HomeMy WebLinkAboutSPRING HOLLOW MINOR SUBDIVISION - 12-95 - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTr
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CONSOLIDATION TEST
PRO. 4544
BORING NO.:L2
DEPTH:3.0
DRY DENSITY:LO3.4 PCF
MOISTURE: L8.L%
0.1 0.25 0.5 1.0 5 10
APPLIED PRESSURE - TSF
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APPLIED PRESSURE - TSF
EMPIRE LRBC,RRTORIES INC.
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Empire Laboratories, Inc.
A Division of The Terracon Companies, Inc.
Empire Laboratories, Inc.
GEOTECHNICAL ENGINEERING 8 MATERIALS TESTING
August 3, 1984
Osprey, Inc.
155 Boardwalk Drive, Suite 250
Fort Collins, Colorado 80525
Attention: Mr. Lou Roeder
Gentlemen:
P.O. Box 429 • (303) 484-0359
214 No. Howes • Fort Collins, Colorado 80522
We are pleased to submit our Report of a Geotechnical Investigation
prepared for the proposed apartment units to be constructed in the
Renaissance Center in east -central Fort Collins, Colorado.
The subsurface conditions encountered by this investigation indicate the
site is suitable for the proposed construction, provided that construction _.
is in accordance with the recommendations included in this report. The
attached report contains the subsurface conditions at the site and our
recommendations for development of the site.
We appreciate the opportunity of consulting with you on this project. I'f ri
you have any questions or if we can be of further assistance, please
contact us.
Very truly yours,
EMPIRE LABORATORIES, INC.
Z" '04c�. xo`�
Gary G. Weeks
Geotechnical Engineer
Reviewed
atn W. He
'
otechnicz
cic
cc: RBD, I
P.O. Box 1135
Longmont, Colorado 80502
(303) 776.3921
Branch Offices
P.O. Box 1744
Greeley, Colorado 80632
(303) 351.0460
\�la,�u,f•r
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Member of Consulting Engineers Council
P.O. Box 10076
Cheyenne, Wyoming 82003
(307) 632.9224
pneumatic -tired rollers, three -wheel power rollers, vibratory compactors,
or other approved equipment well -suited to the soil being compacted. If
a sheepfoot roller is used, it shall be provided with cleaner bars
attached in a manner which will prevent the accumulation of material
between the tamper feet. The rollers should be designed so that effective
weight can be increased.
MOISTURE -DENSITY DETERMINATION
Samples of representative fill materials to be placed shall be furnished
by the contractor to the soils engineer for determination of maximum
density and optimum moisture or percent of Relative Density for these
materials. Tests for this determination will be made using methods
conforming to requirements of ASTM D 698, ASTM D 1557, or ASTM D 2049.
Copies of the results of these tests will be furnished to the owner, the
project engineer, and the contractor. These test results shall be the
basis of control for all compaction effort.
DENSITY TESTS
The density and moisture content of each layer of compacted fill willbe
determined by the soils engineer in accordance with ASTM D 1556, ASTM D
2167, or ASTM D 2922. Any material found not to comply with the minimum
specified density shall be recompacted until the required density is
obtained. Sufficient density tests shall be made and submitted to
support the soils engineer's recommendations. The results of density
tests will also be furnished to the owner, the project engineer, and the
contractor by the soils engineer.
�J
PLACING FILL
No sod, brush, frozen or thawing material, or other unsuitable material
shall be placed in the fill, and no fill shall be placed during unfavorable
weather conditions. All clods shall be broken into small pieces, and
distribution of material in the fill shall be such as to preclude the
formation of lenses of material differing from the surrounding material.
The materials shall be delivered to and spread on the fill surface in a
manner which will result in a uniformly compacted fill. Each layer
shall be thoroughly blade mixed during spreading to insure uniformity of
material and moisture in each layer. Prior to compacting, each layer
shall have a maximum thickness of eight inches, and its upper surface
shall be approximately horizontal: Each successive 6" to 8" lift of
fill being placed on ,slopes or hillsides should be benched into the
existing slopes, providing good bond between the fill and existing
ground.
MOISTURE CONTROL
While being compacted, the fill material in each layer shall as nearly
as practical contain the amount of moisture required for optimum compaction
or as specified, and the moisture shall be uniform throughout the fill.
The contractor may be required to add necessary moisture to the fill
material and to uniformly mix the, water with the fill material if, in
the opinion of the soils engineer, it is not possible to obtain uniform
moisture content by adding water on the fill surface. If, in the opinion
of the soils engineer; the material proposed for use in the compacted,
fill is too wet to permit adequate compaction, it shall be dried in an
acceptable manner prior to placement and compaction.
COMPACTION
When an acceptable, uniform moisture content is obtained, each layer
shall be compacted by a method acceptable to the soils engineer and as
specified in the foregoing report as determined by applicable standards.
Compaction shall be performed by rolling with approved tamping rollers,
APPENDIX C.
Suggested Specifications for Placement of Compacted Earth Fill
and/or Backfills.
GENERAL
A soils engineer shall be on -site to provide continuous observation
during filling and grading operations and shall be the owner's repre-
sentative to inspect placement of all compacted fill and/or backfill on
the project. The soils engineer shall approve all earth materials prior
to their use, the methods of placing, and the degree of compaction
obtained.
MATERIALS
Soils used for all compacted fill and backfill shall be approved.by the,
soils engineer prior to their use. The upper two (2) feet of compacted
earth backfill placed adjacent to exterior foundation walls shall be an
impervious, nonexpansive material. No material, including rock, having
a maximum dimension.greater than six inches shall be placed in any fill.
Any fill containing rock should be carefully mixed to avoid nesting and
creation of voids. In no case shall frozen material be used as a fill
and/or backfill material.
PREPARATION OF SUBGRADE
All topsoil, vegetation (including trees and brush), timber, debris,
rubbish, and other unsuitable material shall be removed to a depth
satisfactory to the soils engineer and disposed of by suitable means
before beginning preparation of the subgrade. The subgrade surface of
the area to be filled shall be scarified a minimum depth of six inches,
moistened as necessary, and compacted in a manner specified below for
the subsequent layers of fill. Fill shall not be placed on frozen or
muddy ground.
r-12
APPENDIX C.
SUMMARY OF TEST RESULTS
Boring
Depth
Moisture
Dry
Density
Compressive
Strength
Swell
Pressure
Soluble
Sulfates
pH
Liquid
Limit
Plasticity
Index
G
Group
P
Classification
AASHTO
Resistivity
Penetration
No.
(Ft.)
(%)
(PCF)
(PSF)
(PSF)
(%)
1%)
1%)
Index
LISCS
IOHM-CM)
Blows/In.
11
7.0- 8.0
27.5
89.3
650
8.0- 9.0
18.9
4/12
14.0-15.0
12.5
18/12
12
0.0- 1.5
9.4
2/6
3/12
3.0- 4.0
18.9
25.0
9.9
0.4
SC A-4(0.4)
4.0- 5.0
22.2
3/12
7.0- 8.0
31.4
8.0- 9.0
28.4
3/12
14.0-15.0
8.9
33/12
4/6
13
0.0- 1.5
14.7
7/12
3.0- 4.0
18.5
103.4
1250
4.0- 5.0
26.4
3/12
7.0- 8.0
8.0- 9.0
22.3
5/12
14.0-15.0
12.0
22/12
8/ 6
14
0.0- 1.5
3.7
23/12
7.0- 8.0
11.8
7/12
10.0-11.0
21.6
11.0-12.0-
27.8
2/12
No Rec
very
3/12
L17.0-18.0
EMPIRE LABOHATOHILb, INU.
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SUMMARY OF TEST RESULTS
Boring
No.
Depth
IFt.)
Moisture
(%)
Dry
DIPCFensitj
Compressive
Strength
Swell
Pressure
(PSF)
Soluble
Sulfates
M
pH
Liquid
Limit
(9r,)
Plasticity
Index
W
Group
Index
Classification
AASHTO
USCS
Resistivity
(OHM -CM)
Penetratic
Blows/In.
8
0.0- 1.5
25.8
4/6
3.0- 4.0
18.2
18/12
4.0- 5.0
19.6
7.0-,8.0
28.6
93.7
510
2/12
8.0- 9.0
33.3
14.0-15.0
19.3
3/12
9/12
9
0.0- 1.5
8.8
28.0
9.6
0.0
SC A-2-4(0)
8/6
3.0- 4.0
14.8
109.5
11,740
610
29/12
4.0- 5.0
20.2
7.0- 8.0
26.8
96.5
2880
12/12
8.0- 9.0
27.0
14.0-15.0
26.1
8/ 12
12/12
10
0.0- 1.5
7.6
7/6
3.0- 4.0
16.7
109.5
2380
27.0
11.2
3.0
CL A-6(3)
27/12
4.0- 5.0
23.0
7.0- 8.0
3/12
8.0- 9.0
25.6
14.0-15.0
19.9
2/12
12/12
11
0.0- 1.5
8.3
7/6
3.0- 4.0
19.6
94.0
1380
15/12 ,
4.0- 5.0
19.5
3/12
SUMMARY OF TEST RESULTS
Moisture
Dry-
Denty
Com ressive
Strength
Swell
Pressure
Soluble
Sulfites
pH
Liquid
9
Limit
Plasticity
Index
Group
Index
Classification
A USCS (OHM
Resistivity
-CM)
Penetration
Blows/In.
Boring
Depth
No.
IFt.)
(%)
(PCF)
(PSF)
(PSF)
(%)
8/12
4
8.0- 9.0
18.6
21/12
14.0- 15.0
14.3
5/6
5
0.0- 1.5
11.3
14/12
3.0- 4.0
21.0
92.4
2250
380
7/12
4.0- 5.0
24.6
7.0- 8.0
31.9
88.8
2130
7/12
8.0- 9.0
30.3
25/12
14.0-15.0
24.3
8/ 6
6
0.0- 1.5
9.6
19/12
3.0- 4.0
15.4
106.6
1980
.0046
2/12
4.0- 5.0
48.8
7.0- 8.0
21.3
4/12
8.0- 9.0
34.5
7/12
14.0-15.0
22.2
7/6
15/12
7
0.0- 1.5
9.0
3.0- 4.0
20.1
104.7
810
1/12
4.0- 5.0
27.1
7.0- 8.0
25.8
1/12
8.0- 9.0
28.8
50/9
14.0-14.8
21.6
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SUMMARY OF TEST RESULTS
Boring
Depth
Moisture
Dry
Density
Compressive
Strength
Swell
Pressure
Soluble
Sulfates
pH
Liquid
Limit
Plasticity
Index
Group
Index
Classification
AASHTO
Resistivity
(OHM -CM)
Penetration Slows/In.
No.
(Ft.)
(%)
(PCF)
(PSF)
(PSF)
1%)
(%)
1%)
USCS
1 0.0- 1.5
12.5
T716-
15/12
3.0- 4.0
14.8
84.3
3630
85
.0276
4.0- 5.0
17.5
9/12
7.0- 8.0
33.0
88.5
2460
8.0- 9.0
29.2
4/12
14.0-15.0
22.3
22/12
6/6
2 0.0- 1.5
7.0
14/12
3.0- 4.0
20.3
94.6
3460
8/12
1.0- 5.0
20.8
7.0- 8.0
30.4
8.0- 9.0
29.9
88.5
1880
5/12
18/12
14.0-15.0
No Rec
very
3 0.0- 1.5
9.5
27.7
11.3
0.8
SC A-60 )
4/6
19/
9/12
3.0- 4.0
16.7
99.2
10,320
580
6/12
4.0- 5.0
15.5
14/12
8.0- 9.0
13.7
17/12
14.0-15.0
20.0
5/ 6
4 0.0- 1.5
9.0
15/12
3.0- 4.0-
12.3
99.2
9420
450
.0100
11/12
4.0- 5.0
15.1
7.0- 8.0
7.4
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CONSOLIDI1TION TEST
PRO. 4544
BORING NO.:10
DEPTH:3.0
DRY DENSITY:106.0 PCF
MOISTURE: 17.4
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0.1
0.25 0.5 1.0
APPLIED PRESSURE - TSF
0.25 0.5 1.0
APPLIED PRESSURE - TSF
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CONSOLIDATION TEST PRO.4544
BORING NO.:?
DEPTH: 3.0
DRY DENSITY:l14.2 PCF
MOISTURE: 16.0 %
0.25 0.5 1.0 5 10
APPLIED PRESSURE - TSF
• 0.1 0.25 0.5 1.0 5 10
APPLIED PRESSURE - TSF
EMPIRE LABORATORIES INC.
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SWELL - CONSOLIDATION TEST PRO.4544
BORING NO.:1
DEPTH: 3.0
DRY DENSITY:86.3 PCF
MOISTURE: 31.8 Y.
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APPLIED PRESSURE - TSF
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LOG OF BORINGS
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••EMPIRE LABORATORIES, INC.
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LOG OF BORINGS
6.10 10-11 00-11
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EMPIRE LABORATORIES, INC.
LOG OF BORINGS
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T.B.H. = Top of Manhole; Elevation = 83.0'
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EMPIRE LAWRATORIES, INC.
KEY TO BORING LOGS
TOPSOIL
GRAVEL
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SAND & GRAVEL
SILT
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SILTY SAND & GRAVEL
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CLAYEY SILT
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SANDSTONE BEDROCK
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SILTY SAND
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LIMESTONE
CLAYEYSAND
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SANDY SILTY CLAY
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SHEL'BYTUBE SAMPLE
STANDARD PENETRATION
DRIVE SAMPLER
WATER TABLE 24 HOURS
AFTER DRILLING
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HOLECAVED
5/12 Indicates
that 5 blows of a 140 pound
hammer falling
30 inches was required to penetrate 12 inches.
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_..... FMPIRF I AnORATORIES.IUC. ... ...
APPENDIX A.
this project. In the event that any changes in the design of the
structures or their locations are planned, the conclusions anc
recommendations contained in this report will not be considered vatic
unless said changes are reviewed and conclusions of this report modified
or approved in writing by Empire Laboratories, Inc., the geotechnica'
engineer of record.
Every effort was made to provide comprehensive site coverage
through careful locations of the test borings, while keeping the site
investigation economically viable. Variations in soil and groundwater
conditions between test borings may be encountered during construction.
In order to permit correlation between the reported subsurface conditions
and the actual conditions encountered during construction and to aid in
carrying out the plans and specifications as originally contemplated, it
is recommended that Empire Laboratories, Inc. be retained to perform
continuous construction review during the excavation and foundation
phases of the work. Empire Laboratories, Inc. assumes no responsibility
for compliance with the recommendations included in this report unless
they have been retained to perform adequate on -site construction review
during the course of construction.
-14-
percent (90%) of Standard Proctor Density ASTM D .698-78. -
(See Appendix C.) Puddling should not be permitted as a
method of compaction.
(4) Plumbing and utility trenches underlying slabs and paved areas
should be backfilled with an approved material compacted to at
least ninety-five percent (95%) of Standard Proctor Density
ASTM D 698-78. Puddling should not be permitted as a method
of compaction.
(5) Gutters and downspouts should be. designed to carry roof i
runoff water well beyond the backfill area.
(6) Underground sprinkling systems should be designed such that
piping is placed a minimum of five (5) feet outside the backfill
of the structure. Heads should be designed so that irrigation
water is not sprayed onto the foundation walls. These
recommendations should be taken into account in the landscape
planning.
(7) Footing and/or grade beams sizes should be proportioned to
equalize the unit loads applied to the soil and thus minimize
differential settlements.
(8) It is recommended that compaction requirements in the project
specifications be verified in the field with density tests
performed under the direction of the geotechnical engineer.
(9) It is recommended that a registered professional engineer design
the substructure and that he take into account the findings and
recommendations of this report.
GENERAL COMMENTS
This
report
has been
prepared
to aid
in the
evaluation of
the
property
and to
assist the
architect
and/or
engineer
in the design
of
-13-
All catch basins and manhole castings shall be separated from the
pavement with expansion joint material. The jointing plan shall be
prepared by the contractor and/or architect and approved by the
engineer prior to pavement. Longitudinal and transverse joint spacing
should be at regular ten (10) to thirteen (13) foot intervals. All
longitudinal and transverse contraction joints should have a depth
approximately equal to one-fourth (1 /4) the pavement thickness. • The
joints should be cut within twenty-four (24) hours of pouring.
Expansion joints must be full -depth and should only be used to isolate
fixed objects abutting or within the pavement area. Joint openings
wider than one-fourth (1/4) inch shall be cleaned and sealed before
opening to traffic. A uniform, gritty final surface texture should be
provided. Curing shall be obtained with uniform coverage with white
membrane curing compound or
by seven-day coverage with white polyethylene or waterproof paper.
The completed pavement shall be closed to automobile traffic for three
(3) days and to truck traffic for seven (7) days. If paving is done
during cold weather, cold weather procedures should be used. The
concrete should be protected from freezing temperatures until it is at
least ten (10) days old. n
GENERAL RECOMMENDATIONS
(1) Laboratory test results indicate that water soluble sulfates in
the soil are negligible, and a Type I cement may be used in
concrete exposed to subsoils. Slabs on grade subjected to
de-icing chemicals should be composed of a more durable
concrete with low water -cement ratios and higher air contents.
(2) Finished grade should be sloped away from the structures on all
sides to give positive drainage. Ten percent (10%) for the first
ten (10) feet away from the structures is the suggested slope.
(3) Backfill around
the outside
perimeter
of the
structures
should
be mechanically
compacted at
optimum
moisture
to at least
ninety
-12-
The base course should be placed on the subgrade at or near optimum
moisture and compacted to at least ninety-five percent (95%) of Standard
Proctor Density ASTM D 698-78. (See Appendix C.) It is important that
the base course be shaped to grade so that proper drainage of the parking
area is obtained.
All asphaltic concrete shall meet City of Fort Collins specifications
and shall be placed in accordance with these specifications.
A feasible pavement alternate would be nonreinforced concrete
pavement. Using a modulus of subgrade reaction of one hundred (100)
pounds per square inch per inch, a design life of twenty (20) years,
and concrete with a modulus of rupture of five. hundred fifty (550)
pounds per square inch, the following pavement thicknesses are
recommended:
Passenger Car Parking
Nonreinforced Concrete - 4}" j
Drive Areas j
Nonreinforced Concrete - 5"
Subgrade below the proposed pavement shall be prepared in accordance
with the recommendations discussed in the "Site Grading and Utilities"
section of this report.
All concrete used in the pavement shall meet ASTM specifications,
and all aggregate shall conform to ASTM C-33 specifications. Concrete
should be designed with a minimum modulus of rupture of five hundred
fifty (550) pounds per square inch in twenty-eight (28). days. It is
suggested that a minimum cement content of six (6) sacks be used for
this mix. It is further recommended that laboratory mix designs be done
to determine the proper proportions of aggregate, cement, and water to
meet this requirement. It is essential that the concrete mix have a low
water -cement ratio, an adequate cement factor, and sufficient quantities
of entrained air. It is recommended that the subgrade be in a moist
condition at the time the concrete is placed. The pavement surface
should be free of depressions in which water may stand.
-11-
Grading and Utilities" section of this report. The surface of the subgrade
should be hard, uniform, smooth, and true to grade. To minimize the
growth of weeds, it is suggested that the subgrade under the paved areas
be treated with a soil sterilant.
AASHTC classification of the material from our original and present
Investigations forming pavement subgrade are A-2-4 and A-7-6 with
group indices of 0 to 30. Based upon a group index of 12, the following
pavement thicknesses are recommended:
Passenger Car Parking
Asphaltic Concrete 2}"
Crushed Aggregate Base Course 7"
Total Pavement Thickness 9"
Drive Areas
Asphaltic Concrete 21"
Crushed Aggregate Base Course 10"
Total Pavement Thickness 121"
The base course overlying the subgrade should consist of a hard,
durable, crushed rock or stone and filler and should have a minimum
"12" value of 80. The composite base course material should be.free from
organic matter and lumps or balls of clay and should meet City of Fort
Collins specifications which follow: -
Sieve Size
% Passing
1"
90-100
314"
60-90
#4
30-65
#10
20-55
#200
5-15
Liquid Limit - 25 Maximum
Plasticity Index - 5 Maximum
I
-10-
L
Proctor Density ASTM D 698-78. (See Appendix C.) The drainage
system should be discharged by gravity to an underdrain beneath the
sanitary sewer or the water from the drain should empty into a sump
provided in the garden -level area. The sump should be a minimum of
eighteen (18) inches in diameter and three (3) feet deep. A minimum of
one (1) foot of clean, graded gravel meeting the above specifications
should be placed adjacent to the bottom and sides of the sump. Water
from the sump should be disposed of by suitable means well beyond the
foundation of the building.
It is further recommended that a drain be provided at the toe of the
irrigation ditch on the south end of the site to ensure that any future
seepage is directed away from the building area. The drain should
travel the full length of the site along the toe of the ditch a minimum of
thirty (30) inches below grade for frost protection. The drain should
be constructed in accordance with the recommendations discussed above.
Water collecting in the toe drain should be discharged by gravity to a
sewer underdrain or to a storm sewer.
In view of the soil and groundwater conditions encountered at the
site, it is recommended that the pool be structurally reinforced and
either poured monolithically or gunited. It is recommended that the pool
be underlain with a minimum of four (4) inches of gravel or crushed
rock devoid of fines. The pool should be a minimum of three (3) feet
above the groundwater table or a drain should be provided around the
lower pool area. If this minimum cannot be met, then the pool should be
designed for the uplift created by the buoyancy force of the
groundwater table. It is further recommended that adequate drainage be
provided around the pool so that splash water from the pool is either
directed into underslab drains or back into the pool area.
Pavement
We recommend that the subgrade below the proposed pavement be
prepared in accordance with the recommendations discussed in the "Site
I
used as fill material to support slab -on -grade construction. The
subgrade should be prepared in accordance with the recommendations
discussed in the "Site Grading and Utilities" section of this report.
Slabs on grade in Area 11 should be underlain by a minimum of four
(4) inches of gravel or crushed rock free of fines. The gravel layer
should act as a capillary break and help to distribute floor loads. We
recommend that slabs on grade be designed and constructed Independent
of bearing members. To minimize and control shrinkage cracks which
may develop in slabs on grade, we suggest that control joints be placed
every ten (10) to fifteen (15) feet and that the total area contained
within these joints be no greater than two hundred twenty-five (225)
square feet.
The garden -level slab in the clubhouse as well as the slabs on grade
in the apartment buildings should be placed a minimum of three (3) feet
above the groundwater table. If this three-foot minimum cannot be met,
then a complete dewatering system will be needed. The drainage system
should be placed around the entire perimeter of the building and should
consist of a four (4) inch diameter, open -jointed or perforated tile
running the full length of the trench. The tile should be surrounded
by clean, graded gravel from three -fourths (3/4) inch to the #4 sieve in
accordance with ASTM C 33-78, Size No. 67. The gravel should extend
from at least two inches below the bottom of the tile the full width of the
trench. To minimize the cost of gravel backfill, it is suggested that the
excavation be limited to the area necessary for construction; however,
the trench should be a minimum of twelve (12) inches wide. We
recommend that the drainage tile be placed at least one (1) foot below
the lower level finished floor elevation and have a minimum grade of
one -eighth (1/8) inch per foot. All lower level slabs surrounded by
perimeter drains should be underlain by a minimum of eight (8) inches of
clean, graded gravel or crushed rock devoid of fines.. The top of the
gravel medium should be covered with an untreated building paper to
help minimize clogging of the medium with earth backfill. To minimize
the potential for surface water to enter the system, it is recommended
that a clay backfill be placed over the system and compacted at or near
optimum moisture to at least ninety-five percent (95%) of Standard
-8-
Garden Levei, Draina e System, and Slabs on Grade
Area I
ansive nature of the soils at subgrade
In view of the moderately exp
elevation, it is our opinion that the only solution for construction of a
concrete slab where movement will not occur is a structural floor slab
However, the cost of this system may be
with a void beneath it. .
prohibitive. It is our opinion that a floating floor slab is a reasonable
alternative, knowing that some risk is involved and that certain
precautions should be taken. The owner should be made aware of and
be willing to accept the risk of future slab movement a d ' related
slab
structural damage. The following recommendations may
movement and its adverse affects.
Slabs on grade should be placed directly on the subgrade which has
been prepared in accordance with the recommendations discussed in the
"Site Grading and Utilities" section of this report or directly on the .I
original, undisturbed soil which has been slightly wetted prior to
concrete placement. A sheet of visqueen beneath the slab will help keep
Slabs on grade should be designed and
the subsoils uniformly damp. i
constructed structurally independent of all bearing members.
Nonbearing partition walls placed on the slabs on grade should be
provided with a slip joint (top or bottom). The slip- joints allow some
slab movement with minimal damage to the partition or structure above.
It should be emphasized that if the subgrade soils remain relatively dry,
movement of the slab will be minimized; however, if excess moisture is
allowed to reach the subgrade soils, heaving of the slabs is anticipated.
it should be reemphasized that even with these precautions the
potential for slab movement exists. Slab -on -grade construction should
be undertaken only if the owner is willing to assume the risk of potential
slab heave and possible structural damage.
Area II
The soils encountered at the proposed subgrade elevation in Area 11
are adequate for supporting normal floor loads on grade and may be
-7-
Two separate and distinct bearing conditions were encountered at the
site, and they have been designated Area I and Area II for the purpose
of this report. I
Area I
Area I includes two apartment buildings on the north end of the site
in the area of Borings 1 through 4 and the apartment building on the
southwest portion of the site in the area of Borings 8 through 10.
Footings and/or grade beams founded at the above depths in Area I may
be designed for a maximum allowable bearing capacity of two thousand
two hundred fifty (2250) pounds per square foot (dead load plus
maximum live load). To counteract swelling pressures which may develop
if the subsoils become wetted, footings and/or grade beams should be
designed for a minimum dead load of seven hundred fifty (750) pounds
per square' foot. The predicted settlement under the above maximum
loading, as determined by laboratory consolidation tests, should be less
than one (1) inch, generally considered to be within acceptable
tolerances.
Area II
Area II includes the apartment building in the southeast portion of
the site in the area of Borings 5 through 7 and the clubhouse in the
south portion of the site in the area of Borings 12 and 13. Footings
founded at the above depths in Area II may be designed for a maximum
allowable bearing capacity of one thousand (1000) pounds per square foot
(dead load plus maximum live load). The predicted settlement under the
above maximum loading, as determined by laboratory consolidation tests,
should be less than one (1) inch, generally considered to be within
acceptable tolerances.
M
-6-
in uniform six (6) to eight (8) inch lifts two percent (2%) wet of
optimum moisture and compacted to a minimum of ninety-five percent
(95%) of Standard Proctor Density ASTM D 698-73.
Utility trenches dug four (4) feet or more into the upper soils
should be excavated on slopes no steeper than 1:1. Where utilities are
placed below the groundwater table, the trenches should be dewatered to
ensure proper construction. Bedding material should be placed around
the pipe prior to backfilling to minimize breakage.
Backfill placed in utility trenches outside of pavement and building
areas should be compacted the full depth of the trench in uniform lifts at
optimum moisture to at least ninety percent (90%) of Standard Proctor j
Density ASTM D 698-78. In addition, the upper four (4) feet of the
trench in building, roadway, or parking areas should be compacted to at
least ninety-five percent (95%) of Standard Proctor Density ASTM D
698-78. Addition of moisture to or drying of the subsoils may be .needed
to achieve proper compaction. j
Qualified geotechnical personnel should be present during the
earthwork to observe stripping of the topsoil, scarification of the subgrade,
and placement and compaction of fill. In -place density tests should be
taken in building and pavement areas and utility trenches to assess the
degree of compaction being attained.
Foundations
Based upon the loads transferred to the soil by the proposed
structures and the soil conditions encountered at the site, it is
recommended that the structures be supported by conventional -type
spread footings and/or continuous grade beams. All footings and/or
grade beams should be placed on natural, undisturbed soil a minimum of
twenty-four (24) inches below present grades. in no case should
footings be founded on the existing fill encountered at the site. The
identification and undisturbed nature of the soil should be verified by
the geotechnical engineer prior to placement of foundation concrete.
Exterior footings and/or grade beams should be placed a minimum of
thirty (30) inches below finished grades for frost protection.
-5-
bedrock extends beyond the depths explored. This weathered
portion of the siltstone bedrock exhibits moderate shear and
bearing characteristics.
(6) Groundwater: Free groundwater was encountered at depths
four and one-half (4-1 /2) to fifteen and one-half (15-1 /2) feet
below the surface. Groundwater conditions at the site are
subject to change due to seasonal variations and fluctuations in
the level of the Sherwood Ditch adjacent to the site.
RECOMMENDATIONS AND DISCUSSION
. It is our understanding that four apartment buildings three -stories
high with masonry or wood frame construction are to be built at the
site. The apartment buildings are to be slab on grade construction. A
clubhouse with garden -level construction and a separate swimming pool
are to be located on the south portion of the site.
Site .Grading and Utilities
�3
The upper one-half (1/2) foot of the fill material which is penetrated
by root growth and organic matter should be stripped in proposed
building and pavement areas. This portion of the fill may be stockpiled
and used for site grading outside building and pavement areas. The
upper one (1) foot of the fill material beneath the portion of the. fill
which has been stripped should be scarified and recompacted in place at
two percent (2%) above optimum moisture content . to a minimum of
ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78.
(See Appendix C.) All finished subgrade below building and paved
areas should be placed a minimum of three (3) feet above existing
groundwater. The on -site fill exclusive of the upper one-half (1/2) foot
and the on -site subsoils are suitable for use as fill material. Any
imported fill material to be used in building and/or pavement areas
should be a granular material approved by the geotechnical engineer.
We recommend that fill material in building and pavement areas be placed
-4-
u
i
the surface. The fill is a heterogeneous mixture of sand, silt,
clay,, and fine gravel. The fill should not be used as bearing
material, but may be used as backfill and upon stabilization for
support of slabs on grade and the pavement.
(2) Sandy Silty Clay: The existing fill is underlain by a brown,
tan and red clay except in Boring 12. The sandy silty clay
extends to depths six (6) to fourteen (14) feet below the
surface. The clay layer contains varying amounts of sand and I
silt with minor lenses of sand and fine gravel encountered
within the clay stratum. In situ, the sandy silty clay is damp
to saturated with the drier portions of the clay exhibiting
moderate swell potential. At or near footing depths, the sandy
silty clay exhibits low to moderate shear strengths and bearing
characteristics. i
(3) Clayey Sandy Silt: This silt layer was encountered below the
fill in Boring 12 and below the clay layer at a depth of seven
(7) feet below the surface in Boring 13. The clayey sandy
silty extends to depths nine (9) to eleven and one-half (11-1/2)
feet below the surface. The silt is moist to saturated in its in
situ condition and exhibits low shear strengths and bearing
characteristics.
(4) Silty Sand and Gravel: The clay and silt layers are underlain
by a silty sand and gravel In all test borings. The sand and
gravel extends to depths thirteen (13) feet below the surface to
beyond the depths explored. The saturated silty sand and
gravel exhibits moderate bearing characteristics.
(5) Siltstone Bedrock: The weathered siltstone bedrock was
encountered below the sand and gravel layer in Borings 1, 2,
3, 7, and 10 at depths thirteen (13) to fourteen and one-half
(14-1 /2) feet. below. the surface. The weathered siltstone
-3-
SITE LOCATION AND DESCRIPTION
The site of the proposed construction is located on the southeast
corner of Spring Park Drive and Remington Street in east -central Fort
Collins, Colorado. More specifically, the site can be described as a
tract of land situate in the Northwest 1 /4 of Section 24, Township 7
North, Range 69 West of the Sixth P.M., Fort Collins, Colorado.
The property is an open, grass- and weed -covered site, which
exhibits minor drainage to the north. The site is bordered on the north
by Spring Park Drive, on the east by Matthews Street, on the south by
Dartmouth Avenue, and on the west by Remington Street. Spring Creek
lies north of Spring Park Drive, and the northern portion of the site is
located within the one hundred (100) year flood plain of Spring Creek.
The Sherwood Ditch is located on the north side of Dartmouth Avenue
and parallels the south property line of the site. The ditch is elevated
above the property.
LABORATORY TESTS AND EVALUATION
Representative samples recovered in the test borings were selected
for tests in the laboratory to evaluate their physical characteristics
and engineering properties. Included in the test program were natural
moisture content, water soluble sulfates, Atterberg limits, dry density,
unconfined compressive strength, swell potential, consolidation
characteristics, and swell -consolidation characteristics. Laboratory test
results are summarized in Appendix B.
SOIL AND GROUNDWATER CONDITIONS
The following are the characteristics of the primary soil strata
encountered at the site.
(1) Fill: Fill was encountered at the surface in all test boring
locations and extends to depths one (1) to nine (9) feet below
-2-
REPORT
OF A
GEOTECHNICAL INVESTIGATION
SCOPE
This report presents the results of a geotechnical evaluation
prepared for the proposed apartment units to be constructed in the
Renaissance Center, Fort Collins, Colorado. The investigation included
test borings and laboratory testing of samples obtained from these
borings.
The objectives of this study were to (1) evaluate the subsurface
conditions at the site relative to the proposed construction, (2) make
recommendations regarding the design of the substructures, (3)
recommend certain precautions which should be taken because of adverse
soil and/or groundwater conditions, and (4) make recommendations
regarding pavement types and thicknesses for the proposed parking
areas to be constructed at the site.
SITE EXPLORATION
The field exploration, carried out on July 19, 1984, consisted of
drilling, logging, and sampling fourteen (14) test borings. Eight (8)
borings were previously drilled at the site by Empire Laboratories, Inc.,
August 3, 1981. The locations of the test borings are shown on the
Test Boring Location Plan included in Appendix A of this report.
Boring logs prepared from the field logs are shown in Appendix A.
These logs show soils encountered, location of sampling, and
groundwater at the time of the exploration.
The borings were advanced with a four -inch diameter, continuous -
type, power -flight auger drill. During the drilling operations, a
geotechnical engineer from Empire Laboratories, Inc. was present and
made continuous observations of the soils encountered.
-1-
h
TABLE OF CONTENTS
Table of Contents ..............................................
Letter of Transmittal ..........................................
Report.........................................................
1
Appendix A ....................................................
A-1
Test Boring Location Plan ....................................
A-2
Key to Borings ...............................................
A-3
Log of Borings .............................................:.
A-4
Appendix B....................................................
B-1
Consolidation Test Data ......................................
B -2
Summary of Test Results ......................................
B-6
Appendix C....................................................
C-1
I
REPORT
OF A
GEOTECHNICAL INVESTIGATION
FOR
RENAISSANCE CENTER
FORT COLLINS, COLORADO
OSPREY, INC.,
FORT COLLINS, COLORADO
PROJECT NO. 4544-2-84
CJt7
EMPIRE LABORATORIES, INC.
214 NORTH HOWES STREET,
FORT COLLINS, COLORADO 80521