moisture Content = 9.8 percent
Dry Density = 81 pcf
Sample of: Calcareous Sandy Silty Clay
From: Pit 7 at 5 Feet
Compression
upon
wetting
0.1
1.0 10
APPLIED PRESSURE — ksf
100
101 821
HEPWORTH---PAWLAK
GEOTECHNICAL. INC.
SWELL CONSOLIDATION TEST RESULTS
Fig. 6
N
0
1
O
{q
0
7
UNCONFINED
COMPRESSIVE
S1ABILOMETER
r�
e
a
Q
h!
n
cry
to
n
N
0)
h
w
O
N
GRADATION
11
N
5
n
m
O
r
O
N
0)
O
CO
N
0
AN
1 _
q e E
E
z 2 0
W
r
CO
SAMPLE LOCATION
I
W
-
m
0]
M
r
W
6)
h
CO
1.0
C1E
t1?
N.
rn
1 .1
HEPWORTH-PAWLAK GEOTECHNICAL, INC.
TABLE II
PERCOLATION TEST RESULTS
JOB NO. 101 821
Page 1 of 4
HOLE NO,
HOLE DEPTH
(INCHES}
LENGTH OF
INTERVAL
(MIN)
WATER DEPTH
AT START OF
INTERVAL
(INCHES)
WATER DEPTH
AT END OF
INTERVAL
(INCHES)
P-1
P-2
P-3
34
:39
38
15
water added
15
15
water added
7
5 3/4
DROP IN
WATER
LEVEL
(INCHES)
1 1/4
5 3/4
4 1/2
1 1/4
4 1/2
3 3/4
3/4
3 314
2 3/4
1
7 1/2
6 3/4
3/4
6 3/4
6
3/4
6
5 1/4
3/4
5 1/4
7 1/2
41/2
6 3/4
3/4
3/4
6 3/4
6
3/4
6
51/2
1/2
5 1/2
5
1/2
5
4 1/2
1/2
4 1/2 •
4
1/2
4
3 1/2
1/2
3 1/2
/01/2
3
8
1/2
21/2
8
6 1/2
1 1/2
6 1/2
5
1 1/2
10 1/2
9 1/2
1
9 1/2
7' 1/2
2
7 1/2
6
1/12
6
4 1/2
1 1/2
4 1/2
3
1 1/2
AVERAGE
PERCOLATION
RATE
(MIN ./INCH)
20
30
10
note: Percolation test holes were hand dug in the bottom of backhoe pits adjacent to
exploratory pits and soaked on December 27, 2003. Percolation tests were conducted
an December 28, 2001. The average percolation rate were based on the last three
readings of each test.
HEPWORTH-PAWLAK GEOTECHNICAL, INC.
TABLE II
PERCOLATION TEST RESULTS
JOS NO. 101 821
HOLE NO.
HOLE DEPTH
(INCHES)
LENGTH OF
INTERVAL
(MIN}
P-4
42
15
water added
P-5
P-6
50 1/2
29 1/2
10
10
WATER DEPTH
AT START OF
INTERVAL
(INCHES)
WATER DEPTH
AT END OF
INTERVAL
(INCHES)
DROP IN
WATER
LEVEL
(INCHES)
9 1/2
7
2 1/2
7
5 1/2 ,
1 1/2
5 112
4 1/2
1
8 1/2
6 1/2
2
6 1/2
5 1/2
1
5 1/2
4 1/2
1
4 1/2
3 1/2
1
3 1/2
2 1/2
1
7111
cns,e-
..,.
6 3/4
6
3/4
6
5 114
3/4
5 1/4
4 3/4
1/2
4 314
4 1/4
112
4 1/4
3 3/4
1/2
3 3/4 .
3.1/4
1/2
3 1/4
8 1/4
2 3/4
7 1/2
1/2
3/4
7 1/2
7
1/2
7
6 1/2
1/2
6 1/2
6
1/2
6
51/2
1/2
5 1/2
5
1/2
5
4 1/2
1/2
4 1/2
4
1/2
• Page 2 of 4
AVERAGE
PERCOLATION
RATE
(MIN./INCH)
15
20
20
Note: Percolation test holes were hand dug in the bottom of backhoe pits adjacent to
exploratory pits and soaked on December 27, 2001. Percolation tests were conducted
on December 28, 2001, The average percolation rate were based on the last three
readings of each test.
HEPWORTH-PAWLAK GEOTECHNICAL, INC.
TABLE If
PERCOLATION TEST RESULTS
HOLE DEPTH
(INCHES)
LENGTH OF
INTERVAL
(MIN)
P-7
P-8
P-9
39
33
42
15
15
15
JOB NO. 101 821
6 1/2
5 1/2
5 1/2
5
112
5
4 1/2
1/2
4 1/2
4
1/2
4
3 1/2
1/2
3 1/2
3
1/2
3
2 1/2
1/2
21/2
11
9 1/2
2
91/2
9
1/2
1 1/2
1/2
Page 3 of 4
AVERAGE
PERCOLATION
RATE
IM IN./INCH)
30
9
8
1
8
7 1/2
1/2
7 1/2
6
112
6
5
1
5
5
0
5
Note:
4 1/2
1/2
30
Percolation test holes were hand dug in the bottom of backhoe pits adjacent to
exploratory pits and soaked on December 27, 2001. Percolation tests were conducted
on December 28, 2001. The average percolation rate were based on the last three
readings of each test.
WATER DEPTH
AT START OF
INTERVAL
(INCHES)
WATER DEPTH
AT END OF
INTERVAL
(INCHES)
DROP IN
WATER
LEVEL
(INCHES)
7 1/2
6 112
1
6 1/2
5 3/4
314
5 3/4
5
3/4
5
4 1/2
112
4 1/2
4
1/2
4
3 1/2
1/2
3 1/2
3
1/2
3
2 119
11)
6 1/2
5 1/2
5 1/2
5
112
5
4 1/2
1/2
4 1/2
4
1/2
4
3 1/2
1/2
3 1/2
3
1/2
3
2 1/2
1/2
21/2
11
9 1/2
2
91/2
9
1/2
1 1/2
1/2
Page 3 of 4
AVERAGE
PERCOLATION
RATE
IM IN./INCH)
30
9
8
1
8
7 1/2
1/2
7 1/2
6
112
6
5
1
5
5
0
5
Note:
4 1/2
1/2
30
Percolation test holes were hand dug in the bottom of backhoe pits adjacent to
exploratory pits and soaked on December 27, 2001. Percolation tests were conducted
on December 28, 2001. The average percolation rate were based on the last three
readings of each test.
! • ' w •a
HEPWORTH-PAWLAK GEOTECHNICAL, INC.
TABLE II
PERCOLATION TEST RESULTS JOB NO. 101 821
Page 4 of 4
HOLE NO.
P-10
P-11
HOLE DEPTH
(INCHES)
42
LENGTH OF
INTERVAL
IMIN)
10
42 15
WATER DEPTH
AT START OF
INTERVAL
(INCHES)
8
WATER DEPTH
AT END OF
INTERVAL
(INCHES)
7 112
DROP IN
WATER
LEVEL
(INCHES)
1/2
7 112
7
1/2
7
6 3/4
114
6 3/4
6 1/2
1/4
6 1/2
6
1/2
6
5 3/4
• 1/4
5 3/4
5 114
1/2
5 1/4
12
5
11
1/4
1
11
10 1/2
1/2
10 1/2
10
. 1/2
10
9
1
9
9
0
9
8 1/2
1/2
8 1/2
8
1/2
8
7 1/2
1/2
AVERAGE
PERCOLATION
RATE
(MIN./INCH)
30
30
Note: Percolation test holes were hand dug in the bottom of backhoe pits adjacent to
exploratory pits and soaked on December 27, 2001. Percolation tests were conducted
on December. 28, 2001. The average percolation rate were based on the last three
readings of each test.
Gtech
HEPWORTH- PAWLAK GEOTECHNICAL
July 15, 2003
Magna Casa, Inc.
Attn: Jack Mancini
1700 E. Las Olas Boulevard, Suite 206
Fort Lauderdale, Florida 33301
Hepworth-Pawlak Oeatedutical, Inc.
5020 County Road 154
Glenwood Springs, Colorado 81601
Phone: 970-945-7988
Fax: 970-945-8454
.email: hpgeoghpgeotech.com
Job No.101821
Subject: Radiation Potential, Proposed Callicotte Ranch, County Roads 112 and
103, Garfield County, Colorado
Dear Mr. Mancini:
As requested by Ron Liston, we have reviewed our previous geotechnical study for the
project with respect to radiation potential. We previously conducted a preliminary
geotechnical study for the project and presented our findings in a report dated April 19,
2002, dab No. 101 821.
The project site is not in a -geologic setting that would indicate high concentrations of
radioactive minerals in the natural soils and underlying rock formation. However, there
is a potential that radon gas is present in the area. Based on our experience, we expect
radon gas concentrations to be low. It is difficult to assess future radon gas
concentrations in buildings before the buildings are constructed. Testing for radon gas
levels could be done when the residences and other occupied structures have been
completed. New buildings are often designed with provisions for ventilation of Iower
enclosed areas should post construction testing show unacceptable radon gas
concentration.
If there are any questions or if we may be of further assistance, please let us know.
Sincerely,
HEPWORTH - PAWLAK . ,�r n� HNICAL, INC.
Daniel E. Hardin, P. . : 244 3 t
o IA Rev. by: SLP ikgre.. .�'�`� 41
y X0,01. e
DEH/ksw �'�ry��S! �� .
cc: High Country Enginee ii�l�'l. Attn: Steven Douglas
Land Design Partnership - Attn: Ron Liston
Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthome 970-468-1989