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HomeMy WebLinkAboutReport Addendum 2 parcels - BLD Engineering / Geo-tech Reports - 4/29/2024 TAHJA ENGINEERING, Inc. PLANNING PO Box 235,Hoodsport, WA 98548 (360) 877-9512 Mason County DCD Building Department 615 W Alder Street Shelton, WA 98584 Dan Rodius 240 Rockview PL Shelton, WA 98584 Re; Geotechnical Report Update/Addendum 360 Kokanee Ridge DR Hoodsport, WA 98548 Parcel No.: 42216-51-00121 Mason County Permits: MEP2014-00026, GE02014-00034 DIS2012-00254/BLD2013-00013 SWG2013-00189 In 20141 authored a geotechnical report for two adjacent properties located in the plat of Lake Cushman, Division 10. My client was Charles& Virginia Hussey. The parcel numbers were 42216- 51-00120&42216-51-00121. Mr. Rodius has acquired parcel number 42216-51-00121 and wishes to develop the property with a residential structure. I've visited the property twice this year. During the past ten years the properties have not been altered and are essentially in the same condition as they were ten years ago. Mr. Rodius has asked me to update the report(s)I authored ten years ago. Ten years ago a neighbor(Morrow)expressed a concern regarding the removal of trees from the downslope on the Hussey property, but they didn't provide any documentation supporting their concerns. I feel my original geotechnical report still is pertinent and should be acceptable as I originally authored it. Please feel free to contact me if there are any questions or concerns regarding this analysis or my findings. Sincerely, $of Water ECIS 18VLV �ssIONAL IS Alan A. Tahja, PE File:C:Trojecus Pdcifec Builders-Rodius Geo-Add 1 of 1 4/29/2024 Mason County Department of Community Development Submittal Checklist For a Geotechnical Report Instructions: This checklist must be submitted with a Geotechnical Report and completed, signed, and stamped by the licensed professional(s)who prepared the Geotechnical Report for review by Mason County pursuant to the Mason County Resource Ordinance. If an item found to be not applicable,the report should explain the basis for the conclusion. Applicant/Owner Charles&Virginia Hussey Parcel ft 42216-51-00120&00121 Site Address 340 N Kokan"Ridge Drive,Hoo& 221L Washineton 98W (1) (a)A discussion of general geologic conditions in the vicinity of the proposed development, Located on page(s) Paves 1-4 (b) A discussion of specific soil types Located on page(s) Pages 2,3.4,5&6 (c) A discussion of ground water conditions Located on page(s) Page 2 (d) A discussion of the upslope geomorphology Located on page(s) Page 2 (e) A discussion of the location of upland waterbodies and wetlands Located on page(s) Page 2 (f) A discussion of history of landslide activity in the vicinity,as available in the referenced maps and records Located on page(s) Page 3 (2) A site plan which identifies the important development and geologic features. Located on Map(s) Pisa Sheets 1 &2&3 (3) Locations and logs of exploratory holes or probes. Located on Map(s) Plan Sheet 3 (4) The area of the proposed development,the boundaries of the hazard,and associated buffers and setbacks shall be delineated (top, both sides,and toe)on a geologic map of the site. Located on Map(s) Plan Sheets i&2 (5) A minimum of one cross section at a scale which adequately depicts the subsurface profile,and which incorporates the details of proposed grade changes. Located on Map(s) Pion Sheets 4&5 and GALENA Stability Analysis oases 1 &3 (6) A description and results of slope stability analyses performed for both static and seismic loading conditions. Analysis should examine worst case failures. The analysis should include the Simplified Bishop's Method of Circles.The minimum static safety factor is 1.5, the minimum seismic safety factor is 1.1.and the quasi-static analysis coefficients should be a value of 0.15. Located on page(s) Pages 5-6 and GALENA Stability Analysis Printout pages 2&4 (7) (a)Appropriate restrictions on placement of drainage features Located on page(s) Page 6 (b) Appropriate restrictions on placement of septic drain fields Located on page(s) Page 7 (c) Appropriate restrictions on placement of compacted fills and footings Located on page(s) Page 7 Page 1 of 2 Form Effective June 2008 Disclaimer. Mason County does not certify the quality of the work done in this Geotechnical Report. Printed From Mason County DMA drip'%°ems rrcrr�ksa^G;�+~:t�r;r:iy LfY'IS (d) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) PaLyc 6 (e) Recommended setbacks from the landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Located on page(s) Page 6 (8) Recommendations for the preparation of a detailed clearing and grading plan which specifically identifies vegetation to be removed, a schedule for vegetation removal and replanting,and the method of vegetation removal. Located on page(s) P8se 7 (9) Recommendations for the preparation of a detailed temporary erosion control plan which identifies the specific mitigating measures to be implemented during construction to protect the slope from erosion, landslides and harmful construction methods. Located on page(s) Page 7 (10) An analysis of both on-site and off-site impacts of the proposed development. Located on page(s) Pace 7 01) Specifications of final development conditions such as, vegetative management,drainage, erosion control,and buffer widths. Located on page(s) Page 7 (12) Recommendations for the preparation of structural mitigation or details of other proposed mitigation. Located on page(s) Pa8es7 (13) A site map drawn to scale showing the property boundaries,scale, north arrow,and the location and nature of existing and proposed development on the site. Located on Map(s) Plan Sheets 1,2&3 I, Alan A.Tahia P E hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnicallgeological engineering or a geologist or engineering geologist licensed in the State of Washington with special knowledge of the local conditions. 1 also certify that the Geotechnical Report, dated 9/16/2013 and entitled Charles&Virginia Hussey Geotechnical Resort meets all the requirements of the Mason County Resource Ordinance, Landslide Hazard Section, is complete and true,that the report demonstrates conclusively that the risks posed by the landslide hazard can be mitigated through the included geotechnical design recommendations,and that all hazards are mitigated in such a manner as to prevent harm to property and public health and safety. (Signature and Stamp) �of •fir 54 fi 11 i\ STs� �`9slONAL$�G1 Page 2 of 2 Form Effective June 2008 Disclaimer Mason County does not certify the quality of the work done in this Geotechnical Report. Printed From Mason County DIIIVIIS I'driled frarn Mason Countyt D Y1u TAHJA ENGINEERING, Inc. PO Box 235,Hoodsport, WA 98548 (360) 877-9512 Mason County DCD Planning Division PO Box 279 Shelton, WA 98584 Charles&Virginia Hussey PO Box 1487 Hoodsport, WA 98548 (360)877-9419 cell(360) 797-7958 RE: Geotechnical Report 340 N Kokanee Ridge Drive Hoodsport, WA 98548 Mason Co.Prcl No.s; 42216-51-00120&00121 Mason Co.Case No.s DIS2012-00254 BLD201340013 Mason County's geotechnical document review process will determine that the proposed Hussey residential property improvements will result in encroachment inside the 50-foot vegetated Hazard Area Buffer required under Resource Ordinance 17.01.100. Stability analysis of the slope below the proposed building location(s)indicates that the structure(s)will satisfy Mason County safety requirements,and the addition of a residence will not result in any adverse effects. Therefore,on behalf of the Husseys, I request that a reduction in the Landslide Hazard Area buffer required in Section 17.01.100 be reduced to as little as zero(0)feet to allow the construction of a residence as promoted in my site plans and geotechnical report dated 9/16/13. Sincerely, WAg a z,D `�fONAL��G1 Alan A. Tahja,P.E. File:C:1Pr rUlume3AHA BeBer Reduction Rq I of 1 9/16/2013 l�r¢n � ,0! V C3 ya w_ ,>a a t-0 cry y C`Y- ed o =tvias n Ov of,t.3hr' TAHJA ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 Mason County DCD Planning Division PO Box 279 Shelton, WA 98584 Charles&Virginia Hussey PO Box 1487 Hoodsport, WA 98548 (360)877-9419 cell (360)797-7958 RE: Geotechnical Report 340 N Kokanee Ridge Drive Hoodsport, WA 98548 Mason Co. Prcl No. 42216-51-00120& 00121 Mason Co. Case No.s DIS2012-00254 BLD2013-00013 INTRODUCTION I was contacted in August of this year by Mr.Charles Hussey who requested my investigation and documentation of slope stability and landslide hazard issues relating to the permitting and development of his residential properties identified as Lake Cushman Division 10,Lots 120& 121. Lot 120 was improved in the past with a residence which was destroyed by fire in June or July of 2012. That lot's address is listed as 340 N Kokanee Ridge Road,Hoodsport,Washington. I've visited the properties in August and September of this year to collect topographic information and verify measurements and feature locations. Measurements were made using a Spectra T5415 Total Station and Range pole,a Sokkia model No. 8047-55 inclinometer, 100 foot and 300 foot long fiberglass surveyor's tapes and other field equipment common to surveying. Software employed in creating a site plan and writing this report included AutoCAD 2006,a Terrain 3-d contour modeling program,GALENA Slope Stability Analysis software,and Microsoft Office Word 2003. The Hussey properties currently both have Onsite Septic Systems with double compartment septic tanks and gravity drainfields.Approximately a third(36%)of Lot 121 and approximately 27%of Lot 120 is within 50-feet of slopes ranging from 601/6 to approximately 80%located along the northerly property lines of each lot.The"Hazard Area(s)"surrounding the property and the County's 50-vegetated buffer line are identified on the attached plan sheets. The septic tank locations shown on the attached site plans are accurately located,but the exact extent of the drainfield beds or trenches has not been determined but are in the general areas shown on the attached plans.Property utilities are served from southerly lot corners along N Kokanee Ridge Drive including communications,electric power and Lake Cushman Community j water. I ' t C:T, ry�cev-tr�r �,,of 8 9/16/2013 Printed FrOF% o bounty DM, f Printed from Mason COLnty DMS TAHJA ENGINEERING,Inc. PO Box 235, Hoodsport, WA 98548 (360) 877-9512 Because of the steep slopes(>40%under Mason County terminology)on or within 300 feet of the planned development activities,Mason County is expected to require a geotechnical report to be prepared to address potential stability issues relating to the properties' developments.The following thirteen elements are required by Mason County to be addressed in geotechnical reports prepared to comply with Mason County's Critical Resource Ordinance Sections 17.01.100 through 17.01.104. 1. SURFACE AND GEOLOGIC CONDITIONS: The properties are located in the mountainous foothills of the southern Olympic Mountain range bound on their northerly boundaries by downslopes varying from 60 to 80%±. Lake Kokanee is located approximately 375 feet northwest of the Hussey properties about 120 feet in elevation below the Hussey properties. Lake Kokanee may be considered a groundwater elevation for the vicinity.The properties are located at the transition from the steep downslope to Lake Kokanee and a foothill plateau extending to the bases of Mt Washington and Mt.Elinore providing a generally flat upslope geomorphology for the sites. Both properties were improved with Onsite Septic Systems at an undocumented time.No permit records were found for either property except Mason County's Case No.;DIS2012-00013 indicating a"fire destroyed building"and a demolition permit(BLD2013-00054)to remove the debris from the demolished structure(lot 120). Lot 120 has an access driveway and cleared central area of the property,generally the yard remaining from the destroyed structure. Lot 121 has no permit records and no specific site address for this lot number. Lot 121 has an existing access driveway,parking,camping and picnicking areas,mainly in the northerly half of the lot.The southerly half the lot along N Kokanee Ridge Drive is generally in a natural condition with medium aged second growth Douglas Fir,Hemlock and Cedar trees.Understory vegetation of Huckleberry,Salal and Oregon Grape.The perimeters of both lots are generally vegetated with second growth trees and low ground cover. No streams,wetlands,or upland water bodies were found in the vicinity of the two properties. Neither driveway included a drain culvert,but the absence of ditching on the property's side of the N Kokanee Ridge Drive road keeps stormwater run-on to the properties to a minimum. A small depression was found in the southerly center of the two lots which had a natural existing relief north along the two property's mutual property line where it disperses over the steep slope to the north. Inspection of the Geologic Map of Shelton 1:100,000 Quadrangle,Washington on the following page finds the Hussey property located in an area between the Olympic Mountain foothills to the north and west and Hood Canal to the east.The map reveals that the area surrounding the Hussey property is mainly a proglacial and recessional outwash(Qgo)soil typically overlying a cemented glacial till substrate. The onsite geologic soil description is provided on the following pages. DNR OFR2003-15 Geologic Map of Shelton 1:100.000 Quadrangle.Washington PrintedF�`r:'���yojiTCount M�of8 9/16/2013 Pfinted from Mason;County DMa TAHJA ENGINEERING, Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 The Geologic Map of Shelton 1:100,000 Quadrangle reveals that the Hussey property is located in the vicinity of several contacts or fault lines identified on the map as(1) the terminus of two faults emanating from the north and terminating approximately 4 miles to the northeast of the Hussey property on the north side of Dow Mountain(2)a fault line runs southwest to northeast through Lake Cushman approximately 3'/, miles northwest of the Hussey site,and(3)a fault line which follows Hood Canal is located approximately 3'/,miles southeast of the Hussey property.The presence of these features does not represent an unusual hazard, and standard seismic analysis of the site is intended to anticipate potential tectonic impacts. Inspection of Washington State Ecology's Landslide Hazard Maps reveals that the Hussey property and surrounding areas are classified as stable,with no landslide areas,either old or recent in the Hussey property area. Further inspection and soil analysis finds the soil to be classified under the Unified Soil Classification System(USCS)as a GP-GC soil division. Soil probing revealed an approximate 3-foot deep layer of weather till (topsoil)overlying a deeper cemented glacial till substrate. /�,� Obd Qit _ opt" D.00 aD 090 Ow r"„t A` am ago Iwo aw' ' Oet Cap Clod Otp F :C:+Pro ect sey.,Geo- 1 of 8 9/16/2013 Painted r6 iMasoc)unt Printed from JVason County WAS TAHJA ENGINEERING, Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 1777-777"1 Advance outwash,late Wisconsinan(Pleistocene)--Gtaciofluvial sand and gravel and lacustrine clay,silt,and sand deposited during the advance of glaciers;sandy units commonly thick,well sorted,and fine grained.with interlayered coarser sand,gravel,and cobbles and silt rip-up lag deposits at their base;may contain nonglacial sedi- ments;generally overlain by till. Fraser Glaciation,fyashon titade Proglacial and recessional out%ash,late%,visconsinan(Pleisto- cene)—Typically poorly to moderately sorted.rounded gravel and sand with localized coarser-and ftner-grained constituents;titholosi- eally varied mixture of mostly northern-provenance clasts,especially containing granitic and metamorphic mcks that identify the unit as being deposited by the Puget lobe of the Cordilleran glacier,also con- tains varying amounts of locally derived Crescent Formation basalt, and in the Mox Chehalis Creek valley,central Cascade Range— derived andesitic clads:typically shades of gray where fresh or brown where stained especially in proglocial and morainal areas;buff Raining near the ground surface:fine sand,silt,and clay constitute local overbank sediments having relatively poor ptmzieabi8ty or del- taic foreset bedding along north sides of valleys with higher permea- bility;porous and permeable enough to yield small to moderate quan- tities of groundwater;vcry poorly consolidated to loose;moderately to well-rounded clads;mostly unweathered with rare weathered reworked clasts:thickness varies and is not well known:most com- monly occupies outwash channels scoured into or through till. 2. SITE PLAN WITH IMPORTANT DEVELOPMENT AND GEOLOGIC FEATURES: A site plan showing the general topography of the area surrounding the Hussey property is attached in the appendix. 3. LOCATIONS OF LOGS OF EXPLORATORY HOLES OR PROBES: The attached site plan sheet 3 shows the locations of soil probing on and around the Hussey properties along with measured depths to the underlying glacial till layer.The undisturbed areas of the Hussey property reveal a fairly typical weathered till layer of soil ranging between 2 and 4 feet thick resting on top of a more dense and cemented glacial till soil. 4. AREA OF PROPOSED DEVELOPMENT&BOUNDARIES OF HAZARDS, BUFFERS,AND SETBACKS: The attached site plans show the locations of the existing and proposed Hussey property improvements,the locations of the hazard areas(slopes>40%),and the boundary of a 50' buffer line out from the crest and toe of the steep slopes in the vicinity of the property.20-foot building setback lines are shown on plan sheets for both properties' sideyard setbacks. A 25-foot front yard building setback line is shown from the edge of N Kokanee Ridge Dr(a private road)for both lots.5-foot sideyard Building Setback Lines are shown on plan sheet 3 for both lots.A 20' backyard building setback is shown on both lots 120& 121.An alternate 10-foot backyard building setback is shown on lot 120 as well as the 5-foot sideyard building setback lines. A 10- foot backyard building setback line on lot 120 is an acceptable geological setback location.A 20- foot geotechnical setback line on lot 121 is recommended which is roughly coincident with the existing crest of the slope on lot 121. c:Pr. I ey�Geo-Rpt _ 4 of 8 9/16/2013 MS ason Printed frorn Mason Cout~l:y 1•?l S TAHJA ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 Probing of the soils in the areas adjacent to the steep slopes typically found competent soil within 3-feet of the ground's surface within 5-feet of the crests of the steep slopes. Geologically, a building setbacks as small as 3-feet back from the horizontal breakout point of the footings on the steep slopes could be supported(see item 7 below). Lot 120.has un-documented fill inside the standard 20-ft back yard building setback. Probing along the crest of the downslope found moderately loose soils within five feet of the crest of the existing slope.Approximately 5-ft back from the crest of the downslope,probe depths to competent bearing soil(1500 psf)was typically 241'f. A 10-ft building setback from the lot's rear property line would provide approximately 10-ft of separation between the old fill slope and a foundation. Lot 121.has been cleared and graded to produce a breaking slope towards the north.The slope below the crest of the slope shown on the attached drawings begins with a modest 32%slope over an approximate 25' distance before it steepens to 60%t.A geotechnical building setback from the crest of the slope which is generally coincident with the standard 20-ft backyard building setback would be acceptable. Installing a deck out over the crest of the steep slopes would be acceptable for either property provided their foundations meet minimum IBC building code requirements for covered decks and the foundations bear on the undisturbed natural glacial till(hardpan)layer. A conjectural residence is shown on lot 121 which shows the building placed roughly along the lot's standard 20' back yard building setback line and the structure foundation.A deck is shown attached to the conjectural residence. Building setback issues aside,a covered deck located on the slope on lot 121 would be acceptable. 5. CROSS SECTION WITH PROPOSED GRADE CHANGES: A cross section view of each of the two properties is provided in the attached plan sheets as well as part of the GALENA Stability Analysis Print-Outs. Current plans for developing the property with a residential structure do no require any grade changes. 6. SLOPE STABILITY ANALYSIS: The property itself does not display any instability indicators. For stability analysis,the hillside soils were investigated and have been characterized as glacial till located at a depth of roughly 3- feet beneath the weathered till surface layer of medium dense soil(weathered glacial till). An infinitely deep glacial till was used in modeling the hillside slopes. Unified Soil Classification System(USCS)typing places the soils in a dual symbol category due to its fines content falling between 5 and 12%. The coarse element of the soil conforms to a GP classification,and the fine soils conform to a GC soil category. The soils are best described as GP-GC soils characterized with the weathered till having a soil unit weight of 123 Ibs/ft3,a phi angle of 30°,and a cohesion character of 150 lbs/ft,and the dense cemented till layer at a depth of 3 feet having a soil unit weight of 125 lbs/ft3,a phi angle of 301,and a cohesion character of 300 Ibs/ft2 or more. Lake Kokanee is located at an elevation approximately 120-feet below the building elevation on the Hussey property and may be considered the water table elevation in File:C:k 'mac lGeo-)g# 5 of 8 9/16/2013 Printed _ � M 4County M Rimed fi a►rs Masf)n Cot nbj-U S TAH3A ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 this area.The stability modeled uses a phreatic surface above the ground's surface to represent a saturated soil condition.The slope geometry and soil characteristics provide a factor of safety for the site in a static and a dynamic analysis that exceeds the County's minimum safety requirements. Analysis of the individual lots produced the following Factors of Safety(FoS); Lot 120 Static FoS 8.8 Dynamic FOS 5.6 Lot 121 Static FoS 9.6 Dynamic FOS 5.6 7. RECOMMENDED SETBACKS&DRAINAGE: Slope stability analysis indicates that the steep bank descending from the Hussey properties' northerly boundaries is stable in its current condition.Planned improvements are located inside of the County's required 50-foot landslide hazard area buffer,so a request that the proposed property improvements(residence)be allowed inside the hazard area buffer has been prepared and attached to this report for County acceptance.A 3-foot building setback from the horizontal break out point of the face of a foundation on the slope is recommended as the minimum geotechnical setback on the properties. The recommended 3' setback dimension may be measured as the horizontal projection of the bottom of the foundation footing out to the existing slope.Foundations other than foe decks should not be planned"on"the slope withoutout further foundation planning and engineering. I T 3'Separation betwem face of footing and break out point on slope.Bottoms of footings to \ bear an undisturbed till substrate. Drainage from the present site sheets to its natural drainage directions fairly evenly to the north and discharges to the greenbelt area north of the Hussey properties.Though the slope below the Hussey property is tali and steep,it is well vegetated and appears to be well drained. Runoff from the Hussey driveways should be dispersed along their lengths into vegetated areas of the properties.Runoff produced by the conjectural structures should be collected and discharged at the buildings' corners to splash blocks located at the outlets.The ground should slope downward away from the structure's foundations/walls.No concentrated stormwater discharges(pipe ends)should disperse any closer than 10-feet back from the steep slopes on the properties. Stormwater runoff collected and delivered to the northerly areas of the properties should be dispersed over as large and area as possible with a level swale(3'xIO'xl' deep),a dispersion pipe(Pipe end fitted with a"T'and two 4 to 5-foot lengths of perforated pipe installed to spread out flows delivered to them—buried or open). Dispersing runoff from the properties' developed impervious areas into vegetated areas of the property is highly recommended.An existing drainage swale runs down the length of the two F; C:t eylGeo-Rpl 6 of 8 9/16/2013 P interx F Projec\� o County TAH3A ENGINEERING,Inc. PO Box 235, Hoodsport, WA 98548 (360)877-9512 properties between them which provides readily available stormwater dispersion and delivery to the vegetated slope along the north side of the two properties. New septic systems are being considered for the two lots,typically in the southern areas of the two properties.The southerly areas of the two properties present no special geological issues, and should be able to conform to standard State and Mason county Health Regulations. 8. CLEARING,GRADING,AND VEGETATION MANAGEMENT: The planned residential property improvements are being planned in already cleared portions of the two properties.Some of the larger trees on the Hussey property are shown on the attached plans.The largest conifer trees in the available building area are 36-inches in diameter or less. It is likely the finished site will revert to native vegetation or landscaping shrubs and lawn as the owner may choose.A detailed clearing and grading plan does not appear warranted for the scope of the planned residential improvements. The currently proposed Hussey property improvements are planned to be constructed in the already cleared areas of the property.Grading will likely be restricted to standard residential foundation excavation along with modest landscaping around any finished improvements. 9. EROSION AND SEDIMENT CONTROL: Inspection of the Soil Survey of Mason County found the site to be located in an area with a Hoodsport(Hd Gravelly sandy loam)soil type,which is not identified in the County's Critical Resource Ordinance as susceptible to severe erosion when disturbed,and does not require the development of site specific permanent stormwater detention features. During the site's development with a residential structure,the construction area's downslope side should have a silt fence installed to provide sediment control and protection to down gradient properties during construction. 10. ON-SITE AND OFF-SITE IMPACTS: Construction and completion of the proposed residential improvements to the Hussey properties is not expected to result in any adverse on-site or off-site impacts.The addition of residences should not result in adverse impacts to either of the subject properties or neighboring properties. 11. SPECIFICATIONS OF FINAL DEVELOPMENT: Structure foundations should be installed no less than 12-inches below the surrounding ground's level.Footings installed less than 3-feet back from the crests of the site's steep slopes should be excavated down to the consolidated till soil layer(hardpan).Footings installed more than 3-feet back from the slope's crest may be installed with a standard height stem wall and footing, provided any weak soils are removed and replaced with a controlled density fill such as compacted crushed rock or lean concrete. 12. RECOMMENDATIONS FOR THE PREPARATION OF STRUCTURAL MITIGATION OR DETAILS OF OTHER PROPOSED MITIGATION: Modeling of the slopes in the proximities of the proposed residences indicates that the locations are safe,and no structural measures appear necessary.No structural fills are being proposed for the structures' installation,and no excavation on the steep slopes is being planned. F C:iProjec ' seylGeo-RM 7 of 8 9/16/2013 f �t eE6 n County PrInte-d from A"asvn crw°uvh"D*,As- TAHJA ENGINEERING, Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 13. SITE PLAN WITH THE LOCATION OF EXISTING AND PROPOSED DEVELOPMENT ON THE SITE: A site plan is attached as an appendix to this report and is hereby made a part of this report along with the cross section view of the property and the stability analysis printouts. Summary&Conclusions: The proposed Hussey property improvements can be developed according to the owner's plans with minimal concerns about the site's stability. Please feel free to contact me if there are any questions or concerns regarding this report or my findings. Sincerely, ot� RA ,t6 r Ile -s0i 4' $e�I3T �ssrONAL ECG, Alan A.Tahja,P.E. Attached: Hazard Area Buffer Reduction Request Plan Views,Cross Section Sheet GALENATM Stability Analysis Printout P �erff a k � � "' County D� f s 9/16/2013 P irA f,Dri M;, on County r-MG r 1 a i]OP Crass sewon �< D V,m DuMIM R --- Lot 202 g� /' �'-- crop Seenon " A ""°°"` Greenbelt x a� -ff A10 40% Lot 202 (So pus>ao° w x y Greenbelt e� N t� )r r Crest of approximate ; Equs the To of the b t jinzard Area. Crest of SI a approxi ttdy�� t f -� c Equals the o e r0'I and Area ��`y w` g r t 1 ' 1 1O `,� Vege ted Buffer Line �� Q Lot 124 Lots 122& 123 / t Lti t r , Lot 119 �-� to Kokanee Ride Drive __ _ L x 8 Lot 118 BV i D t- Cpj��►p �. C WA IM ¢Moon 14 �p Rr V b Opp '�4'isrig���4w�� SCALE: 1"-50' s`YrONAL E, G 0 10 )0 50 Hazard Area 560 Hazard Area . l — -— es> 40%) '----- s8o ` 570 (S}ohs-- Tl > Q z 600 PL 85. 7, �--J3azard Area ° i BH (Slopes>40%) ri Conjectural House& - 10" B F q Deck(10'back yard i 0 Fire i� % bldg setback shown). pit D Dead Tree I L I PO IT 50'HAZARD AREA + ro }g Vegetated Buffer Line i isting r �Se is syste rigi 1 w o I '— tru t e WA 36"BHD ' 5 00 �'1�► . $0 Sy J * Exykting t 0'H ARD AREA Doug Fir " Sgptic Sys / Veg tea ---- -- ��„ u b n c j Compon is d Sutler l.irte t a a tr1 i 120 / 00 SS ONAL O f,r C� > i / i 121 14 HP 3 i i5ou ir + ou�Fir 18"BHD DF with 360 Address• --� T N PL 69 72, C x - PL 9. 6 r5 " t - - _ 7q, b e ° atzee Ridg scAt.�. 1~=ao' ":BHD Brest Heigh Diameter -` Rev# l rpam TAHJA ENGINEERING,INC. SITE PLAN F*Hu ey Alan Tahja,P�E. Charles&VuWma Huswy PO Box 235 PO Box 1487 Hoodsport, WA 98548 Hoodspor4 WA 98548 3 of 5 Mason Co.Prcl No.: 42216-51-00120&0012l (360)877-9512 (360)877-9419 Cell(360)797-7958 v c � o ` A h < o a N Ivy h � -y �D°Oi r o315 ' �ap4tas gip_, O m / ' u A a rlaprS tr � m� J''rr 'OZPir1s-_ r � 1 o aur? Y�r4raS 8plg z�1a-- V ae4aaS gp18,S i i playa% j Jc f o 'I0)u4JoS `aur/a�'rS.olA 33 _ _or° r W411 2 Q ^ N aura` ��4�aSPte.S SSO 8 +P'arlurrrQ u rysrxd aui�rfl+ado� _- b - Rev# 1-aiPti- TAHJA ENGINEERING,INC. CROSS SECTION Hussey Alan Tahjo,P.E. Charles&Virginia Hussey PO Box 235 PO Box 1487 HoodWort WA 98548 Hoodspor4 WA 98548 4 o£5 Mason Ca P cl No.: 42216-51-MI20&00121 (360)877-9512 (360)877-9419 Cell(360)797-7958 Ll o Z. in i 570 0 00 i o o ^ 590 N �r t; Q N c 1 i , + st j V h It Pw'a - - itt, Fj ft "y DWc TAHJA ENGINEERING,INC. CROSS SECTION Alan Tahja,P.E. Charles&VnNi=Horsey HLO-Y PO Box 235 PO Box 1487 Hoodmod, WA 98548 HoodvpoM WA 98548 5 of Mmw Co.prel No.: 42E2 16 5-1-00120&00 121 (360)877-9512 (360)877-9419 Cell(360)797-7958 �520 __ 530 b. 00 — 540 cs — 550 CD A — 560 CA Q all 0 590- _T_ + 600 1 0 Coe) rl IL II L I I I I I I I I 1 11. Z prif;tedfrr rr kolason TAHJA ENGINEERING,Inc. PO Box 235, Hoodsport, WA 98548 (360)877-9512 Huss X-Section A-A(Lot 120)Static Stability Analysis icwLEnrw �snz eeD r O •A eC7STERg ' �S`�ONAL aso Mutt pie Stability A.nalysas Swf- G­ aao &esv� Cnb-�nrra.wmi 3S0 Fedor of S.Wy. 8.75 0 100 ZDO 1100 SOD 500 600 70D .s.r ama weo.nv raw aa FVnied. Hussey-Cushman Div IOW 120 Sim - - ff; CADoaieieMa and SatOrlaV4)wrAfWy OOO ATW* AWW FOOANO W60M L-123-0" Ta*EI7gbmft b, Galena 5.02 Analysis Results Licensee: Tahja Engineering, Inc. DATA: Analysis 1 - Static Material Properties (2 materials) ------------------- Material: 1 (Mohr-Coulomb Isotropic) - Weathered Surface Soil Layer Cohesion Phi UnitWeight Ru 150.00 30.0 123.00 1.10 Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till Substrate (Hardpan Cohesion Phi UnitWeight Ru 300.00 30.0 125.00 1.10 Water Properties ---------------- Unit weight of water: 7.00 Unit weight of water/medium above ground: 62.40 Material Profiles (2 profiles) ----------------- Profile: 1 (2 points) Material beneath: I - Weathered Surface Soil Layer 0.00 700.00 700.00 700.00 Profile: 2 (10 points) Material beneath: 2-Cemented Glacial Till Substrate 0.00 602.00 54.60 600.00 63.30 599.00 248.90 595.00 277.60 577.00 314.50 557.00 336.10 545.00 346.70 537.00 383.70 518.00 675.00 517.00 Slope Surface (11 points) ------------- 0.00 605.00 54.60 603.00 63.30 601.00 237.50 600.00 250.90 599.00 277.60 580.00 314.50 560.00 336.10 548.00 346.70 540.00 383.70 521.00 ,k: r��tfi1, c 0 X Sec.� ns uw 1 of4 9/16/2013 rint'Q'7 oM mason County DM pIrted from"Mason co4un#:Y DMS TAHIA ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 675.00 520.00 Phreatic Surface (2 points) --- 0.00 705.00 700.00 705.00 Failure Surface --------------- Initial circular surface for critical search defined by: XL,XR,R Intersects: XL: 200.00 YL: 600.22 XR: 384.00 YR: 521.00 Centre: XC: 314.34 YC! 612.50 Radius: R: 115.00 Variable Restraints ------------------- Parameter descriptor: XL XR R Range of variation: - 155.00 155.00 100.00 Trial positions within range: 12 12 12 ------------------------------------------------------------------------------ RESULTS: Analysis 1 - Static Bishop Simplified Method of Analysis - Circular Failure Surface -------------- Critical Failure Circle Search using Multiple Circle Generation Techniques Factor of Safety for initial failure circle approximation: 10.16 There were: 1079 successful analyses from a total of 1729 trial circles 650 analyses terminated due to unacceptable geometry Critical (minimum) Factor of Safety: 8.75 Circle and Results Summary (Lowest 17 Factor of Safety circles) -------------------- Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right Radius FoS 1 315.58 565.97 249.32 599.12 376.95 524.46 74.09 8.750 2 329.48 654.26 192.95 600.26 391.05 520.97 146.82 9.657 3 326.99 673.03 178.86 600.34 391.05 520.97 165.00 9.671 4 322.49 661.00 178.86 600.34 391.05 520.97 155.91 9.676 5 334.25 666.17 192.95 600.26 391.05 520.97 155.91 9.684 6 324.37 641.48 192.95 600.26 391.05 520.97 137.73 9.706 7 338.77 677.47 192.95 600.26 391.05 520.97 165.00 9.759 8 317.68 648.15 178.86 600.34 391.05 520.97 146.82 9.764 9 336.42 647.41 207.05 600.17 391.05 520.97 137.73 9.785 10 330.96 634.71 207.05 600.17 391.05 520.97 128.64 9.786 it 326.07 662.18 192.95 600.26 376.95 524.46 146.82 9.794 12 329.54 667.59 278.86 600.34 405.14 520.93 165.00 9.797 13 321.22 650.41 192.95 600.26 376.95 524.46 137.73 9.800 14 315.46 667.64 164.77 600.42 391.05 520.97 165.00 9.810 15 325.00 654.66 178.86 600.34 405.14 520.93 155.91 9.819 16 331.76 648.09 192.95 600.26 405.14 520.93 146.82 9.824 17 330.67 673.34 192.95 600.26 376.95 524.46 155.91 9.841 r File: 1P tsWH L 0 X Sec A-A ysis Pr' t 2 of 4 9/16/2013 Prined c Mason s r" y DM S Pdnteed from tAasm County DMS TAHJA ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 Hussey X-Section A-A(Lot_ 120)Dynamic Stability Anal sis GALENA vw.e aa: am eoo Mo mo _ Mul"W Sb b bty Anely- 1 aso t,waradd. BWWO s.evvrd SW%w cdetir �09RM cmcw ) 0 100 mD c .a+ana fte .awaaa Pmjpa Musser-Cushman Div 10 lot 120 DpwNc Eft CADco1-b aM SdVxQOOWWWy OOGa W4&X)O*Ma FdMalodaaM-MY L-123.9W T*0 Bowed%Inc. Galena 5.02 Analysis Results Licensee: Tahja Engineering, Inc. DATA: Analysis 1 - Dynamic Material Properties (2 materials) ------------------- Material: 1 (Mohr-Coulomb Isotropic) - Weathered Surface Soil Layer Cohesion Phi UnitWeight Ru 150.00 30.0 123.00 1.10 Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till Substrate (Hardpan Cohesion Phi UnitWeight Ru 300.00 30.0 125.00 1.10 Water Properties ---------------- Unit weight of water: 7.00 Unit weight of water/medium above ground: 62.40 Material Profiles (2 profiles) ----------------- Profile: 1 (2 points) Material beneath: 1 - Weathered Surface Soil Layer 0.00 700.00 700.00 700.00 Profile: 2 (10 points) Material beneath: 2 - Cemented Glacial Till Substrate 0.00 602.00 54.60 600.00 63.30 599.00 248.90 595.00 277.60 517.00 314.50 557.00 336.10 545.00 346.70 537.00 383.70 516.00 675.00 517.00 Slope Surface (11 points) ------------- 0.00 605.00 54.60 603.00 63.30 601.00 237.50 600.00 250.90 599.00 rim ror � $ A t` lk 3of4 9/16/2013 TAHJA ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 277.60 580.00 314.50 560.00 336.10 548.00 346.70 540.00 383.70 521.00 675.00 520.00 Phreatic Surface (2 points) --- 0.00 705.00 700.00 705.00 Failure Surface --------------- Initial circular surface for critical search defined by: XL,XR,R Intersects: XL: 200.00 YL: 600.22 XR: 384.00 YR: 521.00 Centre: XC: 314.34 YC: 612.50 Radius: R: 115.00 Earthquake Force ---------------- Pseudo-static earthquake (seismic) coefficient: 0.150 Variable Restraints ------------------- Parameter descriptor: XL XR R Range of variation: 155.00 155.00 100.00 Trial positions within range: 12 12 12 ------------------------------------------------------------------------------------- RESULTS: Analysis 1 - Dynamic Bishop Simplified Method of Analysis - Circular Failure Surface --------------------------------------------------------------- Critical Failure Circle Search using Multiple Circle Generation Techniques Factor of safety for initial failure circle approximation: 6.21 There were: 1079 successful analyses from a total of 1729 trial circles 650 analyses terminated due to unacceptable geometry Critical (minimum) Factor of Safety: 5.56 Circle and Results Summary (Lowest 14 Factor of Safety circles) ------------------- Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right Radius FoS 1 315.46 667.64 164.77 600.42 391.05 520.97 165.00 5.562 2 304.11 661.21 150.68 600.50 391.05 520.97 165.00 5.580 3 300.11 670.48 150.68 600.50 376.95 524.46 165.00 5.599 4 311.48 675.92 164.77 600.42 376.95 524.46 165.00 5.601 5 310.92 654.72 164.77 600.42 391.05 520.97 155.91 5.632 6 318.19 661.16 164.77 600.42 405.14 520.93 165.00 5.646 7 307.18 663.89 164.77 600.42 376.95 524.46 155.91 5.647 8 326.99 673.03 178.86 600.34 391.05 520.97 165.00 5.647 9 322.49 661.00 178.86 600.34 391.05 520.97 155.91 5.659 10 3C6.93 653.52 150.68 600.50 405.14 520.93 165.00 5.674 11 288.91 664.01 136.59 600.58 376.95 524.46 165.00 5.679 12 292.85 653.57 136.59 600.58 391.05 520.97 165.00 5.689 13 323.12 680.43 178.86 600.34 376.95 524.46 165.00 5.698 14 318.78 669.11 178.86 600.34 376.95 524.46 155.91 5.698 r File'CVPr " stffias L D X-ecA-A a/ysis Pwout 4 of 4 9/16/2013 Print+ From Mason County D S Printer!from Mason County DMS TAHJA ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 Hussey X-Section B-B Lot 121)Static Stability Analysis GALENA wo.►� aso VA em 75p a �.: in.ow Q• 3176 ST �, E'8gfo�8�G1 wo _ Bpi I MA*Shbibi An*- 450 Aftew A sNwmwd 400 Bwmk C:iotfwN kOW iOCIN dabw. COX 360 o too 200 3W 400 500 50o 700 P+ fd Hussey-Cushmm On 10 lnt 120 Elm- Tate E%bW inp,W_ Galena 5.02 Analysis Results Licensee: Tahja Engineering, Inc. DATA: Analysis 1 - Dynamic Material Properties (2 materials) ------------------- Material: 1 (Mohr-Coulomb Isotropic) - Weathered Surface Soil Layer Cohesion Phi UnitWeight Ru 150.00 30.0 123.00 1.10 Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till Substrate (Hardpan Cohesion Phi UnitWeight Ru 300.00 30.0 125.00 1.10 Water Properties --------------- Unit weight of water: 7.00 Unit weight of water/medium above ground: 62.40 Material Profiles (2 profiles) ----------------- Profile: 1 112 points) Material beneath: 1 - Weathered Surface Soil Layer 0.00 700.00 700.00 700.00 Profile: 2 (10 points) Material beneath: 2 - Cemented Glacial Till Substrate (Hardpan 0.00 599.00 51.40 598.00 54.90 597.00 193.10 597.00 236.70 595.00 262.00 587.00 311.30 557.00 341.40 537.00 380.70 517.00 511.00 507.00 Slope Surface (11 points) ------------- 0.00 602.00 51.40 601.00 54.90 600.00 193.10 6C0.00 236.70 598.00 File:C-) rs1H 1 X-sec B-B eau PrWOW 1 of 4 9/16/2013 Printed �o �Zaso, ounty DM Printed fyom Masan Coupty DMS TAHJA ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 262.00 590.00 311.30 560.00 341.40 540.00 380.30 520.00 511.00 510.00 675.00 520.00 Phreatic Surface (2 points) --- 0.00 105.00 700.00 705.00 Failure Surface --------------- Initial circular surface for critical search defined by: XL,XR,R Intersects: XL: 200.00 YL: 599.68 XR: 384.00 YR: 519.75 Centre: XC: 314.41 YC: 611.30 Radius: R: 115.00 Variable Restraints ------------------- Parameter descriptor: XL XR R Range of variation: 155.00 155.00 100.00 Trial positions within range: 12 12 12 ------------------------------------------------------------------------------ RESULTS: Analysis 1 - Dynamic Bishop Simplified Method of Analysis - Circular Failure Surface --------------------------------------------------------------- Critical Failure Circle Search using Multiple Circle Generation Techniques Factor of Safety for initial failure circle approximation: 10.14 There were: 1084 successful analyses from a total of 1729 trial circles 645 analyses terminated due to unacce table geometry Critical (minimum) Factor of Safety: 9.63 Circle and Results Summary (Lowest 15 Factor of Safety circles) ------------------- Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right Radius Fos 1 327.56 671.51 178.86 600.00 391.05 519.21 165.00 9.633 2 322.98 659.47 178.86 600.00 391.05 519.21 155.91 9.633 3 318.46 567.37 249.32 594.01 376.95 521.91 74.09 9.651 4 329.98 652.72 192.95 600.00 391.05 519.21 146.82 9.666 5 324.76 639.94 192.95 600.00 391.05 519.21 137.73 9.699 6 31B.09 646.61 178.86 600.00 391.05 519.21 146.82 9.703 7 330.42 665.24 178.86 600.00 405.14 518.12 165.00 9.704 8 334.84 664.63 192.95 600.00 391.05 519.21 155.91 9.709 9 319.68 666.91 178.86 600.00 376.95 521.91 155.91 9.715 10 315.94 666.12 164.77 600.00 391.05 519.21 165.00 9.720 11 321.98 648.18 192.95 600.00 376.95 521.91 137.73 9.724 12 325.74 652.30 178.86 600.00 405.14 518.12 155.91 9.725 13 326.97 659.95 192.95 600.00 376.95 521.91 146.82 9.725 14 324.14 678.23 178.86 600.00 376.95 521.91 165.00 9.730 15 314.99 655.01 178.86 600.00 376.95 521.91 146.82 9.752 fie: jectsWu= L 21 X-Sec XB is Pr mu 2 of 4 9/16/2013 Prinifec"From mason c n r DMS Printed horn Mason County DMS s TAHJA ENGINEERING, Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 Hussey X-Section B-B(Lot 121)Dynamic Stability Analysis GALENA v...em oso eoo a� rso tell SIM �. � d010� 1 4.W- Be"gW~ SW*W chWbr 400- Blau cam per/ F�i'B/II SNf►c 6.l6 350 0 t00 200 3M 4W 500 000 1W Err."Pam A, <MMW3 Hussey-Cushman Div 10 LOI 120 Dyna- 8& Th*Engkos",Inc. Galena 5.02 Analysis Results Licensee: Tahja Engineering, Inc. DATA: Analysis 1 - Dynamic Material Properties (2 materials) ------------------- Material: 1 (Mohr-Coulomb Isotropic) - Weathered Surface Soil Layer Cohesion Phi UnitWeight Ru 150.00 30.0 123.00 1.10 Material: 2 (Mohr-Coulomb Isotropic) - Cemented Glacial Till Substrate (Hardpan Cohesion Phi UnitWeight Ru 300.00 30.0 125.00 1.10 Water Properties ---------------- Unit weight of water: 7.00 Unit weight of water/medium above ground: 62.40 Material Profiles (2 profiles) ----------------- Profile: 1 (2 points) Material beneath: 1 - Weathered Surface Soil Layer 0.00 700.00 700.00 700.00 Profile: 2 (10 points) Material beneath: 2 - Cemented Glacial Till Substrate (Hardpan 0.00 599.00 51.40 598.00 54.90 597.00 193.10 597.00 236.70 595.00 262.00 587.00 311.30 557.00 341.40 537.00 380.70 517.00 511.00 507.00 Slope Surface (11 points) ------------- 0.00 602.00 51.40 601.00 54.90 600.00 193.10 600.00 236.70 598.00 Fik:C.lPro'ectjiff s L121 X-Sec a-B*Wois Priwoat 3 of 4 9/16/2013 Printed From Meson County Dies Printed from Mason Mourlj MAS r TAH3A ENGINEERING,Inc. PO Box 235,Hoodsport, WA 98548 (360)877-9512 262.00 590.00 311.30 560.00 341.40 540.00 380.70 520.00 511.00 510.00 675.00 520.00 Phreatic Surface (2 points) --- 0.00 705.00 700.00 705.00 Failure Surface --------------- Initial circular surface for critical search defined by: XL,XR,R Intersects: XL: 200.00 YL: 599.68 XR: 384.00 YR: 519.75 Centre: XC: 314.41 YC: 611.30 Radius: R: 115.00 Earthquake Force ---------------- Pseudo-static earthquake (seismic) coefficient: 0.150 Variable Restraints ------------------- Parameter descriptor: XL XR R Range of variation: 155.00 155.00 100-00 Trial positions within range: 12 12 12 --------------------------------------------------------------------------- RESULTS: Analysis 1 - Dynamic Bishop Sinplified Method of Analysis - Circular Failure Surface --------------------------------------------------------------- Critical Failure Circle Search using Multiple Circle Generation Techniques Factor of Safety for initial failure circle approximation: 6.24 There were: 1084 successful analyses from a total of 1729 trial circles 645 analyses terminated due to unacceptable geometry Critical (minimum) Factor of Safety: 5.56 Circle and Results Summary (Lowest 14 Factor of Safety circles)--------------- Circle X-Centre Y-Centre X-Left Y-Left X-Right Y-Right Radius Fos 1 300.87 668.32 150.68 600.00 376.95 521.91 165.00 5.559 2 304.51 659.69 150.68 600.00 391.05 519.21 165.00 5.567 3 315.94 666.12 164.77 600.00 391.05 519.21 165.00 5.567 4 312.38 673.74 164.77 600.00 376.95 521.91 165.00 5.572 5 307.95 661.71 164.77 600.00 376.95 521.91 155.91 5.615 6 318.93 658.82 164.77 600.00 405.14 519.12 165-00 5.624 7 311.33 653.19 164.77 600.00 391.05 519.21 155.91 5.628 8 289.56 661.86 136.59 600.00 376.95 521.91 165.00 5.631 9 307.55 651.17 150.68 600.00 405.14 518.12 165.00 5.642 10 296.42 655.40 150.68 600.00 376.95 521.91 155.91 5.657 11 293.17 652.04 136.59 600.00 391.05 519.21 165.00 5.665 12 327.56 671.51 178.86 600.00 391.05 519.21 165.00 5.676 13 322.98 659.47 178.86 600.00 391.05 519.21 155.91 5.683 14 319.68 666.91 178.86 600.00 376.95 521.91 155.91 5.686 ,1e: tat 21 X-&c B-e $is PrWOW 4 of 4 9/16/2013 Prin E om asan aunty DMS Printed frorn Masm County OMS