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Home My WebLink AboutGeoTech Review for BLD2003-00904 - BLD Engineering / Geo-tech Reports - 8/4/2003 TO DE' 4\' ?T ;N TH&USON COUNTY ttWORKS DIRECTOR/COUNTY ROAD ENGINEER PAS R C E L n Shekon,Washington 98584 DATE: August 4`h, 2003 INTER-DEPARTMENTAL COMMUNICATIONS TO: Diane Marcus-Jones, DCD- Planner FROM: Alan A. Tahja, P/W- Co. Hydr. Engr. WO#PLG-03 SUBJ: Geo-Tech Report Review NAME: Deberry(a,North Bay Heights BLD2003-00904 Diane, The geotechnical report prepared for the proposed Charles Deberry Single Family Residence on lot#5D of North Bay Heights, Grapeview,has been received and reviewed by Public Works. The report appears to satisfactorily address County requirements for geotechnical reporting. The report's author indicates that, in his opinion,the proposed development of the property will not cause stability problems for either the subject property or neighboring properties. From the contents of the report, I recommend accepting the report as satisfying the County's requirement(s) for stability investigation. Recommendations contained in the report should be incorporated into the site's development and made conditions for permit issuance (minimum 5 setback from slope areas of 15 percent or greater). With the engineer's recommendations incorporated into the site's development, stability issues appear to have been adequately addressed. Adequate erosion and sediment control features need to be implemented during land disturbing activities to protect neighboring properties and State waters from adverse stormwater runoff impacts. The migration or release of silty water or mud from the applicant's property will be considered a violation of County and State water quality protection regulations. Please feel free to contact me at County extension 461 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. i I S' rely, l a A an A. Tahja { { File: H:\WP\GEO\Reviews\Deberry.doc I WORK ORDER — PUBLIC WORKS DEPT. Date: (E) Work Order PERMIT$: {�,.. Number. Requested by: �� )c 3 (. 0 Aj.fthorized by: Date: LL_ Tempe of Work: dF W `i � LLI � O,ARGE TO: NAME Cn AGENCY/COMPANY BILLING ADDRESS PHONE Pub. Works Person In Charge: qi� -- (C) Project Time Line. (from-to dates) TO Project Start date: Estlmated Rosh Dab: AppraxlMde hours: ESTIMATED TOTAL i'S: COST ESTIMATE (D) 1Z3t4oYw S Rate IM Subtotal Fringe% TOTAL i 60 slr� BALE EQUIPMENT USED; TOTAL rS MATERIAL USED: 1 t3SE�..ar1tcea •.. - .-- ... a:::s: v;•<;•:•.•:. .v. - ::Cjt�.:. �;xx..�.,.<:',��"v�•�N.a, (F) Actual Cost $ BARS: PROD Its: M > DATE Employ" fflmgm Nam Hours SubttW Ff1nce% TOTAL i i EQUIPMENT USED: I4 mn at TOTAL SS MATERIAL USED: i TOTAL ALL (a) BILLED DATE INV/ PAID DATE RECI CKP �ebe trIr SEEL- 'Z47T A TH&USON COUNTY TO , . � Mtw ORKS DIRECTOR/COUNTY ROAD ENGINEER PARCEL Shelton,Washington 98584 DATE: August 4h, 2003 INTER-DEPARTMENTAL COMMUNICATIONS TO: Diane Marcus-Jones,DCD- Planner FROM: Alan A. Tahja, P/W - Co. Hydr. Engr. WO# PLG-03 SUBJ: Geo-Tech Report Review NAME: Deberry na North Bay Heights BLD200 ^f%^f%4 Diane, The geotechnical report prepared for the proposed Charles Deberry Single Family Residence on lot#51) of North Bay Heights, Grapeview,has been received and reviewed by Public Works. The report appears to satisfactorily address County requirements for geotechnical reporting. The report's author indicates that,in his opinion,the proposed development of the property will not cause stability problems for either the subject property or neighboring properties. From the contents of the report,I recommend accepting the report as satisfying the County's requirement(s) for stability investigation. Recommendations contained in the report should be incorporated into the site's development and made conditions for permit issuance (minimum 5' setback from slope areas of 15 percent or greater). With the engineer's recommendations incorporated into the site's development, stability issues appear to have been adequately addressed. Adequate erosion and sediment control features need to be implemented during land disturbing activities to protect neighboring properties and State waters from adverse stormwater runoff impacts. The migration or release of silty water or mud from the applicant's property will be considered a violation of County and State water quality protection regulations. Please feel free to contact me at County extension 461 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. rely, l SiA;aA an A. Tahja File: H: \WP\GEO\Reviews\Deberry.doc Geotechnical Report Parcel 12220-31-00000 Lot 5D North Bay Heights Mason County, WA Prepared for ' Blackhawk Land Company by ' Geotechnical Testing Lab CHANGES Olympia, WA S PRIOR TOaPER ORMING WORK L ' THESE PLANS MUST BE ON THE JOB 5i -6R INSPECT10 %j. 1 GEOTECHmCAL TESTING LABORATORY BLACKHAWK LAND COMPANY 3710 GRANDVtEW ST. ' GIG HARBOR,WA 98335 Attn: Pete Klenak 1 Re: Geotechnical Report Lot 5D of Parcel 12229-31-00000 ' North Bay Heights Grapeview,WA INTRODUCTION This report summarizes the results of our geotechnical consulting services for the proposed home to be located on the above referenced parcel in Mason County, WA. The location of the site is shown relative to the surrounding area on the Vicinity Plan,Figure 1. Our understanding of the project is based on our discussions and review of the site and our explorations. We understand that a new home is }� . to be located on the above referenced lot. Stormwater runoff from the site,roof and hard surfaces, will be collected and directed to the south of the proposed home. The general layout of the site is shown on the Site Map, Figure 2. We further understand that very little grading is required at the site to reach design grade. In general, grading will consist of the excavation of f the foundation in the upper portion of the site; no structural fill is anticipated. ' The eastern portion of the site has slopes that are greater than 40 percent. Mason County therefore requires that a geotechnical report be prepared in accordance with the Critical Areas Ordinance. ' The purpose of our services is to evaluate the surface and subsurface conditions at the site as a basis for providing geotechnical recommendations and design criteria for the project and to satisfy the requirements of the Mason County Critical Areas Ordinance. Geotechnical Testing Lab is therefore providing geologic and hydrogeologic services for the project. Specifically,our scope of services for this project will include the following: 1. Review the available geologic,hydrogeologic and geotechnical data for the site area. ' 2. Conduct a geologic reconnaissance of the site area. 3. Explore the shallow subsurface conditions at the site by soil log boring. 4. Evaluate the landslide and erosion hazards at the site per the Mason County Critical Areas Ordinance ' regulations. ' 10011 Blomberg Street SW, Olympia, WA 98512 Phone#: (360)754-4612 Fax#: (360)754-4848 1 ' GEOTEcnmcAL TESTING LABORATORY 1 5. Provide geotechnical recommendations for site grading, including site preparation,sub-grade preparation, fill placement criteria(including hillside grading),temporary and permanent cut and fill slopes,drainage and ' erosion control measures. 6. Provide recommendations and bdesigne podia for the structural resistance valutes and esion and timates of of settlement.00r slab support, including allowable bearing capacity, s grad 7. Provide preliminary geotechnical recommendations regarding stormwater. 1 SITE CONDITIONS SURFACE CONDITIONS The proposed building site is located in the upland area of the west side of the Case Inlet. The site is situated in an area of modest development along Grapeview Loop Road. The site is bounded by forested vacant lots on every side of the property. The proposed layout of the site is shown on the Site Plan, Figure 2. We conducted a reconnaissance of the site area and monitored the exposed bluff at the site. Elevations in the site area range from approximately 75 feet in the east to about 140 feet in the western portion of the site. The building site is to be located in the level portion of the upper area, where the slopes are between 0%and 5%. The steepest slope is confined to the eastern portion of the lot where the slope exceeds 40 percent. This area is outside of the proposed building area. Site topography is shown on the Site Plan, Figure 2. We observed no evidence of major erosion. No surficial sloughing or soil movement was observed on the steeper portion of the site or adjacent areas. No evidence of deep-seated slope instability was observed in the site area at the time of our site visit. AM The site is vegetated with fir,hemlock, cedar and madrona trees. A moderate to dense understory consists of grass, brush,young alder trees, salal and Oregon grape with local areas of blueberry. No evidence of surface water flow was observed in the site area at the time of our reconnaissance. The general topography of the site area indicates that the site drains towards the east. SITE GEOLOGY The site is generally situated within the Lower Puget Sound highlands. The existing topography, as well as the surficial and shallow subsurface soils in the area,are the result of the most recent Vashon stade of the Fraser glaciation that occurred between about 10,000 and 12,000 years ago,and weathering and erosion that has occurred since. A description of the surficial soils is included in the"Site Soils"section of this report. In general, Vashon ' glacial till underlay the site. SITE SOILS 1 The Mason County Soil Conservation Survey(1960)has mapped the site soils as Sinclair Shotty Loam in the building area of the site. The Sinclair soils develop from very compact Vashon gravelly till. We observed very little active erosion or slope disturbance in the site area during our reconnaissance. SUBSURFACE EXPLORATIONS Subsurface conditions at the site were evaluated by observing a boring log drilled by a rubber tired Mobil B-40 drill with hollow stem auger. The soil was logged to a depth of 20 feet. 10011 Blomberg Street SW,Olympia, WA 98512 Phone#: (360)754-4612 Fax#:(360)754-4848 ' GEOTECMaCAL TESTING LABORATORY 1 -� SUBSURFACE CONDITIONS In general, undisturbed dense sandy silt and gravel till was observed in the building portion of the site. The undisturbed till was observed across the building portion of the lot. No groundwater seepage was observed from the slope areas at the site. Based on the nature of the near surface soils, (intermittent outwash and weathered gravels and sands over undisturbed soils in the building area), seasonally perched groundwater conditions should be expected during periods of extended wet weather. 1 Slope Stability Slopes steeper than 40 percent were observed in the sloping portion of the site. Since slopes of 40 percent or greater with 10 feet or more of vertical relief occur on portions of the site, Mason County requires that a geologic hazards report be ' completed per the Critical Areas Ordinance. In general,the undisturbed native soils in the steep slope portions of the site consist of sandy silt with variable amounts of gravel. These soil components are in a dense to very dense condition ' except where they have been disturbed by weathering activity. The near-surface recessional,weathered advance r outwash is in a dense to very dense condition except at the ground surface. The surfrcial soils are generally in a loose to medium dense condition. These soils are generally stable relative to deep-seated failure. Evidence of deep-seated landslide activity was not observed at the site at the time of our site visit. Weathering, erosion,and the resultant sloughing and shallow landsliding are natural processes that can affect steep slope areas. Instability of this nature is typically confined to the upper weathered or disturbed zone, which has been disturbed and has a lower strength. No evidence of local surfrcial erosion, raveling and sloughing was observed in the site area at the time of our site visit. tSignificant weathering typically occurs in the upper 2 to 3 feet and is the result of oxidation, root penetration, wet/dry cycles, and freeze/thaw cycles. Erosion in steep slope areas such as this can be reduced through proper design and ' construction of the storm water systems. Erosion control recommendations for the sloping areas are provided in the"Building Setback" and"Erosion Control" sections of this report. Proper planning, design and construction techniques will reduce the risk of surficial erosion or ' movement in these areas. ' 10011 Blomberg Street SW, Olympia, WA 98512 Phone#:(360)754-4612 Fax#: (360)7544848 1 GEOTECHNICAL TESTING LABORATORY CONCLUSIONS AND RECOMMENDATIONS GENERAL Based on the results of our site reconnaissance and our experience in the area, it is our opinion that the site is suitable for the proposed home. The slopes located east of the building portion of the site area and the adjacent property are stable relative to deep seated seated instability and will not be affected by the proposed home and drainfield. Proper drainage control measures �dV will reduce or eliminate the potential for erosion in this area,and improve slope stability. Conventional construction equipment may be utilized for work at the site. Conventional spread footings may be utilized at the site for support of the structure. We do recommend that roof and footing drains be installed for the home. A vapor barrier is recommended for all slab-on-grades. Infiltration of the stormwater is not possible at the site. Pertinent conclusions and geotechnical recommendations regarding the design and construction of the proposed home are presented below. LANDSLIDE—EROSION HAZARD AREAS .r, Classification L-W The Mason County Critical Areas Ordinance defines a landslide hazard area as 1)one containing slopes equal to or greater than 40 percent with more than a 10-foot vertical relief, and 2)one containing soils described by the Soil Conservation Service(SCS)Soil Survey as having a"severe"limitation for building site development due to slope. The slopes located in the area of the site are in excess of 40 percent and the vertical relief is in excess of 10 feet. Based on this, the site does meet the technical criteria of a landslide hazard. The soils at the site are mapped as Sincliar shotty loam in the building portions of the site. The Sinclair soils are described as having a low erosion hazard,based on the present slope inclination. These soils do not meet the technical criteria of an erosion hazard. Slope Stability Based on our field observations,explorations and our experience with the soil types encountered on the property, we conclude that although portions of the slopes exceed 40 percent,they are generally stable relative to deep-seated failure in their present configuration. ' 10011 Blomberg Street SW, Olympia, WA 98512 Phone#:(360)754-4612 Fax#: (360)754-4848 1 ' GEOTECUMCAL TESTING LABORATORY ' Peak Shear Stress vs.Normal Stress zsoo ' 38' 2000 1 � a m IS00 m 1 N t moo N —4w--1/4ton Y — 0 ]/2ton d S00 —r Ron 1 0 o soo loon 1500 2000 zsoo Normal Stress (psf) 1 No changes in slope stability are expected as a result of the proposed home on the site. Development will occur in the level portions of the site based on appropriate engineering and building setback recommendations. Grading in the building portion of the site should be conducted in accordance with geotechnical recommendations provided herein. As previously discussed, weathering, erosion, and the resultant surficial sloughing and landsliding are natural processes that affect slope areas. Significant weathering typically occurs in the upper 2 to 3 feet and is the result of oxidation, root penetration,wet and dry cycles and freeze and thaw cycles. These processes can be managed and the risk reduced through proper construction of the residence, including the stormwater system. Erosion control recommendations in the slope and buffer areas are provided in the"Building Setback"and"Erosion Control" sections of this report. ' Building Setback A building setback area from landslide hazard areas is required unless evaluated and reduced by an engineering geologist or a licensed professional engineer. Cleaning and grading within the setback area may be allowed because the slope stability or erosion hazard will not be adversely impacted. Slope stability was modeled using the GEO-SLOPEIW program(version 5.13)in both static and dynamic conditions t (Ca=0.3). Factors of safety were determined using Bishop's,Janbu, and the Morgenstern-Price methods. The Sinclair shotty loam was determined to have a unit weight of 126 pcf, cohesion of 175 psf, and a shear angle(�)of 380. Under static conditions,the slopes remained stable to deep-seated and shallow failure. Under dynamic loading, the 5500 computations demonstrated that the slope may be susceptible to surficial raveling, but large deep-seated failure was not demonstrated by our model. See the following figure for an example solution of a surficial failure with a F.S. greater than 1.0 under dynamic conditions. ' Based on our g eotechnical evaluation of the site and our experience in the area, we recommend a building setback of 5 feet from a slope area of 15 percent or greater. The building setback may be measured from the bottom oft e footing to the face of the steep slope, in accordance with the Unified Building Code. Ai 10011 Blomberg Street SW,Olympia, WA 98512 Phone#:(360)754-4612 Fax#:(360)754-4848 Ai ' GEOTECHNICAL TESTING LABORATORY piA�n a{p�Co Right ' sip c,,�taoe Option:Grid and Radus . . . . . . . . . . Seismic Coen ciord Ho izortM and Vent rn ' tm o p0 120 W 70 ' W SlncieirShotVLoom °0 Shc Modet MW-Cc*" m Lhrit Weight 125 Cohesion:17S �0 Rd:38 w 1 m 0 u ao m W W tW tao tm w tW xvo a� EID 200 390 9W 5¢0 9a Distance(R) ' Dynamic Conditions—F.S.> 1.0 As previously discussed,weathering, erosion and the resultant surficial sloughing and shallow landsliding are natural ast was processes that affect slope area and educe the surficial raveling otential for these natural processes,g from the we observed ecommend the following. portions of the site. To manageP t flow onto the l. No drainage a ay area a should be collected and ghtlined tted surface water or significant o the discharge area slope outh of the Drainage proposed home roof and driveway area with the same setback as the proposed home. etained by retaining walls or constructed as an engineered 2. No filling within the buffer or setback zone unless r �i fill. SEISMIC—LIQUEFACTION BAZARD According to the Seismic Zone Map of the United States contained in Figure 16-2 of the 1997 Uniform Building Code,the project site is located within Seismic Risk Zone 3. Based on the subsurface conditions observed at the site, we interpret the site conditions to correspond to a seismic Soil Profile Type Sc, for Very Dense Soil, as defined by Table 16-J(UBC). This is based on the range of SPT (Standard Penetration Test)blow counts and/or probing with a t/2-inch diameter steel probe rod. The shallow soil conditions were assumed to be representative for the site conditions beyond the depths explored. Based on our review of the subsurface conditions, we conclude that the site soils are not susceptible to liquefaction. The near-surface soils are generally in a dense condition and the static water table is located below the surface. Shaking of the already dense soil is not apt to produce a denser configuration and subsequently excess pore water pressures are not likely to be produced. 10011 Blomberg Street SW, Olympia, WA 98512 Phone#: (360)754-4612 Fax#: (360)754-4848 1 GEOTEcHNICAL TESTING LABORATORY EROSION CONTROL It is our opinion that the potential erosion hazard of the site is not a limiting factor for the proposed development. Removal of natural vegetation on the steep slopes(40%or greater)should be minimized and limited to trimming an F. landscaping consistent with home gardening. Temporary and permanent erosion control measures should be installed and maintained during construction or as soon as practical thereafter to limit the additional influx of water to exposed areas. Erosion control measures should include, but not be limited to,berms and swales with ground cover/protection or silt fencing in exposed areas. Graded areas should be shaped to avoid concentrations of runoff onto cut or fill slopes, ,. natural slopes or other erosion-sensitive areas. No earthwork is anticipated on the steep portions(40%or greater)of the site. EARTHWORK Site Preparation All areas to be excavated should be cleared of deleterious matter including any existing structures,foundations, abandoned utility lines, debris and vegetation. ' Based on our observations, we estimate that stripping on the order of 6 to 8 inches will be necessary to remove the root zone and surficial soils containing organics. Areas with deeper, unsuitable organics should be expected in the vicinity of depressions or heavy vegetation. Stripping depths of up to 1 foot may occur in these areas. These ' materials may be stockpiled and later used for erosion control and landscaping. Materials that cannot be used for landscaping or erosion control should be removed from the project site. Where placement of fill material is required, the exposed subgrade areas should be proof-rolled to a firm and unyielding surface prior to its placement. Excavations for stump removal in the building area should be backfilled with structural fill compacted to the density requirements described in the"Structural Fill"section of this report. If structural fill is needed we recommend 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 compacted, if practical, or over-excavated and replaced with structural fill,based on the recommendations of our ' report. Structural Fill All fill material should be placed as structural fill. The structural fill should be placed in horizontal lifts of appropriate thickness to allow adequate and uniform compaction of each lift. Fill should be compacted to at least 90 percent of MDD(maximum dry density as determined in accordance with ASTM D-1557/698)to within 2 feet of subgrade and 95 percent MDD in the upper 2 feet. The appropriate lift thickness will depend on the fill characteristics and compaction equipment used. We recommend that the appropriate lift thickness be evaluated by our field representative during construction. 10011 Blomberg Street SW, Olympia, WA 98512 Phone#:(360)754-4612 Fax#:(360)754-4848 1 ' GEOTECHwAL TESTING LABORATORY ' The suitability of material for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines(material passing No. 200 sieve)increases, soil becomes increasingly sensitive to small changes J in moisture content and adequate compaction becomes more difficult to achieve. During wet weather, we recommend use of well-graded sand and gravel with less than 10 percent(by weight)passing the No. 200 sieve based on that fraction passing the'/a-inch sieve. If prolonged dry weather prevails during the earthwork and foundation installation phase of construction, a somewhat higher(up to 12 percent)fines content will be acceptable. les greater n 6 Material placed for structural fill should bemafr tea;debris, organic hould be adjusted as necessary fo, trash and r proper compact on. inches in ' diameter. The moisture content of the fill Suitability of On-Site Soils as Fill ' On-site soil should not be considered for use as structural fill because it does not meet the criteria described above in the structural fill section and cannot be compacted as recommended. CUT AND FILL SLOPES All job site safety issues and precautions are the responsibility of the contractor providing services and/or work. The ' following cut/fill slope guidelines are provided for planning purposes. Temporary cut slopes will likely be necessary during grading operations. As a general guide,temporary slopes of 1.5 to 1 (horizontal 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 loose/medium dense condition. Temporary slopes of 1 to I or flatter may A be used in the unweathered dense to very dense sands and gravels or till. These guidelines assume that all surface loads are kept at a minimum distance of at least one half the depth of the cut away from the top of the slope and that significant seepage is not present on the slope face. Flatter cut slopes will be 1 necessary where significant raveling or seepage occurs. Subsurface drainage may be required if seepage areas are discovered. Surface drainage should be directed away from all slope faces. Some minor raveling may occur with time. All slopes should be seeded as soon as practical to facilitate the development of a protective vegetative cover or otherwise protected. FOUNDATION SUPPORT Where foundation elements are located near slopes of 15 percent or more,the footings should be located a minimum ' of 2 times the footing width from the slope face(horizontally), and founded in medium dense or denser native soils or properly prepared structural fill. P* We recommend a minimum width of 2 feet for isolated footings and at least 16 inches for continuous wall footings. Footings founded as described above can be designed using an allowable soil bearing capacity of 2,000 psf(pounds per square foot)for combined dead and long-term live loads in areas of medium dense to dense soils. ' The weigh g t of the footing and any overlying backfill may be neglected. The allowable bearing value may be increased by one-third for transient loads such as those induced by seismic events or wind loads. 1 10011 Blomberg Street SW, Olympia, WA 98512 Phone#:(360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY Lateral loads may be resisted by friction on the bases of footings and floor slabs and as passive pressure on the sides of footings. We recommend that an allowable coefficient of friction of 0.30 be used to calculate friction between the J concrete and the underlying soil. Passive pressure may be determined using an allowable equivalent fluid density of 250 pcf(pounds per cubic foot). r We estimate that settlements of footings designed and constructed as recommended will be less than 1 inch, for the anticipated load conditions,with differential settlements between comparably loaded footings of'h inch or less. Most of the settlements should occur essentially as loads are being applied. However, disturbance of the foundation subgrade during construction could result in larger settlements than predicted. ' FLOOR SLAB SUPPORT Slabs-on-grade should be supported on medium dense or dense native soils or on structural fill prepared as described ' in the"Structural Fill"section of this report. We recommend that floor slabs be directly underlain by a minimum 6- inch thickness of coarse sand and/or gravel containing less than 5 percent fines(by weight). The drainage material should be placed in one lift and compacted to an unyielding condition. ' A synthetic vapor barrier should be used for the control of moisture migration through the slab, in particular where adhesives are used to anchor carpet or tile to the slab. A thin layer of sand may be placed over the vapor barrier and immediately below the slab to protect the liner during steel and/or concrete placement. The lack of a vapor barrier could result in wet spots on the slab, particularly in storage areas. Retaining Wall Retaining walls are not anticipated on this project. Site Drainage All ground surfaces, pavements and sidewalks should be sloped away from the residences and associated structures. Surface water runoff should be controlled by a system of curbs, berms, drainage swales, and directed to a discharge area at least 20 feet from the proposed home and recognizing the same set back from the bluff. We recommend that conventional roof and footing drains be installed for the home and garage. The roof drain should not be connected to the footing drain. If footing drains are installed,the drain invert should be below the bottom of the footing. We do not expect any adverse affects on the recharge condition of the groundwater system. LEWrATIONS L this report for use b Blackhawk Land Company and members of their design team, for use in the We have prepared p y design of a portion of this project. The data used in preparing this report, and this report, should be provided to prospective contractors for their bidding or estimating purposes only. Our report, conclusions and interpretations are based on data from others and our site ' reconnaissance, and should not be construed as a warranty of the subsurface conditions. 1 10011 Blomberg Street SW,Olympia, WA 98512 Phone#:(360)754-4612 Fax#: (360)754-4848 1 GEOTECHNICAL TESTING LABORATORY Variations in subsurface conditions are possible and may also occur with time. A contingency for unanticipated y conditions should be included in the budget and schedule. Sufficient consultation should be made with our firm during construction to confirm that the conditions encountered are consistent with those indicated by the recommendations and for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether earthwork and foundation installation activities comply with contract plans. ~' If our analysis and recommendations are followed, we do not anticipate any on site or off site impact from the d construction. It is our conclusion that potential landslide hazards from the landslide area can be overcome so as no to cause harm to property,public health and safety, or the environment. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods,techniques, sequences or procedures, except as specifically described in our report for consideration in design. If there are any changes in the loads, grades, locations, configurations or type of facilities to be constructed, the conclusions and recommendations presented in this report may not be fully applicable. If such changes are made, we should be given the opportunity to review our recommendations and provide written modifications or verifications, as appropriate. ' Respectfully submitted, GEOTECHNICAL TESTING LABORATORY 114,t6-C Harold Parks, Engineering Geologist 1 sad t3eo� K*a=PIARKS 1 1 1 ' 10011 Blomberg Street SW, Olympia, WA 98512 Phone#: (360)754-4612 Fax#:(360)754-4848 1 GEOTECHNICAL TESTING LABORATORY Geotechnical General notei SOIL PROPERTY SYMBOLS N: Standard "N" penetration: Blows per foot of a 140 pound hammer falling 30 inches on a 2 inch O.D. split-spoon. Q.: Unconfined compressive strength,tons/ft'- Qp: Penetrometer value, unconfined compressive strength, Ibs/ftz V: Vane value,ultimate shearing strength, lbs/ft'- M: Water content,% LL: Liquid limit,% r PI: Plasticity index,% D: Natural dry density, Ibs/ft3 WT: Apparent groundwater level at time noted after completion. DRILLING AND SAMPLING SYMBOLS SS: Split-Spoon- 1 3/8" I.D., 2"O.D.,except where noted. ST: Shelby Tube- 3" O.D., except where noted. AU: Auger Sample. GB: Grab Sample. DB: Diamond Bit. CB: Carbide Bit. WS: Washed Sample. RELATIVE DENSITY AND CONSISTENCY CLASSIFICATION Terms(Non-Cohesive Soils) Standard Penetration Resistance Very Loose 0-2 Loose 2-4 Slightly Compact 4-8 Medium Dense 8- 16 Dense 16-26 Very Dense Over 26 Terms(Cohesive Soils) Q„-(tons/ftZ) Very Soft 0-0.25 Soft 0.25 -0.50 Firm (Medium) 0.50 - 1.00 Stiff 1.00-2.00 Very Stiff 2.00-4.00 Hard 4.00+ PARTICLE SIZE Boulders 8 in. + Coarse Sand 5 mm -0.6 mm Silts 0.074 mm - 0.005 mm Cobbles 8 in.-3 in. Medium Sand 0.6 mm -0.2 mm Clays 0.005 mm & Smaller Gravel 3 in_-5 mm Fine Sand 0.2 mm -0.074 mm r ' 1001 1 Blomberg Street SW,Olympia, WA 98512 Phone#: (360)754-4612 Fax#: (360)7544848 1 ��r _ _ �7 vAu � 1` � GEOTECHNICAL TESTING LAB Date: Mar. 12,03 File#: Boring Log#: 1 Client: North Bay Heights Boring Type: Hollow Stem Auger Depth Drilled: 20 feet Depth Field Change (Ft) Description in Soils %M N %?/:' %-44 %4200 Comments 1.0 Topsoil 2.0 silty_ sand with gravel 3.0 4.0 5.0 oO 72" 14"0 cl &!I., ' .0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 1 .0 15.0 16.0 17.0 �I 18.0 19.0 20.0 silty sand with gravel 21.0 end of boring 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 L3 30.0 1.0 GEOTECHNICAL TESTING LAB Date: Mar.12,03 File#: Boring Log#: 2 lot 5 Client: North Bay Heights Boring Type: Hollow Stem Auger Depth Drilled: 20 feet Depth Field Change (Ft) Description in Soils %M N %3/4" %-#4 ors4200 Conmwnts 1.0 Topsoil ' 2.0 silty sand with gravel 3.0 4.0 5.0 9bo,; 6900 16 ven dense ' .0 7.0 8.0 9.0 ' 10.0 60 very dense 11.0 12.0 13.0 14.0 15.0 60- very d'se 16.0 ' 18.0 .:........................... .................... 1 .0 ... 19.0 .................. 20.0 ven'dense 21.0 end of boring...... 22.0 23.0 ' 24.0 25.0 26.0 27.0 28.0 29.0 30.0 31.0 1 THIS PARCEL INCLUDES PLANS, BLUEPRINTS OR OVERSIZE IMAGES LARGE FORMAT IMAGES HAVE BEEN STORED IN FILE CABINETS) UNDER PARCEL NUMBER PARCEL # CASE #