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Home My WebLink AboutGEO2018-00074 BLD2018-01153 - GEO Geological Review - 12/20/2018 C-_ Eo Zo ie, coo-r4 fez.'614 2616 - 6114 MASON COUNTY Submittal Checkhs'L COMMUNITY SERVICES Geological Assessment Building,Planning,Enwon—run Health.Community Health Instructions: This checklist must be submitted with a Geological Assessment and completed, signed, and stampe � ED professional(s)who prepared the Geological Assessment for review by Mason County pursuant to th Resource Ordinance. If an item is found not applicable,the report should explain the basis for the conclussi��ion..++ Note:Unless specifically documented, this report does not provide compliance to the International Residential Code 6E C,2 0 2018 R403.1.7 for foundations on or adjacent to slopes, Section R403.1.8 for expansive soils or section 1808.7.1 of the International Building Code Section for Foundations on or adjacent to slopes. 615 W. Alder Street Applicant/Owner Cedarland Forest Resources, LLC Parcel# 122205400110 Site Address 281 East Mountain View Drive (1) A discussion of geologic conditions in the general vicinity of the proposed development,with geologic unit designation based on referenced maps. Located on page(s) 2 & 3 (2) (a)A discussion of the ground water conditions at the site, Located on page(s) 3 (b) A discussion of the estimated depth to water, Located on page(s) 3 (c) A discussion of the quantity of surface seepage, Located on page(s) 2 & 3 (d) A discussion of the upslope geomorphology, Located on page(s) 2 (e) A discussion of location of upland waterbodies and wetlands. Located on page(s) 2 (3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand. Located on page(s) -- (4) A discussion of any geomorphic expression of past slope instability(presence of hummocky ground or ground cracks,terraced topography indicative of landslide block movement, bowed or arched trees indicating downslope movement,etc.). Located on page(s) 2, 3 & 4 (5) A discussion of the history of landslide activity in the vicinity, as available in the referenced maps and records. Located on page(s) 2, 3 & 4 (6) An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or setback and the potential for landslide activity at the site in light of the proposed development. Located on page(s) 3 &4 (7) A recommendation by the preparer whether a Geotechnical Report should be required to further evaluate site conditions and the proposed development of the subject property. Rev. February 2018 Located on page(s) 3 (8) If the presence of a hazard is determined within 300 feet of the proposed development, then the following are delineated on a geologic map/site map: (a) the area of the proposed development, Located on Map(s) " (b) the boundaries of the landslide hazard area(top, both sides, and toe), Located on Map(s) -- (c) the associated buffers(top, both sides, and toe), Located on Map(s) '" (d) building or other setbacks(top, both sides, and toe). Located on Map(s) '" (9) 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) Figure 2 Dana Biggerstaff hereby certify under penalty of perjury that I am a civil engineer licensed in the State of Washington with specialized knowledge of geotechnical/geological 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 Geological Assessment, dated December 3, 2018 and entitled Geological Assessment Letter; Proposed Single Family Residence meets all the requirements of the Mason County Resource Ordinance, Geologically Hazardous Areas Section, is complete and true, that the assessment 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. SHOP R�f of 5 40 O�F`S'S OrS7'E� lZ�i�s.0 8 (Signature and Stamp) Page 2 of 2 Disclaimer. Mason County does not certify the quality of the work done in this Geological Assessment. GOREESOURCES -�' earth science & geotechnical engineering 5007 Pacific Hwy E., Suite 16 Fife, WA 98424 253.896.1011 1 www.georesources.rocks December 6, 2018 Mr.Joseph T. Cedarland Cedarland Forest Resources, LLC PO Box 2264 Gig Harbor,Washington 98335 (253)208-8136 joe@cedarlandforestresources.com Geological Assessment Letter Proposed Single Family Residence 281 East Mountain View Drive Mason County,Washington PN: 122205400110 Doc ID: Cedarland.EMtnViewDr.GHA INTRODUCTION This geological assessment letter presents the results of our geological assessment for the proposed single family residence to be constructed at 281 East Mountain View Drive in Mason County,Washington.The general location of the site is shown on the Site Location Map, Figure 1. Our understanding of the project is based on our discussions with you, our understanding of the proposed site development, our November 20, 2018 site visit, and our experience in the area. We understand that you propose to construct a single family residence at the above mentioned site location. Because of the vertical height and inclination of the slopes within the vicinity of the parcel, Mason County is requiring a Geological Assessment be completed per Mason County Resource Ordinance, MCC(Mason County Code)8.52.140"Geologically Hazardous Areas." SCOPE The purpose of our services was to evaluate the site conditions as a basis for assessing potential adverse impacts to and from the slopes located within the site area. Our site evaluation was performed in accordance with the Mason County Resource Ordinance regulations. Specifically, our scope of services for this project included the following: 1. Reviewing existing and publicly available geologic and geotechnical literature for the site area; 2. Visiting the site and conducting a geologic reconnaissance to assess the site's soil, groundwater and slope conditions; and 3. Addressing the geological hazards in accordance with the current Mason County Resource Ordinance, MCC 8.52.140"Geologically Hazardous Areas". h Cedarl and.EMtnViewDr.GHA December 6,2018 page 1 2 The above scope of work was completed in accordance with our Proposal for Services dated November 16, 2018. We received written authorization from you the same day. No subsurface explorations or laboratory testing were completed as part of the scope for this assessment. SITE CONDITIONS Surface Conditions The site consists of a single tax parcel located at 281 East Mountain View Drive in the Allyn area of Mason County, Washington. The subject parcel is in an area of existing residential development. According to the Mason County GIS, the parcel is generally rectangular in shape, measures approximately 68 to 80 feet wide (northeast to southwest) by about 120 to 198 feet deep (northwest to southeast) and encompasses approximately 0.28 acres. The site is currently undeveloped and is bounded by residential development to the northeast and southwest, by undeveloped land to the north and east, and by East Mountain View Drive to the west. The site is situated in the Allyn glacial upland area, located about 1,310 feet southeast of Lake Anderson. According to the information obtained from the Mason County Public GIS, the site generally slopes down from the northwest to southeast. The site is generally at grade with East Mountain View Drive before sloping down to the southeast at about 15 to 20 percent. The lower portion of the site slopes down to the southeast at about 30 to 33 percent. Total topographic relief across the site is on the order of 45 feet. The site topography is illustrated on the attached Site Vicinity Map, Figure 2. Vegetation on the site consists of a moderate stand of maple and fir trees with scattered alders throughout. The site has a dense understory of huckleberry bushes, ferns, salal, and immature alders. No surface water or seepage was observed at the time of our site visit. No evidence of erosion, soil movement, landslide activity or deep-seated slope instability was observed at the site or the adjacent areas at the time of our site visit. Site Soils The Natural Resource Conservation Service (NRCS) Web Soil Survey maps the site as underlain by Alderwood gravelly sandy loam (Ac) soils. The Alderwood soils, mapped across the entire site, are derived from glacial drift and/or glacial outwash over dense glaciomarine deposits and form on slopes of 15 to 30 percent. These soils have a "moderate to severe" erosion hazard when exposed and are included in hydrologic soils group B. A copy of the NRCS soils map is included as Figure 3. No evidence of surficial erosion was observed during the time of our site visit. Site Geology The Geologic Map of the Belfair 7.5-minute Quadrangle, Mason, Kitsap, and Pierce Counties, Washington by Polenz et Al., (2009) indicates the site is underlain by Vashon glacial till (Qgt). These soils were generally deposited during the Vashon Stade of the Fraser Glaciation,some 12,000 to 15,000 years ago. The glacial till consists of a heterogeneous mixture of clay, silt, sand and gravel that was deposited at the base of the continental ice mass and is typically encountered in a very dense condition. The till was overridden by the ice mass, and as such is considered overconsolidated, and exhibits high strength and low compressibility characteristics where undisturbed. An excerpt of the geologic map for the general area is included as Figure 4. GEORESOURCES Cedarland.EMtnViewDr.GHA December 6,2018 page 1 3 No landslides are mapped on or within 300 feet of the site. A landslide deposit is mapped more than 900 feet to the southwest of the site. No evidence of deep seated landslide activity or erosion was observed during of our site visit. The Department of Ecology(DOE) Coastal Zone Atlas indicates the slope stability on the site is "stable" (S). No areas of"unstable recent slides"(URS) or"unstable old slides" (UOS) are mapped in the vicinity of the site. The Coastal Zone Atlas does not identify the area of landslide deposit shown on the geologic map. A copy of the DOE Coastal Zone Atlas is included as Figure 5. Groundwater Conditions No seeps or springs were observed at the site at the time of our site visit. Based on the mapped stratigraphy at the site, we do anticipate that perched groundwater may develop at some depth below the site. Perched groundwater develops when the vertical infiltration of precipitation through a more permeable soil is slowed at depth by a deeper, less permeable soil type. We anticipate fluctuations in the local groundwater levels will likely occur in response to precipitation patterns, off-site construction activities, and site utilization. Based on our review of wells logs in the area (DOE Washington State Well Reports), groundwater appears to be between 190 and 380 feet below the ground surface. CONCLUSIONS Based on our site observations and data review, it is our opinion that the proposed single family residence is feasible from a geotechnical standpoint, provided the recommendations included herein are incorporated into the project plans. Furthermore, it is our opinion that a Geotechnical Report should not be required. Geologically Hazardous Areas per Mason County Resource Ordinance 8.52.140 According to the Mason County Resource Ordinance, the purpose of the landslide hazard assessment is to identify areas that present potential dangers to public health and safety, to prevent the acceleration of natural geological hazards, to address off site environmental impacts, and to minimize the risk to the property owner or adjacent property owners from development activities. The following shall be classified as geologically hazardous areas: (a) Areas with any indications of earth movement such as debris slides, earthflows, slumps and rock falls(see Figure LHA-1). (b) Areas with artificial oversteepened or unengineered slopes, i.e., cuts or fills. (c) Aras with slopes containing soft or potentially liquefiable soils. (d) Areas oversteepened or otherwise unstable as a result of stream incision, stream bank erosion, and undercutting by wave action. (e) Slopes greater than fifteen percent(8.5 degrees)and having the following: (i) Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment or bedrock (e.g., sand overlying clay); and (ii) Springs or groundwater seepage. (f) Any area with a slope of forty percent or steeper and with a vertical relief of ten or more feet except areas composed of consolidate rock. A slope is delineated by establishing its GEORESOURCES Cedarland.EMtnViewDr.GHA December 6,2018 page 1 4 toe and top and measured by averaging the inclination over at least ten feet of vertical relief. In addition, the following information may be used as a guide by the County to indicate areas that have a higher likelihood of meeting the classification criteria above: (a) Landslide hazards mapped by the Washington Department of Natural Resources, Division of Geology and Earth Resources (Washington Geological Survey)such as "Landforms and Hazard Ratings - Mason Watershed," Isabelle Sarikhan and Timothy J.Walsh,August 2007. (b) The areas identified on the Mason County Soil Survey Map as having slopes greater than fifteen percent. (c) The area identified on the Coastal Zone Atlas, Volume 9, of Mason County, Washington as: (i) Unstable-"U"; (ii) Unstable Old Slides-"UOS"; (iii) Unstable Recent Slides -"URS"; (iv) Intermediate Slopes -"I"; (v) Modified Slopes-"M." (d) The area identified as Class 2, 3, 4, or 5 of the maps: "Relative Slope Stability of the Southern Hood Canal Area, Washington," by M. Smith and R.J. Carson, U.S. Geological Survey, Series Map 1-853-F, 1977 (e) Areas described and mapped as areas of poor natural stability and historical and recent landslides by the Washington State Department of Natural Resources, Division of Geology and Earth Resources including "The Geological Map of North Central Mason County, Washington, " by R.J. Carson, Washington State Department of Natural Resources, Division of Earth Resources, 1975; (f) Areas mapped as landslide deposits (Map Unit Qls) on the Geologic Maps of Washington 7.5-Minute Quadrangle (Longbranch, Squaxin Island, Shelton, Summit Lake, Vaughn, Lake Wooten, Mason Lake, Belfair, Skokomish Valley and Union, Lilliwaup, Hoodsport, and Holly). Mason County uses the above referenced checklist to define a Landslide Hazard Area. Based on our observations of the site and review of published information, we offer the following comments. No areas with indications of earth movement were observed at the time of our site visit. The road cut below East Mountain View Drive, at the top of the site, is a constructed slope, but we assume that the slope was engineered as it was cut for road construction. The mapped stratigraphy indicates that the site is underlain by glacial till, soils that are not prone to liquefaction. No areas of oversteepening and instability due to stream erosion and wave action were observed at the time or our site visit. There are slopes greater than 15 percent at the site, but no adverse geologic contacts or seeps or springs were observed at the time of our site visit. We did not observe slopes greater than 40 percent with 10 feet or more of vertical relief. Based on the above, the site does not have any of the above 6 geologically hazardous area indicators, and it does not appear that there is an active landslide hazard on or within 300 feet of the GEORESOURCES Ceda Hand.EMtnViewDr.GHA December 6,2018 page 1 5 site. Per Title 8.52.140.(E), the site meets the conditions of Category D, and a geologic assessment should be sufficient to address the MCC Title 8.52. LIMITATIONS We have prepared this revised report for use by Mr. Joseph T. Cedarland to address code compliance requirements imposed by Mason County. 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 limited site reconnaissance,and should not be construed as a warranty of the subsurface conditions. Variations in subsurface conditions are possible between the explorations and may also occur with time. A contingency for unanticipated conditions should be included in the budget and schedule. Sufficient monitoring, testing and consultation should be provided by our firm during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, 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 contract plans and specifications. The scope of our services does not include services related to environmental remediation and construction safety precautions. Our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time this report was prepared. No other conditions, express or implied,should be understood. GEORESOURCES Cedarland.EMtnViewDr.GHA December 6,2018 page 1 6 We appreciate the opportunity to be of service to you on this project. If you have any questions or require additional services, please contact us. Respectfully submitted, GeoResources, LLC Jordan Kovash,GIT Staff Geologist in Training le of Wash, �0� of NV AtfG nn t P % 25 \5 500 �s6d G eon° �Fcsz-E� SSr0 r tvAL �� KEITH SCOTT SCHEMBS Dana C. Biggerstaff, PE Keith S. Schembs, LEG Senior Geotechnical Engineer Principal JLK:DCB:KSS/jlk Doc ID:Cedarland.EMountainViewDr.GHA Attachments: Figure 1:Site Location Map Figure 2:Site Vicinity Map Figure 3: NRCS Soils Map Figure 4: USGS Geologic Map Figure 5: Coastal Zone Atlas GEORESOURCES y ,i 11A3. \ _.-.--------------- -----._.-----.- - l I, WA 302 7/ COOM- WA3 I - WA 302 Approximate Site Location Map created from Mason County Public GIS(https://gis.co.mason.wa.us/mason/) <N� Iw t S Not to Scale Site Location Map Proposed Single Family Residence 281 East Mountain View Drive GEORESOURCES Mason County, Washington earth science & geotechnical engineering PN: 1 222054001 1 0 5007 Pacific Hwy F.,Suite 16 1 Fife,WA 98424 1 253.896.10111 www.georesources.rocks Doc ID:Cedarland.EMountainViewDr.F November 2018 Figure 1 til PF i Ik( a _ � •� w e. r l 4. a t 1 ` y r4M Ll f��_t�11 / ' 1 Approximate Site Location Map created from Mason County Public GIS(https://gis.co.mason.wa.us/mason/) Not to Scale Site Vicinity Map Proposed Single Family Residence �. 281 East Mountain View Drive GEORESOURCES Mason County, Washington earth science & geotechnical engineering PN: 1 222054001 1 0 5007 Pacific Hwy E.,Suite 16 1 Fife,WA 98424 1 2S3.896.1011 I www.georesources.rocks Doc ID:Cedarland.EMountainViewDr.F T November 2018 Figure 2a �Y. r { ♦.�w � "� T �ir�v Jl �� 5 ,: 1 : ►.;. + 7r w r • F IL ! _ , ti Approximate Site Location Map created from Web Soil Survey(http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx) Soil Soil Name Parent Material Slopes Erosion Hazard Hydrologic Type Soils Group Alderwood gravelly sandy Glacial drift and/or glacial outwash over 15 to 30 Moderate to B Ac loam dense glaciomarine deposits Severe So Sinclair shotty loam Gravelly glacial till 5 to 15 Moderate B c� two% E S Not to Scale NRCS Soils Map Proposed Single Family Residence GE OSORE URCES 281 East Mountain View Drive Mason County, Washington earth science & geotechnical engineering PN: 1 222054001 1 0 S007 Pacific Hwy E.,Suite 16 1 Fife,WA 98424 1253.996.1011 1 www.georesources.rocks Doc ID:Cedarland.EMountainViewDr.F November 2018 Figure 3 Qgt 9a r J- o 1 t 090 Qgt Omw ` -- 0 Oaf am Oa Slow a ) Qga f C, r c ' y r ` ` Lh ` rQb r Ogic , Oaf r. Ogt .Qf i�f 2 agicy /. I. ogol Ogic r QG` � '� Oaf Oaf Qpy 1 Ogo ` - Qaf `yOpu i/f I O f Ogo) Qb Qob rt Op � Qaas `, � � t_.g°op � � Q af Q �t Qaf� I g QQP t ,i^_O., op r' Qb 1 O f OT Qgt _P J 1 OgfOJ :' OG_ r. 1 rJyt J t� � Ogt —Qb j� Qgol ate` {7 _ QDb Ogt Oaf OPU Q7D QITI cis '.^+t —� Ocb 1 a Approximate Site Location Excerpt from the Geological Map of the Belfair 7.5-minute Quadrangle, Mason, Kitsap, and Pierce Counties, Washington by Michael Polenz, Katelin Alldritt, Nicholasj. Hehemann, Isabelle Y. Sarikhan, and Robert L. Logan (2009) Uplifted beach deposits EW Landslide deposits Qgt Vashon till Qpu Pre-Vashon undifferentiated sediments ck (Nv e S Not to Scale USGS Geologic Map Proposed Single Family Residence 281 East Mountain View Drive GEORESOURCES Mason County, Washington earth science & geotechnical engineering PN: 1 222054001 1 0 5007 Pacific Hwy F.,Suite 161 Fife,WA 98424 1 253.896,1011 1 www.georesources.rocks Doc ID:Cedarland.EMountainViewDr.F November 2018 Figure 4 to�•, �'`.� :r w� J� ter_ as t t iy r+ a �a r Approximate Site Location Map created from the Washington State Coastal Atlas Map (https://fortress.wa.gov/ecy/coastalatlas/tools/Map.aspx) Slope stability 0 Stable VIntermediate *40 Modified Unstable Unstable (old slide) *40 Unstable (recent slide) c� S Not to Scale Coastal Zone Atlas Proposed Single Family Residence 281 East Mountain View Drive GEORESOURCES Mason County, Washington earth science & geotechnical engineering PN: 1 222054001 1 0 5007 Pacific Hwy E.,Suite 16 1 Fife.WA 99424 1 253.896.1011 1 www.georesources.rocks Doc ID:Cedarland.EMountainViewDr.F November 2018 Figure 5 GEO Mason County Review Checklist For a Geological Assessment Instructions: This checklist is intended to assist Staff in the review of a Geological Assessment. The Assessment 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 Assessment 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, staff1 should refer the case to the Planning Manager or Director. Applicant's Name: a CJ' Permit#: aW P rcel#'s: Date(s)of the Document(s) reviewed: 1. A discussion of geologic conditions in the general vicinity of the proposed development, with geologic unit designation based on referenced maps. OK? �_Comment: 2. (a) A discus\si/on of the ground water conditions at the site, OK? l� Comment: (b) A discussi n of the estimated depth to water, OK? Comment: (c) A discussion of the quantity of surface seepage, OK? _Comment: (d) A discussion of the upslope geomorphology, OK?_X Comment: (e) A discussio of location of upland waterbodies and wetlands. OK? Comment: 3. The approximate depth to hard or denseLcompetent soil, e.g. glacial till or outwash sand. / j OK? Comment: U�lI trQ-a 0 &UU1 kY1 F/Y I I'�r 1 Gall "1 wa(l y 4. A discussion of any geomorphic expression of past slope instability(presence of hummocky ground or ground cracks, terraced topography indicative of landslide block movement, bowed or arched trees indicating downslope m_ ov�ment, etc.). N O C7H� OK? 7 Comment: 5. A discussion of he history of landslide activity in the vicinity, as available in the referenced maps and records. OK? Comment: 6. An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or setback and the potential for landslide activity at the site in light of the proposed development. OK?_ Comment: 7. A recommendation by the preparer whether a Geotechnical Report should be required to further evaluate site conditions and the proposed development of the subject property. OK? _Comment: 8. If the presence of a hazard is determined within 300 feet of the proposed development, then the following are delineated on a geologic map/site map: Page 1 of 2 Form Effective June 2008 (a) the area of the proposed development, OK? Comment: (b) the boundaries of the landslide hazard area (top, both sides, and toe), OK? —J Comment: (c) the associated buffers(top, both sides, and toe) OK? Comment: (d) building-aF-either setbacks (top, both sides, and toe). OK? Comment: 9. 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. OK? _Comment: Are the Documents signed and stamped? By whom? —Y— ju License#: S ob LA 0 License type: FIRST REVIEW LWApproved ❑ Need more info. If not approved, what is the next action/recommendation for further action? � 1 � Reviewed by I on Time spent in review:_ th Y1 SECOND REVIEW/UPDATE ❑ Approved ❑ Need more info. If not approved, what is the next action/recommendation for further action? Reviewed by on . Time spent in second review: THIRD REVIEW/UPDATE ❑ Approved ❑ Need more info. If not approved, what is the next action/recommendation for further action? 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