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Home My WebLink AboutGEO2024-00063 for BLD2024-00720 - GEO Geological Review - 5/8/2024 9662 - 0075?0 33 �� Portland,Oregon &Et)Kansas City,Missouri V I S TA'\4 —STRUCTURAL RECEIVED JUN 10 2024 May 8,2024 ,. PLANNING n 15 W. Alder Street Terra Firma Foundations 3110 SW Wall St. Portland,OR 97223 Re:Limited Geological Site Evaluation for a Proposed Foundation Underpinning Based on Available Online Data 221 NE Mountain View Drive(Property ID#: 105612760) Vista Structural Engineering,LLC,was asked to perform a limited site evaluation for the proposed underpinning project located at 221 NE Mountain View Drive This report summarizes the findings of the geologic site data and provides recommendations for the proposed project. Project Scope and Site description: The project site is located at 221 NE Mountain View Drive(Figure 1).The existing residence is a single-story wood framed structure with a crawlspace that resides in Mason County and was built in 1971. The lot size is approximately 0.49 acres. Based upon elevation readings provided by TerraFirma Foundation Systems,we understand that the structure has experienced some settlement and minor foundation cracking. The purpose of this proposed underpinning is to support the existing structure from settling any further. Four 2-7/8"-diameter helical piers—Foundation Supportworks model HP288—have been proposed to be installed to help provide foundation stabilization support along the perimeter of the structure,in locations shown on the structural plans. Geological Evaluation The geologic structure in this area is comprised of gravelly sandy loam(GM,SM)and very gravelly loamy sand(SC- SM)(Figure 2)and is located on a relatively flat site. It is our opinion,that settlements are likely due to a combination of improperly compacted construction fills,poor construction practices and/or poor site drainage. According to the Washington Department of Natural Resources,the subject site is underlain by Pleistocene continental glacial drift which consists of Pleistocene till and outwash clay,silt,sand,gravel,cobbles,and boulders deposited by or originating from continental glaciers.This also locally includes peat,nonglacial sediments, modified land,and artificial fill.(Figure 3). VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 - 1- VISTASTRUCTURAL.COM i Portland,Oregon I� VISTA Kansas City,Missouri \�\4: —STRUCTURAL- -N G! N E E R I N G, L L C Earthquake Induced Hazards The subject site is in a very low-risk area for earthquake induced liquefaction(Figure 7),differential seismic settlement,or surface displacement due to lateral spreading. Although there is no landslide inventory in this area,we do not anticipate the site slope stability to be a major concern(Figure 4). We consider the most significant earthquake hazard to be the potential for very strong seismic shaking that is likely to occur in a seismic event(Figure 7). The site also is within the area of faults that are considered to be active and/or potentially active. These active and potentially active faults are capable of producing potentially damaging seismic shaking at the site. It is possible that the subject site will experience ground acceleration as the result of being in an earthquake zone. Below are the site Seismic Parameters per the 2018 International Building code and the Building Code 2021 of Washington,and ASCE 7-16. Latitude(degree) 47.4643338 Longitude(degree) -122.983177 Site Class D Site Coefficient,Fa 1.2 Site Coefficient,Fv 1.726 Mapped Spectral Acceleration at 0.2-sec Period,Ss 1.576 Mapped Spectral Acceleration at 1.0-sec Period,S1 0.574 Spectral Acceleration at 0.2-sec Period Adjusted for Site Class,SMS 1.891 Spectral Acceleration at 1.0-sec Period Adjusted for Site Class,SM1 0.991 Design Spectral Acceleration at 0.2-sec Period,SDS 1.261 Design Spectral Acceleration at 1.0-sec Period,SD1 0.660 Seismic Design Category D Table 1:Seismic Parameters(Ref,(Figure 5)) Conformance to the criteria presented in the above table for seismic design does not constitute any type of guarantee or assurance that significant structural damage or ground failure will not occur during a large earthquake event.The intent of the code is"life safety"and not to completely prevent damage of the structure, since such design may be economically prohibitive. VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -2 - VISTASTRUCTURAL.COM Portland,Oregon I Kansas City,Missouri ► VISTA 4' —STRUCTURAL— GiiV EERINC, LLC Recommendations Based on the attached findings,helical pier systems have historically been an adequate method to mitigate the settlement the structure has experienced. For the vertical piers we recommend that a minimum of T-6" installation depth is achieved. The maximum design service loading,as determined on the structural engineering plans,is 9,362 pounds. This correlates to an installation torque of 2,100 ft-lbs. per pier. Limitations This report is based on the limited available information online. It should be recognized that there is a large degree of uncertainty and limitations as Vista Structural Engineering,LLC has not performed any site-specific testing or engineering. Vista Structural Engineering,LLC makes no guarantees to in-situ conditions. The findings contained in this report are based upon our evaluation and interpretation of the information obtained and as referenced in the attached figures. It is the responsibility of the contractor to consult with the design professional in the event field conditions vary significantly from those assumed in this report.This limited report is not in place of a site-specific geotechnical engineering report. No soil sampling or testing has been completed as part of this study. This does not take the place of a site-specific analysis when required by code or the building official. Our firm appreciates the opportunity to serve you. If you have any questions or if you need anything further, please feel free to contact us. Sincerely, Vista Structural Engineering, LLC Dennis Heier, P.E. IS M 49 0 x 05/08 VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -3- VISTASTRUCTURAL.COM II Portland,Oregon I� V 1 5 TA Kansas City,Missouri \�\4/ —STRUCTURAL— ROUMELIOTIS REST[ D\ T71!tAASR wp W11 at tM4l�ll Y/LM jF" MpMMft O 1:'Ttf96 HODS J (N)101ICAL HERS,TYP. �. Ut 1. Sll FOUNDATION '' PtAV UN S�q t i Sp.l MA-N 1 NTPAN \ N OVERALL SITE LAYOUT 1 C0.0 1'=50'-0' Figure 1:Site Plan VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -4- VISTASTRUCTURAL.COM Portland,Oregon VISTA Kansas City,Missouri % —STRUCTURAL— 11rir.-t- ;r•: rc:;-. , LI_C Engineering Properties-Msen Canty,Washington Map unit symbol and Pet or Hydrolo Depth USDA texture Classification Pet Fragments Percentage passing slew number- Liquid Plastick soil name map gic limit y Index unit group Unified AASHTO �10 340 4 10 40 200 Inches Inches In L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H L-R-H Ab—Alderwood gravelly sandy loam.810 15 percent slopes Alderwood 85 B 0.7 Gravely sandy loam GM,SM A-2.A-1 0-0-10 0-0-10 50.70- 45.64- 35.52- 20.29- 30-35 NP-2.5 75 75 80 35 -45 7.21 Very gravelly sandy SM,GM, A-1,A-2 0.0-10 0-0-20 25.50- 2045. 15.34- 5.16.30 15-26 NP-0.5 loam,gravelly GP-GM 75 75 60 -35 loam.very gravely coarse sandy loam 21.30 Very gravelly sandy GM,GP- A-2,A-1 0.0-10 0.0-20 25-45- 20-40- 15.29- 5.14-35 15-24 NP-0-5 loam,gravelly GM 75 75 60 -30 loam, very gravely coarse sandy loam 30.35 Extremely gravelly GP-GM, A-1 0-D.5 0.0-25 1543- 10.37- 5-26-40 5-12-20 15-17 NP-0-5 coarse sandy GC-GM 50 50 -25 loam.extremely gravely loam, very gravely sandy loam 35.43 Very gravely sandy SC-SM. A-2.A-1 0-0.5 D.0.10 50.55- 45.51- 435.39- 15.19- 15-17 NP-0-5 loam,gravely fine GM 80 80 65 35 -25 sandy loam.very gravely coarse sandy loam,very gravy Amy sand 43-59 Very gravelly sandy SC-SM, A-2,A-1 0.0-5 0-0.10 50-56- 45.51- 3539- 15-19- 15.17 NP-0.5 Imam,very GM 8o so 65 35 -25 gravely coarse sandy loam,very gravely loamy sand,gravely fine sandy loam Figure 2:Engineering Soil Properties Reference: Figure 2:Usda.gov.(2019).Web Soil Survey.[online]Available at:https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx[Accessed 8 May 2024]. VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -5 - VISTASTRUCTURALCOM Portland,Oregon (� VISTA Kansas City,Missouri -STRUCTURAL— ' Ei12G3NEFs RrPV G- LC.4r 1rt 4}�-il #� Legend / Qa,Quaternary alluvium / GIs,Quaternary mass-wasting depositsy QI,Quaternary loess $ of,Pleistocene outburst-Flood deposits Q d Pleistocene continental glacial drift 9 , Gad,Pleistocene alpine glacial drift Sedimentary Rocks and Deposits Search 21 NE Mountain View Dr,Tahuya, gZooml result Washington,98588 to resu QTc,Quatemary—Tertiary continental sedimentary rocks and deposits �� Tc,Tertiary continental sedimentary rocks ---...*c--- MZc,Mesozoic continental sedimentary rocks rY Tn,Tertiary nearshore sedimentary rocks MZn,Mesozoic nearshore sedimentary rocks Figure 3:Geological Map Reference: Figure 3:Available at:https://geologyportal.dnr.wo.govl#wigm[Accessed 8 May 2024]. VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -6- VISTASTRUCTURAL.COM Portland,Oregon +� VISTA Kansas City,Missouri S\4. —STRUCTURAL— cvrin:�sl�arvv, d? DMrwAil,pS y�„� 51ase lark �. Silver dale Bainbridge 1: Scarps ^may\ Scarps and Flanks I"fY.. ,�I�ij;t Grmn MnunL�in Bmmerton Stark 1—$1 D Tug Ch 21 NE Mountain View Dr,Tahuya, Q2oom1 At shington,98588 to results' Landslide Deposit Confidence U yr ❑ High(30-40) i1 • 1�a Moderate(11-29) r Low(1-10) 1n.lsor. i�f_ f 1Ir +(t Jr� SLIP Landslides slaokon115h Confidence rig '� �• ,'to ik�� , J High(30.40) l Moderate(11.29) 5puaun ru-d SLIP Fans UkpNOpp.,►arl0and - ---- R.^-- prtW/litkyr � t 5r �• .A - sau 14ili i 1AC olyll .1pla 7mu sa,e laws• „� + i s 1(ack Hfffs ,SIDA Figure 4:Landslide Hazard Map Reference: Figure 4:Available at:https://geologyportal.dnr.wo.govl#wigm[Accessed 8 May 2024]. VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -7- VISTASTRUCTURALCOM Portland,Oregon � VISTA Kansas City,Missouri \�4 —STRUCTURAL— GfN� V r_ t:'IP4 r LLC LNTC Hazards by Location Search Information ". LokeNip"" Address: 221 NE Mountain View Dr,Tahuya,WA 98588,USA "8 ft ' Coordinates: 47.4643338,-122.983177 Elevation: 448 it 4' Timas lamp: 2024.05-0T T21 26.52.6VW Hazard Type: Seismic c Reference Document: ASCE7-16 Go gle ;, Map data t'20: Risk Category: 11 She Class: D-defauft Basic Parameters Name Value Description SS 1.576 MCER ground motion(period=0.2s) SI 0.574 MCER ground motion(penod-1.0s) SMS 1.892 Site-modified spectral acceleration value Sul 'nua Silo-moddited Spectral acceleration value SOS 1.261 Numeric seismic design value at 0.2s SA SDI 'ow Numeric seismic design value at 1.0s SA See Section 11.4.8 -Additional Information Name Value Description SDC 'null Seismic design category Fa 1.2 Site amplification factor at 0.2s F null Site amplification factor at 1.0s, Figure 5:Seismic Parameters Reference: Figure 5:Atcouncil.org.(2019).ATC Hazards by Location.[online]Available at:https:Hhazards.atcouncil.org[Accessed 8 May2024] VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -8- VISTASTRUCTURAL.COM Portland,Oregon I VISTA Kansas City,Missouri —STRUCTURAL— r�rcitQG.Ci71r'J�, f_e_C Legend Cascadia Seismic Scenario Snaking Intensity(MMI value) Shaking Intensity 4-Light 21rNE Mountain View r L t e D Tahu a 9 Search QZoom Y result �Nashington,98588 to res � S-Moderate Ell X 6-Strong iaup - 7-Very Strong i r ® 8-Severe r q ipo POt r Earthquake d Active Faults.Known or Suspected i<h Visible fault trace Inferred faun trace -• Concealed fault trace s I 'din Figure 6:Cascadia Earthquake Hazard Map Reference: Figure 6:Available at:htt s: eolo ortal.dnr.wa. ov#wi m(Accessed g P //B BYP B / B I e 8 May 2024). VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 -9- VISTASTRUCTURAL.COM Portland,Oregon I� VISTA Kansas City,Missouri \�\// —STRUCTURAL— J - Ground Response Zoom 1 Search 1 P21 NE Mountain View Dr,Tahuya, }} 'to result result Jashington,98588 i Liquefaction Susceptibility ® High + X Moderate to high Moderate e Low to moderate Low Very low to low Very low Bedrock Peat is Ice Water r Figure 7:Earthquake Hazard Map—Liquefaction Reference: Figure 7:Available at:https://geologyportal.dnr.wa.gov/#wigm[Accessed 8 May 2024]. VISTA STRUCTURAL ENGINEERING, LLC 11575 SW PACIFIC HWY#2262 PHONE: 971.233.6099 TIGARD, OREGON 97223 - 10- VISTASTRUCTURAL.COM