HomeMy WebLinkAboutConnections Credit Union Geotechnical Engineering Report '4NSPC.--CTiON
GEOTECHNICAL ENGINEERING REPORT
of
Connections Credit Union
750 North Ten Mile Road
Meridian, ID
Prepared for:
Slighter Architects
660 Ustick Road
Boise, ID 83704
MTI File Number BI404259
An A
iNSPECT/OINg
Ntr. Chad Slichter
Slighter Architects
6611 Ustiek Road
Boise,
U) 81704
i.t13-658-I 6'79
Re: Geotechnical Engineering Report
Connections Credit Union
750 North len Mile Road
Meridian, ID
l)ear Mr. Slichter:
In compliance with your instructions, MI ! has conducted a soils exploration and foundation evaluation for the
above referenced development. Fieldwork for this investigation was conducted on 22 April 2014. Data have
been analyzed to evaluate pertinent geotechnical conditions. Results of this investigation, together with our
recommendations, arc to be found in the following report. We have provided a PDF copy and one paper cop .
for your review and distribution.
Often questions arise concerning soil conditions because of design and construction details that occur on
project. MTI would he pleased to continue our role as geotechnical engineers during project implementation.
Additionally, MI 1 can provide materials testing and special inspection services during construction of this
project. If vou will advise us of the approoriate time to discuss these engineering services. we will meet wit
you at your convenience.
MT! appreciates this opportunity to be of service to you and looks forward to working \vith you in the future,
11)'ou Inn z: questions, please call (208 376-4748,
Respectfully Submitted,
Materials Testing & linpettion, Inc. \
52,
ij
N L. c Jrocdcr, Rericned by. David 0. Cram, P.E.
ticotechnical Services Manager General Manager
J0J
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acr.c # 2 [2�
NSP E C~T 1 ON
.
l'aBI,E OF CONTENTS
mozuuocTo^
'
ProjouDescription -----'-----------_----' ---- --'-----------' --�;
8uUhohual,on
Purpose-' --_---- ---- --------------� ---- ---~ ------------�
Scope ofInvestigation 4
Yvmrantyand Limiting Cm`dihunu
SnsL.NsnRmunv------ ----------------------- -------' ------� --
She Access
Regional Geology
General Site Characteristics � 5
Regional Site Mimx,"|o0/and Qr"chemiso} ----------' ' ' -' -' '-----'- 6
tliroscimnic5eubng..--,--.. —...--..- ----.-- -.--.---' -----.--.----h
bV||,S Exr/0axrKN �
Cxp|umdonuodSamydiugPmoodu/es. 6
Laboratory Testing Program ---- --------------� --------------� --�7
Soil and SedimenPuofile_-------------------------------------_'7
Volatile Organic Scan-- ---- ----_---__------_� -------------_--�7
SouU,m«/Luov
8
G,ouodwom,--� ----� ' -------' --- _- _
Soil Infiltration Rates —.........
Kxnnxnow 8|Ac\AND P»vsm/ vrroscusuowmvoKFcowwFwoxngus---.-------------�9
Foundation Deig» Romnmcndukmo--------------------------- ------'O
FloorSlab-onO,m1 —......—........ ... ............ ... ........ ...—........ ----- .....-- ---- --- .......
' lO
Recommended Pavement Sections |8
plexiNcPovuncn| Sxuiony
-' ' )|
CommonPavement Section Construction bsuv -------------� ---^----------- /}
Cuus/xVcnowCovsmcnTIONS - ---------------� l2
Earthwork |Z
DryYVcmbcr---- ............ ..... — —.—`-- .... ...........--- ......... -- ....... ....... C
Wet Weather
D
SvhSvhg,ade 3vUc------------' .......... .... ..... — . ....... — .......... ----- ............. G
FnvcoSuhgnde Soils 13
Structural BU
°` --^---^-----`' --^-' .......... ..... ..... ............................ ... --- 13
Backfill w[Wa!b
------------------- -------'------------- ----- A
Excavations
|j
�nmm^kvxe,Control--------� ---- ---------- --------- ----- I
Omq:xa .Cvwwev/x
--^—~---^^—^^'------'-----^---^------------ ----- O
xa+xeu(�o
-------^`-'---'---`------- -'--------' ---------- ----- u
Appswn/ou
17
Acronym 17
Geotechnical General Notes
—~--^--------^-~--~---~-^--------.-- ----- |X
0evteJhoica| |ov**i2skm Test Pi/ ----------------------' ---- ----- In
&&8H]l}Pavement Thickness. 1)esign Pmcedurms-------� -------------_ -----2|
Plato | Vicinity Mnp'
PI:tt= ;?.. She MA) 24
iLC) nit
P,NSPECTION
I, .:2:1•1
iNTitOlilICTION
r400 Uli QCOI_Ldlilical investigation and analysiS in uui oi data tailifi.ed iiioi
suuctures as defined in the 2012 International Building Code tiTiC). In lOrmation in simport of ground
and storm water issues pertinent to the practice of Civil Engineering is included (.)bservations and
recommendations relevant to the earthwork phase of the project are also presented. Revisions in plans Or
drawings for the proposed development from those enumerated in this report should he broughl toChi
attention of the soils engineer lo determine whether changes in foundation recommendations are required.
Deviations front noted subsurface conditions, if encountered during construction, should also be brought to
the attention of the soils engineer.
Project Description
The proposed development is within the south‘vestcrn portion of the C'ity of Meridian, Ada County, ID. and
occupies a portion of the NW1/4SW1/it of Section I I, Township 3 North, Range I West, Boise Meridian, This
project will consist of construction of a single-story commercial structure, to be developed with
spread/continuous footings and concrete floor slabs. Total settlements are limited to 1 inch. Loads of tip to
4.000 pounds per lineal font for wall footings. and column loads of up to 50,000 pounds were assumed for
settlement calculations, Additionally, assumptions have been made for traffic loading of pavements.
Retaining \valls are not anticipated as part of the projeet. Mil has not been informed of the proposed grading
plan.
Authorization
Authorization to perform this exploration and analysis was given in the form of a written authorization to
proceed from Mr. Chad Slichter of Slighter Architects to Kevin L. Schroeder of Materials Testing
aid
Inspection, Inc. (MTI), on 17 April 2014. Said authorization is subject to terms, conditions, and limitationi
described in the Professional Services Contract entered into between Slighter Architects and M IL Our scope
of services for the proposed development has been provided in our proposal dated 16 April 2014 and repeated.
below.
Purpose
The purpose of this Geoteehnical Engineering Report is to determine various soil profile components and
their engineering characteristics for use by either design engineers or architects in:
• Preparing or verifying suitabinti of foundation design and placement
e Preparing site drainage designs
▪ Indicating issues pertaining to cardlwork 'rtrucli 'n
PreTarin2 light and heavy du.t. pavemem section design requirf.mienis
,
[i•
'tt VC-11
iNSPEC FOON
h bL1._
•
SeOpe Of IVIVCSliga(ion
SCOpe Or this in\estigation included 1,2.VieW Or geuloci literature and existing a;:ailaitie
sindrc-s of the visual site reeonnaissanee of the immediate site. subsurface explmation of the site. rield
LibOIU1Oly 1ctiu H tilifiellak 0..)1lccie,..1.. and engineer-nig analysis and (tvaluation of fourelation
'‘Varranty and Limiting Conditions
MT:: warrants thai findings and conclusions contained herein have been ti nuilated in aecot donee
jib
generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics.
and engineering geology only tor the site and project described in this report. These engineering methods
have been developed to provide the client with information regarding apparent or potential enginceririg
conditions relating to the site within the scope cited above and are necessarily limited to conditions observed
at the time of the site visit and research. Field observations and research reported herein are considered
sufficient in detail and scope to fornt a reasonable basis for the purposes cited above.
EXC1USiVC Use
This report was prepared for exclusive use of the property owner(s), at the time of the report, anti their
retained design consultants ("Client"). Conclusions and recotrimendations presented in this repnrt ale
based on the agreed-up )n scope of work outlined in this report together with the Contract Coy Prolesional
Services between the Client and Materials 'Vesting and Inspection, Inc. ("Consultant"). Use or misuse of this
report, or reliance upon findings hereof, by parties other than the Client is at their own risk, Neither Client
nor Consultant make representation of warranty to such other parties as to accuracy or Lompleiencess of this
report or suitability of its use by such other parties for purposes whatsoever. known or unknown. to Client or
Consultant. Neither Client nor Consultant shall have liability to indeninify or hold harmless third parties few
losses incurred by actual or purported use or misuse of this report. No other warranties are implied or
expressed.
Report Recommendation arc Limited and Subject to Misinterpretation
There is a distinct possibility that conditions may exist that could not be identified within the scope of thc
investigation or that were not apparent during our site investigation. Findings of this report are limited to data
collected from noted explorations advanced and do not account for unidentified till zones, unsuitable soil
types or conditions, and variability in soil moisture and groundwater conditions. TO avoid possibL,
misinterpretations of findings, conclusions. and implications of this report. MTI should he retained to explain
the report contents to other design professionals as well as construction professionals.
Since actual subsurince et:m(1100ns on the site can only he verified by earthwork, note that construction
recommendations are based on general assumptions tinii selective observatiow; and selective Held
exploratory sampling. Upon commencement of constructionsuch conditions may be identified that required
corrective actions, and these required corrective actions may impact the projeci budgee lilt'atfone
construction recominceulations in Ibis report should he considered preliminary, and Mi I should h...
in 1
suiurlace conditiow_-; donne construction lcnvilic,;
OMISinWt1011 rCCOMMOndatiOnS IS n0A1Cd,
ALL] 201
S 0
rr-;04.25,z
hmtAl.:,; are stthjeci to misinterpretation. do not separate the soil logs iron] the
kaih(21, provide a copy, or andlorr4c for their use, of the complete report to other (le in cr61',:-:sico 1:Y
' )1iln?,Clt'irS,
ins report is also limited tnanon available at the Lini it +A'a•-; piepired ii die Lv,„.11.1 dJ ii
information is provided to M I I following publication or our report, it will be Enwarded to the chew i6;
evaluation in the form received.
Environmental Concerns
Comments in this report concerning either onsite conditions or observations, including soil appearances and
odors, are provided as general information. These comments are not intended to describe, quantify or
evaluate enviromnenzal concerns or situations, Since personnel, skills, procedures, standards, and equipment
dirtier, a geotechnical investigation report is not intended to substitute for a geoenvironmental investigation or
a Phase 11/111. Environmental Site Assessment. If environmental services are needed. MI1 can provide, via a
separate contract, those personnel who are trained to investigate and delineate soil and water contamination.
SITE DESCRIPTION
Site Access
Access to the site may he gained via Interstate 84 to the Meridian Road Exit. Follow Meridian Road north for
i'ipproximately I mile to its intersection with W Pine Avenue, From this intersection proceed \vesi for
approximately 2 miles to its intersection with Ten Mile Road. illhe site occupies the southeast corner of this
intersection. Presently the site exists as a roughly prepared commercial building pad. The location is
depicted in site map plates included in die Appendix.
Regional Geology
The site is located within the Boise Valley, which is directly underlain by a thick sequence of aliuvial sands
and gravels typically deposited on basalt formations, These sediments are loosely named the Boise Rivet
Gravels and were deposited as river floodplain and stream overwash from the Boise Riv(..1.. These gravel
deposits tend to have imbricated vell-rounded clasts. poor sorting and crude stratilication of beds of gravel
and lenses of cross-bedded sand suggesting deposition in braided channels [-Wise River (-Travels t.'rinsist
it
unconsolidated clay, silt, sand, gravel, and cobbles, These gravels have been subdivided into smaller units
based on their age and arc exposed as distinct alluvial terraces, Five of these terraces arc %Yell exposed in the
koise area and range in age from Nliddle Pleistocene to flolocene (Reeent) O - 0,9 million years ago), The
site lies on the Whitney Terrace, the second terrace above the currently delint.sd floodplain tOiliberF and
‘iaLinlii,wd, 9(12)
General Site Characteristics
I
lii proposed clevolo.pment i to Na cort,ortict.NI v iihin an area oirdtovidy lint and level tcyniin. nwnfl rria:;id
fill plat:einem I n place hi ominicrciul U. IThirutq4,houi th,c
IC ' IC ,,a rtical materials appejr sail fIN. 7\.:011e Witt
;
a\ie:spec-rtatim
. . .
N'riDdycan clay , Vegetution la' leco hipped through the centra: portion f the ik ii1 thick
o-tluincer grown remains along the lot street side perimeter,
keL2ronal (iran-fuge is twilit and west toward the Boise. River, Storm water drainage for the site IS achieved
percolation t11f01,101 sttrficial Ihe she is situated so tliia it is unlikely that it will recei‘'e any siorn1 wale,
drainage from off-site sow-cc:,, Storm \vater drainage collection and retention S!!,-`s-lerm, alL nt clitrc. d iin
place on the project :site, but have been incorporated within the adjacent street sections.
Regional Site Climatology and Geochemistry
According to the Western Regional Climate Center, the average precipitation for "Freasure Valley is on the
order of 10 to 12 inches per year, with an annual snowfall of approximately 20 inches and a range from 3 to
49 inches. The monthly mean daily temperatures range from 21 F to 95" 1' with daily extremes ranging frorn
-25° F to 111°F. Winds are generally from the northwest or southeast with an annual average wind speed oh
approximately 9 miles per hour (mph) with a maximum of 62 mph. Soils and sediments in the area are
primarily derived from siliceous materials and exhibit low electro-chemical potential for corrosion of metals
or concretes. Local agi-,regates arc generally appropriate ti-tr Portland cement and lime cement mixtures
Surface waters, .t2roundavaters, and soils in the region typically have pl.! levels ranging from 7.2 to 3.2.
Geoseismic Setting
Soils on site are classed as Site Class L) in accordance with Chaplet 70 of the American Society of Li if
Em2ancers (ASCU.) pualication ASCF/SEI 7-10. Structures constructed on this site should he designed per
IBC requirements for such a seismic classification. Our investigation did not reveal hazards resulting from
potential earthquake motions including: slope instability, liquefaction, and surface rupture caused by faultitq,,
or lateral spreading. Incidence and anticipated acceleration of seismic activity in the area is low.
Soit.s EXPLORATION
1,:xploration and Sampling Procedures
Field exploration conducted to determine engineering characteristics of subsurface materials included a
reconnaissance of the project site and investivation by test pit. Test pit sites were located in the 1.ield
means of visual approximation from on-site features or known locations and are presumed to be accof ate
to
within a few feet. Upon completion of investigation, each test pit was backfilled with loose excavated
materials. Re-excavation and compaction of these test pit areas are required prior to construction of overivinL,
structures.
In addition. samples ,,N'C IV obtained from rfpresentalive soil strata encountered. Samples oh:titled ha\ tcC1•1
visually classified in the held h\ professional staff. identified according 10 test pit number and deptli. plac,:d
in sealed containers, had transported to our laboratory liar additional testing. Subsitthice 111: 1w al
set
described in detail on logs pto\-ideti in tb, Appcndix. ResulLs oh field anti laboratory tc'cas taa- .akca piescrock.1
t‘al these logs. N111 re,..'ommends that Mese loe,s nut be used to estimate WI material quantities
A
Apc;! :W4
Lei.24
N$1;P CTION
Laboratory 'resting Program
Aloiw ith Our held investigation, a supplemental lahoratory testing proigrarri waili conducted to dk-nrii-riii'ia
additional pertinent engineering characteristics of subsurface materials necessary' in an ilk tit,'
anicipated hehavioi of the pi-opcised s.ittuctut es. 1.aborakuy tests weiie concluded in accordance
th
applicable American Society hir Testing and Materials (ASTM) specifications, and resuhs of thesete are, to
he Mind on he accornNnying lot's located in the Appendix. The labciratory testing program for this report
included: Atrerhern .Limits Tests - ASTM 1)413 I 8 and Grain Size Analysis - ASIM Cl I'7,1C1:36,
Soil and Sediment Profile
-Elie profile below represents a generalized interpretation for the project site Note that on site soils shinta
encountered between test pit locations. may vary from the individual soil profiles presented in the logs. which
can be found in the Appendix.
The materials encountered during exploration were quite typical for the geologic area mapped as the \Vhitne,
Terrace. Surficial materials appear to be silty gravelly sand fills placed to level the building pad. Beneath the
fills we encountered sandy lean clays that Were (talk brown to brown in color, exhibited moisture contents ol
slightly moist, and consistencies of very stiff to hard. The sands within the clays was line unlined. Beneath
the clays were sandy silts, that were tan to red brown, slightly moist to dry. and hard. The strength or this soil
is a result of the \veal,: to moderate calcie cementation foimdthroteloin this layer.
The sandy silts transition at depth to silty sands that were red brown to brciwn. dry to sliphtly moist, and
medium dense to very dense. This sediment horizon also exhibited calcic cementation However, through this
layer it was classed as moderate to strong, and was difficult to penetrate with the backhoe. Underneath the
silty sands we encountered poorly graded gravels. These were tan to brown, moist to saturated, and medium
dense to dense. Gravel clasts were predominately 2 inch minus in size. Sands through this layer were medium
grained in size.
Competency of test pit walls varied little across the site. In general, line grained soils remained stable while
more granular sediments sloughed. Moisture contents will also affect wall competency, and saturated soils
had a tendency to readily slough when exposed and unsupported laterally.
Volatile Organic Scan
No environmental concerns were identified prior to commencement of the investigation. I herefore, soils
obtained during on-site activities were not assessed for volatile organic compounds by portable
photoionization cletector SanTles obtained during our exploration activities exhibited 1141 Odor
diSCCIOratiOn typically asociated with this type contamination. Groundmtter encountered did noi 1-'11
ONVIOUS 51;-:2,,I15 COraaMinatiOn,
?u-Li
ilSgSPEC1ION
SITE HYDROLOGY
sistiiT siirfaco d1j11 i liditions are defined in the 41eneral Site Chararteristie. seLtion inafior:
provided in his section ;sluniktit observations made at the time of the investig.inon. tOII er regionai
ordinann:,.,?s may ftquire intOrmat ion beyond the scope iii this report.
Croundwater
During this field investigation, groundwater was encountered in test pits at depths ranging from 10. to (L9
feet bgs, in test pits 1 and 2, respectively. Actual groundwater depths appeared to vary with topography. Soil
moistures in the test pits were generally slightly moist to dry within shallower soils. Additionallycalcie
cementation was noted to extend to depths below 9 feet. This cementation will usually be leached away if
groundwater is reaching these soils. Within the poorly graded sands and gravels, soil moistures graded from
moist to saturated as the water table was approached and penetrated.
In the vicinity of the project site, groundwater levels are controlled in large part by residential and commercial
irrigation activity and leakage from nearby canals. Maximum groundxvitter elevations likely occur during the
later portion of the irrigation season. During previous investigations performed in 2005 ininrc'diatcly to the
west and north, groundwater was encountered as shallow as 7.4 feet of depth, Each of these sites, s' CI,
were lower in elevadon.
Based on evidence of this in vestigat6n and those from the surrounding area. MTI cstintates groundw..ncr
depths to leOlail I greafei than approximately 9 feet bgs throughout the year, This is an estimate, and can l7c
confirmed through lone-term groundwater monitoring.
Soil Infiltration Rates
Soil permeability, which is a ineasuie of die ability of a soil to transmit a fluid, was not tested in the Field.
Given the absence of direct measurementsfor this report an estimation of infiltration is presented using
generally recogni7e1 values for each soil type and gradation. Of soils comprising the generalized soil profile
for this study, lean clay soils generally offer little permeability, with typical hydraulic infiltration rates e less
than 2 inches per hour. The presence of sands may increase this slightly. Sandy silt soils will common's,
exhibit infiltration rates from 2 to 4 inches per hour; though calcium carbonate cementation may reduce this
value to near zero Silty sand sediments usually display rates of 4 to 8 inches per hour. Ilmugh cernentai ion
was also noted through this horizon. Poorly graded gravel sediments typically exhibit infiltration values in
excess of 12 inches per hour. Infiltration testing is generally not required within these sediments because cif
their flee-draining nature.
It is recommended Mat infiltration facilities constructed on the site he extended into native poorN
sands and era'.el s(.-sditrients. Fxc.i.,,vation depths pi'appr(edinaielv 9 feel hgs should he anticip,wicilLI
inesc poorly graded gravel witi sand sediric:nis Because of the nigh soil perrnabilit‘.:..
sand. OF equivaloni, shouid h ift-orpi.u-ated into design olinliltr:iti('n lacilities, Au infiltruiii.)ii
per hour should he used in ciesieu, Actual infiltration rifts should be confirmed At the