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HomeMy WebLinkAboutGEO2009-00003 BLD2009-00010 - BLD Engineering / Geo-tech Reports - 1/26/2009 C-T�Fo a��_��� 3 Mason County Review Checklist For a Geotechnical Report Instructions: This checklist is intended to assist Staff in the review of a Geotechnical Report. The Geotechnical Report is reviewed for completeness with respect to the Resource Ordinance. If an item is found to be not applicable, the Report should explain the basis for the conclusion. The Report is also reviewed for clarity and consistency. If the drawings, discussion, or recommendations are not understandable, they should be clarified. If they do not appear internally consistent or consistent with the application or observations on site, this needs to be corrected or explained. If resolution is not achieved with the author, staff should refer the case to the Planning Manager or Director. Applicant's Name: (;f-LCA) 0 bi<0 CS Permit# F1,p 0,0N-0 0010 Parcel # '3 - , Date(s) of the Document(s) reviewed: (1) (a)A discussion of gener geolo is conditions in the vicinity of the proposed development, OK? `� Comment: (b) discussion of specifi oil types OK? Comment: CL (c) A discussion of ground at conditions OK? �, Comment: sce (d) A discussion of the ups geomor holog OK?j Comment: 3 � (e) A discussion of the to ti n of upland waterbodies and wetlands OK?�_Comment: C-1- ) (f) A discussion of history o landslide activity in the activity in the vicinity, as available in the ref renced maps and records OK? Comment: cD- :,yti_ C F-A,)u.6 y7v. (2) A site plan which identifi s the imp rtan development and ge I c feature OK?�_Comment: ' J (3) Locations and logs of ex Io ory holes or probes. OK? V Comment: Sic 1�-Q g (4) The area of the proposed deAlopment, the lioundaries of the hazard, and associated buffers and setbacks shall be delineated(to . both sides, and toe)o!�geologic map of the site. OK? V Comment: (5) A minimum of one cross section at Ascale which 4de uately depicts the subsurface profile, and which incorporates the details of proposed grade changes. OK? Comment: 10Lf�u- (6) A description and results of slope stabi'ty 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 j naLois coe ients should be a value of 0.15. OK?�_Comment: > > (7) (a)Appropriate restrictions ceme�t�of drainage features OK? _v Comment: t - (.�Gv� (b) ro Hate restrictions on placement of septic drain fields OK? Comment: S -c- 3� � (c) Appropriate restrictions on placeme t of compacted fills and footings OK? !- Comment: c (d) Recommended buffers from t e landslide hazard areas shoreline bluffs and the tops of other slopes on the property. Page 1 of 2 Form Effective June 2008 OK? � Comment: 1bU,a Cv, rBYW. U0 i 0 �' 3 (e) Recommended setbacks from the I ndslide azhazh and areas shoreline bluffs and the tops of her slopes on the property. OK? Comment: (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 re al. , l OK? _Comment: 1 (9) Recommendations for the pr paration of a detlailed temporary erosion control plan which identifies the specific mitigating measures to be implemented during construction to protect the slope from erosion, landsl'des and harm onstruction methods. OK9 Comment: 3 (10) An analysis of both on-site d off-site im s of the proposed development. OK? � G Comment: -J )� (11) Specifications of final develo enYn t condi ions such as, vegetative management, drainage, P P 9 9 9 erosion control, and buffer widths. OK?-'--,1 Comment: Pam, 79 1 l � (12) Recommendations for the pr�i n of struc ural 6tigation or details of other proposed mitigation 1 OK? Comment: (13) A site map drawn to scale showing the property boundaries, scale, north arrow, and the location and nature of existing and pm posed development on the site. OK?�_Comment: � (iy Are the Documents signed and stamped? Type and #of License: � P��ZttiR-Q If not approved, what is the next action/recommendation for further action? Reviewed by , on Time spent in review. SEqQj4D REVIEW/U DATE: ' Reviewed by on l Time spent in second review: THIRD REVIEW/ UPDATE: Reviewed by on Time spent in third review: Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment Page 2 of 2 Form Effective June 2008 e ' Mason County Department of Community Development 6-1r) -�Mn-06003 bub"Wit Checklist For a Geotechnical Repo instructions: -- - - - - - - - — - ---- - ------------- -- Trits checklist rnusi ue submitted wtth a Geotechnical Report and completed, signed, and stamped by the ircensed profes,kor.al(s) who prepared the Ge3technical 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 tt~e conclusion. ApplicanVOwner tic I NN FKOES parcel * 3ZZ3 ZSZ2 00/Z site Address /0/ E, PI E s7 , (,�"/o,�,1 WA 9�S97, (1) (a) A discussion of general geologic conditions In the vicirny of the proposed development, Located on oagats) 3 e F .3 (/ ) (b) A d;scussicn of spednc soil types Located on page(s) .' a F 3 (c) A discussion of ground water conditions Located on page(s) 3 of 3 ( /) (d) A discussion of the upsiope geomorphology Located on page(s) 3 or 2 (a) A discussion of the location of upland waterhodies and wetlands Located on piase(s) 3 o F 3 ' ' (1) A discussion of history of landslide activity in the activity in the vicinity, as available in the referenced maps anti r—mc Located on pagers) ,l�T7ACNME�y7CL�s'T A46,6) (2) A site plan which identifies the important development and geologic features. Located on Map(s) /e F 3 (3) Lrc�catlons and lops of exploratory holes or probes Located on Map(s) / e F 3 4) T+!e area of the proposed development, the boundaries of the hazard, and associated buffers ano setbacks shall be delineated (lop, both sides, and toe) on a geologic map of the site. L acated on Map(s) / a F 3 (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) / OF S (6) A description and results of slope stability analyses performed for both static and seismic loading Weditions. Analysis should examine worst case failures. The analysis should include the S,Impliied bishop's Method of Cl.cles. The minimum static safety lactcr is 1.5, the minlmum seismic safety factor is 1.1. and the quasi-static analysis coefflents should be a value of 0.15. Located on Me(s)__ Z o F,3 (7) (a)Appropriate restrictions on placement of drainage features Local&.] on page(s) _/ p F_? (b) Appropriate restrictions on placement of septic drain fe!ds Located on page(s) ! / of 3 !(;) Appropriate restrictions on placement of compacted Ns and footings Located on page(s) QF 3 Page 1 of 2 Form Effective June 2008 Disclaimer: Masan County does not certify the quality of the work done in this Geotechnical Report. \AA ► !�►�t= M-U 1�Pam' l_ a a id) Recommended buffers from the landslide hazard areas shoreline bluffs and the tops of other slopes on the properly. Located on page(s) I/ go F 13, (e) Recommended setbacks from the landslide hazard areas shoreline tAuKs and the tops cf other slopes on the property. Located on page(s) / OF (5) Recommendations for the pieparatlon of a detailed clearing and grading plan which speriiivally Idendifies vegetation to be removed, a schedule for vegetation removal and replanting, and t!ie method of vegetation remove! Located on page(s) (9) Recommendations for the preparation of a detailed temporary eroslor control plan which ►dentiftes the specific miligalir►y measures to be implemented during construction to protect the slope from erosion, landslides and harmful construction methods. Located on page(s) _-7 jn- _3 ( 9 ) (10) An analysis of both on-sNe and off-site impacts of the proposed development. Located an page(s) 3 QF 3 00) {i 1) Specifications of flnel development conditions such as, vegetative management, drainage, erosion control, and "buffer widths Located on page(s) 3 o F 3 Cf� (12) Recommendations for the prboa(ation of stfuctural nAlgation or details of other proposed mitigation. Located on pages) o F 3 C/2) 13) A site map drawn to scale showing the property boundai:es, scale, north arrow, and the location ar,d nature of existing and proposed development on the site. Located on Ma s! / of-? --- - _, -- - ---— - Mo la-r,4 ___ riereby certify u~vlar penalty of perjury that I ern a civil engineer licensea In the Slate of Washington with specialized knowledge of g Rat schnicaNgeologiceI (engineering or a geologist or engineering geologist licensed In the State of Washington with special knowledge of the local conditions. I also certify that the Geotechn+ca! Report, dated J A A)- 1?P 2-AR and untitled (7r-U'Yt C µ"1 Sd e FN6/AvF-&lei /-6 4gagr meets all the requirements of the Mason County Resource owdinanee, Landslide Hazard Section, is complele and true, that the assessment demonstrates conclusively that the ;sks posed by the iandslide hazard can be mitigated through Me included geotechnical design recommendations, and that ali hazards am mitigated in such a manner as to prevent harm to property and public IpWih s►ntl 4afety. (Signature and Stamp) F�FN P. �10�♦ wAsk � Y �t 2/Zao 9 9 O h R 30758 SJCNALG xa�^ES Page 2 of 2 --- /l Form Effective Jurie 2006 Disclaimer: Mason County does not certify the quality of the work done ;n this Geotechnical Repcn ©o VICINITY MAP � !2/ZdD9 N �, ��* O i � HOOD CANAL �4N P 4f 4�#� e',t�• WAS ��'� p ' ��\ `:) Q O m X 01 E.Pine St. N zz Union,WA 98592 O 284' R 30758 - - - - - - - �GIS1k"R - 286' - 1 EXPtHEs-._L Z��!l 60%SLOPE BOUNDARY - - _ _ - - a PINE STREET SPRUCE STREET rn A b 12"DIA.CULVERT DRAINAGE DITCH Proposed --� DRAINAGE DITCH -- -_-_-_____ - —--- 15'setbedc 26'x50' ---- 80.02' � residence 300' FIRE � HYDRANT PID0,11 0 0 0 0 0 0 0 0 0 0 DRAINFIELD 0� v vv E 0n> l <n> �<n> V<A> V<n> �<n 8 0 290' O L '.7 L -�7 G �7 G '7 L �7 G '7 0 N 11 11 RESERVE AREA �o� v� v`1 � v J af0 �00 nL �7^> �/ �/� �/� �// �/� �/� 482 a N a - - - - - - - 292' g - - - 470 cc 5� ch . .............-...... _.._..._.._.._.._ — _ 294' TYPICAL GEOLOGICAL CROSS-SECTION A-A c�i� LL — - o LOT#1 _.._..__._.._..—.._ 296' w c � N W U v - -2_98_' _ _g U 7 - - - 70%SLOPE BOUNDARYCL °D o \ / W o c O' CV Sal \ CNF milBoring - - Top soil,sand,and gravel(GW-SW)with an allowable soil bearing capacity of 2000 Ibs/sq.ft.per geotechnical engineering probe,5 to 8% ca Existing moisture content. Could not roll a 1/8"worm indicating low moisture a 24'x 56' manufactured content and low plasticity. a 0 home PROPOSED Hi Dark brown very dense glacial till(GW-SM)with an allowable N 00 soil bearing capacity of 2500 psf and an insitu moisture co content ma g n LINDEL CEDAR content of 6 to 8°h. -? HOME O� o - Very dense brown cemented day and gravel(GW-CL)with an Cl) �\ allowable soil bearing capacity of 3000 psf and an insitu g A�oQ -_ moisture content of 7 to 9%. a O c �O d w INSTALL 6"DIA.FLEX DRAIN PIPE J� o rn JUST BELOW THE SURFACE TO `Ois INTERCEPT ALL UNDERGROUND C o M SPRING WATER AS INDICATED e w� hCZ. ZE UNDERGROUNDS S SPRING o 300'DATUM ELEV -• _ - - - - -A _ . . - - - - 65%SLOPE BOUNDARYt o n - - - 4 LL1 o°�Ooa�Ooa�Oo°� o°� o°�Ooa�Oo Oo Ooa) oa o Slope Stability Calculations (Simplified Bishop's Method of Circles) 15' loft ti0� Potential Rotational Failure Plane Not to scale(NTS) Alpha=35.0 deg (70%slope) 1. Compute factor of safety(FS)against sliding-Static Case(Ref: "Stability Charts for Uniform Slopes"by Radoslaw L. Michalowski, F.ASCE) - "Journal of Geotechnical and Geoenvironmental Engineering",April 2002. From Figure 3"Stability charts for uniform slopes"the following parameters are known for native silty glacial till soils: c(cohesion)=200 psf, gamma(insitu unit density)= 145 pcf, H(height of slope)=10 ft, phi(internal friction angle)=33 deg, then c![gamma x H x tan(phi)]=200/(145 x 10 x tan 33)=0.2124 Then for a 35.0 deg(70%)slope from Fig. 3: FS/tan(phi)=FS/tan(33)=3.75 or, FS=Factor of Safety Against Sliding= 5.775>1.500 OKAY 2. Compute factor of safety(FS)against sliding-Quasi-Static(Seismic)Case(Ref: "Stability Charts for Uniform Slopes" by Radoslaw L. Michalowski, FASCE) - "Journal of Geotechnical and Geoenvironmental Engineering",April 2002. From Figure 4"Stability charts for uniform slopes"the following parameters are known for native silty glacial till soils(GW-SM): c(cohesion)=200 psf, gamma(insitu unit density)= 145 pcf, H(height of slope)= 10 ft, phi(internal friction angle)=33 deg, then c/[gamma x H x tan(phi)]=200/(145 x 10 x tan 33)=0.2124 Then for a 35.0 deg slope(70%)slope from Fig.4 for a quasi-static analysis coefficient of 0.1: F/tan(33)=3.1 or FS=Factor of Safety=2.013 For a quasi-static analysis coefficient of 0.2: F/tan(33)=2.6 or FS=Factor of Safety= 1.689 As a result,for a quasi static analysis coefficient of 0.15,the Factor of Safety, FS=(2.013+1.689)/2= 1.851> 1.100 OKAY Slope Stability Analysis for property located at 101 E. Pine St., Union,WA 98592, Parcel#3223 2522 0012 Prepared by: Morta Engineering 8 Testing, 958, 60) E.-9i 82ah St,Aberdeen,WA 98520 (360)289-0958, (800)590-0958,(360)289-9682 fax,Smorta@f10L.com 1 —7 Prepared for:Glenn Ekoes,101 E.Pine St.,Union,WA 98592,Case#SWG 2007-00307,(360)898-1111 Jan.12,2009 Site Visit:Fri.1-9 2009 Sheet 2 of 3 GEOTECHNICAL ENGINEERING REPORT (1)General Geologic Conditions and Upland Geomorphology. During the Quanternary period most of the Pacific Northwest experienced several glaciations (6)Description and results of a slope stability analyses for both the static (11)Specifications of final development conditions such as,vegetative with the most recent(Fraser)glaciation reaching its peak about 14,000 years ago. and seismic loading conditions and should examine worst case failures. management,drainage,erosion control,and buffer widths. All surface The analysis should in Maximum ice thickness dun the Fraser Glaciation was approximately 1 000 feet s s ou d elude the Simplified Bisho 's Method of Circles with „ n9 PP Y ly p p water runoff from toward at Olympia,3,000 feet at Seattle,and over 5,000 feet at Bellingham. The Fraser a quasi-static analysis coefficient of 0.15. the roof shall be directedShee the 6 dra.flex drainpipe on the east side of the property as indicated on Sheet 1 of 3. All bare areas after P Pege ice retreated quickly, leaving behind a landscape sculpted by glacial erosion and As indicated on engineering sheet 2 of 3 a detailed slope stability analysis has construction shall be revegetated or treed to prevent soil erosion with plants covered b n glacial drift normal) identified ill. T been performed for both the static and dynamic cases using a modified form of the newly deposited a dent ed ast he pe dy se Y Y Po 9 Y g that are indigenous to the area. Since the slope on the north side of the cedar location of present-day watennrays and river drainages were established by the Simplified Bishop's Method of Circles. The resulting factor of safety for the home is considered very stable as determined from a detailed slope stability pattern of Fraser glacial erosion and deposition. The geologic map unit is a Qgt, static case was 5.775 which was greater than 1.500 and,therefore,the static slope analysis then a 15'buffer from the slope on the north side is considered more i.e.,late 1%4sconsian(Pleistocene), unsorted, unstratified, highly compacted stability factor of safety was considered satisfactory requiring no setback requirements than adequate for the overall safety of the residence. mixture of clay,silt,sand,gravel,and boulders deposited by glacier ice of the since the slope is considered very stable. Puget lobe. (Ref: Geologic Map of the Shelton 1:100,000 Quadrangle,WA by Simlarly,for the dynamic or seismic case,the resulting factor of safety for a (12)Recommendations for the preparation of structural mitigation or Robert L. Logan, 1003.) quasi-static analysis coefficient of 0.15 was computed to be 1.851. Since this is details of other proposed mitigation. A shallow spring was observed flowing out from underneath a 3'high retaining greater than 1.100,the factor of safety was considered satisfactory and,again, no _ Afooting drain shall be placed around the exterior perimeter of the foundation rock wall as indicated in the drawingon Sheet 1 of 3. More than like) this is setback requirements were deemed necessary due to the overall longterm stability Y eq rY 9t to intercept groundwater that may have a tendency to undermine the bottom surfs r that has percolated i of the slope. P Y 9 Y cY surface Ovate pe cited into the ground until it contacted a hard pan pe of the concrete footing. This engineer to ins h layer and then flawed on to of this layer until it da li hted under the rock wall. g g pest the compaction of the footing Y P Y Y.9 su race usinga 350+lb vibratory compactor with a minimum of 6 slow passes The upland geomorphology is 70 to 80%slopes with similar glacial till deposits. (7)Restrictions on placement of drainage features,septic drain fields and � g Po with this engineer present as stated earlier in this report. There were no upland bodies of water or wetlands since the site is situated on compacted fills and footings,and buffer and setbacks from landslide the side of a hill. hazard areas. It is recommended that all surface water runoff,especially from E There was no evidence of past or present slide events like pistol butted tree downspouts be directed into the 6"dia.flexible tightline located on the south and east (13)A site map drawn to scale showing the property boundaries,scale, g Cn north arrow,and the location and nature of existing and proposed _j o trunks,ground fissures,or hummocky areas at the toe of slope which would have side of the residence as indicated on Sheet 1 of 3. The drainfield area is located on a o development on the site. Refer to sheet 1 of 3 for the site plan. Note that a indicated a past slide event. gradual slope as indicated on Sheet 1 of 3 and,therefore, its location is considered _J the site plan and a typical e an ical topographical cross-section of the site other satisfactory. geodata has been included on the same engineering drawing. a o o (2)Site Plan of the Important development and geologic features. All footings shall be constructed on UNDISTURBED native soils at a minimum F" E The site plan on sheet 1 of 3 shows the proposed 26'x NY Lindel Cedar home of l'below ground to protect the footings from freezing. The footing subgrade shall (14) The services described in this report were prepared under the CO located on Lot#12. This building site was prepared by cutting into the embankment be compacted to 95%of maximum density per ASTM D-1557 with a 350+lb vibratory responsible charge of Steven P. Morta, P.E. Steven P Morta meets ~ with no fill material present. 70 to 80%slopes were observed on the north side of plate compactor with a minimum of 6 slow passes IMTH THIS ENGINEER PRESENT. the qualifications contained in Title 18E,Section 18E.80.030 to prepare $ CO the property as indicated on Sheet 1 of 3 with no signs of any slope instabilities. a landslide hazard geological assessment. Steven P Morta understands p l o the requirements of the current Landslide Hazard Area Chapter 18E.80 8.8 CD LL (3)A log of exploratory test hole. On sheet 1 of 3 the soil boring locations (8)Recommendations for the preparation of a detailed clearing and and the deifinitions of the applicable terms contained within Chapter 18.25. ,a o h and the resulting slope cross-section indicating the soil types is also shown. grading plan which specifically identifies vegetation to be removed, Individuals under the responsible charge of Steven P. Morta have performed W y a schedule of vegetation removal and replanting,and the method of a landslide hazard geological assessment,conducted a field investigation, Y (4)Area of proposed development,hazard boundaries,buffers and vegetation removal. The lot has already been cleared off and ready to and researched historic records on or in the vicinity of the above referenced setback delineated on a geologic map. The Hazardous Slope area has been build on. Any remaining bare soil areas shall be replanted with indigenous site. In my opinion,the scope of services completed for this project is identified at both the top and bottom of the the 70%slope as indicated on trees and vegetation such as junnipers, ivy,fems and vine maple and other adequate to meet the requirements of the Department. �ui U') Sheet 1 of 3. There is no evidense of previous or current landslide indicators local plants that thrive in this cool,wet environment especially along the 70% w o o such as pistol butted tree trunks, hummocky areas at the toe of the gulch,cracking embankment on the north side of the property. No Gearing or grading is 2 �- N or ground fissures at the top of the embankment,wet areas or seeps,or erosional anticipated on this property since it is already flat with no fill soils present. N channels. cc A detailed slope stabilty analysis was performed on the 70%slope just north of the (9)Recommendations for the preparation of a detailed temporary proposed Lindel Cedar Home and indicated that the slope was very stable for both erosion control plan which identifies the specific mitigating measures rl the static and quasi-static cases. As a result,a 16 buffer nortt Qf the s n&ure was to be implemented during construction to protect the slope from erosion, considered satisfactory. The manufactured home to the west which was placed landslides and harmful construction methods. there about 20 yrs ago has a similar setback with no signs of any slope instabilities. Prior to construction activities on the site,geotextile siltation fencing shall be g placed on the downhill side of the building site to prevent soil erosion of the North (6)A minimum of one cross section at a scale which adequately depicts embankment. It is recommended that initial construction take place during ¢�co the subsurface profile,and which incorporates the details of proposed the drier times of the year from mid May to late October and that the cedar home r> 0D grade changes. A detailed cross section is shown on sheet 1 of 3 that be weathered in by the end of November. Otherwise,at other times of the year the indicates that the top layer consists of topsoil,compacted sands and gravels(GV�SW D j contractor shall protect exposed,bare soils from erosion by covering with 6 mil co � with an allowable soil bearing capacity of 2000 psf while the lower layer consists of a visqueen. If rain is expected all bare ground is shall be protected with 6 mil visqueen dense glacial till hardpan(GW-SM)with an allowable soil bearing capacity of to minimize soil erosion of the building site and the resulting water runoff to be L m 2500 psf for the UNDISTURBED soil condition and 6 to 8%moisture. No grade directed into the 6'dia.flex drainpipe on the east side of the property. o a N changes are proposed since the site was already prepared with no fills present. .,04 (10)An analysis of both on-site and off-site impacts of the proposed b development. The proposed residence will be constructed on UNDISTURBED g y native dense glacial till soils. Any surface water runoff shall be directed away from a,5 o m the slopes and into the 6'dia.flex drainpipe located on the east side of the property o w U as indicated on Sheet 1 of 3. It is recommended that indigenous trees and vegetation 'c z m be planted immediately once the main construction of the home has been completed, = w especially,along the 70%embankment to increase overall slope stability and reduce Lb e5 a the likelyhood of a slide event since trees and vegetation protect the soils from erosion, c o and hold the soils in place through their extensive root system,and finally dewater the a ground through the process of evapotranspiration. t Lu a d m SL ope 57-m16«rT y AP- CoA Sr.4L R7oN6- � MAso� CBct�vzy� J Ayres F'a� ri'"t�� .. __ � - �-__. y: Scale 1:24,000 0 s 1 Miles 0 "0 low I Soo Metres 88.n6 LEGEND075CUUMfK: 8.9 nrw »«.mr«ww ro.eyuee ar cc r� ('r r� �N�F—�/f1 t�0/•07f pgmo NOTMW to.Aw^•Y+a^V w�a�4 aroron�. rM rvr cl b4+nV"*nt a tewbC►ur.nea ne wmurs hr enr area ®y�lWpy -s0.u0ieee dt#Kmd an b4"m4+.Fw 40twow woo,n M.-on CdwK,eMc-- w«h-Wcn Rat 049w6Mnt alsorop- jl.._J(. .. ffi • m u D ni S IS)