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HomeMy WebLinkAboutGeological Assessment for DRV2019-00001 - GEO General - 2/28/2019 (6/12/2008) Michael MacSems - Geological Assessment Review Checklist 6-08.doc Page 1 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's Name: ll' C— L L Permit# OQV �Gf - 01 Parcel# Z ZZ Date(s)of the Document(s) reviewed: 3 _ -7 A S (1) A discussion of geologic conditions in the general vicinity of the proposed development,with geologic unit designation based on referenced maps. OK? Comment: 1 4 L (2) (a)A discussion of the ground watg� -on conditions at the site, OK? V Comment: 6P (b) A discussion of the estimated depth to water OK? ✓ Comment: ` — (c) A discussion of the quantity of sAay seepage OK? ✓ Comment: 0-5 (d) A discussion of the upslope geomorphologX OK? V Comment: e 3 S '} (e) A discussion of location of upland waterbodies and wetlands. OK? V Comment: 'L (3) The approximate depth to hard or denp ypetent soil,e.g. glacial till or outwash sand. OK?_V Comment: (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 j i' ting downslope movement,etc.). OK?_/ Comment: (J�`t (5) A discussion of the history of landslide activity in the vicinity,as available in the referenced maps apyl records. OK? yy 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? y Comment: `t (7) A recommendation by the preparer whether a Geotechnical Report should be required to further evaluate site conditionfaq the pro sed clevelopment�the subject property. OK? ✓ Comment: 0w eL.. w-t— y�Clc tr d-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 develop ent, OK? ✓ Comment: /V/W (b) the boundaries of the landslide hazard area(top, both sides,and toe), Page 1 of 2 Form Effective June 2008 (6/12/2008) Michael MacSems-Geological Assessment Review Checklist 6-08.doc Page 2 OK? / Comment: & )A (c) the associated buffers(top, both sides,and to OK?_V Comment: ��/1 (d) building or other setbacks(top,bot sides,and toe). OK?_V Comment: 41 / (9) A site map drawn to scale showing fhe property boundaries,scale, north arrow,and the location and nature of existing and proposed development on the site. OK? Comment: Are the Document(s)signed and stamped?�. Type and#of License: A a�v f�u 5 If not approved,what is the next action/recommendation for further actin ? 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 MASON COUNTY Submittal Checklist ' COMMUNITY SERVICES Geological Assessment M+Ydn¢Ptarruna ErnlronmrrtW Hcahh,Crxnmv+(ry Heuhh 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 is found not applicable, the report should explain the basis for the conclusion. Note:Unless specifically documented,this report does not provide compliance to the International Residential Code Sections 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. t 2 r� Applicant/Owner PC I L-1 L Parcel# I �������� J ��l Q. )0C� 1 Site Address A (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) I � o? (2) (a)A discussion of the ground water conditions at the site, Located on page(s) (b) A discussion of the estimated depth to water, Located on page(s) 2 (c) A discussion of the quantity of surface seepage, Located on page(s) >T (d) A discussion of the upslope geomorphology, Located on page(s) :3 14 (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) i (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) � — 4 (6) An opinion on whether the proposed development is within the landslide hazard area or its associated buffer or setback and the potentia,Uor landslide activity at the site in light of the proposed development. Located on page(s) 'T (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) W (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) ham:. JJAhA , CXJ61,1 Lt GC-1f,vA rQ� (b) the boundaries of the landsf a hazard area (top, both sides,and toe), Located on Map(s) Yl G�, U u r ON 10 (c) the associated buffers(top,both sides, and toe), �y Located on Map(s) '1 f!t & 1(�t�Tl�►'1 I�/�1. (d) building or other setbacks (top, both sides, and toe). Located on Map(s) (g) 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).-VI Uti(-Y o I 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.1 also certify that the Geological As^^^ ^^' 4'`-A � / )- I � and entitled Geological Assessment —T NE Koy Boad Rd. 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. J 014 �O of WAS Y1�1 1 �O 46365 sFcrsTOA Gam? �++ S/0NAl-E� 1 i (Signature and Stamp) i Page 2 of 2 Disclaimer: Mason County does not certify the quality of the work done in this Geological Assessment. 1 Mud Bay Geotechnical Services, LLC February 28,2019 Job: 1043-MAS Page 1 PCI,LLC c/o Dean Mauerman 1415 College St. SE, Lacey, WA 98503 Subject: Geological Assessment NE Roy Boad Rd. Belfair, WA (Parcel# 12328-23-00011) Dear Mr. Mauerman, Per your request, Mud Bay Geotechnical Services, LLC is providing a soils opinion to meet the permit requirements for tree clearing parcel (12328-23-00011) located at NE Roy Boad Rd, Belfair, WA. This report specifically addresses Mason County code section 8.52.140, which pertains to the requirements for land development on or near steep slopes and or landslide hazards. Any development within a geologically hazardous area or within three hundred feet of the geologically hazardous area requires a geological assessment or a geotechnical report, or both. Geologically hazardous areas are defined as any area with a slope of 15 percent or greater and with a vertical relief of ten feet or more and the following: any area with a slope of forty percent or steeper and with a vertical relief of ten or more feet except areas composed of consolidated rock. A geological assessment is also required for tree clearing parcels of this size. We understand that the current scope is to obtain a permit for clearing the land in preparation for future development. The purpose of this report is to assist you in meeting the minimum requirements of the Mason County ordinance for the tree clearing phase. A geotechnical report will be required for the site development,which will be developed under a separate scope. The property is not located within a mapped landslide area, marine bluff area, or erosion hazard area. This report does not address any other permit requirements that may need to be provided in the permit package to the county for permitting. t 2 Location and Description The property consists of a total of 10.0 acres on parcel 12328-23-00011 located at the address of NE Roy Boad Rd.,Belfair,WA.The parcel location is identified on the Site Location map included as Figure 1 attached to this report. At the current time the site is accessed in an area where a paved road ends and an unpaved access road has been cleared. The steep slope area consists of slopes projecting downward to the west from SR-3 down to the NE Roy Boad Rd. access road. The western half of the parcel consists of slopes around 15 percent or less, while the eastern half of the parcel consists of slopes with 15 to 40 percent. There are no mapped waterbodies or wetlands within the vicinity of this parcel. Surface Conditions At some time in the past,the parcel was partially cleared. Scattered conifers such as Douglas fir, cedar, and Western hemlock varieties are still present, which will to be removed as proposed in the scope of this current project.The regrowth on the site since the time of partial clearing consists primarily of deciduous varieties such as Big Leaf Maple, and various smaller conifer trees. Underbrush and surface vegetation consists mostly of native Himalayan Blackberry, English Ivy, and Sword fern. Nov,, h Vt^,%N 0 Site Geology As part of this project, a review of the available geologic data was performed and a site-specific geologic map was prepared.The project vicinity Geologic Map is attached as Figure 2.This figure indicates the project vicinity consists of Quaternary Alluvium and Pleistocene Continental Glacial Drift. Conditions observed at the site are generally consistent with the mapped geology at the site. Along with the site geology, the site soil data was also reviewed for this specific site and is represented in attached Figure 3,USDA Soil Map.The soil in this area was mapped by the United States Department of Agriculture,USDA,and consists of Alderwood gravelly sandy loam with 15 to 30 percent slopes,Everett very gravelly sandy loam with 8 to 15 percent slopes,Indianola sandy loam with 0 to 5 percent slopes,Mukilteo peat with 0 to 2 percent slopes,and Saxon silt loam with 5 to 15 percent slopes. Conditions observed at the site are generally consistent with the mapped soil at the site. It should be noted the percent slopes mapped with these soils is an approximation. Surface Water and Groundwater Conditions The Everett very Gravelly sandy loam and Indianola sandy loam soil units mapped at the project site and vicinity both generally consists of soil materials exhibiting somewhat excessively draining characteristics. The regional groundwater table at the site after initial installation of a monitoring well was found to be at approximately 21 feet. No surface seepage was noted at time of site visit. See the Surface and Subsurface Exploration below. 3 Surface and Subsurface Exploration As part of the investigation,a site visit was performed on February 22,2019 to observe the surface and subsurface conditions on the parcel.At the time of our site visit,a primitive pathway had been cleared at the bottom of the hillside on the east side of NE Roy Boad Rd. Within this cleared pathway a track mounted drill rig was brought in and a 45-foot drilled boring was completed (designated BH-1-19). A groundwater monitoring well was installed in BH-1-19. Surface soil samples were also collected throughout the parcel. See Figure 4, Site Exploration Map for drilling and surface sample locations throughout the parcel. Manual measurements of the groundwater will be recorded on approximately a biweekly basis over the upcoming months in order to satisfy Mason County requirements and Department of Ecology requirements for monitoring the groundwater throughout one wet season, and for a total duration of at least one year. The well was given a Washington State Department of Ecology Unique Well ID#BLI-521. Standard Penetration Tests (SPT) were performed at 5-foot intervals. The split spoon samples recovered from the boring were field classified using the ASTM D2488 Visual-Manual procedure for identification and classification of soils in accordance with the Unified Soil Classification System (USCS). The soil throughout the parcel is consistent with the geologic units found in the Geologic Map,Figure 2,and have been characterized below.Based on the recovered soils samples and drilling conditions observed in boring BH-1-19, the stratigraphy in the immediate vicinity of the boring location consists of approximately 5 to 7 feet of poorly to well graded sand with gravel, underlain by approximately 14 feet of soft to very soft elastic silt and clayey silt. The silt and clay is underlain by very loose to very dense poorly graded sand to the final depth of the boring at 45 feet below the current ground surface. Very dense soils are present starting from a depth of 35 feet below the ground surface. Groundwater was encountered at the time of drilling at 21 feet below the ground surface, immediately below the confining silt and clay layer. As previously mentioned, the groundwater depth will be recorded on a bi-weekly basis. A copy of the final boring log, details on the drilling methods and well installation, and final groundwater measurements will be provided as a separate deliverable or included in the final geotechnical report for the site development of the parcel. The stratigraphy at shallow depths on the slope can also be viewed within soil exposures at selected locations, or by removing the surface vegetation and forest duff overburden locally to expose the underlying native deposits. The surface of the slope consists of soft and spongy organic soil resulting from decay and weathering of the forest floor and surface vegetation. This organic layer is limited in thickness and is underlain by native glacial deposits. Three surface samples were collected (designated S-1-19, S-2-19, and S-3-19). The near surface samples were found to be consistent throughout the parcel, consisting of moist, reddish brown, gravelly sands with no plasticity, (S", note: grain sizes range from medium grain sand to medium grain gravels. The locations can be seen on Figure 4, Site Exploration Map. 4 Landslide Hazard Assessment As part of the investigation of the site, we reviewed the lidar, and landslide hazard mapping available from the Washington Department of Natural Resources available at the 1:100,000 scale. The lidar data for the site vicinity does not appear to show any typical expressions characteristic of deep-seated landslide slumps. The landslide hazard mapping inventory available from the Washington State Department of Natural Resources was used to create a site-specific map of the potential landslide hazard at the site and surrounding vicinity. The Landslide Inventory Map is included as Figure 5 attached to this report. The Landslide Inventory Map does not indicate a potential for landslides at the property site and vicinity. The steep slopes on the western half of the parcel are minimal with a 15 percent or less slope;the eastern half is much steeper with slopes ranging from 15 to 40 percent.A site-specific map of the slope percentage is mapped in Figure 6,Steep Slope Assessment.Vegetation should be encouraged to prevent any serious erosion issues. It's likely within the spring and summer months natural revegetation of the hillside will continue and any erosion is likely to be limited to the 2 to 4 feet of looser material and overburden on the slope. There does not appear to be any over steepened cuts in the site vicinity which could adversely affect the slope of the property. Geotechnical Recommendations Based on a site reconnaissance, subsurface exploration, discussions with the property owner, and a review of all of the site geology and other readily available information presented previously, in the opinion of Mud Bay Geotechnical Services, LLC the potential steep slope hazard is minimal throughout the property.Tree clearing the parcel as proposed should not result in an unstable slope condition for the parcel or surrounding vicinity. Prior to site development of the parcel, we recommend allowing the ground surface vegetation to continue to develop in order to reduce the potential for surface erosion. The tree clearing activities should be done in a way to reduce the amount of surface vegetation removed to the extent possible. Selected areas of bare ground that are found to be susceptible to erosion after the tree clearing should be actively protected by placing and pinning coir,jute, or turf reinforcement mat on the surface of the affected areas to reduce erosion and promote the growth of surface vegetation. The tree clearing will result in a change in the surface stormwater runoff, which will need to be managed as part of a stormwater site plan prepared by others. In the event the site was to be developed with structures,then this steep sloped area of the parcel will require additional geotechnical recommendations. Recommended Additional Services Mud Bay Geotechnical Services, LLC is available to assist you with the geotechnical design for any additional site features or structures requiring design as part of the final permitting for site development. We can also assist with determining the recommended soil infiltration rate for storm water infiltration design and perform a groundwater mounding analysis, if required. 5 Intended Use and Limitations This report was prepared based on observations of the surface and subsurface conditions at the site, review of geology and other information available for the site, and conversations with the property owner about the soil and surface water conditions on the property and the nature of the proposed development. The geotechnical recommendations in this report are based on the current site conditions and understanding of the proposed development as described previously. Any modification of the current property conditions or the nature of the proposed development beyond what is described in this report would render these geotechnical recommendations invalid. It should not be used, in part or in whole for other purposes without contacting Mud Bay Geotechnical Services,LLC for a review of the applicability of such reuse. We have enjoyed the opportunity to work with you and serve your geotechnical needs for this project. Please contact me at your earliest convenience if you have any questions or would like to discuss any of the content of this report. Sincerely, Chris Heathman, P.E. Mud Bay Geotechnical Services,LLC Q�ER d Oy 2-/2$/Z O I J of WASH, � �� � QA O F FOISTEa�° ss��kAL ENG I r. � •�, ? ,, 11 art_•- rl.r' .�—_ .� per• .+ :1 Wit'- f�. y..r,.. f •.. - C .�,� �. s• ♦ a j S ." e.a.. ,r •... �' ` Site Location Minn Mud Bay Geotechnical Services, LLC JOB#: 1043-MAS I Date:January,2019 a.: ✓'f •= Figure 1:Site Map NE Roy Boad Rd, Belfair,Washington Site Development Geotechnical Report 1 LEGEND O Site Location Parcel Boundary Geologic Units 24k Quaternary bog,marsh,swamp,or lake deposits Quaternary alluvium Pleistocene continental glacial drift Pleistocene continental glacial till I W—.Vm D—d Geo gy an0 ECM R..ou2e5.Source.E-.Dg"Gb ,Oea r E„ tI Mud Bay Gaoteehnieal Services, LLC Geopaph,cs.CNES/A—DS.USDA,USGS.rVroGR10.IGN,end N OIS US C—mty 0 0045 0.09 018 Males N JOB#: 1043-MAS I Date:January,2019 OVi"I Figure 2: Geologic Map ReSNINOtONGFOLOWUlSYeV[y Washington Geologic Portal Belfair,Washington Site Development Geotechnical Report 1 T Mud Bay Geotechnical Services, LLC April 3,2019 Job: 1043-MAS Page 1 PCI, LLC c/o Dean Mauerman 1415 College St. SE, Lacey, WA 98503 Subject: Geological Assessment NE Roy Boad Rd. Belfair, WA (Parcel# 12328-23-00011) Dear Mr. Mauerman, Per your request, Mud Bay Geotechnical Services, LLC is providing a soils opinion to meet the permit requirements for tree clearing parcel (12328-23-00011) located at NE Roy Boad Rd, Belfair,WA.This report addresses Mason County comments on the original report dated February 28, 2019. The report specifically addresses Mason County code section 8.52.140, which pertains to the requirements for land development on or near steep slopes and or landslide hazards. Any development within a geologically hazardous area or within three hundred feet of the geologically hazardous area requires a geological assessment or a geotechnical report, or both. Geologically hazardous areas are defined as any area with a slope of 15 percent or greater and with a vertical relief of ten feet or more and the following: any area with a slope of forty percent or steeper and with a vertical relief of ten or more feet except areas composed of consolidated rock. A geological assessment is also required for tree clearing parcels of this size. We understand that the current scope is to obtain a permit for clearing the land in preparation for future development. The purpose of this report is to assist you in meeting the minimum requirements of the Mason County ordinance for the tree clearing phase. A geotechnical report will be required for the site development,which will be developed under a separate scope. 2 The property is not located within a mapped landslide area, marine bluff area, or erosion hazard area. This report does not address any other permit requirements that may need to be provided in the permit package to the county for permitting. Location and Description The property consists of a total of 10.0 acres on parcel 12328-23-00011 located at the address of NE Roy Boad Rd.,Belfair,WA.The parcel location is identified on the Site Location map included as Figure I attached to this report.At the current time the site is accessed in an area where a paved road ends and an unpaved access road has been cleared. The steep slope area consists of slopes projecting downward to the west from SR-3 down to the NE Roy Boad Rd. access road. The western half of the parcel consists of slopes around 15 percent or less,while the eastern half of the parcel consists of slopes with 15 to 40 percent. There are no mapped waterbodies or wetlands within the vicinity of this parcel. Surface Conditions At some time in the past, the parcel was partially cleared. Scattered conifers such as Douglas fir, cedar, and Western hemlock varieties are still present, which will to be removed as proposed in the scope of this current project.The regrowth on the site since the time of partial clearing consists primarily of deciduous varieties such as Big Leaf Maple, and various smaller conifer trees. Underbrush and surface vegetation consists mostly of native Himalayan Blackberry, English Ivy, and Sword fern. Site Geoloev As part of this project, a review of the available geologic data was performed and a site-specific geologic map was prepared.The project vicinity Geologic Map is attached as Figure 2.This figure indicates the project vicinity consists of Quaternary Alluvium and Pleistocene Continental Glacial Drift. Conditions observed at the site are generally consistent with the mapped geology at the site. Along with the site geology, the site soil data was also reviewed for this specific site and is represented in attached Figure 3,USDA Soil Map.The soil in this area was mapped by the United States Department of Agriculture,USDA,and consists of Alderwood gravelly sandy loam with 15 to 30 percent slopes,Everett very gravelly sandy loam with 8 to 15 percent slopes,Indianola sandy loam with 0 to 5 percent slopes,Mukilteo peat with 0 to 2 percent slopes,and Saxon silt loam with 5 to 15 percent slopes. Conditions observed at the site are generally consistent with the mapped soil at the site. It should be noted the percent slopes mapped with these soils is an approximation. Surface Water and Groundwater Conditions The Everett very Gravelly sandy loam and Indianola sandy loam soil units mapped at the project site and vicinity both generally consists of soil materials exhibiting somewhat excessively draining characteristics. The regional groundwater table at the site after initial installation of a monitoring well was found to be at approximately 21 feet.No surface seepage was noted at time of site visit. See the Surface and Subsurface Exploration below. Based on a review of the available maps and data for the site,there are no upland water bodies in the vicinity higher in elevation than the project site. 3 Surface and Subsurface Exploration As part of the investigation,a site visit was performed on February 22,2019 to observe the surface and subsurface conditions on the parcel.At the time of our site visit,a primitive pathway had been cleared at the bottom of the hillside on the east side of NE Roy Boad Rd. Within this cleared pathway a track mounted drill rig was brought in and a 45-foot drilled boring was completed (designated BH-1-19). A groundwater monitoring well was installed in BH-1-19. Surface soil samples were also collected throughout the parcel. See Figure 4, Site Exploration Map for drilling and surface sample locations throughout the parcel. Manual measurements of the groundwater will be recorded on approximately a biweekly basis over the upcoming months in order to satisfy Mason County requirements and Department of Ecology requirements for monitoring the groundwater throughout one wet season, and for a total duration of at least one year. The well was given a Washington State Department of Ecology Unique Well ID#BLI-521. Standard Penetration Tests (SPT) were performed at 5-foot intervals. The split spoon samples recovered from the boring were field classified using the ASTM D2488 Visual-Manual procedure for identification and classification of soils in accordance with the Unified Soil Classification System (USCS). The soil throughout the parcel is consistent with the geologic units found in the Geologic Map,Figure 2,and have been characterized below.Based on the recovered soils samples and drilling conditions observed in boring BH-1-19,the stratigraphy in the immediate vicinity of the boring location consists of approximately 5 to 7 feet of poorly to well graded sand with gravel, underlain by approximately 14 feet of soft to very soft elastic silt and clayey silt.The silt and clay is underlain by very loose to very dense poorly graded sand to the final depth of the boring at 45 feet below the current ground surface.Very dense soils are present starting from a depth of 35 feet below the ground surface. Groundwater was encountered at the time of drilling at 21 feet below the ground surface, immediately below the confining silt and clay layer. As previously mentioned, the groundwater depth will be recorded on a bi-weekly basis. A copy of the final boring log, details on the drilling methods and well installation, and final groundwater measurements will be provided as a separate deliverable or included in the final geotechnical report for the site development of the parcel. The stratigraphy at shallow depths on the slope can also be viewed within soil exposures at selected locations, or by removing the surface vegetation and forest duff overburden locally to expose the underlying native deposits. The surface of the slope consists of soft and spongy organic soil resulting from decay and weathering of the forest floor and surface vegetation.This organic layer is limited in thickness and is underlain by native glacial deposits. Three surface samples were collected (designated S-1-19, S-2-19, and S-3-19). The near surface samples were found to be consistent throughout the parcel, consisting of moist, reddish brown, gravelly sands with no plasticity, (SM), note: grain sizes range from medium grain sand to medium grain gravels. The locations can be seen on Figure 4, Site Exploration Map. 4 Landslide Hazard Assessment As part of the investigation of the site, we reviewed the lidar, and landslide hazard mapping available from the Washington Department of Natural Resources available at the 1:100,000 scale. The lidar data for the site vicinity does not appear to show any typical expressions characteristic of deep-seated landslide slumps. The landslide hazard mapping inventory available from the Washington State Department of Natural Resources was used to create a site-specific map of the potential landslide hazard at the site and surrounding vicinity. The Landslide Inventory Map is included as Figure 5 attached to this report. The Landslide Inventory Map does not indicate a potential for landslides at the property site and vicinity. The steep slopes on the western half of the parcel are minimal with a 15 percent or less slope;the eastern half is much steeper with slopes ranging from 15 to 40 percent.A site-specific map of the slope percentage is mapped in Figure 6,Steep Slope Assessment.Vegetation should be encouraged to prevent any serious erosion issues. It's likely within the spring and summer months natural revegetation of the hillside will continue and any erosion is likely to be limited to the 2 to 4 feet of looser material and overburden on the slope. There does not appear to be any over steepened cuts in the site vicinity which could adversely affect the slope of the property. Geotechnical Recommendations Based on a site reconnaissance, subsurface exploration, discussions with the property owner, and a review of all of the site geology and other readily available information presented previously, in the opinion of Mud Bay Geotechnical Services, LLC the potential steep slope hazard is minimal throughout the property.Tree clearing the parcel as proposed should not result in an unstable slope condition for the parcel or surrounding vicinity. Prior to site development of the parcel, we recommend allowing the ground surface vegetation to continue to develop in order to reduce the potential for surface erosion. The tree clearing activities should be done in a way to reduce the amount of surface vegetation removed to the extent possible. Selected areas of bare ground that are found to be susceptible to erosion after the tree clearing should be actively protected by placing and pinning coir, jute, or turf reinforcement mat on the surface of the affected areas to reduce erosion and promote the growth of surface vegetation. The tree clearing will result in a change in the surface stormwater runoff, which will need to be managed as part of a stormwater site plan prepared by others. In the event the site was to be developed with structures,then this steep sloped area of the parcel will require additional geotechnical recommendations. Recommended Additional Services Mud Bay Geotechnical Services, LLC is available to assist you with the geotechnical design for any additional site features or structures requiring design as part of the final permitting for site development.We can also assist with determining the recommended soil infiltration rate for storm water infiltration design and perform a groundwater mounding analysis, if required. -� 5 Intended Use and Limitations This report was prepared based on observations of the surface and subsurface conditions at the site, review of geology and other information available for the site, and conversations with the property owner about the soil and surface water conditions on the property and the nature of the proposed development.The geotechnical recommendations in this report are based on the current site conditions and understanding of the proposed development as described previously. Any modification of the current property conditions or the nature of the proposed development beyond what is described in this report would render these geotechnical recommendations invalid. It should not be used, in part or in whole for other purposes without contacting Mud Bay Geotechnical Services, LLC for a review of the applicability of such reuse. We have enjoyed the opportunity to work with you and serve your geotechnical needs for this project.Please contact me at your earliest convenience if you have any questions or would like to discuss any of the content of this report. Sincerely, Chris Heathman, P.E. Mud Bay Geotechnical Services, LLC Q��'P J ONh,y WASy�ytc�� U „ y pp 46365 tv4i ��SS�GISTE E G�? SITE DATA CONSTRUCTION NOTES ^ 6 SW 1/4 NW 1/4 SEC 28 TWN 23N RNG 1W WM DIRECTIONS IO ILL y F` PARCEL F: IIB]605000+1 L TMS PLAN IS DwOR,LMMATK.CONTiiACTOR E RESPON.1sEFOR L FROM INTERSTATE S,TANf IXO U]TOWARD WA-16 W. GROSS ACREAGE mo AC PBI MIRITV DATA) COMPLETWO ALL WOP+tWACCOPDANCE WNN ALL APPUCABIF 2 FOLLOW GIGNS FOR WA-16WASNf MA1610R BNEMp1TON. M EXISTING RIO CODES AND PEGIAATION. S. OONTWUE ONTO WA-w W. 3 O.A EXISTING USE V�. 2 THE CONSTRUCTED WiROVEMENTS SHALL NOT BE—TED IMTL USE THE LEFT LANE TO TANS ENIT 36 TOWARD WA-+6W RE JURISDICTION: FINALW SPECTIONAND/OR ACCEPTANCEBY FROJECTENGINEEN. S. CONTNUE ONTO~6.ANY DEVwTpNS TO GNAN—.HOT BE ACCEPTED BY MIOJER 6. TURN LEFT ONTO WA-S.ENGINEERUNLESSAUTHORIZEDBYCONSTRUCTION ENGINEER PRIOR ). TURN RIGHT AFTER STARBUCNS(ON THE RIGHT).SITE COVERAGE DTOCONSTRLrrION. 6. TURN RIGHT ONTOROYBOADROAD. 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[I.b ofWnMP Ir°M.nm Mlunley...amm°vrw.[lo. d SILT FENCE CONSTRUCTION ENTRANCE DETAIL ' DETAIL NDT ovzvnDls s 3 NPOOI Z C-2 �s2 a ♦3 S .� � • 4 Q � � � e..w -•, ` ; `�* -+ Q Site Location • '• Mud Bay Geotechnical Services, LL C JOB#: 1043-MAS I Date: January, 2019 Figure 1: Site Map NE Roy Boad Rd, Belfair, Washington Site Development Geotechnical Report LEGEND 0 Site Location Parcel Boundary Geologic Units 24k Quaternary bog,marsh,swamp.or lake deposits Quaternary alluvium Pleistocene continerital glacial drift Pleistocene continental glacial till Wash.,:ton 0,of:—"y aid E>m Qwseu,cn :our.E,n o$�-il�ob*G�E&E> " Mud Bay Geotechnical Services, LLC J:rA Q`,3>A--,P,D 111N Y.1t 17,'-LKw Ccn'---, o 0.045 0.09 0.18 Maps JOB#: 1043-MAS Date: January, 2019 L Figure 2: Geologic Map WASIIINGIDN SIAT[DL PAl1fMLN1 UI ', a nATURAL RESOURCES Washing g ton Geolo is Portal NE Roy Boad Rd, 4 WA1NtNbhIN GLQtB(:!S At crNvf. a,•;w..•• Belfair, Washington Site Development Geotechnical Report Sov Map—Mason County Washbnpton ° t r Y f o ra. _.�. - } �P ter• LEGEND y & d Ac—Alderwood gravelly sandy ma loam, 15 to 30 percent slopes ❑ Eh—Everett very gravelly sandy x loam, 8 to 15 percent slopes Id Id—Indianola sandy loam, 0 to 5 � n � percent slopes sa Eh Ac Mg—Mukilteo peat, 0 to 2 percent slopes - Sa—Saxon silt loam, 5 to 15 percent slopes y / Parcel Boundary S r s 'tm IM) "'� '� `tmc Mud Bay Geotechnical Services, LLC JOB#: 1043-MAS I Date: January, 2019 a fl o ,o to +x sa Aa Figure 3: USDA Soil Map �pp=n fft '°"'o 'mo o»M-N�ww m'">a"m' NE Roy Boad Rd, +t t1 "aft" Woo Sod Stovey t r?YSO s G •+� Ce.,..r,raW.rtf.rtriu hatgra:Coaprtatirvo Soil Survey P.,oe,or, Belfair, Washington Site Development Geotechnical Report p , ► LEGEND Site Location Sample Collection Location S-1-19 BH-1-19 y ilk- S-1-19 S-3-19 �i Mud Bay Geotechnical Services, LLC JOB#: 1043-MAS Date: January, 2019 Figure 4: Site Exploration Map NE Roy Boad Rd, Belfair, Washington Site Development Geotechnical Report LEGEND } Site Location 1:24,000-scale and Watershed Analysis Study Ex*rA& A _ Miscellaneous Landslides O 1:24,000-scale Landslides from Geologic Watershed Analysis Landslides e s, d � Mud Bay Geotechnical Services, LLC 0 0.35 0.7 1.4 Miles JOB#: 1043-MAS Date: January, 2019 wwsnnc,Ton sTwrc ouwRrncnT or I I I ' nATURAL RESOURCE! Figure Site Landslide Map " ' NEE Roy Boad Rd, W45NIYGTOM4FOlOGKwtSURVF• Washington Geologic Portal g Belfair, Washington Site Development Geotechnical Report LEGEND 1 r i• �� •5 ❑ Slope <15% 1 ❑ • , ` : _ Slope 15-40% Parcel Boundary I f , y Z; Line of Assessment . i 1 FYI I f 1 1 ,: . �e '�,1'� � Mud Ba Geotechnical Services LLC y , Tax Parcels (Zoom in to 1:30.OUO 1.3.058 JOB* 1043-MAS Date: Janua 2019 C y 3 as Q t MI Figure 6: Steep Slope Assessment Mason County,WA GIS Web Map Contours 5 ft NE Roy Boad Rd, o � :,._ � a9 0.16 On Belfair, Washington Site Development Geotechnical Report