HomeMy WebLinkAboutGEO2020-00026 for BLD2020-00410 - GEO Geological Review - 5/27/2020 GEO?�ZU- ADD
Mason County Review Checklist
For a Geological Assessment
Instructions:
This checklist is intended to assist Staff in the review of a Geological Assessment.1-fie".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: I- e Y i' a V 114,q
Permit#: 1771 l / !iy 2,0' Parcel Vs: i 30(0 Dod 1
Date(s)of the Document(s)reviewed: 2 -Z'
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 discussion of the ground water conditions at the site,
OK? ✓ Comment:
(b) A discussion of the estimated depth to water,
OK? �� Comment:
(c) A discussion o the quantity of surface seepage,
OK? Comment:
(d) A discussion the upslope geomorphology,
OK? Comment:
(e) A discussion ocation of upland waterbodies and wetlands.
OK? Comment:
3. The approximate depth to hard or dense competent soil, e.g. glacial till or outwash sand.
OK? ✓ 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 indicating
downslope movement, etc.).
OK? ✓ Comment:
5. A discussion of the 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? 1/Comment:
7. A recommendation by the preparer whether a Geotechnical-Report should be required to further evaluate site
conditions and t "roposed 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:
Pagel of 2 Form Effective June 2008
( ,the area of the proposed development,
O Comment:
(b) the bo aries of the landslide hazard area(top, both sides, and toe),
OK? Comment:
(c) the associated bu (top, both sides, and toe)
OK? Comme
(d) building or other setbacks(tap, th 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 pr sed development on the site.
OK? Comment:
Are the Documents signed and stamped���`7- By h m? ` y I -�i La-el ,Z'�"
License#: License type:
FIRST REVIEW pproved ❑ Need more info.
If not approved, what is the next action/recommendation for further action?
Reviewed by , on 2 7 Time spent in review: ��7 �'il • ty.
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 El 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
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C-teo 2o-w —oc�u �.t� RECEIVED
MAY 112020
615 W.Ajder St
Geological Assessment
Hoch Single Family Residential Property
6151 NE Dewatto Holly Road, Tahuya
Parcel No. 22306-43-00010
Mason County, Washington
April 8, 2020
Project#2041
Prepared For:
Mathew Hoch
PO Box 366
Belfair, Washington 98528
Prepared By:
Envirotech Engineering
PO Box 984
Belfair, Washington 98528
Phone: 360-275-9374
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MASON COUNTY Submittal Checklist
COMMUNITY SERVICES Geological Assessment
Building,Planning,Environmental Health,Community Health
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 Intemational Building Code Section for Foundations on or adjacent to slopes.
Applicant/Owner Mathew Hoch Parcel# 22306-43-00010
Site Address 6151 NE Dewatto Holly Road
(1) A discussion of the geologic conditions in the general vicinity of the proposed development,with geologic unit
designation based on referenced maps.
Located on page(s) 5
(2) (a) A discussion of ground water conditions,
Located on page(s) 6
(b) A discussion of the estimated depth to water,
Located on page(s) 6
(c) A discussion of the quantity of surface seepage,
Located on page(s) 6
(d) A discussion of the upslope geomorphology,
Located on page(s) 3
(e) A discussion of location of upland waterbodies and wetlands.
Located on page(s) 3
(3) The approximate depth to hard or dense,competent soil,e.g.glacial till or outwash sand.
Located on page(s) 5
(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) 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) 7
(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
(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.
Located on page(s) 10
(8) If the presence of a hazard is located within 300 feet of the proposed development,then the following are
delineated on a geologic map/site map:
(a) The area of proposed development,
Located on map(s) n/a
(b) The boundaries of the landslide hazard area(top, both sides, and toe),
Located on map(s) n/a
(c) The associated buffers(top,both sides, and toe),
Located on map(s) n/a
(d) Building or other setbacks(top, both sides, and toe),
Located on map(s) n/a
(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) Site Plan(Appendix A)
I, Michael Staten, 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 April 8,2020 , and entitled Hoch Single Family Residential Property , 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.
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SS�oN L , 4/8/ the work done in this Geological Assessment.
Page 2 of 2
TABLE OF CONTENTS
1.0 INTRODUCTION.................................................................................................................................1
1.1 PROJECT INFORMATION.................................................................................................................... 1
1.2 PURPOSE OF INVESTIGATION AND SCOPE OF WORK........................................................................ 1
2.0 SURFACE CONDITIONS...................................................................................................................3
2.1 GENERAL OBSERVATIONS.................................................................................................................. 3
2.2 TOPOGRAPHY..................................................................................................................................... 3
2.2.1 Upslope Geomorphology............................................................................................................3
2.3 SURFACE DRAINAGE.......................................................................................................................... 3
2.3.1 Upland Water Bodies.................................................................................................................3
2.4 SLOPE AND EROSION OBSERVATIONS...............................................................................................4
3.0 SUBSURFACE INVESTIGATION.....................................................................................................5
3.1 FIELD METHODS,SAMPLING AND FIELD TESTING...........................................................................5
3.2 GEOLOGIC CONDITIONS.................................................................................................................... 5
3.3 SPECIFIC SUBSURFACE CONDITIONS................................................................................................. 5
3.3.1 Groundwater...............................................................................................................................6
4.0 ENGINEERING CONCLUSIONS......................................................................................................7
4.1 LANDSLIDE HAZARDS.........................................................................................................................7
4.1.1 Landslides and Slope Stability Analysis.................................................................................... 8
4.1.2 Surface and Subsurface Drainage............................................................................................8
4.2 EROSION HAZARDS............................................................................................................................8
4.3 SEIsrmc HAZARDS..............................................................................................................................9
4.4 OTHER CONSIDERATIONS..................................................................................................................9
5.0 CLOSURE.............................................................................................................................................10
Appendix A-Site Plan
Appendix B -Soil Information
1.0 INTRODUCTION
Envirotech Engineering, PLLC. (Envirotech) has completed this geological assessment for a
residential property located at 6151 NE Dewatto Holly, identified as parcel number 22306-43-
00010 in Mason County, Washington. As presented herein, this assessment includes information
pertaining to the Project in this Introduction Section; observations of the property and
surrounding terrain in the Surface Conditions Section; field methods and soils descriptions in the
Subsurface Investigation Section; and, assessments for landslides, erosion, seismic hazards, and
other considerations in the Conclusions Section.
An initial geological/ geotechnical evaluation of the project was conducted by Envirotech on
April 2, 2020. It was determined that natural slopes between 15% and 40% were present within
300 feet of the project. Due to these slope grades, a geological assessment is required pursuant to
landslide hazard areas of the Mason County Resource Ordinance(MCRO).
During the evaluation and site visit by Envirotech, surface and subsurface conditions were
assessed in order to determine if further geotechnical studies are required. After completion of the
field work and applicable Project research,Envirotech prepared this geological assessment.
1.1 Project Information
Information pertaining to the project was provided by the proponent of the property, and
observations from a field visit by Envirotech. The proposed development is expected to consist of
a new single family residence, on-site septic system, and other ancillary features typical of this
type of development. Approximate site development with relation to existing site features are
illustrated in the Site Plan in Appendix A of this report.
1.2 Purpose of Investigation and Scope of Work
The purpose of this geological assessment was to evaluate the project in order to confirm that the
proposed development is outside of any landslide hazard area and its associated buffers and
setbacks as determined in the MCRO. The investigation included characterizing the general
project surface and subsurface conditions, and evaluating the suitability of the soils to support the
planned site development. In order to fulfill the purpose of investigation, the geological/
geotechnical program completed for the proposed improvements of the Project include:
• Review project information provided by the proponent of the project;
• Conduct a site visit to document the site conditions that may influence the construction
and performance of the proposed improvements;
• Define general subsurface conditions of the site by observing soils within test pit
excavations review well logs from existing wells near the Project and evaluate
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geological and hazard maps depicting the site geology for the vicinity of the project;
• Perform soils testing, such as visual classifications,to determine selected index properties
of the soils;
• Complete an engineering assessment supported by planned site alterations and the surface
and subsurface conditions that were identified by the field investigation, soil testing, and
applicable project research;and,
• Establish engineering conclusions based on findings and anticipated development.
Envirotech Engineering Geological Assessment
PO Box 984 page 1 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
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Envirotech Engineering Geological Assessment
PO Box 984 page 2 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
2.0 SURFACE CONDITIONS
Information pertaining to the existing surface conditions for the project was gathered on April 2,
2020 by a representative with Envirotech. During the site visit, site features were documented that
may influence construction or reveal potential geological hazards. This Surface Conditions
Section provides information on general observations, vegetation, topography, drainage and
slope/erosion conditions for the project and surrounding areas.
2.1 General Observations
The property is currently vacant land with few improvements such as an existing driveway, and
surrounded by rural residential development. NE Dewatto Holly Road extends along the east side
of the property. Vegetation on and near the property consists primarily of firs, maples, and other
trees and shrubbery common to this area of the Pacific Northwest. An aerial photo of the Project
and immediate vicinity is provided on the following page.
2.2 Topography
The topographic information provided in this section was extrapolated from a public lidar source,
and incorporated observations and field measurements. Where necessary, slope verification
included measuring slope lengths and inclinations with a cloth tape and inclinometer. See the Site
Plan in Appendix A for an illustration of the general slope indicators with respect to the planned
development.
Descending slopes exceeding 15% are located on and beyond the property. Average slope grades
are approximately 8%with a vertical relief of approximately 60 feet.
2.2.1 Upslope Geomorphology
Ascending grades are generally located to the west of the planned development. This
slope is relatively minor within 300 feet of the Project, with no apparent slope grades of
at least 15%. The upland area of the property is situated on a hillside and crest.
Landforms are primarily of glacial origin with centuries of weathering overburden.
Additional geomorphology that is pertinent to both upslope and downslope areas are
provided in the Subsurface Investigation Section of this report.
2.3 Surface Drainage
The majority of the stormwater runoff originating upslope from the anticipated development is
expected to be minimal to moderate. Significant scour, erosion and sediment transport was not
apparent near the project.
2.3.1 Upland Water Bodies
There are no apparent water bodies or wetlands located upslope from the planned
development that would significantly influence the Project.
Envirotech Engineering Geological Assessment
PO Box 984 page 3 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
2.4 Slope and Erosion Observations
The existing moderate slopes near the Project signal a potential landslide or erosion hazard area.
Some indicators that may suggest past slope movements include:
• Outwash of sediments near the bottom of the slope,
• Fissures, tension cracks or naturally stepped land masses on the face or top of the slope,
and parallel to the slope,
• Fine, saturated subsurface soils,
• Old landslide debris,
• Significant bowing or leaning trees,or,
• Slope sloughing or calving.
The above mentioned indicators, or other signs of significant mass wasting on the property or
within the general vicinity of the Project were not observed or discovered during research.
Indications of past landslides, current unstable slopes, deep-seated slope problems, or surficial
slope failures were not observed during the site visit.
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Aerial Photo from Mason County Website
Envirotech Engineering Geological Assessment
PO Box 984 page 4 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
3.0 SUBSURFACE INVESTIGATION
Information on subsurface conditions pertaining to the project was gathered during research and a
site reconnaissance. The site visit was accomplished on April 2, 2020 by a representative with
Envirotech. Specific information on field methods, sampling, field testing, subsurface conditions,
and results from soil testing are presented in this section of the report. Appendix B has pertinent
information on subsurface conditions for the Project,including test pit log(s)representative of the
site soils,and water well report(s)originating from the subject property and/or nearby properties.
3.1 Field Methods,Sampling and Field Testing
Information on subsurface conditions for the Project was accomplished by probing anticipated
foundation areas with hand tools, and observing soils within test pit excavations and/ or earth
cuts. Information on subsurface conditions also included reviewing geological maps within the
Project vicinity, and water well reports originating from nearby properties. No soil samples were
collected for this Project. Envirotech measured the relative density of the in-situ soils by gauging
the resistance of hand tools.
3.2 Geologic Conditions
In general, soils at the project are composed of materials from glacial advances. The geologic
conditions as presented in the "Geologic Map of Washington," compiled by J. Eric Schuster,
2002 indicates Quaternary sediments, Qg. Quaternary sediments are generally unconsolidated
deposits,and dominantly deposited from glacial drift,including alluvium deposits. This project is
located within the Puget Lowland. Typically, "lower tertiary sedimentary rocks unconformably
overlie the Crescent Formation."as revealed in the Geologic Map. Initial sedimentary rocks were
formed from shales, sandstones and coal deposits from rivers. During the Quaternary period, the
Puget Lowland was covered by numerous ice sheets, with the most recent being the Fraser glacier
with a peak of approximately 14,000 years ago. Upon the glacial retreat, the landscape was
formed by glacial erosion glacial drift deposits.
The "Geologic map of the Holly 7.5-minute quadrangle, Jefferson, Kitsap, and Mason Counties,
Washington" by Contreras, Trevor A.; Weeks, Sarah A.; Stanton, Kelsay M. D.; Stanton,
Benjamin W.; Perry, Benjamin B.; Walsh, Timothy J.; Carson, Robert J.; Clark, Kenneth P.;
Mahan, Shannon A.,2012,provides the following caption(s)for the project area:
Vashon ice-contact deposits—Diamicton,cobbly pebble gravel and melt-out
till;yellow-tan to gray;clasts subangular to subrounded;loose to dense;
variously sorted;massive to well-stratified;till is friable and permeable.
3.3 Spec Subsurface Conditions
The following subsurface conditions are estimated descriptions of the project subgrade utilizing
information from the depth of penetration at all testing, sampling, observed and investigated
locations. Soils for this project were described utilizing the Unified Soil Classification System
(USCS). Using the USCS in conjunction with estimated relative densities and other anticipated
engineering properties of the soil, susceptibility for potential landslides, erosion and seismic
hazards may be assessed.
Envirotech Engineering Geological Assessment
PO Box 984 page 5 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
The project is primarily composed of undisturbed, native soils, without indications of substantial
fill. Competent bearing soils were encountered at 12 inches below the existing native ground
surface in locations where the ground was probed. For engineering purposes, these native soils
consist of distinguishable layers,as presented below.
Soils within the upper 3 feet of natural ground were observed to be primarily poorly graded sand
with gravel (SP). Expanded and specific subsurface descriptions, other than what is provided in
this section,are provided in the soil logs located in Appendix B of this report.
According to the "Soil Survey of Mason County," by the United States Department of
Agriculture, Soil Conservation Service (SCS), the site soils are described as Alderwood gravelly
sandy loam, Ab and Ad, with 8% - 50% slopes, and Everett very gravelly sandy loam, Eg and Ek,
with 0% -30% slopes. See the soil map below,and the applicable SCS soil profile(s)in Appendix
B of this report.
A
Soil Survey From USDA Natural Resources Conservation Service
3.3.1 Groundwater
From the water well report(s) and knowledge of the general area,permanent groundwater
is at least 50 feet below the current ground surface at the building location. Surface
seepage or perched groundwater at shallow depths was not observed on-site, nor
indicated on the well reports. However, some seasonal groundwater is expected to flow
directly above the hardpan on occasion.
Envirotech Engineering Geological Assessment
PO Box 984 page 6 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
4.0 ENGINEERING CONCLUSIONS
The following sections present engineering assessments and conclusions concerning the project.
These conclusions have been made available based on the planned construction activities as
outlined in the Introduction Section of this report; general observations of drainage and
topography as summarized in the Surface Conditions Section; and, soil conditions that were
identified by the field investigation and soils testing as outlined in the Subsurface Investigation
Section. Conclusions for the Project that is provided herein, includes pertinent information for
landslide,erosion and seismic hazards.
4.1 Landslide Hazards
For the planned development, as provided in the Introduction Section of this report, it is
Envirotech's opinion that the proposed development is not subjected to or cause adverse impacts
to a landslide hazard area or its associated buffer or setback. These conclusions are based on the
contents provided in this report.
Landslides are natural geologic processes, and structures near slopes possess an inherent risk of
adverse settlement, sliding or structural damage due to these processes. Geotechnical engineering
cannot eliminate these risks for any site with sloping grades because gravity is constantly
inducing strain on the sloping soil mass. Excessive wet weather and/ or earthquakes will
exacerbate these strains. Geotechnical engineering considers excessive wet weather and `design'
earthquakes in order to provide an acceptable factor of safety for developing on or near sloping
terrain. These factors of safeties are based on engineering standards such as defining engineering
properties of the soil,topography, water conditions, seismic acceleration and surcharges.
Surface sloughing or other types of surficial slope movements usually do not affect the deep-
seated structural capability of the slope. However, excessive and/or repeated surficial slope
movements, if not repaired, may represent a threat to the structural integrity of the slope.
Maintenance of the slope should be completed if the situation does arise in order to prevent the
possibility of further surficial or deep seated slope movements that may be damaging to life or
property.
According to the Department of Natural Resources (DNR) "LHZ — Final A-1 Map — Landslide
Inventory— Mason Watershed, by Sarikhan, et. al., May 2007,"previous landslide activity is not
recorded near the project. Per the Resource Map from DNR, the Project is not within terrain
labeled `highly unstable' or `highly erodible' relating to soils. DNR labeled portions of this
project as medium to high slope instability with relation to slopes. This delineation is primarily
dependent upon slopes and convergence. Secondly, lithology and precipitation are modeled
within this delineation. In summary, this designation is based on mapping without field
observations or knowledge of the specific site geology or soils. A resource map from DNR is
provided below:
Envirotech Engineering Geological Assessment
PO Box 984 page 7 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
t .
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SoNs `
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Hydric Sails
f - - Highly Unstable
Highly Erodible
{ / No Data or Gravel Pits
1 ) w Slope stawnty-West
Moderate Slope Instability
On y* • ' ■ High Slope Instability
Map from Washington State Department of Natural Resources Website
4.1.1 Landslides and Slope Stability Analysis
Past landslide activity or high slope instability indicators near the proposed development
was not revealed during the project research. In addition, detrimental landslide activity or
potential high landslide indicators were not observed during the site visit as outlined in
the Surface and Subsurface Conditions Sections of this report. Due to these factors, and
existing/proposed conditions,a slope stability analysis was not deemed necessarX for this
project. Considering the planned construction as summarized in a Introduction Section
of this report; the aforementioned surface and subsurface conditions for the project; the
slope stability assessment provided herein; and the Engineering Conclusions provided
later in this report, it is our opinion that the project is not within a landslide hazard area,
and that the proposed site alterations will not encourage a an s
4.1.2 Surface and Subsurface Drainage
This project does not appear to experience significant subsurface drainage or surface
runoff. It is our opinion that groundwater or surface drainage is not a limiting factor for
this Project.
4.2 Erosion Hazards
Based on the USCS description of the Project soils, the surface soils are considered moderately
erodible. According to the Resource Map from the Washington State DNR, as provided above,
the Project is not within terrain labeled `highly erodible.' This Project is not within an erosion
hazard area as defined by the MCRO. Erosion hazard areas are those with USDA SCS
Envirotech Engineering Geological Assessment
PO Box 984 page 8 Parcel 22306-43-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
designations of River Wash (Ra), Coastal Beaches (Cg), Alderwood Gravelly Sandy Loam on
slopes 15% or greater (Ac and Ad), Cloquallum Silt Loam on slopes 15% or greater (Cd),
Harstine Gravelly Sandy Loam on slopes 15% or greater (Hb), and Mtsap Silt Loam on slopes
15%or greater(Kc).
Temporary and/ or permanent erosion control measures may be required for any site when land
disturbance is involved. Erosion control will mostly depend on the timeliness of construction,
moisture content of the soil,and amount of rainfall during construction. Soil erosion typical to the
existing conditions and planned disturbance of this Project include wind-borne silts during dry
weather, and sediment transport during prolonged wet weather. Sediment transport of disturbed
soils could be from stormwater runoff or tracking off-site with construction equipment. Although
an engineered erosion control plan is not warranted for this project, Best Management Practices
(BMP's) should be employed during and after construction. Ordinary BMP's includes silt
fencing,protection of drainage outlets and vegetating denuded areas.
Erosion control information and specifications may be found in the applicable "Stormwater
Management Manual for Western Washington,"prepared by the Washington State Department of
Ecology Water Quality Program.
4.3 Seismic Hazards
Soils immediately below the expected foundation depth for this Project are generally Type D,
corresponding to the International Building Code (IBC) soil profiles. According to the IBC, the
regional seismic zone is 3 for this Project. The estimated peak ground acceleration ranges from
0.50g to 0.60g. This estimation is based on the United States Geological Survey(USGS)National
Seismic Hazard Project in which there is an estimated 2% probability of exceedance within the
next 50 years.
There are no known faults beneath this project. The nearest Class `A' or 'B' fault to this property
is the Hood Canal Fault Zone. This fault is a Class `A', and is located approximately 2.5 miles to
the northwest of the Project. This information is supported by the USGS Quaternary Fault and
Fold Database for the United States.
The potential for liquefaction and other earthquake induced hazards are believed to be low for
this project. This is based on subsurface conditions such as soil characteristics and the lack of a
permanent and substantial shallow water table. Subgrade characteristics that particularly
contribute to problems caused by seismic events include submerged and confined, poorly-graded
granular soils. Although gravel- and silt-sized soil particles could be problematic, fine and
medium grained sands are typically subjected to these types of seismic hazards.
4.4 Other Considerations
Conclusions in this report are based on the type and location of the anticipated development, and
existing on-site and off-site conditions. Site development that significantly deviates from the
anticipated improvements presented in this report, or nearby development that influences this
Project may require geotechnical design recommendations.
Envirotech Engineering Geological Assessment
PO Box 984 page 9 Parcel 2230643-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
5.0 CLOSURE
Based on the project information and site conditions as presented in this report,it is Envirotech's
opinion that additional geotechnical studies are not required to further evaluate this project.
Due to the inherent natural variations of the soil stratification and the nature of the geotechnical
subsurface exploration, there is always a possibility that soil conditions encountered during
construction are different than those described in this report. Therefore, it is recommended that
Envirotech is promptly notified if project and subsurface conditions found on-site are not as
presented in this report so that we can re-evaluate our recommendations.
This report presents a geological/geotechnical assessment, and is intended only for the owner, or
owners' representative. Furthermore, this report is only valid for the project information and
location described herein.
The services described in this report were prepared under the responsible charge of Michael
Staten, a professional engineer with Envirotech. Michael Staten has appropriate education and
experience in the field of geotechnical engineering in order to assess landslide hazards,
earthquake hazards,and general soil mechanics.
Please contact Michael Staten at 360-275-9374 if you have any questions, comments, or require
additional information.
Sincerely,
Envirotech Engineering ►—�
Jessica Smith, M.S. Michael Staten,P.E.
Staff Geologist Geotechnical Engineer
Envirotech Engineering Geological Assessment
PO Box 984 page 10 Parcel 2230643-00010
Belfair,Washington 98528 Mason County,Washington
Ph. 360-275-9374 April 8,2020
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TOE tf.a%.SLOPE
v b�,
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PROJECT/ OWNER/ LOCATIIH
SINGLE FAMILY PROPERTY
GEOLOGICAL ASSESSMENT
rani
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L LOPE HIOO:ATOM WERE FZ"REAMM T1 DWAUTECK ANV 03 TMLEL E870-40-OW
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ll�ilTTDC N�MN FpE.VITN AELA790i T7 7NE 19Q'iA1Y LIIEi �EYiV� F]®IIIFJ:I�i
NMI at HE34ffm 7r 7w UwwL TIE OMxJCIm An —s fL!!E D�d174t 1!5ITE
P/N6viImaItplumaa IN 7FE�QIEG�/i./SCOLDMAL TAAS M=a sn M AID s 6F�ACE FrA M,S TWIT MY roNE RAW oF�F oF�Air uEs s°�rcn►'a:%MK r r n�sT rEr PLAN
APPENDIX B
SOIL INFORMATION
TEST PIT LOG
TEST PIT NUMBER TP-1
rROJECT: SFR Gedogitcal A.ssessraAnt DATE OF"-OG: 0411J2C120
PROJECT NO: 2041 LOGGED BY: JS
CLIENT: Hoch EXCAVATOR: N/A
LOCATION: Parcel 22306-43-00010 DRILL RIG: None
Mason County,Washington ELEVATION: N/A
INITIAL DEPTH OF WATER: NIA FR%AL DEPTH OF WATER: NIA
IL STRATA, sTAN.ARC PEVSTIATION TC T
SA
DEPTH SAMPLERS USCS DESCRIPTION LL PI CJRVE
AND TEST DATA DEPTH N 10 30 50
0 ..........................................
SP Poorly graded SAND with GRAVEL.
Gravel is fine and subrounded.Sand is
primarily coarse.
1
2
3
Excavation terminated at approximately
3.0 feet
4
5
6
7
8
9
10
No Groundwater Encountered ENVIROTECH ENGINEERING
This information pertains only to this boring and should not be Geotechnical Engineering
interpreted as being indicitive of the entire site.
Map Unit Description Alderwood gravelly sandy loam,30 to 50 percent slopes--Mason
County,Washington
Mason County, Washington
Ad—Alderwood gravelly sandy loam, 30 to 50 percent slopes
Map Unit Setting
National map unit symbol: 2t628
Elevation: 50 to 800 feet
Mean annual precipitation. 25 to 60 Inches
Mean annual air temperature 46 to 52 degrees F
Frost-free period 160 to 240 days
Farmland classification, Not prime farmland
Map Unit Composition
Alderwood and similar soils: 80 percent
Minor components: 20 percent
Estimates are based on observations,descriptions,and transects of
the mapund.
Description of Alderwood
Setting
Landform: Ridges,hills
Landform position(two-dimensional). Backslope
Landform position(three-dimensional): Side slope,nose slope,tali
Down-slope shape: Linear,convex
Across-slope shape: Convex
Parent material Glacial drift and/or glacial outwash over dense
glaciomanne deposits
Typical profile
A-0 to 7 inches: gravelly sandy loam
Bwl-7 to 21 inches very gravelly sandy loam
Bw2-21 to 30 inches: very gravelly sandy loam
Bg-30 to 35 inches: very gravelly sandy loam
2Cdl-35 to 43 inches. very gravelly sandy loam
2Cd2-43 to 59 inches: very gravelly sandy loam
Properties and qualities
Slope 30 to 50 percent
Depth to restrictive feature: 20 to 39 inches to densic material
Natural drainage class: Moderately well drained
Capacity of the most limiting layer to transmit water(Ksat). Very
Itow to moderately low(0.00 to 0.06 inthr)
Depth to water table: About 18 to 37 inches
Frequency of flooding None
Frequency of ponding: None
Available water storage in profile. Very low(about 2.7 inches)
Interpretive groups
Land capability classification(irrigated): None specified
Land capability classification(nonimgated): 7e
Hydrologic Soil Group: B
I Natural Resources Web Sal Survey V712020
NOW Conservation Service National Cooperative Soil Survey Page I of 2
Map Unit Description.Alderivood gravely sandy loam,30 to 50 percent slopes--Mason
County,Washington
Hydric sod rating No
Minor Components
Everett
Percent of map unit 10 percent
Landform Karnes,eskers,moraines
Landform position(two-dimensional): Backslope
Landform position(three-dimensional) Side slope
Down-slope shape. Convex
Across-slope shape Convex
Hydric soil rating No
Indianola
Percent of map unit 5 percent
Landform: Eskers,kames,terraces
Landform position(three-dimensional) Tread
Down-slope shape: Linear
Across-slope shape Linear
Hydnc sal rating No
Shalcar
Percent of map unit 3 percent
Landform: Depressions
Landform position(three-dimensional): Dip
Down-slope shape: Concave
Across-slope shape Concave
Hydric soil rating Yes
Norma
Percent of map unit 2 percent
Landform Depressions,drainageways
Landform position(three-dimensional) Dip
Down-slope shape. Concave,linear
Across-slope shape Concave
Hydric sod rating: Yes
Data Source Information
Soil Survey Area: Mason County,Washington
Survey Area Data Version 15,Sep 16,2019
Natural Resources Web Sod Survey 4f7rAM
Conservation Service National Cooperative Sal Survey Page 2 or 2
Map Unit Description-.Everett very gravelly sandy loam.15 to 30 percent slopes---Mason
County.Washmoon
Mason County, Washington
Ek—Everett very gravelly sandy loam, 15 to 30 percent
slopes
Map Unit Setting
National map unit symbol: 2t62c
Elevation 30 to 900 feet
Mean annual precipitation. 35 to 91 inches
Mean annual air temperature. 48 to 52 degrees F
Frost-free period. 180 to 240 days
Farmland classification Farmland of statewide importance
Map Unit Composition
Everett and similar sods 80 percent
Minor components: 20 percent
Estimates are based on observations,descriptions,and transacts of
the mapunit
Description of Everett
Setting
Landform Karnes,eskers.moraines
Landform positron(two-dimensional) Backslope
Lartdform position(three-dimensional) Side slope
Down-slope shape. Convex
Across-slope shape Convex
Parent material Sandy and gravelly glacial outwash
Typical profile
Ot-0 to 1 inches slightly decomposed plant material
A- 1 to 3 inches very gravelly sandy loam
Bw-3 to 24 inches very gravelly sandy loam
C 1-24 to 35 inches very gravelly loamy sand
C2-35 to 60 inches extremely cobbiy coarse sand
Properties and qualities
Slope 15 to 30 percent
Depth to restrictive feature More than 80 inches
Natural drainage class Somewhat excessively drained
Capacity of the most limiting layer to transmit water(Ksat). High
(1.98 to 5.95 iNhr)
Depth to water table More than 80 inches
Frequency of flooding None
Frequency of ponding None
Available water storage in profile. Low(about 3.2 inches)
Interpretive groups
Land capability classification(irrigated) None specified
Land capability class cation(nonlmgated) 4e
Hydrologic Sod Group. A
i uza Natural Resources Web Soil Survey 4ru2020
AM Conservation Service National Cooperative Sad Survey Page 1 of 2
Map Unit Description Everett very gravelly sandy loam,15 to 30 percent slopes—Mason
County.Washington
Forage suitability group: Droughty Soils(G002XN402WA),
Droughty Soils(G002XS401 WA)
Hydric soil rating. No
Minor Components
Alderwood
Percent of map unit. 10 percent
Landform: Ridges,hills
Landform positron(two-dimensional) Backslope
Landform position(three-dimensional) Side slope,nose slope,talf
Down-slope shape Linear,convex
Across-slope shape Convex
Hydnc soil rating. No
Indianola
Percent of map unit 10 percent
Landform: Eskers,kames,terraces
Landform positron(two-dimensional): Backslope
Landform position(three-dimensional) Side slope
Down-slope shape Linear
Across-slope shape: Linear
Hydnc soil rating No
Data Source Information
Soil Survey Area Mason County,Washington
Survey Area Data. Version 15,Sep 16,2019
A)A Natural Resources Web Sod Survey 4/7/2020
ri Conservation Service National Cooperative Sal Survey Page 2 of 2
i�
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e ttI f more tin one I aid strecture, mad slow tb�c�aess of ainfers aid tMt kind
O 18Y WELL 411bod• All War and wire of tle material In tick strata �pttaetraled vltl
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all (S) DINEN5tOr5 llnel of well 6 lodes t -----•------`-------------------------------
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............................. -......._._.; TEI t
SAD I
Perforations 110
a. Tridppee or ptrrerater used
O Slii of perroratloas Is if it t I I
+p Perforattns from It to ft t I t
G perforation from 1t to (l I I t
R perforations frog ft to ft l t 1
...........-•--------------•-............................t I t
krCiiacctarer's Name M I t I
O Tit AINt3S9 Nodel No.. f RECEIVED:
CE V l I
B n Blot !Ile li from
SI ft t�` « !
Gravel tck�td >i0 S le of ravel
c Gravel placed era it to tI AUG 0 8 ZOO1
Soffit pp1!# TIS To vlat te tb? 11 ft. + ll',i.hin ioii Si.nf �
.�. Nterial istd to seal 1)L1T01f1� ft P
?� Tydt o�rilir+roataia ionsik a kill of strata rl i p'nnrcrtt of Ecology 1 t
Ne�bod of seallel strata off
t:r,:,uu:::aazsaiu enu:::=u u,z.:::::uaaasrnesiz:ra a,' i I
;1) P1.'MP Nanafactnrer't Mace I t I
Z Type l P
y •-ttif........Skit..:::LStLtL,f if litf!=:fi.tt.........
:P........
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y 11) WATER LIYELS Liad-sartate elevation
O +bore Eta sea level ft. I t I
�p Static level t,s ft below lop of well Date/5113/01
Artesia Pressure lbs per snare nob lute
Artesian water coatrolled by I i
.... i .......................................Wort started . : C.Z......ompleted.:__..1
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IS)WELL TESTS- 8raadfil is mail water level is lowered blow WELL COAST10CT01 CSITIFICATION
static level I [ contracted sadlar accept respoutblIItF tar cat-
W Was pimp test made,S� If yes 1FF what I strectioa of Ibis veil, aid Its Xpliaire with all
Tier; lal./na w III tt draidon alter lrs. Wa bintttoi well construction stuaAeaards Naterials istd
sae k€ isforation reported above are trae to ey best
C lecpvery data I
taovtedge and belief
Time Water Level Time Water level Time Water Level i NAME SICIOLSON HILLI4G INC
i IPersoa. fire, or corponhoa) (Type or prial)
ADaIE;s ro A1t3
Date of test // t�
qs Baiter test 10 ``al/ali tl ft drndowa afty 1 brs ISiGNIDI �� Lictisc No fill
O Air teal 1a1(ata, v1 sten set it ft far his.l --
d Artesian flta 1 p I. hie I Coatr ,tor's
Z Temperature of water Was a tittle+? analysis made'10 ;lelistratios No VICO113IGN Note 48/16/11
..t:.........ilk:t,z i:::Lis::t::i...........tlas:Leas[:[tsizi:..ae,zasz:ls,aa.at.....a.S.a.t...z:................„..........+::LL