Loading...
The URL can be used to link to this page
Your browser does not support the video tag.
Report
Tit --"- DESIGN_ .„ r 1 '• ' ., l E ju C N E:4 ,, E ii t . , • CITY OF TIGARD BUILDING DIVISION is , i _ 53 April 1Q, 2010 • /4 57 2:0 ll- e. ci 7 /a 47'np ski/ 546-E i.e.., , , . . Centex Homes 3 . . 11241 Slater Avenue NE, Suite 100 Kirkland, WA 9O33 i 1 'Y i . . g Attention: Mr. Torn Brown i. 1 ,Report of Geotechnical Engineering Sei'yiees and-ItelianCeLetter : Proposed Tigard Residential Development I .t ''..V00d, chLc.g0 GeoDesign Project CehteX16.01 , . . .,. . . , . z _ ,-,•• --,,, .4, , l• , • . , ..*. INTRODUCTION .. . . . This report presents the results of OurgeotechniCalengineering,serviCeS ..:: residential development located at the southwest corner of the intersection Of SW Scholls Ferry .., ... Road and SE 1.35`NAYenUein Tigard; Oregdn, , WeiinclerStand•the site encompa , ; aPProXirriatelY inClUdes:$8 The lots are CurteritlY. vacant but are i . : utilities and riae : I . :'. G6opeiima 6cotechhical„en'giheee of record for the project andproVi4.5 construction observation services to Integrity Development during earthwork, bur inVOlerrieht began in July 2007:and.continued Until March 2008 .‘&0CitaChrii:01,tepait for the property wa 1 completed by GeoPacific Engineehrig, Inc: on January 13, 2006 . entitled Preliminary Geotechnical - - EngiizeeklOR00it Townhomes, SW Barrows and SW Scholls Ferr R - • Washington County, Oregon In addition, deODOSign peeViouSlY'prepared:Stiiiplen , recommendations for use in design of gravity retaining walls in aletter entltleg:qeOteehrii(01: Engineering Services, The Village at Summer Creek, .SIN 'Barrows Road ancl'5'Vt!gc Eei Road, , • • . • , . .:. Tigdi Oi'egan datedjune 6, 2 007 . „ ,.. . 1 . . 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 foUrIstory,:wood-frarne residential struCtureS. We further underqandthatsorne site grading will take place to accommodate design elevation's. Cuts and fills are not expected to 3 1 . . ; e xceed 5 feet, respectively. A site plan showing existing improvements and our hand auger explorations is shown on Figure 1. , 1 . : , 1 ' . . . . aNWIZSAMIPP - ' ' ' WinVily lea I 5575 SW Sequoia Pkwy - Suite IGO i Portland, OR 97224 i off 503.94,8787 I fax 503.968.3068 \ kightinitfaM :' i • 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 to the cracking. 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 s ub s urface conditions in the area generally consist of compacted fill that is medium stiff to stiff silt with varying amounts of clay,' and gravel. The fill generally ranges in thickness from 0.2 foot to 2 feet BGS. The fill was inmost of th'e 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 1 d -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 EO D ES I G N? 2 Centex-16-01:041610 } a • 4 . 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 AN_D,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 .a roadway excavation can create extensive soft areas::and 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 soil: TheprOject . budget. should reflectthe- recommendations below if construction is planned during wet weather or when the surficial soils i are wet. : . If construction occurs when silty, wet 'soils are present site preparation. acti may need to be accomplished using: track, mounted excavating equipment that loads removed mate into trucks on granular haul roads. The :thickness of the 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 mat of:imported granular material is sufficient for light staging 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'ibetween 18 to 2 inches. The actual thickness of haul roads and staging areas 'should be based on the con approach to site development and the amount and tYpe of construction traffic: The imported,granular material should be placed in one i lift over the p p re .tired undisturbe, d su and compacted u sm sin a smooth drum, non .vib;ratory roller. In addition, ageoteXtile fabric may be required .as a barrier between the subgrade and, . i 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 OSSG .00,330.15 (Selected Stone Backfill). The placement of the imported granular fill should be done in conformance with the r. specifications.provided in OSSC 00331 (Subgrade The geotextile should meet.,the_ specifications provided in OSSC 02320.20 (Geotextile Property Values) for soil separation. The i geotextile should be installed in conformance -with the specifications provided ,in OSSC 00350 (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. GEODESIGN? 3 Centex -16- 01:041610 L s 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 analy and experience with similar soils, total post construction settlement should be >les's than 1 inch; with differential .settlerrientcif less•than %z 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 1 and byfriction.on the °base' 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 1 2 Inch: depth' adjacent,: unpaved areas should not be considered when calculating passive resistance In addition in order to rely upon passive resistance, a minimum of 1 0 feet Of horizontal clearance must exist between the face of the footings and adja cent down slopes. For footingsin,contact with the o'n =site native material ; a coefficient of friction equal to may be used, when' calculating resistance to sliding. This valu should be increased to'0:40'for crushed rook or imported granular ":fill. i Foundation Drains Foundation drains should 'be considered on the outside of the perimeter footings ali . buildings and routed to'Ta suitable discharge because of the potential for: shallow groundwater; The foundation drains should consist of 4inch= diameter; perforated drainpipe embedded `in a minimum 2- foot -wide zone of drain rock: Drain rock 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 materi should be free of roots, organic matter, :and other unsuitable r y materials; " Nave less than per`cent 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 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 EODESI 4 Centex -16- 01:041610 G GN? . r 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. 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. f Sincerely, 1 GeoDesign, Inc. Viola C. Lai, P.E., C.E. i l t Project Engineer ' ° TO 1 f At ..FTG, — Brett A. Shipton, P.E., G.E. 'p Y ,' Principal Engineer l Pi :6- ; _-" /0 VCL: BAS: kt Attachments Two copies submitted Document ID: Centex- 1 6 -01- 041 61 0- geolr.doc I © 2010 GeoDesign, Inc. All rights reserved. f I I I I I B 1 s z I s 1 i 4 ' " DESIGN& 5 Centex -16- 01:041610 Printed 6y: cdavls I Print Date: 4/16/2010 1:55:19 PM File Name: \ \geodeslgn.lo ma! \FIIesVobs \A -D \ Centex \Centex.16 \Centex.16.0I Figures \ CAD \Centex -l6- 01.5P01.dwg I Layout FIGURE 1 , 1 ,_...i I I 1 _.1 1 , II 1 I i 1 I . + y a i 1 , i 9 ._ f -,.._o I ° - P - "\;'' - i r .. I f 1= # I _ . i ' mob... r l n — �`\.'' I 1 i - f i 1 ®. i/ I f ' I I '' o� I ° ;1 r ' d I .... ` / V // / i I • iI 1 _ '''''' Il s/ ,," / / y f f �` i i I I x. f % f �� . / / 6 �o, .,�/ . � ' J r f \. l:s \a 1 , , . , \.. D\ ` / 1 • 1" J ` ..P¢S SSS� • f 1 : •S /I ., ....,..:., v O r d - P.+ ,j' , ,.. f E t D / rar 1.1 t l - j •� � . ,./' ,sti s , , \ • / .•'. i si.c El_. - ' ' . .-- \ ''' \\,), ' .,,0 ti i , O i ■ . ; „.. 1 .. I 1 mI ill \ - _ _J Z I l a ,. N 1 -I Id I 1 ( \ ! ;' �10 ii 1 I o 1 1 i ,r.b0' it n,.. .. n.". m 0 t- m x Z = m °W D v 3 D \\ In " FNtB , ` v O F 2. Z Z 0 O D z ui m 0 O r' N z > 0 I h _.- EO CENTEX -16 -01 SITE PLAN sssi 6 y•SW1e 100 Pd PROPOSED TIGARD RESIDENTIAL DEVELOPMENT 011503.968.8]8, Fax S03.968.3068 APRIL 2010 FIGURE 1 • t. TIGARD, OR 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'wer.e 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 Togs included in this attachment,. `iiEODESIGN 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 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 ,. 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) 7 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 MS Moderate Sheen ppm Parts per Million HS Heavy Sheen 155755W Sequoia Parkway Suite loo EXPLORATION KEY TABLE A -1 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 -1 Medium Dense 10 - 30 26 - 74 10 - 30 . Dense 30 - 50 74 i20 30 - 47 ' Very Dense More than 50 More than 120 More than 47 'CONSISTENCY - FINE- GRAINED SOILS . Consistency Standard Penetration Dames & Moose Sampler Dames & Moore Sampler Unconfined °Compressive Re (140 -pound hammer) (300 pound hammer)_ ' . Strength (ts,f) Very Soft Less than 2 Less than 3 Less;tha 2 ,.Less.tha 0.25 Soft 2 -4 • 3 -6 2 - 0:2;5 Medium. Stiff , 4 - 8 .6'- 12 ' 5, -.9 0.50 -_1.0 Stiff 8 -15 12 -,.25 9 :19 1.0 -2.0 Very Stiff 15 -30 25 -65' 19•;'31 ., ,2.0 -.4.0 ' Hard More than 30 More than 65 More than X31. More than 4.0 P SOIL DIVISIONS , GROUP SYMBOL GROUP NAME CLEAN GRAVELS GW or GP GRAVEL GRAVEL (< 5% fines) GRAVEL WITH FINES GW -GM or -GM GRAVEL with silt (more than 50% of > 5% an s 12% f i n e s `" coarse fraction • ( ) G1iV GC° or GC GRAVEL wit "cla COARSE - GRAINED retained on GM silty GRAVEL • No. 4 s ieve) GR WITH FINES SOILS - CC cl G R A VEL (> 12 %'fines) - GCGM. ' silty, elayeyGI: VEL (more than 50% CLEAN SANDS ' . retained on SAND (<5 /fine o fines) SW or SP SAND No, 200 sieve) (50 %'or more of SANDSWITH F INES SW SM or.'SP SM. ' ' SAND with silt, (- 5% and < 12% fines) SW SC or SP SC. SAND with clay coarse fraction - • passing SM silty SAN ' SANDS WITH FINES No. . 4 Sieve) SC _ ..clayey SAND ' (> 12% fines) SC =SM silty; 'clay ML SILT; .y.: FINE - GRAINED CL CLAY SOILS Liquid limit less than 50 CL ML silty CLAY , (50% or more SILT AND CLAY O.L ORGANIC SILT or OR_ GANIC CLAY • passing MH . . ' "SILT Liquid limit 50 or No. 200 sieve) : CH CLAY greater OH ,ORGANIC SILT or ORGANIC CLAY HIGHLY ORGANIC SOILS • PT ; PEAT MOISTURE ADDITIONAL CONSTITUENTS CLASSIFICATION Secondary granular components or other mater ials Term Field Test such `as organics, man =made debri etc.. Silt and Clay In 'Sand and Gravel Inc very low moisture, Percent - Fine - Grained Coarse- Percent Fine -Grained Coarse- dry dry to touch Soils Grained Soils Soils Grained Soil 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 M > 30 sandy /g ravelly sandy /gravelly kw SOIL CLASSIFICATION SYSTEM TABLE 1 P 5575 SW Sequoia Parkway p 100 100 Portland OR 97224 Off 'S03.968.8787 Fax 503.968.3068 ,1 1. z O A BLOW COUNT DEPTH o Q z • MOISTURE FEET a MATERIAL DESCRIPTION wo 2 CONTENT% COMMENTS Q cL w I N 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- �. hick root zone) - : FILL. r 1.8 z.s — Medium stiff, light brown SILT (ML), some clay, trace organics (rootlets); moist (alluviurn). ' becomes stiff at 3.5 feet stiff to very stiff, orange mottles at 4.0 ® Surface elevation was not \feet - r 4.5 measured at the time of 5.0 Exploration completed at a depth of 4.5 exploration. feet. • 7.5 — • HA -2 0 50 100 - o , 50 100 0.0 - - H and - au eyed tour borings within Loose, gray brown SAND (SP), trace t� 9 9 Y minor gravel; wet FILL r 0.5 a 10 foot radius of HA -2 and • encountered concrete at 0:25 to - Exploration terminated due to refusal 0:5'foot. ` on concrete at 0.5 foot._ Surface elevation was not rrtea'sured at the time of exploration. 2.5 — z 0 L.7 - z V o 5.0 — w u u 0 a _ o – I 7.5 _ – - ' 0 50 u DRILLED BY: Geopesign, Inc. staff LOGGED BY: JPW 'COMPLETED: 04/09/10 0 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 - inch `C E DES9G Nz CENTEX -16 -01 HAND AUGER o — Q 15575 SW Sequoia Parkway - Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT 6 7 Fax Off 503.93679 Fax 224 APRIL 2010 FIGURE A -1 68.8787 Fax 503.968.3068 TIGARD, OR - • • z o 0 i t A BLOW COUNT DEPTH u Q a z - • MOISTURE FEET a MATERIAL DESCRIPTION w o N aa g CONTENT% COMMENTS _1 W Q W i -' N u HA -3 o so 100 0.0 Stiff, brown SILT (ML), some clay, trace organics (rootlets) and gravel; moist — - , (1- inch -thick root,zbne) - FILL. J - 1.0 Soft to medium stiff, brown SILT (ML), - _ trace clay and organics (roots and r 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 measut the time of 5.0— feet. explorar tionn. 7.5 — 0 so 100 HA-4 o so 100 0.0 Stiff, brown SILT (ML) :trace' clay, t - organics (rootlets), gravel; and asphalt fragments; moist (1 inch thick root zone) •- FILL. • rz: stiff to medium stiff, light brown at 1.5 c El feet 2.s- Z Stiff, gray SILT_(ML), trace fine sand, — 3.0 - organics (rootlets), and gravel; moist, u low plasticity - FI Z t o grades to gray and light brown at 4.5 o 5.0— feet — - _, with orange mottles at 5,0 feet Stiff to medium stiff, light brown SILT J 5.5 (ML), some clay, trace organics (rootlets); moist (alluvium). Surface elevation was not Exploration completed at a depth of 7.0 7.0 mea at the time �f 7.5 — feet. exploou measured ration. H Z W 0 w 0 a. a N Z 0 50 100 D .Q v DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04 /09/10 O . 3 BORING METHOD: hand -auger (see report text) . BORING BIT DIAMETER: 3 -inch z v CENTE 16 O1 HAND AU G }EODESIGN (continued) 0 Z 15575S1N_Sequola Parkway- Suite.100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT _ - Portland OR 97224 APRIL 2010 = Off 503.968.8787 Fa;5 503.968.3068 TIGARD, OR FIGURE A -2 z 0 2 u A, BLOW COUNT DEPTH u Q � a z a ® MOISTURE FEET MATERIAL DESCRIPTION w N CONTENT% COMMENTS J W Q 1-- HA -5 0 so 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 • Exploration completed at a depth of 4.0 4.0 measured at the time of feet. exploration. 5.0— 7.5 — HA -6 0 50 100 so 100 o.o Loose GRAVEL with' silt and fine sand r 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 z feet Surface elevation was not • Exploration completed at a depth of 3.0 3.0 measured at the time of exploration. feet. • U u - z u 0 5.0 U a y U m Q • 2 O - • 7.5 — z - w U w - , u a 50 100 z 0 DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 3 0 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch a . a HAND AUGER G`s DES G n l CENTEX -16 -01 ES U \1 (continued) C 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 • It • z o xi— z A BLOW COUNT DEPTH u Q a a ®MOISTURE FEET MATERIAL DESCRIPTION w o 2 CONTENT% COMMENTS J W < w F V HA -7 0 so 100 0.0 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, El trace gravel; moist - FILL. - Stiff, light brown with gray mottled SILT 33 (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-i8 0.0 o so 100 Stiff, brown ' SILT (ML), minor trace ; organics (rootlets) and gra moist (1 Inch thi root zon FILL. • c - Medium' Stiff to stiff; light brown with 2 0 F- • 2.5 — orange and gray mottled SILT.'(ML), some clay, trace organics (rootlets); moist (alluvium): F 0 U — z (.3 . Surface elevation was not o 5.0 measured at the time of Exploration completed at a depth of 5.0 5.0 exploration. a. feet. a 0 7 • 7.5 — w w — u z 0 50 100 u DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 a 0 BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch CENTEX -16 -01 HAND AUGER o :E a- DESIGN u ? (continued) • Z 15575 Sequoia Parkway -Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT = 6& 8 7 B7 Fax 224 APRIL 2010 TIGARD, OR FIGURE A -4 Off 503.968.8787 Fax 503.968,3068 1 I i ,' _ .. . --_, . , GutsbEN 'DESIGN u z RECEIVE)) - JUN 9 2 011 H CITY OF TIGARD . • • . BUILDING DIVISION April 1 , 2010 . . . . :. • , • i, i . . ' . . • . Centex Homes . , • 1 11241 Slater Avenue E, Suite 100 Kirldand, WA 0 . 3 I :1 ; . . Attention: Mr. Tom Brown i • .1 , ...... , Report of Geotechnic tridiiieei10g.,::s4r,Vicas • Ailtiteiii-leeietter PropoSedTigkr4ReSidentiarqevelOprnent 1 , . " • ' ,--, _ — -1 : Tigard ())*gOn , . •1 • . GeoDesigri,:PrOjett: Centex 6,01 . , . . , . . , . :: ; . , . ; . • I " . . ■ • . . . :'. . , • . . . ..., 1 . , , __. . . . •. . . . INTRODUCTION , • . .• - . - . . . . • . ..„,... , . . 1 . , . This report presents the reults of our-gebteChnicalrenginering reidee,itialeveicio0eh10eatoci:i of the intersection of SW Scholls Ferry Road and SE 10;'*e40e'•,in ti604,07.edOn: :•::::•: ,--,,:?:.•:.:.1 ;,,, v-.::=• . - , ,!,,,,',• :::,• • • - , •-t ••• ,; ,,- , ,•-•• ,'-•' , - •,' - 40prmmately,s,-5 includes:,:88 The lots :are'currentlyvacart:but are . : developed with utilitie -- curbs ,a.hol paved roadways for future residential de •. .. . „. • . .. : Geol)esign of•reCOrilfor the.prOjct.4nOPrOyigta construction , .01:ispes(apO'..e,Ob.!js.::to Integrity Development OkitiO;e4t1;001 began in July 2007 and continued until March 2008 'A geoteChniCal report for: was completed by GeoPacific Engineering Inc: Onjandary. IA, 2006 ,61ititle.d - ; Ehgirieeeirigke0oet. TOwilluiirie,,,SW13i4eeet1;y:s Washington i.:CPahty, Oregon In :oaition oee.,\00s1419.r00,:afg(l'$010.00tii.O.:001 • i recommendations for use in design of gravity retaining walls in a..1etter entitledgegtOilicial: Engineering Services, The Vill at Summer Creek, SW r Creek Burrows Road Oncli5/1/4etioll5 Ferry Road, . •,. • Tigaect, Oeegoh 0*djurie 6, 2007.. ; The current plan is to construct residential structures On the 88 lots that have been prepp.r'ed.: ..... ... .., , Foundation loads were unknown at the time of this report; we have assumed that they Will be 3 . , typical of one to fourlstory, residential strOctures. We further understand that some 1 site grading will take place to accommodate design elevations Cuts and fiils are not e xpe c ted to exceed 5 feet, respeCtively. A site plan showing existing improvements and our hancl explorations is shown on Figure 1 1 1 . . . ; • -141 15575 SW Sequoia Pkwy • Suite 100 1 Portland, OR 97224 I Off 5 i Fa* 503.968.3068 ''l ./ itte4446WeittglOrA ', i 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 Area's .Of ponded water were'obseryed 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 the site The approximate boring location's 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 and 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 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. GEO D ES I G N? 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 its pllanned 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 "oils are present, site preparation activities may need to be accomplished using` track mounted excavating equipment that,loads removed material into (rucks supported on graritila(liaul roads. The thickness of:tli granular materialrfor haul roads and staging areaswill depend on the amount and type of construction traffic. Generally, a 12- to 1 8 inch thick mat imported granular material is sufficient for light staging areas and the basic building pad but is :.generally not,expectedto 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' 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, subgrade "and compacted using, a smooth drum, non vibratory 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 Oregon Standard Specifications for Construction (OSSC) 00330.14 (Selected Granular Backfill) and OSSC00330.15 (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 0.2320.20 (Geotextile Property Values) for soil separation. The geotextile should be installed in conformance -with the specifications provided,in OSSC 00350 (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. "EO DES I G N? 3 Centex -16- 01:0 41610 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 settlement 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 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 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'materi'al, a coefficient "of friction equal . to`0.30 may be used;when calculating resistance to "sliding. This value should beincreased to "0.40 for crushed nick 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 of 4 inch= diameter perforated drainpipe embedded a minimum 2=foot- wide of drain rock: Drain rock should consist of angular granular material with a maximum par'ticle'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 mechani fractured faces. Drain rock should be wrapped in a geotextile fabric that meet's the specifications provided in OSSC 00350 (Geosynthetic Installation) and OSSC 02320 (Geosynthetics) for drainage geotextiles. CONSTRUCTION CONSID All footing and floor subgrades should be evaluated by the project geotechnical engineer or their representative t� confirm suitable bearing conditions. Observations should also confirm that all QE'O DESIG N? 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 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 0 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. l Viola C. Lai, P.E., G.E. , ' 4 " —i ;i f) Project Engineer �¢ Brett A Shipton P.E., G.E. Principal Engineer VCL: BAS: kt Attachments Two copies submitted Document ID: Centex- 16- 01704161O,geolr.doc 2010 GeoDeign, Inc. All rights reserved. g q k yy GEO DES I G Nz 5 Centex -16- 01:041610 Printed By: cdavls I Print Date: 0/16/2010 I :55:I 9 PM File Name: \ \geodes lgn.Iocal \PIIes\Iobs \A -D\ C entex \Centex.l6 \Centex.16.01 \Figures \CAD \Cente x-1 6- 0I -SP01 .dwg I Layout: FIGURE 1 I H I ll I ! - !I i ! p" 4 l' ;::: , % i J f 4 a ).,, \ , 1 1 v , -, -, ./ ,.....,,,, ,.),‘„).:,, , i ! ! ".., i i --r i I i I ! I > yti, • -..+.a+it : ' . .___ _ _ ` ......, ( / / / yy / 1 1f z 1 e, ; j f - w .w I1B 6 jl ' / I; v /., /l/ i i I � � I `."'.�\ '�Q \ yet �,� _ J k 7 .. _I 1 I t 1, I / / ,�/ \. \ '.., /, — , 1 I l k ` " ' � � ~ . , a / f 1 .4 / i \ .. .ma x . 3, . _ r, \ i / I J v . ' 4 / :/// ; 1 II __ *- •- *7 Fr444%% i D I � j J( ( • N zss ./- ' j / 1 7 t j 777 f ( I 1 i {, Ivy i Pn • f —__ A / _ _...rtt-'' rrr -- 1 i n't rr. -I o L- m SZ T. m o D 3 D o v T. p • Z Z o O y Z Z wq. m O O vI N n c oz - n n ,. O m < A m o co GEODESIGN= CENTEX -16.01 SITE PLAN SS75 SW Se9uola Parkway -Suite 100 - tiiiirlarid OR 972. APRIL 2010 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT r FIGURE 1 Orr 503.968, 5787 fax 503.968.3068 TIGARD, OR 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",(Tabl,e 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. GEO DESIGN? 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 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 V 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 iE@ DESIGN 15575 SW Sequoia Parkway Suite l00 EXPLORATION KEY TABLE A -1 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 - 12 30. - 47 . .. Very Dense More than 50 More than 120 • More than 47 CONSISTENCY - FINE- GRAINED SOILS Consistency St rd Penetration Dames & Moore Sampler Dames &Moore Sampler , Unconfined Compressive Resistance (140 -pound hammer) (300 pound hammer) Stren (tsf) Very Soft Less than 2 Less than 3 Less than 'Less :tha 0.25 Soft 2 -4 3 -6 2 -5._ ,0 - 0.5 0 Mediu Stiff 4 - 8 ,6`- 12 5 - 9 0.5 m : -.'1.0 Stiff .8 -15 12 -25 9 - 1.0 -2.0 Very Stiff 15'- 30. 25 7 65 1`9,- 3.1 , 2.0 - 4.0 Hard More than re 30 MOO 65 More than 31 More than 4.0 PRIMARY SOIL DIVISIONS GROUP SYMBOL GROUP NAME CLEAN GRAVELS GW or GP GRAVEL GRAVEL (< 5% fines) GRAVEL WITH GW -GM or GP -GM GRAVEL with silt (more than 50% of (> 5% and 5 12% fines) GW -GC or GP -GC GRAVEL with'eld coarse fraction Y coa retained on COARSE GRAINED GM silty GRAVEL No. GRAVELS WITH FINES 4 sieve) SOILS CC clayey GRAVEL (> 12% fines) GCGM silty, clayey.GRAVEL (more than 50% CLEAN SANDS ' retained on SW or SP SAND • ` No.'200 sieve) SAND ( <5% fine (50 %'or more of SAND :WITH FINES SW; or '1 SAND with silt ( >_ 5% and _.- 12%'fines). ,SW-SC or SP SC,,.. SAND with coarse fraction - 'Clay passing.. _ ; -. . ' SM 1 silty SAND • • No. 4 sieve SANDS WITH FINES claye SAND .' (> 1 Z% fines) SC SC -SM silty; clayey. SAND • ML SILT, - FINE - GRAINED CL CLAY SOILS Liquid limit less than 50 CL-ML . , , ' ilty CLAY (50% or more SILT AND CLAY OL ORGANIC SILT or ORGANIC 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 such as organics, man -made debris, etc., Silt and Clay In Sand and Gravel In: very low moisture, Percent . Fine - Grained Coarse- Percen Fine - Grained Coarse- dry dry to touch Soils Grained Soils Soils Grained Soils moist damp, without < 5 tra 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 ° ' v > 30 sandy /gravelly sandy /gra 1 SW Sequoia Parkway -suite 100 SOIL CLASSIFICATION SYSTEM TABLE A -2 Portland OR 97224 • Off 503.968.8787 Fax 503.968.3068 Z O ®BLOW COUNT DEPTH U Q Z 11? MOISTURE FEET a MATERIAL DESCRIPTION w 11-1 Q CONTENT% COMMENTS u w w H HA -1 0 so 100 o.o 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- -1 \thick root zone) - FILL. , , J r 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 too HA -2 0 so 100 0.0 Loose, gray- brown SAND (SP), trace to M . 9 9 Hand augered tout - borings s within minor gravel; wet - FILL. os a 10 foot radius of HA -2 and a encountered concrete at 0.25 to e - Exploration terminated due to refusal 0 .5 ; foot,. ` _ o 0,5 foot._ Surface elevation was not measured at the time of a - • exploration. 2.5 z - t- 0 Z V _ o 5.0 — V V 2 o — th • 7 7.5 z a _ rd 0 50 100 DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW - COMPLETED: 04/09/10 O BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch c G :I DESOGNz CENTEX -16 -01 HAND AUGER � 155755WSequoia Parkway -Suite too PROPOSED TIGARD RESIDENTIAL DEVELOPMENT = Portland OR 97224 APRIL 2010 Off 503.968.8787 Fax 503.968.3068 TIGARD, OR FIGURE A -1 z o 2= u 11 , A BLOW COUNT DEPTH u Q a z ® MOISTURE COMMENTS FEET d MATERIAL DESCRIPTION w o 2 CONTENT J W < 2 W • F- N V HA -3 0.0 0 5o 100 Stiff, brown SILT (ML), some clay, trace organics (rootlets) and gravel; moist El — -- (1- inch -thick root zone) - FILL. J - 1.o Soft to medium stiff, brown SILT (ML), — - - trace clay and organics (roots and 1.8 \rootlets); moist (buried topsoil). 2.5— Medium stiff, light brown with orange El 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 measured at the time of a .s Exploration completed at a depth of 4.5 exploration. 5.0— feet. 7.5 — HA- . _ o so 100 co o so 100 Stiff, b,ro (ML); trace' clay, - - o (rootlets), gravel and asphalt mvi fragments; moist ( inch thick root zone) FILL. stiff to medium stiff, light brown at 1.5 Q feet o 2.5 — z Stiff 'gray SILT (ML), trace fine sand, - 3.0 organics: (rootlets), and gravel; moist, O - lo plasticity - - FILL. z u ° s.o grades to gray and light brown at 4.5 o Lu feet - - .-. with orange mottles at 5:0 feet u Stiff to medium stiff, light brown SILT s.s e (ML), some clay, trace organics V T (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. exploration. z u u u a u a N • N Z o 50 100 Q u DRILLED BY: GeoDesign, Inc. staff LOGGED BY: JPW COMPLETED: 04/09/10 0 0 _I o BORING METHOD: hand -auger (see report text) BORING BIT DIAMETER: 3 -inch a < C 'r � u CE NTEX 16 01 HAND AUGER , EC�. ®ES�G IN (continue Z 15575 SW Sequoia Parkway -Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT 2 Portland OR 97224 APRIL 2010 Off 503.968.8787 fax 503.968.3068 TIGARD, OR FIGURE A-2 0 u w ® BLOW COUNT DEPTH u Q z MOISTURE COMMENTS FEET a MATERIAL DESCRIPTION wo 17, 2 CONTENT% w w Q o u HA -5 0 s0 10 o.o Medium stiff to stiff, brown SILT (ML), minor clay, trace organics (rootlets); moist (2- inch -thick root zone). 2.5 — Surface elevation was not 4 .o measured at the time of • Exploration completed at a depth of 4.0 exploration. • feet. 5.0- 7.5— HA-6 0 50 100 • 0 50 100 Lodse GRAVEL with : silt and fine and 02 t(GP) (2 inches),- FILL. / Stiff, light brown SILT (ML), some clay, trace organics (rootlets); moist. a - o with orange and gray mottles at 2.0 • 2.5 z feet Surface elevation was not Exploration completed at a depth of 3.0 3.0 explo mea ration. at the time of feet. Q. • 5.0 — w EL" • — x 7.5 — w w — Q cC 50 100 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 HAND AUGER �'� ��` � V CENTEX -16 -01 GE-0 r E� ,, .DESIGN± . (continued) Q 15575 SW Sequoia Parkway - Suite loo PROPOSED TIGARD RESIDENTIAL DEVELOPMENT = Portland OR 97224 APRIL 2010 FIGURE A-3 Off 503.968.'8787 Fax 503.968.3068 TIGARD, OR • z o O = 1 „ A BLOW COUNT DEPTH u Q n Z o_ !� MOISTURE COMMENTS FEET a MATERIAL DESCRIPTION > 0 N 2 CONTENT w < u w I IA HA -7 0 50 100 0.0 - - 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). 5.0 ® Surface elevation was not 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 =8 o 50 100 0.0 0 so 100 Stiff, brown SILT (ML), minor clay, trace organics (root(ets) and gravel; moist (1 =inch -thick root zone) F ILL. • Medium`stiff to stiff., light brown with 2.0 • 2.5— orange'and gray mottled SILT (ML), some clay, trace orga.niics (rootlets); moist (alluvium). F- 0 u - z u _ o Surface elevation,was not o 5.0 Exploration completed at a depth of 5.0 5.0 measured at the time of feet. exploration. o 7.5 — z w Q _ w N 0 50 100 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 cc C - C u CENTEX -16 -01 HAND AUGER s GN? (continued) 15575 SW Sequoia Parkway - Suite 100 = Portland OR 97224 APRIL 2010 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT FIGURE A-4 Off 503.968.8787 Fax 503.968.3063 TIGARD, OR