HomeMy WebLinkAboutSoils ReportCTI s T'HOMPSON
YEARS
FOUNDED
u I H C O R P O R A T■ D
GEOTECHNICAL ENGINEERING INVESTIGATION
CLUBHOUSE AND POOL
HIGH ASPEN RANCH
491 HIGH ASPEN DRIVE
GARFIELD COUNTY, COLORADO
Prepared For:
GREEN LINE ARCHITECTS
64 North 4th Street, Suite 5
Carbondale, CO 81623
Project No. GS06546.000-125
April 16, 2021
234 Center Drive I Glenwood Springs, Colorado 81601
Telephone: 970-945-2809 Fax: 970-945-7411
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TABLE OF CONTENTS
SCOPE..............................................................
SUMMARY OF CONCLUSIONS ......................
SITE CONDITIONS ..........................................
PROPOSED CONSTRUCTION .......................
SITE GEOLOGY AND GEOLOGIC HAZARDS
SUBSURFACE CONDITIONS ..........................
SITE EARTHWORK ..........................................
Excavations...................................................
Subexcavation and Structural Fill ..................
Foundation Wall Backfill ................................
FOUNDATIONS ................................................
Footings on Structural Fill .............................
DrilledPiers ...................................................
SLAB -ON -GRADE CONSTRUCTION ..............
STRUCTURALLY -SUPPORTED FLOORS......
FOUNDATION WALLS .....................................
SUBSURFACE DRAINAGE ..............................
EARTH RETAINING WALLS ............................
POOL CONSTRUCTION ..................................
SURFACE DRAINAGE .....................................
CONCRETE......................................................
CONSTRUCTION OBSERVATIONS ...............
STRUCTURAL ENGINEERING SERVICES....
GEOTECHNICAL RISK ....................................
LIMITATIONS ........................................
FIGURE 1 -VICINITY MAP
FIGURE 2 -AERIAL PHOTOGRAPH
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FIGURE 3 - PROPOSED CONSTRUCTION
FIGURE 4 - SUMMARY LOGS OF EXPLORATORY PITS AND BORINGS
FIGURES 5 THROUGH 7 - SWELL -CONSOLIDATION TEST RESULTS
FIGURE 8 - GRADATION TEST RESULTS
FIGURES 9 AND 10 - FOUNDATION WALL DRAIN CONCEPTS
TABLE I - SUMMARY OF LABORATORY TESTING
GREEN LINE ARCHITECTS
NEW CLUBHOUSE AND POOL
PROJECT NO. GS06546.000-125
SCOPE
CTL I Thompson, Inc. has completed a geotechnical engineering investiga-
tion for the clubhouse and swimming pool proposed at 491 High Aspen Drive
within High Aspen Ranch in Garfield County, Colorado. We conducted this investi-
gation to evaluate subsurface conditions at the site and provide geotechnical engi-
neering recommendations for the planned construction. The scope of our investi-
gation was set forth in our Proposal No. GS 20-0323. Our report was prepared
from data developed from our field exploration, laboratory testing, engineering
analysis, and our experience with similar conditions. This report includes a de-
scription of the subsurface conditions observed in our exploratory pits and explora-
tory borings and provides geotechnical engineering recommendations for design
and construction of foundation and floor systems and details influenced by the
subsoils. We should be provided with architectural plans, as they are further devel-
oped, so we can provide geotechnical/geo-structural engineering input. A sum-
mary of our conclusions is below.
SUMMARY OF CONCLUSIONS
Subsurface conditions encountered in our exploratory pits and ex-
ploratory borings at the site generally consisted of about 8 inches of
aggregate base course and nil to 2 feet of existing fill, underlain by
natural sandy clay to the total explored depth of 35 feet. Free
groundwater was not found in our pits and borings during our subsur-
face investigation.
2. The natural sandy clay at this site has potential for moderate
amounts of expansion when wetted. Without mitigation, expansion of
the clay soil is likely to result in differential heave and damage to the
building. We judge the clubhouse can be constructed on a footing
foundation, provided the soils are subexcavated to a depth of at least
3 feet below footings and replaced with moisture -treated, structural
fill. A drilled pier foundation is a positive alternative that would further
mitigate risk of building movement.
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3. If a slab -on -grade floor will be constructed in the building, we recom-
mend subexcavation of the soils below the slab to a depth of at least
3 feet and replacement with moisture -treated, structural fill to miti-
gate potential heave of the slab. A minimum structural fill thickness
of 2 -feet is recommended below the pool deck, patios, and side-
walks. A positive alternative to reduce risk of differential heave would
be construction of a building floor that is structurally -supported by the
foundation system with a crawl space below.
4. Soils below the swimming pool shell should be subexcavated to a
depth of 3 feet and replaced with moisture -treated structural fill. In-
stallation of a drain system below the pool will be critical for perfor-
mance.
5. if a structurally -supported floor system with a crawl space is utilized
for the building, we recommend a foundation wall drain be con-
structed around the perimeter of the crawl space. Surface grading
should be designed and constructed to rapidly convey surface water
off concrete flatwork and away from the building.
SITE CONDITIONS
The subject site is located at 491 High Aspen Drive (a.k.a. Lot 31, High As-
pen Ranch) within High Aspen Ranch in Garfield County, Colorado. A vicinity map
with the location of the site is included as Figure 1. An irrigation ditch trends down
to the southwest along an alignment that is uphill (north) of the subject site. A club-
house, swimming pool, tennis courts, and paved parking area were previously lo-
cated at the site. These structures are shown on Figure 2, which is an aerial pho-
tograph from June 2017. These structures were deconstructed during the time be-
tween excavation of our exploratory pits and drilling of our exploratory borings.
The new clubhouse and swimming pool are planned at the location of the previous
tennis courts. This area has been graded as a relatively flat bench. A photograph
of the proposed building site at the time of our exploratory drilling is below.
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PROJECT NO. GS06546.000-125
Looking southeast across site with drill rig at TH-2
PROPOSED CONSTRUCTION
Architectural plans for the proposed clubhouse and swimming pool were
preliminary at the time of our geotechnical engineering investigation. We were pro-
vided with a site plan and floor plan by Green Line Architects (dated April 12,
2021). The clubhouse is contemplated as a one-story building with the footprint
shown on Figure 3. We expect wood and steel -frame construction. The current
plans suggest a slab -on -grade floor with no below -grade areas, such as a crawl
space or basement. Foundation loads for this type of construction are expected to
be less than 3,000 pounds per linear foot of foundation wall with maximum interior
column loads of less than 30 -kips.
The swimming pool is proposed south of the building. Details showing the
planned swimming pool construction, including depth, were not developed. Signifi-
cant areas of concrete pool deck, patio, and sidewalk are proposed adjacent to the
building and swimming pool. It appears that structural fill as thick as about 8 feet is
planned below the south and east sides of these areas. The site plan indicates a
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PROJECT NO. GS06546.000-125
10
two-tiered earth retaining wall will be needed to provide lateral support for the
structural fill. The specific earth retaining wall system has not been determined.
We should be provided with architectural plans, as they are further developed, so
we can provide geotechnical/geo-structural engineering input.
SITE GEOLOGY AND GEOLOGIC HAZARDS
As part of our geotechnical engineering investigation, we reviewed geologic
mapping by the Colorado Geological Survey (CGS) titled, "Geologic Map of the
Carbondale Quadrangle, Garfield County, Colorado", by Kirkham and Widmann
(dated 2008). The mapping indicates that trachyandesite bedrock (Pliocene
Epoch) is at or near the ground surface at the site. We did not encounter bedrock
in our exploratory pits and exploratory borings. The natural sandy clay soils we
found in our pits and borings are likely part of the undivided deposits of alluvium
and colluvium (Holocene and Late Pleistocene Epochs) that are mapped to the
west of the subject site.
We also reviewed the CGS map "Collapsible Soils and Evaporite Karst Haz-
ard Map of the Roaring Fork Valley, Garfield, Pitkin and Eagle Counties", by Jona-
than L. White (dated 2002). This map indicates unconsolidated deposits in the ar-
eas adjacent to the subject site. These deposits are described as including collu-
vium, sheetwash, and alluvium. The map descriptions indicate these types of soils
are geologically recent and typically loosely -packed, porous, and dry. These soil
deposits are often prone to collapse when wetted, especially under applied building
loads. Our laboratory testing on samples from our exploratory borings indicate the
soils at this site have potential for expansion and not collapse. We judge that ex-
pansion of the soils is the primary hazard for structures at the site.
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SUBSURFACE CONDITIONS
Subsurface conditions at the site were investigated by directing excavation
of three exploratory pits (TP -1 through TP -3) and drilling three exploratory borings
(TH-1 through TH-3) at the approximate locations shown on Figures 2 and 3. The
pits were excavated with a trackhoe on February 10, 2021. Exploratory borings
were drilled on April 8, 2021 with solid -stem auger and a track -mounted drill rig.
Exploratory excavation and drilling operations were directed by our representa-
tives, who logged subsurface conditions encountered and obtained representative
samples. Graphic logs of the soils encountered in our exploratory pits and explora-
tory borings are shown on Figure 4.
Subsurface conditions encountered in our exploratory pits and borings at
the site generally consisted of about 8 inches of aggregate base course and nil to
2 feet of existing fill, underlain by natural sandy clay to the total explored depth of
35 feet. Free groundwater was not found in our pits and borings during our subsur-
face investigation. The pits were backfilled immediately after excavation opera-
tions were completed. PVC pipe was installed in our borings to facilitate future
checks of groundwater.
Samples of the soils obtained from our exploratory pits and borings were re-
turned to our laboratory for pertinent testing. Six samples of the sandy clay se-
lected for one-dimensional, swell -consolidation testing exhibited 0.3 to 3.0 percent
swell when wetted under an applied pressure of 1,000 psf. Gradation analyses on
two clay samples indicated 31 percent gravel, 10 and 12 percent sand, and 59 and
57 percent silt and clay size material (passing the No. 200 sieve). Engineering in-
dex testing on one sample showed high plasticity with a liquid limit of 54 percent
and a plastic index of 30 percent. One sample of soil tested had a water-soluble
content of 0.00 percent. Swell -consolidation test results are shown on Figures 5
through 7. Gradation test results are provided on Figure 8. Laboratory testing is
summarized on Table I.
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SITE EARTHWORK
Excavations
We expect maximum excavation depths of less than 10 feet for the proposed
construction, including the recommended 3 -feet of subexcavation. Based on our
subsurface investigation, excavations at the site can be made with conventional ex-
cavating equipment. Sides of excavations need to be sloped or braced to meet lo-
cal, state and federal safety regulations. The sandy clay soil at the site will likely
classify as a Type B soil based on OSHA standards governing excavations. Tem-
porary excavation slopes that are not retained should be no steeper than 1 to 1
(horizontal to vertical) in Type B soils. Contractors are responsible for maintaining
safe excavations. Contractors should identify the soils encountered and ensure that
OSHA standards are met.
Free groundwater was not encountered in our exploratory pits and borings.
We do not expect that excavations for the proposed construction will penetrate a
free groundwater table. Excavations should be sloped to a gravity discharge or to
a temporary sump where water from precipitation and snowmelt can be removed
by pumping.
Subexcavation and Structural Fill
It appears that structural fill as thick as about 8 feet is planned below the
south and east sides of the pool deck and patio areas. These areas should be
stripped of vegetation and organics, prior to placement of structural fill. Addition-
ally, we recommend subexcavation of the soils to a depth of at least 3 feet below
footings and floor slabs (if constructed) and below the swimming pool to mitigate
the potential for soil expansion and heave -related damage. The subexcavation
process should extend laterally at least 1 foot beyond the perimeter of the building
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and swimming pool footprint. A minimum structural fill thickness of 2 -feet is recom-
mended below the pool deck, patios, and sidewalks.
Structural fill to raise grades for exterior areas, and to reattain construction
elevations in subexcavated areas, can consist of the natural sandy clay soils exca-
vated from the site, provided they are free of rocks larger than 3 inches in diame-
ter, organic matter, and debris. As an alternative, a CDOT aggregate base course
can be imported to the site for use as structural fill. A sample of desired import soil
should be submitted to our office for approval.
Structural fill soils should be moisture -conditioned to within 2 percent of op-
timum moisture content, placed in loose lifts of 8 inches thick or less, and com-
pacted to at least 98 percent of standard Proctor (ASTM D 698) maximum dry
density. Moisture content and density of structural fill should be checked by a rep-
resentative of our firm during placement. Observation of the compaction procedure
is necessary.
Foundation Wall Backfill
Proper placement and compaction of foundation wall backfill is important to
reduce infiltration of surface water and settlement from consolidation of backfill
soils. This is especially important for backfill areas that will support concrete slabs,
such as the pool deck, patios, and sidewalks. The natural sandy clay soil can be
used as backfill, provided it is free of rocks larger than 3 -inches in diameter, organ-
ics, and debris.
Backfill should be placed in loose lifts of approximately 10 inches thick or
less, moisture -conditioned to within 2 percent of optimum moisture content and
compacted to at least 95 percent of maximum standard Proctor (ASTM D 698) dry
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density. Moisture content and density of the backfill should be checked by a repre-
sentative of our firm during placement. Observation of the compaction procedure
is necessary.
FOUNDATIONS
Our laboratory testing indicates the natural sandy clay at this site has po-
tential for moderate amounts of expansion when wetted. Without mitigation, ex-
pansion of the in-situ clay soil is likely to result in differential heave and damage to
the building. We judge the clubhouse can be constructed on a footing foundation,
provided the soils are subexcavated to a depth of at least 3 feet below footings
and replaced with moisture -treated, structural fill. The subexcavation and structural
fill should be in accordance with the Subexcavation and Structural Fill section.
A drilled pier foundation is a positive alternative that would further mitigate
risk of building movement. Drilled piers in expansive soils are designed and con-
structed to resist uplift from heave by anchoring in the soils below the depth of po-
tential wetting. Typically, drilled foundations experience less movement, as com-
pared to footing foundations.
Design criteria for footings on structural fill and drilled piers are below.
These criteria were developed from our analysis of field and laboratory data and
our experience.
Footings on Structural Fill
Footings should be supported by at least 3 feet of moisture -treated,
structural fill in accordance with the Subexcavation and Structural Fill
section.
2. Footings on the structural fill can be sized using a maximum net al-
lowable bearing pressure of 3,000 psf. The weight of backfill soil
above the footings can be neglected.
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3. A friction factor of 0.35 can be used to calculate resistance to sliding
between concrete footings and the structural fill soil.
4. Continuous wall footings should have a minimum width of at least 16
inches. Foundations for isolated columns should have minimum di-
mensions of 24 inches by 24 inches. Larger sizes may be required,
depending upon foundation loads.
5. Grade beams and foundation walls should be well -reinforced. We rec-
ommend reinforcement sufficient to span an unsupported distance of
at least 12 feet.
6. The soils under exterior footings should be protected from freezing.
We recommend the bottom of footings be constructed at a depth of at
least 36 inches below finished exterior grades. The Garfield County
building department should be consulted regarding required depth.
Drilled Piers
Piers should be designed for a maximum allowable end bearing
pressure of 12,000 psf and an allowable skin friction value of 1,200
psf. Skin friction should be neglected for the portion of the upper 3
feet of pier below grade beams.
2. Piers should be designed for a minimum deadload pressure of 500
psf based on pier cross-sectional area. If this deadload cannot be
achieved through the weight of the structure, the pier length should
be increased beyond the minimum values specified in the next para-
graph. The clay soil should be assigned a skin friction value of 1,200
psf for uplift resistance.
3. Piers should have minimum lengths of 25 feet. The pier length
should not exceed about 30 times the pier diameter.
4. Piers should be reinforced to full length with at least three No.5
(16mm), Grade 60 (420 Mpa) reinforcing bars (or the equivalent) to
resist a potential uplift tension. Reinforcement should extend into
grade beams and foundation walls.
5. A 6 -inch continuous void will be required beneath all grade beams
and foundation walls, between piers, to allow for potential soil heave
and concentrate the deadload of the building on the piers.
6. Piers should be carefully cleaned prior to placement of concrete. To
reduce potential for problems during pier installation, we recommend
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that a "drill and pour" construction procedure be used, in which con-
crete is placed in the pier holes immediately after the holes are
drilled, cleaned and inspected by our representative. Concrete
should not be placed by free fall in pier holes containing more than 3
inches of water.
7. Concrete should have sufficient slump to fill the pier holes and not
hang on the reinforcement. We recommend a slump in the range of 5
to 7 inches.
8. Formation of mushrooms or enlargements at the top of piers should
be avoided during pier drilling and subsequent construction opera-
tions.
9. Installation of drilled piers should be observed by a representative of
CTL I Thompson, Inc. to identify the proper bearing strata.
SLAB -ON -GRADE CONSTRUCTION
The current architectural plans suggest a slab -on -grade floor in the building
with no below -grade areas, such as a crawl space or basement. Significant areas
of concrete pool deck, patio, and sidewalk are proposed adjacent to the building.
We recommend subexcavation of the soils below the interior floor slab to a depth of
at least 3 feet and replacement with moisture -treated, structural fill to mitigate po-
tential heave of the slab. A minimum structural fill thickness of 2 feet is recom-
mended below the pool deck, patios, and sidewalks. The subexcavation and struc-
tural fill should be in accordance with the Subexcavation and Structural Fill section.
A positive alternative to reduce risk of differential heave would be construc-
tion of a building floor that is structurally -supported by the foundation system with a
crawl space below. Design and construction issues associated with structurally -
supported floors include lateral loads on foundation walls and ventilation of crawl
spaces. Additional discussion is in the STRUCTURALLY -SUPPORTED FLOORS
section.
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We recommend the following precautions to enhance potential performance
of slab -on -grade construction at this site.
Slabs should be separated from exterior walls and interior bearing
members with slip joints that allow free vertical movement of the
slabs.
2. The use of underslab plumbing should be minimized. Underslab
plumbing should be pressure tested for leaks before the slabs are
constructed. Plumbing and utilities which pass through slabs should
be isolated from the slabs with sleeves and provided with flexible cou-
plings to slab supported appliances.
3. Exterior concrete flatwork should be isolated from the building. These
slabs should be well -reinforced to function as independent units.
Movements of these slabs should not be transmitted to the building.
4. Frequent control joints should be provided, in accordance with Ameri-
can Concrete Institute (ACI) recommendations, to reduce problems
associated with shrinkage and curling.
STRUCTURALLY -SUPPORTED FLOORS
A positive alternative to reduce risk of differential heave would be construc-
tion of a building floor that is structurally -supported by the foundation system with a
crawl space below. Design and construction issues associated with structurally -
supported floors include lateral loads on foundation walls and ventilation of crawl
spaces. Building codes normally require a clear space of at least 18 inches be-
tween exposed earth and untreated wood components of the structural floor. For
non-organic systems, we recommend a minimum clear space of 12 inches. This
minimum clear space should be maintained between any point on the underside of
the floor system (including beams, plumbing pipes, and floor drain traps and the
soils.
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1111,
Utility connections, including water, gas, air duct, and exhaust stack connec-
tions to appliances on structural floors should be capable of absorbing some deflec-
tion of the floor. Plumbing that passes through the floor should ideally be hung from
the underside of the structural floor and not laid on the bottom of the excavation. It
is prudent to maintain the minimum clear space below all plumbing lines. If trench-
ing below the lines is necessary, we recommend sloping these trenches, so they
discharge to the foundation drain.
Control of humidity in crawl spaces is important for indoor air quality and per-
formance of wood floor systems. We believe the best current practices to control
humidity involve the use of a vapor retarder or vapor barrier (10 mil minimum)
placed on the soils below accessible subfloor areas. The vapor retarder/barrier
should be sealed at joints and attached to concrete foundation elements. It may be
appropriate to install ventilation systems that are controlled by humidistat.
FOUNDATION WALLS
Foundation walls which extend below -grade should be designed for lateral
earth pressures where backfill is not present to about the same extent on both
sides of the wall, such as in crawl spaces. Many factors affect the values of the de-
sign lateral earth pressure. These factors include, but are not limited to, the type,
compaction, slope, and drainage of the backfill, and the rigidity of the wall against
rotation and deflection.
In general, for a very rigid wall where negligible or very little deflection will
occur, an "at -rest" lateral earth pressure should be used in design. For walls that
can deflect or rotate 0.5 to 1 percent of wall height (depending upon the backfill
types), design for a lower "active" lateral earth pressure may be appropriate. Our
experience indicates below -grade walls in typical buildings deflect or rotate slightly
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under normal design loads, and that this deflection results in satisfactory wall per-
formance. Thus, the earth pressures on the walls will likely be between the "active"
and "at -rest" conditions.
For backfill soils conforming with recommendations in the Foundation Wall
Backfill section that are not saturated, we recommend design of below -grade walls
at this site using an equivalent fluid density of at least 45 pcf. This value assumes
deflection; some minor cracking of walls may occur. If very little wall deflection is
desired, a higher design value for the at -rest condition using an equivalent fluid
pressure of 60 pcf is recommended. An equivalent fluid pressure of 300 pcf can be
used for the "passive" earth pressure case. We should be provided with construc-
tion plans, when available, so we can confirm these recommendations.
SUBSURFACE DRAINAGE
Water from precipitation, snowmelt, and irrigation frequently flows through
relatively permeable backfill placed adjacent to a building and collects on the sur-
face of less permeable soils at the bottom of the foundation excavation. This pro-
cess can cause wet or moist conditions in below -grade areas, such as crawl
spaces, and result in water pressure developing outside foundation walls. If a
structurally -supported floor system with a crawl space is utilized for the building,
we recommend construction of a foundation wall drain around the perimeter of the
crawl space.
The exterior foundation wall drain should consist of 4 -inch diameter, slotted,
PVC pipe encased in free -draining gravel. A prefabricated drainage composite
should be placed adjacent to foundation walls. Care should be taken during back-
fill operations to prevent damage to drainage composites. The drain should dis-
charge via a positive gravity outlet or lead to a sump where water can be removed
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by pumping. Gravity outlets should not be susceptible to clogging or freezing. In-
stallation of clean -outs along the drain pipes is recommended. The foundation wall
drain concepts are shown on Figures 9 and 10.
EARTH RETAINING WALLS
The site plan provided to us indicates a two-tiered earth retaining wall is
proposed to provide lateral support for the structural fill below the south and east
sides of the pool deck and patio area. It appears the wall heights would be less
than 6 feet. The specific earth retaining wall system has not been determined. In
our opinion, mechanically stabilized earth (MSE) structures could be utilized for
these walls.
An MSE structure consists of alternating layers of compacted structural fill
and geogrid reinforcement. Mobilized friction between the geogrid and structural fill
results in a zone of reinforced earth that essentially acts as a gravity retaining
structure. The structure is faced with masonry blocks that are connected to the ge-
ogrid reinforcement. The facing blocks prevent erosion and sloughing of the mate-
rials at the front of the reinforced earth zone and create an aesthetically pleasing
wall. The bottom course of blocks is typically placed on a layer of densely -com-
pacted, granular structural fill. A drainage layer is required behind the facing
blocks. MSE structures are relatively tolerant to ground movement.
CTL can assist with design of MSE structures for the project. We can pro-
vide additional recommendations as architectural plans are further developed. A
survey of existing and proposed grades will be important to facilitate design of the
MSE system.
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POOL CONSTRUCTION
Details showing the planned swimming pool construction, including depth,
were not developed at the time of our investigation. Considering the site surface
conditions, we recommend that the pool footprint be excavated to a depth of at
least 3 feet below the planned bottom of the pool shell. A 2.5 -feet thick layer of
moisture -treated, structural fill in accordance with the Subexcavation and Struc-
tural Fill section should be placed. We recommend placement of a geotextile sepa-
rator fabric above the structural fill. We recommend a 6 -inch thick drain layer of
screened rock with an embedded PVC pipe network between the separator fabric
and the bottom of the pool. The drain pipes should lead to a collector pipe and a
positive gravity outlet.
In many cases, the bottom and sides of pool shells are integrated and con-
structed with concrete or shotcrete. Backside forms for pouring concrete or shot-
crete application for wall construction are often set away from the excavation
sides. Flowable fill (low -strength concrete) is a positive choice to fill the void be-
tween the back of the concrete or shotcrete walls and the excavation sides. The
pool deck should be constructed on a 2 feet thickness of moisture -treated, struc-
tural fill as outlined in the Subexcavation and Structural Fill section.
CTL/Thompson, Inc. should be provided with detailed pool plans, as they become
available, so we can refine our recommendations.
SURFACE DRAINAGE
Surface drainage is critical to the performance of foundations, floor slabs,
and concrete flatwork. Surface drainage should be designed to provide rapid run-
off of surface water away from the proposed buildings and swimming pool area.
Proper surface drainage and irrigation practices can help control the amount of
surface water that penetrates to foundation levels and contributes to heave of soils
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that support foundations, slabs, and other structures. Positive drainage away from
foundations and avoidance of irrigation near foundations also help to avoid exces-
sive wetting of backfill soils, which can lead to increased backfill settlement and
possibly to higher lateral earth pressures, due to increased weight and reduced
strength of the backfill. We recommend the following precautions.
The ground surface surrounding the exterior of the building should
be sloped to rapidly convey surface water off concrete flatwork and
away from the building in all directions. We recommend a minimum
constructed slope of at least 12 inches in the first 10 feet (10 per-
cent) in landscaped areas around the building, where practical.
2. Backfill around the foundation walls should be moisture -treated and
compacted pursuant to recommendations in the Foundation Wall
Backfill section.
3. The building should be provided with roof gutters and downspouts.
The downspouts should discharge well beyond the limits of all back-
fill soils. Splash blocks and/or extensions should be provided at all
downspouts so water discharges onto the ground beyond the back-
fill. We generally recommend against burial of downspout discharge.
Where it is necessary to bury downspout discharge, solid, rigid pipe
should be used, and it should slope to an open gravity outlet.
4. Irrigation should be limited to the minimum amount sufficient to main-
tain vegetation; application of more water will increase likelihood of
slab and foundation movements. Plants placed close to foundation
walls should be limited to those with low moisture requirements. Irri-
gated grass should not be located within 5 feet of the foundation.
Sprinklers should not discharge within 5 feet of foundations. Plastic
sheeting should not be placed beneath landscaped areas adjacent to
foundation walls. Geotextile fabric will inhibit weed growth yet still al-
low natural evaporation to occur.
CONCRETE
Concrete in contact with soil can be subject to sulfate attack. We measured
a water-soluble sulfate concentration of 0.00 percent in one sample of the natural
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CLUBHOUSE AND POOL
PROJECT NO. GS06546.000-125
sandy clay from the site (see Table 1). For low levels of soluble sulfate concentra-
tion, ACI 332-08 indicates there are no special requirements for sulfate resistance.
In our experience, superficial damage may occur to the exposed surfaces of
highly -permeable concrete, even though sulfate levels are relatively low. To con-
trol this risk and to resist freeze -thaw deterioration, the water-to-cementitious ma-
terials ratio should not exceed 0.50 for concrete in contact with soils that are likely
to stay moist due to surface drainage or high-water tables. Concrete should have a
total air content of 6% +/- 1.5%.
CONSTRUCTION OBSERVATIONS
We recommend that CTL I Thompson, Inc. be retained to provide construc-
tion observation and materials testing services for the project. This would allow us
the opportunity to verify whether soil conditions are consistent with those found
during this investigation. If others perform these observations, they must accept
responsibility to judge whether the recommendations in this report remain appro-
priate. It is also beneficial to projects, from economic and practical standpoints,
when there is continuity between engineering consultation and the construction
observation and materials testing phases.
STRUCTURAL ENGINEERING SERVICES
CTL I Thompson, Inc. is a full-service geotechnical, structural, materials, and
environmental engineering firm. Our services include preparation of structural fram-
ing and foundation plans. We can also design earth retention systems. Based on
our experience, CTL I Thompson, Inc. typically provides value to projects from
schedule and economic standpoints, due to our combined expertise and
GREEN LINE ARCHITECTS ,� 7
CLUBHOUSE AND POOL
PROJECT NO. GS06546.000-125
experience with geotechnical, structural, and materials engineering. We can pro-
vide a proposal for structural engineering services, if requested.
GEOTECHNICAL RISK
The concept of risk is an important aspect of any geotechnical evaluation.
The primary reason for this is that the analytical methods used to develop ge-
otechnical recommendations do not comprise an exact science. The analytical
tools which geotechnical engineers use are generally empirical and must be tem-
pered by engineering judgment and experience. Therefore, the solutions or recom-
mendations presented in any geotechnical evaluation should not be considered
risk-free and are not a guarantee that the interaction between the soils and that
the proposed structure will lead to performance as desired or intended. The engi-
neering recommendations in the preceding sections constitute our estimate of
those measures necessary to help the building and structures perform satisfacto-
rily.
This report has been prepared for the exclusive use of the client for the pur-
pose of providing geotechnical design and construction criteria for the proposed
project. The information, conclusions, and recommendations presented herein are
based upon consideration of many factors including, but not limited to, the type of
structures proposed, the geologic setting, and the subsurface conditions encoun-
tered. The conclusions and recommendations contained in the report are not valid
for use by others. Standards of practice continuously change in the area of ge-
otechnical engineering. If the proposed project is not constructed within three
years, we should be contacted to determine if we should update this report.
GREEN LINE ARCHITECTS ,�
CLUBHOUSE AND POOL
PROJECT NO. GS06546.000-125
LIMITATIONS
Our exploratory pits and exploratory borings provide a reasonable charac-
terization of subsurface conditions below the site. Variations in the subsurface
conditions not indicated by the pits and borings will occur. We should be provided
with architectural plans, as they are further developed, so we can provide geotech-
nical/geo-structural engineering input.
This investigation was conducted in a manner consistent with that level of
care and skill ordinarily exercised by geotechnical engineers currently practicing
under similar conditions in the locality of this project. No warranty, express or im-
plied, is made. If we can be of further service in discussing the contents of this re-
port, please call.
rr
CTL I THOMPSON dKWO,
q.,
a es D. Kell644,� °"•a`
Dision Manager`;
JDK:abr
GREEN LINE ARCHITECTS 9
CLUBHOUSE AND POOL
PROJECT NO. GS06546.000-125
0 1000 2000
SCALE: 1' = 2000'
NOTE: SATELLITE IMAGE FROM GOOGLE EARTH
(DATED JUNE 2017)
GREEN LINE ARCHITECTS Vicinity
491 HIGH ASPEN DRNE
PROJECT NO. GS06546.000-125 Map
Fig. 1
0 50 100
SCALE: 1" = 100'
LEGEND:
TP -1 APPROXIMATE LOCATION OF
■ EXPLORATORY PIT
TH---1 APPROXIMATE LOCATION OF
EXPLORATORY BORING
NOTE: SATELLITE IMAGE FROM GOOGLE EARTH
(DATED JUNE 2017)
GREEN LINE ARCHITECTS
491 HIGH ASPEN DRIVE
PROJECT NO. GS06546.000-125
Aerial
Photograph F,A. 2
0 20 40
SCALE: 1" = 40'
LEGEND:
TP -1 APPROXIMATE LOCATION OF
0 EXPLORATORY PIT
TH-1 APPROXIMATE LOCATION OF
• EXPLORATORY BORING
NOTE: BASE DRAWING BY GREEN LINE
ARCHITECTS (DATED APRIL 12, 2021)
TH-i^TP-1GRAM 4 50=
-
TP -2
/r
►ZFJ WT AVRVA
�x
. sroo w yr
0 > \,
o
F
\�
TP -3
o A?
/I
GREEN LINE ARCHITECTS
491 HIGH ASPEN DRIVE
PROJECT NO. GS06546.000-125
Proposed
Construction Fig. 3
0-
m
v
n
m
m
N
5
10
15
at,
25
30
35
TP -1
TP -2 TP -3 TH-1 TH-2
50/12 15/12
'00
22/12 r Tl 18/12
17/12 i /-119/12
31/12 1 TI 22/12
50/9 1. F130/12
TH-3
GREEN LINE ARCHITECTS
491 HIGH ASPEN RANCH
CTLIT PROJECT NO. GS06546.000-125 SUMMARY LOGS OF EXPLORATORY PITS AND BORINGS FIG. 4
LEGEND:
0
AGGREGATE BASE COURSE.
FILL, GRAVEL, CLAYEY, MEDIUM DENSE,
BROWN, GRAY.
7/12 5
CLAY, SANDY, MOIST, STIFF TO VERY STIFF,
BASALT PIECES, BROWN, GRAY, RUST, TAN.
(CH, CL)
13/12 10
INDICATES BULK SAMPLE FROM EXCAVATED SOILS.
DRIVE SAMPLE. THE SYMBOL 50/11.5 INDICATES 50 BLOWS OF
A 140 -POUND HAMMER FALLING 30 INCHES WERE REQUIRED
15/12 15
TO DRIVE A 2.5 -INCH O.D. CALIFORNIA BARREL SAMPLER 11.5
o
INCHES.
m
v
n
m
-mi
NOTES:
18/12 20
1.
EXPLORATORY PITS WERE EXCAVATED WITH A
TRACKHOE ON FEBRUARY 10, 2021. THE PITS WERE
BACKFILLED IMMEDIATELY AFTER EXPLORATORY
EXCAVATION OPERATIONS WERE COMPLETED.
1.
EXPLORATORY BORINGS WERE DRILLED WITH 4 -INCH
25
DIAMETER, SOLID -STEM AUGER AND A
TRACK -MOUNTED DRILL RIG ON APRIL 8, 2021.
3.
GROUNDWATER WAS NOT FOUND IN EXPLORATORY
PITS OR BORINGS AT THE TIME OF EXCAVATION AND
DRILLING. PVC PIPE WAS INTALLED IN TH-1, TH-2, AND
TH-3 TO FACILITATE FUTURE CHECKS OF
30/12 30
GROUNDWATER.
4.
LOCATIONS OF EXPLORATORY PITS AND BORINGS
ARE APPROXIMATE.
5.
THESE LOGS ARE SUBJECT TO THE EXPLANATIONS,
35
LIMITATIONS AND CONCLUSIONS CONTAINED IN THIS
REPORT.
GREEN LINE ARCHITECTS
491 HIGH ASPEN RANCH
CTLIT PROJECT NO. GS06546.000-125 SUMMARY LOGS OF EXPLORATORY PITS AND BORINGS FIG. 4
3
2
1
z 0
O
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z
13-
-1
x
W
0
z -2
O
U)
V)
W -3
a
O
U -4
0.1
APPLIED PRESSURE - KSF
Sample of CLAY, SANDY (CL)
From TH-1 AT 10 FEET
3
2
1
z 0
O
F5
z
Q
a -1
x
W
0
Z -2
O
U)
W
W -3
d
E
O
U -4
1.0
Li
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
10 100
DRY UNIT WEIGHT= 102 PCF
MOISTURE CONTENT= 20.7 %
IEXPANSION UNDER CONSTANTt�`777I
PRESSURE DUE TO WETTING
0.1
APPLIED PRESSURE - KSF
Sample of CLAY, SANDY (CL)
From TH-1 AT 15 FFFT
GREEN LINE ARCHITECTS
491 HIGH ASPEN RANCH
PROJECT NO. GS06546.000-125
1.0
10
100
DRY UNIT WEIGHT= 102 PCF
MOISTURE CONTENT= 23.0 %
Swell -Consolidation
Test Results
FIG. 5
3
2
1
z 0
O
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z
d -1
x
W
0
z -2
O
U)
U)
W -3
W
a
E
O
U -4
0.1
APPLIED PRESSURE - KSF
Sample of CLAY, SANDY (CL)
From TH-1 AT 20 FEET
3
2
1
0
z
O
z
a
x
W -2
0
z
0 -3
W
a
-4
O
U -5
1.0
0.1 1.0
APPLIED PRESSURE - KSF
Sample of CLAY, SANDY (CL)
From TH-2 AT 15 FEET
GREEN LINE ARCHITECTS
491 HIGH ASPEN RANCH
PROJECT NO. GS06546.000-125
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
10 100
DRY UNIT WEIGHT= 102 PCF
MOISTURE CONTENT= 23.0 %
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
10 100
DRY UNIT WEIGHT= 78 PCF
MOISTURE CONTENT= 39.1 %
Swell -Consolidation
Test Results
FIG. 6
3
2
1
0.1
APPLIED PRESSURE - KSF
Sample of CLAY, SANDY (CL)
From TH-2 AT 20 FEET
3
2
1
z 0
O
0)
z
Q
a -1
x
W
0
Z -2
O
W
W -3
a
O
U -4
0.1
APPLIED PRESSURE - KSF
Sample of CLAY, SANDY (CL)
From TH-3 AT 30 FFFT
GREEN LINE ARCHITECTS
491 HIGH ASPEN RANCH
PROJECT NO. GS06546.000-125
1.0
1.0
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
10
100
DRY UNIT WEIGHT= 100 PCF
MOISTURE CONTENT= 23.8 %
EXPANSION UNDER CONSTANT
PRESSURE DUE TO WETTING
10 100
DRY UNIT WEIGHT= 105 PCF
MOISTURE CONTENT= 20.1 %
Swell -Consolidation
Test Results
FIG. 7
Sample of CLAY, SANDY (CL) GRAVEL 31 % SAND 10 %
From TP - 1 AT M FEET SILT & CLAY 59 % LIQUID LIMIT %
PLASTICITY INDEX %
12 %
SILT & CLAY —57% LIQUID LIMIT
%
PLASTICITY INDEX
°fo
Gradation
Test Results
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Sample of CLAY, SANDY (CL) GRAVEL 31 % SAND 10 %
From TP - 1 AT M FEET SILT & CLAY 59 % LIQUID LIMIT %
PLASTICITY INDEX %
sample or CLAY, SANDY (CL)
From TP - 2 AT 5-6 FEET
GREEN LINE ARCHITECTS
491 HIGH ASPEN DRIVE
PROJECT NO. GS06546.000-125
GRAVEL 31 % SAND
12 %
SILT & CLAY —57% LIQUID LIMIT
%
PLASTICITY INDEX
°fo
Gradation
Test Results
•/ 11 // , •, , /
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sample or CLAY, SANDY (CL)
From TP - 2 AT 5-6 FEET
GREEN LINE ARCHITECTS
491 HIGH ASPEN DRIVE
PROJECT NO. GS06546.000-125
GRAVEL 31 % SAND
12 %
SILT & CLAY —57% LIQUID LIMIT
%
PLASTICITY INDEX
°fo
Gradation
Test Results
FIG. 8
STRUCTURAL FLOOR
SLOPE
BACKFILL
PREFABRICATED
DRAINAGE
COMPOSITE
(MIRADRAIN 6000
OR EQUIVALENT)
ATTACH PLASTIC SHEETING
SLOPE
TO FOUNDATION WALL
CRAWL SPACE
PER
f-
OSHA
COVER ENTIRE WIDTH OF
GRAVEL WITH NON -WOVEN
GEOTEXTILEFABRIC IRAFl •�
140N OR E
VAPOR BARRIER
RECOMMENDED
,. .
n4 i•�•';• �...Ar�.
y v .- •
~- 2" MINIMUM
8" MINIMUM
OR BEYOND
1:1 SLOPE FROM
BOTTOM OF FOOTING
(WHICHEVER IS GREATER)
4 -INCH DIAMETER PERFORATED DRAIN PIPE. THE
PIPE SHOULD BE PLACED IN A TRENCH WITH A
SLOPE OF AT LEAST 1/8 -INCH DROP PER FOOT
OF DRAIN.
ENCASE PIPE IN 1/2" TO 1-1/2" SCREENED
ROCK. EXTEND GRAVEL LATERALLY TO FOOTING
AND AT LEAST 1/2 HEIGHT OF FOOTING. FILL
ENTIRE TRENCH WITH GRAVEL
NOTE:
THE BOTTOM OF THE DRAIN SHOULD BE AT LEAST 2 INCHES BELOW BOTTOM OF
FOOTING AT THE HIGHEST POINT AND SLOPE DOWNWARD TO A POSITIVE GRAVITY
OUTLET OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING.
GREEN LINE ARCHITECTS
491 HIGH ASPEN DRIVE
PROJECT NO. GS06546.000-125
Foundation
Wall Drain
Concept
Fig. 9
STRUCTURAL FLOOR
SLOPE
4 -INCH DIAMETER PERFORATED RIGID DRAIN PIPE
THE PIPE SHOULD BE PLACED IN A TRENCH WITH
A SLOPE OF AT LEAST 1/4 -INCH DROP PER
FOOT OF DRAIN.
ENCASE PIPE IN 1/2" TO 1-1/2" WASHED GRAVEL.
FILL ENTIRE TRENCH WITH GRAVEL EXTEND GRAVEL
LATERALLY TO VOID AND AT LEAST 1/2 HEIGHT OF
VOID.
NOTES:
1.) THE BOTTOM OF THE DRAIN SHOULD BE AT LEAST 2 INCHES BELOW BOTTOM OF VOID
AT THE HIGHEST POINT AND SLOPE DOWNWARD TO A POSITIVE GRAVITY OUTLET OR
TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING.
GREEN LINE ARCHITECTS
491 HIGH ASPEN DRIVE
Project No. GS06546.000-125
Foundation
Wall Drain
Concept
Fig. 10
PREFABRICATED
DRAINAGE
COMPOSITE
........ .......
(MIRADRATN 6000
OR EQUIVALENT)
SLOPE
PER
OSHA
ATTACH PLASTIC SHEETING
TO FOUNDATION WALL
�- CRAWL SPACE
COVER ENTIRE WIDTH OF
BACKFlLL_)
GRAVEL WITH NON -WOVEN
GEOTEXTILE FABRIC (MIRAFT
140N OR EQUIVALENT).
VAPOR
VAPOR BARRIER
I ;r•
:;r..
�``/�•'j
VOID
2" MIN. ✓ .......................
4 -INCH DIAMETER PERFORATED RIGID DRAIN PIPE
THE PIPE SHOULD BE PLACED IN A TRENCH WITH
A SLOPE OF AT LEAST 1/4 -INCH DROP PER
FOOT OF DRAIN.
ENCASE PIPE IN 1/2" TO 1-1/2" WASHED GRAVEL.
FILL ENTIRE TRENCH WITH GRAVEL EXTEND GRAVEL
LATERALLY TO VOID AND AT LEAST 1/2 HEIGHT OF
VOID.
NOTES:
1.) THE BOTTOM OF THE DRAIN SHOULD BE AT LEAST 2 INCHES BELOW BOTTOM OF VOID
AT THE HIGHEST POINT AND SLOPE DOWNWARD TO A POSITIVE GRAVITY OUTLET OR
TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING.
GREEN LINE ARCHITECTS
491 HIGH ASPEN DRIVE
Project No. GS06546.000-125
Foundation
Wall Drain
Concept
Fig. 10
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