HomeMy WebLinkAboutSTONERIDGE PUD, FIRST FILING FINAL - 21-92D - SUBMITTAL DOCUMENTS - ROUND 1 - GEOTECHNICAL (SOILS) REPORTREPORT
OF A
GEOTECHNICAL INVESTIGATION
FOR
STONE RIDGE P.U.D.
FORT COLLINS, COLORADO
MR. LESTER KAPLAN
FORT COLLINS, COLORADO
PROJECT NO. 9271-92
CI
EMPIRE LABORATORIES, INC.
301 NORTH HOWES STREET
FORT COLLINS, COLORADO 80521
A
above maximum loading, as determined by laboratory consolidation tests,
should be less than three -fourths (3/4) inch, generally considered to be
within acceptable tolerances.
The upper clay soils encountered at the site are plastic and may be
susceptible to swelling if they are allowed to dry below their in situ
moisture levels and then are rewetted. Therefore, to prevent drying of
the clay soils below their in -place moisture levels, foundation and
building excavations should not be allowed to remain open for extended
periods of time.
Basements, Dewatering Systems and Slabs on Grade
In view of the aepth to ground water and high moisture contents
encountered at the site, it is our opinion basement construction is.
feasible, provided complete dewatering systems are provided around the
lower basement areas. It is recommended that basements be placed a
minimum of one (1) foot above ground water levels at the time of
construction. To help lower water levels in the area and to provide an
outlet fur perimeter drains around individual basements, it is
recommended that an underdrain system be constructed below the
sanitary sewer system at the site. The drainage system should be
designed fur the anticipated flows and should have a suitable outlet.
The dewatering system around each basement should contain a four
(4) inch diameter perforated pipe, underslab gravel, a sump and pump,
and/or other suitable drain outlet. The perforated pipe should be
placed around the entire perimeter of the lower basement area. All
piping in the perimeter trench should be surrounded by clean, graded
gravel from three -fourths (3/4) inch to the #4 sieve in accordance with
ASTM C 33-86, Size No. 67. The gravel should extend from at least
three (3) inches below the bottom of the pipe to a minimum of two (2)
feet above the ground water above the pipe, the full width of the
trench. The trench should be a minimum of twelve (12) inches wide.
The top of the gravel backfill aajacent to foundation walls should be
MCI
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 a clay backfill be placed
over the system and compacted at or near optimum moisture to at least
ninety percent (90%) of Standard Proctor Density ASTM D 698-78. (See
Appendix C.) We recommend the drainage pipe be placed at least one
0 ) foot below the lower basement slab 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 drainage
system should empty into an adequately sized sewer underdrain designed
to accept the anticipated flows, or the water from the drain should
empty into a sump provided in the lower basement 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. The sump should be provided with a pump designed
to discharge all flow to the sump. Water from the sump should be
disposed of by suitable means well beyond the foundation of the
building.
The subsoils at the site are suitable for slab -on -grade construction.
Structures requiring FHA or VA approval should be designed and
constructed in accordance with the requirements of these agencies.
Subgrade below slabs on grade should be prepared in accordance with
the recommendations discussed in the "Site Grading, Excavation and
Utilities" section of this report. 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. All other slabs on grade should
be underlain bya minimum of four (4) inches of gravel or crushed rock
devoid of fines. The gravel layer will act as a capillary break and will
help to distribute floor loads. It is recommended that all slabs on grade
be designed structurally independent of bearing members.
To minimize and control shrinkage cracks which will develop in slabs
on grade, it is suggested that control joints be placed every fifteen (15)
to twenty (20) feet, and the total area contained within these joints
should be no greater than four hundred (400) square feet. In addition,
-8-
if building construction is dune during winter months, it is recommended
that slabs on grade not be placed on frozen ground and that they be
protected from freezing temperatures until they are properly cured.
Streets
At the time of the preparation of the report, traffic data was not
available to provide pavement design for other than minimum volume
residential streets. It is our opinion flexible pavement is suitable for
the proposed street construction at the site. A flexible pavement
alternate should consist of asphalt concrete underlain by crushed
aggregate base course and subbase or asphalt concrete underlain by
plant mix bituminous base course. The design criteria described below
will be utilized in determining the pavement thicknesses at the site. All
soils data needed fur pavement design has been provided and is included
in this report. When traffic data becomes available, pavement sections
will be provided in an addendum to this report.
City of Fort Collins "Design Criteria and Standards for Streets"
dated July 1986 and AASHTO Guide for Design of Pavement
Structures 1986
18 kip ESAL - 36,500 based on an assumed 18 kip EDLA of 5 for low
traffic residential streets
Resilient Modulus MR of 3775 psi based on an "R" value of 5
Reliability Factor - 70
Overall Deviation - .44
Initial Serviceability Index - 4.5
Terminal Serviceability Index - 2.0
Drainage Coefficient - 1
20-Year'Design Life
Structural Number - 1.24
Strength Coefficients:
Asphalt Concrete - 0.44
Plant Mix Bituminous Base Course - 0.34
Crushed Aggregate Base Course - 0.11
-9-
Select Subbase - 0.10
The following minimum pavement thicknesses are recommended for low
traffic volume residential streets:
Asphalt Concrete 3"
Crushed Aggregate Base Course 8"
Total Pavement Thickness 11"
Asphalt Concrete 2"
Plant Mix Bituminous Base Course 4"
Total Pavement Thickness 6"
The select subbase should meet City of Fort Collins Class 1
specifications, and the crushed aggregate base course should meet City
of Fort Collins Class 5 or 6 specifications. The subgrade below the
proposed asphalt pavement should be prepared in accordance with the
recommendations discussed in the "Site Grading, Excavation and Utilities"
section of this report. Due to the plastic nature of the upper subsoils,
stabilization of portions of the subgrade is anticipated. Where unstable
conditions exist, the street subgrade should be stabilized with granular
pit -run material, geotextiles, lime, fly ash, or by other suitable means.
Upon proper preparation of the subgrade, the subbase and base course
should be placed and compacted between optimum moisture and two
percent (2%) wet of optimum moisture to at least ninety-five percent
(95%) of Standard Proctor Density ASTM D 698-78. (See Appendix C.)
It is recommended the asphalt concrete and/or• plant mix bituminous
base course be placed in two (2) to three (3) inch lifts. All plant mix
bituminous base course and asphalt concrete shall meet City of Fort
Collins specifications and shall be placed in accordance with these
specifications. All subbase material shall have an "R" value between 50
and 69, the crushed aggregate base course shall have an "R" value
between 70 and 77, the plant mix bituminous base course shall have an
Rt value of 90 or greater, and the asphalt concrete shall have an Rt
value of 95 or greater. The "R" value of the pavement materials used
should be verified by laboratory tests. Field density tests should be
-10-
taken in the aggregate base course, bituminous base course, and asphalt
concrete under the direction of the geotechnical engineer.
Riqid Pavement
A feasible pavement alternate at the site would be rigid pavement.
Using the eighteen (18) kip equivalent daily load application described
above, a modulus of subgrade reaction of one hundred (100) pounds per
square inch per inch based on an "R" value of 6, a design life of twenty
(20) years, and concrete designed with a modulus of rupture of six
hundred fifty (650) pounds per square inch, the following minimum
pavement thickriess is recommended:
Residential Streets
Nonreinforced Concrete - 6"
Concrete pavement should be placed directly on the subgrade that has
been uniformly and properly prepared in accordance with the above
recommendations. All concrete used in the paving shall meet ASTM
specifications, and all aggregate shall conform to ASTM C 33
specifications. The concrete should be designed with a minimum modulus
of rupture of six hundred fifty (650) pounds per square inch in
twenty-eight (28) days. It is recommended laboratory mix designs be
done to determine the proper proportioiis of aggregates, cement, and
water necessary to meet these requirements. It is essential the concrete
have a low water -cement ratio, an adequate cement factor, and sufficient
quantities of entrained air. Joints should be carefully designed and
constructed in accordance with the City of Fort Collins "Design Criteria
and Standards for Streets" specifications to ensure good performance of
the pavement. It is recommended all concrete pavement be placed in
accordance with City of Fort Collins specifications. If paving is done
during cold weather, acceptable cold weather procedures as outlined in
the City of Fort Collins specifications should be utilized. The concrete
pavement should be properly cured and protected in accordance with the
above specifications. Concrete injured by frost should be removed and
replaced. It is recommended the pavement not be opened to traffic until
-11-
a flexural strength of four hundred (400) pounds per square inch is
obtained or a minimum of fourteen (14) days after the concrete has been
placed.
GENERAL RECOMMENDATIONS
(1) Laboratory Lust results indicate water soluble sulfates in the
soil are negligible, and a Type 1-II 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
percent (90%) of Standard Proctor Density ASTM D 698-78.
(See Appendix C.) Puddling should not be permitted as a
method of compaction.
(4) Gutters and downspouts should be designed to carry roof
runoff water well beyond the backfill area.
(5) Underground sprinkling systems should be designed such that
piping is placed a minimum of five (5) feet outside the backfill
of the structures. 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.
(6) Footing sizes should be proportioned to equalize the unit loads
applied to the soil and thus minimize differential settlements.
-12-
(7) It is recommended compaction requirements specified herein be
verified in the field with density tests performed under the
direction of the geotechnical engineer.
(8) It is recommended a registered professional engineer design the
substructures, and he should take into account the findings
and recommendations of this report.
GENERAL COMMENTS
This report has bean prepared to aid in the evaluation of the
property and to assist the architect and/or engineer in the design of
this project. In the event any changes in the design of the structures
or their locations are planned, the conclusions and recommendations
contained in this report will not be considered valid unless said changes
are reviewed and conclusions of this report modified or approved in
writing by Empire Laboratories, Inc., the geotechnical 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 ground water
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 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.
-13-
APPENDIX A
No. 14
0
T.B.M.
SE CORNER OF
CONC. PAD
STORM SEWER MH
ELEV. = 4928.44
CARIBOU DR.
FOX RUN P.U.D.
PHASE 1
1 V
A-2
ru0ioc i n0n0A7r%0ic0 iKin
SCALE: 1" = 200'-0"
77,
�� �v
TOPSOIL
®
FILL
SILT
i�
CLAYEY SILT
SANDY SILT
®
CLAY
®
SILTY CLAY
SANDY CLAY
L Li
SAND
KEY TO BORING LOG' )
••�;
GRAVEL
`
LA
SAND & GRAVEL
• i
Lai
SILTY SAND & GRAVEL
& a -1
COBBLES
SAND, GRAVEL & COBBLES
®
WEATHERED BEDROCK
SILTSTONE BEDROCK
®
CLAYSTONE BEDROCK
SANDSTONE BEDROCK
��•
SILTY SAND
® LIMESTONE
CLAYEY SAND
° "
GRANITE
I R 1[
SANDY SIL1Y CLAY
❑
SHELBY TUBE SAMPLE
STANDARD PENETRATION
DRIVE SAMPLER
WATER TABLE 3 dayS
AFTER DRILLING
C HOLECAVED
5/12 Indicates that 5 blows of a 140 pound hammer falling 30 inches was required to penetrate 12 inches.
A-3
EMPIRE LA90RAT'ORIES• INC.
TABLE OF CONTENTS
Table of Contents .............................................. i
Letterof Transmittal .......................................... ii
Report......................................................... 1
AppendixA .................................................... A-1
Test Boring Location Plan .................................... A -2
Keyto Borings ............................................... A-3
Lug of Borings ............................................... A-4
AppendixB.................................................... B-1
Consolidation Test Data ...................................... B-2
H veem Stabilometer Data ..................................... 137-6
Summary of Test Results ..................................... B-8
AppendixC.................................................... C-1
ELEVATION:
4925
4920
1915
4910
501 1
LOG OF BORINGS
No. 1 No. 2 No. 3
No. 4
I,
IAAFKAFFA
L
MA
�
•
n • '
rPAA
A�AlaNvA
FAJ
sVA
TRI, SE corner of concrete pad @ storm sewer manhole, elevation =
4928.44'
A-4
EMPIRE LABORATORIES, INC.
ELEVATION:
No. 5
LOG OF
No. 6
BORINGS
No. 7 No. 8
4925
YPiLL
LOG OF BORINGS
ELEVATION: No. 9 No. 10 No. 11
4925
4920
4915
4910
4905
4900
Q
®e.?
M�
_
_FFA,
voe
vse
e� si
v
w
A-6
EMPIRE LABORATORIES, INC.
ELEVATION:
No. 12
LOG OF BORINGS
No. 12A No. 13
n n
7/12
4925
6/12
i
4920
5/12
9/12
4/12
4915
n
34/12
;' n
4/12
°
4910
n
20/12
°
4905
4900
A-7
EMPIRE LABORATORIES, INC.
LOG OF BORINGS
ELEVATION: No. 13A No. 14 No. 14A
MIA
4925 "
o. .
4920
7/12
OF
4915 5/12
0
4/12
4910
4905 7/12 0
4900
A-8
EMPIRE LABORATORIES, INC.
APPENDIX a
.700
.680
6 6 cl
640
60-
.2
60
5:i* cl
560 40 5
520
4 0
iii
cl cl
—4 Cl
iT
iT
A cl
ii
12 .0
16 . cl
CONSOLIDATION TEST
PRO. 92?J
DEPTH: 7.0
DRY DEHS1TY:1D,:7j.7 PCF
MOISTI-IRE: 26.2 %
0. ��5 0. 5 1, cl
APPLIED PRESSURE — TSF
0.25 Cl. 5 1, cl
APPLIED PRESSURE — TSF
5 10
5 1 ci
EHFIFE LHE;0FFlTQFIES IHC.
B-2
CONSOLIDATION TEST
P RC, . 9 2 ? I
DEPTH: 3.0
TIRY TIENSITV: 90.2 PCF
HOJ!'STURE: 27. 1
14,
4
LJ
iii
C.
cl
12
174
-4 it
H
I
fil
Q
-F; cl
5 1 . 1-1 5 1 cl
APPLIED PRESSURE - TOIF
C, -1.5 1 . cl 5
APPLIED PRESSURE - TSF
10
EHPIRE LFiE:0R*FiTC)F-,,IE,z; INC
B-3
CONSOLIDATION TEST
PRO. 927J
l
C
DEPTH: 7.0
DRY DEt-.JSlT7:11,2.7 PCF
MOISTURE: 21.6 %
-
4 . Cl
w
I
111
L . cl
cl . cl
-4 F-1
iii
-5
5 0 L119
APPLIED PRESSURE — TSF
5 1
APPLIED PRESSURE — TSF
5 10
EHPIRE LABORATORIES INC.
B-4
7 5 0
74C,
7 _'A
720
I cl
7 00
690
.680
6: 7 Ci
F. R H
CONSOLIDATION TEST
PRO. 92P 1
DEPTH: 3.0
DRY DUTS'ITY: 94.0 PCF
lli')ISTURE. 26.2Il
'. 25 Cl. 5 1.0 5 1 cl
APPLIED PRESSURE - TSF
C
4 . C,
Ltd
A: 2 .0
iii
cl cl t
-2 Ci
ii
-4 .0
-6 C,
Cl. 1 C1.25 cl . 5 1 cl 5
APPLIED PF-.*E!ISUF,,E TSF
EHFIRE LFiB(:)F.,.FiTC)PIE:E; INC.
B-5
Empire�abd atories, Inc.
GEOTECHNICAL ENGINEERING & MATERIALS TESTING
May 1, 1992
Mr. Lester Kaplan
1060 Sailors Reef
Fort Collins, Colorado 80525
Dear Les:
CORPORATE OFFICE
P.O. Box 503 • 301 No. Howes
Fort Collins, Colorado 80522
(303) 484-0359
FAX No. (303) 484-0454
We are pleased to submit our Report of a Geotechnical Investigation
prepared for the proposed residential subdivision located on Horsetooth
Road in east Fort Collins, Colorado.
Based upon our findings in the subsurface, it is our opinion the site is
suitable for the proposed construction, providing the design criteria and
recommendations set forth in this report are met. The accompanying
report presents our findings in the subsurface and our recommendations
based upon these findings._
r.x
Very truly yours, yti`'` '`..c
c F _,
EMPIRE LABOR T RIES, INC. �UV.
£ AIPGAR
Zt
i
N(?If R. Sher od �9� ^M�••._...•- �`c ..
Senior- Engineering Geologist
9 g 9 fcr-•CIJ� f
Reviewed by:
X;4� ��
Chester C. Smith, P.E.
President
cic
cc: RBD, Inc. - Mr. Stan Meyers
,' TER C
,�........,� �f,
p,,. �GrST•Fq'•.���
s" P Fo eti
N 4808
frTF0T COL
fr
Branch Offices
P.O. Box 16859 P.O. Box 1135 P.O. Box 1744
Colorado Springs, CO 80935 Longmont, CO 80502 Greeley, CO 80632
(719) 597-21 16 (303) 776-3921 (303) 351-0460
Member of Consulting Engineers Council
P.O. Box 5659
Cheyenne, WY 82003
(307) 632-9224
RESISTANCE R-VALUE AND EXPANSION PRESSURE
OF COMPACTED SOIL
A' T it — D2`844
CLIENT: LE:-Z. I:APLHH
FF:1:1.JECT: FO;; RUN F'.I_I, D.
LOCATION F,F :-:;AMPLE: C.IIMF'OSITE SAMPLE E:URIHG f10. 2 @ 0." - 4.C+'
SAMPLE DATA
TE:3T =;PEC I HEH
1
2
COh1F'ACTIrill PRE!:;'31-IF:E
- PSI
O
40
DEH_;IT''i' - F'i_F
102.6
104.9
MOI:=:TIIR..E -
23.4
21.7
E'-'PAh1=;IF!hl PRE_;:11RE
- PS I
0.CIO
0.00
HORIZ011TAL PREE=S.TIRE
@ 1G.C, p_i
154
146
:SAMPLE HEIGHT - in.
2.52
2.50
E,;UDAT I Oft P1:E8S1-1R.E
- F'S I
135
288
II11CORREC:TED F:-', ALI_IE
1 . 8
5.0
Ci iF:F:ECTED R-'%'ALUE
1.8
5.0
F:-'.r'ALUE AT '00 F'SI
E ;UDATION
PRESSURE =
5.2
1
W R l_1
J
IT
1Y 4 Cl
L
3
10 4
26.0
0.06
149
2.`0
453
9.5
9.5
............. ..............
..............
i
'
......'..........
...4.............i.............
............
......!.......
....... �.............
!.............1...................
I.......
11_t 0c, �_� 1=� 400 500 E, cl rl
E".:.LIDATIOH PRESSURE — psi
EIIF'IF,E LFIEC;F:AT0F;IES' IIIC.
Q-6
700 Goo
WSISTFINCE R-VHLUE
HND
EXPANSION
PRESSURE
OF
COMPACTED
SOIL
RSTH
— D 2844
CLIDIT: LE! - ; l:::APLAH
F R CI J E C T F 0:; F: 1111 P.
LFii::AT10H OF:;AHPLE. _;0HP0::,.ITE
_;AHPLE BORING 110. 1'2 @
0.5" 4.0'
c-AlIPLE DATA
TEST 3FEUIHEH
1
2
:3
C10HPACTI1011 F,F,,E':;::'-I-IF:E - F-3I
0
10
80
D E 11::: 1 TY P C: F
93.5
103. 3
106. 5
I-101-JURE %
25.2
21.7
19.9
E::::F,Al1S10lJ F*F:E!:;':;I-lf-:E - Pc;l
0.00
0.06
0. 18
H A F: 171-1 t I T A L P R E!:,,:; 11 R E Id I GO
S i 156
142
1 1, 1
SIAHPLE HEIGHT it -I.
2. 52
2.54
2. 50
E::-','-'L,AT I Fill PRE: --,:URE - PSI
179
309
497
UflCFIRREFJED R-'-,-'FiLlJE
1.2
5.8
14.3
I-%. u P: F: E I-: T E D R L 11 E
1.2
5.8
14.3
R'y'ALUE AT :_:00 F"-:I E',--.lJDHT10fl PRESSURE = 5.3
LL 4 A
I c1cl 21 0 ci cl cl 40C 500 600
E ";;'. 11 D A T ICIH PRES*SURE — psi
- EIIF'IF.,.E LFiE;1-_)F.*RT0F,,IES INC.
B-7
7 00 800
SUMMARY OF TEST RESULTS
Boring
Depth
Moisture
Dry
Density
Compressive
Strength
Swell
Pressure
Soluble
Sulfates
pH
Liquid
Limit
Plasticity
Index
Group
Classification
A
Resistivity
(OHM-C MI
Penetration
BIows/I n.
No.
IFt.I
(%)
(PCF)
(PS F)
(PSF)
(%)
(%I
(%)
Index
US
1
0.5-1.5
21.6
8/12
3.0-4.0
27.7
90.4
1630
M-5.0
23.4
5/12
7.0-8.0
26.0
8.0-9.0
24.1
4/'
14.0-15.0
8.6
27/12
2
0.5-1.5
21.8
7/12
3.0-4.0
28.5
93.2
820
.0027
4.0-5.0
20.9
4/12
7.0-8.0
22.8
100.0
8.0-9.0
22.7
4/12
14.0-15.0
16.8
6/12
omposi
Sample
0.5-4.0
35.5
17.8
12.5
-6(13); CL
3
0.5-1.5
21.5
7/12
3.0-4.0
25.6
93.8
1070
4.0-5.0
24.5
3/12
7.0-8.0
21.3
111.2
280
8.0-9.0
18.7
9/12
14.0-15.0
29.3
20/12
4
0.5-1.5
20.3
8/12
3.0-4.0
22.7
89.7
780
EMPIRE LABORATORIES, INC.
01,
SUMMARY OF TEST RESULTS
g
Depth
Moisture
Dry
Density
Compressive
Strength
Swell
Pressure
Soluble
Sulfates
PH
Liquid
Limit
Plasticity
Index
Group
Index
CAASHTO n
Resistivity
(OHM -CM)
Penetration
Blows/In.
(Ft.)
(%)
(PCF)
(PSF)
(PSF)
1%I
I%)
(%)
LISCS
rNo.4
4.0-5.0
31.3
4/12
7.0-8.0
21.4
107.5
1140
.0017
8.0-9.0
20.8
7/1?
14.0-15.0
21.1
27/12
5
0.5-1.5
25.4
8/12
3.0-4.0
27.0
92.2
1490
4.0-5.0
22.1
4/12
7.0-8.0
30.2
73.6
8.0-9.0
24.9
6/12
14.0-15.0
14.4
10/12
6
0.5-1.5
23.3
7/12
3.0-4.0
18.1
107.0
0
4.0-5.0
15.6
4/12
7.0-8.0
28.4
85.5
180
8.0-9.0
22.1
6/12
14.0-15.0
10.4
14/12
7
0.5-1.5
22.6
12/12
3.0-4.0
23.5
101.9
4.0-5.0
19.6
9/12
7.0-8.0
22.4
94.1
1240
.0022
8.0-9.0
18.8
5/12
14.0-15.0
24.9
8/12
EMPIRE LABORATORIES. INC.
Q
1
0
SUMMARY OF TEST RESULTS
Boring
Depth
Moisture
Dry
Densi
Compressive
Stren th
g
Swell
Pressure
Soluble
Sulfates
pH
Liquid
Limit
Plasticity
Index
Group
Index
Classification
AASHTO
Resistivity
(OHM -CM)
Penetration
Blows/in.
No.
(F t.)
IY.1
(PCF)
)
(P$F)
(PSF)
1%)
1%)
1%)
USCS
8
0.5-1.5
23.1
9/12
3.0-4.0
18.8
97.1
1190
4.0-5.0
30.6
6/12
700-8.0
19.3
108.4
1180
8.0-9.0
20.7 .
4/•
14.0=15.0
17.3
20/12
9
0.5-1.5
20.5
6/12
3.0-4.0
18.8
101.6
1580
.0020
4.0-5.0
39.1
5/12
7.0-8.0
29.1
95.7
8.0-9.0
27.7
4/12
15/12
14.0-15.0
21.9
10
0.5-1.5
20.4
8/12
3.0-4.0
25.2
96.7
2120
30
4.0-5.0
26.1
5/12
7.0-8.0
27.9
82.9
8.0-9.0
15.6
9/12
14.0-15.0
13.7
27/12
11
0.5-1.5
20.9
7/12
3.0-4.0
24.6
95.2
1580
EMPIRE LABORATORIES, INC.
I
r
r-�
SUMMARY OF TEST RESULTS
Boring
Depth
Moisture
Dry
Density
Compressive
Strength
Swell
Pressure
Soluble
Sulfates
pH
Liquid
Limit
Plasticity
Index
Group
Index
Classification
AASHTO
ResistivityPenetration
(OHM-CM)
n.
Blows/in.
No.
IF 0IY.)
(pCF)
(PSF)
(PSF)
(%)
1%1
1%)
uses
11
4.0-5.0
22.5
5/12
7.0-8.0
20.1
102.2
1100
8.0-9.0
19.9
6/12
14.0-15.0
14.9
30/12
12
0.5-1.5
18.6
7/12
3.0-4.0
22.1
94.4
1430
4.0-5.0
21.9
6/12
7.0-8.0
26.1
96.4
740
8.0-9.0
24.1
5/12
14.0-15.0
23.1
34/12
omposi
Sample
0.5-4.0
35.6
18.2
12.8
-603); CL
13
0.5-1.5
21.8
9/12
3.0-4.0
27.6
88.1
1510
4.0-5.0
20.9
4/12
7.0-8.0
25.9
89.0
270
8.0-9.0
22.3
4/12
14.0-15.0
16.8
20/12
EMPIRE LABORATORIES, INC.
SUMMARY OF TEST RESULTS
Dry
Compressive
Swell
Soluble
Liquid
Plasticity
C
Classification
AASHTO
ResistivityPenetration
Boring
Depth
Moisture
(�)
Density
Strength
Pressure
Sulfates
pH
Limit
Index
lndex
USCS
(OHM -CM)
BlowsAn.
No.
(Ft.)
(PCF)
(PSFI
(PSF)
W
M
N
7/12
14
0.5-1.5
21.0
3.0-4.0
25.1
92.6
2080
40
4.0-5.0
21.3
5/12
7.0-8.0
27.6
92.3
630
8.0-9.0
24.1
4/-
14.0-15.0
17.1
7/12
omp
ample le
e
0.5-4.0
34.2
16.5
8.9
A-6(9); CL
EMPIRE LABORATORIES, INC.
Boring
No.
Depth
(ft)
SUMMARY OF TEST RESULTS
% Oxidation -Reduction
Moisture Potential mU
Resistivity
ohm -cm Sulfide ... pH
2
0.5-5.0
29.6
259
2000 trace 8.0
14
0.5-5.0
32.3
317
1600 trace 8.1
B-13
APPE14DIX C
APPENDIX C.
Suggested Minimum Specifications for Placement of Compacted
Earth Fill and/or Backfills
GENERAL
The geotechnical engineer shall be the owner's, architect's,
engineer's or contractor's representative to observe placement of
compacted fill and/or backfill on the project. The geotechnical engineer
or his representative shall approve all earth materials prior to their use,
the method of placement and the degree of compaction.
MATERIALS
Soils used for all compacted fill and backfill shall be approved by
the geotechnical engineer or his representative prior to their use. Fill
material shall be free from organic matter, frozen material and other
unsuitable substance and shall not contain rocks or lumps having a
diameter greater than six (6) inches.
SUBGRADE PREPARATION
All topsoil,
vegetation, trees, brush, timber, debris, rubbish and all
other unsuitable
material shall be removed to a depth satisfactory to the
geotechnical engineer or his representative. The material shall be
disposed of by
suitable means prior to beginning preparation of the
subgrade. The
subgrade shall be scarified a minimum depth of six (6)
inches, moisture
conditioned as necessary and compacted in a suitable
manner prior to
placement of fill material. Fill shall riot be placed until
approval by the
geotechnical engineer or his representative; and in no
case, shall fill
material be placed on frozen or unstable ground.
Subgrade which
is not stable may require the use of imported granular
material, geotextiles
or other methods for stabilization as approved by the
geotechnical engineer.
FILL PLACEMENT
Fill material shall not
be placed during unfavorable weather
conditions. Material
proposed
for use as fill shall be
approved by the
geotechnical engineer
or his representative prior to use.
Proposed import
material shall be
approved
by the geotechnical
engineer or his
representative prior
to hauling
to the project site. Fill
material shall be
C-2
REPORT
OF A
GEOTECHNICAL INVESTIGATION
SCOPE
This report presents the results of a geotechnical investigation
prepared for the proposed single-family residential development located
on Horsetooth Road one-half mile east of Timberline Road in east 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 ground water conditions, and (4) make recommendations
regarding pavement types ana thicknesses for the proposed streets to be
constructed at the site.
SITE EXPLORATION
The field exploration, carried out on April 24, 1992, consisted of
drilling, lugging, and sampling fourteen (14) test borings. Three
additional shallow borings were drilled in Horsetuoth Road to determine
existing pavement thicknesses. The test borings were located by Empire
Laboratories, Inc. from reference to the south and west property lines
using conventional chaining methods. 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 lugs are shown in
Appendix A. These logs show soils encountered, location of sampling,
ana ground water at the time of the exploration.
The borings were advanced with a four -inch diameter, continuous-
typt:, puwer-flight auger drill. During the drilling operations, a
geotechnical engineer from Empire Laboratories, Inc. was present and
made continuous observations of the soils encountereo.
-1-
w
uniformly mixed such as to preclude the formation of lenses of material
differing from the surrounding ,material. All clods shall be broken into
small pieces. The contractor shall construct the fill in approximately
horizontal lifts extending the entire length of the fill. The thickness of
the layers before compaction shall not be greater than eight (8) inches.
Fill being placed on slopes or hillsides shall be benched into the existing
slope. A minimum two (2) foot horizontal bench shall be cut into the
existing excavated slope for each four (4) feet vertical of fill, or each lift
should be benched slightly into the existing grade.
MOISTURE CONTROL
Prior to and during compaction operations, the fill material being
placed shall be maintained within the range of optimum moisture specified.
A general recommendation is to maintain the fill material within two
percent (2%) plus or minus of optimum moisture so that proper compaction
to the specified density may be obtained with a minimal effort. In
building pad and paved areas, material exhibiting swelling potential shall
be maintained between optimum moisture and two percent (2%) wet of
optimum moisture content. The moisture content of the fill material shall
be maintained 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 geotechnical
engineer, it is not possible to obtain uniform moisture content by adding
water on the fill surface. If, in the opinion of the geotechnical 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. Uniform mixing may require discing, blading
or other methods approved by the geotechnical engineer or his
representative.
Adjustments of moisture content shall be made on the basis of
determinations of moisture content by field tests as construction
progresses.
COMPACTION
The contractor shall furnish and operate the necessary types and
kinds of equipment to perform the operations required to obtain the
specified compaction. This equipment may include approved tamping
rollers, rubber tired rollers, smooth wheeled rollers and vibratory
rollers. If a sheepsfoot roller is used, it shall be provided with cleaner
bars so attached as to prevent the accumulation of material between the
tamper feet. Fill areas which are not accessible to full-sized construction
equipment shall be placed in maximum four (4) inch lifts and compacted
with power tampers to the specified density.
C-3
0
Compaction should meet the minimum percentages of maximum density
as set forth in the project specifications or the recommendations of the
report. The contract specifications supercede the recommendations given
in this report.
MOISTURE DENSITY RELATIONSHIP DETERMINATION
Samples of representative fill materials to be placed shall be
furnished by the contractor to the geotechnical engineer for determination
of maximum density and optimum moisture or relative density. Sufficient
laboratory moisture density or relative density curves will be made to
determine the optimum moisture content and maximum density for the
various soils placed as fill. Tests for this determination will be made
using the appropriate method conforming to the requirements of ASTM D
698 (Standard Proctor), ASTM D 1557 (Modified Proctor) or ASTM D 4253,
D 4254 (Relative Density). Tile materials used for fill shall be classified
in accordance with ASTM D 2487 in order to permit correlation between
the moisture density relationship data and the material being placed and
compacted. Copies of the results of these tests will be furnished to the
client and others as directed by the client. These test results shall be
the basis of control for all compaction effort.
FIELD DENSITY AND MOISTURE TESTS
The in -place density and moisture content of compacted fill will be
determined by the geotechnical engineer or his representative in
accordance with ASTM D 1556 (sand cone method) or ASTM D 2922, D
3017 (nuclear methods). Material not meeting the required compaction
and/or moisture specifications shall be recompacted and/or moisture
conditioned until the required percent compaction and/or moisture content
is obtained. Sufficient compaction tests shall be made and submitted to
support the geotechnical engineer's or his representative's
recommendations. The results of density tests will also be furnished to
the client and others as directed.
C-4
SITE LOCATION AND DESCRIPTION
The site is located on Horsetooth Road directly north of the new
English Ranch Subdivision in east Fort Collins, Colorado. More
particularly, the site is described as Stone Ridge P.U.D., a subdivision
situate in the Southeast 1/4 of Section 29, Township 7 North, Range 68
Nest of the Sixth P.M., City of Fort Collins, Larimer County, Colorado.
The site consists of an existing farm located on the north side of
Horsetooth Road half a mile east of Timberline Road. The property
consists of plowed, irrigated ground, is relatively flat and has minor
drainage in an east-northeast direction. Several irrigation laterals
traverse the site, and a large irrigation ditch runs along the south edge
of the property adjacent to Horsetooth Road. An existing two-story
farmhouse and outbuildings including a barn and horse corral are located
in the southwest corner of the property. A large well is also located in
this area. Existing farm land is located to the west, north and east,
and the site is bordered on the south by Horsetooth Road, which is
currently being widened south of the site.
LABORATORY TESTS
Samples obtained from the test borings were subjected to testing In
the laboratory to provide a sound basis for evaluating the physical
properties of the soils encountered. Moisture contents, dry unit
weights, unconfined compressive strengths, water soluble sulfates,
swelling potentials, resistivity, oxidation-reduction potential, sulfides,
pH and the Atterberg limits were determined. A summary of the test
results is included in Appendix B. Consolidation and Hveem stabilometer
characteristics were also determined, and curves showing this data are
included in Appendix B.
-2-
SOIL AND GROUND WATER CONDITIONS
The soil profile at the site consists of strata of materials arranged
in different combinations. In order of increasing depths, they are as
follows:
(1) Silty Topsoil: The majority of the area tested is overlain by a
six (6) inch layer of cultivated silty topsoil. The topsoil has
been penetrated by minor amounts of root growth and organic
matter. The topsoil should not be used as a bearing soil or as
a fill and/or backfill material.
(2) Existing Pavement: Two (2) to two and one-half (2-1/2) inches
of asphalt underlain by six (6) to six and one-half (6-1/2)
inches of gravel base material were encountered in three
borings drilled through Hursetooth Road. The existing asphalt
is in fair condition.
(3) Fill Material: A layer of fill underlies the pavement in Burings
12A, 13A and 14A and extends to depths of two (2) to two and
one-half (2-1/2) feet below the surface. The fill consists of a
mixture of silty and/or sandy silty clay with minor amounts of
gravel.
(4) Silty Clay: This stratum underlies the topsoil and/or fill in all
borings and extends to depths of three and one-half (3-1/2) to
six (6) feet below the surface. The silty clay is moderately
plastic, contains minor amounts of fine sand and exhibits low
bearing . characteristics in its moist in situ condition. When
wetted and upon loading, consolidation of the clay stratum
readily occurs.
(5) Sandy and/or Sandy Gravelly Silty Clay: This stratum
underlies the brown silty clay and extends to depths of ten and., --
one-half (10-1/2) to fourteen and one-half (14-1/2) feet below
-3-
the surface. The red sandy silty clay contains varying
amounts of gravel, is moist to saturated and exhibits generally
low bearing characteristics. When wetted and upon loading,
consolidation of the lower clay stratum readily occurs.
(6) Silty and/or Clayey Sand and Gravel: The granular stratum
was encountered in all but Boring 7 at depths of ten and
one-half (10-1/2) to fourteen and one-half (14-1/2) feet below
the surface and extends beyond the depths explored. The
sand and gravel varies from a clean to silty and/or clayey sand
and gravel. The sand and gravel is medium dense, is poorly
graded and exhibits generally moderate bearing characteristics.
(7) Ground Water: At the time of the investigation, free ground
water was encounterea at depths of five and one-half (5-1/2) to
ten (10) feet below the surface. Water levels in this area are
subject to change due to seasonal variations and irrigation
demands on and/or adjacent to the site.
RECOMMENDATIONS AND DISCUSSION
It is our understanding the majority of the site is to be developed
for single-family residential lots, and single-family patio homes are
planned along the west edge of the site. Interior streets will be
constructed, and Horsetooth Road will be widened adjacent to the south
edge of the property. Site grading of the property is anticipated to be
minimal.
Site Grading, Excavation and Utilities
Specifications pertaining to site grading are included below and in
Appendix C of this report. It is recommended the upper six (6) inches
of topsoil penetrated by root growth and organic matter below building,
filled and paved areas be stripped and stockpiled for reuse in planted
areas. The upper six (6) inches of the subgrade below building, paved
and filled areas should be scarified and recompacted between optimum
-4-
moisture and two percent (2%) wet of optimum moisture to at least
ninety-five percent (950) of Standard Proctor Density ASTM D 698-78.
(See Appendix C.) Fill should consist of the on -site soils or imported
granular material approved by the geotechnical. engineer. Fill should be
placed in uniform six (6) to eight (8) inch lifts and mechanically
compacted between optimum moisture and two percent (2%) wet of
optimum moisture to at least ninety-five percent (95%) of Standard
Proctor Density ASTM D 698-78. In computing earthwork quantities, an
estimated shrinkage factor of eighteen to twenty-three percent may be
used for the on -site clays compacted to the above -recommended density.
All excavations should be dug on safe and stable slopes. The
slope of the sides of the excavations should comply with local codes or
OSHA regulations. Where this is not practical, sheeting, shoring
and/or bracing of the excavation will be required. The sheeting,
shoring and bracing of the excavatiun should be done to prevent sliding
or caving of the excavation walls and to protect construction workers
and adjacent structures. The side slopes of the excavation or
sheeting, shoring or bracing should be maintained under safe conditions
until completion of backfilling. In addition, heavy construction
equipment should be kept a safe distance from the edge of the
excavation.
Where utilities are excavated below ground water, dewatering will be
needed during placement of pipe and backfilling for proper construction.
All piping should be adequately bedded for proper load distribution.
Backfill placed in utility trenches in open and planted areas should be
compacted in uniform lifts at uptimum moisture to at least ninety percent
(90%) of Standara Proctor Density ASTM D 698-78 the full depth of the
trench. Backfill placed in utility trenches under building and paved
areas shuuld be compacted at or near optimum moisture to at least
ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78.
Due to the muist nature of the subsoils, extensive drying of the subsoils
may be needed fur proper compaction.
Stripping, grubbing, subgrade preparation, and fill and backfill
placement should be accomplished under continuous observation of the
geotechnical engineer. Field density tests should be taken daily in the
-5-
compacted subgrade, fill, and backfill under the direction of the
geotechnical engineer.
Laboratory resistivity tests, pH, oxidation-reduction potential and
sulfide tests performed in the laboratory indicate the subsoils at the
site are noncorrosive, and protection of metal utility pipe, in our opinion
will riot be required.
Cuts and fills for any proposed detention basin should be placed on
slopes no steeper than 3:1. Cut areas in the detention pond should be
scarified a minimum of eight (8) inches and compacted between optimum
moisture and two percent (2%) wet of optimum moisture to at least
ninety-five percent (95%) of Standard Proctor Density ASTM D 698-78.
Fill in detention pond areas should consist of the on -site clay material
placed in accordance with the above recommendations. For ease of
construction and maintenance, the top of any proposed detention basin
should have a minimum width of ten (10) feet. Tu minimize erosion, the
slope and bottom of the detention basin should be seeded. Pipes or
apertures through the detention basin should be surruunded by a
minimum of two (2) feet of the on -site clay soil compacted to ninety-eight
percent (98%) of Standard Pructor Density ASTM D 698-78.
Foundations
In view of the loads transmitted by the proposed residential
construction and the soil conditions encountered at the site, it is
recommended the structures be supported by conventional -type spread
footings. All footings should be founded on the original, undisturbed
soil or on a structural fill extended to the undisturbed soil a minimum of
thirty (30) inches below finished grade for frost protection. The
structural fill should be constructed in accordance with the
recunimendations discussed in the "Site Grading, Excavation and Utilities"
section of this report. The structural integrity of the fill as well as the
identification and undisturbed nature of the soil should be verified by
the geotechnical engineer prior to placement of any foundation concrete.
Footings founded at the above levels 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
-6-