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HomeMy WebLinkAboutGEO BLD2004-00165 - BLD Engineering / Geo-tech Reports - 3/11/2004 ' MASON COUNTY PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER Shelton,Washington 98584 DATE: March l Ph, 2004 INTER-DEPARTMENTAL COMMUNICATIONS TO: Diane Marcus-Jones, DCD - Planner FROM: Alan A. Tahja, P/W - Co. Hydr. Engr. WO# PLG-04 SUBJ: Geo-Tech Report Review NAME: Fish SFR &425 E Rauschert Rd BLD2004-00165 The geotechnical report prepared for the proposed Michael & Linda Fish Single Family Residence(SFR)replacement to be constructed at 425 East Rauschert Road, 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 and geotechnical reporting. Recommendations contained in the report should be incorporated into the site's development and made conditions for permit issuance. The engineering geologist recommends a minimum 35' building setback from the top of the coastal bluff,which should be made a condition for permit issuance. 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. �— • In summary,the geotechnical report appears acceptable, and the proposed residential development of the property should be allowed to proceed, subject to the engineer's recommendations. 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. Si ely, AI nA. Tahj TO BE KEPT IN TFI PARCEL FILE File: H: \WP\GEO\Reviews\Fish.doc Geotechnical Report Az 425 East Rauschert Rd. Parcel #121181300011 Mason County, WA Prepared for Michael & Linda Fish Albany, OR by Geotechnical Testing Lab Olympia, WA September 15, 2003 RECEIVED FEB 13 2004 426 Wv CE"p-STe GEOTECHNICAL TESTING LABORATORY MICHAEL AND LINDA FISH 339 8T"AVENUE SW. ALBANY, OR 97321 Re: Geotechnical Report Parcel No. 121181300011 425 East Rauschert Road N47018.681' W122051.157' INTRODUCTION This report summarizes the results of our geotechnical consulting services for the proposed replacement of the existing residence located approximately 2 miles southwest of Grapeview,Washington. The location of the site is shown relative to the surrounding area on the Vicinity Map, Figure 1. Our understanding of the project is based on our discussions with you and our explorations and review of the site. We understand that the existing structure is to be replaced by a new structure of the same dimensions. The general layout of the site is shown on the Site Map,Figure 2. We further understand that minor grading may be required at the site to reach design grade. In general, grading will consist of the excavation of the foundation material. We understand that water and sewer services are currently provided onsite. The steepest slope measured onsite was in excess of 100 percent along the coastal bluff. Therefore, Mason County 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: 10011 Blomberg Street SW, Olympia,WA 98512 1 Phone#: (360) 7544612 Fax#: (360) 7544848 GEOTECHNICAL TESTING LABORATORY 1. Review the available geologic,hydrogeologic,and geotechnical data for the site area. 2. Conduct a geologic reconnaissance of the site area. 3. Evaluate the landslide and erosion hazards at the site per the Mason County Critical Areas Ordinance regulations. 4. Provide geotechnical recommendations for site grading including site preparation, subgrade preparation,fill placement criteria(including hillside grading), suitability of on-site soils for use as structural fill,temporary and permanent cut and fill slopes, drainage and erosion control measures. 5. Provide recommendations d design criteria for the structural foundation and floor slab support, including allowable bearing capacity, subgrade modulus,lateral resistance values and estimates of settlement. an SITE CONDITIONS SURFACE CONDITIONS The proposed building site is located in an area of sparse residential development in the Puget Sound glacial upland area located north of Pickering Passage. The layout of the site is shown on the Site Plan, Figure 2. We conducted a reconnaissance of the site area on August 27, 2003. Onsite elevations range from approximately zero to 40 feet. Elevations at the building area are about 10 feet in relief. The building site slopes gently westward toward a natural drainage. The southern portion of the site is fronted by a vertical coastal bluff. k .e At the time of the site visit, we observed no evidence of surface erosion. No evidence of deep-seated slope instability was observed on the site slopes or areas adjacent to this site at the time of our investigation. The building area of the site has vegetation indigenous to the northwest. The vegetation includes madrona and fir trees as well as ferns,Himalayan blackberries, and grasses. No evidence of surface water flow was observed onsite at the time of our reconnaissance. The general topography of the site area indicates that drainage flows toward the southwest. 10011 Blomberg Street SW, Olympia,WA 98512 2 Phone#: (360) 754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY SITE GEOLOGY The site is generally situated within the lower Puget Sound glacial upland. 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,the soils on the site are predominantly represented by Vashon glacial till deposits. SITE SOILS The Mason County Soil Conservation Survey(1960)has mapped the site soils as a Sinclair shotty loam, 5-15 percents slopes(So),at the proposed building location. The Sinclair soils x have typically developed from very compact Vashon gravelly to 'Q till. Surface drainage is well to moderately well established. Internal drainage is restricted by the substratum of cemented till. Typically,there is no occurrence of a high water table. We .. observed no active erosion or slope disturbance in the site area during our reconnaissance. The soils are not considered hydric. The Coastal Zone Atlas, Volume 9, Mason County(MA-14) maps the site as Vashon till(Q,t). The glacial till is a tough, dense material of low permeability. It provides excellent foundation support. Slope stability is described as "stable"at the building location. The chance of flooding is less than one percent. Foundation stability is "excellent." Seismic stability is described as"good." SUBSURFACE EXPLORATIONS Subsurface conditions at the site were evaluated by observing soils exposed at the site and along the coastal bluff. Over- consolidated and cemented sandy gravelly soils (up to 4-inches) 10011 Blomberg Street SW, Olympia,WA 98512 Phone#: (360)754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY were found at a depth of 22 feet below the building area. SUBSURFACE CONDITIONS In general,undisturbed shotty loam was observed at the surface throughout both the site and the proposed building location. Groundwater seepage was not observed at the site. Based on the nature of the near surface soil(cemented Vashon glacial till in the building area), seasonally perched groundwater conditions may not be expected during periods of extended wet weather. SLOPE STABILITY Slopes in excess of 100 percent were observed on 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 according to the Critical Areas Ordinance. The near-surface till soils are in a medium dense to dense condition except at the ground surface. The surficial soils are generally in a medium dense condition. Cementation is well exposed along the coastal bluff. In general,the undisturbed native soils of the site consist of a mixture of variable amounts of sand, silt,and gravel. These soil materials are in a dense condition except where they have been disturbed by weathering activity. These soils are generally stable relative to deep-seated failure. No evidence of deep-seated landslide activity or significant erosion was observed at the site at the time of our investigation. Weathering,erosion,and the resultant sloughing and shallow landslidmg 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. Evidence of minor surficial erosion,raveling and sloughing was observed on the coastal bluff at the time of our investigative visit. Significant 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 by encouraging vegetation and discouraging runoff from the steep slope. A drainpipe can be used to control the flow from top to bottom. Erosion control recommendations for the sloping areas are provided in the"Building Setback"and"Erosion Control' sections of this report. CONCLUSIONS AND RECOMMENDATIONS GENERAL Based on the results of our site reconnaissance and subsurface observations,and our experience in the area, it is our opinion that the site is suitable for the proposed home. The slope is stable relative to deep-seated instability and will not be affected by the proposed structure replacement. Proper drainage control measures will reduce or eliminate the potential for erosion in this area and improve slope stability. 10011 Blomberg Street SW, Olympia,WA 98512 4 Phone#: (360) 754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY In general,the site soils are not suitable for use as structural fill material. Although saturated soil conditions are not associated with these soils during or following extended periods of rainfall, we recommend that earthwork be undertaken during favorable weather conditions to reduce grading time and construction costs. 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 with normal spread footings. A vapor barrier is recommended for all slab-on-grades. Pertinent conclusions and geotechnical recommendations regarding the design and construction of the proposed home are presented below. LANDSLIDE—EROSION HAZARD AREAS Classification The Mason County Critical Areas Ordinance(17.01.100)defines a landslide hazard area as one containing slopes equal to or greater than 40 percent with more than a 10-foot vertical relief. Themeastal slope bordering Pickering Passage is in excess of 100 percent and the verti re re is in excess o ased on this,this site does meet the technical criteria of a landslide hazard_ The"Relative Slope Stability of the Southern Hood Canal Smith&Carson(1977), categorizes the site as a Class 1. The classification indicates the s s rs e underer nlconditions and represents the most stable of all the classes. The Mason County Critical Areas Ordinance(17.01.104)defines an erosion hazard area as: Areas in Mason County underlain by soils which are subject to severe erosion when disturbed. Such soils include, but are not limited to, those for which potential for erosion is identified in the Soil Survey of Mason County, USDA Soil Conservation Service, 1960, or any subsequent revisions or additions to this source. These soils include, but are not limited to, any occurrence of River Wash ("Ra') or Coastal Beaches ("Cg') and the following when they occur on slopes 1 S%or steeper: a.Alderwood gravelly sandy loam ("Ac"and "Ad') b. Cloquallum silt loam ("Cd') e. Harstine gravelly sandy loam ("Hb') d. Kitsap silt loam ("Kc') The soils at-the site are mapped as Sinclair shotty loam. This site does not meet the technical criteria of an erosion hazard area. 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 on the lot exceed 100 percent,they are generally stable relative to deep- seated failure in their present configuration. The following figure represents a shear angle for the Vashon glacial till. 10011 Blomberg Street SW, Olympia,WA 98512 5 Phone#: (360) 754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY Peak Shear Stress vs.Normal Stress �a m 1Fl Eon 1 Eon 0 Normal Stress�sn Changes.in slope stability are not expected to result from any proposed excavations in the development of the site. Development will occur in the building 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/dry cycles and freeze/thaw cycles. These processes can be managed and the risk . J reduced through proper construction of the 1 Fish Site • . /' residence. Erosion control recommendations in Analysis Method:Morgenstern-Price / the slope and buffer areas are provided in the Direction of Slip Movement Left to Right, , . ,f - „ Slip Surface Option:Grid and Radius _ Building Setback "Erosion Erosion Control Seismic Coefficient:Horizontal and vertical / sections of this report. Building Setback • • • A building setback from landslide hazard areas is required inuired unless evaluated and reduced by an engineering geologist $f� . • • . . � gist or a licensed professional . . � � 1 i`/ •� engineer. Based on our geotechnical evaluation j j ��j . . . . . . . of the site and our experience in the area, a Proposed / , buildingsetback will be needed for this lot. A 50 Building 40 A, Building Building setback of 35 feet from the top of the coastal 30 cNt She C I Model:Mohr-C�Mm bluff to the bottom of the footing should > z0 nit weight:12e otherwise be observed, see right.�e building w 10 ohesion:50 h setback may be measured ftbV%e'bottom of ° 0 10 20 30 40 50 60 70 80 90 1D0 110 120130 140 150 160 the footing to the face of theslope, in Distance(ft) accordance with the Unified Building Code. 10011 Blomberg Street SW, Olympia,WA 98512 6 Phone#: (360) 7544612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY Slope stability was modeled using the GEO-SLOPE/W program(version 5.13) in both static and dynamic conditions (ca=0.3). Factors of safety were determined using Bishop's, Janbu, and the Morgenstern-Price methods. The site geology was modeled by using a single layer of glacial till(Q,,). Previously,the glacial till was determined to have a unit weight of 125 pcf, cohesion of 50 psf,and a shear angle(�)of 390. Under static conditions,the slopes adjacent to the existing structure remained stable to deep-seated and shallow failure. Under dynamic loading,the 1936 computations demonstrated that the slope is not susceptible to surficial raveling;large deep-seated failure was not demonstrated by our model. The following figure illustrates a moment F.S. of 1.42,the lowest value derived from modeling the proposed building location. Fish Site Analysis Method: Morgenstern-Price Direction of Slip Movement: Left to Right Slip Surface Option: Grid and Radius Seismic Coefficient: Horizontal and Vertical . . . . 50 k t 40ite Buildings �� � �� O 30 20 Soil Model: Mohr-Coulomb nit Weight: 125 14 N 10 Cohesion: 50 LLl i: 3 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 Distance (ft) As previously weathering,erosion and the resultant surficial sloughing and shallow landsliding are natural processes that affect slopreas. Non-significant surficial raveling or sloughing from the past was observed in the sloping portions of the site. To manage and reduce the potential for these natural processes,we recommend the following: 1. No drainage of concentrated surface water or significant sheet flow onto the west slope area. Drainage from the roof and driveway area should be collected and tight-lined to the bottom of the slope. 2. No filling within the setback zone unless retained by retaining walls or constructed as an engineered fill. 10011 Blomberg Street SW, Olympia,WA 98512 7 Phone 4: (360) 7544612 Fax#: (360) 7544848 GEOTECHNICAL TESTING LABORATORY SEISNIIC—LIQUEFACTION HAzARD According to the Seismic Zone Map of the United States contained in Figure 16-2 of the 1997 UBC (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 '/z-inch diameter steel probe rod. The shallow soil conditions were assumed to be representative of the site conditions beyond the depths explored. Y k ` 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 well below the surface. Shaking of the a: already dense soil is not apt to produce a denser configuration and subsequently excess pore water pressures are not likely to be produced. 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 should be minimized and limited to the active construction areas. Yard landscaping around the home is permissible,but natural growth should be encouraged on the slopes as much as possible as a Perrent to erosion. Temporary and permanent erosion control measures should be implemented and maintained during construction and/or as soon as practical thereafter to limit the additional influx of water to exposed areas and protect potential receiving waters. Erosion control measures should include, but not limited to, silt fences,berms and swales with ground cover/protection in exposed areas. A typical silt fence detail follows this report. Any re-contouring of the site for a level area for the house will create a need for erosion control measures as listed above. EARTHWORK Site Preparation All areas to be excavated should be cleared of deleterious matter including any existing structures, debris, utilities, and vegetation. Based on our explorations,we estimate that stripping will be minimal because a structure currently exists at the site. 10011 Blomberg Street SW, Olympia,WA 98512 8 Phone#: (360)754-4612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY Where placement of fill material is required,the exposed subgrade areas should be proof-rolled to a firm and unyielding surface prior to placement of any fill. Unless locat o a slope,we recommend that trees be removed with the roots. Excavations for tree stump removal in any building area should be backfilled with structural fill,and compacted to the density requirements described in the"Structural Fill" section of this report. Any soft, loose or otherwise unsuitable areas delineated during construction or probing should be compacted, if practical, or over-excavated and replaced with structural fill, based on the recommendations of our site representative. 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. 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 in moisture content and adequate compaction becomes more difficult to achieve. During wet weather,we recommend the use of well-graded sand and gravel with less than 5 percent(by weight)passing the No. 200 sieve based on that fraction passing the 3/4-inch sieve. If prolonged dry weather prevails during the earthwork and foundation installation phase of construction, a somewhat higher(up to 10 percent)fines content will be acceptable. Material placed for structural fill should be free of debris, organic matter,trash and cobbles greater than 6 inches in diameter. The moisture content of the fill material should be adjusted as necessary for proper compaction. Suitability of On-Site Soils as Fill On-site Sinclair soils should not be used as structural fill. In general,the native soils (shotty loam)encountered on the site may have more than 10 percent fines (material passing the US No. 200 Sieve)and are not suitable for use as structural fill. FOUNDATION SUPPORT 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 soils bearing capacity of 2,000 psf(pounds per square foot)for combined dead and long-term live loads in areas of dense to very dense soils. The weight 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. 10011 Blomberg Street SW, Olympia,WA 98512 9 Phone#: (360) 7544612 Fax#: (360) 7544848 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 0.40 be used to calculate friction between the concrete and the underlying soil. 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 inch or less. Most of the settlements should occur essentially as loads are being applied. However, disturbance of the foundation sub-grade 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 3 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, particularly where adhesives are used to anchor carpet or the 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. SITE DRAINAGE Surface water runoff should be controlled by a system of curbs,berms,drainage swales,and/or catch basins,and conveyed to the bottom of the slope. We recommend that conventional roof drains be installed for the home and garage. The roof drain should not be connected to the footing drain. All footing drains should be placed with the invert below the bottom of the footing. All drains should be conveyed to the bottom of the slope. Stormwater runoff from the site, roof and hard surfaces,will be collected and directed to the base of the slope. We do not expect any adverse affects on the recharge condition of the groundwater system. Irrigation to lawn areas should be closely monitored. LINIITATIONS We have prepared this report for the use of Michael and Linda Fish and members of their design team,to use in the 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. Sufficient consultation with our firm during construction should continue to confirm that the conditions encountered are consistent with those indicated by our observations,to provide recommendations 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 our specifications. 10011 Blomberg Street SW, Olympia,WA 98512 10 Phone#: (360)754-4612 Fax#: (360)754-4848 GEOTECHNICAL TESTING LABORATORY If our analysis and recommendations are followed, we do not anticipate any on site or off site impact from the construction. It is our conclusion that potential landslide hazards from the landslide area can be overcome so as not to cause harm to property,public health and safety, or the environment. The scope of our services sloes 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 types 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, GEOTECH)NII�CAL TESTING LAB Harold Parks, L.G., L.E.G. _ Senior Engineering Geologist p iAIROL©MR1tS `, 10011 Blomberg Street SW, Olympia,WA 98512 11 Phone#: (360) 7544612 Fax#: (360) 754-4848 GEOTECHNICAL TESTING LABORATORY Filter fabric material in continuous rolls. Use staples or wire rings to attach fabric to wire. Wire mesh support fence for filter fabric 2 ft. Ground surface IF 5 ft. A -- 77� 2.5 ft. 6 ft. max. Bury bottom of filter material in 8 2 in. by 2 in. wood posts. in. by 12 in.trench Standard or better or equivalent Wire mesh support fence (to be located on the downhill side of the filter fabric) 6 in. Filter fabric material 2 ft. 5 ft. Provide washed gravel backfill, '/a in. 12 nl. 17TI7 to 3 in. in trench and on both sides of filter fence fabric on the surface —0. 8 in. min. Bury bottom of filter material in 8 in. 2 in. by 2 in. by 5 ft. wood posts by 12 in.trench Standard or better or equivalent SILT FENCE DETAIL Not to scale 10011 Blomberg Street SW, Olympia,WA 98512 12 Phone#: (360) 7544612 Fax#: (360) 7544848 GEOTECHNICAL TESTING LABORATORY Gootochnicol General dotes 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/ft2 Qp: Penetrometer value,unconfined compressive strength, lbs/ft2 V: Vane value,ultimate shearing strength,lbs/ft2 M: Water content,% LL: Liquid limit,% PI: Plasticity index,% D: Natural dry density, lbs/ft3 NW: 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/ft2) 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 10011 Blomberg Street SW,Olympia,WA 98512 Phone#:(360)754-4612 Fax#: (360)754-4848 UEO'I'EC;HNIC;AL I L+'SULING LAt3UKATUKY VICINITY MAP ii r Iwt 1J fJ/ � � 1 } roe 1 1 / 4 Dougall Pol it. 1 G ter•• -f r rr �• / Figure 1 ' 10011 Blomberg Street SW,Olympia, WA 98512 Phone#:(360)754-4612 Fax#: (360)754-4848 O WELL 30 i 0 / l 36 EN E 10 s 6 4 _ \ \ NORTH \ SCALE 1'-4U 2 \ C.I.0 DANM ASSUMED THIS IS NOT A SURVEY 0 10 20 30 40 0 N ERI G P ASS A E PROJECT NAME: Date:09WP2003 SCALE,Ik h•40%d Geotechnical Testing Laboratory FISH SITE Dedgned by LL Drawn by:LL Geotechnical Services 10011 8bmberg SLSW 425 RALISCHERT Checked by LL QA/QC � Olympia,WA M12 PARCEL 121181300011 Dwg#.Oe03-W Phone:(,60)7544612 FIGURE 2 Testing Services F-.(380)754-4848 Mason County Department of Planning Building I * 411 N. 5th Street * P.O. Box 279 Shelton, Washington 98584 * (360) 427-9670 April 5, 2004 TO: Mason County Hearing Examiner FROM: Planning Staff—Diane Marcus Jones RE: Variance from the Mason County Resource Ordinance (VAR2004-00008) SUMMARY: The request is for a variance from the Resource Ordinance to reconstruct and expand an existing cabin and provide a garage addition, partially within the footprint of the existing structure. The existing structure is located in a protected buffer of a Type IV stream and associated wetlands as well as, a Type I Shoreline buffer along Pickering Passage in the Grapeview area. The project involves replacing the existing 1,100 square foot structure with a house and garage totally 2, 472 square feet. The new structure proposed would be placed 50' from the marine shoreline bluff and 27 feet from the Type IV stream. The existing structure is 55 feet from the bluff and 16 feet from the stream. The Squaxin Tribe commented on the Habitat Management Plan. STAFF REPORT 1. Introduction. This report evaluates a request for a variance from the Mason County Resource Ordinance No. 77-93, specifically the reconstruction and expansion of a cabin from 1,100 square feet to a total of 2,472 square foot home and garage within a type IV stream buffer and Type I saltwater shoreline buffer. II. Applicant: Michael and Linda Fish III. Property Location. 425 Rauschert Rd. Grapeview, WA. Parcel#121181300011. IV. Evaluations. A. Characteristics of the site. The subject property, approximately 2.5 acres, is located off Rauschert Rd. in the Grapeview Loop area. The property is slightly fan shaped with the southern boundary line fronting the shoreline approximately 120' in width, the northern boundary line approximately 230' in width. The parcel measures a little over 600' in length. The cabin is situated on marine bluff overlooking Case Inlet/Pickering Passage. A type IV stream and associated wetlands is located to the west of the cabin,, the entire length of the property eventually draining into the Pickering Passage. An active feeder bluff is located between the marine shoreline and the upland area. A pathway leads from the cabin down to a deck area and the shoreline. A portion of the shoreline is bulkheaded, adjacent to the deck area. B. Characteristics of the area. The lots to the east and west are similar to the subject property, sparsely developed containing one cabin or residence located on the marine fs fronting the shoreline. The adjacent property to the east, approximateI ---�lelongs to the Rauscherts, the homesteaders in the area, with one cabin and am. The adjacent property to the west contains a residence approximately 40 feet from the subject property'slboundary line and shares a common shoreline,with both properties bulkheads adjoining one another. Further to the west, approximately 500' from the subject property's western property line is subdivision called Mountain Shores. The subdivision is 40 lots,primarily second homes and recreational cabins. C. Comprehensive Plan Designation. The Mason County Comprehensive Plan designation for the site is Rural Residential 5. D. Date of application. The planning department asserts that applicant is vested as of the date of their completed application March 3, 2004. E. SEPA Compliance. This activity is SEPA exempt per WAC 197-11-800 (1), (i). F. Other Permits or Approvals. The proposal will require a Mason County Building Permit for the garage and addition construction. The proposal required review and comment by Washington Department of Fish and Wildlife and the Squaxin Tribe. Notification was sent on March 3, 2004. A 28-day review period followed. Comment was received in writing from Michelle Stevie, biologist for the tribe. Ms. Stevie's letter is attached (see exhibit--). Ms. Stevie's comments were focussed on the opportunity for the applicant's to seek alternative placement of the structure tha4T oposed so as to not further decrease nearshore habitat f inction,Jn-addi!Re_n_ increased" encroachment on feeder bluff. Ms. Stevie's also stated her concern that steps should be taken in development planning such that, in the future, it will not be necessary to construct bulkheads to protect residences abutting the shoreline. Notice of Public Hearing was published in the Shelton Journal on March 18, 2004. V. Analysis: The specific request is a variance from the Mason County Resource Ordinance (MCRO No. 77-93), Fish and Wildlife Conservation Areas, Chapter 17.01.110, Table 3,which provides specific buffer and building setback dimensions from regulated water bodies and Section 17.01.150, Variances from Standards, which establishes variance procedures and criteria. The regulated water bodies on site are a Type IV stream to the west of the cabin, and the shoreline of Pickering Passage to the south. The required buffer setback for a Type IV stream is 100 feet plus 15 foot building setback for a total of 115 feet setback from the stream per Resource Ordinance Fish and Wildlife Habitat Conservation Area Chapter 17.01.110. Stream typing is per Washington Department of Natural Resources stream typing criteria and planning staff field observations. The minimum shoreline setback under the requirements of the Mason County Shoreline Master Program (SMP)was determined to be the default urban shoreline setback of 15'per SMP chapter 7.16.080. Greater setbacks prevail, however through the Mason County Resource Ordinance, Fish and Wildlife Conservation Areas Chapter 17.01.110, Table 3. Setbacks from the shoreline were derived using the shoreline common line procedure. Setbacks on curved shorelines are derived using an average of the two adjacent residences setbacks. In this instance, where no residences are located within 150' of the property to the east, a standard 100' buffer is required as measured from the OHWM for new development. A residence to the west is located 65' from the OHWM. The average shoreline setback was determined to be 82.5 feet. almost die-entire site is within the Stream buffer and a: -of-it is within the shoreline buffer. The addition, of approximatelyl, 372 square feet to the existing 1,100 cabin is proposed at approximately 50' from the marine shoreline bluff and 27 feet from the Type IV stream. The existing structure is 55 feet from the bluff and 16 feet from the Type IV stream. The proposed addition will be five feet closer to the marine shore and I6 feet further from the Type IV stream. Section 17.01.110.G.c. of the Mason County Resource Ordinance states that"new residential construction ...is not permitted within FWHCA or its buffer, except...as approved through a variance or reasonable use exception." Staff has been instructed that the reasonable use exception may only be pursued after the variance option has been exhausted. Section 17.01.120.Q. states that"except when application from this Chapter would deny all reasonable use of a site, an applicant who seeks an exception from the regulations of the Chapter shall pursue a variance as provided in Section 17.01.150. Section 17.01.110.G.1 requires that a Habitat Management Plan (HMP)be prepared in association with the proposed development. The HMP shall consider measures to preserve and protect wildlife habitat and shall identify how the impacts from the proposed use or activity will be avoided or mitigated through habitat mitigation. Xtl-e 44 VI. Variance Criteria. Mason County Resource Ordinance Fish and Wildlife Conservation Areas Chapter 17.01.110 details stream and saltwater buffer requirements and the content of the Habitat Management Plan. Variances from Standards chapter 17.01.150 establishes variance procedures and criteria. Variance Review Standards Section 17.01.150 (E),provides that no variance shall be granted unless the County makes findings of fact showing that the following circumstances exist: 1. The granting of the variance shall be consistent with the purpose and intent of this Chapter and conditions shall be imposed to ensure compatibility with surrounding conforming uses. Staff Response: The general purposes of MCRO 77-93 are to protect natural resources, and critical areas, and establish uniform processes to review land use/ development proposals in critical areas. The purpose of a variance,per MCRO 77-93, section 17.01.150 is to allow the County to consider requests to vary or adapt certain numerical standards, where strict application of said standards would deprive owners of reasonable use of their property. Regarding the proposed expansion of the cabin and new garage: Staff finds that the existing cabin could be replaced/reconstructed in the existing footprint, plus possibly enlarged an additional 10 percent, providing that such an expansion does not increase any intrusion into the aquatic management area or buffer. In addition vertical expansion of the structure would be allowed without a Resource Ordinance Variance, as long as the vertical expansion met County Shoreline and Development regulations. In addition, staff finds that other opportunities exist to reconstruct and expand cabin and construct a garage. The parcel is of sufficient size and configuration to construct in a way that avoids compromising much of the marine shoreline and provide less impacts to the stream buffer than as proposed by this proposal before the examiner. Section 17.01.020 outlines the purposes of the Mason County Resource Ordinance. Paragraph four states a purpose to "protect the identified critical areas in their natural functions, along with air and water quality, to sustain the County's quality of life. The fifth paragraph of this section states a purpose to "encourage creative development techniques and land use practices which help accomplish these goals". The proposal is configured to attach to the existing footprint. It is located in an area that will require removal of a few mature Douglas fir and madrona trees, and possibly cause root disturbance and damage to others, along the shoreline bluff. This area has already been heavily thinned and the removal of additional trees may further decrease habitat values and bank stability. The nearshore area of the site, as described, in the Geotechnical Report (see---), Habitat Management Plan (see---) and Squaxin tribal biologist, (---), consist of a moderately steep feeder bluff. This feeder bluff is contributing essential beach gravels through natural erosion process to augment the marine beaches. Removal of additional trees and further encroachment of the structure, as the proposal requests, may jeopardize this process. The Geotechnical report states, "evidence of minor surficial erosion, raveling and sloughing was observed on the coastal bluff at the time of our investigative visit...Significant 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 by encouraging vegetation and discouraging runoff from steep slopes." (Harold Parks 9-2003). Although, the Geotechnical Report continues to state, "no evidence of deep-seated landslide activity or significant erosion was observed at the site at the time of our investigation."Nevertheless, a less impactive location to the shoreline buffer would be to situate the expansion and reconstruction away from the marine bluff, further to the north, not closer to the bluff as indicated now. Reorienting the expansion further landward of the marine bluff will cause less likelihood that a bulkhead would be requiredlto protecf& structure. Impacts to the stream buffer would most likely still exists, since the lot width at this point is approximately 125' and the stream s lA m this area. However, this area would require little or no tree removal but may result in a separate freestanding garage rather than attached to w-^ residence. With respect to compatibility, nearby residences exist along the marine shoreline ` bluff; although it is beyond the scope of this report to determine which other t � residences may be situated on primary feeder bluffs. The nearest neighbor, to the west, is located approximately 55' from the stream and 65' from the marine shoreline. Correspondingly, the type IV stream buffer also impacts the adjacent residence to the west. Beyond, the adjacent residents,no other structures are in the immediate vicinity of this stream. If placement of the structure is approved as proposed, the shoreline commonline buffer average for future adjacent development w4auld change accordingly. -, %-- t",V r_v \ 2. The granting of the variance shall not permit the establishment of any use,which is prohibited by this Chapter. Staff Response: Variances are allowed and procedures established whereby individuals may seek relief from dimensional and performance standards provided they meet specific criteria. The proposal is for 1,900 square foot residential reconstruction and expansion and a 572 square foot attached garage,which is an allowable use. 3. The granting of the variance must be necessary for the reasonable use of the land or building and the variance as granted by the County is the minimum variance that shall accomplish this purpose. The findings shall fully set forth the circumstances by which this Chapter would deprive the applicant of a reasonable use of his land. Mere loss in value shall not justify a variation. Staff Response: A variance would be required to allow for the proposed expansion of the existing shoreline cabin and garage, as the proposed setbacks and buffers from the unnamed type IV stream and Pickering Passage shoreline do not meet the minimum requirements of MCRO chapter 17.01.110. The existing cabin is approximately 1,100 square feet, and the variance request is to add approximately 800 square feet of living space and a 572 square foot garage. A 360-foot section of the cabin footprint will be abandoned and replaced as proposed. These additions would lead to a more than doubling in size of the existing structure. Historically, the property has been for recreational use and the cabin as a vacation homesite. Accordingly, staff has no knowledge that the use of the site and structure would change at this time. As mentioned the existing structure is approximately 1,100 square feet, and the total pproxiin to size of the p roposed structure would be 2,472 square feet. 7�ccarding to he variance application'the purpose of this variance request is to make improvements o an existing older cabin. Although this request seems reasonable, it has not been shown in the variance application how this proposal is the minimum that accomplishes this purpose. 4. The granting of the variance shall not impair or substantially diminish property values of surrounding neighborhood properties. Staff Response: The garage and residential addition will be new and built to current codes. They would add value to this and surrounding properties. ` 5. The granting of the variance shall not confer on the applicant any special privilege that is denied by this Chapter to other lands or buildings in the same designation. Staff response: Variances are contemplated and procedures are established by the provisions of Chapter 17.01.110 (D)(2). However, the granting of this variance appears to afford the applicant the privilege of a near doubling of footprint and constructing in a suboptimal location VII. Conclusions. Based on the proposal as presented and discussed herein, the request for expansion of the existing shoreline cabin and construction of garage, appears to be inconsistent with the variance criteria detailed in Section 17.01.150. Although staff recommends denial of the current proposal as configured,portions of the request appear to be reasonable. The Mason County Resource Ordinance allows a 10%increase in the footprint of existing non-conforming structures, so some expansion would be allowed. It should be noted that staff would likely be more supportive of the expansion of the existing structure, if the configuration and location of the expansion would be as landward of the marine shoreline bluff as possible. VIII. Conditions: If the variance is approved staff recommends the following conditions. 1. Individuals shall be required to control erosion during construction of the proposed addition,removal of vegetation shall be avoided and any areas disturbed within the construction zone shall be restored to prevent erosion and other environmental impacts. 2. The existing natural vegetative buffer and wetland adjacent to the stream shall remain undisturbed by any construction and/or development on the parcel. This area shall be marked off to protect it from disturbance including from any heavy equipment. 3. Provisions for the Shoreline Bluff buffer plantings as set forth in the Habitat Management Plan(HMP) and planting plan shall be a condition of this project's approval, and must be completed prior to final inspection of the addition. If proposed construction extends beyond one construction season, applicant may be required to complete segmental implementation of the plan prior to that time, for resource protection and mitigation. 4. Provisions for the Riparian Buffer restoration should incorporate supplemental plantings as set forth in the Habitat Management Plan. Mitigati dshouAd a so address the nearshore/esturary interface portion of the stream, additionho the removal of the concrete dam structure located within the stream channel. These measure a-ted as a condition o t is project's approval. 5.Monitoring of the site will begin the first fall following tree plantings and maintained on a seasonal basis for the duration of three years. 6. Approval of this variance requires Mason County Environmental Health approval of a septic system and hook-up within 60 days of final variance approval. 7. Wintering bald eagle may be present near the site between October 31 and March 31. It is recommended that high noise level construction be minimized during these dates. It is also recommended that the Washington Department of Fish and Wildlife be apprised of any activity. 8. The recommendations and setbacks as set forth in the Geotechnical Report shall be a condition of this project's approval. IX. Choice of Action 1. Approval. 2. Approve with conditions. 3. Deny(reapplication or resubmittal is permitted). 4. Deny with prejudice (reapplication or resubmittal is not allowed for one year). 5. Remand to for further proceedings and/or evidentiary hearing in accordance with Section 15.09.090 of Title 15.