HomeMy WebLinkAboutWESTBURY PUD - PRELIMINARY - 11-94 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTLinder Real Estate Terracon
ELI Project No. 20945005
1
Field Exploration: A total of four test borings were drilled on January 18, 1994 to a depth of
approximately 15 feet at the locations shown on the Site Plan, Figure 1. The borings were drilled
in areas of the proposed buildings. All borings were advanced with a truck -mounted drilling rig,
utilizing 4-inch diameter solid stem auger.
The location of borings were positioned in the field by pacing from property lines. The accuracy
of boring locations should only be assumed to the level implied by the method used to determine
the locations.
Continuous lithologic logs of each boring were recorded by the engineering geologist during the
drilling operations. At selected intervals, samples of the subsurface materials were taken by
1 means of pushing thin -walled Shelby tubes, or by driving split -spoon barrel samplers.
Penetration resistance measurements were taken with each sampling with the split -spoon by
driving the sampler with a 140-pound hammer falling 30 inches. When properly interpreted, the
penetration resistance is a useful index to the consistency, relative density or hardness of the
materials encountered.
Groundwater conditions were evaluated in each boring at the time of site exploration, and two
days after drilling.
Laboratory Testing: All samples retrieved during the field exploration were returned to the
laboratory for evaluation by the project geotechnical engineer, and were classified in accordance
with the Unified Soil Classification System described in Appendix C. Samples of bedrock were
classified in accordance with the general notes for Bedrock Classification. At that time, the field
descriptions were confirmed or modified as necessary, final boring logs prepared, and an applicable
laboratory testing program was formulated to determine engineering properties of the subsurface
materials. Boring Logs for the project are presented in Appendix A.
Selected soil and bedrock samples were tested for the following engineering properties:
• Water content • Expansion
• Dry density • Plasticity
• Compressive strength
The significance and purpose of each laboratory test is described in Appendix C. Laboratory test
results are presented in Appendix B, and were used for the geotechnical engineering analyses, and
the development of preliminary foundation and earthwork recommendations. All laboratory tests
were performed in general accordance with the applicable ASTM, local or other accepted standards.
2
f
LOG OF BORING No. 4 Page 1 of 1
CLIENT ARCHITECT/ENGINEER
Linder Real Estate I Stewart & Associates
SITE Shields Street & Harmony Road PROJECT
Fort Collins, Colorado I Richardson Farm
SAMPLES
TESTS
0
J
fa
H
DESCRIPTION
}
N
�
zLL
W
z
HF_
0:
=
2
W
I (n
F
O
ZZ
JCn
H
(n
m
W
o
3
0
ow
J(n
a
a
U
E
M
U
Fo
H
>-LL
L)MLL.
WWLL
Q
7Cn(L
O:
O
z
H
W
Nm
E
Od
CnCL(L
co
^ ^ ^
0.5 6" TOPSOIL
LEAN CLAY
CL
1
SS
12"
8
28.9
rz�'
Dark brown, moist
PA
Stiff to -medium stiff
3.0
7.0
WEATHERED SILTSTONE/
CT AYSTONE
Olive, moist, soft
STT TSTONE/CLAYSTONE
Tan/olive, moist, moderately hard
BOTTOM OF BORING
2 ST 1 12"
3 SS 12"
5 PA
10
.0 121 3620 185
d I 4 1 SS 12" I 50 111.0
-I I IPA
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN -SITU, THE TRANSITION MAY BE GRADUAL.
WATER LEVEL OBSERVATIONS
Empire Laboratories
Incorporated
Division of Terracon
BORING STARTED 1-I8-94
WL
g None W.D.
= None A.B.
BORING COMPLETED 1-18-94
WL
RIG CME-55
FOREMAN DML
�'I-
Water checked 24 hrs. A.B.
APPROVED LRS
JOB N 20945005
_
SUMMARY OF TEST RESULTS
Boring
No.
Depth
Ft.
Moisture
%
Dry
Density
(PCF)
Compressive
Strength
(PSF)
Swell
Pressure
(PSF)
Soluble
Sulfates
%
pH
Liquid
Limit
%
Plasticity
Index
%
Group
Index
Classification
AASHTO
USCS
Resistivity
(OHM -CM)
Penetration
Blow/In.
1
.5-1.5
18.3
10/12
4-5
17.6
95.0
1670
95
5-6
15.5
7/12
8-9
14.2
12/12
14-15
12.4
19/1.-,
2
.5-1.5
18.8
14/12
4-5
13.5
11/12
7-8
4.1
118.5
8-9
5.6
26/12
14-15
16.3
11/12
3
.5-1.5
22.0
7/12
3-4
17.8
107.1
3000
33.8
17.5
7.7
A-6(8); CL
4-5
18.0
13/12
8-9
14.9
7/12
14-15
16.1
18/12'
4
.5-1.5
28.9
8/12
3-4
13.0
121.4
3620
185
4-5
12.0
33/12
8-9
11.0
50/12
14-14.4
10.6
50/5
C
r(do
LOG OF BORING No. 3 Page 1 of 1
CLIENT
ARCHITECT/ENGINEER
Linder Real Estate
Stewart & Associates
SITE Shields Street & Harmony Road
PROJECT
Fort Collins, Colorado
Richardson Farm
SAMPLES
TESTS
m
W
0
z
W
F-
>.
x
W
>
O
W
lL
z\
I fA
3
aJ
fA LO
W
M
7
F-
LA
O
E
y
z
W
O
MU
C7 n.
z=
H F-
LL CD
zz
ow
Zfrn
HHJ
7 (A D-
U H
W a-
m W\
0:F-J
WHO-
t_
4: J J
CD
O
U
=
0.
W
DESCRIPTION
L~L
2
F-
a-
O
J
E
}
U)
W
U>_WO
O
""
0.5 6" TOPSOIL
CL
1
SS
12"
7
22.0
LEAN CLAY
Dark brown, moist, medium stiff
PA
0/'//
2.5
34/16/18
CL
2
ST
12"
17.8
107
3000
3
SS
12"
13
18.0
SANDY LEAN CLAY
5
PA
Red/tan, moist
Medium stiff to stiff
4
SS
12"
7
14.9
PA
10
14.5
15
5
SS
12"
18
116.1
15.0 WEATHERED SILTSTONE/
CLAYSTONE
Olive, moist, soft
BOTTOM OF BORING
THE STRATI F1 CAT I= REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN -SITU, THE TRANSITION MAY BE GRADUAL.
WATER LEVEL OBSERVATIONS
BORING STARTED 1-18-94
Empire Laboratories
W-
Q None W.D.
= None A.B.
BORING COMPLETED 1-18-94
Incorporated
Division of Teaacon
W,
RIG CME-55
FOREMAN DML
a I
Water checked 24 hrs. A.B.
APPROVED LRS
JOB s 20945005
LOG OF BORING No. 2
Page 1 of 1
CLIENT
ARCHITECT/ENGINEER
Linder Real Estate
Stewart & Associates
SITE Shields Street & Harmony Road
PROJECT
Fort Collins, Colorado
Richardson Farm
SAMPLES
TESTS
\
>-
r�
J
J
LLL
r_
>-
W
W
coo
Z S
DESCRIPTION
to
w
Z
M
LL CD
H
Lx
w
2
W
>
I fA
H
O
Z Z
a.
U
ca
dU
F-O
H
>-LL
U(xc LL
W
W
M
>.
W
dJ
O
MU
ZH(A
(D
O
O
Z
F-
X
too
E
MO.
7U)(L
0,5 6" TOPSOIL
CL
1
SS
12"
14
18.8
rAA�A
po'
LEAN CLAY
Dark brown, moist, stiff
PA
4.0
CL
2
SS
12"
11
13.5
SANDY LEAN CLAY
WITH GRAVEL
5
PA
Red/tan, moist, medium stiff
7.0
SW
3
ST
12"
4.1
119
4
SS
12"
26
5.6
WELL GRADED
PA
SAND WITH GRAVEL
Red, dry to wet, medium dense
10
i
Q
14.5
15
5
SS
12"
11
16.3
15.0 WEATHERED SILTSTONE/
t0livefmo!iSt,!so�_ft
BOTTOM OF BORING
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN -SITU, THE TRANSITION MAY BE GRADUAL.
WATER LEVEL OBSERVATIONS
BORING STARTED 1-18-94
Empire Laboratories
Incorporated
Division of Tecxacon
WI-
Q 13.6 W.D
= 11.3 A.B.
BORING COMPLETED 1-18-94
wL
RIG CME-55
FOREMAN DML
WL
Water checked 24 hrs. A.B.
APPROVED LRS
JOB k 20945005
r
I
LOG OF BORING No. 1
Page 1 of 1
CLIENT
ARCHITECT/ENGINEER
Linder Real Estate
Stewart & Associates
SITE Shields Street & Harmony Road
PROJECT
Fort Collins, Colorado
Richardson Farm
SAMPLES
TESTS
z
z
H�
z
H
DESCRIPTION
r
N
�
zLL
=
2
W
�
I Cn
F=-
0
zz
JN
0-
F-
a
(n
U
m
s
W
o-
O
c)
3
�_o
m
H
}IL
ow
umu_
J (n
wwu_
x
w
O
(n
M
z
}
H
w
D_
D__i
WM
o
E
zU
ME
zI—m
5ina-
moan
waa
CD
A-A'Al
0.5 6" TOPSOIL
LEAN CLAY
CL
1
SS
12"
10
18.3
Dark brown, moist, stiff
PA
2.0
CANDY LEAN CLAY
WITH GRAVEL
Red/tan, moist, medium stiff
95
CL
2
ST
12"
17.6
95
1670
5
3
SS
12"
7
15.5
PA
8.5
4
SS
12"
12
14.2
PA
WELL GRADED
SAND WITH GRAVEL
Red, moist, medium dense
10
SW
5
SS
12"
19
12.4
�
15.0
15
BOTTOM OF BORING
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES
BETWEEN SOIL AND ROCK TYPES: IN -SITU, THE TRANSITION MAY BE GRADUAL.
WATER LEVEL OBSERVATIONS
Empire Laboratories
IriCOrporated
Division of Terracon
BORING STARTED 17-94
wL
g 14.0 WD•
i 12.1 A.B.
BORING COMPLETED 1-18-94
WL
W.C.I.
W.C.I.
RIG CME-55
FOREMAN DML
WL
Water checked 24 hrs. A.B.
APPROVED LRS
JOB H 20945005
i
Gi. e0 i 4�
�LI. 1� ->• gym, 2o�4soos_ 'Empire Laboratories, Inc.
A Division of The Terracon Companies, Inc.
Linder Real Estate
ELI Project No. 20945005
Terracon
This report is for the exclusive purpose of providing geotechnical engineering and/or testing
information and recommendations. The scope of services for this project does not include, either
specifically or, by implication, any environmental assessment of the site or identification of
contaminated or hazardous materials or conditions. If the owner is concerned about the potential
for such contamination, other studies should be undertaken.
14
Linder Real Estate Terracon
ELI Project No. 20945005
r
• Subsurface Drainage: Free -draining, granular soils containing less than five percent fines
(by weight) passing a No. 200 sieve should be placed adjacent to walls which retain earth.
A drainage system consisting of either weep holes or perforated drain lines (placed near the
base of the wall) should be used to intercept and discharge water which would tend to
saturate the backfill. Where used, drain lines should be embedded in a uniformly graded
filter material and provided with adequate clean -outs for periodic maintenance. An
impervious soil should be used in the upper layer of backfill to reduce -the potential for
water infiltration.
GENERAL COMMENTS
JIt is recommended that the Geotechnical Engineer be retained to provide a general review of final
design plans and specifications in order to confirm that grading and foundation recommendations
have been interpreted and implemented. In the event that any changes of the proposed project
t are planned, the conclusions and recommendations contained in this report should be reviewed
and the report modified or supplemented as necessary.
The Geotechnical Engineer should also be retained to provide services during excavation, grading,
foundation and construction phases of the work. Observation of pier and/or footing excavations
should be performed prior to placement of reinforcing and concrete to confirm that satisfactory
bearing materials are present and is considered a necessary part of continuing geotechnical
engineering services for the project. Construction testing, including field and laboratory evaluation
of fill, backfill, pavement materials, concrete and steel, should be performed to determine whether
applicable project requirements have been met. It would be logical for Empire Laboratories, Inc.
to provide these additional services since we are most qualified to determine consistency of field
conditions with those data used in our analyses.
The analyses and recommendations in this report are based in part upon data obtained from the
field exploration. The nature and extent of variations beyond the location of test borings may not
I become evident until construction. If variations then appear evident, it may be necessary to
reevaluate the recommendations of this report.
j Our professional services were performed using that degree of care and skill ordinarily exercised,
under similar circumstances, by reputable geotechnical engineers practicing in this or similar
l localities. No warranty, express or implied, is made. We prepared the report as an aid in design
of the proposed project. This report is not a bidding document. Any contractor reviewing this
report must draw his own conclusions regarding site conditions and specific construction
techniques to be used on this project.
i'
13
rZ
Linder Real Estate
ELI Project No. 20945005
Terracon
encountered at the time of construction, the actual conditions should be evaluated to
determine any excavation modifications necessary to maintain safe conditions.
As a safety measure, it is recommended that all vehicles and soil piles be kept to a
Jminimum lateral distance from the crest of the slope equal to no less than the slope height.
The exposed slope face should be protected against the elements.
The contractor should retain a geotechnical engineer to monitor the soils exposed in all
excavations and provide engineering services for slopes. This will provide an opportunity
to monitor the soil types encountered and to modify the excavation slopes as necessary.
It also offers an opportunity to verify the stability of the excavation slopes during
construction.
Drainage:
• Surface Drainage:
1. Positive drainage should be provided during construction and maintained throughout
the life of the proposed residences. Infiltration of water into utility or foundation
excavations must be prevented during construction. Planters and other surface
features which could retain water in areas adjacent to the residences or pavements
should be sealed or eliminated.
2. In areas where sidewalks or paving do not immediately adjoin the structures, we
recommend that protective slopes be provided with a minimum grade of
approximately 10 percent for at least 10 feet from perimeter walls. Backfill against
footings, exterior walls, and in utility and sprinkler line trenches should be well
compacted and free of all construction debris to reduce the possibility of moisture
infiltration.
3. Downspouts, roof drains or scuppers should discharge into splash blocks or
extensions when the ground surface beneath such features is not protected by
exterior slabs or paving.
4. Sprinkler systems should not be installed within 5 feet of foundation walls.
Landscaped irrigation adjacent to the foundation system should be minimized or
eliminated.
12
Linder Real Estate Terracon
ELI Project No. 20945005
Miscellaneous backfill................................ 90
5. If a well defined maximum density curve cannot be generated by impact compaction
in the laboratory for any fill type, engineered fill should be compacted to a minimum
of 80 percent relative density as determined by ASTM D4253, D4254.
6. On -site clay soils beneath pavements should be compacted within a moisture
content range of 2 percent below to 2 percent above optimum. On -site clay soils
beneath foundations should be compacted within a moisture range of optimum to
2 percent above optimum.
• Slopes:
1. For permanent slopes in compacted fill areas, recommended maximum
configurations for on -site materials is 2'/z:1 (horizontal to vertical). If steeper slopes
are required for site development, stability analyses should be completed to design
the grading plan.
• Compliance: Performance of slabs -on -grade, foundations and pavement elements
supported on compacted fills or prepared subgrade depends upon compliance with
"Earthwork" recommendations. To assess compliance, observation and testing should be
performed under the direction of the geotechnical engineer.
• Excavation and Trench Construction: Excavations into the on -site soils will encounter
caving soils and possibly groundwater, depending upon the final depth of excavation. The
individual contractor(s) should be made responsible for designing and constructing stable,
temporary excavations as required to maintain stability of both the excavation sides and
bottom. All excavations should be sloped or shored in the interest of safety following
local, and federal regulations, including current OSHA excavation and trench safety
standards.
If any excavation, including a utility trench, is extended to a depth of more than 20 feet,
it will be necessary to have the side slopes designed by a professional engineer.
The soils to be penetrated by the proposed excavations may vary significantly across the
site. The preliminary soil classifications are based solely on the materials encountered in
widely spaced exploratory test borings. The contractor should verify that similar conditions
exist throughout the proposed area of excavation. If different subsurface conditions are
11
(if f 4
I
Linder Real Estate
ELI Project No. 20945005
Terracon
• general site grading • exterior slab areas
0 foundation areas • pavement areas
• interior floor slab areas • foundation backfill
2. On -site bedrock materials are not recommended for use beneath structural ares of
the site or as backfill. Should bedrock materials be used for general site grading,
placement in fills at non-structural locations on the site is recommended.
3. Select granular materials should be used as backfill behind walls which retain earth.
4. Frozen soils should not be used as fill or backfill.
5. Aggregate base should conform to Colorado Department of Transportation Class 5
or 6 specifications.
0 Placement and Compaction:
1. Place and compact fill in horizontal lifts, using equipment and procedures that will
produce recommended moisture contents and densities throughout the lift..
2. Uncompacted fill lifts should not exceed 10 inches loose thickness.
3. No fill should be placed over frozen ground.
4. Materials should be compacted to the following:
Material
Minimum Percent
Compaction (ASTM D698)
On -site soils or approved imported fill:
Beneath foundations ............................ 95
Ronoath Blahs ................................ 95
Beneath pavement ............................. 95
Utility trenches beneath construction (upper 4 feet) ...... 95
Utility trenches beneath construction (below 4 feet) ...... 90
Utility trenches in open areas ...................... 90
Aggregate base (beneath pavement) ...................... 95
10
Linder Real Estate
ELI Project No. 20945005
Terracon
2. Excavations penetrating the claystone-siltstone bedrock may require the use of
specialized heavy-duty equipment.
3. Depending upon depth of excavation and seasonal conditions, groundwater may be
encountered in excavations on the site. Pumping from sumps may be utilized to
control water within excavations.
• Slab Subarade Preparation:
1. Where existing clay soils will support floor slabs, the soils should be scarified,
moisture -conditioned and compacted to a minimum depth of 6 inches.
2. A minimum 4-inch layer of clean -graded gravel should be placed beneath slabs.
3. A minimum 8-inch layer of free -draining gravel should be placed beneath basement
floor slabs in conjunction with the underslab drainage system.
i
• Pavement SubQrade Preparation:
1'
1. The subgrade should be scarified, moistened as required, and recompacted for a
minimum depth of 6 inches prior to placement of fill and pavement materials.
2. On -site clay soils may pump or become unstable or unworkable at high water
contents. Workability may be improved by scarifying and drying. Overexcavation
of wet zones and replacement with granular materials may be necessary.
Lightweight excavation equipment may be required to reduce subgrade pumping.
Use of lime, fly ash, kiln dust, cement or geotextiles could also be considered as a
stabilization technique. Laboratory evaluation is recommended to determine the
effect of chemical stabilization on subgrade soils prior to construction.
• Fill Materials:
1. Clean on -site soils or approved imported materials may be used as fill material for
the following:
9
Linder Real Estate Terracon
ELI Project No. 20945005
Although fills or underground facilities, such as septic tanks, cesspools, basements, and/or
utilities, were not observed during site reconnaissance, such features might be encountered
during construction.
• Site Clearing:
1. Strip and remove existing vegetation and other deleterious materials from proposed
building and pavement areas.
2. If unexpected fills or underground facilities are encountered during site clearing,
such features should be removed and the excavation thoroughly cleaned prior to
backfill placement and/or construction. All excavations should be observed by the
geotechnical engineer prior to backfill placement.
3. Stripped materials consisting of vegetation and organic materials should be wasted
from the site or used to revegetate exposed slopes after completion of grading
operations.
4. Drainage blankets, consisting of free -draining gravel enclosed in filter fabric, should
be placed in any natural drainage beneath fill sections which exceed 12 feet in
height. Drainage blankets should be led to a positive gravity discharge.
5. Sloping areas steeper than 2:1 (horizontal: vertical) should be benched to reduce the
potential for slippage between existing slopes and fills. Benches should be level and
wide enough to accommodate compaction and earth moving equipment.
6. The site should be initially graded to create a relatively level surface to receive fill
and to provide for a relatively uniform thickness of fill beneath proposed building
structures.
7. All exposed areas which will receive fill, once properly cleared and benched where
�. necessary, should be scarified to a minimum depth of 6 inches, conditioned to near
optimum moisture content, and compacted.
• Excavation:
1. It is anticipated that excavations into the on -site soils can be accomplished with
l conventional earth -moving equipment.
tea:
8
Linder Real Estate Terracon
ELI Project No. 20945005
Basement Construction: Groundwater was encountered at depths of 11 to 12 feet in the
northwest portion of the site. At the present time, it appears full -depth basement construction
is feasible in this area, provided the basement excavation extends no deeper than 7 feet below
existing grade. However, it is recommended that the groundwater level in the northwest portion
of the site be monitored for a sufficient period of time to better determine the need for complete
underslab dewatering systems in this area.
a Groundwater was not encountered in the south portion of the site to the maximum depth of
exploration, 15 feet. Therefore, full -depth basement construction is considered acceptable in this
i
area. However, water seepage may occur when water runs through the canal in the southwest
portion of the property. In addition, a perched water table may occur on the surface of the
shallow bedrock in the southeast portion of the property. Therefore, complete underslab
dewatering systems are recommended for basements constructed in the south portion of the
property east of the canal.
Floor Slab Design and Construction Within 2 Feet of Bedrock: The development of substantial
swelling pressures within the claystone-siltstone bedrock near approximate slab subgrade elevation
could result in differential movement of floor slab -on -grade if the potentially expansive bedrock
increases in moisture content. Use of structural floor systems, structurally supported independent
of the subgrade, is a positive means of eliminating the potentially detrimental effects of floor
movement. It is our opinion that with certain precautions and knowing that some risk is involved,
a floating floor slab may be a reasonable alternative. If the owner is willing to assume the risk of
future slab movement and related structural damage, the subgrade soils should be prepared as
outlined in the "Earthwork" section of this report.
Floor Slab Design and Construction On At Least 2 Feet of Nonexaansive Soils: Where non -
expansive, or low -swelling soils will be supporting the floor slabs, some differential movement of
a slab -on -grade floor system is possible should the subgrade soils increase in moisture content.
Such movements are considered within general tolerance for normal slab -on -grade construction.
To reduce any potential slab movements, the subgrade soils should be prepared as outlined in the
"Earthwork" section of this report.
Earthwork:
® 0 General Considerations: The conclusions contained in this report for the proposed
-;, construction are contingent upon compliance with recommendations presented in this
section.
0
7
�3
,10
Linder Real Estate
ELI Project No. 20945005
Terracon
For axial compression loads, piers may be design for a maximum end -bearing pressure between
15,000 and 25,000 pounds per square foot (psf), and skin friction between 1,500 and 2,500 psf
for the portion of the pier in unweathered bedrock.
Required pier penetration should be balanced against potential uplift forces due to expansion of
the subsoils and bedrock on the site. For design purposes, the range of uplift force on each pier
can be determined on the basis of the following equation:
Uo = [15 to 201 x D
Where: up = the uplift force in kips, and
D = the pier diameter in feet
Uplift forces on piers should be resisted by a combination of dead -load and pier penetration below
a depth of 7 feet and in the bearing strata.
Drilling to design depths should be possible with conventional single flight power augers. Shafts
will probably remain open without stabilizing measures. However, pier concrete should be placed
soon after completion of drilling and cleaning. Due to potential sloughing and raveling, foundation
concrete quantities may exceed calculated geometric volumes. Pier concrete with slump in the
range of 5 to 7 inches is recommended.
l FoundationSystems - West Portion of the Site: Due to the presence of low -swelling soils on the
west portion of the site, spread footing foundations' bearing upon undisturbed subsoils are
recommended for support for the proposed residences in this area. The footings may be designed
fora maximum bearing pressure between 1,500 and 2,00 psf. Exterior footings should be placed
a minimum of 30 inches below finished grade for frost protection. Interior footings should bear
a minimum of 12 inches below finished grade.
Finished grade is the lowest adjacent grade for perimeter footings and floor level for interior
l footings. The design bearing capacities apply to dead loads plus design live load conditions.
d Foundations and masonry walls should be reinforced as necessary to reduce the potential for
distress caused by differential foundation movement. The use of joints at openings or other
discontinuities in masonry walls is recommended.
Foundation excavations should be observed by the geotechnical engineer. If the soil conditions
encountered differ significantly from those presented in this report, supplemental recommendations
will be required.
6
Linder Real Estate Terracon
ELI Project No. 20945005
Because of variations in the engineering properties of the on -site soils and bedrock, foundation
bearing levels, structural loads, and possible final grades, the following foundation systems were
evaluated for use on the site:
• grade beams and straight shaft piers drilled in to bedrock; and
• spread footings bearing on undisturbed soils.
Design criteria for alternate foundation systems is subsequently outlined. Use of the alternative
foundation systems outlined in this report should be determined for individual residential structures
on the basis of supplemental geotechnical exploration of each lot prior to construction.
J Slab -on -grade construction, for basement or garage areas, is considered acceptable for use when
subgrade soils consist of the on -site clays or well -graded sands with gravel, provided that design
and construction recommendations are followed. Given the engineering characteristics of
siltstone-claystone bedrock, consideration should be given to use of structural floor systems in
basement areas where the bedrock will be encountered. Evaluation of expansion tests conducted
on individual lots during supplemental geotechnical exploration is recommended to assess the need
1 for structural floor systems.
Due to the potential for seepage to occur along the canal in the southwest portion of the site and
the potential for a perched water table to form on the shallow bedrock in the southeast portion
of the site, a complete underslab dewatering system is recommended for any basements
1 constructed in the south portion of the property east of the canal.
The need for complete underslab dewatering systems for basements constructed in the northwest
portion of the property should be determined after the groundwater level has been monitored for
a sufficient period of time in this area.
Consideration should be given to (1) constructing a toe drain along the east side of the canal and
(2) constructing an area drain which would empty into the proposed detention area in the
southeast corner of the property.
Foundation Systems - Southeast Portion of Site: Due to the presence of shallow and potentially
Jexpansive claystone-siltstone bedrock in the southeast portion of the site, a grade beam and drilled
pier foundation system is recommended for support of proposed residences in this area. Straight
shaft piers, drilled a minimum of 5 feet into the unweathered bedrock, with a minimum shaft
Jlength of 10 feet are recommended.
IJ
5
Linder Real Estate Terracon
ELI Project No. 20945005
bedrock encountered in Boring 4 is highly weathered; however, the underlying bedrock
encountered in Boring 4 is moderately hard.
Field and Laboratory Test Results: Field test results indicate that the clay soils vary from medium
j stiff to stiff in consistency. The underlying granular soils are medium dense. The weathered and
unweathered bedrock are soft and moderately hard, respectively. The soils and bedrock at
anticipated foundation bearing depths have moderate and high load bearing capabilities,
—� respectively.
I� Preliminary laboratory test results indicatethat the clay subsoils and weathered siltstone-claystone
bedrock have low expansive potential.
Groundwater Conditions: Groundwater was encountered at depths of 13'/z to 14 feet in Borings
1 and 2 at the time of field exploration. When checked two days after drilling, groundwater was
measured at. depths of 11 to 12 feet in these borings. Groundwater was not encountered in
Borings 3 and 4 at the time of field exploration, nor when checked two days after drilling. These
— observations represent only current groundwater conditions, and may not be indicative of other
times, or at other locations. Groundwater levels can be expected to fluctuate with varying
seasonal and weather conditions.
Zones of perched and/or trapped groundwater may also occur at times in the subsurface soils
1 overlying bedrock, on top of the bedrock surface or within permeable fractures in the bedrock
materials. The location and amount of perched water is dependent upon several factors, including
hydrologic conditions, type of site development, irrigation demands on or adjacent to the site,
fluctuations in water features, and seasonal and weather conditions.
Fluctuations in groundwater levels can best be determined by implementation of a groundwater
monitoring plan. PVC pipe was installed in each test boring at the time of drilling. Groundwater
levels should be measured periodically in the test borings over a sufficient period of time.
The possibility of groundwater fluctuations should be considered when developing design and
construction plans for the project.
CONCLUSIONS AND RECOMMENDATIONS
Site Development Considerations: The site appears suitable for the proposed construction.
Potentially expansive bedrock will require particular attention in the design and construction of the
residences.
4
E
Linder Real Estate
ELI Project No. 20945005
SITE CONDITIONS
Terracon
The site consists of approximately 21.7 acres of an L-shaped tract of land near the southwest
corner of West Harmony Road and South Shields Street, south of Fort Collins, Colorado.
Approximately 7'Y2 acres of land directly at the southwest corner of West Harmony Road and
South Shields Street are not included as part of this exploration. The south portion of the site is
vegetated with low grasses. The north portion of the site is vegetated with low grasses and a
thick growth of small trees. The Pleasant Valley and Lake Canal runs through the southwest
portion of the site. The property is bordered by West Harmony Road to the north, two single-
family residences and Crest Gallery to the northeast, South Shields Street to the east, a pasture
to the south and a small open area, a ditch and The Ridge Subdivision to the west. The area
exhibits slight surface drainage to the east.
SUBSURFACE CONDITIONS
Soil and Bedrock Conditions: As presented on the Logs of Boring, the subsurface soils were
encountered in order of increasing depths as follow:
•. Topsoil: The areas tested are overlain by a '/z-foot layer of silty topsoil. The topsoil has
been penetrated by root growth and organic matter and should not be used as a bearing
soil or as a fill and/or backfill material.
• Lean Clay: A layer of dark brown lean clay was encountered below the topsoil and extends
to depths of 2 to 4 feet below the surface.
• Sandy Lean Clay (With Gravel): A layer of red sandy lean clay with and without gravel was
encountered below the upper dark brown lean clay layer in Borings 1, 2 and 3 and extends
to depths of 7 to 14'/2 feet below the surface.
• Well -Graded Sand With Gravel: The granular stratum was encountered below the lower
red clay layer in Borings 1 and 2 and extends to the underlying bedrock stratum or to the
depth explored.
• Siltstone-Claystone Bedrock: The bedrock stratum was encountered at a depth of 14Yz
feet below the surface in Borings 2 and 3 and at a depth of 3 feet below the surface in
Boring 4. The Yz-foot of bedrock encountered in Borings 2 and 3 and the upper 4 feet of
3
EJ
IPRELIMINARY GEOTECHNICAL ENGINEERING REPORT Terracon
RICHARDSON FARM
HARMONY ROAD AND SHIELDS STREET
SOUTH OF FORT COLLINS, LARIMER COUNTY, COLORADO
ELI PROJECT NO. 20945005
JANUARY 26,1994
INTRODUCTION
This report contains the results of our preliminary geotechnical engineering exploration for the
proposed project to be located south of Harmony Road and west of Shields Street, south of Fort
Collins, Colorado. The site is located in the Northeast 1 /4 of the Northeast 1 /4 of Section 3,
Township 6 North, Range 69 West of the 6th Principal Meridian.
The purpose of these services is to provide information and preliminary geotechnical engineering
recommendations relative to:
• subsurface soil and bedrock conditions
• groundwater conditions
• foundation design and construction
• basement construction
• floor slab design and construction
• earthwork
• drainage
The conclusions and recommendations contained in this report are based upon the results of field
and laboratory testing, engineering analyses, and experience with similar soil and structural
conditions.
PROPOSED CONSTRUCTION
It is our understanding the site will be developed for a residential subdivision, including a total of
approximately 65 residential building lots. Although final site grading plans were not available
prior to preparation of this report, ground floor levels are anticipated to be at or near existing site
grades.
SITE EXPLORATION
The scope of the services performed for this project included site reconnaissance by an
engineering geologist, a subsurface exploration program, laboratory testing and engineering
3
analyses.
Linder Real Estate Terracon
ELI Project No. 20945005
We recommend the proposed residences in the east portion of the site be supported on a grade
beam and straight -shaft pier foundation system. Given the engineering characteristics of near
surface bedrock which may support slabs in this area, consideration should be given to the use
of structural floor systems if no movement can be tolerated.
Other design and construction details, based upon geotechnical conditions, are presented in the
report.
We have appreciated being of service to you in the preliminary geotechnical engineering phase of
this project, and are prepared to assist you during the construction phases as well. If you have
any questions concerning this report or any of our testing, inspection, design and consulting
services, please do not hesitate to contact us.
Sincerely,
EMPIRE LABORATORIES, INC.
A Division of The Terracon Companies, Inc.
R , �Saw_YLP
sa R. Schoenfeld, P.E.
Geotechnical Engineer
Reviewed by:
Chester C. Smith, P.E.
Division Manager
LRS/CCS/cic
Copies to: Addressee (3)
� �..• c°SC HG °a T/�
C.
4808
Empire
Laboratories, Inc.
A Division of The Terracon Companies, Inc.
P.O. Box 503 • 301 No. Howes
Fort Collins, Colorado 80522
(303) 484-0359
FAX No. (303) 484-0454
Chester C. Smith, P.E.
Neil R. Sherrod, C.P.G.
January 26, 1994
Linder Real Estate
3500 JFK Parkway, Suite 221
Fort Collins, Colorado 80525
Attn: Mr. Mark Linder
Re: Preliminary Geotechnical Engineering Report, Richardson Farm
Harmony Road and South Shields Street
South of Fort Collins, Larimer County, Colorado
ELI Project No. 20945005
Empire Laboratories, Inc. (ELI) has completed a preliminary geotechnical engineering exploration
for the proposed project to be located south of Harmony Road and west of Shields Street, south
of Fort Collins, Colorado. This study was performed in general accordance with our proposal
number D2094008 dated January 12, 1994.
The results of our preliminary engineering study, including the boring location diagram, laboratory
test.results, test boring records, and the preliminary geotechnical recommendations needed to aid
in the design and construction of foundations and other earth connected phases of this project are
attached.
The subsurface exploration indicated conditions which are typical of soils commonly found in the
Fort Collins area. The subsurface soils at the site generally consisted of lean clay and sandy lean
clay overlying well -graded sand with gravel and claystone-siltstone bedrock. The information
obtained by the results of field exploration and laboratory testing completed for this study
indicates that the soils and bedrock at the site have low expansive potential. The soils at
anticipated foundation bearing depth have moderate load bearing capability. The bedrock at
anticipated foundation bearing depth has high load bearing capability.
Based on the preliminary geotechnical engineering analyses, subsurface exploration and laboratory
test results, we recommend that the proposed residences in the west portion of the site be
supported on a spread footing foundation system. Slab -on -grade may be utilized for the interior
t floor systems provided that care is taken in the placement and compaction of the subgrade soil.
Offices of The Terracon Companies, Inc. Geotechnical, Environmental and Materials Engineers
Arizona: Tucson ■ Colorado. Colorado Springs, Denver, Ft. Collins, Greeley, Longmont N Idaho: Boise E Illinois: Bloomington,
Chicago, Rock Island ■ Iowa: Cedar Falls, Cedar Rapids, Davenport, Des Moines, Storm Lake E Kansas: Lenexa, Topeka,
Wichita ■ Minnesota: St. Paul g Missouri: Kansas City ■ Nebraska: Lincoln, Omaha 0 Nevada: Las Vegas
■ Oklahoma: Oklahoma City, Tulsa ■ Texas: Dallas ■ Utah: Salt Lake City 0 Wyoming: Cheyenne
QUALITY ENGINEERING SINCE 1965
Linder Real Estate
ELI Project No. 20945005
TABLE OF CONTENTS (Cont'd)
Terracon
APPENDIX A
Figure No.
SITEPLAN ......................................................... 1
Logs of Borings ..........................................
Al thru A4
APPENDIX B
Summary of Test Results .........................................
131
APPENDIX C: GENERAL NOTES
Drilling & Exploration ............................................
C1
Unified Soil Classification .........................................
C2
Bedrock Classification, Sedimentary Bedrock ............................
C3
Laboratory Testing, Significance and Purpose
........................... C4
Report Terminology .............................................
C5
/-
Linder Real Estate Terracon
ELI Project No. 20945005
TABLE OF CONTENTS
Page No.
Letter of Transmittal................................................... ii
INTRODUCTION..................................................... 1
PROPOSED CONSTRUCTION ........................................... 1
SITEEXPLORATION .................................................. 1
Field Exploration ............................................... 2
Laboratory Testing .............................................. 2
SITE CONDITIONS ................................................... 3
SUBSURFACE CONDITIONS ............................................ 3
Soil and Bedrock Conditions ....................................... 3
. Field and Laboratory Test Results .................................... 4
Groundwater Conditions .......................................... 4
CnNCIusInNS AND RECOMMENDATIONS ................................. 4
Site Development Considerations ....................................
4
Foundation Systems - Southeast Portion of Property ......................
5
' Foundation Systems - West Portion of the Site ..........................
6
Floor Slab Design and Construction Within 2 Feet of Bedrock ................
6
Floor Slab Design and Construction On At Least 2 Feet of Natural Soils .........
6
Earthwork....................................................
7
General Considerations ......................................
7
Site Clearing .............................................
7
Excavation..............................................
8
Slab Subgrade Preparation ....................................
8
Pavement Subgrade Preparation ................................
8
FillMaterials .............................................
9
Placement and Compaction ...................................
9
Slopes................................................
10
Compliance.............................................
10
Excavation and Trench Construction ..........................
11
Drainage ....................................................
11
SurfaceDrainage ......................................
11
Subsurface Drainage .......................................
12
GENERAL COMMENTS ...............................................
12
PRELIMINARY GEOTECHNICAL ENGINEERING REPORT
Now KAfowN kt
RICHARDSON FARM o wLsrmkky
HARMONY ROAD AND SHIELDS STREET
SOUTH OF FORT COLLINS, LARIMER COUNTY, COLORADO
ELI PROJECT NO. 20945005
Prepared for.
LINDER REAL ESTATE
3500 JFK PARKWAY, SUITE 221
FORT COLLINS, COLORADO 80525
ATTN: MR. MARK LINDER
Empire Laboratories, Inc.
A Division of the Terracon Companies, Inc.
PRELIMINARY GEOTECHNICAL ENGINEERING REPORT
Now Kovow'v kt
RICHARDSON FARM o wFrr"BURY
HARMONY ROAD AND SHIELDS STREET
SOUTH OF FORT COLLINS, LARIMER COUNTY, COLORADO
ELI PROJECT NO. 20945005
A Division of
The Terracon Companies, Inc.
0