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HomeMy WebLinkAboutGeo-Tech Report Review for BLD2006-00114 - BLD Engineering / Geo-tech Reports - 3/10/2006 MASON COUNTY n u PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER ° o N Shelton, Washington 98584 A NY DATE: March 10, 2006 \B31d2006-0011 INTER-DEPARTMENTAL COMMUNICATIONSTO: Chuck McCoy PARCEL#22325-50-06007FROM: Alan Berbisco, Proiect Engineer-PW BUILDING PERMIT NUMBER: SUBJECT: Geotech. Report Review NAME: Vincent Watson Chuck, The Geotechnical Report prepared for the proposed mobile home located at 80 NE Steelhead Dr. South Belfair,has been received and reviewed by Public Works. The report appears to meet the County's requirements for geotechnical reporting. However there are no appropriate recommendations for storm water. From the content of the report,the steep slope,which is 200 feet from the edge of the site, is stable.According to the Slope Stability Analysis,the slope has a Factor of Safety of 1.20 and 1.50 in Seismic and Static respectively and the proposed development should not have significant impact onsite or offsite if the author recommendations are followed. I recommend accepting the report as satisfying the county's requirement(s)for stability investigation and geotechnical reporting. Stormwater management features and other recommendation should be incorporated in site development plans. Adequate Erosion and Sediment(E&S)control features need to be implemented during land disturbing activities to protect neighboring properties and State waters from adverse stormwater runoff impacts.It shall be the responsibility of the property owner and the permittee to ensure that accelerated erosion does not occur during and after the project construction.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 461 if you have any questions regarding these comments,or if you feel any features need further discussion or attention. Sincerely, an erbisco� Pro ect Engineer 1 RECEI Y GD WORK ORDSR l-PUBLic WORKS DOT, � MAR W. Dse. .�1lob M EN ;?uL F MITE; 1-P, �© -ccI t �ue ta►d . c rEv Au�thadW bys ' Type of wgslu �77-7 Dates CMRGe Tas NAME AGENCY10OMPANY . GlUUNG ADDRRBe PHON/I Pub. . ' S c� On a e�l m.W dole* To- Mo AeNd Gist hotr ' pTrNATp rOTAI. t ' lM Wit! _.,,!��"�!.�....,_ 1Bu�. . 1l�ot • flddMLd' �� • � OIIR ; ._GAM #louts WAL J � • V ZWPMENT USED: TOTAL$a 3)' 1AII.I,RQ DATA.,,_. PO Box 44890 Tacoma WA 98444 253-537-9400 253-537-9401fax E3RA March 8, 2006 T06057 Vincent Watson 21 NE Steelhead Drive North Belfair,Washington 98528 (360)275-2185 Subject: Geotechnical Report Parcel#22325 50 06007 80 NE Steelhead Drive South Belfair, Washington Dear Vincent: E3RA is pleased to submit this report describing the results of our geotechnical engineering evaluation for your residential parcel at the intersection of NE Steelhead Drive North and NE Steelhead Drive South. Plans call for the placement of a mobile home on the site.We understand that personnel from Mason County have stated that a full Geotechnical Report is needed,because of a steep slope within 250 feet ofthe site,before the mobile Mhome can be placed. The purpose of our evaluation, therefore, is to address The Mason Critical Areas Ordinances as they relate to landslide and erosion hazards and to provide geotechnical conclusions-and recommendations concerning residential development at the site. As outlined in our proposal letter,our scope of work comprised site reconnaissance,geotechnical test holes, geotechnical research,and geotechnical engineering analysis. This report has been prepared for the exclusive use of Vincent Watson and his consultants,for specific application to this project,in accordance with generally accepted geotechnical engineering practice. 1.0 SITE AND PROJECT DESCRIPTION The project site is located on the north side of Hood Canal near Belfair,Washington,as shown on the enclosed Location Map(Figure 1). The site is a roughly rectangular parcel that measures about 100 by 120 feet. It is located west of Big Mission Creek approximately two miles from Belfair State Park. Plans call for the placement of a mobile home on a level terrace on the site. 2.0 EXPLORATORY METHODS We explored surface and subsurface conditions at the project site on February 21, 2006. Our exploration program comprised the following elements: NA surface reconnaissance of the site and the geology of nearby excavations; • Three test holes(designated TH-1 through TH-3)across the site;and A review of published geologic and seismologic maps and literature. 1 i i FlLit.,.;: ; COF" i GEOTECHNICAL REPORT PARCEL # 223255006007 80 NE STEELHEAD DRIVE SOUTH BELFAIR, WASHINGTON Submitted to: Mr. Vincent Watson 21 NE Steelhead Drive North Belfair, WA 98528 THESE PLAND MUST BE MUST MEET ALL CUR►ZEN1 ON THE JOB SITE WASHINGTON STATE CODES FOR INSPECTION. Submitted by: E3RA, Inc. _ R _.; PO Box 44890 C� Tacoma, WA 98444 SUBMIT C :GE`. PRION iu PERF&- 19illinimilRn�,�,, March 8, 2006 � VED ASON BUILT?1"a INSPECTOR T06057 FHA ��.� �<1�, 0 APPRO L DA: Documents attached tQ approved plans: Geu. Site Plan (j Plan review chcckl' : — - Pages Engineering: Y N, Lateral Vertical Number of pages — GEOTECHNICAL REPORT PARCEL # 223255006007 80 NE STEELHEAD DRIVE SOUTH BELFAIR, WASHINGTON Submitted to: Mr. Vincent Watson 21 NE Steelhead Drive North Belfair, WA 98528 Submitted by: E3RA, Inc. PO Box 44890 Tacoma, WA 98444 March 8, 2006 T06057 PO Box 44890 Tacoma WA 98444 253-537-9400 253-537-9401fax E3RA March 8,2006 T06057 Vincent Watson 21 NE Steelhead Drive North Belfair,Washington 98528 (360)275-2185 Subject: Geotechnical Report Parcel#22325 50 06007 80 NE Steelhead Drive South Belfair, Washington Dear Vincent: E3 RA is pleased to submit this report describing the results of our geotechnical engineering evaluation for your residential parcel at the intersection of NE Steelhead Drive North and NE Steelhead Drive South. Plans call for the placement of a mobile home on the site.We understand that personnel from Mason County have stated that a full Geotechnical Report is needed,because of a steep slope within 250 feet of the site,before the mobile home can be placed. The purpose of our evaluation, therefore, is to address The Mason Critical Areas Ordinances as they relate to landslide and erosion hazards and to provide geotechnical conclusions and recommendations concerning residential development at the site. As outlined in our proposal letter,our scope of work comprised site reconnaissance,geotechnical test holes, geotechnical research,and geotechnical engineering analysis. This report has been prepared for the exclusive use of Vincent Watson and his consultants,for specific application to this project,in accordance with generally accepted geotechnical engineering practice. 1.0 SITE AND PROJECT DESCRIPTION The project site is located on the north side of Hood Canal near Belfair,Washington,as shown on the enclosed Location Map(Figure 1). The site is a roughly rectangular parcel that measures about 100 by 120 feet. It is located west of Big Mission Creek approximately two miles from Belfair State Park. Plans call for the placement of a mobile home on a level terrace on the site. 2.0 EXPLORATORY METHODS We explored surface and subsurface conditions at the project site on February 21, 2006. Our exploration program comprised the following elements: • A surface reconnaissance of the site and the geology of nearby excavations; • Three test holes(designated TH-1 through TH-3)across the site;and • A review of published geologic and seismologic maps and literature. 1 March 8. 2006 ORA, Inc. T06057/Watson Geotechnical Report Table 1 summarizes the approximate functional locations and termination depths of the septic test pit explorations,and Figure 2 depicts their approximate relative locations. TABLE 1 APPROXIMATE LOCATIONS AND DEPTHS OF EXPLORATIONS Termination Depth Exploration Functional Location (feet) TP-1 On lower terrace near planned mobile home footprint,central site 3 TP-2 Toe of upper terrace,west site 3 TP-3 Upper terrace 3 Elevation datum:Unavailable We estimated the relative location of each exploration. Consequently, the data listed in Table 1 and the locations depicted on Figure 2 should be considered accurate only to the degree permitted by our data sources and implied by our measuring methods. It should be realized that the explorations observed for this evaluation reveal subsurface conditions only at discrete locations across the project site and that actual conditions in other areas could vary. Furthermore,the nature and extent of any such variations would not become evident until additional explorations are performed or until construction activities have begun. If significant variations are observed at that time,we may need to modify our conclusions and recommendations contained in this report to reflect the actual site conditions. 2.1 Hand Excavated Test Holes Our hand-excavated test holes were advanced to relatively shallow depths using a shovel. An engineering geologist from our firm excavated the holes and logged the subsurface conditions. The enclosed Test Hole Logs describe the vertical sequence of soil materials encountered at each test hole location,based on our field classifications. Where a soil contact was observed to be gradational or undulating, our logs indicate the average contact depth. We estimated the relative density and consistency of the in-situ soils by means of the excavation characteristics and the stability of the boring sidewalls. Our logs also indicate the approximate depths of any sidewall caving or groundwater seepage observed in the explorations. 3.0 SITE CONDITIONS The following sections of text present our observations,measurements,findings,and interpretations regarding, surface,soil,groundwater,seismic,and liquefaction conditions. 3.1 Surface Conditions The project site consists of two level terraces,graded level,with two benches. The first,east terrace comprises the east two thirds of the site; is located adjacent to and at the same elevation as NE Steelhead Drive South, and is where the mobile home will be located.A 7-foot high bench,graded at 2H:1 V,forms the west border of the lower, east terrace and the east border of the upper,west terrace. The west terrace extends almost to the west site boundary and ends at a second bench,which forms the west boundary of the site. This bench rises to the west at a grade of about 2H:1 V over an elevation change of about 9 feet. Original grades on the site appear to have measured less than 20 percent. 2 March 8, 2006 E3RA, Inc. T06057/Watson Geotechnical Report A series of graded terraces, separated by short benches and supporting neighboring houses,a garage,and a road right of way,trend up to the west for a horizontal distance of about 200 feet. Original grades over this distance appear to measure less than 20 percent. About 200 feet west of the site,slopes rise abruptly at the toe of a steep hillside. No other steep slopes are within 350 feet of the site. A large cut has been made in the toe of the steep slope,approximately 200 feet west of the site. Soils in the upper 20 feet of the cut consist of dense glacial outwash sand,either advance Vashon or pre-Vashon in origin. Underlying the dense sand layer, we observed dense to very dense sandy gravel with few fines and some cobbles. Vegetation has been removed from much of the project site;although a few fruit trees and a grassy patch grow near the northeast corner.Vegetation on the steep hillside 200 feet west of the site consist of fir forest with an under story of ferns and brush. No indications of recent or past land sliding, such as tension cracks, scarps, or hummocky terrain, were observed onsite.No indications of slope instability were observed on parcels immediately adjacent to the site. No signs of surface hydrology,such as stream beds,ponds,etc.,were observed on the site or west of the site. Big Mission Creek flows 100 to 200 feet east of the site.No seeps, springs,or other surface expressions of subsurface hydrology were observed on the site or on the steeply sloped hillside 200 feet west of the site. 3.2 Soil Conditions Our test hole explorations revealed that soils onsite consist of mostly of gravelly glacial outwash sand with some silt and scattered cobbles. Fill, consisting of reworked site soils (gravelly sand with some silt and scattered cobbles),was observed in test hole TH-3,located at the toe of the bench at the west boundary of the site. Because the site has been graded,most likely in a cut and fill manner,small quantities of fill can probably be assumed to be on the surface of both benches on the site. Site soils and reworked site soils appear to be stable and resistant to erosion,however,as no indications of sloughing or rilling were visible As mentioned earlier,soils in the cut at the toe of the steep slope 200 feet to the west consist of glacially over- ridden,dense to very dense,glacial outwash,which is sandy above the toe and gravelly at the toe. The enclosed exploration logs provide a description of the soil encountered in our test hole explorations,and our Geologic Cross Section(Figure 3),depicts our interpretation of shallow soil conditions onsite and in the steep slope to the west. 3.3 Groundwater Conditions At the time of our site reconnaissance(February 21,2006),we did not observe groundwater in our test hole explorations,nor did we observe surface expressions of ground water,such as seeps or springs,on the surface of the site or in the cut at the toe of the steep slope offsite,or on the surface of the steep slope. 3.4 Seismic Conditions Based on our analysis of subsurface exploration logs and our review of published geologic maps,we interpret Y P g P the on-site soil conditions to correspond with a seismic site class So,as defined by Table 1615.1.5 of the 2003 International Building Code (IBC).According to the IBC,the site is Seismic Region 3. 3 March 8 2006 ORA. Inc. T06057L Watson Geotechnical Report 3.5 Liquefaction Potential Liquefaction is a sudden increase in pore water pressure and a sudden loss of soil shear strength caused by shear strains,as could result from an earthquake. Research has shown that saturated,loose sands with a fines (silt and clay)content less than about 25 percent are most susceptible to liquefaction. The on-site subsurface explorations and our observation of soils at elevations lower than the site along Patton Drive did not reveal saturated(or potentially saturated),loose,silty sand layers or lenses. 3.6 Slope Stability Analysis We analyzed the slope stability under selected conditions. The following sections describe our method of analysis and present our results. Method of Analysis Slope stability analyses typically involve five basic slope parameters: (1)location and shape of the potential failure surface,(2)internal friction angle of the various soils,(3)cohesion of the various soils,(4)density of the various soils,and(5)location of the piezometric groundwater surface. These parameters were estimated on the basis of visual observations,field testing,empirical correlations,and experience with similar soil types. These parameters were then used to establish the critical slip surface and associated safety factor of the slope. A critical slip surface is defined as the most likely surface along which a soil mass will slide,and a safety factor is defined as the ratio of the sum of all moments resisting slope movement versus the sum of all moments tending to cause slope movement. Consequently,a slope that possesses a safety factor of 1.0 is on the verge of sliding, whereas a slope with a safety factor greater than 1.0 has some resistance to sliding. According to standard geotechnical engineering practice,a static safety factor of 1.50 and a seismic safety factor of 1.10 are considered the desirable minimum values for most slopes,but 1.25 and 1.01,respectively,are often regarded as acceptable values. Slope stability conditions for the project site were analyzed by means of Bishop Circular Analysis.. All calculations were performed by means of the computer program WINSTABLE. This program utilizes topographic,soil,and groundwater information input by the user to determine the most critical slip surface. Our estimated values of internal friction angle,cohesion,and density for each soil layer,which are conservative relative to accepted values for glacial soils,are listed in Table 2. To model the foundation load applied by the mobile home we applied a vertical force of 250 pounds per square foot. Our analysis yielded a Seismic Factor of Safety Of 1.2 and a Static Factor of Safety of 1.5. 4 March 8, 2006 ORA, Inc. T06057/Watson Geotechnical Report TABLE 2 ESTIMATED PROPERTIES OF ON-SITE SOILS FOR STABILITY ANALYSIS Soil Type Density Cohesion Internal Friction (pct) (psf) Angle (degrees) Glacial Till(Steep slope offsite) 130 100 38 Advance Sandy Glacial Outwash(Steep slope offsite 120 0 34 Advance Sandy Glacial Outwash(Steep slope offsite 130 0 36 Dense gravelly sand(onsite) 125 0 35 4.0 CONCLUSIONS AND RECOMMENDATIONS Development plans call for the placement of a mobile home on a level terrace on a site that had original grades of less than 20 percent. The west edge of the site is approximately 200 feet from the toe of a steep, stable, slope. We offer the following general geotechnical conclusions and recommendations concerning this project. • Feasibility: Based on our field explorations,research,and analyses,the proposed construction appears feasible from a geotechnical standpoint, provided that the recommendations in Section 4 are followed. • Landslide Hazards: Our site reconnaissance did not reveal recent or ancient slide activity onsite,no landslide indicators were observed onsite or on nearby offsite. The Coastal Zone Atlas does not identify unstable slopes or landslide areas onsite or nearby offsite.Our slope stability analysis indicates that an ample factor of safety exists for the planned development. In our opinion,the site does not currently present a landslide hazard and will not present a landslide hazard due to site development,provided our recommendations are followed. Original grades onsite and within 200 feet of the site appear to have been less than 20 percent, and no areas with grades greater that 20 percent over an elevation change of more than 10 feet are not present within 200 feet of the site.In our opinion,the site doe not meet Mason County Criteria for classification as a Critical Area with respect to landslide hazards • Setbacks and Buffers: No buffers or setbacks are warranted due to slope conditions on the site, in our opinion. • Erosion Hazards:During construction,we recommend that standard erosion control measures, consisting of properly placed silt fences or straw bales and interceptor ditches,as described in Section 4.1, be implemented in the construction area. Areas of bare soils should be re- vegetated as soon as possible to permanently control site erosion. • Development Impact: Based on our slope analysis and site observations, the proposed development should not have significant impact onsite or offsite if our recommendations are followed. 5 March 8. 2006 ORA, Inc. T06057/Watson Geotechnical Report • Clearing and Grading_The building site on the upland has been cleared and graded. Further clearing on the upland part of the site,outside of the vegetative buffer,is permitted provided that bare soils are re-vegetated as soon as possible after construction is complete. Grading recommendations are included in the Site Preparation section. 4.1 Site Preparation Preparation of the project site should involve erosion control,temporary drainage,clearing,stripping,cutting, filling,excavations,and subgrade compaction. Erosion Control: Before new construction begins,an appropriate erosion control system should be installed. This system should collect and filter all surface run offthrough either silt fencing or a series of properly placed and secured straw bales. We anticipate a system of berms and drainage ditches around construction areas will provide an adequate collection system. If silt fencing is selected as a filter,this fencing fabric should meet the requirements of WSDOT Standard Specification 9-33.2 Table 3. In addition, silt fencing should embed a minimum of 6 inches below existing grade. If straw baling is used as a filter,bales should be secured to the ground so that they will not shift under the weight of retained water. Regardless of the silt filter selected,an erosion control system requires occasional observation and maintenance. Specifically,holes in the filter and areas where the filter has shifted above ground surface should be replaced or repaired as soon as they are identified. Temporary Drainage: We recommend intercepting and diverting any potential sources of surface or near-surface water within the construction zones before stripping begins. Because the selection of an appropriate drainage system will depend on the water quantity, season, weather conditions, construction sequence,and contractor's methods,final decisions regarding drainage systems are best made in the field at the time of construction. Based on our current understanding of the construction plans,surface and subsurface conditions we anticipate that curbs berms or ditches laced around the work areas will adequately intercept P � P q Y P surface water runoff. Temporary Cut Slopes: All temporary soil slopes associated with site cutting or excavations should be adequately inclined to prevent sloughing and collapse.Temporary cut slopes in site soils should be no steeper than 1'/4 H:1V,and should conform to WISHA regulations. Subgrade Compaction: Exposed subgrades for footings, slabs, and floors should be compacted to a firm, unyielding state before new concrete or fill soils are placed. Any localized zones of looser granular soils observed within a subgrade should be compacted to a density commensurate with the surrounding soils. In contrast,any organic,soft,or pumping soils observed within a subgrade should be overexcavated and replaced with a suitable structural fill material. Site Filling: Our conclusions regarding the reuse of on-site soils and our comments regarding wet-weather filling are presented subsequently. Regardless of soil type,all fill should be placed and compacted according to our recommendations presented in the Structural Fill section of this report. Specifically,building pad fill soil should be compacted to a uniform density of at least 95 percent(based on ASTM D-1557). 6 March 8, 2006 ORA. Inc. T06057/Watson Geotechnical Report On-Site Soils: We offer the following evaluation of these on-site soils in relation to potential use as structural fill: • Surficial Organic Soils: Surficial organic soils are not suitable for use as structural fill under any circumstances,due to high organic content. Consequently,these materials can be used only for non-structural purposes,such as in landscaping areas. • Weathered and Unweathered Glacial Outwash Sand: The weathered and unweathered gravelly glacial outwash sand on the site is relatively insensitive to moisture content variation, and will be reusable in all but the wettest of weather conditions. All particles larger than 6 inches should be removed before reuse. Permanent Slopes: All permanent cut slopes and fill slopes should be adequately inclined to reduce long-term raveling,sloughing,and erosion. We generally recommend that no permanent slopes be steeper than 2H:l V. For all soil types, the use of flatter slopes (such as 2%ZH:IV) would further reduce long-term erosion and facilitate revegetation. Slope Protection:We recommend that a permanent berm,swale,or curb be constructed along the top edge of all permanent slopes to intercept surface flow. Also,a hardy vegetative groundcover should be established as soon as feasible,to further protect the slopes from runoff water erosion. Alternatively,permanent slopes could be armored with quarry spans or a geosynthetic erosion mat. 4.2 Footings It is likely that strip footings will support the planned mobile home. We make the following general footing recommendations: Bearing SubUydes Footings should bear on medium dense or denser, undisturbed native soils which have been stripped of surficial organic soils,or on properly compacted structural fill which bears on undisturbed native soils which have been stripped of surficial organic soils.In general,before footing concrete is placed, any localized zones of loose soils exposed across the footing subgrades should be compacted to a firm, unyielding condition,and any localized zones of soft,organic,or debris-laden soils should be overexcavated and replaced with suitable structural fill. SubgEyde Observation: All footing subgrades should consist of firm,unyielding,native soils or structural fill materials compacted to a density of at least 95 percent(based on ASTM:D-1557).Footings should never be cast atop loose,soft,or frozen soil,slough,debris,existing uncontrolled fill,or surfaces covered by standing water. Bearing Pressures: In our opinion,for static loading,footings that bear on properly prepared subgrades can be designed for a maximum allowable soil bearing pressure of 2,000 pounds per square foot(psf).A one-third increase in allowable soil bearing capacity may be used for short-term loads created by seismic or wind related activities. Footing Settlements:We estimate that total post-construction settlements ofproperly designed footings bearing on properly prepared subgrades will not exceed 1 inch. Differential settlements for comparably loaded elements may approach one-half of the actual total settlement over horizontal distances of approximately 50 feet. Footing Backfill: To provide erosion protection and lateral load resistance, we recommend that all footing excavations be backfilled on both sides of the footings and stemwalls after the concrete has cured. Either 7 March 8, 2006 OR& Inc. T06057/Watson Geotechnical Report imported structural fill or non-organic on-site soils can be used for this purpose, contingent on suitable moisture content at the time of placement. Regardless of soil type, all footing backfill soil should be compacted to a density of at least 90 percent(based on ASTM:D-15 5 7). Lateral Resistance: Footings that have been properly backfilled as recommended above will resist lateral movements by means of passive earth pressure and base friction. We recommend using an allowable passive earth pressure of 300 pcf in and an allowable base friction coefficient of 0.35 for site soils. 4.3 Structural Fill The term "structural fill' refers to any placed under foundations, retaining walls, slab-on-grade floors, sidewalks,pavements, and other structures. Our comments,conclusions,and recommendations concerning structural fill are presented in the following paragraphs. Materials: Typical structural fill materials include clean sand, gravel,pea gravel,washed rock,crushed rock, well-graded mixtures of sand and gravel(commonly called"gravel borrow"or"pit-run"),and miscellaneous mixtures of silt,sand,and gravel. Recycled asphalt,concrete,and glass,which are derived from pulverizing the parent materials,are also potentially useful as structural fill in certain applications. Soils used for structural fill should not contain any organic matter or debris,nor any individual particles greater than about 6 inches in diameter. The glacial outwash onsite should provide a good source of structural fill. Fill Placement: Clean sand, gravel,crushed rock, soil mixtures,and recycled materials should be placed in horizontal lifts not exceeding 8 inches in loose thickness,and each lift should be thoroughly compacted with a mechanical compactor. Compaction Criteria: Using the Modified Proctor test(ASTM D-1557)as a standard, we recommend that structural fill used for various on-site applications be compacted to the following minimum densities: Fill Application Minimum Compaction Footing subgrade and bearing pad 95 percent Foundation and subgrade wall backfill 90 percent Slab-on-grade floor subgrade and subbase 95 percent SubgLa de Observation and Compaction Testing: Regardless of material or location,all structural fill should be placed over firm,unyielding subgrades prepared in accordance with the Site Preparation section ofthis report. The condition of all subgrades should be observed by geotechnical personnel before filling or construction begins.Also,fill soil compaction should be verified by means of in-place density tests performed during fill placement so that adequacy of soil compaction efforts may be evaluated as earthwork progresses. Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on their grain-size distribution and moisture content when they are placed. As the"fines" content(that soil fraction passing the U.S.No.200 Sieve)increases,soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, unyielding condition when the moisture content is more than 2 percentage points above or below optimum. For fill placement during wet-weather site work,we recommend using"clean"fill,which refers to soils that have a fines content of 5 percent or less(by weight)based on the soil fraction passing the U.S.No.4 Sieve. 8 March 8, 2006 E3RA. Inc. T06057/Watson Geotechnical Report 5.0 RECOMMENDED ADDITIONAL SERVICES Because the future performance and integrity of the structural elements will depend largely on proper site preparation, drainage, fill placement, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. Consequently,we recommend that E3RA be retained to provide the following post-report services: • Review all construction plans and specifications to verify that our design criteria presented in this report have been properly integrated into the design; • Prepare a letter summarizing all review comments(if required by Mason County);and • Prepare a post-construction letter summarizing all field observations, inspections, and test results(if required by Mason County). 6.0 CLOSURE The conclusions and recommendations presented in this report are based,in part,on the explorations that we observed for this study;therefore,if variations in the subgrade conditions are observed at a later time,we may need to modify this report to reflect those changes. Also,because the future performance and integrity of the project elements depend largely on proper initial site preparation, drainage, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process.E3RA is available to provide geotechnical monitoring of soils throughout construction. We appreciate the opportunity to be of service on this project. If you have any questions regarding this report or any aspects of the project,please feel free to contact our office. Sincerely, E3RA, Inc. . z � X A—" 42� re leering Geologis ffi b n Sid REX B. HUMPHREY Fred E.Rennebaum,L.E.G. fee James E.Brigham,P.E. Senior Geologist Principal Engineer FER/JEB Enclosures: Figure 1 — Location Map Figure 2 — Site&Exploration Plan Figure 3 — Cross Section A-A' Test Hole Logs TH-1 through TH-3 9 March 8. 2006 ORA, Inc. T06057/Watson Geotechnical Report TEST HOLE LOGS Depth (feet) Material Description Test Hole TH-1 Location: Near planned residence,lower terrace Approximate ground surface elevation:Unknown 0.0—3.0 Medium dense,brown,gravelly sand with some silt and cobbles(Glacial Outwash)(SP-SM). Test hole terminated at approximately 3 feet No caving observed No groundwater encountered Test Hole TH-2 Location: Upper terrace,toe of small slope Approximate ground surface elevation:Unknown 0.0—3.0 Loose to medium dense,brown,gravelly sand with some silt and cobbles(Re-worked Glacial Outwash) (Fill)(SP-SM). Test hole terminated at approximately 3 feet No caving observed No groundwater encountered Test Hole TH-3 Location: Upper terrace Approximate ground surface elevation:Unknown 0.0—3.0 Medium dense,brown,gravelly sand with some silt and cobbles(Glacial Outwash)(SP-SM). Test hole terminated at approximately 3 feet No caving observed No groundwater encountered Logged by: FER on 2/21/06 111 111 i� 111 - I r (I ��*`����1�' • ' I I` t 11 �i �/f Ell i NOW, if fill 111 111 i' 111 E3RA, Inc. • • • • - - • Box 44890 Tacoma, WA 98444 , 108' r� �l _ I 8 ff` rf TP-1 f a i PROPOSED ' HOME A i I ` CD CD M CJJ1 \ 20 0 20 40 } 2 ; i TEST PIT LOCATION CD I � TB I Client: Vincent & Ruth Watson 129' �`e�", 31 NE Steelhead Dr. N Belfair, WA 98528 I NOTE: BOUNDARY AND TOPOGRAPHY ARE BASED ON MAPPING PROVIDED TO E3RA AND OBSERVATIONS MADE IN THE FIELD. THE INFORMATION SHOWN DOES NOT CONSTITUTE A FIELD SURVEY BY E3RA. PROJECT: Watson Residence E3RAInc. Proposed Home P.O.BOX 44890 TITLE- SITE AND EXPLORATION PLAN TACOMA, WA 98444 253-537-9400 off 253-537-9401 fax DESIGNER: CRL FIGURE: 2 DRAWN BY: CRL SCALE: 1"=20' www.e3ra.com CHECKED BY: JEB SHEET: 1 DATE: 2/23/06 FILE:TO6057 A A, East Boundary West Boundary 260 -_......_.,._- _,_......__., ._...... - — ......... - _ -- ------------- i F £ s € £ .i.—.� —��............. € f f. £ -.-.v......---a,.-_—......,.mod..,... "'f ? e , , , > E i `, £ r £ f i < € : € F S >_ a € f S ' e _ y x , -............... - r........................ ... -- _ ....... > _... _- .. .. ._ f € w { j € 77 t € € € — f r f e k € £ s i ' { 1 .. p...—........t.__.........E ��---- _ Dense 'San� f f € s, ........... , 3 s . , , { ... , f w f : 140 I Dense Sand _. ...... Grave ' -I----^..w...,- .... ' f"""'_'w"�:""----"'-.•_...--"--"-^---{ € € 3 € 1 i € TP-2 - -- PROPOSED _.._..__,_ _ - _ _ _ 5 Dens.eGrave.11 ! _ _ HOME P 1 TP-3 Y -` I 100 140 180 220 260 3�00 340 € � 380 � f I I � � � tt I I t € t 420 460 500 540 580 620 NClient: Vincent & Ruth Watson 31 NE Steelhead Dr. N I Belfair, WA 98528 40 0 40 80 NOTE: BOUNDARY AND TOPOGRAPHY ARE BASED ON MAPPING PROVIDED TO E3RA AND OBSERVATIONS I MADE IN THE FIELD. THE INFORMATION SHOWN DOES NOT CONSTITUTE A FIELD SURVEY BY E3RA. PROJECT: Watson Residence E3RAI n.c. Proposed Home P.O.BOX 44890 TITLE: PROFILE TACOMA, WA 98444 253-537-9400 off 253-537-9401 fax DESIGNER: CRL FIGURE: 3 DRAWN BY: CRL SCALE: 1"=40' www.e3ra.com CHECKED BY: JEB SHEET: 1 DATE: 2/23/06 FILE:T06057 c PO Box 44890 Tacoma WA 98444 253-537-9400 253-537-9401 fax E3RA February 22,2006 Vincent Watson 21 NE Steelhead Drive North Belfair, Washington 98528 (360)275-2185 Subject: Proposal for Geotechnical Services Geotechnical Report Parcel#22325 50 06007 80 NE Steelhead Drive South Belfair,Washington Dear Vincent: E3RA is pleased to submit this proposal to provide you with a Geotechnical Report for your parcel at 80 NE Steelhead Drive South in the Big Mission Creek area near Belfair Washington. Plans call for the placement of a new mobile home on the site. An engineering Geologist visited the site on February 21, 2006 and observed site and soil conditions. We understand that personnel from Mason County have stated that a full Geotechnical Report is necessary, because a steep slope is located within 350 feet of the site. The purpose of our report will therefore be to address the Mason Critical Areas Ordinances as they relates to landslide and erosion hazards on the site,and to provide geotechnical engineering recommendations for the planned project. SITE AND PROJECT DESCRIPTION The project site is roughly square and measures an average of about 100 feet on a side.It is located at the intersection of NE Steelhead Drive and NE Steelhead Drive South, near Big Mission Creek in Mason County, Washington. Slopes onsite average less than 20 percent, and are limited to two terraces, one of which is about 10 feet high and the other is about 7 feet highli A steep slope,approximately 100 feet high with grades of about 65 to 70 percent, is located about 200 feet west of the site. SCOPE OF SERVICES Based on our understanding of the project, our experience with Mason County, and our observation of subsurface conditions at the site,we infer that our assessment will need to include the following: • A geologic reconnaissance of the site and nearby areas; • Subsurface explorations; • Geologic research; and • A Geotechnical Report, which includes slope analysis, a Geologic Cross section, and a site plan that includes 2-foot contour intervals. February 22, 2006 E3RA, Inc. Watson Mason County Proposal There is no guarantee that Mason County, upon review of our Geotechnical Report, will not require further work. In that event,we will provide a new proposal for services for any additional work required by county personnel. COST ESTIMATE Our services will be performed on a lump-sum basis for a total of$2,100 under the conditions outlined in the attached General Conditions. A retainer of$500 has already been received. Our services are based on the following cost and time estimates: ITEM SCOPE OF WORK COST 1 Field Reconnaissance and Travel Time $600.00 2 Research,Report Preparation,and Office Review $ 1,200.00 3 Engineering Review $300.00 BUDGET TOTAL $2,100.00 Retainer Received Previously $-500.00 REVISED BUDGET TOTAL $ 1,600.00 To authorize our proposed scope of work,please have an appropriate authority sign this form and return a copy to us. CLOSURE We look forward to provide you with the services set forth above. Our services can be authorized by signing a copy of this proposal and returning it to our office. If you have any questions or desire additional information,please do not hesitate to call. Sincerely, E3RA, Inc. Authorized by Signature and Date /v Fred E Rennebaum,L.E.G. Name and Title Senior Geologist Enclosure: General Conditions 4 E3RA ORA, INC. STANDARD TERMS AND CONDITIONS 1) ENTIRE AGREEMENT.Upon authorization by the CLIENT and commencement of performance hereunder,these terms and E3RA,s Proposal constitute the entire agreement between the parties concerning its subject matter. Any changes or additional conditions proposed by CLIENT are hereby rejected,unless expressly stated in this Agreement or incorporated by a change order. 2) CHANGES.Upon receipt of notice from CLIENT of a change in the scope of the work hereunder,E3RA will promptly notify the CLIENT if there is an impact on the schedule,price or terms of this Agreement. Thereafter,an estimate of any impact on this Agreement will be prepared and submitted to the CLIENT. The parties agree to promptly negotiate and implement changes to this Agreement. 3) SITE INFORMATION AND ACCESS.The CLIENT shall make available to E3RA all relevant information and documents under his control regarding past,present and proposed conditions of the site. The information shall include,but not be limited to,plot plans,topographic surveys, hydrologic data and previous soil and geologic data including borings,field or laboratory tests and written reports. The CLIENT shall immediately transmit to E3RA any new information that becomes available or any change in plans. The CLIENT shall also ensure uninterrupted site access for E3RA throughout performance of this Agreement. 4) PERMITS AND UTILITIES. Unless otherwise stated in the Proposal,the CLIENT shall apply for and obtain all required permits and licenses and shall make all necessary arrangements for right of entry to provide E3RA access to the site for all equipment and personnel at no charge to E3RA. The CLIENT shall also provide E3RA with the location of all underground utilities and structures in the exploration area. Unless otherwise stated in the proposal,E3RA is not responsible for location or identification of utilities. 5) PAYMENT. Unless otherwise stated in the Proposal,invoices will be submitted by E3RA either at the completion of the work or on a monthly basis and will be due and payable on the invoice date. If full payment is not received by E3RA within thirty(30)days of the invoice date,the CLIENT agrees to pay an additional finance charge on the outstanding balance from the date of the invoice at an annual percentage rate of eighteen percent(18%),or the highest rate permitted under local law,whichever is less. 6) OWNERSHIP RIGHTS. Any documents produced by E3RA shall be the sole property of E3RA. At the request and expense of the CLIENT, E31RA shall provide the CLIENT with copies of any or all drawings,specifications and other documents prepared by E3RA. 7) ATTORNEYS FEES. In the event either party makes a claim or brings an action against the other for any act arising out of the performance or interpretation of this Agreement,including the payment of professional fees,the unsuccessful party shall pay all reasonable attorney's fees and legal costs incurred by the prevailing party in such claim or action. 8) STANDARD OF CARE. In the performance of professional services,E3RA will use that degree of care and skill ordinarily exercised under similar circumstances by reputable members of its profession practicing in the same or similar localities. No warranty,either express or implied,is made or intended b this Agreement or furnishing oral or written reports of the findings.E3RA is to be liable only for damage proximately caused by Y g Y 9 P 9 the negligence of E3RA. The CLIENT recognizes that subsurface conditions may vary from those encountered at the location where borings, surveys or explorations are made by E31RA and that the data,interpretations and recommendation of E3RA are based solely on the information available to it.E3RA will not be responsible for the interpretation by others of the information developed. 9) INSURANCE.E3RA will maintain insurance forthis Agreement in the following types:1)worker's compensation insurance atstatutorily required levels,2)comprehensive general liability(CGL)insurance and 3)automotive insurance. 10) ENVIRONMENTAL LIABILITY. Because CLIENT owns and/or operates the site where work is being performed,CLIENT has and shall retain all responsibility and liability associated with the environmental conditions at the site. Unless specifically identified in E3RA's Proposal,CLIENT'S responsibility and liability includes the handling and disposal of any samples or hazardous materials generated on the site as a result of E3RA's performance hereunder. 11) CONSEQUENTIAL DAMAGES.E3RA shall NOT be responsible for any consequential,incidental or indirect damages. 12) LIMITATION OF LIABILITY.Notwithstanding any other provision ofthis Agreement,the total liability ofE3RA,its officers,directors and employees for liabilities,claims,judgments,demands and causes of action arising under or related to this Agreement,whether based in contract or tort,shall be limited to the total compensation actually paid to E3RA for the Services or$50,000,whichever is more. All claims by CLIENT shall be deemed relinquished unless filed within three(3)years after substantial completion of the Services. 13) DISPUTES. Any dispute arising hereunder shall first be resolved by taking the following steps,where a successive step is taken ifthe issue is not resolved at the preceding step: 1) by the technical and contractual personnel for each party performing this Agreement, 2) by executive management of each party,3)by mediation,4)by arbitration if both parties agree or 5)through the court system of the jurisdiction of the E3RA office that entered this Agreement. 14) WARRANTY OR AUTHORIZATION TO SIGN. The person signing this Agreement warrants that he has authority to sign as,or on behalf of,the CLIENT for whom or for whose benefit E3RA's services are rendered. If such a person does not have such authority, he agrees that he is personally liable for all breaches of this Agreement,and that in any such action against him for breach of such warranty,reasonable attorney's fees and legal costs shall be included in a judgement rendered. 15) ASSIGNMENT. With the exception of duties stated in the proposal, neither the CLIENT nor E3RA may delegate,assign,sublet or transfer his duties or interest in this Agreement without the written consent of the other party. 16) CHOICE OF LAWS. This Agreement shall be governed by the laws of the State of Washington. Rev.01/2004