HomeMy WebLinkAboutLAKE STREET TOWNHOME PUD - Filed GR-GEOTECHNICAL REPORT/SOILS REPORT -TABU OF CONTE S
Table of -Contents e,........ee.. 000.oae00..o0404e0oe00«.o.
Letter ofTransmittal..........:......:....er.,..e..., ii
ru.Mo'art'#we..00.oa.oa.o-000.r..r.o..re..ese...aoat.,-a....:.......a.. 1
Appendix A A-1
lost Boring Location Plan .... 4o00008*00.o0.00,.e0041 oa A•2
to Borings o..00}l.orrtoor`.....e,o..erse.e,..00er;ao..as.o` A-3
Log of Borings A-4
Appendix 1 •o..r.o-.r i+le+tlo,A.rs+i.o.r0e.4.a0aooe0009e0eO'r40*o0oa
ConsolidationTest .Data B-2 Sumary+
of..Test Results B-4 Aoperndix
G.o.00000..o.•so....toeo..roa0aaaerrae......r,o.o0 Val
M
0
e IAboratories, Inc.
MATERIALS AND FOUNDATION ENGINEERS
214 No. Howes Fort Collins; Colorado 80522
P.O. Box 429 (303) 484-0359
Febnuzvcy 26, 1979
8xa.d6otd L. Smith and Associates
155 Noxth Cot2ege Avenue
Foxt Cot2ins, CoZonado 80524
Attention: Joe RoesseA, Jt., P.F.
Gentlemen:
Branch Offices
1242 Bramwood Place
Longmont, Colorado 80501
P.O. Box 1135
303)776-3921
3151 Nation Way
Cheyenne, Wyoming 82001
P.O. Box 10076
307) 632.9224
We ate pteaded to submit out Repoxt o6 a Geotechnica2 Investigation
ptepated Got the pxopoaed Lake StAeet Townhome, P.U.D., Poxi CotZin6,
Cotoxado.
The subsut6ace' condi ;iona teveated by this investigation ate zuita.bte
Sot the .intended eonsttuction, provided constolcuetion ,is in aecoxdanee
with the tecommendatioms contained, .in th 's nepoxt. The attached %epo't
pnesent,a the subsut6ace conditions at the site and oun recommendations
box. 6oundation design and constiucation.
We appnec iaie .this oppoxtu.ni ty of consulting with you on thtz ptoject.
16 you have any que 6t ions ox.:i6 we can be o 6 huh the& assistance, please
contact u.6.
V et y nutty youAz,
EMPIRE LABORATORIES, IINNCC..
James E. Veith, P. E.
Geotechnicat Enginee,%
Reviewed by:
C
ChesteA C. Smith, P. B.
Puzident
E.
IQ..
Vol
4808
a
IiCaOtj1
MEMBER OF CONSULTING ENGINEERS COUNCIL
I"
REPORT
OFA, GEOTEOMICAL
IWESTIGATION SSE
This
report presents the results of a geotechnical investigation prepared.
for the proposed Lake, Street. Townhoee, P.U.D., Fort Collins, Colorado.
The investigation included test borings,, laboratory testing, engfneering.
evaluation,.and preparation of this.report. The
purposes of teainvestigation were to determine subsurface condi tions
i.tionsatthe site and; to provide 'recampeodations for .site development as, influenced -
by the subsurface.conditions. SITE Y
StII I_IOB Six (6)
test borings wem drilled at the,site on.February 16, 1979. Locations of
the test borings are shown on,tie Test Boring Location Plan included in
Appendix A. The test borings were established in the field by referencing
to existing topographic features:. The borings
were advanced with continuous -flight augers to depths fourteen and
one-half (141j) feet below present grades. Samples were recovered with
two and one-half ( )inch Shelby tubes and the standard penetration sample
technique.. During drilling, an engineering geologist of Empire
Laboratories, %no was present and made a continuous visual inspection of
soils encountered. Logs prepared fry the field Logs are included in
Appendix k of this report. Indicated on the logs are the prjoary. strata
encountered; locations of .samples, and groundwater conditions.
SITE LOCATION AND DESCRIPT12
The reference -site is Ideated between Prospect and lake Streets
east'of.Shields Street in Fort Collins, Colorado. More specifically, it
can be described as a tract,of aand.s tuate in the southwest 1/4 of
Section 14, Township 7 North, :Range 69 West of the Sixth P.N., Fort
Collins, Colorado
The. project site -is presently an open area with flat to gently
rolling topography.. Pr1mafy' slope and drainage are to the north. Two
2) small irrigation Bite m trdverse the south portion ofthe property
In an east -west direction.', The east on west property lines are presently
fared.
j AABt1RATORY TESTS AW .p MD ATIORS
Representative samplat recovered in t ,tett borings were selected:.
for tests in the laboratory to. determine 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 ,' Onsalidawn potential,: Snell .potential,
and swel l sconsol idati on potential'.. Laboratory test results are stsimarized
in Appendix R .,,j
301h., AM W OtlRDiIATCR fI ONS
The following are the„ characteristics of the primary. soil strata-
encountered at the site.
41 i To I The site, Is overlein by d layer of sandy topsoil.
twelve `l) inches thick. The upper six .(s) inches of the
topsoil' have been penetrated by root growth and organic utter
and should not be used for foundation bearing or as bactfill
saiteri al .
2) SiltX,C't= Sand: The topsoil 1s underlain by: red and brown
silio.clayey sand -extending to the depths explored. This
stratum contains Sim gravel .and :occasional thin sews and
layers of fine, sand.: With increasing depth Into this atre tO%
the material becomes, more moist and softer,, The.. silty clayey
sand exhibits moderate -sheer strength and bearing qualities, In
its undisturbed natural state, Upon vatting, the silty clayey
s ' exhibits I.W swell potential.
3) Groundwater. No water was encountered within the depths
explor+ed at the timethis investigation. Groundwater` oflevels
at -the site are, however, subject to fluctuation' depending
on seasonal conditions and variations and irrigation 3I
demands
on and adjacent to the property. I ai
EMENDATIONS AND DISC.0S 2! plans provided
Ito' us indicate that five (5) town haute units will be
Constructed at the site. . anticipate that ,the buildings will be one (
1) or two (2.)' sto r and. may have basements. . The following are OUT, recommendations
for site davelop=nt as influenced by the subsurfaces conditions' encountered
6 ' the test bofr O$. Site 6radirg
ate anticipate
that some.cutting and fi"tiing will be required on the Ply to.
achieve desired finished grades. As building foundations and/or
slabs on grade my be supported on-filljwe recoomw that fill placeeent be
in, accordance' with Flit. Data Sheet- 79G.. The following are our recommendations
for situ grading and placement of reacted fill. The upper
six (6) inmost:of all. topsoil should be .stripped in proposed cut
and fill treat and :in building and pavementLaren which will remain.
at present grades, ,"iho topsoil can be stockpiled on tine : 52
site and used for final grading outside Of -building and pavement areas.
At cut subgrade elevation and in areas to receive fill A the upper six
6j' inches of the subgrade should be scarified and recompacted at two
percept AM pet of optimum moisture content to,.4 Minimto of ninety
percent J90%) of Standard Proctor Density AS'iWO 698-704 (See Appendix
The or! -site silty clayey. -Sand is suitable for :fill in proposed
building -and pavement area6. :Ayr additional off -site fi11 required
should be a material approved.. by geotechnical engineer. recommendthe
that all fill be placed in horizontal six (6) to eight Winch lifts at
two percent (2%) wet of optimum moistu;content and compacted to a
percent ty ASTK Dtnieirofninetyfire rcent 955 of Standard Procter* t nsi
s9-fop
tyre fill .is placed, on slopes, greater than 4,-1 # horizontal benches:;
should, be cut in the. sl'op6.5 to .insure integrity of the new fill on the
existing slopes* for stability9.+re.,.recommend that ell .cut .and fill
slopes be no steeper than 2:v, flatter. slope; are suggested for ease of
maintenance. finished slopes should be seeded with native gasses to y
minimize -erosion.
Qualified geotechnlcal ,personnel should be present during all
phases of eartbwrb-to observe. -stripping of the topsolI scarification,
of the subgrades and placement and compaction- of fill, in -place density
tests should be taken dait,y todetermine the degree of compaction. being 7
attained
and compliance with project specifications. W
anticipa te'that no unusual .proble mill. be-oncountered daring excavation
for ,utilities. Temporary cut -.slopes in the silty clayey sand Willi
be stable .an ll, sloppsplotter slopes. and/or shoring will be required if
groundwater or, seepage is, encountered. All baekfill.
pYaced in utflty.treraches in open and planted areas should be
compacted in:uniform lifts at optimum Moisture to at least . r inetjv .
percent 90Sj of Standard Proctor Density AST14 D 698-70 the full depth of
the. trench* The upper four (4) feet of backfill placed in utility trenches
under roadways and paved areas should be compacted at yr near
optima moisture to at least ninety-five percent (95%) of Standard Proctor density
ASTN D 698m70'9 and"the icier portion of these trenches
should be compactedto it -least ninety percent (90%) of Standard Proctor Density .
D 698-70. Addition of moisture to,the subsoils may be required
to assure pr4per•..compaction:. It is.reaxuended.,tha all compaction requirements
for uttlttp..trenches be verified.ln the field with density. tests
performed under, toe. direction of the soils engineer.. foundetto
Based
upon the subsurface conditions encountered at. the site and the •
1 oads transmitted. by ..the proposed construction, wo,,recomend that 914-
sutures be supported, by..conventionil continuousor isolated sproad footings
bearing in,undisturbed natural', soil or, Ill l,placed as recommended above.:
As . on-iOte materials will. be used for ff 11 ', strut- triral . fill
placed and comp$cted as.reccesended _above will .have coia- M parable shear
strength and bearing qualities % those -of -,,the -in situ moterials. Exter9or`
footings . should bear a minimn of thirty(30) itches below
exterior finished grades for frost protection.; The nature of true ,
bearing soil. should, -tie : verified by qualified Wtechnicil personnel 01gr to
placement of. fo da iron toncrot+e Footings bearing
at a above- -recommended depths mac be designed fQr;,a .
ma ximum allowable sofT'.pr+essure of three thousand . (3,OQO) pounds per:..,square
foot under: dead ;plus maximum live loads.:- To resist swelling p ssures,
which will develop' if the, subsoils become wetted ' .l footings shpuld. be
designed for,,a-no0j upn dead., load pressure of 'five hundred 500) Pounds
pper square . fogt .., . The anticipated
settlement. under the above -recommended maxim prnssuress, based
aapon.labp tort.tests and analyses, should not exceed 0.$ inch.
Basements and
dabs on Grade The subsurface
profile revealed by this investigation will permit excavationofbasnts for
the structures. Based upon field and labora- tory test results an.
d.eXAMhations of eeco"red samplest we anticipate
that,no dewatering Systems.wilI be required beneath basements._ Preparation
to slab'on grade.subgrade elevation should be acccltshed as twended
above.
All. slabs an grade should_be: underlain by a minima of four (4)
i.nohes of gravel or crushed rock free of fines.. The gravel layer vol
act as a capillary break and will. help to distribute floor loads. It is , f
L
recooded that slabs on grode,be:designed.and constructed independent i
of. .alI bearing 'members, Tp "minimize and control shrinkage cracks which
miiiI develop in slabs, on grade,'"it is suggested that control .joints be
placed every fifteen (t5) to 'twinty (RB) feet and than the total :area,
ontai'ned within these t ints`.be no greater than four hundred (460)
f J
444re foot." Garage fl000r stabs should be, reinforced With :wire Mesh
running . ,through the" control joints'
Pavewnt
4y'
Ifthitt areas to be -paved, preparation to subgr'aoe elevation should
be accomplished as reco"'. d: ,tn the *Site Grading!'.'section of , thus
report. .
A.A S M.T#o. classification, of :the material forming pavement
subgrade is A- -4_.with a group .index of 0. Based upon a group index of
Q the following pavement, thickness is reccomended
Coll Restdnottal
Select Base Course 6. OF
Asphaltic Co MUI 2" 20
Total "Thickness $ - .. . 6
The above-recomomWed thickness for residential ,stnets should be
used"for .off-street parking areas. Asphaltic concrete should meet City
of Fort Collins'specifications.and be"placed'in accordance with those
apec#fications#
The, base- course- overlying -the subgrade should consist of a hard,
durable,.crushed rock or stone and -filler and should have a minimum
C.04R. value of 80. The composite base course materia] should be free.
from vegetable Matter and 'lumps -or balls of clay and should apt the
Colorado Department of :Highways Specification ,Class 6 Aggregate Base
Course which follows:
5ieve.Size° I Passing
3/a200 04.
30-65 ,; , 8
25451 l200
Y 3-12 Liquid,
Limit - 3O+ akitmxa Plasticity.
Index 6 Maximum 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 698-70._ , (See Appendix C;) - It is important that the
base course:be shaped to grade sa,'that.proper'drainage of the parking area
is,obtalned. GENERAL
REC"LILATIONS I)
Laboratory testsAndl'eate that water soluble sulfates in the subsoils
are negligible. , A Type I cement May be used in all concrete
exposed to subsoils. 2)
finished grade should: be'sloped away from the structures on all-
sides .to give positive drainage.,. Five percent (5S) for: the
first five (5) feet a from the -structures is the suggested slope.
3) Backfil.l around the outside perimeter of the structures
should be mechanically compacted at optimum moisture to at
least ninety -five -percent, (95%) of Standard,Proctor Density
AS'iM 698-70. (See Appendix C.) Puddling should not-
permi'tted as a method'of compaction.
4). Gutters and. downspouts should be designed to carry roof runoff
water well beyond thee.backfill area.
5) underground sprinkling systems should not be installed within
ton (10) fuel . of the, - structures:, . and this recommendation
should be taken into account in the landscape planning.
6) 3t is mended that '411 compaction requirements_ specified
herein be verified in the field with density tests performed
under the supervision of an experienced.geotechnical engineer.
7). It'is_-reconmended that a registered prafe$sional engineer
design the foundations, using the recomanndations presented in
this 'report.
GFAERAL COMENTS
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
this prtaJect. In . the event that any changes in the des lgn of the
structures or their locations are planned, the conclusions and recom
mendations contained in this report will not -be considered.valid unless
said changes.acre reviewed and.'conclusions of this report modified or
approved in writing :by- moire :l aboratories, . Inc-., the soils engineer, of
record.
N' N
Every effort was .made to provide comprehensive site coverage
through careful locations of the test borings# -while keeping the site
investigation scono i-ally feasible. Variations in soil and groundwater
conditions between test ,bor°ings may be encountered during construction.
In order .to `perms t correlation. ,between the reported . subsurface eon-
ditions and the actual -conditions encountered during construction and ,to
aid Wcarryi ng out the plans. and. specifications as originally con -
plated, it is re; nddd that Empire Laboratories, Inc. be retained
to performs continuous .cotruction review during the excavation and
foundation phases of the work.:. ire Laboratories, Inc. assumes no
responsibility for cbmpl Uncn. Frith the reconnen.dations included in this,
report unless -they have been retained to perform adequate.on»site
construction review during the course of construction.
APPENDIX A.
3 i
KEY TO BORING LOGS
TOPSOIL L• GRAVEL
FILL SAND & GRAVEL
SILT is SILTY SAND & GRAVEL.
1
CLAYEY SILT ep COBBLES
I.
SANDY SILT SAND, GRAVEL &COBBLES
CLAY WEATHERED BEDROCK.
i
SILTY CLAY SILTSTONE BEDROCK
SANDY CLAY CLAYSTONE BEDROCK
SAND SANDSTONE BEDROCK
SILTY SAND
Ed LIMESTONE
CLAYEY SAND K x
K K
GRANITE
SANDY SILTY CLAY
SHELBY TUBE SAMPLE
STANDARD PENETRATION DRIVE SAMPLER
WATER TABLE 24 HOURS AFTER DRILLING
C HOLECAVED
T
5/12 Indicates that 5 blows of a 140 pound hammer falling 30 inches was required to penetrate 12 inches.
A-3
EMPIRE LABORATORIES, INC.
100
95
90
85
10/12
80 _
95
90
APPENDIX B.
41
39
ua .o S 10
APPLIED PRESSURE—TONS/SQ. FT.
0
JJW
tl
Z
0
Q
0
QJ
N
Z
O
i
5 10
APPLIED PRESSURE—TONS/SQ. FT.
EMPIRE LABOPXA ORIES, INC.
52
51
b0
9.49
a
0
o .48
47
46
45
44
0
1
W
2
II
0 3
a
0
4
z
O
u
5
6
10
APPLIED PRESSURE—TONS/SQ. FT.
Eli1111
111 11111
III 11111
11111 IIIII
n lllli\11111
IIIII 11111
5 to
APPLIED PRESSURE—TONS/'SQ. FT.
B-3
EMPIRE LABORATORIES, INC.
Z,
O=
NU
Q Z-
O N N r N N N N
H O to co
Z 3 r-- r c S N r
dm
W
co Vol
w uQ M
cn
J W
N
W au Z
OG a vi
H p i LU
NU M CD CD C) p
Ce
aW U
N
N LO M O
LL. W W0N
M L1)
O OOm
LLi
G
N
iq
ZLL
00
V O M 10
r0
W
D
r
Co
N r
O M
r
CD co O O
Lo
O 01 O
LO
O O. O CD
11)
Im-d 0 al r . Cf ci O Ol r t Lo m 01
O O O O O O O O
1-
O tl7
1
O
1
O
I
O
1
O
1
tfy
M a ^ co M M ct Ct 1 CO M
LO
OZ
m
B-5
SUMMARY OF TEST RESULTS
Swelling Pressures
Boring Depth Moisture Dry Density Swelling
Number Ft.) Before Test _ PCF Pressure PSF
2 3.0-4.0 4.9 109.5 335
7.0-8.0 5.7 95.4 255
4 3.0-4.0 4.2 109.6 205
5 7.0-8.0 4.3 114.1 660
6 3.0-4.0 7.6 116.3 325
Atterberg Summary
Boring Number 1 @ 4 @
and Depth 30-4.0 3.0-4.0
Liquid Limit 24.6 20.2
Plastid Limit 16.1 18.2
Plasticity Index 8.5 2.0
Passing #200 Sieve 30.9 33.8
Group Index 0 0
1
Classification
Unified SC-SM SC-SM
AASHTO A-2-4(0) A-2-4(0)
B-
APPENDIX C.
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.
C-2
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 Iconditions. 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,
G-3
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 will be
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.
c-a