The URL can be used to link to this page

Home My WebLink About03031 - Technical Information Report - Geotechnical UEC-28-2001 �9�19 P.�6 - G�OTECHN[CAL ENGIN��RING STUDY � RENTQN EMPORIUM '� i5X SOUTNWEST SUNSET BOULEVARD �� RENTQN, WASHINGTON ' E-9942 iNTRO�uCnON Generat This report presents the resuits of the geotechnical engineering study completed by Earth �onsulLanis, inc. (ECI} #or the proposed Renton Emporium in Renton, Washington. TF�e `general tocation of the site is shown on th� Vicinity Map, Plate 1. The purpose of this siudy was to explore the subsurf�ce conditions at the site and based on th� condrtio�s encourrtered to develop geotechnical recamrnendations for the proposed site development_ Project Description ' We understand it is planned to develop the site with a twv story commercial and I residential building. At the time our study was performed, the site, proposed building locations, and our I exploratory tocati�ns were approximately as shown on the Test Pit LocatiQn Plan, Plate 2. ' The proposed development will include asphalt-surfaced parking and driveway areas. We ', ant�cipate tr�ffic will consist of p�ssenger vehicles and oGcasional service and delivery tfUCkS. tf the above design Criteria are incprrect or ch�nge, we should be consulted to review the recommendations cantained in this report. In any case, ECI should be retained to perform a general review of the final design. , � �A ) � � Eertfi Consultants, Inc. I \/ �3 3 � DEC-28-2001 �9�20 P.07 GEOTECHNtCAL �NGiNEERING STUDY � A & D Quality Construction . E-9942 November 26, 2001 P�ge 2 SI'fE CONDITJONS Surfa ce The s�bjeCt site is located just west of 150 Southwest Sunset Bouteva�d, Renton, Washington (see Plate 1, Vicinity Map}. The a�ea of the building is rectangular in shape, extending about 75 feet in the north-south direction and 100 feet in the east-west direction. A triangular area of parking extends to Sunset Boulevsrd io the south and a rectangular parking area extends to Langston Avenue to the east. The site is bordered on the east by a Chevron gas station, qn the west by an apartment entr�nce and on tt�e southwest by Sunset Boulevard. The site topagraphy is genera(ly flat with a gentie slope at the east adjacent to Langston Avenue. At time of visit, the site contained an old pa�king lot and asphalt section at the south adjaGent to Southwest Sunset Soulevard, and black5erries and tall grass at the north. Su6surtace Subsurf�ce conditions were evaluated by excavating four te5t pits at the approximate focations shown on Plate 2. PlQase �efer to the Test Pit Logs, Plates A2 through A5r for a more detailed description of the conditions encountered at each location expbred. A d�scription of the field exploration methads is included in Appendix A. The #ollowing is a generalized descript+on of the subsurface conditior�s encountered. Our test pits indicate the site is immediately underlain by a six to twelve inch thick layer of topsoit and rootmass. This soi( unit is characterized by its brown �o black color and the presence of organic material. This soil {ayer is not considered su�table for use in support of foundations, slabs-on-grade, or pavements. In addition, it is not suitable for use as a structu�al fill, nor should it be mixed with material to be used as structural fiit, Underlying a concrete sfab in Test Pit TP-2, we encountered about six inches of pea gravel. The concrete slab should be removed. The native s�ils consisted of silty sand w+th gravel (Unified Classification SM) to sandy silt iML?. The native soils were gsnerally dense below twa to three feet below the existing grade. Earth Consultants,Inc. � DEC-28-2001 09�20 P.� GEt7TECHNICAL ENGINEERING STUDY ` A & D Quality Construction E-9942 November 26, 2007 Page 3 Groundwater Groundwater seepage was encauntered in our test pits one foat below the existing grade. Groundwater seepage should be expected in all excavatians. The contr�c#or should be made aware thai groundwater is not static. There wi�l be fluctuations in the level depending on the season, amount of r�infafl, surfave water runoff, and other factors. Generalfy, the water level is higher �nd seepage rate i� greater i� the wetter winter months (typically October through May). Laboratory Testing Laboratory tests were conducted on sever�f representative soil samples ta verify or mpdify the field soit classification and to evaluate the general physical properties and enginesring characteristics of the soil encountered. Visual field classifications were s�pplemented by grain size analyses on representative soil samples. Moisture conter�t tests were performed on ail samptes- The results of laboratory tests performed on specific samples 2�e provided either at the appropriate sample depth on the ind�vidual boring logs or on a separate data 5heet contained in Appendix B. It is important to note that ihese test resufts may not accurateiy represent the overall in-situ soi! conditions. Ou� geotechnica! recommendations are based on our interpte#ation of these �est results and their use in guiding our engineering judgment. ECI cannot be respansible for the interpretation of these data by others. in accordance with our Standard Fe� Schedule and Gener�l Conditions, Lhe soi! samples for this project will be discarded aft�r a period of fifteen days following completion of this report vniess we are atherwise directed in writing. QISCUSStON AND RfCOMMENDATlQNS General Based on the results of our study, it is our opinion the proposed development can be constructed generally as planned. Building support may be provided using convention�l spread and continuous foundation systems bearing on competent native soils or on Structural fill used to madify sit� grades. Slab-on-grade floors may be similarly supported. Earth Consultents. Inc. g DEC-28-��1 09�� P.eS , GEQTECHNICAL ENGINEERING STUDY A & D Quality Ganstructifln E-9942 November 26, 2001 P�ge 4 Th�s report has been prep�red for specific app�ication to t�is project oniy and in a manne� consistent with that Ievel of c�r�e and skill ordinarily exercised by other members of the profession currently practicing under simiiar conditions in this area for the exclusive use of A & � Qua{i#y Construction �nd their represerttatives. No warranty, expressed or implied, is rnade. This report, in its entirety, shauld be included in the pro�eCt contract documents for the information of the contractor. Site Prep�ration and C�eneral Earthwork Based on the pretiminary site plan, it appears site grading will consist of grading the site I� to provide a level building pad, inst�fting underground utilities and grading the parking �' areas. '�I The building anci pavement areas shou)d b� stripped and cieared of foundatiQns, sur-face �� vegeta#ion, org�nic matter, and oti�er deleterious material. Existing utility pipes to be �! abandoned should be piugged or removed so that they do not provide a conduit for water �' �nd cause soil saturation and stability problems_ BasBd on th� thickness of the topsoil layer, encountered at our test pit loc�tions, we ', astimate a stri}�pir�g depth of twelve inches. Stripped materials should not he mixed with I materiafs to be used as struCtural fill. �otlowing the stripping, the ground surface where struciurat ti!(, foundations, or slabs are to be p(aced should be obs�rved by a represer�tative of ECI. Proofrolling may be necessary in order to identify soft or ur►Stable �reas. Proofrolling should be pertormed ' under the observation of a representative of ECI. Soil in {oose or soft areas, i# rscvmpacted and still yielding, should b� overexcavated and reptaced with struc#ural fi�l to a depth that will provide a sta�le base beneath the general structuraf fill. The optionai use of a geotextile fabric placed directly on the overexcavated surf�c8 mSy heEp #o bridge unst�ble areas. Eerth Consuitants, Inc. � DEC-28-2001 09�21 P.10 GEOTECHNICAL ENGINEERING S7UDY A & D Quality Construction E-9942 Novembsr 26, 204� Page 5 The sdils encountered during the site exploration ar� moisture sensitive dus to their high fines content. As such, in an exposed condition, they witl become disturbed from norma! const�uction �ctivity, especially when in a wet or saturated co�dition. Once disturbed, in a wet conditian, they will be unsuitable for suppon of foundations, slabs, or �avements. Therefore, during construction where these soils are expased �nd will support new structures, care must be exercised not to disturb their condition. Consideration should be given to placement o#�rock or ather methqds to protect exposed native, undisturbed soils that wil( support faundations or new structural fill. If disturbed conditions develop, the affected soils must be removed and replaced with structural fill. The depth of removal will be dependent on the (eve! of disturbance developed during ct�nstruction. Given the above, a summer earthwQrk schedule is recommended. Structur�l fil! is defined as compacted fill placed under builciings, rp�dways, slabs, pavements, or other load-bearing areas. Structural fill under flaar slabs and footings should be placed in horizont�l lifts not exceeding twelve (12) inch�s in loose thickness and compac[ed to a minimum of 90 percent of its iaboratory maximum dry density determined in accordance with ASTM 7est Design�tion D-1557-91 {Modified Proctor). The f�41 materials should be placed at or near their optimum moisture content. Fitl under pavements and walks should also be piaced in horizonial lifts and compacted to 90 percent of maximum density except for the top tweive (12) inches which shou(d be compacted to 95 percent of maximum density. During tfry weather, most soils which are compactible and non-organic can be used as structural fil(. Based on the results of our laboratory tests, the site sails at the time of our exploration appear to. be over the optimum moisture content and witl require moisture conditioning (drying out) prior #o their use as structur2�1 fill. Based on laboratory testing, the native soil has between 14 and 56 percent fines passing the No. 2Q0 sieve. Soil with fines +n this range wilf degracfe if exposed to excessive moisture, and compa�tion and grading will be difficult if the soil moisture in�reases significantly above its apiimum condition. if the �ativ� soil is cannot be moisture conditioned and compacied then it may be neCessary to import a soil which can be compacted. During dry weather, most �on- organic compactible soil with a maximum particle size of six inches can be used. Fill for use during wet weather should cansist of a fairly well graded granular material having a maxirnum �article size of six inches and no more than 5 percent fines p�ssing the No. 200 sieve based on the minus 3l4inch fraCtio�. A contingency in the earthwork budget shauld be ineluded for this possibility. Earth Consultants, Inc. �� DEC-28—c001 09-21 P.11 GEGTEGHNtCAL EIVGlNEERiNG STUDY A & D Quality Const�uction E-9942 November 26, 2Q01 Page 6 Found�tions Based on the resutts of our study, it is our opinion the proposed building may be supported an a canventional spread and continuous footing foundation bearing on competent native soil or on structural fill used to modify site grades. For fiost protection consideratior�s, exterior foundatian elements shQuld be placed at a minimum depth of eighteen (18? inches below final exterio� grade. Inte�ior spread foundations can be placeti at a minimum depth of tweive (12) inches below the top of slab, except in unheated areas, where inter;or foundation elements should be founded at a minimum depth af eighteen {18) inches. With foundation support obtained as described, for design, an allowab{e bearing capacity pf two thousand five�hundred {2,500) pounds per square foot {psfl for structural filt or competent native soil can be used. Continuaus and ind�vidual spread footings shau�d have mi�imum widths af eighteen (18} and twenty-four {24) inches, respectively. Loading of this magnitude wou{d be provided with a theoretica! factar-ot-safety in excess of three against actua! shear failure. �or short-terrn dynamic Ioading canditions, a one- third increase in the above allowable bearing capacities cart be used. With structura4 loading as expected, total settlement in the range of orte inch is anticipated with differential movernent of 2bout one-half inch. Most o'F the anticipated settlements should occur during construction as dead (oads are applied. Horizontal loads can be �esisted by friction between the base of the foundation and the suppoRing soil and by passive soil pressure acting on the face of the buried portion of the foundation. For the latter, the foundetion must be poured "neat" against the Competent native soils or backfilfed with structura! fill. For frictional capacity, a coefficient af .35 can be used. Fo� passive earth ptessure, the available resis#ance can be computed using an equivalent fluid pressure of three hundred fifty (350) pounds per cubic foat (pcf}. 7hese lateral �esistance v�lues are allowable values, a factor-of-safety of 1 .5 has been inc(uded. As movem�nt of the foundatipn element is required to mabilize full passive �esistance, the passive resistance should be neglected if such movement is not acceptable. Footing excavations shpuld be observed by a representative of ECI, prior to pla�ing forms or rebar, to verify thet conditions are as anticipated in this report. Earth Consultants, Inc. � b � DEC-28-2001 �9�22 � P. 12 GECJTECHNICAL ENGiNEERING STUDY � A & D Quality Construction E-9942 Nov�mber �6, 2001 Page 7 Retaining and Foundation W�IIs Retaining wa(Is and foundation walls that act as retaining wa{Is shauld be designed to resist lateral earth pressures impdsed by the retained soils. Walls that a�e designed to yield can be designed to �esist the lateral earth pressures imposed by an equival�nt fluid with a unit weight of thirty-five i35) pcf. if w�lls are to be restrainsd at the top frorn free movement, the equivalent fluid weight should be increased to fifty {50) pcf. �C'hese values are based on horizontal backfill and that surcharges due to b�ckfill slopes, hydrostatic pressures, traffic, structurai loads or other surcharge ioads wi{1 not act on the wail. If such surcharges are to apply, they should be added to the above design iateral pressu�e. The passive pressure and f�iction coefficients previously provided in the Faundations section are applicable to retaining walls. If design against eaRhquake iaading is desired, a rectangular pressure distribution equal to six tirnes the wall height t6H) should be added to the abave lat�ral earth pressure values. In order to reduce the patential for hydrostatic forces b�ilding up behind the walls, retaining walls shvu�d be backfilled with a suita6le firee-draining materia! extending at le�st eighteen {18) inches behind the wall. The rem�inder of the ba�kfill shauld cansist o# structural fill_ The free-drai�ing backfill should confofm to the WSdOT specification for gr�vel backfilf for walls (WSDOT 9-03.12(2)?- A perfprated drainpipe shoulc! be placed a# the base ofi the wail and st�ould be surrounded by a minimum of one CubiC foat p�r line�l fQot with three-eighths inch pea gfavel. S1ab-an-Grade Floors Slab-on-gr8de floors may be supported an competent native soil subgrade or on strUctucal fill. Disturbed subgrade soil mi�st either be recompacted Qr replaced with structura�( fill. Goncrete slabs resting on saii ultimatsly cause the mo�sture content of the underlying soils to rise. This results from continued capipary rise and the ending of normal evapotr�nspira#ion. As concrete is permeable, moisture wiil eventually pQnetrate the siab resulting in a condition cammonly known as a "wet slab" and poor adhesion of ftoor coverings. Therefore if slab moisturQ is a eoncern, the slab should be provided with a minimum of four inches of frs�-draining sand or gravel. 1n arsas where slab moisture is undesirabie, a vapor b�rrier such as�a fi-mil plastic membrane may �e piaced beneath th� sfab. Two inches of damp sand may be ptaced over the membrane for prOt�CtiOn du�ing cnnstruction and to aid in curing of the concrete. Earth Consuttants, InC, � � DEC-28-2091 09�22 P.13 G�07�CHNICAL ENGINEERING S7UDY - A & D auatrty Constructian E-9942 November 2fi, 2001 Page 8 Seismic Design Consid�ratians The Puget Lowland is ciassified as a S�ismic Zone 3 in the 1997 Uniiorm Suilding Code (U6�1. Earthquakes occur in the Puget l.owland with regulerity, however, the majbrity of these events are of such iow magn"stude they are not detected withQut ins#ruments. Large earthquakes do�occur, as indicated by the 1949, 7.1 magnitude earthquake in the Qlympia erea, the 1965, 8.5 magnitude earthquake in the Midway area, and the 7.8 magnitude earthqueke qf February 2$, 2001, in the �lympia area. There are three potential gedlogic hazards associated with a strong motion seismic event at this site: ground rupture, liquefaction, and ground motion rQsponse. Graund Rupture: The strongest earthquakes in the Puget Lowland are widespread, su�crustal events, ranging in dapth from thirty (3q) to fifty-five (55? miles. Surface faulting from ihese deep euents has not been documented to date. Therefare, it is our opir�ion, that the risk of ground rupture during a strong motion seismic event is neg(igible. Uquefaction: Liquefaction is a phenornenon in which soils lose al) shear strength fa� short periods of time du�ing an e�rthquake. Grc�undshaking of suffiCient duration resuttS in the Ioss of grain to grain contact and �apid increase in pore water p�essure, causing the soil to behave as a flvid. To have a potential for liquefa�tivn, a soil must be coh�sionless with a gr�in size distribution of a speCified range fgeneratiy sands and silt); it must be toose to medium dense; it must b� be(ow the groundwater table; and it must be subject ta sufficient magnitude and duration of groundshaking. The effects of liquefaction may be large total andlor differentia! settlement for structures faunded in the liquefying soils. Based on the density of the site soils, it is our opinion the potential for liquefaction over the site during a seismic event is negti�ible. Ground Motion Response; In accordance with Table 1�-J of the 1997 UBC, soil type S� should be used in design. Excavations a�d Sto�es The foilowing inform�tion is provided solely as a service to our client. Under no circumstances should this information be interp�eted to mean that ECI is assuming responsibility for constn�ction site safety ar the Contractor's activities; such responsibility is not be9ng implied and should not be inferred. Eerth ConsultantE, Inc. Y � UEC-28—�001 �9�23 N,14 GEOTECHNICAL ENGINEERING SNDY A & D Quality Construction E-9942 November 26, 2001 Page 9 In no case shoufd excavativn slopes be grEater than the limits specified in local, state and Federal safety regulations_ Based on the information obtained from our field exploration and laboratory testing, the medium dense native soils would be classifi�d as Type B by QSk�A. Temporary cuts greater than four feet in height in Type B soils should be sloped at an inclination of 7 H:1 V (H�rizontal=Vertical). If slopes of this inclination, or ffatter, cannot be constructed, tempQrary shoring msy be necessary. St►orir►g wil! help protect against slop� or excav�tion cailapse, and will provide protection to workers in the excavation. If temporary shoring is required, we will be av�ilable to provide shoring design criteria. Permanent cut and till slopes should be inclined no steeper than ZH:1 V. Cut slapes should be observed by �CI during excavat'san to verify that conditions are as anticipated. Supplementary recommendations can then be developed, if needed, to improve stability, including flattening vf slvpes or installation of surface or subsurface drains. In any c�se, w�ter should not be allpwed tQ flaw uncantrolled over the top of slopes. Permanently exposeci slopes shoufd be seeded with an app�opriate species af vegatation to reduce erosion and im�rove stabiEity o# the surfic+al I�yer pf sail. Site �rainage Groundwater seepage was encountered in our test pits a# one foot below the existing grade. Seepage should be expected in footing and utitity �xcavations. Seepage encauntered in foundation or grade beam excavations during construction should be conirollable by sloping the bottom of t�e excavation to one or more shalfow sump pits. The collected water can then be pumped #rom these pits to a positive and permanent discharge, such as a nearby storm drain. Depending on the magnitude ofi such seepage, it may alsa be necessary to interconn�ct the sump pits by a system af connector trenches. . The appropriate loc�tions of subsurface drains, if needed, should be established during grading operatians by ECI's representative at which time the seepage areas, if present, may be more clearly defin�d. Earth Consultante, Iha. �� G�aTECHNIGA�. ENGiNEER1I�G STUDY ` A & D Quality Construction E-9942 November 26, 2Qp1 Page 11 Pavement Areas The adepv�Cy of site pavements is related in part to the condition of the underlying subgrade. T'o pr'ovide a pro�erly prepared subgrade for pavemenis, the subgrade should be tre�ted and prepared as described in the Site Preparation section of this report. This means at least th� top twelve (12} inches of �the subgrade should be compacted to J5 perc�nt of the maximum dry density i�er ASTM D-1557-97). !t is pdssible that some localized area5 ofi soft, wet or unstable subgrade may still exist after this pro�ess. Therefore, a greater thickness of structura! fill or crushed rock may be neEded t� stabilize these loc�fized areas. The following pavement sectian can be Used fflr lightly-(o�ded areas (c�r tr�ffi�): • Two inch�s of asph�k concrete (AC) ov�r four in�hes ofi crushed rock base (CRB) material, or • Twa inches of AC vver three inches of �sphait treated base �ATB) materiai. Heavier truck-traffic areas wiN require thicker sections depending upon site usage, pavement life and sitE trafific. We will be pleased to assist in deveioping appropriate pavement sections for heavy traffic zones, if needed. Pavement materials shavld conform to WSU07 specifications. The use of a Class B asphalt mix is suggested. L.IMI7ATIONS Ou� recommendations and conclusions are based on the site materials observed, seleCtive laboratory testing and engineering analyses, the design information provided us, and our experience and engineering judgment. The conclusians and recommendations are profe$sional apinions derived in a manner cansistent with that level of c�re and skill ordinarily exercised by other members of the profession currently prac�i�ing under similar canditions in this area. Nv warranty is expressed ar implied. Earth Consulianis,InC. J � F. 17 �.CLr-��J-�V-� t-- � � GE4TECMNICAL ENGINEERING STUDY - A & D Q�,ality Construction E-9942 November 2fi, 2001 Page 12 The recommendations submitted in this report are based upon the data obtained frpm the test pits. Soil and groundwater Conditions between test pits may vary from those encountered. The nature and exten# af variations between our exploratory locations may not become evident untii construction_ If variations do appear, ECI shoufd be requested to reevalu�te the recommendations of this report and to modi#y or verify them in writing prior to proceeding with the construction. Additional Services As �he geotechniCal engineer of record, ECI should be retained to perform a general review of the iinal design and specifications to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the construction specifications. ECf should als4 be retained to provide geotechnical services during construction. This is to observe compliance with the design concepts, specifications or recommendations and to ailow design changes in the event subsurface conditions differ from those anticip�ted prior to the start of construction. We do not accept responsibility for the performance of the foundation or �arthwo�k unless we are retained to review the const�uction drawings and specifications, and to provide const�uction observation and testing services. ��m ca,�,��e�,i��. � �