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Report (29) MST2012-00074 11023 SAGE TER MST2012-00075 11015 SAGE TER MST2012-00076 11007 SAGE TER MST2012-00077 10999 SAGE TER rrovrn , CE Iz APR 1 1 2012 CITY OF TIGA 'D BUILDING DIVISION April 16, 2010 Centex Homes 11241 Slater Avenue NE, Suite 100 Kirkland,WA 98033 Attention: Mr.Tom Brown Report of Geotechnical Engineering Services and Reliance Letter Proposed Tigard Residential Development Tigard, Oregon GeoDesign Project: Centex-16-01 INTRODUCTION OFFICE COPY This report presents the results of our geotechnical engineering services for the proposed residential development located at the southwest corner of the intersection of SW Scholls Ferry Road and SE 135'h Avenue in Tigard,Oregon. We understand the site encompasses approximately 8.5 acres and includes 88 individual lots. The lots are currently vacant but are developed with utilities, curbs, and paved roadways for future residential development. GeoDesign assumed the role of geotechnical engineer of record for the project and provided construction observation services to Integrity Development during earthwork; our involvement began in July 2007 and continued until March 2008. A geotechnical report for the property was completed by GeoPacific Engineering, Inc. on January 13, 2006 entitled Preliminary Geotechnical Engineering Report,Scholls Ferry Townhomes, SW Barrows and SW Scholls Ferry Road, 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 Barrows Road and SW Scholls Ferry Road, 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. 15575 SW Sequoia Pkwy•Suite 100 I Portland.OR 97224 1 Off 503.968.8787 Fax 503.968.3068 SCOPE OF SERVICES nformance with the that our previous work is in c endo ons for in ur ose of our work was to confirm provide supplemental recomm feted the usefilowrng Thep p and to p Specifically,we C°mp ructreport development. geotechnical engineeringof the proposed design and construction scope of services: existing information on subsurface conditions in the site vicinity, inform ort for the site. Reviewed in-house files forprevious geotechnical rep to confirm that no additional • • prior earthwork,and the p site and completed a visual surface m letion of the project. acow ground surface(BGS). Visited the depth of 7 feet belsand • augers to a maximum p that ow resents our findings( earthwork has beenhand aug ted since c as a reliance letter, provided in the previous • Completed eightwhich also serves recommendations Prepared this report, provides updates to the Conclusions and recom geotechnical report. SITE CONDITIONS our visit,we observed that the During As discussed above, SURFACE CONDITIONS from the north. retaining walls,and down towards the south walks,curbs, with small a visual surface reconnaissance at the site. e We completedeslope grass,ground surface is slightlyVep The lots are covered by gportion of the ed with associated utilities, s the lots have been round area at the east grass, h 32.s roadwaysrrybrush allow access to proposed playground 1 p,35,and 30 asphalt-paved near the prop on Lots 5,9, patches of Areas of ended water were observedCoriander lane. As noted in property- ponded SW which may halt roadway using propane torches, observed the cracks a the asphalt placement While on site,we asphalt was reheated during our field reports the have contributed to the cracking $ at selected locations across CONDITIONS s(HA-1 through HA ) SUBSURFACE COND au er boring on Figure 1. feted eight shallow hand-auger are shown consist of the completed approximate boring generally site. sand,and gravel. The explorations,the shallow subsurface conditions s in the of clay, red imost of on our fillthat isThe amounts was en Basedmedium stiff to stiff silt with varying ro osed playground area compacted that 0.2 foot to 2 feet BGS.ed near the proposed a rings rangesepino thicknessH5nd fromwhich were compclay fill generallyt for HA 5 and HA- ' layer of loose with silt and was the thbe portion property. A thin consists gravel medium stiff sand was some encountered the eatth surfacef e 6. Native alluvium the in HA- at and trace organics. HA-2 and sand with minor gravel and encountered ed refusalef radion concrete loose borings w►thin a to a proxi a encounteredesWe drilled four more 6 inches BGS. The area of the sand fill over concrete appears approximately BGS. Fi urs 1 rough 49. The approximate area is shown on 9 encountered concrete�t 3 to 6 inches extend over 1.0 Centex-16-01:041610 2 WIDESIGNx FOUNDATION SUPPORT ns and Capacities acities p Cfor 15 inches wide. bottom of exteriorontinuous footings shouldfootings bestudatbearing least 18walls inchesshould belowbe et ll adjacent exteriorThe 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,with differential settlement of less than%2 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 base 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 material, a coefficient of friction equal to 0.30 may be used when 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 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 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 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 GEODESIGN= 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. ♦ ♦ + 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. 13 15 .4"\\\ Viola C.Lai, P.E.,G.E. , Project Engineerffizi. { r r REG X c der vel< O Brett A.Shipton, P.E.,G.E. FTT !e Principal Engineer A EXPIfiES:6'.&7 -__2(—",/0 VCL'BAS:kt Attachments Two copies submitted Document ID:Centex-16.01-041610-geolr.doc ©2010 GeoDesign,inc. All rights reserved. G EO DEs IG Nz 5 Centex-16-01:041610 FIGURES Printed CK edaN1 I Prig Date:4/16/2010 6:55;19 PN fiat name:\\9La1mIgn.IDtilVII.AJpb Nk-D\CeMex%C<nitx-I6\CtMar-16.0I\g9YnslCALACenlex-16A1.SP0[fl.dvr9 I layout Mind 1*1, 1 i' `� 1j 're3 I -�.� D 1 ,\1 II, I i / "�� A,.� � i ` //g.\\ ` L 6ii O' o: fir••._----------- a / 1 — i h1 q �i ril /,% I. r II 1i a 1:rw 7/ .f/'''' , r a /.f '' / 1114214 f. **I / / I /....,/: ' e- r' a, a 'rj• /J/ /1 A 1 L J .!r • /I _, i l.ar d" �� v / [[ �� / Via` J / J y 'e ,�c ! x �1 J n R a i : , . ... .,. . ir,.. _ it N 6 a �• W ,. V ix�.�1� ryR ` §' 1 Jl.../ „d • I 0-z.9 .a r . f ./ zip • \ �� ! �+ 19°,1 1+ID I �Di. fJ � ❑ v9�r'' ' .,/r/`/J/ ado y M 1n 1-1,-------' /�-�J �/� ^' —o r F1- x�z tr x m 0. n 41. o v FE1!7'D2Fpp U Z Z v p az a N a J, n n c P, o, D A o ,N m p m -C G EODESIGN' CENTEX-16-01 SITE PLAN I MIS*Smola'ado.,W.MO .wanaeKarau APRIL 1010 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT on$113.161.00'l$l1.99l.wa FIGURE 1 OR ATTACHMENT 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-I) 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. G EODESIGN A-1 Centex-16-01:041610 SYMBOL SAMPLING DESCRIPTION Location of sample obtained in general accordance with ASTM D 1586 Standard Penetration Test E . with recovery Location of sample obtained using thin-wall Shelby tube or Geoprobe®sampler in general II accordance with ASTM D 1 587 with recovery S 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 „� 4''i--- Observed contact between soil or rock units ',..=.1,-' (at depth indicated) Rock coring interval Inferred contact between SZ soil or rock units Water level during drilling (at approximate depths —- indicated} 1 Water level taken on date shown :. '' _4' . M 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 G EC}DESIG N.V EXPLORATION KEY TABLE A-1 15575 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 Loose0-4 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(tsf) 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- 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 31 More than 4.0 PRIMARY SOIL DIVISIONS GROUP SYMBOL GROUP NAME CLEAN GRAVELS GW or GP GRAVEL (<5%fines) GRAVEL (more than 50%of GRAVEL WITH FINES GW-GM or GP-GM GRAVEL with silt coarse fraction (z 5%and 5 12%fines) GW GC or GP GC GRAVEL with clay COARSE-GRAINED retained on GRAVELS WITH FINES GM silty GRAVEL SOILS No.4 sieve) (> 12%fines) GC clayey GRAVEL GC-GM silty,clayey GRAVEL (more than 50% CLEAN SANDS retained on SAND (<5%fines) SW or SP SAND No.200 sieve) (50%or more of STH FINES SW-SM or SP-$M SAND with silt coarse fraction (> 5ANDS%andWI<12%fines) SW 5C or SP SC SAND with clay passing SANDS WITH FINES SM silty SAND No.4 sieve) (> 12%fines) SC clayey SAND SC-SM silty,clayey SAND ML SILT FINE-GRAINED CL CLAY SOILS Liquid limit less than SO CL-ML silty CLAY (50%or more SILT AND CLAY OL ORGANIC SILT or ORGANIC CLAY passing Liquid limit 50 or MH SILT 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 materials Term Field Test such as organics,man-made debris,etc. Silt and Clay In: Sand and Gravel In: d very low moisture, Percent Fine-Grained Coarse- Percent Fine-Grained Coarse- ry dry to touch Soils Grained Soils Soils Grained Soils moist damp,without <S 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 .*- , `7:; :;Qa > 30 sandy/gravelly sandy/gravelly GE0DES1GNz 153755W Sequoia Parkway•Suite 100 SOIL CLASSIFICATION SYSTEM TABLE A-2 Portland OR 97224 Off 503,966.8787 few 503,958.3068 z u 1L" i ♦BLOW COUNTQ z •MOiSTUREDEPTHMATERIAL DESCRIPTION > CONTENT% COMMENTS FEETa K HA-i u 0 50 loo 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- 1.8 `thick root zone)-FILL. 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 measured at the time of -—� f 4.s exploration. 5.0— Exploration completed ata depth of 4.5 _ feet. 7.5— 0 SO 100 HA-2 0 so 100 0.0 Loose,gray brown SAND(SP),trace to N Hand angered tour-borings within Y — ' minor ravel;wet FILL. 0.s a i 0-foot radius of HA-2 and g ` encountered concrete at 025 to - Exploration terminated due to refusal 0.5 foot. on concrete at 0.5 foot. Surface elevation was not - measured at t• he time of 1- _ exploration. a a 2.5— z rt a.a Y. u 0 5.0— U u ;L u a - x o - io 6 7.5— w u w ` u_. N VI 0 SO 100 Y 0 U DRILLED BY:GeoDesign.Inc.staff LOGGED BY:Jew COMPLETED:04!09110 O Fe, BORING METHOD:hand-auger(see report text) BORING 81T DIAMETER:3•Inch re a GEODESIGNZ CENTEX-16-01 HAND AUGER 0 Z 15575 SW Sequoia Parkway-Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT FIGURER- = Portland OR 97224 APRIL 2010 TIGARD,OR Off 503.968.8787 Fax 503.968.3068 U z o d 2 a LL, A BLOW COUNT DEPTH MATERIAL DESCRIPTION w>cul F ii •MOISTURE COMMENTS a FEET Q CONTENT% 1.2 Lt7 I- H HA-3 0.0 0 50 100 Stiff, brown SILT(ML), some clay,trace - organics (rootlets)and gravel; moist El ----I(1-inch-thick root zine)-FILL. ,- 1.0 _ Soft to medium stiff, brown SILT(ML), El -- trace clay and organics (roots and r1s traotlets); 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 Exploration completed at a depth of 4.5 4.5 measured at the time of 5.0- feet. exploration. 7.5— _ HA-4 o so 100 0.0 0 so 100 Stiff, brown SILT(ML), trace clay, organics (rootlets),gravel,and asphalt O - fragments; moist(1-inch-thick root _ zone)- FILL. a stiff to medium stiff, light brown at 1.5 El 6 - feet ° 2.5— Stiff, gray SILT(ML),trace fine sand, - 3.0 I- organics (rootlets),and gravel; moist, ° low plasticity-FILL. U z U - o grades to gray and light brown at 4.5 o 5.0— feet 6' — -..1 with orange mottles at 5.0 feet ,- s.s u _ Stiff to medium stiff,light brown SILT a (ML),some clay,trace organics _ (rootlets); moist(alluvium). Surface elevation was not Z,:' measured at the time of Exploration completed at a depth of 7.0 7.0 exploration. 8 7.5— feet. ,, - W U V a d - d a. i' 0 50 100 0 u DRILLED BY:GeoDesign,Inc.staff LOGGED BY:JPW COMPLETED:04/09110 O J 3 BORING METHOD:hand-auger(see report text) BORING BIT DIAMETER:3-Inch cd G EO DES I G Nz CENTER-16 01 HAND AUGER o (continued) z 15575 SW Sequoia Parkway 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT i Portland OR 97224 APRIL 2010 Off 503.9683787 Fax 503.9683068 TIGARD,OR FIGURE A-2 Z 0 21 Z •BLOW COUNT DEPTH v a d 0_ ••MOISTURE COMMENTS FEET MATERIAL DESCRIPTION >o I— Q CONTENT% W I— " U HA-5 0 s0 100 0.0 Medium stiff to stiff,brown SILT(ML), minor clay,trace organics(rootlets); - moist(2inch-thick root zone). 2.5- - ® Surface elevation was not - Exploration completed at a depth of 4.0 measured at the time of p p p 4'0 exploration. - feet. 5.0- 7.5— o 50 loo o so ioo 0.0 -4) Loose GRAVEL with silt and fine sand r 0.2 1(GP)(2 inches)- FILL. - Stiff, light brown SILT(ML), some clay, trace organics (rootlets); moist. with orange and gray mottles at 2.0 2.5J feet Surface elevation was not Exploration completed at a depth of 3.0 3.0 remeasured at the time of p p p exploration. - feet. L.? z U _ o 5.0— w V n. u eo ` 6 7.5— z w U w - U c w a - N 0 50 100 z 0 ij DRILLED BY:GeoDesign,Inc.staff LOGGED BY:.1PW COMPLETED:04109/10 O BORING METHOD:hand-auger{see report text) BORING BIT DIAMETER:3-inch v CENTEX-16-01 HAND AUGER G`EO DESI G Nz (continued) 0 z 15575 SW Sequoia Parkway-Suite 100 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT Portland= off 503.968.8787 Fax750FIGURE A-3 3.968.3068 APRIL 2010 TIGARD,OR Z 0 2 LI ♦BLOW COUNT DEPTH u wa •MOISTURE COMMENTS FEET MATERIAL DESCRIPTION A Q CONTENT% I— <n 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). ® 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-8 o so 100 0 50 100 0.0 ^ Stiff,brown SILT(ML), minor clay,trace organics (rootlets)and gravel; moist (1-inch-thick root zone)-FILL. P o — Medium stiff to stiff, light brown with 2.0 w 2 5— orange and gray mottled SILT(ML), some clay,trace organics (rootlets); moist(alluvium). U - z U _ ® Surface elevation was not o 5.0 Exploration completed at a depth of 5.0 5.0 measured at the time of feet. exploration. u of - R - • 7.5— C- tY tf til - eL w - N z0 SO 100 z u DRILLED BY:GeoDesign,Inc.staff LOGGED BY:.IPW COMPLETED:09/09/10 0 BORING METHOD:hand-auger(see report text) BORING BIT DIAMETER:3-inch Er, • G EO D ES I G NCENTEX-1 6-01 HAND AUGER (continued) a z 15575 SW Sequoia Parkway-Suite 100 = Portland OR 97224 APRIL 2010 PROPOSED TIGARD RESIDENTIAL DEVELOPMENT FIGURE A-4Off 503.968.8787 Fax 503.968.3068 TIGARD,OR