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Report - t . - ift. f , ,, • , U Z 'DESIGN_ " ECEIVE 1,,,,n JUN 9 2011 CITY OF TIGARD . • BUILDING DIVISION :• April 1, 29.0 . , Centex Homes . ' 77_/ 5E 'I 1241-1Slater Av,enue NF, Suite 100 /09F9 Ski /46 Kirkland, WA 98033 : f . , 1 !. Attention: Mr. Toni Brown -1 i. . . . •,. , . . , . Report of Geotehnie41 Ettirteeririg•5eryliees I • arld,Relianee•„Letter Proposed Tigard . „ .., .... ,'. . Tigard; Oregon i . . GeoDesign Centek-16=01 • . . , • {,• , -, . ... • : i . • , . . , • , INTRODUCTION i This report presents the results OPoUr.geoteChnital.engineering'seryicS'fOr the proposed resideritial•deVeloPrrient'. southwest corner of the interSectiOnOfSWSCh011s Ferry i site Road and SE 1:5ip. 74:igaf:a;ptegpn::.W:k;Unde 4106k 0:5:::a:Ce!:af.0 inel4des .. S8;'!.individtiat IdiS:..Thei60 currently vacant but are develppecViith and paved roadways for future residential developmen ri . . GeoDesign assumed the role of j,eote engin of record for the proj andprOV,ided cOristrOCtiOn-ObSer,VatiOri SerVieeS Development durihgearthWOrk;oUr involvement began in July 2007="ancl'',COritinued until March 2008 . :kgetitehiiid1,r0Ort fOf:# completed by GeoPacific Engi lig Inc on January 13, 200 :e6-tifle:ti PrelfrOirldryqeOie?hriical Eriiiii tdv and SW 50014 Ferry 1.0.04; Washington County Oregon in addition' GeoDesign previously prepared supplemental recommendations for use in design of gravity retaining walls in a letter entitled Geotechnical Engineering Services, The Village at Summer Creek, sW.garrows' Road aqd :$14% Scholls'rehy Road; ,:. Tigard di:ego,n, 04toci :June 6, 2 007 . . I .. . The current plan is to construct residential structures on the 88 lots that have been prepared. Foundation loadS' Were unknown at the time of this report; we have asSUMed that they will be . : typical of one to locir residential struCtureS. We further understand that some site grading will take place to accommodate design elevations. Cuts and fills are not expected to exceed 5 feet, respectively. A site plan showing existing improvements and our hand explorations is shown on Figure 1. 1 , 1 , I . , . liffiariMEM .' • '''' ' ' - — ., . • VIViliaWiAnW4574:. 15575 SW Sequoia Pkwy • Suite 100 1 Portland, 08 97224 I Off 503.968,8787 i Fax 503.968.3068 aftlklilreAkIVetifiti4 r i ' lWieerniarireAakiliaw0., ' • SCOPE OF SERVICES The purpose of our work was to confirm that our previous work is in conformance with the geotechnical engineering report and to provide supplemental recommendations for use in design and construction of the proposed development. Specifically, we completed the following scope of services: • Reviewed in -house files for existing information on subsurface conditions in the site vicinity, prior earthwork, and the previous geotechnical report for the site. • Visited the site and completed a visual surface reconnaissance 'to confirm that no additional earthwork has been conducted since completion of the project. • Completed eight hand augers to a maximum depth of 7 feet below ground surface (BGS). • Prepared this report, which also serves as a reliance letter, that presents our findings and provides updates to the conclusions and recommendations provided in the previous geotechnical report. SITE CONDITIONS SURFACE CONDITIONS We completed a visual surface reconnaissance at the site During our visit, we observed that the ground surface is slightly sloped down towards the south from the north. .A. As discussed above, the lots have been developed with associated utilities, sidewalks, curbs, retaining walls: and asphalt -paved roadways to allow access to the lots. The lots are covered by grass, with small patches of blackberry brush near the proposed playground area at the east portion of the property. Areas of ponded.water were observed on Lots' 5, 9, 10, 35, and 30 through 32. While on site we observed the cracks in the= asphalt roadway on SW Coriander lane. As noted in our field reports, the asphalt was reheated during placement using propane torches, which may have contributed:to the cracking. SUBSURFACE CONDITIONS We completed eight shallow hand, =auger borings (HA -1 through HA-8) at selected locations across thesite. The approximate boring locations are shown on Figure 1. Based on our explorations, the shallow subsurface conditions in the area generally consist of compacted fill that is medium stiff to stiff silt with varying amounts of clay, sand, and gravel. The fill generally ranges in thickness from 0.2 foot to 2 feet BGS: The fill was encountered in most of the borings except for HA -5 and HA -6, Which were completed near the proposed playground area at the east portion of the property. A thin layer of loose gravel with silt and "sand was encountered at the surface in HA -6. Native alluvium consists of medium stiff silt with some clay and trace organics. In HA -2, we encountered loose sand with minor gravel and encountered refusal on concrete at approximately 6 inches BGS. We drilled four more borings within a 1d-foot radius of HA -2 and encountered concrete at 3 to 6 inches BGS. The area of the sand fill over concrete appears to extend over Lots 47 through 49. The approximate area is shown on Figure 1. EO DES IGN? 2 Centex -16- 01:041610 a � I Based on our explorations, the average depth of stripping in lightly vegetated areas will be approximately 1 to 2 inches. Stripping activities should be completed as recommended in the previous geotechnical report. CONCLUSIONS AND,RECOMMENDATIO.NS In general, we anticipate that the geotechnical recommendations provided in the previous geotechnical report are still applicable to the site with the exception af.the additional 1 to 2 inches of stripping anticipated at the site and our revised shallow foundation recommendations. WET WEATHER/WET SOIL GRADING The silty soils at the site are easily disturbed during the wet season and when they are moist. If not carefully p executed, site re _aration; utility trench work and roadway excavation can create extensive soft areas significant subgrade repair costs can result. If construction is planned when the surficial soils are wet or may become wet, the construction methods and schedule !. should be carefully considered with respect to protecting the subgrade to reduce the need to over - excavate disturbed, or. softened Oil. The project budget should reflect,the recommendatio ns below if construction is planned during wet- weather or when the surficial soils are wet. i , If construction occurs when silty, wet soils are present, site preparation activities may need to be i accomplished using track mounted e equipment that Loads removed material into trucks•suppo.rted on granular t aut roads. The thickness ofthe granular material for haul roads and staging areas will depend on the amount and type of construction traffic. Generally, a 12- to 1 8.irich thick:.mat,of imported granular material Is sufficient for light s taging areas and'the basic • building pad but is.:generally not expected to be adequate to support heavy equipment or truck traffic. The•.granular mat.for haul roads and areas with repeated heavy construction traffic . typically needs to be Increased to'between 1 8.to 24 inches. The actual thickness of haul roads and staging areas should be based on the contractor's approach to site development and the. amount and type, of construction traffic: The imported granular material should be placed in one lift over the prepared, undisturbed subgrade and' compacted. using; a smooth drum, non=,vibratory roller. In addition, a. fabric may be required:as a barrier between the subgrade and imported granular material in areas of repeated construction traffic. The imported granular material should be pit -.or quarry-run rock,.crushed rock, or crushed,gravel and sand and should meet the requirements set forth in the 2008 Oregon Standard Specifications for Construction (OSSC) 00330:14 (Selected. Granular Backfill) and OSSC ,00, 3 30.15 (Selected Stone Backfill). The placement of the imported granular fill should be done in conformance with the specifications provided in OSSC 00331 (Subgrade Stabilization): The geotextile should meet the specifications provided in OSSC 02320.20 (Geotextile Property Values) for soil separation. The geotextile should be installed in conformance, with the specifications provided in OSSC 0 035 (Geosynthetic Installation) material should be fairly well- graded between coarse and fine material and have less than 5 percent by dry weight passing the U.S. Standard No, 200 Sieve. GEODESIGM ? 3 Centex -16- 01:041610 FOUNDATION SUPPORT Dimensions and Capacities Continuous footings for stud bearing walls should be at least 15 inches wide. The bottom of exterior footings should be at least 18 inches below the lowest adjacent exterior grade. The bottom of interior footings should be established at least 12 inches below grade. Footings bearing on subgrade prepared as `recommended above should be sized based on an allowable bearing pressure of 2 pounds per square foot. This is a net bearing pressure; the weight of the footing and overlying backfill can be ignored in calculating footing sizes. The recommended allowable bearing pressure applies to the total of dead plus long -term live loads and can be increased by one -third for short -term loads (such as those resulting from wind or seismic forces).. Based on our analysis and experience with similar soils, total post - construction settlement should be less than 1 inch,'with differential:settlernent of less than 4 inch over 4,50-foot span. Resistance to Slidiing Lateral loads on footings can be resisted by passive earth pressure on'the•sides of the structures and by friction on the of the footings: Our analysis indicates that the available passive earth pressure for footings confined by on site soils and structural fills is 3'50 pounds per cubic foot, modeled as an equivalent fluid pressure. Adjacent concrete slabs, pavements, or the upper 12 inch'depth'of adjacent, unpaved areas should not be considered when calculating passive resistancec.:ln addition, in order to rely upon passive resi a minimum 'of 10 feet , of horizontal clearance must exist between ` the face of°the footings and adjacent down slopes. For footings in contact with the on =site native material, -a coefficient of friction equal to0.30 may be used: when calculating resistance to sliding. This value'should be increased to 0 :40 'for crushed COCk or imported granular fill. Foundation Drains • Foundation drains' `be considered on the outside of the perimeter footings =.of all buildings and routed to a suitable discharge because of the potential for shallow groundwater: The foundation drains should consist 4 inch" diameter,' perforated drainpipe embedded in a minimum 2 - foot - wide zone of drain rock: Draintrock should consist of angular, granular material with a maximum particle size of 2 inches and should meet OSSC 00430.11 (Granular Drain Backfill Material). The material should be free of roots, organic matter and other unsuitable materials; have less than 2 percent by dry weight passing the U.S. Standard No 200 Sieve (washed. analysis), and`have at least at least two mechanically fractured faces. Drain rock should be wrapped in a geotextilefabric that meets the specifications provided in OSSC'00350 (Geosynthetic Installation) and OSSC 02320 (Geosynthetics) for drainage geotextiles. CONSTRUCTION CONSIDERATIONS All footing and floor subgrades should be evaluated by the project geotechnical engineer or their representative to confirm suitable bearing conditions. Observations should also confirm that all 't EODESIGNY t1 , Centex- 16-01:041610 ` f loose or soft material, organics, unsuitable fill, prior topsoil zones, and softened subgrades (if present) have been removed. Localized deepening of footing excavations may be required to penetrate deleterious materials. If footing excavations are conducted during wet weather conditions, we recommend that a minimum of 3 inches of granular material be placed and compacted until well -keyed at the base of the excavations. The granular material reduces subgrade disturbance during placement of forms and reinforcement and provides clean conditions for the reinforcing steel. 4 , We appreciate the opportunity to be of continued service to you. Please call if you have questions concerning this report or if we can provide additional services. Sincerely, GeoDesign, Inc. 'Viola C. Lai, P.E , G.E. !� l Project Engineer '. , - Brett A. Shipton, P.E., G.E. 14 ' V Principal Engineer VCL: BAS: kt Attachments Two copies submitted Document ID: "Centex -1 6 -01- 041610- geolr.doc Co 2010 GeoDesign, Inc. All rights reserved. 9 i Gra DESIGNz 5 Centex -16- 01:041610 Printed By: cdavls I Print Date: 4/16/2010 1:55:19 PM Hie Name: \ \geodezign. local \FllesVobs \A -D \ Centex \ Centex -l6 \Centex - 16-01 \ Figures \CAD \Centex -16.01 -SP01.dwg I Layout: FIGURE I • 1 , r r . 1 3: I 11 • . t 11 I - r x Y - --_ , - 3 � D , f I 1 I ' i .- / - i ' ( .....4 f t �� 1 ® , 1 ---- -- i r - �/ I 1 1 1 - 1 -- ---1---,.;_,_ , p ° ` o b / / / ° o. d i ;:;! I m / / ® / \ , y r / li • I I i t -- . / ' ...- �;i- -o. -_7.. -- _ "s`07',. / / / ?. ( ® 1,-L , .._ / / v \\;t--- /// 1 i 1 n 1 ' , j, '---...., ---„, ,,, --,.. =:: -„ , i 1 cn er / / �� �\ M i, ,,, , -.., , C4 -- im 1! ti / /d \� � / / 1 , I �Ft: j f !dam ® N \ � F 1;,''/y7: L 4 Ji // , • / , e - �� \ j / i , ju t % /' " a \ ! ,/,, t¢ e. / �' , 4 w ry �i f / — /� 4.„4.-": > t9\ • i f l / / ___... I , I . \ ••?' • ,. ! • f l? . / WA I I ! 1 {.r . ` / / .. P ( —..._ t. T Z X _ +�` • 7 i 1. i � I i 4° 1 .'ION �� (d.. _ ado \\ n • m N -I"' v ° m =z x m xx n z tel tn 0 0 33 2 rr7 01 I -,:,., ° z z oz N n c - n 0 A 0 O m 0 th GEODESIGNY_ CENTEX -16 -01 SITE PLAN 1 55]3 s✓/sejuela Parkway -Satre 100 Ponhgd oa 97221 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT Ore 503.968 BM Fax 903.3684063 APRIL 2010 FIGURE 1 TIGARD, OR a , ATTACHMENT • FIELD EXPLORATIONS GENERAL We explored subsurface conditions by performing eight hand -auger borings (HA -1 through HA -8) to depths ranging from 0.5 foot to 7.0 feet BGS on April 9, 2010. We obtained representative samples of the various soils encountered in the exploration. Classifications and sampling intervals are presented on the exploration logs included in this attachment. The approximate locations of our explorations are shown on Figure 1. The locations of the explorations were determined in the field by pacing from existing site features. This information should be considered accurate only to the degree implied by the methods used. SOIL CLASSIFICATION The soil samples were classified in accordance with the "Exploration Key' (Table A -1) and "Soil Classification System" (Table A- 2) are included in this attachment. The exploration logs indicate the depths at which the soils or their characteristics :change, although the change could be gradual. A horizontal line between soil types indicates an observed (visual or drill `action) change. If the change between sample locations_ and was not observed or obvious, the depth was interpreted and the change is indicated using a dashed line Classifications and sampling intervals are presented on the exploration logs included in this attachment. G EO DES I G hl? A -1 Centex -16- 01:041610 • SYMBOL SAMPLING DESCRIPTION Location of sample obtained in general accordance with ASTM D 1 586 Standard Penetration Test with recovery Location of sample obtained using thin -wall Shelby tube or Geoprobe® sampler in general 1 accordance with ASTM D 1 587 with recovery Location of sample obtained using Dames & Moore sampler and 300 -pound hammer or pushed with recovery Location of sample obtained using Dames & Moore or 3- inch -O.D. split -spoon sampler and 140 - pound hammer or pushed with recovery Graphic Log of Soil and Rock Types Location of grab sample w; ,,.. Observed contact between soil or rock units • (at depth indicated) Rock coring interval Inferred contact between soil rock ac 0 Water level during drilling (at approximate depths : =. — indicated) • I V Water level taken on date shown GEOTECHNICAL TESTING EXPLANATIONS ATT Atterberg Limits P Pushed Sample CBR California Bearing Ratio PP Pocket Penetrometer CON Consolidation P200 Percent Passing U.S. Standard No. 200 Sieve DD Dry Density RES Resilient Modulus DS Direct Shear SIEV Sieve Gradation HYD Hydrometer Gradation TOR Torvane MC Moisture Content UC Unconfined Compressive Strength MD Moisture - Density Relationship VS Vane Shear OC Organic Content kPa Kilopascal ENVIRONMENTAL TESTING EXPLANATIONS CA Sample Submitted for Chemical Analysis ND Not Detected P Pushed Sample NS No Visible Sheen PID Photoionization Detector Headspace SS Slight Sheen Analysis ppm Parts per Million MS Moderate Sheen HS Heavy Sheen EODESIGN? EXPLORATION KEY TABLE A -1 15 575 SW Sequoia Parkway - Suite 100 Portland 01297224 Off 503.968.8787 Fax 503.968.3068 RELATIVE DENSITY - COARSE - GRAINED SOILS Relative Density Standard Penetration Dames & Moore Sampler Dames & Moore Sampler Resistance (140 -pound hammer) (300 -pound hammer) Very Loose 0 -4 0 -11 0 -4 Loose 4 - 10 11 - 26 4 - 10 Medium Dense 10 - 30 26 - 74 10 - 30 Dense 30 - 50 74 - 120 • . 30 - 47 Very Dense More than 50 More than 120 More than 47 CONSISTENCY - FINE- GRAINED SOILS Consistency Standard Penetration Dames & Moore Sampler Dames &,Moore Sampler Unconfined Compressive Resistance (140 -pound hammer) (300 -pound hammer) Strength (tsfj Very Soft Less than 2 Less than 3 Less than 2 Less than 0.25 Soft 2 - 4 3 -6 2 -5, 0.25 -.0.50 Medium Stiff 4 - 8 6 1 2 5 - 9 . 0.50. -'1.0 Stiff 8 -15 12 -25 9 -19 ' '1.0 -2.0 Very Stiff 15 - 30 25 - 65 1'9: 2.0 - 4.0 Hard More than 30 More than 65 More than 31 More than 4.0 PRIMARY SOIL DIVISIONS GROUP SYMBOL GR NAME CLEAN GRAVELS GW or GP GRAVEL GRAVEL (< 5 %fines) (more than 50% of GRAVEL WITH FINES GW -GM or GP -GM GRAVEL with silt ( 5% and 5 12% fines) GW -GC or G P -GC G RAVEL with'cla coarse fraction Y COARSE- GRAINED retained on GM silty`GRAVEL No. 4 siege) GRAVELS WITH FINES SOILS GC cl GRAVEL (> 12 %fines) GC=GM silty, clayey,GRAVEL (more than 50% CLEAN SANDS retained on SW or SP SAND No 200 sieve) SAND ( 5 %fines) (50% or more of SANDS.WITH FINES SW -SM or SP -SM S wit silt coarse fraction ( >_ 5% and <_ 12 %' f i nes) SW SC, or SP -SC , S AND „with clay passing SM silty SAND No. 4 sieve) SANDS WITH FINES (> 12% fines) SC clayey SAND ' SC -SM silty clayey SAND ML , SILT FINE - GRAINED CL CLAY SOILS Liquid limit less than 50 CL -ML silty CLAY (50% or more SILT AND CLAY OL ,ORGANIC SILT or ORGAN AY IC CL passing MH SILT • No. 200 sieve) Liquid limit 50 or CH CLAY greater OH ORGANIC SILT or ORGANIC CLAY HIGHLY ORGANIC SOILS .. PT PEAT MOISTURE ADDITIONAL CONSTITUENTS CLASSIFICATION Secondary granular components or other materials Term Field Test such as organics, man -made debris, etc. Silt and Clay In: Sand and Gravel In: very low moisture, Percent Fine - Grained Coarse- Percent Fine - Grained Coarse- dry dry to touch Soils Grained Soils Soils Grained Soils moist damp, 'without < 5 trace trace < 5 trace trace visible moisture 5 - 12 minor with 5 - 15 minor minor wet visible free water, > 12 some silty /clayey 15 - 30 with with usually saturated ' lit” - ' f > 30 sandy /gravelly sandy /,gravelly �IIEO SOIL CLASSIFICATION SYSTEM TABLE A - 15 575 SW Sequoia Parkway - Suite 100 Portland OR 97224 Off 503.968.8787 Fax 503.968.3068 Z p Ox L7 w A BLOW COUNT DEPTH < Z ® MOISTURE FEET d MATERIAL DESCRIPTION w o r" 2 CONTENT% COMMENTS -J w < w H- U HA -1 0 50 100 0.0 Medium stiff to stiff, light brown with orange and gray mottled SILT (ML), some clay, trace gravel, milled wood, red plastic fragments, organics (rootlets), and charcoal; moist (1 -inch- - thick root zone) - FILL. _ 1'8 2.5— Medium stiff, light brown SILT (ML), some'clay, trace organics (rootlets); moist (alluvium). becomes stiff at 3.5 feet stiff to very stiff, orange mottles at 4.0 Surface elevation was not \feet ,- 4.5 measured at the time of 5.0 Exploration completed at a depth of 4.5 exploration. feet. 7.57- • • • HA -2 0 50 100 0.0 50 100 • Loose gray brown SAND (SP), trace to �. Hand augered tour borings within \minor gravel; wet FILL.. 0.s a 1Q-foot radius of HA -2 and encountered concrete at 0.25 to Exploration terminated `due•to refusal 05 foot _ on co to at 0 fo o t . " Surface `elevation was not measured at the time of exploration. 1- • 2.5 —. • F- O U - z U O • 5.0 V U. co • 7.5 — z - w U U a a - z w _ N } 0 50 100 Z �u DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 0 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -Inch w HAND AUGER CENTEX -16 -01 j ,ESICNZ z ¢ 1 5576 SW ' Sequoia parkway -Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT = Portland OR 97224 APRIL 2010 Off 503.968.8787 Fax 503.968.3068 TIGARD, OR FIGURE A -1 z o O = u L , A BLOW COUNT DEPTH U Q a z a • MOISTURE COMMENTS FEET a MATERIAL DESCRIPTION w o I g CONTENT w I- tli u HA -3 0 so loo 0.0 Stiff, brown SILT (ML), some clay, trace - organics (rootlets) and gravel; moist (1- inch -thick root zbne) - FILL. Soft to medium'stiff; brown SILT (ML), J -o El - - - trace clay and organics _(roots and 1.8 \rootlets); moist (buried topsoil). / 2.5— Medium stiff, light brown with orange _ mottled SILT (ML), some clay, trace organics (rootlets); moist (alluvium). becomes stiff at 3.5 feet stiff, light brown mottles at 4.0 feet ® Surface elevation was not Exploration completed at a depth of 4.5 4.5 measured at the time of 5.o— feet. exploration. 7.5 — HA -4 o so 100 • 0 so too 0.0 Stiff, brown SILT (ML); :trace clay; . Y organics (rootlets), gravel, and asphalt - El fragments; moist (1- inch -thick root zone) FILL. stiff to medium stiff, light brown at 1.5 IN feet C' 2.5— i Stiff gray SILT'(ML), trace fine sand, - 3.0 XI I– – org anics. (r and gravel; moist, u low plasticity FILL. u w grades to gray and light brown at 4.5 • 0 5.0— feet — -..- with orange mottles at 5.0 feet u Stiff to medium stiff, light .brown SILT J s.s a (ML), some clay, trace organics VI _ (rootlets); moist (alluvium). Surface elevation was not tb Exploration completed at a depth of 7.0 7.0 measured at the time of x7 7 .5 — feet. exploraa td tion. IL u w u a w a N H F- 0 50 100 Z 0 0 DRILLED BY GeoDesign, Inc. staff LOGGED BY JPW COMPLETED: 04/09/10 3 0 J 3 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER* 3 -inch z HAND AUGER = u CENTEX -16 -01 - - ESIGfVZ (continued) Z 155755WequoiaParkway -S uite loo Sequoia PROPOSED TIGARD RESIDENTIAL DEVELOPMENT = Port OR 97224 APRIL 2010 Off 503.968.8787 Faz 503.968.3068 TIGARD, OR FIGURE A 2 z m u w ♦ BLOW COUNT DEPTH Q a z a ® MOISTURE FEET d MATERIAL DESCRIPTION w o N 2 CONTENT% COMMENTS Q w F Ln HA -5 0 50 100 0.0 Medium stiff to stiff, brown SILT (ML), minor clay, trace organics (rootlets); moist (27inch -thick root zone). 2.5 — • Surface elevation was not measured at the time of Exploration completed at a depth of 4.0 4.0 exploration. feet. 5.0 — 7.5 — 0 So 100 HA =6 0 s0 100 0.0 O ' -I Loose GRAVEL with silt and fine sand / 0.2 \(GP) (2 inches),- FILL. Stiff, light brown SILT (ML), some clay, trace organics (rootlets); moist. -® o with orange and gray mottles at 2.0 • 2.5 — feet ® Surface elevation was not Exploration completed at a depth of 3.0 3.0 mea tion. at the time of explo feet. 0 u - 5.0 — w v _ F_ 0 7.5 — z w U w U Q a - En w 0 50 100 z e DRILLED BY: Geo0esign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER 3-inch a o �I u CENTEx 16 01 HAND AUGER a�= ES 9 pp I V? (continued) 0 15575 SW Sequoia Parkway - Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT = Portland OR 97224 APRIL 2010 FIGURE A -3 Off 503.968:8787 Fax 503.968.3068 TIGARD, OR z o = u 11 , A BLOW COUNT DEPTH v Q a Z 0_ • MOISTURE FEET a - MATERIAL DESCRIPTION w o N 2 CONTENT% COMMENTS w < ce w I-- u HA -7 0 so 100 0.o Medium stiff to stiff, brown SILT (ML), some clay, trace organics (rootlets), gravel, and concrete fragments; moist (1- inch -thick root zone) - FILL. Very stiff, light brawn -gray with 2.0 2.5 orange mottled SILT (ML), some clay, trace gravel; moist - FILL, Stiff, light brown with gray mottled SILT 3.3 (ML), some clay, trace organics (roots); moist (alluvium). 5.0 Surface elevation was not sand at 5.0 feet s.o measured at the time of Exploration completed at a depth of 5.0 exploration. feet. 7.5— so 100 HA -8 0.0 o so loo Stiff, brown SILT (MP, minor clay, trace organics (rootlets) and gravel; moist (1' inch - thick root zone) L FILL. Medium`'stiff to stiff; light with 20 2.5 orange :and gray mottled SILT (ML), • - some clay, trace organics (rootlets); • moist (alluvium). F- 0 - z o Surface elevation was not ° 5.0 Exploration completed at a depth of 5.0 S.° measured at the time of feet. exploration. 0 ,S 7.5- 6 V U .4 K v. N Z 0 50 100 DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch r u C ENTER 16x01 HAND AUGER f ®ES�G (continued) Z 15575SW,Sequoia Parkway - Suite loo PROPOSED TIGARD RESIDENTIAL DEVELOPMENT Portland OR 97224 APRIL 2010 Off 503.968.8787 Fax 503.968.3068 TIGARD, OR FIGURE-A-4 I I 1 :.• ; r''' . :. — - ' :U M.: L .i';.=;.:: M DESIGN u z , - i RECEIVED • i JUN 9 2011 • ; . CITY OF TIGARD • April 16, 2010 BUILDING DIVISION 1 . ,. Centex Homes . . ; . . 1 1241 Slater Avenue NE, Suite 100 • •-* Kirkland, WA 98033 l I i Attention: Mr. Tom Brown I, 1 , . . 1 , I Report of Geotechnical Engineering Services 4)14, . . Proposed Tigard Residential peV'eidPment Tigard, Oregon . GeoDesign Project: Qeritek 6;01 . . 1 . . . . .. . INTRODUCTION .. . _ , . . . . . . . . This report presents the results of geotedinkal ,engineering...servreeS 3 ,I .] residential deVelopment IOCated'at'the southwest corner of the interSeetibri of SW SebOlIS Ferry i ; ! Road and SE 135!!' in Tigard, Oregon. We* site encompasses ! app 8 5...aeres and includes , 88 1 indiyidUAIOt:S.:Thelek.:41 4 e - eurrentlYVaCant:but are . . develOpedW.ith utifiti6,:6fi-3,.aiid paved roadways for fututereSidential'deVelcipnient.', , I GeoDesign assumed the role Of•geoteChniCal•engineer of record for the.projeCt and.079N 1 . • . . 1 construction observation services to Integrity Development during earthwork,- our involvement began in July 200.7 and continued until Mar 200$. .A.gebteChniCal,repOrt• for the property was completed by GeoPacific Engineering, Inc. on January 13; 2006 entitled Prooliiiary ceowf ihked ... ,..:, Engineering Report, SPh011s:Fer6/Townkoni6 Bdrreity SW SelleillS Washin County, 004 In addition, GeoDesign previously pi supplemental .,UpPlerri , I . . , .7 . e •‘ • : recommendationSfor use in.design of gravity retaining wails in a letter *entitled 6 Engineering Services, The Village at SumirerCrek, SW Borrows Road and Siit!Scholls Road, i Tigard, Oregon, dated June 6, 2007. ,. . The current plan is to construct residential structures on the 88 lots that have been prepared. Foundation loads were unknown at the time of this report; we have assumed that they will be • typical of one to four story wood-frame residential structures. We further understand that some site grading will take place to accommodate design elevations. Cuts and fills are not expected to exceed 5 feet, respectively. A site plan showing existing improvements and our hand-auger • explorations is shown on Figure 1. 1 . I . __. ....._. . .. . ... . I 15575 SW Sequoia Pkwy • Suite 100 i Portland, OR 97224 1 off 503.968,8787 I Fax 503.968.3068 410,451404tit 1 SCOPE OF SERVICES The purpose of our work was to confirm that our previous work is in conformance with the geotechnical engineering report and to provide supplemental recommendations for use in design and construction of the proposed development. Specifically, we completed the following scope of services: • Reviewed in -house files for existing information on subsurface conditions in the site vicinity, prior earthwork, and the previous geotechnical report for the site. • Visited the site and completed a visual surface reconnaissance to confirm that no additional earthwork has been conducted since completion of the project. • Completed eight hand augers to a maximum depth of 7 feet below ground surface (BGS). • Prepared this report, which also serves as a reliance letter, that presents our findings and provides updates to the conclusions and recommendations provided in the previous geotechnical report. SITE CONDITIONS SURFACE CONDITIONS We completed a visual surface reconnaissance at the site During our visit, we observed that the ground surface is slightly sloped down towards the south from the north. As discussed above, the lots have been developed with associated utilities, sidewalks, curbs, retaining walls; and asphalt - paved roadways to allow access to the lots, The lots are covered by grass, with small patches of blackberry brush near the proposed playground area at the east portion of the property Areas, of ponded water were observed on Lots' 5, 9, 10, 35, and 30 through 32. While on site we observed the cracks in the :asphalt roadway on SW Coriander lane. As noted in our field reports; the asphalt was reheated during placement using propane torches, which may have contributed t� the cracking. i SUBSURFACE CONDITIONS We completed eight'shallow hand= auger'borings (HA -1 through HA-8) at selected locations across the site The approximate boring_locations are shown on Figure 1. Based on our explorations, the shallow subsurface conditions in the area generally consist of compacted fill that is medium stiff to stiff silt with varying amounts of clay, sand, and gravel. The fill generally ranges in thickness from 0.2 foot to 2 feet BGS. The fill was encountered in most of the borings except for HA -5 and HA -6, which were completed near the proposed playground area at the east portion of the property. A thin layer of loose gravel with silt and sand was encountered at the surface in HA -6. Native alluvium consists of medium stiff silt with some clay and trace organics. In HA -2, we encountered loose sand with minor gravel and encountered refusal on concrete at approximately inches BGS. We drilled four more borings within a 10 -foot radius of HA -2 and encountered concrete at 3 to 6 inches BGS. The area of the sand fill over concrete appears to extend over Lots 47 through 49. The approximate area is shown on Figure 1. G E o ri{DESIGN? Centex -16- 01:041610 ° Based on our explorations, the average depth of stripping in lightly vegetated areas will be approximately 1 to 2 inches. Stripping activities should be completed as recommended in the previous geotechnical report. CONCLUSIONS AND RECOMMENDATIONS In general, we anticipate that the geotechnical recommendations provided in the previous geotechnical report are still applicable to the site with the exception of the:additional 1 to 2 inches of stripping anticipated at the site and our revised shallow foundation recommendations. WET WEATHER/WET SOIL GRADING The silty soils at the site are easily disturbed during the wet season and when they are moist. If not carefully executed,. Site preparation, utility trench work, and roadway; excavation can create extensive soft areas. and significant subgrade.repair costs can result, If construction is, when' the surficial soils are wet or may become wet, the construction methods and schedule should be carefully considered with respect to protecting the subgrade to reduce the.need.to over - excavate- disturbed: or softened soil: The project budget should reflect,the recommendations. below if .Construction is planned during wet weather or when the surficial soils are wet:: .. If construction Occurs when silty; wet soils are present, site prepa ration activities may need to be !. accomplished using` track mounted excavating equipment that loads removed material into trucks supported on granular haul roads. The thickness ofthe granular material for haul roads and staging areas will depend on the amount and type of construction traffic Generally, a 12- to 1 8 inch thick imported granular material is sufficient for light staging areas andithe basic building pad but is::generally not expected to -be adequate to support heavy equipment or truck traffic. T he. granular mat for haul roads and areas with repeated heavy construction traffic. typically needsIo be increased to between 18 to 24' inches, � The actual. thickness of haul roads and staging areas should be based on the contractor's approach to site development and the • amount and type'of construction traffic. The'imported granular material „should be placed in one lift over the prepar undisturbed subgrade -'and compacted using.a smooth drum, nonvibratory roller. In addition, a geotextile fabric may be required'as a barrier between the subgrade and imported granular material in areas of repeated construction traffic. The imported granular material should be pit - or quarry-run rock, crushed rock, or crushed,gravel and sand and should meet the requirements set forth in the 2008 Standard Specifications for Construction (OSSC) 00330.14 (Selected Granular Backfill) and.OSSC 00330.15 (Selected Stone Backfill)- The placement of the imported granular fill should be done in conformance with the specifications provided in OSSC 00331 (Subgrade Stabilization): The geotextile should meet the specifications provided in OSSC 02320.20 (Geotextile Property Values) forsoil separation. The geotextile should be installed in conformance-with the specifications provided,in OSSC 00350 (Geosynthetic Installation) material should be fairly well-graded coarse and fine material and have less than 5 percent by dry weight passing the U.S. Standard No, 20Q Sieve. EEO DESIGN? 3 Centex -16- 01:041610 FOUNDATION SUPPORT Dimensions and Capacities Continuous footings for stud bearing walls should be at least 15 inches wide. The bottom of exterior footings should be at least 18 inches below the lowest adjacent exterior grade. The bottom of interior footings should be established at least 12 inches below grade. Footings bearing on subgrade prepared as recommended above should be sized based on an allowable bearing pressure of 2,500 pounds per square foot. This is a net bearing pressure; the weight of the footing and overlying backfill can be ignored in calculating footing sizes. The recommended allowable bearing pressure applies to the total of dead plus : long -term live loads and can be increased by one -third for short -term loads (such as those resulting from wind or seismic forces). • Based on our analysis °and experience with similar soils, total post= construction settlement should be less than 1 inch;'vvith differential.settlenient of less than YZ inch' over a.50 -foot span. Resistance to Sliding Lateral loads on footings can be resisted by passive:earth pressure on the sides of the structures and by faction on t y .. he base the footings. rOur analysis indicates that the available passive. earth pressure for footings confined by on =site soils and structural fills is 350 pounds per cubic foot; modeled as an equivalent fluid pressure. Adjacent concrete slabs, pavements, or the upper 12 inch'depth of adjacent, unpaved areas should not be considered when calculating passive resistance., In - addition; in order to rely upon passive resistance, a minimum of 10 "feet of horizontal clearance must exist between the` face of the footings and adjacent down slopes. For footings" in contact with the on= site' native material,' a coefficient °of friction equal to "0:30 may be usedA0en calculating resistance to sliding. This value should be increased to 0:40 for crushed °rock.or imported granular fill. • Foundation Drains - Foundation drains 'should be considered on the outside of the perimeter footings.: of all buildings and routed to a - suitable discharge because Of the potential for shallow groundwater. The foundation drains should consist of 4 inch `diameter; perforated drainpipe embedded in a minimum 2400t- wide',zone of drain rock: Drain should consist of angular, granular. material with a maximum particle size of 2 inches and should meet OSSC 00430.1 1 (Granular Drain Backfill Material). The material should be free of roots, organic matter, and ° other unsuitable materials; have less than 2 percent by dry weight passing the U.S Standard No 200 Sieve (washed analysis); and`have at least at least two mechanically fractured faces. Drain rock should be wrapped in a geotextile fabric that meet's the speci provided in OSSC 00350 (Geosynthetic Installation) and OSSC 02320 (eosynthetics) for drainage geotextiles. CONSTRUCTION CONSIDERATIONS All footing and floor subgrades should be evaluated by the project geotechnical engineer or their representative to confirm suitable bearing conditions. Observations should also confirm that all G EO DESI GNZ 4 Centex -16- 01:041610 loose or soft material, organics, unsuitable fill, prior topsoil zones, and softened subgrades (if present) have been removed. Localized deepening of footing excavations may be required to 3 penetrate deleterious materials. If footing excavations are conducted during wet weather conditions, we recommend that a minimum of 3 inches of granular material be placed and compacted until well -keyed at the base of the excavations. The granular material reduces subgrade disturbance during placement of forms and reinforcement and provides clean conditions for the reinforcing steel. 4♦e We appreciate the opportunity to be of continued service to you. Please call if you have questions concerning this report or if we can provide additional services. Sincerely, GeoDesign, Inc. Viola C. Lai, P.E., G.E. Project Engineer ' t 1O�cy. ffffffffff f x j r � �� :r t 4 Brett A.:Shipton, P.E., G.E. TCA 3� Principal Engineer VCL:BAS :kt Attachments Two copies submitted Document ID: Centex- 16 -01- 041610 - geolr.doc © 2010 GeoDesign, Inc. All rights reserved. 1 V EO DES I G N? S. Centex -16- 01:041610 Printed By: cdavls I Print Date: 9/16/2010 1:55:19 PM File Name: \ \geodes ign.local\FIIesVobs\A -D\ Centex \Centex.I6 \Centex - 16.01\ Figures \CAD \Centex- I6- 01- SPO1.dwg I Layout: FIGURE 1 • nit }_ 11 t i _7 1 , a_ . ............_ _ - ' I _..- >r D i f f �.\ i t 1 f / / I j I 1 � i t / - i I I I / / ,,/ ,> , : ._�� ... od•....4., PPP ix 1 . i iv ' ' , . v / , > / / I B o ' x - f! -a / i I + c j� /r ' I � x r ♦ / / i 7 � j i y B ��� � ,s Y' 'x � „ ,,...,,. ,. ,,, tr / i P s C' / :.„,..•-/ F a. �� z Q / 1f i 5`^93 t JF Y �O' f :, ] 1”. 1 , •,--„,,,, .: • , , _ .,, i • tti'y i �j m SA • i v } i 2 - - f : ' : . ,-/ / i , „. _ 1 1. � -:: nD a z x • � o . ii ' ate .. O = // / �� , 1 ifi \ � \ „ I � / / — °' � 0� � • \ \ ° te - PI 1-n rn = - -o m Cl m m h s O D A Z m rn v O T -o O y w� z Z 0 0 r., Z g N z D o n c - n o A A 0 _ P — O o m O w GEODESIGN? CENTEX -I6 -01 SITE PLAN 1 557 SW SepuOla Parkway • Sune 100 Portland OR 99:34 APRIL 2010 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT ' ' Off S00.960.6087 Fax 503.960.3060 TIGARD, OR FIGURE 1 ATTACHMENT FIELD EXPLORATIONS GENERAL We explored subsurface conditions by performing eight hand -auger borings (HA -1 through HA -8) to depths ranging from 0.5 foot to 7.0 feet BGS on April 9, 2010. We obtained representative samples of the various soils encountered in the exploration. Classifications and sampling intervals are presented on the exploration logs included in this attachment. The approximate locations of our explorations are shown on Figure 1. -The locations of the explorations were determined in the field by pacing from existing site features. This information should be considered accurate only to the degree implied by the methods used. SOIL CLASSIFICATION The soil:samples were classified in accordance with the "Exploration Key" (Table A -1) and "Soil Classification System" (Table A -2), which are included in this attachment. The exploration logs indicate the depths at which the soils or their characteristics change, although the change could be gradual. A horizontal line between soil types indicates. an observed (visual or drill action) change. If the change occurred between sample locations and was not observed or obvious, the depth was interpreted and the change is indicated using a dashed line. Classifications and sampling intervals are presented on the exploration logs included in this attachment. t 1 `EO DES I G N? A -1 Centex -16- 01:041610 SYMBOL SAMPLING DESCRIPTION Location of sample obtained in general accordance with ASTM D 1 586 Standard Penetration Test • with recovery Location of sample obtained using thin -wall Shelby tube or Geoprobe® sampler in general 1;- accordance with ASTM D 1587 with recovery • Location of sample obtained using Dames & Moore sampler and 300 -pound hammer or pushed with recovery Location of sample obtained using Dames & Moore or 3- inch -O.D. split -spoon sampler and 140 - pound hammer or pushed with recovery Graphic Log of Soil and Rock Types Location of grab sample Observed contact between soil or rock units (at -depth indicated) Rock coring interval • Inferred contact between 0 Water level during drilling soil or rock units (at approximate depths indicated) Water level taken on date shown GEOTECHNICAL TESTING EXPLANATIONS ATT Atterberg Limits P Pushed Sample CBR California Bearing Ratio PP Pocket Penetrometer CON Consolidation P200 Percent Passing U.S. Standard No. 200 Sieve DD Dry Density RES Resilient Modulus DS Direct Shear SIEV Sieve Gradation HYD Hydrometer Gradation TOR Torvane MC Moisture Content UC Unconfined Compressive Strength MD Moisture - Density Relationship VS Vane Shear OC Organic Content kPa Kilopascal ENVIRONMENTAL TESTING EXPLANATIONS CA Sample Submitted for Chemical Analysis ND Not Detected P Pushed Sample NS No Visible Sheen PID Photoionization Detector Headspace SS Slight Sheen Analysis ppm Parts per Million MS Moderate Sheen HS Heavy Sheen ESIG N ? EXPLORATION KEY TABLE A -1 1 5575 SW Sequoia Parkway -Suite 100 Portland OR 97224 Off 503.968.8787 Fax 503.968.3068 RELATIVE DENSITY - COARSE - GRAINED SOILS Relative Density Standard Penetration Dames & Moore Sampler Dames & Moore Sampler Resistance (140 -pound hammer) (300 -pound hammer) Very Loose 0 -4 0 -11 0 -4 Loose 4 -10 11 -26 4 -10 Medium Dense 10 - 30 26 - 74 10 - 30 Dense 30 - 50 74,126 ' 30 - 47 Very Dense More than 50 More than 120 More than 47 CONSISTENCY - FINE- GRAINED SOILS Consistency Standard Penetration Dames & Moore Sampler Dames & Moore Sampler , Unconfined Compressive Resistance (140 - pound hammer) (300 pound hammer) Strength (tsf) Very Soft Less than 2 Less than 3 Less than 2 Less than 0.25 Soft 2 -4 3 -6 2 - , . .0.2'5 - 0.50 Medium Stiff 4 - 8 ,6'- 12 5- 9 ` 0.50 -'1.0 Stiff 8 - 15 12 - 25 9. -' 19 1.Q - 2.0 Very Stiff 15' - 30 25 19 2.0 -4.0 , Hard More than 30 More than 65 More than 31 More than 4.0 PRIMARY SOIL DIVISIONS GROUP SYMBOL GROUP 'NAME CLEAN GRAVELS GW or GP GRAVEL GRAVEL (< 5 % , . GRAVEL WITH FINES GW -GM or ,G_P GM, G RAV EL witH_,s (more than 50% of and < 12% fines coarse fraction (> 5% - ) G1N GC or GP GC GRAVEL with' COARSE GRAINED retained on GM silty GRAVEL.; SOILS No 4 sieve) GRAVELS WITH FINES (> 12/ fines) GC clayey GRAVEL. GC - GM. silty, clayey GRAVEL (more than 50% CLEAN SANDS retained On o SW or SP SAND No 200 sieve) SAND ( <5 /fines) (50% or more of SANDS'WITH FINES SW -SM or S P S M SA with , silt • coarse fraction (. 5% And _< 12% fines) SW -SC or SP SC SAND wiith, passing SM.. Ski/ SAND SANDS, WITH FINES No •4 sieve) SC Ski/ clayey SAND' . (> 1 2% fines) SC =S.M silty; clayey SAND ML SILT FINE - GRAINED CL CLAY SOILS Liquid limit less than 50 CL -ML silty CLAY (50% or more SILT AND CLAY OL ,ORGANIC SILT or.'ORGANI( CLAY passing MH SILT No. 200 sieve) Liquid limit 50 or CH ,CLAY greater OH ...ORGANIC SILT or ORGANIC CLAY HIGHLY ORGANIC SOILS PT PEAT MOISTURE,' ADDITIONAL CONSTITUENTS CLASSIFICATION Secondary granular components or other materials . Term Field Test suet) "as organics, man =made debris, etc.. • Silt and Clay In , Sand and Gravel In very low moisture, Percent . Fine - Grained Coarse- Percent Fine - Grained Coarse= dry dry to touch Soils Grained Soils Soils Grained Soils moist damp, without < 5 trace . trace < 5 trace trace visible moisture 5 - 12 Minor with 5 - 15 minor minor we visible free water, > 12 some silty /.clayey . 15 - 30• with with . usually saturated g � oix m it r > 3 0 sandy'/gravelly sandy/gravelly G ° 3 DESIG NY 1 SW Sequoia Parkwy -Suite 100 SOIL CLASSIFICATION SYSTEM TABLE A -2 Portland OR 97224 Off 503.968.8787 Fax 503.968.3068 o = u w A BLOW COUNT DEPTH _u <„ Z a • MOISTURE FEET d MATERIAL DESCRIPTION > o r- 2 CONTENT% COMMENTS 11.1 W I N U HA -1 _ 0 50 100 0.0 Medium stiff to stiff, light brown with orange and gray mottled SILT (ML), El some clay, trace gravel, milled wood, red plastic fragments, organics (rootlets), and charcoal; moist (1 -inch- - 1 thick root zone) - FILL. J � 1.8 2.5— Medium stiff, light brown SILT (ML), some clay, trace organics (rootlets); moist (alluvium). becomes stiff at 3.5 feet • stiff to very stiff, orange mottles at 4.0 Surface elevation was not \feet . 4.5 measured at the time of 5.0 — Exploration completed at a depth of 4.5 exploration. feet. 7.5 — 0 50 100 HA -2 50 100 0.0 - Hand au eyed tour boring s within Loose, gray -brown SAND (SP), trace to 9 9 minor gravel; wet " FILL. 0.5, a 10 =foot radius of HA -2 and encountered concrete at 0.25 to 'Exploration terminated due•`to refusal 0:5'104 on concrete 'at 5 foot. Surface 'elevation was not .w 0: measured at the time of - exploration. 2.5— z a i-. 0 - z U w o 5.0 — w U U am - o - x 7.5 — F- z w a _ a _ 0 50 100 1 U DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 0 0 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch , ;er ®ES6GfVz u CENTEX 16 01 HAND AUGER o E 15575 SW Sequoia Parkway - Suite 100 PROPO TIGARD RESIDENTIAL DEVELOPMENT = Portland OR 97224 APRIL 2010 FIGURE A -1 Off 503.968.8787 Fax 503.968.3068 TIGARD, OR . . z o Q i u 11J A BLOW COUNT DEPTH Q a z ®MOISTURE FEET a MATERIAL DESCRIPTION wo I- 2 CONTENT% COMMENTS w Q u w i— v) HA -3 0 so 100 0.0 Stiff, brown SILT (ML), some clay, trace organics (rootlets) and gravel; moist EI — - _ (1- inch -thick root zone) - FILL. -/- l.o Soft to medium'stiff, brown SILT (ML), — -1 trace clay and organics (roots and r 1.8 rootlets); moist (buried topsoil). 1 2.5— Medium stiff, light brown with orange IX mottled SILT (ML), some clay, trace organics (rootlets); moist (alluvium). becomes stiff at 3.5 feet stiff, light brown mottles at 4.0 feet ® Surface elevation was not Exploration completed at a depth of 4.5 4.5 measured at the time of 5.0— feet. exploration. 7.5 — • 0 50 100 HA - 4 0.0 o so loo Stiff, brown SILT (ML), trace clay, organics (rootlets) gravel; and asphalt - El fragments moist (1 inch - thick root zone) - FILL. if - st f to medium stiff, light brown at 1.5 a feet o 2.5— r z Stiff, gray : SILT '(ML), trace fine sand, 3.0 F - organics: ("rootlets), and gravel; moist, u - low plasticity - - FILL. Z • U w grades to gray and light brown at 4.5 O 5 . 0 - feet — - with orange mottles at 5.0 feet u _ Stiff to medium stiff, light brown SILT J s.s a (ML), some clay, trace organics El (rootlets); moist (alluvium). Surface elevation was not Exploration completed at a depth of 7.0 7.0 measured at the time of 7.5 — feet. exploraa td tion. I- 3 u U '0 w a N Z 0 50 100 0 u DRILLED BY GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 (D 0 J BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch ce a w u CENTEX -16 -01 HAND AUGER REC7 Nz (continued) z 1 5575 Sequoia Parkway - Suite .I0 = Portland OR 97224 APRIL 2010 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT FIGURE A-2 Off 503.968.8787 Fax 503.968.3068 TIGARD, OR z O = 17 „, A BLOW COUNT DEPTH u Q a z a ® MOISTURE FEET MATERIAL DESCRIPTION w w w ¢ CONTENT % COMMENTS w V HA -5 o so 100 0.0 Medium stiff to stiff, brown SILT (ML), minor clay, trace organics (rootlets); El moist (2- inch -thick root zone). 2.5 — Surface elevation was not • Exploration completed at a depth of 4.0 4.0 measured at the time of feet. exploration. • 5.0— 7.5 — HA-6 ` - 0 so 100 o so 1°o 0.0 - l Loose GRAVEL with silt and fine sand r 0.2 t2 \(GP) (2 inches) - FILL. � • Stiff light brown SILT (ML), some clay, rpi trace organics (rootlets); moist. o with orange and gray mottles at 2.0 2.5 Z feet ® Surface elevation was not measured at the time of Exploration completed at a depth of 3.0 3.0 exploration. feet. • o u _ • • 0 5.0 — w a - _ i 2 - o - x 7.5 — IL SO 1 00 w w - a - N u DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 a O BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch v CENTEX -16 -01 HAND AUGER \JEO DESIGN ? (continued) C 15575 SW Sequoia Parkway -Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT Portland APRIL 2010 FIGURE A -3 Off 5°3.968.68. 8787 Fax x 503.968.3068 TIGARD, OR z • o Q i u 13 A BLOW COUNT DEPTH Q z ii • MOISTUR FEET d MATERIAL DESCRIPTION wo F CONTENT% COMMENTS W Q W F V1 lJ HA -7 0.0 0 50 100 Medium stiff to stiff, brown SILT (ML), some clay, trace organics (rootlets), gravel, and concrete fragments; moist (1- inch -thick root zone) - FILL. Very stiff, light brown -gray with 2.0 2.5— orange mottled SILT (ML), some clay, trace gravel; moist - FILL. - Stiff, light brown with gray mottled SILT 3.3 (ML), some clay, trace organics (roots); moist (alluvium). Surface elevation was not 5.0 sand at 5.0 feet 5.0 measured at the time of Exploration completed at a depth of 5.0 exploration. feet. 7.5 — HA-f3 0 so loo 0.0 :.. - 0 so 1'00 Stiff; brown SILT(ML), minor clay, trace organics (rootlets) and gravel moist (1- inch -thick root zone) - FILL. Medium 'stiff to stiff,'Iight;brown with 2.0 2.s— orange and gray mottled SILT (MLj, • - some clay, trace organics (rootlets); moist (alluvium). • Z ® Surface elevation was not o 5.0 Exploration completed at a depth of 5.0 S•0 measured at the time of U feet. exploration. U 2 O — b 7.5 Z V w — rL w N 0 50 100 7 0 U DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 0 BORING METHOD: hand-auger (see report text) BORING BIT DIAMETER: 3-Inch a G may' ` v CENTEX -16 -01 HAND AUGER CE _ ES��� (continued) 0 Z 155756W Sequoia Parkway -Suite loo PROPOSED TIGARD RESIDENTIAL DEVELOPMENT = Portland OR 97224 APRIL 2010 Off 503.968.8787 Fax 503.968.3068 TIGARD, OR FIGURE A 4