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Home My WebLink AboutGEO2010-00024 BLD2010-00413 - BLD Engineering / Geo-tech Reports - 7/8/2010 MASON COUNTY DEPARTMENT OF COMMUNITY DEVELOPMENT Planning Division P O Box 279, Shelton, WA 98584 flo (360)427-9670 Geotechnical Assessment Review Acceptance Letter July 08, 2010 PATRICIA ROMOS PO BOX 505 MANCHESTER WA 98363 Case No.: GE02010-00024 Parcel No.: 122175000053 Proiect Description: GEO FOR NEW SFR (BLD2010-00413) The Geotechnical Assessment for PATRICIA ROMOS has been received and reviewed by the Planning Department. The assessment was prepared by Paul Austin dated 5/25/2010. Based on the certification provided by the licensed engineer/geologist, the referenced Geological Assessment was prepared in general accordance with the requirements in the Mason County Resource Ordinance, Landslide Hazard Areas 17.01.100.E.4. Mason County considers the review valid until such time as scope of project, site conditions, and/or regulations change. Should the scope of work, site conditions, and/or regulations change after the original review, then an addendum from the original author of the assessment may be required to address these changes. The assessment would only be re-reviewed if a permit for development were submitted after these changes occur. Mason County does not certify the quality of the work done in this Geological Assessment. Please contact me at (360) 427-9670, ext. 365 if you have questions. Sin ely � � G Allan Borden Land Use Planner Mason County Planning Department Comments: 7/8/ M6N�IWHOdlld Page 1 of 1 GE02010-00024 �o Zo►o- ��i� o NG Mason County Department of Community Development Submittal Checklist For a Geological Assessment Instructions: This checklist must be submitted with a Geological Assessment and completed, signed, and stamped by the licensed professional(s) who prepared the Geological Assessment 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 , _` .1en Parcel# I Z_2_/ 7 S 000 D Site Address '3o) x7 R4 i (1) A discussion of geologic conditions in the general vicinity of the proposed development,with geologic unit designation based "DUCEIW-T on referenced maps. JJ Located on page(s) / (2) (a) A discussion of the ground water conditions at the site, Located on page(s) MASON COUNTY (b) A discussion of the estimated depth to water Located on page(s) :Z (c) A discussion of the quantity of surface seepage Located on page(s) Z- (d) A discussion of the upslope geomorphology Located on page(s) i (e) A discussion of location of upland waterbodies and wetlands. Located on page(s) (3) The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand. Located on page(s) a (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) (5) A discussion of the history of landslide activity in the vicinity, as available in the referenced maps and records. Located on page(s) �s (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) (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. Page 1 of 2 Form Effective June 2008 Located on page(s) (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) -5 li.� s'�r13 fE' (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) IF 1 � (d) building or other setbacks (top, both sides, and toe). Located on Map(s) -S �I/�' s n R�`L (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) 5 '&* STG P 1.P 1, (A 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 c.5 ' b and entitled �Q A meets all the requirements of the Mason Co( ty Resource Ordinance, Landslide Hazard 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. (Signature and Stamp) a -,-,//,O ct S(,7- pvL Lo z y � 16g68 O�VAL Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment. Page 2 of 2 Form Effective June 2008 y , Plats Plus Engineering Consulting Civil Engineers 2182 Eaton Lane Bremerton,WA 98311 360-698-1661 (fax)-698-1469 May 25,2010 Project No. 1726-A Mr. Particio Romos P.O. Box 505 Manchester,WA. 98353 Geologic Assessment Report Tax Parcel 122175000053 301 E Rainier Ct Allyn,Washington Presented herein are the results of a limited geotechnical evaluation study directed at evaluating potential erosion and landslide hazards at the referenced site in accordance with the requirements of the Mason County Resource Ordinance No. 77-93, sections 17.01.100"Landslide Hazard Areas", 17.01.102"Seismic Hazard Areas", and 17.01.104"Erosion Hazard Areas." Fieldwork for the study was undertaken on May 6,2010. Site Conditions and Proposed Development The subject parcel is 0.26 acres in size and is located on E Rainier CT Allyn in Section 20 Township 22 N Range 1W as shown on Figure 1, Vicinity Map. The parcel is rectangular in shape and bordered by single family residences (SFRs) to the north and East. Existing site vegetation consists of scattered mature evergreen trees with secondary brush. The site generally slopes from west to the east with an elevation change from 260 on the western portion of the lot to 220 feet on the easterner portion. The topography of the parcel is shown on Figure 2, Site Topography. The slopes on site are less than 40 percent so no slope stability was needed. It is our understanding that the proposed SFR is to be two story and wood construction. Figure 3 shows the approximate building footprint of the SFR. Methodology Soil and slope conditions of the subject property were visually examined and evaluated using available soil exposures and road cuts in the site vicinity. This information along with mapped soil conditions(see below)provided a basis for a general understanding of the local soil and geologic conditions. Actual subsoil conditions and thickness may vary. In addition to the observation of available soil exposures and reconnaissance of the area, the readily available resources listed below were reviewed: • "Washington State Coastal Zone Atlas", Washington State Department of Ecology and Mason County Volume 9. • U.S.D.A. Soil Survey Mason County,September, 1960. 2182 NE Eton Lane • Bremerton,Washington 98311 • (360) 698-1661 • Fax: (360) 698-1469 f Project No. 1726 May 25,2010 , Paee No.2 • "Geologic Map of Washington, Northwest Quadrant", Washington State Division of Geology and Earth Resources,2002. • U.S.G.S. 7.5 minute series topographic map,"Vaughn,Washington Quadrangle". • "Relative Slope Stability of The Southern Hood Canal Area, Washington", map I-853-F, Washington State Department of Natural Resources, Division of Geology and Earth Resources, 1977. • Geology and Related Ground-Water Occurrence, Southeastern Mason County, Washington, Plats 1 and 2, by Molenaar and Noble. Dated 1970. Site Soil Conditions The Washington Division of Geology and Earth Resource(WDGER), Geologic Map of Washington indicates that the site is underlain by glacial till (Qgt). The site appears to be relatively near the contact with glacial advance outwash soils. The glacial till typically consists of an unsorted, non-stratified mixture of sand, silt, gravel and cobbles. The till is typically very dense or hard, as a result of compaction under the weight of the glacial ice. The soils encountered at this site are typical of advance outwash and glacial till. The advance outwash is typically present below the glacial till, since this material was deposited in advance of the glacier and then was overridden by the glacial ice. The advance outwash is typically comprised of relatively stratified sand and gravel with occasional silt and clay interbeds. Groundwater Conditions No groundwater seepage was observed during our fieldwork. A subsurface investigation was not performed for this project. We estimate that the static groundwater table is at least 150 feet below the ground surface (Washington State Department of Ecology Well Logs). A perched water table may develop within or above the glacial outwash. There are no upland water bodies or wetlands from the subject site. There was no visible evidence of significant water surface flow on the lot at the time of the site visit. Surface Conditions Present slope grades and surface conditions were examined across the property and adjacent properties.The site slope has a gradual elevation change of 40 feet over a distance of approximately 148 feet as shown on Figure 2. There was no evidence of landslides or creep seen during the site visit. General site topography is shown on Figure 2. The Washington State Department of Ecology Coastal Zone Atlas indicates that the subject parcel is located in an area considered to be stable. The slope stability map "Relative Slope Stability of the Southern Hood Canal Area, Washington" identifies the site areas as being of class 1 stability. Class 1 stability areas are described as "Areas believed to be stable. Slopes generally less than 15%,but may be greater locally in areas too small to be shown at the map scale. Normal,proper engineering practices generally are adequate to insure stability in these areas." CONCLUSIONS Recommendations &Buffers No Upland drainage features should be installed. No septic drain fields are to be placed on the site.No upland fills will be allowed. There are no restrictions on the footings. Standard or prescriptive footings should be allowed. There are no buffers on this site. The setback from the existing offsite cut slope should be 25'. All upland areas should remain vegetated as much as possible. Clearing for the proposed house is acceptable. No significant impacts on or off site should be experienced as long as vegetation, drainage and erosion control consistent with a SFR are imposed. So special buffers or structural mitigation is necessary. 2182 NE Eton Lane • Bremerton,Washington 98311 • (360) 698-1661 • Fax: (360) 698-1469 Project No. 1726 May 25,2010 Page No.3 Landslide Hazards Based on our site observations and review of pertinent materials, it is our opinion that the subject parcel is not within a landslide hazard area (as defined in the Mason County Resource Ordinance, Geologically Hazardous Areas 17.01.100.A) or its associated buffer or setback. There is a slope that meets the definition of a landslide hazard area (due to slope greater than 40 percent with vertical relief greater than 10 feet) within 300 feet of the proposed construction (Figure 3). However, the slope is approximately 25 feet away and will not be impacted by the construction. In addition the majority of the construction will be within the building footprint and no impact on the stability of the subject parcel slope is expected. For these reasons, we do not recommend that a Geotechnical Report be required for the proposed construction. Seismic Concerns In our opinion,the site does not meet the definition of a seismic hazard area. Erosion Concerns The Soil Survey of Mason County (as accessed through the United States Department of Agriculture, Natural Resources Conservation Services Web Soil Survey website - websoilsurvey.nres.usda.gov) indicates the site is underlain by Alderwood gravelly sandy loam with 15 to 30 percent slopes. Although the soil survey website indicates the site slopes are less than 15 percent, the topographic map indicates that some site slopes are steeper than 15 percent. Therefore,the site slopes steeper than 15 percent meet the definition of an Erosion Hazard Area as presented in the Mason County Resource Ordinance section 17.01.104.A. Please see section 17.01.104.D for requirements related to development within an Erosion Hazard Area. REPORT LIMITATIONS This report has been prepared for the exclusive use of Mr. Particio Romos and his agents for use in planning of the referenced development. The conclusions and recommendations in this report are based on our interpretation of site conditions, as they presently exist, anticipated future construction activities, and the expectation that the exploratory efforts adequately define the subsurface conditions across the site. The soil conditions described in this report and the conclusions and recommendations contained in this report are provided for this specific site only and should not be expanded for use on adjacent properties without additional exploration and review of those sites by our firm.The data and report should be provided to prospective contractors for their bidding or estimating purposes, but the report conclusions and interpretations should not be construed as a warranty of the subsurface conditions. There are possible variations in subsurface conditions. In the event that the scope or location of the project should change or subsurface conditions different from those encountered during this study be observed or suspected,we should be advised. At that time a review of the changed conditions will be made,and alternative or remedial recommendations given as required. NOTE: No subsurface explorations were made as part of this study. Evaluation of subsurface soil and groundwater conditions were made based on soil exposed at the surface and published information. Therefore, the subsurface conditions actually present may be different from those assumed in this report. We have not evaluated the site for the potential presence of contaminated soil. The evaluation of possible environmental or geo-environmental considerations is beyond the scope of this report. The owner and the contractor should make themselves aware of and become familiar with applicable local, state, and federal safety regulations, including current WISHA excavation and trench safety standards. Construction site safety generally is the sole responsibility of the contractor. The contractor shall also be solely responsible for the means, method, techniques, sequences, and operations of construction operations. Plats Plus Engineering LLC is providing the preceding information and recommendations solely as a service to Mr. Particio Romos. Under no circumstances should the provision of this information or recommendations be construed to mean that EnviroSound Consulting, Inc. 2182 NE Eton Lane • Bremerton,Washington 98311 9 (360) 698-1661 • Fax: (360) 698-1469 r j� Project No. 1726 May 25,2010 • Page No.4 is assuming responsibility for construction site safety or the contractor's activities; such responsibility is not implied and should not be inferred. Within the limitations of scope, schedule, and budget for this work, it is warranted that the work has been done in accordance with generally accepted practices followed in this area at the time this is report was made. No other warranty, expressed or implied is made. Should you have any questions or concerns, which have not been addressed, or if we may be of additional assistance, please call our office at(360) 698-1661. Sincerely, n 0 1696$ Q SIGNAL NOTE: DRAWING COPY IS INSCRIBED WITH DIGITIZED &DATE. ORIGINAL ED DRAVANG IS ARCHIVEDEIN THE SIG NA ENGINEER'S OFFICE Paul Austin P.E. 2182 NE Eton Lane • Bremerton, Washington 98311 • (360) 698-1661 • Fax: (360) 698-1469 �... �§ �y sue.; ' Project No. 1726 May 25,2010 Page No.5 y r. Page 1 c.I �•��: 1141tL.p��-Vag'.-lei f c 1 r ll i I R i P + sanle 11'4 CA I Wes i i ! Y1J Usti. ,...1 il,arca K � � ez1r � , e-,,_ •. 1:=1'�dl§_�2g��1c'h �at.. ��`�' -... 2182 NE Eton Lane • Bremerton. Washington 98311 • (360) 698-1661 • Fax: (360) 698-1469 Project No. 1726 - May 25,2010 . - Page No.6 /,' 1 lilt��2 �0.'":4 I ✓av � .� - I .'. - •Y " 2� :12'.� i i jai N i y �r r! i •a ,QS T. f 1 r rr - - LT _ ��• 1CL,T h _ � � 2182 NE Eton Lane • Bremerton, Washington 98311 • (360) 698-1661 • Fax: (360) 698-1469 r y M Project No. 1726 May 25,2010 Page No. 7 y � Aw- 71, r. N i l � £fin _s} s S Yn R --- M rr � r - x Y t 7 l Yl4 w, tv Ilr.'f!4T.¢ IYr�tl,CF II,L'l'KR IWW,KG IYYR.Yhlt IR'N.ri.4" YY!V. 'w.k' L ky R t. N Y� T 2182 NE Eton Lane • Bremerton,Washington 98311 • (360) 698-1661 • Fax: (360) 698-1469 P �A N N N G MASON COUNI`Y: -WiALL ET BA" ARE M . `;SU# i:D FROM THE FURTHEST �- F 'PO EC' ON OF THE BUILDING 12. 2 1 IS Z 40 q gq E 000,53 VV75000054 f d 99 40 ) S CA IE 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, staff should refer the case to the Planning Manager or Director. Applicant'sName: f` S IV 10 006 Z� Sb 3 Permit# Parcel# 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 referencerd maps. OK? V Comment: (2) (a)A discu sign of the ground at r conditions at the site, OK?V Comment: (b) A disc ssion of the estimated depth to water OK? Comment: (c) A d i s ssion of the quantity of surface seepage OK? Comment: (d) AZdisssion of the upslope geomorpho ogOK? Comment:(e) Asion of location of upla d aterbodies and wetlands. OK? Comment: (3) The approxi ate depth to hard or dense competent soil, e.g. glacial till or outwash sand. OK? Comment: !/ (4) A discussion of any geomorphi ex ression of past slope instability(presence of hummocky ground or ground cracks, terraced topography indicative of landslide block moveme , bowed or arched trees indicating downslope movement, etc.). OK? Comment: 55 (5) A discussion of the history of lan4slid6 activity in the vicinity, as available in the referenced aps and records. f OK? Comment: (6) An opinion on whether the propose 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 propowd development. OK? V Comment: (7) A recommendation by the preparer wh th r a Geotechnical Report should be required to further evaluate site conditions and the pr p sed,development of the subject property. OK? Comment: 12 (8) If the presence of a hazard is determin4 Whin 300 feet of the proposed development, then the following are delineated on a geologic map/site map: (a) the area of the proposed development, OK? Comment: f 1 Page 1 of 2 Form Effective June 2008 (b) the boundaries of the landslide hazard area (top, both sides, and toe), { OK? Comment: (c) the associated buffers (top, both sides, and toe) OK? Comment: (d) building or other 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? Commend Are the.Document(s)signed and stamped? Type and #of License: X14 It X2 t 6 If not approved, what is the next action/recommendation for further action? Reviewed by , on Time spent in review: SECOND REVIEW/UPDATE: Reviewed by on ' 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