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HomeMy WebLinkAbout502311002 Geotech Assessment~. Geotechnical Report 313723 Highway 101 Brinnon, WA Prepared for: Cynthia Cuzick & Wayne Devaney ~]~~EI~~I'~ L r~~ ~~~f~~SO~ ~~~~ D~~ by C eotechnical Testing Laboratory Olympia, Washington July 19, 2005 GEOTEC~Il~iICAL TESTING LABORATORY CYNTHIA CUZICx 19~ WAYNE DEYANEY 313723 HIGHWAY 101 BRU~n~rON, WA 9a31A RE: GEOTEC~rICAL REPORT 313723 HIGHWAY 101 BRIl~rNON, WA 98320 NEl/4, T25N, 531, R2W PARCEL NUMBBR 502311002 N47~7.003' W122°58.676' INTRODUCTION This report sunarrarizes the results of our geotechnical cxmsulting services for the relocation of the existing strucfi~re located al~g the west shore of the Hood Canal in Jefferson County, Washington. The site (0.45 acre) is located 5.5 miles southwest of Brinnon, Washington. The location of the site is shown relative to the surrotu~ding area ~ the Vicinity Map, Figure 1. Our understanding of the project is based an our discussia~ with you and our explorations and review ~ the site. We understate that the parcel is to be re-developed by moving the existing strucx~ure 6 feet iht~ fmm the Hood Canal. The site is acxessed by a driveway from U.S. Highway 101. Lr general, grading will cx of the excavate of the famdatian and retaining wall. The purpose of our services is to evaluate the surface and subsurface conditions at the site as a basis for providing geotechnical reooaun~datians and design crheria for the project and to satisfy the recNires ~ the Jefferson County Critical Areas Ordinance. GeabocLnical Testing Laboratory is therefome provicting goologic and hydrogeologic services for the project. Specis~uy, our scope of services fm this project will inchxie the fdlowing: 10011 Blcasbeag Street SW, Olympia, WA 98512 1 Phone #: (360) 754-4612 Fax #: (360) 754-4848 The site slopes predominarrtly south towards the Hood Canal from U.S. F~way 101. The steepest slope measured onsite was in excess of 100 percent. Therefore, Jefferson County requires that a geotechnical report beprepared in accordance with the Critical Areas Ordimance. GEOTECHNICAL TESTING LABORATORY 1. Review the available geologic, hydrogeologic, and ~ootechnicai data for the sine area. 2. Conduct a geologic of the site area and strrr+orrnding vicinity. 3. Investigate shallow subsurface conditions at the site by observing the exposed soil and reviewing published well logs. 4. Evaluate the landslide and erosion hazards at the site per the Jefferson County Critical Areas thdinance ~• 5. Provide geotechnical rExoir~ndations for sift grading including site preparation, subgrade preparation, fill placenrazt criteria (inchrdmg hillside grading), temporary and pemranedt art and fill slopes, drainage and erosion control measures. SITE CONDITIONS SURFACE CONDITIONS The proposed building site is located in an area of sparse residential developrrrent in the Puget Sound glacial lowland next to the Hood Canal. The site has mostly southeastern exposure. We conducted a of the site area on June 29, 2005. Site elevations range approximately frnna zero to over 40 £eet. The building locetion is a narrow level area boarded by the Hood Canal ca the south and a steep hill abutting U.S. Highway 101 on the north. Exposed sorb was observed in the northern portioa of the site where minor slope et~osion aad sloughing has occurred firm previous oonst<u~on. The site is vegetated with a well-mixed variety of plauo~s comma~n to the Nathv~st. The vegetation includes fir, c;odar, msdrone, and alder tnxs as well as sword fern, blry, salal, Scat's broom, and . Vegetated areas appear to be undisdubed. 'The general topography of the site area indicates that chain8ge is to the south froaa the northern slope. Groundwater was Trot ~ ce observed arse. Evidence o+f mirror surface flow was observed along the northern slope. Slope instability was not observed near the proposed building location. Minor slou~g and raveling was observed onsite. Surface water (pcuding) was not observed arsiLe. 10011 Blanberg Strcet SW, Olympia, WA 98512 2 Phone #: (360) X54-4612 Fax #: (360) '754-4848 GEOTECHNICAL TESTING LABORATORY SrrE G$OtoGY The. site is generally situated within the Puget Sound glacial lowland. The existing topography, as well as the surficial and shallow subsurface eels in the area, are the result of the most recent Vashon stale (stage) of the Fraser that occurred betvveext about 8,000 and 11,000 years ago, and weathering and erosion that has occurred since. A description of the sur6cial soils is inch~dod in the "Site Soils" section of this report. hn general, the sods are composed of glacially derived material. SITE Sons The Soil Survey of.lc~'erso» County, USDA Soil Co»servatton Service (19'75) has mapped the site soils as Grove ~Y 8~~Y ~Y sand, 15 to 30 Percent slopes (GoD). The survey reads, This moderately steep soil is on hilly glacial outwash terraces along the breaks of steep carniyons or waterways of the foothills. The surface layer and subsoil are I S to 20 inches deep over a substratum of gravelly and very gravelly sand Included in this soil in mapping are small areas of gravelly loam soils a~ soils that have a consolidated substratum. Rura,,~ji`'is mecum, and the hazard of water erasion is slight to moderate. The Geologic Map of Washington -Northwest Quadrant (2002) has mapped the site geologS- as glacial outwash deposits (Qgo) of coatine~al glacial origin. The report reads: Undi,~'erted oxtwash -Recessional and proglacial stratified sand gravel, and cobbles with minor silt and clay interbeds deposited in delta, ice-contact, beach, and meltwater stream em~ironments; may include advance outwash. Ir~ludes part of the Partridge Gravel, part of the Everson Glaciomarine Dri, fT, and part of the Yashon Drift undivided. 10011 Blomberg Street SW, Olympia, WA 98512 3 Phone #: (360) 754-4b12 Fax #: (360) 754-4848 GEUTEC~INICAL TESTING LABORATORY SvssvgFwc~ ExrjojuTtorrs Subsurface conditions at the site were evaluated by observing the exposed building site soil and reviewing available well logs. Depth to oompete~ soil is approximately 6 inches throughout the proposed building location. Grro`endwater was not observed or ~. Sussv~wc~ CotaIDlTioNs In general, wodisturbed dense gravelly sandy bum was observed throughout the proposed building location. Basod on die site topography and the nature of the near surface soil, seasaially perched groundwater conditions should not be expected chuimg periods of extended wet vveatber. Siors STwan1'rY Slopes in excess of 100 percent were observed onsite. Since the site area is mapped as `~mstable" by 7~ie Coasml Zone Atlas, Yolume 11, Jefferson County {JE-lb), Jefferson Courrty requires that a geoterlmic~i report be coanpleted according to the Critical Areas Ordinance. The Coastal Zone Atlas, Volume 11, Jefferson County (JE-16) maps the site as Unstable. Unstable (U) slopes are considered unstable because of geology, groundwater, slope and/or erosional factors. They include areas of landslides and talus too small or obscure to be individually mapped. Unstable soils are found on the coastal side of the property. The near-surface soils are in a dense to Very dense COlldltlOII eXCept at the ground surface. The surficial soils are generally in a medium dense condition. In general, the u~sturbed native-soils of the site consist of a mixture of variable amo~mts of sand, silt, and gravel. These soil rriateriaLt are in a dense condition except where they have been disturbed by v~ activity. These soils are generally stable relative todeep-seated failure. s~,k ~:?~.ooo ~,:. o , ~,~, ` ~~ ' ,Q ~ -.:, u~ ~~ $. v ~ F- ~. ~~ Npna <ne et deca~aren -~:": .vary /, s S ~ ,o„„, e,,, «~..,.~~, a... l Weathering, erosiaq and the resultant sloughing and shallow landsliding are natural processes that can affiect steep slope areas. Instability of this nature is fiypically confined to the upper weathered or disturbed zone, which has been disturbed and has a bwer strength. Significant weathering typically occurs in the upper 2 to 3 fcet and is the resuh of oxidation, root penetration, wet/dry cycles, and fireezeJtbaw cycles. Erosion in steep slope areas such as this can be reduced by eanceuraging vegetation and discouraging runoff fio~n the steep slope. Erosion control reconons for the sbping areas are provided in the "Erosion Control" section of this report. 10011 Bbanberg Street SW, Olympia, WA 98512 4 Phone #: (360) 754-4612 Fax #: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY i~~ tip: :_ G CONCLUSIONS AND RECOMMENDATIONS Ba,~ed an the results of our ~ reconnaissance, subsurfacx observations, and our experience in the area, it is our opinion that the site is suitable for the proposed project. The building location slopes are stable relative to dcep- seated instability and will not be affected by the proposed structure if our reooannendatioos are respecoad. The P~ structure relocation wi11 not wine adjsoeat strucdrres, slopes, or U.S. Highway 101. Proper drainage co~rnl measures will reduce or eliminate the paterrtial for erosion in this area and innprove slope stability. The hazards of the lauidslide arcs tin be overcome in such a roamer as to pr+evea~ harm to property and public health and safety, and the project will case no siigrific~rt enviromrredai impact. In , ~ ~Y Y ' ~Y soils observed ~ the site are srrNaWe for use as stnrcdual fill material. Safiuated soil may be associated with these soils during or following arten3od periods of rainfall. Iio~wever, to reduce gradigg time and construction costs, we recommend that earthwork be undertaken during favorable weather cx~cos. Conventional ooaatruction equipoarnt may be utilizod For work at the site. C'anverrtionsl spread footiggs may bs utilized at the site for support of the structure. A vapor barrier is rrxded fce all slab~a-grades. Pert~t conclusions and gootecbnical reconnnt~atians regarding the design and oohruction of the proposed single-family residence are preae~od bekyw. 10011 Bkxnberg Street SW, Olympia, WA 98512 5 Phone #: (360) 754-4612 Fax #: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY CLASS~cwTTOrr LANDSLIDE -EROSION HAZARD AREAS The Relative Slope Stability of the Southern Hood Canal Area, Washington, (1977) describes the site area as Class 2. Class 2 is described as: Areas believed to be stable order normal conditions, but may becor~ unstable if disturbed by man's activities, f slope is oversteepened by erosion, or if subjected to strong seism~rc shaking. Slopes generally steeper than 1 S percent, but may be less in some areas of weak geologic materials. lnchu~s areas underlain by: well~cirained sand and gnavel~ mostly on valley sidles that lack bawn slope failures; glacial till with steep slopes; and bedrock The Jefferson Cou~y Critical Areas Ordinance (3.6.7) defines a landslide hazard area as: Areas potentially subject to mass movement due to a combination of geologic, topographic and hydrologic factors including; A. Areas of historic failures or potentially unstable slopes, such as: 1. areas described and mapped as having severe or very severe building Itmttations for dwellings without basements within the United States Department ofAgriculture/Soil Conser-~atton Service Soil Suru~ey for Je,,~erson County; Z. areas deescribed and mapped as recent or old landsliaes or slopes of unstable materials within the Washington State Department ofF.aology Coastat 7,~»~e Atlas ofJe,,~ierson County; and 3. areas deescribed and mapped as areas of poor natural stability, former landslides and recent landslides by the Washington State Department of Natural Resources, Division of Geology and Earth Resources. B. Areas potentially unstable as a result of rapid stream incision, stream bank erosion, or undercutting by wave action; and C. Areas with any indiaations of earth mo-aement, such as: 1. roakrlides; 2. earthjlows; 3. mudjlaws; and 4. landslides. Slopes in excess of 100 percent were observed ansite. Since the site area is mapped as `~mstable" by The Coastal Zone Atlas, Yohtme Il, Je,,~i`erson County (JU16), the site meets the recNire:neat of a landslide hazard area and a gecrtecbnical report is to be crotnpleted acoordmg to the Critical Areas Ordinance. The Jefferson Couutj- Critical Areas Ordinance (3.6.?) defines as erosion hazard area as: Areas conmini~eg soils or soil com~laaes described and mwpped within die tlrritod States Deparb~ of Agriculture! Soil C;omervation Service Sod Survey for Jet~exson Ca~m~ly as having a severe or vrry severe erosion haarmd potential Soil Survey of Je~fcrson County, USDA S~1 Cortservrrtion Service (1975) describes the site area erosion potertial as slight to mode,~e. SI.OI-E S~wsII1Tx Based on our field dhw~vations, explorations and our experience with the soil types encou~red on the property, we conclude that although portions of the slopes on the lot exceed 100 perant, the sift is generally stable relative to deep-seated failure in its pmsent c;onfiguratioe~. 10011 Blomberg Street SW, Olympia, WA 98512 (> Phone #: (360) 754-4612 Fax #: (360) 754-4848 GEO`TECHNICAL TESTING LABORATQRY To prevart minor sliding, ~~ted fill material and axy underlying vegetation slfail be removed in order to construct the foundation. Excavation and back-filling will ovcur based on appropriate engineering and earthwork reootnmaend~atia~s found in the follogvi~ "iarthwork" section. Grading in the bcaldiog portion of the site should be cued in aceordauce with g~ recotrurrendatioai provided herein. As pnwiously discussed, wearing, erosion, and the resultant surficiai s and laadssliding are natural .processes that affect slope areas. S~ vveatbering typic~ily occurs in the upper 2 to 3 feet and is the result of oxidation, root p~tratioa, wetldry cycles and freeze/thaw cycles. Over excavation maybe necessary to ensare the removal of deleterious material. These processes can be managed and the risk reduced proper construction of the residence. Erosion control rdations in the slope arxi buffer areas are provided in the "Building Setback" and "Erosion Control" sections of this report. BUILDING SETBACK Based on our geotechnical evaluation of the site and our experience in the area, a building setback will be needed for this lot. A building setback of 3-feet from the toe of slopes to the bottom of the footing should otherwise be observed. The building setback may be measured from the bottom of the footing to the face of the steep slope in accordance with the 2003 International Building Code (IBC). Fowadation elements must be constructed in native material and not fill material. Peak Shear Stress vs. Normal Stress M rO a x~oo -. _. - - -__- __ -_- - --- _..__ _- - - .-__ 43' woo' i 1500 i 1000 'I 30D o ! --x-1/4 ton -a-trztcn -k- ~ ton sac ~ooo ~30o woo woo ~ooo Normal Blress (psQ 10011 Blomberg Street SW, Olympia, WA 985I2 7 Phone #: (360) 754-4612 Fax #: (360) 7544848 GEOTECHNICAL TESTING LABORATORY Slope stability was modeled using the GEO-SLOPE/'W program (version 5.20) ~ both static and ext~ne dya~mic conda<ions (c, = 0.3). Factors of safiery were determined using Bishop's, Janbu, and the Morge~n-Price methods. The glacial soil was determined to have a unit weight of 134.6 pci; cohe~an of 200 psi; and a shear angle (~) of 43°. Under static oondibians, the slopes were stable to shallow failure. Under dynamic loading, the 3328 aa~ denwnsgatod that the slopes are not susoeptibk to sur6cial raveling and doep-seatod faihue. The Sgure ~ the mamern factor of safcty for slope "A" under the existing . The £igm+e is the solution of greatest concern and exlu'bits the Hood fnr a building setba~dc of 3 f~oct from the toe of slopes. Foundation elements must be oonstrttdod in native material or eagmeerad fill material. Cuzick I Devaney Site Analysis Method: Morgenstern-Price Direction of Slip Movement: Left to Right Seismic Coefficient: Horizontal and Vertical .. J • ~~ .- O tU W 50 45 40 35 30 25 20 15 10 5 0 Distance (ft) __ __ 10011 Blomberg street SW, Olympia, WA 98512 g Phone #; (360) 754-4612 Fax #: (360) 754-4848 0 20 40 60 80 1011 120 GEUTECIINICAL TESTING LABQRATURY As previously wed, weatberiag, eon and >be ~ sru6cial sia and shallow 1~ are natural processes that aft'ect slope areas. Minor surficial raveli~ and sloughing were observed onsite. To manage and reduce the pa~artial fear these natural pmoesses, we reoosmnarad the folloowing: 1. No a of concentrated surfsoe water or significazrt sheet Bow onto the sloped areas. 2. No soil rano~val within the setback gone unless retainod by retaining walls a unretracted as an engineered fill. 3. Tra S$rs~c -1 According to the Seismic Zone Map of the United States contained in the 2003 International Building Code (IBC), the project site is lor~ted where the maximum spectral response acceleration is 45 perreut of gravity (g). Based on the subsurface conditions observed at the site, we interpret the site conditions to c~rrespo®d to a seismic Soil Profile Type C, for Very Dense Soil, as defined by Table 1615.1.1 (IBC). This is based an the range of SPT (Standard Peneara~n Test) blow counts and/or probing with a yrinch diameter steel probe rod. The shallow soil conditions were asstmsed to be representative for the site conditions beyond the depths explored. The Liquefaction Susceptibility Map of Je,~4'erson County, Washington by Palmer, Magsino, Poelstra, Bilderback, Folger, and Niggemarn (September 2004) maps the site area as having a very law to krw ligvefa~ion potential. The Site Class .A~p of Je,~`erson County, Washington by Palmer, Magsino, Bilderback, PceLstra, Fo}ger, and Niggelnann (September 2(Hl4} maps the site area as site class C to D. Site class C is a very stiff soil or soft rode and site class D is a stiff soil. Based an our review of doe subsurface oooditioag, we conchxie that the site soils are only mildly susceptible to h~- 1001 I Bbrnbetg Street SW, Oly~ia, WA 98512 9 Phone #: (360) 754-4612 Faac #: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY The near-surfave soils are g~ly iu a dense ooncMion anti the static water table is bcated near the tev~d of the Hood Canal. Shaking of the already dense soil is not apt to produce a denser configuration and subse~tly excess pore water pressures are not ~y to be produced. EROSION CONTROL It is our opim~ that the potential erosion hazard of the site is not a limiting factor for the proposed development. Removal of natural vegetation should be minimized and limited to tlsr active oo~rtrdion areas. Yard around the borne is permiss~le, but imderstory growth an the slopes should be encouraged as much as possible as a deterrent to erosion. Trees located on steep slopes may be removed only if the remain to deter . Texriporary and pennane~ erosioa control measures should be installed and maintainod during oaustruc~io~n or as soon as practical thereafter to limit the additional influx of water to exposed areas and protect partial recxiving waters. F.rosiar cxmtnol rr~easures should include, but not be limited to, silt fences, berms and swales with ground coverJprotection in exposed areas. Atypical silt fence detail is included on Figure 2. Any rr-asYtau~g of the site will create a need for erosion control measures as listed above. Areas of exposed soil must be seoded as soon as possible. Srr~ PREPARATION ~, EARTHWORK All areas to be excavated shoidd be cleared of deleteria~rs matter inch any existing structures, debris, doily and von. Based on our ob®ervatioos, we estimate that on the order of 8 tD 12 inches will be nooeasary to remove the remaining surficial sods coo organics. Areas with deeper, ur~uitable organics should be expected in the vicinity of dep~essio~ or heavy vegetation. Stripping depths of up to 18 inches may occur in these areas. These materials may be stod~slod and later used fce erosion control and landscaping. b~terials tkrat cannot be used for lawdsc~ag or erosion cootrd should be removed fran the project site. 10011 Blomberg Street SW, Qlympia, WA 98512 10 PLone #: (360) 754-4612 Fax #: (360) 7544848 GE(1TECHNICAL TESTING LABORATQRY Where places of fill material is mired, the exposed subgrade areas should be proms-relied to a firm and unyiediag surface prior to placement of any fill. We recmrunend that trees be reixaved with the moats, unless located on a slope. F~avatmns for tree stamp t+emo~val in any building area should be backfitiod with ~ fill, Gampacted to the de~icy recrurements descnbed in the "Structural Fill" section of this report. if saxucttual fill is needed, we reoonunead that a member of our staff evaluate the exposed subgrade conditions after removal of vegetation and topsoil stripping is completed. Any soft, loose or otherwise unsuitable areas delineated during foundation preparation or probing should be vompacted, if practical, or over-excavated and replaced with structural fill, based an the reooa~tla~ions of our report. STRUCTtr~L FII.i. All fill material should be placid as structural fill. The structural fill should be planed in horizontal lifts of appropriate thicioness to allay adequate and umif~orm coanpaction of each lift. Fill should be vompacted to at least 90 percent of MDD (maximum dry density as determ»~ed in acxordance with ASTM D•ISST) to within 2 feet of subgrade and 95 pex~nt MDD in the upper 2 feet. The appropriate lift thiciooess will depend on the fill clharacteristics and campac~ian ~ used. We recommend that the appropriate lift thicla~s be evacuated by our field restive during caostructian. The suitability of material for use as structural fill will depend on the gradation and moisture contest of the soil. As tip amount of fines (material passing No: 200 sieve) increases, soil beoon~es increa~ngly se~tive to smelt. in moisture content and adequate compaction becomes more difficult to achieve. During wet w~deer, we reoomrreend the use of well~radod sand and gravel with less than 7 percent (by weight) passing the No. 200 sieve based on that fi~cGion passing. the'/,-inch sieve. If prolonged dry weather prevails during the eazthwork cad foundation installation phase of caostrudion, a ssx~what higher (up to IO percent) fines contetrt viii be acceptable. Material placed for strudurai fill should be free of debris, organic matter, trash, and cobbles ' than 6 inches in diaaieter. The mo~ure cou~ent of the fill m~erial should be adjusted as necessary fce Prop~x ooonp~cn. GEOTECHIVICAL TESTING LAB(}RATORY Surr~itanr of Ors SoIIS ~s ~. onsite soils may be considered for use as structural fill. m general, the native soils (saaid, boon, and minor gravel) enaxectered oa the site must have kss than 10 pea+onnt fines (material passing the US 1vo. 200 sieve) to be suitable for use as structural fill. Corr Arm >~.i, SLOr~s All job site safety issues and precautions are the a+espoositi'biliiRyy of the contractor providir~ services and/or work. The follotiving ca~t/fili slope guidelines are Provided for planning ptuposes. Teariporary cart slopes will likely be necessary during grading operations. As a general guide, temporary slopes of I.S to 1 (horinoatal to vertical) or flatter may be used for temporary cuts in the upper 3 to 4 feet of the glacially consolidated soils that are weathered to a condition. Temporary slopes of 1 to 1 or Batter may be used in the unvueathered dense to very dense sates and gaavd. These guidelines assume that all surface loads are kept at a minimum distance of at least one half the depth of the cut away &~ the top of the slope and that significant soepage is not presort on the slope face. Ferber cut slopes will be necessary where significant raveling or seepage occaus. Surface shall be directed away firm all slope faces. All slopes should be enacted as soon as practical to facilitate the d~ of a protective vegetative ever or otherwise protected. FovxnwTtoN SUPPORT Where foundation elements are located near slopes between S and 30 percetrt, the footiaq;s should be located a minimum of 2 dunes the footing width fi~oan the slope face (ho~oaaralty), and foandod in dense or very dea,se native soils or properly pa+epaa+od structural fill. We recommend a minimum width for isolated footings and for sous wall footings tb meet IBC 2003 standards. Footings founded as described above can be designed using an allowable soil bearing capacity of 2,000 psf {pounds Per square foot) for coanbinod dead and laig-team live bads itt atoms of doe~e to very lease sails. The weiglrt of the foatinig and an3- overlying backfill may be neglected. The allowable bearing value may be increased byone-third for transiea~ b®ds such as those incinced by seismic events or wind bads. Lateral buds may be resisted by friction an the bases of footings and 8oce slabs and as passive pressure on the sides of footings. We aeoomancad that an albwable ooe~cient of friction of 0.40 be used to calculate friction betweeat the concrete and the underlying soil. Passive pressure may be domed using an allawabllc equivalent Said deauity of 2S0 pcf (poutids per cubic foot). We that ~ of footings designed and oonstruct~od as reoaarmueadod wdl be less than 1 inch for the anticipated load conditions, with diffiea~rbial settietnents betw~oea ooaag~arably baalod footings of ~ inch os less. Most of the settlelneflts should occur esseakially as b~ are beia~ applied. Iiow~ever, ~aturbanoe of the f+oundatiau subgrade during oohruction cvuW aesuh ffi larger s than predicted. 10011 Bloanlberg Street SW, Olyr~-ia, WA 48S l2 12 Phone #: (360) ?54-4612 Fax #: (360} 754-4&18 GEOTECHNICAL TESTING LABORATORY T~IAOB SLAB SvPro~tT Sla6~s-an-gade should be supported on medium cka~e or dense native soils ~ vn structual fill prepared as descn~ed ~ the "Structural Fill" section of this relwrt. We t+evomme~nd that Boor slabs be direcxly underlain by a mn~im~nn 6- inch thidrness of coarse sand and/or gavel containing less than 3 percxad fines (by weight). The a mateaiai shoitid be placed in one lifl and eoa~ctod to an wryiddiug condition. A synthefic vapor barrier may be used for the oontt~ol of moisture migatian du~ough the slab, partiwlarly where adhesives are used to anchor carpet or file to the slab. A thin layer of sand may be p~eod an+er the vapor barrier and imnnediately below the slab to protect the liner during stoel and/or concrete place~tt. The lack of a vapor barrier could result in wet spots on the slab, Particsilarly in storage areas. RETAINING WALLS Retaining walls may be utilized on the ~oPmB Portion of the site to retain fill material. The lateral P ~8 ~ the subgrade and retaining walls will depend upon the nature aml density of the soil behind the wall. B is also depetxient upon the Presence or absence of hydrostatic pressure. If the adjacent exterior wall space. is badcfilied with clean gaaular, well rained soil (washed rocky the design active pressure may be taken as 0.30 (~cietrt). This design value a a level backslope and drained conditions as desgn'bed below. Retaining walls located oa or near the toe of a slope that extends up behind the wall should be designed for a lateral pressstre, which includes the surcharge effects of the steep slope in Proximity to the wall. Although not expaded at thin site, the following data is provided for p purposes. For an irregular or composite slope, the equivalent slope angle may be deterntined by extending a line upward from the toe of the wall at an angle of 1 to 1 (l~oriaoatal to Vertical) to a point where the line interseds the ground surface. The surcharge effects may be modeled by increasing the equiva~ fluid pressure for Bat gt+ound by the per+~tage given in the following table: SLOra INCLINATION: EQvIVALL-NT FLt7ID P Sbpe Angle Peroeat IncreaseF~quivakust Fluid Pressure Hori~otrtai 0',/0 35 pcf 3H:1 V 25Yo 44 pcf 2H:1 V 50.0 53 pcf 1H:IV 7S'1` 61 pcf If the walls are Ste' than 4 foot in height, exchtseve of the footing, addiEional design considerations should be Positive drainage, which controls the develapnneat o[hrydroatatic Pressure, can be a~ by plecrog a none of coarse sand and gravel beLimd the walls. The gratrular drainage material sllauid oot~ain less thaw 5 percent fines. The drainage zoo should extend imti~oaRally at least 1 a inches froth the back o£the wall. The drainage zeta should also extend from the base of the wall to within 1 foot of the top of the wall. The drainage none shatld be eoa~tad to approotimately 90 pe~noevt of the MDD. Over oa~otptiction should be avvidod as this can lead to excessive lateral P• 10011 Blomberg Street SW, Olympia, WA 98S 12 13 Phone #; (360) 754-4612 Fax #: (360) 754-4848 GEOTEC~INICAL TESTING LABORATORY A perforated PVC pipe with a nrinimum diameter of 4 inches sho~uW be placed in the drainage zone ala~g the base of the wall to direct accxumila#ed water t4 an appropriate discharge location. We recommend that anon-woven geotaxtile filter fabric be placed betvveea the drainage material and the remain wall backfill to reduce silt migration into the drainage zone. The infiltration of silt into the drainage zone can, with time, reduce the permcabiMy of the greuaalar material. Ttm fitter fabric shoukt be placed in such a way drat it fully separates the drainage material and the baclcfill, and should be exbendod over the tap of the drai~e zone. Lateral loads may be resisted by friction ao the bases of focbngs and as passive pressure on ~e sides of footings and the buried porticos of the wall. We reoommead that an allorovable ~ of firictian of 0.40 be used to cakailate friction between the canc,~e and the imderlyiog soil. RETAINING WALL ALTERNATIVES Typically, block welt systems are mome cost effective for long~m walls than the other options. Specific design criteria for these options can be provided at your request by the block manufacxurers. SITE DBAINAGE All Bound surfaces, pavanents, and sideway should be sloped away from the residence and associated ~. Surface water runoff should be corrtr+aitod by a system of curbs, henna, drama8e svvaks, and/or etch basins and tightained to an appropriate infiltration area. Footigg drains shalt be ~ataliod f+~ the singio-famsily resideaoe. Roof drains should nEk be oo~onoded to the footinig drain. For footing drains, the drain im+ert strould be below the bottom of the foaling. Dram control meas~ues are included on Figure 3. We do not anticipate any advcxse affects on the recharge candibion of the gr+oundvvater syskm. 1001 Z Blomberg Street SW, Olympia, WA 98512 l4 Phone #: (360) ?54-4b12 Fax #: (360) 754.4848 GEOTECHNICAL TESTING LAB{)RATURY SEPTIC U~ACT The existi~ drainfield location is beyond the scope of this report. LIMITATIONS We have prepared this report for Cynthia G~zick and Wayne Devaney aad members a£ then design team, ~ use in the design of a portion of this project. The data used in p this repast, and ~ report, shook! be p;aviKied to Prospective carutractors for their bidding or P~P~ may. Our report, conclusions and i~oderpretatioos are based m dada from others and om site recoanaiss~rce, and should not be oooatruod as a warramdry of the subsurface conditions. This report is quantified as a >uicro-study and not amacro-sd~dy. Geatectmical Testing L,aboramory and its persomrel c~nnat be resparrsibk for ua#oreseexr and widespread ~ologic eveads (such as earthquakes, larSe scale faultia8, and mass wast~g) be7'ood the scope of this pro~ocx. Variations in subsurface candmicns are possible and wary occrv with time. A copy for unansGic~od conditions should be included m the budget and schedule. Sufficient consultation vtith our firm during construction shaild corrt~ie, tD c~fimn thax the conditions erroon are c~asistent widh thQSe by air a~ to provide reoorrm~tions for design changes should the conditions revealed during the work differ from those anticipaded, and to evaluade rarthvvorlt and famdadion installation activities aoa~ly with our . ff our analysis and r+ecarrnr>cedadions are followed, we dD nd anticipate any aasitc or ofisite impact frown the prgxased oorastrru~oo~. It is our won that P hazards can be oweroome so as nat m cause harm ~ PAY, Public heahh and safety, ce the enviinnrrsrrrt. The scope of our services does not inchyde services related to eaviroarneadai remodiation and ooan safely precautions. Our rooamnerrdatians are not intended to direct the contractor's methods, technigrxs, segtxaces or praxdures, except as specifically dcscn~bed in our report for consideration in dear. If there are airy changes in the loads, grades, , oonfiguratioas or types of facilities Lo be consduc~ed, the canclrrsiaos and n~rorrmseadaticns prey in this report may not be fully aQpliatble. If such are made, we should be given the apportrmity to review our rooaanrreadatiaos and prtirvide written ~ ar vam, as rrpproQriate. Respectfully submit6ed, GEOTECHNICAL TESTING LABORATORY ~~_/J ~erea~a ~ . dZ7 `yam Harold Parks, L.G., L.E.G. ~t° ~~ 3f -© IOOI l Blomberg Street SW, Olympia, wA 98512 15 Pho®c #: (364) 754-4612 Fax #: (360} 754-48+18 ,. __.. } ITEOTEC~INIL1iL TESTING LABOR-ATOR~' Vicinity Map ., !i', 0 c~ Figure 1 10011 Blanberg Street SW, Olympia, WA 9'8512 Phcme #: (360) 754-4612 Fax #: (360) X54-4848 O d ~~~~~ - ~ ~ ~~ s ~ ~ ; . ~ ,,~~~, 1 111 ' ~~ ~~\`~ ~~~~ ~~ ; ; ~~ ~~ ~~ \ ~~ ,~ ~1 I~ \ ono°o ~ i ~ ~ ~ `~\~~ ~~~ ~. `~~~I ~\\~i~~ O vO C~ ~~\I\i ~ii,~''~_'~i~1~1 ~1 ~ ee ~ ^^2 i ~ ~ ~ ~ iii ~ ~'r` .' i i v ~ °Oe C Y/ j j I 1 ~ 1J I~IIJI I 1 ~ ~ ems.: m li l~ i i i i~; i i~` % % `\`~~rr~~ eo ~ i~ll~ll~~li~~ ~ ~ ~ V iee /~ ~ ~ I i ~' 11 1 I j 11 11, 1` 1\ ~, ,~. Z eO ~yll~ll~~~~~~ ~ ~ ~ 11 II ~ ~ ~ r \ ee°e i l l I ; I, ~, , , , ;~, ~, ~ 1\ lip i ~~ ~~ii ~~~~~~` lip i ~ i 1 I ~ 11~ I 1~~ I ~ .e e e ~ s ^. ae g ..,jref t# a ~ ~ ~~ ~ ~~~ ~i ~~~I1~~ # a =~ is ~ I~1. ~ ,,~ ~i ~p=f ~_ ~ ~~1 = ai ~ M 1 ~~ .r ~.~,A !~ a =ai ~ ~ ~~~aa~ ~a ~ i °~i >rx~a r i ~ ~ f. i. ! ~~ ~ ~ ~.~ ~ ~" ~~ aid ~~~~ ~ ~R @ ~a~ i~ !! ~ ~~~ ~ ~~1~ 2 ~ ~a ! t ~ ~~ . ~ ~ ~ ~~ ~ ~~ ~~ ~~6 ~~ ~ ~p ~~~~; ~~~ ;~~~~~ ~ ~ ~~~ ~ . ~ ~ f ~. ~~~~ ~~ ~ a ~ ~ ~ ~~ ~;~ i ~~ _~~~~~ ~~~~ ~~ ~ ~~ ~ ~~ ~ ~ ~ ~ ~ ~ ~ a ~ ~ ~ ~~ ~ ~ ~~~ ~ .~ .x ~~ ~~ ~~ ~~ ~! ~ ~ E f ~ ~ ~ ~ M~ ~n ~ ~ ~~~~~ ~ ~ ~ ~~ $ ~ r y ~ Z ~ `~ ~. 1/2 INCH MINIMUM DIAMETER STEEL ROD (STRAP) CLAMPED SECURELY TO PIPE CORRUGATED TIGHTLINE 4 INCH MINIMUM, 6 INCH SUGGESTED FLARE END SECTION QUARRY SPALL .:.. , ....'+-~agi?~~c OR ENERGY •` `~ .~ , -. ,x, DISPERSION DEVICE „ •• _ . ,.-;:x~~yu ~ ' GRASS-LINED SWALE SHOULD BE A MINIMUM ONE FOOT WIDE AT THE _ BOTTOM AND ONE FOOT DEEP WITH A MAXIMUM SLOPE OF 5 PERCENT. ININIMUM 4 FEET LEVEL SECTION GEOTEXTILE FABRIC FIGURE 3 ~ to DRAINAGE DETAIIS TIGHTLINE ANCHORED 1MTH TWO, 3 FOOT REBAR LENGTHS OR BOLTS.